Composite Bonding Material for High-Temperature Power Device Joints
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Solution Overview
Problem
Conventional bonding materials, such as solder materials containing Sn, Pb, or the like, struggle to provide adequate heat resistance when used in bonded structures with SiC or GaN elements, which generate high temperatures due to increased current handling.
Innovation Solution
A bonding material comprising single particles of a low melting point metal, composite particles with a central core of the low melting point metal coated with fine particles of a high melting point metal, and a flux containing a reducing agent, which forms an intermetallic compound to enhance heat resistance and bonding strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If solder material containing Sn, Pb, or the like is used as bonding material, then bonding can be performed at low temperature, but heat resistance cannot be secured when bonding portion temperature reaches 200°C to 250°C
Solution Approach 1:
The bonding material uses a composite particle structure consisting of a low melting point metal core (Sn, Pb, or their alloys) combined with a high melting point metal shell (Ag, Cu, Au, or their alloys). This composite structure enables the material to melt at low temperatures for easy bonding while the high melting point metal shell provides heat resistance to withstand temperatures of 200°C to 250°C, thus resolving the contradiction between ease of bonding and heat resistance.
2Loss of time
If high melting point metal nanoparticles are used to shorten interdiffusion time, then bonding time is reduced, but nanoparticles encapsulate the low melting point metal surface and deteriorate meltability
Solution Approach 1:
The high melting point metal is selectively distributed only on the surface of the low melting point metal core in the form of a thin shell or coating, rather than being uniformly distributed throughout. This local quality distribution allows the surface to provide heat resistance and reduce interdiffusion time, while the bulk low melting point metal core maintains its meltability, thus resolving the contradiction between bonding time and meltability.
3Productivity
If SiC elements or GaN elements are used to control power with high efficiency, then power control efficiency is improved, but temperature of bonding portion increases to 200°C to 250°C
Solution Approach 1:
The composite particle structure with low melting point metal core and high melting point metal shell enables the bonding material to withstand the elevated temperatures (200°C to 250°C) generated by SiC or GaN elements, allowing these high-efficiency power devices to operate without compromising bonding portion integrity.
4Ease of manufacture
If conventional solder material is used, then bonding can be performed easily, but bonding strength is insufficient at high temperatures
Solution Approach 1:
The composite particle structure combines the ease of bonding from low melting point metals with the high temperature strength of high melting point metals, achieving both easy manufacturing process and sufficient bonding strength at elevated temperatures simultaneously.
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 proposed bonding material achieves high bonding strength and excellent heat resistance by shortening the bonding time, reducing thermal damage, and preventing deterioration of meltability, thus addressing the limitations of conventional materials in high-temperature applications.
Implementation Method 1
a high melting point metal and a low melting point metal are brought into contact with each other to melt the low melting point metal, and interdiffusion therebetween forms an intermetallic compound with the high melting point metal
Implementation Method 2
a flux including a reducing agent component, in which the first metal and the second metal have properties of forming an intermetallic compound of the first metal and the second metal, and the reducing agent component of the flux is present between the central core and the at least one coating layer
Data Source
AI summary
A bonding material includes: a single particle that is a particle of a first metal; a composite particle including a central core that is a particle of the first metal, and at least one coating layer covering an entire surface of the central core, the at least one coating layer including a fine particle of a second metal; and a flux including a reducing agent component, in which the first metal and the second metal have properties of forming an intermetallic compound of the first metal and the second metal, and the reducing agent component of the flux is present between the central core and the at least one coating layer.