Accelerated aging and thermal cycling of low melting temperature alloys as wet thermal interface materials

• LMAs offer extremely low thermal resistances at a thin bond line thickness (BLT)
• LMAs were able to survive as long as 2700 hours of aging at 130 °C
• LMAs placed between bare Cu disks were able to withstand 1400 cycles from -40 to 80 °C
• LMAs are reliable, outperform the commercial TIMs in high-temperature aging and thermal cycling
• The alloy-copper interaction makes the thermal joint even more reliable

This paper focuses on developing an effective thermal interface material (TIM) using low melt alloys (LMAs) containing gallium (Ga), indium (In), bismuth (Bi) and tin (Sn). The investigation described herein involved the thermal performance evaluation of LMAs after accelerated life cycle testing, which included isothermal aging at 130 °C and thermal cycling from - 40 °C to 80 °C. Three alloys (75.5Ga/24.5In, 100Ga, and 51In/32.5Bi/16.5Sn) were chosen as candidate LMA TIMs. The testing methodologies followed ASTM D5470 protocols and the performance of the alloys was compared to commercially available thermal grease and liquid metal TIMs. To understand the LMA-substrate interactions, the alloys were applied to different surfaces (bare copper, nickel coated copper and tungsten coated copper). It was found that the proposed alloys between bare copper substrates were able to survive as long as 2700 h of aging at 130 °C and 1400 cycles from − 40 °C to 80 °C without significant performance degradation.