Soldering flux and soldering paste

Abstract

This flux is characterized by containing rosin, a polymer having a repeating unit represented by general formula (p1), a solvent, a thixotropic agent containing a polyamide, a specific dicarboxylic acid, and a specific compound having a benzotriazole skeleton. In general formula (p1), R1 represents a methyl group or a hydrogen atom. And R2 is alkyl with 1-2 carbon atoms or a hydrogen atom. According to the flux, the cohesiveness of the solder alloy powder during reflow soldering is high, blackening of flux residues is suppressed, precipitation along with time is unlikely to occur, and the stability over time is good.

Description

Technical Field

[0001] This invention relates to fluxes and solder pastes.

[0002] This application claims priority based on Japanese Patent Application No. 2023-090350, filed in Japan on May 31, 2023, the contents of which are incorporated herein by reference. Background Technology

[0003] In the assembly of electronic components, the fixing of components to a substrate and the electrical connection of components to a substrate are typically achieved through soldering. Soldering utilizes flux, solder alloys, and solder paste, a mixture of flux and solder alloy powders. Flux has the ability to chemically remove metal oxides present on the surfaces of the metals being soldered and in the solder alloy, and to allow metal elements to move at the boundary between them. Therefore, by using flux for soldering, an intermetallic compound is formed between the two materials, resulting in a strong bond.

[0004] In welding, methods such as flow welding and reflow welding are used depending on the size of the objects to be joined.

[0005] In flow soldering, flux is first applied to a substrate on which the component is mounted. Then, while conveying the substrate with the component, molten solder jetted from below is brought into contact with the soldering surface, thereby performing soldering.

[0006] In reflow soldering, solder paste is first printed onto a substrate. Then, components are mounted on the substrate, and the substrate with the components mounted is soldered in a heated furnace called a reflow oven.

[0007] In recent years, lead-free solder has been used in welding due to concerns about its adverse environmental impact. Lead-free solder, with Sn as its main component, has a high melting point, requiring it to be heated to even higher temperatures to melt during welding. The higher the temperature of the molten solder, the more oxides are formed.

[0008] In contrast, from the perspectives of reducing thermal damage to the substrate and saving energy, solder alloys containing Sn and Bi that can be soldered at lower temperatures are gradually being used. When using solder alloys containing Sn and Bi, since Bi is a metal element that is easily oxidized, corresponding fluxes have been proposed to date (for example, see Patent Document 1).

[0009] Existing technical documents Patent documents Patent Document 1: Japanese Patent No. 7075028 Summary of the Invention The problem to be solved by the present invention In solder paste, during reflow soldering, when the solder alloy powder melts, it is desirable for the solder alloy powder to have high cohesion (making it difficult to form solder balls).

[0010] The cohesiveness of the solder alloy powder was evaluated using the "4.2 Solder Ball Test" in JIS Z3284-4:2014. Low cohesiveness of the solder alloy powder during reflow soldering can easily lead to the formation of solder balls. These solder balls may cause short circuits on the substrate.

[0011] Through research, the inventors have discovered that dicarboxylic acid is effective as an activator in flux for improving the cohesiveness of solder alloy powders.

[0012] However, when flux containing dicarboxylic acid is used in solder paste, flux residue in the solder joint may turn black over time after reflow soldering, resulting in a decrease in electrical reliability.

[0013] The inventors have found through further research that using compounds with a benzotriazole skeleton is effective in blackening the flux residue.

[0014] However, in fluxes that combine dicarboxylic acids and compounds with a benzotriazole skeleton, a new problem has emerged: over time, compounds with a benzotriazole skeleton tend to precipitate out of the flux.

[0015] The present invention was made in view of the above circumstances, and provides a flux with high cohesiveness of solder alloy powder during reflow soldering, suppression of blackening of flux residue, difficulty in generating precipitation over time, and good stability over time, as well as a solder paste using the flux.

[0016] Problem-solving methods To address the aforementioned issues, the present invention employs the following configuration.

[0017] [1] A flux comprising rosin, a polymer (P) having repeating units as shown in the following general formula (P1), a solvent, a thixotropic agent, a dicarboxylic acid and a compound having a benzotriazole skeleton.

