There are generally two methods for reworking BGA chips: BGA rework stations and manual rework with hot air guns. Most factories or repair shops choose BGA rework stations because of their high success rate and simple operation, requiring minimal skills from operators and featuring one-click operation, suitable for batch rework. The second method, manual rework, requires higher technical skills, especially for larger BGA chips. So, how can we improve the yield of BGA rework with manual rework?
Being able to manually solder BGA chips is indeed valuable, as the number of BGA-packaged chips continues to increase. However, many people are still apprehensive about manually soldering BGAs, mainly due to the high cost of these packaged chips, leading to uncertainty. However, success comes with practice. Here are some key points to note:
- After removing the BGA chip, it is essential to reapply solder because some areas may desolder during removal. Both the BGA chip and the mainboard need solder reapplication for good contact. Apply solder paste and use a soldering iron to drag it to ensure good contact.
- When using hot air, the temperature should not be too high, around 280 degrees Celsius is sufficient. Keep the hot air gun at a moderate distance from the soldering board, and move it around to prevent solder beads from scattering.
- The first application of solder may not be uniform. Use a scraper to flatten any uneven spots, then apply solder and reheat.
- After placing the BGA chip, apply flux to it and use the hot air gun to evenly distribute it, ensuring that the solder joints on the BGA chip are well-connected.
- When placing the BGA chip on the mainboard, apply flux to both the BGA chip and the mainboard. This lowers the melting point and allows the BGA chip to connect well with the solder joints on the mainboard. After applying flux, lightly press the edges of the BGA chip with tweezers to ensure good contact.
This method is effective for small BGA chips, but for larger chips like the Northbridge, the success rate is much lower. For larger BGA chips, it is recommended to use a BGA rework station to improve the yield of BGA rework.
In summary, to improve the yield of BGA rework, good rework tools are essential, and controlling the soldering temperature is crucial. High temperatures can damage both the chips and the PCB, while low temperatures may prevent soldering. When manually soldering BGAs, it is important to control the temperature at different stages. Using a BGA rework station can completely avoid this issue.
