This kind of defect cannot be found through a normal continuity test, what method should be used?
How to conduct effective testing of PCB vias defect?
The traditional continuity test uses a uniform threshold value. During the test, problems such as holes, thin copper, and slightly open circuit gaps cannot be effectively detected.Xiechen launched the four-wire four-terminal flying probe test, which can effectively detect such defects and ensure the quality and reliability of the delivered products.
Four-wire & four-terminal test principle:
The four-wire & four-terminal test passes two pins on each test point, so that the test current and the tested voltage do not affect each other, and the measured resistance can be accurately measured: R=U/I.
Four-wire flying probe test technical requirements:
The flying probe test are a pair of mirror structures, and the tip error of the two blades is within 10μm;
Insulation treatment needs to be done in the middle of the two blades, and no contact short circuit condition can occur during the test;
The distance between the two blades should be controlled within 20μm;
The test needle pressure needs to be adjusted to 10-25g.
Four-wire & four-terminal-through hole problem test
When the resistance deviation of the circuit board is more than 1 milliohm, the condition of the hole is already very poor, especially for the current high-rise board and automotive board, it must be ensured that the hole copper thickness 100% meets the requirements. For hole-to-hole testing, two test pins need to be planted on the edge of the hole at the same time. Traditional pass/special testing machines cannot simultaneously plant two test pins on the edge of the hole, and the test probe structure of the flying probe tester can ensure that the through hole is effective. test. Therefore, when testing through-hole problems, the hole-to-hole test method must be used. The following hole copper anomalies can be detected:Four-wire & four-terminal-blind buried hole and line problem test
The problem of blind buried holes, the residual glue after laser drilling in the process, and the poor conduction caused by poor electroplating. After the high-temperature welding of the client, it is more likely to be completely OPEN, causing customer complaints. In addition, the defects of the inner and outer lines, such as line scratches, scratches on the inner line, poor patching, and short circuit between coils, may also cause customer complaints. Such defects can be effectively detected by the four-wire four-terminal flying probe test. The following hole copper anomalies can be detected:At present, PCB boards with high reliability requirements such as automobile boards and 5G communication boards are becoming more and more common. The four-wire & four-terminal test has been applied to the test as a standard process. It has been recognized by many printed circuit board manufacturers and has been widely used.
