PCB, commonly known as printed circuit board, is an indispensable part of electronic components and plays a core role. In a series of PCB production processes, there are many matching points. If you are not careful, the board will have defects. If you pull one hair and move the whole body, PCB quality problems will emerge in endlessly. Therefore, after the circuit board is made into shape, the detection test becomes an indispensable link.

1) PCB is often layered while using. Because of supplier material or process issues. Poor material selection and copper distribution is also relative. If the storage time is too long, the PCB board is affected by moisture. Improper packing or storage, damp may also have influence.

-Counter measures: select a good package, use constant temperature and humidity equipment for storage. Do a good job of PCB Factory reliability test, for example: thermal stress test in PCB reliability test, the supplier in charge takes more than 5 times of delamination as the standard, which will be confirmed in the sample stage and each cycle of mass production, while the general manufacturer may only require two times, and only once in a few months. The IR test of simulated mounting can also prevent the outflow of defective products, which is necessary for excellent PCB factories. In addition, TG PCB board should be selected above 145 ℃, which is more safe.

-Reliability test equipment: constant temperature and humidity box, stress screening cold and hot shock test box, PCB reliability test equipment

2) Poor solder-ability of PCB board

Because over storage time, leading to moisture absorption, the plate was polluted and oxidized, black nickel abnormal, solder proof scum (shadow), anti solder pad. So that we should pay close attention to the quality control plan of PCB Factory and the standard of maintenance. For example, for black nickel, it is necessary to see if the PCB production plant has chemical gold out of the factory, whether the concentration of the chemical solution is stable, whether the analysis frequency is enough, whether the regular gold stripping test and phosphorus content test are set to detect, whether the internal solder test is well performed, etc.

3) PCB bending and warping

Due to unreasonable supplier selection, poor control of heavy industry, improper storage, abnormal operation line, obvious difference in copper area of each layer, and not firm enough production of broken holes.

-Counter measures: the sheet is pressurized with wood pulp board and then packaged for shipment, so as to avoid deformation in the future. If necessary, clamp is added to the patch to prevent the device from bending under excessive pressure. Before packaging, PCB needs to simulate the mounting IR condition to avoid the bad phenomenon of bending after the furnace.

4) Poor impedance of PCB board

Because of the impedance difference between PCB batches is large. Therefore the manufacturer is required to attach batch test report and impedance bar when delivery, and provide the comparison data of inside board wire diameter and board edge line diameter when necessary.

5) Anti welding blistering / falling off

Because there are differences in the selection of solder proof ink, abnormal solder proofing process of PCB board, rework or high chip temperature. So PCB suppliers should formulate PCB reliability test requirements and control them in different production processes.

6) Galvanic effect

Because in the process of OSP, electrons will dissolve into copper ions, resulting in potential difference between gold and copper.