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How fine can you etch with toner transfer?

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  • lcdpublishing
    Hi guys, From this ground I have learned about toner transfer and PCB making and have been doing it for a couple of years now. Recently, I have been starting
    Message 1 of 11 , Oct 1, 2008
      Hi guys,

      From this ground I have learned about toner transfer and PCB making
      and have been doing it for a couple of years now. Recently, I have
      been starting to work more and more with surface mount components.
      As they are smaller and you can fit more stuff in the same space, I
      am finding that I want to use traces that are more narrow than I have
      been doing.

      I am about 85~90% reliable with my current process doing traces that
      are .015" (380 microns). I would like to get down to .008"~.010"
      (200 to 254 microns).

      Most of my current failures with narrow traces are in getting the
      toner to stick and I think I can improve that part of the process (I
      just started using a laminator instead of a clothes iron).

      I etch with Ferric Chloride and bubbles. I am wondering wherein the
      limit is there with regard to narrow traces. I recall a long while
      back that there seemed to be a certain barrier where the trace width
      was so narrow, "under etching" would cause breaks in the traces.

      Anyone one care to share some experiences with narrow traces and DIY
      processes?

      Also, I am not opposed to using PCBs pre-coated with etch resist if
      that would improve results.

      Thanks

      Chris
    • Dylan Smith
      ... With toner transfer, 10/10 is quite easy. I ve made my own board for a 0.4mm pitch LQFP-80 package, which will be something like 8/8. The biggest problem I
      Message 2 of 11 , Oct 1, 2008
        On Wed, 1 Oct 2008, lcdpublishing wrote:

        > I am about 85~90% reliable with my current process doing traces that
        > are .015" (380 microns). I would like to get down to .008"~.010"
        > (200 to 254 microns).

        With toner transfer, 10/10 is quite easy. I've made my own board for a
        0.4mm pitch LQFP-80 package, which will be something like 8/8. The biggest
        problem I found was not broken traces, but shorts due to paper fragments
        getting stuck between the fine gaps between traces and preventing full
        etching. The trouble is you can't scrub the paper remnants off too harshly
        because the thin etch resist with 0.2mm traces and 0.2mm spacing is very
        easy to break (and it means it takes quite a long time to prepare the
        board for etching). I use a clothes iron for the transfer process. 10/10
        seems about an order of magnitude easier to do than 8/8.

        So I've decided for when I'm doing stuff with a 0.4mm pitch components,
        I'll send it off to a board house :-) (Which offers some other advantages
        such as smaller vias and gives me more flexibility about where I put vias,
        for the tradeoff of extra cost and time waiting for the boards to come
        back).
      • Leon
        ... From: lcdpublishing To: Sent: Wednesday, October 01, 2008 10:54 AM Subject: [Homebrew_PCBs] How
        Message 3 of 11 , Oct 1, 2008
          ----- Original Message -----
          From: "lcdpublishing" <lcdpublishing@...>
          To: <Homebrew_PCBs@yahoogroups.com>
          Sent: Wednesday, October 01, 2008 10:54 AM
          Subject: [Homebrew_PCBs] How fine can you etch with toner transfer?



          > Anyone one care to share some experiences with narrow traces and DIY
          > processes?
          >
          > Also, I am not opposed to using PCBs pre-coated with etch resist if
          > that would improve results.

          I get 8 mil without any problems with photo-etch, although I normall use 10
          mil. I have got 5 mil on test boards but haven't actually tried it on a real
          design.

          Leon
          --
          Leon Heller
          Amateur radio call-sign G1HSM
          Yaesu FT-817ND transceiver
          Suzuki SV1000S motorcycle
          leon355@...
          http://www.geocities.com/leon_heller
        • Stefan Trethan
          I have found that a sponge, or piece of foam rubber, will take those off easily. The foam rubber is soft enough not to damage the traces, and you can rub quite
          Message 4 of 11 , Oct 1, 2008
            I have found that a sponge, or piece of foam rubber, will take those off
            easily.
            The foam rubber is soft enough not to damage the traces, and you can rub
            quite firmly with it.

            ST

            On Wed, Oct 1, 2008 at 12:01 PM, Dylan Smith <dyls@...> wrote:

            > The biggest
            > problem I found was not broken traces, but shorts due to paper fragments
            > getting stuck between the fine gaps between traces and preventing full
            > etching.


            [Non-text portions of this message have been removed]
          • DJ Delorie
            I ve gotten down to 8.33 mil with TT with a fair degree of reliability. 6.66 I can do if I m careful and put extra copies of the board on the print - there s
            Message 5 of 11 , Oct 1, 2008
              I've gotten down to 8.33 mil with TT with a fair degree of
              reliability. 6.66 I can do if I'm careful and put extra copies of the
              board on the print - there's usually one short or open somewhere,
              often I can fix it with a knife or solder. Note the off-mil sizes; my
              laser printer is 600dpi or 1.33 mil per pixel, so I use multiples of
              that to get consistent results. The limitation with my printer is its
              ability to place the toner particles precisely.

