Flux and solder paste

Abstract

A flux in which solder wettability can be maintained and with which it is possible to suppress the amount of residue after soldering and realize low residue. This flux includes 65-99 wt % of a solvent, and also includes 1-13 wt % of at least one acid selected form a dimer acid that is a reaction product of oleic acid and linoleic acid; a trimer acid that is a reaction product of oleic acid and linoleic acid; a hydrogenated dimer acid obtained by hydrogenating dimer acid that is a reaction product of oleic acid and linoleic acid; and a hydrogenated trimer acid obtained by hydrogenating a trimer acid that is a reaction product of oleic acid and linoleic acid.

Claims

1. A flux comprising: 1 wt % or more and 13 wt % or less of at least one acid selected from, a trimer acid which is a reaction product of oleic acid and linoleic acid, a hydrogenated dimer acid obtained by hydrogenating a dimer acid which is a reaction product of oleic acid and linoleic acid, and a hydrogenated trimer acid obtained by hydrogenating the trimer acid which is a reaction product of oleic acid and linoleic acid; and 65 wt % or more and 99 wt % or less of a solvent, wherein a weight after 10 mg of the flux is heated from 25° C. to 250° C. at a temperature rising rate of 1° C./sec in an N.sub.2 atmosphere is 15% or less of the weight before heating.

2. The flux according to claim 1, comprising 85 wt % or more and 95 wt % or less of a solvent.

3. The flux according to claim 1, further comprising: 0 wt % or more and 5 wt % or less of a different organic acid 0 wt % or more and 10.0 wt % or less of rosin; 0 wt % or more and 5 wt % or less of an amine; 0 wt % or more and 5 wt % or less of an organohalogen compound; and 0 wt % or more and 1 wt % or less of an amine hydrohalide.

4. The flux according to claim 2, further comprising: 0 wt % or more and 5 wt % or less of a different organic acid; 0 wt % or more and 10.0 wt % or less of rosin 0 wt % or more and 5 wt % or less of an organohalogen compound; and 0 wt % or more and 1 wt % or less of an amine hydrohalide.

5. The flux according to claim 1, wherein the flux is free of rosin.

6. The flux according to claim 5, further comprising: 0 wt % or more and 5 wt % or less of a different organic acid; 0 wt % or more and 5 wt % or less of an amine 0 wt % or more and 5 wt % or less of an organohalogen compound; and 0 wt % or more and 1 wt % or less of an amine hydrohalide.

7. The flux according to claim 1, further comprising at least one additional ingredient selected from the group consisting of a base material, a surfactant, a thixotropic agent, and an antioxidant.

8. The flux according to claim 3, further comprising at least one additional ingredient selected from the group consisting of a base material, a surfactant, a thixotropic agent, and an antioxidant.

9. The flux according to claim 5, further comprising at least one additional ingredient selected from the group consisting of a base material, a surfactant, a thixotropic agent, and an antioxidant.

10. The flux according to claim 6, further comprising at least one additional ingredient selected from the group consisting of a base material, a surfactant, a thixotropic agent, and an antioxidant.

11. The flux according to claim 1, wherein the flux further comprises a dimer acid which is a reaction product of oleic acid and linoleic acid.

12. The flux according to claim 1, wherein the solvent comprises at least one of isobornyl cyclohexanol and 2,4-diethyl-1,5-pentanediol.

13. A flux comprising: 1 wt % or more and 13 wt % or less of at least one acid selected from a dimer acid which is a reaction product of oleic acid and linoleic acid, a trimer acid which is a reaction product of oleic acid and linoleic acid, a hydrogenated dimer acid obtained by hydrogenating the dimer acid which is a reaction product of oleic acid and linoleic acid, and a hydrogenated trimer acid obtained by hydrogenating the trimer acid which is a reaction product of oleic acid and linoleic acid; and 65 wt % or more and 99 wt % or less of a solvent, wherein a weight after 10 mg of the flux is heated from 25° C. to 250° C. at a temperature rising rate of 1° C./sec in an N.sub.2 atmosphere is 15% or less of the weight before heating, wherein the solvent comprises at least one of isobornyl cyclohexanol and 2,4-diethyl-1,5-pentanediol.

