Glass-to-Metal Sealing for Initiators and EEDs
An initiator has to work after years in storage, often in harsh conditions. A glass-to-metal seal keeps the charge sealed off from moisture while letting electrical pins pass through. Here is how these seals are made and tested.
Key points
- A glass-to-metal seal keeps moisture out, insulates the pins from the body, and holds against internal pressure.
- Seals are made by firing glass preforms around pins inside a header, then cooling them under control.
- Matched seals and compression seals are the two common designs.
- Visual inspection, helium leak testing and electrical testing confirm each seal before it moves on.
Why do initiators need a hermetic seal?
An initiator has to work after years in storage, often in harsh conditions. Moisture is the main threat: it can degrade energetic materials and the bridgewire interface. A glass-to-metal seal keeps the charge sealed off from the outside air while letting electrical pins pass through.
The seal does three jobs at once: it keeps moisture out, it insulates the pins from the body, and it holds against internal pressure when the device functions.
How is a glass-to-metal seal made?
- Prepare the metal parts. The body (header) and pins are cleaned and prepared so the glass will bond to them.
- Load the glass. Glass preforms are placed around the pins inside the header, held in fixtures that keep the pins aligned.
- Fire the assembly. The fixtured parts go through a furnace under a controlled atmosphere. The glass melts, wets the metal and bonds to it.
- Cool in a controlled way. Cooling sets the seal. The cooling profile matters as much as the heating profile.
What is the difference between matched and compression seals?
There are two common designs:
- Matched seals: the glass and metal expand and contract at nearly the same rate, so the bond carries little stress.
- Compression seals: the outer metal body shrinks more than the glass as it cools, squeezing the glass into a tight, strong seal.
How are glass-to-metal seals inspected and tested?
- Visual inspection for cracks, voids and the shape of the glass where it meets the metal.
- Helium leak testing to confirm hermeticity.
- Electrical testing, such as insulation resistance between the pins and the body.
- Lot traceability, so each sealed header can be traced back through its process records.
Glass-to-metal sealing at Valor Tactical
Valor seals in-house, alongside bridgewire welding, laser hermetic sealing, and crimp and epoxy sealing. Because sealing, loading and testing sit under one quality system, the sealed header and the finished device share one traceable record. See initiators, squibs and EEDs and our manufacturing capabilities.
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Send it to our team for a quote. Valor Tactical is ITAR registered, ISO 9001 and ISO 14001 certified, and CMMC Level 2.
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