Reliability Assessment of a New Power Electronics Packaging Material: Silver Diamond Composite

Abstract

A reliability analysis of silver diamond composites in terms of both thermal and mechanical properties is presented. This new material is an attractive solution for power electronics packaging, because an improvement of 50% in terms of thermal management and channel temperature can be obtained when using silver diamond composites as a base plate in packages compared with the more traditionally used materials such as CuW. However, to date, little is known about the reliability of this new material, such as changes induced in its properties by thermal cycling. Assessment of the reliability of silver diamond composites is the aim of this work. Samples were submitted to 10 thermal cycles from room temperature to 350°C, and subsequently, a further 500 cycles of thermal shock as well as thermal cycling from −55°C to 125°C following typical standards used in space and military applications. In the worst-case scenario, thermal conductivity only decreased from 830 W/m·K to ∼700 W/m·K. An increase in the coefficient of thermal expansion and a change in diamond stress, were also observed after thermal cycling. Some structural modifications at the silver-diamond interface were found to be the underlying reason for the observed material properties change. These structural changes take place after the initial thermal cycling, and are constant thereafter. Changes found in thermal properties are satisfactory for enabling a significant improvement to standard CuW packaging materials.