JP6402148B2 - Solder composition and electronic substrate - Google Patents

Description

  The present invention relates to a solder composition and an electronic substrate.

The solder composition is a mixture obtained by kneading solder powder and a flux composition (such as a rosin resin, an activator, and a solvent) into a paste (for example, Patent Document 1). This solder composition is required to have solderability such as solder meltability and solder wettability (solder wettability), solder ball and void suppression, and printability.
On the other hand, with the diversification of functions of electronic devices, for example, lower surface electrode parts are used for LED mounting boards and PC motherboards. The bottom electrode component has a solder joint surface on the bottom surface side, but the bottom electrode component itself also has a solder joint. Therefore, a high melting point solder alloy is used for the solder joint portion of the lower surface electrode component itself, and a low melting point solder alloy is used for the lower surface side solder joint surface.

Japanese Patent No. 5782474

  When soldering the lower surface electrode component, since a solder alloy having a low melting point (for example, a melting point of 160 ° C. or lower) is used, the set temperature under reflow conditions is relatively low. As the reflow conditions, for example, the preheat temperature is set to 80 ° C. or higher and 100 ° C. or lower, and the peak temperature is set to 160 ° C. or higher and 180 ° C. or lower. In addition, the lower surface electrode component also has a feature that it is mounted so as to cover the printed portion of the solder composition, so that there is also a problem that the generated void is difficult to be removed. Therefore, from the viewpoint of suppressing solder balls and voids, it has been studied to use a low boiling point solvent as a solvent in the flux composition. However, it has been found that when a low-boiling solvent is used, the printability deteriorates when printing is resumed after leaving it for a long time (for example, 1 hour) after printing.

  Accordingly, an object of the present invention is to provide a solder composition capable of sufficiently suppressing solder balls and voids and having sufficient printability when soldering a lower surface electrode component, and an electronic substrate using the same. And

In order to solve the above problems, the present invention provides the following solder composition and electronic substrate.
The solder composition of the present invention comprises a solder composition comprising (A) a rosin resin, (B) an activator, and (C) a flux composition containing a solvent, and (D) a solder alloy having a melting point of 160 ° C. or lower. The component (C) includes a solvent (C1) having a melting point of 50 ° C. or higher and a boiling point of 240 ° C. or lower, and the solder alloy in the component (D) is Sn-Bi-based And at least one selected from the group consisting of Sn—Bi—Ag based solder alloys and Sn—Bi—Cu based solder alloys, wherein the blending amount of the component (A) is a flux composition The amount of the component (C1) is 3% by mass or more and 18% by mass or less with respect to 100% by mass of the flux composition. Is.

In the solder composition of the present invention, the component (A) preferably contains (A1) a hydrogenated product of an unsaturated organic acid-modified rosin.
In the solder composition of the present invention, the component (C) preferably further contains (C2) a solvent having a temperature of 25 ° C. and a boiling point of 240 ° C. or less.
In the solder composition of the present invention, the component (C1) is preferably 2,5-dimethylhexane-2,5-diol.
The solder composition of the present invention is preferably used for a bottom electrode part.
The electronic substrate of the present invention is characterized by including a soldering portion using the solder composition.

  ADVANTAGE OF THE INVENTION According to this invention, when soldering a lower surface electrode component, a solder composition which can fully suppress a solder ball and a void, and has sufficient printability, and an electronic substrate using the same can be provided.

  The solder composition of the present invention contains a flux composition described below and (D) solder powder described below.

[Flux composition]
First, the flux composition used for this invention is demonstrated. The flux composition used in the present invention is a component other than the solder powder in the solder composition, and contains (A) a rosin resin, (B) an activator, and (C) a solvent.

