Flux composition, solder composition, and electronic board

Abstract

To provide a flux composition that excels in the temperature cycle reliability of flux residue and exhibits excellent printing quality.SOLUTION: A flux composition comprises (A) a resin, (B) an activator, and (C) a solvent. The component (A) comprises (A1) an acrylic resin. The component (B) comprises (B1) an organic acid. The (B1) component comprises dodecanedioic acid. The component (C) comprises (C1) dibutyl maleate.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a flux composition, a solder composition, and an electronic board. [Background technology]

[0002] The solder composition is a mixture of solder powder and flux composition (rosin resin, activator, solvent, etc.) kneaded into a paste (for example, Patent Document 1). This solder composition is required to have solderability such as solder meltability and the property that solder easily wets and spreads (solder wettability), as well as temperature cycle reliability of flux residue. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 5756067 Summary of the Invention [Problem to be solved by the invention]

[0004] In order to improve the temperature cycle reliability of the flux residue, it has been proposed to use acrylic resin. On the other hand, since acrylic resin itself has almost no ability to remove the metal oxide film of the solder powder and the base material, it is common to use organic acid in combination. However, organic acids with small molecular weights are difficult to dissolve in acrylic resin. Also, if the organic acid does not dissolve and precipitates in the flux, it may have a negative effect (clogging, etc.) when printing the solder composition. In addition, the flux components may become non-uniform, which may cause quality problems. Therefore, it is possible to use acrylic resin and rosin resin in combination, but while increasing the proportion of rosin resin makes the activator more soluble, this in turn impairs the temperature cycle reliability.

[0005] An object of the present invention is to provide a flux composition, a solder composition, and an electronic board which have excellent temperature cycle reliability of the flux residue and excellent printability. [Means for solving the problem]

[0006] According to the present invention, there are provided a flux composition, a solder composition, and an electronic board as described below. [1] A flux composition comprising: (A) a resin; (B) an activator; and (C) a solvent, The component (A) contains an acrylic resin (A1), The component (B) contains an organic acid (B1), The component (B1) contains dodecanedioic acid, The component (C) contains (C1) dibutyl maleate. Flux composition. [2] The flux composition according to [1], The blending amount of the (A1) component is 50% by mass or more relative to 100% by mass of the (A) component. Flux composition. [3] A flux composition according to [1] or [2], and (D) a solder powder, Solder composition. [4] A soldered portion using the solder composition according to [3] is provided. Electronic board. Effect of the Invention

[0007] According to one aspect of the present invention, it is possible to provide a flux composition, a solder composition, and an electronic board having excellent temperature cycle reliability of flux residue and excellent printability. [Brief description of the drawings]

[0008] [Figure 1] 1A is a photograph of the solder composition obtained in Example 1, and FIG. 1B is a photograph of the solder composition obtained in Comparative Example 1. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] [Flux composition] First, the flux composition according to this embodiment will be described. The flux composition according to this embodiment is a component other than the solder powder in the solder composition, and contains (A) resin, (B) activator, and (C) solvent, which will be described below. It is also necessary that the (A) component contains (A1) acrylic resin, the (B) component contains (B1) organic acid, the (B1) component contains dodecanedioic acid, and the (C) component contains (C1) dibutyl maleate.

[0010] The reason why the flux composition according to the present embodiment has excellent temperature cycle reliability of the flux residue and excellent printability is not necessarily clear, but the present inventors speculate as follows. That is, the flux composition of the present invention contains (A1) acrylic resin as (A) resin. The (A1) component can improve the temperature cycle reliability of the flux residue. On the other hand, in a flux composition containing the (A1) component, crystals of an organic acid having a small molecular weight are precipitated in the flux, and in some cases, large crystals are generated. When large crystals are generated, clogging and the like are easily caused, and printability is reduced. In contrast, in the flux composition of the present invention, dodecanedioic acid is used in combination as the organic acid, and this dodecanedioic acid can suppress the organic acid having a small molecular weight from becoming a large crystal. Furthermore, in the flux composition of the present invention, (C1) dibutyl maleate is used as the (C) solvent, and this (C1) component can suppress the crystallization of the organic acid having a small molecular weight. In this way, it is possible to prevent the generation of large crystals and ensure excellent printability. The present inventors presume that the above-mentioned effects of the present invention are achieved in the above-mentioned manner.

