Solder composition and electronic substrate

Abstract

To provide a solder composition which can sufficiently suppress voids, and is excellent in solder melting property in a fine land.SOLUTION: A solder composition comprises a flux composition comprising (A) a rosin-based resin, (B) an activator, (C) a solvent, (D) a thixotropic agent and (E) an antioxidant, and (F) solder powder comprising 90% or more of powder having a melting point of 200°C or higher and 250°C or lower and a particle diameter of 10 μm or more and 25 μm or less by mass ratio, wherein the component (C) comprises (C1) any one dialkyl ether of dialkylene glycol, trialkylene glycol and tetraalkylene glycol, and a blending amount of the component (C1) is 40 mass% or more with respect to 100 mass% of the component (C).SELECTED DRAWING: None

Description

[Technical Field]

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

[0002] A solder composition is a paste-like mixture obtained by kneading a flux composition (including rosin-based resin, activator, solvent, etc.) into solder powder (see, for example, Patent Document 1). This solder composition is required to have not only solderability including solder meltability and the property that solder easily wets and spreads (solder wet spreading), but also void suppression, printability, and the like. On the other hand, due to the diversification of functions of electronic devices, large electronic components such as LGA (Land Grid Array) have come to be mounted on electronic substrates. Mounting LGAs requires fine lands, and in this case, the solder composition is required to have good solder meltability on fine lands. Further, among large electronic components, there are electronic components having a large electrode terminal area (e.g., QFN (Quad Flatpack No-lead), power transistors). In such electronic components, voids tend to easily occur because the printing area of the solder composition is large. [Prior Art Literature] [Patent Literature]

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

[0004] Furthermore, in order to accommodate narrow-pitch components such as LGA, it is necessary to reduce the particle size of the solder powder. However, when using solder powder with such small particle size, voids tend to occur more easily, and solder meltability tends to decrease. As described above, it has been difficult to achieve both solder meltability at minute lands and void suppression effects in a solder composition.

[0005] The present invention aims to provide a solder composition that can sufficiently suppress voids and exhibits excellent solder melting properties at minute lands, as well as an electronic substrate using the same. [Means for solving the problem]

[0006] According to the present invention, the following solder composition and electronic substrate are provided. [1] A flux composition containing (A) a rosin resin, (B) an activator, (C) a solvent, (D) a thixotropic agent, and (E) an antioxidant, and (F) solder powder having a melting point of 200°C or higher and a particle size of 10 μm or higher and 25 μm or lower, which accounts for 90% or more of the total by mass ratio. The aforementioned component (C) contains a dialkyl ether which is one of (C1) dialkylene glycol, trialkylene glycol, and tetraalkylene glycol. The amount of component (C1) is 40% by mass or more relative to 100% by mass of component (C). Solder composition. [2] In the solder composition described in [1], The (C1) component is at least one selected from the group consisting of diethylene glycol dibutyl ether and tetraethylene glycol dimethyl ether. Solder composition. [3] In the solder composition described in [1] or [2], The aforementioned component (E) contains pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] Solder composition. In the solder composition described in any of [4] [1] to [3], The flux composition further contains an imidazole compound. Solder composition. In the solder composition described in any of [5] [1] to [4], Used when reflow soldering QFN Solder composition. [6] A soldering part comprising a soldering part using the solder composition described in any of [1] to [5], Electronic circuit board. [Effects of the Invention]

[0007] According to one aspect of the present invention, a solder composition that can sufficiently suppress voids 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]

[0008] The solder composition according to this embodiment contains a flux composition containing (A) a rosin-based resin, (B) an activator, (C) a solvent, (D) a thixotropic agent, and (E) an antioxidant, and (F) solder powder having a melting point of 200°C or higher and a particle size of 10 μm or higher and 25 μm or lower, which accounts for 90% or more of the total by mass ratio. The (C) solvent contains a dialkyl ether which is one of (C1) dialkylene glycol, trialkylene glycol, and tetraalkylene glycol. Furthermore, the amount of this (C1) component is 40% by mass or more relative to 100% by mass of component (C).

[0009] According to this embodiment, a solder composition can be obtained that can sufficiently suppress voids and has 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, (C) solvent is (C1) a dialkyl ether selected from dialkylene glycol, trialkylene glycol, and tetraalkylene glycol. This (C1) component has a high void suppression effect and can also improve solder meltability in minute lands. Furthermore, in this embodiment, in order to accommodate narrow-pitch components, the particle size of the solder powder is reduced so that powder with a particle size of 10 μm or more and 25 μm or less accounts for 90% or more of the total by mass ratio. When solder powder with such small particle size is used, voids tend to be more likely to occur and solder meltability tends to decrease. In response to this, in this embodiment, this is addressed by using (E) an antioxidant. Normally, solder meltability is addressed by the composition of activators such as organic acids, but depending on the type of organic acid, it can be a cause of void generation. Therefore, in this embodiment, solder meltability is maintained by component (E), which does not cause void generation. The inventors surmise that the effects of the present invention described above are achieved in this manner.

