Power Module Brazed Substrate Assembly to Prevent Flexure
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Solution Overview
Problem
The existing bonding methods between ceramic substrates and base plates in power modules face issues with flexure and porosity defects due to thermal expansion coefficient differences and the use of solder paste and preforms, leading to increased process costs and reliability concerns.
Innovation Solution
A power module design featuring a ceramic substrate with separated lower electrode layers and recess grooves on the base plate, where the lower electrode layer is inserted into the grooves, and brazing is performed with a filler to achieve reliable bonding, controlling volume and area ratios to prevent flexure and porosity defects.
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 and porosity defects occur due to thermal expansion coefficient differences and high temperature
Solution Approach 1:
The patent changes the bonding method from soldering to brazing, which operates at a different temperature range and uses a filler metal to accommodate thermal expansion differences. This parameter change in the bonding process eliminates flexure and porosity defects while maintaining heat dissipation performance
Solution Approach 2:
The patent introduces a brazing filler as an intermediary material between the base plate and ceramic substrate. This filler metal mediates the bonding process, allowing reliable attachment while compensating for thermal expansion coefficient differences between the dissimilar materials
2Reliability
If solder paste and solder preform are used for bonding, then bonding is achieved, but process cost increases due to vacuum bonding equipment requirements
Solution Approach 1:
The patent extracts and eliminates the requirement for vacuum bonding equipment and solder preforms from the manufacturing process. By using brazing with a filler metal, the process can be performed without vacuum equipment, significantly reducing manufacturing complexity and cost while maintaining bonding reliability
3Stability of the object's composition
If the lower electrode layer is continuous, then electrical connection is maintained, but flexure occurs due to thermal expansion mismatch between base plate and ceramic substrate
Solution Approach 1:
The patent segments the lower electrode layer into multiple separate regions rather than maintaining it as a continuous layer. This segmentation allows each electrode region to independently accommodate thermal expansion differences, preventing flexure while maintaining electrical connectivity through the segmented structure
4Reliability
If the lower electrode layer volume is large, then electrical connection is ensured, but porosity defects occur during bonding
Solution Approach 1:
The patent optimizes the volume and dimensions of the lower electrode layer as a parameter change. By controlling the electrode layer volume to be appropriate rather than excessively large, the patent prevents porosity defects during bonding while ensuring sufficient electrical connection capability through the optimized geometry
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 reliability, prevents flexure and porosity defects, simplifies the process, and improves heat dissipation by ensuring accurate alignment and bonding force, while reducing the need for vacuum equipment and solder preforms.
Implementation Method 1
A brazing filler may be disposed between the lower electrode layer and the recess grooves, and may braze the ceramic substrate and the base plate
Data Source
AI summary
The present invention relates to a power module and a method for producing same, in which the bottom electrode layer of a ceramic substrate is inserted into recesses of a base plate, and with the ceramic substrate stacked on the base plate, adhesion via brazing is carried out, thus improving adhesion reliability, preventing flexure, and provides highly efficient heat dissipation.