The adhesion strength of a lead-free solder hot-dipped on copper substrate

Eutectic Sn-Zn-AZ solder alloy was used [composition: 91Sn-9(5Al-Zn)] to in vestigate the effects of dipping parameters such as the temperature, rate a nd time dipping on the adhesion strength between Bolder and substrate using dimethylammonium chloride (DMAHCl) flux. The optimum conditions for the hi ghest adhesion strength(about 8 MPa) were determined as dipping at 350 degr ees C, and a rate of 10.8 similar to 11.8 mm/s for 5 similar to 7.5 min. A poor solder coating was obtained as dipped at 250 degrees C. Some defects b y non-wetting were found as dipped at a slow rate (slower than 8.2 mm/s). Q uite different from the most tin-based solders for copper substrate, gamma- Cu5Zn8 intermetallic compound particles were found by x-ray diffraction (XR D) analysis at the interface of solder and substrate as dipped at 300 degre es C after pull-off test by etching out the unreacted solder layer. The mor phology of the intermetallic compound formed was observed by scanning elect ron microscopy (SEM). The elements of Al (near Cu), Zn (near Sn) are enrich ed at the interface of solder and copper substrate as determined by the lin e scanning and mapping analysis.