Just to add a bit..
The solder balls indicate a few possible things:
Either there was excess paste used;
or all the surfaces never reached and stayed at the minimum reflow temp for
long enough time;
or the heat ramp was too sharp and the flux was not given time enough to
activate.

The silver content does call for a bit more precision in balancing the time
phases of the process, but with generic 63/37 paste, it's not as hairy and
is harder to damage anything. Starting with silver content in the paste is
not a good idea IMHO.

When following the paste maker's process curve for times & temps, I have
never had soldr balls or a mess of any kind.

I suggest that the entire process needs to be controlled to get consistent
results - ramp-up, flow, and cool.

Then again, the new Salton Toaster-oven my wife bought recently is only
capable of under-cooking or burning everything from white bread to
pumpernickle bagels....so perhaps you have already out-achieved the rest of
the crew there..


> *>I went back to the E-Z bake method, and had some success.  I had a
> *>thermocouple buried in my board, which made it easier to control.  I
> baked
> *>it at 60C for four minutes, (actually just let the board sit in a
> *>preheated oven shut off) then cranked the oven up, which
> brought it to
> *>215C for over one minute.
> *>
> *>I found there was a lot of solder balls left on the board,
> and I had to
> *>mechanically remove them quite vigorously.  Underneath was
> a good solder
> *>joint.  I tried a toothbrush, which would not touch it,
> then the end of
> a
> *>needle, which scraped it off pretty well.  I finally just
> got out a fine
> *>wire brush and removed the stuff wholesale.  This is never a problem
> with
> *>a hand soldering iron.
> *>
> *>Do other people have to remove this stuff after reflow?
> Does it seem to
> *>take a vigorous amount of work?  I would have a hard time
> applying less
> *>solder, using a syringe, I just touch the pad, don't
> squeeze any on at
> *>all.  I added extra flux to the board, and I am using a
> combo solder,
> RMA
> *>flux.  It has 2% silver content, which might make it a little higher
> *>temperature solder.
>
> Obtain a bottle of flux remover (I use a spray can tm CRC,
> with built in
> brush). Brush the board with the stuff, let it sit for 1
> minute, blow if
> off with compressed air. Done.

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