Blue Laser Copper Welding to Eliminate Spatter and Unstable Keyholes
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Solution Overview
Problem
Laser welding of copper is challenging due to its high reflectivity, thermal conductivity, and heat capacity, leading to issues such as micro-explosions, spatter, and unpredictable weld quality, particularly in high-performance electronics and automotive applications where reliable bonding of copper foils and thicker materials is required.
Innovation Solution
The use of a blue laser with a wavelength range of 405 nm to 500 nm for copper welding, which achieves efficient power coupling and stable welding by minimizing vaporization and spatter through conduction or keyhole mode welding, with controlled power density and assist gases, resulting in welds with identical microstructures to the base material and reduced porosity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If IR laser (1030 nm) is used to weld copper, then welding capability is achieved through keyhole formation, but micro-explosions and spatter occur due to rapid vaporization
Solution Approach 1:
The patent changes the fundamental parameter of laser wavelength from infrared (1030 nm) to blue/violet (405-500 nm). This parameter change fundamentally alters the interaction mechanism with copper, enabling conduction mode welding without keyhole formation, thereby eliminating micro-explosions and spatter while maintaining weld quality
Solution Approach 2:
The patent replaces the mechanical keyhole formation process with a conduction mode heating process. Instead of relying on vapor pressure to create and maintain a keyhole (mechanical process), the blue laser directly heats the copper surface through thermal conduction, eliminating the harmful mechanical explosions associated with keyhole collapse
2Length of stationary object
If high-power IR laser (>1 kW) is used to initiate keyhole weld, then welding depth is improved, but process control becomes difficult due to rapid power coupling transition
Solution Approach 1:
Changing the laser wavelength to blue/violet range fundamentally alters the power coupling characteristics. The absorption coefficient of copper at blue wavelengths is much higher and more stable, eliminating the rapid 5% to 100% coupling transition that occurs with IR lasers. This enables stable process control at lower power levels while achieving adequate penetration depth
Solution Approach 2:
The patent uses lower laser power levels (avoiding the >1 kW requirement of IR lasers) combined with the favorable absorption characteristics of blue light to achieve effective welding. This partial action approach provides sufficient heat input for conduction mode welding without exceeding the threshold that would trigger unstable keyhole formation and difficult-to-control vaporization
3Reliability
If ultrasonic welding is used to bond copper foils, then bonding capability is achieved, but sonotrode wear causes process variability and debris contamination
Solution Approach 1:
The patent replaces the mechanical ultrasonic vibration process with a thermal laser welding process. Instead of using mechanical sonotrodes that physically contact and vibrate the copper foils (causing wear and debris), the blue laser delivers energy contactlessly through optical focusing, eliminating mechanical wear and contamination while achieving reliable bonding
Solution Approach 2:
The patent introduces laser energy as an intermediary between the power source and the copper foils. This intermediary enables energy transfer without direct mechanical contact, eliminating the wear and debris problems associated with physical sonotrode contact while maintaining effective bonding capability
4Productivity
If IR laser welding is used on copper, then welding speed can be increased, but weld quality becomes unpredictable due to narrow processing window
Solution Approach 1:
The patent changes the laser wavelength parameter to blue/violet range, which fundamentally broadens the processing window. The higher and more stable absorption coefficient of copper at blue wavelengths creates a more tolerant process that maintains consistent weld quality across a wider range of welding speeds and power levels, eliminating the narrow processing window limitation of IR lasers
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 enables high-quality, reproducible welds with improved reliability and reduced defects, suitable for high-performance electronics and automotive components, by efficiently transferring heat and maintaining the microstructure integrity of copper materials.
Implementation Method 1
the high reflectivity of the copper at this wavelength makes it difficult to couple power into the material to heat and weld it
Implementation Method 2
directing a blue laser beam at the work piece, whereby a weld is formed
Implementation Method 3
it initially heats it up to the melting point
Data Source
AI summary
A visible light laser system and operation for welding materials together. A blue laser system that forms essentially perfect welds for copper based materials. A blue laser system and operation for welding conductive elements, and in particular thin conductive elements, together for use in energy storage devices, such as battery packs.