[0011] [Component (A)] The resin (A) used in this embodiment must contain an acrylic resin (A1), which can improve the temperature cycle reliability of the flux residue. The acrylic resin is obtained by polymerizing at least one monomer such as acrylic acid, methacrylic acid, various esters of acrylic acid, various esters of methacrylic acid, crotonic acid, itaconic acid, maleic acid, maleic anhydride, esters of maleic acid, esters of maleic anhydride, acrylonitrile, methacrylonitrile, acrylamide, methacrylamide, vinyl chloride, and vinyl acetate. Among these acrylic resins, acrylic resins obtained by polymerizing monomers containing methacrylic acid and a monomer having an alkyl group with 2 to 6 carbon atoms, and further acrylic resins obtained by polymerizing monomers containing methacrylic acid and a monomer having an alkyl group with 2 carbon atoms are preferred.

[0012] The blending amount of the (A1) component is preferably 50% by mass to 100% by mass, more preferably 65% ​​by mass to 95% by mass, and particularly preferably 80% by mass to 90% by mass, based on 100% by mass of the (A) component. If the blending amount of the (A1) component is equal to or more than the lower limit, the temperature cycle reliability of the flux residue tends to be further improved, while if it is equal to or less than the upper limit, the printability tends to be improved.

[0013] It is preferable that the component (A) further contains a rosin-based resin (A2), which makes it easier for organic acids with small molecular weights to dissolve in the flux composition. Examples of the rosin-based resin include rosins and rosin-based modified resins. Examples of the rosins include gum rosin, wood rosin, and tall oil rosin. Examples of the rosin-based modified resin include disproportionated rosin, polymerized rosin, hydrogenated rosin, and derivatives thereof. Examples of the hydrogenated rosin include fully hydrogenated rosin, partially hydrogenated rosin, and hydrogenated products of unsaturated organic acid-modified rosins (also called "hydrogenated acid-modified rosin"), which are modified rosins of unsaturated organic acids (aliphatic unsaturated monobasic acids such as (meth)acrylic acid, aliphatic unsaturated dibasic acids such as α,β-unsaturated carboxylic acids such as fumaric acid and maleic acid, unsaturated carboxylic acids having aromatic rings such as cinnamic acid, etc.). These rosin-based resins may be used alone or in combination of two or more. Among these rosin-based resins, it is preferable to use fully hydrogenated rosin and hydrogenated acid-modified rosin, and it is more preferable to use fully hydrogenated rosin and hydrogenated acid-modified rosin in combination.

[0014] The mass ratio of the (A1) component to the (A2) component ((A1) / (A2)) is preferably 1 or more and 10 or less, more preferably 3 / 2 or more and 8 or less, and particularly preferably 4 or more and 6 or less, from the viewpoint of a balance between the temperature cycle reliability of the flux residue and the printability.

[0015] The amount of component (A) is preferably 35% by mass or more and 80% by mass or less, and more preferably 40% by mass or more and 75% by mass or less, based on 100% by mass of the flux composition. If the amount of component (A) is equal to or more than the lower limit, the oxidation of the copper foil surface of the soldering land is prevented, making the surface more easily wetted with molten solder, and the so-called solderability can be improved, and solder balls can be sufficiently suppressed. Also, if the amount of component (A) is equal to or less than the upper limit, the amount of flux residue can be sufficiently suppressed.

[0016] [(B) Component] The activator (B) used in this embodiment must contain an organic acid (B1). This component (B1) can improve the solderability. Examples of the component (B1) include other organic acids in addition to monocarboxylic acids and dicarboxylic acids, etc. These may be used alone or in combination of two or more. 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, and glycolic acid. Dicarboxylic acids include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, dodecanedioic acid, fumaric acid, maleic acid, tartaric acid, and diglycolic acid. Other organic acids include 3-hydroxy-2-naphthoic acid, dimer acid, trimer acid, levulinic acid, lactic acid, acrylic acid, benzoic acid, salicylic acid, anisic acid, citric acid, and picolinic acid.

[0017] In this embodiment, the component (B1) must contain dodecanedioic acid, which can prevent the crystals of the component (B1) from becoming gigantic. The amount of dodecanedioic acid blended is preferably 15% by mass or more and 60% by mass or less, more preferably 20% by mass or more and 50% by mass or less, and particularly preferably 30% by mass or more and 40% by mass or less, based on 100% by mass of the (B1) component. The blending amount of the (B1) component is preferably 2% by mass or more and 25% by mass or less, more preferably 5% by mass or more and 20% by mass or less, and particularly preferably 7% by mass or more and 12% by mass or less, based on 100% by mass of the flux composition. If the blending amount of the (B1) component is equal to or more than the lower limit, the activation action tends to be improved, whereas if it is equal to or less than the upper limit, the insulating properties of the flux composition tend to be maintained.

