Flux and solder paste using the same

Flux comprising:

• rosin-based resin;
• a solvent;
• a thixotropic agent;
• and
• an activator,
• wherein the thixotropic agent includes both of hardened castor oil and bisamide-based thixotropic agent,
• wherein the contents of the hardened castor oil are within the range of 4 wt. % or more and 10 wt. % or less based on the total weight of the flux and the contents of the bisamide-based thixotropic agent are within the range of 1 wt. % or more and 5 wt. % or less based on the total weight of the flux,
• wherein the contents of the thixotropic agent are within the range of 5 wt. % or more and 15 wt. % or less based on the total weight of the flux,
• wherein the activator includes hydrohalide, a halogenated aliphatic compound, and an imidazole compound, and the contents of a halogen in the flux are within the range of 9000 ppm or more and 50000 ppm or less, and
• wherein the flux exhibits hot slump properties according to the patterns shown in FIG. 6 in the hot slump test of JISZ3284-3 established in 2014, such that a minimum interval between the patterns not united after heating of 90 degrees C./3 min is evaluated to 1.2 mm or more.