Situation Laser welding is used to assemble a variety of plastic components. Such parts usually have flat surfaces, however, laser welding also can be used to join tubing to fittings, creating hermetic seals and maintaining the strength of the assemblies. Typical applications include medical and fluid transfer devices, which involve joining the outer surface of a rigid or flexible tube to the inner surface of another tube or fitting. Achieving a strong weld while maintaining the aesthetic appearance of the joint can pose a significant challenge in these types of applications.Typical methods of bonding large surface areas: • Adhesives create a bond between the parts rather than a true weld. However, they can degrade, require long cure times and create aesthetic problems. In addition, they can contaminate channel areas. • Solvent bonding uses chemicals to attack and melt the plastic to form a bond. In addition to aesthetic problems, use of large volumes of solvents in the workplace can give rise to environmental and safety concerns. • Ultrasonic welding forms a bond by vibrating the plastic molecules to the point of melting. However, vibration can generate particulates which may present problems in medical and electronic devices.

Laser welding Laser welding uses near-infrared (NIR) energy that passes through an IR-transmissive substrate to an IR-absorbing substrate, where the energy is converted to heat to produce a weld between the two substrates. Infrared laser welding provides the following advantages: • Produces a strong, hermetic seal. • Resulting weld has low mechanical and thermal stress. • Does not involve vibration, so electrical components are not damaged and particles are not generated. • Permits pre-assembly of parts, high weld speeds, and three-dimensional contour joints.

APPLICATION NOTE 5:LASER WELDING TUBES TO FITTINGS

6 Emma St., Binghamton, NY 13905, USA • P: 607.296.4721 • F: 607.729.3322 • E: clearweld@clearweld.com • www.clearweld.com

Laser Welding Tubes to Fittings

Part Design • Colorless parts - A thin Clearweld coating can be applied by spraying the outer circumference of the tubing in the area where the tubing will be welded to the fitting. An ultrasonic spray nozzle can produce uniform coatings over small surface areas. Tubing is rotated under the spray nozzle as the coating is applied. • Transparent colored parts – An IR absorber can be incorporated into the resin, which can be molded or extruded to form one of the substrates. Since the entire substrate contains the absorbing material, this approach is best suited for the smaller part, normally the fitting. It is also possible to co-extrude one of the substrates using a weldable resin for the mating surface layer. • Dark, opaque parts - Carbon black also can also be used, however the finished part will be a dark, opaque color.

Materials The Clearweld process can be used to join most thermoplastic materials, including TPU, PMMA, PC, COC, PETG, SAN, PA, PSU, PP, PE, PVC, ABS, TPEs and others.

Requirements • An IR-absorbing coating, a Clearweld or traditional carbon black absorber blended into the resin, or a co-extruded or intermediate layer. • Infrared laser (diode, Nd:YAG or fiber) 808-1090nm. • Fixtures to hold and apply pressure to the parts during welding operation. The need for external clamping can be eliminated by using a compression joint or press fit.

®Clearweld is a registered trademark of TWI. The Clearweld logo is a registered trademark of Gentex Corporation.Patented. Crysta•Lyn Chemical Co. is the exclusive licensee of Clearweld products.

®®