What Soldering actually is?
Soldering is a process by which two items are joined together by melting a filler metal with low melting point and pouring liquid metal onto a joint , is a process through which many important metal working processes today, from manufacturing electronics to installing plumbing pipes.
For a long period of time, much of the soldering process in use by various industries relied on the use of tin-lead based solders, the health and environment impact of which led to passage of legislation like the 1986 safe drinking water act. Lead based solders were major contributor of of lead which leaches into water supplies and such solder pipes have contributed to health crises such as the high level of lead in drinking water. High level of lead in drinking water and indirectly into human body can lead to developmental issues in in children as well as high blood pressure and kidney damage in adults.
Importance of Soldering and problem with lead
For many years, lead-based materials were the most popular choice for soldering in electronics applications for a few reasons. Lead-based solders were cost-effective, have a low melting point, high strength and good resistance to corrosion. Although the body of knowledge on the poisonous effects of lead on humans and the environment grew throughout the 20th century, there were no lead-free solders which had similar characteristics to lead-based solders available to replace the use of lead in electronics products.
In the world of electronics, soldering is a crucial step in tiny electronic component within a device in such a way that allow an electric current to flow, allowing the electronic function of the device to take place. Circuits can be created on solderless breadboard but without solders, a circuit will deteriorate over the course of few days. Although soldering is also used to join pipes in plumbing action, the type of solder used is different, solder used for electronic application is a much a smaller gauge than a plumbing solders and plumbing solders uses an acid flux component which is corrosive for electronic application.
First Approach made
In late 1990, the U.S. microelectronics industry was taking step to develop lead-free solution for soldering electronic component. Electronic standard development in 1997 by the Association connecting electronic industries began the electronic industry’s move away from the use of lead based solder in response to legislative and regulatory pressure. Internationally, the regulatory environment surrounding the use of lead based solders, in electronic manufacturing ramped up through the first decade.
An Error discovery
Anderson’s discovery actually arose out of an error which he saw in tin-silver-copper ternary diagrams in use at the time. Although the melting temperature of the Sn-Ag-Cu alloy was 30°F higher than lead-based alloys, it was still much lower than previously thought and at a low enough temperature that typical electronic components for circuits and equipment could tolerate. Anderson and his team also experimented with improving mechanical and temperature stability characteristics in the solder by doping the material with nickel, zinc and/or aluminum.
The Advent of Lead-Free Solder
The research of Anderson and his team led to the issue of U.S. Patent No. 5527628, titled Pb-Free Sn-Ag-Cu Ternary Eutectic Solder, issued on June 18th, 1996. It claimed a lead-free electrical conductor solder consisting of essentially about 3.5 to 7.7 weight percent silver, about 1 to 4 weight percent copper and at least about 89 weight percent tin to promote formation of intermetallic compounds that improve solder strength and fatigue resistance. The patent also notes that the invented solder is cost-competitive with lead-based solders and are readily available for high volume use.
U.S. Patent No. 5527628
The present invention provides a Pb-free solder that satisfies these needs. In particular, the present invention provides a Pb-free solder comprising a heretofore unknown ternary eutectic composition consisting essentially of about 93.6 weight % Sn-about 4.7 weight % Ag-about 1.7 weight % Cu having a eutectic melting temperature of about 217.degree. C. and variants of the ternary eutectic composition. In the variants of the ternary eutectic composition in accordance with the invention, the relative concentrations of Sn, Ag, and Cu deviate from the ternary eutectic composition to provide a controlled melting temperature range (liquid-solid “mushy” zone) relative to the eutectic melting temperature while providing an advantageous microstructure including beta Sn phase and at least two different intermetallic compounds distributed in the beta Su phase, one compound including Cu and Sn and another compound including Ag and Sn. Preferably, the solder components are adjusted relative to one another to provide a melting temperature range that extends no more than 15.degree. C. above the ternary eutectic melting temperature.
Conclusion
With royalties for this patent alone reaching into the tens of millions, it’s clear the work of Anderson and the research team at the University of Iowa has had tremendous value for industry. This is interesting given the fact that this invention seems very similar to the one declared patent-ineligible by the U.S. Supreme Court in Mayo Collaborative Services v. Prometheus Laboratories, where the court found that a patent covering a less-invasive blood test for diagnosing fetal conditions was invalid because it incorporated a law of nature.
The future development of lead-free solders is expected to improve performance for expanded consumer applications, including automotive electronics and more rugged electronic devices. As of his 2017 induction into the National Inventors Hall of Fame, Anderson held 39 patents. In 2010, he was the recipient of the Iowa State University Award for Achievement in Intellectual Property. In 2015, Anderson was recognized as a Fellow of The Mineral, Metals and Materials Society.
