Definition
A defective soldered electrical connection in which the solder did not reach a high enough temperature to flow properly and fuse with the metal surfaces being joined. The joint looks dull, grainy, or lumpy rather than smooth and shiny, and it forms a weak mechanical and electrical bond that may have high resistance, behave intermittently, or fail completely under vibration.
Plain English
A bad solder connection. The solder didn't get hot enough to melt and bond properly, so the wires are barely held together and the electrical signal may not pass through reliably.
Context Anchor
Seen in aircraft electrical maintenance, avionics repairs, and troubleshooting intermittent electrical faults.
Derivation
Called 'cold' because the joint was made without enough heat. Solder must reach its melting point and flow into the metal to form a proper bond. If it cools too quickly or never fully melts, the joint is 'cold' — physically and electrically inferior.
Why Pilots Care
Such joints create intermittent or complete electrical failures in instruments, radios, and navigation systems, which can appear suddenly in flight.
Analogy
It is like tape that was pressed onto a dusty surface. It may look attached at first, but the bond is weak and can fail when moved or shaken.
Intuition Check
Do not read “cold” as the present temperature of the connection. Here it means the solder connection was made without enough heat to form a proper bond.
Example Sentence 1
The avionics technician traced the intermittent radio failure to a cold-solder joint inside the microphone connector.
Example Sentence 2
Vibration in flight finally broke the cold-solder joint in the nav light circuit, causing the light to fail.