|
"...I noticed something old...a stretch of solder which appears bronze in color..."
The "printing" on printed circuit boards is actually copper foil, which appears "coppery," or bronze in color. Copper is an excellent electrical conductor, accepts soldering very well, and is ductile—so is perfect for this application.
When these electronic circuits are manufactured, an automated, high-speed method is used for soldering the entire board at once (sometimes called "wave soldering" or "phase change soldering"). This in essence solders the entire board, not just the connections points. So all of the copper on the board gets a solder coating, even though it's only the electrical connections that benefit from it.
A downside of automated soldering is that the blend of metals results in a solder composition that is physically weak, crystallizes (and breaks), and is usually thin on coverage.
95% of the time you can fully recover a flaky relay by manually resoldering all the connections using a soldering iron (or gun) and good quality electronics solder, available at Radio Shack. Use an iron (25 Watts, or so) on the smaller connections and a gun (200 Watts, or so) on the heavy connections that mount the relay to the pcb, and at the spade lugs.
The pictures below illustrate an OD relay "before and after." In the top pix, cracks are visible at several connections. The bottom pix shows the same relay after resoldering.
Don Foster (near Cape Cod, MA)
|
