Mechanism of Liquid Gallium Corrosions on Metal Heatsinks

High powered electronic devices require liquid gallium (Ga) and Ga-based alloys as high conductive thermal interface materials to efficiently dissipate heat from devices into heatsink often made of aluminum (Al) and copper (Cu). However, the fast and continuous reaction of Ga with metal heatsinks can cause severe corrosion of the heatsink, which can significantly shorten the use life of the electronic devices. This drives us to deep dive the dynamic reaction mechanism of Ga with Al and Cu. The comparable study of Ga corrosion on Al and Cu sheets was captured by in situ digital optical microscope at device operating temperature of 50°C above the melting point of Ga (29.5°C). It was found that liquid Ga penetrates much faster into Al than into Cu at 50°C, therefore, it causes much worse surface corrosion on Al than on Cu. Based on detailed Ga penetration depth analysis, a linear relationship between the penetration depth and reaction time is established, which corresponds well with scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) findings of liquid Ga penetrating Al through its grain boundaries. Based on our qualitative and quantitative studies, the dynamic reaction model of Ga with metal heatsinks is established. Furthermore, to block Ga penetration pathway into Al, nanometer Iridium (Ir) coating was sputtered on the surface of Al, and it was observed that Ga corrosion on Ir coated Al sheets is completely stopped, and there is no Ga corrosion on Ir coated Al sheets. Our research findings showcase an innovative thermal cooling architecture with liquid Ga based alloys sandwiched between high powered electronic devices and nanometer level Ir coated metal heatsinks.