What it looks like: You shat all over the board.
What it smells like: Nasty chemicals but only when hot.
What it does: it helps distribute heat, and causes the solder to be less viscuous and stick to metals readily.
What it feels like to start using it: Wow, it’s like I just gained one year of soldering experience!
What it feels like to remove it from the board after soldering: Aargh… I swear, one more board and I go buy an ultrasonic cleaner. (Some brands are easier but I usually need to employ a spudger, brush, then alcohol annd Q-tip)
Note that some solder comes with a core that contains flux or some similar substance of that effect.
It removes the oxide layer from existing surfaces so the solder sticks and flows better
It increases surface tension of the liquid solder so you get a nice round shape and no whiskers and less bridges
It helps distribute the heat a bit. It works a little bit like thermal paste, especially when the contact area between the tip and the pad/component is very small.
Generally, flux is your friend and soldering without flux is terrible.
What does flux actually do?
What it looks like: You shat all over the board.
What it smells like: Nasty chemicals but only when hot.
What it does: it helps distribute heat, and causes the solder to be less viscuous and stick to metals readily.
What it feels like to start using it: Wow, it’s like I just gained one year of soldering experience!
What it feels like to remove it from the board after soldering: Aargh… I swear, one more board and I go buy an ultrasonic cleaner. (Some brands are easier but I usually need to employ a spudger, brush, then alcohol annd Q-tip)
Note that some solder comes with a core that contains flux or some similar substance of that effect.
Cleans and keeps the solder points clean. Prevents oxygen from reaching the solder joint
This is the best answer. It removes oxides which allows the solder to flow and bond with the metal.
Generally, flux is your friend and soldering without flux is terrible.
It makes the tin non sticky. Heat up a blob of solder for a minute or so to evaporate the flux and then try working with it.
Lower the melting point of solder
It may seem like it melts easier since the parts have better thermal contact. But the melting point is intrinsic to the metal alloy