Some years ago when I was a Materials Engineer for Hewlett Packard, solder was one of my categories.
The purpose of flux is to "reduce" (eat away) the oxide coating on the copper so the solder can stick to it and also as a wetting agent to reduce the surface tension of the molten solder and to prevent oxygen from contacting the metal while soldering is taking place. There are three main types: Acid flux is the type used by plumbers for soldering pipes and should never be used for electronic work. Water-soluble flux is OK for electronic work only if it is washed off after the soldering job is complete. Rosin flux is the type normally used for hand-soldering electronic assemblies. It comes in various activity levels. Fully-activated (RA) flux works the best but is the most corrosive. Mildly-activated (RMA) flux is what is usually used. RMA flux does not need to be removed after soldering - the rosin seals in the activator where it can do no harm. However, if you do decide to remove it using alcohol or some other solvent, it is very important that it be removed completely. If you leave a film of left-over flux on the board it can cause long-term corrosion. Lead-free solder is all the rage now as it is required in Europe for environmental reasons. However, standard tin-lead solder is easier to use (lower melting temperature) and cheaper so I recommend it for hobby use. If you're worried about lead poisoning, wash your hands after use. Plumbers use a 50/50 tin-lead alloy. It is cheaper than electronic solder and has a temperature range where it is kind of "pasty", neither solid or liquid, which is useful when soldering pipes. For electronics use, you want 60/40 or 63/37. The 63/37 is "eutectic" which means there is no "pasty" range - it changes directly from solid to liquid at 360 degF (182 degC). The 60/40 alloy has a slightly higher melting point but is so close to eutectic that you won't notice the difference. The 0.048-inch diameter solder is fine for soldering through-hole components, but would be a bit awkward for surface-mount parts, especially the small ones. Your 0.028-inch/0.7-mm stuff would probably work better. I use 0.014-inch (0.36 mm) rosin-core solder which is adequate even for fine-pitch ICs. Al N1AL On Wed, 2008-04-02 at 00:15, David Ferrington, M0XDF wrote: > Well, all this talk of mods got me wondering and I liek some opinions > from this group - I KNOW some of you know a lot about solder. > > Resin core solder - thats not acid flux is it? > > Most of my solder came from my time with electronics in defense over > 30 years ago. > > I have 2 reels that are labelled: > > Ersin non-corrosive flux made by Ersin Multicore Solder and has 362 > Flux, DTD599, BS441, Type 1 written on the label. > This is 18 SWG, .048", 1.2mm (this is a time when you got told every > which way) > > The other roll is only 2 years old, is from RS (that's Radio Spares in > UK) but made by Multicore and supposedly low temp (melts at 183 C). > It has 'Crystal 400 60/40 Tin/Lead EN29453, S-Sn60Pb40E on it and is > 0.7mm > > So I'm guessing that the later would be preferable for use on the K3 > and on my XV144 which I'm about to start. > 73 de M0XDF, K3 #174 _______________________________________________ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
