Page 174 - Make Your Own PCBs with EAGLE from Schematic Designs to Finished Boards

Traditionally, solder (Figure 7-4) has been made from tin and lead. Usually, this is in the proportion
of 60 percent tin and 40 percent lead. The solder looks like a solid metal wire, but actually will
normally have a core of flux rosin that helps the lead to flow when it melts. Legislation on the use of
toxic chemicals has resulted in a reduction in the use of lead-based solder in favor of lead-free

solder.

FIGURE 7-4 A reel of 0.7-mm tin, lead solder.

This type of solder is an alloy of tin, silver, copper, and small amounts of other metals. It looks
like lead solder and still has a rosin core but is somewhat brittle and has a melting temperature of
about 200°C (392°F) versus about 190°C (374°F) for leaded solder.
The differences do not end there. Many people find lead-free solder much harder to work with. It
does not flow as easily as lead solder.

Lead solder is still widely available, and unless you are producing a product that you are going to
sell, it is really a matter of personal preference which type of solder you use. I know electronics
enthusiasts who have a roll of lead-free solder that they use most of the time and then a roll of the

“good stuff” (lead solder) that they use when they have something tricky to solder.
Whatever type of solder you use, you will have another choice to make: the gauge of the solder
you buy. Two popular sizes are 0.7 and 1.2 mm in diameter. Use 0.7-mm or similar solder when