Bonding Condition Evaluation using a Melting-Point-Change Type Conductive Paste

摘要

Nowadays advanced board structures are made of two different circuit boards interconnected to each other. As these circuit boards are made of different materials and have to go through different manufacturing processes, the use of a specific conductive paste is needed for a reliable interconnection. To realize this complex structure, we worked on the development of an innovative conductive paste overcoming the weaknesses of the conventional one. It is a melting-point-change type conductive paste in which a large spherical copper (Cu) powder is used as a conductive filler and an alloy of tin (Sn) and bismuth (Bi) is coated on its surface. The conductive paste is expected to stabilize the bonding by tolerating the scatter of the thickness, it also has to maintain a long-term electrical reliability. In this paper, we determined the fundamental composition of the paste to answer these needs. To evaluate the performance of the bonding we studied the influence of the electrical reliability of the paste at its optimum bonding condition, the aggregability of the resin and the bonding strength. Finally, we created a complex structure with the paste to analyze the tolerance of the bonding height and its electrical resistance through a thermal cycle (TC) test.