Many types of solder are available today, such as acid-core, silver, rosin-core and aluminum solder. What kind should I use for building antennas and radio equipment? Why?
From test question: T7D08
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First of all, acid-core solder is never used for electronics any more, that just isn't what it's for. I think it's still used for plumbing or other soldering where there aren't sensitive components involved.
Second, aluminum solder isn't a thing. The best I can find is that there's some solder specifically for soldering aluminum to other stuff, but you shouldn't use that for electronics soldering either.
By silver solder, I can only assume you mean lead-free solder, which also contains silver. That's fine, as is standard lead-tin solder. Rosin-core solder can be either tin-lead or lead-free, it just has a core of flux which helps to remove the oxidization on the surface of components for better soldering.
I know this is an old thread but I thought I'd chime in anyway.
Lead-free solder is used for plumbing since the early eighties, because you don't want lead on contact with potable water.
For electronics, the danger from soldering is from inhaling the flux smoke. The temperatures used aren't high enough to vaporize the lead, so there is minimal lead exposure from soldering.
So, for electronics leaded solder is my preference unless I want to build something that is sold into the EU, where it is prohibited.
The best solder for Amateur and hobby use is eutectic solder, which solidifies without crystallizing regardless of the speed of cooling down. This eliminates so-called cold solder joints, which can sometimes appear to be solid, but may make poor electrical connection.
Traditionally, eutectic solder was made of 63% tin and 37% lead, and is easy to use because it has a very low melting point, but laws are tightening to eliminate lead, which is poisonous, from all electronics. An example replacement is made of Tin-Silver-Copper alloy.