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Standard through-hole components soldered surface mount

Discussion in 'Electronic Design' started by Father Haskell, Apr 14, 2013.

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  1. Surface mounting components for 10 milliamp average guitar pedal and
    assorted other noisemaking circuits. A couple of obvious advantages
    -- easier to mount a board with a smooth back, and no holes to drill.
    What would it take to make such a joint fail, joint being defined as a
    clean, solid 63-37 alloy joint between 1/8" of component lead and
    associated copper foot pad?
  2. Sure, bend the lead to give it a little 'foot' to sit on the smd pad,
    and flow solder around it.

    George H.
  3. Phil Allison

    Phil Allison Guest

    "Father Haskell"

    ** Don't do it.

    Such an arrangement is hopelessly unreliable in high impact / vibration

    There is NOTHING holding the components except a bit a very crappy glue use
    to attach the pads to the board material.

    Through hole mounting is *enormously stronger* as it does not rely on the
    pads being glued at all.

    Forget it.

    ..... Phil
  4. Jasen Betts

    Jasen Betts Guest

    vibration and flexing, most likely failure mode is the pads coming
    off the board.

    you'll probably be more resistant to flexing than standard SMD (due
    to the leads) but less resistant to vibration due to heavier parts
    and lower frequency resonances in the wires.
  5. Needs shock absorbers, I guess. Nice, soft feet.
  6. Phil Allison

    Phil Allison Guest

    "Father Haskell"
    "Phil Allison"
    Needs shock absorbers, I guess. Nice, soft feet.

    ** Huh ???

    You can expect a guitar "pedal" to be dropped from at least 1 metre onto a
    hard floor, many times in its life.

    Build it accordingly.

    Drill the friggin holes.

    .... Phil
  7. Robert Macy

    Robert Macy Guest

    Besides the obvious, cantilevered parts that will have mechanical
    advantage and rip themselves off the board; there is the matter of
    heat conduction out through the leads, not just out through the body
    to the air. Derate accordingly.

    If you pot the board, use potting compound designed for such, again to
    get the heat our. If there is much heat in a pedal circuit.

    Do you have room to put a 'blank' baord on the back. Just sandwich
    onto the backside and you get a somewhat smooth surface. Mill off
    excess through-hole extenders, swiss cheese up the blank board on one
    side, and glue it on.
  8. Phil Allison

    Phil Allison Guest


    There are plenty of guitar pedals with surface mounted components. But the
    jacks and pots and other large parts that can experience a torque during
    normal use should always, always be through hole. AND fitted to the case
    for strain relief. No other way.

    ** There is one better way, as used by Roland in most of their older models.

    Jacks, footswitches, pots and DC inlets were mounted ( often bolted ) onto
    the alloy case and connected to the PCB with flexible leads.

    A tiny bit of extra human time spent and the product is made near bullet

    The phantom powered "FET DI" that I make takes it one step further - the
    die cast box has 2 jacks, one male XLR and a flush mounted "on" LED. No
    switches and no battery option.

    So there is nothing to set or break and no need for the owner to ever open
    the box.

    No repairs for me either.

    ..... Phil
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