Effect of radius of cylinder on thermal resistance of line contact cooling block for semiconductor

Conduction cooling using a line contact cooling block made of highly heat-conducting ceramics is discussed. The line contact is created by a flat surface block in contact with a cylindrical surface, the gap on either side being filled by grease. Measurements show that the thermal resistance increases as the radius of the cylinder increases. This is especially marked when the dimensionless radius r /S<100 (r is the radius of the cylinder and S is the width of the contact). The total thermal resistance consists of two parts. One is the contribution of the gap between the flat surface and the geometric surface parallel to it and tangent to the cylindrical surface; the other is due to the remainder of the space between the flat and cylindrical surfaces. When r/S≫100, the thermal resistance approaches that of a grease-filled gap of 10-μm width between two flat surfaces. The influence of surface roughness is negligible for Ra<0.5 μm