Ceramic Circuit Base Joint Layer for Thermal Cycling Crack Resistance
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Solution Overview
Problem
Existing circuit bases with copper metal layers and ceramic bases are prone to cracking due to repeated heating and cooling, leading to instability and reduced lifespan.
Innovation Solution
A circuit base design featuring a ceramic base, a joint layer containing aluminum, silicon, and oxygen, and a copper metal layer, with optional intermediate layers of titanium, tungsten, or molybdenum, to enhance bonding strength and resist cracking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a brazing material containing silver and copper is used to join the ceramic base and copper metal layer, then good electrical conductivity and initial bonding strength are achieved, but cracking occurs during repeated heating and cooling cycles
Solution Approach 1:
An aluminum-containing joint layer is introduced as an intermediary between the ceramic base and copper metal layer. This intermediate layer has a thermal expansion coefficient that bridges the gap between ceramic and copper, reducing thermal stress and preventing cracking during thermal cycling while maintaining bonding strength.
Solution Approach 2:
The thermal expansion coefficient parameter of the joint layer is specifically optimized to be between 5×10^-6/K and 10×10^-6/K, which is lower than conventional silver-copper brazing materials. This parameter change allows the joint layer to accommodate differential thermal expansion between ceramic and copper, preventing cracking while maintaining reliability.
2Strength
If conventional silver-copper brazing material is used, then initial bonding is achieved, but the joint layer cracks under thermal stress
Solution Approach 1:
The aluminum-containing joint layer serves as a mediator that absorbs and distributes thermal stress between the ceramic base and copper metal layer. Its specific thermal expansion coefficient allows it to act as a buffer zone, preventing stress concentration and cracking while maintaining bonding strength.
Solution Approach 2:
The joint layer is formulated as a composite material containing aluminum, silicon, and oxygen in specific proportions. This composite structure provides both mechanical strength for bonding and controlled thermal expansion properties for stress resistance, simultaneously achieving bonding strength and thermal stress resistance.
3Reliability
If the joint layer contains aluminum, silicon, and oxygen in specific proportions, then thermal expansion mismatch is reduced, but manufacturing complexity increases
Solution Approach 1:
The composition parameters of the joint layer (Al: 60-90 wt%, Si: 5-30 wt%, O: 1-20 wt%) are optimized to achieve the target thermal expansion coefficient range. By controlling these compositional parameters, the joint layer attains both crack resistance and manageable manufacturing complexity.
Solution Approach 2:
The joint layer composition is locally optimized at the interface between ceramic and copper, with aluminum, silicon, and oxygen distributed in specific proportions to create the desired thermal expansion properties. This localized quality control enables crack resistance while keeping manufacturing processes relatively simple.
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 design provides a stable circuit base that withstands repeated heating and cooling cycles without cracking, ensuring long-term reliability and improved heat dissipation.
Implementation Method 1
As a joint layer that connects the base and the metal layer, for example, a brazing material containing silver and copper as main components is used
Implementation Method 2
The circuit base used in such applications includes a base and a metal layer that is located on the base and is made of copper having excellent heat dissipation
Implementation Method 3
Ceramic having both excellent insulating properties and mechanical strength is used for the base
Data Source
AI summary
A circuit base of the present disclosure includes a base made of ceramic, a joint layer located on the base, and a metal layer located on the joint layer. The metal layer contains copper. The joint layer contains aluminum, silicon, and oxygen.