PCBA Tech - PCBA assembly manufacturer-BGA solder joints are not full reasons

PCBA assembly BGA solder joints are not full reasons

For the problem of insufficient solder joints for BGAs, the root cause is insufficient solder paste. Another common cause of underfilled solder joints encountered in PCBA assembly BGA rework is the wicking phenomenon of the solder. The BGA solder flows into the through hole due to the capillary effect to form information. SMD deviation or printed tin deviation and BGA pads and betrayal vias without solder mask isolation may cause wicking, resulting in insufficient BGA solder joints. Special attention should be paid to the fact that if the solder mask is damaged during the rework process of BGA devices, the wicking phenomenon will be aggravated, which will lead to the formation of underfilled solder joints.

Incorrect PCB design can also lead to insufficient solder joints. If a hole in the disk is designed on the BGA pad, a large part of the solder will flow into the hole. If the amount of solder paste provided at this time is insufficient, a low Standoff solder joint will be formed. The way to make up is to increase the amount of solder paste printed. When designing the stencil, consider the amount of solder paste absorbed by the holes in the plate, and increase the thickness of the stencil or increase the size of the opening of the stencil to ensure sufficient solder paste; One solution is to use micro-via technology to replace the hole in the disk design, thereby reducing the loss of solder.

Another factor that produces underfilled solder joints is the poor coplanarity between the device and the PCB. If the amount of solder paste printing is sufficient. However, the gap between BGA and PCB is inconsistent, that is, poor coplanarity will cause insufficient solder joints. This situation is especially common in CBGA.

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Solution to insufficient BGA solder joints in PCBA assembly

1. Print enough solder paste;

2. Cover the vias with solder mask to avoid solder loss;

3. Avoid damaging the solder mask during the rework stage of PCBA assembly and BGA;

4. Accurate alignment when printing solder paste;

5. The accuracy of BGA placement;

6. Correctly operate BGA components during the rework phase;

7. Meet the coplanarity requirements of PCB board and BGA to avoid warpage. For example, proper preheating can be adopted in the rework stage;

8. The BGA in PCBA assembly uses micro-hole technology to replace the hole-in-disk design to reduce the loss of solder.