Solder composition and electronic substrate

Abstract

To provide a solder composition that can sufficiently suppress voids, has sufficient tack strength, and exhibits excellent solder melting properties at minute lands. [Solution] A solder composition comprising a flux composition containing (A) a rosin resin, (B) an activator, (C) an amine compound, and (D) a solvent, and (E) solder powder, wherein the (D) component contains (D1) an ester compound of a dicarboxylic acid having 3 to 7 carbon atoms and an n-alkanol having 2 to 5 carbon atoms.

Description

Technical Field

[0001] The present invention relates to a solder composition and an electronic substrate.

Background Art

[0002] A solder composition is a mixture obtained by kneading a flux composition (such as a rosin-based resin, an activator, and a solvent) with solder powder into a paste form (for example, Patent Document 1). In this solder composition, solderability such as solder melting property and the property that solder easily wets and spreads (solder wetting and spreading), as well as suppression of voids and printability, are required. On the other hand, due to the diversification of functions of electronic devices, large electronic components such as LGA (Land Grid Array) are being mounted on electronic substrates. In order to mount an LGA, micro lands are required. In this case, the solder composition is required to have solder melting property at the micro lands. Also, of course, suppression of voids is required. Furthermore, after mounting an electronic component on an electronic substrate, it is also required that the solder composition has a certain degree of adhesiveness (tack force). Conventionally, in a solder composition, usually, a combination of glycol ether solvents is used as a solvent. However, when using only a combination of glycol ether solvents, void discharge is insufficient, it is difficult to reduce voids, and there are also problems in terms of solder melting property and tack force at micro lands.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The present invention aims to provide a solder composition that can sufficiently suppress voids, has sufficient tack force, and exhibits excellent solder melting properties at minute lands, as well as an electronic substrate using the same. [Means for solving the problem]

[0005] According to the present invention, the following solder composition and electronic substrate are provided. [1] A solder composition comprising (A) a rosin resin, (B) an activator, (C) an amine compound, and (D) a solvent, and (E) solder powder, The aforementioned component (D) contains an ester compound of a dicarboxylic acid having 3 to 7 carbon atoms and an n-alkanol having 2 to 5 carbon atoms. Solder composition. [2] In the solder composition described in [1], The aforementioned component (D1) is dibutyl adipate. Solder composition. [3] In the solder composition described in [1] or [2], The (C) component is at least one selected from the group consisting of (C1) imidazole compounds and (C2) triazole compounds. Solder composition. [4] An electronic circuit board comprising a soldered portion using the solder composition described in any of [1] to [3]. [Effects of the Invention]

[0006] According to one aspect of the present invention, a solder composition that can sufficiently suppress voids, has sufficient tack force, and exhibits excellent solder melting properties at minute lands, as well as an electronic substrate using the same, can be provided. [Modes for carrying out the invention]

[0007] First, the solder composition according to this embodiment will be described. The solder composition according to this embodiment is a solder composition containing a flux composition containing (A) a rosin-based resin, (B) an activator, (C) an amine compound, and (D) a solvent, and (E) solder powder. The (D) component contains (D1) an ester compound of a dicarboxylic acid having 3 to 7 carbon atoms and an n-alkanol having 2 to 5 carbon atoms.

[0008] According to this embodiment, a solder composition can be obtained that can sufficiently suppress voids, has sufficient tack force, and exhibits excellent solder melting properties at minute lands. The reason for this is not entirely clear, but the inventors speculate as follows. In other words, in the solder composition according to this embodiment, (D) solvent is (D1), an ester compound of a dicarboxylic acid having 3 to 7 carbon atoms and an n-alkanol having 2 to 5 carbon atoms. This (D1) component has a high void suppression effect and can also improve solder meltability in minute lands. Furthermore, when using solder powder with a small particle size to accommodate narrow-pitch components, solder meltability tends to decrease. In this embodiment, this is addressed by using (C) an amine compound. Moreover, this (D1) component can impart sufficient tack strength to the solder composition. The inventors surmise that the effects of the present invention described above are achieved in this manner.

[0009] [Flax composition] Next, the flux composition used in this embodiment will be described. The flux composition used in this embodiment is a component of the solder composition other than the solder powder, and contains (A) a rosin-based resin, (B) an activator, (C) an amine compound, and (D) a solvent, which will be described below.

