Semiconductor Case Reinforcement for Screw Torque Cracking
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Solution Overview
Problem
Semiconductor devices experience stress concentration and potential cracking when attached to a heat sink due to the protrusion of the substrate, leading to reduced reliability and increased torque requirements for screw attachment.
Innovation Solution
The semiconductor device incorporates a case design with attachment portions featuring parallel attachment frames, a connecting frame, and reinforcing portions that distribute stress, reducing concentration at the screw attachment points and enhancing torque resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the substrate protrudes from the rear surface of the case to facilitate attachment to the heat sink, then the attachment process is simplified, but stress concentration occurs around the screw holes causing cracks and reducing reliability
Solution Approach 1:
The case is divided into multiple frames (first side frame, second side frame, third side frame, fourth side frame) that are respectively attached to the four sides of the substrate. This segmentation distributes the mechanical stress across multiple attachment points rather than concentrating it at screw holes, preventing cracks while maintaining attachment capability
Solution Approach 2:
Reinforcing portions are locally added at specific positions where the first side frame, one of the pair of first attachment frames, and the first corner meet. This local reinforcement strengthens the case structure precisely at the stress concentration zones without requiring overall case thickening, thereby preventing cracks while maintaining ease of attachment
2Ease of operation
If screws are inserted into screw holes at the center of short sides to attach the device to the heat sink, then attachment is achieved, but stress concentration around the screw holes causes cracks
Solution Approach 1:
Instead of using single screw holes at the center of short sides, the case uses multiple frames attached to all four sides of the substrate. This distributes the attachment stress across numerous contact points between the frames and substrate, eliminating stress concentration at specific screw hole locations while maintaining secure attachment to the heat sink
Solution Approach 2:
Reinforcing portions are strategically placed at the corners and junctions of the frames to locally strengthen the case structure. This local reinforcement increases the case's overall strength and resistance to cracking without adding significant weight or complexity to the entire device
3Ease of manufacture
If the case structure is simplified without reinforcement, then manufacturing is easier, but the case cracks under stress during screw attachment
Solution Approach 1:
Rather than complicating the entire case structure, reinforcing portions are added only at the specific locations where stress concentration occurs (corners and frame junctions). This localized approach maintains ease of manufacturing for the majority of the case while providing targeted reinforcement to prevent cracking during screw attachment
Solution Approach 2:
The case is designed as an assembly of multiple frames attached to the substrate sides, with reinforcing portions at critical junctions. This segmented design with strategic reinforcement points provides the necessary strength and reliability while keeping the manufacturing process relatively simple through modular construction
Data Source
AI summary
A frame body includes reinforcing portions. The reinforcing portions are each provided in the region formed by a side frame and one of a pair of attachment frames in plan view. Each reinforcing portion is in contact with the side frame, the one of the pair of attachment frames, and the corner at which the side frame and one of the pair of attachment frames are joined.