Silver diamond composite as a new packaging solution: A thermo-mechanical stability study

Abstract

In this work, thermo-mechanical stability of silver diamond composite materials, with thermal conductivities as high as 830 W/mK, was studied. These novel materials have great potential for applications in thermal management and electronic packaging industry. As demonstrated in our previous work, an improvement of 50% in terms of thermal management can be obtained with silver diamond composite with respect to the traditional CuW when used as base plates; however, to date their thermo-mechanical stability has not been assessed yet. Their stability is important for application such as space where thermal cycling is typical. Samples were submitted to ten thermal cycles from room temperature to 350°C, and then to 200 thermal cycles from -55°C to 125°C. Thermal properties such as thermal conductivity and coefficient of thermal expansion as well as diamond particles stress were measured before and after thermal cycles. We found that after thermal cycling, thermal conductivity decreased from 830 W/mK to 760 W/mK at room temperature. An increase in the coefficient of thermal expansion from 6 ppm/K to 7.5 ppm/K, and a diamond stress partial relaxation were also observed after thermal shock. Furthermore, some samples were submitted to a much higher temperature, namely, 780°C and slightly more pronounced degradations were obtained. Such changes in thermal properties are acceptable for many applications and still nevertheless provide a significant improvement to standard CuW heat-sinking materials. Changes in the silver-diamond interface are likely the underlying reasons for the material properties change observed. We can conclude that this material presents a good stability given the harsh conditions under which the tests were performed.