Hmm, looks like overexposed/overdeveloped.... Did You make a Exposure-Set? Eg. get a piece of Pcb-Board, a piece of cardboard and Your film with a Circuit. Put it on the UV-Lamp with all but a 10mm stripe covered by the cardboard, expose half=20 the usual time. move the cardboard to expose 10 more mm, expose one more tenth oft the usual time. Repeat until two times usual time are reached.
I did print it on an plastic sheet (acetate) on a laser. I mirrored it and then put the ink side down. And then a sheet of glass on top of it to keep it flat.
I haven't done a test strip yet but will maybe try that today.
Okay - I think I have some improvement here but this is still with very big tracks. Can I get some feedback on this:
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...and I would appreciate it if I can get an idea of how good/bad this is. The board I need to do is smd and very dense so I need a good process layed down first.
Just as a side note - it was extreme underexposure - 20sec vs. 2 mins that I'm doing now - I'll maybe try more and see how it goes.
I started at 20secs though because I have 6 x 15W tubes.
I thought glass wasn't naturally UV opaque unless it had additives like with plastic. Most glass (for pictures, internal windows, etc.) doesn't as far as I know.
I've always associated a 'green' tinge with additives and additivies to the posiblity of UV resistance and hopefully the lack of tint with no UV resistance - but I could be totally wrong ;)
All glass is UV resisting, which is why most film lighting lights have glass in them while UV suntanning lights don't.
The exposure unit that we have at the old factory places the material directly in front of a big mercury tube, but rotates the material after you have loaded it so the rays don't escape.
I think you will find the Epron erasers use direct UV light as well, they use a draw or a switched cover for safety.
Peter
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Okay - I've started trying to make some d/s boards and have run into another funny. It seem that the image after developing is 'smudged' - its not actually smudged but it looks like that. It looks like the image is missing an area like it has been rubbed off or something.
This only happens on one side and irrespective of how carefull I am placing it in the developer/etc.
This is as good as I've gotten it so far - as you can see there is still a problem with the second side, although the one side is perfect. Each step is done vertically so I'm really struggling to figure out whats going wrong.
I take it the trace widths and pad sizes are the same on both sides? Traces and pads are thicker on side 2.
Side 2 looks like it was one (or more) of:
o under etched o under developed resist o bad artwork o under exposed resist
My guess: under etched.
You may want to lift the board and spin it 1/2 turn at the midpoint of the etching time: that way both sides should get etched the same amount (maybe). Increasing etching time for 2 may result in over etch on 1.
Sorry to disagree: Underetched woud show blank copper where the Traces are too big, but as You can see there ist violet resist all over the traces. If the resist would change colour at the faulty Traces, i woud suggest underdevelopment, but i still think=20 there's something wrong with the exposing process..
Michael.
P.S.: If this resist don't change colour when being exposed, it can also be underdevelopment (Board not lifted while developing, so there was no NaOH at he bottom side?)
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