Thermal Spray Deposition Technology for Production of Complex Heat Transfer Devices

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Electronic circuits dissipate most of the electrical energy they receive as heat, which must be removed. Circuit boards are mounted on metal plates that have internal passages through which water is circulated. Research into the design of flow passages has shown that heat transfer increases as the channel diameter is reduced, but this increases the pressure drop through them. Also, it is difficult to drill networks of small diameter (< 1mm) channels using conventional techniques. We have developed a new method of fabricating cooling channels in copper and aluminum plates using thermal spray techniques. Channels are milled on the surface of a metal plate in any desired pattern. Inserts in the exact shape of the channels are made using a 3D printer out of a water-soluble polymer. The inserts are placed in the channels and molten metal is sprayed on the surface of the metal plate using a twin wire-arc system. The plate is then placed in an ultrasonic water bath for several hours to dissolve the polymer inserts, leaving open the channels under the sprayed surface. The plates fabricated were found to provide significantly higher heat transfer than commercial cold plates. It was possible to machine multiple passes of the cooling channel in the same plate area, increasing the surface area wetted by the liquid. A longer flow path, and multiple bends in the channel, promoted turbulence in the flow and enhanced heat transfer. This technique can be used to make novel designs of cold plates that can be optimized for specific circuit board layouts. We can make channels on the surface of curved cooling plates, which is important for applications such as battery cooling. This Market Assessment Proposal will help identify commercial demand for this technology in making cooling systems that can be used in the computer, automotive and other industries.