Power Module Brazing Assembly to Restrain Substrate Flexure
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Solution Overview
Problem
The existing methods for bonding a base plate and a ceramic substrate in power modules face issues with thermal expansion coefficient differences leading to flexure and require costly vacuum bonding equipment, resulting in low bonding reliability and increased process costs.
Innovation Solution
A method involving the application of a brazing filler layer on the base plate, followed by lamination between upper and lower jigs that are adjusted to pressurize the substrate, allowing brazing at high temperatures without the need for vacuum equipment, using materials like Ag, Cu, and AgCuTi, and jigs made of S45C, SKD11, or SUS to constrain deformation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If soldering is used to bond the base plate to the ceramic substrate, then heat dissipation is improved, but flexure occurs due to thermal expansion coefficient difference at high temperatures
Solution Approach 1:
The patent changes the bonding temperature parameter from low temperature (≤250°C) to high temperature (780-900°C) and uses brazing filler material with appropriate melting point to achieve reliable bonding at high temperature, eliminating flexure issues while maintaining heat dissipation performance
Solution Approach 2:
The patent replaces the mechanical bonding method (soldering) with a metallurgical bonding method (brazing), where the brazing filler layer creates a metallurgical bond between the base plate and ceramic substrate, providing superior high-temperature stability and eliminating flexure problems
2Reliability
If vacuum bonding equipment and solder preform are used, then bonding process is achieved, but process costs increase and equipment complexity increases
Solution Approach 1:
The patent uses a disposable brazing filler layer applied directly to the base plate surface, eliminating the need for expensive vacuum bonding equipment and solder preforms, achieving reliable bonding through a simple, cost-effective process
Solution Approach 2:
The patent extracts and eliminates the vacuum bonding equipment from the bonding process, using only simple heating equipment to melt the brazing filler layer, thereby reducing equipment complexity and process costs while maintaining bonding reliability
3Reliability
If low temperature bonding (≤250°C) is used with AlSiC, then bonding is achieved, but process costs increase due to solder paste and vacuum equipment
Solution Approach 1:
The patent changes the bonding temperature from low (≤250°C) to high (780-900°C) and uses brazing instead of soldering, eliminating the need for expensive vacuum equipment and solder paste, thereby reducing manufacturing costs while achieving reliable bonding
Solution Approach 2:
The patent replaces the complex vacuum bonding process with a simple brazing process that uses only heating equipment, substituting expensive vacuum equipment and solder paste with a cost-effective brazing filler layer and atmospheric heating process
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 approach enhances bonding strength, simplifies the process, reduces costs, and improves heat dissipation and dimensional accuracy by restraining flexure and facilitating efficient heat transfer between the base plate and ceramic substrate.
Implementation Method 1
brazing the brazing filler layer through melting
Implementation Method 2
pressurizing the base plate and the ceramic substrate by adjusting a gap distance between the upper jig and the lower jig
Implementation Method 3
improves heat dissipation and dimensional accuracy by restraining flexure and facilitating efficient heat transfer between the base plate and ceramic substrate
Data Source
AI summary
The present invention relates to a method of manufacturing a power module. The method involves joining a base plate and a ceramic substrate by brazing while pressing same with an upper jig and a lower jig, and thus can suppress bending, improve joint reliability, and increase heat dissipation.