[sdiy] unleaded solder

[Tony Clark]

On Sat, Apr 2, 2016 at 12:19 PM, Phillip Harbison <alvitar at xavax.com> wrote:
> Last night I was soldering for the first time in many years. I
> am trying to use lead-free solder. I believe it is 99% tin and
> 1% copper. In the lead solder days I never had a problem with
> getting good joints. Last night I had lots of problems. Perhaps
> it is more a matter of declining vision and unsteady hands, but
> I'm inclined to believe the solder is part of the problem. When
> using lead solder it was quick work so my eyes and hands did
> not have as much time to become fatigued. It seemed to take
> forever to get the solder flowing. I had my iron set at 430•C.
> I'm not sure if that is sufficient temperature, but it is near
> the iron's maximum temperature. I struggled to assemble a kit
> with a ZIF socket, a dozen discrete components, and a handful
> of connectors on a 1.25" x 4" board. I did not time myself but
> I'm guessing at least 90 minutes. Any suggestions on what I
> might be doing wrong? Should I give up on lead-free solder? I
> would appreciate any advice anyone can offer.

As others may have mentioned (tl:dr), you are using the wrong kind of solder.

SAC305 is the current standard lead-free solder and working
temperature is no different than regular solder (700F or 370C).  It
also comes in standard rosin, water soluable, and no-clean flux
varieties.

Using too high of a temperature will generally cause your soldering
tips to oxidize and crust too fast, causing all sorts of problems, but
mainly causing your iron to stop working properly.  This has to do
with the flux more than it does the solder.

The main problem that most people don't understand (and it took me a
long time to figure it out) is that lead-free soldering requires more
thermal transfer from soldering iron to the work surface.  In order to
combat that, you have to use a beefier soldering iron and a much
heavier soldering tip, one that has as much mass as you can possibly
get.  That has the downside of doing fine-pitch SMT work much more
difficult, but it's a tradeoff.

So if you plan to continue doing lead-free work, I would suggest two things:

1) Get a soldering iron with as high a wattage pencil as possible
(minimum 60 Watts, higher is definitely better).
2) Get wedge shaped soldering tips for the iron, not conical points.
The wider tips have more mass and will help transfer the heat better.

Hope that helps!

Tony.

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Tony Clark
Great Lakes Modular
www.greatlakesmodular.com
Design, Engineering, and Manufacturing Services
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