PCB etching adventure...

[greysun]

Hey guys - posted this over at BYOC too. Let me know if it's in the wrong forum, but I have my adventure in the first go-around of PCB etching. Here's what I wrote:

So I had a few boards that I wanted to etch because, frankly, I'm sick of doing perf board for complex circuits and I think I can fit more into a smaller space when I can design it.

So i ordered all the etching supplies from Jameco after looking through (BYOC) forum and watching this video: http://www.youtube.com/watch?feature=pl ... Wnfnt2rNO0

Keeping in mind that the only thing I had to start were 2 tubs to hold the chemical compounds, the pricing comes out to about $175-$185 for everything. That will buy you 3 PCB's (including the 2 in the developer/etchant kit), the developer/etchant kit, the drill/bit/stand kit (which I'm now realizing the stand would have held my dremel, so that's money down the drain), the lamp and light, the tinit kit (for tinning the board when you're done) and miscellaneous small items (gloves, red light bulb, nail polish remove, etc.).

SO... The video (sponsored by Jameco) says a 13watt CFL bulb for 8 minutes on the image over the PCB in a photo frame is good, but the instructions say 100watt incandescent for 10 minutes, or 14 minutes for bigger boards. The instructions in one PCB said 1:10 ratio for developer/water - and in the other they said 1:3. So there are instruction continuity problems already...

I went ahead and did everything per the video since that worked for him with these specific parts. The first board developed okay (but I couldn't use half the smaller boards on it once etched). The second board did absolutely nothing in the developer for 15 minutes. I placed the tub into a hot bath (keep in mind, the developer wasn't cold at this point), and then it started doing something, but VERY slowly - I added a little more developer, but it still took almost 2 hours to "fully" develop (quotes used because it never actually fully developed - there was green ghosting all over as I found during the etching process).

So the etching process worked, but the developer part threw me obviously - cause it was just not working very well. I would say I have 50% of my boards are useable - not very pretty by any means, but useable so far as I can see.

This method was touted all over a few boards - I found some that said they had issues with the photoresist boards not developing quickly sometimes. I still have one 3x4 board that I could etch 4 smaller boards out of, but...

The other method is the toner tranfer method, I think it's blue pcb transfer paper or something? I'm considering that since this method was kind of a dud for me. I don't plan on doing a lot of these - the boards i'm etching are my own designs and/or boards that aren't available anymore but have single-sided etch art. I'd like to not spend much more money on these things.

Any advise, pointers, etc?

[pedalman]

First of all, not to knock Jameco but try to stay away from kits. Jump into the forums before making a purchase and ask questions. Then ask more questions. What i like to do is when i start to hear the same answer then give it a try. Everybody likes to do things differently, not what a kit says you need. I go to the swimming pool area at Lowes and get a gallon of Muratic Acid for just a few bucks and it lasts forever.
Id start with what the labels say on the bottles and do a small project. adjust the dosage and times as needed. Go to the thrift shop and buy a bunch of tupperware for marinating your boards. Dont go cheap on the safety gear I use a rubber lined apron good quality gloves and safety glasses with side guards
I found these dental hooks at harbor freight that work great for taking boards in/out of the bath

[aballen]

I've also hear the method you are trying is superior, but the cost of a lamp an photoresist boards kept me away.

PnP blue works really well.  And it's pretty easy.  You just need a laser printer.  I picked up a new HP P1005 for like 90$ just for this purpose.

[greysun]

well, it wasn't really a "kit" so much - more of a bundle where you buy the developer and etchant (ferric chloride, in this case) and it comes with 2 photoresist boards.

I had done research on a few boards, and it did say this was the best method, as the press n peel transfer had issues with smudging, and other methods required an expensive laminator and foils.

A friend of mine does press n peel blue, but doesn't think he has any paper left. He says he gets about 50% success rate on them, and has to fix the rest with a circuit pen or just start over...

I have one pre-coated board left, I think I'll give it one last go and hope that I can get all the boards that were miffed up onto it. I really don't want to get into the etching business, but the costs of paying someone to do it for me were about equal for all the ones I wanted - I'm regretting not having someone do them for me, LOL.

[davent]

I've also hear the method you are trying is superior, but the cost of a lamp an photoresist boards kept me away.

PnP blue works really well.  And it's pretty easy.  You just need a laser printer.  I picked up a new HP P1005 for like 90$ just for this purpose.

All you need as far as a lamp is any old flourescent tube. I screwed a piece of plexiglas to the joists above my workbench where the lights are recessed between the joists and just pop the exposure package up there when i need to do boards. Half an hour from printing out a transparency to having the etched board in hand.  Before the joist trick i would stack up phonebooks, fat electronic catalogues etc. on the kitchen counter until i could get the exposure pkg within an inch of the tube under the kitchen cupboards.



