Flux and Solder Paste

A flux, comprising:

• 5 wt % or more and 20 wt % or less of any one of a dimer acid, a trimer acid, a hydrogenated dimer acid obtained by hydrogenating the dimer acid, and a hydrogenated trimer acid obtained by hydrogenating the trimer acid, or, in total, of two or more of a dimer acid, a trimer acid, a hydrogenated dimer acid obtained by hydrogenating the dimer acid, and a hydrogenated trimer acid obtained by hydrogenating the trimer acid;
• 30 wt % or more and 70 wt % or less of a thermosetting resin;
• and
• 3 wt % or more and 15 wt % or less of an amine,
• wherein for evaluation of solder wettability,
• a first sample is prepared by printing the flux with a thickness of 0.1 mm on a Cu-OSP electrode and placing a solder ball having a 0.3 mm diameter thereon and then heating from 25° C. to 250° C. in an N2 atmosphere at a first temperature rising rate of 1° C./sec using a first reflow furnace, and
• the first sample is visually checked and the solder is wet,
• wherein the solder ball of the first sample comprises a composition of 3.0 wt % of Ag, 0.5 wt % of Cu, and a balance of Sn,
• wherein for evaluation of a void,
• a second sample is prepared by applying the flux onto a glass plate and placing a ball grid array thereon and then heating from 25° C. to 250° C. in an N2 atmosphere at a second temperature rising rate of 1° C./sec using a second reflow furnace, and
• the second sample is observed from the back side of the glass plate and the void occurrence rate is 50% or less,
• wherein the ball grid array of the second sample comprises a size of 10 mm on one side and 192 solder bumps, wherein each solder bump comprises a pitch of 0.5 mm;
• a diameter of 0.3 mm;
• and a composition of 3.0 wt % of Ag, 0.5 wt % of Cu, and a balance of Sn.

A solder paste, comprising:

• solder powder;
• and
• a flux, the flux comprising:
• 5 wt % or more and 20 wt % or less of any one of a dimer acid, a trimer acid, a hydrogenated dimer acid obtained by hydrogenating the dimer acid, and a hydrogenated trimer acid obtained by hydrogenating the trimer acid, or, in total, of two or more of a dimer acid, a trimer acid, a hydrogenated dimer acid obtained by hydrogenating the dimer acid, and a hydrogenated trimer acid obtained by hydrogenating the trimer acid;
• 30 wt % or more and 70 wt % or less of a thermosetting resin;
• and
• 3 wt % or more and 15 wt % or less of an amine,
• wherein for evaluation of solder wettability,
• a first sample is prepared by printing the flux with a thickness of 0.1 mm on a Cu-OSP electrode and placing a solder ball having a 0.3 mm diameter thereon and then heating from 25° C. to 250° C. in an N2 atmosphere at a first temperature rising rate of 1° C./sec using a first reflow furnace, and
• the first sample is visually checked and the solder is wet,
• wherein the solder ball of the first sample comprises a composition of 3.0 wt % of Ag, 0.5 wt % of Cu, and a balance of Sn,
• wherein for evaluation of a void,
• a second sample is prepared by applying the flux onto a glass plate and placing a ball grid array thereon and then heating from 25° C. to 250° C. in an N2 atmosphere at a second temperature rising rate of 1° C./sec using a second reflow furnace, and
• the second sample is observed from the back side of the glass plate and the void occurrence rate is 50% or less,
• wherein the ball grid array of the second sample comprises a size of 10 mm on one side and 192 solder bumps, wherein each solder bump comprises a pitch of 0.5 mm;
• a diameter of 0.3 mm;
• and a composition of 3.0 wt % of Ag, 0.5 wt % of Cu, and a balance of Sn.