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Method for ambient-temperature metal-to-metal bonding

IP.com Disclosure Number: IPCOM000020726D
Publication Date: 2003-Dec-10
Document File: 3 page(s) / 142K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method for ambient-temperature metal-to-metal bonding. Benefits include improved functionality, improved reliability, and improved environmental friendliness.

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Method for ambient-temperature metal-to-metal bonding

Disclosed is a method for ambient-temperature metal-to-metal bonding. Benefits include improved functionality, improved reliability, and improved environmental friendliness.

Background

         Electrically joining two metal surfaces together conventionally requires elevated temperatures, such as with soldering and welding. When the metals being joined are attached to substrates and a large coefficient of thermal expansion (CTE) mismatch exists, the resulting joint is subjected to large stresses after cooling to room temperature. The stresses can cause the joined part to fail. For example, in conventional microelectronic processing, the integration of mechanically fragile low-dielectric constant (k) interlayer dielectric (ILD) materials with flip-chip packaging is proving to be problematic. The package puts high stress on the die after the high-temperature chip-join process. The stress is caused by the large CTE mismatch between the die and the package.

         Conventionally, two metal surfaces on substrates with large CTE mismatches are soldered together using a soft solder material, such as Pb-Sn alloy. It can absorb the CTE mismatch-induced stresses by undergoing plastic deformation (see Figure 1).

General description

The disclosed method is ambient-temperature metal-to-metal bonding. The method uses chemicals for forming metal-to-metal electrical connections. The process utilizes a custom-designed electroless Pt plating solution for electrically connecting two metal surfaces together (see Figure 2). Because the process occurs at room temperature, the disclosed method is particularly useful for connecting the metal surfaces on two sub...