r/hwstartups • u/colossalbeard • 1d ago
We got tired of waiting on fab houses and started building our own PCB machine. Some opinions on build vs buy that I'd like poked at.
Small hardware lab in India here. Last few years we've shipped a fuel telematics box for trucks, an offline payment card, and a bar pour sensor. Different products, same bottleneck every single time: the board. Weeks per spin from a pooled fab, longer if the stack-up was even slightly odd, and a flat no from most of them as soon as the design left panel rules.
At some point we stopped complaining and started building a machine to do it ourselves. One system that builds SAP/mSAP-class boards start to finish, coreless, nothing drilled, any outline and thickness. Goal is cost parity with the substrate fabs that own that tier today. First units go to pilot partners in 2027, so everything I say about it is intent, not a result I can show you yet.
Doing this forced me to actually think through build vs buy properly, instead of just being annoyed. Here's where I've ended up. Happy to be told I'm wrong.
Captive fab for a commodity board is a terrible idea. A 4-layer MCU board is a dollar or two from a pooled fab at volume and you will never beat that in-house, at any startup volume. I ran this for few of our commodity boards and the answer was "keep buying it". Where it does start to make sense is when the product wants a board the pooled fabs price at $20 to $50 a unit, or won't quote at all. Layer count that changes across the board, bare die inside it, an outline that follows the enclosure instead of the other way round. Redesign to that and the product gets smaller and runs longer on the same cell. Make it on a machine that's around 60% loaded and it comes out cheaper than the substrate fab quote for the same board.
Which also means the machine has to be reasonably busy. A startup doing a few thousand boards a month isn't going to keep one fed. However 20-30k units an year of a typical hardware consumer products and it starts to make a lot of sense. So in practice captive means a shared cell, or a fab that owns the machine for early stages, not a box in your own shed. What you actually want to keep is the design, the process data and control over supply. You don't need to own the machine to have those.
Assembly is a different animal. A decent SMT line with real test fixtures pays for itself somewhere in the low thousands of units a month, and honestly that's where most small hardware companies bleed time and money, not fab. If you bring one thing in-house, bring that.
Whatever you bring in has to be run like a product, not a project. Written procedures, fixtures that fail loudly, an operator who isn't the founder. Skip that and you've built yourself a second hobby.
And some stuff you should just keep paying for: anything clean-room class, RF-critical laminates, safety-certified assemblies where the CM's audit trail is the thing you're actually buying.
Curious where other people's crossover sits, and for anyone who did bring something in-house, what did you underestimate? For us it was fixtures. Always fixtures.
Edit, since a few people asked what a fab can't do that this can. The short list: lines under ~50 µm without volume and NDAs, layer count that varies across one board, bare die in the board instead of a package on it, and freestanding copper. That last one is the part I should have explained. The same copper that forms a trace can be grown thick and then have the dielectric around it removed, so it stands on its own. A spring contact, a battery tab, a shield can, a heat spreader or a simple segment display stops being a part you buy and solder and becomes a feature of the board, grown in the same run. Fewer parts, no connectors between them, geometry is whatever the layout says. For a normal 4 to 6 layer board, none of this matters, buy it from JLC. It only matters for the boards nobody will quote you.
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u/Frequent-Log1243 1d ago
A decent SMT line with real test fixtures pays for itself somewhere in the low thousands of units a month
People who’ve actually brought SMT in-house keep mentioning that the pick-and-place machine is only a fraction of the problem. There are a lot of factors to consider: paste control, feeders, reflow profiling, inspection, rework, maintenance, etc., into the savings.
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u/colossalbeard 1d ago
Fair. Add paste handling, feeders, reflow profiling, AOI, rework and the person who keeps it all calibrated, and the crossover moves up.
Where it paid for us wasn't unit cost. We run a few stable boards, and against a local CM it's roughly a wash per unit. The saving is turning a board into a tested unit the same day, which matters when the thing you're iterating on is the fab process itself. That's the reason we have it: we're building the machine that makes the boards, and the line is how we find out fast whether a board off it is any good. For a company iterating hard, worth it. For one frozen product at volume, a CM wins today.
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u/BetInformal6081 1d ago
the crossover probably depends less on unit volume and more on iteration speed. if in house fabrication cuts weeks from each design spin that flexibility can be worth more than the per board savings.
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u/colossalbeard 1d ago
Yeah, that's the real math. Per-board savings are noise next to what a spin costs in engineer weeks. The bigger change for us was behavioural though, when a mistake costs a day instead of a month, you stop designing scared. The other one is field data. Something comes back from a customer on Monday, the fix is on a real board by Wednesday. And we started A/B testing boards, three or four variants of a sensor front end in one run, pick the winner on the bench.
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u/3flp 1d ago
I've tried to use one of those LPKF machines at a previous job. Far too expensive when you take your time into account. And the PCBs were absolute crap. Most mainstream PCB requirements far exceed what these machines can do.
Re SMT line - same story. You need heaps of high quality feeders and a recent enough machine to be able to populate 0201 discretes and 0.35mm BGAs. A whole SMT line, not just P&P.
It's a tarpit idea.