Bimetallic Interface Element for Aluminum-Copper Wire Bonding
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Solution Overview
Problem
The difference in thermal expansion coefficients between aluminum and copper materials used in electronic devices leads to weakening of soldering connections, particularly under high operating temperatures and mechanical stresses, causing bond lift-off or heel cracks, which reduces the efficiency and reliability of electronic devices.
Innovation Solution
An interface element with two layers of different metals, where one layer matches the material of the contact pad and the other layer matches the bonding wire or lead, is used to create a robust and reliable electric connection by ensuring same-material soldering, even when the pad and wire/lead are made of different materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If bonding wires of copper material are soldered to contact pads of aluminum material, then electrical conductivity is improved, but soldering strength deteriorates due to different thermal expansion coefficients
Solution Approach 1:
The patent applies composite materials by creating a bimetallic interface element consisting of two different metal layers (aluminum and copper) bonded together. This composite structure allows the interface element to match the thermal expansion characteristics of both the aluminum contact pad and the copper bonding wire, thereby preventing soldering failure while maintaining electrical conductivity.
Solution Approach 2:
The bimetallic interface element acts as an intermediary component between the aluminum contact pad and the copper bonding wire. This intermediate element with matching thermal expansion coefficients for both materials eliminates the direct incompatible soldering connection, preventing bond lift-off and heel cracks while enabling reliable electrical connection.
2Productivity
If high operating temperatures and mechanical stresses are applied, then device performance is maintained, but soldering connection deteriorates due to thermal expansion mismatch
Solution Approach 1:
The patent applies parameter changes by selecting materials with specific thermal expansion coefficients that match both the aluminum contact pad and copper bonding wire. The bimetallic interface element's thermal expansion parameters are chosen to be intermediate between the two materials, allowing the connection to withstand high operating temperatures and mechanical stresses without soldering failure.
3Reliability
If different metal materials are used for contact pads and bonding wires, then electrical conductivity is improved, but manufacturing complexity increases due to material compatibility requirements
Solution Approach 1:
The patent resolves material compatibility complexity by using a composite bimetallic interface element that integrates both aluminum and copper layers. This single composite component satisfies the compatibility requirements for both aluminum contact pads and copper bonding wires, simplifying the manufacturing process while maintaining the benefits of using different high-conductivity materials.
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
This solution enhances the reliability of electronic devices by reducing the risk of soldering failure and maintaining efficient operation under varying temperatures and mechanical stresses, ensuring consistent electric flow.
Implementation Method 1
the different metal elements included in such materials determine different thermal expansion coefficients (for example, aluminum has a thermal expansion coefficient that is approximately double than a thermal expansion coefficient of copper). This difference between the thermal expansion coefficients may cause a weakening of the soldering between the two materials
Data Source
AI summary
An electronic device includes a chip with an integrated electronic component and a terminal made of a first metal material. The device further includes a lead made of a second metal material different from the first metal material. A bonding wire made of a selected one of the first and second metal materials has opposite ends coupled with the terminal and the lead. An interface element having a first layer made of a selected one of the first and second metal materials and a second layer made of an unselected one of the first and second metal materials has the first layer coupled with the bonding wire and the second layer coupled with a component, wherein the component is ether the terminal or the lead.