Power Semiconductor Terminal Bonding with Smooth Wire-Bond Surface
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Solution Overview
Problem
Existing methods for connecting terminals to substrates in power semiconductor modules, such as ultrasound welding, often result in rough surfaces that are not suitable for further electrical connections, leading to potential reliability and efficiency issues.
Innovation Solution
A method involving ultrasound welding with a smoothening step to smooth the second connection area after welding, allowing for reliable and efficient electrical connections, such as wire bonds, by removing the knurling pattern and improving surface smoothness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If ultrasound welding is used to connect terminal to substrate, then connection reliability is improved, but surface roughness increases making further electrical connections difficult
Solution Approach 1:
The terminal is divided into two distinct connection areas: a first connection area for ultrasound welding to the substrate, and a second connection area for subsequent electrical connections. This segmentation allows each area to be optimized for its specific function without compromising the other.
Solution Approach 2:
Different surface qualities are applied to different areas of the terminal. The first connection area receives the ultrasound welding treatment for reliable bonding, while the second connection area maintains or receives a smooth surface finish suitable for electrical connections, creating local quality differentiation.
2Productivity
If laser welding is used to join terminal to substrate, then connection speed is improved, but brittle intermetallic phases form reducing reliability
Solution Approach 1:
The patent replaces laser welding (thermal process) with ultrasound welding (mechanical-vibrational process). This substitution avoids the formation of brittle intermetallic phases that occur with laser welding of dissimilar materials, while maintaining efficient connection through mechanical vibration and friction.
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
This approach ensures a high-quality, stable, and reliable connection between the terminal and substrate, enhancing the long-term stability and efficiency of the power semiconductor module.
Implementation Method 1
Connecting the terminal to the substrate by acting on the second connection area with an ultrasound welding tool
Implementation Method 2
Welding, such as ultrasound welding (USW), also called ultrasonic welding, is a known technique for connecting a terminal to a substrate metallization
Data Source
Figure 1~3
AI summary
The invention relates to a method of connecting a terminal (24) to a substrate (12) for forming a power semiconductor module (10) by using ultrasound welding, wherein the terminal (24) comprises a first connection area (28) being located at a terminal foot (26), wherein the first connection area (28) is adapted for connecting the terminal (24) to the substrate (12), wherein the terminal (24) further comprises a second connection area (32), the second connection area (32) being located opposite to the first connection area (28) at the terminal foot (26), and wherein the substrate (12) comprises a third connection area (30) which is adapted for being connected to the first connection area (28) of the terminal (12), characterized in that the method comprises the following steps: a) Bringing the first connection area (28) in contact to the third connection area (30); b) Connecting the terminal (24) to the substrate (12) by acting on the second connection area (32) with an ultrasound welding tool (38); and c) Smoothening the second connection area (32) by performing a smoothening step after having performed step c) wherein after step c), the method comprises the further step of: d) Connecting at least one electrical connection to the second connection area (32).