Re: [OT] surface mount components

Chuck Harris

If you use a glue, you must make sure that it doesn't
end up on the solder pads.

I don't know about you, but I cannot control crazy glue
that well.

Complicated boards get a tiny dot of epoxy dead center
in the footprint to hold the part down. These boards are
populated by robotic pick and place machines, and the
epoxy is placed there by that machine.

The solder paste is put on by wiping it over the holes
in a specially made etched solder paste mask.

Smaller less complicated boards often use the solder paste
to hold the parts down.

-Chuck Harris

Tony Fleming wrote:

Nice information for people who do not use SMD's very often.
Some people use Crazy Glue to hold the part down - just a small drop -
before soldering it.
Is there anyone who thinks that using glue is not a good idea?

On Thu, May 16, 2019 at 9:43 AM Chuck Harris <cfharris@...> wrote:

If you do the soldering right, heating all of the joints
at once, the surface tension of the solder will rotate the
part around into alignment.

One of the contracts we all have with Murphy relative to SMD
rework is that we must melt all of the solder joints at the
same time so that we can avoid introducing tensions in the
parts that can cause breakage. The issue is especially bad
with fragile leadless parts like SMD capacitors. If you see
a capacitor that is "tombstoned" (eg. one side higher than
the other) it is under stress.

-Chuck Harris

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