14. A solder paste comprising: solder powder; and a flux, the flux comprising: 1 wt % or more and 13 wt % or less of at least one acid selected from a trimer acid which is a reaction product of oleic acid and linoleic acid, a hydrogenated dimer acid obtained by hydrogenating a dimer acid which is a reaction product of oleic acid and linoleic acid, and hydrogenated trimer acid obtained by hydrogenating the trimer acid which is a reaction product of oleic acid and linoleic acid; and 65 wt % or more and 99 wt % or less of a solvent, wherein a weight after 10 mg of the flux is heated from 25° C. to 250° C. at a temperature rising rate of 1° C./sec in an N.sub.2 atmosphere is 15% or less of the weight before heating.

15. The solder paste according to claim 14, wherein the flux further comprises 0 wt % or more and 5 wt % or less of a different organic acid; 0 wt % or more and 10.0 wt % or less of rosin; 0 wt % or more and 5 wt % or less of an amine; 0 wt % or more and 5 wt % or less of an organohalogen compound; and 0 wt % or more and 1 wt % or less of an amine hydrohalide.

16. The solder paste according to claim 14, wherein the flux is free of rosin.

17. The solder paste according to claim 16, wherein the flux further comprises 0 wt % or more and 5 wt % or less of a different organic acid; 0 wt % or more and 5 wt % or less of an amine; 0 wt % or more and 5 wt % or less of an organohalogen compound; and 0 wt % or more and 1 wt % or less of an amine hydrohalide.

18. The solder paste according to claim 15, wherein the flux further comprises at least one additional ingredient selected from the group consisting of a base material, a surfactant, a thixotropic agent, and an antioxidant.

Description

EXECUTED EXAMPLES

(1) Fluxes of Executed Examples and Comparison Examples were prepared with the compositions shown in Tables 1 and 2 below to verify the solder wet spreadability and the residue amount. The composition rates in Tables 1 and 2 are expressed in wt (weight) % when the total amount of each flux is 100.

(2) <Evaluation of Solder Wet Spreadability>

(3) (1) Verification Method

(4) Each of the fluxes of the Executed Examples and the Comparison Examples was printed on a Cu plate with a diameter φ of 0.34 mm and a thickness t=0.2 mm. Then, solder balls made of solder containing 3 wt % of Ag, 0.5 wt % of Cu, and the balance Sn (Sn-3Ag-0.5Cu) were mounted. The solder balls each have a diameter φ of 0.3 mm. The number of targets to be evaluated is 50 in each Executed Example and each Comparison Example. The test objects made as described above were heated up to from 25° C. to 250° C. in a N.sub.2 atmosphere at a temperature rising rate of 5° C./sec using a reflow furnace. Then, the wet spreading diameter of the molten solder was measured. (2) Criterion for Determination

(5) ∘: The wet spreading diameter was 350 μm or more.

(6) x: The wet spreading diameter was less than 350 μm.

(7) <Evaluation of Residue Amount>

(8) (1) Verification Method

(9) As a test evaluation method by the TG method (thermogravimetry), an aluminum pan was filled with 10 mg of each of the fluxes of Executed Examples and Comparison Examples, and TGD9600 manufactured by ULVAC was used for heating up to from 25° C. to 250° C. in a N.sub.2 atmosphere at a temperature rising rate of 1° C./sec. It was measured whether the weight of each of the fluxes after heating arrived at 15% or less of the weight before heating.

(10) (2) Criterion for Determination

(11) ∘: The weight was 15% or less of the weight before heating.

(12) x: The weight was greater than 15% of the weight before heating.

(13) The flux whose weight after heating is 15% or less of the weight before heating can be said to be a flux that does not require washing after reflow because the components in the flux are sufficiently volatilized by heating. It can be said that, in the flux whose weight was greater than 15% of the weight before heating, the components in the flux were insufficiently volatilized. If the components in the flux are insufficiently volatilized, resulting in a large amount of residues, it may cause poor conductivity due to moisture absorption or the like.

