Solder Melting Point

On Dec 3, 12:17, Marvin wrote: of metals, melts at typically Yes, yes, no; see below... as That's not *exactly* true; the solidus point (the temperature at which it begins to melt) remains almost exactly the same, but the liquidus point rises. In between, though, the solder is rather pasty. That's great for old-fashioned plumbing, but it's apt to produce dry joints in electronics, so for practical purposes, the useful temperature rises just as Marvin says. For example, 40/60 solder has a liquidus point of 227C (440F) and 60/40 has a liquidus point of 188C (370F). Adding certain other metals, especially bismuth, lowers the melting point, though many other additives, such as antimony, raise it. According to my Multicore Solder list, the recommended bit temperature for 40/60 general-purpose electronics solder is 354C (670F), and for 60/40 it's 308C (585F). Personally, I'm never that precise; I just twist the setscrew on my Oryx TC irons until they work right! "Silver solder" comes in a variety of grades, the ones with the lowest melting points are ArgoSwift and EasyFlo2 which melt at 600-610C (1100-1130F, that's a dull red heat). EasyFlo2 is 42% silver, 17% copper, 16% zinc, and 25% cadmium. Most engineering silver solders are silver+brass based like this. A few are silver-bronze (bronze being an alloy of copper and tin). The "silver-loaded" solder Tony and others mentioned is a soft solder containing 62% tin, 36% lead, and 2% silver. It has a melting point of 179C (354F) and a recommended bit temperature of 300-310C (570-590F). Other silver/tin/lead solders like Comsol (I bet Tony has come across that) and LM5 are high-melting point soft solders, with a high lead content. I've seen them used for fusible resistors and the like. I expect this is at least four times as much as most of you ever wanted to know about that silvery-grey stuff that holds the components on... -- Pete Peter Turnbull Dept. of Computer Science University of York