Solderable coatings for the attachment of optical components made of sapphire and industrial glass (endoscopy, telecommunications, laser)
Soldering has some advantages over conventional methods of fixing components, such as clamps, screws or chucking devices:
- No additional mechanical parts are needed for fixation
- The soldered system is impervious to liquids and gas
- It is largely free of stress
Soldering boasts resistance to much higher temperatures than adhesive systems and is suitable for use in autoclave applications.
Composition of a solderable coat on sapphire, YAG or mineral glass
The solderable layering consists of a substrate bonding coat, a diffusion barrier coat and a topcoat with wetting action. The barrier coat prevents the metal coatings from alloying with each other during the soldering process. The thickness of the layers depends on the solder, the soldering temperature and the materials which are being joined (coefficients of thermal expansion). The coating quality determines the adhesion of the soldered coats, as does the cleanliness of the surfaces.
Solderable coats can be applied using PVD on its own or in combination with electroplating.
Blösch AG offers the following coats as standard:
- Cr/Cu/Ni/Au and Ti/Au for AuSn (80/20) solder
- Cr/Cu/Ni/Sn for Ag/Sn solders
- Other combinations on request
Technical data for the solderable coats
Strength of adhesion on glass: > 10 N/mm2
Suitability of metal coating for autoclave applications on sapphire: > 300 cycles
Temperature resistance: min. 400° C (depending on soldering time)