Ceramic Circuit Substrate Bonding Layer Design
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Solution Overview
Problem
Conventional ceramic circuit substrates face durability and reliability issues due to thermal expansion differences between copper and ceramic materials, leading to copper peeling off and substrate cracking when thicker copper is used for improved heat dissipation.
Innovation Solution
The use of an active metal brazing material in bulk form, alloyed with constituent metals, forms a bonding layer with a higher ratio of active metal compound layer to ceramic substrate interface, enhancing bonding durability and thermal stress resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the copper circuit and copper heat sink are thickened to improve heat dissipation capability, then the heat dissipation capability is improved, but the thermal expansion difference between copper and ceramic substrate increases, leading to copper peeling off and substrate cracking
Solution Approach 1:
The bonding layer is designed as a composite material system consisting of multiple layers with different functions: a first bonding layer containing active metal compounds (Ti, Zr) for strong chemical bonding with ceramic, a second bonding layer for metal bonding, and an intermediate layer for stress management. This composite structure resolves the contradiction by combining materials with complementary properties to simultaneously achieve strong bonding and thermal stress resistance.
Solution Approach 2:
The invention changes the chemical composition parameters of the bonding layer by incorporating specific active metal compounds (Ti, Zr) and controlling the ratio of different bonding materials. This parameter optimization allows the bonding layer to accommodate thermal expansion differences while maintaining strong adhesion, thus resolving the contradiction between heat dissipation and bonding durability.
2Strength
If conventional active metal soldering is used to bond copper to ceramic substrate, then bonding is achieved, but the bonding layer has insufficient resistance to thermal stress, causing copper peeling and substrate cracking when thicker copper is used
Solution Approach 1:
The bonding layer is segmented into multiple functional layers: a first bonding layer with active metal compounds for ceramic bonding, a second bonding layer for copper bonding, and an intermediate layer for stress management. This segmentation allows each layer to specialize in one function, resolving the contradiction by distributing thermal stress across multiple layers rather than concentrating it in a single bonding interface.
Solution Approach 2:
An intermediate layer is introduced between the first bonding layer (bonded to ceramic) and the second bonding layer (bonded to copper). This intermediate layer acts as a mediator that gradually transitions the thermal expansion properties between the ceramic and copper sides, reducing thermal stress concentration and preventing bonding failure under thermal cycling conditions.
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 effectively suppresses copper peeling off and substrate cracking under thermal stress, achieving improved durability and reliability of ceramic circuit substrates with enhanced heat dissipation capabilities.
Implementation Method 1
active metal soldering is normally applied. The active metal soldering is one aspect of bonding methods through brazing, and is a method for bonding a metal and a ceramic by using an active metal brazing material
Implementation Method 2
the active metal in the active metal brazing material concentrates on a bonded interface between the brazing material component and the ceramic, allowing oxygen and nitrogen in the ceramic to react to exert a bonding force
Implementation Method 3
The powder of the metals in the active metal brazing material then melts to form a bonding layer between the ceramic substrate and the copper circuit
Data Source
Figure 1(a)~1(b)
Figure 2~3b
AI summary
A ceramic circuit substrate according to the present invention includes a ceramic substrate, a copper circuit made of a copper-based material bonded, via a bonding layer, to a surface of the ceramic, and a copper heat sink made of the copper-based material bonded, via a bonding layer, to the other surface of the ceramic. The bonding layers each include a brazing material component including two or more kinds of metals, such as Ag, and an active metal having a predetermined concentration. The bonding layers each include a brazing material layer including the brazing material component, and an active metal compound layer containing the active metal. A ratio of a bonding area of the active metal compound layer in a bonding area of each of the bonding layers is 88% or more.