Structured Sonotrode Surface for Compact Ultrasonic Weld Joints
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Solution Overview
Problem
Conventional welding techniques for electronics applications result in welded joints with large footprints, leading to inefficient use of board area and potential for electrical shorts and mechanical stress due to material expansion and burr formation during the welding process.
Innovation Solution
An ultrasonic welding apparatus with a sonotrode featuring a structured working surface comprising apexes, nadirs, and planar sidewalls that intersect at acute angles, along with curved surfaces forming rounded depressions, which reduces material displacement and burr formation by increasing the volume for deformed material flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional welding techniques are used, then welded joints can be formed, but the footprint of the welded joint becomes large
Solution Approach 1:
The sonotrode working surface is designed with non-uniform geometry featuring apexes, nadirs, and planar sidewalls with specific acute angles. This local variation in surface topology creates zones of concentrated and distributed material flow, allowing the material to deform into the nadir regions rather than expanding laterally, thus reducing the overall joint footprint while maintaining welding reliability
Solution Approach 2:
The structured working surface introduces a vertical dimension through the formation of nadirs (depressions) between apexes. Material is directed to flow vertically into these depressed regions during welding, transforming what would be lateral material expansion into vertical accommodation, thereby reducing the horizontal footprint of the welded joint
2Reliability
If conventional welding techniques are used, then welded joints can be formed, but material expansion causes electrical shorts and mechanical stress
Solution Approach 1:
The planar sidewalls with acute angles and the resulting nadirs, which initially appear as geometric features, are actually designed to capture and contain the material expansion that would otherwise cause harm. The material flow into the nadirs converts potentially harmful lateral expansion and burr formation into controlled vertical material accumulation, eliminating electrical shorts and reducing mechanical stress on the substrate
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 enables the formation of welded joints with enhanced mechanical and electrical reliability, reducing the joint's footprint and increasing the density of connections, thus minimizing the risk of electrical shorts and mechanical stress on the substrate.
Implementation Method 1
a transducer that is mechanically coupled to the sonotrode and is configured to cause the sonotrode to vibrate at an ultrasonic frequency
Implementation Method 2
increasing the volume for deformed material flow
Data Source
Figure 1
Figure 2
Figure 3A
AI summary
An ultrasonic welding apparatus includes a sonotrode comprising a structured working surface that comprises a plurality of apexes, a plurality of nadirs between immediately adjacent ones of the apexes, and planar sidewalls that extend between the nadirs and the apexes, and for each of the apexes the planar sidewalls on either side of the respective apex extend along first and second planes that intersect one another at an acute angle.