Fig. 1. Sketch map of lap specimen

Fig. 2. Schematic of ultrasonic C-scan imaging detection

Fig. 3. Surface morphologies of solder joints in 1-9 groups. (a) Group 1; (b) group 2; (c) group 3; (d) group 4; (e) group 5; (f) group 6; (g) group 7; (h) group 8; (i) group 9

Fig. 4. Ultrasonic C-scanning images. (a) Group 1; (b) group 7; (c) group 9

Fig. 5. Ultrasonic A-scan signals of joints in different regions. (a) Nugget zone; (b) heat-affected zone; (c) adhesive zone;(d)cavity zone

Fig. 6. Interactive effect of laser power and welding time with peak loads

Fig. 7. Macro-morphologies of fatigue fractures. (a) Group 1; (b) group 7; (c) group 9

Fig. 8. Micro-morphologies of fatigue fractures. (a) Point A; (b) point B; (c) point C; (d) point D