Its a turn Knob switch for setting timer and push start in Samsung microwave oven I also want to desolder this component. How to do that?
It is probably a rotary encoder with a switch.
It looks like it is a rotary encoder riveted to the copper side of a single sided board. You could drill/grind the rivets from the back of the board and see if the encoder detaches. It might not be soldered on. If it is, you might need a hot air gun to desolder it.
I'd guess that there are no solder points, there's a body with the rotor in it, riveted to the pcb, and that rotor has spring contacts that bear on pads directly printed on the board i.e. the board forms part of the assembly and it won't be any use by itself - just like the snap action switches on that board, they will bear down onto pads printed in the board itself.
Here's a transparent rotary switch that shows what is printed on the pcb that's part of this assembly. Typically these small encoders are quadrature encoders, so there's two traces with sectors offset from each other, and a center pad for the push action.
As for repairing this board - check the connections at the end of the ribbon cable, looks like there are some corroded joints there.
It is a surface mount component. You can apply heat to the rear of the board behind the part with a heat gun to remove it.
The trace in the top right corner of the red circle could be broken. Maybe it's enough to fix the trace.