Miniaturization of electronics demands packing with excellent thermal conductivity. Superior thermal management is elementary to long-term performance of electronic gadgets. Therefore, diamond particles dispersed copper matrix composite is attracting significant interests. In the preparation of copper/diamond composites, a major restriction emanates from the mismatch between the thermal expansion coefficients of diamond and copper, which induces thermal stress easily. Moreover, the non-carbide forming nature of copper as well as the contact angle between copper and diamond translates to lack of strong chemical bonds at the joining interface.
Currently, it is popular to enhance the bonding by introducing another component between diamond and copper. This is usually done through surface metallization of diamond particles or alloying copper matrix. Titanium carbide is known to link diamond reinforcements with the copper matrix tightly.
Researchers led by professor Xitao Wang from the University of Science and Technology in Beijing produced copper-titanium/diamond composites by gas pressure infiltration and investigated the influence of titanium on the microstructure as well as thermal stability with respect to the diamond surface state and structure of the composite. In their work, they found that the amount of titanium added must be limited in a bid to maintain good thermal conductivity in the copper matrix. Their work is published in peer-reviewed journal, Composites: Part A.
The authors observed that diamond particles were evenly distributed in the copper matrix and no defects like cracks were noticed at the interface. The conventional pull-out of diamond particles was rarely seen on the polished surface. That indicated strong interface bonding between copper and diamond particles. These observations indicated superior quality of the composites formed by gas pressure infiltration.
As observed from the fractured surfaces, copper matrix adheres closely to the diamond particles. Some diamond particles were found to fracture trans-granularly. However, this only occurred when bonding strength was higher than the fracture resistance of the particles. Therefore, the addition of titanium improved the interfacial bonding between diamond and copper matrix.
The copper-titanium diamond composites were prepared by gas pressure infiltration, with a discontinuous layer of titanium carbide formed at the joining interface. The presence of titanium carbide was favorable to the enhancement of the interfacial thermal conductance. The findings of this paper suggest that titanium alloying in the copper-matrix composites is an efficient approach to achieving good thermal conductivity of copper-diamond composites.
Jianwei Li, Hailong Zhang, Luhua Wang, Zifan Che, Yang Zhang, Jinguo Wang, Moon J. Kim, and Xitao Wang. Optimized thermal properties in diamond particles reinforced copper titanium matrix composites produced by gas pressure infiltration. Composites: Part A, volume 91 (2016), pages 189-194.Go To Composites Part A: Applied Science and Manufacturing