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Batch Fabricated, Polished Copper Heat Sink Fabrication using an Interconnecting Web

IP.com Disclosure Number: IPCOM000088552D
Original Publication Date: 1977-Jun-01
Included in the Prior Art Database: 2005-Mar-04
Document File: 3 page(s) / 30K

Publishing Venue

IBM

Related People

Hutchins, GL: AUTHOR

Abstract

A process has been developed so that GaAs/GaA1As laser chips can be bonded to polished copper heat sinks, with a copper foil beam lead and a silver epoxy connection to the chip top, as shown in Fig. 1. With this process, the chips can be uniformly bonded with excellent adhesion, low thermal resistance, (<2/0/-cm/2//Kw), and low strains (<1x10/-4/) if the chip metallurgies are favorable. The top contacts are applied with 100% yield and do not change the mounted laser characteristics.

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Batch Fabricated, Polished Copper Heat Sink Fabrication using an Interconnecting Web

A process has been developed so that GaAs/GaA1As laser chips can be bonded to polished copper heat sinks, with a copper foil beam lead and a silver epoxy connection to the chip top, as shown in Fig. 1. With this process, the chips can be uniformly bonded with excellent adhesion, low thermal resistance, (<2/0/- cm/2//Kw), and low strains (<1x10/-4/) if the chip metallurgies are favorable. The top contacts are applied with 100% yield and do not change the mounted laser characteristics.

Generally, high quality copper heat sinks can be batch-fabricated in array form to provide large numbers of precision heat sinks at relatively low cost. Two- dimensional arrays containing about 200 heat sinks are routinely fabricated by attaching a ground copper plate to a lapped stainless steel carrier plate by a sparse-array of 13 screws. The copper slide is then criss-cross slotted nearly through the plate to delineate the overall heat sink dimensions, leaving a 0.005 inch web connecting the heat sinks. The array is then surface ground and mechanically polished with a presuspended Linde "A" Al(2)O(3), slurry to a quality optical finish.

More specifically mesas are etched photolithographically in the polished Cu surface, and bonding metallurgy films are deposited on the array. After the bonding metallurgy, the array's metallized surface is inverted and waxed down to another flat carrier plate, and the original carrier plate is removed, exposing the bottom surface of the heat sink plate. Photoresist protection pads are applied to this surface and FeCl(3) etching of the 0.005 inch web separates the heat sinks into approximately 200 individual units.

There are a variety of difficulties in the heat-sink array fabrication process. Firstly, the process has to be a high-yield process to justify the cost of fabrication. The processing operations are arranged so that each is independently optimizable. Copper slotting techniques had to be developed for the process.

For example, the array slot milling is done in two steps. The first cut is 0.040 inch deep and the second cut is 0.020 inch deep. Attempts at cutting the slots in one pass resulted in distortions which rendered the plate useless.

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