A Diecast heatsink uses the Diecast process by forcing molten metal under high pressure into a molded cavity. The molded cavity is created using a hardened tool steel die which is carefully machined into a predesignated shape. The casting equipment and the metal dies represent large capital cost which tend to limit the process to high volume production applications.
Radian’s Diecast heatsink utilizes a hot-chamber die casting process which relies upon a pool of molten metal to feed the die. A pneumatic or hydraulic powered piston forces molten metal into the die. The advantages of this system include fast cycle times (approximately 15 cycles a minute). Radian diecast heatsinks are primarily manufactured using aluminum based alloys (356.0, A380).
In the process, two halves of a die are required in the die casting process. One half is called the “cover die half” and the other is called the “ejector die half”. A parting line is created on the part where the two die halves meet. The die is designed so that the finished casting will slide off the cover half of the die and remain in the ejector half as the die is opened. The ejector half contains ejector pins to push the casting out of the ejector die half. In order to prevent damage to the casting, an ejector pin plate accurately drives all of the pins out of the ejector die at the same time and with the same force. The ejector pin plate also retracts the pins after ejecting the casting to prepare for the next shot.
Excess material such as metal extension can be removed from the ejected die cast heatsink through a secondary machining operation. Casting metal extension removal cost can be reduced if the amount of metal extension to be removed and the removal method to be employed are considered in the early stages of the design. For Multi-slide casting machine allow very complex designs but adds additional costs. For more information on the casting process we would recommend the following:
Radian can also provide rapid prototyping to cast prototypes in the same alloy without hard tooling which allows for addition changes to the mold.
The following are the typical steps in Radian’s die casting process:
• Create the Die mold
• Lubricate the Die
• Fill the die with molten metal
• Ejection from the cover die half
• Shakeout from the ejector die half
• Trimming and then grinding the excess material
• Powder coat, Paint, or Anodize
Diecast Heatsink Material
Using Aluminum with a high purity produces a good heatsink that is efficient in removing heat from electronic components. Aluminum can be difficult to die cast, so impurities are often added to aid in the die casting process. This does affects the thermal performance of the metal due to reduced thermal conductivity. Most aluminum diecast companies use A380 which hel[p the structural strength of the product. Radian uses 356.0 for the improved thermal properties which is similar to the thermal conductivity of aluminum used in extruded or machined heatsinks of 160-200 W/m-K.
Die-casting is ideal for high volume applications that can support initial Non-recurring Engineering charge. Typically at around 5,000 pieces the initial NRE is covered by the reduced part cost. Once set up the manufacturing process time is shorter than other methods and saves money when producing heatsinks in higher volumes. Another benefit is that die-casting can support complex geometries that can be challenging to produce by other processes. By casting parts that are near the final shape of the product, you can eliminate or reduce the final machining operation.
Cast Roundpin Heatsinks
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