Laser Microwelding Pattern for Reflective Dissimilar Metals
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Solution Overview
Problem
Laser welding of bright and dissimilar metals is challenging due to high reflectivity, leading to unreliable and weak welds, with existing methods being complex, expensive, and prone to intermetallic formation causing brittleness and weakness.
Innovation Solution
A method using nanosecond fibre lasers emitting at 1 μm wavelength with pulse energies of around 1 mJ to create microwelds with a characteristic feature size of 20 μm to 100 μm, forming a welding pattern parallel to the surface, minimizing intermetallic mixing by flowing one material into a hole in the other, and using controlled laser signals to inhibit intermetallic formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If high power density laser beams are used to overcome surface reflectivity of bright metals, then laser energy coupling is initiated, but the melt pool grows extremely rapidly making the process difficult to control
Solution Approach 1:
The patent applies periodic pulsed laser action instead of continuous wave laser to control the welding process. The pulse duration is specifically selected to allow the material to cool and resolidify between pulses, preventing runaway melt pool growth while still achieving sufficient energy coupling during each pulse. This periodic action enables reliable control of the welding process on highly reflective bright metals.
2Use of energy by moving object
If high power densities are used to overcome reflectivity, then welding can be initiated, but over penetration occurs resulting in unreliable joints
Solution Approach 1:
Pulsed laser delivery with carefully selected pulse duration enables precise control of energy input. The periodic nature of the pulses allows the material to respond in a controlled manner, achieving sufficient penetration without over-penetration that would compromise joint reliability.
Solution Approach 2:
The patent employs dynamic control of laser parameters including pulse duration, peak power, and pulse repetition frequency. These parameters are optimized based on material properties and desired weld characteristics, allowing adaptive control of penetration depth while maintaining process stability.
3Reliability
If lower power densities are used to avoid over penetration, then process control improves, but pulse duration must be increased causing thermal heat sinking and overheating
Solution Approach 1:
The pulsed laser delivers energy in periodic bursts with optimized pulse duration that is long enough to overcome surface reflectivity and initiate welding, but short enough to prevent excessive heat diffusion to surrounding areas. This timing control prevents thermal heat sinking while maintaining weld integrity.
Solution Approach 2:
The patent optimizes multiple laser parameters including pulse duration, peak power, and pulse repetition frequency to achieve the desired balance between weld penetration and heat affected zone size. By changing these parameters, the process achieves reliable control without excessive overheating.
4Reliability
If visible green wavelength lasers are used to reduce reflectivity of bright metals, then weld repeatability improves, but system complexity and cost increase due to frequency doubling requirements
Solution Approach 1:
The patent changes the laser wavelength parameter from visible green (532 nm) to near-infrared (1064 nm or 1030 nm), accepting higher initial reflectivity in exchange for eliminating frequency doubling optics. The pulsed laser parameters are then optimized for the new wavelength to achieve reliable welding results.
Solution Approach 2:
By using direct 1064 nm or 1030 nm laser sources, the patent removes the frequency doubling crystal and associated optics from the laser system. This extraction of the frequency doubling stage simplifies the system while maintaining weld reliability through optimized pulsed operation.
5Strength
If conventional laser welding is used on dissimilar metals, then joining is achieved, but intermetallic formation occurs causing brittleness and weakness
Solution Approach 1:
Pulsed laser welding creates rapid heating and cooling cycles that limit the time available for intermetallic phase formation at the dissimilar metal interface. The periodic nature of the pulses allows controlled heat input that achieves welding while minimizing harmful intermetallic growth.
Solution Approach 2:
The relatively short pulse duration causes the welding process to proceed quickly through the critical temperature range where intermetallics form, reducing the time for these harmful phases to develop. This rushing through the dangerous temperature window minimizes intermetallic formation.
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 method produces strong, reliable welds with reduced ohmic resistance and consistent results, suitable for joining reflective and dissimilar metals, enhancing applications in electronics and electrical engineering.
Implementation Method 1
The function of the laser beam on a bright material approximates a discreet function with a very narrow operating window from beam hold-off (reflection) and absorption
Implementation Method 2
once the surface reflectivity is overcome by sufficient laser intensity, a melt of the surface is initiated
Implementation Method 3
The pulse causes the material to melt which resolidifies to form the weld
Data Source
AI summary
A weld (3) between a first material (1) and a second material (2), the first material (1) being a first metallic material, and the second material (2) being a second metallic material, the weld (3) has a width (4) between 0.5 mm and 7 mm, the weld (3) comprises at least one microweld (8), the microweld (8) forms a welding pattern (5) defined parallel to a surface (6) of the first material (1), and the microweld (8) has a characteristic feature size (7) of between 20 μm and 400 um.