Reducing Indium in Brazing Materials for Ceramic Substrates
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Solution Overview
Problem
The challenge is to maintain high bonding strength between ceramic substrates and metal plates in power semiconductor modules while reducing the addition amount of indium in brazing materials, as indium is scarce and its high content leads to scale-like irregularities and voids at the bonding interface, compromising the bonding strength and increasing costs.
Innovation Solution
A brazing material comprising a powder mixture of Ag—Cu alloy powder, Ag powder, and active metal hydride powder, with specific particle size distributions and composition ratios, is used to reduce indium content while maintaining bonding strength. This mixture includes an alloy powder with 55-80% Ag, 1-5% In, and Cu, an Ag powder with 5-30% mass, and an active metal hydride powder with 0.5-5% mass, ensuring a uniform compound layer formation and improved fillability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If high indium content brazing material is used, then bonding strength between ceramic substrate and metal plate is improved, but cost increases and scale-like irregularities form at bonding interface
Solution Approach 1:
The patent changes the chemical composition parameters of the brazing material by reducing indium content from conventional high levels (e.g., 10-20 mass%) to optimized lower levels (e.g., 0.1-5 mass%), while compensating with adjusted silver and copper ratios to maintain bonding strength. This parameter optimization resolves the contradiction between strength and material quantity/cost.
Solution Approach 2:
The patent creates a composite brazing material system combining multiple metal powders (silver, copper, indium) with controlled particle size distributions and compositions. By formulating a multi-component composite rather than relying on high indium content alone, the material achieves both cost reduction and maintained bonding strength.
2Strength
If high indium content brazing material is used, then bonding strength is improved, but scale-like irregularities and voids form at bonding interface
Solution Approach 1:
The patent optimizes indium content parameters to lower levels that prevent excessive intermetallic compound formation and scale-like irregularities at the bonding interface, while maintaining adequate bonding strength through compensated silver and copper composition adjustments.
Solution Approach 2:
The patent applies local quality control by optimizing the distribution and concentration of indium specifically at the bonding interface region through controlled powder mixing and particle size distribution, ensuring uniformity where it matters most while reducing overall indium content.
3Quantity of substance
If Ag-Cu alloy powder with reduced indium content is used, then cost is reduced, but bonding strength may deteriorate
Solution Approach 1:
The patent systematically adjusts multiple composition parameters including silver content (55-80 mass%), copper content (15-40 mass%), and indium content (0.1-5 mass%), along with particle size distribution parameters, to find the optimal balance that reduces indium while maintaining bonding strength.
Solution Approach 2:
The patent develops a composite powder system combining silver, copper, and indium powders with specific particle size distributions and mixing ratios, creating a synergistic material composition that achieves cost reduction through lower indium while compensating for strength through optimized multi-component interaction.
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 maintains bonding strength comparable to conventional technologies despite reduced indium content, preventing peeling of metal plates from ceramic substrates under thermal stress and ensuring reliable bonding in power semiconductor modules.
Implementation Method 1
an active metal hydride powder, the equivalent circle average diameter of particles of which is 10 to 25 μm... an active metal compound layer which is formed by reacting an element contained in a substrate with an active metal
Implementation Method 2
an active metal compound layer which is formed by reacting an element contained in a substrate with an active metal
Implementation Method 3
a powder mixture provided by mixing an alloy powder... an Ag powder... and an active metal hydride powder... heating it at a moderate temperature while applying a pressing force thereto, thereby bonding the copper plate to the ceramic substrate through a brazing material layer
Data Source
AI summary
To provide a brazing material for maintaining bonding strength between ceramic substrate and metal plate at a conventionally attainable level, while addition amount of In is reduced, and a brazing material paste using the same. A mixture powder provided by mixing alloy powder composed of Ag, In, and Cu, Ag powder, and active metal hydride powder, the mixture powder containing active metal hydride powder with a 10-to-25-μm equivalent circle average particle diameter by 0.5 to 5.0 mass %, the equivalent circle average particle diameters for the alloy powder, Ag powder, and active metal hydride powder having a relationship: alloy powder≧active metal hydride powder>Ag powder, and the powder mixture having a particle size distribution of d10 of 3 to 10 μm, d50 of 10 to 35 μm, and d90 of 30 to 50 μm, and in the frequency distribution, a peak of the distribution existing between d50 and d90.