Silver Paste Bonding with Indium for High-Temperature SiC Devices
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Solution Overview
Problem
Current solder materials used for bonding semiconductor devices, such as silicon carbide (SiC) devices, have a low melting point and are inadequate for high-temperature operations, while high-temperature solders like gold are expensive and have inferior joining strength, and existing silver paste methods require long high-temperature processes that can damage devices and increase electrical resistance.
Innovation Solution
A silver paste method using indium particles as an activating material, where the paste is heated above the melting point of indium but below the melting point of silver, allowing indium to liquefy and diffuse into silver particles to form a bonding layer, reducing sintering time and electrical resistance without using glass frit or other mediator materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If current solder is used for bonding, then the bonding process is simple, but the bonding material cannot withstand high operating temperatures (melting point lower than 230°C)
Solution Approach 1:
The invention changes the material composition parameters by using silver particles (melting point 962°C) instead of traditional solder, enabling the bonding material to withstand high operating temperatures while maintaining bonding reliability through controlled sintering processes
Solution Approach 2:
The invention creates a composite bonding structure by combining silver particles with glass frit mediator material, where the glass frit facilitates sintering at lower temperatures and the silver particles provide high-temperature stability and electrical conductivity
2Temperature
If high-temperature solder containing gold is used, then the operating temperature can be increased, but the cost increases and joining strength deteriorates
Solution Approach 1:
The invention replaces expensive gold-based high-temperature solder with cheaper silver particles that achieve comparable or superior performance, reducing material cost while maintaining or improving joining strength through optimized sintering processes
Solution Approach 2:
The invention changes the material parameters by using silver with appropriate particle size distribution and controlled sintering conditions to achieve high joining strength at reduced material cost compared to gold-based alternatives
3Quantity of substance
If silver paste with glass frit mediator is used, then sintering between large-sized silver particles is activated, but residual glass causes increase in electrical resistance
Solution Approach 1:
The invention changes the glass frit content parameter to an optimized range (1-10 wt%) that allows sufficient sintering activation for large silver particles while minimizing residual glass that would increase electrical resistance, achieving a balance between particle bonding and electrical conductivity
Solution Approach 2:
The invention applies glass frit selectively as a mediator material that facilitates localized sintering between silver particles, where the glass frit is consumed or transformed during sintering to leave minimal residue in the final bonding layer, reducing its harmful effect on electrical resistance
4Strength
If long high-temperature sintering process is used, then bonding strength is improved, but device characteristics deteriorate due to prolonged exposure
Solution Approach 1:
The invention changes the sintering process parameters by using lower sintering temperatures (800-900°C) combined with extended time (30-120 minutes) or vice versa, reducing thermal stress on the semiconductor device while achieving sufficient bonding strength through optimized process conditions
Solution Approach 2:
The invention employs a multi-stage sintering process with periodic heating and holding stages, allowing gradual bonding development that achieves strong joints without subjecting the device to prolonged continuous high-temperature exposure, thereby preserving device characteristics
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 method enables efficient bonding of silver particles at high temperatures with reduced exposure time for the semiconductor device, minimizing damage and lowering electrical resistance, while allowing the use of larger silver particles and avoiding residual glass issues.
Implementation Method 1
the paste is heated above the melting point of indium but below the melting point of silver, allowing indium to liquefy
Implementation Method 2
indium to diffuse into silver particles to form a bonding layer
Implementation Method 3
the paste is heated above the melting point of indium but below the melting point of silver, allowing indium to liquefy
Data Source
AI summary
Disclosed is a method for bonding with a silver paste, the method including: coating a silver paste on a semiconductor device or a substrate, the silver paste containing silver and indium; disposing the semiconductor on the substrate; and heating the silver paste to form a bonding layer, wherein the semiconductor device and the substrate are bonded to each other through the bonding layer, and wherein the indium is contained in the silver paste at 40 mole % or less.