[(A) component]
Examples of the (A) rosin resin used in the present invention include rosins and rosin modified resins. Examples of rosins include gum rosin, wood rosin and tall oil rosin. Examples of rosin-based modified resins include disproportionated rosin, polymerized rosin, hydrogenated rosin (fully hydrogenated rosin, partially hydrogenated rosin, and unsaturated organic acids (aliphatic unsaturated monobasic such as (meth) acrylic acid). Unsaturated organics that are modified rosins of acid, fumaric acid, maleic acid and other aliphatic unsaturated dibasic acids such as α, β-unsaturated carboxylic acids, and unsaturated carboxylic acids having aromatic rings such as cinnamic acid) Examples include hydrogenated products of acid-modified rosin (also referred to as “hydrogenated acid-modified rosin”) and derivatives thereof. These rosin resins may be used alone or in combination of two or more.

In the present invention, from the viewpoint of printability, it is preferable that (A) the rosin-based resin contains a hydrogenated product of (A1) unsaturated organic acid-modified rosin. Moreover, it is more preferable to use together this (A1) component and rosin-type resin ((A2) component) other than (A1) component.
Moreover, when using the said (A1) component, it is preferable that mass ratio ((A1) / (A)) of the said (A1) component with respect to the said (A) component is 30/100 or more and 70/100 or less.

  The blending amount of the component (A) needs to be 35% by mass or more with respect to 100% by mass of the flux composition. When the blending amount of the component (A) is less than 35% by mass, the printability of the solder composition becomes insufficient. Moreover, it is preferable that the compounding quantity of the said (A) component is 35 to 70 mass%, and it is more preferable that it is 40 to 55 mass%. If the blending amount of the component (A) is equal to or more than the lower limit, the so-called solderability can be improved by preventing the copper foil surface of the soldered land from being oxidized and making the surface of the solder solder wet easily. Can be suppressed. Moreover, if the compounding quantity of (A) component is below the said upper limit, flux residual quantity can fully be suppressed.

[Component (B)]
Examples of the activator (B) used in the present invention include an organic acid, a non-dissociative activator comprising a non-dissociable halogenated compound, and an amine-based activator. These activators may be used individually by 1 type, and may mix and use 2 or more types. Among these, from the viewpoint of environmental measures and from the viewpoint of suppressing corrosion at the soldered portion, it is preferable to use an organic acid or an amine-based activator (one containing no halogen), and an organic acid is used. It is more preferable.

Examples of the organic acid include other organic acids in addition to monocarboxylic acid and dicarboxylic acid.
Monocarboxylic acids include formic acid, acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, enanthic acid, capric acid, lauric acid, myristic acid, pentadecylic acid, palmitic acid, margaric acid, stearic acid, tuberculostearic acid Arachidic acid, behenic acid, lignoceric acid, glycolic acid and the like.
Examples of the dicarboxylic acid include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, fumaric acid, maleic acid, tartaric acid, diglycolic acid and the like.
Examples of other organic acids include dimer acid, levulinic acid, lactic acid, acrylic acid, benzoic acid, salicylic acid, anisic acid, citric acid, and picolinic acid.

  Examples of the non-dissociative activator include non-salt organic compounds in which halogen atoms are bonded by a covalent bond. The halogenated compound may be a compound formed by covalent bonding of chlorine, bromine and fluorine, such as chlorinated, brominated and fluoride, but any two or all of chlorine, bromine and fluorine may be used. The compound which has the following covalent bond may be sufficient. In order to improve the solubility in an aqueous solvent, these compounds preferably have a polar group such as a hydroxyl group or a carboxyl group such as a halogenated alcohol or a halogenated carboxyl compound. Examples of the halogenated alcohol include 2,3-dibromopropanol, 2,3-dibromobutanediol, trans-2,3-dibromo-2-butene-1,4-diol, 1,4-dibromo-2-butanol, Brominated alcohols such as tribromoneopentyl alcohol, chlorinated alcohols such as 1,3-dichloro-2-propanol and 1,4-dichloro-2-butanol, fluorinated alcohols such as 3-fluorocatechol, and the like Compounds. Examples of the halogenated carboxyl compound include 2-iodobenzoic acid, 3-iodobenzoic acid, 2-iodopropionic acid, 5-iodosalicylic acid, 5-iodoanthranilic acid, and the like, 2-chlorobenzoic acid, 3-chloro Examples thereof include carboxylated carboxyl compounds such as chloropropionic acid, brominated carboxyl compounds such as 2,3-dibromopropionic acid, 2,3-dibromosuccinic acid and 2-bromobenzoic acid, and the like.

