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Archive for May, 2013

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May

Service

Phytron Stepper Motor - ZSH

Industrial Repair Group delivers fast and reliable Phytron Stepper Motor Repair Service. We understand that damaged equipment can wreak havoc on your bottom line. We pride ourselves by delivering guaranteed repairs and fast turn around times when you need it most. We do this by partnering with you on each and every repair.

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Every Phytron Stepper Motor Repair is subjected to dynamic function testings to verify a successful repair and then backed by an Industrial Repair Group 18 Month Repair Warranty. Industrial Repair Group fully tests and replaces all high failure components such as ICs, PALs, EPROMs, GALs, and surface mounted components. Factory sealers and conformal coatings are re-applied as needed with each Phytron Stepper Motor Repair to restore your equipment back to its' OEM specs.

Commonly Supported Models
Stepper Motors ZSS: 19 – 56 mm
NEMA Stepper Motors ZSH: 57 – 107 mm
Vacuum Stepper Motors VSS / VSH: 19 – 125 mm
Harsh Environment Stepper Motors HSS / HSH: 55 -120 mm
Extreme Environment Stepper Motors: ESS / ESH: 45 – 100 mm

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How Stepper Motors Work

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A stepper motor (or step motor) is a brushless, synchronous electric motor that can divide a full rotation into a large number of steps. The motor’s position can be controlled precisely without any feedback mechanism (see Open-loop controller), as long as the motor is carefully sized to the application. Stepper motors are similar to switched reluctance motors (which are very large stepping motors with a reduced pole count, and generally are closed-loop commutated.)

Frame 1: The top electromagnet (1) is turned on, attracting the nearest tooth of a gear-shaped iron rotor.

With the teeth aligned to electromagnet (1), they will be slightly offset from electromagnet (2).

Frame 2: The top electromagnet (1) is turned off, and the right electromagnet (2) is energized, pulling the nearest teeth slightly to the right. This results in a rotation of 3.6° in this example.

Frame 3: The bottom electromagnet (3) is energized; another 3.6° rotation occurs.

Frame 4: The left electromagnet (4) is enabled, rotating again by 3.6°. When the top electromagnet (1) is again enabled, the teeth in the sprocket will have rotated by one tooth position; since there are 25 teeth, it will take 100 steps to make a full rotation in this example.

Because of power requirements, induction of the windings, and temperature management, motors cannot be powered directly by most digital controllers. Some circuitry that can handle more power — a motor controller such as an H-bridge — must be inserted between digital controller and motor’s windings. The above image shows the basic circuit of a motor controller that can also sense motor current. The circuitry to control one winding of a motor is shown; a stepper motor would use a circuit that could control four windings, and a normal DC motor would need circuitry to control two windings. All of this circuitry is typically incorporated in an integrated H-bridge chip.

Fundamentals of operation

Stepper motors operate differently from DC brush motors, which rotate when voltage is applied to their terminals. Stepper motors, on the other hand, effectively have multiple “toothed” electromagnets arranged around a central gear-shaped piece of iron. The electromagnets are energized by an external control circuit, such as a microcontroller. To make the motor shaft turn, first one electromagnet is given power, which makes the gear’s teeth magnetically attracted to the electromagnet’s teeth. When the gear’s teeth are thus aligned to the first electromagnet, they are slightly offset from the next electromagnet. So when the next electromagnet is turned on and the first is turned off, the gear rotates slightly to align with the next one, and from there the process is repeated. Each of those slight rotations is called a “step”, with an integer number of steps making a full rotation. In that way, the motor can be turned by a precise angle.

Stepper motor characteristics

  1. Stepper motors are constant power devices.
  2. As motor speed increases, torque decreases. (most motors exhibit maximum torque when stationary, however the torque of a motor when stationary ‘holding torque’ defines the ability of the motor to maintain a desired position while under external load).
  3. The torque curve may be extended by using current limiting drivers and increasing the driving voltage (sometimes referred to as a ‘chopper’ circuit; there are several off the shelf driver chips capable of doing this in a simple manner).
  4. Steppers exhibit more vibration than other motor types, as the discrete step tends to snap the rotor from one position to another (called a detent). The vibration makes stepper motors noisier than DC motors.
  5. This vibration can become very bad at some speeds and can cause the motor to lose torque or lose direction. This is because the rotor is being held in a magnetic field which behaves like a spring. On each step the rotor overshoots and bounces back and forth, “ringing” at its resonant frequency. If the stepping frequency matches the resonant frequency then the ringing increases and the motor comes out of synchronism, resulting in positional error or a change in direction. At worst there is a total loss of control and holding torque so the motor is easily overcome by the load and spins almost freely.
  6. The effect can be mitigated by accelerating quickly through the problem speeds range, physically damping (frictional damping) the system, or using a micro-stepping driver.
  7. Motors with a greater number of phases also exhibit smoother operation than those with fewer phases (this can also be achieved through the use of a micro stepping drive)

Open-loop versus closed-loop commutation

Steppers are generally commutated open loop, i.e. the driver has no feedback on where the rotor actually is. Stepper motor systems must thus generally be over engineered, especially if the load inertia is high, or there is widely varying load, so that there is no possibility that the motor will lose steps. This has often caused the system designer to consider the trade-offs between a closely sized but expensive servomechanism system and an oversized but relatively cheap stepper.

A new development in stepper control is to incorporate a rotor position feedback (e.g. an encoder or resolver), so that the commutation can be made optimal for torque generation according to actual rotor position. This turns the stepper motor into a high pole count brushless servo motor, with exceptional low speed torque and position resolution. An advance on this technique is to normally run the motor in open loop mode, and only enter closed loop mode if the rotor position error becomes too large — this will allow the system to avoid hunting or oscillating, a common servo problem.

Types

There are three main types of stepper motors:[1]

  1. Permanent Magnet Stepper (can be subdivided in to ‘tin-can’ and ‘hybrid’, tin-can being a cheaper product, and hybrid with higher quality bearings, smaller step angle, higher power density)
  2. Hybrid Synchronous Stepper
  3. Variable Reluctance Stepper
  4. Lavet type stepping motor

Permanent magnet motors use a permanent magnet (PM) in the rotor and operate on the attraction or repulsion between the rotor PM and the stator electromagnets. Variable reluctance (VR) motors have a plain iron rotor and operate based on the principle that minimum reluctance occurs with minimum gap, hence the rotor points are attracted toward the stator magnet poles. Hybrid stepper motors are named because they use a combination of PM and VR techniques to achieve maximum power in a small package size.

Two-phase stepper motors

There are two basic winding arrangements for the electromagnetic coils in a two phase stepper motor: bipolar and unipolar.

Unipolar motors

A unipolar stepper motor has two windings per phase, one for each direction of magnetic field. Since in this arrangement a magnetic pole can be reversed without switching the direction of current, the commutation circuit can be made very simple (e.g. a single transistor) for each winding. Typically, given a phase, one end of each winding is made common: giving three leads per phase and six leads for a typical two phase motor. Often, these two phase commons are internally joined, so the motor has only five leads.

A microcontroller or stepper motor controller can be used to activate the drive transistors in the right order, and this ease of operation makes unipolar motors popular with hobbyists; they are probably the cheapest way to get precise angular movements.

Unipolar stepper motor coils

(For the experimenter, one way to distinguish common wire from a coil-end wire is by measuring the resistance. Resistance between common wire and coil-end wire is always half of what it is between coil-end and coil-end wires. This is because there is twice the length of coil between the ends and only half from center (common wire) to the end.) A quick way to determine if the stepper motor is working is to short circuit every two pairs and try turning the shaft, whenever a higher than normal resistance is felt, it indicates that the circuit to the particular winding is closed and that the phase is working.

Bipolar motor

Bipolar motors have a single winding per phase. The current in a winding needs to be reversed in order to reverse a magnetic pole, so the driving circuit must be more complicated, typically with an H-bridge arrangement (however there are several off the shelf driver chips available to make this a simple affair). There are two leads per phase, none are common.

Static friction effects using an H-bridge have been observed with certain drive topologies[citation needed].

Because windings are better utilized, they are more powerful than a unipolar motor of the same weight. This is due to the physical space occupied by the windings. A unipolar motor has twice the amount of wire in the same space, but only half used at any point in time, hence is 50% efficient (or approximately 70% of the torque output available). Though bipolar is more complicated to drive, the abundance of driver chip means this is much less difficult to achieve.

An 8-lead stepper is wound like a unipolar stepper, but the leads are not joined to common internally to the motor. This kind of motor can be wired in several configurations:

  • Unipolar.
  • Bipolar with series windings. This gives higher inductance but lower current per winding.
  • Bipolar with parallel windings. This requires higher current but can perform better as the winding inductance is reduced.
  • Bipolar with a single winding per phase. This method will run the motor on only half the available windings, which will reduce the available low speed torque but require less current.

