Ran across this URL - it's pretty interesting.

http://www.geocities.com/jf_moreira/pcb_en.html

Toshi

That stuff is hard to do, but if you can pull it off just right it can be done

I've found the best way (if you're not inclined to use those new fangled Express PCB/PCB Train type services) is to get friendly with your local type-setting bureau. Print out you're PCBs as PostScript/PDF and then get them to print them off on their Photo-typesetter. The resultant transparency is the dogs-wottsits for making UV exposed boards from....

Other than that it's still the printing out on laser OHP slides for me and into the UV exposure box....

I've checked out a bunch of the methods, including exposing with UV light, pen, toner transfer, CNC machining etching, etc.

I've had very good luck with toner transfer method, it works quite well. I've gotten excellent resolution with it. I use a HP Laserjet 4 with the HP glossy laser jet paper and a small laminator unit.. To be honest, until I found that paper, I had a ton of trouble. This glossy paper seems to release the toner very well, and I have been successful getting traces between surfacemount pads - so it has been working well.

Not a lot of pitting that some people mention, I do use a higher density setting to get a good quantity of toner on the paper, and check it before hand to see the quality of the print.

Just my $0.02, but like I've said, it has worked well for me, and I usually use it for test boards up to 2 layers that I want to test fast. I use (I believe it's called) cupric chloride for etchant (a mix of h2o2, distilled water and muriatic acid (available from hardware stores like lowes)).

-Tony

_________________
-Tony
KG4WFX

Hey Tony,

Could you put together a short description giving more details as to how your process works? Sort of a step by step guide.

Include your layout software, the paper details (part #), your laminator make & model, method of attaching the paper to the board, board prep, etching tank description, etching times, etc.

I for one would like to try this method for my prototypes too.

Thanks!!!

Daryl

Hi Daryl,

I'll do my best to consolidate what I do.

First off supplies I use:
1) 3 larger tubs - I use a plastic type, I think by rubbermaid, transparent, from walmart - Tubs: 1 - Etching tub, always holds etchant, 1 - Rinse/stop tub always contains distilled water, 1 - separating bath (I'll explain later) distilled water slightly warmed if possible

2) Muriatic acid. I just bought a gallon of it from Lowes

3) Hydrogenperoxide (sp?) - won't need to much of this, I keep a large bottle of it around, it's lasted quite a while

4) Distilled water (conveniently I keep a lot of this on hand as my photoprinter requires it) - i'd get a few gallons at least. A lot depends on the size of the tub you plan to use

5) Laser printer - I use a Laserjet 4m Plus

6) Paper to do the transfer - I use HP High Gloss Laser Paper, 200 sheets to a box, 95 brightness, partnumber Q2419A

7) Iron or a laminator - I use a GBC H200 laminator, much easier then iron.

PCB layout software (I use a variety of packages, mostly when doing at home I use AutoTRAX EDA and Multisim 7)

9) Masking tape (always good to use a higher quality tape, easier to remove)

10) Acitone or non-acitone polish remover, or rubbing alcohol

11) Baking Soda (I'm pretty sure this is what I used, it counter acts the acid).



Other equipment I have / use, but not requied

10) light box for aligning paper.

11) CNC unit to do drilling (I use a MaxNC10 OL, if I'd do it again, I'd get a closed loop model instead)


Making the cupric chloride...

This is the one part I don't feel comfortable talking about. I am not a chemist, and followed directions off of a website I don't have the link to, but if you search for cupricchloride pcb etching, you should find the recipe. Basically it's a portion of HCl (muriatic acid), mostly distilled water and a little H2O2 (kicks off the process). There is an order to doing this which is why I don't feel comfortable telling you how - one order is safer then the other as it is less likely to splash.

The beauty of this mixture is that it lasts forever and can be easily neutralized when done. I have my batch that I started over a year ago, and it still works. if it gets a little slow to start, I just add some H2O2, and it works well again.



Ok, I think that's it.... Here's what I do basically...

