Power Semiconductor Module Curved Intermediate Member Stress Reduction

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Solution Overview

Problem

The reliability of power semiconductor devices is compromised due to excessive residual stress in the connecting members, leading to decreased heat dissipation performance and potential breakage, which affects the reliability of power semiconductor modules and conversion devices.

Innovation Solution

A power semiconductor module design featuring a circuit body housed within a case with opposing heat dissipating members connected via an intermediate member with a curvature, where the intermediate member's thickness is thinner than the heat dissipating members, and a protrusion is formed to reduce stress and enhance adhesion, allowing for efficient heat dissipation and improved reliability.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a connecting member is used to connect the circuit body to the case, then the heat dissipating path is secured, but excessive residual stress causes the connecting member to crack or detach

Engineering Contradiction:

Improvereliability of power semiconductor deviceVSAvoidstrength of connecting member

Core Design Contradiction:

ReliabilityVSStrength

Solution Approach 1:

The patent changes the geometric parameters of the intermediate member by introducing a curvature with a specific radius (R1) and reducing wall thickness in the curved portion compared to the straight portions. This parameter optimization reduces residual stress concentration while maintaining structural integrity and heat dissipation capability.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent applies curvature to the intermediate member connecting the first and second heat dissipating members. The curved portion with radius R1 distributes stress more evenly compared to a straight connection, preventing crack initiation and detachment while maintaining the mechanical strength needed for reliable heat dissipation.

Inventive Principle:

Principle #14Spheroidality (Curvature)

2Ease of manufacture

If the intermediate member has uniform thickness, then manufacturing is simplified, but stress concentration occurs at connection points

Engineering Contradiction:

Improveease of manufacturing caseVSAvoidresidual stress in connecting member

Core Design Contradiction:

Ease of manufactureVSStress or pressure

Solution Approach 1:

The patent applies local quality by making the wall thickness of the intermediate member non-uniform: the curved portion has a smaller thickness than the straight portions. This local variation reduces stress concentration at the connection points between the heat dissipating members and the intermediate member, while the overall structure remains manufacturable through standard processes.

Inventive Principle:

Principle #3Local quality

3Temperature

If heat dissipation is enhanced, then power semiconductor element performance improves, but thermal deformation increases

Engineering Contradiction:

Improveheat dissipation efficiencyVSAvoidthermal deformation of case

Core Design Contradiction:

TemperatureVSStability of the object's composition

Solution Approach 1:

The curved design of the intermediate member with radius R1 provides thermal deformation compensation. The curvature allows the structure to flex and absorb thermal expansion and contraction forces, maintaining the stability of the power semiconductor element's mounting surface while still achieving effective heat dissipation from the opposing heat dissipating members.

Inventive Principle:

Principle #14Spheroidality (Curvature)

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 effectively reduces residual stress and enhances the reliability of power semiconductor modules by improving heat dissipation and maintaining structural integrity, thereby increasing the reliability of power conversion devices.

Implementation Method 1

an intermediate member which is formed on a periphery of the first heat dissipating member and connected to the side wall, and the intermediate member including a curvature that is projected toward a housing space of the case, wherein the intermediate member has a wall-thickness which is thinner than the wall-thickness of the first heat dissipating member

Methodology Applied

Scientific EffectStress distribution:

Implementation Method 2

a first heat dissipating member and a second heat dissipating member which are disposed in opposed relation to each other while interposing the circuit body in between

Methodology Applied

Scientific EffectThermal conduction: Conduction (thermal)

Data Source

PatentEP2682986B1Power semiconductor module, power semiconductor module manufacturing method, and power conversion apparatus

Publication Date: 2019.11.20 HITACHI AUTOMOTIVE SYST LTD

Figure 1(a)~1(c)
Figure 2(a)~2(e)
Figure 3(a)~3(b)

AI summary

A power semiconductor module includes: a circuit body having a power semiconductor element and a conductor member connected to the power semiconductor element; a case in which the circuit body is housed; and a connecting member which connects the circuit body and the case. The case includes: a first heat dissipating member and a second heat dissipating member which are disposed in opposed relation to each other while interposing the circuit body in between; a side wall which joins the first heat dissipating member and the second heat dissipating member; and an intermediate member which is formed on the periphery of the first heat dissipating member and connected to the side wall, the intermediate member including a curvature that is projected toward a housing space of the case.