My first PCB

Discussion in 'General Electronics Chat' started by strantor, Jul 10, 2012.

  1. strantor

    Thread Starter AAC Fanatic!

    Oct 3, 2010
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    Hey guys, thought I would share this with you. I got super gung-ho last year about making a PCB, even bought a laser printer just to do toner transfer. I read Bill's thread about making PCBs and I wasn't able to have any success because my printer was a Brother brand printer which apparently has some special toner that only melts on the surface of the sun.

    I made this tonight, mostly from memory from what I studied last year, and I think it turned out not too shabby. I printed it out on the printer at work and used the laminator at work too; I had these tools at my disposal the whole time! DOH!

    pic#1: I don't know why, but this portion of toner lifted off with the paper.

    Pic#2: I just filled in the missing portions with Sharpie marker. Actually worked! go figure.

    Pic #3: etching in ferric chloride. They sell this at Frys now I found out, along with a whole new selection of DIY PCB stuff. exciting! I believe SgtWookie was looking for stick on pads/traces last year and everybody said they are no longer made. They have those as well.

    Pic #4: finished etching, looking much better than I expected.

    Now I just have to find the tiny carbide bits I bought last year and make my holes! (more pics to come)

    EDIT: oh yeah, constructive criticism welcome; are my traces spaced well? There will be 120V on some of them, 1000V on the upper left, and 12V everywhere else.

    EDIT2: pics removed, wait, will repost.

    EDIT3: pics re-posted
     
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    Last edited: Jul 10, 2012
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  2. Sensacell

    Well-Known Member

    Jun 19, 2012
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    Love your comment about the Sharpie pen- I used to make boards by drilling holes in bare board then just drawing the circuit on with a Sharpie pen, you have to use a new juicy pen to get a good etch resist.
     
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  3. strantor

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    Attached pic of where 1000V and 120VAC is ran. Everything not circled is 12V or less.
     
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  4. nerdegutta

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    Dec 15, 2009
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    Looks good, Strantor.

    Just make sure you don't get any solder-blobs near the three oval pads.

    [​IMG]

    Which software did you use?

    Did you consider copper-fillings?

    Mounting holes?
     
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  5. strantor

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    Thanks, yeah those 3 pads are nearly (if not already) touching. I will remedy that with a razor knife. It's that way because I expanded the pads before printing, so the drill hole would be smaller.

    I used Eagle.

    I don't know what copper fillings are. Are you talking about large planes of copper to reduce the amount that needs to be etched?

    mounting holes? I'm going to drill it tomorrow with my carbide bits.
     
  6. nerdegutta

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    Dec 15, 2009
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    Sometimes I need to do the same. After the board is etched, I'm using a DMM to check the board for shorts. I also do that during soldering, to avoid and remove what might look like solder-blobs..

    I use three different dimensions on my drill bits. 0.7mm 1.5mm and 3.2mm.
    0.7 is usually for resistors and LEDs.
    1.5 is usually for SIL and TO-220 packages
    3.2 is for my mounting screws.

    Nice!
    Yes, that's what I'm talking about. It reduces the etch time, and you can use the same etchant for a longer time.
     
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  7. takao21203

    Distinguished Member

    Apr 28, 2012
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    To remove shorts you can simply mill them out using a 1mm bit, a 700W electric drill used freehand at 30 degree angle (carefully). It is possible to mill away stuff but don't put too much tension on the bit + don't use high speed. And wear googles.

    I don't make PCBs myself, tried a few times, but too much effort, and not relieable enough.
     
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  8. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
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    Google "creepage and clearance distances" for recommended spacings between traces based on voltage levels.
     
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  9. Wendy

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    Mar 24, 2008
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    I have found that taking a high res picture makes for an excellent inspection tool. Problems are much easier to spot on a photo, don't know why.

    I am thinking of doing a similar article using photographic techniques. Mine works great, but the absolute requirement of a good laminator and printer is a pain in the assets for a lot of people.
     
  10. nerdegutta

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    Some of the boards I make, are nearly transparent. When I hold them up against a light, it's easy to see if the traces connects. I that for visual inspections.
     
  11. SgtWookie

    Expert

    Jul 17, 2007
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    It wasn't me who was looking for the press-on pads/traces - maybe Shortbus or Spinnaker, perhaps?

    When you're working with higher voltages, it's a good idea to avoid making sharp corners/points in traces, as those are usually the place where you will get a flashover, as it is easier to ionize air at the point. Points also tend to attract carbon, which eventually will form carbon tracks. Eagle has a feature where you can radius your traces, and even radius copper pour areas.
     
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  12. strantor

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    not sure. I just spent 5 minutes searching for that thread and can't find it. Maybe whoever it was will stumble across this one.
     
  13. shortbus

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    It was me:) @strantor, if your in there again would you get a brand name or part number for them, please. Just went to Fry's web site and they don't show them.
     
  14. strantor

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    It's MG Chemicals brand, link. My Frys location now stocks a whole line of their products, including ferric chloride ethchant tanks, UV exposure beds, and lots more. I was very surprised to see it, a step in the right direction.
     
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  15. shortbus

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    Thank you!! Missed it on the site, just looked in the PCB pages. Guess who is going to order some?
     
  16. strantor

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    The bits I have are
    .0330" (#66(.84mm))
    .0625" (1/16th"(1.59mm))
    .0785" (#47(2mm))

    Its been a long time since I bought them, but IIRC SgtWookie recommended these sizes. Or I might be incorrectly attributing something to him again.
     
  17. tpny

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    May 6, 2012
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    Question: What could go wrong in terms of reliability? Thanks!
     
  18. WBahn

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    Mar 31, 2012
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    It has been a long time (decade?) since I've done my own boards. But I used to make double-sided boards by simply printing onto transparency and then taping the transparency to some UV-transparent plexiglass (i.e., the cheap stuff). I would then put the two pieces together with the transparencies on the inside (and oriented the right way!) and line them up. Then I would drill two holes in opposite corners (opposite mounting holes for the PCB if it had them). I would then take a piece of presensitized board (never had much luck with the sprays or washes and could never afford the adhesive sheets) and use one of the plexiglass plates as a template to drill the two registration holes. I would then assemble the whole thing and use pins that were a tight fit in the holes in order to get good registration. Then I would expose the boards and proceed to develop and etch. I did a number of boards using 50 mil components and boards with as many as 300 holes.

    The first board I did this way was for buzzer systems for our Physics Bowl competition (I was a junior at the time) and each system had to support three teams and record which order they buzzed in and lock out teams that had already buzzed in if the first team(s) gave wrong answers. I didn't even know about microcontrollers at the time, so I did the logic design using only one 555 timer and nine quad NAND gates. I was actually pretty proud of the design. It worked great, but I got a really good lesson in battery life!

    One thing I found that made the drilling a lot easier -- I would etch the center of each pad that needed to be drilled. This made a wonderful guide for the bit.
     
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  19. #12

    Expert

    Nov 30, 2010
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    It seems that nobody has mentioned using a proper conformal coating on the board when it is all finished...or was that in a thread I missed? Not only keeps humidity out of the board, it suppresses surface leakage between traces and avoids corrosion of the copper from atmospheric contaminants.
     
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  20. strantor

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    conformal coating is on order :)
     
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