Low Inductance Power Module Bus Bar Design
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Solution Overview
Problem
Conventional semiconductor power modules face inefficiencies due to high power loop commutation inductance and limited space for semiconductor devices, making them unsuitable for high power density and current applications, and they offer limited testing opportunities for individual components.
Innovation Solution
A power module design featuring a low inductance bus bar structure with multiple bus bars and conductive traces on both sides of a substrate, allowing for a continuous electrical path and reduced inductance, enabling faster switching and full utilization of wide band-gap semiconductor devices, along with flexible fabrication and robust testing capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If bus bars are placed in close proximity to the substrate to reduce inductance, then power loop commutation inductance is reduced, but substrate area available for semiconductor devices is significantly occupied
Solution Approach 1:
The bus bar structure transitions from a planar configuration to a three-dimensional configuration with tabs extending vertically from the substrate surface. This dimensional change allows the bus bars to achieve low inductance through close proximity to traces while occupying minimal substrate area, as the bulk of the bus bar structure extends in the vertical dimension rather than consuming horizontal substrate real estate.
Solution Approach 2:
The bus bar structure is segmented into multiple tabs distributed across the substrate surface, with each tab connecting to specific conductive traces. This segmentation allows for optimized electrical connections to reduce inductance while distributing the physical footprint across multiple locations rather than requiring a single large planar bus bar that would consume excessive substrate area.
2Loss of energy
If conventional planar bus bar configurations are used to reduce inductance, then power loop commutation inductance is reduced, but manufacturing testing opportunities are limited
Solution Approach 1:
The bus bar structure is divided into separate tabs that can be independently connected to different conductive traces and semiconductor devices. This segmentation enables modular assembly where individual tabs and their corresponding connections can be tested independently during manufacturing, allowing for targeted testing of specific electrical paths without requiring complete module assembly.
Solution Approach 2:
The bus bar tabs are pre-formed and positioned before final connection to semiconductor devices, allowing for preliminary testing of the bus bar structure itself and its electrical connections to substrate traces. This preliminary action enables quality control testing at intermediate stages of manufacturing rather than only after complete assembly.
3Ease of manufacture
If single layer metal traces are used on ceramic substrate, then manufacturing is simplified, but power loop commutation inductance increases
Solution Approach 1:
The electrical connection system utilizes three-dimensional bus bar tabs extending vertically from the substrate surface, creating multiple electrical paths through the vertical dimension. This dimensional addition provides multiple parallel current paths that reduce overall commutation inductance while maintaining the simplicity of single-layer planar traces on the substrate for manufacturing ease.
Data Source
AI summary
A power module includes a first bus bar having a first plurality of tabs, wherein each of the first plurality of tabs is electrically coupled to a respective conductive trace of a plurality of conductive traces disposed on a first side; a second bus bar having a second plurality of tabs, wherein each of the second plurality of tabs is electrically coupled to a respective conductive trace of a plurality of conductive traces disposed on a second side; and a third bus bar having a third plurality of tabs, wherein at least one tab of the third plurality of tabs is electrically coupled to a respective conductive trace of the plurality of conductive traces disposed on the first side and at least one tab of the third plurality of tabs is electrically coupled to a respective conductive trace of the plurality of conductive traces disposed on the second side.