[0010] [(A) component] Examples of (A) rosin-based resins used in this embodiment include rosins and rosin-modified resins. Examples of rosins include gum rosin, wood rosin, and tall oil rosin. Examples of rosin-modified resins include disproportionated rosin, polymerized rosin, hydrogenated rosin, and derivatives thereof. Examples of hydrogenated rosin include fully hydrogenated rosin, partially hydrogenated rosin, and hydrogenated unsaturated organic acid-modified rosin (also called "hydrogenated acid-modified rosin") which is a rosin modified with unsaturated organic acids (aliphatic unsaturated monobasic acids such as (meth)acrylic acid, aliphatic unsaturated dibasic acids such as fumaric acid and maleic acid, and unsaturated carboxylic acids having aromatic rings such as cinnamic acid). These rosin-based resins may be used individually or mixed in groups of two or more.

[0011] The amount of component (A) is preferably 20% to 60% by mass, and more preferably 30% to 50% by mass, based on 100% by mass of the flux composition. If the amount of component (A) is above the lower limit, oxidation of the copper foil surface of the soldering land can be prevented, making it easier for molten solder to wet the surface, thereby improving solderability and sufficiently suppressing solder balls. Furthermore, if the amount of component (A) is below the upper limit, the amount of flux residue can be sufficiently suppressed.

[0012] [(B) Component] The (B) activator used in this embodiment preferably contains an (B1) organic acid. This (B1) component can improve solder meltability.

[0013] (B1) Component examples include monocarboxylic acids, dicarboxylic acids, and other organic acids. These may be used individually or in combination of two or more. Examples of monocarboxylic acids include formic acid, acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, enanthic acid, capric acid, lauric acid, myristic acid, pentadecyl acid, palmitic acid, margaric acid, stearic acid, tubercurostearic acid, arachidic acid, behenic acid, lignoceric acid, and glycolic acid. Examples of dicarboxylic acids include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, dodecanediic acid, fumaric acid, maleic acid, diglycolic acid, phenylsuccinic acid, and tartaric acid. Other organic acids include 1,2,3-propanetricarboxylic acid, 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.

[0014] The amount of component (B1) is preferably 2% by mass or more and 15% by mass or less, and more preferably 4% by mass or more and 10% by mass or less, based on 100% by mass of the flux composition. If the amount of component (B1) is above the lower limit, the meltability tends to be improved, while if it is below the upper limit, the insulating properties of the flux composition tend to be maintained.

[0015] Component (B) may further contain other activators (such as halogenated activators and amine activators) in addition to component (B1), as long as they do not inhibit the effects of the present invention. The total amount of component (B1) is preferably 80% by mass or more, more preferably 90% by mass or more, and particularly preferably 95% by mass or more, based on 100% by mass of component (B).

[0016] The blending amount of component (B) is preferably 2% by mass or more and 15% by mass or less, and more preferably 4% by mass or more and 10% by mass or less with respect to 100% by mass of the flux composition. If the blending amount of component (B) is at least the above lower limit, the activating action tends to be improved, while if it is at most the above upper limit, the insulating property of the flux composition tends to be maintained.

[0017] [Component (C)] Examples of the (C) amine compound used in this embodiment include (C1) imidazole compounds and (C2) triazole compounds. This component (C) can improve soldering property or storage stability without adversely affecting voids. These may be used alone or in combination of two or more. In particular, it is preferable to use the (C1) component and the (C2) component in combination.

[0018] The component (C1) is preferably an imidazole compound having an alkyl group, and more preferably an imidazole compound having no phenyl group. Examples of the component (C1) include 2-ethyl-4-methylimidazole, 2,4-dimethylimidazole, 2-ethylimidazole, 2-pentylimidazole, and 2-undecyl-4-methylimidazole. Among these, it is preferable to use 2-ethyl-4-methylimidazole. When using the component (C1), its blending amount is preferably 1% by mass or more and 10% by mass or less, and more preferably 2% by mass or more and 7% by mass or less with respect to 100% by mass of the flux composition.

[0019] The component (C2) is preferably a triazole compound having a benzene ring. Examples of the component (C2) include benzotriazole, carboxybenzotriazole, methylbenzotriazole, 2-(2-hydroxy-5-methylphenyl)benzotriazole, and 1,2,4-triazole. Among these, it is preferable to use benzotriazole. When component (C2) is used, its amount is preferably 0.1% by mass or more and 3% by mass or less, and more preferably 0.2% by mass or more and 1% by mass or less, based on 100% by mass of the flux composition.

