In the LED thread I detailed proper soldering technique. Here's it is lifted in its entirety:
Soldering... It's a bit of an art form. It you're an expert you could probably solder the stars with anything but a torch. But if you aren't accomplished a 'just right' soldering iron is required. Something around 25 to 40watts. The biggest problem would be one too small as then you damage what you are soldering by sitting there with the heat on, waiting, and waiting for the solder temperature to be reached. Meanwhile the device is being roasted.
You need "rosin core solder." Make absolutely sure it's not 'ACID' core solder. Acid core is solder for soldering radiators and copper pipe. The acid remains and will dissolve your electronics in short order. No-core or plain solder is also very bad as there is no cleaning action which is vital to an acceptable solder joint.
You want lead solder too - NOT "lead free".
Let your iron heat up fully. Then wet it with your rosin core solder until it's blobbed up in a wad. This lets the rosin act on the tip to clean it. Wipe this blob off on a moist sponge,(not sopping wet, just barely damp). If you have no sponge use a damp folded up paper towel.
Wipe with a very fast twirling dragging motion as you are trying to clear all the solder off the tip before you cool the tip to the point that the solder freezes again.
Apply a weee bit of solder to the tip and then immediately apply the tip to the star's pad. As soon as you apply the tip to the pad take your solder and touch it to the exact point where the tip meets the pad. You are trying to maximize heat transfer from the tip to the pad. You do this by filling all the voids with a molten metal thermal bridge. Pause for, perhaps, one or two seconds move the solder to a distant place on the pad and hold it there. When the pad heats up enough to melt the solder feed the solder in at a good clip until the pad has a large mound of solder on it.
Do the same thing to your wire if it is un-tinned. (actually do this before you do the pad!) Better(superior) would be to use only pre-tinned wire in the first place.
Now once you have your mound of solder on the star pad bring over your wire, hold it on the Star's pad. Place the tip on top of the wire. You want to reheat the pad thru the wire. When the wire sinks into the blob hold the position and watch the blob. You want the entire blob to melt again. The instant the blob has remelted remove the tip while holding the wire EXACTLY where it is. No wiggling allowed! Coffee shakes need not apply. Once the solder has refrozen move on to the next connection.
