Flux composition, solder composition, and method for manufacturing electronic substrate

Abstract

To provide a flux composition that exhibits superior ionic cleanliness, excels in the removal of flux residue with aqueous cleaners, and demonstrates superior solder melting capability in atmospheric reflow.SOLUTION: A flux composition comprises (A) a rosin-based resin, (B) an activator, (C) a solvent, and (D) an imidazole compound. The component (B) comprises (B1) at least one selected from the group consisting of tricarboxylic acids and tetracarboxylic acids with a molecular weight of 500 or less. The content of the (B1) component is 1 mass% or more relative to 100 mass% of the flux composition. The mass ratio of the component (D) to the (B1) component ((D) / (B1)) is 0.25 or more.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a flux composition, a solder composition, and a method for producing an electronic substrate. [Background technology]

[0002] The solder composition is a paste-like mixture obtained by kneading a solder powder with a flux composition (rosin-based resin, an activator, a solvent, etc.) (see Patent Document 1). When soldering is performed using a solder composition, flux residue remains around the joint after soldering. This residue contains activator components, etc., and there is a concern that moisture may penetrate into the residue distributed across the electrodes due to condensation, etc., which may cause ion migration. Therefore, it is desirable to minimize the amount of ionic residue that could cause ion migration. This can be evaluated by ionic cleanliness. Furthermore, the presence of flux residue on the surface may cause defects in the molding or coating process or poor bonding in wire bonding. Therefore, it is desirable to remove this residue by cleaning after bonding.

[0003] Conventionally, cleaning has been carried out using cleaning agents whose main component is organic solvents with high cleaning power. However, because these agents contain a large amount of solvent, regulations have been strengthened from the viewpoints of preventing water pollution, fires, and air pollution, as well as from the viewpoint of occupational health. Therefore, in recent years, the amount of solvent used has been reduced and water-based cleaning chemicals, which are mainly composed of water, have come to be used. However, due to the change in cleaning chemical components, the cleaning performance of flux residues has tended to deteriorate, which has become a problem. Additionally, due to factors such as equipment costs, there is an increasing need for reflow soldering under atmospheric conditions. Air reflow soldering causes oxidation of the solder powder, resulting in reduced solder meltability. This tendency is more pronounced in the joints of small components, where the amount of solder composition printed is small. Furthermore, air reflow soldering tends to increase the amount of metal salts contained in the flux residue after soldering due to the effects of metal oxidation, which also tends to make the flux residue less easy to clean. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 5887330 Summary of the Invention [Problem to be solved by the invention]

[0005] An object of the present invention is to provide a flux composition and a solder composition that have good ionic cleanliness, excellent cleaning properties for flux residues with aqueous cleaners, and excellent solder melting properties in air reflow, as well as a method for producing an electronic substrate. [Means for solving the problem]

[0006] According to the present invention, there are provided the following flux composition, solder composition, and method for producing an electronic substrate. [1] A flux composition comprising (A) a rosin-based resin, (B) an activator, (C) a solvent, and (D) an imidazole compound, the component (B) contains (B1) at least one selected from the group consisting of tricarboxylic acids and tetracarboxylic acids, which have a molecular weight of 500 or less; the blending amount of the (B1) component is 1% by mass or more relative to 100% by mass of the flux composition, the mass ratio of the component (D) to the component (B1) ((D) / (B1)) is 0.25 or more; Flux composition. [2] In the flux composition according to [1], Further, (E) a hindered phenol-based antioxidant is contained, Flux composition. [3] The flux composition according to [1] or [2], Further, (F) a hindered amine antioxidant is contained, Flux composition. [4] A flux composition according to any one of [1] to [3] and (G) a solder powder. Solder composition. [5] The solder composition according to [4], The solder alloy in the component (G) contains at least one selected from the group consisting of tin, copper, zinc, silver, antimony, lead, indium, bismuth, nickel, gold, cobalt, and germanium. Solder composition. [6] A method for manufacturing an electronic substrate by soldering using the solder composition according to [4] or [5], applying the solder composition onto an electronic substrate; placing an electronic component on the solder composition; a step of mounting the electronic component on the electronic substrate by heating under predetermined conditions in a reflow furnace; and cleaning the flux residue on the electronic substrate using a water-based cleaning agent. Manufacturing method for electronic substrates. [Effects of the Invention]