1) Do my schematic capture in software, either AutoTRAX or Multisim or WinQCad if I'm desperate

2) Layout my pcb, with this process I can make fairly large PCB's, so have to be careful not to go hog wild. I did traces as small as .01 width which allowed me to run between SMT pads, which was really helpful

3) After checking your PCB layout (usually I print once on regular paper to make sure the traces look good, none too thin or too close - this is a bit of a judgement call as I really don't know what kind of resolution you can get. I've heard of getting excellent tight traces, but since I don't know for sure, I can't comment) run a front and rear print on the high gloss printer - I use 600dpi setting, high density. Make sure to mirror print the bottom of the board, as well as the top of the board (it's been a few months since I made my last board, so this is by memory here - since the print on both pages will be facing each other, you have to make sure they line up correctly and that everything will look right when looking "thru" the paper, otherwise it'll end up backwards on the board...)

4) Cut and Clean the board roughly to size - live a little overage of board so you have something to tape to - I assume that everyone here does this, but for those that don't, wash thoroughly, clean with a green scrub sponge without detergent in the sponge, do this to remove any oils from the board, and to give the surface some texture for the toner to grip onto. After drying the board, I usually do a second rinse with rubbing alcohol to make sure.

5) Now comes attaching the paper. Ok, now how you will align is up to you, when you tape the paper down ONLY tape along one edge on either side; otherwise you might get an airbubble or crinkle in the paper distorting your traces... - options include:

A - Having a set of alignment holes on the paper, drill thru the paper, thru the board. Use a light source and make sure the first sheet is lined up and tape it down on one edge. Place second sheet on other side, carefully flip first sheet up and align the other sheet and tape it down. Which side you have the light source on is up to you - depends on what is easier for you.

B - Have the two sheets of paper and a little piece of PCB materieal. Tape sheet one to the little piece of PCB material, place sheet two on the other side, using a light table, shift the pages until they line up and tape the loose paper to the little piece of pcb material. Now, slide your main piece of pcb into the "sleeve" you've created and tape down both sides. Carefully remove or cut away the temporary little piece just used for alignment.

C - Get a 1/16" piece of acrylic as a spacer, and 2 smaller pieces as edge holders. Tape one page of the to the two edge holders (one on the left and right edge), take this and place it on a light table (like for viewing slides or tracing), now place the piece of 1/16" acrylic spacer on top of the schematic (this will simulate the spacing of the PCB itself), place the second sheet of paper with traces facing down on top. Shift until the bottom and top sheets are aligned. Once there, tape the top to the two edge holders. Slide out the inner acrylic and slide in your PCB. Tape both the top and bottom sheets to the PCB, only along one edge (I use the narrow edge)

How you do that is personal preference, and will take a little practice. If you decide to drill holes for alignment, I'd suggest doing it before you clean the board.

6) Make sure the laminator is on, and set to high heat. Also make sure your tub of luke warm distilled water for separation is ready, and turn on cold water in sink.

7) Now comes passing the board thru the laminator - your use of this may vary, and you will have to experiment to find the exact number of times to pass the board thru. I pass it thru between 6 and 8 times. Tape edge first, angle in second (not quite 45deg, but a bit of an angle), angle in third (opposite angle), tape edge (4th optional) - flip the board over and repeat on back (use a mit from the kitchen, makes dealing with the board much easier)

After last pass thru the laminator take immediately and place under cold running water for a few seconds for each side, then put it in the separation bath. It won't take long, you will be able to tell easily when the paper is coming up. Gently peel the paper off. You may need to rub the board carefully with the waste paper or your finger to remove any excess residue.

9) Place in the etching tank. Depending on how strong you have made it, this may be a long or short process. Shortest I've had it go is about 30 seconds (WAY too strong) and longest was about 10 minutes.

10) Watch it, once it starts, it will go fast. Once done, remove and place in stop bath rinse tank, this tank should contain distilled water and some baking soda (as I recall) to stop the acid.

