SPD Terminal-Spring Solder Joint Geometry for Stable Thermal Links
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Solution Overview
Problem
Traditional soldering interfaces between springs and metal oxide varistors in surge protection devices (SPDs) suffer from unstable soldering strength due to inconsistent volume and uniformity of solder paste application, leading to unreliable operation during overvoltage conditions.
Innovation Solution
Incorporation of openings, bends, and protrusions in the soldering joints of surge protection devices to control the application of soldering paste, allowing air bubbles to escape and maintaining a consistent gap between flat surfaces, ensuring precise soldering strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If traditional soldering interface is used between spring and MOV electrode, then the structure is simple, but the soldering strength is unstable due to inconsistent solder paste volume and uniformity
Solution Approach 1:
The flat surface of the spring is designed with a specific geometry featuring a bend that creates a gap between the flat surface and the metal terminal. This local geometric modification ensures uniform solder paste distribution and consistent soldering strength at the critical soldering interface, while the rest of the spring structure remains simple and unchanged.
2Reliability
If openings are added to the flat surface, then air bubbles can escape during soldering improving reliability, but the structure becomes more complex
Solution Approach 1:
The flat surface is segmented by adding one or more openings that divide the surface into multiple regions. These openings provide escape paths for air bubbles during the soldering process, preventing void formation and ensuring reliable solder joints. The segmentation is minimal and strategically placed to achieve the reliability improvement with minimal added complexity.
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
Enhances soldering strength and reliability by preventing air bubbles and controlling solder paste amount, resulting in a stable thermal link that forms an open circuit during overvoltage events, preventing damage to the SPD and connected circuits.
Implementation Method 1
The spring has a flat surface that is connected to the metal terminal using a soldering paste
Implementation Method 2
When an abnormal condition occurs, the solder melts and the spring moves, resulting in an open circuit
Data Source
AI summary
A surge protection device includes a metal terminal and a spring. The metal terminal is located between two metal oxide varistors, where the metal terminal extends beyond the metal oxide varistors. The spring has a flat surface that is connected to the metal terminal using a soldering paste. The flat surface has a bend on one end which forms a gap between the flat surface and the metal terminal.