[0007] According to one aspect of the present invention, it is possible to provide a flux composition and a solder composition that have good ionic cleanliness, excellent cleaning properties for flux residues with aqueous cleaners, and excellent solder melting properties in air reflow, and a method for producing an electronic substrate. DETAILED DESCRIPTION OF THE INVENTION

[0008] [Flux composition] First, the flux composition according to this embodiment will be described. The flux composition according to this embodiment contains the following components other than the solder powder in the solder composition: (A) a rosin-based resin, (B) an activator, (C) a solvent, and (D) an imidazole compound, as explained below. The (B) component must contain (B1) at least one selected from the group consisting of tricarboxylic acids and tetracarboxylic acids, each having a molecular weight of 500 or less. The amount of the (B1) component must be 1% by mass or more relative to 100% by mass of the flux composition. The mass ratio of the (D) component to the (B1) component ((D) / (B1)) must be 0.25 or more.

[0009] The reasons why the flux composition according to this embodiment has good ionic cleanliness, excellent cleaning ability for flux residue with an aqueous cleaner, and excellent solder melting property in air reflow are not entirely clear, but the inventors speculate as follows. That is, among the (B) activators, organic acids have a high activation effect and are effective in improving solder meltability during air reflow. Furthermore, imidazole compounds are effective in improving solder meltability and solderability during air reflow. However, it has been found that an excess of organic acids or imidazole compounds deteriorates ionic cleanliness. Furthermore, by combining a low-molecular-weight polycarboxylic acid such as (B1) 1,2,3-propanetricarboxylic acid with an (D) imidazole compound in a predetermined ratio, it is possible to maintain good ionic cleanliness and sufficiently improve solder meltability during air reflow while maintaining cleaning properties for flux residue. The inventors believe that the above-mentioned effects of the present invention are achieved in this manner.

[0010] [Component (A)] The rosin-based resin (A) used in this embodiment includes 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 rosins include fully hydrogenated rosin, partially hydrogenated rosin, and hydrogenated products of unsaturated organic acid-modified rosins (also referred to as "hydrogenated acid-modified rosin"), which are rosins modified with unsaturated organic acids (e.g., 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, and unsaturated carboxylic acids having an aromatic ring such as cinnamic acid). These rosin-based resins may be used alone or in combination of two or more. Among these rosin-based resins, polymerized rosin and hydrogenated acid-modified rosin are preferred, and a combination of polymerized rosin and hydrogenated acid-modified rosin is more preferred. It is more preferable to use polymerized rosin in combination with other rosin-based resins (such as hydrogenated acid-modified rosin, formylated rosin, or modified rosin).

[0011] The blending amount of component (A) is preferably 30% by mass to 70% by mass, more preferably 35% by mass to 60% by mass, and particularly preferably 40% by mass to 50% by mass, based on 100% by mass of the flux composition. When the blending amount of component (A) is above the lower limit, oxidation of the copper foil surface of the soldering land is prevented, making the surface more easily wettable with molten solder, thereby improving so-called solderability and sufficiently suppressing solder balls. Furthermore, when the blending amount of component (A) is below the upper limit, the amount of flux residue can be sufficiently suppressed.

[0012] [(B) Component] The activator (B) used in this embodiment must contain at least one tricarboxylic acid and tetracarboxylic acid (B1) having a molecular weight of 500 or less. This component (B1) has little adverse effect on the cleaning properties of flux residue. Furthermore, by combining this component (B1) with the component (D) described below, solder melting properties during air reflow can be improved while maintaining good ionic cleanliness. From the same viewpoint, the molecular weight of the component (B1) is preferably 400 or less, more preferably 300 or less, and particularly preferably 250 or less. Examples of the component (B1) include 1,2,3-propanetricarboxylic acid (molecular weight 176), 1,2,3,4-butanetetracarboxylic acid (molecular weight 234), and trimellitic acid (molecular weight 210). These may be used alone or in combination of two or more.

