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Re: [ORE_bits] Any Tips for making PC Boards?

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  • aaron
    Warning in advance: extremely long email follows: Friday, December 31, 2004, 3:13:29 PM, you wrote: f just wondering if anyone has any tips for making my own
    Message 1 of 2 , Jan 1, 2005
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      Warning in advance: extremely long email follows:

      Friday, December 31, 2004, 3:13:29 PM, you wrote:

      f> just wondering if anyone has any tips for making my own PC boards, for
      f> things like motor controllers, etc...

      f> I'm thinking of the RadioShack PC Board kit, with chem, trays, ink,
      f> and boards, for $20.
      f> I see that Active has chemicals and boards, too.

      I used to make my own boards quite a bit. I started off with the radio
      shack kit and a felt pen and drew my first PCB by hand. Not pretty,
      but it worked fine. I then moved onto doing the pcb layout in Eagle
      (http://www.cadsoftusa.com) and then printing onto a certain type of
      paper with my laser printer. I then used an iron to transfer the laser
      ink from the paper onto the PCB and etch with the radio shack kit.
      That actually worked really well. I was able to do double sided boards
      with this method. I've also done boards using the 'real' photo method
      with a real etch tank (rather than just holding a tray and kiggling it
      around for 45 minutes like the RS kit) and I found that the home
      method gives equivalent results, just with a little more manual
      labour. Finally I ended up building my own small bubbler tank for
      etching the boards so I didn't have to manually do it.

      The paper that I used wasn't anything special, just bought at Staples.
      The advice I found online at the time was to find a thick paper with a high clay
      content and a shiny face to it. Easier said than done... no-one lists
      how much clay they have in their paper. <grin> I just ended up buying
      the thickest paper that I could find that seemed a little shiny and it
      worked great. I also bought some paper from Digikey that was
      specifically made for this type of thing, but never ended up using it
      as the cheap staples paper worked well for me.

      There are a couple tricks that I ran across when making my boards:

      1) don't do traces smaller than 10mil... 16 is even better. Smaller
      traces have a higher chance of having breaking in them due to
      over-etching, so use the largest traces that you can.
      2) if you have big empty spaces on your PCB, leave it filled with
      copper. Otherwise, you'll end up waiting a lifetime for the etchant to
      take it off the board, and you have a larger possibility of etching
      off your traces accidently.
      3) Make the spaces between traces/pads/copper-fills bigger than you
      would normally on a manufactured board. Eagle defaults to 10mil
      traces/10 mil spaces. Change that to 10mil traces and 20mil spaces
      or even bigger. Makes soldering later much easier.
      4) clean and lightly sand the copper board before transferring the
      design onto it
      5) After transferring your design onto the copper, take a good look at
      it and fix up any incomplete traces with a sharpie felt pen
      6) Expect to spend 45 minutes to an hour sitting in front of the tv
      while moving the tray with your etchant and pcb in it... it's boring
      as hell
      7) Buy yourself a dremel and a dremel drill press for drilling out
      the holes. Also head down to Princess Auto and pick up some dremel
      drills. They have great kits in the surplus section with something
      like 8 to 10 drills in a little box for $3 buck or so. Pick up a bunch
      because you'll likely break a few (especially if you cheap out and
      don't buy the drill press like I didn't). These drills are MUCH more
      expensive elsewhere. I paid a fortune for them before finding them at
      princess auto.

      Once the board is etched and drilled, you then need to go and fill all
      the vias (if you are making a double sided board). I was using the
      ends of resistors and caps that I cut off and throw away to fill the
      holes.

      When doing double sided boards, I got bit big time and wasted a few
      boards before I figured it out. I was using the autorouter in Eagle
      because it makes complicated boards seem a little easier. The trick is
      that it will route traces to pins on the top side of the board. Seems
      innocent enough right??? NOPE! Not with a board manufactured in your
      basement. Remember that the holes that you drilled out aren't plated
      thru-holes like on a real board... meaning there isn't an electrical
      connection between the top and bottom unless you manually solder both
      top and bottom (like the vias above) The problem is that it is a
      complete and utter bitch to solder onto the topside of a board if you
      have something like a socket sitting there. DOH! I wasted many a board
      because i forgot that simple rule. Usually what would happen is that I
      would be halfway thru soldering a board (an hour or two into it) and I
      would come across something that was basically impossible to solder.
      GRRRRR. Made for some ugly ugly patches on the board.

      After doing this for a couple years. I finally decided that I'd rather
      just pay the $$$ and have someone else manufacture the boards for me.
      I've used a bunch of the cheaper manufacturers now and can recommend
      two:

      http://www.olimex.com
      http://www.pcbnet.com

      Olimex is a budget PCB house based in Bulgaria. They have a neat
      pricing model where you buy a certain PCB size up-front (10x16 or
      20x32 cm) and you can fill up that pcb in any way... if you are making
      small boards, this works out really well. Other manufacturers charge
      per board, so Olimex can end up much cheaper. It's $26 for the smaller
      double sided boards. The board quality isn't always perfect (I've had
      the occasional short on complex boards), but the price is right.

      PCBNet is a manufacturer that I use out of the states. The prices are
      about the best that I've found from the lower-cost manufacturers and
      the quality is excellent. For boards that are bigger than 10x16cm, the
      price here actually beats Olimex. I use their 'advertised specials'
      normally. Means that I have to buy 5 ($15 a board) or 10 ($10 a
      board), but it works out when I need more than one of course. The size
      of the boards can be up to 20 square inches for that price which is a
      pretty good size. I've done 4 and 6 layer boards here also and things
      are fantastic everytime.

      The nice thing about using the board houses is that you get a solder
      mask and plated thru holes, not to mention a silk-screen. The solder
      mask means that the traces on the board are covered so you won't
      accidently solder to them (so you don't have to follow point 3 from
      above). The plated thru holes means that you don't have to spend an
      hour or two plating your own holes (my 2 layer boards typically have
      between 100 and 500 vias on them... that's alot of soldering when
      doing it manually). Also not having to drill your own holes is nice
      (a couple of hours saved).

      Of course, making your own boards is faster and slightly cheaper (if
      using the radio shack kits). If you get serious, it can be quite a bit
      cheaper (buy the chemicals and PCB boards from places other than radio
      shack) but you will spend more time building up the board.

      One thing I never got around to trying was making my own
      soldermask/silkscreen for the home-built boards. Using the same method
      as the traces, you could iron on the soldermask after etching the
      board. It would be black instead of green, but I think that it could
      be made to look pretty nice.

      So, if anyone made it to the end of this email, I'm impressed. As a
      rewards, I've got a couple goodies for anyone who wants them.

      I've got a bubbler tank (without the bubbler) to give away, a 3 by 4
      foot piece of double sized copper and a 4 or 5 sheets of the 'real'
      transfer paper (from digikey) to give away. Take some of it, take all
      of it, doesn't matter to me. Anyone interested in making their own
      boards?

      Aaron
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