Isotropic Thermal Expansion Properties of Cast Aluminum Plate
Cast aluminum plate delivers isotropic thermal expansion across all orthogonal axes due to its stress-relieved equiaxed grain structure.
Thermal Contact Conductance
Meaning
Interface heat transfer properties describe the ability of thermal energy to flow across the joint between two solid surfaces. This metric, thermal contact conductance, is determined by the microscopic contact area and the presence of any interface materials. In high-power semiconductor modules, maximizing this value prevents localized overheating by facilitating rapid heat dissipation to the heatsink.
Surface Geometry
Microscopic surface roughness creates air gaps that act as thermal barriers because air is a poor conductor of heat. Even finely polished surfaces only touch at the peaks of their roughness profile, restricting the actual heat flow path to these isolated points. Machining tolerances must be tightly controlled to minimize these gaps and improve the overall heat transfer efficiency.
Joint Pressure
Clamping force increases the real contact area by flattening the surface peaks and bringing more material into direct contact. This mechanical load reduces the thickness of any gas gaps and directly raises the interface conductance. Mechanical engineers specify torque values for fasteners to maintain this pressure across all operating temperatures.
Filler Influence
Thermal interface materials such as grease or phase-change compounds are applied to fill the microscopic gaps. These materials displace the trapped air and provide a higher conductivity path than the empty gaps they replace. Solid sheets of indium or copper are selected when grease migration poses a contamination risk in sensitive optical or space environments.
Thermal engineers measure this parameter in test fixtures to qualify the compound before approving it for production assemblies.