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PCB toner transfer

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Check to see how they treat/store the paper at the store. If they are not keeping it in a sealed pouch/container the top sheet could have been contaminated.

With any of the toner transfer methods you need to be very serious about not touching any surface that takes part in the transfer.

3v0
 
With any of the toner transfer methods you need to be very serious about not touching any surface that takes part in the transfer.
Yes, we are always aware of the copper, and keeping that clean, but that is good advice for the paper too, and perhaps that was where the problem was. Anyway, can't wait to try the foil.
 
I was reading here and there about different methods of creating pcbs...

Could you guys tellm e how you make the vias (holes)? Cause I cannot imagine myself drilling so many holes for my design ...
 
BOBKA said:
I was reading here and there about different methods of creating pcbs...

Could you guys tellm e how you make the vias (holes)? Cause I cannot imagine myself drilling so many holes for my design ...

I'm new to this so I'm not speaking from a whole lot of experience, but I did make some vias today and they looked OK. Here's how I did it:

I did the vias before putting on any components. I took a pre-tinned copper wire the same size as the hole, pushed it clear through and soldered the other side to the board. Trimmed off the other side using electrician's wire cutters. These cutters will give you a nice, flush surface. Then I flipped the board, put it on a flat surface, soldered the other side and trimmed it off.
 
Well there are 3 things here. The basic component througholes on a one-sided design are one thing. Yeah, you may have to drill a great number of holes.
The component holes on a 2-sided may be a bit more tricky because the lead needs to solder to both the top and bottom layer. I think in most cases the wicking action of the solder should carry it to the top layer but it's good to check. Some components obscure the pins in a way which makes it difficult to see or add solder to the top pads.

Vias are holes to join the top and bottom traces, but do not contain a component lead. This is easy enough to fill with a piece of lead or wire soldered in to make the connection. However, with vias under most SMD components I don't see how to do it, the leaded via won't be completely flush so an SMD component won't sit on top of it.

Unfortunately, since SMDs often have densely packed leads and some are pitched so close together you can't put a trace between pins, vias under the component are THE most likely place to have to put them.

There are some PCB milling machines which can drill holes too. They're expensive.

There's a process where you drill the component holes and vias and apply some conductive gel or paint or something and put it in a plating solution which plates the holes. That might be how they do it commercially, I dunno, but it sounds tough to do at home.

There is a system where you get a bunch of tiny tubes that you press into the via holes to make the via. Not sure if they are flush so they won't keep an SMD from mounting properly on top of it. It sure sounds like it needs soldering to guarantee good contact too.

Anybody know of any processes I missed?
 
Some components obscure the pins in a way which makes it difficult to see or add solder to the top pads.
Yes, that is the killer. I've drilled a small hole through the pad, and filled it with a wire, soldered it, then ground the surface down so the connector would sit flat, but this is so time consuming, and not really effective. Now I just try to keep all the traces running to such things on the bottom. I did get some eyelets, but they are way too large, and clunky!
There's a process where you drill the component holes and vias and apply some conductive gel or paint or something and put it in a plating solution which plates the holes. That might be how they do it commercially,
I think they use vacuum to draw the conductive material through at the same time it is drilled. It would sure be nice to have, but if I got plated through holes at home, next I'd want solder mask...
How do you guys register your double sided boards? I have been etching one side, then drilling a few holes, and using a wire poked through the holes, into the top layer paper, before I iron it to the copper. It works, but it's slow, as you have to etch twice.
 
BeeBop said:
Yes, that is the killer. I've drilled a small hole through the pad, and filled it with a wire, soldered it, then ground the surface down so the connector would sit flat, but this is so time consuming, and not really effective. Now I just try to keep all the traces running to such things on the bottom. I did get some eyelets, but they are way too large, and clunky!

I think they use vacuum to draw the conductive material through at the same time it is drilled. It would sure be nice to have, but if I got plated through holes at home, next I'd want solder mask...
How do you guys register your double sided boards? I have been etching one side, then drilling a few holes, and using a wire poked through the holes, into the top layer paper, before I iron it to the copper. It works, but it's slow, as you have to etch twice.

Then don't etch it twice! - iron one side on, then drill some of the holes, align the other side with the holes and iron that - then etch both sides at the same time.
 
Duh!
- iron one side on, then drill some of the holes, align the other side with the holes and iron that - then etch both sides at the same time.
I deserve to live in poverty!

Thanks Nigel, I'll try that one today.
 