[0020] (C) The amount of component (C) is preferably 2% to 12% by mass, and more preferably 3% to 7% by mass, based on 100% by mass of the flux composition. If the amount of component (B) is above the lower limit, solderability tends to be improved, while if it is below the upper limit, the insulating properties of the flux composition tend to be maintained.

[0021] [(D) component] The solvent (D) used in this embodiment must contain an ester compound of a dicarboxylic acid having 3 to 7 carbon atoms (D1) and an n-alkanol having 2 to 5 carbon atoms (C2). This (D1) component can suppress the generation of voids, provide sufficient tack force, and improve solder meltability at minute lands. The ester compound is preferably a diester. Furthermore, the number of carbon atoms in the dicarboxylic acid of component (D1) is preferably 4 to 6, and particularly preferably 5 or 6. The number of carbon atoms in the n-alkanol of component (D1) is preferably 3 to 5, and particularly preferably 3 or 4. Examples of component (D1) include dibutyl adipate (boiling point: 305°C), dipropyl adipate (boiling point: 144°C), dibutyl succinate (boiling point: 274°C), diethyl succinate (boiling point: 217°C), and diethyl pimelate (boiling point: 193°C). Among these, dibutyl adipate or dibutyl succinate is preferred from the viewpoint of void suppression. In this specification, the boiling point refers to the boiling point at 1013 hPa.

[0022] The amount of component (D1) is preferably 40% by mass or more, more preferably 55% by mass or more, and particularly preferably 70% by mass or more, relative to 100% by mass of component (D). If the amount of component (D1) is above the lower limit, the generation of voids can be suppressed more reliably, and solder meltability can be improved. The amount of component (D1) may be 100% by mass or less, or 90% by mass or less, relative to 100% by mass of component (D).

[0023] Component (D) may contain solvents other than component (D1) (component (D2)) to the extent that the objectives of the present invention can be achieved. The boiling point of component (D2) is preferably 240°C or higher and 320°C or lower. Examples of component (D2) include diethylene glycol monohexyl ether, diethylene glycol monobutyl ether, α,β,γ-terpineol, benzyl glycol, diethylene glycol mono-2-ethylhexyl ether (EHDG, boiling point: 272°C), tripropylene glycol, diethylene glycol monobenzyl ether, tripropylene glycol monomethyl ether, tripropylene glycol monobutyl ether, dipropylene glycol monobutyl ether, diethylene glycol monoethyl ether acetate, and 2,2-dimethyl-1,3-propanediol. These may be used individually or in combination of two or more. Among these, diethylene glycol mono-2-ethylhexyl ether is preferred.

[0024] The amount of component (D) is preferably 20% to 60% by mass, more preferably 25% to 50% by mass, and particularly preferably 30% to 40% by mass, based on 100% by mass of the flux composition. If the amount of solvent is within the above range, the viscosity of the resulting solder composition can be appropriately adjusted to an appropriate range.

[0025] [Sickling] The flux composition used in this embodiment may further contain a thixotropic agent from the viewpoint of printability and other factors. Any known thixotropic agent can be used as appropriate in this embodiment. Examples of thixotropic agents include hydrogenated castor oil, amides, kaolin, colloidal silica, organic bentonite, and glass frit. These may be used individually or in combination of two or more.

[0026] When using a thixotropic agent, the amount is preferably 1% to 12% by mass, more preferably 2% to 10% by mass, and particularly preferably 3% to 8% by mass, based on 100% by mass of the flux composition. If the amount of thixotropic agent is above the lower limit, thixotropy is achieved, and sagging during printing can be suppressed. If the amount of thixotropic agent is below the upper limit, the thixotropy will not be too high, and printing defects can be suppressed.

[0027] [Antioxidant] The flux composition used in this embodiment may further contain an antioxidant from the viewpoint of solder meltability and other factors. Any known antioxidant can be used as the antioxidant in this embodiment. Examples of antioxidants include sulfur compounds, hindered phenol compounds, and phosphite compounds. Among these, hindered phenol compounds are preferred.

[0028] Examples of hindered phenol compounds include pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], bis[3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionic acid][ethylenebis(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. Among these, pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] is particularly preferred from the viewpoint of solder meltability. Furthermore, these compounds may be used individually or in combination of two or more, but it is preferable to use them in combination of two or more. Specifically, it is preferable to use pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] in combination with other hindered phenol compounds.

[0029] When an antioxidant is used, the amount it is added is preferably 1% to 10% by mass, and more preferably 2% to 6% by mass, based on 100% by mass of the flux composition. The amount of antioxidant added is preferably within the above range from the viewpoint of balancing solder fusion properties and other physical properties.

