Abstract: The front layer 1 shown in FIG. 1 is being tape cast in the direction of the arrow A from alumina ceramic material 2 onto a mylar layer 3. The doctor blade 4, which regulates the thickness T of the ceramic layer has serrations 5, which form parallel grooves 6 in the front surface 7 of the layer. After the material has set, by evaporation of the moisture allows the material to be sufficiently fluid for its casting, vias apertures 8 are punched in it, whilst it is still supported on the mylar, FIG. 2. They are filled with via material 9, FIG. 3, as described in more detail below. After via filling, the mylar layer is peeled from the tape cast ceramic.