Thermal compression bonding for fine pitch solder interconnects

Thermal Compression Flip Chip bonding (TCFC) is a new interconnection technology in electronic packaging. With decreasing pitch of solder interconnects, traditional mass reflow solder bump faces the risk of shorting and non-wets for very fine pitch devices. The drive for ever-increasing numbers of interconnects, coupled with limited package size, necessitates finer pitch flip-chip solutions. In this paper, we introduce a TCFC-bonded copper pillar with solder cap interconnect solution, using non-conductive paste (NCP) on a laminate substrate with busless surface finish. This TCFC interconnect provides improved ELK performance relative to traditional mass reflow. The challenges to achieve a reliable TCFC solder joint structure will be discussed from different aspects such as assembly process, substrate surface finish and reliability testing.