Assembly challenges of high density large fine pitch lead-free flip chip package

Assembly challenges for a high density, high performance integrated circuit package have been studied with respect to leadfree solder, fine pitch, large die on an organic substrate. The stresses induced by the large die size, higher reflow temperature due to lead-free solder and the low solder standoff due to fine-pitch configuration has shown to affect the quality of the assembly package. Solder crack was observed immediately after reflow of the large die package and the crack solder has been resolved by increasing the solder standoff of the package. A more compliant thin silicon die of 300 microns thickness is able to have good solder joint with lower solder standoff than 600microns thick silicon die. Underfill/flux materials system is used to enhance the package's reliability performance. The underfill/flux material system has been selected based on the processability, adhesion strength and reliability performance. The study conducted indicated that high adhesion strength is preferred for high reliable package