This Hobby Is Actually Useful!
tothwolf at concentric.net
Sat Aug 1 19:17:36 CDT 2015
On Sat, 1 Aug 2015, Robert Jarratt wrote:
> PS A related question. I struggled somewhat with the Weller Magnastat
> No. 8 tip, when trying to solder leads to the ground plane, I could not
> get the solder to stay molten very long. I was using lead-free solder,
> its melting point is much lower than the temperature which a No. 8 tip
> reaches. The iron is 50W. Clearly the ground plane was taking heat away,
> but is it a problem with the tip not being hot enough, the iron not
> powerful enough, or perhaps some operator error?
The Weller just didn't have enough thermal mass and a fast enough recovery
for the task.
While some people prefer the digital readouts and pushbuttons on some of
the newer soldering stations, I find older Hakko systems with a
temperature control knob to be far easier to use. For a single sided or
double sided plated-though board soldered with tin/lead alloy, I usually
run a lower temperature somewhere around 600-650F. For a multi-layer board
with large ground/power planes, or a board assembled with lead-free
solder, 650-700F or slightly higher is often required.
I also suggest using traditional tin/lead alloy solder instead of the
lead-free stuff. I only use lead-free where I absolutely have to and
prefer to use a 63/37 tin/lead alloy even for repairing lead-free boards.
Adding tin/lead solder to an existing lead-free joint before desoldering
will also lower the melting temperature and help with the desoldering
process. It usually isn't advisable to mix tin/lead solder with lead-free
solder unless you are going to remove it though as some lead-free alloys
do not mix well with traditional tin/lead.
When installing new components on a board where you are soldering to areas
with a large thermal mass such as a ground or power plane, you might also
want to consider using supplemental flux, such as a flux pen (even with
through-hole components). The extra flux will help pre-clean the pads and
component leads and will allow the solder to wet quicker. A more active RA
flux can also help, however if you are working with a multi-layer board
with internal ground/power planes (4 layers or more), a no-clean,
low-solids rosin, or non-rosin flux might be required since some of those
boards can wick a traditional RA or RMA rosin-based flux between the
layers which will leave permanent dark spots inside the board.
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