etching using acetate

[scaesic]

is it possible to transfer ink from acetate to copper board, instead of using pnp? no one will let me put pnp near their machines.

[Aharon]

Use glossy photo paper.

[scaesic]

aye, but is it possible to use acetate? i have it on acetate already.

[The Tone God]

I'm somewhat surprised by the lack of understanding towards p'n'p'. I thought they had a label that they included that you could hand to a print shop telling them its ok. I know other products do that.

Anyways yes you can use acetate which is esentially laser transperencies.

http://www.geocities.com/thetonegod/etch/etch.html

Andrew

[Mark Hammer]

Well that's the thing.  Those acetate sheets that people laser-print overhead slides onto are the very same thing that PnP is on.  The difference is that the emulsion on the acetate that the toner sticks to on an overhead is reasonably clear (so light can penetrate it), while the emulsion on PnP is a tiny bit thicker and all opaque (so etchant can't permeate it). But it's the same damn acetate sheet and it is the melting of the sheet the guys at the copy centres are so concerned about.

I have a bunch of laser transparency sheets lfet over from the pre-Powerpoint days.  and I've been meaning to try out some transfers with them as an experiment.  Andrew, any tips on using them, or is this more in the realm of a generic assurance that the toner laid down will come off the sheet when you want it to?

[The Tone God]

Well that's the thing.  Those acetate sheets that people laser-print overhead slides onto are the very same thing that PnP is on.  The difference is that the emulsion on the acetate that the toner sticks to on an overhead is reasonably clear (so light can penetrate it), while the emulsion on PnP is a tiny bit thicker and all opaque (so etchant can't permeate it). But it's the same damn acetate sheet and it is the melting of the sheet the guys at the copy centres are so concerned about.

Yet most shops do laser transparencies without a care. I do see their concern and ultimately it is the shop's call to as too will they allow it but it does seem silly. I'm sure trying to explain this to them would not help in many cases as most business owners attitude towards non-standard uses would be negative with the understanding that they need their equipment working to operate and we are such a limit group. This is one of the advantages to using regular laser transperencies over other products. You don't have to tell what you are using it for. Photo paper would also be included in this as well.

Andrew, any tips on using them, or is this more in the realm of a generic assurance that the toner laid down will come off the sheet when you want it to?

As with most things in life it really comes down to a "feel". There is some difference between transparencies in terms of how well they hold the toner and how well it releases. Plus the glossy-ness of the transparencies comes into play as some are not truly smooth thus reducing contact of the toner for transferring. Heat-wise there is little concern. I have never managed to melt a sheet.

Prep work on the copper board also affects things a great deal. You want smooth and glossy. Any bumps will reduce the transfer ability greatly. Don't rub too hard or too much when heated otherwise the toner will smudge. Do keep a sharpie-type marker near by to do any touch ups if necessary. It is always easier to cut/grind off any extra copper then to solder bridges.

Once you transfer the toner it is very tough. You can even try out my current sponge/direct rub method that I have become fond of as the toner will hold up very well. Fast boards I tells ya!

Andrew

[Satch12879]

Go to your local library; for a nickel a copy (most places) you can PNP (yuck) all you want.

[Mark Hammer]

This is one of the advantages to using regular laser transperencies over other products. You don't have to tell what you are using it for. Photo paper would also be included in this as well.

I get to say this about once every 7 weeks, but I'll say it again anyways.  Most of the projects you'll see layouts for at either Tonepad or GGG and similar places will work just fine with glossy photo paper.  Occasionally you get the odd one with very narrow traces and too many tiny pads clustered too closely, but the vast majority will come out flawlessly without needing PnP.

