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Browse Prior Art Database

Uniform Via Height Preparation

IP.com Disclosure Number: IPCOM000046192D
Original Publication Date: 1983-Jun-01
Included in the Prior Art Database: 2005-Feb-07
Document File: 2 page(s) / 49K

Publishing Venue

IBM

Related People

Bakos, P: AUTHOR [+3]

Abstract

Multilayer ceramic substrates are provided with interconnecting vias. The vias may take the form of holes which are primed and then completely filled with conductive metal to achieve the necessary electrical connection between the layers of the multilayer ceramic. In doing this, the holes are screened in a metal paste form and later subjected to an elevated temperature to burn off the excess organic materials to obtain a pure metal for electrical conductivity. During this procedure, the excessive stress caused by shrinkage of the ceramic results in protruding vias. Subsequently, the required top surface layer of cermet and chrome-copper-chrome is deposited onto the ceramic and via surfaces, and this metallurgy follows the uneven surface which in turn results in severe defects when photoengraving is carried out.

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Uniform Via Height Preparation

Multilayer ceramic substrates are provided with interconnecting vias. The vias may take the form of holes which are primed and then completely filled with conductive metal to achieve the necessary electrical connection between the layers of the multilayer ceramic. In doing this, the holes are screened in a metal paste form and later subjected to an elevated temperature to burn off the excess organic materials to obtain a pure metal for electrical conductivity. During this procedure, the excessive stress caused by shrinkage of the ceramic results in protruding vias. Subsequently, the required top surface layer of cermet and chrome-copper-chrome is deposited onto the ceramic and via surfaces, and this metallurgy follows the uneven surface which in turn results in severe defects when photoengraving is carried out.

It was found that the protruded vias could be reduced by using a sandblast technique to produce the desired results. The use of a finely powdered material, such as aluminum oxide, provided the necessary reduction in the height of the via protrusion. In this operation, the uneven flatness of the ceramic did not cause any problems. To ensure that no residue, metal or sandblast powder remains on the substrate, vaporblast cleaning is implemented. With the combination of sandblast and vaporblast, rejected multilayer ceramic substrates may be reworked, metallized and photoengraved to achieve the necessary circuitization. For circui...