(14) <Comprehensive Evaluation>

(15) ∘: All of the wet spreading evaluation and the residue amount evaluation were ∘.

(16) x: Either or both of the wet spreading evaluation and the residue amount evaluation was/were ×.

(17) TABLE-US-00001 TABLE 1 Number of Executed Executed Executed Executed Executed Executed Material carbon atoms Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Organic Dimer which is reaction Dimer acid 36 5 2.5 acid product of oleic acid Hydrogenated 36 5 2.5 and linoleic acid dimer acid Trimer which is reaction Trimer acid 54 5 2.5 product of oleic acid Hydrogenated 54 5 2.5 and linoleic acid trimer acid Different organic acid Malonic acid 3 Succinic acid 4 Glutaric acid 5 Adipic acid 12 Rosin Hydrogenated rosin — Amine 2-Phenylimidazole — Halogen Amine hydrohalide Diphenylguanidine-HBr — Organohalogen Trans-2,3-dibromo-2- — compound butene-1,4-diol Solvent Isobornyl cyclohexanol — 75 75 75 75 75 75 2,4-Diethyl-1,5- — pentanediol 1,3-Butylene glycol — 20 20 20 20 20 20 Wet spreading evaluation ○ ○ ○ ○ ○ ○ Residue amount evaluation ○ ○ ○ ○ ○ ○ Comprehensive evaluation ○ ○ ○ ○ ○ ○ Number of Executed Executed Executed Executed Material carbon atoms Example 7 Example 8 Example 9 Example 10 Organic Dimer which is reaction Dimer acid 36 5 13 5 5 acid product of oleic acid Hydrogenated 36 and linoleic acid dimer acid Trimer which is reaction Trimer acid 54 product of oleic acid Hydrogenated 54 and linoleic acid trimer acid Different organic acid Malonic acid 3 5 Succinic acid 4 5 Glutaric acid 5 Adipic acid 12 Rosin Hydrogenated rosin — Amine 2-Phenylimidazole — Halogen Amine hydrohalide Diphenylguanidine-HBr — Organohalogen Trans-2,3-dibromo-2- — compound butene-1,4-diol Solvent Isobornyl cyclohexanol — 67 70 70 2,4-Diethyl-1,5- — 75 pentanediol 1,3-Butylene glycol — 20 20 20 20 Wet spreading evaluation ○ ○ ○ ○ Residue amount evaluation ○ ○ ○ ○ Comprehensive evaluation ○ ○ ○ ○

(18) TABLE-US-00002 TABLE 2 Number of Executed Executed Executed Executed Executed Material carbon atoms Example 11 Example 12 Example 13 Example 14 Example 15 Organic Dimer which is reaction Dimer acid 36 5 5 5 5 1 acid product of oleic acid Hydrogenated 36 and linoleic acid dimer acid Trimer which is reaction Trimer acid 54 product of oleic acid Hydrogenated 54 and linoleic acid trimer acid Different organic acid Malonic acid 3 5 Succinic acid 4 Glutaric acid 5 5 Adipic acid 12 5 Rosin Hydrogenated rosin — 5 Amine 2-Phenylimidazole — 5 Halogen Amine hydrohalide Diphenylguanidine-HBr — 1 Organohalogen Trans-2,3-dibromo-2- — compound butene-1,4-diol Solvent Isobornyl cyclohexanol — 70 70 70 70 73 2,4-Diethyl-1,5 — pentanediol 1,3-Butylene glycol — 20 20 20 20 20 Wet spreading evaluation ○ ○ ○ ○ ○ Residue amount evaluation ○ ○ ○ ○ ○ Comprehensive evaluation ○ ○ ○ ○ ○ Number of Executed Executed Executed Executed Material carbon atoms Example 16 Example 1 Example 2 Example 3 Organic Dimer which is reaction Dimer acid 36 5 0 10 0.1 acid product of oleic acid Hydrogenated 36 and linoleic acid dimer acid Trimer which is reaction Trimer acid 54 product of oleic acid Hydrogenated 54 and linoleic acid trimer acid Different organic acid Malonic acid 3 5 Succinic acid 4 Glutaric acid 5 Adipic acid 12 Rosin Hydrogenated rosin — 40 Amine 2-Phenylimidazole — Halogen Amine hydrohalide Diphenylguanidine-HBr — Organohalogen Trans-2,3-dibromo-2- — 5 compound butene-1,4-diol Solvent Isobornyl cyclohexanol — 70 75 20 79.9 2,4-Diethyl-1,5 — pentanediol 1,3-Butylene glycol — 20 20 30 20 Wet spreading evaluation ○ x ○ x Residue amount evaluation ○ ○ x ○ Comprehensive evaluation ○ x x x

