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?
Sure, bend the lead to give it a little 'foot' to sit on the smd pad, and flow solder around it.
George H.
"Father Haskell"
** Don't do it.Such an arrangement is hopelessly unreliable in high impact / vibration environments.
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
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.
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e use
Needs shock absorbers, I guess. Nice, soft feet.
"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
In both cases, the circuit needs to be potted.
Joe Gwinn
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.
Hmmm. I don't think any load-bearing part should ever be surface mounted. That would be a jack, a switch, a pot, anything that will have force appli ed to it during normal use.
I once had the dubious pleasure of repairing a Viewsonic tablet computer. My friend had managed to break the power jack off the board. It was surfac e mounted. Not only that, it did not have any strain relief - it dead-ende d a couple millimeters from the case. Finally, it was a non-locking jack s o he was in the habit of cranking on the cord to get it to charge. His cha rger died, and in his efforts to get the charge light to go on, he busted t he silly surface-mount jack's leads right off the pcb.
That was a fun repair. I think that I put enough super glue under it that it's stronger than it originally was.
But if you wanna know how much force it takes to yank a lead off a surface- mount pad - not a whole lot, really. Don't do it.
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 n ormal use should always, always be through hole. AND fitted to the case fo r strain relief. No other way.
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