[0013] The blending amount of component (B1) must be 1% by mass or more relative to 100% by mass of the flux composition. If the blending amount of component (B1) is less than 1% by mass, the solder melting property during air reflow becomes insufficient. Furthermore, the blending amount of component (B1) is preferably 1.2% by mass or more and 10% by mass or less, more preferably 1.5% by mass or more and 7% by mass or less, and particularly preferably 1.5% by mass or more and 4% by mass or less, relative to 100% by mass of the flux composition. If the blending amount of component (B1) is equal to or greater than the lower limit, the solder melting property tends to be further improved, while if it is equal to or less than the upper limit, the insulating properties of the flux composition tend to be maintained.

[0014] The component (B) may contain an organic acid other than the component (B1) (hereinafter also referred to as the component (B2)). The component (B2) is preferably a dicarboxylic acid. Examples of component (B2) include glutaric acid, adipic acid, suberic acid, azelaic acid, sebacic acid, dodecanedioic acid, eicosanedioic acid, and 8,13-dimethyl-8,12-eicosadienedioic acid. These may be used alone or in combination of two or more.

[0015] The blending amount of component (B2) is preferably 1% by mass or more and 12% by mass or less, more preferably 2% by mass or more and 10% by mass or less, and particularly preferably 3% by mass or more and 8% by mass or less, based on 100% by mass of the flux composition. If the blending amount of component (B2) is equal to or more than the lower limit, solder melting property tends to be further improved, while if it is equal to or less than the upper limit, ionic cleanliness tends to be maintained at a good level.

[0016] In addition to components (B1) and (B2), component (B) may also contain another activator (hereinafter also referred to as component (B3)) to the extent that the object of the present invention can be achieved. Examples of component (B3) include halogen-based activators and amine-based activators.

[0017] The blending amount of component (B) 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 4% by mass or more and 12% by mass or less, based on 100% by mass of the flux composition. If the blending amount of component (B) is equal to or more than the lower limit, the activation effect tends to be improved, while if it is equal to or less than the upper limit, the insulating properties of the flux composition tend to be maintained.

[0018] [(C) component] As the solvent (C) used in this embodiment, any known solvent can be used as appropriate, and it is preferable to use a solvent with 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, and dibutyl maleic acid. These solvents may be used alone or in combination of two or more.

[0019] The blending amount of component (C) is preferably 10% by mass to 60% by mass, and more preferably 20% by mass to 50% by mass, 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 resulting solder composition can be appropriately adjusted to an appropriate range.

[0020] [(D) component] As the imidazole compound (D) used in this embodiment, any known imidazole compound can be used as appropriate. However, from the viewpoint of further reducing adverse effects on ionic cleanliness, the molecular weight of the imidazole compound is preferably 70 to 150, and more preferably 70 to 120. Examples of component (D) include 2-methylimidazole (molecular weight 82.1), 2-ethylimidazole (molecular weight 96.1), 2-ethyl-4-methylimidazole (molecular weight 110.2), 1,2-dimethylimidazole (molecular weight 96.1), and 2-phenylimidazole (molecular weight 144.2).

[0021] In this embodiment, the mass ratio ((D) / (B1)) of component (D) to component (B1) must be 0.25 or greater. If the mass ratio ((D) / (B1)) is less than 0.25, the solder melting property or ionic cleaning property will be insufficient. From the same viewpoint, the mass ratio ((D) / (B1)) is preferably 0.3 to 5, more preferably 0.5 to 3, and particularly preferably 0.75 to 2.

[0022] The blending amount of component (D) is preferably 0.5% by mass to 10% by mass, more preferably 1% by mass to 7% by mass, and particularly preferably 2% by mass to 5% by mass, based on 100% by mass of the flux composition. If the blending amount of component (D) is equal to or greater than the lower limit, solder melting properties tend to be improved, while if it is equal to or less than the upper limit, cleaning properties for flux residue tend to be maintained.

