Resistor Al-Si Brazing for Thermal Stability
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Solution Overview
Problem
Existing resistors face issues with thermal deterioration and joint strength degradation due to high joining temperatures and residual stress when ceramic substrates and metal terminals are joined using traditional methods, especially when exposed to high temperatures from large current flows.
Innovation Solution
A resistor design utilizing an Al-Si-based brazing filler material for joining the ceramic substrate and Al member, along with ultrasonic joining of metal electrodes and terminals to a metal member with a high melting point, eliminates thermal deterioration and enhances joint reliability by maintaining sufficient strength even at high temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If traditional brazing filler material (Ag-Cu-Ti) is used to join ceramic substrate and metal terminal, then joint strength is achieved, but joining temperature becomes too high (850°C) causing thermal deterioration of resistive element
Solution Approach 1:
The patent changes the material parameter of the brazing filler from traditional Ag-Cu-Ti to Al-Si-based composition, which fundamentally alters the joining temperature from 850°C to below 700°C. This material substitution resolves the contradiction by achieving sufficient joint strength at a lower temperature that prevents resistive element deterioration.
Solution Approach 2:
The invention uses a composite approach by combining Al-Si-based brazing filler material with specific metal terminal compositions (Cu or Cu alloy) to achieve optimal joint properties. This composite material system enables strong bonding between ceramic substrate and metal terminal while maintaining compatibility with heat-sensitive resistive elements.
2Strength
If traditional brazing method is used to join ceramic substrate and metal terminal, then joint strength is achieved, but great residual stress is generated in the joint portion
Solution Approach 1:
By changing the brazing filler material to Al-Si-based composition with lower melting point and different physical properties, the patent reduces the thermal gradient and phase transformation stress during joining. This results in significantly lower residual stress in the joint portion while maintaining adequate joint strength.
3Temperature
If soldering method is used to join metal electrode and metal terminal, then joining temperature is reduced, but joint strength becomes insufficient at high temperatures (150°C or higher)
Solution Approach 1:
The patent changes the joining method from soldering to brazing with Al-Si-based filler, which raises the operating temperature range of the joint. The Al-Si brazed joint maintains sufficient strength and reliability at high temperatures (150°C and above) where soldered joints would fail, while keeping the actual joining process temperature controlled.
4Strength
If high joining temperature is used to achieve strong joint, then joint strength is improved, but resistive element undergoes thermal deterioration
Solution Approach 1:
The patent fundamentally changes the joining temperature parameter by selecting Al-Si-based brazing filler material with melting point below 700°C, compared to traditional materials requiring 850°C. This temperature reduction protects the resistive element from thermal deterioration while the brazing process still achieves adequate joint 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 solution provides excellent heat resistance and maintains joint integrity up to 300°C or higher, preventing thermal degradation and ensuring reliable electrical connections, while reducing manufacturing complexity and costs.
Implementation Method 1
the ceramic substrate and the Al member are joined together using an Al-Si-based brazing filler material
Implementation Method 2
the metal electrode and the metal terminal are respectively joined to a first end and a second end of a metal member having a melting point of 450°C or higher
Implementation Method 3
Joule' heat is generated in accordance with the value of applied voltage, and the resistor generates heat
Data Source
Figure 1
Figure 2A~2D
Figure 3A~3B
AI summary
In this resistor, a heat sink (Al member) (23) and the other surface (11b) of a ceramic substrate (11) are joined together using an Al-Si-based brazing filler material. The Al-Si-based brazing filler material has a melting point in a range of approximately 600°C to 700°C. When the heat sink (23) and the ceramic substrate (11) are joined together using the Al-Si-based brazing filler material, it is possible to prevent the derogation of the heat resistance and thermal deterioration during joining at the same time.