Power Module Package Structure with Stiffness-Gradient Springs
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Solution Overview
Problem
Integrated power modules face challenges in heat dissipation due to excessive stress caused by varying elastic moduli of materials, leading to potential damage or poor heat transfer under environmental vibrations and impacts.
Innovation Solution
A package structure for power modules featuring a body with protruding structures and springs of different equivalent stiffness, utilizing plastic for the body and metal for the springs, with strategically placed openings and bending portions to distribute stress uniformly and reduce deformation, and a groove to prevent direct stress concentration on the direct bonded copper.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the elastic modulus of the module material is increased to improve stiffness, then the module becomes more resistant to deformation, but excessive stress is generated due to the amplification effect, causing damage to the module or built-in parts
Solution Approach 1:
The package structure is divided into multiple components with different stiffness characteristics: a rigid body portion for structural support, flexible side walls for stress absorption, and elastic latching components for stress distribution. This segmentation allows each part to perform its optimal function without generating excessive stress.
Solution Approach 2:
The patent employs parameter changes by using materials with different elastic moduli for different parts of the package structure. The body uses high-stiffness material while side walls and latching components use more flexible materials, creating a gradient of stiffness parameters that prevents stress concentration.
2Stress or pressure
If the elastic modulus of the module material is decreased to reduce stress, then the module becomes more flexible and resistant to stress, but the module deforms easily and the heat-dissipating paste cannot properly contact regions with larger deformation, resulting in poor heat dissipation
Solution Approach 1:
The package structure separates heat dissipation functions from structural flexibility functions. The bottom surface and heat dissipation regions maintain high stiffness for stable thermal contact, while side walls and latching areas use flexible materials for stress absorption, allowing each region to optimize its performance independently.
Solution Approach 2:
Different regions of the package structure are assigned different material properties: the body and heat dissipation surfaces use high-stiffness materials for stable thermal contact, while side walls and latching components use lower-stiffness materials for stress resistance. This local differentiation resolves the contradiction between flexibility and heat dissipation.
3Strength
If the thickness of the body is increased to improve equivalent stiffness, then the module becomes more rigid and resistant to deformation, but the weight and material usage increase
Solution Approach 1:
The package structure divides the body into regions with different thickness requirements: the bottom surface and central support areas use greater thickness for stiffness, while side walls and non-critical regions use reduced thickness for material efficiency. This segmented approach achieves required equivalent stiffness with minimized material usage.
4Stress or pressure
If the thickness of the metal spring is reduced to decrease equivalent stiffness, then the latching component becomes more flexible and stress-distributing, but the strength and load-bearing capacity decrease
Solution Approach 1:
The latching component uses composite construction combining metal spring elements with plastic housing. The thin metal spring provides flexibility and stress distribution, while the plastic housing and integrated latching features provide structural strength and load-bearing capacity. This composite approach allows the thin spring to function effectively without sacrificing overall strength.
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 solution enhances stress transfer efficiency, reduces deformation, and improves immobility and supportability under vibrations and impacts, ensuring uniform stress distribution and effective heat dissipation.
Implementation Method 1
a spring having two ends respectively embedded in the first and second protruding structures. The stress is transferred to the first and second protruding structures via the spring respectively
Data Source
AI summary
A package structure of a power module is provided. The package structure includes a body having a sidewall, a first protruding structure protruding outward from one end of the sidewall, a second protruding structure protruding outward from another end of the sidewall and opposite to the first protruding structure, and a spring having two ends embedded in the first and the second protruding structures, respectively. The stress is transferred to the first and the second protruding structures via the spring, respectively. The equivalent stiffness of the spring is different from that of the body so that the package structure as a whole suffers the stress uniformly.