Sonotrode Surface Depressions to Contain Pin Welding Whiskers
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Solution Overview
Problem
Existing ultrasonic welding technologies are limited in their ability to address the issue of unwelded material forming 'whiskers' in conductive pin welding, which can cause short circuits in workpieces.
Innovation Solution
The development of sonotrodes with specific surface features such as linear depressions, annular depressions, and peripheral walls to capture and mitigate unwelded material, align conductive pins, and contain whiskers during the welding process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional ultrasonic welding is used for conductive pins, then welding speed and productivity are maintained, but unwelded material forms whiskers that cause short circuits
Solution Approach 1:
The patent converts the harmful unwelded material that forms whiskers into a beneficial contained structure by designing the sonotrode with a cavity and peripheral wall. The peripheral wall captures and contains the unwelded material within the cavity, transforming the harmful whisker-forming material into a contained residue that cannot cause short circuits, thus converting the harm into a benefit for welding reliability
Solution Approach 2:
The patent extracts the harmful function of unwelded material by removing its ability to form whiskers through the peripheral wall structure. The peripheral wall separates the unwelded material from the workpiece surface, extracting its harmful electrical conductivity and mechanical bridging capability, thereby eliminating the short circuit risk while maintaining the welding process
2Reliability
If sonotrode surface features are added to capture unwelded material, then whisker formation is reduced, but device complexity increases
Solution Approach 1:
The sonotrode working surface is segmented into distinct functional zones: a cavity region for capturing unwelded material, a peripheral wall structure for containment, and a smooth portion for optimal welding contact. This segmentation allows each zone to perform its specific function efficiently while maintaining overall structural integrity and relatively simple manufacturing
Solution Approach 2:
The patent adds a vertical dimension to the sonotrode working surface by creating a cavity with depth and a peripheral wall with height. This dimensional change transforms a simple flat surface into a three-dimensional structure that provides containment volume for unwelded material, achieving whisker suppression without requiring complex lateral extensions or multiple components
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 sonotrodes effectively minimize the formation of unwelded material strands, preventing short circuits and enhancing the reliability of ultrasonic pin welding operations.
Implementation Method 1
Ultrasonic welding may use an ultrasonic converter (e.g., carrying a sonotrode) for converting electrical energy into mechanical movement/scrub (e.g., linear movement/scrub, torsional movement/scrub, etc.)
Implementation Method 2
The working surface defines a plurality of linear depressions. Each of the plurality of linear depressions follows a path that does not intersect the aperture... The working surface further defines an annular depression between the aperture and an edge of the working surface
Data Source
AI summary
A sonotrode configured for use in an ultrasonic welding system is provided. The sonotrode includes a body portion terminating at a tip portion, the tip portion including a working surface. The working surface defines an aperture configured to hold a conductive pin during an ultrasonic welding process. The working surface also defines a plurality of linear depressions. Each of the plurality of linear depressions follows a path that does not intersect the aperture.