Package Sealing Techniques

Hermetic packages for electronic components generally consist of a seal-header (base plate) and a cap that houses the actual component. Both the cap and header are hermetic and their interconnection must also be vacuum-tight.

For the assembly of glass-to-metal seals with caps to create hermetically sealed housings, various processes are used:

Resistance welding
Laser welding
Press-fit welding
Cold welding

The most common technique is resistance welding, which is used in two variations:

Phase controlled welding
Capacitor discharge welding

These techniques require a suitable design for the outer metal part of the glass-to-metal seal. Since this part is generally produced by stamping and given welding ridges in the process, the conditions for a hermetic seal of the housing are met (fig. 12).

Other designs include a welding ridge on the cap or the so-called slanted-edge cap, which are combined with a plane flange or a plane surface of the header (fig. 13). Miniaturized components or components drawn from thin sheet metal can be designed without welding ridges because of the reduced contact area (fig. 14). Another variation of the sealing technique is used for hybrid packages. These are sealed by a rolled seam, using resistance welding (fig. 15). To minimize the thermal and mechanical stresses to which glass-to-metal seals are exposed in all sealing processes, pressure and energy must be carefully matched.