Fig. 1. Principle of circuit extrusion

Fig. 2. Morphologies of extruded conductive silver paste circuit. (a) Optical microscope image; (b) laser confocal image

Fig. 3. Principle of “hot airflow + laser” composite sintering. (a) Schematic; (b) temperature curve

Fig. 4. “Hot airflow + laser” composite sintering system. (a) Physical drawing; (b) structure

Fig. 5. Image of temperature field during sintering circuit

Fig. 6. Relationship between laser power and conductive circuit resistivity under different sintering processes

Fig. 7. Relationship between scanning speed and conductive circuit resistivity under different sintering processes

Fig. 8. Surface morphologies of circuit after laser sintering and circuit after “hot airflow + laser” composite sintering

Fig. 9. Relationship between laser power and cross-sectional area of circuit under two sintering processes

Fig. 10. Relationship between scanning speed and cross-sectional area of circuit under two sintering processes

Fig. 11. Surface morphologies and surface roughnesses of circuit after laser sintering and circuit after “hot airflow + laser” composite sintering. (a) SEM image of circuit after 10 W laser sintering; (b) SEM image of circuit after “200 ℃ hot airflow +10 W laser” composite sintering; (c) surface roughness of circuit after 10 W laser sintering; (d) surface roughness ofcircuit after “200 ℃ hot airflow +10 W laser” composite sintering

Fig. 12. Cross-sectional CT images of sintered circuits under two sintering processes

Fig. 13. Thermogravimetric analysis of nano-silver paste

Fig. 14. Schematics of “hot airflow + laser” composite sintering . (a) Schematic of hot airflow sintering; (b) schematic of laser sintering after hot airflow sintering

Fig. 15. Relationship between laser power and circuit resistance under two sintering processes

Fig. 16. Relationship between scanning speed and circuit resistance under two sintering processes

Fig. 17. Volume fractions of circuit pores under different sintering processes. (a) Effect of laser power on volume fraction of stomatal defect; (b) circuit after 6 W laser sintering; (c) circuit after “6 W laser +200 °C hot air flow” composite sintering

Fig. 18. SEM images of cross sections of circuits. (a) “200 ℃ hot air flow +2 W laser” composite sintering; (b) “200 ℃ hot air flow +6 W laser” composite sintering; (c) “200 ℃ hot air flow +10 W laser” composite sintering