What Is an In-Circuit Board Tester?
In-Circuit Board Tester is a testing device used to evaluate the electrical characteristics of individual electronic components mounted on an electronic circuit board inside an electronic device.
For an electronic device to function properly, the internal electronic circuit board must operate properly. In-Circuit Board Tester inspects the board with the electronic components mounted on it.
In-Circuit Board Testers can test the electrical characteristics of individual components mounted on the board with a very small amount of power. They can locate defective parts without damaging the board, and can reliably detect defective parts that are difficult to detect with the naked eye.
In-Circuit Board Tester Applications
In-Circuit Board Testers are widely used in the inspection process of development and mass production lines in factories that handle electronic circuit boards with electronic devices and components. There are two types of In-Circuit Board Testers: press-type In-Circuit Board Testers and Flying Probe Testers.
Press-type In-Circuit Board Testers are capable of high-speed inspection and are suitable for mass-production boards. They are also used for inspection jigs. Flying Probe Testers do not require inspection jigs and are suitable for low-volume, high-mix boards, while handling fine patterns.
Specific inspection items include short/open defects of solder mounting components, defects due to wrong constants of capacitors, coils, and resistors, defects of missing components such as capacitors, coils, resistors, diodes, and transistors, and lead float defects of ICs and connectors, photocouplers and digital transistors. The test is also used to check the operation of photocouplers, digital transistors, and Zener diodes.
Special tests include image inspection of electrically inaccessible components, adhesion (solder) defect inspection of SOPs, QFPs, etc., and simple function tests.
In-Circuit Board Tester Principle
In-Circuit Board Tester extracts defects such as component constants and functions, as well as open or short signal lines including internal vias, by applying a probe to the required location on the electronic board and causing a very small electrical signal to be applied separately from the bias during normal operation.
The system has the internal configuration necessary to smoothly perform various types of inspections, and usually consists of a measurement section for electrical inspection, a scanner section for capturing and recognizing measurement lines, a probing section for bringing the measurement lines into energized contact with specific locations on the board to be inspected, and a control section for controlling these sections. The scanner is used to capture and recognize the measurement line.
The constant of an electronic component is measured from the values of voltage and current when a measurement signal is applied to the probing unit. Since electric circuits generally form a network, it is difficult to measure the constants of individual elements. However, many In-Circuit Board Testers are equipped with various functions to improve inspection accuracy.
Other Information on In-Circuit Board Testers
1. In-Circuit Board Tester Functions
Guarding function
This function electrically isolates the effect of errors caused by current due to parallel connections.
Phase Separation
When an AC signal is applied to a circuit network composed of resistors, inductors, and capacitors, a phase difference is generated between the current and voltage. This phase difference can be used to accurately measure the constants of each element.
2. Flying Checker
A flying checker is one type of In-Circuit Board Tester, which is an inspection device that primarily applies a probe to determine open-shorts of mounted components on a board. It takes longer to inspect than a standard press-type In-Circuit Board Tester, but is used when the emphasis is on the fact that it does not require preparation of a program or pin board.
Also called a flying probe checker, it creates a net list from Gerber data and uses that data to inspect for broken wires by applying a probe to the beginning and end of the board. It then inspects for shorts by applying a probe between one of its nets and an adjacent net.
Many types of flying checkers are modified from bare board checkers and can be used as general in-circuit tests after mounting. The specific inspection method involves clamping the board from both sides with two or four probes. This testing equipment inspects the open and short-circuit conditions of a printed circuit board. There are two types of testing equipment, one that checks electrical continuity and the other that measures C-capacitance to find short circuits, with the C-capacitance method generally taking less time.
3. Function Tester
A Function Tester serves a distinct purpose compared to the In-Circuit Board Tester, despite often being compared in the context of inspecting similar boards during the board manufacturing process. While the primary role of the In-Circuit Board Tester is to examine the board’s assembly condition, including components and circuit continuity (such as identifying open or short circuits), the Function Tester is designed to verify whether the circuit’s functionality, such as input and output operations, is operating correctly.
This test is usually called a function test, in which electrical signals specified in the specifications are applied to the input terminals of the board to be tested. The purpose is to verify whether the board functions correctly by checking if the specified output signals are generated in accordance with the specifications. Other tests are also performed for components such as switches and LEDs that are difficult to check with just an open-short test using In-Circuit Board Tester, as well as for integrated circuit operations and software writing for MCUs and various types of ICs.
In general, when comparing in-circuit testing and function testing, function testing is more important from the perspective of confirming product operation, and most products prioritize function testing.