Cold Forging Process application in LED heatsink process
A Cold forged heatsink is a good alternative to casting to form complex shapes with excellent thermal conductivity. The Cold forging process can make almost perfectly straight allowing for more fins per square mm. Cold forged heatsink shapes include plate fin heat sinks, round pin heat sinks, and elliptical fin heat sinks. Cold forged heatsink manufacture lends itself very well to using copper because high temperatures are not required to shape the copper heatsink, and it can be formed with minimal damage. Secondary machining operations such as hole, chamfer, and steps can be usually included in the cold forged heatsink manufacture reducing waste. Forging involves the shaping of metal using localized compressive forces.
A Forged heatsink is manufactured using a modification of this process called cold forging. Cold forging uses high pressure and low temperature to ensure that no air bubbles, or other impurities are trapped in the material. This improves the thermal properties of the heatsink, and increases the density of the material. Radian Thermal Products utilizes special open die tooling and intense pressure to produces high precision heatsinks with high aspect ratios. A Forged heatsink is typically manufactured one part at a time, and can be can be made from AL 6063 or C1100. Aspect ratio up to 35:1 are feasible, and no draft angles required on fins. Fins can be round, elliptical, straight or any combination on the same part.
An added benefit of this process is that a forged heatsink of the same design can be manufactured with different heights using only one set of forging die. When working with high aspect ratio, or dense fins a forged heatsink has no thermal interface between the fins/pins, and the base which will provide better performance compared with stamped-fin or bonded-fin heat sinks. Heat distribution can be further improved in aluminum heatsinks by embedding a copper inserts into the base during the forging. As this process is fairly expensive, for small volumes it may be worth exploring extrusion with a cross cut to produce square pins. For larger volumes die cast is a good alternative.
The low thermal resistance of pin fin heat sink mainly benefits from the following characteristics: cylindrical pin, omnidirectional structure of pin array and its large surface area, as well as the high thermal conductivity of base and pin, which help to improve the performance of heat sink. Compared with square or rectangular fins, the resistance of cylindrical pins to air flow is low, and the omni-directional structure of pin array helps the surrounding air flow in and out of pin array conveniently.