(19) The fluxes of the Executed Examples and the Comparison Examples were verified. The flux containing dimer acid with 36 carbon atoms which was a reaction product of oleic acid and linoleic acid in an amount of 5 wt % which fell within the range defined in the present invention; and isobornyl cyclohexanol in an amount of 75 wt % and 1,3-butylene glycol in an amount of 20 wt % as solvents, the total amount of the solvents being 95 wt % which fell within the range defined in the present invention, as indicated in Executed Example 1, provided a solder wet spreading diameter of 350 μm or more and good solder wet spreading, so that a sufficient solder wet spreading effect was obtained. Also, when the residue amount was 15 wt % or less, a sufficient effect of suppressing the residue amount to attain low residue was obtained. In addition, due to the inclusion of isobornyl cyclohexanol as a solvent, the viscosity of the flux at normal temperature before heating could be increased to such an extent that the solder balls can be retained.

(20) Also, the flux containing hydrogenated dimer acid obtained by adding hydrogen to (hydrogenating) dimer acid with 36 carbon atoms which was a reaction product of oleic acid and linoleic acid, in an amount of 5 wt % which fell within the range defined in the present invention; and isobornyl cyclohexanol in an amount of 75 wt % and 1,3-butylene glycol in an amount of 20 wt % as solvents, the total amount of the solvents being 95 wt % which fell within the range defined in the present invention, as indicated in Executed Example 2, provided a sufficient solder wet spreading effect. Further, a sufficient effect of suppressing the residue amount to attain low residue was obtained.

(21) Also, the flux containing trimer acid with 54 carbon atoms which was a reaction product of oleic acid and linoleic acid in an amount of 5 wt % which fell within the range defined in the present invention; and isobornyl cyclohexanol in an amount of 75 wt % and 1,3-butylene glycol in an amount of 20 wt % as solvents, the total amount of the solvents being 95 wt % which fell within the range defined in the present invention, as indicated in Executed Example 3, provided a sufficient solder wet spreading effect. Further, a sufficient effect of suppressing the residue amount to attain low residue was obtained.

(22) Also, the flux containing hydrogenated trimer acid obtained by adding hydrogen to (hydrogenating) trimer acid with 54 carbon atoms which was a reaction product of oleic acid and linoleic acid in an amount of 5 wt % which fell within the range defined in the present invention; and isobornyl cyclohexanol in an amount of 75 wt % and 1,3-butylene glycol in an amount of 20 wt % as solvents, the total amount of the solvents being 95 wt % which fell within the range defined in the present invention, as indicated in Executed Example 4, provided a sufficient solder wet spreading effect. Further, a sufficient effect of suppressing the residue amount to attain low residue was obtained.

(23) Also, the flux containing dimer acid with 36 carbon atoms which was a reaction product of oleic acid and linoleic acid in an amount of 2.5 wt % and trimer acid with 54 carbon atoms which was a reaction product of oleic acid and linoleic acid in an amount of 2.5 wt %, the total amount of the dimer acid and the trimer acid being 5 wt % which fell within the range defined in the present invention; and isobornyl cyclohexanol in an amount of 75 wt % and 1,3-butylene glycol in an amount of 20 wt % as solvents, the total amount of the solvents being 95 wt % which fell within the range defined in the present invention, as indicated in Executed Example 5, provided a sufficient solder wet spreading effect. Further, a sufficient effect of suppressing the residue amount to attain low residue was obtained.

