Research on low temperature bonding using nanoporous copper

In order to extend the performances of integrated circuit (IC), new bonding approaches are being explored. Since copper has good electrical and thermal conductivity, and relatively low cost, it is widely used as the bonding material for advanced packaging. Unfortunately, the normal direct copper-to-copper bonding demands relatively high temperature, which greatly limits its applications. A low temperature thermo-compression bonding technology using nanoporous copper (NPC) was presented in this work. The low temperature bonding using nanoporous copper with less bonding duration was studied, as well as the bonding qualities of nanoporous copper samples of different thickness. Uniaxial tensile tests were performed to the bonded samples. The section-view SEM images of the bonded layers were captured. Both the images and the test results indicated that the bonded samples with 500nm thick NPC possess a higher bonding quality. However the bonded samples with thicker or thinner NPC failed to reveal good bonding qualities.