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In-circuit testing (ICT) is an example of white box testing where an electrical probe tests a populated printed circuit board (PCB), checking for shorts, opens, resistance, capacitance, and other basic quantities which will show whether the assembly was correctly fabricated. [1] It may be performed with a "bed of nails" test fixture and specialist test equipment, or with a fixtureless in-circuit test setup.
A common form of in-circuit testing uses a bed-of-nails tester. This is a fixture that uses an array of spring-loaded pins known as "pogo pins". When a printed circuit board is aligned with and pressed down onto the bed-of-nails tester, the pins make electrical contact with locations on the circuit board, allowing them to be used as test points for in-circuit testing. Bed-of-nails testers have the advantage that many tests may be performed at a time, but have the disadvantage of placing substantial strain on the PCB.
An alternative is the use of flying probes, which place less mechanical strain on the boards being tested. Their advantages and disadvantages are the opposite of bed-of-nails testers: the flying probes must be moved between tests, but they place much less strain on the PCB.
While in-circuit testers are typically limited to testing the above devices, it is possible to add additional hardware to the test fixture to allow different solutions to be implemented. Such additional hardware includes:
While in-circuit test is a very powerful tool for testing PCBs, it has these limitations:
The following are related technologies and are also used in electronic production to test for the correct operation of Electronics Printed Circuit boards:
A multimeter is a measuring instrument that can measure multiple electrical properties. A typical multimeter can measure voltage, resistance, and current, in which case can be used as a voltmeter, ammeter, and ohmmeter. Some feature the measurement of additional properties such as temperature and capacitance.
A printed circuit board (PCB), also called printed wiring board (PWB), is a medium used to connect or "wire" components to one another in a circuit. It takes the form of a laminated sandwich structure of conductive and insulating layers: each of the conductive layers is designed with a pattern of traces, planes and other features etched from one or more sheet layers of copper laminated onto and/or between sheet layers of a non-conductive substrate. Electrical components may be fixed to conductive pads on the outer layers in the shape designed to accept the component's terminals, generally by means of soldering, to both electrically connect and mechanically fasten them to it. Another manufacturing process adds vias, plated-through holes that allow interconnections between layers.
JTAG is an industry standard for verifying designs and testing printed circuit boards after manufacture.
Automatic test equipment or automated test equipment (ATE) is any apparatus that performs tests on a device, known as the device under test (DUT), equipment under test (EUT) or unit under test (UUT), using automation to quickly perform measurements and evaluate the test results. An ATE can be a simple computer-controlled digital multimeter, or a complicated system containing dozens of complex test instruments capable of automatically testing and diagnosing faults in sophisticated electronic packaged parts or on wafer testing, including system on chips and integrated circuits.
Boundary scan is a method for testing interconnects on printed circuit boards or sub-blocks inside an integrated circuit. Boundary scan is also widely used as a debugging method to watch integrated circuit pin states, measure voltage, or analyze sub-blocks inside an integrated circuit.
An electronic component is any basic discrete electronic device or physical entity part of an electronic system used to affect electrons or their associated fields. Electronic components are mostly industrial products, available in a singular form and are not to be confused with electrical elements, which are conceptual abstractions representing idealized electronic components and elements. A datasheet for an electronic component is a technical document that provides detailed information about the component's specifications, characteristics, and performance.
Design for testing or design for testability (DFT) consists of IC design techniques that add testability features to a hardware product design. The added features make it easier to develop and apply manufacturing tests to the designed hardware. The purpose of manufacturing tests is to validate that the product hardware contains no manufacturing defects that could adversely affect the product's correct functioning.
A bed of nails tester is a traditional electronic test fixture used for in-circuit testing. It has numerous pins inserted into holes in an epoxy phenolic glass cloth laminated sheet (G-10) which are aligned using tooling pins to make contact with test points on a printed circuit board and are also connected to a measuring unit by wires. Named by analogy with a real-world bed of nails, these devices contain an array of small, spring-loaded pogo pins; each pogo pin makes contact with one node in the circuitry of the DUT. By pressing the DUT down against the bed of nails, reliable contact can be quickly and simultaneously made with hundreds or even thousands of individual test points within the circuitry of the DUT. The hold-down force may be provided manually or by means of a vacuum or a mechanical presser, thus pulling the DUT downwards onto the nails.
In-system programming (ISP), or also called in-circuit serial programming (ICSP), is the ability of some programmable logic devices, microcontrollers, chipsets and other embedded devices to be programmed while installed in a complete system, rather than requiring the chip to be programmed prior to installing it into the system. It also allows firmware updates to be delivered to the on-chip memory of microcontrollers and related processors without requiring specialist programming circuitry on the circuit board, and simplifies design work.
