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Gallium Intermetallics (IMCs) as a Thermal Interface Material for Electronic Packages

IP.com Disclosure Number: IPCOM000101736D
Publication Date: 2005-Mar-16
Document File: 3 page(s) / 148K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method that uses a gallium intermetallic as a thermal interface material (TIM) for electronic packages. Benefits include lowering processing temperature, minimizing the stress on the die, and improving package reliability.

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Gallium Intermetallics (IMCs) as a Thermal Interface Material for Electronic Packages

Disclosed is a method that uses a gallium intermetallic as a thermal interface material (TIM) for electronic packages. Benefits include lowering processing temperature, minimizing the stress on the die, and improving package reliability.

Background

When a silicon die is attached on a copper heat spreader, a large stress is generated on the die due to the high processing temperature and the large CTE mismatch between the silicon die and the copper heat spreader. The high stress on the die may impact die performance and package reliability as well.

General Description

The disclosed method proposes a low-temperature process to bond the die to a heat spreader, using pure gallium or a gallium amalgam:

Pure Gallium Approach

When a very thin layer of pure gallium is placed between the die backside metallization (BSM) and the nickel/gold surface finish of the copper heat spreader, the gallium dissolves the thin gold layers quickly, then reacts with the nickel layers to form Ga-Ni IMCs during the curing process. The nickel layers need to be thick enough so that the pure gallium layer is completely converted into IMCs (see Figure 1).

Gallium Amalgam Approach

The gallium amalgam is a mixture of a liquid metal alloy (e.g. gallium, gallium/indium, gallium/tin, etc.) and fine metal particles (e.g. nickel or copper). The liquid metal alloys react with the metal particles and solidify at various low temper...