How do you drill holes in PCB?

Discussion in 'General Electronics Chat' started by strantor, Feb 3, 2011.

  1. strantor

    Thread Starter AAC Fanatic!

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    I have just spent a whole day trying to make my first PCB (2sided) via toner transfer method, close to what's described in this post.
    I finally got all the bugs worked out of my system, then went on to drill the holes in the first side, so I can align the second side to it, and I screwed it up. Totally thrashed the backside of the copper as the bit was coming out. I am using a hand drill and a small drill bit (probably NOT carbide, found it on my garage floor). I have deduced that I need a carbide bit, but do I need a Dremel? I already have a hand drill...
    How fast should I be going? I was going really slowly. Should I apply alot of pressure? I saw a guy on youtube using a hammer & punch to make starter holes - seemed kinda stupid to me, but is that really a good idea? Could I have possibly made the copper brittle by heating it too much/too long, or by brillo'ing the hell out if?

    On a side note - What do you use to coat the PCB after it's done and before you solder your components? Most professionally made PCBs have a lacquered look. how much insulation does this coating provide?
     
  2. spinnaker

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    You are going to need to use a carbide bit and you will need a drill press. Some people use a Dremel hobby press but I get by just fine with a conventional drill press.


    Found on the garage floor? You are kidding right? How big is that thing? Holes for PCBs should be tiny.
     
  3. strantor

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    thanks, lol what I used to think of as tiny, or, about twice as big as what I need
     
  4. SgtWookie

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    I like to use a #66 carbide bit; the short ones with a 1/8" shank, in my drill press for most of the holes. They aren't something you'll find at Big Blue or Big Orange hardware stores.

    They look similar to these:
    http://blog.onshoulders.org/Images/drill_bits_carbide.jpg
    found on this page:
    http://blog.onshoulders.org/index.php?blogID=Mill&startAt=0&order=&e=

    The drills are short so they don't tend to "wander" much. If you're trying to drill by hand, you'll break a LOT of bits unless you have an incredibly steady hand. With a drill press, I can usually get through several boards before I'll snap one - and that's usually because I failed to hold the board in place.

    You can often find re-sharpened carbide bits at places that sell surplus items; the resharpened drills are generally much less expensive than new ones.
     
  5. strantor

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    SgtWookie:
    Thanks for the pointer. That blog makes me think that I'm chasing small fish though, and looks like a really cool project.
     
  6. Wendy

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    If you go to the back of my thread (the one you pointed to) we discussed that in depth (mostly drill bits). I would say a drill press is almost mandatory. I also use a magnifier headpiece to see what the heck I'm doing!

    No one said it was easy, just fun. Beats the heck out of wiring it via breadboard or protoboard.

    I let the drill bit do the work, and use very light pressure. If you can find a Dremel drill press mount you are ahead of the game.
     
  7. jpanhalt

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    This reiterates most of what's been said and adds a little.

    Did you have it against a flat backing board? As the drill exits, it tends to push material ahead of it. Put something hard, but drillable behind it to take that push. I typically use birch or maple as it has fine grain. If you need to, tape the board around its edges to the backing to keep it from lifting. I do not do that and would not recommend using double-sided tape, unless it was extremely thin and did not cover any areas where you were drilling holes.

    It can be done with HSS, but carbide is preferred. #66 or 1/32 is fine for most holes.

    I would not center punch unless absolutely necessary. It may crack the support if done too forcefully and cause easier separation of the copper plating. If you must do it, only a small prick is needed, not a big indent. In your layout software, you can make the hole centers very small. After etching that has the effect of center-punching. If using Eagle, it is called drill-aid ULP. As for speed, it is a matter of feel mostly. Too slow and you get lousy holes and break drills; too fast and your center punching will be less effective and you risk burning drills (HSS). Remember feed rate (how hard you press) is affected by drill speed.

    It is usually an acrylic lacquer and is called a conformal coating. I suggest doing it after soldering. Before soldering, I use a paste flux, then wash it off after soldering and then add the conformal coating.

    John
     
    Last edited: Feb 4, 2011
  8. nerdegutta

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    I think I would transfer artwork, both sides, etch and then drill. Then you are only drilling in the epoxy or whatever the PCB is made of.
     