[0018] In addition to the component (B1), the component (B) may further contain other activators (such as a halogen-based activator (B2) and an amine-based activator (B3)) within the scope of the present invention. The total amount of the component (B1) is preferably 80% by mass or more, and more preferably 90% by mass or more, based on 100% by mass of the component (B).

[0019] The blending amount of the (B) component is preferably 3% by mass or more and 25% by mass or less, more preferably 6% by mass or more and 20% by mass or less, and particularly preferably 8% by mass or more and 12% by mass or less, based on 100% by mass of the flux composition. If the blending amount of the (B) component is equal to or more than the lower limit, the activation action tends to be improved, whereas if it is equal to or less than the upper limit, the insulating property of the flux composition tends to be maintained.

[0020] [(C) component] The solvent (C) used in this embodiment must contain dibutyl maleate (C1), which can suppress crystallization of organic acids with small molecular weights. From the above viewpoints, the blending amount of the (C1) component is preferably from 2 to 20% by mass, more preferably from 3 to 15% by mass, and particularly preferably from 4 to 10% by mass, relative to 100% by mass of the flux composition.

[0021] The (C) component may contain a solvent other than the (C1) component (hereinafter also referred to as the (C2) component). As the (C2) component, a known solvent can be appropriately used. As such a solvent, it is preferable to use a solvent having a boiling point of 170°C or higher. Examples of such solvents include diethylene glycol, dipropylene glycol, triethylene glycol, hexylene glycol, 1,5-pentanediol, methyl carbitol, butyl carbitol, 2-ethylhexyl diglycol, octanediol, phenyl glycol, diethylene glycol monohexyl ether (DEH), tetraethylene glycol dimethyl ether, etc. These solvents may be used alone or in combination of two or more.

[0022] The blending amount of the (C) component is preferably 5% by mass or more and 20% by mass or less, and more preferably 7% by mass or more and 15% by mass or less, based on 100% by mass of the flux composition. 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.

[0023] [Thixilation agent] The flux composition according to the present embodiment may contain a thixotropic agent (D) from the viewpoint of suppressing sagging during printing or heating. As the thixotropic agent, a known thixotropic agent can be appropriately used. Examples of the thixotropic agent used here include hardened castor oil, amides, kaolin, colloidal silica, organic bentonite, and glass frit. These may be used alone or in combination of two or more.

[0024] The blending amount of the thixotropic agent is preferably 2% by mass or more and 20% by mass or less, more preferably 3% by mass or more and 15% by mass or less, and particularly preferably 5% by mass or more and 10% by mass or less, based on 100% by mass of the flux composition. If the blending amount is equal to or more than the lower limit, sufficient thixotropy is obtained and sagging tends to be suppressed. On the other hand, if the blending amount is equal to or less than the upper limit, the thixotropy is not too high and printing defects tend not to occur.

[0025] [Antioxidants] The flux composition according to the present embodiment may further contain an antioxidant from the viewpoint of solder melting property, etc. As the antioxidant used here, a known antioxidant can be appropriately used. Examples of the antioxidant include sulfur compounds, hindered phenol compounds, and phosphite compounds. Among these, hindered phenol compounds are preferred.

[0026] Examples of the hindered phenol compound include pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], bis(3-tert-butyl-4-hydroxy-5-methylbenzenepropanoic acid)ethylene bis(oxyethylene), N,N'-bis[2-[2-(3,5-di-tert-butyl-4-hydroxyphenyl)ethylcarbonyloxy]ethyl]oxamide, and N,N'-bis{3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl}hydrazine. These may be used alone or in combination of two or more.

[0027] When an antioxidant is used, its content is preferably 0.1% by mass or more and 5% by mass or less with respect to 100% by mass of the flux composition. If the content of the antioxidant is equal to or more than the lower limit, the solder melting property tends to be improved, whereas if it is equal to or less than the upper limit, the insulating property of the flux composition tends to be maintained.

[0028] [Other ingredients] In addition to the (A), (B), and (C) components, the thixotropic agent, and the antioxidant, other additives may be added to the flux composition used in this embodiment as necessary. Examples of the other additives include imidazole compounds, antifoaming agents, modifiers, matting agents, and foaming agents. The amount of these additives to be added is preferably 0.01% by mass or more and 5% by mass or less with respect to 100% by mass of the flux composition.

