Multilayer Conductive Material for Low-Temperature Circuit Bonding
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Solution Overview
Problem
Conductive materials used in circuit boards face challenges such as chemical instability, high electric resistance, and thermal damage due to high melting points, which affect connectivity and reliability, especially when used in high-density multi-layer structures and electronic components with varying thermal expansion coefficients.
Innovation Solution
A conductive material comprising a first metal part, a second metal part with a lower melting point that forms an intermetallic compound, and a third metal part capable of eutectic reaction, where the second and third metals react to form a metallic compound with a high melting point, allowing for low-temperature bonding and increased thermal stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a conductive material with high melting point is used, then thermal stability is improved, but bonding temperature must be high causing thermal damage to circuit board
Solution Approach 1:
The conductive material is divided into a core portion (first metal) and a coating portion (second metal), where each layer serves a different function: the core provides structural integrity and electrical conductivity, while the coating enables low-temperature bonding. This segmentation allows the material to bond at low temperatures without requiring high thermal stability throughout the entire structure.
Solution Approach 2:
Different regions of the conductive material have different properties: the core portion has high melting point for structural stability, while the coating portion has low melting point for bonding. This local differentiation of material properties allows the overall material to achieve both low bonding temperature and adequate thermal stability where needed.
2Reliability
If conventional conductive materials are used, then manufacturing is simple, but chemical stability and electrical conductivity are insufficient
Solution Approach 1:
The invention uses a composite material structure with a core portion made of one metal and a coating portion made of another metal. This composite structure combines the advantages of different metals: the core provides structural integrity and electrical conductivity, while the coating provides chemical stability and enables low-temperature bonding, achieving superior overall performance.
3Productivity
If high-density multi-layer structures are used, then mounting density is improved, but thermal stress from varying expansion coefficients causes reliability issues
Solution Approach 1:
The invention changes the thermal parameters of the conductive material by using a low-melting-point metal coating, which reduces the bonding temperature and consequently reduces thermal stress. This parameter change in bonding temperature helps mitigate thermal expansion issues in high-density multi-layer structures.
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 conductive material achieves low electric resistance, high thermal stability, and reliable connections at temperatures below the circuit board's heat-resistant temperature, reducing thermal stress and maintaining connectivity during soldering processes.
Implementation Method 1
a third metal part whose main ingredient is a third metal, which third metal can make a eutectic reaction with the second metal
Implementation Method 2
a second metal part formed on the first metal part and whose main ingredient is a second metal, the second metal having a melting point lower than a melting point of the first metal, which second metal can form a metallic compound with the first metal
Data Source
AI summary
A conductive material includes a first metal part whose main ingredient is a first metal; a second metal part formed on the first metal part and whose main ingredient is a second metal, the second metal having a melting point lower than a melting point of the first metal, which second metal can form a metallic compound with the first metal; and a third metal part whose main ingredient is a third metal, which third metal can make a eutectic reaction with the second metal.