Transfer-Molded Power Module Pin Structure for Low Inductance
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Solution Overview
Problem
Existing semiconductor device modules face issues with signal pin deformation or breakage during insertion, high stray inductance due to single leadframe formation, and challenges in attaching power modules to thermal-dissipation appliances, leading to reliability and cost concerns.
Innovation Solution
The solution involves arranging signal pins and power tabs on a primary surface of the module rather than along the edge, using pre-molded signal pins with spring portions and mechanical stops to prevent deformation, and attaching a substrate to a thermal-dissipation appliance first to ensure consistent adhesive layers and reduce thermo-mechanical stresses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If signal pins are arranged along the edge of the module, then electrical isolation spacing can be achieved, but the overall module dimensions increase and thermo-mechanical stresses increase
Solution Approach 1:
The patent transitions signal pins from an edge-based linear arrangement to a surface-based two-dimensional arrangement on the primary surface of the module. This dimensional change allows signal pins to be positioned closer together while maintaining electrical isolation through the molding compound, thereby reducing overall module dimensions without compromising isolation effectiveness.
2Ease of operation
If signal pins are bent to facilitate insertion into PCB, then ease of insertion is improved, but deformation or breakage occurs during insertion
Solution Approach 1:
The patent incorporates a spring portion in the signal pin structure that acts as a pre-designed cushioning element. This spring portion absorbs insertion forces and provides mechanical compliance, allowing the signal pin to be inserted into the PCB without excessive bending or risk of breakage, thereby maintaining both insertion ease and structural integrity.
3Reliability
If guide part or tool is used to prevent signal pin deformation, then signal pin integrity is improved, but system integration complexity increases and total system cost increases
Solution Approach 1:
The patent designs the signal pin with an integrated spring portion that provides self-protection against deformation during insertion. This self-service mechanism eliminates the need for external guide parts or specialized insertion tools, thereby maintaining signal pin integrity while reducing system integration complexity and total system cost.
4Ease of manufacture
If single body stamping process is used to form leadframe, then manufacturing simplicity is improved, but stray inductance between power tabs increases
Solution Approach 1:
The patent divides the leadframe into multiple separate components rather than using a single stamped piece. This segmentation allows for optimized current paths and reduced loop areas between power tabs, thereby reducing stray inductance while maintaining manufacturing simplicity through separate fabrication and assembly processes.
5Temperature
If power module is attached to thermal-dissipation appliance after package assembly, then thermal management is achieved, but adhesive layer consistency deteriorates and voids increase
Solution Approach 1:
The patent performs the attachment to the thermal-dissipation appliance before completing the package assembly process. This preliminary action ensures that the substrate is firmly positioned and the adhesive layer is applied under controlled conditions, preventing warping and oxidation issues that would otherwise cause inconsistent adhesive thickness and void formation during later assembly steps.
6Strength
If thermal processing is used for attachment to thermal-dissipation appliance, then attachment strength is improved, but internal solder re-melting occurs and thermo-mechanical stresses increase
Solution Approach 1:
The patent modifies the attachment process parameters by using eutectic solder with a lower melting point and controlling the thermal processing conditions to stay below the re-flow temperature. This parameter change allows achieving sufficient attachment strength through optimized thermal conditions while preventing internal solder re-melting and reducing thermo-mechanical stresses on the module.
Data Source
Figure 1A~2C
Figure 3A
Figure 3B~3D
AI summary
In a general aspect, an electronic device assembly includes a substrate arranged in a plane. The substrate has a first side and a second side, the second side being opposite the first side. The assembly also includes a plurality of semiconductor die disposed on the first side of the substrate and at least one signal pin. The at least one signal pin includes a proximal end portion coupled with the first side of the substrate, a distal end portion, and a medial portion disposed between the proximal end portion and the distal end portion. The medial portion is pre-molded in a molding compound, the proximal end portion and the distal end portion exclude the molding compound. The at least one signal pin is arranged along a longitudinal axis that is orthogonal to the plane of the substrate.