[0030] [Other ingredients] In addition to components (A), (B), (C), and (D), a thixotropic agent, and an antioxidant, the flux composition used in this embodiment may optionally contain other additives and other resins. Examples of other additives include defoamers, modifiers, matting agents, and foaming agents. The amount of these additives is preferably 0.01% by mass or more and 5% by mass or less based on 100% by mass of the flux composition. Examples of other resins include acrylic resins.

[0031] [Solder composition] Next, the solder composition according to this embodiment will be described. The solder composition according to this embodiment contains the flux composition used in the above-mentioned embodiment and the solder powder (E) described below. The amount of flux composition is preferably 5% to 35% by mass, more preferably 7% to 18% by mass, and particularly preferably 8% to 15% by mass, based on 100% by mass of the solder composition. If the amount of flux composition is less than 5% by mass (when the amount of solder powder exceeds 95% by mass), there is insufficient flux composition as a binder, making it difficult to mix the flux composition with the solder powder. On the other hand, if the amount of flux composition exceeds 35% by mass (when the amount of solder powder is less than 65% by mass), it tends to be difficult to form a sufficient solder joint when using the resulting solder composition.

[0032] [(E) component] The solder powder (E) used in this embodiment is preferably a solder powder with a melting point of 200°C or higher and 250°C or lower. In this embodiment, assuming that solder powder with a melting point of 200°C or higher and 250°C or lower is used, a component (D) with an appropriate boiling point is used. In this solder powder, a solder alloy mainly composed of tin (Sn) is preferred. The second element of this alloy may include silver (Ag), copper (Cu), zinc (Zn), bismuth (Bi), indium (In), and antimony (Sb). Furthermore, other elements (third and subsequent elements) may be added to this alloy as needed. Other elements may include copper, silver, bismuth, indium, antimony, and aluminum (Al). Here, lead-free solder powder refers to powder of solder metal or alloy without the addition of lead. However, the presence of lead as an unavoidable impurity in lead-free solder powder is permissible, but in this case, the amount of lead is preferably 300 ppm by mass or less.

[0033] Examples of solder alloys used in lead-free solder powder include Sn-Ag and Sn-Ag-Cu alloys. Among these, Sn-Ag-Cu solder alloys are preferred from the viewpoint of solder joint strength. The melting point of Sn-Ag-Cu solder is usually between 200°C and 250°C (preferably between 200°C and 240°C). Among Sn-Ag-Cu solders, those with a low silver content have a melting point of 210°C to 250°C (preferably between 220°C and 240°C).

[0034] Component (E) preferably consists of powder with a particle size of 10 μm to 25 μm, which accounts for 90% or more by mass. Meeting these conditions makes it possible to use electronic circuit boards with narrow solder pad pitches. The average particle size of component (E) is more preferably 1 μm to 25 μm, even more preferably 2 μm to 22 μm, and particularly preferably 3 μm to 20 μm, from the viewpoint of being compatible with electronic substrates with narrow solder pad pitches. The average particle size can be measured using a dynamic light scattering particle size analyzer.

[0035] [Method for manufacturing solder composition] The solder composition according to this embodiment can be manufactured by blending the flux composition described above and the solder powder (E) described above in the predetermined proportions and stirring them together.

[0036] [Electronic circuit board] Next, the electronic circuit board according to this embodiment will be described. The electronic circuit board according to this embodiment is characterized by having a soldered portion using the solder composition described above. The electronic circuit board according to this embodiment can be manufactured by mounting electronic components on an electronic circuit board (such as a printed circuit board) using the solder composition. The solder composition according to this embodiment, as described above, can sufficiently suppress large-diameter voids even when the printed area of ​​the solder composition is large. Therefore, it can be used particularly suitably when QFN is used as an electronic component. The coating equipment used here includes screen printing machines, metal mask printing machines, dispensers, and jet dispensers. Furthermore, electronic components can be mounted on an electronic circuit board by a reflow process, in which electronic components are placed on a solder composition applied by the coating apparatus, and the solder is heated under predetermined conditions in a reflow oven to mount the electronic components onto a printed circuit board.

[0037] In the reflow process, the electronic components are placed on the solder composition and heated in a reflow oven under predetermined conditions. This reflow process enables sufficient solder bonding between the electronic components and the printed circuit board. As a result, the electronic components can be mounted on the printed circuit board. The reflow conditions should be set appropriately according to the melting point of the solder. For example, the preheat temperature is preferably 140°C to 200°C, and more preferably 150°C to 160°C. The preheat time is preferably 60 seconds to 120 seconds. The peak temperature is preferably 230°C to 270°C, and more preferably 240°C to 255°C. Furthermore, the holding time at a temperature of 220°C or higher is preferably 20 seconds to 80 seconds.

