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What is PCBA Assembly Reliability Design?
Mar 22, 2018

Assembly reliability, also known as process reliability, usually refers to the ability of PCBA not to be damaged by normal operation during assembly. If not designed properly, it is easy to damage or damage soldered solder joints or components.Stress-sensitive devices such as BGAs, chip capacitors, and crystal oscillators are easily damaged by mechanical or thermal stress. Therefore, the design should be laid out in a place where the PCB is not easily deformed, or a ruggedized design, or appropriate measures can be taken to avoid them.

 

(1) Stress-sensitive components should be placed as far as possible where they are bent away from PCB assembly. If you want to eliminate the bending deformation when the daughter board is assembled, you should place the connector cloth on the daughter board that is connected with the mother board as far as possible on the edge of the daughter board. The distance to the screw should not exceed 10 mm.

 

For another example, in order to avoid stress fracture of the BGA solder joints, the layout of the BGA in the PCB assembly where bending tends to occur is avoided. The poor design of the BGA makes it very easy to crack the solder joints when holding the board with one hand.

 

(2) Reinforce the corners of large-size BGA.

 

When the PCB is bent, the solder joints in the four corners of the BGA are subjected to the greatest stress and are most likely to crack or fracture. Therefore, the reinforcement of the four corners of the BGA is very effective for the prevention of cracking of corner joints. It should be reinforced with special glue, or it can be reinforced with patch glue. This requires space for components to be laid out and indicates the requirements and methods for reinforcement in the process documentation.

 

The above two suggestions are mainly based on design considerations. On the other hand, the assembly process should be improved to reduce the stress. For example, to avoid holding the board with one hand and using the supporting tooling with the screws. Therefore, the design of assembly reliability should not be limited to component layout improvements. More importantly, it should start from reducing the stress of assembly—using appropriate methods and tools, strengthening personnel training, and standardizing the operation. Only in this way can the assembly phase take place. Solder joint failure.

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