              With photomask I've been able to do 6 mil with high reliability, and 5
              if I'm careful. In theory I can do 4, but I haven't needed to try to
              get that to work since I don't use parts that small. The limitation
              here, with my printer, seems to be its ability to feed the paper
              accurately. Quarter sheets are too small for a good grip, half sheets
              work much better.
            • lcdpublishing
              Thanks guys, that gives me a bit of confidence to give it a go with toner transfer. I also checked into various forms of photoresist and it turns out that it
              Message 6 of 11 , Oct 3, 2008
                Thanks guys, that gives me a bit of confidence to give it a go with
                toner transfer.

                I also checked into various forms of photoresist and it turns out that
                it isn't all that expensive to go that way. Using dry film resists and
                the developer isn't as expensive as I thought. But still more
                expensive than toner transfer.

                chris
              • calvingrier
                ... the ... my ... its ... 8.33mil? is that a multiple of 1.33? ;-) --Calvin
                Message 7 of 11 , Oct 22, 2008
                  --- In Homebrew_PCBs@yahoogroups.com, DJ Delorie <dj@...> wrote:

                  > I've gotten down to 8.33 mil with TT with a fair degree of
                  > reliability. 6.66 I can do if I'm careful and put extra copies of
                  the
                  > board on the print - there's usually one short or open somewhere,
                  > often I can fix it with a knife or solder. Note the off-mil sizes;
                  my
                  > laser printer is 600dpi or 1.33 mil per pixel, so I use multiples of
                  > that to get consistent results. The limitation with my printer is
                  its
                  > ability to place the toner particles precisely.

                  8.33mil? is that a multiple of 1.33? ;-)

                  --Calvin
                • DJ Delorie
                  ... Sigh, wrong math, right results. 1/600 is 1.666 mil, not 1.333 mil, resulting in possible trace widths of: Pixels Width (mils) ... 0 0.000 1
                  Message 8 of 11 , Oct 22, 2008
                    "calvingrier" <cgrier@...> writes:
                    > > laser printer is 600dpi or 1.33 mil per pixel, so I use multiples
                    > > of that to get consistent results. The limitation with my printer
                    > > is its ability to place the toner particles precisely.
                    >
                    > 8.33mil? is that a multiple of 1.33? ;-)

                    Sigh, wrong math, right results. 1/600 is 1.666 mil, not 1.333 mil,
                    resulting in possible trace widths of:

                    Pixels Width (mils)
                    ------ -----
                    0 0.000
                    1 1.666
                    2 3.333
                    3 5.000
                    4 6.667
                    5 8.333
                    6 10.000
                    7 11.667
                    8 13.333

                    Traces of other widths will be printed as either the next smaller or
                    next larger size, depending on your rasterizer. Same with the space
                    between traces. So you could be off by as much as 0.833 mil (half a
                    pixel).

                    Switching to a 2880 DPI inkjet lets me choose any size and get within
                    0.2 mil of the right size.
                  • martin_schoenegg
                    ... within ... No this only means, hat you can adress this resolution. May be the stepsize comes in this region, but there is nothing said about the size of
                    Message 9 of 11 , Oct 23, 2008
                      > Sigh, wrong math, right results. 1/600 is 1.666 mil, not 1.333 mil,
                      ...
                      > Switching to a 2880 DPI inkjet lets me choose any size and get
                      within
                      > 0.2 mil of the right size.


                      No this only means, hat you can adress this resolution. May be the
                      stepsize comes in this region, but there is nothing said about the
                      size of one pixel. Especialy inkjets are designed to produce
                      overlapping pixels.

                      Martin
                    • DJ Delorie
                      ... Well, yeah. Relatively speaking though, I can compare 0.833 mil to 0.174 mil and say it s much more accurate . What I really mean is that the line sizes
                      Message 10 of 11 , Oct 23, 2008
                        "martin_schoenegg" <Martin.Schoenegg@...> writes:
                        > No this only means, hat you can adress this resolution. May be the
                        > stepsize comes in this region, but there is nothing said about the
                        > size of one pixel. Especialy inkjets are designed to produce

                        Well, yeah. Relatively speaking though, I can compare 0.833 mil to
                        0.174 mil and say "it's much more accurate". What I really mean is
                        that the line sizes - as drawn - will be much more consistent, because
                        a variation of one pixel is a much smaller percentage of the line
                        size.

                        This means that, if I know my process can handle 6 mil lines, I won't
                        have to worry about the 5 mil lines, or the spaces between 6.666 mil
                        lines - because the films will more accurately reflect my desired
                        sizes, compared to a laser printer.

                        My inkjet is good to about 0.5 mil as far as drop placement accuracy
                        goes. However, I know that "fuzzy edge" will be in the same spot
                        every time. So, if I know I can do 6/6 rules with a 0.5mil fuzzy
                        edge, at least the results will be consistent - a one pixel difference
                        is negligible. One pixel on a laser printer is BIG compared to what
                        I'm trying to achieve.

                        On a laser printer, for 6/6 rules (er, 6.66 rules), off by one pixel
                        means the line is 25% smaller. On an inkjet, off by one pixel would
                        only be 5% smaller.
                      • Ground Grunging
                        Hello, I think that this URL might be useful for those who want understand the chemistry behind an etching process. Bye  
                        Message 11 of 11 , Nov 3, 2008
                          Hello,
                          I think that this URL might be useful for those who want understand the chemistry behind an etching process.
                          Bye
                           
                          http://members.optusnet.com.au/~eseychell/PCB/etching_CuCl/index.html
                           




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