Rubber stamp PCB?

I've done considerable experimentation over the years. I liked a flatbed pen plotter best, but with .005" resolution, mine ran out of gas years ago.

I switched to toner transfer. I use a laserjet 4MP at 600DPI with real HP toner. I use a gerber viewer and have it print with a scale factor of .987. The printout isn't exactly 1:1.

The secret is in the paper. Hardest part is to get the paper off the copper without taking the traces. Shiny photo-paper works best. There's lots of discussion of this on the web.

I augment the etch with an eyedropper. Getting uniform etch is difficult if you just stick it in the etchant. The plastic traces aren't as robust as one might like. There's not a whole lot of room for overetch with narrow traces.

Takes some experimentation, but turnaround is quick and cheap.

I'd worry about ink thickness with a rubber stamp. I don't know anything about the ink suggested, but the stuff that worked best in the pen plotter was so nasty that they couldn't sell it in the USA. I got one plot session out of a pen before the plastic dissolved.

I've used two prototyping methods in the past. One is to use prelaminated PCB material that i illuminated with a simple uv tube. As mask i used normal transparencies that were printed on a thermosublimation printer, as they put down a pretty decently thick film of ink with little sidewallroughness. The other method is actually cooler, involving a milling system (doesn't need to be super fancy LPKF ones), where you would just do isolation milling. The cool thing about this one is that once you take your board out it's even already got holes. Obviously no conductive vias possible with both methods.

think its more trouble than getting a real pcb made and less likely to work

try Press-n-Peel if you just need a quick simple pcb

-Lasse

My idea exactly. When I have a small PCB made I order two panels. The PCB house I order from has a special prototyping tarif where you get two boards. Because of the start-up costs the price for a small PCB is the same as a larger one (say the size of a euro card). So for around ?100 I get 10 to 30 PCBs. I estimate that a simple adapter board is so small you can easely fit 30 pieces in one panel.

--
Failure does not prove something is impossible, failure simply
indicates you are not using the right tools...
nico@nctdevpuntnl (punt=.)
--------------------------------------------------------------

" snipped-for-privacy@fonz.dk" wrote in news: snipped-for-privacy@j11g2000vbc.googlegroups.com:

For a one-off, if this is a leaded part (not J leaded) just glue it to the board and hand wire it. 0.5 mm is tricky to hand wire, but far from impossible IF you use fine enough solid tinned wire (e.g. a single strand taken from some stranded wire) and have an iron with a fine enough bit. No coffee that morning!

--
Ian Malcolm.   London, ENGLAND.  (NEWSGROUP REPLY PREFERRED) 
ianm[at]the[dash]malcolms[dot]freeserve[dot]co[dot]uk 
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This is probably the best chance, especially since the wiring should be all straight out from the pin to the pad. At least, I'd try this first.

For the other approaches:

0.5 mm is probably beyond the capability of a rubber stamp to lay down with sufficient accuracy or to leave a uniform resist layer on bare copper.

Press-n-Peel Blue could probably do it but it requires some finesse with fine pitch artwork as well as a laser printer (not ink jet) that uses a compatible toner. Helps to have a hot-roller laminator, too; much better reproducibility than a clothes iron. I have done 10/10 rule boards with P-n-P but other than the glory of doing it, it's a P-in-the-A. Pro tip: bare copper isn't the sweetest thing for soldering, especially fine pitches. MG Chemicals has a "liquid tin" solution that can be used to lay down a thin tin layer which makes the soldering easier. More shelf-stable, too, as compared to the dry mix tinning powder.

There are carrier boards that might be adopted, e.g., over at .

But I'd bite the bullet and get a "real" PCB fabricated. There's a time versus cost trade-off, of course. A double sided, silk-screened, solder masked prototype from Sunstone could be in your hands fairly quickly or go with SeeedStudio for a really low cost ($1/board for 5cm x 5cm) but a longer wait.

--
Rich Webb     Norfolk, VA

"Winston" schreef in bericht news: snipped-for-privacy@news6.newsguy.com...

Seems too risky. Best way is a professional double sided PCB with the actual components footprint on top and the main PCB footprint on the bottom. If you place the vias in the middle of the pads of the bottom and (let) mill the outer half of them, you can solder them pretty easely.

BTW What's the component you're talking about or at least what's its package?

petrus bitbyter

(Toner Transfer)

OK. Thanks for your thoughts, Mike.

Whoa.

--Winston

(...)

I tried that and actually made a usable PCB. Then I learned all about 'actinic keratosis'. :)

I used my cnc mini-mill to make a couple double-sided boards that way. Very time consuming but *much* better quality than anything I have tried, before or since. (With the exception of PCB houses of course.)

