Study the Suitability of Super Duplex Stainless Steel Used for the Application of Lead-free Soldering Equipment

by Huei- Sen Wang, Ken-Do Hsu, Mei-Hui Wu, Mau-Sheng Chiou

Publisher - I-Shou University Taiwan, China Steel Corporation Kaohsiung, Taiwan

Category - General Novel

To determine the suitability of the super duplex stainless steel (SDSS) used for the wave soldering container materials, SAF2507 SDSS and 304L stainless steel (conventional material for tin-lead soldering equipment) were immersed in a molten lead-free solder (Sn-3.0Ag-0.5Cu) and were exposed to a variety of immersion times and temperatures. The test samples were then, polished and examined using optical microscopy (OM), scanning electron microscopy (SEM) and semi-quantitative phase identification under an energy dispersive spectrometer (EDS) in order to investigate their microstructure evolution, corrosion depth, and failure types. Due to the higher Cr and Mo content of 2507 SDSS, the material passive film was strengthened; it was found that 2507 SDSS has better corrosion resistance to lead-free solder when compared to the 304L SS. If the test temperature was below 450o C, no obvious dissolution occurred for 2507 SDSS, whereas 304L SS exhibited severe dissolution. However, if the immersion temperature was higher than 450o C, the dissolution rates of 2507 SDSS increased significantly. Failure types for both materials were very similar and related to Sn diffusion, formation of reaction layer (RL),and finally dissolution. It was confirmed that the failure type for both materials is Liquid Metal Corrosion.

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