Gallium Solder Joints for Flexible Low-Temperature Bonding
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Solution Overview
Problem
Conventional low temperature solders struggle to provide flexible and strong joints on deformable substrates, such as flexible electronic components, especially when the substrate is subjected to deformation, due to their limited temperature range and mechanical properties.
Innovation Solution
A solder joint method using copper or copper-nickel alloy as the metal base material and gallium alloy as the solder, with a melting point of 30°C or lower, to generate CuGa2 or (Cu, Ni)Ga2 intermetallic compounds, allowing for joints at 90°C or lower and providing flexibility and strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If conventional low temperature solder (BiIn alloy) is used, then the melting point is reduced to around 100°C, but the joint lacks flexibility and breaks easily when the substrate is deformed
Solution Approach 1:
The invention changes the chemical composition parameters of the solder alloy by introducing Ga (gallium) as the main component with specific content ranges (40-100 at%, preferably 60-100 at%). This parameter change results in a dramatic reduction of melting point to 30°C or lower while simultaneously improving the mechanical properties and flexibility of the joint, resolving the contradiction between low melting point and joint strength
Solution Approach 2:
The invention creates a composite intermetallic compound structure consisting of CuGa2 and/or (Cu, Ni)Ga2 formed between the Ga-based solder and the Cu-Ni alloy substrate. This composite material structure provides both the low melting point characteristic of Ga and the mechanical strength and flexibility needed for deformable substrates, effectively resolving the contradiction between temperature reduction and joint reliability
2Temperature
If the solder temperature is reduced for flexible substrate application, then low heat resistance components can be joined, but the joint becomes brittle and lacks flexibility
Solution Approach 1:
By changing the solder composition to Ga-based with melting point ≤30°C, the invention enables soldering at extremely low temperatures (90°C or lower) while the formed CuGa2 and/or (Cu, Ni)Ga2 intermetallic compounds provide the necessary flexibility and ductility to tolerate substrate deformation, thus resolving the contradiction between low temperature soldering and adaptability to deformable substrates
Solution Approach 2:
The Cu-Ni alloy layer acts as an intermediary between the Ga-based solder and the substrate, facilitating low temperature bonding while the形成的 intermetallic compounds (CuGa2 and/or (Cu, Ni)Ga2) serve as a flexible intermediary structure that accommodates substrate deformation, resolving the contradiction between low temperature processing and mechanical flexibility
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
Enables reliable and flexible solder joints on deformable substrates, maintaining electrical connectivity even under substrate deformation, and is applicable to low heat resistance components like LEDs and pressure sensors, with improved mechanical and electrical conductivity.
Implementation Method 1
the solder being a solder alloy containing Ga and inevitable impurities or a solder alloy containing Ga as a main component and having a melting point of 30° C. or lower
Implementation Method 2
heating the first metal base material and the second metal base material to a temperature of 90° C. or lower in one of a noble gas atmosphere, an atmospheric air, and a liquid, to generate CuGa2 or (Cu, Ni)Ga2 between the first metal base material and the second metal base material, thereby joining the first metal material and the second metal material
Data Source
AI summary
In a method for manufacturing a solder joint part, at least one of a first metal base material and a second metal base material is an alloy containing Ni in an amount of more than 0 wt % and less than 44 wt % and Cu in an amount of more than 56 wt %, and solder is a solder alloy containing Ga and inevitable impurities or a solder alloy containing Ga as a main component and having a melting point of 30° C. or lower. The method includes applying the solder to a surface of the first metal base material and placing the second metal base material on the applied solder, and heating the first and second metal base materials to a temperature of 90° C. or lower in a specified atmosphere or in a liquid to generate CuGa2 or (Cu, Ni)Ga2 between the first and second metal base materials, thereby joining the first and second metal material.