Higher-phase count stepper motors

Multi-phase stepper motors with many phases tend to have much lower levels of vibration, although the cost of manufacture is higher. These motors tend to be called ‘hybrid’ and have more expensive machined parts, but also higher quality bearings. Though they are more expensive, they do have a higher power density and with the appropriate drive electronics are actually better suited to the application[citation needed], however price is always an important factor. Computer printers may use hybrid designs.

Stepper motor drive circuits

Stepper motor performance is strongly dependent on the drive circuit. Torque curves may be extended to greater speeds if the stator poles can be reversed more quickly, the limiting factor being the winding inductance. To overcome the inductance and switch the windings quickly, one must increase the drive voltage. This leads further to the necessity of limiting the current that these high voltages may otherwise induce.

L/R drive circuits

L/R drive circuits are also referred to as constant voltage drives because a constant positive or negative voltage is applied to each winding to set the step positions. However, it is winding current, not voltage that applies torque to the stepper motor shaft. The current I in each winding is related to the applied voltage V by the winding inductance L and the winding resistance R. The resistance R determines the maximum current according to Ohm’s law I=V/R. The inductance L determines the maximum rate of change of the current in the winding according to the formula for an Inductor dI/dt = V/L. Thus when controlled by an L/R drive, the maximum speed of a stepper motor is limited by its inductance since at some speed, the voltage U will be changing faster than the current I can keep up. In simple terms the rate of change of current is L X R (e.g. a 10mH inductance with 2 ohms resistance will take 20 ms to reach approx 2/3 of maximum torque or around 0.1 sec to reach 99% of max torque). To obtain high torque at high speeds requires a large drive voltage with a low resistance and low inductance. With an L/R drive it is possible to control a low voltage resistive motor with a higher voltage drive simply by adding an external resistor in series with each winding. This will waste power in the resistors, and generate heat. It is therefore considered a low performing option, albeit simple and cheap.

Chopper drive circuits

Chopper drive circuits are also referred to as constant current drives because they generate a somewhat constant current in each winding rather than applying a constant voltage. On each new step, a very high voltage is applied to the winding initially. This causes the current in the winding to rise quickly since dI/dt = V/L where V is very large. The current in each winding is monitored by the controller, usually by measuring the voltage across a small sense resistor in series with each winding. When the current exceeds a specified current limit, the voltage is turned off or “chopped”, typically using power transistors. When the winding current drops below the specified limit, the voltage is turned on again. In this way, the current is held relatively constant for a particular step position. This requires additional electronics to sense winding currents, and control the switching, but it allows stepper motors to be driven with higher torque at higher speeds than L/R drives. Integrated electronics for this purpose are widely available.

Phase current waveforms

A stepper motor is a polyphase AC synchronous motor (see Theory below), and it is ideally driven by sinusoidal current. A full step waveform is a gross approximation of a sinusoid, and is the reason why the motor exhibits so much vibration. Various drive techniques have been developed to better approximate a sinusoidal drive waveform: these are half stepping and microstepping.

Different drive modes showing coil current on a 4-phase unipolar stepper motor

Wave drive

In this drive method only a single phase is activated at a time. It has the same number of steps as the full step drive, but the motor will have significantly less than rated torque. It is rarely used.

Full step drive (two phases on)

This is the usual method for full step driving the motor. Two phases are always on. The motor will have full rated torque.

Half stepping

When half stepping, the drive alternates between two phases on and a single phase on. This increases the angular resolution, but the motor also has less torque (approx 70%) at the half step position (where only a single phase is on). This may be mitigated by increasing the current in the active winding to compensate. The advantage of half stepping is that the drive electronics need not change to support it.

Microstepping

What is commonly referred to as microstepping is actually “sine cosine microstepping” in which the winding current approximates a sinusoidal AC waveform. Sine cosine microstepping is the most common form, but other waveforms are used [1]. Regardless of the waveform used, as the microsteps become smaller, motor operation becomes more smooth, thereby greatly reducing resonance in any parts the motor may be connected to, as well as the motor itself. Resolution will be limited by the mechanical stiction, backlash, and other sources of error between the motor and the end device. Gear reducers may be used to increase resolution of positioning.

Step size repeatability is an important step motor feature and a fundamental reason for their use in positioning.

Example: many modern hybrid step motors are rated such that the travel of every full step (example 1.8 Degrees per full step or 200 full steps per revolution) will be within 3% or 5% of the travel of every other full step; as long as the motor is operated within its specified operating ranges. Several manufacturers show that their motors can easily maintain the 3% or 5% equality of step travel size as step size is reduced from full stepping down to 1/10 stepping. Then, as the microstepping divisor number grows, step size repeatability degrades. At large step size reductions it is possible to issue many microstep commands before any motion occurs at all and then the motion can be a “jump” to a new position.

Theory

A step motor can be viewed as a synchronous AC motor with the number of poles (on both rotor and stator) increased, taking care that they have no common denominator. Additionally, soft magnetic material with many teeth on the rotor and stator cheaply multiplies the number of poles (reluctance motor). Modern steppers are of hybrid design, having both permanent magnets and soft iron cores.

To achieve full rated torque, the coils in a stepper motor must reach their full rated current during each step. Winding inductance and reverse EMF generated by a moving rotor tend to resist changes in drive current, so that as the motor speeds up, less and less time is spent at full current — thus reducing motor torque. As speeds further increase, the current will not reach the rated value, and eventually the motor will cease to produce torque.

Pull-in torque

This is the measure of the torque produced by a stepper motor when it is operated without an acceleration state. At low speeds the stepper motor can synchronise itself with an applied step frequency, and this pull-in torque must overcome friction and inertia. It is important to make sure that the load on the motor is frictional rather than inertial as the friction reduces any unwanted oscillations.

Pull-out torque

The stepper motor pull-out torque is measured by accelerating the motor to the desired speed and then increasing the torque loading until the motor stalls or misses steps. This measurement is taken across a wide range of speeds and the results are used to generate the stepper motor’s dynamic performance curve. As noted below this curve is affected by drive voltage, drive current and current switching techniques. A designer may include a safety factor between the rated torque and the estimated full load torque required for the application.

Detent torque

Synchronous electric motors using permanent magnets have a remnant position holding torque (called detent torque or cogging, and sometimes included in the specifications) when not driven electrically. Soft iron reluctance cores do not exhibit this behavior.

Stepper motor ratings and specifications

Stepper motors nameplates typically give only the winding current and occasionally the voltage and winding resistance. The rated voltage will produce the rated winding current at DC: but this is mostly a meaningless rating, as all modern drivers are current limiting and the drive voltages greatly exceed the motor rated voltage.

A stepper’s low speed torque will vary directly with current. How quickly the torque falls off at faster speeds depends on the winding inductance and the drive circuitry it is attached to, especially the driving voltage.

Steppers should be sized according to published torque curve, which is specified by the manufacturer at particular drive voltages or using their own drive circuitry.

Applications

Computer-controlled stepper motors are one of the most versatile forms of positioning systems. They are typically digitally controlled as part of an open loop system, and are simpler and more rugged than closed loop servo systems.

Industrial applications are in high speed pick and place equipment and multi-axis machine CNC machines often directly driving lead screws or ballscrews. In the field of lasers and optics they are frequently used in precision positioning equipment such as linear actuators, linear stages, rotation stages, goniometers, and mirror mounts. Other uses are in packaging machinery, and positioning of valve pilot stages for fluid control systems.

Commercially, stepper motors are used in floppy disk drives, flatbed scanners, computer printers, plotters, slot machines, and many more devices.

See also

  • Fractional horsepower motors
  • Piezoelectric motor
  • Servo motor
  • Brushless DC electric motor
  • Three-phase AC synchronous motors
  • Solenoid

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Category : Electronic repair service | Industrial Repair Group | Stepper Motor Repair | Blog
17
May

Service


Power Wise EZ-GO Charger Repair by Industrial Repair Group

Industrial Repair Group delivers fast and reliable EZ-GO PowerWise Golf Cart Charger Repair Service. We understand that damaged equipment can wreak havoc on your bottom line. We pride ourselves by delivering guaranteed repairs and fast turn around times when you need it most. We do this by partnering with you on each and every repair.

