pre-sensitised pcb

[cakeworks]

Hey, I (stupidly) bought pre sensitised pcb yesterday instead of the regular stuff. I say stupidly because I don't have any oht's and won't be getting any in the near future.
My question is; am I able to simply draw the design on with a sharpie for the uv exposure?

thanks once again

-Jack

[QSQCaito]

I believe yes, some people (i don't remember, someone in the forum posted his method, use search function) Used transparencies printed with inkjet laser, you just need something that avoids the UV light have contact with the pcb(i think)

[Dave_B]

I believe yes, some people (i don't remember, someone in the forum posted his method, use search function) Used transparencies printed with inkjet laser, you just need something that avoids the UV light have contact with the pcb(i think)

I use an standard Epson inkjet to print the artwork.  I don't have an exhaustive tutorial, but here are some photos of the process.   

[The Tone God]

Unless you have developer then you will not be able to remove the exposed sensitizer. If you want to learn how to do photo etching or need the accuracy then go ahead but you might be better off removing the sensitizer so you are down to copper and treated it as normal copper clad board after that.

Andrew

[QSQCaito]

don't wanna hijack your thread but, the exposed sensitizer is the thing removed by th UV right?

[The Tone God]

don't wanna hijack your thread but, the exposed sensitizer is the thing removed by th UV right?

Not quite. The sensitizer is "broken down" by the UV light. After the exposure you have to run the board through a developer solution. This removes the sensitizer that was exposed to the UV light. The sensitizer that was not exposed to UV stays on the board and protects the copper during etching.

Andrew

[calpolyengineer]

I'm pretty sure that the uv coating is a photo negative process. Where you black it out is where it will be etched. The uv light hardens the coating in the areas you want to keep as traces.

-Joe

[The Tone God]

I'm pretty sure that the uv coating is a photo negative process. Where you black it out is where it will be etched. The uv light hardens the coating in the areas you want to keep as traces.

Ah point I forgot to mention. There are negative and posistive exposure processes. Be sure to check which one you got.

Andrew

[captntasty]

The sharpie should work and would be fine for simple layouts but would be laborious on layouts with a lot of traces - probably want to get some transparencies made at kinkos - 82 cents per sheet.  If you don't have developer and just want to etch the board using sharpie you can remove the coating with isopropanol - good ole rubbing alcohol - might need higher % stuff.  Not hard to find at the drug store.  If you go for exposure, definitely need to know whether neg/pos.

[Dave_B]

Yeah, obviously mine is positive.

[Dan N]

In this thread:

http://www.diystompboxes.com/smfforum/index.php?topic=48675.0

Ardric mentions using presensitized with plain paper.

[captntasty]

That seems like it would work - the sun is the best UV source available - and with the strength of the light source it's probably necessary to have some opaqueness.  Hmmm...     Could I save myself 82 cents and avoid the 5 minute carride?  Damn, I'm pretty sure it's going to rain tomorrow...   

Yeah, obviously mine is positive.

I was referring back to the original post...  aren't they all pretty much positive?

[markm]

I believe yes, some people (i don't remember, someone in the forum posted his method, use search function) Used transparencies printed with inkjet laser, you just need something that avoids the UV light have contact with the pcb(i think)

I use an standard Epson inkjet to print the artwork.  I don't have an exhaustive tutorial, but here are some photos of the process.   

Dave,
Your PCBs look excellent!
Make me wanna yurn in my PNP and start photo-etching my boards.
Nice work!

[calpolyengineer]

I was referring back to the original post...  aren't they all pretty much positive?

I guess most of the stuff that hobbyists get is positive, for obvious reasons of simplicity. I'm a student right now and I learned about commercial processes which are almost exclusively negative. I don't actually use photoetch on my boards but I thought the pos/neg thing would be good to get straight since he didn't intend to buy sensitized boards in the first place.

-Joe

[Dave_B]

Dave,
Your PCBs look excellent!
Make me wanna yurn in my PNP and start photo-etching my boards.
Nice work!

Thanks, Mark.     When I started getting back into this, I never got the hang of PNP.  After a few failed attempts, I went back to my old photo-etch habit.  It's really not an expensive or complicated process and the results haven't required any patching or cleanup.  If you start off with a blacklight floodlamp (which was good enough for the 4"x4" Polyphase board), it shouldn't cost more than $20 to get started.  The blacklight fluorescent tubes are a nice step up, but mine are still packed away... somewhere.

[cakeworks]

what do you wash the photo-sensitive resin off with?

[gez]

what do you wash the photo-sensitive resin off with?

You can buy purpose made cleaner, but nail polish remover works for me.

[markm]

Dave,
Your PCBs look excellent!
Make me wanna yurn in my PNP and start photo-etching my boards.
Nice work!

Thanks, Mark.     When I started getting back into this, I never got the hang of PNP.  After a few failed attempts, I went back to my old photo-etch habit.  It's really not an expensive or complicated process and the results haven't required any patching or cleanup.  If you start off with a blacklight floodlamp (which was good enough for the 4"x4" Polyphase board), it shouldn't cost more than $20 to get started.  The blacklight fluorescent tubes are a nice step up, but mine are still packed away... somewhere.

Is a Black Light reccomended for doing this?
Thinking about giving this a try as an alternative to PNP for PCBs.

[Dave_B]

Is a Black Light reccomended for doing this?
Thinking about giving this a try as an alternative to PNP for PCBs.

I know that ordinary flourescent tubes are an option and to a lesser degree, normal sunlight.  I started with a blacklight lamp because it was the cheapest option at the time.

If it helps, here's the instruction sheet that comes with my PCB's.  They recommend using a contact frame to hold everything together, but an ordinary piece of window glass (non-UV) works fine and only costs about $2US.

[markm]

Nice!
Thanks alot.