  Examples of the amine activator include amines (polyamines such as ethylenediamine), amine salts (amines such as trimethylolamine, cyclohexylamine, diethylamine, and organic acid salts such as amino alcohols and inorganic acid salts (hydrochloric acid, sulfuric acid, odors). Hydroacid, etc.)), amino acids (glycine, alanine, aspartic acid, glutamic acid, valine, etc.), amide compounds and the like. Specifically, diphenylguanidine hydrobromide, cyclohexylamine hydrobromide, diethylamine salt (hydrochloride, succinate, adipate, sebacate, etc.), triethanolamine, monoethanolamine, etc. And the hydrobromide of the amine.

  The blending amount of the component (B) is preferably 1% by mass or more and 20% by mass or less, more preferably 1% by mass or more and 15% by mass or less, with respect to 100% by mass of the flux composition. The content is particularly preferably 2% by mass or more and 10% by mass or less. If the blending amount of component (B) is equal to or greater than the lower limit, solder balls can be more reliably suppressed. Moreover, if the compounding quantity of (B) component is below the said upper limit, the insulation of a flux composition is securable.

[Component (C)]
The (C) solvent used in the present invention must contain (C1) a solvent having a melting point of 50 ° C. or higher and a boiling point of 240 ° C. or lower. By containing this component (C1), it is possible to sufficiently reduce solder balls and voids while maintaining printability. The melting point of the component (C1) is preferably 50 ° C. or higher and 130 ° C. or lower, more preferably 70 ° C. or higher and 120 ° C. or lower, and particularly preferably 80 ° C. or higher and 110 ° C. or lower. Moreover, it is preferable that the boiling point of (C1) component is 120 degreeC or more and 230 degrees C or less. In addition, in this specification, a boiling point means the boiling point in 1013 hPa.
In addition, in the present invention, from the viewpoint of suppression of solder balls and voids and printability, the component (C) is (C2) a liquid having a temperature of 25 ° C. and a boiling point of 240 ° C. or lower. It is preferable to do. In order to be liquid at a temperature of 25 ° C., the melting point may be 25 ° C. or lower, or the freezing point may be 25 ° C. or lower. The component (C2) may be a liquid at room temperature. Moreover, it is preferable that the boiling point of (C2) component is 100 degreeC or more and 240 degrees C or less.

  Examples of the component (C1) include 2,5-dimethylhexane-2,5-diol (melting point: 86 to 90 ° C., boiling point: 214 to 215 ° C.), 2,2-dimethyl-1,3-propanediol. (Melting point: 127-130 ° C, boiling point: 210 ° C), 2-methyl-2-propyl-1,3-propanediol (melting point: 56-60 ° C, boiling point: 230 ° C) and 1,8-octanediol (melting point) : 57-61 ° C., boiling point: 172 ° C.). These may be used alone or in combination of two or more. Among these, 2,5-dimethylhexane-2,5-diol is more preferable.

The blending amount of the component (C1) needs to be 3% by mass or more and 18% by mass or less with respect to 100% by mass of the flux composition. When the blending amount of the component (C1) is less than 3% by mass, the void suppressing effect is insufficient. On the other hand, when the amount of the component (C1) exceeds 18% by mass, the generation of solder balls increases. From the viewpoint of suppressing solder balls and voids, the blending amount of the component (C1) is more preferably 4% by mass or more and 16% by mass or less, more preferably 10% by mass with respect to 100% by mass of the flux composition. It is particularly preferably 15% by mass or less.
Further, from the viewpoint of suppressing solder balls and voids, the mass ratio ((C1) / (C)) of the component (C1) to the component (C) is preferably 10/100 or more and 40/100 or less. 11/100 or more and 36/100 or less is more preferable.