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HOHER AUTOMATION WESTAMP INC & WESTINGHOUSE
HONEYWELL WESTINGHOUSE
HONEYWELL & NEMATRON CORP WHEDCO
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HUBBELL & FEMCO XENTEK INC
HUBNER & AMICON XYCOM & WARNER ELECTRIC
HURCO MFG CO YASKAWA ELECTRIC
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How Power Supplies Work


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A power supply is a device that supplies electrical energy to one or more electric loads. The term is most commonly applied to devices that convert one form of electrical energy to another, though it may also refer to devices that convert another form of energy (e.g., mechanical, chemical, solar) to electrical energy. A regulated power supply is one that controls the output voltage or current to a specific value; the controlled value is held nearly constant despite variations in either load current or the voltage supplied by the power supply’s energy source.

Every power supply must obtain the energy it supplies to its load, as well as any energy it consumes while performing that task, from an energy source. Depending on its design, a power supply may obtain energy from:

  • Electrical energy transmission systems. Common examples of this include power supplies that convert AC line voltage to DC voltage.
  • Energy storage devices such as batteries and fuel cells.
  • Electromechanical systems such as generators and alternators.
  • Solar power.

A power supply may be implemented as a discrete, stand-alone device or as an integral device that is hardwired to its load. In the latter case, for example, low voltage DC power supplies are commonly integrated with their loads in devices such as computers and household electronics.

Constraints that commonly affect power supplies include:

  • The amount of voltage and current they can supply.
  • How long they can supply energy without needing some kind of refueling or recharging (applies to power supplies that employ portable energy sources).
  • How stable their output voltage or current is under varying load conditions.
  • Whether they provide continuous or pulsed energy.

Power supplies types

Power supplies for electronic devices can be broadly divided into linear and switching power supplies. The linear supply is usually a relatively simple design, but it becomes increasingly bulky and heavy for high-current equipment due to the need for large mains-frequency transformers and heat-sinked electronic regulation circuitry. Linear voltage regulators produce regulated output voltage by means of an active voltage divider that consumes energy, thus making efficiency low. A switched-mode supply of the same rating as a linear supply will be smaller, is usually more efficient, but will be more complex.

Battery

A battery is an alternative to a line-operated power supply;[1] it is independent of the availability of mains electricity, suitable for portable equipment and use in locations without mains power. A battery consists of several electrochemical cells connected in series to provide the voltage desired. Batteries may be primary (able to supply current when constructed, discarded when drained) or secondary (rechargeable; can be charged, used, and recharged many times)

The primary cell first used was the carbon-zinc dry cell.[1] It had a voltage of 1.5 volts; later battery types have been manufactured, when possible, to give the same voltage per cell. Carbon-zinc and related cells are still used, but the alkaline battery delivers more energy per unit weight and is widely used. The most commonly used battery voltages are 1.5 (1 cell) and 9V (6 cells).

Various technologies of rechargeable battery are used. Types most commonly used are NiMH, and lithium ion and variants.

DC power supply

A home-made linear power supply (used here to power amateur radio equipment)

An AC powered unregulated power supply usually uses a transformer to convert the voltage from the wall outlet (mains) to a different, nowadays usually lower, voltage. If it is used to produce DC, a rectifier is used to convert alternating voltage to a pulsating direct voltage, followed by a filter, comprising one or more capacitors, resistors, and sometimes inductors, to filter out (smooth) most of the pulsation. A small remaining unwanted alternating voltage component at mains or twice mains power frequency (depending upon whether half- or full-wave rectification is used)—ripple—is unavoidably superimposed on the direct output voltage.

For purposes such as charging batteries the ripple is not a problem, and the simplest unregulated mains-powered DC power supply circuit consists of a transformer driving a single diode in series with a resistor.

Before the introduction of solid-state electronics, equipment used valves (vacuum tubes) which required high voltages; power supplies used step-up transformers, rectifiers, and filters to generate one or more direct voltages of some hundreds of volts, and a low alternating voltage for filaments. Only the most advanced equipment used expensive and bulky regulated power supplies.

AC power supply

An AC power supply typically takes the voltage from a wall outlet (mains supply, often 230v in Europe) and lowers it to the desired voltage (eg 9vac). As well as lowering the voltage some filtering may take place. An example use for an AC power supply is powering certain guitar effects pedals (e.g. the Digitech Whammy pedal) although it is more common for effects pedals to require DC.

Linear regulated power supply

The voltage produced by an unregulated power supply will vary depending on the load and on variations in the AC supply voltage. For critical electronics applications a linear regulator may be used to set the voltage to a precise value, stabilized against fluctuations in input voltage and load. The regulator also greatly reduces the ripple and noise in the output direct current. Linear regulators often provide current limiting, protecting the power supply and attached circuit from overcurrent.

Adjustable linear power supplies are common laboratory and service shop test equipment, allowing the output voltage to be adjusted over a range. For example, a bench power supply used by circuit designers may be adjustable up to 30 volts and up to 5 amperes output. Some can be driven by an external signal, for example, for applications requiring a pulsed output.

AC/DC supply

Main article: AC/DC (electricity)

In the past, mains electricity was supplied as DC in some regions, AC in others. Transformers cannot be used for DC, but a simple, cheap unregulated power supply could run directly from either AC or DC mains without using a transformer. The power supply consisted of a rectifier and a filter capacitor. When operating from DC, the rectifier was essentially a conductor, having no effect; it was included to allow operation from AC or DC without modification.

Switched-mode power supply

Main article: Switched-mode power supply

A computer’s switched mode power supply unit.

A switched-mode power supply (SMPS) works on a different principle. AC input, usually at mains voltage, is rectified without the use of a mains transformer, to obtain a DC voltage. This voltage is then switched on and off at a high speed by electronic switching circuitry, which may then pass through a high-frequency, hence small, light, and cheap, transformer or inductor. The duty cycle of the output square wave increases as power output requirements increase. Switched-mode power supplies are always regulated. If the SMPS uses a properly-insulated high-frequency transformer, the output will be electrically isolated from the mains, essential for safety.

The input power slicing occurs at a very high speed (typically 10 kHz — 1 MHz). High frequency and high voltages in this first stage permit much smaller transformers and smoothing capacitors than in a power supply operating at mains frequency, as linear supplies do. After the transformer secondary, the AC is again rectified to DC. To keep output voltage constant, the power supply needs a sophisticated feedback controller to monitor current drawn by the load.

SMPSs often include safety features such as current limiting or a crowbar circuit to help protect the device and the user from harm.[2] In the event that an abnormal high-current power draw is detected, the switched-mode supply can assume this is a direct short and will shut itself down before damage is done. For decades PC power supplies have provided a power good signal to the motherboard whose absence prevents operation when abnormal supply voltages are present.

SMPSs have an absolute limit on their minimum current output.[3] They are only able to output above a certain power level and cannot function below that point. In a no-load condition the frequency of the power slicing circuit increases to great speed, causing the isolated transformer to act as a Tesla coil, causing damage due to the resulting very high voltage power spikes. Switched-mode supplies with protection circuits may briefly turn on but then shut down when no load has been detected. A very small low-power dummy load such as a ceramic power resistor or 10-watt light bulb can be attached to the supply to allow it to run with no primary load attached.

Power factor has become a recent issue of concern for computer manufacturers. Switched mode power supplies have traditionally been a source of power line harmonics and have a very poor power factor. Many computer power supplies built in the last few years now include power factor correction built right into the switched-mode supply, and may advertise the fact that they offer 1.0 power factor.

By slicing up the sinusoidal AC wave into very small discrete pieces, a portion of unused alternating current stays in the power line as very small spikes of power that cannot be utilized by AC motors and results in waste heating of power line transformers. Hundreds of switched mode power supplies in a building can result in poor power quality for other customers surrounding that building, and high electric bills for the company if they are billed according to their power factor in addition to the actual power used. Filtering capacitor banks may be needed on the building power mains to suppress and absorb these negative power factor effects[citation needed].

Programmable power supply

Programmable power supplies

Programmable power supplies allow for remote control of the output voltage through an analog input signal or a computer interface such as RS232 or GPIB. Variable properties include voltage, current, and frequency (for AC output units). These supplies are composed of a processor, voltage/current programming circuits, current shunt, and voltage/current read-back circuits. Additional features can include overcurrent, overvoltage, and short circuit protection, and temperature compensation. Programmable power supplies also come in a variety of forms including modular, board-mounted, wall-mounted, floor-mounted or bench top.

Programmable power supplies can furnish DC, AC, or AC with a DC offset. The AC output can be either single-phase or three-phase. Single-phase is generally used for low-voltage, while three-phase is more common for high-voltage power supplies.

