Power Semiconductor Package With Stress Relief Region
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Solution Overview
Problem
Power semiconductor packages face challenges in achieving optimal power density, minimizing parasitics, ensuring mechanical integrity and reliability, and controlling manufacturing costs, particularly due to limitations in cooling, interconnection methods, and material usage.
Innovation Solution
A power semiconductor package design featuring a stress relief region between mounting regions with differential rigidity, formed by apertures or bends in the stamped body, providing mechanical protection and flexibility while maintaining electrical conductivity, and optionally incorporating additional semiconductor chips or passive elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a traditional mold process is used for package integrity, then mechanical protection is provided, but the top exposure area is limited and manufacturing complexity increases
Solution Approach 1:
The package structure is segmented into distinct functional regions: mounting regions for electrical connections, a stress relief region with reduced stiffness for thermal expansion accommodation, and exposed top surfaces for heat dissipation. This segmentation allows each region to optimize its function without compromising overall package integrity.
Solution Approach 2:
The body is designed with spatially varying mechanical properties through the stress relief region that has different stiffness characteristics compared to the mounting regions. This local quality variation allows the stress relief region to flex and accommodate thermal stresses while the mounting regions maintain structural integrity for reliable electrical connections.
2Object-generated harmful factors
If clip bonding is used to eliminate wire bonds and reduce parasitics, then parasitic resistance and inductance are reduced, but the top exposure area is limited and traditional mold process is required
Solution Approach 1:
The mounting regions serve dual functions: providing electrical connections through clip bonding to eliminate wire bonds and reducing parasitics, while also serving as structural support elements. The integration of electrical and mechanical functions in the same components simplifies the overall manufacturing process.
3Object-generated harmful factors
If chip-only ball grid array is used for interconnection, then wire bonds are eliminated, but connection to certain active components is problematic and mechanical integrity is compromised at upper power limits
Solution Approach 1:
The package employs a composite structure combining different interconnection methods: clip bonding in mounting regions for low-parasitic connections and ball grid array where appropriate. The stamped metal body provides a composite of mechanical strength and thermal management capabilities, supporting both connection technologies.
4Ease of manufacture
If the package size is minimized to achieve 1:1 ratio with active element, then manufacturing cost is reduced, but thermal stress management becomes more difficult
Solution Approach 1:
The stress relief region is designed with dynamic mechanical properties, having reduced stiffness to allow controlled deformation and stress relaxation during thermal cycling. This dynamic response enables the compact package to accommodate thermal expansion differences between dissimilar materials without compromising reliability.
5Temperature
If thermally conductive features are exposed to ambient environment for heat dissipation, then power density is improved, but mechanical protection of silicon features is reduced
Solution Approach 1:
The package design exposes only specific thermally conductive features (mounting regions with electrical contacts) to the ambient environment for heat dissipation, while the stamped metal body provides mechanical protection to the silicon die. This localized exposure strategy optimizes thermal management while maintaining mechanical integrity where required.
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
The design enhances mechanical strength, reduces thermal stresses, and allows for efficient heat dissipation, improving the operational performance and reliability of the package while minimizing material usage and manufacturing complexity.
Implementation Method 1
The stress relief region is configured to create differential rigidity between the stress relief region and the remaining portions of the body such that the remaining portions have a greater stiffness associated therewith than the stress relief region
Implementation Method 2
exposing thermally conductive features, such as metal and silicon, of the active components of the package to an ambient environment
Implementation Method 3
The stress relief region may be formed from a plurality of apertures in the stamped body
Data Source
AI summary
The present invention features a power semiconductor package and a method of forming the same that includes forming, in the body, a stress relief region disposed between a pair of mounting regions and attaching a semiconductor die in each of the mounting regions. The semiconductor die has first and second sets of electrical contacts with the first set being on a first surface of the semiconductor die and the second set being disposed upon a second surface of the semiconductor die opposite to the first surface. The first set is in electrical communication with the mounting region. Walls are formed on outer sides of the pair of mounting regions, defining a shaped body, with the shaped body and walls defining an electrically conductive path that extends from the first set and terminates on side of the package common with the second set.