  As the component (C2), dipropylene glycol (boiling point: 229 to 232 ° C.), triethylene glycol (melting point: −7 ° C., boiling point: 125 to 127 ° C.), hexylene glycol (boiling point: 197 ° C.), 1, 4-butenediol (freezing point: 7 ° C., boiling point: 234 ° C.), methyl carbitol (boiling point: 193 ° C.), butyl carbitol (melting point: −68 ° C., boiling point: 230 ° C.), diethylene glycol mono-2-ethylhexyl ether ( EHDG, boiling point: 229 ° C., phenyl glycol (boiling point: 237 ° C.), and the like. These may be used alone or in combination of two or more.

The component (C) may contain a solvent (component (C3)) other than the component (C1) and the component (C2) within a range in which the object of the present invention can be achieved.
As the component (C3), diethylene glycol (melting point: −8 ° C., boiling point: 245 ° C.), hexyl diglycol (boiling point: 258 ° C.), 1,5-pentanediol (melting point: −18 ° C., boiling point: 242 ° C.) Diethylene glycol monohexyl ether (melting point: −40 ° C., boiling point: 261 to 265 ° C.), tetraethylene glycol dimethyl ether (melting point: −30 ° C., boiling point: 275 to 276 ° C.), and dibutylmaleic acid (melting point: −85 ° C., Boiling point: 281 ° C.). These may be used alone or in combination of two or more.

  The blending amount of the component (C) is preferably 20% by mass or more and 60% by mass or less, more preferably 25% by mass or more and 55% by mass or less, with respect to 100% by mass of the flux composition. It is particularly preferable that the content is not less than 50% by mass and not more than 50% by mass. If the blending amount of the solvent is within the above range, the viscosity of the obtained solder composition can be appropriately adjusted to an appropriate range.

[Thixotropic agent]
In the present invention, a thixotropic agent may be further contained from the viewpoint of printability and the like. Examples of the thixotropic agent used in the present invention include hardened castor oil, amides, kaolin, colloidal silica, organic bentonite, and glass frit. These thixotropic agents may be used alone or in combination of two or more.

  When the thixotropic agent is used, the blending amount is preferably 3% by mass or more and 20% by mass or less, more preferably 5% by mass or more and 12% by mass or less with respect to 100% by mass of the flux composition. . When the blending amount is equal to or more than the lower limit, sufficient thixotropy can be obtained, and sagging can be sufficiently suppressed. If the blending amount is less than or equal to the above upper limit, the thixotropy is too high and printing does not become defective.

[Other ingredients]
In the flux composition used in the present invention, in addition to the component (A), the component (B), the component (C), and the thixotropic agent, if necessary, other additives, and other Resin can be added. Examples of other additives include antifoaming agents, antioxidants, modifiers, matting agents, and foaming agents. Examples of other resins include acrylic resins.

[Solder composition]
Next, the solder composition of the present invention will be described. The solder composition of the present invention contains the flux composition of the present invention and (D) solder powder described below.
The blending amount of the flux composition is preferably 5% by mass to 35% by mass, more preferably 7% by mass to 15% by mass, and more preferably 8% by mass with respect to 100% by mass of the solder composition. % To 12% by mass, more preferably 9% to 10% by mass. When the blending amount of the flux composition is less than 5% by mass (when the blending amount of the solder powder exceeds 95% by mass), the flux composition as the binder is insufficient, so the flux composition and the solder powder are mixed. On the other hand, when the blending amount of the flux composition exceeds 35% by mass (when the blending amount of the solder powder is less than 65% by mass), when the obtained solder composition is used, It tends to be difficult to form a sufficient solder joint.

[(D) component]
The solder powder (D) used in the present invention is a solder powder made of a solder alloy having a melting point of 160 ° C. or lower. As the solder alloy in the solder powder, a solder alloy containing tin (Sn) and bismuth (Bi) is preferable. Examples of the third element of this alloy include silver (Ag), copper (Cu), zinc (Zn), indium (In), aluminum (Al), and antimony (Sb).
Specific examples of these solder alloys include Sn—Bi solder alloys, Sn—Bi—Ag solder alloys, and Sn—Bi—Cu solder alloys.
The melting point of these solder alloys is preferably 130 ° C. or higher and 160 ° C. or lower, and more preferably 130 ° C. or lower and 150 ° C. or lower.

