Ag-Cu-Sn Braze Material for Ceramic Circuit Substrates
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Solution Overview
Problem
Conventional ceramic circuit substrates face reliability issues due to thermal stress and bonding defects caused by differences in thermal expansion coefficients between ceramic and metal components, leading to reduced thermal cycling resistance and operational reliability.
Innovation Solution
A ceramic circuit substrate with a metal plate bonded using an Ag—Cu—Sn braze material, where the average size of Cu-rich phases is 3.5 μm or less and the number density is 0.015/μm² or higher, and the braze material contains 0.5 to 4.0 parts by mass of active metals like titanium, zirconium, or niobium, along with 93.0 to 99.4 parts by mass of Ag and 0.1 to 5.0 parts by mass of Cu, to enhance thermal cycling resistance properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If 5% or more of low-melting-point metal is blended into Ag-Cu braze material to lower melting point, then bonding temperature is reduced and thermal stress is decreased, but the braze material layer structure becomes non-uniform and thermal cycling resistance is lowered
Solution Approach 1:
The invention changes the compositional parameters of the braze material by limiting low-melting-point metal content to less than 5 mass% and adding specific amounts of In (0.1-3 mass%), Zn (0.1-3 mass%), Cd (0.1-3 mass%), or Sn (0.1-3 mass%). This parameter optimization maintains uniform microstructure while achieving adequate bonding temperature reduction and thermal stress mitigation without compromising thermal cycling resistance.
Solution Approach 2:
The invention creates a composite braze material system combining Ag-Cu base alloy with controlled additions of low-melting-point metals and reactive metal elements. This composite structure achieves synergistic effects: the Ag-Cu matrix provides strength and uniformity, while the controlled low-melting-point additions reduce bonding temperature, and reactive metals enhance interfacial bonding, collectively improving thermal cycling resistance.
2Stress or pressure
If low-melting-point metal is added to reduce bonding temperature, then thermal stress generation is reduced, but the formation time of braze material layer is prolonged and structure uniformity is compromised
Solution Approach 1:
The invention optimizes the compositional parameters by strictly controlling low-melting-point metal content below 5 mass% and adding reactive metal elements (Ti, Zr, Hf, Nb, or Ta) at 0.01-5 mass%. This composition control ensures rapid and uniform brazing process, completing bonding within 10-60 minutes at 855-900°C, thereby reducing thermal stress without prolonging process time and maintaining structural uniformity.
3Strength
If reactive metal elements are added to braze material, then wettability and bonding strength are improved, but manufacturing complexity increases
Solution Approach 1:
The invention optimizes the compositional parameters by adding reactive metal elements (Ti, Zr, Hf, Nb, or Ta) at controlled levels of 0.01-5 mass% to the Ag-Cu base alloy. This precise compositional control significantly improves wettability and bonding strength at the ceramic-met al interface while maintaining straightforward manufacturing processes for producing the braze material and performing the bonding operation.
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 a highly reliable ceramic circuit substrate with a bonding void ratio of 1.0% or lower and a crack ratio less than 1.0% after 2000 heat cycling tests, significantly improving thermal cycling resistance and operational reliability.
Implementation Method 1
Cu-rich phases in an Ag-Cu-Sn braze material layer structure formed continuously at the bonding interface
Implementation Method 2
a metal plate bonded, by an Ag-Cu-Sn braze material, to at least one main surface of a ceramic substrate
Implementation Method 3
there is a large difference between the thermal expansion coefficients of ceramic substrates and metal plates, and the load from repeated hot-cold cycles generates thermal stress caused by the differences in the thermal expansion coefficients
Data Source
AI summary
A ceramic circuit substrate having a metal plate bonded, by a bonding braze material, to at least one main surface of a ceramic substrate, wherein the bonding braze material contains, as metal components, 0.5 to 4.0 parts by mass of at least one active metal selected from among titanium, zirconium, hafnium, and niobium, with respect to 100 parts by mass, in total, of 93.0 to 99.4 parts by mass of Ag, 0.1 to 5.0 parts by mass of Cu, and 0.5 to 2.0 parts by mass of Sn; and Cu-rich phases in a bonding braze material layer structure between the ceramic substrate and the metal plate have an average size of 3.5 μm or less and a number density of 0.015/μm2 or higher. A method for producing a ceramic circuit substrate includes bonding at a temperature of 855 to 900° C. for a retention time of 10 to 60 minutes.