Creating PCB's Q- UV Light

[QSQCaito]

I was thinking seriously about creating my PCB's using this method. Some questions still remain unclear to me. I should buy this prensitized PCB making myself sure it's positive. I should procede to put a Transparency with the Layouts in it. Then, give something to hold that in place, not scotch because that scotched part won't be eaten by the Etchant(percloruro ferrico.- In spanish). After that i should grab my uv light, and here is were i have some doubts. I should use special UV light.. Will a normal fluroescent tube work? For how long should it be exposed?, After this is done, it should be put in a solution, i read somewere caustic soda could be used,is this right?If not, which other solutions will work.. Well after that is the normal proces of etching a board..

Thanks a lot!

Bye bye

DAC

[captntasty]

Positive acting presensitized pcb is what to look for... I'm using EverMuse brand right now but another good option is from MG Chemicals... the MG Chem developer I use is a Sodium Hydroxide solution, not sure if that is a "caustic soda".  When I expose the board I carefully position the transparency onto the pcb without securing it and carefully/gently place a pane of plexi over that to keep it in place... glass would be a better option as it is ridgid, heavier and doesn't scratch.  It's important that the transparency is completely flat on the board otherwise light bleeds in and will cause problems on a layout with tight traces/smaller pads.

[Torchy]

I got an old flatbed scanner out of a skip, gutted it and put short uv striplights in it. I used pre-sensitized boards with it no problems.

[calpolyengineer]

You definately need to use a light designed for uv. A flourescent does put out some uv but the way it glows is because a special coating on the inside of the glass absorbs most of the uv. The uv bulbs are a bit expensive but pretty much necessary. When I did uv exposure boards in school we exposed them for about 90 seconds. You really can't overexpose it, but the longer you let it run the more likely that the uv bleeds into places you don't want it.

-Joe

[gez]

A fluorescent works fine, I've used them many times.  Exposure time is no different than UV provided close contact is made.

Transparencies, once printed on, aren't totally opaque.  Lay your transparency over a piece of tracing paper, then on top of this place your blank board.  This will block more light and give better results.  Use fresh paper and replace often (as it yellows it blocks UV and ruins boards).

Exposure time depends on the board you use.  Your supplier should provide details on their website/catalogue, or provide a data sheet when sold.

Plenty in the archives about this.  I've posted a few times on using fluorescents.

[QSQCaito]

ok! i'll search again.. i've missed your posts i think.. when i finish studying i'll search, and if any doubt remains, i'll let you know


thanks a lot

bye bye

DAC

[gez]

Try a search for 'fluorescent'.  Might narrow things down a little.

[QSQCaito]

Did some search, i think i can get some uv light in easy(home depot of argentina ).. about the developer, i also think i can get some from an electronic store.

To develop the board, you need a solution of 10g NaOH in 1 l water. Don't use hot water.

NaOH is caustic soda.. is dangerous.. gotta be careful if used.. it can be used as developer..

gotta look the specs of the presensitized board and see what i get..

bye bye

dac

ps sorry for bad english, im in a hurry

[gez]

To develop the board, you need a solution of 10g NaOH in 1 l water. Don't use hot water.

NaOH is caustic soda.. is dangerous.. gotta be careful if used.. it can be used as developer

There are a number of 'safe' developers on the market which you might be able to buy through a local electronics supplier.  Seno is one brand, available throughout the EU.  Although they're more expensive they're more forgiving if you leave the board in the developer for too long.

[QSQCaito]

Thanks a lot!

I'll see what i can get, make some tests, and tell you if i can get something reasonable.. if not i'll tell you anyway

Bye bye

DAC

[SISKO]

I wonder if there is a method to make a presensitized board out of a normal board...
I remember once, seeing this "product", a kind of spray or something like that. But, could it be DIY?.
Bye

ROCK ON
SISKO

[QSQCaito]

That's a good question.. if it's a spray, i think it might be difficult to get regular/repetitive results

[Paul Perry (Frostwave)]

Blieve it or not...... back in the Old Days, people used to put the raw copper PCB on a turntable & pour the sensitive solution on it & rely on the spinning to turn it into an even coat. I nevr saw this done.. but it sounds pretty tricky.
As to spray, it sounds pretty expensive!

[calpolyengineer]

It is no longer made anymore, but my school has a stockpile of sensitizer that you apply with a regular laminating machine. Works pretty well but it is sooooo expensive.

-Joe

[gez]

Yes, you can buy sprays and brush on stuff.  Easier to buy board - there's not much difference price wise - as getting an even coat is a pain.

Useful for etching boxes though.