[0010] [Flax composition] First, 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) a solvent, (D) a thixotropic agent, and (E) an antioxidant, which will be described below.

[0011] [(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.

[0012] 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.

[0013] [(B) Component] The (B) activator used in this embodiment preferably contains (B1) an organic acid having 10 or more carbon atoms. This (B1) component is resistant to deactivation and can improve melting properties in minute areas. Furthermore, this (B1) component tends not to contribute to copper corrosion.

[0014] (B1) Examples of components include dodecanedioic acid, eicosanedioic acid, dimer acid, trimer acid, 1-hydroxy-2-naphthoic acid, 3-hydroxy-2-naphthoic acid, and 1,4-dihydroxy-2-naphthoic acid. These may be used individually or in combination of two or more.

[0015] The blending amount of component (B1) is preferably 2% by mass or more and 15% by mass or less, more preferably 4% by mass or more and 10% by mass or less, based on 100% by mass of the flux composition. If the blending amount of component (B1) is not less than the above lower limit, the meltability in a micro area tends to be improved; on the other hand, if the blending amount is not more than the above upper limit, the insulating properties of the flux composition tend to be maintained.

[0016] Component (B) may contain (B2) an organic acid having less than 10 carbon atoms within the range where the effects of the present invention can be achieved. Examples of component (B2) include monocarboxylic acids having less than 10 carbon atoms, dicarboxylic acids, and other organic acids. Examples of monocarboxylic acids having less than 10 carbon atoms include formic acid, acetic acid, propionic acid, and butyric acid. Examples of dicarboxylic acids having less than 10 carbon atoms include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, and azelaic acid. Examples of other organic acids having less than 10 carbon atoms include lactic acid, benzoic acid, salicylic acid, and citric acid.

[0017] Component (B) may further contain other activators (such as (B3) halogen-based activators and (B4) amine-based activators) in addition to component (B1) and component (B2), within a range that does not impair the effects of the present invention. The total blending amount of component (B1) and component (B2) 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).

[0018] The blending amount of component (B) is preferably 4% by mass or more and 20% by mass or less, more preferably 7% by mass or more and 18% by mass or less, and particularly preferably 10% by mass or more and 16% by mass or less, based on 100% by mass of the flux composition. If the blending amount of component (B) is not less than the above lower limit, the activation effect tends to be improved; on the other hand, if the blending amount is not more than the above upper limit, the insulating properties of the flux composition tend to be maintained.

[0019] [(C) component] The solvent (C) used in this embodiment must contain a dialkyl ether from among (C1) dialkylene glycol, trialkylene glycol, and tetraalkylene glycol. The (C1) component can suppress the generation of voids and also improve solder meltability in minute lands. Considering the melting point of component (F), the boiling point of component (C1) is preferably 230°C or higher and 290°C or lower. Examples of component (C1) include diethylene glycol dibutyl ether (boiling point: 256°C) and tetraethylene glycol dimethyl ether (boiling point: 275°C). Among these, diethylene glycol dibutyl ether is preferred from the viewpoint of void suppression. In this specification, the boiling point refers to the boiling point at 1013 hPa.

[0020] The amount of component (C1) is 40% by mass or more relative to 100% by mass of component (C). If the amount of component (C1) is less than 40% by mass, the amount of glycol-based solvent having hydroxyl groups in its molecule may increase, resulting in insufficient solder meltability at minute lands. From a similar viewpoint, the amount of component (C1) is preferably 50% by mass or more, more preferably 60% by mass or more, and particularly preferably 70% by mass or more, relative to 100% by mass of component (C). It is particularly preferable that the flux composition used in this embodiment does not contain glycol-based solvent having hydroxyl groups in its molecule.

[0021] Component (C) may contain a solvent other than component (C1) (component (C2)) to the extent that the objectives of the present invention can be achieved. Examples of component (C2) include diethylene glycol monohexyl ether (HeDG), diethylene glycol monobutyl ether, α,β,γ-terpineol, benzyl glycol, diethylene glycol mono-2-ethylhexyl ether (EHDG), 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.