What this means is that you can print out loads of layouts to scale, cut up the sheets with scissors and play a little jigsaw puzzle game arranging 20 of them on a single letter-sized sheet.  Tape em down with clear matte tape, trot over to the copy centre, and ask them to copy it to photo paper with the contrast cranked.  Much like photo developing outlets, I find copy places that charge you for labour (or rather, charge you slightly inflated copy prices because they're providing the labour) will only charge you for the copies that come out well.  So if they screw up the first one, they'll only charge you for the good copy that comes after it.  The laser printer photo paper is actually a lot cheaper than the ink-jet-friendly paper for color inkjet printers, so don't let the price tags of the photo paper you normally buy scare you off.  I regularly buy this stuff from them at 20 cents a sheet.

[Paul Perry (Frostwave)]

PnP isn't EXACTLY the same as plain acetate. It's got that layer of blue stuff on it, that serves two functions: 1. helps the toner stick, and 2. when the toner bonds to the PCB, it rips away & releases from the acetate base, so you get a sharp edge.

Although WE know PnP is OK in copiers, I can understand others being paranoid, because I've seen copier drums ruined by all manner of adhesive tape & oddball plastic sheets melting. I can see passing up 10c copier fee, rather than risk  $500 repair bill

[The Tone God]

I didn't like photo paper as much. Firstly there are some photo papers that do not work at all. After that there is the issue of all the work to take it off. I know with the transperencies that as soon as it is cool enough I can just peel it away carefully and be ready to go without possible having to clean the board again.

Beyond that I consider them equivilant.

Andrew

[rockgardenlove]

I use the Kinko's paper, works great for me.  I tried overhead transparencies, but it didn't work at all. 

[Wimpy]

I believe overhead transparencies are made of polyester but I may be wrong

I tried those and perhaps I used too hot iron and it shrinked and wrinkled, I had better luck with photo paper

[Mark Hammer]

There are different types of overhead transparencies, including those you draw on directly with a pen, those you stick in an ink jet printer, and those you stick in a photocopier.  I'm talking about the 3rd type.  The acetate sheets used for those are no different than PnP.  As Paul points out, the difference is the emulsion applied over top of those sheets.  The emulsion on PnP does not change whether it can safely pass through a toner/thermal-fusing safely.  What it changes is what can be done with the sheet AFTER the toner and pattern is fused to the blue layer.

Generally, the glossier the photo paper, the better a job it does detaching from the paper backing.  In one sense, thicker paper is better and hardier.  In another sense, one of the cues that *I* find useful for judging when transfer is completed is the slightly raised area where the toner is, and thinner paper helps you see than more clearly to let you know when you're "done".

There are probably differences in granularity and resolution of photo paper, but I'm not enough of a photographer to have any knowledge or opinion of brands.  In principle, though, some paper backing is more fibrous and the emulsion will tear away from the paper with rougher edges, yielding slightly more ragged traces...if you look closely.  That raggedyness isn't a problem if you are making a Fuzz Face bt if you are aiming for the Femto-verb or something using SOIC spacing, you will more than likely want to use PnP or at least the hghest grade photo paper you can get.  I've said it before and will repeat: a 300dpi x 300dpi laser print is more than sufficient.  Higher resolution printer will give nicer pictures, but not necessarily yield finer resolution PCBs.  The limiting factor is not the printer, but the interface between emulsion and backing.

[The Tone God]

The first photo paper I used failed because the top layer that the toner sat on was some type of plastic. When heated the whole layer would attach to the board along with the toner. This of course would prevent proper etching. When I tried using another brand of photo paper it worked. I am noting this just to make people aware.

Andrew

[Mark Hammer]

Good point.

And here is where the dreaded Kinko's guy can actually be your friend.  I have bought the requisite paper from the service counter of my local Staples (Business Depot or whatever they call it where you live).  They would obviously not use paper which would not meet laser printer (= photocopier) standards, so just ask them if you can buy a few sheets of glossy photo paper.  It will be suitably heat resistant, and whether you make the transfer sheets at home or in the store, you know they will not glom onto your copper board like Andrew's unfortunately did.

[jrem]

I tried a bunch of different paper and ended up using the paper from a Carvin catalog.  I snagged some transparencies from work, though, and will give those a try.