Method of fabricating multilayer circuits

Claim 1

In the method of claim 1, wherein the paths are filled with the molten conductor only after the ceramic is sintered to a dense state.

Claim 4

A method for manufacturing a multilayer ceramic circuit board having conductors disposed in and interconnecting different layers, said method comprising the steps of: preparing a plurality of ''''green'''' ceramic sheets of ceramic material dispersed in a heat volatile binder, individually positioning each of the ''''green'''' sheets in juxtaposed relationship with one of a plurality of masks, each mask having a predetermined pattern of apertures therein, the dimensions of the various portions of the aperture pattern in the mask conforming to the desired via hole and channel personality for the juxtaposed ''''green'''' sheet, and individually exposing each of the ''''green'''' sheets through the pattern of apertures in the juxtaposed mask to laser radiation of constant power level in the range of 0.01 to 0.1 joules per 25 square mils of area exposed to the radiation for a given time of 1 millisecond to form simultaneously the via holes and channels in that ''''green'''' sheet, the depth of the formed holes and channels being determined by the dimensions of the apertures of the various portions of the pattern in the juxtaposed mask, stacking said sheets one upon another in registry such that patterns on and holes in different sheets are superposed in a desired circuit pattern, laminating said sheets, heating said laminated sheets at a temperature high enough to drive off said binders and sinter said ceramic to a dense state with continuous paths through the densified ceramic as defined by the locations for the via holes and channels of said circuit pattern, and filling said paths with a molten conductor to complete said circuit pattern.