Somebody told me not to keep a soldering iron on the pin of a through hole package for more than 2 seconds. I am not aware of where he got this number from.
When soldering we come across discrete passive and discrete active components, then we have integrated circuits that connect the die to the package via very thin bonding wires. We have very passive tiny surface mount components like SMD resistors and also really huge power transistors.
How do we know for how long we can keep the soldering iron tip on the component without damaging it? What temperature does one usually use when soldering, is it the same for all applications? If this time duration is not enough and we need to put the tip back to complete soldering, how long do we need to wait so we can apply the soldering iron for full duration without damaging the component? Finally what determines what shape of tip to use when soldering?