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Clad AL substrate - high current interconnect

Discussion in 'Electronic Design' started by legg, Nov 12, 2006.

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  1. legg

    legg Guest

    Any bright ideas out there for high current connections to power
    circuits, surface mounted on clad Al substrates?

    At the moment, the only practical hardware seems to be SMD .050sq post
    double-row male pins. There may be registration issues with these. The
    Al substrate is not friendly to locating retainers.

    RL
     
  2. John  Larkin

    John Larkin Guest

    Got any links to the clad Al substrates? Is this the Bergquist stuff?
    Is the Al always insulated from PCB traces?

    I assume that, if it's a pc board bonded to an aluminum plate, you
    must use all surface-mount connectors.

    Is this stuff cost-effective? You could just bolt a PC board onto a
    hunk of aluminum or a heat sink, but then you could provide clearance
    holes for serious thru-hole connector pins, and use the mounting bolts
    (with proper washers!) to connect to the substrate and use it as a
    conductive layer.
    I like to use 0.25" faston blades on pc boards for high currents, with
    the female mate crimped onto harness wires. You can parallel these for
    higher currents, with the wires acting as current-balancing ballasts.
    But if you're limited to surface-mount, you'd have to be careful, use
    a *lot* of copper on the board, so that the connect/disconnect forces
    don't rip the tabs off the board.

    How much current? How many circuits?

    John
     
  3. As John said, define high current. I've used several different methods.
    For low current, I've use 0.50sq posts, these provided control signal
    connections. For high current the easiest method was to simply sandwich
    Cu bar between the AL clad substrate and another FR4 PCB. Another
    method was custom clips shaped sort of like a U with a flat bottom and
    the top of the U pinched together. This was soldered on the metal clad
    and Cu 'legs' slid in. Similar to the clips used to hold EMI shield in
    place on a PCB, just heftier.

    Robert
     
  4. legg

    legg Guest

    The requirement for SMD connectors is driven by application of the
    substrate.
    I'd considered using faston pins, as there are methods of adapting the
    socket component for bottom entry.

    SMD of the pin could be a bit hit and miss, particularly if it has to
    have any length.

    Current is in the region of 40A/connection and subdivisions of same.

    Although cost isn't currently the issue - this having been resolved
    before starting, so as not to waste the design effort - the processing
    of a troublesome interface could be an added cost that wasn't
    anticipated.

    RL
     
  5. legg

    legg Guest

    How did you establish/maintain good contact/pressure in the sandwich?

    RL
     
  6. Bolts/nuts and belleville washers. Works quite well. Used it for
    PCB/PCB sandwich as well.

    BTW on the small posts we didn't have much in the way of registration
    problems between boards, can't say as I'd want to fit together a large
    number of pins though. We were using a 4x2 IIRC.

    Robert
     
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