Silver nano-particle (AgNP) sintering has been a promising bonding material for high-temperature applications. There is an increasing demand for designs implemented as multi-chip module (MCM) in the high-temperature markets, like the oil and gas industry, primarily because of MCM's smaller size, higher-performance capability, and higher overall reliability when compared to traditional high Tg printed circuit boards.
In this work, pressure-less AgNP sintering paste was used in the assembly of multi-chip modules. The assemblies included die-mounted on aluminum nitride and alumina substrates that were metallized with various thin and thick films. Sintered silver nano-particle attachments were also attempted for surface-mounted technology (SMT) chip components. Different assembly parameters such as bonding line thickness and sintering profiles were evaluated to discover the optimal assembly process window that would yield acceptable reliability for 250°C and higher ambient temperature applications. The assemblies were subjected to various tests including thermal cycling, high-ramp rate thermal shocks, and high-temperature storage tests. Shear strength measurements and analysis of the cross sections and fracture surfaces were performed to understand failure mechanisms.
One of the findings was a certain and unique failure mode associated with bonding of thin-film gold metallized surfaces using pressure-less silver nano-particles sintering. That failure mode begins after a short exposure to temperatures of 200°C and higher. However, silver nano-particle sintering on substrates metallized with thin-film silver and some thick-film formulations yields dramatically better results.
Fabrication of Ceramic Thin Film Type Pressure Sensors for High-Temperature Applications and Their Characteristics