Transistor Package Bus Tab Segmentation for Current and Heat
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Solution Overview
Problem
Traditional transistor packages in power distribution systems, such as those used in aircraft electrical systems, face limitations in efficiently handling current and heat due to their reliance on a single large flat surface for attachment to a printed wiring board (PWB), which restricts their ability to handle high currents and dissipate heat effectively.
Innovation Solution
The design introduces a transistor package with bus tabs extending from opposite sides of a die case, allowing for high-capacity current flow and improved heat dissipation, where the bus tabs and gate elements can be bent at 90-degree angles to connect with power bus rails and a PWB, reducing the need for thick copper layers on the PWB.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a single large flat surface is used to attach to PWB, then the structure is simple, but current handling capability and heat dissipation are limited
Solution Approach 1:
The single large flat surface is segmented into multiple bus tabs (source bus tab and drain bus tab) that extend from opposite sides of the die case. This segmentation allows current to be distributed across multiple separate connection points, increasing current handling capability while maintaining manufacturing simplicity through modular construction.
Solution Approach 2:
The bus tabs extend in multiple directions (first direction from die case, second direction perpendicular to first) creating a three-dimensional configuration. This dimensional change allows the bus tabs to reach power bus rails positioned away from the PWB surface, improving current handling and heat dissipation without requiring thick copper layers on the PWB.
2Ease of manufacture
If a single large flat surface is used to attach to PWB, then manufacturing is easier, but heat dissipation efficiency is reduced
Solution Approach 1:
The heat dissipation function is segmented across multiple bus tabs extending from opposite sides of the die case. Each bus tab provides an independent thermal pathway to the PWB, increasing the total heat dissipation surface area and efficiency while keeping the attachment structure simple and manufacturable.
Solution Approach 2:
The bus tabs extend in multiple dimensions to reach power bus rails positioned away from the PWB surface. This three-dimensional arrangement creates additional thermal pathways through the bus tab structure itself, improving heat dissipation efficiency without requiring thick copper layers on the PWB.
3Reliability
If thick copper layers are used on PWB, then current handling improves, but the requirement for thick copper layers increases complexity and cost
Solution Approach 1:
The bus tabs extend in multiple directions (first direction from die case, second direction perpendicular to first) creating a three-dimensional configuration. This dimensional change allows the bus tabs to reach power bus rails positioned away from the PWB surface, improving current handling and heat dissipation without requiring thick copper layers on the PWB.
Solution Approach 2:
The bus tabs act as intermediary conductors between the die case and the power bus rails on the PWB. These bus tabs carry the high current locally, eliminating the need for thick copper layers across the entire PWB while maintaining high current handling capability at the critical connection points.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration enables higher current handling and better heat dissipation compared to traditional packages, as it allows for increased thickness in bus tabs and minimizes the requirement for thick copper layers on the PWB, enhancing the overall performance of the transistor package.
Implementation Method 1
a source bus tab extending from a first side of the die case, and a drain bus tab extending from a second side of the die case
Implementation Method 2
carry current and heat in and out of the FET
Data Source
AI summary
In accordance with another aspect, a power switch assembly includes a transistor package including a die case, a source bus tab extending from a first side of the die case, a drain bus tab extending from a second side of the die case, a first power bus rail operatively connected to the source bus tab of the transistor package and a second power bus rail operatively connected to the drain bus tab of the transistor package.