11) Drill. I use my CNC mill with a drill file to drill out the holes to save me a lot of trouble.

12) Clean off the board with non-acetone or rubbing alcohol - this will remove the toner fairly easily. The non-acetone seems to work a little better then the alcohol.

13) thru hole anything you want to (I use thru hole inserts, can't remmeber where I bought them, I don't use to many so they have lasted me a while).

14) Use.

this is really in a nutshell, and may not be explained well, for which I do apologize; what's become a habbit is sometimes hard to itemize out.

If you have any questions, feel free to ask and I will try to help. There are a lot of wonderful sites out there that have tons of info on this, plus the homebrew pcb list on yahoo has a lot of information.

-Tony

_________________
-Tony
KG4WFX

Tony,

Thanks for the details. I may just try this for some of my future IO boards. I've always wanted to try it.

Thanks again!!!

Daryl

I'll add a couple comments.


.
.


I tried a number of different papers looking for something that would work
fairly well and be commonly available.
I settled on Epson "photo quality glossy paper" S041124
which worked far better than anything else I tried. It generaly just floats
off after a brief soak in warm water. Usually some of the sizing
(which acts as a release) remains, I just gently brush it off with a paint
brush under running water. None of the paper ever remained on the
board and my experience is that it's real easy to damage the pattern
trying to rub paper off the pattern (the fibers remain embedded in the ink)
and if you don't get all the paper off it messes up the result (although,
I've gotten acceptable results for things that didn't need really fine detail
with plain old photo copies)
I didn't have any luck with any of the HP papers I tryed, but I don't recall
which ones exactly I did try. I do recall that the absolute worst
paper (for this usage) was an HP photo print type paper made specifically
for laser printers (just about needed a chisel to get it off the board )


.
.


I've always heard this called peroxy-acid or acid-peroxide

Not sure where the term cupric chloride is comming from, except that that
may be what you get when you etch a board using hydrochloric (Muriatic)
acid in the mix. I believe they add copper sulfate to the etchant,
if they're using sulfuric acid, as a sort of stabilizer or buffer to make the
action of the etchant more predicatable.
Perhaps the same sort of thing is done with hydrochloric acid (though I
didn't see any mention of that in the above description).

I think it's more usual to use sulfuric acid but I wouldn't swear to that.
I use the same stuff, pool acid, fuming hydrochloric acid
with a little sulfuric acid thrown in as a stabilizer, sold in two gallon boxes
for $4-6 around here, used to adjust pool PH

If you've never used the stuff be advised.
IT'S FUMING ACID, IT GIVES OFF ACID FUMES ANYTHING THAT'S REMOTELY
MOIST THAT THE FUMES COME IN CONTACT WITH WILL BECOME ACID!
(yours skin, your eyeballs, your lungs)
One good lungful will probably only make you wish you could die, two
will probably kill you
Having said that, it's not all that dangerous as long as you're carefull and
don't spill/splash it and work with good ventilation.
I use it for cleaning the bathroom fixtures and the like.
They sell a slightly less potent form of basically the same thing
(25% acid versus 35%) (at a much higher price, several dollars a quart)
for cleaning toilet bowls.
And if you get a whiff you'll know it, but you may not notice it attacking
your eyeballs untill they fog over or something. (no, I never let that
happen to me, I'm just guessing )

Peroxide-acid mixtures are reputed to decompose spontaneously in a runaway
exothermic reaction if you get them too hot (imagine it as taking the lid off
a bottle of warm soda only with a fuming acid mixture that eat's metal)
I've tryed to cause this to happen and never managed it so I don't think it's
much of a danger, but be advised.

I use ordinary 3% medicinal hydrogen peroxide which I reduce by about
2/3 by heating gently on the stove top in a stainless steel pan, and I do
mean gently. If it's forming bubbles at all, it's probably too hot.
I'm really just warming it some to encourage evaporation, nothing close
to boiling or simmering.

