noob flux question

[ratso]

okay time to sound stupid so go easy on me. i have bitten the bullet, bought a soldering iron and a lot of books (not to mention
those learn to solder kits for high school kids) and am determined to learn how to do this. i am very confused however about flux. i get what it does and have a small understanding of the different kinds. what i dont get is it seems some solders have the flux built in. but you can also buy seperate tins of flux? is this only used for solder without flux built in? or do you use it with all solders? how do you use it, just put a small goop on the pin to be soldered? SHOULD you use it??

[AndrewT]

Hi,
I think almost all electronics solders are flux cored. They have a fairly precise flux to solder ratio. Most also have a flux that does not destroy the components, but some must be washed off, either with a solvent or water. The solvent version are usually non corrosive.

The tins of flux paste are usually for plumbing work and generally are not good for electronics.

If you can still source it, go for flux cored 63/37 tin/lead solder for electrical work, 1% or 2% flux and easy clean, non corrosive, or no clean if you're lazy.
Don't breathe the flux fumes. They can start allergic reaction after prolonged exposure and some are worse.
If you want a silver loaded solder then 62/36/2 tin/lead/silver is good and melts at about 4C below 63/37.
Both these will eat copper soldering irons. Use nickel or better, iron plated tips.
There are a variety of copper loaded solders that are kinder to tips, but I think most melt at significantly higher temperatures.

Best to keep two or three diameters. 16g is too thick. Try 18g or 20g and 22g or 24g. 24g can just about be used for smd but I'm told that 26g is better.
Get a stand and sponge.

Does any one know of a low temp, low cost, copper loaded solder?

[ratso]

thanx much, sir. that info is very helpful.