Fraunhofer Institute for Applied Optics and Precision Engineering IOF
Motivation
So far adhesive bonding has primarily been used to assemble and adjust hybrid optical systems. Applications are limited due to the properties of the used organic polymers. To meet higher requirements in terms of humidity resistance, UV-stability, thermal cycling and life time reliability the development of new joining technologies for optical systems is necessary. Reflow soldering or laser beam soldering are innovative alternatives.
Applications
- Fixation of optical components on substrates and mountings
- Integration of optical subsystems
- Assembly of vacuum suitable optical systems
Advantages
Laser beam soldering of optical components allows for temporary and regionallydefined energy input and temperature controlled direct and indirect heating of joining areas. Joining by reflow soldering allows for processing in vacuum or application of reducing gas. The parts to be joined can be metallized with solder and solder-aiding layers by DC-magnetron sputtering. The coating technology of all layers takes place in one vacuum process and yields high adhesive strength of the thick layers too. Flux free solders, preferable the eutectic Au80Sn20-solder, are used. This high melting solder offers superior strength, high reliability and low creep affinity. External solder, like solder preforms, can be applied externally on selected metallizations.