Stress-sensitive devices such as BGA, chip capacitors, and crystal oscillators are easily damaged by mechanical or thermal stress. Therefore, the design should be placed in a place where the PCB is not easily deformed, or a reinforcement design should be performed, or appropriate measures should be taken to avoid it.

(1) Stress-sensitive components should be placed as far as possible away from places that are prone to bending during PCB assembly. For example, in order to eliminate the bending deformation during the assembly of the daughter board, the connector connecting the daughter board with the mother board should be placed on the edge of the daughter board as much as possible, and the distance from the screw should not exceed 10mm.

For another example, in order to avoid stress fracture of BGA solder joints, avoid placing the BGA in places that are prone to bending during PCB assembly. The poor design of the BGA can easily cause its solder joints to crack when the board is held with one hand.

(2) Reinforce the four corners of the large-size BGA. When the PCB is bent, the solder joints at the four corners of the BGA are subjected to the greatest force and are most likely to crack or break. Therefore, it is very effective to strengthen the four corners of the BGA to prevent the cracking of the corner solder joints. Special glue should be used for reinforcement, or patch glue can be used for reinforcement. This requires space for component layout, and the reinforcement requirements and methods are indicated on the process document.

The above two suggestions are mainly from design considerations. On the other hand, the assembly process should be improved to reduce the generation of stress, such as avoiding holding the board with one hand and using support tooling for installation screws. Therefore, the design of assembly reliability should not be limited to the improvement of the layout of components, but should start from reducing the stress of assembly - using appropriate methods and tools, strengthening personnel training, and standardizing operating actions, only in this way can the occurrence of the assembly stage be solved. Solder joint failure problem.