  9. strantor

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    I see that now, I didn't read far enough. Well good news is I got my dremel working (only had a bad brush).

    Also ordered:
    (5) DC208-0785-040D #47 (0.0785)
    (1) DC208-0330-040D-10Pack #66 (0.0330)
    (1) DC208-0625-040D-10Pack 1/16 (0.063)
    66$ with 2day shipping from precisebits.com

    Now I need to find a press to mount my dremel. I have an old school hand-me-down craftsman hobby hand drill press that I'm going to try to adapt to hold the dremel. if that doesn't work, then I need to wait until next week's paycheck to go buy a real one.

    Thanks!
     
  10. spinnaker

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    Let us know how that goes. If it is the same Sears still offers then I would be curious of how well it works.
     
  11. strantor

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    I was drilling against my particleboard shop table top, it's very uneven, I'll try some hardwood as you suggested.


    AH!, Beautiful. I AM using eagle and very new to it. that's a great trick. Thanks!

    paste flux: I assume to prevent oxidation? do you need it if you plan so solder immediately? How do you wash it off?

    John
     
  12. jpanhalt

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    If I am soldering the board immediately, I may not do the paste flux coating, and it is probably not necessary for through-hole components. I use SMD's almost exclusively and the little bit of stickiness -- it is just the thinnest of coating -- from the flux helps keep 805 parts in position and the solder flows better. There are other tricks to using SMD's too.

    John
     
  13. Wendy

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    Speaking for myself, if I were to try for a two sided board I would make one side, do a toner transfer on the second side, then do the second side. However, it is a major problem keeping the etchant off the side you are not working on, so this may not be practical. Alignment is a huge critical hassle, which is why I would it that way.

    Having said that, I've never made a two sided board. I use the toner method to make a silk screen layer, and generally lay jumpers to compensate.
     
  14. jpanhalt

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    I have only made a few two-sided boards -- mostly when I wanted a ground plane with V+ on the reverse side. I etched both sides at the same time. Why not? In any event, if you want a two-step process, why not use regular packaging tape to cover the first etched side?

    John
     
    Last edited: Feb 4, 2011
  15. strantor

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    My plan was to toner transfer on one side, then drill the 4 outermost holes as guides to align the second side, then toner transfer the second side, then etch the whole board at once
     
  16. Wendy

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    You could also make the wax paper sheets larger than they need to be, and have fidicials on the wax paper to match the two sheets to each other.

    I think there has to be a better solution than the laminator. Another thought is to use two ¼" (or thicker) smooth plates of aluminum with a couple of C clamps. Assemble with the clamps tight, pop in the oven, bake at mumble degrees for mumble minutes, and there you go.

    Laminators work well, but they tend to move the transfer around, which is a real pain.
     
  17. strantor

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    So, you're suggesting aligning the 2 sheets of wax paper (oversized) and taping them sort of into pocket and slide the blank board into the pocket, then heat from both sides simultaneously? I was using an iron strapped down to the ironing board with bungee cords (stack of index cards between ironing board and pcb) but maybe I could use an Iron bungee'd to another Iron. I have 2 irons but I don't have any aluminum plates - I know, a little backwards eh?
     
  18. Wendy

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    If it works...

    So, how well does it work?
     
  19. strantor

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    I'll find out and let you know. If not tomorrow, next weekend. I'll post pics along with my drill press mod.
     
  20. marshallf3

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    I never had luck with a normal laminator, they just were not hot enough.

    As to drilling nothing can replace a cheap Harbor Freight drill press even if you've got to buy an auxiliary chuck to hold the tiny drill bits which, matter of fact, they sell for next to nothing for a bag of them. The more expensive option is a Dremel drill press.

    Watch for the sales at Harbor Freight and you can often pick up one heck of a decent one for $50 or so that will drill through 1/2 steel with a 1" bit given proper lubrication. I've got one at home, one at work and even though they're the cheap Chinese rated motors as to HP they have not let me down.

    For PC boards the middle belt setting is fine, a bit of cutting oil or flux is always a good idea but remember all you're trying to do is keep the drill bit itself cool to prolong its life.

    Subscribe to their newsletter and you'll get coupons that can save you a heck of a lot over their normal prices: http://www.harborfreight.com
     
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