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.
