Low Height Ultra-thin Fin on A5083 Aluminum Plate Fabricated by Friction-stir Forming

Recent demands on miniaturization of an electronic apparatus have caused board-space constraints, and thermal management is getting increasingly difficult. Thermal management employing heat sinks is often compromised by the space constraints for a product design. Lower profile passive heat sinks having thin fins are among necessary solutions to these space limitations. Most such products have been generated by conventional or back pressure applied forging. However, thinness of its fin is limited, though a higher density of fins is more effective. This paper describes a new forming technology, friction-stir forming (FSF), to generate a low profile, ultra-thin fin. The suggested process is as follows. The authors put a material plate on a die and conducted friction stirring on its back surface. The material deformed and precisely filled narrow grooves of the die due to high pressure and heat caused by friction stirring. This study investigates the forming conditions and the corresponding results including the height limit of the fin. Consequently, we successfully generated low-profile, ultra-thin fins with 0.5mm thickness and less on 3mm-thick JIS A5083P-O aluminum plate.