Semiconductor Module Connector Coating for Low-Resistance Bus Bar Joints
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Solution Overview
Problem
Conventional semiconductor module external connectors face reliability issues due to inadequate contact resistance and torque support during connection to bus bars, leading to potential gaps and increased tightening torque that may cause cracks.
Innovation Solution
The external connector design includes a conductor with a glossy nickel first metal layer and a gold or silver second metal layer, both supported by a nickel bottom surface layer, integrated with a nut that securely engages the bus bar, ensuring low contact resistance and adequate torque distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional single-layer metal coating is used on the external connection terminal, then the manufacturing process is simple, but the contact resistance is high and connection reliability is poor
Solution Approach 1:
The external connection terminal uses a composite metal layer structure consisting of a nickel bottom surface layer, a first metal layer (glossy nickel), and a second metal layer (gold, silver, or copper tin alloy). This multi-layer composite structure combines the advantages of different materials: nickel provides hardness and torque support, while gold/silver/copper tin alloy provides low contact resistance. The composite structure resolves the contradiction by achieving both low contact resistance and high connection reliability without excessive complexity.
Solution Approach 2:
Different metal layers are applied to different surfaces of the external connection terminal based on local requirements. The bottom surface has a nickel layer for torque support and thread engagement, while the upper surface has a combination of nickel and precious metal layers for optimal electrical contact. This local differentiation of material properties optimizes both electrical performance and mechanical connection strength.
2Strength
If the nut is made with insufficient engagement depth, then the assembly is easier to manufacture, but the torque support is inadequate and nut rotation occurs
Solution Approach 1:
The nickel bottom surface layer is pre-formed on the external connection terminal before nut assembly, creating a hardened engagement surface that prevents nut rotation during tightening. This preliminary preparation of the engagement surface ensures adequate torque support without requiring excessive nut engagement depth or complex nut designs.
3Strength
If the first metal layer has high hardness, then the torque support and crack prevention are improved, but the contact resistance may increase
Solution Approach 1:
The solution employs a composite metal layer structure where the nickel first metal layer provides high hardness for torque support and crack prevention, while the second metal layer (gold, silver, or copper tin alloy) provides low contact resistance. This composite approach resolves the contradiction by assigning different functional requirements to different layers: structural integrity to the nickel layer and electrical conductivity to the precious metal layer.
Data Source
AI summary
External connection reliability is improved with an external connector including an external connection terminal, and a nut provided on a bottom surface side of the external connection terminal. The external connection terminal has a conductor, a first metal layer provided on an upper surface of the conductor, a second metal layer provided on the first metal layer, and a bottom surface metal layer provided on a bottom surface of the conductor.