Spring Contact Element Structure for Power Module Solder Stress
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Solution Overview
Problem
Mechanical stress from thermal expansion or shrinkage can damage solder joints in external contact elements of power semiconductor modules, leading to electrical failures.
Innovation Solution
An external contact element with a bonded blank strip comprising a first metal sheet and a second metal sheet, where the second sheet is omitted from the contact portions to reduce mechanical stress, and a spring portion connects the contact portions to compensate for movement, ensuring reliable electrical connections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a bonded blank strip with multiple metal sheets is used to provide reliable electrical connections, then the electrical connection reliability is improved, but the mechanical stress from thermal expansion increases causing solder joint damage
Solution Approach 1:
The patent removes the second metal sheet from the contact portions of the bonded blank strip, extracting only the necessary parts. This reduces thermal expansion complexity at critical solder joint locations while maintaining the multi-metal structure in non-contact areas for electrical reliability.
Solution Approach 2:
The patent applies different structural configurations to different parts of the contact element. The contact portions have a simplified single-metal structure to reduce stress, while other portions maintain the bonded multi-metal structure for optimal electrical performance.
2Duration of action of stationary object
If the second metal sheet is omitted from contact portions to reduce mechanical stress, then the solder joint lifetime is improved, but the electrical connection capability may be compromised
Solution Approach 1:
The second metal sheet is selectively removed only from the contact portions that require soldering, while being retained in other areas where it contributes to electrical performance and mechanical stability.
Solution Approach 2:
Different metal sheet configurations are applied locally: single-metal construction at solder joints for stress reduction, and multi-metal construction in other areas for electrical optimization.
3Manufacturing precision
If spacers are added to define solder joint thickness, then the manufacturing precision is improved, but the device complexity increases
Solution Approach 1:
The spacers are pre-integrated into the contact element structure during manufacturing, establishing the solder joint thickness definition before the actual soldering process occurs. This preliminary structural arrangement ensures consistent thickness without requiring complex external fixtures or multi-step processes.
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 significantly increases the lifetime of solder joints by reducing mechanical stress and maintaining reliable electrical connections, contributing to energy and resource savings and green technology solutions.
Implementation Method 1
a spring portion connecting the first and second contact portions to each other and configured to compensate a movement along the thickness direction
Implementation Method 2
a first contact portion configured to be coupled to the power semiconductor module by a first solder joint
Implementation Method 3
the bonded blank strip comprises a first sheet comprising a first metal or first metal alloy and a second sheet comprising a different second metal or second metal alloy
Data Source
AI summary
An external contact element for a power semiconductor module includes a bonded blank strip, the bonded blank strip being formed such that the external contact element includes: a first contact portion configured to be coupled to the power semiconductor module by a first solder joint, a second contact portion spaced from the first contact portion in a thickness direction out of the plane of the first contact portion, the second contact portion being configured to be coupled to an external appliance, and a spring portion connecting the first and second contact portions to each other and configured to compensate a movement along the thickness direction. The bonded blank strip includes a first sheet of a first metal or first metal alloy and a second sheet of a different second metal or second metal alloy. The second sheet is omitted from at least a substantial part of the first contact portion.