  The average particle diameter of the component (D) is usually 1 μm or more and 40 μm or less, but is preferably 1 μm or more and 35 μm or less, more preferably 3 μm or more, from the viewpoint of corresponding to an electronic board having a narrow soldering pad pitch. A thickness of 30 μm or less is particularly preferable. The average particle size can be measured with a dynamic light scattering type particle size measuring device.

[Method for producing solder composition]
The solder composition of the present invention can be produced by blending the above-described flux composition and the above-described (D) solder powder in the above-mentioned predetermined ratio and stirring and mixing them.

[Electronic substrate]
Next, the electronic substrate of the present invention will be described. The electronic board of the present invention is characterized by including a soldering portion using the solder composition described above. The electronic substrate of the present invention can be manufactured by mounting an electronic component (lower surface electrode component) on an electronic substrate (such as a printed wiring board) using the solder composition.
Examples of the coating apparatus used here include a screen printer, a metal mask printer, a dispenser, and a jet dispenser.
In addition, the electronic component is placed on the solder composition applied by the coating device, heated under a predetermined condition by a reflow furnace, and the electronic component is mounted on the printed wiring board by a reflow process. Can be implemented.

In the reflow process, the electronic component is placed on the solder composition and heated in a reflow furnace under predetermined conditions. By this reflow process, sufficient soldering can be performed between the electronic component and the printed wiring board. As a result, the electronic component can be mounted on the printed wiring board.
What is necessary is just to set reflow conditions suitably according to melting | fusing point of solder. For example, when using a Sn—Bi solder alloy, the preheating temperature may be set to 80 to 100 ° C., the preheating time may be set to 60 to 120 seconds, and the peak temperature may be set to 160 to 180 ° C.

Further, the solder composition and the electronic substrate of the present invention are not limited to the above-described embodiments, and modifications, improvements and the like within the scope that can achieve the object of the present invention are included in the present invention.
For example, in the electronic board, the printed wiring board and the electronic component are bonded by the reflow process, but the invention is not limited to this. For example, instead of the reflow process, the printed wiring board and the electronic component may be bonded by a process of heating the solder composition using laser light (laser heating process). In this case, the laser light source is not particularly limited, and can be appropriately selected according to the wavelength matched to the metal absorption band. As the laser light source, for example, a solid laser (ruby, glass, YAG, etc.), semiconductor laser (GaAs, InGaAsP, etc.), (such as a dye) liquid laser, a gas laser (He-Ne, Ar, CO 2, etc. excimer) is Can be mentioned.

EXAMPLES Next, although an Example and a comparative example demonstrate this invention further in detail, this invention is not limited at all by these examples. In addition, the material used in the Example and the comparative example is shown below.
((A1) component)
Rosin resin A: hydrogenated acid-modified rosin, trade name “Pine Crystal KE-604”, manufactured by Arakawa Chemical Industries, Ltd. (component (A2))
Rosin resin B: Completely hydrogenated rosin, trade name “Foral AX”, manufactured by Sojitz Corporation (component (B))
Activator A: Suberic acid activator B: Glutaric acid activator C: 2-iodobenzoic acid activator D: Dibromobutenediol (component (C1))
Solvent A: 2,5-dimethylhexane-2,5-diol (melting point: 86-90 ° C., boiling point: 214-215 ° C.)
((C2) component)
Solvent B: Diethylene glycol mono-2-ethylhexyl ether (boiling point: 229 ° C.), trade name “EHDG”, solvent C manufactured by Nippon Emulsifier Co., Ltd .: 1,4-butenediol (freezing point: 7 ° C., boiling point: 234 ° C.)
((D) component)
Solder powder A: Alloy composition is Sn-57Bi-1Ag, particle size distribution is 20-38 μm, solder melting point is 137-139 ° C.
(Other ingredients)
Thixotropic agent A: trade name “Sripacs ZHH”, Nippon Kasei Co., Ltd. thixotropic agent B: trade name “Hima-Koh”, solder powder B: KF Trading Co., Ltd .: alloy composition Sn-3.0Ag-0.5Cu, particle size distribution Is 20-38 μm, solder melting point is 217-220 ° C

