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Top Surface Metallurgy of Multilayered Ceramic Modules

IP.com Disclosure Number: IPCOM000082613D
Original Publication Date: 1975-Jan-01
Included in the Prior Art Database: 2005-Feb-28
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

McIntosh, CM: AUTHOR [+2]

Abstract

A multilayer ceramic (MLC) substrate is formed through the usual processing steps, including firing, but without its usual top layer and without fan-out conductive lines on the second layer from the top. Instead, the vias in the second layer have enlarged refractory metal pads on them.

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Top Surface Metallurgy of Multilayered Ceramic Modules

A multilayer ceramic (MLC) substrate is formed through the usual processing steps, including firing, but without its usual top layer and without fan-out conductive lines on the second layer from the top. Instead, the vias in the second layer have enlarged refractory metal pads on them.

A green sheet having a low firing ceramic body with very low shrinkage upon firing, is laminated to the top of the previously fired MLC structure at elevated pressure and temperature.

The green sheet has via holes and on top carries metal paste in a suitable pattern, and on the bottom a mirror image of the fan-out pattern. The metal paste is applied by screen printing or, preferably, by coating the surface of the green sheet with a smooth layer of a material which is not attacked by the vehicle in the metal paste, for example, polyamide or polyvinylalcohol, indenting the pattern with a die carrying a photoetched raised pattern, filling the indentations with a metal paste, and wiping off the surplus paste. The metal paste may contain for example, gold particles, gold coated nickel particles, or copper particles.

The low firing ceramic green sheet is fired in an inert or reducing atmosphere, typically at 800 degrees C to fuse the low firing ceramic body to the surface of the MLC structure.

Input/output pins are brazed to the unplated refractory metal pads on the bottom of the MLC structure onto screened on nickel paste, using a n...