STC Optronics Ltd.

Lamp Sealing

The first project was to look at alternative methods of sealing halogen lamp bulbs. The standard method is to use Platonised Molybdenum foil and then the quartz envelope is crimped on to the foil. By using foil, the cross section is minimised so the TCE mismatch between the molybdenum (5.4 x 10-6) and the quartz (0.5 x 10 -6) does not cause early failure due to stress cracking.  However, after a time, leakage does occur, leading to filament failure.

STC proposed using a graded seal so that the TCE stresses could be controlled giving a longer life and the opportunity to operate the bulbs at higher temperatures with a smaller seal area. The project successfully produced engineering samples using a graded seal.  We registered a design of our seal with the Patent Office, registration number 4001901.

Low stress hermetic seal

Unit 72, Greenway Business Centre, Harlow, Essex, CM19 5QE

Tel: +44 (0)1440 706031 | christanner@stcoptronics.com | martincoleman@stcoptronics.com