Thinning of a die-cast heat sink is required to meet weight reduction demands by automakers. Our laboratory focused on the property of Al-25%Si that it is hard to solidify, and produced thin walled heat sinks, which are said to be quite difficult to manufacture. Using ADC12, the fin tips of thin walled heat sinks were unfilled. This result made us think that various alloys have a difference in filling and we investigated the relation between aluminum types and the condition of the fin tips. The result showed that whether the temperature of molten metal in mold can be maintained or not was most important factor, not the alloy types.