[0023] [(E) component] The flux composition according to this embodiment may further contain (E) a hindered phenol-based antioxidant from the viewpoint of solder melting properties and the like. Examples of hindered phenol antioxidants include pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], bis[3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionic 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.

[0024] The blending amount of component (E) is preferably 0.1% by mass or more and 5% by mass or less, more preferably 0.5% by mass or more and 4% by mass or less, and particularly preferably 1% by mass or more and 3% by mass or less, based on 100% by mass of the flux composition. If the blending amount of component (E) is equal to or more than the lower limit, the solder melting property tends to be improved, while if it is equal to or less than the upper limit, the insulating property of the flux composition tends to be maintained.

[0025] [Component (F)] The flux composition according to this embodiment may further contain (F) a hindered amine antioxidant. Component (F) has a structure represented by the following general formula (F1). Component (F) can improve solder melting properties during air reflow.

[0026] [ka]

[0027] In general formula (F1), R 1 are independently a methyl group or an ethyl group, and are preferably a methyl group. X is hydrogen, an alkyl group having 1 to 12 carbon atoms, or an alkoxy group having 1 to 12 carbon atoms. When X is hydrogen, the structure is represented by the following general formula (F1-1). When X is an alkyl group having 1 to 12 carbon atoms, the structure is represented by the following general formula (F1-2). When X is an alkoxy group having 1 to 12 carbon atoms, the structure is represented by the following general formula (F1-3). In component (F), the structure of the portion beyond the wavy line is not particularly limited. The number of structures represented by general formula (F1) in one molecule of component (F) is preferably 1 or more and 10 or less, and more preferably 2 or more and 4 or less.

[0028] [ka]

[0029] In general formula (F1-1), R 1 are independently a methyl group or an ethyl group, and are preferably a methyl group. Examples of compounds having a structure represented by general formula (F1-1) include bis(2,2,6,6-tetramethyl-4-piperidyl)sebacate, tetrakis(2,2,6,6-tetramethyl-4-piperidyl)butane-1,2,3,4-tetracarboxylate, and 2,2,6,6-tetramethyl-4-piperidyl methacrylate.

[0030] [ka]

[0031] In general formula (F1-2), R 1 are independently a methyl group or an ethyl group, and are preferably a methyl group. R 2 is an alkyl group having 1 to 12 carbon atoms, preferably an alkyl group having 1 to 8 carbon atoms, more preferably an alkyl group having 1 to 3 carbon atoms, and particularly preferably a methyl group. Examples of compounds having a structure represented by general formula (F1-2) include bis(1,2,2,6,6-pentamethyl-4-piperidyl)-[[3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl]ethyl]butylmalonate, bis(1,2,2,6,6-pentamethyl-4-piperidyl)sebacate, 1-(methyl)-8-(1,2,2,6,6-pentamethyl-4-piperidyl)sebacate, tetrakis(1,2,2,6,6-pentamethyl-4-piperidyl)butane-1,2,3,4-tetracarboxylate, and 1,2,2,6,6-pentamethyl-4-piperidyl methacrylate.

[0032] [ka]

[0033] In general formula (F1-3), R 1 are independently a methyl group or an ethyl group, and are preferably a methyl group. R 3 is an alkyl group having 1 to 12 carbon atoms, preferably an alkyl group having 4 to 11 carbon atoms, more preferably an alkyl group having 8 to 11 carbon atoms, and particularly preferably an octyl group or an undecyl group. Examples of compounds having a structure represented by general formula (F1-3) include bis(1-octyloxy-2,2,6,6-tetramethyl-4-piperidyl)sebacate and bis(1-undecaoxy-2,2,6,6-tetramethylpiperidin-4-yl)carbonate.

[0034] The blending amount of component (F) is preferably 0.1% by mass to 5% by mass, more preferably 0.5% by mass to 3% by mass, and particularly preferably 1% by mass to 2% by mass, based on 100% by mass of the flux composition. If the blending amount of component (F) is equal to or greater than the lower limit, solder meltability during air reflow tends to be improved, especially when the time required to reach the melting temperature during reflow is long. On the other hand, if the blending amount is equal to or less than the upper limit, the insulating properties of the flux composition tend to be maintained.

