Two-Layer Molding for Semiconductor Power Module Short Circuit Protection
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Solution Overview
Problem
Power semiconductor modules using hard potting materials are prone to damage during short circuit events due to overheating and cracking of substrates, as these materials may break under high current flow.
Innovation Solution
A semiconductor power module with a two-layer molding configuration, where a hard epoxy material encapsulates the semiconductor device and bond wire connections, while a softer silicone gel encapsulates a portion of the bond wire, allowing it to fuse and interrupt the circuit during a short circuit, preventing further damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a hard potting material is used to protect the semiconductor device, then the mechanical strength and structural stability are improved, but the module becomes prone to cracking and breakage during short circuit events
Solution Approach 1:
The patent divides the potting material into two distinct layers: a hard epoxy layer (first molding material layer) that provides mechanical strength and structural stability, and a soft silicone gel layer (second molding material layer) that provides flexibility and short circuit protection. This segmentation allows each layer to perform its specialized function without compromising the other.
Solution Approach 2:
Different regions of the module are assigned different material properties: the epoxy layer is positioned to provide rigid protection where structural strength is needed, while the silicone gel layer is positioned to provide flexible protection where shock absorption and short circuit resistance are critical. This local differentiation of material properties resolves the contradiction between strength and reliability.
2Stability of the object's composition
If a hard potting material is used to encapsulate the bond wire, then the structural stability is improved, but the bond wire cannot fuse safely during overcurrent conditions
Solution Approach 1:
The encapsulation structure is segmented into two layers with the soft silicone gel layer specifically positioned to encapsulate the bond wire. This allows the bond wire to be surrounded by a material that permits safe fusion during overcurrent events, while the overall module structure maintains stability through the hard epoxy layer.
Solution Approach 2:
The soft silicone gel layer acts as an intermediary between the hard epoxy structure and the bond wire. It provides a compliant environment that allows the bond wire to fuse safely during short circuits while being supported by the rigid epoxy framework, thus mediating between structural stability and safe failure modes.
3Ease of manufacture
If a single hard molding material is used, then the manufacturing process is simple, but the module lacks the ability to absorb thermal and mechanical stress during short circuit events
Solution Approach 1:
The patent employs a composite molding structure combining epoxy and silicone gel materials. While this requires a two-step molding process, each step uses a single material type, maintaining relative manufacturing simplicity. The composite structure provides both the mechanical strength of epoxy and the thermal shock resistance of silicone gel, achieving short circuit protection without excessive manufacturing complexity.
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 two-layer molding configuration enhances the reliability and lifetime of power modules by combining high reliability with safety features under short circuit conditions, reducing the risk of substrate cracking and maintaining module endurance.
Implementation Method 1
a short circuit event may cause a flow of high current within a short time resulting in overheating of the semiconductor device and adjoining assembly materials
Data Source
AI summary
According to an aspect, a semiconductor power module includes a substrate, a semiconductor device coupled to the substrate, a bond wire coupled to the semiconductor device, and a first molding material layer disposed on the substrate. The first molding material layer encapsulates a first portion of the bond wire. The bond wire has a second portion disposed outside of the first molding material layer. The semiconductor power module includes a second molding material layer disposed on the first molding material layer. The second molding material layer encapsulates the second portion of the bond wire. The second molding material layer has a hardness less than a hardness of the second molding material layer.