What Is a Vacuum Feedthrough and Why You Need to Know?

Have you ever wondered how machines like spaceships and refrigerators can send enormous amounts of power through their systems without any of that power ever leaking anywhere?

You’ve seen plumbing leaking before, right? So what’s the difference between your faulty plumbing and the high-precision systems of these machines?

The answer: vacuum feedthrough.

At this point, you’re probably wondering what vacuum feedthrough is. Well, right now you are going to get all of the information you need to know what it is and why it is so important.

If you are involved in engineering any kind of equipment that transmits power, or even high-pressure liquids and gases, then you need to know what vacuum feedthrough is and how it works. So, let’s jump straight in and answer all of these questions.

What Is a Vacuum Feedthrough?

A vacuum feedthrough is a particular kind of device that passes energy (perhaps an electrical current or photon pulse) or a substance (liquid or gas) from outside a vacuum into inside the vacuum.

The main reason why a vacuum feedthrough is so important is that it is the element that ensures no energy or substance is allowed to leak from the system. This is critical to machines working safely and efficiently, from refrigerators to spaceships.

Vacuum feedthrough is sometimes also referred to as electrical feedthrough when it is specifically used for passing an electrical current. These feedthroughs are usually made from glass or ceramic.

For this reason, vacuum feedthroughs are sometimes also referred to as glass feedthrough or ceramic feedthrough.

One further name you might know this piece of equipment by is hermetic feedthrough. Hermetic, like a vacuum, just means that an area has been completely sealed up.

Although the name may change from context to context, vacuum feedthrough performs more or less the same function in each. However, let’s start to look at the particular ways in which vacuum feedthroughs do differ from one another.

Vacuum Feedthrough Materials

The main thing that differentiates vacuum feedthrough types is the material they are made out of. When choosing the material for vacuum feedthrough, these are the primary factors that need to be considered:

• The substance or power component being transferred
• The volume being transferred
• The pressure of the transfer
• The heat of the system
• The cost of manufacture

Different feedthrough materials are better and worse suited to different types of environments, so there is no simple answer to which is best. Let’s look at the different materials one by one and see what their advantages and drawbacks are.

Glass to Metal

Traditionally, glass-to-metal and ceramic-to-metal seals have been the most popular. This is because they offer excellent reliability in high-pressure and high-thermal conditions.

Glass feedthroughs are most valuable in situations in which there are fluctuations in temperature, pressure, or humidity within a system.

Ceramic to Metal

A ceramic-to-metal feedthrough will usually cost more than glass feedthrough. This is because the manufacturing process is more intense, with more tooling being involved.

However, there is a good reason why ceramic feedthroughs are still a popular choice. While glass handles fluctuations well, it is difficult to beat the way ceramic handles extreme pressure and temperature.

A ceramic seal provides the greatest guarantee of non-leakage. But it is also highly resistant to mechanical shock, as well as being corrosion-resistant. This means that ceramic feedthrough, while expensive, will usually prove to be the most endurable.

Epoxy

Glass and ceramic both have the drawback that they are usually more expensive to manufacture. They are also more difficult materials to customize into new vacuum feedthrough pieces.

Coming in behind these seal types is epoxy and rubber. These solutions do not offer the same levels of performance as the other glass and ceramic, but they are much more economical.

Importantly, vacuum pieces made from epoxy have also improved in quality over the years. Traditionally, epoxy seals were linked to significant outgassing issues and were not thought to be able to handle heats of over 100 degrees C.

However, developments in epoxy technology have meant that epoxy feedthroughs can handle thermal environments of above 200 degrees C. Modern epoxy feedthroughs have also met NASA’s own minimum outgassing requirements, meaning they can be used in high-precision environments such as space shuttles.

Rubber

Rubber remains the cheapest option for low-level vacuum feedthroughs. Technically, even glue can constitute a vacuum feedthrough. But, obviously, glue is not going to withstand the high pressures or temperatures of advanced environments.

It is, however, the most cost-effective solution in low-pressure and low-temperature environments.

Why Are Vacuum Feedthroughs Important? 

Now you know all about the different types of vacuum feedthrough. But perhaps you are still wondering why the differences are so important.

Well, the importance is going to change from situation to situation. If you are dealing with low temperatures and low pressure, then a little bit of leakage may be fine.

However, if the system you are working with is transferring a significant current or temperatures at a high temperature and pressure, it is essential that the vacuum feedthrough does not leak. If Gas or electrical current escapes, this may cause real danger.

This is why NASA’s outgassing limits are the gold standard across all engineering industries—if the vacuum feedthrough can transport astronauts safely, it can probably do anything safely.

The Best Vacuum Feedthrough Is the Right Vacuum Feedthrough for Your System

We all want to know what the best of the best is. But, when it comes to vacuum feedthroughs, the best device is going to vary from system to system.

So, don’t get carried away buying the most expensive vacuum feedthrough available. Take the time to consider exactly what the parameters of your system are.

Are you dealing with high, medium, or low pressures? What is your thermal scale? What is it you are transferring?

Answering those questions accurately is going to lead you to the right vacuum feedthrough for your needs.

If you’ve found this information useful, why not check out some of our other great articles on mechanics and technology?