[0035] [Thixotropic agent] The flux composition of this embodiment may further contain a thixotropic agent from the viewpoint of printability, etc. Examples of thixotropic agents used here include hydrogenated castor oil, amides, kaolin, colloidal silica, organic bentonite, and glass frit. These may be used alone or in combination of two or more.

[0036] The blending amount of the thixotropic agent is preferably 1% by mass or more and 20% by mass or less, and more preferably 2% by mass or more and 12% by mass or less, relative to 100% by mass of the flux composition. If the blending amount is less than the lower limit, thixotropy is not obtained and sagging tends to occur easily, while if the blending amount is more than the upper limit, the thixotropy is too high and printing defects tend to occur easily.

[0037] [Other ingredients] In addition to the components (A), (B), (C), (D), (E), and (F), and the thixotropic agent, other additives and even other resins may be added to the flux composition used in this embodiment as needed. Examples of other additives include antioxidants other than components (E) and (F), antifoaming agents, modifiers, matting agents, and foaming agents. The amount of these additives added 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 and polybutadiene.

[0038] [Solder composition] Next, the solder composition of this embodiment will be described. The solder composition of this embodiment contains the flux composition of this embodiment described above and the solder powder (G) 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 18% by mass or less, and particularly preferably 8% by mass or more and 15% by mass or less, relative to 100% by mass of the solder composition. If the amount of the flux composition is less than 5% by mass (if the amount of the solder powder exceeds 95% by mass), there will be an insufficient amount of flux composition as a binder, making it difficult to mix the flux composition and the solder powder. On the other hand, if the amount of the flux composition is more than 35% by mass (if the amount of the solder powder is less than 65% by mass), it will be difficult to form a satisfactory solder joint when using the resulting solder composition.

[0039] [(G) component] The solder powder (G) used in the present invention is preferably made of lead-free solder powder alone, but may also 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), antimony (Sb), lead (Pb), indium (In), bismuth (Bi), nickel (Ni), gold (Au), cobalt (Co), and germanium (Ge). The solder alloy in this solder powder is preferably an alloy containing tin as a main component. Furthermore, this solder alloy more preferably contains tin, silver, and copper. Furthermore, this solder alloy may contain at least one of antimony, bismuth, and nickel as an additive element. According to the flux composition of this embodiment, even when using a solder alloy containing easily oxidized additive elements such as antimony, bismuth, and nickel, the generation of voids can be suppressed. Here, lead-free solder powder refers to a powder of solder metal or alloy to which no lead is added. Although the presence of lead as an unavoidable impurity in lead-free solder powder is permitted, in this case, the amount of lead is preferably 300 ppm by mass or less.

[0040] 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.

[0041] The average particle size of component (G) is usually 1 μm or more and 40 μm or less, but from the viewpoint of compatibility with electronic boards with narrow solder pad pitches, 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 using a dynamic light scattering particle size measuring device.

[0042] [Method for manufacturing solder composition] The solder composition of this embodiment can be produced by blending the above-described flux composition and the above-described (G) solder powder in the above-described predetermined ratio, and stirring and mixing them.

[0043] [Electronic substrate manufacturing method] Next, a method for manufacturing an electronic substrate according to this embodiment will be described. The method for manufacturing an electronic substrate according to this embodiment is characterized by using the solder composition described above. According to the method for manufacturing an electronic substrate according to this embodiment, an electronic substrate can be manufactured by mounting electronic components on an electronic substrate (such as a printed wiring board) using the solder composition. The solder composition of the present embodiment described above has excellent cleaning properties for flux residue with an aqueous cleaner, so that flux residue can be easily cleaned with an aqueous cleaner after soldering. In the method for manufacturing an electronic substrate of this embodiment, first, a solder composition is applied onto an electronic substrate using an application device. Examples of the coating device used here include a screen printer, a metal mask printer, a dispenser, and a jet dispenser. Furthermore, an electronic component can be mounted on an electronic board by a reflow process in which an electronic component is placed on the solder composition applied by the application device, and heated under predetermined conditions in a reflow furnace to mount the electronic component on a printed wiring board.

