Glass-to-Metal Sealing of Reed Switches
Reed Switch Sealing comprises of two reed blades and a glass tube with matching coefficient of thermal expansion. These are filled with a special mix of inert gases. The Open ends of the glass tubes are sealed at 1000C with wound special heaters.
The actual sealing process can be accomplished by using any of the different heat sources ranging from wire-wound heaters, band heaters, infrared lamps, or lasers, but the Wound heaters ensure excellent seal shape.
The two reed blades are inserted into either ends of the open glass tube and are then brought closer to make contact. After this step, the gap is calculated and one of the reed blades is moved back by a few microns depending on the magnetic sensitivity calculations. At this point, the gas is turned on and the heating cycle hermetically closes the two ends of the glass tube.
Finished reed switches are then tested for hermetic seal integrity and sent for further inspection.