Development and analysis of noble-metal wire interconnections on Au thick film using parallel gap welding technique for MEMS and microsystems

Many engineering applications, particularly that of electronic packaging interconnect design, require reduced feature size and use of heat stable materials. Parallel gap welding is an attractive joining method for the formation of thermally and mechanically stable Pb-free bonds in electronic and electrical devices. This type of welding is useful in producing strong interconnections on thick-film pads on ceramic substrates. A solid phase-thermo compression type bond is formed using parallel gap resistance welder. The service temperature of these joints is much higher than their fabrication temperature depending upon the material system involved. This study is focused at noble metal wire welding on thick gold film using parallel gap welding technique. Screen printed gold thick films are prepared on ceramic substrate. Interconnections are prepared with variable operations including voltage and pulse duration; electrode type, size and gap; and force on the weld head. Surface impression of thick film and at joint for different parameter settings of the welder are analyzed and optimized. This joining technique is very useful in MEMS packaging and gas sensor micro-hot plate connections where high temperature stable joints are required.