Having said all that about the acid, it's the hot concentrated peroxide that's
dangerous. My experience is:

>>IT WILL EAT THE FLESH OFF YOUR BONES<<

Get a splash of fuming hydrochloric acid on you're hand, no sweat, go rinse
thouroughly.
Get a drop of hot concentrated peroxide on your hand, too late, you've got
a patch of dead skin.

No I've never had it literally eat the flesh off my bones but I have managed
to get a drop on my hand and personally, I wear goggles when I'm doing
this stuff.

I believe, when diluting acid with water, it's generally recommended to
slowly add the acid to the water. The idea being that since it generates
heat as it dilutes you'd rather have some boiling water/dilute acid than
the acid boiling and possibly spattering (if you did it the other way around)
I'm not sure how that should be applied to mixing the peroxide and acid,
but I add the peroxide to the acid because I'd much rather get spattered
with the acid than the peroxide (if that's what's going to happen. I've
never had anything like that happen and I've tryed to get some
boiling/spattering reaction to happen too, just to get an idea of what's
involved and never managed it)

I mix one part of (33%-35%) acid to two or three parts of the concentrated
(3% peroxide, reduced by 2/3) peroxide.

I always make a fresh batch, I've never had the stuff last more than a day
or two. I think the peroxide decomposes.

Perhaps I've made this sound really dangerous, I believe it is dangerous

but I don't think anyone should have any problems if they're careful and
prepared for accidents. I don't think it's any more dangerous than alot of
other things one does daily.


I don't have a laminator and I haven't tryed to make double sided boards (yet).

I've found that it works far better with less spreading of the
toner/etchresist if I heat the board and then press the pattern on to it.
Better to not get the paper hot enough to melt the toner at all.
I pop the board in the oven an a low heat untill it's just starting to change
color (the copper begining to oxidize I expect) then quickly slap the pattern
down on it put a couple of paper towels over it and then press it on with
a rolling pin.
You might think this would damage the board. Maybe it does, but I've
never had any problems, even when I screwed up and got the board so
hot that it started to curl .
I think the board only gets up to ~350 F.


Not really directly applicable to press and peel type boards, but might
want to poke around here:

http://www.thinktink.com/

lot's of interesting info.

oops



I meant to say goggles and gloves

Hi,

Just wanted to clear a few things up....

What is made is a cupric chloride etching solution, the copper on the boards mixes with the hcl/water/h202, that is why the etchant turns a green color, ultimately it will become cupric chloride. The formula (which took me a while to locate again is...

H2O2 + Cu (from pcb) + 2HCl --> CuCl2 + 2H2O

You don't have to dump the excess, "recharging" is done easily by adding H2O2 (don't need a lot), and if it's etching REALLY slowly, maybe a little HCl (there are better ways to recharge then H2O2, see this site: http://www.pcbfab.com/iepart5.html it talks about CuCl2 and recharging, but I have been using H2O2, and it has worked for me fairly well; I never add a lot). Heck, I'm still working with a batch I mixed up months ago.

I don't warm up my solution, or mix it hot. I know it would probably etch better if I did, but I feel more comfortable with it at room temp, and it seems to work OK.

What is remaining (when I said excess paper, I didn't really know what else to call it) is probably sizing - I do like the idea of a paint brush to remove it tho.

This high gloss paper isn't "photo paper", but rather labeled for "brilliant images" on brocures, proposals, and presentations. It may react very poorly with an iron - to be honest, I never had any success with an iron AT ALL, even when I used official "toner transfer paper", which is why I moved to a laminator.

And Bogax does have a lot of good safety tips. This stuff is dangerous if not handled correctly. Spending a few hours reading and doing everything carefully can save you a lot of pain.

Also remember - use all of this info - from me, bogax and any other site out there at your own risk.... This is dangerous stuff (heck, any etchant is, whether you buy that nasty stuff from Radio Shack, or roll your own), so be careful.

-Tony

_________________
-Tony
KG4WFX