At 18.39 2013.05.19, David VanHorn wrote:
>Those caps are delicate.  Automotive heating and board flex from vibration
>can kill them.
>There are special caps that are more forgiving, look on Digikey for
>automotive and boardflex ratings.  Also, higher voltage parts are generall=
y
>more robust. Thicker layers.


Thanks, this is very interesting.

I digged some info and these are Samsung caps, so they shouldn't be too cra=
p.
I can't be the ESD I first guessed, also because they are 10uF and no speci=
al
ESD was there (it wasn't even installed on the engine the 2 times it happen=
ed!).

So now I discovered the world of MLCC cracking, thank you.

The board definitely suffered physical stress (bending etc..) during work.

It must have to do also with my hand soldering technique: I first solder on=
e
pad (using a small spoon-like tip), this way the 0603 cap is now tacked and
it'll let me solder the other pad (tons of liquid flux and again the spoon
like small tip), I finally add flux to the first pad and resolder it again =
to
get a better joint than the first I managed to make (which never gets perfe=
ct
and is useful mostly to get the component tacked in place).

Now I am concerned that this soldering technique will damage these delicate
MLCC SMD caps.

As I already bought a (costly) reel, I'd prefer to avoid to buy another of
higher voltage spec (which would make them more robust, I reckon).

Rather, would soldering them only to one pad "vertically" and then solderin=
g
a wire to the other "pin" and PCB pad remove a lot of physical stress? What
do you think?

Last, I then have to pot everything in epoxy resin. I may leave the MLCC 10=
uF
caps out of this process by covering them first with e.g. silicone (hoping =
it
won't be too corrosive). Will this be better for the MLCC (being potted wit=
h
silicone instead of epoxy resin)?

Thanks a lot for your tips and experience-sharing.

Cheers,
Mario

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