Standard through-hole components soldered surface mount

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.

 

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

 

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.

 

<>

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
proof.

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