Method for selective solder paste application for BGA rework

The reflow soldering of BGA (ball grid array) packaged components always raise quality and reliability issues since bridges and open joints can form easily due to the warpage of PCBs and packages. Since the highly integrated circuit boards are relatively expensive the rework of failed BGA packages is absolutely necessary. During the rework process the deposition of solder paste is one of the key issues, which is usually carried out by mini stencil printing and always gives a challenge for engineers in the case of large size fine pitch BGA packages. A solution can be to apply the solder paste by dipping the BGA package into the paste in the same way as in package on package (PoP) technology. Experiment and testboard was designed in order to investigate the quality of reworked BGA solder joints, which meant to be dipped into a newly developed low viscosity solder paste. In the experiment we plan to rework BGA packaged components in two ways; on one hand solder paste is deposited by stencil printing and on the other hand the packages are dipped into the newly developed paste. The solder joints are planned to be inspected by X-ray microscopy.