US Patent 7378746 Composite bump

A composite bump suitable for disposing on a substrate pad is provided. The composite bump includes a compliant body and an outer conductive layer. The coefficient of thermal expansion (CTE) of the compliant body is between 5 ppm/° C. and 200 ppm/° C. The outer conductive layer covers the compliant body and is electrically connected to the pad. The compliant body can provide a stress buffering effect for a bonding operation. Furthermore, by setting of the CTE of the compliant body within a preferable range, damages caused by thermal stress are reduced while the bonding effect is enhanced.