Emerging lead-free, high-temperature die-attach technology enabled by low-temperature sintering of nanoscale silver pastes

A low-temperature joining technology based on silver sintering, which is being implemented in manufacturing of power electronics modules, holds the promise of achieving 5times higher temperature cycling capability, 3times better total module resistance, and chip junction temperature up to 175degC. Because of its RoHS compliance, the technology is also aggressively pursued by the makers of automotive power electronics components. However, a serious drawback of the technology is the use of high quasi-static pressure (> 40 MPa or 400 kg-force per cm² chip area) necessary to lower the sintering temperature of existing thick-film silver pastes to less than 300degC. In this paper, we describe the die-attach application of a nanoscale silver paste that can be sintered at low temperature without pressure. Mechanical, thermal, and thermo-mechanical properties of the sintered silver joints are reported.