I have read some online tutorials about soldering through hole components which say that transistors and ICs are delicate components and can be easily damaged by heat. So they recommend to keep the soldering iron in contact with the leads not more than 2-3 seconds and also to use heatsink while soldering.
Here is a quote from one of the tutorials
Some components, such as transistors, can be damaged by heat when soldering so if you are not an expert it is wise to use a heat sink clipped to the lead between the joint and the component body.The heat sink works by taking some of the heat being supplied by the soldering iron and this helps to prevent the component's temperature increasing too much.
But when it comes to soldering surface mount IC and components, some prefer to use a reflow oven which heats up the entire board as well as the delicate IC to a temperature above the melting point of solder.
SO why don't those components get fried?
What makes the tiny components survive such temperatures while big through hole components can't even if they have larger surface to dissipate heat?