Definition
A metal-joining process in which two or more metal parts are bonded together by melting a filler metal (solder) into the joint between them. The filler metal has a melting point below 840°F (450°C) and below the melting point of the parts being joined, so the base metals are not themselves melted. The molten solder flows into the joint by capillary action and forms a metallurgical bond as it cools.
Plain English
A way of joining metal parts by melting a softer metal between them, like a glue that hardens. The parts being joined are not melted — only the filler metal is.
Context Anchor
Seen in aircraft maintenance when discussing electrical connections, wire repairs, and some small metal joints.
Derivation
From the Old French 'souder,' meaning 'to make solid,' which itself comes from the Latin 'solidare' — to make firm or whole. The name reflects what the process does: it makes a solid, continuous joint out of separate pieces.
Why Pilots Care
Soldered joints carry electrical current and hold structural connections in avionics, lighting, and instrumentation. A poorly made solder joint can cause intermittent radio failures, instrument errors, or electrical fires — all of which matter in flight.
Intuition Check
Soldering is not the same as welding. In soldering, the added metal melts and flows; the parts being joined do not melt.
Example Sentence 1
The technician used soldering to attach the new wire to the terminal on the navigation light.
Example Sentence 2
Careful temperature control during soldering prevents damage to nearby insulation on aircraft wiring.