July, 2019
www.us-
tech.com
SN100C Achieves 20 Years of Reliable Service
By Keith Howell, Technical Director, Nihon Superior USA T
he implementation of the European Union’s RoHS directive mandated the use of lead-free solders in the electronics industry by 2006. However, five years before, Japan’s appliance recy-
cling waste electronic and electrical equipment (WEEE) regulation went into effect. This regula- tion covered home electrical goods, air condition- ers, refrigerators,
freezers, TVs, washing
machines, and clothes dryers. A new category of waste type, a category that
includes precious metals, as well as such toxic sub- stances as lead (Pb) and polybrominated biphenyls (PBBs) was included in the WEEE regulation. For the solution to replace tin-lead solder, the industry looked to lead-free alloys, including tin-copper (SnCu). But, the SnCu did not perform
as expected as a eutectic solder. The industry was forced to research improvements to turn SnCu into a user-friendly solder.
The Birth of SN100C In 1998, Tetsuro Nishimura, then
Nihon Superior’s technical manager, now CEO, in partnership with the audio and video division of Panasonic Corporation extensively investigated the causes of the poor performance of SnCu. Nishimura identified nucleation of the second phase of the eutectic
Cu6Sn5 as the problem. Adding a trace amount of nickel,
0.05 percent, was discovered as the most effective method of enhancing the performance of the solder. During solidification, nickel works by facilitat- ing the nucleation of the intermetallic
Cu6Sn5, making it possible to solidify as a eutectic, such as tin-lead solder. With the microalloying of nickel
to SnCu, SN100C was born. During the development, a germanium (Ge) addition was identified as the most effective way to control the oxidation that generates dross. Nishimura was awarded “Best
Inventor” by SMT Today magazine during the 2015 SMTA International conference and exhibition in recogni- tion throughout the electronics industry as the inventor of SN100C and the pioneer of microalloyed sol- ders.
This award recognizes an indi-
vidual or team whose innovations have not only addressed a need and solved a problem, but also have been used to drive improved efficiency, pro- ductivity and performance within the electronics manufacturing industry. “The small amount of nickel is
like the effect of salt in a dish. A small amount has no taste, no effect, but a large amount overpowers the dish, ruining the taste. A good dish requires the right amount of salt, just as SN100C has the right amount of nickel. On the other hand, germani- um is like pepper, which gives a good taste, but the amount may be varied,” says Nishimura.
Commercial Debut The first commercial use in mass
production for the newly developed SN100C solder was in 1999 for a Panasonic VCR. Since then, SN100C has been widely accepted and has gained a reputation as a reliable solder. The reliability of SN100C has
been proven in a wide range of elec- tronics assembly products, from appliances to industrial, automotive and aerospace. The alloy delivers a silver-free stable microstructure that
SnCu (left) and SN100C (right).
can accommodate the long-term and impact strains to which a solder joint can be subjected. The eutectic character of SN100C alloy and the associated high fluidity provides faster wetting and increased spreadability over SAC305, which is beneficial in wave and hand soldering applications, as well as in reflow. Due to the significant increase in eco-
friendly hybrid and electric vehicles, the demand for solder joints to resist thermal fatigue is also growing. Vehicles are often exposed to extreme temperatures during service and the solder must function in a range of environments.
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