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[OT] Using a Dremel tool for drilling PCBs

Discussion in 'Electronic Design' started by Matt, Jun 19, 2007.

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  1. Matt

    Matt Guest

    I need some advice about PCB prototyping.

    I plan to use a laser printer, an electric iron, toner-transfer paper,
    and etchant to make a few PCBs. Then I will need to drill the PCBs. I
    expect to have about 150 holes per board.

    I have a Dremel tool with RPM adjustable from 5000 to 35000. Would it
    be practical to use it to drill the holes by hand? I know Dremel makes
    a drill press for the tool ... would it be a big advantage?

    What kind of collet or chuck should I use?

    How long should I expect the drill bits to last? What type should I get
    (HSS, carbide, diamond, other)?
     
  2. colin

    colin Guest

    thats a lot of holes by hand, hope its not many boards you are doing.

    IME the solid carbide drills dont last long unless you have a good chuck and
    stand.
    cos they break so easily, although depends what size >1mm is probably ok
    the ordinary HSS last a while before they go blunt,
    but probably work out cheaper for hand use.

    carbide coated are somewhere inbetween.

    I was interested in the direct ink jet printing of etch resistant ink.

    Colin =^.^=
     
  3. mpm

    mpm Guest

    Depending on the circumstances, I very often find for 1-off stuff its
    easier and cheaper to get boards from ExpressPCB. The money end of
    that makes sense IF (Repeat "IF"), the board dimensions can be kept to
    exactly 3.8" x 2.5". They call it their "Mini Board" service.

    You get QTY-3 boards for $51 + $8 to ship them 2nd day. (You have
    them in 3 days.)
    Double-layer, plated through holes, but no solder masks or
    silkscreens.

    They are not paying me to say this. In fact, there are probably
    "better" deals out there??

    But from the sound of it, you'd be spending a lot of time using the
    Dremel.
    Unless you enjoy that activity of course, your time is probably more
    valuable.
    Just a thought. Plus, the plated-through holes should add to
    reliability.

    They have free layout software, as to most of their competitors.
    And for $60 more, they will come off the Gerbers (for those interested
    in that..)

    www.expressPCB.com

    Keep in mind larger, or differently dimensioned boards will cost a lot
    more.
    This restriction may not apply to other vendors who offer a small run
    prototyping service.

    -mpm
     
  4. kell

    kell Guest

    Can the expressPCB software generate Gerber files?
     
  5. Matt

    Matt Guest

    Thanks. I forgot to ask---what speed should I use?
     
  6. kell

    kell Guest

    I hear dental burs are the best for hand drilling pc boards.
     
  7. Robbo

    Robbo Guest

    I've got a solid pedestal drill - running at about 2000 or 3000 RPM and HSS
    bits it works better than the Dremel at any speed. Carbide bits work really
    well in the dremel at higher speeds but are very easily broken. Try running
    the vacuum cleaner continuously to grab the dust.
     
  8. Matt

    Matt Guest

    mpm wrote:

    Thanks for the expressPCB link. I may use them, but I will still need
    to make at least some boards by hand.
    Should I solder from both sides if the holes are not plated? Would I
    need to stick a piece of wire through for hand-drilled vias, or would a
    plug of solder establish the connection?
     
  9. Guest

    Sigh.

    www.olimex.com
     
  10. HSS will be getting dull after around one board or two. They are
    cheap, you can buy an envelope of them. Cobalt should be slightly
    better (but more expensive).

    They generally have a shank the diameter of the hole they make.
    Professional PCB drilling generally uses solid carbide drill bits with
    a 1/8" shank. They are easy to break with a cheap drill press setup,
    but some people have been successful using the Dremel.

    As with any cutting tool, buy only good name-brand bits, cheap junk
    like the TiN stuff sold to hobbyists will bring you only grief. Some
    of them are amazingly soft, barely suitable for hardwood.

    You can drill 150 holes pretty quickly with good lighting and proper
    RPM-- just a few minutes for the bulk of them which will probably be
    around 0.8mm.


    Best regards,
    Spehro Pefhany
     
  11. Ecnerwal

    Ecnerwal Guest

    Use wire, bent over on both sides and soldered.
     
  12. Mike

    Mike Guest

    Oh yeah, it's very practical. I use the same process for all my boards.
    A drill press is an absolute necessity! Without one you WILL break your bits.
    Use the standard collet, it fits the carbide bits with a 1/8" shaft.
    I have never dulled a bit. I always get in a hurry and break them before they get dull.
    I've never measured the speed, but just set it till it sounds right.
    It is fairly slow for the Dremel tool. A few practice holes will tell you.
    150 holes in a board is not problem. I can do 100-200 before I need to take a break.