(24) Also, the flux containing hydrogenated dimer acid obtained by adding hydrogen to (hydrogenating) dimer acid with 36 carbon atoms which was a reaction product of oleic acid and linoleic acid in an amount of 2.5 wt % and hydrogenated trimer acid obtained by adding hydrogen to (hydrogenating) trimer acid with 54 carbon atoms which was a reaction product of oleic acid and linoleic acid in an amount of 2.5 wt %, the total amount of the hydrogenated dimer acid and the hydrogenated trimer acid being 5 wt % which fell within the range defined in the present invention; and isobornyl cyclohexanol in an amount of 75 wt % and 1,3-butylene glycol in an amount of 20 wt % as solvents, the total amount of the solvents being 95 wt % which fell within the range defined in the present invention, as indicated in Executed Example 6, provided a sufficient solder wet spreading effect. Further, a sufficient effect of suppressing the residue amount to attain low residue was obtained.

(25) Also, the flux containing dimer acid with 36 carbon atoms which was a reaction product of oleic acid and linoleic acid in an amount of 5 wt % which fell within the range defined in the present invention; and 2,4-diethyl-1,5-pentanediol in an amount of 75 wt % and 1,3-butylene glycol in an amount of 20 wt % as solvents, the total amount of the solvents being 95 wt % which fell within the range defined in the present invention, as indicated in Executed Example 7, provided a sufficient solder wet spreading effect. Further, a sufficient effect of suppressing the residue amount to attain low residue was obtained. In addition, due to the inclusion of 2,4-diethyl-1,5-pentanediol as a solvent, the viscosity of the flux at normal temperature before heating could be increased to such an extent that the solder balls can be retained.

(26) Also, the flux containing dimer acid with 36 carbon atoms which was a reaction product of oleic acid and linoleic acid, in an amount of 13 wt % which fell within the range defined in the present invention; and isobornyl cyclohexanol in an amount of 67 wt % and 1,3-butylene glycol in an amount of 20 wt % as solvents, the total amount of the solvents being 87 wt % which fell within the range defined in the present invention, as indicated in Executed Example 8, provided a sufficient solder wet spreading effect. Further, a sufficient effect of suppressing the residue amount to attain low residue was obtained.

(27) Also, the flux containing dimer acid with 36 carbon atoms which was a reaction product of oleic acid and linoleic acid in an amount of 5 wt % which fell within the range defined in the present invention; further malonic acid with 3 carbon atoms in an amount of 5 wt % which fell within the range defined in the present invention as an organic acid; and isobornyl cyclohexanol in an amount of 70 wt % and 1,3-butylene glycol in an amount of 20 wt % as solvents, the total amount of the solvents being 90 wt % which fell within the range defined in the present invention, as indicated in Executed Example 9, provided a sufficient solder wet spreading effect. Further, a sufficient effect of suppressing the residue amount to attain low residue was obtained.

(28) Also, the flux containing dimer acid with 36 carbon atoms which was a reaction product of oleic acid and linoleic acid in an amount of 5 wt % which fell within the range defined in the present invention; further succinic acid with 4 carbon atoms in an amount of 5 wt % which fell within the range defined in the present invention as an organic acid; and isobornyl cyclohexanol in an amount of 70 wt % and 1,3-butylene glycol in an amount of 20 wt % as solvents, the total amount of the solvents being 90 wt % which fell within the range defined in the present invention, as indicated in Executed Example 10, provided a sufficient solder wet spreading effect. Further, a sufficient effect of suppressing the residue amount to attain low residue was obtained.

