Solder composition and electronic board

Abstract

A solder composition of the invention contains solder powders and a flux composition. The flux composition contains (A) a resin and (B) an activator. The (B) component contains (B1) an organic acid, and (B2) a pyridine compound represented by a formula (1) below. A chlorine concentration is 900 mass ppm or less, a bromine concentration is 900 mass ppm or less, an iodine concentration is 900 mass ppm or less and a total halogen concentration is 1500 mass ppm or less in the solder composition. ##STR00001##
In the formula (1), X.sup.1, X.sup.2 and X.sup.3 are the same or different, each of X.sup.1, X.sup.2 and X.sup.3 representing a hydrogen atom, a hydroxyl group, a methyl group, an ethyl group or a propyl group, and all of X.sup.1, X.sup.2 and X.sup.3 are not simultaneously hydrogen atoms.

Claims

1. A solder composition comprising: solder powders; and a flux composition, wherein the flux composition comprises (A) a resin and (B) an activator, the (B) component comprises (B1) an organic acid and (B2) a pyridine compound represented by a formula (1) below, (B2) the pyridine compound being symmetry in the structure, the (B2) component is at least one selected from the group consisting of 4-hydroxypyridine, 2,6-dihydroxypyridine, 3,5-dihydroxypyridine, 2,4,6-trihydroxypyridine, 3,4,5-trihydroxypyridine, 2,6-dimethyl-4-hydroxypyridine, 3,5-dimethyl-4-hydroxypyridine, 2,6-diethyl-4-hydroxypyridine, 3,5-diethyl-4-hydroxypyridine, 2,6-dipropyl-4-hydroxypyridine and 3,5-dipropyl-4-hydroxypyridine, and a chlorine concentration is 900 mass ppm or less, a bromine concentration is 900 mass ppm or less, an iodine concentration is 900 mass ppm or less, and a total halogen concentration is 1500 mass ppm or less in the solder composition, ##STR00005## where, in the formula (1), X.sup.1, X.sup.2 and X.sup.3 are the same or different, each of X.sup.1, X.sup.2 and X.sup.3 representing a hydrogen atom, a hydroxyl group, a methyl group, an ethyl group or a propyl group, and all of X.sup.1, X.sup.2 and X.sup.3 are not simultaneously hydrogen atoms.

2. The solder composition according to claim 1, wherein a mass ratio (B1/B2) of a content of the (B1) component to a content of the (B2) component ranges from 1/9 to 9/1.

3. The solder composition according to claim 1, wherein a mass ratio (B1/B2) of a content of the (B1) component to a content of the (B2) component ranges from 6/4 to 4/6.

4. The solder composition according to claim 1, wherein the (B1) component is at least one organic acid selected from the group consisting of dicarboxylic acids having 3 to 22 carbon atoms and tricarboxylic acids having 3 to 22 carbon atoms.

5. The solder composition according to claim 1, wherein the (B1) component is at least one organic acid selected from the group consisting of dicarboxylic acids having 4 to 7 carbon atoms and tricarboxylic acids having 6 to 9 carbon atoms.

6. The solder composition according to claim 1, wherein the (B1) component is at least one organic acid selected from the group consisting of succinic acid, glutaric acid, adipic acid, pimelic acid, propane tricarboxylic acid, hexane tricarboxylic acid, cyclohexane tricarboxylic acid, and benzene tricarboxylic acid.

7. The solder composition according to claim 1, wherein the (B1) component is at least one organic acid selected from the group consisting of succinic acid, propane tricarboxylic acid, and dimer acid.

8. The solder composition according to claim 1, wherein the (B1) component is at least one organic acid selected from the group consisting of succinic acid, and propane tricarboxylic acid.

9. The solder composition according to claim 1, wherein the (B2) component is at least one selected from the group consisting of 4-hydroxypyridine and 2,6-dimethyl-4-hydroxypyridine.

10. The solder composition according to claim 1, wherein the (B2) component is 4-hydroxypyridine.

11. The solder composition according to claim 1, wherein a content of the (B1) component is in a range from 0.1 mass % to 25 mass % with respect to 100 mass % of the flux composition, and a content of the (B2) component is in a range from 0.1 mass % to 10 mass % with respect to 100 mass % of the flux composition.

12. The solder composition according to claim 1, wherein the (A) component is (A1) a rosin-based resin, and the flux composition further comprises (C) a solvent and (D) a thixotropic agent.

13. The solder composition according to claim 12, wherein the (C) component is at least one solvent selected from the group consisting of diethylene glycol, dipropylene glycol, triethylene glycol, hexylene glycol, hexyl diglycol, 1,5-pentanediol, methyl carbitol, butyl carbitol, 2-ethylhexyl diglycol, octanediol, phenyl glycol, diethylene glycol monohexylether, tetraethylene glycol dimethylether, and dibutyl maleic acid.