A test engineer is a professional who determines how to create a process that would best test a particular product in manufacturing and related disciplines, in order to assure that the product meets applicable specifications. Test engineers are also responsible for determining the best way a test can be performed in order to achieve adequate test coverage. Often test engineers also serve as a liaison between manufacturing, design engineering, sales engineering and marketing communities as well.
A test probe is a physical device used to connect electronic test equipment to a device under test (DUT). Test probes range from very simple, robust devices to complex probes that are sophisticated, expensive, and fragile. Specific types include test prods, oscilloscope probes and current probes. A test probe is often supplied as a test lead, which includes the probe, cable and terminating connector.
Automated optical inspection (AOI) is an automated visual inspection of printed circuit board (PCB) manufacture where a camera autonomously scans the device under test for both catastrophic failure and quality defects. It is commonly used in the manufacturing process because it is a non-contact test method. It is implemented at many stages through the manufacturing process including bare board inspection, solder paste inspection (SPI), pre-reflow and post-re-flow as well as other stages.
An electronic circuit is composed of individual electronic components, such as resistors, transistors, capacitors, inductors and diodes, connected by conductive wires or traces through which electric current can flow. It is a type of electrical circuit. For a circuit to be referred to as electronic, rather than electrical, generally at least one active component must be present. The combination of components and wires allows various simple and complex operations to be performed: signals can be amplified, computations can be performed, and data can be moved from one place to another.
Bead probe technology (BPT) is technique used to provide electrical access to printed circuit board (PCB) circuitry for performing in-circuit testing (ICT). It makes use of small beads of solder placed onto the board's traces to allow measuring and controlling of the signals using a test probe. This permits test access to boards on which standard ICT test pads are not feasible due to space constraints.
In the manufacture of electronic printed circuit boards, flying probes are used for testing both bare circuit boards and boards loaded with components. Flying probes were introduced in the late 1980’s. Flying probes can be found in many manufacturing and assembly operations. A flying probe tester uses one or more test probes to make contact with the circuit board under test; the probes are moved from place to place on the circuit board to carry out tests of multiple conductors or components. Flying probe testers are an alternative to bed of nails testers, which use multiple contacts to simultaneously contact the board and which rely on electrical switching to carry out measurements.
In condensed matter physics, scanning SQUID microscopy is a technique where a superconducting quantum interference device (SQUID) is used to image surface magnetic field strength with micrometre-scale resolution. A tiny SQUID is mounted onto a tip which is then rastered near the surface of the sample to be measured. As the SQUID is the most sensitive detector of magnetic fields available and can be constructed at submicrometre widths via lithography, the scanning SQUID microscope allows magnetic fields to be measured with unparalleled resolution and sensitivity. The first scanning SQUID microscope was built in 1992 by Black et al. Since then the technique has been used to confirm unconventional superconductivity in several high-temperature superconductors including YBCO and BSCCO compounds.
Capacitors have many uses in electronic and electrical systems. They are so ubiquitous that it is rare that an electrical product does not include at least one for some purpose. Capacitors allow only AC signals to pass when they are charged blocking DC signals. The main components of filters are capacitors. Capacitors have the ability to connect one circuit segment to another. Capacitors are used by Dynamic Random Access Memory (DRAM) devices to represent binary information as bits.
An ESR meter is a two-terminal electronic measuring instrument designed and used primarily to measure the equivalent series resistance (ESR) of real capacitors; usually without the need to disconnect the capacitor from the circuit it is connected to. Other types of meters used for routine servicing, including normal capacitance meters, cannot be used to measure a capacitor's ESR, although combined meters are available that measure both ESR and out-of-circuit capacitance. A standard (DC) milliohmmeter or multimeter cannot be used to measure ESR, because a steady direct current cannot be passed through the capacitor. Most ESR meters can also be used to measure non-inductive low-value resistances, whether or not associated with a capacitor; this leads to several additional applications described below.
Circuit Check is an American company with about 225 employees and seven direct operations in six countries. Headquartered in Maple Grove, Minnesota, it is one of the largest manufacturers of electronic and mechanical test fixtures in North America, . The company also manufactures Automatic Test Equipment for end-of-line manufacturing test. The company uses either a Microsoft Excel-driven "CCITest" software platform, or the National Instruments LabVIEW software platform. They have a variety of clients in different industries which include: Automotive, Military & Aerospace, Medical, Industrial, and Computer Networking.
In the electronics industry, embedded instrumentation refers to the integration of test and measurement instrumentation into semiconductor chips. Embedded instrumentation differs from embedded system, which are electronic systems or subsystems that usually comprise the control portion of a larger electronic system. Instrumentation embedded into chips is employed in a variety of electronic test applications, including validating and testing chips themselves, validating, testing and debugging the circuit boards where these chips are deployed, and troubleshooting systems once they have been installed in the field.