Paste containing electrically conducting powder to form conducting solid filler in cavity in ceramic substrate

In a method of filling up a cavity in a substrate comprised of a ceramic material, of a device having at least two electrically conducting parts separately fixed to the substrate with an electrically conducting solid filler such that the solid filler provides electrical connection between the conducting parts, the method comprising the steps of filling up the cavity with a paste containing an electrically conducting powder and subsequently firing the substrate in atmospheric air at a temperature in the range of about from 1100.degree. C. to 1650.degree. C. to cause sintering of the paste in the cavity into the solid filler,

• said paste containing an electrically conducting powder mixture comprising a platinum powder and a ceramic material powder selected from the group consisting of an alumina powder and a zirconia powder dispersed uniformly in an organic liquid vehicle, the proportion of said platinum powder to said ceramic powder being in the range from 51:49 to 78:22 by volume, the specific surface area of said powder mixture being in the range from 1.0 to 10.0 m.sup.2 /g, the proportion of said powder mixture to said vehicle being in the range from 70:30 to 50:50 by weight.