14. The solder composition according to claim 12, wherein the (D) component is at least one thixotropic agent selected from the group consisting of hardened castor oil, polyamines, polyamides, bisamides, dibenzylidene sorbitol, kaolin, colloidal silica, organic bentonite and glass frit.

15. The solder composition according to claim 12, wherein the (C) component comprises hexyl diglycol, and the (D) component comprises polyamides.

16. The solder composition according to claim 1, wherein the (A) component is (A2) a thermosetting resin, and the flux composition further comprises (D) a thixotropic agent.

17. The solder composition according to claim 1, wherein the solder powders are made of a SnAgCu solder alloy.

18. The solder composition according to claim 1, wherein no halogen is present in the flux composition except for inevitable impurities.

19. The solder composition according to claim 1, wherein a chlorine concentration is 300 mass ppm or less, a bromine concentration is 300 mass ppm or less, an iodine concentration is 300 mass ppm or less, and a total halogen concentration is 500 mass ppm or less in the solder composition.

20. An electronic board comprising a soldered portion using the solder composition according to claim 1.

21. The solder composition according to claim 1, wherein the (B2) component is 2,6-dimethyl-4-hydroxypyridine.

22. The solder composition according to claim 1, wherein the (B2) component is at least one selected from the group consisting of 2,6-dihydroxypyridine, 3,5-dihydroxypyridine, 2,4,6-trihydroxypyridine, 3,4,5-trihydroxypyridine, 2,6-dimethyl-4-hydroxypyridine, 3,5-dimethyl-4-hydroxypyridine, 2,6-diethyl-4-hydroxypyridine, 3,5-diethyl-4-hydroxypyridine, 2,6-dipropyl-4-hydroxypyridine and 3,5-dipropyl-4-hydroxypyridine.

Description

EXAMPLES

(1) Next, the invention will be further described in detail based on Examples and Comparatives. However, it should be understood that the scope of the invention is by no means limited by the Examples and Comparatives.

(2) Materials used in the Examples and Comparatives are as Follows.

(3) (A1) Component

(4) rosin-based resin: modified hydrogenated rosin, trade name PINECRYSTAL KE-604, manufactured by ARAKAWA CHEMICAL INDUSTRIES, LTD.
(B1) Component Organic acid A: succinic acid Organic acid B: propane tricarboxylic acid Organic acid C: dimer acid, trade name UNIDYME14, manufactured by Arizona Chemical Ltd.
(B2) Component pyridine compound: 4-hydroxypyridine
(C) Component Solvent: hexyl diglycol
(D) Component Thixotropic agent: polyamide thixotropic agent, trade name TALEN, manufactured by Kyoeisha Chemical Co., Ltd
(E) Component Solder Powders: Particle diameter distribution ranging from 20 to 38 m (average particle diameter being approximately 30 m), solder melting point ranging from 217 to 220 degrees C., composition of solder being Sn/Ag3.0/Cu0.5
Other Components Amine A: n-octyl amine Amine B: 2-phenyl-4-methylimidazole, trade name 2P4MZ, manufactured by SHIKOKU CHEMICALS CORPORATION Amine C: 2-hydroxypyridine Halogen activator: trans-2,3-dibromo-2-butene-1,4-diol

Example 1

(5) A flux composition was prepared by mixing 55 parts by mass of rosin-based resin, 2.5 parts by mass of the organic acid A, 2.5 parts by mass of pyridine compound, 7 parts by mass of thixotropic agent, and 33 parts by mass of solvent. Further, 11 parts by mass of flux composition and 89 parts by mass of solder powders (100 parts by mass in total) were mixed to prepare a solder composition.

Examples 2 to 5 and Comparatives 1 to 4

(6) A flux composition and a solder composition were prepared in the same manner as in Example 1 except that composition of the materials was changed as shown in Table 1.

(7) Evaluation of Solder Composition

(8) The solder compositions were evaluated as follows (in terms of halogen-free, capillary balls, solder spreadability (albata), preservation stability, and leak touch). The obtained results are shown in Table 1.

(9) (1) Halogen-Free

(10) Halogen concentration (unit: mass ppm) in each of the solder compositions was calculated based on the components of the solder composition and contents thereof. Then, the degree of halogen-free was evaluated and categorized as follows based on the value of the halogen concentration. A: Halogen concentration being 1500 mass ppm or less. C: Halogen concentration being more than 1500 mass ppm.
(2) Capillary Balls

(11) A test board was prepared as follows. On an evaluation board (SP-TDC manufactured by Tamura Corporation) on which chip components (1608 chips) can be mounted, the solder composition was printed using a metal mask of 120 m thick. Further, 60 chip components were mounted on the evaluation board and the solder composition was melted in a reflow furnace (manufactured by Tamura Corporation) for soldering. The reflow process was conducted under the conditions of: preheat temperature ranging from 150 to 180 degrees C. (for 60 seconds), a period with a temperature at 220 degrees C. or more being 50 seconds, and a peak temperature being 245 degrees C. The obtained test board was observed through a magnifier to count the solder balls (per a chip: capillary balls) generated on sides of each of the chip components.

