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via and current? — Parallax Forums

via and current?

mctriviamctrivia Posts: 3,772
edited 2009-07-06 16:33 in General Discussion
What is better for high current situations?

lots of small vias or 1 or 2 big vias?

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Comments

  • LeonLeon Posts: 7,620
    edited 2009-07-06 08:13
    I don't think it makes any difference. You need to calculate the current-carrying capacity of the vias anyway - it depends on the size, board thickness and plating thickness. The Pulsonix software I use has a built-in calculator for this.

    Leon

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Amateur radio callsign: G1HSM
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  • LoopyBytelooseLoopyByteloose Posts: 12,537
    edited 2009-07-06 09:00
    When in doubt, a large via can be pluged with solder much more easily. A lot of small vias may offer some added benefit as cooling from the backside - at least in theory.

    Try being pragmatic rather than theoretical. Sometimes that is where the real answer lies.

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  • LeonLeon Posts: 7,620
    edited 2009-07-06 09:19
    Solder has a much higher resistivity than copper.

    Leon

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Amateur radio callsign: G1HSM
    Suzuki SV1000S motorcycle
  • CounterRotatingPropsCounterRotatingProps Posts: 1,132
    edited 2009-07-06 14:16
    Advanced Circuits (Pulsonix reseller) trace calc:

    http://www.4pcb.com/index.php?load=content&page_id=95

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  • LoopyBytelooseLoopyByteloose Posts: 12,537
    edited 2009-07-06 14:40
    Nice trace calculator. So where is the via calculator?

    If the added resistance of tin or lead solder were significant, we would all be using silver solder. I'll restate that - Being pragmatic is likely to offer a better solution.

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Ain't gadetry a wonderful thing?

    aka G. Herzog [noparse][[/noparse] 黃鶴 ] in Taiwan

    Post Edited (Loopy Byteloose) : 7/6/2009 2:45:17 PM GMT
  • mctriviamctrivia Posts: 3,772
    edited 2009-07-06 14:48
    I personally have never seen a via calculator. In the past I have always used lots of small ones but my current project is critical that it not fail. My high current is a 20 amp 200ms pulse and did not think a couple 12mil vias would be enough.

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    propmod_us and propmod_1x1 are in stock. Only $30. PCB available for $5

    Want to make projects and have Gadget Gangster sell them for you? propmod-us_ps_sd and propmod-1x1 are now available for use in your Gadget Gangster Projects.

    Need to upload large images or movies for use in the forum. you can do so at uploader.propmodule.com for free.
  • CounterRotatingPropsCounterRotatingProps Posts: 1,132
    edited 2009-07-06 14:52
    > Nice trace calculator. So where is the via calculator?

    picky picky ;-P

    I think it's only built into Pulsonix (I've only started looking at it a few weeks ago).

    Leon?

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  • LeonLeon Posts: 7,620
    edited 2009-07-06 15:25
    That's their own calculator, it's not the Pulsonix one. I can do some calculations with the Pulsonix calculator if anyone needs them, or you could download the Pulsonix demo.

    Leon

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Amateur radio callsign: G1HSM
    Suzuki SV1000S motorcycle
  • LeonLeon Posts: 7,620
    edited 2009-07-06 15:28
    Loopy Byteloose said...
    Nice trace calculator. So where is the via calculator?

    If the added resistance of tin or lead solder were significant, we would all be using silver solder. I'll restate that - Being pragmatic is likely to offer a better solution.

    It would still be a good idea to calculate it. I don't like trusting to luck.

    Leon

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Amateur radio callsign: G1HSM
    Suzuki SV1000S motorcycle
  • mctriviamctrivia Posts: 3,772
    edited 2009-07-06 15:37
    I do use silver solder usually because of rohs compliance. But I would like to automate assembly on this.

    Leon how many 12mil vias does your calculator say for 20 amp pulse? Heat not to much an issue no more then 1 pulse an hour.

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    propmod_us and propmod_1x1 are in stock. Only $30. PCB available for $5

    Want to make projects and have Gadget Gangster sell them for you? propmod-us_ps_sd and propmod-1x1 are now available for use in your Gadget Gangster Projects.

    Need to upload large images or movies for use in the forum. you can do so at uploader.propmodule.com for free.
  • LeonLeon Posts: 7,620
    edited 2009-07-06 16:33
    Lead-free solder only has a very small amount of silver. Silver solder is different stuff.

    Assuming that the plating thickness is 0.001" and the board is 1.6 mm thick, I make the resistance of one via to be 0.00136353 ohms. That gives 0.545411 W for that via, at 20A.

    If it's a pulse you might need to take account of things like inductance, in which case several small vias would be better than a few large ones.

    Leon

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Amateur radio callsign: G1HSM
    Suzuki SV1000S motorcycle

    Post Edited (Leon) : 7/6/2009 4:39:29 PM GMT
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