PCB Blog - 6 methods to reduce the defect rate of automobile PCB

Automotive PCB electronic market is the third largest application category of PCB circuit board after computer and communication. With the gradual evolution and development of automobile from a traditional machine commodity to a high-tech commodity of intelligence, informatization and mechatronics, the use of electronic technology in automobile has been very common. Electronic commodities have been adopted without exception, whether it is the starter system, the chassis system, the safety system, the information system and the internal environment system. Obviously, the automobile market has become another bright spot in the electronic consumer market. The development of automobile electronics has naturally driven the development of automobile PCB.

In today's key objects of printed circuit board, automobile PCB occupies an important position. However, due to the special task environment, safety and high current requirements of the automobile, it has high requirements for PCB reliability and environmental compliance, and involves a wide range of PCB technology types, which is a challenge for PCB enterprises; For manufacturers who want to open up the Automotive PCB market, they need to do more understanding and analysis of the new market.

Automotive PCB circuit board emphasizes high reliability and low DPPM. Can our enterprise have the accumulation of technology and experience in high reliability manufacturing? Can it be different from the direction of commodity development in the future? In process control, can you do well according to the requirements of TS16949? Have you ever achieved low DPPM? These should be carefully evaluated. It will damage the PCB enterprise itself to see this attractive cake and consciously enter it.

PCB is mostly closely connected with concepts such as consumer electronics and 5G. However, with the development of new energy vehicles getting better, the application of PCB in automotive electronics has also begun to attract market attention.

On the one hand, in the automotive industry, PCB is mainly used for auxiliary driving, on-board communication, electric control and other links. In terms of traditional fuel vehicles, the average consumption of PCB is 1 square meter, while that of high-end models is 2-3 square meters. The value of PCB per vehicle is about 500-600CNY.

However, due to the addition of BMS, MCU and other devices in new energy vehicles, the PCB use area has increased to 3-5 square meters, and the PCB value of a single vehicle exceeds 2000CNY, up to four times that of traditional fuel vehicles. According to prismark data, the PCB output value in the global automotive field last year was US $6.19 billion. It is expected that the output value will reach US $8.75 billion in 2024, accounting for 10.6% of the global PCB output value, and the compound growth rate from 2020 to 2024 can reach 9%.

On the other hand, it is the subdivided field FPC (flexible circuit board / flexible board). In traditional fuel vehicles, the consumption of single vehicle FPC is more than 100 pieces, which is mainly used in on-board display group and vehicle electronic equipment, electronic control automatic systems such as engine system, seat, door and vehicle control, and automatic safety systems such as automobile image system and sensor.

The following provides some special practices of representative local professional consumer Automotive PCB board enterprises in the testing process for reference:

1. Secondary test method

Local PCB multi-layer board consumer enterprises adopt the "secondary test method" to improve the rate of defective boards after the first high voltage breakdown.

2. Broken board anti stupidity test

More and more PCB manufacturers have installed "good board marking system" and "bad board error proof box" in the light board testing machine to effectively prevent man-made leakage. The good board marking system is used to stop the testing machine from marking 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 proofing box refers to the signal of fragmentary input box opening when the pass board is tested during the test process; On the contrary, when a bad board is tested, the box is closed so that the operator can correctly place the tested circuit board.

3. Establish ppm quality system

At present, ppm (parts per million) quality system is widely used in PCB manufacturers. Among many of our customers, Hitachi chemical in Singapore is the most worthy of self creation for its use and effectiveness. More than 20 people in the factory are specially responsible for the statistical analysis of online PCB quality abnormalities and PCB quality abnormal returns. The SPC consumption process statistical analysis method is used to classify and analyze each bad board and each returned defective board, and combined with auxiliary tools such as micro slicing to analyze which manufacturing process has broken and defective board. According to the statistical data results, purposefully deal with the results presented in the process.

4. Analogy Test Method

Some customers use two different brands of PCB board in different batches to stop comparative testing, and track the PPM status of the corresponding batch, so as to understand the function of the two testing machines, so as to select a better testing machine to stop testing Automotive PCB boards.

5. Progress test parameters

Select higher test parameters to detect such PCB boards. Because, if higher voltage and threshold are selected and high-voltage leakage reading times are added, the detection rate of PCB defective boards can be improved. For example, a large Taiwan funded PCB enterprise in Suzhou uses 300V, 30m and 20 Ω to stop testing Automotive PCB.

6. Current calibration tester parameters

After the tester is temporarily operated, the internal resistance and other relevant test parameters will be biased. Therefore, the machine parameters need to be adjusted regularly to ensure the accuracy of test parameters. Test equipment in a considerable part of large printed circuit board enterprises stop taking care of parts and adjusting external functional parameters for half a year or a year. The pursuit of "zero defect" Automotive PCB multi-layer board is the direction of continuous efforts for a wide range of PCB circuit board people, but subject to the limitations of process equipment, raw materials and other aspects, IPCB is still exploring ways to reduce ppm from time to time.