Using Wire-Arc Thermal Spray to Seal Narrow Gaps in Aluminum Plates

Electronic cooling systems utilize aluminum heat sinks with machined internal channels for water flow. Cavities in the heat sinks are closed by metal plates that are held in place by screws and sealed with gaskets, or the plates are permanently joined using brazing or friction stir welding. However, these methods present certain challenges. We demonstrate that wire arc spray offers a rapid and economical method for joining aluminum plates and sealing the gaps between them. Aluminum plates were placed on ledges along the edges of cavities in aluminum heat sinks with a 4 mm wide gap between the chamber and the aluminum lid. A twin-wire arc system was used to spray aluminum into the gap, forming a water-tight seal and securing the lid. We varied the angle of the gap sidewalls (from 30° to 90°), the substrate temperature (25 °C or 150 °C) and the standoff distance from the spray torch to the substrate (4", 6" and 9"). Cross-sections of the sprayed joints were taken to measure porosity. The results show that the best seal is achieved by spraying on a groove with a 45° tilted sidewall, using a 6"standoff distance and a substrate temperature of 150 °C.