High silicon Si–Al alloys (50–70 wt% Si) have been developed by Osprey Metals Ltd for use in electronic packaging. They have the advantages of a coefficient of thermal expansion that can be tailored to match ceramics and electronic materials (6–11 ppm/K), low density (<2.8 g/cm3) high thermal conductivity (>100 W/m K). These alloys are also environmentally friendly and are easy to recycle.These Osprey alloys can be fabricated readily into electronic packages by conventional machining with tungsten-carbide or polycrystalline diamond (PCD) tools and electro-discharge machining (EDM). Generally more than one of these conventional machining operations is required in the fabrication process. A new and much faster method has been developed which has been used to produce complete electronic packages from plates of Si–Al alloys in a single machining step. In this novel method, known as thin-shell electroforming (TSE), an accurate model of the package is produced directly from the drawing in wax using a 3D Systems ThermoJet Modeller. This model is mounted into a frame and it is then plated with a thin copper electroform. The wax model is then melted leaving the electroform attached to the frame. This is backfilled with solder and used as the EDM tool for machining the package from a plate of Si–Al alloy.
Through the techniques developed by integrating electroforming, rapid prototyping and electro-discharge machining, a number of industrial applications were found. This paper describes their utilisation with Silicon-Aluminium alloys for packaging of electronic and microwave circuitry and the time and cost reductions of this process against conventional packaging manufacture. Industrially/commercially attractive to Osprey Metals Ltd, Neath, Swansea (contact: Dr Andrew Ogilvy, 01639 634121). RAE_import_type : Journal article RAE_uoa_type : General Engineering