Plate-shaped Lead Terminal Segmentation for Thermal Stress
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Solution Overview
Problem
Semiconductor devices in power modules face stress issues due to thermal cycles, leading to cracking in sealing resins and potential damage to signal wiring, as the linear expansion coefficients of materials like Cu, epoxy resin, and semiconductor elements differ, causing stress concentration and propagation.
Innovation Solution
A semiconductor device design featuring a plate-shaped lead terminal with recesses or projections that partially separate the linearly extending portion, reducing stress on the sealing resin and preventing crack propagation, and using a sealing resin with a linear expansion coefficient intermediate between the lead terminal and semiconductor element to minimize stress differences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stress or pressure
If the linear expansion coefficient of the sealing resin is made close to that of the lead terminal to reduce stress, then stress in the sealing resin is reduced, but the difference in linear expansion coefficient between the sealing resin and the semiconductor element increases, causing signal wires to be cut
Solution Approach 1:
The lead terminal is divided into multiple linearly extending portions separated by recesses or projections. This segmentation disperses the stress that would otherwise concentrate on a single continuous linear structure, reducing the stress transmitted to the sealing resin while maintaining the intermediate expansion coefficient benefit
Solution Approach 2:
The sealing resin is selected with a specific linear expansion coefficient that is intermediate between the lead terminal and semiconductor element. This parameter optimization balances the thermal expansion characteristics to minimize stress on both the sealing resin and signal wires during thermal cycles
2Ease of manufacture
If the lead terminal is made linear to simplify structure, then manufacturing is easier, but stress concentrates on the end surface, causing cracks to propagate
Solution Approach 1:
The linearly extending portion is segmented into multiple sections by recesses or projections. This maintains the overall linear configuration for easy manufacturing while breaking the continuous stress path that would allow crack propagation along the lead terminal
Solution Approach 2:
The recesses or projections, which add structural complexity, actually convert the harmful stress concentration into beneficial stress dispersion. The discontinuities created by these features interrupt crack propagation paths while the overall linear layout preserves manufacturing simplicity
3Stress or pressure
If silicone sealing resin with low Young's modulus is used to reduce stress, then stress on the sealing resin is reduced, but repeated stress from heat generation causes bonding portion fatigue
Solution Approach 1:
Instead of changing the sealing resin material properties (Young's modulus), the invention optimizes the linear expansion coefficient parameter. This approach reduces stress through thermal expansion compatibility rather than material compliance, avoiding the fatigue issues associated with soft materials under repeated thermal stress
Solution Approach 2:
The segmented lead terminal structure disperses repeated thermal stress across multiple sections rather than concentrating it on bonding portions. This reduces cumulative fatigue damage even when using standard sealing resins with higher Young's modulus
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 the longevity and reliability of semiconductor devices by dispersing stress, preventing cracking in the sealing resin and protecting signal wiring from damage, while allowing for efficient thermal expansion without compromising inductance or resin integrity.
Implementation Method 1
a stress is generated in a sealing resin near the lead terminal due to a difference in linear expansion coefficient between the lead terminal and the sealing resin in the module
Implementation Method 2
the lead terminal includes a recess or a projection to horizontally and partially separate the linearly extending portion into parts. Since the lead terminal includes the recess or the projection to horizontally and partially separate the linearly extending portion into parts, a linear stress generated in the lead terminal can be dispersed
Data Source
AI summary
A semiconductor device includes a semiconductor element having a lower surface bonded to an insulating substrate side, and a plate-shaped lead terminal bonded to an upper surface of the semiconductor element, and having a horizontally extending portion. The horizontally extending portion in the lead terminal is bonded to the semiconductor element and includes a linearly extending portion in a planar view. The semiconductor device further includes a sealing resin that seals the semiconductor element together with the linearly extending portion in the lead terminal. A linear expansion coefficient of the sealing resin shows a value intermediate between a linear expansion coefficient of the lead terminal and a linear expansion coefficient of the semiconductor element, and the lead terminal includes a recess or a projection to horizontally and partially separate the linearly extending portion into parts.