[0018] [Chemical Formula 1]

[0019] [In the formula, R] 1 It can be a methyl group or a hydrogen atom. R 2 It consists of a hydrocarbon group with 1 to 2 carbon atoms or a hydrogen atom. [2] According to the flux described in [1] above, wherein the weight-average molecular weight of the polymer (P) is 300 to 8000.

[0020] [3] According to the flux described in [1] or [2] above, wherein the content of the polymer (P) is 1% by mass or more and 15% by mass or less relative to the total mass of the flux.

[0021] [4] The flux according to any one of [1] to [3] above, wherein the solvent contains monoalkyl propylene glycol.

[0022] [5] According to the flux described in [4] above, wherein the monoalkyl propylene glycol contains at least one selected from butylpropylene triethylene glycol and butylpropylene diethylene glycol.

[0023] [6] According to the flux described in [4] or [5] above, wherein the content of the monoalkyl propylene glycol is 5% by mass or more and 50% by mass or less relative to the total mass of the flux.

[0024] [7] The flux according to any one of [4] to [6] above, wherein the mixing ratio of the polymer (P) to the monoalkyl propylene glycol is 0.05 or more by mass, expressed as polymer (P) / monoalkyl propylene glycol.

[0025] [8] The flux according to any one of [1] to [7] above, wherein the dicarboxylic acid is a compound represented by the following general formula (c1).

[0026] [Chemical Formula 2]

[0027] [In the formula, R represents an alkylene group, a phenylene group, or a single bond with 1 to 10 carbon atoms. The methylene group constituting the alkylene group may also be substituted with an oxygen atom.] [9] The flux according to any one of [1] to [8] above, wherein the content of the dicarboxylic acid is 0.5% by mass or more and 7.5% by mass or less relative to the total mass of the flux.

[0028]

[10] The flux according to any one of [1] to [9] above, wherein the compound having a benzotriazole skeleton is at least one selected from the compounds shown in the following general formula (AZ1-1) and the compounds shown in the following general formula (AZ1-2).

[0029] [Chemical Formula 3]

[0030] [In the formula, R] 11 It can be an organic group or a hydrogen atom. R 12 For substituents. n1 represents an integer from 0 to 4. R 21 It can be an organic group or a hydrogen atom. R 22[This is a substituent. n2 represents an integer from 0 to 4.]

[11] The flux according to any one of [1] to

[10] above, wherein the content of the compound having a benzotriazole skeleton is 1% by mass or more and 10% by mass or less relative to the total mass of the flux.

[0031]

[12] The flux according to any one of [1] to

[11] above, wherein the mixing ratio of the dicarboxylic acid and the compound having a benzotriazole skeleton is 0.2 or more and 3 or less by mass ratio of dicarboxylic acid / compound having a benzotriazole skeleton.

[0032]

[13] The flux according to any one of [1] to

[12] above, wherein the rosin content is 10% by mass or more and 40% by mass or less relative to the total mass of the flux.

[0033]

[14] The flux according to any one of [1] to

[13] above, wherein the rosin contains at least one selected from acrylic acid modified hydrogenated rosin, hydrogenated rosin and polymerized rosin.

[0034]

[15] The flux according to any one of [1] to

[14] above, wherein the thixotropic agent contains polyamide.

[0035]

[16] The flux according to any one of [1] to

[15] above, wherein the content of the thixotropic agent is 2% by mass or more and 15% by mass or less relative to the total mass of the flux.

[0036]

[17] The flux according to any one of [1] to

[16] above, wherein the flux further contains a phenyl-substituted imidazole.

[0037]

[18] The flux according to any one of [1] to

[17] above, wherein the flux does not contain halogen compounds.

[0038]

[19] A solder paste comprising solder alloy powder and any one of the fluxes described in [1] to

[18] above.

[0039]

[20] According to the solder paste described above

[19] , wherein the solder alloy powder is composed of a solder alloy containing Sn and Bi.

