A new approach to minimize package warpage in reflow process

Package warpage is often a problem in surface mount reflow process especially for thin package. Large warpage prevents package solder balls to be connected to PCB pads and results in low process yield. In order to effectively minimize warpage in reflow process, this paper proposed a new approach to reduce package warpage by temporally bonding the back of the packaged component to a rigid plate. In the reflow process, the bonded rigid plate reduces the bending of package and makes sure that its warpage is in process limit at all temperatures. The component is soldered on PCB after reflow process. The last step is to remove the plate that is bonded to the packaged component. We employed a thin Flip Chip Ball Grid Array (FCBGA) package with flexible substrate as an example to prove the effectiveness of the new warpage minimization approach.