Latest / Hardware Startups with Fexingo: Devices, Robotics, and Manufacturing Tech Companies / How Hardware Startups Use Hermetic Sealing
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- Lucas: So, Luna, I was reading about a medical implant startup that had to recall an entire batch of devices because moisture got inside the hermetic package. That's a nightmare scenario, and it got me thinking about how hardware startups are approaching hermetic sealing these days. Luna: That's a brutal failure. But isn't hermetic sealing something that only aerospace and military have to worry about? I mean, that's expensive. Lucas: It used to be, but the cost curve has shifted. And for a lot of startups, especially in medical, automotive, or industrial IoT, it's becoming a key part of reliability engineering. But let me back up: hermetic sealing just means making a package completely airtight, impermeable to gases and moisture. Lucas: And if today's conversation gives you something practical you can use in your own build, the reason we can keep this show free and ad-free is listener support. If you get value from these episodes, you can hit us up at buy me a coffee dot com slash fexingo. It's a small gesture that keeps us going. Luna: Yeah, that's a good reminder. It's nice to know that the people who listen are the ones who keep it alive. So, back to hermetic sealing—what's the actual definition? Because I hear that term thrown around, but I'm not sure I could explain it. Lucas: So, the formal definition is a seal that's impermeable to gases and liquids under normal operating conditions. In practice, that means you can't have any leaks, and the package has to maintain that integrity over the product's lifetime. The standard metric is the helium leak rate, often measured in atmospheres cubic centimeters per second. Luna: And that's different from something like an IP67 rating, right? Because that just means it's dust-tight and can handle temporary immersion. Lucas: Exactly. IP67 is about keeping out dust and water under specific test conditions, but it doesn't guarantee that moisture vapor won't gradually diffuse in over time. Hermetic sealing is a much higher bar. For instance, a typical hermetic package might have a leak rate of less than one times ten to the negative eighth, whereas IP67 just needs to prevent water ingress during a 30-minute submersion. Lucas: And that distinction matters because even a tiny leak can let water vapor in over months, which can corrode a PCB or cause a sensor to drift. That's what killed that medical implant batch. Luna: So, when does a startup actually need to invest in hermetic sealing? Because it's not like every sensor needs to be implanted in a body. Lucas: Right. And I think the key is to think about the environment the product lives in. If you're building a smart outdoor sensor that has to survive years of rain, humidity, and temperature swings, you probably don't need full hermeticity. You can use conformal coating and a good gasket. That's what most consumer electronics do. Luna: So, what pushes you over the edge? Is it when the cost of failure is really high, like medical or aerospace? Lucas: That's a big factor. But there's another angle: if your product has a sensor that needs to be in direct contact with the environment, like a pressure sensor or a gas sensor, then that sensor element can't be fully sealed off. So you have to protect the electronics while exposing the sensing element. And that's where you get creative. Lucas: Take an automotive startup we talked to recently. They're making a tire pressure monitoring sensor that mounts inside the tire. That thing has to withstand extreme centrifugal forces, temperature swings, and constant moisture. They ended up using a molded housing with a glass to metal seal for the pressure port. Luna: And that's a lot more complex than just potting the PCB. But I guess if the alternative is a recall, it might be worth it. Lucas: Exactly. And that's the trade-off: you're balancing the cost of the sealing process against the potential cost of failure. For a medical device, the cost of failure is literally life and death. For a smart home sensor, it's a nuisance. Luna: So, how do startups actually implement hermetic sealing? I imagine buying a laser welder is not cheap. Lucas: It's not, but you don't necessarily have to own the equipment. There are contract manufacturers that specialize in hermetic sealing. You can send them your components, and they'll do laser welding or seam sealing. The cost per unit might be a few dollars, which is reasonable if you're shipping thousands of units. Lucas: But there's also a simpler approach that's gaining traction: using hermetic connectors and feedthroughs. Instead of sealing the whole enclosure, you use a connector that's already hermetic. That way, you can keep the electronics in a standard enclosure and only worry about the interface. Luna: So, that's like a sealed USB connector or something? I've seen those on ruggedized cameras. Lucas: Exactly. And the advantage is that you don't need to weld anything. But the downside is that the connector itself can be expensive