Another genius trying to etch a PCB

[robmdall]

Starting to Photo Etch (Positive method) and want to run some things by you.

Mind you I have tried a couple of times using a small circuit only to have no success.

Using a 100 Watt Reptile UVA / UVB bulb (I keep turtles, so it seemed like a good idea)
Using an Ink Jet printer (HP (cant remember the model number) 1200 X 1200 dpi)
HP Transparencies
MG Chemicals Developer
30 % Hydrogen Peroxide (3 parts) and Muriatic Acid (1 Part)
Old glass picture frame.

This was my test setup.

Lamp set 12 "above glass, transparencies were sandwiched between the glass and the Positive PCB (removed the protective layer in the dark)
Exposed 1st board for 8 minutes – developed and saw a very light circuit remaining on the board.
Stuck it in the acid bath and in a minute, board was 100% copper free.

Second test used a mask to expose smaller sections of the PCB from 8 minutes to 32 minutes. Lamp still at 12 inches above board.
After developing, I could see the circuit faintly, once in acid, the circuit portion started to dissolve before the 'blank' part of the copper.

What can I be doing wrong? Any ideas?

After exposure, should I be able to see an outline of the circuit? Are picture frames UV resistant?

Bob

[Ice-9]

The photo resist board i use states the exposure time on the datasheet, and it's 2minutes 20 seconds, now i know different makes will vary but it sounds like your problem might be due to over exposure. Also the transparency print out should be very dark, usually done with a laser printer, i have never had any success with an inkjet printer as the print isn't opaque enough.  Although i think you should get a decent result with an inkjet, i beleive you exposure time is way too long. also i use an 8 Watt uv bulb only at about 2" from the glass screen.
Yes after i have developed my pcb i can clearly see the pcb pattern.

[therecordingart]

Probably the sodium hydroxide. I had lots of issues with sodium hydroxide either under developing or over developing (like in your case) my boards. I switched to something else (I'll find the name when I'm home tonight) and it was wonderful!

[Gurner]

I'd hazard a guess you aren't getting enough contrast at the exposure stage.

When it comes to getting a good positive, you just can't beat a laser.

Rather than use transparencies (which I think is awful stuff to work with) I prefer to use 90gm tracing paper - I'm getting decent results., here's part of 1206 component based SMD board I've just made earlier tonight...



With transparancies, even a laser printer can have some difffs ...this is because the blacks just aren't black (hold your transaparency up to the light & see what I mean)  - I'm talking from a reasonable amount of experimentation (having tried about 4 or 5 high end lasers at work!!), so when I do use use transparencies, I print two & double them up  (put some registration marks on your image to help align & use super glue on the edges to bond the two transparancies together)....in fact the best results I've ever had was doubling up transparancies - the blacks are jet black....but it's a bit of a faff, so like I say, I use tracing paper - much nicer to put through a laser.

I develop with bog standard caustic soda (the other silicate based stuff may be nicer, but they're taking the absolute piss with the price!) - what I've noticed when using caustic soda,  is that the development can be moved along more rapidly by removing the board after the image starts apearing faintly - remove the board from the causitc soda & rinse it under water (to remove the residual dilute caustic soda from the board!) , then rub your fingerpad over the developing image on the copper - ...the exposed copper will start to shine through brightly)...plop it back into the caustic soda to finish off for 30-40 seconds (I use a jeweler's loupe as I do SMD & the tracks are very fine!)

One of the better sites wrt homemade pcbs here here....

http://www.electricstuff.co.uk/pcbs.html


** No animals were hurt in the making of this PCB.

[culturejam]

Muriatic acid doesn't work very well with the photo-resist boards, unfortunately. The resist breaks down at about the same speed as the copper, which results in pitted traces and sometimes the resist of an entire section just slides off early. I found out the hard way as well.

[robmdall]

Guys, Thank You for all of the informative responses.

The consensus seems to be exposure issues at this point. I guess my next step should be to get a hold of a laser printer.

Mick, Thank you for your input! I used a formula from the MG website to calculate exposure time; However I have to believe that exposure is a big issue. What developer do you use?

therecordingartist, thanks for the heads up - waiting patiently for your reply.

Gurner, nice looking board! I have read about the tracing paper route, after seeing your board I am a believer. Are you using a Muriatic acid based enchant?

CultureJam, Thanks, what enchant have you found to be best?

Thanks again.

Bob

[culturejam]

CultureJam, Thanks, what enchant have you found to be best?

I was able to make some PCBs with photo-resist boards and muriatic, but they don't look great.

The best for photo resist is the dreaded ferric chloride. 

[KazooMan]

Culturejam:  Have you tried the sodium (or ammonium) persulfate etchant on the photoresist boards?

I recently bought some of the photoresist boards to have a crack at them, but haven't had the opportunity to try them.  One thing I have read on the forums is that many people print out two transparencies and carefully stack them to get a more opaque mask.