Properly centered, I might add. :)

Axial component leads and wires placed through holes work well.

Thanks, Adrian.

--Winston

Why not have some real PCBs made? AP Circuits will do a few boards for under $100, plated through. Put a bunch of patterns on each board, and shear them up.

We did a few thousand of this adapter:

--

John Larkin                  Highland Technology Inc
www.highlandtechnology.com   jlarkin at highlandtechnology dot com   

Precision electronic instrumentation
Picosecond-resolution Digital Delay and Pulse generators
Custom timing and laser controllers
Photonics and fiberoptic TTL data links
VME  analog, thermocouple, LVDT, synchro, tachometer
Multichannel arbitrary waveform generators

OK. Thanks!

I

I had this board made 'way out of country as well. Fab was very speedy but the board still took 8 weeks to get to me.

Yikes.

Thanks guys.

--Winston

Your original post didn't get here in it's entirety and I don't know why that is. Thanks for your thoughts.

Sounds like a futile exercise to me, given the thermal conductivity of the wire and its resulting tendency to part company with the component when soldering to the pad ~ 1 mm away (or vise versa).

One stamp vendor claims resolution of better than 0.045 mm. (I agree that it would look very rough.)

Yup. I've used that stuff and like it too.

Say! That'd work! Sixty smackers! (Thud)

OK. Thanks, Rich.

--Winston

(...)

OK, thanks.

It's the LTC5564IUD in the 16 pin 3 mm QFN package with pads on

0.5 mm centers:

Thanks, Petrus.

--Winston

(...)

I've bought from AP Circuits as well and have been delighted with their quality. I will have to check back with them now because I recall they didn't allow milled channels inside a board in the past, for their inexpensive prototypes.

Kewl! Looks like Petrus and you think similarly.

(Perhaps I will just spin the artwork and send it to AP Circuits.)

Thanks, John.

--Winston

What I've done in the past when I've needed similar small "jumpers" is to strip a length of 30 AWG wire-wrap wire and then, with some shaping of the curve, a piece or two of Kapton tape (high melting point), and holding my tongue just right, lay the wire so that it bridges the gap between the pin and pad and stays in place *before* applying solder. Flux it up and then sort of drag-solder both the pin and pad. Tada! Doing this to 0.5mm pitch pins is challenging but quite do-able.

--
Rich Webb     Norfolk, VA

Winston wrote in news: snipped-for-privacy@news7.newsguy.com:

Not futile at all. Start with a reasonably long piece of wire, solder wire to pin, bend it till it lies freely along and in contact with the pad, tape down across the wire beyond the pad to hold it there and solder it to the pad. Yes the joint to the pin may reflow, but there isn't enogh stress in the wire to spring it clear and the tape stops it going anywhere. After the wire is soldered down, cut off the excess with a very small scalpel or a small flat-blade jeweller's screwdriver sharpened to a polished knife edge.

--
Ian Malcolm.   London, ENGLAND.  (NEWSGROUP REPLY PREFERRED) 
ianm[at]the[dash]malcolms[dot]freeserve[dot]co[dot]uk 
[at]=@, [dash]=- & [dot]=. *Warning* HTML & >32K emails --> NUL

(...)

Thanks, Rich and Ian.

You guys have much more faith in my solder-fu than I do. :)

It's the LTC5564IUD in the 16 pin 3 mm QFN package with pads on 0.5 mm centers:

Side-glued 30 AWG kynar would get me my .5 mm spacing with little error but I'd still be worried about capacitive coupling to the central ground plane, particularly on the RF input (pin 1). Were this an analog, or even low-freqency digital issue, I'd consider trying that.

As it is, I think I'll just spin the PCB.

Thanks for your thoughts on this, guys.

--Winston

Winston wrote in news: snipped-for-privacy@news1.newsguy.com:

Ah, QFN yechh! No I wouldn't care to do that myself. I DID say any leaded package (except J lead)! ;)

I see that it has a RF input of between 600 MHz and 15 GHz. Even with a high precision double sided PTH daugerterboard that's far from being a sure thing. A respin is probably cheaper and is certainly the best way forward.

--
Ian Malcolm.   London, ENGLAND.  (NEWSGROUP REPLY PREFERRED) 
ianm[at]the[dash]malcolms[dot]freeserve[dot]co[dot]uk 
[at]=@, [dash]=- & [dot]=. *Warning* HTML & >32K emails --> NUL

(...)

So you did.

I should have played fair and revealed the package type on my first post. Sorry about that. I wish I'd chosen the 'small', accurate 'QFN' library footprint instead of the 'incredibly enormous', accurate 'QFN' library footprint. :)

While the respin is being fabbed, I can do firmware development on the present board.

Thanks again. :)

--Winston