    Three things that really help:
    1 - A #10 Optivisor. A #7 might be ok you have good enough eyes.
    2 - Lots of light. I use a gooseneck lamp with a 23W screw in fluorescent bulb.
    You need the light adjustable because reflection from the board changes when
    I have to rotate the board and the light position makes a big difference.
    3 - Make sure your layout is printed with drill guide holes etched in the center of the pads.
    I set my software to print 0.025" dia guide holes.

    I drill all the holes to.032 then go back and enlarge all the holes that need it.
    This works much better. The larger bits don't tend to fall into the etched guide
    holes nearly as well, but fall nicely into the .032 holes. They don't follow
    the guide holes well if the speed is too high either.

    I also setup my shop vac just behind the Dremel tool to keep the fiberglass debris down.
    This makes it easier to see the guide holes and results in much less of a mess. Use a
    fairly small nozzle and get it close as possible without interfering.
    Don't forget to use breathing mask! It's much easier on the lungs.

    Mike




    When truth is absent politics will fill the gap.
     
  13. Matt wrote:
    (snip)
    Solder will not reliably form a thread through an unplated
    hole. Definitely, use a wire. Silver plates wire wrap wire
    works well. Strips and wets very easily. Good for at least
    an ampere.
     
  14. Depends on drill diameter and drill material. Up to 0.05" or so, with
    carbide, the Dremel can't go too fast. Try about 1/3 the speed for HSS
    (so about 10,000 RPM at 0.05" and 20,000 at 0.025" etc.) You can
    always go slower than the recommended RPM, but that reduces the
    optimum feed rate (takes longer to drill each hole).

    http://www.taconic-stl.com/fr4 processing_guide.pdf



    Best regards,
    Spehro Pefhany
     
  15. You NEED a stand.

    Collet is best for aligment - must be metal collets though, not plastic.

    Must use carbide - PCBs eat HSS in no time. You MUST use a stand when drilling with carbide bits
    otherwise they will snap very easily.
    A carbide bit should last many hundred holes easily. HSS maybe a few dozen.

    see www.electricstuff.co.uk/pcbs.html for plenty of info on making good homemade PCBs.
     
  16. DJ Delorie

    DJ Delorie Guest

    Yup. I made my own: http://www.delorie.com/pcb/dremel-stand/

    I can use 13 mil drills with it, without breaking them, and with
    reasonable accuracy.
     
  17. mpm

    mpm Guest

    No, it cannot.
    Here's how it works:

    You place an order with them. (Using their free layout software, which
    is actually pretty good*)
    Then you call them back with the order confirmation number and tell
    them you want the Gerber Files. They charge your credit card $60 US,
    and email you the Gerbers.

    A few threads back, someone was going to post an alternate solution
    involving raster-to-Gerber conversion. (The ExpressPCB has 300dpi
    output capability, but I don't know if this alternate solution would
    provide acceptable results as I've never tried it...)

    It just seemed that Matt was about to embark on a fairly involved
    creation effort, and I wanted to give him the heads-up. In small
    quantities, these little PCB fab houses are hard to pass up.

    And honestly, I no longer have the patience or eyesight required to
    thread wire for "plated-thru" holes.
    I do however, has enough aspirin for same....
     
  18. Joel Kolstad

    Joel Kolstad Guest

    Does it occur to anyone that there might be fewer of these "little PCB fab
    houses" making "pretty good" software if you create software (a raster to
    gerber converter) that forces them all to compete strictly on price and no
    longer on what tools they provide?

    Just something to think about...
     
  19. D from BC

    D from BC Guest

    I make my own PCB's...
    I could almost write a book on the subject.

    I use as much SMD as possible...I hate drilling holes.
    Maybe use more SMD.
    I also hate hand soldering..That's why I hot plate.
    But when I do drill holes..Yes..I use a dremel on a dremel drill
    press.
    I buy bits at the local hobby shop. Dunno what type they are but it's
    cheap and I have no idea how long they last.. I seldom drill.
    As soon as I sense slow drilling or burning, I change to another bit.

    By the way, I also hate toner-transfer paper :)
    D from BC
     
  20. legg

    legg Guest

    You'll find centering to be a problem unless the art provides for
    etched centers. Many gerbers do not do this, simply relying on
    electronic drill file.

    RL
     
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