The ancient Egyptians produced lead and other important metals like gold and silver as early as 5000 BC. In the Roman era, lead was used for coinage, jewelry and other everyday items including the production of Lead pipes for the transportation of water. Remarkably, many of these water systems have been found virtually intact by modern day archeologists’. One important property of lead is its reluctance to breakdown over time. And as we will see later, that is also part of the problem.
Lead has many properties that make it attractive to countless industries, especially electronics. Lead is malleable; it has a low melting point, good electrical and thermal conductivity and is available in large quantities with a relatively low cost. As a common metal Lead has a mass density only rivaled by Gold. Lead is Heavy!
Lead’s widespread use in the electronics industry has been well documented as a shielding material for X-rays, RF and Audio, as well as a sound insulator in professional studio applications. Lead/acid batteries power our cars, and lead based solder compounds help form tight durable electrical connections.
Scientific data now shows the cumulative effect that Lead has on the bodies’ central nervous system and the formation of red blood cells. We also know that children are especially vulnerable to high toxicity levels and less likely to tolerate abuse. But although today the problems with Lead are no longer in doubt, clearly the questions about Lead’s affect on the environment and on those who come in contact with it, have been around nearly as long as Lead itself.
Remarkably as far back as the 1st century BC some Roman engineers suggested using clay instead of Lead pipes for water systems. This opinion was not based on a long-term government sponsored study, rather the engineers noticed that many lead workers (Plumbers) were getting sick and lacked vigor. They concluded quite rightly, that if the Plumbers were suffering from exposure to lead, others who came in contact with it would probably get sick as well! In spite of these revelations and other more recent warning signs Lead was continually used in many industries until recent times.
Great strides have been made in the health and safety field in the last few decades. As a result, a total ban on the use of Lead additives in paint and gasoline took effect in the 1970’s and ‘80s, and according to current Federal Law, Lead may no longer be used in or around drinking water or in the food industry. The effects of reducing lead pollution in the atmosphere and the water supply are beginning to pay off in the form of a cleaner environment.
In electronics manufacturing however, lead has continued to be used and will be around for some time to come. Lead of course, is one of the major components in solder. Many in the electronic industry have lobbied for exemptions to the banning of lead based solder products on various grounds and as of yet manufacturers have managed to stave off government regulation. Currently, electronics industry associations have begun to implement voluntary bans on the use of Lead with the goal of total elimination in the near future.
While the amount of Lead found in the circuitry of your average VCR or home stereo would at first thought appear to be insignificant, think about how many of these products get tossed away every year! All this stuff ends up in someone’s “back yard”, there to remain forever, like the Roman water pipes of old! Recycling used electronic gear to extract small amounts of Lead is extremely expensive. So, far better to eliminate the problem at the source by reducing or eliminating Lead during manufacture.
Most at Risk
As Technicians, most of our exposure to Lead comes when we repair or build equipment using Lead based solder. Sadly, even if there was an outright ban on any further use of lead solder in the electronics industry, many potential problems would remain whenever we repair older equipment that still has Lead solder forming the joints. In addition to all this, significant health problems can arise from simply breathing in the solder smoke. So, lets take a closer look at how solder is actually used in the electronic industry.
Soldering is the act of joining two metallic surfaces by the use of low melting point metal alloys. Modern electronic Solder is not made entirely of Lead but rather a mixture of elements. Because pure Lead has poor mechanical strength Tin is added to Lead to make the solder connection stronger. In addition, the Tin / Lead mixture has a lower melting point than using Lead alone, a prime consideration in electronics. 60/40 solder contains 60% Tin and 40% Lead.
To promote uniform solder flow (wetting), and also for joint cleaning, a Flux material is added to the 60/40 mix. The smoke that is released when solder is melted comes from heating the flux. For electronics a non-corrosive Rosin-resin flux is used. Although Rosin is a “natural” product made from pine trees (pine tar) its use along with other chemicals added to the flux make the solder fumes naturally acidic and potentially harmful to man. Even naturally produced products can be harmful!