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Re: [SeattleRobotics] Photo etching

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  • Jon & Tammy
    If you build a multi unit light box measure the center to center distance of your lights and use this figure to set the height of your glass above the bulbs
    Message 1 of 20 , Mar 2, 2006
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      If you build a multi unit light box measure the center to center
      distance of your lights and use this figure to set the height of your
      glass above the bulbs
      and this will minimize undercutting and provide a more even illumination
      especially on longer exposures

      Jon

      --
      109 Mardan Dr
      Grants Pass,OR 97527
      541 474 7782

      Wherever you go, there you are.
    • PeterBalch
      ... grow ... How about those UV lights for checking forged banknotes? They re pretty cheap and come in a nice box. I got one second hand for a few dollars a
      Message 2 of 20 , Mar 3, 2006
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        On 3/2/06, Jim McBride <mcbride7@...> wrote:
        > So I guess I just have to play around and do a time strip from hell. A
        grow
        > light for plants is UV light, right? That might be the cheapest/easiest
        > route...

        How about those UV lights for checking forged banknotes? They're pretty
        cheap and come in a nice box. I got one second hand for a few dollars a
        couple of years ago but haven't tried it with pcb etching yet - great for
        looking at rocks.

        And what about UV LEDs? I've never played with one. There are plenty of
        times when you just want a small pcb. Are UV LEDs useful for anything? Can
        you erase EPROMs with them?


        > "Kenneth Maxon" <kmaxon@...> wrote
        > I put
        > a piece of quartz glass that had no UV filters across the top.

        Do other kinds of glass reduce the UV significantly?

        Peter
      • Jonathan Peakall
        Hi All, Can one easily photo sensitize PCB boards at home? One reason I haven t tried photo etching in years is that most of my boards are small and buying
        Message 3 of 20 , Mar 5, 2006
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          Hi All,

          Can one easily photo sensitize PCB boards at home? One reason I haven't
          tried photo etching in years is that most of my boards are small and buying
          pre-sensitized boards and using only a small part of it is expensive.

          I have a UV lamp from an aquarium sterilizer. I bet that would work well.
          It's a small lamp, would have to set it up to move back and forth.

          Jonathan


          >
        • Barry Smith
          I did this in the 70 s, when I was in high school. I manually used the printed circuit drafting patterns (line, pads, dip patterns, etc) on clear sheets (like
          Message 4 of 20 , Mar 5, 2006
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            I did this in the 70's, when I was in high school.
            I manually used the printed circuit drafting patterns (line, pads, dip
            patterns, etc) on clear sheets (like view graph sheets, back then) to
            make the cirucit pattern (traces would be in black at this point).
            Then, in a light-tight bathroom, made a contact print of that on a photo
            negative sheet and developed that.
            Then, on a clean PCB, sprayed it with some UV resist and let that dry.
            When dry, the photo negative was placed on the sensitived PCB and
            exposed to UV light.
            (I made a frame with glass and foam rubber so the negative and board
            were pressed together while exposing it.)
            After a while, the PCB was removed and rinsed in a solvent (something
            like xylene(?) or tylene(?), I don't remember).
            That would remove the unexposed resist, leaving the resist traces
            exposed to the UV.
            The board was etched and then cleaned (I think, with acetone).

            Of course its easier now that that all the photo steps can be replaced
            with generating the negative directly on a laser printer.
            Just spray and sensitive the board and go from there. I think the spray
            was even available at Radio Shack then.
            It is certainly something that can be done at home.

            Barry






            Jonathan Peakall wrote:

            >Hi All,
            >
            >Can one easily photo sensitize PCB boards at home? One reason I haven't
            >tried photo etching in years is that most of my boards are small and buying
            >pre-sensitized boards and using only a small part of it is expensive.
            >
            >I have a UV lamp from an aquarium sterilizer. I bet that would work well.
            >It's a small lamp, would have to set it up to move back and forth.
            >
            >Jonathan
            >
            >
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            >
            >Visit the SRS Website at http://www.seattlerobotics.org
            >Yahoo! Groups Links
            >
            >
            >
            >
            >
            >
            >
            >
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          • Jonathan Peakall
            Barry, ... So, what is the modern method? Does one use a laser printer to print the art on a transparency? Or does one have to transfer the printed art? I
            Message 5 of 20 , Mar 5, 2006
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              Barry,

              >
              > Of course its easier now that that all the photo steps can be replaced
              > with generating the negative directly on a laser printer.
              > Just spray and sensitive the board and go from there. I think the spray
              > was even available at Radio Shack then.
              > It is certainly something that can be done at home.
              >
              > Barry

              So, what is the modern method? Does one use a laser printer to print the art
              on a transparency? Or does one have to "transfer" the printed art?

              I may give this a whack, as the modern toner transfer method can be
              tempermental and not so good on fine traces.

