PCB Technical - How to make up for automotive PCB defects

In today's key PCB applications, automotive PCBs occupies an important position. However, due to the special working environment, safety and high current requirements of the car, it has high requirements on the reliability and environmental adaptability of the PCB, and the types of PCB technology involved are also wide. This is a problem for PCB companies. Challenge; For manufacturers who want to develop the automotive PCB market, they need to do more understanding and analysis of this new market.

Automotive PCBs especially emphasize high reliability and low DPPM. So, in terms of process control, can it be done well in accordance with the requirements of TS16949? Has a low DPPM been achieved? All these need to be carefully evaluated. Just seeing this attractive piece of cake and entering blindly will bring harm to the enterprise itself.

The following are some of the special practices in the testing process of some representative companies specializing in the production of automotive PCBs for the majority of PCB colleagues for reference:

1. The second test method

Some PCB manufacturers adopt the "second test method" to increase the rate of finding defective boards after the first high-voltage electrical breakdown.

2. Bad board foolproof test system

More and more PCB manufacturers have installed "good board marking system" and "bad board error prevention box" in the light board testing machine to effectively avoid human leakage. The good board marking system marks the tested PASS boards for the testing machine, which can effectively prevent the tested boards or bad boards from flowing into the hands of customers. The bad board error-proof box means that during the test, when the PASS board is tested, the test system outputs the signal that the box is opened; on the contrary, when the bad board is tested, the box is closed to allow the operator to correctly place the tested circuit board.

3. Establish a PPm quality system

At present, PPm (Partspermillion, parts per million defect rate) quality system has begun to be widely used in PCB manufacturers. Many people are responsible for the statistical analysis of online PCB quality abnormalities and PCB quality abnormal returns. Using the statistical analysis method of SPC production process, each bad board and each returned defective board are classified and statistically analyzed, and combined with auxiliary tools such as microsectioning to analyze in which production process the bad and defective boards are produced. According to the statistical data results, we can solve the problems in the process purposefully.

4. Comparative test method

Some customers use two different brands of PCBs for comparative testing in different batches, and track the PPm of the corresponding batches, so as to understand the performance of the two testers, and then choose a better performance tester to test automotive PCBs.

5. Improve test parameters

Choose higher test parameters to strictly detect such PCBs. Because, if you choose a higher voltage and threshold, increase the number of high-voltage read leakage, can improve the detection rate of PCB defective boards. For example, a large Taiwanese-funded PCB company in Suzhou uses 300V, 30M, and 20 ohms to test automotive PCBs.

6. Periodically verify the parameters of the testing machine

After long-term operation of the tester, the internal resistance and other related test parameters will all deviate. Therefore, the machine parameters need to be adjusted regularly to ensure the accuracy of the test parameters. Test equipment is maintained in a considerable part of large PCB companies for half a year or a year, and internal performance parameters are adjusted. The pursuit of "zero defect" automotive PCB has always been the direction of the efforts of the majority of PCB people. However, due to the limitations of process equipment and raw materials, the world's top 100 PCB companies are still exploring ways to reduce PPm.