Semi-pro PCB making

[Andy Harsley]

Think I have a reasonably cheap way to produce short run boards.

 

A4 size double-sided copper clad boards are £3. That'd do 16 business card sized PCBs.

 

We need a fast CNC dremel style router to machine the tracks front and back. We know we can hit 50um accuracy on this, and I have a machine that could be rebuilt to do it. It runs up to 6m per minute, so it'd do a whole A4 panel in minutes.

 

Then we use dry film solder mask with a laminator / heat press and a UV light box. We'd need to print the pad / via template on acetate with a laser printer and buy or build a UV exposure box, which is pretty easy.
 

http://www.ebay.co.uk/itm/Dry-Film-Solder-Mask-Roll-of-12-in-x-42-5-in-bigger-lenght-by-request-/161140135802?pt=LH_DefaultDomain_0&hash=item2584b3577a

 

The mask works out to about £4 per A4 side, so £8 for a double sided board.

This machine would work as the press - and have other uses:

http://www.ebay.co.uk/itm/New-15-x-15-Digital-Clamshell-Heat-Press-Transfer-T-Shirt-Sublimation-Machine-/251427253040?pt=LH_DefaultDomain_3&hash=item3a8a3b6b30


We then optionally plate the pads with liquid tinning solution (£15):

 

http://www.ebay.co.uk/itm/Liquid-Tinning-Solution-for-Home-Brew-PCB-Tin-Plating-Copper-Clad-Circuit-Board-/321312395604?pt=UK_BOI_Electrical_Components_Supplies_ET&hash=item4acfb61154

 

An optional "silk screen" can also be printed over the board using the press and standard T-shirt transfer paper.

Finally we re-CNC the board to drill the holes and route-out the individual panels. Any shape you like!

 

Works out to about £12 per A4 sized board (double sided), so less than £1 per arduino sized PCB.

 

andy

 

 

 

[Chris Marr]

If you're thinking A4, then you can use tracing paper (velum) that's suitably thin and print using a laser printer to that to get your UV masks (it's what I use when I'm putting boards together). KiCad is good for this as it'll export the board file, the drill file, solder mask and silk screens (I think eagle does the same thing, but you're limited to a Eurocard size 160x100mm board).

I'd recommend a proper roller laminator to apply the films, I've tried using an iron and a hacked laminator, they're very hit and miss (although there's a larger laminator that would probably be an easier hack than the one I've used) as they're not designed for 1.6mm thick board - you may be able to use some sort of press, but you may struggle to apply the requisite pressure for good adhesion, a laminator is definitely the better option here.

For the same price (delivered - delivery cost of that press was £350!) you could get a proper laminator that would allow you to go up to A3 sized boards and permit the use of other materials: https://www.megauk.com/dry_film_laminators.php

You can get away without tinning the plates if you're going to solder straight away, it will be better to tin them though. Via's can be installed as tiny copper rivets with a small arbor press type installer (an arbor press that's suitably adapted may be a good investment though as it's got more uses than the single use via/rivet installer - may need to machine up suitable anvils to do the installation)

[Andy Harsley]

Been having a play with CNCing PCBs. Seems I can do a 20-component 100x40mm board in about 8mins. (Not including drilling and cutting out the panel, so maybe 15mins all in.) Can possibly speed that up with more practice.

It also takes a few hours to prep the design, but that's a one-off job.

Lest I lose the link, these are recommended for the PCB transfer method, and they should do solder mask as well:

http://www.ebay.co.uk/itm/Apache-AL13P-Professional-13-Wide-A3-4-Roll-Hot-Cold-Laminator-for-Document-and-/131119556437?pt=LH_DefaultDomain_0&hash=item1e8755a755

andy

[Chris Marr]

Any laminator that can take up to 1.6mm will do it - that one will go up to 1.2mm, so it'll be a bit tight, but perhaps up to the job - cheaper than the one I pointed out, so a fairly low risk, I say bag one up!

[Andy Harsley]

Haven't tried either of these yet, but they were posted recently on the Nottinghack website:

http://dirtypcbs.com/index.php

http://imall.iteadstudio.com/open-pcb/pcb-prototyping.html


andy

[Chris Burton]

Hi,

 I've been using Iteadstudio for the past year or so and I've had one back from DirtyPCBs so far - I'd say they're of similar quality on a good day.

Iteadstudio: http://dnshistory.org/dump/IMAG0612sm - easy to spot the alignment issues on the middle PCB.

DirtyPCBs: http://dnshistory.org/dump/IMAG0615sm

I doubt there's going to be much in it but I gave similar jobs to both on the 4th Aug to see which one would get here first.

Chris.