THERMAL CONDUCTIVITY AND THERMAL AGING PERFORMANCE OF Sn WITH 0.7 wt.% Cu and VARIOUS GRAPHENE ADDITIONS

The effect of graphene content (0.08, 0.16 and 0.33wt.%) on the thermal conductivity and thermal aging performance of an Sn based composite material with 0.7wt.% Cu and various graphene additions was investigated via X-ray diffraction (XRD), scanning electron microscope (SEM) and accelerated thermal aging test. The XRD results showed that the graphene diffraction intensity was weak (approximately 10∘) due to little content and distribution of the graphene on the surface of the composite materials. After thermal aging testing the diffraction intensity on some crystal planes of the composite materials was enhanced, proving that preferential growth occurs on the crystal plane. SEM results showed that before aging testing no whiskers were generated on the surface of the composite materials. After the accelerated thermal aging at 100∘C for 24h, whisker growth became apparent in the composite materials. All the whiskers were located in the grains rather than on the grain boundaries of the composite materials. The highest thermal conductivity was obtained at 0.16wt.% graphene addition (indicated as 0.16wt.% graphene–0.7wt.% Cu/Sn). After the accelerated thermal aging at 100∘C for 24h, the bamboo-shaped whiskers with a low aspect ratio grew in large quantities on the surface of the 0.16wt.% graphene–0.7wt.% Cu/Sn composite material, while when the aging was at 100∘C for 366h the thermal conductivity decreased from 67Wm−1K−1 to 52Wm−1K−1. When the graphene addition was 0.33wt.% (indicated as 0.33wt.% graphene–0.7wt.% Cu/Sn) the thermal conductivity maintains a value above 59Wm−1K−1 after the accelerated thermal aging.