Bonding development for non-conductive paste (NCP)

Non-conductive paste (NCP) bonding offers fine pitch, simplified process, low packaging cost, and a lead-free interconnect system for flip-chip packaging. However, NCP bonding faces challenges in bonding yield rates. This paper studies bonding optimization through a closed-loop feedback system in order to understand the interaction of NCP materials with the bonding process for gold stud bumps on a rigid substrate. The bonding process is also correlated to conventional bonding study through differential [jgb1] scanning calorimetry (DSC) and macroscopic analysis of the interconnection structure. The study reveals that a significant temperature gradient exists across NCP materials between the die and the substrate, suggesting the existence of an optimal bonding temperature to activate the cross linking of the polymer. A certain threshold force is necessary to provide good physical contact between the gold studs and the bonding pads due to the co-planarity of the bumps. Sufficient dwell time is also necessary to ensure the joints remain in contact while the NCP material is cross linked. This approach simplifies the bonding process for flip-chip assembly