A Comparison Between Solders & Transient Liquid Phase Sintered Interconnects in High Temperature Multilayer Ceramic Capacitors

Abstract

There is a long-established market for high temperature multilayer ceramic capacitors (MLCCs) that operate at 150°C and higher in downhole oil and gas exploration, and military and aerospace applications. To maximize the capacitance density and achieve a high degree of mechanical robustness, stacks and leaded form factors have been used with high melting point–Pb-containing solders as the preferred interconnects. However, Pb-containing solders are limited to temperatures below 300°C and are banned from many commercial and automotive applications with further legislation limiting their use planned in the future. Common Pb-free solders such as SAC 305 or SnSb alloys are in widespread use, but their performance at prolonged exposures at 200°C is limited. Exposures to high reflow temperatures during assembly, especially successive reflow operations, can also compromise interconnect integrity. Higher temperature gold-containing solders are widely available, but these are cost-prohibitive and so are not viable ...