Effect of temperature and flux concentration on soldering of base metal

The present study used the acoustic emission (AE) technique to evaluate int eractions among soldering temperature, flux treatment, and the resultant ul timate tensile strength (UTS). Scanning electron microscopy (SEM) was used to examine fracture surfaces of the solder joints. Specimens were cast from removable partial denture alloy and then placed in a jig with a gap distan ce of 1.0 mm. A high-frequency soldering machine with an optical pyrometer was used for soldering at 1150 degreesC and 1200 degreesC, respectively. Th e flux concentrations were 67% and 75%. The soldered specimens were subject ed to tensile test at a crosshead speed of 0.05 mm/min. During testing, aco ustic emissions in the frequency range of 100-1200 kHz were collected, filt ered; recorded, and processed by a sensing device. The results were analyse d by ANOVA and Tukey LSD test. UTS at different temperatures showed no sign ificant difference according to either mechanical or acoustic results. But in the 1200 degreesC group, the UTSs and AE counts showed significant diffe rences (P<0.05) at both flux concentrations. SEM showed that the 1200C grou p had better dendritic crystal structure than did the 1150<degrees>C group. In the 1200 degreesC group specimens with 67% flux had fewer nux inclusion bodies and dendritic crystals than did specimens with 75% flux. The 75% fl ux subgroup produced high-amplitude (60-70 dB) acoustic signals within the elastic deformation zone, while the 67% flux subgroup produced similar sign als within the plastic deformation zone, either beyond the 0.2% yield point or before fracture.