The incomplete solder joint in BGA repair indicates an insufficient volume of solder, leading to unreliable connections in BGA welding. This is characterized by the significantly smaller size of the joint compared to others during AXI inspection. The root cause of this issue is often insufficient solder paste, as well as the core-suction phenomenon of the solder, causing the solder to flow into the through hole due to the capillary effect. Patch offset, solder print offset, and BGA pad and defect through the hole without solder resistance film isolation can also contribute to incomplete solder joints. Additionally, damaged welding resistance film during the repair process and incorrect design, such as holes on the BGA pad, can further aggravate the problem.
To address this issue, the following measures can be taken:
- Ensure enough solder paste is printed
- Cover holes with solder resistance to prevent solder loss
- Take care to avoid damaging the solder resistance layer during BGA repair
- Ensure accurate alignment when printing solder paste
- Ensure the accuracy of BGA patch
- Properly operate BGA components during the repair stage
- Meet coplanarity requirements of PCB and BGA to avoid warping, such as through appropriate preheating
- Consider using microhole technology instead of plate hole design to reduce solder loss.
