Latest / Hardware Startups with Fexingo: Devices, Robotics, and Manufacturing Tech Companies / Why Hardware Startups Need Temperature Cycling for Reliability
Transcript
- Lucas: You know that moment when a hardware prototype works flawlessly on the bench, but a month later, in the field, it just stops working? No physical damage, no obvious cause — the board just gave up. Luna: I've heard founders call that 'the ghost in the machine.' Usually it's a solder joint that cracked from the board expanding and contracting every time the device heated up and cooled down. Lucas: Exactly. And that's exactly what temperature cycling is designed to catch. It's an environmental stress test where you repeatedly expose the product to extreme hot and cold temperatures — say, negative forty degrees Celsius to plus eighty-five — and watch for failures. Luna: So it's not about the device operating at those extremes? It's about the stress of going back and forth? Lucas: Right. The damage comes from the transition. Different materials expand at different rates — that's the coefficient of thermal expansion mismatch. Solder, copper, silicon, epoxy — they all grow and shrink differently. Over dozens or hundreds of cycles, that mechanical stress fatigues the solder joints, and eventually a microscopic crack propagates until the connection opens. Luna: And that's what kills a product in the field — especially if it lives in a car, or outdoors, or near a heat source. Lucas: Exactly. So the standard most hardware startups reference is JEDEC JESD22-A104. It defines how many cycles, what temperature ranges, and how fast you ramp from hot to cold. A typical profile might be 500 cycles from minus forty to plus one twenty-five Celsius, with a ten-minute dwell at each extreme and a transition time of less than a minute. Luna: That's a harsh profile. But isn't there a cheaper way to get similar information? Like, thermal shock chambers use two separate zones and a basket that transfers the product in seconds. Lucas: Great point. Thermal shock is faster — the transition is almost instantaneous — but it's more expensive and can overstress the part. Temperature cycling uses a single chamber that slowly ramps the air temperature. That's usually more representative of real-world conditions, unless your product literally goes from an air-conditioned building into a desert. Luna: So for most startups, a temperature cycling chamber in the ten to twenty thousand dollar range is enough to validate design margins before you commit to tooling. Lucas: And you don't even need to buy one right away. Many test labs rent chamber time by the hour. A typical 500-cycle profile takes about a week to run, and you can get it done for a few thousand dollars. That's cheap insurance compared to a field failure. Luna: Let me throw out a concrete example. I talked to a drone startup last year that was using a commodity camera module in their gimbal. The module worked fine in the lab, but after ten cycles in a temperature chamber, the connector between the camera and the main board started intermittently losing connection. Lucas: Classic. That's exactly the kind of latent defect that only shows up after thermal stress. If they'd shipped without that test, they would have seen a few percent field failure rate after six months. Luna: Right. They fixed it by switching to a locking connector and adding a dab of epoxy to relieve strain on the solder tails. Total cost maybe fifty cents per unit. Lucas: And that's the whole point. Temperature cycling isn't about making your product indestructible. It's about finding the weakest link early, so you can fix it for pennies instead of dealing with a recall. Luna: How many cycles do you think a startup should aim for before first production? The JEDEC standard is often 500 or 1000, but that feels like a lot for a hardware startup that's cash-constrained. Lucas: I'd say 100 cycles is a good starting point for a minimum viable reliability test. That will catch most gross design issues — like a component that cracks because its package can't handle the stress. For a more mature product, 300 to 500 cycles gives you confidence that the design will survive years of normal use. Luna: And you can combine it with electrical testing during the cycles too, right? Some chambers have feedthroughs so you can monitor functionality in real time. Lucas: That's a pro move. You wire up the board and run a simple power-on self-test every hundred cycles. If the board fails at cycle 200, you know exactly how much margin you have. That's way more informative than just checking at the end and seeing a dead board. Luna: Let me ask about the flip side. Are there cases where temperature cycling gives you a false sense of security? Where the test passes but the product still fails in the field? Lucas: Sure. If your temperature profile doesn't match the actual use environment, you can miss failures. For example, if your product lives in a data center where the temperature is tightly controlled, you might not need the full automotive-grade minus forty to plus eighty-five range. But if you test only at room temperature plus ten, you won't catch failures that happen during shipping in a hot truck. Luna: So you need to think about the full lifecycle — manufacturing, shipping, storage, and then operation. Lucas: Exactly. And there's another nuance: the number of cycles matters more than the temperature range in some cases. A product that sees 10,000 small temperature cycles over its life — like a wearable that goes on and off your wrist — might fail from low-cycle fatigue even though the temperature swing is only twenty degrees. Luna: Right. So you have to model your expected thermal history and then accelerate it. That's the science behind the test. Lucas: And if you want to dive deeper, there's a whole field called accelerated life testing that uses the Arrhenius equation to relate temperature to failure rate. But that's a topic for another episode. Luna: Speaking of topics that keep this show going — if you're finding these conversations useful for what you're building or running, listener support is what keeps this podcast ad-free and independent. We don't have a big media company behind us, just listeners who chip in. Lucas: Yeah, it's a small way to ensure we can keep digging into these practical topics without chasing sponsors. You can find that at buy me a coffee dot com slash fexingo. And genuinely, thank you to everyone who already does — it makes a difference. Luna: Alright, back to hardware. So let's say a startup has a design that passes 100 cycles. What's the next reliability test they should consider? Lucas: The logical next step is vibration testing, especially if the product will be in a vehicle or near any rotating machinery. Temperature cycling catches thermal fatigue; vibration catches mechanical fatigue from shock and random vibration. Luna: And you can combine them in a sequence — thermal cycling first to weaken the joints, then vibration to see if they break. That's a common qualification sequence in aerospace and automotive. Lucas: Right. But even standalone temperature cycling is one of the highest-value tests a hardware startup can run. It's relatively cheap, it's well-understood, and it catches the kind of latent defects that would otherwise become customer complaints six months after launch. Luna: And the fix is almost always cheaper than the test. So there's really no excuse to skip it. Lucas: Not if you want your product to last. So next time you're reviewing a BOM, ask yourself: have you run it through a few hundred cycles yet? If not, you might be shipping a ghost.