The way I did it on the (very few) double sided boards I've bothered to make is basically like nigel said. I'm not sure how his specific recommendation would work, since you'd have the pattern exposed on the first side while ironing the second side, and it might stick to the table (maybe you could iron against a plastic sheet that it didn't stick to...) When I did mine, I drilled a few of the holes through the paper patterns themselves, ironed one side (leaving the paper on), drilled the same holes through the board, placed a pin through each hole, dropped the other pattern down onto them, tacked it in place, removed the pins, and finished ironing. The accuracy of relying on holes drilled through your transfer paper is questionable, of course. This might be easier when using semi-transparent transfer sheets like Press-n-Peel, as you could drill through the first pattern AFTER ironing it on, and then line up the second pattern by just shining some light through the holes, no pins needed. I'll have to give that a shot someday...

Some people leave an inch or two of extra paper on one side of the pattern, place them face-to-face, carefully line them up using a bright light, and then tape that one edge, forming a sort of 'clamshell' of the pattern. I've never tried it, but it seems if you're careful during ironing (especially when initially positioning and tacking the patterns) it could work out alright.

I'd be quite interested to hear from people who do double-sided boards more regularly and can share their tried-and-true methods...
 
Yes, seems to me I did try Nigel's way in the past, and yes, the toner sticking to the surface below was the problem, and the reason I started doing one side then the other.
The pulsar paper is totally opaque, so the second way is out.

Something I've been thinking about trying, though, is the use of a silkscreen, which I'm thinking would not only work well for registration, but you could make multiple copies of a board. One could use a photo resist on the screen to make the image of the traces, then screen print using acrylic paint. Now I curse the day I discarded my silkscreen!

At some point though, it would be just as effective, and a much better result to send the gerbers off to a board house.
 
BeeBop said:
Something I've been thinking about trying, though, is the use of a silkscreen, which I'm thinking would not only work well for registration, but you could make multiple copies of a board. One could use a photo resist on the screen to make the image of the traces, then screen print using acrylic paint. Now I curse the day I discarded my silkscreen!
Well if you're going to go to those lengths, just switch to the photoresist method, and enjoy the ease of duplication and pattern accuracy better than you can get with any other DIY methods... I can't imagine a homemade silkscreen pattern would be anywhere near good enough to do solid, crisp traces, much less get anywhere near 10 mil widths (or less)...
 
I can't imagine a homemade silkscreen pattern would be anywhere near good enough to do solid, crisp traces, much less get anywhere near 10 mil widths (or less)...
I've seen some pretty amazing 3 color screens with lines about that size, however, I think you are right. There is a point of diminishing returns, and for all the trouble, I would just be as well off to send the design off to sparkfun.

Now back to that board, see if I can even finish one today with toner transfer!
 
BeeBop said:
Yes, seems to me I did try Nigel's way in the past, and yes, the toner sticking to the surface below was the problem, and the reason I started doing one side then the other.
The pulsar paper is totally opaque, so the second way is out.
.
I would think if you covered the toner with the green foil it would not be sticky. I use the foil but never tested for sticky.

The pulsar paper is dense but you can align the holes with a light table or by holding it up to a light. We have done that here and it is mentioned on the pulsar site.

So far I have made two 2 sided boards. I etched one side, drilled all the holes and then masked and etched the 2nd side. To protect the side I am not etching I covered it with box tape. It leaked in about 1/8 inch around the edges but the blank was a bit bigger then the finished board so it did not matter.

Etching by rubbing with a sponge is much faster then any submerged method. It makes etching twice less painful. I have not tried it on boards larger then 2 by 4 inches.

3v0
 
BeeBop said:
I think they use vacuum to draw the conductive material through at the same time it is drilled. It would sure be nice to have, but if I got plated through holes at home, next I'd want solder mask...

The guy who made the post was just mushing the paste into the holes by hand. He was tired of soldering wires into his vias.

3v0
 
the way i do double sided boards is use 1/32" pcb and make top and bottom on seperate boards drill the holes then glue them together sand the edges and you'll never know it was 2 seperate boards to start with.I tried the other way and the problem was 3/4 of the holes would line up perfect but the other 1/4 wouldn't and I figured there was a certain amount of shrinkage going on from the heat that you never notice on a single sided board but it's there,plus if your using an iron the shrinkage is really random could be in the middle of the board or just one end but it's always there.I have not had a single problem making them with 2 seperate boards as for glue anything you want to use because once everything is soldered the 2 boards are not moving anywhere I usally use crazy glue
 
Wow. Well, on one hand, that is definitely something I never would have thought of and seems kind of crazy, but on the other hand, that's sort of how multilayer (4+) boards are made...

Hey, whatever works :)
 
I would print both disigns on the same piece of paper in reverse of each other and the thickness of the PCB separating the two. I would then fold the piece of paper round the PCB and iron each side.
 
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