When shopping how do you identify headers that good (easy to solder) vs bad (difficult to solder)?
I have some male no-name headers that appear to be bright nickel plated on top of something that is non-magnetic. They show a remarkable reluctance to take solder despite using plenty of rosin flux, good quality solder and a hot iron.
At the other extreme I have some gold coloured female headers that have tarnished just while sitting in a box, but are very easy to solder even without removing the tarnish. I have no idea what alloy they are made from.
What key words should I be looking for when searching so I don't end up with more of the rubbish kind?
I've not had such problems and have used a variety of different types, some supplied with the module and some bought loose on Ebay.
I put the header pin in place, apply heat from the soldering iron tip directly onto the exposed end of the header pin (without touching the solder pad) then touch the solder wire filament again directly onto the exposed part of the pin, but away from the soldering iron tip. Finish it off by touching the solder pad as well.
I tend to use leaded solder.
I have also had problems just lately, the headers were supplied by Elegoo with multi-packs of Nanos. No amount of cleaning, heat or flux will make a nice joint.
I'm not doubting anyone's experience. I am simply curious about what the problem is. Here is what Wiki says about the "solderability" of various metals: Solderability - Wikipedia
As components are in storage the pins will grow a layer of oxide (unless they are gold plated),
making soldering progressively harder.
The right iron temperature and good rosin flux is needed, but once the oxide film has grown
too thick you'll need to deal with that first - emery paper is quite good (yes a row of headers is
very fiddly to clean like this). Careful scraping with a craft knife blade can help (although it
might remove the plating entirely).
Basically soldering requires clean surfaces and rosin flux to be reliable.
Generally nickel and copper oxidize quite fast, tin plate is better (it melts into the solder,
breaking up the oxide coating too). Gold plating is by far the best, if expensive.
If you use lead-free solder only use the 4% silver version, and the kind without silver isn't
eutectic and is basically unworkable. The 4% silver stuff is fine though (needs somewhat
higher temperatures than leaded solder).
You used to be able to get rubber blocks with fine abrasive in them, great for cleaning
parts prior to soldering - haven't seen these for ages though.