[Example 1]
Rosin resin A 25.5% by mass, Rosin resin B 21% by mass, Activator A 1% by mass, Activator B 2% by mass, Activator C 0.5% by mass, Activator D 0.8% by mass, Solvent A 10% by mass, Solvent B32.2 mass%, thixotropic agent A 5 mass%, and thixotropic agent B 2 mass% were put into a container and mixed using a planetary mixer to obtain a flux composition.
Thereafter, 9.4% by mass of the obtained flux composition, 90.4% by mass of solder powder and 0.2% by mass of solvent B (100% by mass in total) are put into a container and mixed by a planetary mixer. A solder composition was prepared.

[Examples 2 and 3]
A solder composition was obtained in the same manner as in Example 1 except that each material was blended according to the composition shown in Table 1.
[Comparative Examples 1-5]
A solder composition was obtained in the same manner as in Example 1 except that each material was blended according to the composition shown in Table 1.

<Evaluation of solder composition>
Evaluation of the solder composition (QFN void, heating drool, inter-pin ball, chip side ball, printability) was performed by the following method. The obtained results are shown in Table 1.
(1) QFN void A solder composition using a metal mask having a thickness of 100 μm on an evaluation substrate (“SP-TDC” manufactured by Tamura Corporation) having a QFN (Quad Flatpack No Lead) pattern with a pitch of 0.5 mm. Is printed, QFN parts are mounted, the solder composition is dissolved in a reflow furnace (manufactured by Tamura Corporation), and soldered to obtain a test plate. The reflow conditions here are a preheat temperature of 80 to 100 ° C. (60 seconds), a temperature of 140 ° C. or higher for 50 seconds, and a peak temperature of 170 ° C. In the case of Comparative Example 5 only, the reflow conditions are a preheat temperature of 150 to 180 ° C. (60 seconds), a temperature of 220 ° C. or higher for 50 seconds, and a peak temperature of 245 ° C. The obtained test plate was observed using an X-ray measuring device (“SMX-160E” manufactured by Shimadzu Corporation), and the area occupied by voids generated on the lower surface of the 0.5 mm pitch QFN (area where voids were generated) / QFN area).
(2) Heating Sagging Heating sagging was evaluated according to the method described in Appendix 10 of JIS Z 3284-1994. Specifically, among the pattern holes arranged in 0.1 mm steps from 0.2 mm to 1.2 mm, the minimum interval at which the printed solder composition was not integrated was measured. Here, the heating temperature is 130 ° C. Only in the case of Comparative Example 5, the heating temperature is 150 ° C.
(3) Ball between pins Solder composition using a metal mask with a thickness of 100 μm on an evaluation substrate (“SP-TDC” manufactured by Tamura Corporation) having a QFP (Quad Flat Package) pattern with a pitch of 0.8 mm Is printed, and the solder composition is dissolved in a reflow oven and soldered to obtain a test plate. The reflow conditions here are a preheat temperature of 80 to 100 ° C. (60 seconds), a temperature of 140 ° C. or higher for 50 seconds, and a peak temperature of 170 ° C. In the case of Comparative Example 5 only, the reflow conditions are a preheat temperature of 150 to 180 ° C. (60 seconds), a temperature of 220 ° C. or higher for 50 seconds, and a peak temperature of 245 ° C. The obtained test plate was observed with a magnifying glass, and the number of solder balls (pieces / pin) generated at the interval between the pins of the 0.8 mm pitch QFP land was measured.
(4) Chip side ball A solder composition is printed on a substrate for evaluation (“SP-TDC” manufactured by Tamura Corporation) on which a chip component (1608CR chip) can be mounted using a 100 μm-thick metal mask. A test plate is prepared by mounting 60 parts, dissolving the solder composition in a reflow furnace (manufactured by Tamura Corporation), and performing soldering. The reflow conditions here are a preheat temperature of 80 to 100 ° C. (60 seconds), a temperature of 140 ° C. or higher for 50 seconds, and a peak temperature of 170 ° C. In the case of Comparative Example 5 only, the reflow conditions are a preheat temperature of 150 to 180 ° C. (60 seconds), a temperature of 220 ° C. or higher for 50 seconds, and a peak temperature of 245 ° C. The obtained test plate was observed with a magnifying glass, and the number (number) of solder balls generated on the side of the chip component was measured.
(5) Printability 100 substrates having a diameter of 0.26 mmφ were provided on 10 evaluation substrates (“SP-059” manufactured by Tamura Corporation), and a metal mask having a thickness of 100 μm was used. A test plate (after starting) is obtained by continuously printing the solder composition. Also, after printing, it is left for 1 hour, and then the solder composition is applied to 10 substrates for evaluation (“SP-059” manufactured by Tamura Corporation) using the same metal mask as above. What was continuously printed is taken as a test plate (after standing for 1 hour). Then, the obtained test plate was analyzed by an image inspection machine, and the average value (volume ratio of missing volume) of the solder composition with holes removed was measured. The printability was evaluated according to the following criteria.
○: The missing volume ratio is 75% or more.
X: The missing volume ratio is less than 50%.

