Hypoeutectic Gold Alloy Bonding for High-Temperature MEMS
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Solution Overview
Problem
In the manufacture of micromachined devices and microelectromechanical systems, existing bonding methods fail to create a robust joint that can withstand high temperatures and environmental conditions while being formed at relatively low temperatures.
Innovation Solution
A bonding method using a hypoeutectic alloy formed by heating eutectic bonding materials, such as germanium, tin, or silicon, with gold to a temperature above their eutectic point, resulting in a solid solution alloy with at least 97 atomic percent gold, which provides a strong and durable bond.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If conventional bonding methods are used to join components, then the joint can be formed at relatively low temperatures, but the bond cannot withstand relatively high temperatures and harsh environmental conditions
Solution Approach 1:
The invention changes the compositional parameters of the bonding material by using a hypoeutectic alloy with specific composition (at least 97 atomic percent gold) to achieve a bonding temperature of 1064°C while maintaining bond durability at temperatures exceeding 1064°C. This parameter change in alloy composition enables the bond to withstand temperatures higher than the bonding temperature itself.
Solution Approach 2:
The invention uses a composite bonding structure consisting of a hypoeutectic alloy layer combined with eutectic bonding materials (such as germanium, tin, or silicon). This composite material system allows the bond to be formed at 1064°C and withstand temperatures above 1064°C, resolving the contradiction between low bonding temperature and high temperature durability.
2Temperature
If eutectic bonding materials are used to form a bond, then the bonding temperature can be reduced, but the bond strength and robustness decrease
Solution Approach 1:
The invention creates a composite bonding system where a hypoeutectic alloy layer (at least 97 atomic percent gold) is combined with eutectic bonding materials containing germanium, tin, or silicon. This composite structure achieves both low bonding temperature (1064°C) and high bond strength, as the eutectic materials facilitate bonding while the hypoeutectic alloy provides structural integrity.
Solution Approach 2:
The invention applies different material properties to different layers of the bonding structure. The eutectic bonding materials (germanium, tin, or silicon) are positioned to facilitate chemical bonding and adhesion, while the hypoeutectic alloy layer (at least 97 atomic percent gold) provides overall bond strength and temperature resistance. This local differentiation of material quality achieves both low bonding temperature and high bond strength.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The method allows for bonding at low temperatures while achieving a bond with a high melting temperature, suitable for withstanding harsh environments and processing steps, without the need for solder, fluxes, or braze materials.
Implementation Method 1
heating the first and second eutectic bonding materials to a temperature above a eutectic temperature of an alloy of the first and second eutectic bonding materials to allow a hypoeutectic alloy to form
Implementation Method 2
cooling the hypoeutectic alloy to form a solid solution alloy bonding the first and second components together
Data Source
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AI summary
A method for bonding two components together including the steps of providing a first component, providing a second component, and locating a first eutectic bonding material between the first and second component. The first eutectic bonding material includes at least one of germanium, tin, or silicon. The method further includes the step of locating a second eutectic bonding material between the first and second component and adjacent to the first eutectic bonding material. The second eutectic bonding material includes gold. The method further includes the step of heating the first and second eutectic bonding materials to a temperature above a eutectic temperature of an alloy of the first and second eutectic bonding materials to allow a hypoeutectic alloy to form out of the first and second eutectic bonding materials. The method includes the further step of cooling the hypoeutectic alloy to form a solid solution alloy bonding the first and second components together.