Metal Matrix Composite (MMC) materials are finding increasing use within the electronics packaging industry due to their excellent coefficient of thermal expansion (CTE), stiffness and thermal management properties. Unfortunately, these composites are not easily electroplated due to the nonconducting phases that make up a high proportion of the surface. Such limitations can be overcome by utilising a spray formed aluminium/silicon alloy which can be compositionally modulated to achieve thermal matching to the electronic materials currently in use. This group of alloys, manufactured by Osprey Metals and known as the CE alloys, may be easily electroplated. These 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 back-filled with solder and used as the EDM tool for machining the package from a plate of Si-Al alloy This paper describes the process of TSE and its application to electronic packages.