WHO DARES TO USE VACUUM POTTING?

Bubble-free potting sounds easy but it’s a big challenge. The vacuum method is the one to use but it’s not at all straightforward. Getting the preparations right, that’s the key.

When the corks pop at a party and champagne spurts out of the bottle or bubbles over the rim of your glass you may like the sheer spectacle but probably rue the fact that there’s less for you to enjoy. The culprits for this spillage are the air bubbles. You may now be wondering what champagne has to do with potting. Well, bubbles can wreak havoc when it comes to dispensing potting compounds because air is the last thing you want in a component or assembly. It can even be life-threatening.

Vacuum potting: Vacuum chamber in operation with multiple dispensers
EV electronics | Vacuum potting
Sebastian Nadler
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With over 10 years of experience and a deep understanding of dispensing technology and our customers, Sebastian Nadler is our global sales expert. He combines in-depth technical knowledge with a keen appreciation of market requirements so he can offer our customers the innovative, tailor-made dispensing solutions they need.

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SO WHAT CAN HAPPEN?

Well, assemblies are there to protect electronics from external influences. For example, they protect the inside of a car door handle from rain, wires from touching one another, and the electronics in an electric car from being supplied false information. If electronics are not reliably protected they may fail completely.

The assembly may overheat and even catch fire. There are various materials designed to protect electronics from vibrations. If these materials contain air the temperature in the assembly may rise, which in turn will increase the risk of the electronic components failing. Just imagine you’re driving along with an automatic braking system that is no longer working, yet the ABS computer is telling you that all is still OK. That qualifies as a worst case scenario.

BETTER SAFE THAN SORRY

That can all be avoided by potting under vacuum. Admittedly, it’s a more complicated process than potting under atmospheric pressure. However, when used correctly, it is clearly the better option where bubble-free results are concerned. Three potting groups – epoxy, PU and silicone – can be processed under vacuum, with either 1k or 2k materials.

But why do we ask who dares to use vacuum potting? Simply because vacuum potting is a special process that requires precise preparation involving a number of different steps. So what are the key criteria?

Scheugenpflug vacuum chamber with multi-nozzle dispensing
Multi-Nozzle Dispensing under vacuum: Vacuum dispensing system with multi-nozzles
Speed

Speed is definitely important but it is not possible to process at any speed. The material needs to be at the right viscosity, and the material has to be heated to achieve that. The more fluid, the faster the material can flow.

However, heating certain materials is often a balancing act between pot life and viscosity, as heating tends to reduce the pot life for most materials, meaning they harden faster. This can be beneficial or detrimental for subsequent processes.

To compensate for evacuation times, multiple outlets on the dispensing head can be used under vacuum. Such a multi-nozzle dispenser produces multiple components simultaneously.

HEAT

A cold start is rarely good, and that’s true also for vacuum potting. The material should be pre-tempered, thoroughly stirred and bubble-free. Any bubbles present can expand violently in the presence of heat during the vacuum process, which means that the material will behave like overheated milk in a saucepan or like our champagne poured too quickly into a glass. Once it starts it’s impossible to stop. It starts bubbling over. The mixing ratio should be correct to prevent any possible crumbling of the material.

What matters therefore is getting the preparations right. But all the effort is well worth it for potting results that meet the highest reliability standards.

Potted Electronic Component with Coil: Bubble-Free Thanks to Vacuum Potting
No bubbles

And finally, the all-important absence of bubbles. The process takes place in a vacuum to ensure that no air bubbles remain in the assembly that could impair any further processing. We’ve already described what that could mean. Take, for example, coils of incredibly thin wire. No matter how close they are to one another there must be no contact between them. Any air bubble could provide an electrical bridge. And that could be dangerous.

So be the one who dares. It's well worth it.

FUN FACT:

Pacemakers are produced under a vacuum. Everything has to work perfectly. It’s literally vital that they do. No excuses.

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