Ething PCB

[tatapoum]

Hello all,

I will certainly buy the necessary tool kit to make my own PCB.

I've seen that it is possible to etch with Sodium Persulfate instead of dirty Ferric Chloride.

It seems to be more home usage friendly and safer for environment.

Any feedback about this chemical ?

The only drawback is that the etching machine is more expensive (around 175 euros).

ludo

[Tanstaafl]

machine?

I just use my 8" X 10" darkroom trays.  5 bux each.  buy the chemical in bulk.... kilogram for about 15 bux.

Sodium Persulfate  works faster than the ferric chloride.. but it's not as clean a burn in my book. 

gb

[illogik]

hey, chek this thread for info on various etching chemicals

http://69.56.171.55/~midibox/forum/index.php?PHPSESSID=602029061d3d6fb2b7cecbba935f3442&topic=1964.0

i'm using sodium persulfate (Na2S2O8); you don't need an expensive machine for that!

First i did it by heating the etching fluid to the right temperature in a pan 8), then pouring the fluid in a container with the pcb, rocking the container gently while etching (so the fluid moves). for a good/complete description g00gle (try "bergfotron"; saw it first there) because there are precautions you should follow!

BUT BUT BUT!!! this is faster/cleaner/safer ;D>>>

i now etch in my home built etching tank (plexiglass, aquarium heater and airpump); i'll look it up tomorrow, or try and find it on google yourself(diy etching tank or so);

cheers, marcel

[tatapoum]

Thanks to you for your advises and for the thread.

I'm not a fan of the solution with the darkroom trays.

But why sodium persulfate need a special machine with aquarium heater and bubbles ? Is it because the temperature range is not the same as ferric chloride ?

Because there are cheap machines, around 50 euros, like this one :

.

ludo

[Tanstaafl]

as with all chemical reactions, heat and aggitation are the easiest way to accelerate the process.

I have not used a packaged system for doing this but have experimented with heating my solutions.... with varying results.  Living in Texas... our ground water comes out of the tap at approx. 28-32 degrees C, depending on the time of day.  So accelerating the reaction through temperature is not a factor. I have found if I heat up the solution too much... in the area of more than about 39 C i have problems with the solution invading the etch resist to aggressively, and obliterating it!  (I have ruined quite a few pcb's because of this....better to let the temperature be about ambient  I believe)((unless you live in the Sahara  ;D ))

The bubbles on the other hand are a good thing... you don't have to  'shake the tray', as it were.

anyway... nur meine zwei pfennig!

gb

[raphael]

But why sodium persulfate need a special machine with aquarium heater and bubbles ? Is it because the temperature range is not the same as ferric chloride ?

To get best results, Sodium persulfate needs a temperature around 40-45°C

Ferric chloride works even at room temperature very well, with Sodium persulfate you will see (nearly) no reaction at room temperature (20°C).

The heating has to be regulated because Sodium persulfate crystalizes out above 50°C. That's why the etching machines are more expensive. But you can get one from Reichelt (www.reichelt.de) for 99€. But for a delivery to France you will have to order at least for 150€ :(

Raphael

[Jidis]

For anyone interested, I read a tip in a link for toner reactive foil that Davo posted a few days ago. It involves "wiping on" the etching solution. I'm coincidentally soaking some paper off an MTC display board in the other room, and was going to try it for the first time. If I'm not too tired, I'll post what happens tonight (otherwise tomorrow).

http://www.pulsar.gs/PCB/a_Pages/5_Support/4b_Tips_Tricks/Tips_Tricks.html

-George

[tatapoum]

Thank you for the Tips about Reichelt.

But my german is far away of me. How do you spell etching machine in german ?

Or What the path in the site ? I'm navigating in and couldn't find PCB related tools.

ludo

[tatapoum]

I've found : Platinen-Ätzgerät.

Yeah, that's the same sells at 150 euros.

Thank you very much !

ludo

[illogik]

yo;

check dis;

http://www.embeddedtronics.com/etchant.html

it's the one i use and i'm sure u can get this stuff where you live (unless aquariums are forbidden there)

cheers, marcel

[raphael]

I've found : Platinen-Ätzgerät.

Yeah, that's the same sells at 150 euros.

I spoke of the "ÄTZGERÄT 1" which costs 99.95€ . That's a smaller on for PCBs up to 250x175mm. Enough for all the MIDIBOX stuff.

"ÄTZGERÄT 2" (159.95€) is for bigger PCBs.

[Davo]

For anyone interested, I read a tip in a link for toner reactive foil that Davo posted a few days ago. It involves "wiping on" the etching solution. I'm coincidentally soaking some paper off an MTC display board in the other room, and was going to try it for the first time. If I'm not too tired, I'll post what happens tonight (otherwise tomorrow).

http://www.pulsar.gs/PCB/a_Pages/5_Support/4b_Tips_Tricks/Tips_Tricks.html

-George

Let us know about the ironing process, ok?  I have terrible results there, so I'm planning to get that toner-applicator/laminator discussed on the Pulsar page.

[tatapoum]

It's a little bit out off topic, but can someone explain me how works the reichelt ordering ?

I never type my credit card number, but the order seems take into account and I've received an e-mail 'Ihre Bestellung' (your order).

I have to wait they valid the command ?

Do you know if they speak english or french ?

Thanks,

ludo

[raphael]

If you don`t give your credit/EC card number they will send the package "contre remboursement" (as my dictionayry says).

Just give em a call. I'm shure they have also english speaking guys.

Raphael

[Jidis]

Let us know about the ironing process, ok?  I have terrible results there, so I'm planning to get that toner-applicator/laminator discussed on the Pulsar page.

