Open-celled copper foam is a promising heat exchanging material in high performance electronics cooling.  The copper foam structure fully-penetrates the flow of liquid coolant conducting heat away from the substrate into the liquid.  Lower amounts of pores-per-inch (PPI) copper foam provide enhanced mixing of the flowing coolant.  Higher amounts of PPI copper foam provide microchannel cooling.

             The challenge of brazing open-celled foam to a substrate is to effectively attach a multitude of individual foam ligaments and cell nodes to the substrate without corrupting the structure.  For a given density of foam, the ligaments are at their largest diameter for low PPI foam, however, the number of ligaments and cell nodes are few compared to high PPI foam.  However, at the same given density, the ligaments are at their smallest diameter for high PPI foam.  Additionally, high PPI foams are susceptible to braze filler metal corruption of the foam’s reticulated structure. 

            This paper will discuss numerous brazing methods and materials for attaching open-celled copper foam to copper substrates.  The use of braze filler metal slurries, foils, and plated-substrates will be discussed.  Additionally, some novel techniques will be presented.