Power Module Support Tab Buffering Molding Stress
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Solution Overview
Problem
Conventional power modules using direct bonding copper (DBC) substrates face substrate failure due to stress applied by support pins during the molding process, leading to ceramic layer cracking or breaking, which reduces thermal resistance and isolation breakdown voltage.
Innovation Solution
A power module design incorporating a support tab made of ductile metals like copper, aluminum, or iron, which acts as a buffer against mechanical stress, reducing the likelihood of substrate failure and allowing for the use of less expensive ceramic materials and thinner layers, thereby maintaining low thermal resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a support pin is used to press the DBC substrate during molding, then the flatness of the substrate is maintained and mold flash is prevented, but stress is applied to the substrate causing ceramic layer cracking or breaking
Solution Approach 1:
A support tab made of ductile metal is introduced as an intermediary element between the support pin and the DBC substrate. The support tab absorbs and distributes the mechanical stress from the support pin, preventing direct transmission of stress to the brittle ceramic layer while maintaining substrate flatness during molding.
Solution Approach 2:
The support tab is pre-installed on the DBC substrate before the molding process. This cushioning element is positioned in advance to absorb the compressive force from the support pin during molding, preventing ceramic layer failure before it occurs.
2Strength
If a thick ceramic layer is used in the DBC substrate, then mechanical strength and reliability are improved, but thermal resistance increases and manufacturing cost increases
Solution Approach 1:
The support tab serves as a stress-distributing intermediary that allows the ceramic layer to be thinner while maintaining adequate mechanical strength. By distributing the load across a larger area through the ductile metal tab, the ceramic layer does not need to be as thick to prevent cracking, thereby reducing thermal resistance.
3Reliability
If a thick ceramic layer is used in the DBC substrate, then substrate reliability is improved, but manufacturing cost increases
Solution Approach 1:
The support tab acts as a cost-effective intermediary that enhances substrate reliability without requiring expensive thick ceramic layers. The ductile metal tab provides the necessary mechanical support at a lower cost than increasing ceramic thickness, improving reliability while reducing manufacturing cost.
4Ease of manufacture
If the ceramic layer is made thinner to reduce cost and thermal resistance, then manufacturing cost and thermal performance are improved, but the substrate becomes more susceptible to cracking under stress
Solution Approach 1:
The support tab is a ductile metal element that compensates for the reduced strength of the thinner ceramic layer. It absorbs and distributes mechanical stresses that would otherwise concentrate on the thin ceramic, preventing cracking while allowing the use of thinner, more cost-effective ceramic material.
Solution Approach 2:
The invention changes the material parameter of the support structure from brittle ceramic to ductile metal for the support tab. This parameter change allows the support tab to deform plastically under stress, absorbing energy and preventing crack propagation in the thin ceramic layer.
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 support tab effectively prevents ceramic layer cracking, allows for cost-effective fabrication with reduced ceramic layer thickness, enhances process reliability, and maintains high thermal performance, suitable for various power modules such as smart power, plasma display panel, and insulated gate bipolar transistor modules.
Implementation Method 1
a support tab formed to buffer a stress applied by a support pin onto the substrate, thereby virtually always preventing a ceramic layer included in the substrate from cracking or breaking
Implementation Method 2
The epoxy molding compound is used as an isolation material and simultaneously used as a heat transfer path
Data Source
AI summary
A power module with low thermal resistance buffers the stress put on a substrate during a package molding operation to virtually always prevent a fault in the substrate of the module. The power module includes a substrate, a conductive adhesive layer formed on the substrate, a device layer comprising a support tab, a power device, and a passive device which are formed on the conductive adhesive layer, and a sealing material hermetically sealing the device layer. The support tab is buffers the stress applied by a support pin to the substrate, thereby virtually always preventing a ceramic layer included in the substrate from cracking or breaking. As a result, a reduction in the isolation breakdown voltage of the substrate is virtually always prevented and the failure of the entire power module is do to a reduction in the breakdown voltage of the substrate is virtually always prevented.