[0040] Effects of the present invention According to the present invention, a flux with high cohesiveness of solder alloy powder during reflow soldering, suppressed blackening of flux residue, low precipitation over time, and good stability over time, and a solder paste using the flux, are provided. Attached Figure Description

[0041] Figure 1 This is a diagram showing the distribution of reflow solder in the evaluation of this embodiment.

[0042] Figure 2 This is a schematic diagram illustrating the wetting and spreading evaluation method in this embodiment.

[0043] Figure 3 This is a diagram showing the state of blackening of flux residue in the "Evaluation of Blackening Inhibition of Flux Residue" of this embodiment.

[0044] Figure 4 This is a diagram showing the state of flux floating (separating) on ​​the surface of the solder paste after a specified storage period, in the "Evaluation of Time-Related Stability (with Flux Separation over Time)" of this embodiment. Detailed Implementation

[0045] (Fluoride) One embodiment of the flux contains rosin, a polymer (P) having repeating units of the general formula (P1) described below, a solvent, a thixotropic agent, a dicarboxylic acid, a compound having a benzotriazole skeleton, and other ingredients as desired.

[0046] The flux of this embodiment is characterized in that, as a means of suppressing precipitation that occurs over time, i.e., suppressing the precipitation of compounds having a benzotriazole skeleton, a polymer (P) having repeating units shown in the general formula (P1) is used.

[0047] <Rosin> The flux in this embodiment contains rosin.

[0048] In this invention, "rosin" includes natural resins containing a mixture of abrasive acid and its isomers, with abrasive acid as the main component, as well as substances obtained by chemically modifying natural resins (sometimes referred to as rosin derivatives).

[0049] As an example, the content of rosin acid in natural resin is 40% by mass or more and 80% by mass or less relative to natural resin.

[0050] In this specification, "main component" refers to a component that constitutes a compound and is present in a concentration of 40% or more by mass.

[0051] Representative examples of isomers of abietic acid include neorosinic acid, longleaf abietic acid, and L-piperidine.

[0052] Examples of "natural resins" include, for example, rosin, wood rosin, and oil rosin.

[0053] In this invention, "substances obtained by chemically modifying natural resins (rosin derivatives)" include substances obtained by subjecting the "natural resins" to one or more treatments selected from hydrogenation, dehydrogenation, neutralization, epoxide addition, amidation, dimerization and polymerization, esterification and Diels-Alder cyclization addition.

[0054] Examples of rosin derivatives include purified rosin and modified rosin.

[0055] Examples of modified rosin include hydrogenated rosin, polymerized rosin, polymerized hydrogenated rosin, disproportionated rosin, acid-modified rosin, rosin esters, acid-modified hydrogenated rosin, acid anhydride-modified hydrogenated rosin, acid-modified disproportionated rosin, acid anhydride-modified disproportionated rosin, phenol-modified rosin, and α,β-unsaturated carboxylic acid modified products (acrylated rosin, maleated rosin, fumaric acid-modified rosin, etc.), as well as purified products, hydrides and disproportions of the polymerized rosin, and purified products, hydrides and disproportions of the α,β-unsaturated carboxylic acid modified products, rosin alcohol, rosin amine, hydrogenated rosin alcohol, rosin esters, hydrogenated rosin esters, rosin soap, hydrogenated rosin soap, acid-modified rosin soap, etc.

[0056] Examples of rosin amines include, for example, dehydrorosin amines and dihydrorosin amines. Rosin amines refer to so-called disproportionated rosin amines.

[0057] In the flux of this embodiment, rosin can be used alone or in combination with two or more types.

[0058] The rosin preferably contains rosin derivatives, more preferably contains one or more selected from acid-modified rosin, hydrogenated rosin, polymerized rosin, acid-modified hydrogenated rosin and rosin esters, even more preferably contains one or more selected from acid-modified hydrogenated rosin, hydrogenated rosin and polymerized rosin, and particularly preferably contains at least acid-modified hydrogenated rosin.

[0059] Acrylic acid-modified hydrogenated rosin is preferred as an acid-modified hydrogenated rosin.

