Reliability investigation of nano-enhanced thermal conductive adhesives

This paper deals with silver (Ag) coated silicon carbide nanoparticles (SiC@Ag NPs) for thermal conductive interconnect and die attach applications. The development of thermal interface materials with high thermal conductivity and excellent reliability has already been identified by the microsystems industry as one of the major bottlenecks hindering further integration at packaging level. In this paper, a new nano-enhanced high thermal conductive adhesive (TCA) has been developed and characterized. The composition is based on a high temperature conductive epoxy matrix and micro-sized Ag flakes. Efficient heat transfer is achieved through adding SiC@Ag NPs into the material. This special nanoparticle could increase thermal conductivity of the entire system (compared to no addition of nanoparticles) while having little effect on the electrical performance. To achieve these special double-layer nanoparticles, a new method was developed to do the silver plating. Transmission Electron Micro-scope (TEM) results indicate that a consistent silver layer was deposited homogeneously on the surface of SiC. Thermal conductivity test was performed after the SiC@Ag NPs were added into TCA. The results show that no obvious changes of thermal conductivity were observed when the ratio of nanoparticles increased from 0 to 1%, and the value is about 4.0w/(m*K). However, a significant improvement of thermal conductivity (8.3 w/(m*K)) was observed when the weight percentage of nano-particles reached to 3%. This increment was 100% higher than the case without nanoparticles. Further, electrical properties and reliability characterization were also studied in this work. The bulk resistivity results showed that adding a small amount of nanoparticles had little effect on the electrical performance of the entire system. The effects of addition of nanoparticles on the viscosity of the TCA were also measured.