Lead-Free Solder Vs. Lead Solder
Lead-free solder is becoming more common, replacing the traditional solder made from lead and tin. The lead in solder allowed it to melt at a low temperature, and the tin gave the connection more strength. However, concerns have arisen over the use of lead in consumer products and the safety of people who work with it. In 2006 the European Union banned lead in products sold there. Others have raised concerns about the disposal of lead-containing products in landfills. The use of lead solder for plumbing was discontinued in the 1980s.
To make lead-free solder that worked as well as lead solder, manufacturers combined tin with copper and sometimes silver. These new alloys have higher melting temperatures than lead/tin solders. Traditional solder melts at about 190 degrees C, while the newer solder usually melts at 220 degrees C or higher.
Eutectic Or Not
The combination of tin and lead was considered ideal because it was a eutectic mixture. This designation means that the combination of the two metals melts at a lower temperature than either metal alone. The electronics industry has not been able to find another combination that is truly eutectic. It did manage to come up with lead-free solders that work quite well.
Traditional solder has been in radios, computers, TVs, toys and many other products. Because its properties were well-known and it was reliable, the industry resisted the change to lead-free solder for years. Lead-free solder hasn't been tested as much. Some fear that lead-free solder won't last as long and products using it may fail. The answer to these questions will only arrive as time passes and lead-free solder becomes the standard.
Of course, the reason for switching is that lead is a poison. It can build up in the body due to many small exposures over many years. Lead has been removed from paint and gasoline. Solder is one of the last common products that still contains it. Lead can enter your body through your skin. You can also inhale or ingest it.
In an industrial setting, lead may be in the air or on surfaces that workers touch. Even for a hobbyist, the lead from solder can be in the smoke, and handling the solder may present a health risk. Anyone who works with solder regularly must consider these risks. Lead is especially dangerous for young children.
The Switch to Lead-Free Solder
Lead/tin solder has many desirable qualities for electronics construction, but the winds of change are blowing. Any industry that uses solder on a large-scale basis is likely to change to lead-free soon, if they haven't already. Hobbyists may not be able to buy lead/tin solder soon.
As with any change, some resist because they are comfortable doing things the old way. But when it comes to the health and safety of human beings, the change to a safer product is desirable and probably inevitable.