(29) Also, the flux containing dimer acid with 36 carbon atoms which was a reaction product of oleic acid and linoleic acid in an amount of 5 wt % which fell within the range defined in the present invention; further glutaric acid with 5 carbon atoms in an amount of 5 wt % which fell within the range defined in the present invention as an organic acid; and isobornyl cyclohexanol in an amount of 70 wt % and 1,3-butylene glycol in an amount of 20 wt % as solvents, the total amount of the solvents being 90 wt % which fell within the range defined in the present invention, as indicated in Executed Example 11, provided a sufficient solder wet spreading effect. Further, a sufficient effect of suppressing the residue amount to attain low residue was obtained.

(30) Also, the flux containing dimer acid with 36 carbon atoms which was a reaction product of oleic acid and linoleic acid in an amount of 5 wt % which fell within the range defined in the present invention; further adipic acid with 12 carbon atoms in an amount of 5 wt % which fell within the range defined in the present invention as an organic acid; and isobornyl cyclohexanol in an amount of 70 wt % and 1,3-butylene glycol in an amount of 20 wt % as solvents, the total amount of the solvents being 90 wt % which fell within the range defined in the present invention, as indicated in Executed Example 12, provided a sufficient solder wet spreading effect. Further, a sufficient effect of suppressing the residue amount to attain low residue was obtained.

(31) Also, the flux containing dimer acid with 36 carbon atoms which was a reaction product of oleic acid and linoleic acid in an amount of 5 wt % which fell within the range defined in the present invention and hydrogenated rosin as rosin in an amount of 5 wt % which fell within the range defined in the present invention; and isobornyl cyclohexanol in an amount of 70 wt % and 1,3-butylene glycol in an amount of 20 wt % as solvents, the total amount of the solvents being 90 wt % which fell within the range defined in the present invention, as indicated in Executed Example 13, provided a sufficient solder wet spreading effect. Further, in the case where the residue amount was 15 wt % or less, even if rosin was contained, a sufficient effect of suppressing the residue amount to attain low residue was obtained.

(32) Also, the flux containing dimer acid with 36 carbon atoms which was a reaction product of oleic acid and linoleic acid in an amount of 5 wt % which fell within the range defined in the present invention and 2-phenylimidazole as an amine in an amount of 5 wt % which fell within the range defined in the present invention; and isobornyl cyclohexanol in an amount of 70 wt % and 1,3-butylene glycol in an amount of 20 wt % as solvents, the total amount of the solvents being 90 wt % which fell within the range defined in the present invention, as indicated in Executed Example 14, provided a sufficient solder wet spreading effect. Further, a sufficient effect of suppressing the residue amount to attain low residue was obtained.

(33) Also, the flux containing dimer acid with 36 carbon atoms which was a reaction product of oleic acid and linoleic acid in an amount of 1 wt % which fell within the range defined in the present invention; further malonic acid with 3 carbon atoms in an amount of 5 wt % which fell within the range defined in the present invention as an organic acid; an amine hydrohalide in an amount of 1 wt % which fell within the range defined in the present invention as a halogen; and isobornyl cyclohexanol in an amount of 73 wt % and 1,3-butylene glycol in an amount of 20 wt % as solvents, the total amount of the solvents being 93 wt % which fell within the range defined in the present invention, as indicated in Executed Example 15, provided a sufficient solder wet spreading effect. Further, a sufficient effect of suppressing the residue amount to attain low residue was obtained.

(34) Also, the flux containing dimer acid with 36 carbon atoms which was a reaction product of oleic acid and linoleic acid in an amount of 5 wt % which fell within the range defined in the present invention; further an organohalogen compound in an amount of 5 wt % which fell within the range defined in the present invention as a halogen; and isobornyl cyclohexanol in an amount of 70 wt % and 1,3-butylene glycol in an amount of 20 wt % as solvents, the total amount of the solvents being 90 wt % which fell within the range defined in the present invention, as indicated in Executed Example 16, provided a sufficient solder wet spreading effect. Further, a sufficient effect of suppressing the residue amount to attain low residue was obtained.

