Laser welding is a method of joining two materials together by using a laser beam as a concentrated heat source to melt and fuse the materials at their contact point. It offers advantages over traditional welding techniques like faster speed, easier automation, improved quality and precision, and expanded material options. Cold laser welding refers to a subset of laser welding methods that involve much lower heat input compared to standard laser welding. But how does it work and what are the main cold laser welding techniques used today?
Lower Heat Input
By definition, cold laser welding uses significantly less laser power density and heat input than hotter fusion welding methods. This allows more heat-sensitive materials like plastics or thin foils to be joined with less deformation, burning or other thermal damage compared to hotter laser welding.[1]
Typical cold laser welding techniques supply only 25-30% of the energy input used in conventional laser welding. This equates to power densities below 1 megawatt per square centimeter and peak temperatures below 2500°F at the bond line surfaces.[2]
The lower heat minimizes part warping and risky metallurgical changes in components being welded. It also allows successful bonds in highly reflective materials like aluminum or copper that would normally deflect higher amounts of laser energy rather than absorbing it.[3]
Main Cold Laser Welding Techniques
The three main laser welding categories considered cold techniques include:
1. Low Power Density Laser Welding
This involves reducing the power density of standard solid-state or fiber lasers to 0.5 megawatts per cm2 or below. It allows welds up to 0.5mm depth while minimizing heat input and metallurgical impact on sensitive alloys.[4]
2. Scanning Laser Welding
This method rapidly oscillates or scans the laser beam over the seam while pulse-firing. The combination of a broader beam and rapid movement constrains heat input despite using power densities above 2 megawatts per cm2. It facilitates welding exotic aerospace alloys and battery tabs.[5]
3. Laser Microwelding
This uses infrared laser diodes emitting wavelengths tuned to the absorption peaks of polymers. Carefully controlling emission below 150 watts creates narrow welds less than 0.1mm deep but strong enough for components like medical catheters and microelectronics.[6],[7]
Advantages vs Standard Laser Welding
While maximum weld speeds and depths are constrained, cold laser techniques offer advantages including:
- Minimizing part distortion and deleterious metallurgy changes
- Avoiding heat damage and loss of temper in sensitive alloys
- Facilitating strong precision bonds in highly reflective and conductive materials previously unweldable
- Joining thermoplastics and polymer dissimilar material pairings prone to thermal degradation
- Allowing automated welding of extremely thin foils down to 0.05mm thickness [8]
So cold laser welding fills an important niche - facilitating intricate joining of metals, plastics and material mixtures incompatible with hotter conventional laser welding methods.
Applications Taking Advantage
The aerospace, electronics and medical device industries in particular adopt cold laser welding solutions to leverage benefits like enabling demanding material joints with minimal distortion on small, intricate components.
Example applications include:
- Hermetic sealing of pacemaker titanium enclosures [9]
- Welding outer vacuum chambers for mass spectrometers [10]
- Joining nickel foil coils in electric generators while preserving magnetic properties [11]
- Sealing polymers in drug delivery patches without heat liquefying adhesives [12]
So while working at smaller scales, cold laser techniques enable mission-critical bonds in space-grade alloys, diagnostic instruments and life-saving medical components where maintaining base material properties and dimensions is paramount.
In Summary
Cold laser welding utilizes reduced energy density laser techniques that limit heat input during precision welding. Keeping temperatures low minimizes part distortion and metallurgical damage while allowing bonds in highly reflective and thermally sensitive components previously off limits to hot fusion welding. Though working at micro-scales, cold laser enables intricate joining of exotic and dissimilar material pairings critical for applications from satellites to surgical implants.
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References:
[1] Katayama, S. Handbook of Laser Welding Technologies. Woodhead Publishing. 2013. p. 342.
[2] Ion JC Laser Processing of Engineering Materials: Principles, Procedure and Industrial Application. Elsevier. 2005. p 203-204.
[3] Dawes C. Laser Welding: A Practical Guide. Woodhead Publishing. 1992. p 88.
[4] Kah P, Suoranta R, Martikainen J, Magnus C. Techniques for joining dissimilar materials: metals and polymers. Rev Adv Mater Sci. 2014;36:152-164.
[5] Kah P, Suoranta R, Martikainen J. Advanced techniques for laser welding of transparent polymers. Physics Procedia. 2015;78:182-190.
[6] Acherjee B, Mondal B, Tudu B, Misra D. Advancement and recent innovations in laser beam welding technology. Optics and Lasers in Engineering. 2021; 140:106877.
[7] Roesner A, Scheik S, Olowinsky A, Gillner A, Reisgen U, Schleser M. Laser Welding of Polymers Using High-Intensity Lasers. Journal of Laser Micro Nanoengineering. 2019;14(1):1-6.
[8] Katayama S. Laser welding phenomena in thin foil welding. Journal of Laser Applications. 2011 Jun 1;23(2):022005.
[9] L respectivelyampe T, Roos E. Investigations on fusion welding of titanium alloys for pacemakers. Medical device materials II: proceedings from the Materials & Processes for Medical Devices Conference. 2004 Nov 8. p. 12-6.
[10] Synowicki RA. Material issues for welded titanium vacuum chambers in mass spectrometry applications. 18th Topical Meeting on the Science of Fusion Energy. 1999 Oct 28.
[11] Dilger K, Nussbaum C, Nusbickel W, Rodman R. Laser welding of electrical steels and its technological consequences on AC magnetic cores. IEEE Transactions on Magnetics. 1992 Sep;28(5):2260-3.
[12] D commandssingh SP, Wieduwilt TJ. Use of laser transmission welding process for sealing of prosthetic devices for implantation. United States patent application US 06/938,069. 1974 Dec 4.