Increased System Performance and Reduced Surface Touch (Skin) Temperature in Mobile Electronics Utilizing Composites of Graphite with Ultra-High Spreading Capacity and Insulation with Ultra-Low Thermal Conductivity

Graphite foils with ultra-high spreading capacity and insulation sheets with ultra-low thermal conductivity were combined in a thermally stressed Google Pixel 3XL to reduce steady-state surface touch (skin) temperatures (TS) by up to 3.2 °C with <; 1 °C increase in max junction temperature (TJ) as compared to single-component thermal solutions of graphite, insulation, and air. An axisymmetric conduction model was simulated in COMSOL to determine trends in surface temperature reductions of five unique thermal solutions of comparable thickness (~350μm). Four of these solutions were fabricated, tested and validated experimentally in Google Pixel 3XL thermal stress testing. The composite yielding the greatest Ts reduction was utilized to demonstrate an increase in steady-state system performance while maintaining a surface temperature suitable for user comfort and safety. The steady-state 3DMark - Slingshot Extreme benchmark score increased from 3401 to 3823 resulting in a 12.4% increase in steady-state system performance. The enhanced device performance was linked with material properties by means of steady-state heat flow and thickness testing for through-plane thermal conductivity of insulation, and thermal diffusivity testing for in-plane thermal conductivity of graphite. In-plane conductivity of graphite was validated experimentally in a steady-state heat spreading test where 100 μm foils of high-performance graphite measured ~30% higher spreading capacity than 100 μm foils of synthetic and natural graphite.