Quality Control Experience: Six Ways to Reduce the Defect Rate of Automotive PCBs

Preface

The automotive electronics market is the third largest application area for PCBs after computers and communications. As automobiles have gradually evolved from traditional mechanical products to high-tech products that are intelligent, information-based, and mechatronic, electronic technology has been widely used in automobiles. Whether it is the engine system, chassis system, safety system, information system, or in-car environment system, electronic products are used without exception. The automotive market has obviously become another bright spot in the consumer electronics market. The development of automotive electronics has naturally driven the development of automotive PCBs.

Among the key applications of PCB today, automotive PCB occupies an important position. However, due to the special working environment, safety and high current requirements of automobiles, the reliability and environmental adaptability of PCBs are relatively high, and the types of PCB technologies involved are also relatively wide, which is a challenge for PCB companies; and for manufacturers who want to develop the automotive PCB market, they need to do more understanding and analysis of this new market.

Automotive PCBs particularly emphasize high reliability and low DPPM. So, does our company have the technology and experience accumulated in high reliability manufacturing? Is it consistent with the future product development direction? In terms of process control, can it comply with the requirements of TS16949? Has it achieved low DPPM? These all need to be carefully evaluated. Blindly entering the market just by seeing this tempting cake will bring harm to the company itself.

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

1. Secondary testing method

Some PCB manufacturers adopt the "secondary testing method" to increase the rate of finding defective boards that have been broken down by the first high voltage electricity.

2. Bad board foolproof test system

More and more PCB manufacturers have installed "good board marking system" and "bad board error prevention box" on bare board testers to effectively avoid human leakage. The good board marking system allows the tester to mark the tested PASS board, which can effectively prevent the tested board or bad board from flowing into the hands of customers. The bad board error prevention box is that during the test process, when a PASS board is tested, the test system outputs a signal to open the box; conversely, when a bad board is tested, the box is closed, allowing the operator to correctly place the tested circuit board.

3. Establish PPm quality system

At present, the PPm (Parts per million, defect rate) quality system has begun to be widely used in PCB manufacturers. Among many of our company's customers, Hitachi ChemICal in Singapore has the most worthy of reference for its application and achievements. In this factory, more than 20 people are responsible for the statistical analysis of online PCB quality abnormalities and PCB quality abnormality returns. Using the SPC production process statistical analysis method, each bad board and each returned defective board is classified and statistically analyzed, and combined with auxiliary tools such as micro-sectioning to analyze which production process produces bad and defective boards. According to the statistical data results, the problems in the process are purposefully solved.

4. Comparative testing method

Some customers use two different brands of machines to conduct comparative tests on different batches of PCBs, and track the PPm of the corresponding batches to understand the performance of the two test machines and choose the test machine with better performance to test automotive PCBs.

5. Improve test parameters

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

6. Regularly check the parameters of the test machine

After long-term operation, the test parameters such as internal resistance of the test machine will deviate. Therefore, it is necessary to adjust the machine parameters regularly to ensure the accuracy of the test parameters. A considerable number of large PCB companies perform machine maintenance and adjust internal performance parameters every six months or a year. The pursuit of "zero defect" automotive PCBs has always been the direction of the efforts of the majority of PCB people, but due to the limitations of process equipment, raw materials and other aspects, the world's top 100 PCB companies are still exploring ways to reduce PPm.