Microweld Patterning for Dissimilar Metal Laser Joining
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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 weld using nanosecond fibre lasers at a 1 μm wavelength with pulse energies of around 1 mJ, forming microwelds with a characteristic size of 20 μm to 100 μm, which minimizes intermetallic mixing and enhances peel strength and reliability by creating a welding pattern with discrete zones of unmixed materials.
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, then laser energy coupling is initiated, but the melt pool grows extremely rapidly making the weld difficult to control
Solution Approach 1:
The patent applies periodic pulsed laser action instead of continuous high power density beams. The laser delivers short pulses at controlled intervals, allowing the material to cool between pulses. This prevents the runaway melt pool growth while still achieving sufficient energy coupling to overcome the high reflectivity of bright metals.
Solution Approach 2:
The patent uses preliminary surface treatment or coating application before laser welding to modify the surface properties. This preliminary action reduces the initial reflectivity barrier, enabling better laser energy coupling at lower power densities and preventing excessive melt pool formation.
2Reliability
If lower power density lasers are used to avoid over penetration, then thermal heat sinking causes overheating of surrounding regions, but weld strength is maintained
Solution Approach 1:
The pulsed laser delivers energy in periodic bursts with controlled duty cycles. The off-periods between pulses allow heat to dissipate from the heat affected zone, preventing thermal accumulation and overheating of surrounding regions while maintaining adequate weld temperature during the on-periods.
Solution Approach 2:
The patent dynamically adjusts laser parameters including pulse duration, repetition rate, and power level based on real-time process conditions. This dynamic control optimizes the balance between delivering sufficient energy for welding and allowing heat dissipation to prevent overheating of surrounding areas.
3Reliability
If green wavelength lasers are used to reduce reflectivity, then weld repeatability is improved, but system complexity and cost increase due to frequency doubling requirements
Solution Approach 1:
The patent changes the fundamental laser parameter from wavelength to pulse characteristics. By using nanosecond pulsed infrared lasers instead of continuous green lasers, the system achieves reliable welding through temporal modulation rather than spectral conversion, eliminating the need for frequency doubling optics and associated complexity.
Solution Approach 2:
The patent replaces expensive, complex frequency-doubled green laser systems with simpler, more cost-effective nanosecond pulsed infrared laser systems. The shorter pulse duration compensates for the lower wavelength efficiency, providing a cheaper and simpler solution that maintains weld reliability.
4Strength
If conventional laser welding is used on dissimilar metals, then joining is achieved, but intermetallic formation causes brittleness and joint failure
Solution Approach 1:
The nanosecond pulsed laser delivers energy in extremely short bursts that melt and join dissimilar metals before significant intermetallic compound formation can occur. The rapid heating and cooling cycles limit the time available for diffusion and intermetallic growth, producing stronger, more reliable joints.
Solution Approach 2:
The ultra-short nanosecond pulses rush through the welding process so quickly that the laser completes the joining operation before harmful intermetallic phases can form and compromise joint integrity. This time-limited approach skips over the problematic intermetallic formation stage entirely.
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 consistent, strong, and reliable welds with reduced ohmic resistance, suitable for electronics and electrical engineering applications, including batteries, solar cells, and electronic circuit boards.
Implementation Method 1
A weld using nanosecond fibre lasers at a 1 μm wavelength with pulse energies of around 1 mJ
Implementation Method 2
forming microwelds with a characteristic size of 20 μm to 100 μm
Implementation Method 3
the surface reflectivity is overcome by sufficient laser intensity, a melt of the surface is initiated
Data Source
AI summary
A method for forming a weld includes providing a first metal part formed of a first material and a second metal part formed of a second material, the first material being a first metallic material, and the second material being a second metallic material. The method also includes providing a laser for emitting laser pulses, forming a first hole in the first metal part with a laser pulse defined by a pulse energy, the pulse energy being selected such that the first hole does not penetrate fully through the first metal part and pulsing the laser such that at least some of the first material is injected into the second metal part, and wherein the laser is able to emit laser pulses having pulse widths between 100 ps and 3000 ns.