[0044] In the reflow process, the electronic component is placed on the solder composition and heated under predetermined conditions in a reflow furnace. This reflow process allows for sufficient solder bonding 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 atmosphere may be a nitrogen atmosphere, but since the solder composition of this embodiment has excellent solder melting properties in air reflow, air may be used. The reflow conditions may be set appropriately depending on 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. Furthermore, the holding time at a temperature of 220°C or higher is preferably 20 seconds or higher and 60 seconds or lower.

[0045] After the reflow process, flux residue on the electronic substrate is cleaned using a water-based cleaner. The cleaning method may be an immersion method, a jet method, or the like. For example, in the immersion method, the electronic substrate is immersed in a water-based cleaning agent, and ultrasonic waves may be applied at this time. Known water-based cleaning agents for flux residue can be used. Here, water-based refers to those whose main component is water (50% by mass or more). Commercially available products include "VIGON US" manufactured by Zestron Japan. The temperature of the aqueous cleaner during cleaning is, for example, 30°C or higher and 70°C or lower. The cleaning time is, for example, 1 minute or more and 10 minutes or less. After cleaning with an aqueous cleaner, rinsing may be performed. The rinsing conditions are not particularly limited, and the rinsing should be performed with water at a temperature of 20°C to 50°C for 0.5 to 5 minutes. Rinsing may be performed two or more times.

[0046] Furthermore, the solder composition and electronic substrate of the present embodiment are not limited to the above-described embodiment, and modifications and improvements within the scope of achieving the object of the present invention are included in the present invention. For example, in the above-mentioned method for manufacturing an electronic substrate, the printed wiring board and the electronic component are bonded together 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 together 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 depending on the wavelength that matches the absorption band of the metal. Examples of laser light sources include solid-state lasers (ruby, glass, YAG, etc.), semiconductor lasers (GaAs, InGaAsP, etc.), liquid lasers (dye, etc.), and gas lasers (He-Ne, Ar, CO2, excimer, etc.). [Example]

[0047] 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 listed below. (Component (A)) Rosin-based resin A: Polymerized rosin, product name "China Polymerized Rosin 140", manufactured by Arakawa Chemical Industries, Ltd. Rosin resin B: Acrylic acid-modified hydrogenated rosin, product name "Pine Crystal KE-604", manufactured by Arakawa Chemical Industries, Ltd. Rosin-based resin C: Formylated rosin, trade name "FORAL-AX", manufactured by Eastman Chemical Company Rosin-based resin D: Specially modified rosin, product name "Haritack FG-90", manufactured by Harima Chemicals Co., Ltd. ((B1) component) Organic acid A: 1,2,3-propanetricarboxylic acid (molecular weight 176), trade name "Rikacid TCR-100", manufactured by New Japan Chemical Co., Ltd. Organic acid B: 1,2,3,4-butanetetracarboxylic acid (molecular weight 234), trade name "Rikacid BT-W", manufactured by New Japan Chemical Co., Ltd. Organic acid C: Trimellitic acid (molecular weight 210) ((B2) component) Organic Acid D: Glutaric Acid Organic Acid E: Adipic Acid Organic acid F: Sebacic acid Organic acid G: Dodecanedioic acid Organic acid H: Eicosanedioic acid, trade name "SL-20", manufactured by Okamura Oil Mills ((C) component) Solvent: Diethylene glycol monohexyl ether (DEH, hexyldiglycol) ((D) component) Imidazole compound A: 2-ethyl-4-methylimidazole (molecular weight 110.2), trade name "2E4MZ", manufactured by Shikoku Chemicals Corporation Imidazole compound B: 2-methylimidazole (molecular weight 82.1), trade name "2MZ", manufactured by Shikoku Chemicals Corporation Imidazole compound C: 2-ethylimidazole (molecular weight 86.1), trade name "2EZ", manufactured by Shikoku Chemicals Corporation Imidazole compound D: 2-phenylimidazole (molecular weight 144.2), trade name "2PZ", manufactured by Shikoku Chemicals Corporation ((E) component) Hindered phenolic antioxidant: bis[3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionic acid][ethylenebis(oxyethylene)], trade name "Irganox 245", manufactured by BASF (Component (F)) Hindered amine antioxidant: a compound having two structures represented by general formula (F1-2) in one molecule, bis(1,2,2,6,6-pentamethyl-4-piperidyl)-[[3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl]ethyl]butylmalonate, trade name "Tinuvin PA144", manufactured by BASF (Other ingredients) Thixotropic agent A: Trade name "Slipax H", manufactured by Nippon Kasei Co., Ltd. Thixotropic agent B: Trade name "Himakou", manufactured by KF Trading Co., Ltd. Additive: Polybutadiene, product name "BI-2000", manufactured by Nippon Soda Co., Ltd. ((G) component) Solder powder: alloy composition Sn-3.0Ag-0.5Cu, particle size distribution 20-38μm, solder melting point 217-220℃

