Power Device Package Bushing for Bolt Coupling Stress
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional power device packages experience damage and reliability issues due to compressive and shear stresses when coupling a heat sink using a bolt member, leading to potential cracking and insulation breakdown.
Innovation Solution
Incorporating a bushing member with a through hole for the bolt, formed from materials like aluminum or copper alloys, which reduces stress and provides a secure coupling mechanism without direct contact with the mold member, preventing damage during bolt coupling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a bolt member is used to couple the heat sink to the power device package, then the heat dissipation efficiency is improved, but compressive stress and shear stress cause cracks in the mold member
Solution Approach 1:
A bushing member is introduced as an intermediary component between the bolt member and the mold member. The bushing member has a through hole that accommodates the bolt, allowing the heat sink to be coupled to the substrate while the bushing absorbs the mechanical stress. This prevents direct contact between the bolt and the mold member, eliminating the harmful compressive and shear stresses that would otherwise cause cracks in the mold member.
2Device complexity
If the bolt member directly contacts the mold member, then the coupling is simple, but cracks are formed in the mold member due to applied stress
Solution Approach 1:
The bushing member serves as a mediator that is integrated into the mold member structure. It provides a through hole for the bolt while distributing the mechanical stress away from the mold member's critical regions. This maintains the simplicity of the coupling structure while significantly improving reliability by preventing crack formation in the mold member.
3Ease of manufacture
If the mold member is directly coupled to the heat sink, then the manufacturing process is simple, but moisture permeation and insulation breakdown occur due to cracks
Solution Approach 1:
The bushing member is manufactured as an integrated feature within the mold member using the existing transfer molding process. This maintains ease of manufacture without requiring additional assembly steps. The bushing's through hole allows bolt passage while its presence prevents stress-induced cracks, thereby eliminating the pathways for moisture permeation and preventing insulation breakdown.
4Strength
If a bushing member is added to provide a through hole for the bolt, then the mold member is protected from damage, but the device structure becomes more complex
Solution Approach 1:
The bushing member is merged with the mold member as an integrated component during the transfer molding process. Rather than being a separate part requiring additional assembly, the bushing is formed as an inherent feature of the mold member structure. This minimizes the increase in device complexity while maintaining the protective function against bolt-induced damage.
Data Source
AI summary
Provided are a power device package coupled to a heat sink using a bolt and a semiconductor package mold for fabricating the same. The power device package includes: a substrate; at least one power device mounted on the substrate; a mold member sealing the substrate and the power device; and at least one bushing member fixed to the mold member to provide a through hole for a bolt member for coupling a heat sink to the mold member.