Page 184 - Programming the Photon Getting Started With the Internet of Things

solder it usually comes in two types: leaded and lead free. When solder was first around, it
was generally made up of an alloy using both lead and tin; since then it has become known
that lead can be quite harmful when exposed to in large amounts. Lead was used in solder

because it has a great low melting point and it created really good solder joints, which
produced a highly reliable circuit board. Unfortunately, in the European Union leaded
solder is not Restriction of Hazardous Substances (RoHS) compliant, and this restricts the
use of leaded solder in electrical equipment and hence why lead-free solder is commonly

used. Lead-free solder is usually made up of other metals such as silver and copper. Lead-
free solder does come with its own downfalls—for example, it has a much higher melting
point because of the tin content and as such requires a high-powered soldering iron.

Lead-free solder often contains a flux core, which helps give the same quality effect as
leaded solder. Flux is a chemical agent that aids in flow and creates much better contacts

when finished.

Figure A.5 Solder spool.