Laser Transmission Welding of Thermoplastic Materials

Laser transmission welding (LTW) is a non-contact joining technique in which a laser beam passes through a laser-transparent thermoplastic component to be absorbed by an adjoining laser-absorbent part, generating localized heating and melt pooling at the interface. The key advantages include high precision, reduced thermal distortion, rapid processing and suitability for complex or miniaturised geometries. By careful selection of laser wavelength and power density, LTW can be applied either with added absorbers such as carbon black or titanium dioxide, or without additives by exploiting intrinsic polymer absorption bands in the near-infrared. The process finds extensive use across automotive, medical device and consumer electronics sectors, where lightweight, hermetic and biocompatible polymer joints are required. Critical factors governing joint strength include optical transparency of the transmissive partner, absorber concentration and dispersion, laser scanning strategy, clamping pressure and heat-affected zone control. Recent advances have focused on surface pretreatment to enhance interfacial adhesion, numerical simulation for process optimisation, novel irradiation modes to reduce joint defects and exploration of high-performance engineering resins such as polyetheretherketone (PEEK) and composites. Challenges remain in balancing melt flow, minimising thermal degradation and ensuring reproducible weld quality across large-scale manufacturing. Integration of real-time monitoring and predictive modelling is driving the technology towards more reliable and sustainable polymer assembly solutions globally.

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Laser Transmission Welding of Thermoplastic Materials publication trend

The graph below shows the total number of articles in laser transmission welding of thermoplastic materials across all publications each year (not limited to Nature Index journals).

Technical terms

Laser transmission welding (LTW): A joining process where a laser beam passes through one polymer part and is absorbed by another to generate interfacial melting.

Heat affected zone (HAZ): The region adjacent to the weld interface that experiences thermal cycles without complete melting, influencing mechanical properties.

Absorber: An additive or intrinsic polymer feature that converts laser radiation into heat to enable welding.

Clamping pressure: Mechanical load applied during welding to ensure intimate contact and control melt flow.

Inter-diffusion: Molecular migration across the molten interface that contributes to joint strength.

References

1. Weldability improvement of immiscible polycarbonate/GFRP by femtosecond laser surface treatment. Journal of Materials Processing Technology (2023).
2. Numerical Simulation of Laser Transmission Welding—A Review on Temperature Field, Stress Field, Melt Flow Field, and Thermal Degradation. Polymers (2023).
3. Laser Transmission Welding of Semi-Crystalline Polymers and Their Composites: A Critical Review. Polymers (2021).
4. Study on microstructures and mechanical performance of laser transmission welding of poly-ether-ether-ketone (PEEK) and carbon fiber reinforced PEEK (CFR-PEEK). Journal of Laser Applications (2022).