PCB Tech - ​Methods to reduce the defect rate of automotive PCB

The automotive electronics market is the third largest application category of PCB circuit boards after computers and communications. As automobiles have gradually evolved and developed into intelligent, informatized, and mechatronics high-tech products from traditional machine products, the use of electronic technology in automobiles has become very common, no matter whether it is the engine system or the chassis system., Safety system, information system, car environment system, etc. all use electronic goods without exception. The automotive market has obviously become another bright spot in the electronic consumer market. The development of automotive electronics has naturally driven the development of automotive PCB circuit boards.

In today's key use of printed circuit boards, automotive PCB circuit boards occupy an important position. However, due to the special task environment, safety and high current requirements of the car, it has higher requirements for PCB reliability and environmental compliance, and the types of PCB circuit board technology touched are also wide. This is about PCB circuit board companies. Said, it is a challenge; and for manufacturers who want to open up the automotive PCB circuit board market, they need to do more understanding and analysis of this new market.

Automotive PCB circuit boards particularly emphasize high reliability and low DPPM. So, can our company have the accumulation of technology and experience in high-reliability manufacturing? Can it diverge from the direction of future product development? In terms of process control, can it be done well in accordance with the requirements of TS16949? Have you ever achieved a low DPPM? All these need to be evaluated carefully. Just seeing this attractive piece of cake and consciously entering it will bring damage to the enterprise itself.

The following are some of the special practices in the testing process of representative local professional consumer PCB multi-layer board companies for automotive use, which should be provided for reference by broad PCB colleagues:

1. The second test method

Some PCB multi-layer board consumer companies use the "second test method" to improve the rate of finding defective boards after the first high-voltage electrical breakdown.

2. Bad board foolproof test system

More and more PCB multi-layer board manufacturers have installed "good board marking system" and "bad board error prevention box" in the light board tester to effectively prevent man-made leakage. The good board marking system is the stop marking of the tested PASS board by the testing machine, which can effectively prevent the tested board or the bad board from flowing into the hands of the customer. The bad board error-proof box is in the test process, when the PASS board is tested, the signal that the box opens is tested; on the contrary, when the bad board is tested, the box is closed so that the operator can correctly place the tested circuit board.

3. Establish a PPm quality system

At present, the PPm (Partspermillion, parts per million defect rate) quality system is beginning to be widely used among PCB manufacturers. Among the many customers of our company, HitachiChemICal in Singapore is the most worthy of creation for its use and the results obtained. There are more than 20 people in the factory who are dedicated to the statistical analysis of online PCB quality abnormalities and PCB quality abnormal returns. Using the statistical analysis method of SPC consumption process, each broken board and each returned defective board are classified and analyzed statistically, and combined with auxiliary tools such as micro-slicing to stop analyzing in which manufacturing process the broken and defective board occurred. According to the statistical results, the results presented in the process are dealt with purposefully.

4. Comparison test method

Part of the customer’s different batches of PCB circuit boards use two different brands of models to stop the comparison test, and track the PPm status of the corresponding batches, so as to understand the function of the two testers, and then choose the better function tester to stop testing the car. PCB circuit board.

5. Improve test parameters

Choose higher test parameters to rigorously detect such PCB circuit boards. Because, if a higher voltage and threshold are selected, and the number of high-voltage reading leakage times is added, the detection rate of PCB defective boards can be improved. For example, a large Taiwanese-funded PCB company in Suzhou used 300V, 30M, and 20 ohms to stop testing automotive PCB circuit boards.

6. Check the parameters of the testing machine on a regular basis

After the testing machine is temporarily operated, the internal resistance and other related test parameters will be biased. Therefore, it is necessary to adjust the machine parameters regularly to ensure the accuracy of the test parameters. Test equipment in a large number of large-scale printed circuit board companies have stopped part maintenance for half a year or a year to adjust external functional parameters. The pursuit of "zero defect" automotive PCB multi-layer boards continues to be the direction of the broad PCB circuit board people. However, due to the limitations of process equipment and original materials, the world's top 100 PCB circuit board companies are still exploring ways to reduce PPm from time to time. Method.