How to ensure the quality of automotive pcb board ?

How to ensure high-reliable automotive PCB to meet product requirementsis the goal pursued by many PCB manufacturers. During the production control, some problems that are prone to insufficient performance in reliability testing which need to be analyzed to give the industry as a reference.

1. High and low temperature cycle test.

Automotive PCBs for power control systems and brake control systems require higher reliability in design and manufacturing processes. For example, automotive control systems usually require 500 times high and low temperature cycles, and individual key components even require up to 2000 times high and low temperature cycles.

A. High and low temperature cycle test conditions and requirements. Low to high temperatures: -40c-125 ℃, conversion time: 10s, reaches the maximum (low) temperature lasting time: 15 min, interconnection resistance change rate <10% (part of the customer requirements <5%).

B. Improving direction. Cracks appearing after high temperature sections,it’s related to the Tg value sheet, hole quality, front etchback of PTH, reduced thickness swelling degree square shaft 2 should make the best choice of material.

2. Drilling

Three different types of pads (phenolic pads, wooden pads and melamine pads) were used for drilling experiments. After drilling, the hole wall sludge was observed by SEM, the results show that the sludge on both sides of the hole wall of the phenolic pad is relatively more; when the wooden pad is used, there is more sludge on the side of the hole wall and the sludge on the other side is less; when the melamine pad is used, the drilling sludge is evenly distributed on the wall of the hole, the amount of sludge is relatively small

3. Etchback. With different etchback methods, the amount of etchback on the hole wall will be slightly different. How to effectively remove epoxy  stains, ensure that the hole wall roughness meets the requirements and reduce the wicking effect, is a headache problem for many PCB processing manufacturers. Because the hole wall roughness is too large, it will lead to air blow holes during welding and coating breakage during high and low temperature cycles; large wicking effect may cause electromigration between holes and form short circuits; if the amount of etchback is relatively small, cracks at the joints may occur after high and low temperature cycling.

4. Electromigration problem: under the conditions of high temperature and high humidity environment, due to the existence of the primary battery phenomenon, the electromigration phenomenon (also known as electrocorrosion) may occur in the PCB, which will cause the insulation resistance between the insulators to continue to decrease with time, or even secondary hazards such as short circuit, component heating, and fire. Therefore, automotive manufacturers attach more and more attention to this aspect.