A Conversion-Electron Mssbauer Study of Tin-Based Compounds Formed During Pads Treatment (Plasma-Assisted Dry Soldering) of a Solder Foil

We have used conversionelectron Mössbauer spectroscopy (CEMS) to examine the surfaces of solder foils treated in a plasma assisted dry soldering (PADS) system which has been developed1 to convert surface oxides to more desirable fluorides in order to protect the solder surface prior to assembly and to eliminate the need for flux during the soldering process. CEMS samples only the outer 1 μm of a solder foil and this, coupled with the fortuitous fact2 that Mössbauer spectroscopy is 10–20 times more sensitive to oxides and fluorides than to the metallic form of solder, means that surface layers of oxides and fluorides as thin as 10 nm can be detected and chemically identified. We have followed the evolution of surface layers produced in PADS treatments ranging from 7 minutes to several hours. Our results show that fully treated foils contain surface layers of SnF2 and Sn2F6. Partially treated foils also contain some SnO2 and perhaps a small amount of SnO. No Sn2OF2 or SnF4 was produced during any portion of the PADS treatment cycle.

The Effects of Ar-Bombardment on the Dissolution and Reprecipitation of Carbonitrides Implanted Into Low Carbon Steel

ABSTRACTThe effects of Ar post-bombardment on the dissolution and reprecipitation of carbonitrides present in implanted 1020 low carbon steel are investigated using conversion electron Mössbauer spectroscopy (CEMS). The results are compared with similar experiments where samples of the same steel were post-bombarded with He. The experimental data show that the Ar is more efficient in the dissolution of precipitates and also more efficient in the precipitate retention at 450 °C, for the same peak concentration.