Copper Pad-Wire Bond Structure That Avoids IMC and Corrosion
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Solution Overview
Problem
Aluminum pads in electronic packages experience electrolytic corrosion and form intermetallic compounds (IMCs) when bonded with conductive wires made of different materials, leading to embrittlement and reliability issues due to material consumption and void formation.
Innovation Solution
A package structure featuring a nanotwinned copper (NT-Cu) pad with an anisotropic crystal structure, where the conductive wire has a distinct grain arrangement and penetrates an oxide layer to directly contact the NT-Cu pad, preventing IMC formation and enhancing bonding strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If aluminum pads are bonded to conductive wires made of different materials, then electrical connectivity is achieved, but electrolytic corrosion and intermetallic compound formation occur leading to embrittlement and reliability problems
Solution Approach 1:
The patent applies homogeneity by making the conductive pad and conductive wire both composed of copper material. This eliminates the material difference between the pad and wire, preventing intermetallic compound formation at their interface and avoiding the associated embrittlement and reliability problems while maintaining electrical connectivity
2Reliability
If different materials are used for aluminum pads and conductive wires, then electrical connectivity is established, but electrolytic corrosion occurs in humid environments due to potential differences
Solution Approach 1:
The patent eliminates electrolytic corrosion by using the same copper material for both the conductive pad and conductive wire. This material homogeneity removes the galvanic potential difference between dissimilar materials, preventing electrolytic corrosion in humid environments while maintaining electrical connectivity
3Strength
If intermetallic compounds form between different materials, then bonding is achieved, but material consumption occurs resulting in embrittlement and conductivity reduction
Solution Approach 1:
The patent prevents material consumption and embrittlement by using copper for both the conductive pad and wire. This eliminates intermetallic compound formation that would otherwise consume material from the aluminum pad, preserving the pad's mechanical properties and electrical conductivity while maintaining strong bonding
Data Source
AI summary
A package structure is provided. The package structure includes a substrate, a conductive pad, and a conductive wire. The conductive pad is disposed over the substrate. The conductive wire includes an end portion connected to the conductive pad, wherein a grain arrangement of the end portion is distinct from a grain arrangement of the conductive pad.