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Copper or Brass for a heat sink? — Parallax Forums

Copper or Brass for a heat sink?

RonPRonP Posts: 384
edited 2011-07-07 10:58 in Robotics
I can't decide on what metal to use, copper or brass for a heat sink on a L293D H-Bridge. Its going to span the 4 GND pins on the chip and extend out an undetermined distance.
                ┌──────────┐
               ─┤1  (B)  16├─  
               ─┤2       15├─  
               ─┤3   L   14├─  
           GND ─┤4   2   13├─ GND
           GND ─┤5   9   12├─ GND
               ─┤6   3   11├─  
               ─┤7   D   10├─  
               ─┤8   *    9├─  
                └──────────┘

So before I go to the hardware store and stand there trying to decide :confused: I thought I would ask maybe some one can give me a reason to use one or the other. I know its not that important but I can't seem to make a decision. :depressed:
Thanks for any input

-Ron

Comments

  • LeonLeon Posts: 7,620
    edited 2011-07-07 10:22
    I used a piece of Al channel from a local DIY shop when I needed a heatsink once. It was cheap, easy to cut and drill, and worked very well.
  • RonPRonP Posts: 384
    edited 2011-07-07 10:28
    Leon wrote: »
    I used a piece of Al channel from a local DIY shop when I needed a heatsink once. It was cheap, easy to cut and drill, and worked very well.

    I need a metal that will accept solder (solder doesn't stick to Al or does it?) so the heat will transfer from the pins. I plan on putting it under the board or between the IC and the board, I am still not sure.
    Thanks
  • Duane DegnDuane Degn Posts: 10,588
    edited 2011-07-07 10:28
    I'm going to guess copper would be better.

    If you look at the expensive heat sinks available they are often made of copper.

    I should be able to give you a better answer based on heat capacity and how fast heat transfers through the material (I majored in chemistry), but I don't have all the data to compare.

    I bet pretty much any metal will work. Metal is a good conductor of heat. Some are better than others but I'd suggest just buying something that is the right size and not too expensive.

    Duane
  • Duane DegnDuane Degn Posts: 10,588
    edited 2011-07-07 10:30
    RonP wrote: »
    I(solder doesn't stick to Al or does it?)

    All my attempts to solder to Al have failed.
  • Mike GreenMike Green Posts: 23,101
    edited 2011-07-07 10:40
    You have to use special Al solder and flux. I don't recommend it.

    Aluminum has the best heat conductivity. Copper comes in second and brass comes in last (of the three).

    Because copper is expensive, as with the tabs on regulators and power transistors, often you'll have a piece of copper that you can solder to, then the piece of copper is bolted to a substantial aluminum heatsink with a little bit of heatsink compound between the two surfaces.
  • LeonLeon Posts: 7,620
    edited 2011-07-07 10:46
    Soldering a heat sink shouldn't be necessary. The devices are usually bolted to it, and any other connections can easily be made with a suitable terminal, bolt and nut.
  • RonPRonP Posts: 384
    edited 2011-07-07 10:48
    Second place is good enough for me Copper it is. With the copper or brass question resolved, I think I might have freed up some more Brain Power to get back into the counters and PWM.

    Thanks All

    -Ron
  • RonPRonP Posts: 384
    edited 2011-07-07 10:58
    Leon wrote: »
    The devices are usually bolted to it

    Not in this case Leon its a 16 pin DIP going on a perf board.

    -Ron
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