Cu-Sn Layer Brazing for Ceramic Substrate Thermal Stress
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Solution Overview
Problem
The existing bonding method between ceramic and Cu foil substrates using Cu-Mg-Ti brazing filler material forms a rigid intermetallic compound layer, leading to increased thermal stress and cracking in ceramic substrates during thermal cycles, and inadequate bonding between the ceramic and circuit layers.
Innovation Solution
A bonded body and power module substrate are developed using a Cu-Sn layer formed with a Cu-P-Sn-based brazing filler material and Ti paste, which disperses intermetallic compounds containing P and Ti, preventing the formation of a rigid intermetallic compound layer and enhancing bonding between the ceramic and Cu members.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If Cu-Mg-Ti brazing filler material is used to bond ceramic substrate and Cu foil, then bonding between ceramic and Cu member is achieved, but a thick rigid intermetallic compound layer is formed 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 alloy, which fundamentally alters the intermetallic compound formation behavior. This parameter change prevents the formation of thick rigid intermetallic layers while maintaining bonding strength, thereby resolving the contradiction between bonding strength and cracking resistance during thermal cycles
Solution Approach 2:
The invention uses a composite brazing filler material system comprising Cu-P-Sn-based alloy combined with Ti paste. This composite approach creates a multi-phase bonding interface where intermetallic compounds containing P and Ti are dispersed within a Cu-Sn matrix, providing both strong bonding and stress distribution capabilities to prevent cracking
2Strength
If Cu-Mg-Ti brazing filler material is used to bond ceramic substrate and Cu foil, then bonding is achieved, but bonding rate between ceramic substrate and circuit layer is decreased
Solution Approach 1:
Changing the brazing filler material composition to Cu-P-Sn-based alloy with added Ti paste modifies the bonding kinetics. This parameter change enables faster bonding rates while achieving sufficient bonding strength, as the new material system forms effective bonds more rapidly than the conventional Cu-Mg-Ti system
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 solution reduces thermal stress in ceramic substrates during thermal cycles, preventing cracking and improving the bonding rate between ceramic and circuit layers, ensuring reliable bonding and efficient heat dissipation.
Implementation Method 1
The circuit layer is formed by bonding a Cu foil (Cu member) to one surface of a ceramic substrate (ceramic member) through the heating of the Cu foil which is disposed on the one surface of the ceramic substrate with a Cu-Mg-Ti brazing filler material interposed between the Cu foil and the ceramic substrate
Implementation Method 2
a Cu-Sn layer, in which Sn forms a solid solution with Cu and which is formed at a bonded interface between the ceramic member and the Cu member
Implementation Method 3
The power module substrate is formed by bonding the Cu foil to the ceramic substrate through the heating of the Cu foil
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, in which Sn forms a solid solution with Cu, is formed at a bonded interface between the ceramic member and the Cu member, and intermetallic compounds containing P and Ti are dispersed in the Cu-Sn layer.