[0048] [Example 1] 25 mass% of rosin-based resin A, 15 mass% of rosin-based resin B, 1 mass% of organic acid A, 8 mass% of organic acid H, 35 mass% of solvent, 1.5 mass% of imidazole compound A, 2 mass% of hindered phenol-based antioxidant, 1 mass% of hindered amine-based antioxidant, 4 mass% of additive, 7 mass% of thixotropic agent A, and 0.5 mass% of thixotropic agent B were charged into a container and mixed using a planetary mixer to obtain a flux composition. Thereafter, 12% by mass of the obtained flux composition and 88% by mass of the solder powder (total of 100% by mass) were placed in a container and mixed with a planetary mixer to prepare a solder composition.

[0049] [Examples 2 to 18] 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 5] 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.

[0050] <Evaluation of solder composition> The solder compositions were evaluated (ionic cleanliness, cleaning properties, solder melting properties (air reflow), and wetting effectiveness) by the following methods. The results are shown in Table 1. (1) Ionic cleanliness A solder composition was printed on a JIS type 2 comb-shaped substrate and melted in a reflow furnace (manufactured by Tamura Corporation) to obtain a test substrate. The reflow conditions were a preheat temperature of 130 to 180°C (approximately 100 seconds), a time at or above 220°C for approximately 60 seconds, a peak temperature of 240°C, and a nitrogen atmosphere with an oxygen concentration of 1000 ppm. The test substrate was placed in an omegameter, and a 75% IPA solution was poured into the test cell as the test liquid. The change in the resistance of the test liquid was measured, and the eluted ions of the specimen were calculated. The amount of eluted ions was converted to an NaCl equivalent value, which was used as the ionic cleanliness. The ionic cleanliness was then evaluated according to the following criteria. ○: Ionic cleanliness is 1.50 μg NaCl / cm 2 is less than. △: Ionic cleanliness is 1.50 μg NaCl / cm 2 More than 1.60μgNaCl / cm 2 is less than. ×: Ionic cleanliness is 1.60 μg NaCl / cm 2 That's all. (2) Cleanability A solder composition was printed on a substrate capable of mounting chip components, chip components (size: 1.6 mm × 0.8 mm) were mounted, and the solder composition was melted and soldered in a reflow furnace (manufactured by Tamura Corporation) to obtain a substrate for evaluation. The reflow conditions were a preheat temperature of 130 to 180°C (approximately 100 seconds), a time at a temperature of 220°C or higher for approximately 60 seconds, a peak temperature of 240°C, and a nitrogen atmosphere with an oxygen concentration of 1000 ppm. Next, the obtained evaluation substrate was immersed in a container containing an aqueous cleaner (Zestron Japan's "VIGON US," 20% concentration) and cleaned with ultrasound (liquid temperature: 60°C, cleaning time: 5 minutes). After that, the liquid was removed with an air knife, and then the substrate was immersed in a container containing pure water at room temperature for a first rinse (rinse time: 1-2 minutes), and then further immersed in a container containing pure water at 45°C for a second rinse (rinse time: 1-2 minutes). After that, the liquid was removed with an air gun, and the substrate was dried for 10 minutes in a hot air drying oven (oven temperature: 70°C). After cleaning with aqueous cleaners, all chips were removed from the evaluation boards and inspected for flux residues under the chips. The number of chips with residual flux and the ratio to the total number of chips (residual ratio) were then counted, and the cleaning performance was evaluated based on the residual ratio according to the following criteria. ○: The residual ratio is less than 25%. △: The residual ratio is 25% or more and less than 50%. ×: The residual ratio is 50% or more. (3) Solder melting property (air reflow) A solder composition was printed on a substrate capable of mounting chip components, a 1005 chip component (size: 1.0 mm × 0.5 mm) was mounted, and the solder composition was melted and soldered in a reflow furnace (manufactured by Tamura Corporation) to obtain a substrate for evaluation. The reflow conditions were air reflow, with a preheat temperature of 130 to 180°C (approximately 100 seconds), a time at a temperature of 220°C or higher for approximately 60 seconds, and a peak temperature of 240°C. Then, the number of unmelted portions in the chip bonding portions of the evaluation board was counted, and the solder meltability (air reflow) was evaluated according to the following criteria. ◯: The unmelted ratio is less than 50%. △: The unmelted ratio is 50% or more and less than 70%. ×: The unmelted ratio is 70% or more. (4) Wetting effect The solder wettability (dewetting) test was conducted according to the method described in JIS Z 3284 (2014). Two types of metal plates, A (brass, size: 30 mm × 30 mm, thickness: 0.3 mm) and B (42 alloy, size: 30 mm × 30 mm, thickness: 0.3 mm), were prepared and polished with an abrasive. A solder composition was printed on the metal plates using a 0.2 mm thick metal mask with a 6.5 mm diameter circular pattern hole to obtain a test plate. The test plate was heated in a solder bath maintained at 270°C and melted for 5 seconds. The test plate was observed under a microscope, the wet spread area ratio was measured, and the wetting effectiveness (brass, 42 alloy) was evaluated according to the following criteria. ○: The wet spread area ratio is 70% or more. △: The wet spread area ratio is 50% or more and less than 70%. ×: The wet spread area ratio is less than 50%.