No need for a safe light (red) the board isn't sensitive enough that the ambient light of the room will wreck the board before you expose it proper. Under flourescent lamps it takes ~10 min. exposure. Just work in an unlit room with abit of light from a cracked door. I've loaded up boards put them under the lights only to realize my transparency is wrong side up, turn the lights out correct the package, back under the lights and the boards tumed out as good as ever.

Dollar store plastic tubs, as small as will still allow the board to fit in flat against the bottom. I've read of people using heavy duty ziplock bags.

For an exposure pack i use an Ikea frameless picture holder, a clip on each side holds the glass to the backing board, takes seconds to load the art and board in and get it up under the lights. Again dollar store might have something.



+1 for muriatic acid and hydrogen peroxide.
Developer i use is MG Chemicals 1:10 with water, takes about a minute to develope when fresh but i'll use the same batch over and over until its almost black.

To figure out your exposure time take a small strip of board and load it in you frame with a pcb transparency, put it under your light for say seven minutes then cover about  a 1/2 inch with a piece of opaque cardboard, wait two minutes slide the cardboard over to cover another 1/2"... every two minute cover a bit more of board with cardboard until theres no more board left exposed.

Develop the board and you'll have strips that were exposed for from 7min to say 15min in 2 minute intervals. One of those strips will show the minimum time (what you are aiming for) that you need to expose the boards with your lighting setup for a perfectly exposed board. (and there really is a great deal of latitude as the boards aren't very sensitive... slow in old photo parlance.) You only need to do this once unless you change your lighting setup, all the different brands of boards i've tried end up around 9-10 minutes with the lights above the workbench.

Take care,
dave

[pedalman]

The shop monkey ! Guardian of all that dwells around the workbench. Also keeps a close eye on whats being exposed to the light

[davent]

Little known Mayan Pedal Deity.

edit;spelling... blah

[greysun]

So I've neglected to update here, but its been a time consuming project. To update:

I went back, adjusted the light distance and exposure time, used fresh chemicals and only did one board (with 4 smaller boards on it). It went great. No hiccups, no issues, and you can see the difference for sure.

I drilled and tinned this this weekend and went back over them with solder to touch up the less-than-perfect first batch's problem spots (on what was salvageable, anyway). All of these look perfectly usable to me now. I labeled them with rub-onz transfer paper. Not perfect, but it tells me where things should go.

Attaching a couple pics.

Top row: 3 madbean eggheads and a rub-a-dub reverb redesigned for a njm2082l chip.

Middle row: 3 madbean stubbii's (2 redesigned to give more padding between the traces and ground plane - I'm putting them in a 1590b anyway)

Bottom left: dual tap tremolo (bottom right and left are for audio lines, middle bottom is the LDR, and top is the LFO. Its a big board, but its going in a big enclosure).

Bottom right: top is 3 JMK blenders (redesigned for a njm2082l chip); bottom is 2 madbean modulatorers (redesigned to be THIN and have mounted 9mm pots - these will go into my 1776 multiplex builds)

[jimilee]

Sounds like you got it down now! Enjoy

[stevie1556]

They look really good! What are you using to cut the board's with? I'm keep scoring them with a Stanley knife until it cuts through, very time consuming and the edges ain't great.

Also, to save yourself some time and money on the tinning, after they have been etched don't remove the remaining photo resist layer. It protects the copper and melts under the heat of the soldering iron.

Sent from my thumbs using Tapatalk!

[greysun]

I scored them with a utility knife on one side, then again on the other (you can see the line on the etched side through the PCB), then I just get it on the edge of a solid surface (counter, table, etc.) and press down until it breaks off - it doesn't take TOO much pressure. I'll probably use 1/32 thickness PCB next time, though, just to make it easier.

Then I sand the edges with 150grit to either smooth it out, or get it a little closer to where I need it.

For smaller sizes, you can always use a C-clamp to hold down what you don't want, and break off what you do want - but just watch the positioning of the clamp... you could scrape up your fingers pretty good when that thing breaks off. Ask me how I know. ;-)

[stevie1556]

I got the economy PCBs so I can't see the score marks when I look at the other side of the PCB, so I'll just have to keep scoring it at the mo. My next order is going to include normal photo PCBs, anything to make the job a bit quicker!

Where I get most of my electronics stock from sells these PCB cutters, but the cheapest one is £180 so I keep looking for a decent alternative. Thinking about trying a tile cutter as they are fairly cheap.

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[davent]

If you have a Dremel or other small rotary tool get yourself a diamond cutoff wheel, goes through like a hot knife through butter.  (don't forget the dust mask/respirator and eye shield.)

dave

And those boards look like they turned out really well. Now it's easy.