Thermal resistance of eutectic Ga-In-Sn/particles binary thermal interface materials

Abstract

With the continuous improvement of the integration of microelectronic chips, the heat dissipation of microelectronic chips is becoming more and more challenging. The interface thermal resistance is particularly prominent in the heat dissipation, and the use of thermal interface materials (TIMs) is generally considered to be an effective way to reduce interface thermal resistance. Low melting temperature alloy (LMTA) is an ideal thermal interface material due to its low interface thermal resistance and good thermal conductivity. However, LMTAs are always prone to failure or cause circuit failure due to its good fluidity and low viscosity in work environment. The eutectic Ga-In-Sn low melting temperature alloy (Ga-In-Sn LMTA) has a melting point of about and a thermal conductivity of about 39, which make it applicable as a TIM. In this paper, thermal conductive particles, such as diamond and Tungsten, were added into the Ga- In-Sn LMTA to fabricate composite TIMs. By this method, the overflow of the LMTA may be effectively retard, and the thermal conductivity of the TIMs can also be enhanced. To improve the wetting contact property and the interface combination status between diamond fillers and liquid metal matrix, chromium transition layer was coated on the surfaces of diamond particles by magnetron sputtering method. The interfacial microstructure between diamond and the LMTA is analyzed by field emission scanning electron microscope (SEM) and x-ray energy dispersive spectroscopy (EDS). Thermal resistance of the composite TIMs is measured by a steady-state heat flow analysis using a specific layer structure sample, and a corresponding theoretical simulation model is constructed subsequently. Meanwhile, the effect of agglomeration of thermal conductive particles on the thermal flux density of LMT A/particles composite TIMs is also explored. The results show that addition of chromium-coated diamond particles and tungsten micro particles can dramatically increase the thermal conductivity of eutectic Ga-In-Sn LMTA at room temperature. The SEM images show that the diamond and tungsten particles were coated effectively by the eutectic Ga-In-Sn LMTA, which suggest good wetting and good interfacial contact. Particularly, the wettability between chromium coated diamond and eutectic Ga- In-Sn LMTA is significantly enhanced, indicating that chromium can be used as the medium layer between heat-conducting particles and the metal substrates to maintain longterm reliable service of eutectic Ga-In-Sn LMTA TIMs. Thermal flux results of finite element analysis show that the efficient heat transfer channels were established by connecting the heat-conducting fillers with eutectic Ga-In-Sn LMTA, and play a significant role in the composite TIMs.