Programmable power supplies are now used in many applications. Some examples include automated equipment testing, crystal growth monitoring, and differential thermal analysis.[4]

Uninterruptible power supply

Main article: Uninterruptible power supply

An uninterruptible power supply (UPS) takes its power from two or more sources simultaneously. It is usually powered directly from the AC mains, while simultaneously charging a storage battery. Should there be a dropout or failure of the mains, the battery instantly takes over so that the load never experiences an interruption. Such a scheme can supply power as long as the battery charge suffices, e.g., in a computer installation, giving the operator sufficient time to effect an orderly system shutdown without loss of data. Other UPS schemes may use an internal combustion engine or turbine to continuously supply power to a system in parallel with power coming from the AC . The engine-driven generators would normally be idling, but could come to full power in a matter of a few seconds in order to keep vital equipment running without interruption. Such a scheme might be found in hospitals or telephone central offices.

High-voltage power supply

High voltage refers to an output on the order of hundreds or thousands of volts. High-voltage supplies use a linear setup to produce an output voltage in this range.

Additional features available on high-voltage supplies can include the ability to reverse the output polarity along with the use of circuit breakers and special connectors intended to minimize arcing and accidental contact with human hands. Some supplies provide analog inputs (i.e. 0-10V) that can be used to control the output voltage, effectively turning them into high-voltage amplifiers albeit with very limited bandwidth.

Voltage multipliers

Voltage multipliers, as the name implies, are circuits designed to multiply the input voltage. The input voltage may be doubled (voltage doubler), tripled (voltage tripler), quadrupled (voltage quadrupler), etc. Voltage multipliers are also power converters. An AC input is converted to a higher DC output. These circuits allow high voltages to be obtained using a much lower voltage AC source.

Typically, voltage multipliers are composed of half-wave rectifiers, capacitors, and diodes. For example, a voltage tripler consists of three half-wave rectifiers, three capacitors, and three diodes (see Cockcroft Walton Multiplier). Full-wave rectifiers may be used in a different configuration to achieve even higher voltages. Also, both parallel and series configurations are available. For parallel multipliers, a higher voltage rating is required at each consecutive multiplication stage, but less capacitance is required. The voltage capability of the capacitor limits the maximum output voltage.

Voltage multipliers have many applications. For example, voltage multipliers can be found in everyday items like televisions and photocopiers. Even more applications can be found in the laboratory, such as cathode ray tubes, oscilloscopes, and photomultiplier tubes.[5][6]

Power supply applications

Computer power supply

Main article: Computer power supply

A modern computer power supply is a switch with on and off supply designed to convert 110-240 V AC power from the mains supply, to several output both positive (and historically negative) DC voltages in the range + 12V,-12V,+5V,+5VBs and +3.3V. The first generation of computers power supplies were linear devices, but as cost became a driving factor, and weight became important, switched mode supplies are almost universal.

The diverse collection of output voltages also have widely varying current draw requirements, which are difficult to all be supplied from the same switched-mode source. Consequently most modern computer power supplies actually consist of several different switched mode supplies, each producing just one voltage component and each able to vary its output based on component power requirements, and all are linked together to shut down as a group in the event of a fault condition.

Welding power supply

Main article: Welding power supply

Arc welding uses electricity to melt the surfaces of the metals in order to join them together through coalescence. The electricity is provided by a welding power supply, and can either be AC or DC. Arc welding typically requires high currents typically between 100 and 350 amps. Some types of welding can use as few as 10 amps, while some applications of spot welding employ currents as high as 60,000 amps for an extremely short time. Older welding power supplies consisted of transformers or engines driving generators. More recent supplies use semiconductors and microprocessors reducing their size and weight.

AC adapter

Switched mode mobile phone charger

Main article: AC adapter

A linear or switched-mode power supply (or in some cases just a transformer) that is built into the top of a plug is known as a “plug pack”, “plug-in adapter”, “adapter block”, “domestic mains adapter” or just “power adapter”. Slang terms include “wall wart” and “power brick”. They are even more diverse than their names; often with either the same kind of DC plug offering different voltage or polarity, or a different plug offering the same voltage. “Universal” adapters attempt to replace missing or damaged ones, using multiple plugs and selectors for different voltages and polarities. Replacement power supplies must match the voltage of, and supply at least as much current as, the original power supply.

The least expensive AC units consist solely of a small transformer, while DC adapters include a few additional diodes. Whether or not a load is connected to the power adapter, the transformer has a magnetic field continuously present and normally cannot be completely turned off unless unplugged.

Because they consume standby power, they are sometimes known as “electricity vampires” and may be plugged into a power strip to allow turning them off. Expensive switched-mode power supplies can cut off leaky electrolyte-capacitors, use powerless MOSFETs, and reduce their working frequency to get a gulp of energy once in a while to power, for example, a clock, which would otherwise need a battery.

Overload protection

Power supplies often include some type of overload protection that protects the power supply from load faults (e.g., short circuits) that might otherwise cause damage by overheating components or, in the worst case, electrical fire. Fuses and circuit breakers are two commonly used mechanisms for overload protection.[1]

Fuses

A fuse is a piece of wire, often in a casing that improves its electrical characteristics. If too much current flows, the wire becomes hot and melts. This effectively disconnects the power supply from its load, and the equipment stops working until the problem that caused the overload is identified and the fuse is replaced.

There are various types of fuses used in power supplies.

  • fast blow fuses cut the power as quick as they can
  • slow blow fuses tolerate more short term overload
  • wire link fuses are just an open piece of wire, and have poorer overload characteristics than glass and ceramic fuses

Some power supplies use a very thin wire link soldered in place as a fuse.

Circuit breakers

One benefit of using a circuit breaker as opposed to a fuse is that it can simply be reset instead of having to replace the blown fuse. A circuit breaker contains an element that heats, bends and triggers a spring which shuts the circuit down. Once the element cools, and the problem is identified the breaker can be reset and the power restored.

Thermal cutouts

Some PSUs use a thermal cutout buried in the transformer rather than a fuse. The advantage is it allows greater current to be drawn for limited time than the unit can supply continuously. Some such cutouts are self resetting, some are single use only.

Current limiting

Some supplies use current limiting instead of cutting off power if overloaded. The two types of current limiting used are electronic limiting and impedance limiting. The former is common on lab bench PSUs, the latter is common on supplies of less than 3 watts output.

A foldback current limiter reduces the output current to much less than the maximum non-fault current.

Power conversion

The term “power supply” is sometimes restricted to those devices that convert some other form of energy into electricity (such as solar power and fuel cells and generators). A more accurate term for devices that convert one form of electric power into another form (such as transformers and linear regulators) is power converter. The most common conversion is from AC to DC.

Mechanical power supplies

  • Flywheels coupled to electrical generators or alternators
  • Compulsators
  • Explosively pumped flux compression generators

Terminology

  • SCP – Short circuit protection
  • OPP – Overpower (overload) protection
  • OCP – Overcurrent protection
  • OTP – Overtemperature protection
  • OVP – Overvoltage protection
  • UVP – Undervoltage protection
  • UPS – Uninterruptable Power Supply
  • PSU – Power Supply Unit
  • SMPSU – Switch-Mode Power Supply Unit

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Category : Analog Circuit Board Repair | Charger Repair | Electronic repair service | EZ-GO PowerWise | Industrial Repair Group | Industrial Repair Service | Power Supply Repair | Blog
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  • Every Circuit Board Repair comes with an 18 month repair warranty
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  • Most repairs are completed, tested, and returned within 10 business days
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The End Result

  • Guaranteed service, complete satisfaction, and a 10% competitor price guarantee
  • Reduced overhead and operational expenditure
  • Your business is up and running quickly

Best in Class Service with Every Circuit Board Repair

Every Circuit Board Repair is subjected to dynamic function testings to verify a successful repair and then backed by an IRG 18 month repair warranty. Industrial Repair Group fully tests and replaces all high failure components such as ICs, PALs, EPROMs, GALs, and surface mounted components. Factory sealers and conformal coatings are re-applied as needed with each Circuit Board Repair to restore your equipment back to its' OEM specs.

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Category : AC, DC, VFD, Servo Drives | Analog Circuit Board Repair | Electronic Repair Services | Industrial Controls Repair | Blog
6
May

Service

Industrial Repair Group performs extensive component level repairs, touching up solder traces, replacing bad components, as well as full testing of ICs, PALs, EPROMs, GALs, surface mounted components and much more. Every Femco Repair Service by Industrial Repair Group is subjected to dynamic function tests to verify successful repair and then backed by our 18 month repair guarantee. Sealers and conformal coatings are re-applied as needed with each repair restoring your equipment back to its original OEM specs.

Industrial Repair Group is more than a service provider for your industry. We are a partner and a dedicated resource for your team members to rely upon. Feel confident that we don't play the lingo game. We are real people, with real goals. Our company is always open minded and intent on isolating problems to keep organizations up and running 24/7. We are a leading service provider that believes educated personal is the best policy.

