Suggestions on PCB Assembly for Low Volumes

I am getting ready to graduate my Arduino prototype to its own custom board; however, I'll still be using Arduino to program it. My PCB has around 47 total components (mostly resistors, caps, and some other passives) with the nRF52840. I am trying to find places that can assemble my PCB for reasonable costs in batches of 10 (low volumes).

I can source all of my components from Digi-Key. I was wondering if anyone had suggestions on where I can have this work performed? I was looking into ScreamCircuits and Seeed. I live in TX, USA. Any help is greatly appreciated. Thank you!

pcbng.com does good work, and their assembly is done in the US. Pricing is also very simple - their assembly charges are by board area. Note that they only assemble the SMD stuff, not through-hole stuff (get with the times, nobody uses through-hole parts these days).

Though if you have access to a reflow oven, I'd be tempted to just sit my ass down, get a pair of tweezers, crank up the speakers and start placing parts.

I would, but the nRF52840 is the part I don’t think I can do myself. The rest of the board I could probably attempt (it’d my first attempt at SMD and using a reflow oven). And thank you for the suggestion!

Eh, it doesn't look that bad to me. But then again, I do this all the time...

DrAzzy:
get with the times, nobody uses through-hole parts these days

Of course... if only film capacitors and electrolytic capacitors were available in SMD... or SMD offered the same mechanical strength as THT so you can unplug connectors without risking ripping them off the board... I'd be happy to do my boards in SMD-only.

But as long as PP (~170°C) has a lower melting point than solder, and PETs melting point (~260°C) is about the same as tempereatures used in reflow ovens, those caps will come out of the oven looking like a gooey mess on the inside, and we'll continue to have to use THT mounting for those.

SMD does make assembly easier, indeed. Unfortunately reality gets in the way of doing everything SMD.

I am going to try PCB:NG; however, I'm not entirely sure if they are still in business. I don't see a lot of activity. The order process works, so we'll see.

Having said that, I do think the cost is high for my use-case. I think I would be willing to pay someone to place these components rather than go through a PCB house. Would I post something like that in the Gigs? It's 31 unique parts and 42 total placements (mostly passives). I would only need 2 boards done. I can have the PCB's manufactured at JLCPCB since I've had great success so far.

if you buy the right CNC engraver you can make your own, and when you are done you still have the CNC engraver

Will a CNC Engraver place the components and solder them onto my PCB? Or is that just for cutting the board?

the PCB engraver just cuts

Engravers are pretty much useless for modern PCB design, and don’t do the placement/assembly that the OP was originally asking about anyway.

(sigh. I had a much longer message about this, but the forum logged me out and threw it away.)

(sigh. I had a much longer message about this, but the forum logged me out and threw it away.)

I'm still interested in hearing what you have to say :slight_smile: I ended up placing an order with PCB:NG. So far, things seem to be working out. I'll be receiving my boards in hopefully a few weeks. Admittedly, PCBA services are extremely pricey regardless; however, this service seems to be the most reasonable for short runs.

Making a PCB is cheap.

Assembly itself is pretty cheap, too - it's the setup cost that is the problem, typically USD 200-400 for small board. But that's a one-off, regardless of whether you order one board or 10,000 boards. The correct parts have to be loaded into the pick and place machine, the machine has to be programmed, etc. That's the killer for small boards.

Yeah. I am definitely learning... I was previously using pre-made dev boards, but I needed a different power-supply (LiFePO4) for the circuit. My hardware costs were high since I was sourcing different pre-made dev boards and putting them onto my PCB.

So, I now have a completely custom PCB, and my hardware costs are definitely lower; however, I certainly do not possess the skill to solder these small components (especially the micro-controller). Where I cut costs on hardware, I've increased costs on assembly. But I guess in volume, each individual hardware component is decreased in price which decreases overall price.

Usually my PCB doesn't cost less than the development boards.... Those are so cheap thanks to mass production, while my PCBs are small quantity, same for the parts.

For soldering SMD parts you need a reflow oven. Check out your local makerspace, hack a toaster oven or look into the skillet method.

wvmarle:
For soldering SMD parts you need a reflow oven. Check out your local makerspace, hack a toaster oven or look into the skillet method.

A hotplate (for circuit boards) is cheaper, and IMHO usually works better than a reflow oven for small runs.
Warm your boards for 5-10 minutes to 160C, and use your hot air soldering gun (set to ~230C) to flow the solder.
Leo..

A hotplate (for circuit boards) is cheaper

I never seen one of those! A few questions about that.

  1. Does it matter what kind of solder paste to use for soldering SMD?

  2. Is the process for using the hot plate the following:
    Stencil → solder paste → place the components → hot plate → hot air gun?

I’ve attached a picture of my bare board (non-assembled). The pads are so stinkin’ small, but I’ll try and see if I can solder it myself via stencil and hot plate. It’s worth a shot and could save myself $50 per board.

I've been using a simple oven - just a drawer where you put your project on, and have it run its temperature program.

No stencil, but carefully (with toothpick) place bits of solder paste where it's needed and with tweezers place the components. The hardest part is of course to get the quantity of solder right :slight_smile: Luckily the whole process is quite forgiving.

I have a stencil, so I'm hoping it makes things a little easier (the stencil came with the board from JLCPCB). Do you use a particular kind of solder paste? I've read reviews that certain solder paste works better than others.

Normal leaded paste has a lower melting point than lead-free solder,
and is therefore much easier to use for a beginner.

Forget about the stencil for just a few parts.
Using a stencil can be harder for a beginner.
Paste/stencil/board temperature must be just right.
Same actually for the toothpick method.
Less paste is usually better, and press the part a bit in the solder so you don't have any tombstoning.
Leo..

Edit: Just saw the 8-pin chip U4 and the multi-pin U5 part on your circuitboard.
That might need a stencil (and some experience).
I make a jig on a piece of MDF from old/bare boards where the board first in tightly.
Then put the stencil on, and use strong tape on one side to secure it in place.
Hinge it up to use/stencil more boards.
Leo..

SOP8 (1.27 mm pitch) is easy with the toothpick method: just place a thin continuous strand of solder paste across the leads, then drop the part in place on top of it, gently pushing it down. As long as you make sure this is thin enough surface tension will draw it under the pads, breaking up the solder bridges.

Haven't tried this with SSOP parts yet. YouTube says it works just the same. That's where I got that first trick as well.

I forgot the exact profile of the oven... iirc it's going to 230C for soldering. Using lead-free solder paste. Not interested in adding even more highly poisonous lead to our environment. If living in Europe there's actually no choice in this matter any more.