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Re: [beam] Roll yer own PCB's.

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  • Bruce Robinson
    ... I use a #69 carbide bit (.0292 ) for my IC, resistor, and capacitor holes. The leads on these devices are typically in the .022 to .025 range. For larger
    Message 1 of 9 , Jun 18, 2001
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      Scott Burns wrote:
      >
      > What diameter carbide bit would you recommend for PCBs with
      > discrete components such as resistors and caps, plus 74 series
      > ICs (or sockets for these ICs)? Would the same diameter be
      > used for making thru-holes?

      I use a #69 carbide bit (.0292") for my IC, resistor, and capacitor
      holes. The leads on these devices are typically in the .022" to .025"
      range.

      For larger leads, such as square leads on LEDs and some types of
      connectors, I use a #59 carbide bit (.041"). The diagonal on dimension
      on these devises is typically .035".

      I drill my boards on a milling fixture, so I can place the holes within
      a thousandth of an inch. That means I can get away with holes that are
      only .004" to .006" bigger than the lead size. That makes soldering
      easier and quicker. I also tends to hold the components in place when I
      turn the board upside down to apply solder.

      If you're going to freehand drill, especially with ICs, you may want to
      use a #65 drill (.035") for the extra clearance.

      All my PCB are short, carbide drills with 1/8" shanks. That makes them
      easy to mount in and ordinary chuck (or dremel-style machine), and they
      can be changed quickly if you need one or two slightly bigger holes. Buy
      extra, especially if you're going to freehand drill.

      For occaisonal jobs, you can buy individual number drills from most
      industrial supply houses (they may have to order them in). These will be
      High Speed Steel, rather than carbide, but they'll do several small
      circuit boards before they wear out. I find they usually break before
      they get too dull. These drills have straight shanks, so they probably
      won't fit in an ordinary chuck. You'll need an adaptor, or a pin vise
      (tiny chuck, fits in an ordinary chuck).

      Bruce
    • Adam
      could someone that belongs to the alt-beam list go to this link and send me a copy of the message? http://groups.yahoo.com/group/alt-beam/message/8403 thanx,
      Message 2 of 9 , Jul 29, 2003
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        could someone that belongs to the alt-beam list go to this link and
        send me a copy of the message?
        http://groups.yahoo.com/group/alt-beam/message/8403

        thanx,
        Adam

        --- In beam@yahoogroups.com, Bruce Robinson <Bruce_Robinson@t...>
        wrote:
        > Jesse Willis wrote:
        > >
        > > ... What I did was swing by my local art store and pick up
        > > an Eberhard Faber DESiGN Art Marker, Broad Nib 311 Colorless
        > > Blender (only about 2 dollars). With this, you simply photocopy
        > > the circuit you wish, and then take lay the photocopy face down
        > > on the PCB. Run the marker over the -back- of the photocopy, and
        > > the image transfers to the copper. Might be more trouble than
        > > it is worth, though, unless you have a laser printer or copier
        > > and are only making small circuits. (But boy can you make them
        > > small!)
        > > I'll be sure to check up on that photo-etching thing, though.
        > > I wasn't aware that they sold anything like that. Thanks for
        > > the heads up!
        >
        > There's more than a few threads on PCB photoetching in the
        archives, and
        > in the alt-BEAM archives as well. Here's some advice I offered:
        >
        > http://groups.yahoo.com/group/beam/message/10105
        >
        > If you look for messages with the same subject around this time
        you'll
        > get the full picture. Also, David Perry discusses the MG Chemical
        system
        > (same one I use) at:
        >
        > http://groups.yahoo.com/group/beam/message/6772
        >
        > Finally, a number of BEAMers have had success printing (laser
        printer)
        > onto plastic film (for overhead projectors) and then ironing the
        image
        > onto the circuit board. Jim Mullins also offered a suggestion for
        > improving the quality of a printed image at:
        >
        > http://groups.yahoo.com/group/alt-beam/message/8403
        >
        > > ... When etching, do NOT let the PCB settle on the bottom of the
        > > basin. Have it facing down, but floating at the top of the
        etchant.
        > > Otherwise, a vacuum seal will form and no etchant will get
        through.
        > > I learned this by experience. ...
        >
        > "Conventional wisdom" says, invert he board, or the exposed copper
        will
        > get covered up with the ferric precipitate that forms during the
        > reaction. This effectively blocks the copper from the etchant and
        stops
        > the etching process.
        >
        > However, many professionals recommend that the etched side should
        be
        > face up, so you can monitor the etching process. If you gently
        agitate
        > the solution, or push your circuit board around with a small
        plastic rod
        > (e.g., a swizzle stick), this will flush off the precipitate. MG
        > chemicals recommends using a foam brush to gently brush the surface
        > clean (that's the way I do it).
        >
        > Finally, you get the best etching results if your ferric chloride
        > solution is warm. This speeds up the etching process and avoids
        > undercutting at the edges of traces. Ideal etching temperature is
        50
        > degrees (C) ... 120 F, but don't go above 57 C (135 F) or your
        solution
        > will start to fume (hydrochloric acid -- very corrosive). I have a
        > shallow glass etching tray with a handles sticking out the end.
        To heat
        > the etchant, I suspend this tray in a container (Rubbermaid) of hot
        > water, using a couple of flat sticks under the handles. I marked
        the
        > water container with a permanent marker to indicate the height of
        the
        > water before the tray is suspended in it. This lets me fill the
        > container to exactly the right height, and not worry about spilling
        > water when I place the etching tray in it. I use water heated to
        55 C --
        > it cools down slightly when the heavy glass tray is placed in it.
        This
        > speeds up the etching dramatically.
        >
        > Remember, be safe, be consistant, and don't get discouraged if your
        > first few efforts fail. Use your notes and make minor changes.
        Start
        > small until you get the technique exactly right.
        >
        > Bruce
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