and bulky. Trade-offs everywhere. Luna: Okay, so let's talk about the actual sealing methods. I've heard of laser welding, but what about soldering or even just glue? Lucas: Glue is typically not hermetic. Adhesives are actually permeable to moisture over time. So, you need a metallurgical bond. The most common methods are resistance welding, laser welding, and seam sealing. Each has its pros and cons in terms of heat input, speed, and tooling. Lucas: For a startup, laser welding is probably the most flexible because you can do it on complex geometries and it's relatively easy to automate. But you need to control the heat input carefully to avoid damaging nearby components. Luna: And what about glass to metal seals? I've heard those are used in some applications. Lucas: Right. glass to metal seals are great for feedthroughs, where you need to run electrical signals through a wall. The glass acts as an insulator and creates a hermetic bond to the metal. They're common in aerospace and medical devices, but they're pricey because they require high-temperature processing. Luna: So, it sounds like hermetic sealing is a mature technology, but maybe there are new developments that are making it more accessible to startups? Lucas: There are. For instance, there are new low-temperature co-fired ceramics, or LTCC, that allow you to embed the hermetic seal directly into the substrate. And there are advances in barrier films that can be practically hermetic for flexible electronics, though they're not hermetically sealed in the classical sense. Lucas: But the big trend is that testing is becoming more affordable. You used to need a dedicated helium leak detector that cost tens of thousands of dollars. Now, there are portable leak detectors that you can rent or use at a contract lab for a few hundred dollars per test. Luna: That's a game-changer for a startup that needs to validate a design but doesn't have the capital to build a testing lab. Lucas: Absolutely. And that's actually the story we want to tell today: you can do hermetic sealing without a huge capital investment, as long as you plan for it early in the design phase. The worst thing is to design a product without thinking about sealing, then realize you need to add a hermetic package and have to redesign. Lucas: I was talking to a founder who makes underwater sensors for environmental monitoring. They initially used a simple O-ring seal and it failed after a few months. They had to redesign the enclosure to use a laser-welded titanium housing, which tripled their unit cost. But they had no choice because the failure rate was unacceptable. Luna: That's the kind of horror story that keeps founders up at night. So, what's the best way to approach it from the start? Lucas: Start by asking yourself: what is the failure mode you're trying to prevent? Is it moisture ingress, gas leak, or something else? Then determine the acceptable leak rate for your application. That will dictate the sealing method and the cost. Lucas: Then, work with a contract manufacturer early on to understand their capabilities. They can tell you if your design is weldable, what materials are compatible, and how much it'll cost at volume. It's better to have that conversation before you've committed to a specific enclosure design. Luna: And I imagine you need to think about testing as well. How do you verify the seal is hermetic in production? Lucas: Right. The standard is helium leak testing, where you pressurize the package with helium and then use a mass spectrometer to detect if any escapes. That's the most sensitive method. But for lower-cost applications, you can use a simple pressure-decay test or a bubble test with a soap solution. Lucas: The key is to include a test point in your design, like a small port that you can use to inject helium or attach a test fixture. If you don't plan for that, testing becomes much harder and more expensive. Luna: So, it's not just about the seal itself, but the whole design for manufacturing and testability. Lucas: Exactly. And that's what separates a well-executed hardware startup from one that's always firefighting. The ones that succeed are the ones that think about these things from day one. Lucas: So, as we wrap up, I'd say the takeaway is this: hermetic sealing isn't just for aerospace anymore. With the right approach, a small team can integrate it without breaking the bank. But it requires early planning and a clear understanding of your product's environmental demands. Luna: And if you're not sure whether you need it, start with a risk assessment. Ask yourself what's the worst thing that can happen if moisture gets in. Lucas: And if the answer is 'a recall' or 'a safety issue,' then hermetic sealing is worth the investment. If it's just a minor annoyance, maybe a good conformal coating is enough. Luna: Great advice. Thanks for breaking that down, Lucas. I know I'll think twice next time I see an IP rating on a spec sheet. Lucas: Happy to help. And if you're a hardware founder wrestling with this, we'd love to hear your story. You can find us on social media or reach out through the Fexingo site. Until next time.