Glass-to-Metal Seals and their Role in Technologies

glass-to-metal seals

Glass-to-metal seals are one of the most important elements of the construction of all tools and probably one of the least known by the average person.

Why are they so important? Because glass-to-metal seals are critical in the construction and proper functioning of vacuum tubes, electric discharge tubes, and incandescent light bulbs. It is also important for glass encapsulated semiconductor diodes, reed switches, pressure-tight glass windows in metal cases, and metal or ceramic packaging of electronic components.

When properly built, they create a hermetic seal, meaning they are vacuum-tight preventing the passage of air, oxygen, or other gases.

glass-to-metal seal
High vacuum analytical chamber of auger spectrometer.

How Glass-to-Metal Becomes a Hermetic Seal

In order to achieve such a hermetic seal, a few things must occur. The molten glass must be able to wet the metal in order to form a tight bond. In addition, the thermal expansion of the glass and metal must be closely matched so that the seal remains solid as the assembly cools.

glass-to-metal seals

For example, think about a metal wire in a sealed glass bulb. The metal glass contact can break if the coefficient of thermal expansion or CTE is not aligned. If the CTE of the metal is larger than the CTE of the glass, the seal is likely to break as it cools. As the temperature lowers, the metal wire shrinks more than the glass does. This leads to a strong tensile force on the glass and breakage. On the other hand, if the CTE of the glass is larger than the CTE of the metal wire, the seal tightens upon cooling. Compression is applied to the glass resulting in fracturing and breakage.

Obviously, aligning the CTE of both materials is a necessity. Providing this glass-to-metal seal on a custom basis is a specialty that distinguishes just a few companies in the U.S., such as Precision Electronic Glass.

glass-to-metal seals
In an insulin-dependent diabetic person, this sensor must be dependable. The glass-to-metal seal ensures that the AI is able to perform even in the harsh biology of the human body.

Biological Possibilities Expand with Glass-to-Metal Seals

The vacuum-tight environment provided by the glass-to-metal seal is optimal for a wide range of applications under adverse conditions. This is especially important for human and animal medical implants.

For example, glass ceramic-to-metal seals keep hearing implants working by protecting the receiver-stimulator from the biological environment. Also, similar hermetic seals encapsulate the artificial intelligence environment of implantable medical sensors.

One common use is a glucose sensor. In an insulin-dependent diabetic person, it is critical that the sensor is dependable and has a fail-safe design. The glass-to-metal seals ensure that the AI is safe and able to perform even in the harsh biology of the human body.

ventilators and vaccines
Ventilators and vaccines have depended on glass-to-metal seals during the global Covid-19 pandemic in 2020-21.

Glass-to-Metal Seals and their Role in Pharmaceutical Development

The team at Precision Electronic Glass is proud to work with several companies in the battle to fight Covid. They are working with components for both vaccine development and ventilators. The company has supported medical research, development, and treatment since its founding in 1962.

Glass-to-metal seals are increasingly important in lab environments. This is especially true when it comes to replacing components in heavily used equipment for testing and diagnostics. For example, clients often approach PEG to inquire about customizing replace parts for equipment purchased overseas. This has been especially important during the pandemic when shipping has been unreliable and factories have been prone to closures.

PEG engineers help customize glass and metal replacement components as well as examine the opportunity to produce other products domestically for clients in order to alleviate international shipping concerns.

aerospace and defense
Aerospace and defense allow for the continuing adaptation of glass-to-metal components and other materials to manage extreme temperatures.

Aerospace and Defense Systems Improve Glass-to-Metal Seals

Ongoing research and refining of aerospace and defense knowledge allow for continuing adaptation of materials to accommodate extreme temperature ranges. While some applications might seem a bit futuristic, scientists see many new opportunities. Work is ongoing across industries for the adaptation of new technologies to existing glass processes.

Precision Electronic Glass, a family-owned company based in New Jersey for almost 60 years, has evolved with glass technologies. And this evolution helps create unique components for hundreds of new technologies that improve our daily lives.

Today, hermetic components are in LED lights in your cars, microwave ovens, cell phones, and night vision. In addition, they are in fire detectors, GPS, security x-ray, lasers, spectrometers, and more. Anywhere that sensitive components need protecting from the elements, you will find glass-to-metal seals.