Platinum Metals Rev., 1988, 32, (3), 118
Wiring Up Microelectronic Implants
Fine platinum and platinum-iridium wires, when insulated with silicone rubber, PTFE or a synthetic enamel, are suitable conductor materials for wiring up microelectronic implants, being neutral with regard to body tissues and the fluids they come into contact with. Of the possible ways of making connections to such wires, mechanical clamping is too clumsy, soldering is generally mechanically weak, while welding is inconvenient and may damage the wire; fortunately, a recent technical note from the Medical Research Council’s Neurological Prosthesis Unit describes a micro-brazing process which enables strong bonds to be made (“Technical Note: Microbrazing Fine Platinum Wires”, P. E. K. Donaldson, J. Med. Eng. Technol., 1988, 12, (1), 24–25).
Pure gold, in the form of a helix of 75μ m diameter wire, is threaded over the platinum wires to be joined and is then heated to a temperature between 1063 and 1755°C. This may be done in a variety of ways, and the circuit of a suitable micro-arc generator for forming the braze is given.