Laser welding of thin polymer films to container substrates for aseptic packaging

Keyhole laser welding of polymers is a subject well covered and researched, but relatively little information exists regarding the welding of thin pol ymer films, particularly to a heavier substrate. This paper presents the de sign of a suitable test apparatus for laser welding thin film to a heavier substrate, and shows the results of an investigation into the feasibility o f laser welding multi-layer polymer film lids to tubs for the manufacture o f aseptic food containers. A consistent weld, free from defects, is the key to process success. Typical welding defects have been synthesised in order to investigate, and consequently remove, their cause. The result is a reli able welding method based on even film clamping. With careful attention to machine design, a seal of high mechanical strength and chemical integrity i s possible. (C) 2000 Elsevier Science Ltd. All rights reserved.