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Pinning Technique for Ceramic Module Disclosure Number: IPCOM000074811D
Original Publication Date: 1971-Jun-01
Included in the Prior Art Database: 2005-Feb-23
Document File: 2 page(s) / 42K

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A ceramic substrate may be pinned by the following process:

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Pinning Technique for Ceramic Module

A ceramic substrate may be pinned by the following process:

A pressed unfired ceramic substrate having through holes in the desired locations is provided. A nonwetting material, such as graphite, is machined into a mold and locating fixture 12. Ceramic substrate 10 is inserted onto fixture 12 with pins 14 into substrate and fixture, as shown in Fig. A. The pins are of predetermined diameter and length for proper volume control.

The assembly is run through the ceramic-firing cycle which cures the ceramic and melts the pins, while taking advantage of (1) ceramic shrinkage from green state to fired state (17-20%), (2) graphite low coefficient of expansion (3.5), and,
(3) copper's high coefficient of expansion (18-20). The ceramic shrinks around the copper after solidification at 1083 degrees C. The graphite will release the copper pin as the copper pin shrinks and the pin will assume the shape of the graphite mold. The end result gives a pinned part which has the pin 14 locked into the ceramic 10 but not into the graphite mold 12. The process requires control of ceramic curing cycle and good graphite fixturing. The process is low cost, since the pressed ceramic must be fired in any case and no additional processes are added to pin the substrate.

A normal positive pressure belt furnace holding a hydrogen atmosphere is suitable for both firing and casting of the pin 14. Since the copper vaporizes at one atmosphere pressure and 2569...