              Thanks!

              Jonathan
            • The Earl
              Screen printing can use photo resist, but I do not know how well it would stand up to etchant. They sell the photo mask in a bottle, an you expose it to
              Message 6 of 20 , Mar 5, 2006
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                Screen printing can use photo resist, but I do not know how well it
                would stand up to etchant.
                They sell the photo mask in a bottle, an you expose it to artwork,
                then wash out the parts
                you dont need. I do not remember if it is positive or negative
                exposure, but if you go to a
                local craft shop they can probably talk you through it.

                I also saw a film that was applied to steel to create solder masks.
                They exposed the film covered sheet then etched it with ferric
                cloride, which is the same etchant used for PCBs.
                I do not know where you would get the film, and you would have to be
                careful about applying it to a pcb, but it would give you a nice even
                coating.

                Anyway.


                On 3/5/06, Jonathan Peakall jpeakall-at-madlabs.info |6812-the|
                <...> wrote:
                > Barry,
                >
                > >
                > > Of course its easier now that that all the photo steps can be replaced
                > > with generating the negative directly on a laser printer.
                > > Just spray and sensitive the board and go from there. I think the spray
                > > was even available at Radio Shack then.
                > > It is certainly something that can be done at home.
                > >
                > > Barry
                >
                > So, what is the modern method? Does one use a laser printer to print the art
                > on a transparency? Or does one have to "transfer" the printed art?
                >
                > I may give this a whack, as the modern toner transfer method can be
                > tempermental and not so good on fine traces.
                >
                > Thanks!
                >
                > Jonathan
                >
                >
                >
                >
                > Visit the SRS Website at http://www.seattlerobotics.org
                > Yahoo! Groups Links
                >
                >
                >
                >
                >
                >
                >
                >
              • Jim McBride
                Speaking for myself and my cash limited budget, I used a laser printer (at work) to print my circuit on transparencies. I used the positive method. (ie circuit
                Message 7 of 20 , Mar 6, 2006
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                  Speaking for myself and my cash limited budget, I used a laser printer (at
                  work) to print my circuit on transparencies. I used the positive method.
                  (ie circuit is black lines.) My circuit is double sided. I cut the top
                  transparency 1/8th inch larger than the board outline all around. The
                  bottom transparency was cut about 1 inch larger. I lined them up and taped
                  them together on three sides. To cut my smaller boards out I like the score
                  and snap method. I use a utility knife and a straight edge to deeply score
                  both sides of the circuit board. I then put it in a vise or against a
                  sharp, straight edge of a table and break it. (If using a vise be sure to
                  use wood or something to keep the vise from denting the board.) Use a file
                  to round off the raised edges of the copper where the cuts were made. I
                  also like to taper the leading corners of the board that is going to be
                  slid between my transparency pieces. If you leave them sharp they can
                  scratch your transparencies. Wrap the left over pieces of board back in
                  there black bag they came in. I bought a 75W gro-light (flood) for around 6
                  bucks. I made a transparency with 4 traces on it of different thicknesses.
                  Every 1/8th inch I put a pad on one of the traces, 20 total. I work in the
                  garage since it is pretty dark even in the daytime. (Place keep out sign on
                  door.) I have found that my flat panel computer screen gives me enough
                  light to work by with the lights out. Peel off protective layer from board,
                  place on desk, place test strip trans. on board, place glass on trans. I
                  then used a piece of black plastic to cover everything but the first pad of
                  my test strip and turned on the gro light about 9 inches away. Every minute
                  I moved the black plastic over one pad. After 20 repetitions I turned off
                  the light and placed the strip into the developer. Then rinsed with water.
                  Using this process I found 10 minutes was a good exposure time for my
                  setup. I did the real boards with this method, etched and drilled. Once
                  populated the boards worked fine.

                  JIMc

                  At 10:57 AM 3/5/2006, you wrote:
                  >Barry,
                  >
                  > >
                  > > Of course its easier now that that all the photo steps can be replaced
                  > > with generating the negative directly on a laser printer.
                  > > Just spray and sensitive the board and go from there. I think the spray
                  > > was even available at Radio Shack then.
                  > > It is certainly something that can be done at home.
                  > >
                  > > Barry
                  >
                  >So, what is the modern method? Does one use a laser printer to print the art
                  >on a transparency? Or does one have to "transfer" the printed art?
                  >
                  >I may give this a whack, as the modern toner transfer method can be
                  >tempermental and not so good on fine traces.
                  >
                  >Thanks!
                  >
                  >Jonathan
                  >
                  >
                  >
                  >
                  >Visit the SRS Website at http://www.seattlerobotics.org
                  >Yahoo! Groups Links
                  >
                  >
                  >
                  >

                  JIMc
                  x22661
                  National
                  Ignition
                  Facility



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