[Gurner]

One thing I have read on the forums is that many people print out two transparencies and carefully stack them to get a more opaque mask.

lol, you probably read that just four posts up from your's...  

when I do use use transparencies, I print two & double them up   (put some registration marks on your image to help align & use super glue on the edges to bond the two transparancies together)....in fact the best results I've ever had was doubling up transparancies - the blacks are jet black....but it's a bit of a faff, so like I say, I use tracing paper - much nicer to put through a laser.

rob - since you ask, I use ferric chloride & dispose of it on my neighbour's rose bed in the dead of night....this is of course is a win/win situation.

[culturejam]

Culturejam:  Have you tried the sodium (or ammonium) persulfate etchant on the photoresist boards?

No, I have not.

I recently bought some of the photoresist boards to have a crack at them, but haven't had the opportunity to try them.  One thing I have read on the forums is that many people print out two transparencies and carefully stack them to get a more opaque mask.

I used a laser printer when I was doing photo-resist. I never had a problem with opacity on the transparencies. But I always printed at 600dpi, which may or may not have provided greater density on the images.

I use ferric chloride & dispose of it on my neighbour's rose bed in the dead of night....this is of course is a win/win situation.

I hope your neighbor doesn't get his water from an on-site well. That's a lot of copper to be putting into the localized water table. It's probably not a huge deal, but copper is some very bad stuff for living organisms.

[gmoon]

I'll sandwich two identical layers of the mask together when I'm using inkjet transparencies. That's dense enough for the photo process.

Eyeballing the registration isn't a problem, and once aligned and taped two layers work fine. Typical PCBs masks, at least the ones we all use, are low resolution. For super-fine SMD work the sandwich trick is stretching it a bit, though.

An inkjet transparency is nowhere near as dense as real litho film, which I used to use...

[KazooMan]

lol, you probably read that just four posts up from your's...  

Crap!  How did I miss that???

[davent]

I use muriatic acid/hydrogen peroxide to etch MG Chemicals' photo pcb's all the time and have never had a problem. For developer i just use the MG developer, doubled up laesrjet transparency (printer is dying) and expose for 9 minutes an inch away from regular flourescent tubes. 

   

On ebay i've seen a photo sensitive film offered for use with your own copperboards but only as a negative process. The info seems to imply that a different developer is needed that the one used with the positive process. Anybody have any experience/information on this stuff? Thanks

dave

[danielzink]

On ebay i've seen a photo sensitive film offered for use with your own copperboards but only as a negative process. The info seems to imply that a different developer is needed that the one used with the positive process. Anybody have any experience/information on this stuff? Thanks
dave

<hand raised> ooo ! ooo ! pick me !
The negative process is a PITA. I still have some film downstairs.....anyone want it ?
I bought a laminator and modded the snot out of it... You have your bare copper single side FR4, working in dim light you peel a layer off the film and stick it on the copper side. run it through the laminator (hopefully the film doesn't wrinkle - or get wrapped around the laminator rollers - hence the modifying). then expose it,remove another layer of clear film, develop it......the developer is a swimming pool chemical available everywhere. Now - the developing isn't like our positive resist boards...the film is much (much) thicker and it doesn't like to come out from between very fine traces. My success rate has been <10% with the negative DIY film vs 99% with the positive stuff.

Dan


So.....

[culturejam]

I use muriatic acid/hydrogen peroxide to etch MG Chemicals' photo pcb's all the time and have never had a problem.

I haven't used that brand. I may have to give it another go if it works will with muriatic.

Thanks

[G. Hoffman]

Ink jet printers usually use a dye based ink.  This will cause a problem, as dyes are very fine, and mostly transparent, or at least translucent.  A few brands use a pigment based ink, which will work much better.  The advantage to ink jets is that the toner is basically just bits of opaque plastic that get very precisely melted onto the paper - which works great.  Thus, the ink jet printer is not what most people recommend for photo masks, and laser printers work much better.


Gabriel

[robmdall]

Dave, thanks for the info, nice looking boards by the way.

Gabriel, I took everyones advice and am picking up a used laser later today!

I will post back here.

[KazooMan]

I finally tried my boards from MG yesterday.  I used the "two layers of laser printer transparency" mask and had the board about one inch from a two tube fluorescent fixture.  The instructions indicated about a 5 - 8 minute exposure and said that longer would be better.  I tried the 8 minutes and it was way too much.  Parts of what should have been masked had been exposed and came off with the developer.  Second try was 5 minutes.  The instructions indicated that the developer might take up to 2 minutes to work, but it actually took less than 10 seconds.  The result was by far the cleanest result I have ever gotten in preparing a board.  MUCH better than toner transfer. 

I used ferric chloride to etch the board and it worked great.  The instructions indicated that ammonium persulfate is incompatable with some of the phhotoresists so I did not try it.   

The instructions indicate that it is not necessary to remove the remaining photoresist before soldering, but I didn't trust that so I went ahead and drilled and then wiped with acetone.

End result is a terrific board.  I think my days of ironing toner on boards are over.

[KazooMan]

Has anyone tried the negative film resist to prepare a mask for etching a pedal enclosure?  Does it hold up any better than the toner transfer?