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At Industrial Repair Group, our goal is to offer the best repair in the industry and the most competitive quotes. Our wide selection of services and industry leading 18 month repair guarantee are sure to provide you with the perfect repair solution for all of your industrial needs. We specialize in industrial electronics, electric motor rebuilds, and complete customer satisfaction.

AC TECHNOLOGY INDRAMAT
ACCO BABCOCK INC INDRAMAT & STEGMANN
ACCO BRISTOL INELCO & HS ELECTRONIC
ACCU SORT INEX INC
ACME ELECTRIC & STANDARD POWER INC INLAND MOTOR
ACOPIAN ACRISONS INFRANOR
ACROMAG & MOORE PRODUCTS INGERSOLL RAND
ADEPT TECH INIVEN
ADTECH POWER INC INNOVATIVE TECHNOLOGY INC
ADVANCE BALLAST INTEL
ADVANCED MICRO CONTROLS INTERMEC
ADVANCED MOTION INTERNATIONAL POWER
AEROTECH & MOTOROLA INTROL DESIGN
AGASTAT IRCON
AGILENT ISHIDA
AGR ISI ROBOTICS
AIRCO ISSC
ALLEN BRADLEY ISSC & SCI
AMBITECH IND JOHNSON CONTROLS & YOKOGAWA
AMETEK KTRON
AMGRAPH KTRON & KB ELECTRONICS
AMICON KB ELECTRONICS
AMPROBE KB ELECTRONICS & RIMA
ANAHEIM AUTOMATION KEARNEY & TRECKER
ANALOGIC KEB COMBIVERT
ANDOVER CONTROLSANILAM & SEQUENTIAL INFO SYS KEB COMBIVERT & TOSHIBA
ANORAD KEITHLEY & HOLADAY
ANRITSU KEPCO
AO SMITH & MAGNETEK KEYENCE CORP
APC KIKUSUI
APPLIED AUTOMATION KME INSTACOLOR
APPLIED MATERIAL KNIEL
APPLIED MICORSYSTEMS KOEHLER COMPANY
APV AUTOMATION KONE
APW MCLEAN KONSBERG
ARBURG KRAUSS MAFFEI
ARCAIR KRISTEL CORPORATION
ARCOM LABOD ELECTRONICS
ARGUS LAMBDA
AROS ELECTRONICS LAMBDA & QUALIDYNE CORP
ARPECO LANTECH
ARTESYN TECHNOLOGIES LEESON ELECTRIC CO
ASCO & ITT LEESONA & ELECTRIC REGULATOR
ASEA BROWN BOVERI & STROMBERG LEINE & LINDE
ASHE CONTROLS LENORD & BAUER
ASI CONTROLS LENZE
ASI KEYSTONE & ANALOGIC LEROY SOMER
ASR SERVOTRON LESTER ELECTRIC
ASSOCIATED RESEARCH LEUZE
ASTROSYSTEMS LH RESEARCH
ATC LINCOLN ELECTRIC
ATHENA LITTON
ATLAS LOVE CONTROLS
ATLA COPCO LOVEHOY & BOSTON
AUTOCON TECHNOLGIES INC LOYOLA
AUTOMATED PACKAGING LUST ELECTRONICS
AUTOMATION DIRECT MAGNETEK
AUTOMATION INTELLIGENCE MAGNETEK & GEMCO ELECTRIC
AUTOMATIX MAN ROLAND
AVERY MAPLE SYSTEMS
AVG AUTOMATION MARKEM
AYDON CONTROLS MARQUIP
B & K MARSCH
B & R MAHTSUSHITA ELECTRIC & FANUC
BABCOCK & ASEA BROWN BOVERI MAZAK
BAKER PERKINS MCC ELECTRONICS
BALANCE ENGINEERING MEMOTEC
BALDOR & ASR SERVOTRON MERRICK SCALE
BALWIN & BEI INDUSTRIAL ENCODER METRA INSTRUMENTS
BALL ELECTRONIC METTLER TOLEDO
BALUFF MHI CORRUGATING MACHINERY
BALOGH MIBUDENKI
BANNER ENGINEERING MICRO MEMORY
BARBER COLMAN MICRO MOTION
BARBER COLMAN MICROSWITCH
BARDAC MICROSWITCH & HONEYWELL
BARKSDALE MIKI PULLEY & BOSTON
BARR MULLIN MILLER ELECTRIC
BASLER ELECTRIC & WESTINGHOUSE MILLER ELECTRIC & LINCOLN ELECTRIC
BAUMULLER MINARIK ELECTRIC CO
BEI INDUSTRIAL ENCODER MINARIK ELECTRIC CO & LEESON ELECTRIC CO
BENDIX DYNAPATH MITUSUBISHI
DENDIX SHEFFIELD MOELLER ELECTRIC
BENSHAW MOOG
BENTLEY NEVADA MONTWILL& SCHAFER
BERGER LAHR MOTOROLA
BEST POWER MOTORLA SEMICONDUCTOR
BIKOR CORP MOTORTRONICS
BK PRECISION MSA
BOBST MTS SYSTEMS CO
BOGEN COMMUNICATION MULLER MARTINI & GRAPHA ELECTRONIC
BOMAC MURR ELEKTRONIK
BORG WARNER & DANFOSS NACHI
BOSCH NATIONAL CONTROLS
BOSCHERT & ARTESYN TECHNOLOGIES NEMATRON CORP
BOSTON NEWPORT
BRANSON NEXT
BRIDGEPORT NIKKI DENSO
BURTON & EMERSON NIOBRARA R&D CORP
BUTLER AUTOMATIC NJE CORPORATION
CAROTRON NORDSON
CE INVALCO NORDSON & DANAHER CONTROLS
CHROMALOX NORTH AMERICAN MFG
CINCINNATI MILACRON & ADVANTAGE ELECTRONICS NORTHERN TELECOM
CLEAVELAND MOTION CONTROL NOVA
CONDOR NSD
CONRAC NUM
CONTRAVES NUMERIK
CONTREX OLEC
CONTROL CONCEPTS OKUMA
CONTROL TECHNOLGY INC OMEGA ENGINEERING
COSEL OMRON
COUTANT & LAMBDA OPTO 22
CROMPTON ORIENTAL MOTOR
CROWN ORMEC
CUSTOM SERVO OSG TAP & DIEP&H HARNISCHFEGER
CYBEREX PACKAGE CONTROLS
DANAHER CONTROLS PANALARM
DANAHER MOTION PARKER
DANFOSS & DART CONTROLS PAYNE ENGINEERING & BURTON
DART CONTROLS PEPPERL & FUCHS
DATA ACQUISITION SYS PJILLIPS & PHILLIPS PMA
DAYKIN PHOENIX CONTACT
DAYTRONIC PILZ
DEC PINNACLE SYSTEMS
DELTA PIONEER MAGNETICS
DELTA ELECTRONICS PLANAR SYSTEMS
DELTRON & POWER MATE POLYCOM
DEUTRONIC POLYSPEDE
DIGITEC POWER CONTROL SYSTEM
DISC INSTURMENTS & DANAHER CONTROLS POWER CONVERSION
DISPLAY TECH POWER ELECTRONICS
DOERR POWER GENERAL & WESTINGHOUSE
DOMINO PRINTING POWER MATE
DREXELBROOK POWER ONE
DRIVE CONTROL SYSTEMS POWER PROP
DUNKERMOTOREN POWER SOURCE
DYNAGE & BROWN & SHARPE POWER SWITCH CORP
DYNAMICS RESEARCH POWER SYSTEMS INC
DYNAPOWER & DANAHER CONTROLS POWER VOLT
DYNAPRO & FLUKE POWERTEC INDUSTIRAL MOTORS INC
DYNISCO PULS
EATON CORPORATION PYRAMID
EATON CORPORATION & DANAHER CONTROLS QEST
ECCI QUINDAR ELECTRONICS
EG&G RADIO ENERGIE
ELCIS RAMSEY TECHNOLOGY
ELCO RED LION CONTROLS & SABINA ELECTRIC
ELECTRIC REGULATOR RELIANCE ELECTRIC
ELECTRO CAM RENCO CORP
ELECTRO CRAFT & RELIANCE ELECTRIC ROBICON
ELECTROHOME ROSEMOUNT & WESTINGHOUSE
ELECTROL RTA PAVIA
ELECTROMOTIVE SABINA ELECTRIC
ELECTROSTATICS INC SAFTRONICS
ELGE SANYO
ELO TOUCH SYSTEMS SCHROFF & STYRKONSULT AB
ELPAC & CINCINNATI MILACRON SCI & ISSC
ELSTON ELECTRONICS SELTI
ELWOOD CORPORATION SEMCO
EMS INC SEQUENTIAL INFO SYS
ENCODER PRODUCTS SEW EURODRIVE & TOSHIBA
ETA SHINDENGEN
EUROTHERM CONTROLS SICK OPTIC ELECTRONIC
EXOR SIEMENS
FANUC SIEMENS MOORE
FANUC & GENERAL ELECTRIC SIERRACIN POWER SYSTEMS
FENWAL SIGMA INSTRUMENTS INC
FIFE CORP SMC & CONAIRSOCAPEL
FIREYE & ITT SOLA ELECTRIC
FIRING CIRCUITS SOLITECH
FISCHER & PORTER SONY
FISHER CONTROLS SORENSEN
FLUKE STANDARD POWER INC
FORNEY STATIC CONTROL SYSTEMS
FOXBORO STEGMANN & INDRAMAT
FOXBORO & BALSBAUGH SUMITOMO MACHINERY INC & TOSHIBA
FUJI ELECTRIC SUMTAK CORP
FUTEC SUNX LTD
GAI & ASEA BROWN BOVERI SUPERIOR ELECTRIC
GALIL MOTION CONTROLS SWEO ENGINEERING & ROCHESTER INSTRUMENT SYSTEMS
GD CALIFORNIA INC T&R ELECTRIC & SYRON ENGINEERING
GEM80 TAMAGAWA & RELIANCE ELECTRIC
GENERAL ELECTRIC TAPESWITCH
GENERAL ELECTRIC & FANUC TB WOODS & FUJI ELECTRIC
GIDDINGS & LEWIS TDK
GLENTEK TECNO ELETTRONICA
GOLDSTAR TECTROL
GORING KERR TEIJIN SEIKI
GOSSEN TEKEL
GRAHAM TODD PRODUCTS CORP
GRAINGER TOEI ELECTRIC
GRAPHA ELECTRONIC TOSHIBA
GREAT LAKES INSTRUMENTS TOTKU ELECTRIC & GENERAL ELECTRIC
GROUPE SCHNEIDER TRACO ENGINEERING
HAAS UNICO
HAMMOND UNIPOWER
HATHAWAY VAREC
HAYSEEN VECTOR VID
HEIDELBERG VERO ELECTRONICS & TELEMOTIVE
HEIDENHAIN CORP VIDEO JET
HIRATA VIEW TRONIX
HITACHI & FANUC VIVID
HITRON ELECTRONICS VOLGEN & POWER SOURCE
HOBART BROTHERS CO WARNER ELECTRIC & EMERSON
HOHER AUTOMATION WESTAMP INC & WESTINGHOUSE
HONEYWELL WESTINGHOUSE
HONEYWELL & NEMATRON CORP WHEDCO
HORNER ELECTRIC WIRE ELECTRIC
HUBBELL & FEMCO XENTEK INC
HUBNER & AMICON XYCOM & WARNER ELECTRIC
HURCO MFG CO YASKAWA ELECTRIC
IEE ZENITH
IMMERSION CORPORATION ZYCRON

