Latest / Hardware Startups with Fexingo: Devices, Robotics, and Manufacturing Tech Companies / How Hardware Startups Use Conformal Coating to Survive the Field
Transcript
- Lucas: You might not have thought about it, but every circuit board in a product that survives rain, dust, or vibration probably has a thin layer of plastic or polymer sprayed onto it. That's conformal coating. Luna: I've seen it on boards. It looks like a clear varnish. But I bet most people have no idea it's there or why it matters. Lucas: Exactly. And for hardware startups, ignoring conformal coating can be fatal. I talked to a founder of a smart outdoor sensor company last month. They skipped coating on their first production run to save three dollars per unit. Six months later, forty percent of deployed units had failed due to moisture intrusion. Luna: Ouch. And that's not just replacement cost — that's reputation. Industrial buyers will blacklist you for that. Lucas: Right. So conformal coating is one of those boring, invisible steps that separates a toy from a reliable product. Today we'll walk through what it is, the main types, and how startups should think about it from day one. Luna: Let's start with the basics. What exactly is conformal coating? Lucas: It's a thin polymeric film — typically 25 to 75 microns thick — applied to a printed circuit board. It conforms to the board's contours, covering components and solder joints. It protects against moisture, dust, chemicals, and vibration. Think of it as a raincoat for your electronics. Luna: And there are different materials, right? I've heard of acrylic, silicone, and parylene. Lucas: Those are the three big ones. Acrylic is the most common for startups. It's easy to apply, relatively cheap, and can be removed for rework. It's good for moderate humidity and dust. The downside is it doesn't handle solvents or high temperatures well. Luna: So if your device goes inside a factory or a car engine, acrylic might not cut it. Lucas: Exactly. Silicone coating handles higher temperatures and more aggressive chemicals, but it's softer and harder to remove for repairs. Parylene is the gold standard — it's vapor-deposited, so it gets into every tiny gap. It's incredibly thin and uniform. But it's also the most expensive and requires specialized vacuum equipment. Luna: And I assume cost scales differently. For a startup doing a few thousand units, what's the price range? Lucas: Acrylic can be as low as fifty cents to a dollar per board for manual spray. Silicone might be one to two dollars. Parylene can be five to ten dollars or more per board, depending on complexity. But that's just the coating material and labor — you also need masking for connectors and sensitive components. Luna: Masking. That's another hidden cost. You have to cover parts that shouldn't be coated — like battery contacts, sensors, or ports. Lucas: Right. Masking can actually be more labor-intensive than the coating itself. For high volume, you design the board so that no-critical areas can be masked with a simple silicone boot or a solder mask defined keep-out zone. But startups often don't think about that until they're in production. Luna: So when should a startup start thinking about conformal coating? During PCB layout? Lucas: Yes. Ideally, you design the board with coating in mind. You avoid tall components that create shadows where coating can't reach. You specify which areas need masking. You choose components that can withstand the coating's curing temperature. One startup I know had to respin their board because a humidity sensor got coated and stopped working. Luna: That's a classic 'learn it the hard way' moment. So what's the best application method for a startup? Lucas: For low volume, manual spray with a handheld airbrush is common. It's flexible but inconsistent. For mid-volume, selective robotic spraying is better — you program a robot to spray only the areas you want. For high volume, you might use dip coating or even parylene deposition. The choice depends on your volume and quality requirements. Luna: And how do you test if the coating is good? Just visual inspection? Lucas: Visual inspection catches big misses, but you really need a combination of techniques. Thickness measurement with an eddy current probe or UV fluorescence if the coating has a tracer. Also, you should do accelerated life testing — like a temperature-humidity bias test at 85 degrees Celsius and 85 percent relative humidity for a thousand hours. If your boards survive that, your coating is probably good. Luna: That sounds expensive. But I guess less expensive than field failures. Lucas: Exactly. And you can outsource that testing to a lab like Intertek or UL. It might cost a few thousand dollars, but it gives you confidence. Some industrial customers require it as part of their qualification process. Luna: Let's talk about rework. What happens when a coated board fails and you need to replace a component? Lucas: That's where acrylic shines — you can dissolve it with a solvent, make the repair, and reapply. Silicone is harder to remove; you often have to peel it off mechanically. Parylene is practically impossible to remove completely — you usually replace the whole board. So if you expect to need repairs, choose your coating accordingly. Luna: And I imagine that also affects warranty costs. If you choose parylene and a board fails, you're replacing the whole unit. Lucas: Right. That's a trade-off. Parylene gives you the best protection, but it makes the product less repairable. For disposable or low-cost devices, that's fine. For expensive industrial equipment, you might want acrylic or silicone so you can fix it in the field. Luna: What about environmental regulations? Some coatings have VOCs or are under scrutiny. Lucas: Good point. Acrylic and silicone coatings often contain solvents. You need proper ventilation and maybe solvent recovery systems. Parylene is solvent-free because it's applied in a vacuum chamber. Some startups are now looking at water-based acrylics to reduce VOC emissions, but they have longer cure times. Luna: So there's a lot to consider. But the core message is: don't treat conformal coating as an afterthought. Lucas: Exactly. It's a design decision that affects reliability, cost, manufacturability, and repairability. And it's one of those things where a small upfront investment pays off hugely in the field. Luna: You know, all this talk about protecting boards — it reminds me that we only have these conversations because people find them useful. If today's episode helped you think about your own product's reliability, that's the whole point. Lucas: And if it was worth a coffee to you, we do have a link. It's buy me a coffee dot com slash fexingo. Just something that keeps the show ad-free and focused on topics like this. Luna: Yeah, no pressure. But it helps us keep digging into the nitty-gritty of hardware. Lucas: Alright. So let's wrap with one more practical tip. If you're a startup and you don't have a coating line yet, you can use a conformal coating service bureau. Companies like HZO or Parylene Applications will coat your boards for you. That way you don't have to invest in equipment until you're at higher volume. Luna: And they can also advise on which coating to use. That's a smart way to de-risk. Lucas: Exactly. You get their expertise, you get consistent quality, and you can scale up when you're ready. Just make sure you design your board to be coatable from the start. Luna: So to sum up: conformal coating isn't glamorous, but it's one of those hidden factors that determines whether your product survives in the real world. Lucas: Right. And the best time to think about it is before you finalize your PCB layout. A little planning saves a lot of headaches — and a lot of returns. Luna: Great advice. Thanks, Lucas. And thanks to everyone listening. Lucas: Catch you next time.