Allen KA5N wrote: Most of the time, except for looks, rosin from good solders does no harm. You can do more harm than good if your cleaning isn't done properly.
--------------- Allen makes an good point and he identifies a misconception that comes up regularly - that rosin harms the board over time. The argument is that since it's capable of removing the oxidation from metals to promote soldering, it will continue to attack the metals as long as it's left on the board. That is not true. Elecraft recommends solder such as Kester #44. Here's what the data sheet from Kester says: "...Throughout its many years of wide usage, 44 Rosin Flux has produced many billions of soldered connections. In all these billions of solder joints, involving the most delicate and critical of electrical and electronic components, there has never been an authentic instance of corrosion by the flux residue under normal conditions of use...." The full data sheet is available on line (http://tinyurl.com/agzxs) Still, many builders do not like the appearance of an obvious amount of rosin on the finished joints. The easiest, safest (in terms of avoiding damage to your circuit board) way to avoid excess rosin is to use a the right diameter solder, certainly nothing bigger than 0.031" for circuit board work. I prefer smaller sizes such as 0.02" or 0.025". That helps avoid getting too much solder on the joints too. Too much solder on the pads is an on-going problem for many builders. Remember, the Elecraft boards do NOT require "fillets" of solder standing above the solder pad. Indeed, they can be a problem. On some kits (KX1 and T1 tuner, for example) the clearance between boards is so small that fillets can cause shorts or prevent the boards seating correctly. On rigs like the K2 where clearances are not so critical solder fillets have caused grief by allowing shorts to occur on the component side of the board when solder flows through the hole. One common place this causes trouble is under the crystals. Excess solder can flow through and collect around the pin under the crystal where it can't be seen. A little too much solder and the fillet under the crystal will touch the case, shorting out the signal path. It's really tough to find those! Bottom line ------------------------ Use the solder recommended by Elecraft. Use small diameters (0.031" or less) for pcb work to avoid excess flux or solder. Avoid producing fillets or "bumps" above the solder pad. In most cases this won't hurt, but the right amount of solder fills the hole in the pad without making a fillet. Flux won't hurt the board. And ALWAYS WASH YOUR HANDS after handling solder to remove minute lead residue from your skin. The residue can migrate through your skin over time or be transferred to food when you eat. Ron AC7AC _______________________________________________ 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
