Low Temperature Direct Aluminum Soldering Paste

Abstract

For economic and weight considerations using aluminum to make connections to copper has been important in electronic components and making these connections via soldering provides an excellent thermal and electrical pathway. Soldering aluminum to copper in many applications involves the use of low temperature solder bonding to prevent damage to heat sensitive parts such as sealed copper heat pipes and sensitive electronic components. Typically, aluminum soldering is accomplished by plating over the aluminum to make that surface solderable, which is an expensive extra step in this processing. The development of a low temperature direct aluminum soldering paste eliminates the costly plating operation needed to make certain aluminum alloys solderable. The low temperature direct aluminum soldering paste, performing below 200 °C, provides for a soldering option that will work via induction, oven reflow, hot plate, or soldering iron techniques. The paste consists of a special flux medium and a proprietary low temperature lead-free solder alloy. Evaluation of the solderpaste was by several methods. Solderability testing compared the paste on a variety of aluminum alloys. Soldering joint cross-sectioning followed by scanning electron analysis proves the viability of the solder joints. Tensile strength testing of the solder joints measured the strength of the copper to aluminum and aluminum to aluminum solder joints.