What is soldering?

• A. The process of joining two or more metals at temperatures below their melting point.
• B. The process of joining two or more metals at temperatures above their melting point.
• C. The process of joining plastics using heat.
• D. A method of fabricating by welding.

Answer: (A)

Soldering is the process of joining metals by using a filler metal that melts at a lower temperature than the base metals, so the parts themselves don’t melt. The joint forms as the solder melts, flows into the seam by capillary action, and then cools to solidify the bond. Flux helps by cleaning oxides and improving wetting so the solder can spread evenly over the surfaces. This keeps the base metals solid while the filler metal creates the connection. It’s different from welding, which fuses the base metals by melting them, and from brazing, which uses a higher-melting-point filler metal but still keeps the bases from melting.