Thermocompression bonding describes a wafer bonding technique and is also referred to as diffusion bonding, pressure joining, thermocompression welding or solid-state welding. Two metals, e.g. gold-gold (Au), are brought into atomic contact applying force and heat simultaneously.[1] The diffusion requires atomic contact between the surfaces due to the atomic motion. The atoms migrate from one crystal lattice to the other one based on crystal lattice vibration.[2] This atomic interaction sticks the interface together.[1] The diffusion process is described by the following three processes:
This method enables internal structure protecting device packages and direct electrical interconnect structures without additional steps beside the surface mounting process.[3]