[0022] The amount of component (C) is preferably 20% to 60% by mass, more preferably 24% to 50% by mass, and particularly preferably 28% 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.

[0023] [(D) component] In this embodiment, any known thixotropic agent (D) can be used as appropriate. Examples of component (D) 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.

[0024] The amount of component (D) 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 component (D) is above the lower limit, thixotropy is obtained and sagging during printing can be suppressed. If the amount of component (D) is below the upper limit, the thixotropy will not be too high and printing defects can be suppressed.

[0025] [(E) component] In this embodiment, any known antioxidant can be used as the (E) antioxidant. Examples of component (E) include sulfur compounds, hindered phenol compounds, and phosphite compounds. Among these, hindered phenol compounds are preferred. This (E) component allows solder meltability to be maintained even when using solder powder with small particle size.

[0026] 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.

[0027] The amount of component (E) is preferably 1% to 12% by mass, more preferably 2% to 8% by mass, and particularly preferably 3% to 6% by mass, based on 100% by mass of the flux composition. The amount of component (E) is preferably within the above range from the viewpoint of balancing solder meltability and other physical properties.

[0028] [Imidazole compounds] In the flux composition used in this embodiment, an imidazole compound may be further included from the viewpoint of further improving solder meltability. As the imidazole compound used here, any known solvent can be used as appropriate. Examples of such imidazole compounds include 2-ethylimidazole and 2-ethyl-4-methylimidazole. When using an imidazole compound, the amount of the compound is preferably 0.01% to 14% by mass, more preferably 1% to 12% by mass, and particularly preferably 3% to 10% by mass, based on 100% by mass of the flux composition. If the amount of the imidazole compound is within the above range, solder meltability can be improved while maintaining viscosity stability during storage.

[0029] [Other ingredients] In addition to components (A), (B), (C), (D), (E), and imidazole compounds, 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.

[0030] [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 (F) 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.

[0031] [(F) component] The solder powder (F) used in this embodiment is a solder powder having a melting point of 200°C or higher and 250°C or lower. In this embodiment, assuming the use of solder powder with a melting point of 200°C or higher and 250°C or lower, a suitable boiling point of component (C) 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.

[0032] 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).

[0033] Component (F) must consist of powder with a particle size of 10 μm or more and 25 μm or less, accounting for 90% or more by mass. If powder with a particle size of 10 μm or less, or 25 μm or more, accounts for 10% or more by mass, it will not be suitable for electronic circuit boards with narrow solder pad pitches. The average particle size of component (F) 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.

[0034] [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.

[0035] [Electronic circuit board] Next, the electronic substrate 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.

[0036] 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 60 seconds.

[0037] 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]

[0038] 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: 3-hydroxy-2-naphthoic acid, manufactured by Tokyo Chemical Industry Co., Ltd. Organic acid B: Dimer acid, product name "UNIDYME14", manufactured by Maruzen Oil & Chemical Trading Co., Ltd. ((B2) component) Organic acid C: Malonic acid Organic acid D: Adipic acid ((C1) component) Solvent A: Diethylene glycol dibutyl ether (boiling point: 256°C), product name "HighSolve BDB", manufactured by Toho Chemical Industry Co., Ltd. Solvent B: Tetraethylene glycol dimethyl ether (boiling point: 275°C), product name "HySolve MTEM", manufactured by Toho Chemical Industry Co., Ltd. ((C2) component) Solvent C: Diethylene glycol monohexyl ether (hexyl diglycol, HeDG, boiling point: 258°C), manufactured by Nippon Emulsifier Co., Ltd. Solvent D: Diethylene glycol mono-2-ethylhexyl ether (2-ethylhexyl diglycol (EHDG), boiling point: 272°C), manufactured by Nippon Emulsifier Co., Ltd. Solvent E: Tripropylene glycol monobutyl ether (BFTG, boiling point: 276°C) ((D) component) Thixolytic agent: High-grade fatty acid polyamide, product name "Talen VA-79", manufactured by Kyoeisha Chemical Co., Ltd. ((E) component) 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. (Other ingredients) Imidazole compound: 2-ethyl-4-methylimidazole (Component F) 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.

[0039] [Example 1] Rosin resin A (35% by mass), rosin resin B (5% by mass), organic acid A (2% by mass), organic acid B (5% by mass), organic acid C (2% by mass), organic acid D (5% by mass), solvent A (30.5% by mass), antioxidant A (4% by mass), antioxidant B (1% by mass), imidazole compound (5% by mass), and thixotropic agent (5.5% 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.

[0040] [Example 2] 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.

