Lead Free Solder

Lead has been used for a variety of things for a long time. One of the most detrimental uses it had to humanity was as the pipes that the Ancient Romans used for their aqueducts. Today we know that lead, even in small quantities, can be detrimental if not downright dangerous to a person’s health. In this same vein, lead has been used as an important part of solders. To increase the safety of people working regularly with these materials there has been a move to make lead free solders compulsory in industries where they are used. While the purpose is certainly well motivated, there are certain problems with lead free solders that are making the transition rather hard.

A solder is a fusible metallic alloy with a very low melting point – relatively speaking in terms of other metals – that can be used to join metallic surfaces. It is used a lot in plumbing and with recent innovations is also an integral part of all sorts of electronics. The most prevalent solder that was used was tin and lead solder that was mixed to such a degree that it is known as a eutectic mixture. This mixture has two important properties that make it an ideal solder. It has a low melting point at about 361.4º Fahrenheit (183º Celsius) and that this point is actually where it melts at precisely and not a range where it might melt. This solder was often used in plumbing with a higher lead content as it allowed the solder to be smeared to make the pipes more watertight. When the true repercussions of lead became known, however, this was phased out pretty quickly in favor of lead free solders.

A lead free solder is practically what the name claims it to be. These lead replacements can be a number of materials but the most prevalent ones today are bismuth, indium, zinc, copper, tin, silver, antimony, or other metals in varying amounts. The problems with these lead free solders, however, is that they invariably have a much higher melting point. This means that production and manufacturing in electronics has to be reevaluated and changed to make allowance for this higher melting point. The joints formed by these solders are also not always as strong which means they may have a higher maintenance. ‘Tin Whiskers’ are another effect of some lead free solders where the tin crystals start to grow out of the solder. These ‘whiskers’ can eventually bridge the gaps between electric circuits causing a short circuit or malfunction.