[0038] Furthermore, the solder composition and electronic substrate according to this embodiment are not limited to the above-described embodiment, and any modifications, improvements, etc., within the scope that can achieve the objectives of the present invention are included in the present invention. For example, in the aforementioned electronic substrate, the printed circuit board and electronic components are bonded by a reflow process, but this is not the only method. For example, instead of the reflow process, the printed circuit board and electronic components 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 absorption band of the metal. Examples of laser light sources include solid-state lasers (ruby, glass, YAG, etc.), semiconductor lasers (GaAs, and InGaAsP, etc.), liquid lasers (dyes, etc.), and gaseous lasers (He-Ne, Ar, CO2, and excimers, etc.). [Examples]

[0039] Next, the present invention will be described in more detail with reference to examples and comparative examples, but the present invention is not limited in any way by these examples. The materials used in the examples and comparative examples are listed below. (Component A) Rosin-based resin A: Hydrogenated acid-modified rosin, product name "Pine Crystal KE-604", manufactured by Arakawa Chemical Industries, Ltd. Rosin-based resin B: Special modified rosin, product name "Haritack F-85", manufactured by Harima Chemicals Co., Ltd. ((B1) component) Organic acid A: Adipic acid Organic acid B: Malonic acid Organic acid C: Phenylsuccinic acid ((C1) component) Amine compound A: 2-ethyl-4-methylimidazole ((C2) component) Amine compound B: 1,2,3-benzotriazole (Component D1) Solvent A: Dibutyl adipate (boiling point: 305°C) ((D2) component) Solvent B: Diethylene glycol mono-2-ethylhexyl ether (2-ethylhexyl diglycol (EHDG), boiling point: 272°C), manufactured by Nippon Emulsifier Co., Ltd. Solvent C: Diisobutyl adipate (boiling point: 293°C) Solvent D: Diethylene glycol dibutyl ether (boiling point: 256°C), product name "HighSolve BDB", manufactured by Toho Chemical Industry Co., Ltd. (Other ingredients) Thixolytic agent: High-grade fatty acid polyamide, product name "Talen VA-79", manufactured by Kyoeisha Chemical Co., Ltd. Antioxidant A: Pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], trade name "ANOX20", manufactured by Shiraishi Calcium Co., Ltd. Antioxidant B:N,N'-bis{3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl}hydrazine, trade name "Irganox MD1024", manufactured by BASF. ((E) component) Solder powder: Alloy composition is Sn-3.0Ag-0.5Cu, particle size distribution is 15-25 μm (corresponding to IPC-J-STD-005A Type 5), solder melting point is 217-220°C.

[0040] [Example 1] Rosin resin A (32% by mass), rosin resin B (9.5% by mass), organic acid A (7% by mass), organic acid B (1% by mass), solvent A (36% by mass), antioxidant A (2% by mass), antioxidant B (1% by mass), amine compound A (5% by mass), amine compound B (0.5% by mass), and thixotropic agent (6% by mass) were placed in a container and mixed using a planetary mixer to obtain a flux composition. Subsequently, 12% by mass of the obtained flux composition and 88% by mass of solder powder (100% by mass in total) were placed in a container and mixed in a planetary mixer to prepare the solder composition.

[0041] [Examples 2-4] 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 1-3] 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.

