Flying probe

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In the testing of printed circuit boards, a flying probe test or fixtureless in-circuit test (FICT) system may be used for testing low to mid volume production, prototypes, and boards that present accessibility problems. A traditional "bed of nails" tester for testing a PCB requires a custom fixture to hold the PCBA and the Pogo pins which make contact with the PCBA. In contrast, FICT uses two or more flying probes, which may be moved based on software instruction. [1] The flying probes are electro-mechanically controlled to access components on printed circuit assemblies (PCAs). The probes are moved around the board under test using an automatically operated two-axis system, and one or more test probes contact components of the board or test points on the printed circuit board. [2]

Printed circuit board Board to support and connect electronic components

A printed circuit board (PCB) mechanically supports and electrically connects electronic components or electrical components using conductive tracks, pads and other features etched from one or more sheet layers of copper laminated onto and/or between sheet layers of a non-conductive substrate. Components are generally soldered onto the PCB to both electrically connect and mechanically fasten them to it.

Pogo pin

A pogo pin or spring-loaded pin is a type of electrical connector mechanism that is used in many modern electronic applications and in the electronics testing industry. They are used for their improved durability over other electrical contacts, and the resilience of their electrical connection to mechanical shock and vibration.

Contents

Flying probe testing is commonly used for test of analog components, analog signature analysis, and short/open circuits. They can be classified as in-circuit test (ICT) systems or as Manufacturing Defects Analyzers (MDAs). They provide an alternative to the bed-of-nails technique for contacting the components on printed circuit boards. The precision movement can probe points on integrated circuit packages without expensive fixturing or programming required.

Analog signature analysis is electronic component and circuit board troubleshooting technique which applies a current-limited AC sinewave across two points of an electronic component or circuit.

In-circuit test (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. It may be performed with a bed of nails type test fixture and specialist test equipment, or with a fixtureless in-circuit test setup.

The main advantage of flying probe testing is the substantial cost of a bed-of-nails fixture, costing on the order of US $20,000 [3] , is not required. The flying probes also allow easy modification of the test fixture when the PCBA design changes. FICT may be used on both bare or assembled PCB's. [4] However, since the tester makes measurements serially, instead of making many measurements at once, the test cycle may become much longer than for a bed-of-nails fixture. A test cycle that may take 30 seconds on such a system, may take an hour with flying probes. Test coverage may not be as comprehensive as a bed of nails tester, because fewer points are tested at one time. [5]

Uses

Boundary scan

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.

Power-off testing is often necessary to test the printed circuit assembly (PCA) board due to uncertainty as to the nature of the failure. When the PCA can be further damaged by applying power it is necessary to use power off test techniques to safely examine it. Power off testing includes analog signature analysis, ohmmeter, LCR Meter and optical inspection. This type of testing also lends itself well to troubleshooting circuit boards without the aid of supporting documentation such as schematics.

Benefits of fixtureless in-circuit test

Integrated circuit electronic circuit manufactured by lithography; set of electronic circuits on one small flat piece (or "chip") of semiconductor material, normally silicon

An integrated circuit or monolithic integrated circuit is a set of electronic circuits on one small flat piece of semiconductor material that is normally silicon. The integration of large numbers of tiny MOS transistors into a small chip results in circuits that are orders of magnitude smaller, faster, and less expensive than those constructed of discrete electronic components. The IC's mass production capability, reliability, and building-block approach to circuit design has ensured the rapid adoption of standardized ICs in place of designs using discrete transistors. ICs are now used in virtually all electronic equipment and have revolutionized the world of electronics. Computers, mobile phones, and other digital home appliances are now inextricable parts of the structure of modern societies, made possible by the small size and low cost of ICs.

Resistor Passive electrical component providing electrical resistance

A resistor is a passive two-terminal electrical component that implements electrical resistance as a circuit element. In electronic circuits, resistors are used to reduce current flow, adjust signal levels, to divide voltages, bias active elements, and terminate transmission lines, among other uses. High-power resistors that can dissipate many watts of electrical power as heat, may be used as part of motor controls, in power distribution systems, or as test loads for generators. Fixed resistors have resistances that only change slightly with temperature, time or operating voltage. Variable resistors can be used to adjust circuit elements, or as sensing devices for heat, light, humidity, force, or chemical activity.

Capacitor Passive two-terminal electronic component that stores electrical energy in an electric field

A capacitor is a device that stores electrical energy in an electric field. It is a passive electronic component with two terminals.

