Delamination cracking in encapsulated flip chips

In this paper, finite element analyses of delamination in flip chip assemblies are described to investigate delamination at the encapsulant/chip interface along the thickness of the chip under thermal loading, and to determine the potential for interconnection failures resulting from this type of delamination. It is shown that operating conditions, the mismatch in thermal expansion between the silicon chip of a flip chip assembly and an organic substrate subjects the solder joints to extremely large strains, which may result in premature failure of the solder connections. Although underfill encapsulation can reduce the strains in the solder joints, it results in the potential for cracking at the chip-underfill-substrate interfaces during temperature cycling.