[0042] <Evaluation of solder composition> The solder composition was evaluated (LGA voids, tack force, microland meltability, BGA non-fusion) using the following method. The results are shown in Table 1. (1) LGA void A solder composition was printed onto a substrate using a metal mask with a mask thickness of 80 μm and a mask aperture ratio of 80%. Next, a 0.5 mm PLGA (plastic land grid array package, 228 pads, surface treatment: NiAu) was mounted, and then a reflow process was performed under the following conditions: preheating temperature of 150-180°C for 80 seconds, holding time of 220°C or higher for 50 seconds, and peak temperature of 245°C to fabricate an evaluation substrate. Then, using a Nordson "Dage XD7600 Diamond" X-ray inspection device, the solder joints of the 0.5mm PLGA were observed, and the total void area ratio [(total void area / total pad area) × 100] in the pad area was calculated. The voids were then evaluated according to the following criteria. ◎: The total void area ratio is 30% or less. ○: The total void area ratio is between 30% and 35%. △: The total void area ratio is between 35% and 40%. ×: The total void area ratio exceeds 40%. (2) Tack power • Adhesion test (initial stage) The tackiness of the obtained solder compositions was measured immediately after preparation in accordance with the conditions specified in JIS standard Z3284-3 "Tackiness Test". The thickness of the metal mask used was changed to 40 μm. The tackiness measuring device used was Malcolm's "Tackiness tester TK-1 (product name)". The tack force of the measured solder compositions was defined as the initial tack force (N1). • Adhesion test (after 24 hours) The tackiness of the obtained solder composition was measured after being left for 24 hours at 25°C and 50% humidity, under the same conditions as specified in the initial tackiness test described above. The tack force of the measured solder composition was defined as the tack force (N2) after 24 hours. • Adhesion test (rate of change) The tack force (N1) and tack force (N2), measured in the initial adhesion test and the adhesion test after 24 hours, were evaluated using the following formula to calculate the percentage change in tack force, and the tack force was evaluated according to the following criteria. Tack force change rate (%) = (N2 - N1) / N1 ○: The rate of change in tack force is between -10% and 10%. △: The tack force change rate is -50% or more but less than -10%, or more than 10% but 50% or less. ×: The tack force change rate is less than -50% or greater than 50%. (3) Meltability of microlands A metal mask with 97 holes of 0.2 mm diameter and a thickness of 100 μm was used to print a solder composition onto a substrate at a printing speed of 50 mm / sec and a printing pressure of 0.2 N. Subsequently, a reflow process was performed with a preheating temperature of 150-180°C for 80 seconds, a holding time of 220°C or higher for 50 seconds, and a peak temperature of 245°C to produce a test substrate. Of the printed areas (97) on the test substrate, the areas where the solder melted were measured, and the meltability of the micro-lands was evaluated according to the following criteria. ○: There are 90 or more melted areas. △: There are 50 or more but less than 90 melted areas. ×: There are fewer than 50 melted areas. (4) BGA unfused A BGA component (228 pins, 0.5 mm pitch) was prepared and subjected to degradation treatment by being placed in a constant temperature and humidity chamber at 85°C and 85% RH for 24 hours. This was used as a sample of the BGA component. Next, a solder composition was printed onto a substrate (Tamura Corporation's "SP-TDC") capable of mounting this BGA component using a 120 μm thick metal mask, the BGA component was mounted, and a reflow process was performed under the conditions of preheating at a temperature of 150-180°C for 80 seconds, holding at 220°C or higher for 50 seconds, and peak temperature of 245°C to produce an evaluation substrate. The BGA components were peeled off the obtained evaluation boards, and their backsides were visually inspected. The occurrence rate of dots where the BGA balls and molten solder were not fused (unfused dots) [(unfused dots / total dots) × 100] was measured. Based on the occurrence rate of unfused dots, the BGA unfused components were evaluated according to the following criteria. ◎: The occurrence rate of unfused dots is 1% or less. ○: The occurrence rate of unfused dots is greater than 1% and less than or equal to 3%. △: The occurrence rate of unfused dots is between 3% and 10%. ×: The occurrence rate of unfused dots is over 10%.

[0043] [Table 1]

[0044] As is clear from the results shown in Table 1, the solder compositions of the present invention (Examples 1-4) were confirmed to have good results in all aspects, including LGA voids, tack force, microland meltability, and BGA non-fusion. Therefore, it has been confirmed that the solder composition of the present invention can sufficiently suppress voids, has sufficient tack strength, and exhibits excellent solder melting properties at minute lands. [Industrial applicability]

[0045] The solder composition of the present invention can be suitably used as a technique for mounting electronic components on electronic circuit boards such as printed circuit boards of electronic devices.

Claims

1. A solder composition comprising (A) a rosin-based resin, (B) an activator, (C) an amine compound, and (D) a solvent, and (E) solder powder, The (D) component contains an ester compound of (D1) a dicarboxylic acid having 3 to 7 carbon atoms and an n-alkanol having 2 to 5 carbon atoms. Solder composition.

2. In the solder composition according to claim 1, The (D1) component is dibutyl adipate. Solder composition.

3. In the solder composition according to claim 1 or claim 2, The (C) component is at least one selected from the group consisting of (C1) imidazole compounds and (C2) triazole compounds. Solder composition.

4. An electronic circuit board comprising a soldering portion using the solder composition described in claim 1 or claim 2.

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