CHAPTER 21 ■ SOLDERING EQUIPMENTTable 21-2 lists suppliers for liquid flux. Paste flux stays in place, but liquid flux leaves fewer residues.
I prefer liquid flux.
Flux only removes oxides. Solder and flux won’t work if the metal is dirty. Contaminants prevent heat
and solder from reaching the bare metal, causing intermittent or failed connections. Before soldering, clean
dirty contacts with a scrubbing pad or fine sandpaper and then wash to remove all chemicals, oils, or grime,
thus exposing clean bare metal that bonds well.
Soldering Iron
A soldering iron heats up at its tip to transfer heat to the metal joint being soldered. Choose a low-wattage
soldering iron (25 W to 40 W). Inexpensive stand-alone stick irons or soldering pencil-shaped models run as
low as $10.
Don’t use a soldering gun on circuit boards. The gun’s thicker tip is obtrusive and the more substantial
heat can damage small electrical components. Soldering guns are designed for water pipes, stained-glass
windows, and larger parts.
Most soldering irons have tip temperatures from 600°F to 900°F (about 315°C and 480°C). In practice,
temperatures between 700°F and 800°F (about 370°C and 425°C) are preferred. More expensive soldering
irons have adjustable temperatures and have displays that show the current tip temperature (see Figure 21-4).
Table 21-2. Suppliers of Liquid Flux
Supplier Part Number Price Description
Electronix Express 060722 $6.95 “No-Clean” Flux Pen Formula 951
Electronix Express 25835-4OZ $8.75 Liquid Rosin Flux No-Clean
Digi-Key CW8400 $15.23 Circuit Works No-Clean Liquid Flux Pen
Mouser 590-835-100ML $8.58 Liquid flux 125 mL
Figure 21-3. Liquid flux (left) and paste flux (right)