I made another try with the desoldering iron/air pump, but without
satisfaction.  This time I stuffed copper desolder braid up into the iron
for better heat transfer.  I packed it tight, and it restricted airflow
somewhat.  Insulated the soldering iron with fiberglass braid, and cranked
it up to 140volts, which gave me about 60 watts.   I was able to melt wire
solder easily, but wasn't satisfied with the results on the board.  I am
sure the soldering iron would burn out rapidly at this voltage.

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.


-- Lawrence Lile



--
http://www.piclist.com hint: The PICList is archived three different
ways.  See http://www.piclist.com/#archives for details.