Cu-P-Sn Brazing for Power Module Substrates
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Solution Overview
Problem
The existing power module substrates with a Cu foil bonded to a ceramic substrate through a Cu-Mg-Ti brazing filler material form rigid intermetallic compounds near the ceramic substrate, leading to increased thermal stress and reduced bonding rates, which can result in cracking during thermal cycles.
Innovation Solution
A bonded body and power module substrate are developed using a Cu-P-Sn-based brazing filler material and Ti, where a Cu-Sn layer forms close to the ceramic member, and an intermetallic compound layer containing P and Ti is formed between the Cu member and the Cu-Sn layer, preventing the formation of rigid intermetallic compounds near the ceramic substrate, thereby enhancing bonding and reducing thermal stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If Cu-Mg-Ti brazing filler material is used to bond Cu foil to ceramic substrate, then bonding between Cu member and ceramic member is achieved, but rigid intermetallic compounds form near the ceramic substrate causing increased thermal stress and cracking during thermal cycles
Solution Approach 1:
The invention changes the chemical composition parameters of the brazing filler material from Cu-Mg-Ti to Cu-P-Sn-based, which fundamentally alters the intermetallic compound formation behavior. This parameter change prevents the formation of rigid intermetallic compounds near the ceramic substrate while maintaining bonding strength, thereby resolving the contradiction between bonding strength and thermal cycle resistance
Solution Approach 2:
The invention creates a composite intermetallic compound layer structure consisting of multiple phases (Cu-P-Sn-based intermetallic compounds with controlled composition). This composite structure provides both bonding strength and flexibility to accommodate thermal expansion differences, preventing cracking during thermal cycles while maintaining strong bonding between Cu member and ceramic member
2Ease of manufacture
If Cu-Mg-Ti brazing filler material is used, then bonding process can be completed, but the bonding rate between ceramic substrate and circuit layer decreases due to rigid intermetallic compound formation
Solution Approach 1:
By changing the brazing filler material composition to Cu-P-Sn-based, the invention modifies the bonding process characteristics. The new composition enables faster bonding rates while maintaining ease of manufacture, as the intermetallic compounds formed are less rigid and allow for more efficient bonding process optimization
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
This configuration effectively limits cracking in the ceramic member during thermal cycles and improves the bonding rate between the ceramic and Cu members, ensuring reliable bonding and thermal stability.
Implementation Method 1
a Cu-Sn layer, which is positioned close to the ceramic member and in which Sn forms a solid solution with Cu, and an intermetallic compound layer which is positioned between the Cu member and the Cu-Sn layer and contains P and Ti, are formed at a bonded interface between the ceramic member and the Cu member
Implementation Method 2
a Cu-Sn layer, which is positioned close to the ceramic member and in which Sn forms a solid solution with Cu
Data Source
Figure 1~2
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AI summary
The bonded body of the present invention includes: a ceramic member made of ceramics; and a Cu member which is made of Cu or a Cu alloy and bonded to the ceramic member through a Cu-P-Sn-based brazing filler material and a Ti material, wherein a Cu-Sn layer, which is positioned close to the ceramic member and in which Sn forms a solid solution with Cu, and an intermetallic compound layer which is positioned between the Cu member and the Cu-Sn layer and contains P and Ti, are formed at a bonded interface between the ceramic member and the Cu member.