Glass Seal Design Guidelines
Tekna Seal engineers will work directly with your team to make certain your feedthrough performance requirements are met. Our extensive experience in material bonding can help you design a part that provides the most effective seal and highest performance.
A compression hermetic seal is made with the housing material thermal expansion rate much higher than that of the glass. Upon solidification of the seal during the manufacturing process, the housing will contract around the glass, applying a desirable compression stress on the glass bead. The strength of the glass-to-metal seal is reinforced mechanically as well as chemically, creating a stronger, more reliable part as compared to matched seals. Compression seals are often made using steel or stainless steel housings, nickel iron pins and barium alkali glass.
To create a matched hermetic seal, housing and glass materials are selected to have a similar coefficient of thermal expansion. The strength of a matched seal comes primarily from a chemical bond between the glass and an oxide formed on the metal parts. Matched seals are most often made with Kovar housings and pins, and borosilicate glass. Matched seals are used often when the microelectronics are sensitive to the effects of thermal changes.
Recommended Proportions for Compression Glass Seals
Individually sealed pins
The minimum Ø D should be 2.5 times larger than Ø d. The minimum distance between adjacent pins or housing should be greater than or equal to Ø D. The illustration shows the optimal spacing (Ø S ≥ 3D) around each pin. Thickness T should be approximately equal to Ø D optimum thickness T range: 2.54 ±1.27 mm, .100 ± .050 inches.
Multiple Pins in a Single Glass Bead
The minimum distance between adjacent pins or housing should be greater than or equal to Ø d. The illustration shows the optimal spacing (Ø G ≥ 3d) around each pin. The optimal seal thickness T should be greater than Ø D/3.