SmartGuard protection system with the 15-μm thick diaphragm is bonded to a carrier ring using mask welding. Inset illustrates mask welding. The surfaces in the shadow of the mask are not irradiated.

Swiss-made hearing aids are being produced using a recent laser-welding technique. SmartGuard hearing aids by Phonak AG, Stafa, Switzerland, uses a 15-µm thick polymer diaphragm mounted on a thermoplastic carrier ring to protect the device’s sound outlet from cerumen (earwax) and moisture, common problems for hearing aids. The mask-welding method was developed by Leister Process Technologies LLC headquartered in Kaegiswil, Switzerland, and with U.S. distribution from Itasca, Ill.

Mask welding works on the principle of laser penetration welding, which connects a transparent part to an absorbing joining partner. In the case of the cerumen protection, the diaphragm is transparent to laser radiation. The black carrier ring, made from a thermoplastic, absorbs the laser radiation. A mask inserted between the laser source (diode laser) and component lets laser radiation hit only parts to be joined (those not blocked by the mask).

Other medical applications for the process include microfluidics components and welded foils on microfiltration plates.