Browse Prior Art Database

Laminated Metal Core Circuit Card with Controlled Thermal Expansivity

IP.com Disclosure Number: IPCOM000049735D
Original Publication Date: 1982-Jul-01
Included in the Prior Art Database: 2005-Feb-09
Document File: 3 page(s) / 173K

Publishing Venue

IBM

Related People

Aakalu, NG: AUTHOR [+3]

Abstract

This method of packaging is designed to permit mounting of large scale integration chips directly onto a "printed" wiring carrier. It also allows screened-on resistors and modules on the same carrier.

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 53% of the total text.

Page 1 of 3

Laminated Metal Core Circuit Card with Controlled Thermal Expansivity

This method of packaging is designed to permit mounting of large scale integration chips directly onto a "printed" wiring carrier. It also allows screened- on resistors and modules on the same carrier.

Fig. 1 shows a cross section of the carrier. In the example shown, the metal core is a three-layer sandwich or laminate. INVAR* is the metal 10 at the center of the sandwich. The outer metals 12, 14 can be copper, aluminum, low-carbon steel, or stainless steel. In most instances both outer layers will be of the same thickness and of the same metal or alloy. By varying the proportion of the thicknesses of the inner to the outer layers, thermal expansivity and the thermal conductivity of the final composite can be controlled. The table below shows a number of combinations together with comments on merits thereof. (see original).

The sandwich is made by compaction of the three constituent layers at elevated temperatures under a protective atmosphere. The next step is to put the three-layer sandwich through drilling, metal punching, and so forth, to produce the desired form. Now the metal core is ready to receive an insulation cover on its surfaces.

The insulation cover 16 can be in the form of porcelain. In that case, it is preferred that the outer metal 12, 14 be "enamel grade" steel for good adhesion to porcelain. The porcelain is a mixture of borosilicate glass with zirconia and other minor ingredients. The porcelain composition should be tailored to the thermal expansivity of the carrier in order that the porcelein will not be subjected to excessive thermal stresses, and should be low alkaline or alkaline-free. After the porcelain is fired, the flat surfaces are ready to receive wiring. The purpose of using low alkaline or alkaline-free porcelain is for high electrical resistance between the metal laminate and the conductors on the surface of the porcelain.

The wiri...