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Abstract

An improved method of manufacturing thick film circuits that effectively eliminates the trade-off between thickness and definition, permitting dielectric layers of increased thickness with no pin-holes, and at the same time, more precise definition of dielectric features, such as via openings and solder stops. The method utilizes a dielectric material that can be co-fired with an underlying conductor, and preferably, that remains porous after firing. A layer of the dielectric material (FDL) is printed atop a dried but not yet fired conductor of the first circuit layer, and then co-fired with the conductor. Spreading of the FDL prior to firing is minimized due to the porosity of the dried but unfired conductor, which absorbs solvent from the FDL. The FDL can be printed in a ring, enclosing a portion of the underlying conductor to form a via definition ring, or VDR. After the FDL and conductor have been co-fired, a relatively thick cover layer of conventional dielectric material is printed over the first circuit layer, partially over-lapping the fired VDR. Again, spreading of the cover layer of dielectric is minimized, this time due to the porosity of the fired VDR, which absorbs solvent from the cover layer dielectric. The cover layer dielectric is then fired, and a second cover layer of conventional dielectric is printed atop the first cover layer to achieve the desired overall dielectric thickness. Spreading of the second cover layer is also inhibited by the fired VDR, resulting in a via with greatly improved definition compared to previously known processes. Alternatively, the FDL can be printed atop a dried but un-fired conductor and then co-fired with the conductor to form a solder stop with significantly improved feature definition. As with the via, the improved definition occurs because the porous un-fired conductor inhibits spreading of the FDL.

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First Claim