Folks,
We work with it everyday so we take it for granted. Soldering is a miracle. Soldering enables us to bond mechanically and electrically two pieces of copper (Tm = 1085C) at temperatures below 232C (Tm of tin). Without this tremendous reduction in temperature (more than 850C) electronics products would not be possible at any reasonable price. The main reason being that modern electronics must use plastics, which are damaged at temperatures above 235-260C.
Another aspect of electronic soldering that we may not think about is that tin is the fundamental metal. The intermetallics that form in the solder joint are predominantly two forms of SnCu. So essentially all solder alloys are carriers for tin. The other metals serving mainly to lower tin's melting temperature, wettability, or other process variables.
So remember, it is a miracle!
Dr. Ron