Glass to Metal Seals

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Glass-to-Metal Seals

Concept Group has specialized in the design and manufacture of compression glass-to-metal seals since the 1970s. We take the job from start to finish, including design support, machining, and joining. Manufactured with stainless steel, our seals are hermetic, weld-ready, and tested to the highest quality standards.

Things to consider before you buy glass-to-metal seals

Differences in glass-to-metal seals can have a dramatic effect on your overall costs. Beyond cost is an even more fundamental consideration: the highly leveraged role glass-to-metal seals can play in the performance of your own products.


Concept Group seals have superior hermeticity, testing orders of magnitude better than competitors.

Electrical Performance

Our rigorous inspection process holds parts to higher standards, resulting in seals with more reliable electrical performance.

Glass Density

Our seals use special, dense glasses that give a mechanically stronger, longer lasting seal.
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Concept Group produces weld-ready, untarnished, oxide-free seals that require no additional cleaning.

Manufacturing Process

Our manufacturing process eliminates bubbles and voids, creating seals of even greater density and reliability.


Concept Group’s plating shop exclusively plates glass-to-metal seals.

Frequently Asked Questions

What does it mean for seals to be weld-ready?

If your company does secondary welding, joining the hermetic seals to packages and other assemblies, you should use untarnished, weld-ready hermetic seals.

The manufacturing process used by many hermetic seal suppliers can leave a tarnish residue that’s actually visible on the seals’ metal surfaces. This thin tarnish layer melts at higher temperatures than welding metal, so it isn’t eliminated during your secondary welding. When you weld the tarnished seal into your packages and other sub-assemblies, the tarnish can get trapped in the new weld, producing a weld defect that’s very difficult to detect, even with radiography. This defect weakens the weld. It can cause weld cracking and subsequent performance failure.

When is it important to use special, dense glasses?

If your hermetic glass-to-metal seals will face particularly challenging environments, such as those with high temperatures or high pressures, it’s important to select seals that are made with especially dense, strong glass. These denser glasses resist the cracking and other performance breakdowns that can occur when less-dense glasses are subjected to such extreme conditions.

Your hermetic seals should also be manufactured under conditions of increased positive pressure. This positive-pressure manufacturing process creates glasses of even greater density and reliability, by eliminating bubbles and voids that would likely remain if the manufacturing were done at lower or ambient pressures.

Do we clean incoming hermetic seals?

Many companies have to clean their incoming seals before they forward them to manufacturing.

Cleaning is an important step – if it’s needed. Visible tarnish on the seals’ metal surfaces can cause defects in your secondary welds, and these defects can produce weld cracking and other performance failures. That’s why the tarnish should be removed before you invest welding time (and other parts) in the seals.

Unfortunately, cleaning glass-to-metal seals takes up valuable time, and that’s an added cost for your company. To eliminate this added cost, use weld-ready, tarnish-free hermetic seals that don’t need additional cleaning. In fact, in most applications, our seals can be used right out of the shipping container.

What if my design specifications change?

Maybe a customer’s new requirements are driving a change in your hermetic seals’ specifications. Or maybe your engineering team has come up with a tweak to the existing design, one that will improve performance. There are lots of good reasons why seal designs can change over time.

When the time comes for your design to change, the last thing you want from your supplier is bureaucratic pushback or endless scheduling queues. What you do want is a supplier with the deep engineering expertise to clearly understand your new requirement, and the flexible, positive attitude to deliver it quickly and accurately – just the way you want it. Ask how spec changes are handled. Make sure you have a capable, can-do team who will work with you, 24/7.

What if my glass-to-metal seals require plating?

It’s not uncommon for hermetic glass-to-metal seals to be plated as a final manufacturing step. If this is true of your own seals, it would be good to find out where the plating is being done.

Most plating shops plate everything from door knobs to car bumpers. That’s bad for hermetic seals, because it can be a significant source of cross-contamination. Impurities from such contamination can result in your hermetic seals blistering and turning brittle. The plating process can even deposit particulate contaminants, leading to rust.

If you need plating, it’s best to use an operation that specializes in plating glass-to-metal hermetic seals, one that works on nothing else. That way, you can be certain not only that the risk of cross-contamination is eliminated, but also that your precision-made seals are handled with appropriately rigorous quality control standards.

Submit an Inquiry

We respond to inquiries within 1-2 business days. For more urgent matters, please call (561) 320-9995.

The Concept Group Difference

Glass-to-metal seals can play a highly leveraged role in overall system performance. Concept Group engineers are available to provide support in order to optimize functional performance of our seals in your system.

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