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Re: [Homebrew_PCBs] Re: calcium carbonate, HF acid...

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  • Todd F. Carney / K7TFC
    I think I ve already admitted my stupidity here, and that I regret my off-the-cuff response. I guess all that s left is to apologize to you personally, and to
    Message 1 of 65 , Mar 20, 2013
      I think I've already admitted my stupidity here, and that I regret my
      off-the-cuff response. I guess all that's left is to apologize to you
      personally, and to thank you for your work as moderator.


      K7TFC / Medford, Oregon, USA / CN82ni / UTC-8
      QRP (CW & SSB) / EmComm / SOTA / Homebrew / Design

      On Wed, Mar 20, 2013 at 8:19 PM, AlienRelics <alienrelics@...> wrote:

      > **
      > -You- inserted sarcasm into my question. I had a pretty good idea that HF
      > meant hydrofluoric acid. I was asking partly for those on the list who
      > don't know what it is (and it is not guaranteed that the first Google
      > result is the correct hit), and partly to remind people to spell out what
      > they mean now and then.
      > I wasn't aware that "HF" was a "big fancy word".
      > I notice you said nothing about the part about hijacking the thread.
      > As for me being a troll, I'm the listowner, Einstein. Something you could
      > have looked up easily enough. Dunning-Kruger?
      > Steve Greenfield AE7HD
      > your occasionally fed-up moderator
      > --- In Homebrew_PCBs@yahoogroups.com, "Todd F. Carney / K7TFC" <k7tfc@...>
      > wrote:
      > >
      > > Google "hf acid." The very first item on the page--big as life--will
      > answer
      > > your question and tell you all about it. Oh, I'm not a chemist, either.
      > I'm
      > > just a guy of normal intelligence who knows how to use a web browser. I
      > > also know better than to broadcast my stupidity for intelligent people to
      > > see.
      > >
      > > Sorry about this peevish (look that up, too) response, but this kind of
      > > "Okay, *Einstein*, what does that big fancy word mean, anyway?" attitude
      > > really bugs me. I actually think it's mostly trolls who do this kind of
      > > thing, so it's just one more thing to ignore.
      > >
      > > I must be in a "mood." I guess I better go solder something together.
      > >
      > > 73,
      > >
      > > Todd
      > > ----------------------------------------------------------
      > > K7TFC / Medford, Oregon, USA / CN82ni / UTC-8
      > > ----------------------------------------------------------
      > > QRP (CW & SSB) / EmComm / SOTA / Homebrew / Design
      > >
      > >
      > > On Mon, Mar 18, 2013 at 2:39 PM, AlienRelics <alienrelics@...> wrote:
      > >
      > > > **
      > > >
      > > >
      > > > OK, so keepitsimplestupid hijack's Ricks thread, and smilingcat hijacks
      > > > keepitsimplestupid's hijacked thread. Interesting.
      > > >
      > > > For those of us who are not chemists, what is HF acid?
      > > >
      > > > Steve Greenfield AE7HD
      > > >
      > > > --- In Homebrew_PCBs@yahoogroups.com, "smilingcat90254" <smilingcat@>
      > > > wrote:
      > > > >
      > > > > Calcium carbonate for that matter most carbonate will react with even
      > > > trace amount of hydrochloric acid remaining in your etchant. And yes it
      > > > will foam because CO2 is being released in the reaction. So if your
      > > > solution keeps foaming keep adding the carbonate. It will neutralize
      > the
      > > > acid for safe disposal.
      > > > >
      > > > > Reaction of Copper chloride and Calcium carbonate probably will be
      > much
      > > > slower than Copper chloride and sodium carbonate. But it should work.
      > not
      > > > 100% plus sure.
      > > > >
      > > > > **** HF acid ****
      > > > > I was in semiconductor manufacturing business so I'm quite aware of
      > HF
      > > > acid. Very dangerous stuff. No you can not store in a glass. It will
      > etch
      > > > glass. No you can not store in stainless steel container!!
      > > > >
      > > > > HF chemical burn is severe even at low concentration. It will
      > penetrate
      > > > bare skin and the flourine ion will interact with the calcium in your
      > bone.
      > > > HF will dissolve your bone under all the tissue.
      > > > >
      > > > > I didn't think you can buy it unless you can show you are a business
      > or
      > > > a researcher of some sort.
      > > > >
      > > >
      > > >
      > > >
      > >
      > >
      > > [Non-text portions of this message have been removed]
      > >

      [Non-text portions of this message have been removed]
    • Rick Sparber
      Here is an update of my progress: The spray on (negative type) photo resist and developer will arrive on Thursday. In the mean time, I took some nominally
      Message 65 of 65 , Mar 26, 2013
        Here is an update of my progress:

        The spray on (negative type) photo resist and developer will arrive on
        Thursday. In the mean time, I took some nominally 1.125 " diameter copper
        pipe and cut off a 1/2" piece. Then I turned some cold rolled steel down for
        an interference fit. I left a shoulder on the steel. I was then able to
        force fit the soft copper onto the steel using my bench vise. Then I put the
        assembly back on the lathe to true it all up and drill a center hole. My
        finished outside diameter of 1.125" means my scale must be 3.545" long.

        I then drew a 6" line with my CAD program and printed it out. To my
        surprise, the printed line was 6.000" so no correction factor is needed. I
        then drew a simple scale with 10 segments and 4 small tick marks per
        segment. I also put numbers to the right of each segment line. After
        printing out, I taped it to the OD of the copper and it was a perfect fit.

        So next I will print it out on clear plastic, trim the excess, and wait for
        the chemicals. If I understand the term "negative type" correctly, what is
        black on the artwork will be copper free after etch. If true, that sure
        saves toner.


        -----Original Message-----
        From: Homebrew_PCBs@yahoogroups.com [mailto:Homebrew_PCBs@yahoogroups.com]
        On Behalf Of KalleP
        Sent: Monday, March 25, 2013 7:45 AM
        To: Homebrew_PCBs@yahoogroups.com
        Subject: [Homebrew_PCBs] Re: etching the OD of a cylinder to create a
        graduated dial

        This will not work as is for a cylinder but for a conical scale it might

        Instead of projecting a line and then indexing the dial you could look at
        some of the long wave UV photo cure polymers that are used for 3D stereo
        lithography. You would dip the scale in the resin, pull it out and project
        an image with a UV modified DLP video projector, no need to dry the resist
        as you would be hardening it in-situ with the UV image. Have to keep the
        projector as far as convenient to maximise the focus depth if you have a
        conical scale (long focus lens) but you could have arbitrary complexity of
        the artwork that could be changed on every scale.

        You would rinse and post cure the resin and then try out various etching
        methods to get a good bite. You could paint fill and then strip the resin
        off with a suitable solvent.

        This method might have some value in making DIY PCBs as well, I know there
        are very (very) expensive industrial machines that do just this and have
        many of these projectors and expose a 50mmx50mm square (or whatever) and
        scan across the material and have the image track the material motion to get
        a continuous scan while having a largish projection area (instead of a
        single laser spot or scan line that is too slow). Imagine a video projector
        and a simple jig to position a pcb in 50mm grid, you could manually project,
        move, project and expose arbitrary image. Using the 3D printing resins
        might be a way to do a wet photo resist at home but I have not tried it.
        The materials are still a bit expensive but the layer required for etch
        resist should be fairly affordable.

        A Google search found these two interesting hits, the second is just an
        abstract unless you pay or are a member of some secret cabal.




        Johannesburg, South Africa
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