On Sat, Nov 10, 2007 at 04:10:43PM -0800, Dave N6NZ wrote: > > > DJ Delorie wrote: > > I just had an occasion to remove a bunch of SMT parts from a proto > > board (so they can be moved to the production board). I used the > > hotplate, because many of them had solder under the part, not next to. > > What are you using for a hot plate? > > The SparkFun site talks about using a cheap US$20 hot plate from Target. > They mention uneven heating. A friend who happens to be a Mech E with > a specialty in heat transfer suggested using one of the "liquid filled" > hot plates, which are more expensive, but have a hollow core filled with > oil or something that distributes the heat more evenly by convection.
I recently used a very cheap aluminum-core stainless steel skillet on my stovetop to do some soldering. (Cheap knock-off of the All-Clad style tri-ply cookware.) This was to handle a chip that had an exposed pad on the bottom, not accessible to a soldering iron. I only did that chip that way, not the whole board, so it wasn't really a great test of evenness of heating, but I suspect it wasn't too bad. Anyway, that was a 4-layer board with two inner planes, which should have augmented the aluminum core of the skillet somewhat in spreading heat. I am a little nervous about the SparkFun suggestion, since it involves a non-stick coating. Don't those start to break down at right around the same temperature that solder melts, leading to the release of toxic fumes? Anyway, if you have a skillet that you trust to distribute heat evenly for cooking, give it a try. Just be sure to avoid getting any lead solder on something you intend to cook with in the future. Double-sided boards that come from a real fab will have solder coating on any exposed copper on the bottom. I used some parchment paper between the board and the skillet. The paper got a bit blackened, but never actually smoked or caught fire. (The stuff is meant to go in the oven, after all.) I wonder if the paper improved or degraded the evenness of heating? -- Randall _______________________________________________ geda-user mailing list geda-user@moria.seul.org http://www.seul.org/cgi-bin/mailman/listinfo/geda-user