[0029] [Solder composition] Next, the solder composition according to the present embodiment will be described. The solder composition according to the present embodiment contains the flux composition according to the present embodiment described above and the solder powder (D) described below. The amount of the flux composition is preferably 5% by mass or more and 35% by mass or less, more preferably 7% by mass or more and 15% by mass or less, and particularly preferably 8% by mass or more and 12% by mass or less, relative to 100% by mass of the solder composition. When the amount of the flux composition is less than 5% by mass (when the amount of the solder powder exceeds 95% by mass), the flux composition as a binder is insufficient, so that it tends to be difficult to mix the flux composition and the solder powder. On the other hand, when the amount of the flux composition is more than 35% by mass (when the 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.

[0030] [(D) component] The solder powder (D) used in this embodiment is preferably made of only lead-free solder powder, but may be lead-containing solder powder. The solder alloy in this solder powder preferably contains at least one selected from the group consisting of tin (Sn), copper (Cu), zinc (Zn), silver (Ag), gold (Au), antimony (Sb), lead (Pb), indium (In), bismuth (Bi), nickel (Ni), cobalt (Co) and germanium (Ge). The solder alloy in the solder powder is preferably an alloy mainly composed of tin, more preferably containing tin, silver and copper, and may further contain at least one of antimony, bismuth and nickel as an additive element. Here, lead-free solder powder refers to a powder of solder metal or alloy to which no lead is added. However, the presence of lead as an unavoidable impurity in the lead-free solder powder is permitted, but in this case, the amount of lead is preferably 300 ppm by mass or less.

[0031] Specific examples of alloy systems for lead-free solder powder include Sn-Ag-Cu systems, Sn-Cu systems, Sn-Ag systems, Sn-Bi systems, Sn-Ag-Bi systems, Sn-Ag-Cu-Bi systems, Sn-Ag-Cu-Ni systems, Sn-Ag-Cu-Bi-Sb systems, Sn-Ag-Bi-In systems, and Sn-Ag-Cu-Bi-In-Sb systems.

[0032] The average particle size of component (D) is usually 1 μm or more and 40 μm or less, but from the viewpoint of compatibility with electronic boards having narrow pitches of solder pads, it is more preferably 1 μm or more and 35 μm or less, even more preferably 2 μm or more and 35 μm or less, and particularly preferably 3 μm or more and 32 μm or less. The average particle size can be measured by a dynamic light scattering type particle size measuring device.

[0033] [Method of manufacturing solder composition] The solder composition of this embodiment can be produced by blending the above-described flux composition and the above-described (D) solder powder in the above-described predetermined ratio, and stirring and mixing them.

[0034] [Electronic board] Next, the electronic board according to the present embodiment will be described. The electronic board according to the present embodiment is characterized by having a soldered portion using the solder composition according to the present embodiment. The electronic board according to the present embodiment can be manufactured by mounting electronic components on an electronic board (such as a printed wiring board) using the solder composition. Examples of the coating device used here include a screen printer, a metal mask printer, a dispenser, and a jet dispenser. In addition, electronic components can be mounted on an electronic board by a reflow process in which electronic components are placed on the solder composition applied by an application device and heated under specified conditions in a reflow furnace to mount the electronic components on a printed wiring board.

[0035] In the reflow process, an electronic component is placed on the solder composition and heated in a reflow furnace under predetermined conditions. This reflow process allows a sufficient solder joint to be formed between the electronic component and the printed wiring board. As a result, the electronic component can be mounted on the printed wiring board. The reflow conditions may be appropriately set according to the melting point of the solder. For example, the preheat temperature is preferably 140°C or higher and 200°C or lower, and more preferably 150°C or higher and 160°C or lower. The preheat time is preferably 60 seconds or higher and 120 seconds or lower. The peak temperature is preferably 230°C or higher and 270°C or lower, and more preferably 240°C or higher and 255°C or lower. The holding time at a temperature of 220°C or higher is preferably 20 seconds or higher and 60 seconds or lower.

