Thermal performance and reliability assessment of nano-sintered silver die attach materials

Thermal test vehicles were fabricated with three different commercially available die attach materials: two Nano-Sintered Silver (NSS) materials and a Silver Filled Die Attach (SFDA). The thermal resistances of individual components were determined after their initial assembly and as they accumulated a total of 1500 thermal shocks from -55°C to +125°C. Initial testing showed that the package-level thermal resistance of test vehicles with NSS was approximately half that of the test vehicles with SFDA. This improvement was maintained during the course of the thermal cycling, in which the average thermal resistance of all of the packaged devices increased. Finite element modeling indicated that the effective thermal conductivity of the NSS materials was considerably better than the SFDA, but also indicated that the thermal cycling degraded their performance to a much greater extent. Test vehicles with the NSS materials were also more likely to exhibit poor adhesion of the encapsulant, which indicates that these materials may require alternate processing steps to ensure high reliability.