Davo,

I had to decline on the wipe-on etch thing. It appears you need the TRF to do that. I guess you'd wipe the print off without it. I'll probably be ordering the green and white this week when I get up a good DigiKey order. I'm looking forward to doing some white on black, but I'm wondering how easy it will be to check over the black toner transfer before you apply the white. I usually don't hit a perfect transfer on my first attempt, but it's really easy to wipe it off and do another. This last one was an eight digit, green numeric display. It's only about 1.5" by 4 or something, with four of the full size (20mm?) dual modules, the three 595's, the resistors, and a five pin header. It's packed real tight with some really small traces, but I had to go with a bunch of jumpers on the top. They're multi-colored, insulated leads, smushed down under the components, so they actually look sort of cool.

Every time I do these things I have to remember the heat/pressure/time ratio. That's why I usually don't get a good one on the first attempt. Two things I'm catching on to: Less pressure for less time, moved frequently around the board with the tip of the iron, and also making the boards an eighth inch or more larger around than my print. They trim down fairly easy on a belt sander. I've found the edge traces to be the ones which don't always stay on the copper, so I do that as well as thickening up the outer ones until they hit the edge. If there are pieces of traces which come off, there are usually one or two in a small area where I didn't apply enough heat (never really anything long). I've discovered that it's easier to draw a splotch of sharpie ink over the whole area, rather than trying to redraw the small missing chunks of trace. You can slice out the center parts to separate the traces with a pencil tip x-acto blade after the etching and still have nice straight lines. My total ironing time probably isn't much more than 3 minutes. When I initially hit it, I will usually press the full base of the iron over the whole board for a bit, so that it glues itself down and I don't risk having ripples in it by working from end to end. Gootee's got similar instructions on his site. 

With this new Staples paper and the printer I'm using, it doesn't look like there's much danger in extending the ironing time. I think if I keep the iron moving, applying light pressure in small spots, I won't overheat it and I'll have less chance of having any parts that didn't stick. I've blurred the traces a bunch of times from either pressing too hard or letting the heat sit too long in one spot. I'm also wiping the top of the paper afterward with a wet paper towel to cool it, and I've been squashing the iron into it one last time after it's soggy. I keep a spoon handy in case it tries to stick to the iron. I don't know if this helps, but I see lots of mentions of briefly reheating stuff after the main heating for better bonding. The Staples paper is weird. It sort of rolls off in beads after you get it wet, and leaves a film of paper stuck to the surface. This comes off with more rubbing, or a toothbrush and water. That stuff is all or nothing. The parts that stick properly are hard to get off, unless you use solvent or steel wool. I also usually wipe it with a wad of wet paper towel to get the initial thick layers of paper off. Pulling it off the board seems more dangerous. The old paper would peel off clean, leaving a slight gooey residue after it got wet enough, but it seemed the traces were more fragile and more likely to lift off with it. It still worked pretty well, but the procedure is a bit different. I think that type of photo paper may be the easier one to find.

The printer I just got is a Sharp FO-2850 fax/laser. Gootee uses the HP LaserJet 4. I think a bunch of the HP's use the same toner, but many printers may work just as well. The Sharp was given to me.

I looked at that Pulsar laminator too. I'm not sure what it handles. It looks like it may just be for the paper or something (5mil maybe). The model is actually a GBC Creative Laminator (I think I saw the model# too). It wasn't really made for PCB's and there are about a zillion different similar units on eBay,etc., so if you go that route, you may look around to see if there's a heftier one which is used for the same stuff. I wish they'd start selling the colored TRF in rolls without the whole bundle. The green and white are very affordable. I couldn't find anyone outside of Pulsar selling it. Let me know if you see any.

                                                                                         -George

PS-- I "flipped" the plastic tray of ferric chloride off the bathroom sink on the last etch :o  It splattered across me, the wall, the floor, the cabinet and the bathroom door. First and LAST time for that one.     

[ImAlive]

Just etched the 1st PCB in my life... pretty crappy, but I think it'll work  ::)

I did it by the "Iron" method: Printed the layout (AIN) on Reichelt catalogue paper with a laser printer, and ironed it on the copper board (well, I still have to improve my skill with that technique, the tracks are a little fuzzy, and I had to scratch off quite a few short ciruits, but now I think I'm fine - the toner did not stick to the copper very well and came off partially when removing the paper. But luckily, water-resistant pen worked fine for masking. Maybe I should prepare the copper better before ironing, and apply more heat?).

Then, I threw the board into FeCl3 (250g into 500ml of water, in a plastic bowl contained in a warm water bath, a little too cold in the beginning so I had to pour in some more hot water), and after 20 minutes, the layout looked pretty decent (Ferric Chloride: awful stuff. I looked pretty funny I think with that goggles and gloves and stuff, but you better be safe...).

Removed the toner with nail cleaner (didn't have pure acetone around), but now it sticked pretty hard to the surface, heh. And done! The small letters (MHBP_AINX4...) are well readable, so with some practice (and a masker pen), I think this method is suitable. Learn from your mistakes and have lots of fun, that's what DIY is all about, right?  8)

Okay, now that this worked, I'll iron my next 3 boards (2x core, another AIN, since I'm building 2 boxes in cooperation with a pal).

EDIT: The 2nd AIN came out really good. The problem is the cores. I had quite some trouble with those, hence the toner didn't stick good now as well. Bigger boards are harder to make, using this method, I think. Also, someone mentioned that HP toner doesn't seem to be suitable for this, and as I used HP toner, I might agree with that. But for now, the cores at least seem usable (no disconnected traces, but quite a few shorts and fuzzy lines).