Use of Sn91Zn9 Lead-Free Solder in Resistance Element Soldering Technology

Resistance Element Soldering (RES) is one of the new methods of joining dissimilar materials by resistance heating using an element. Sn60Pb40 solder, which has been used for decades in tin smithing and the electrical industry, has already been tested for joining galvanized steel sheet with thermoplastic using RES. However, legal restrictions are currently moving towards prohibiting the use of lead in mass production. For this reason, the possibility of replacing Sn60Pb40 solder with Sn91Zn9 lead-free solder was verified. The results showed that with an appropriate choice of flux and resistance heating conditions, it is possible to replace Sn60Pb40 solder with Sn91Zn9 solder when joining galvanized steel sheet with thermoplastic using RES. With a suitable heat input during soldering, good conditions were achieved for wetting the base material with molten solder with a sufficient volume of remelted solder in the core of the Cu/Sn91Zn9 bimetallic element. The strength of the soldered joint made at a heat input of 901 J was measured at the level of 94% of the strength of Sn91Zn9 solder.