Definitions (cont.): Soldering
Share This Copy. Soldering circuit boards is both a science and an art. Mostly art. Practice on defunct circuit boards, first. Skinny solder is for delicate work and medium soder is for general soldering. Most electronic soldering uses 60 percent lead 40 percent tin rosin core solder. Not to be used are acid core solder 50/50 plumbing solder, or salvaged solder drips. 15 watt soldering irons are for delicate electronics, 25 watts for general use, and some connections need a big iron such as you would heat up over a gas stove or propane torch. Dual wattage irons are handy and professional. NOT to be used are soldering guns, which produce heat by passing a heavy current through the tip. Soldering guns are recognised by the tip being a bent rod with two electrical connections. Voltage is transferred to delicate electronics, which burns them out. Do not exceed 500 degrees F. 60/40 solder melts at 440 f. Check temperature by touching solder to tip. It should rapidly start to melt smoothly without much smoking. Before soldering begins, the face of the circuit board, component leads, the solder and the tip of the iron are cleaned with fine steel wool, even if they appear bright and shiny, and the tip of the iron is reshined every two minutes. Before any soldering is started, each component is placed into it's holes, leads are bent neatly, insulators and ferrite mini donuts are held captive, component standoffs and clearances are observed, and spacing problems are solved.
When soldering, the copper foil side of the board faces up (gravity), and for transistors, a thoroughly water soaked piece of paper towel protects the soldered leads, from passing high temperatures, into the transistor's heart. The solder joint is brought to a hot uniform melt, as quickly as possible, then cooled, without moving or spattering the joint. Leads are then clipped short, and the solder side is washed clean, with rubbing alcohol. Completed boards are sometimes coated with varnish, for weather protection. Soldering newbies need to beware of burns, and misplacing the iron, and teachers should watch students closely. If you burn yourself, immediately lick the burn, before you even feel it, to cool it off. It's a good practice to use safety glasses when doing close soldering.