[0036] Furthermore, the flux composition, the solder composition, and the electronic board according to the present embodiment are not limited to the above-described embodiment, and modifications and improvements within the scope of the present invention that can achieve the object of the present invention are included in the present invention. For example, in the electronic substrate, the printed wiring board and the electronic component are bonded by a reflow process, but this is not limiting. 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 adopted depending on the wavelength that matches the absorption band of the metal. Examples of the laser light source include solid lasers (ruby, glass, YAG, etc.), semiconductor lasers (GaAs, InGaAsP, etc.), liquid lasers (dye, etc.), and gas lasers (He-Ne, Ar, CO 2 , and excimers. EXAMPLES

[0037] The present invention will now be described in more detail with reference to examples and comparative examples, but the present invention is not limited to these examples. The materials used in the examples and comparative examples are shown below. (Component (A1)) Acrylic resin: Acrylic resin obtained in Preparation Example 1 below ((A2) component) Rosin resin: Acrylic acid modified hydrogenated rosin, product name "Pine Crystal KE-604", manufactured by Arakawa Chemical Industries Co., Ltd. ((B1) component) Organic acid A: Dodecanedioic acid Organic acid B: Malonic acid Organic acid C: Adipic acid Organic Acid D: Azelaic Acid Organic acid E: 3-hydroxy-2-naphthoic acid ((B2) component) Halogen-based activator A: 2-iodobenzoic acid Halogen-based activator B: Dibromobutenediol ((C1) component) Solvent A: Dibutyl maleate, manufactured by Daihachi Chemical Industry Co., Ltd. ((C2) component) Solvent B: Hexyl diglycol, manufactured by Nippon Nyukazai Co., Ltd. (Other ingredients) Thixotropic agent A: higher fatty acid polyamide, product name "Talen VA-79", manufactured by Kyoeisha Chemical Co., Ltd. Thixotropic agent B: fatty acid amide, product name "Slipax H", manufactured by Nippon Kasei Co., Ltd. Thixotropic agent C: Trade name "Himako", manufactured by KF Trading Co., Ltd. Antioxidant A: bis(3-tert-butyl-4-hydroxy-5-methylbenzenepropanoic acid) ethylene bis(oxyethylene), trade name "Irganox 245", manufactured by BASF Antioxidant B: N,N'-bis{3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl}hydrazine, trade name "Irganox MD1024", manufactured by BASF ((D) component) Solder powder: alloy composition is Sn-3.0Ag-0.5Cu, particle size distribution is 20-38μm (equivalent to type 4 of IPC-J-STD-005A), solder melting point is 217-220℃

[0038] [Preparation Example 1] A solution was prepared by mixing 10% by mass of methacrylic acid, 51% by mass of 2-ethylhexyl methacrylate, and 39% by mass of lauryl acrylate. Thereafter, 200 g of diethylhexyl glycol was charged into a 500 mL four-neck flask equipped with a stirrer, a reflux tube, and a nitrogen inlet tube, and this was heated to 110° C. Next, 0.2% by mass to 5% by mass of dimethyl 2,2′-azobis(2-methylpropionate) (product name: V-601, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was added as an azo radical initiator to 300 g of the above solution and dissolved. This solution was added dropwise to the four-neck flask over 1.5 hours, and the components in the four-neck flask were stirred at 110°C for 1 hour before the reaction was terminated to obtain an acrylic resin. The weight-average molecular weight of the acrylic resin was 7,800, the acid value was 40 mgKOH / g, and the glass transition temperature was -47°C.

[0039] [Example 1] 53 mass% acrylic resin, 17 mass% rosin resin, 4 mass% organic acid A, organic acid sol (0.5 mass% organic acid B in 3 mass% solvent B), 1.5 mass% organic acid C, 1.5 mass% organic acid D, 3 mass% organic acid E, 0.5 mass% halogen-based activator A, 0.5 mass% halogen-based activator B, 2 mass% antioxidant A, 1 mass% antioxidant B, 4.5 mass% solvent A, 2 mass% thixotropic agent A, 5 mass% thixotropic agent B, and 1 mass% thixotropic agent C were charged into a container and mixed using a planetary mixer to obtain a flux composition. Thereafter, 11% by mass of the obtained flux composition and 89% by mass of solder powder (total of 100% by mass) were placed in a container and mixed with a planetary mixer to prepare a solder composition.

[0040] [Examples 2 to 3] A solder composition was obtained in the same manner as in Example 1, except that the materials were mixed according to the composition shown in Table 1. [Comparative Examples 1 to 3] A solder composition was obtained in the same manner as in Example 1, except that the materials were mixed according to the composition shown in Table 1.