(35) On the other hand, as shown in Comparison Example 1, the flux containing no dimer acid which was a reaction product of oleic acid and linoleic acid, trimer acid which was a reaction product of oleic acid and linoleic acid, hydrogenated dimer acid obtained by adding hydrogen to (hydrogenating) the dimer acid which was a reaction product of oleic acid and linoleic acid or hydrogenated trimer acid obtained by adding hydrogen to (hydrogenating) the trimer acid which was a reaction product of oleic acid and linoleic acid, and containing malonic acid with 3 carbon atoms in an amount of 5 wt % which fell within the range defined in the invention as an organic acid; isobornyl cyclohexanol 75 wt % and 1,3-butylene glycol in an amount of 20 wt % as solvents, the total amount of the solvents being 95 wt % which fell within the range defined in the invention provided a low residue effect. However, even though an organic acid, other than the dimer acid which was a reaction product of oleic acid and linoleic acid, the trimer acid which was a reaction product of oleic acid and linoleic acid, the hydrogenated dimer acid obtained by adding hydrogen to (hydrogenating) the dimer acid which was a reaction product of oleic acid and linoleic acid and the hydrogenated trimer acid obtained by adding hydrogen to (hydrogenating) the trimer acid which was a reaction product of oleic acid and linoleic acid, was contained in the amount which fell within the range defined in the invention, the solder wet spreading diameter was less than 350 μm, and the solder did not wet-spread, so that the solder wet spreading effect was not obtained.

(36) As indicated in Comparison Example 2, even when containing dimer acid which was a reaction product of oleic acid and linoleic acid in an amount of 10 wt % which fell within the range defined in the present invention, the flux containing hydrogenated rosin as rosin in an amount of 40 wt % which fell beyond the range defined in the present invention; and isobornyl cyclohexanol in an amount of 20 wt % and 1,3-butylene glycol in an amount of 30 wt % as solvents, the total amount of the solvents being 50 wt % which fell below the range defined in the present invention, provided a solder wet spreading effect. However, the residue amount exceeded 15 wt % and could not be suppressed, so that the low residue effect was not obtained.

(37) As indicated in Comparison Example 3, even when containing dimer acid which was a reaction product of oleic acid and linoleic acid, the flux containing the dimer acid which was a reaction product of oleic acid and linoleic acid in an amount of 0.1 wt % which fell below the range defined in the present invention; and isobornyl cyclohexanol in an amount of 79.9 wt % and 1,3-butylene glycol in an amount of 20 wt % as solvents, the total amount of the solvents being 99.9 wt % which fell beyond the range defined in the present invention provided a low residue effect. However, the solder wet spreading diameter was less than 350 μm, and the solder did not wet spread, so that the solder wet-spreading effect was not obtained.

(38) In view of the above, the flux containing: 1 wt % or more and 13 wt % or less of any one of dimer acid which is a reaction product of oleic acid and linoleic acid, trimer acid which is a reaction product of oleic acid and linoleic acid, hydrogenated dimer acid obtained by adding hydrogen to (hydrogenating) the dimer acid which is a reaction product of oleic acid and linoleic acid, and hydrogenated trimer acid obtained by adding hydrogen to (hydrogenating) the trimer acid which is a reaction product of oleic acid and linoleic acid, or, in total, of two or more of dimer acid which is a reaction product of oleic acid and linoleic acid, trimer acid which is a reaction product of oleic acid and linoleic acid, hydrogenated dimer acid obtained by adding hydrogen to (hydrogenating) the dimer acid which is a reaction product of oleic acid and linoleic acid, and hydrogenated trimer acid obtained by adding hydrogen to (hydrogenating) the trimer acid which is a reaction product of oleic acid and linoleic acid; and 65 wt % or more and 99 wt % or less of a solvent provided good solder wet spreading. Further, the residue amount was suppressed.

(39) These effects were not inhibited even in the cases of incorporating a different organic acid, an amine, an amine hydrohalide, and an organohalogen compound as activators within the ranges defined in the present invention. Moreover, the effects were not inhibited even in the case of incorporating rosin within the range defined in the present invention.