As is clear from the results shown in Table 1, when the solder composition of the present invention containing a predetermined amount of the component (A) and a predetermined amount of the component (C1) was used (Examples 1 to 3), It was confirmed that QFN void, heating droop, inter-pin ball, chip side ball and printability were good. Therefore, it was confirmed that the solder composition of the present invention can sufficiently suppress solder balls and voids and has sufficient printability when soldering the lower surface electrode component.
On the other hand, when the solder composition not containing the component (C1) is used (Comparative Examples 1 and 3), when the component (C1) is too much (Comparative Example 2), or when the component (A) is too little ( In Comparative Example 4), it was found that at least one of QFN void, heating droop, inter-pin ball, chip side ball and printability was inferior. Further, it was found that when a high melting point solder alloy was used (Comparative Example 5), the inter-pin ball and the chip side ball could not be suppressed.

  The solder composition of the present invention can be suitably used as a technique for mounting an electronic component on an electronic board such as a printed wiring board of an electronic device.

Claims (6)

(A) a rosin resin, (B) an activator, (C) a flux composition containing a solvent, and (D) a solder powder made of a solder alloy having a melting point of 160 ° C. or lower,
The component (C) contains (C1) a solvent having a melting point of 50 ° C. or higher and a boiling point of 240 ° C. or lower,
The solder alloy in the component (D) is at least one selected from the group consisting of Sn—Bi solder alloys, Sn—Bi—Ag solder alloys, and Sn—Bi—Cu solder alloys. Yes,
The blending amount of the component (A) is 35% by mass or more with respect to 100% by mass of the flux composition,
The compounding quantity of the said (C1) component is 3 to 18 mass% with respect to 100 mass% of flux compositions. The solder composition characterized by the above-mentioned. The solder composition according to claim 1,
The component (A) contains a hydrogenated product of (A1) unsaturated organic acid-modified rosin. In the solder composition according to claim 1 or 2,
The solder composition, wherein the component (C) further contains (C2) a solvent having a temperature of 25 ° C. and a boiling point of 240 ° C. or less. In the solder composition according to any one of claims 1 to 3,
The solder composition, wherein the component (C1) is 2,5-dimethylhexane-2,5-diol. In the solder composition according to any one of claims 1 to 4,
A solder composition characterized by being used for a bottom electrode part.   An electronic board comprising a soldering portion using the solder composition according to any one of claims 1 to 5.