[0041] <Evaluation of solder composition> The solder composition was evaluated (crystal precipitation, printability, inter-pin ball, void area ratio, flux residue thermal cycle test) by the following methods. The obtained results are shown in Table 1. (1) Crystallization The solder compositions were observed under a microscope and evaluated for crystal precipitation according to the following criteria: A micrograph of the solder composition obtained in Example 1 is shown in Fig. 1(A), and a micrograph of the solder composition obtained in Comparative Example 1 is shown in Fig. 1(B). ◯: No crystals with a major axis exceeding 30 μm were observed. ×: Crystals with a major axis exceeding 30 μm were observed, but no crystals with a major axis exceeding 70 μm were observed. ××: Crystals with major diameters exceeding 70 μm are observed. (2) Printability Using a printing machine MK-878SV (manufactured by Minami Co., Ltd.), a 0.1 mm thick metal mask, and a metal squeegee, the solder composition is printed on an SP-TDC board (a board having a 100-dot pattern, dot diameter: 0.2 mmφ) at a printing speed of 50 mm / s. After printing on 20 SP-TDC boards, the transfer rate (average value of the volume rate of 100 dots) is measured using a three-dimensional shape analyzer. Then, the average transfer rate after leaving it (average value of the transfer rate of 10 boards, unit: %) is calculated. (3) Ball between pins A solder composition was printed on an evaluation board (Tamura Manufacturing's "SP-TDC") having a 0.8 mm pitch QFP (Quad Flat Package (80 pins, no resist between pins)) pattern using a 120 μm thick metal mask, and the solder composition was melted in a reflow furnace and soldered to prepare an evaluation board. The reflow conditions here were a preheat temperature of 150 to 180°C (60 seconds), a time at a temperature of 220°C or higher for 50 seconds, and a peak temperature of 245°C. The evaluation board obtained was observed with a magnifying glass, and all the solder balls generated between the pins were counted. The number was divided by the number of pins to calculate the number of balls between pins per pin (unit: balls / pin). (4) Void area ratio QFN (size: 6mm x 6mm, land: tin plating, land area: 36mm 2 A solder composition was printed on a substrate having electrodes on which a QFN can be mounted, using a metal mask (thickness: 0.13 mm) having a corresponding pattern. Then, a QFN was mounted on the solder composition, and reflow (in air) was performed under the conditions of preheating at 150 to 180°C for 80 seconds and melting time at a peak temperature of 240°C for 40 seconds to prepare an evaluation substrate. The solder joints in the obtained evaluation substrate were observed using an X-ray inspection device (NLX-5000, manufactured by NAGOYA ELECTRIC WORKS). Then, the void ratio [(void area / land area) x 100] (unit: %) in the QFN after reflow was calculated. (5) Flux residue thermal cycle test A solder composition was printed on a patterned evaluation board (Tamura Manufacturing's "SP-TDC") using a 120 μm thick metal mask, and the solder composition was melted in a reflow furnace and soldered to prepare an evaluation board. The reflow conditions here were a preheat temperature of 150 to 180°C (60 seconds), a time at 220°C or higher for 50 seconds, and a peak temperature of 245°C. The evaluation board was placed in a thermal cycle tester and subjected to a thermal cycle test in which one cycle consisted of 30 minutes at a low temperature of -40°C and 30 minutes at a high temperature of 125°C. The flux residue thermal cycle test was evaluated according to the following criteria. ◯: No cracks were observed in the flux residue on the evaluation board after 1000 cycles. Δ: No cracks were observed in the flux residue on the evaluation board after 100 cycles, but cracks were observed in the flux residue on the evaluation board after 1000 cycles. ×: Cracks were observed in the flux residue on the evaluation board after 100 cycles.

[0042] [Table 1]

[0043] As is clear from the results shown in Table 1, the solder compositions of the present invention (Examples 1 to 3) were confirmed to be excellent in all aspects of crystal precipitation, printability, inter-pin balling, void area ratio, and flux residue thermal cycle tests. Therefore, it was confirmed that the solder composition of the present invention has excellent temperature cycle reliability of the flux residue and excellent printability. [Industrial Applicability]

[0044] The flux composition and solder composition of the present invention can be suitably used as a technique for mounting electronic components on electronic substrates such as printed wiring boards of electronic devices.

Claims

1. A flux composition comprising: (A) a resin; (B) an activator; and (C) a solvent, The component (A) contains an acrylic resin (A1), The component (B) contains an organic acid (B1), The component (B1) contains dodecanedioic acid, The component (C) contains (C1) dibutyl maleate. Flux composition.

2. 2. The flux composition according to claim 1, The blending amount of the (A1) component is 50% by mass or more with respect to 100% by mass of the (A) component. Flux composition.

3. A flux composition according to claim 1 or 2, and (D) a solder powder. Solder composition.

4. A soldered portion comprising the solder composition according to claim 3. Electronic board.

Images