(12) Then, the capillary balls were evaluated and categorized as follows based on the number of the solder balls (number per a chip). A: The number of solder balls per a chip being 1 or less. B: The number of solder balls per a chip being 1 or more and less than 5. C: The number of solder balls per a chip being 5 or more.
(3) Solder Spreadability (Albata) 0.30 g0.03 g of the solder composition was placed on an albata board (30 mm30 mm0.3 mm (thick)) and was heated on a hot plate at 240 degrees C. for 30 seconds. The height of the spread solder was measured using a micrometer and a spread rate (Sr) was calculated according to a formula (F1) below. An average of these operations repeated five times was calculated to obtain the spread rate of the test piece.
Sr=(DH)/D100(F1)
D=1.24V.sup.1/3(F2) Sr: Spread rate (%) H: Height of spread solder (mm) D: Diameter (mm) of the solder, which was deemed to be a sphere V: Mass/density of solder used in the test

(13) Then, the solder spreadability was evaluated and categorized as follows based on the results of the spread rate (Sr). A: Spread rate of 70% or more. C: Spread rate of less than 70%.
(4) Preservation Stability

(14) Initially, viscosity of each of the solder compositions (samples) was measured. The samples were then put into hermetic containers, which were immersed in a constant-temperature bath whose temperature was set at 30 degrees C. to be preserved for 14 days. Subsequently, the viscosity of each of the preserved samples was measured. A difference (21) between a pre-preservation viscosity value (1) and the viscosity value (2) after being preserved for 14 days at 30 degrees C. was calculated. It should be noted that the viscosity was measured through a spiral method (measurement temperature: 25 degrees C., rotation speed: 10 rpm).

(15) Then, the preservation stability was evaluated and categorized as follows based on the results of the difference in viscosity values. A: The difference in the viscosity values being more than 50 Pa.Math.s and less than 50 Pa.Math.s. B: The difference in the viscosity values being more than 100 Pa.Math.s and 50 Pa.Math.s or less, or 50 Pa.Math.s or more and less than 100 Pa.Math.s. C: The difference in viscosity values being 100 Pa.Math.s or less or 100 Pa.Math.s or more.

(16) TABLE-US-00001 TABLE 1 Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 Comp. 1 Comp. 2 Comp. 3 Comp. 4 Components (A) (A1) Rosin-Based Resin 55.0 51.0 55.0 55.0 55.0 55.0 55.0 55.0 53.0 of Flux (B) (B1) Organic Acid A 2.5 1.5 3.5 2.5 2.5 2.5 Composition Organic Acid B 2.5 (parts by Organic Acid C 5.0 mass) (B2) Pyridine Compound 2.5 2.5 2.5 3.5 1.5 Other Amine A 2.5 Components Amine B 2.5 Amine C 2.5 Halogen Activator 5.0 (C) Solvent 33.0 36.5 30.5 33.0 33.0 33.0 33.0 33.0 34.0 (D) Thixotropic Agent 7.0 7.5 7.0 7.0 7.0 7.0 7.0 7.0 8.0 Flux Composition 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 in Total Components of Flux Composition 11 11 11 11 11 11 11 11 11 Solder Composition (E) Solder Powders 89 89 89 89 89 89 89 89 89 (mass %) Solder Composition 100 100 100 100 100 100 100 100 100 in Total Evaluation (1) Halogen-Free A A A A A A A A C Results (2) Capillary Balls A A B A B B B C B (3) Solder Spreadability A A A A A A A A A (4) Preservation Stability A A A A A C C C B

(17) As is clearly shown in the results in Table 1, the solder compositions of the invention (Examples 1 to 5) exhibit excellent results in terms of all of halogen-free, capillary balls, solder spreadability (albata) and preservation stability, showing sufficient solder-melting property and preservation stability. In contrast, it is found that the preservation stability of each of the solder compositions of Comparatives 1 to 3 is insufficient. From the above, it is surprisingly found that the use of the specific pyridine compound (e.g. 4-hydroxypyridine), which is selected from among a large number of amines, in combination with the organic acid unexpectedly does not result in deterioration in preservation stability. It should be noted that 2-hydroxypyridine used in Comparative 3 is a compound having a pyridine ring and a hydroxyl group just like 4-hydroxypyridine used in Examples 1 to 5. Nevertheless, it is found that the results of capillary balls of the solder composition of Comparative 3 are insufficient.

(18) Further, the results of halogen-free of the solder composition of Comparative 4 are insufficient. From the above, it is found that the solder composition of the invention can provide sufficient solder-melting property and preservation stability even when the solder composition is halogen-free.