Abstract
The goal of this research is to study the applicability of the diffusion boriding process as a high-temperature thermochemical heat treatment to enhance the lifetime of steel selective soldering tools. The main purpose of the work is to discuss the behavior of double-phase (FeB/Fe2B) iron-boride coating on the surface of different steels (DC04, C45, CK60, and C105U) against the stationary SAC309 lead-free solder liquid alloy. The boride coating was formed on the surface of the steel samples through the powder pack boriding technique. The microstructure of the formed layer was examined by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The borided samples were first cut in half and then immersed into a stationary SAC309 lead-free solder liquid alloy (Sn–3Ag–0.9Cu) for 40 days. Microstructure examinations were performed by SEM with energy-dispersive spectroscopy and an elemental distribution map after the dissolution test. Excessive dissolution/corrosion of the original steel surface was observed at the steel/SAC interfaces, leading also to the formation of Fe–Sn intermetallic phases. This was found to be the major reason for the failure of selective soldering tools made of steel. On the contrary, no dissolution and no intermetallic compounds were observed at the FeB/SAC and at the Fe2B/SAC interfaces; as a result, the thicknesses of the FeB and Fe2B phases remained the same during the 40-day dissolution tests. Thus, it was concluded that both FeB and Fe2B phases show excellent resistance against the aggressive liquid solder alloy. The results of the dissolution tests show a good agreement with the thermodynamic calculations.
Highlights
THE degradation of selective soldering tools has increased significantly with the application of lead-free solders
Formation of the intermetallic compound phases, FeSn and FeSn2, between iron and tin takes place according to the iron-tin equilibrium phase diagram at the soldering temperature.[5]
The phases formed near the surface of the borided steels were identified by X-ray diffraction (XRD) phase analysis
Summary
THE degradation of selective soldering tools has increased significantly with the application of lead-free solders. These solders comply with the European Union directives—no lead content—the new tin-based solders damage the iron base material of the tool and an intermetallic compound phase is formed in Manuscript submitted August 17, 2021; accepted November 30, 2021. During the renewal of the soldering tools, the intermetallic FeSn2 layer is removed from the surface of the tool and a nickel coating is formed, which is well wetted by the lead-free solder. Nickel forms an intermetallic compound with the tin and tool failure occurs.[4,14] this solution is not a complete or long-term one for extending the life of selective soldering tools. Because soldering companies are secretive regarding handling of these problems within the industry, there is hardly any literature in this field of science
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