Related Research Articles

Breadboard board of holes that allows for electronics to be wired without soldering

A breadboard is a construction base for prototyping of electronics. Originally the word referred to a literal bread board, a polished piece of wood used for slicing bread. In the 1970s the solderless breadboard became available and nowadays the term "breadboard" is commonly used to refer to these.

Wave soldering Electronics soldering process

Wave soldering is a bulk soldering process used in the manufacture of printed circuit boards. The circuit board is passed over a pan of molten solder in which a pump produces an upwelling of solder that looks like a standing wave. As the circuit board makes contact with this wave, the components become soldered to the board. Wave soldering is used for both through-hole printed circuit assemblies, and surface mount. In the latter case, the components are glued onto the surface of a printed circuit board (PCB) by placement equipment, before being run through the molten solder wave. Wave soldering is mainly used in soldering of through hole components.

Automatic test equipment apparatus used in Hardware testing

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.

Laser trimming

Laser trimming is the manufacturing process of using a laser to adjust the operating parameters of an electronic circuit.

OrCAD electronic design automation software

OrCAD Systems Corporation was a software company that made OrCAD, a proprietary software tool suite used primarily for electronic design automation (EDA). The software is used mainly by electronic design engineers and electronic technicians to create electronic schematics, perform mixed-signal simulation and electronic prints for manufacturing printed circuit boards. OrCAD was taken over by Cadence Design Systems in 1999 and was integrated with Cadence Allegro since 2005.

Selective soldering

Selective soldering is the process of selectively soldering components to printed circuit boards and molded modules that could be damaged by the heat of a reflow oven or wave soldering in a traditional surface-mount technology (SMT) or Through-hole technology assembly processes.This usually follows an SMT oven reflow process; parts to be selectively soldered are usually surrounded by parts that have been previously soldered in a surface-mount reflow process, and the selective-solder process must be sufficiently precise to avoid damaging them.

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 device under test (DUT), also known as equipment under test (EUT) and unit under test (UUT), is a manufactured product undergoing testing, either at first manufacture or later during its life cycle as part of ongoing functional testing and calibration checks. This can include a test after repair to establish that the product is performing in accordance with the original product specification.

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-reflow as well as other stages.

SPEA is an Italian company that designs and manufactures Automatic Test Equipment (ATE) for testing MEMS, Sensors, microchips and Printed circuit board.

Bead probe technology

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.

Non contact wafer testing is a normal step in semiconductor device fabrication, used to detect defects in integrated circuits (IC) before they are assembled during the IC packaging step.

Contact pad

Contact pads or bond pads are designated surface areas of a printed circuit board or die of an integrated circuit. Possibilities to contact to pads include soldering, wirebonding, flip chip mounting, or probe needles.

Circuit Check

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.

Pad cratering is a mechanically induced fracture in the resin between copper foil and outermost layer of fiberglass of a printed circuit board (PCB). It may be within the resin or at the resin to fiberglass interface.

A SmartFixture is a test fixture with a computer and instrumentation inside, that allows a user to develop a complete Functional Testing (manufacturing).

Digital image correlation analyses have applications in material property characterization, displacement measurement, and strain mapping. As such, DIC is becoming an increasingly popular tool when evaluating the thermo-mechanical behavior of electronic components and systems.

Specctra is a commercial PCB auto-router originally developed by John F. Cooper and David Chyan of Cooper & Chyan Technology, Inc. (CCT) in 1989. The company and product were taken over by Cadence Design Systems in May 1997. Since its integration into Cadence's Allegro PCB Editor, the name of the router is Allegro PCB Router. The latest version is 17.2.

References

  1. Stephen F. Scheiber (2001). Building a Successful Board-test Strategy. Newnes. pp. 303–. ISBN   978-0-7506-7280-1.
  2. R. S. Khandpur, Printed Circuit Boards:Design, Fabrication, Assembly and Testing, Tata-McGraw Hill, ISBN   0070588147, 2005, page 572
  3. "ICT Performs Comprehensive Testing". NexLogic. NexLogic Technologies Inc. Retrieved 30 September 2019.
  4. Keith Brindley (22 October 2013). Automatic Test Equipment. Elsevier. pp. 12–. ISBN   978-1-4831-0115-6.
  5. Alec Cohen, Prototype to Product: A Practical Guide for Getting to Market, O'Reilly, 2015, ISBN   1449362281, pp. 83, 84