How Circuit Boards Work

Thank you for choosing Industrial Repair Group. If you would like a printable version of How Circuit Boards Operate, please follow this link: IRG-Circuit-Boards

 

Part of a 1983 Sinclair ZX Spectrum computer board; a populated PCB, showing the conductive traces, vias (the through-hole paths to the other surface), and some mounted electrical components

A printed circuit board, or PCB, is used to mechanically support and electrically connect electronic components using conductive pathways, tracks or signal traces etched from copper sheets laminated onto a non-conductive substrate. It is also referred to as printed wiring board (PWB) or etched wiring board. A PCB populated with electronic components is a printed circuit assembly (PCA), also known as a printed circuit board assembly (PCBA). Printed circuit boards are used in virtually all but the simplest commercially-produced electronic devices.

PCBs are inexpensive, and can be highly reliable. They require much more layout effort and higher initial cost than either wire wrap or point-to-point construction, but are much cheaper and faster for high-volume production; the production and soldering of PCBs can be done by totally automated equipment. Much of the electronics industry’s PCB design, assembly, and quality control needs are set by standards that are published by the IPC organization.

History

The inventor of the printed circuit was the Austrian engineer Paul Eisler who, while working in England, made one circa 1936 as part of a radio set. Around 1943 the USA began to use the technology on a large scale to make rugged radios for use in World War II. After the war, in 1948, the USA released the invention for commercial use. Printed circuits did not become commonplace in consumer electronics until the mid-1950s, after the Auto-Sembly process was developed by the United States Army.

Before printed circuits (and for a while after their invention), point-to-point construction was used. For prototypes, or small production runs, wire wrap or turret board can be more efficient. Predating the printed circuit invention, and similar in spirit, was John Sargrove’s 1936-1947 Electronic Circuit Making Equipment (ECME) which sprayed metal onto a Bakelite plastic board. The ECME could produce 3 radios per minute.

During World War II, the development of the anti-aircraft proximity fuse required an electronic circuit that could withstand being fired from a gun, and could be produced in quantity. The Centralab Division of Globe Union submitted a proposal which met the requirements: a ceramic plate would be screenprinted with metallic paint for conductors and carbon material for resistors, with ceramic disc capacitors and subminiature vacuum tubes soldered in place.[1]

Originally, every electronic component had wire leads, and the PCB had holes drilled for each wire of each component. The components’ leads were then passed through the holes and soldered to the PCB trace. This method of assembly is called through-hole construction. In 1949, Moe Abramson and Stanislaus F. Danko of the United States Army Signal Corps developed the Auto-Sembly process in which component leads were inserted into a copper foil interconnection pattern and dip soldered. With the development of board lamination and etching techniques, this concept evolved into the standard printed circuit board fabrication process in use today. Soldering could be done automatically by passing the board over a ripple, or wave, of molten solder in a wave-soldering machine. However, the wires and holes are wasteful since drilling holes is expensive and the protruding wires are merely cut off.

In recent years, the use of surface mount parts has gained popularity as the demand for smaller electronics packaging and greater functionality has grown.

Manufacturing

Materials

 

A PCB as a design on a computer (left) and realized as a board assembly populated with components (right). The board is double sided, with through-hole plating, green solder resist, and white silkscreen printing. Both surface mount and through-hole components have been used.

 

A PCB in a computer mouse. The Component Side (left) and the printed side (right).

 

The Component Side of a PCB in a computer mouse; some examples for common components and their reference designations on the silk screen.

Conducting layers are typically made of thin copper foil. Insulating layers dielectric are typically laminated together with epoxy resin prepreg. The board is typically coated with a solder mask that is green in color. Other colors that are normally available are blue, black, white and red. There are quite a few different dielectrics that can be chosen to provide different insulating values depending on the requirements of the circuit. Some of these dielectrics are polytetrafluoroethylene (Teflon), FR-4, FR-1, CEM-1 or CEM-3. Well known prepreg materials used in the PCB industry are FR-2 (Phenolic cotton paper), FR-3 (Cotton paper and epoxy), FR-4 (Woven glass and epoxy), FR-5 (Woven glass and epoxy), FR-6 (Matte glass and polyester), G-10 (Woven glass and epoxy), CEM-1 (Cotton paper and epoxy), CEM-2 (Cotton paper and epoxy), CEM-3 (Woven glass and epoxy), CEM-4 (Woven glass and epoxy), CEM-5 (Woven glass and polyester). Thermal expansion is an important consideration especially with BGA and naked die technologies, and glass fiber offers the best dimensional stability.

FR-4 is by far the most common material used today. The board with copper on it is called “copper-clad laminate”.

Copper foil thickness can be specified in ounces per square foot or micrometres. One ounce per square foot is 1.344 mils or 34 micrometres.

Patterning (etching)

The vast majority of printed circuit boards are made by bonding a layer of copper over the entire substrate, sometimes on both sides, (creating a “blank PCB”) then removing unwanted copper after applying a temporary mask (e.g. by etching), leaving only the desired copper traces. A few PCBs are made by adding traces to the bare substrate (or a substrate with a very thin layer of copper) usually by a complex process of multiple electroplating steps. The PCB manufacturing method primarily depends on whether it is for production volume or sample/prototype quantities.

Commercial (production quantities, usually PTH)

  • silk screen printing -the main commercial method.
  • Photographic methods. Used when fine linewidths are required.

