Browse Prior Art Database

Diffusion Process for Improved Ceramic-To-Metal Bond

IP.com Disclosure Number: IPCOM000041365D
Original Publication Date: 1984-Jan-01
Included in the Prior Art Database: 2005-Feb-02
Document File: 3 page(s) / 25K

Publishing Venue

IBM

Related People

Sullivan, JF: AUTHOR

Abstract

A variety of semiconductor packaging technologies utilize ceramic substrates that must have attached to them metallic mounting pins. Often as well, plated through holes or metallic composition filled holes (vias) extend through a ceramic layer so that metallic contacts can be made at both sides of the substrate. Currently, the contact pins attached to the substrate are brazed on the bottom surface for attachment to a printed circuit board, for example. The pins are normally brazed with an 80% gold/20% tin eutectic alloy. This is a very expensive alloy, and copper and silver eutectics are often employed to avoid some of the expense. However, the copper/silver eutectic is expensive as well and must be brazed at temperatures of 900ŒC or higher.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 54% of the total text.

Page 1 of 3

Diffusion Process for Improved Ceramic-To-Metal Bond

A variety of semiconductor packaging technologies utilize ceramic substrates that must have attached to them metallic mounting pins. Often as well, plated through holes or metallic composition filled holes (vias) extend through a ceramic layer so that metallic contacts can be made at both sides of the substrate. Currently, the contact pins attached to the substrate are brazed on the bottom surface for attachment to a printed circuit board, for example. The pins are normally brazed with an 80% gold/20% tin eutectic alloy. This is a very expensive alloy, and copper and silver eutectics are often employed to avoid some of the expense. However, the copper/silver eutectic is expensive as well and must be brazed at temperatures of 900OEC or higher. The copper/silver eutectic is also known to be very susceptible to silver migration and enbrittlement. A highly effective alternative is described that is an order of magnitude less expensive than any of the other mentioned processes. It is also a non-brazing, non-melting process. It can be conducted in the range of 600-650OEC and results in a strong diffusion bonding between the metallic contact pins and the ceramic substrate. The structure is illustrated in the figure where a ceramic substrate 1 that may have a metallic filled via 2 (typically filled with molybdenum alloy or the like) has joined to it a metal pin 3 by a bonding material 4 and 5. It is the nature of the bonding material 4 and 5 and the process for bonding that are described. The joining process is performed as follows: 1) The ceramic substrate is cleaned using the following steps: a) the substrate is dipped in de-ionized water, b)

the substrate is rinsed in isopropyl alcohol, and c) the

substrate is baked for 15 minutes in a

vacuum ovenOEat 150 C to drive off any remaining water and

organic residues. 2) An approximately 0.004" thick layer of copper paste is screen-deposited on and extending over the top

projection of the substrate contact material 2. The top

projection has been previously plated wit...