[0041] <Evaluation of solder composition> The solder composition was evaluated (micro-land meltability, QFN voids, LGA voids) using the following method. The results are shown in Table 1. (1) Meltability of microlands A solder composition was printed onto a substrate using a 0.1 mm thick metal mask. 100 test patterns each of copper foil pads with diameters of 0.28 mm, 0.26 mm, 0.24 mm, 0.22 mm, and 0.20 mm were printed. Then, a reflow process was performed under the following conditions: preheating temperature of 140-200°C for 120 seconds, holding time above 220°C for 40 seconds, and peak temperature of 250°C to prepare test substrates. The test substrates were observed under a microscope, and the diameter of the smallest molten pad (unit: mmφ) was measured. The meltability of the micro-lands was then evaluated according to the following criteria. ○: The minimum molten pad diameter is 0.20 mm. ×: The minimum molten pad diameter is 0.22 mm or larger. (2) QFN void A solder composition was printed onto a substrate using a 0.1 mm thick metal mask, and 0.5 mm pitch QFNs (Quad Flat Non-leaded packages) were mounted. Furthermore, a reflow process was performed under the same conditions as for the evaluation of micro-land meltability to create an evaluation substrate. Then, using a Maastoken Solutions "MUX-3400" X-ray inspection device, voids were measured, and the void area ratio [(total void area / total land area) × 100] in the pad area of ​​the QFN was calculated using the device's standard application. The voids were then evaluated according to the following criteria. ○: The void area ratio is 20% or less. △: The void area ratio is between 20% and 25%. ×: The void area ratio is greater than 25%. (3) LGA void A solder composition was printed onto a substrate using a 0.1 mm thick metal mask, and a 0.5 mm pitch LGA (Land Grid Array) was mounted. Furthermore, a reflow process was performed under the same conditions as for evaluating the meltability of micro-lands to create an evaluation substrate. Then, using a Maerstoken Solutions "MUX-3400" X-ray inspection device, voids were measured, and the void area ratio [(total void area / total land area) × 100] in the LGA pad area was calculated using the device's standard application. The voids were then evaluated according to the following criteria. ○: The void area ratio is 20% or less. △: The void area ratio is between 20% and 25%. ×: The void area ratio is greater than 25%.

[0042] [Table 1]

[0043] As is clear from the results shown in Table 1, the solder compositions of the present invention (Examples 1-2) were confirmed to have good results in all aspects, including microland meltability, QFN voids, and LGA voids. Therefore, it has been confirmed that the solder composition of the present invention can sufficiently suppress voids and exhibits excellent solder melting properties at minute lands. [Industrial applicability]

[0044] 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) a solvent, (D) a thixotropic agent, and (E) an antioxidant, and (F) solder powder having a melting point of 200°C or higher and a particle size of 10 μm or higher and 25 μm or lower, which accounts for 90% or more of the total by mass ratio, The aforementioned component (C) has a boiling point of (C1) of 230°C or higher and 290°C or lower, and contains a dialkyl ether selected from dialkylene glycol, trialkylene glycol, and tetraalkylene glycol. The amount of component (C1) is 40% by mass or more relative to 100% by mass of component (C), The aforementioned component (E) contains pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], The amount of component (A) is 20% by mass or more and 60% by mass or less based on 100% by mass of the flux composition. The amount of component (B) is 4% by mass or more and 20% by mass or less based on 100% by mass of the flux composition. The amount of component (C) is 20% by mass or more and 60% by mass or less based on 100% by mass of the flux composition. The amount of component (D) is 1% by mass or more and 12% by mass or less based on 100% by mass of the flux composition. The amount of component (E) is 1% by mass or more and 12% by mass or less based on 100% by mass of the flux composition. The amount of the flux composition is 5% by mass or more and 35% by mass or less, relative to 100% by mass of the solder composition. The amount of component (F) is 65% by mass or more and 95% by mass or less, relative to 100% by mass of the solder composition. Solder composition.

2. In the solder composition according to claim 1, The (C1) component is at least one selected from the group consisting of diethylene glycol dibutyl ether and tetraethylene glycol dimethyl ether. Solder composition.

3. In the solder composition according to claim 1 or claim 2, The flux composition further contains an imidazole compound, The amount of the imidazole compound is 0.01% by mass or more and 14% by mass or less, relative to 100% by mass of the flux composition. Solder composition.

4. In the solder composition according to claim 1 or claim 2, Used when reflow soldering QFN, Solder composition.

5. A soldered portion is provided which has been soldered using the solder composition described in claim 1 or claim 2. Electronic circuit board.

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