Hobbyist/prototype (small quantities, usually not PTH)

  • Laser-printed resist: Laser-print onto paper (or wax paper), heat-transfer with an iron or modified laminator onto bare laminate, then etch.
  • Print onto transparent film and use as photomask along with photo-sensitized boards. (i.e. pre-sensitized boards), Then etch. (Alternatively, use a film photoplotter).
  • Laser resist ablation: Spray black paint onto copper clad laminate, place into CNC laser plotter. The laser raster-scans the PCB and ablates (vaporizes) the paint where no resist is wanted. Etch. (Note: laser copper ablation is rarely used and is considered experimental.)
  • Use a CNC-mill with a spade-shaped (i.e. 45-degree) cutter or miniature end-mill to route away the undesired copper, leaving only the traces.

There are three common “subtractive” methods (methods that remove copper) used for the production of printed circuit boards:

  1. Silk screen printing uses etch-resistant inks to protect the copper foil. Subsequent etching removes the unwanted copper. Alternatively, the ink may be conductive, printed on a blank (non-conductive) board. The latter technique is also used in the manufacture of hybrid circuits.
  2. Photoengraving uses a photomask and developer to selectively remove a photoresist coating. The remaining photoresist protects the copper foil. Subsequent etching removes the unwanted copper. The photomask is usually prepared with a photoplotter from data produced by a technician using CAM, or computer-aided manufacturing software. Laser-printed transparencies are typically employed for phototools; however, direct laser imaging techniques are being employed to replace phototools for high-resolution requirements.
  3. PCB milling uses a two or three-axis mechanical milling system to mill away the copper foil from the substrate. A PCB milling machine (referred to as a ‘PCB Prototyper’) operates in a similar way to a plotter, receiving commands from the host software that control the position of the milling head in the x, y, and (if relevant) z axis. Data to drive the Prototyper is extracted from files generated in PCB design software and stored in HPGL or Gerber file format.

“Additive” processes also exist. The most common is the “semi-additive” process. In this version, the unpatterned board has a thin layer of copper already on it. A reverse mask is then applied. (Unlike a subtractive process mask, this mask exposes those parts of the substrate that will eventually become the traces.) Additional copper is then plated onto the board in the unmasked areas; copper may be plated to any desired weight. Tin-lead or other surface platings are then applied. The mask is stripped away and a brief etching step removes the now-exposed original copper laminate from the board, isolating the individual traces. Some boards with plated through holes but still single sided were made with a process like this. General Electric made consumer radio sets in the late 1960s using boards like these.

The additive process is commonly used for multi-layer boards as it facilitates the plating-through of the holes (to produce conductive vias) in the circuit board.

  • PCB copper electroplating machine for adding copper to the in-process PCB

  • PCB’s in process of adding copper via electroplating

The dimensions of the copper conductors of the printed circuit board is related to the amount of current the conductor must carry. Each trace consists of a flat, narrow part of the copper foil that remains after etching. Signal traces are usually narrower than power or ground traces because their current carrying requirements are usually much less. In a multi-layer board one entire layer may be mostly solid copper to act as a ground plane for shielding and power return. For printed circuit boards that contain microwave circuits, transmission lines can be laid out in the form of stripline and microstrip with carefully-controlled dimensions to assure a consistent impedance. In radio-frequency circuits the inductance and capacitance of the printed circuit board conductors can be used as a delibrate part of the circuit design, obviating the need for additional discrete components.

Etching

Chemical etching is done with ferric chloride, ammonium persulfate, or sometimes hydrochloric acid. For PTH (plated-through holes), additional steps of electroless deposition are done after the holes are drilled, then copper is electroplated to build up the thickness, the boards are screened, and plated with tin/lead. The tin/lead becomes the resist leaving the bare copper to be etched away.

Lamination

Some PCBs have trace layers inside the PCB and are called multi-layer PCBs. These are formed by bonding together separately etched thin boards.

Drilling

Holes through a PCB are typically drilled with tiny drill bits made of solid tungsten carbide. The drilling is performed by automated drilling machines with placement controlled by a drill tape or drill file. These computer-generated files are also called numerically controlled drill (NCD) files or “Excellon files”. The drill file describes the location and size of each drilled hole. These holes are often filled with annular rings (hollow rivets) to create vias. Vias allow the electrical and thermal connection of conductors on opposite sides of the PCB.

Most common laminate is epoxy filled fiberglass. Drill bit wear is partly due to embedded glass, which is harder than steel. High drill speed necessary for cost effective drilling of hundreds of holes per board causes very high temperatures at the drill bit tip, and high temperatures (400-700 degrees) soften steel and decompose (oxidize) laminate filler. Copper is softer than epoxy and interior conductors may suffer damage during drilling.

When very small vias are required, drilling with mechanical bits is costly because of high rates of wear and breakage. In this case, the vias may be evaporated by lasers. Laser-drilled vias typically have an inferior surface finish inside the hole. These holes are called micro vias.

It is also possible with controlled-depth drilling, laser drilling, or by pre-drilling the individual sheets of the PCB before lamination, to produce holes that connect only some of the copper layers, rather than passing through the entire board. These holes are called blind vias when they connect an internal copper layer to an outer layer, or buried vias when they connect two or more internal copper layers and no outer layers.

The walls of the holes, for boards with 2 or more layers, are made conductive then plated with copper to form plated-through holes that electrically connect the conducting layers of the PCB. For multilayer boards, those with 4 layers or more, drilling typically produces a smear of the high temperature decomposition products of bonding agent in the laminate system. Before the holes can be plated through, this smear must be removed by a chemical de-smear process, or by plasma-etch. Removing (etching back) the smear also reveals the interior conductors as well.

Exposed conductor plating and coating

PCBs[2] are plated with solder, tin, or gold over nickel as a resist for etching away the unneeded underlying copper.[3]

After PCBs are etched and then rinsed with water, the soldermask is applied, and then any exposed copper is coated with solder, nickel/gold, or some other anti-corrosion coating.[4][5]

Matte solder is usually fused to provide a better bonding surface or stripped to bare copper. Treatments, such as benzimidazolethiol, prevent surface oxidation of bare copper. The places to which components will be mounted are typically plated, because untreated bare copper oxidizes quickly, and therefore is not readily solderable. Traditionally, any exposed copper was coated with solder by hot air solder levelling (HASL). The HASL finish prevents oxidation from the underlying copper, thereby guaranteeing a solderable surface.[6] This solder was a tin-lead alloy, however new solder compounds are now used to achieve compliance with the RoHS directive in the EU and US, which restricts the use of lead. One of these lead-free compounds is SN100CL, made up of 99.3% tin, 0.7% copper, 0.05% nickel, and a nominal of 60ppm germanium.

It is important to use solder compatible with both the PCB and the parts used. An example is Ball Grid Array (BGA) using tin-lead solder balls for connections losing their balls on bare copper traces or using lead-free solder paste.

Other platings used are OSP (organic surface protectant), immersion silver (IAg), immersion tin, electroless nickel with immersion gold coating (ENIG), and direct gold plating (over nickel). Edge connectors, placed along one edge of some boards, are often nickel plated then gold plated. Another coating consideration is rapid diffusion of coating metal into Tin solder. Tin forms intermetallics such as Cu5Sn6 and Ag3Cu that dissolve into the Tin liquidus or solidus(@50C), stripping surface coating and/or leaving voids.

Electrochemical migration (ECM) is the growth of conductive metal filaments on or in a printed circuit board (PCB) under the influence of a DC voltage bias.[7][8] Silver, zinc, and aluminum are known to grow whiskers under the influence of an electric field. Silver also grows conducting surface paths in the presence of halide and other ions, making it a poor choice for electronics use. Tin will grow “whiskers” due to tension in the plated surface. Tin-Lead or Solder plating also grows whiskers, only reduced by the percentage Tin replaced. Reflow to melt solder or tin plate to relieve surface stress lowers whisker incidence. Another coating issue is tin pest, the transformation of tin to a powdery allotrope at low temperature.[9]

Solder resist

Areas that should not be soldered may be covered with a polymer solder resist (solder mask) coating. The solder resist prevents solder from bridging between conductors and creating short circuits. Solder resist also provides some protection from the environment. Solder resist is typically 20-30 micrometres thick.

Screen printing

Line art and text may be printed onto the outer surfaces of a PCB by screen printing. When space permits, the screen print text can indicate component designators, switch setting requirements, test points, and other features helpful in assembling, testing, and servicing the circuit board.

Screen print is also known as the silk screen, or, in one sided PCBs, the red print.

Lately some digital printing solutions have been developed to substitute the traditional screen printing process. This technology allows printing variable data onto the PCB, including serialization and barcode information for traceability purposes.