[0051] [Table 1]

[0052] As is clear from the results shown in Table 1, the solder compositions of the present invention (Examples 1 to 18) were confirmed to have good results in all aspects of ionic cleanliness, cleaning properties, solder melting properties (air reflow), and wetting effectiveness. Therefore, it was confirmed that the solder composition of the present invention has good ionic cleanliness, is excellent in cleaning flux residue with an aqueous cleaner, and has excellent solder melting properties in air reflow. [Industrial Applicability]

[0053] 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 rosin-based resin, (B) an activator, (C) a solvent, and (D) an imidazole compound having a molecular weight of 70 or more and 120 or less, the component (B) contains (B1) at least one selected from the group consisting of tricarboxylic acids and tetracarboxylic acids, which have a molecular weight of 500 or less; the component (D) is at least one selected from the group consisting of 2-methylimidazole, 2-ethylimidazole, 2-ethyl-4-methylimidazole, and 1,2-dimethylimidazole; The blending amount of the (B1) component is 1 mass % or more relative to 100 mass % of the flux composition, the mass ratio of the component (D) to the component (B1) ((D) / (B1)) is 0.25 or more; Flux composition.

2. 2. The flux composition according to claim 1, Further, (E) a hindered phenol-based antioxidant is contained, Flux composition.

3. The flux composition according to claim 1 or 2, Further, (F) a hindered amine-based antioxidant is contained. Flux composition.

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

5. The solder composition according to claim 4, The solder alloy in the component (G) contains at least one selected from the group consisting of tin, copper, zinc, silver, antimony, lead, indium, bismuth, nickel, gold, cobalt, and germanium. Solder composition.

6. A method for manufacturing an electronic substrate by soldering using the solder composition according to claim 4, applying the solder composition onto an electronic substrate; placing an electronic component on the solder composition; a step of mounting the electronic component on the electronic substrate by heating under predetermined conditions in a reflow furnace; and cleaning the flux residue on the electronic substrate using a water-based cleaning agent. Manufacturing method for electronic substrates.

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