There are some bad BGA soldering issues in PCBA board sometimes. If there is a problem with the soldering of a BGA, as a result, then the whole board will have issue. In this case, BGA repair is required.
Four methods for PCBA processing to do BGA rework
1) Formal Installation Method (Using Ball-Setting Fixture)
1. Place the cleaned and flat BGA pads upwards and place them on the BGA support platform at the bottom of the ball placement fixture.
2. Prepare a small template that matches the BGA pad. The opening size of the template should be 0.05-0.1mm larger than the diameter of the solder ball; The disc is aligned and secured.
3. Place the BGA with the paste flux or solder paste printed on the BGA support platform at the bottom of the ball placement tool, with the printing side facing up.
4. Move the stencil to the top of the BGA (the position that has been aligned in the front), evenly skim the solder balls on the stencil, and shake the ball-setting tool so that there is exactly one solder ball in each leak hole on the surface of the stencil. The solder balls are pulled off the stencil with tweezers.
5. Remove the template.
6. Check whether there is a lack of solder balls on each pad of the BGA device, and fill up the solder balls with tweezers.
2)Manual Placement of Solder Balls
1. Place the BGA chips with the paste-like flux or solder paste printed on the workbench, with the flux-like or solder paste face up.
2. Like the SMT assembly, use tweezers or a suction pen to place the solder balls one by one on the printed paste flux or solder.
3)Directly print an appropriate amount of solder paste and form solder balls through reflow soldering
1. Increase the thickness of the template when SMT is processing the template, and slightly enlarge the opening size of the template.
2. Printing solder paste.
3. Reflow soldering. Solder balls are formed after soldering due to surface tension.
4)Reflow Soldering
Perform reflow soldering as described in the previous section on BGA Repair Process. When soldering, the solder balls of the BGA chips are facing upward, and the amount of hot air is adjusted to the minimum to prevent the solder balls from being blown away. After the reflow soldering process, the solder balls are fixed on the BGA chips. It is carried out in a reflow soldering furnace. The soldering temperature is slightly lower than that of the reflow soldering of the assembly board. After the ball placement process is completed, the BGA chips should be cleaned and mounted and soldered as soon as possible to prevent the solder balls from being oxidized and the device getting damp.
Conclusion
Among the above 4 ball placement methods, the front mounting method (using the ball placement fixture) has the best effect;The flip-chip method (using the ball placement equipment) is the method used for BGA chips packaging, because we purchase the solder balls from the solder paste manufacturer. Poor dimensional accuracy, resulting in some solder balls with small diameters that cannot be activated by paste flux or solder paste; The efficiency of manually placing solder balls is relatively low; Directly printing Shixing solder paste and forming solder by reflow soldering The ball method is the easiest, but this kind of solder ball has poor density and is prone to voids.