Test

Unpopulated boards may be subjected to a bare-board test where each circuit connection (as defined in a netlist) is verified as correct on the finished board. For high-volume production, a Bed of nails tester, a fixture or a Rigid needle adapter is used to make contact with copper lands or holes on one or both sides of the board to facilitate testing. A computer will instruct the electrical test unit to apply a small voltage to each contact point on the bed-of-nails as required, and verify that such voltage appears at other appropriate contact points. A “short” on a board would be a connection where there should not be one; an “open” is between two points that should be connected but are not. For small- or medium-volume boards, flying probe and flying-grid testers use moving test heads to make contact with the copper/silver/gold/solder lands or holes to verify the electrical connectivity of the board under test.

Printed circuit assembly

After the printed circuit board (PCB) is completed, electronic components must be attached to form a functional printed circuit assembly,[10][11] or PCA (sometimes called a “printed circuit board assembly” PCBA). In through-hole construction, component leads are inserted in holes. In surface-mount construction, the components are placed on pads or lands on the outer surfaces of the PCB. In both kinds of construction, component leads are electrically and mechanically fixed to the board with a molten metal solder.

There are a variety of soldering techniques used to attach components to a PCB. High volume production is usually done with machine placement and bulk wave soldering or reflow ovens, but skilled technicians are able to solder very tiny parts (for instance 0201 packages which are 0.02 in. by 0.01 in.)[12] by hand under a microscope, using tweezers and a fine tip soldering iron for small volume prototypes. Some parts are impossible to solder by hand, such as ball grid array (BGA) packages.

Often, through-hole and surface-mount construction must be combined in a single assembly because some required components are available only in surface-mount packages, while others are available only in through-hole packages. Another reason to use both methods is that through-hole mounting can provide needed strength for components likely to endure physical stress, while components that are expected to go untouched will take up less space using surface-mount techniques.

After the board has been populated it may be tested in a variety of ways:

  • While the power is off, visual inspection, automated optical inspection. JEDEC guidelines for PCB component placement, soldering, and inspection are commonly used to maintain quality control in this stage of PCB manufacturing.
  • While the power is off, analog signature analysis, power-off testing.
  • While the power is on, in-circuit test, where physical measurements (i.e. voltage, frequency) can be done.
  • While the power is on, functional test, just checking if the PCB does what it had been designed for.

To facilitate these tests, PCBs may be designed with extra pads to make temporary connections. Sometimes these pads must be isolated with resistors. The in-circuit test may also exercise boundary scan test features of some components. In-circuit test systems may also be used to program nonvolatile memory components on the board.

In boundary scan testing, test circuits integrated into various ICs on the board form temporary connections between the PCB traces to test that the ICs are mounted correctly. Boundary scan testing requires that all the ICs to be tested use a standard test configuration procedure, the most common one being the Joint Test Action Group (JTAG) standard. The JTAG test architecture provides a means to test interconnects between integrated circuits on a board without using physical test probes. JTAG tool vendors provide various types of stimulus and sophisticated algorithms, not only to detect the failing nets, but also to isolate the faults to specific nets, devices, and pins.[13]

When boards fail the test, technicians may desolder and replace failed components, a task known as rework.

Protection and packaging

PCBs intended for extreme environments often have a conformal coating, which is applied by dipping or spraying after the components have been soldered. The coat prevents corrosion and leakage currents or shorting due to condensation. The earliest conformal coats were wax; modern conformal coats are usually dips of dilute solutions of silicone rubber, polyurethane, acrylic, or epoxy. Another technique for applying a conformal coating is for plastic to be sputtered onto the PCB in a vacuum chamber. The chief disadvantage of conformal coatings is that servicing of the board is rendered extremely difficult.[14]

Many assembled PCBs are static sensitive, and therefore must be placed in antistatic bags during transport. When handling these boards, the user must be grounded (earthed). Improper handling techniques might transmit an accumulated static charge through the board, damaging or destroying components. Even bare boards are sometimes static sensitive. Traces have become so fine that it’s quite possible to blow an etch off the board (or change its characteristics) with a static charge. This is especially true on non-traditional PCBs such as MCMs and microwave PCBs.

Design

  • Schematic capture or schematic entry is done through an EDA tool.
  • Card dimensions and template are decided based on required circuitry and case of the PCB. Determine the fixed components and heat sinks if required.
  • Deciding stack layers of the PCB. 4 to 12 layers or more depending on design complexity. Ground plane and Power plane are decided. Signal planes where signals are routed are in top layer as well as internal layers.[15]
  • Line impedance determination using dielectric layer thickness, routing copper thickness and trace-width. Trace separation also taken into account in case of differential signals. Microstrip, stripline or dual stripline can be used to route signals.
  • Placement of the components. Thermal considerations and geometry are taken into account. Vias and lands are marked.
  • Routing the signal trace. For optimal EMI performance high frequency signals are routed in internal layers between power or ground planes as power plane behaves as ground for AC.
  • Gerber file generation for manufacturing.

Safety certification (US)

Safety Standard UL 796 covers component safety requirements for printed wiring boards for use as components in devices or appliances. Testing analyzes characteristics such as flammability, maximum operating temperature, electrical tracking, heat deflection, and direct support of live electrical parts.

“Cordwood” construction

 

A cordwood module.

Cordwood construction can save significant space and was often used with wire-ended components in applications where space was at a premium (such as missile guidance and telemetry systems) and in high-speed computers, where short traces were important. In “cordwood” construction, axial-leaded components were mounted between two parallel planes. The components were either soldered together with jumper wire, or they were connected to other components by thin nickel ribbon welded at right angles onto the component leads. To avoid shorting together different interconnection layers, thin insulating cards were placed between them. Perforations or holes in the cards allowed component leads to project through to the next interconnection layer. One disadvantage of this system was that special nickel leaded components had to be used to allow the interconnecting welds to be made. Some versions of cordwood construction used single sided PCBs as the interconnection method (as pictured). This meant that normal leaded components could be used. Another disadvantage of this system is that components located in the interior are difficult to replace.

Before the advent of integrated circuits, this method allowed the highest possible component packing density; because of this, it was used by a number of computer vendors including Control Data Corporation. The cordwood method of construction now appears to have fallen into disuse, probably because high packing densities can be more easily achieved using surface mount techniques and integrated circuits.

Multiwire boards

Multiwire is a patented technique of interconnection which uses machine-routed insulated wires embedded in a non-conducting matrix (often plastic resin). It was used during the 1980s and 1990s. (Kollmorgen Technologies Corp., U.S. Patent 4,175,816) Multiwire is still available in 2010 through Hitachi. There are other competitive discrete wiring technologies that have been developed (Jumatech [2]).

Since it was quite easy to stack interconnections (wires) inside the embedding matrix, the approach allowed designers to forget completely about the routing of wires (usually a time-consuming operation of PCB design): Anywhere the designer needs a connection, the machine will draw a wire in straight line from one location/pin to another. This led to very short design times (no complex algorithms to use even for high density designs) as well as reduced crosstalk (which is worse when wires run parallel to each other—which almost never happens in Multiwire), though the cost is too high to compete with cheaper PCB technologies when large quantities are needed.

Surface-mount technology

Main article: Surface-mount technology
 

Surface mount components, including resistors, transistors and an integrated circuit

Surface-mount technology emerged in the 1960s, gained momentum in the early 1980s and became widely used by the mid 1990s. Components were mechanically redesigned to have small metal tabs or end caps that could be soldered directly on to the PCB surface. Components became much smaller and component placement on both sides of the board became more common than with through-hole mounting, allowing much higher circuit densities. Surface mounting lends itself well to a high degree of automation, reducing labour costs and greatly increasing production and quality rates. Carrier Tapes provide a stable and protective environment for Surface mount devices (SMDs) which can be one-quarter to one-tenth of the size and weight, and passive components can be one-half to one-quarter of the cost of corresponding through-hole parts. However, integrated circuits are often priced the same regardless of the package type, because the chip itself is the most expensive part. As of 2006, some wire-ended components, such as small-signal switch diodes, e.g. 1N4148, are actually significantly cheaper than corresponding SMD versions.

See also

Nuvola apps ksim.png Electronics portal
 

Schematic Capture. (KiCAD)

 

PCB layout. (KiCAD)

 

3D View. (KiCAD)

  • Breadboard
  • C.I.D.+
  • Design for manufacturability (PCB)
  • Electronic packaging
  • Electronic waste
  • Multi-Chip Module
  • Occam Process – another process for the manufacturing of PCBs
PCB Materials
  • Conductive ink
  • Heavy copper
  • Laminate materials:
    • BT-Epoxy
    • Composite epoxy material, CEM-1,5
    • Cyanate Ester
    • FR-2
    • FR-4, the most common PCB material
    • Polyimide
    • PTFE, Polytetrafluoroethylene (Teflon)
PCB layout software
  • List of EDA companies
  • Comparison of EDA software

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