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Aluminum Chrome Copper Circuitry for Ceramic Substrates

IP.com Disclosure Number: IPCOM000078688D
Original Publication Date: 1973-Feb-01
Included in the Prior Art Database: 2005-Feb-26
Document File: 2 page(s) / 20K

Publishing Venue

IBM

Related People

Clark, RJ: AUTHOR [+2]

Abstract

This metallization method takes advantage of the basic metallurgical properties of the materials, and provides a means of economically manufacturing photoetched circuitry on ceramic semiconductor packages.

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Aluminum Chrome Copper Circuitry for Ceramic Substrates

This metallization method takes advantage of the basic metallurgical properties of the materials, and provides a means of economically manufacturing photoetched circuitry on ceramic semiconductor packages.

The figure shows a portion of a ceramic substrate 1 upon which integrated circuit chips, not shown, are to be face bonded. Conductive electrodes 2 provide connection between chip terminal pads 3 and module pin sites 4. Pads 3 and 4 and electrode 2 are formed by sequentially evaporating layers of aluminum, chromium, and copper onto substrate 1. Thereafter, two standard photolithographic etching techniques are used to first define electrode and pad geometries and second to selectively remove copper, except in the shaded solder pad areas 3 and 4.

Adhesion to the metallized substrate is provided by the aluminum/ ceramic interface. The intrinsic stress levels of evaporated aluminum are less than that of chrome deposited under identical conditions. The required layer of chrome is present to prevent the diffusion of copper into the aluminum, during the joining process that forms solder joints in the pad areas 3 and 4. Copper metallization will be present only in the pad areas and will be delineated, by the inherently formed protective oxides on the chrome and aluminum electrodes. The tenacious oxides also provide corrosion resistance.

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