High Reliability Engineered Copper SMT Bonding Material

Abstract

We set out to affirm the high reliability of a novel nanocopper-based highly conductive bond agent that allows the formulation of an entire suite of Tunable Engineered Copper (TEC) pastes and inks suited for a wide range of SMT die-bonding and packaging applications. In this paper, we present comprehensive thermal cycling and thermal shock data on 3×3 mm silicon carbide (SiC) dies bonded to patterned direct-bond copper (DBC) aluminum nitride (AlN) substrates. We found a 100% survival rate for over 100 devices tested across 3 different test series substantiating the high reliability provided by TEC. Some parts even survived repeated 100 kg shear loads (>110 MPa) after thermal treatment without failing. The pressure-less, fused-copper interfaces exhibit superior electrical (as high as 70% IACS) and thermal (as high as 330 W/m·K) conductivity compared to common tin-based solders and sintered silver. Therefore, TEC offers for the first time a viable all-copper SMT material completely decoupling process-temperature from operating temperature that enables all-copper packaging systems that eliminates brittle IMC formation. High-temperature stability has already been tested to over 500°C. With these properties, it is vastly superior to sintered silver and processable without the need for pressure during fusion with just a few minutes processing time. TEC has been under development for over 10 years and recently matured to the point that it can be integrated into commercial products.