Peter Peres wrote:
>Dan Michaels wrote:
>>H2O-based flux, scrubbed with toothbrush, look clean
>
>What about under the parts ? I have had evil problems with stuff under SMD
>connectors and chips with other people's boards. Was that a SMT board ?
>Anyway I swear by rosin ...
>

The particular situation I was talking about was all thru-hole
stuff. And actually, I was wondering about this situation myself,
ie, with thru-hole soldering, why don;t you ever get much flux
on the top of the board? I suspect solder being heavier sinks
[assuming you're not soldering upside down], and flux floats.
[would be nice if simple physics could explain something in
electronics - just **once**].

However, on a side note, many board stuffer companies use h2o-clean
solder now, and have a big washer that I assume sloshes water all
over both surfaces of the pcb. So this should help get the
flux out from under the smt devices. Possibly smt paste under the
chips prevents other evil stuff from getting under there too.
Hmmm, I wonder if paste is h2o-cleanable?

Also, because of the slosh clean step, you do have to be a little
careful with non-sealed parts, like trimpots.

BTW, in my experience, sometimes the solder sticks and sometimes
it doesn't - and it mainly has to do with how much garbage is on
the surface of the component leads. Some parts come with nice
clean leads, and others with nasty stuff on the leads. I was
wondering if the board stuffers who use h2o-clean flux may go
thru an extra pre-step of cleaning the leads before part
insertion ??????

- danM

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