[0060] The rosin used in the flux of this embodiment can be acid-modified hydrogenated rosin, a combination of acid-modified hydrogenated rosin and hydrogenated rosin, a combination of hydrogenated rosin and polymerized rosin, or polymerized rosin.

[0061] In this embodiment, the rosin content in the flux is preferably 10% by mass or more relative to the total mass (100% by mass) of the flux, more preferably 10% by mass or more and 40% by mass or less, even more preferably 15% by mass or more and 40% by mass or less, particularly preferably 20% by mass or more and 35% by mass or less, and most preferably 20% by mass or more and 30% by mass or less.

[0062] When the rosin content is above the lower limit of the above-mentioned preferred range, the wetting and spreading properties of the solder paste in the pads become better; when the rosin content is below the upper limit of the above-mentioned preferred range, it is easier to reduce flux residue.

[0063] <Polymer (P) having repeating units as shown in the general formula (P1)> The flux of this embodiment contains a polymer (P) (hereinafter also referred to as "(P) component"), which has repeating units shown in the following general formula (P1) (hereinafter also referred to as "repeating unit (P1)"). By containing the (P) component, the precipitation of compounds with a benzotriazole skeleton in the flux can be suppressed, making it difficult for precipitation to occur over time in the flux, thereby improving its stability over time.

[0064] [Chemical Formula 4]

[0065] [In the formula, R] 1 It can be a methyl group or a hydrogen atom. R 2 It consists of a hydrocarbon group with 1 to 2 carbon atoms or a hydrogen atom. Repeating Unit (p1) In the above formula (p1), R 1 Methyl is preferred.

[0066] R 2 The hydrocarbon group with two carbon atoms in R can be a saturated hydrocarbon group (ethyl) or an unsaturated hydrocarbon group (vinyl, ethynyl). 2 Preferably, it is a hydrocarbon group with 1 to 2 carbon atoms, and more preferably, it is a methyl group.

[0067] The following is a specific example of a repeating unit (p1).

[0068] [Chemical Formula 5]

[0069] (P) The repeating unit (P1) of the component can be used alone or in combination with two or more.

[0070] As a repeating unit (p1), it preferably contains at least one repeating unit selected from any one of the repeating units shown in the chemical formulas (p1-1), (p1-2), (p1-3), (p1-4), and (p1-5), more preferably it contains at least one repeating unit selected from any one of the repeating units shown in the chemical formulas (p1-3), (p1-4), and (p1-5), and even more preferably it contains at least one repeating unit selected from any one of the repeating units shown in the chemical formulas (p1-3) and (p1-4).

[0071] The proportion of repeating units (P1) relative to the total amount (100 mol%) of all repeating units constituting the component (P) can be more than 10 mol%, more than 20 mol%, more than 50 mol%, or 100 mol% (i.e., homopolymer).

[0072] Repeating Unit (p2) (P) component can be a polymer having repeating units (p1) and other repeating units (hereinafter also referred to as "repeating units (p2)").

[0073] As repeating units (p2), examples include repeating units derived from alkenes and repeating units derived from butadiene.

[0074] The following is a specific example of a repeating unit (p2).

[0075] [Chemical Formula 6]

[0076] (P) The repeating unit (p2) of the component can be used alone or in combination with two or more.

[0077] The proportion of repeating units (p2) relative to the total amount (100 mol%) of all repeating units constituting the component (P) can be more than 50 mol%, or 70 to 90 mol%, or 75 to 85 mol%.

[0078] In the flux of this embodiment, component (P) can be used alone or in combination with two or more components.

[0079] The (P) component used in this embodiment is a polymer having at least the repeating unit (p1), preferably a polymer having the repeating unit (p1) as a main component, more preferably a polymer in which the proportion of the repeating unit (p1) to the total amount (100 mol%) of all repeating units constituting the (P) component exceeds 50 mol%, or it may be a homopolymer composed of repeating units (p1).

[0080] As preferred (P) components, examples include homopolymers composed of repeating units shown in the chemical formulas (p1-3), homopolymers composed of repeating units shown in the chemical formulas (p1-4), homopolymers composed of repeating units shown in the chemical formulas (p1-5), copolymers having repeating units shown in the chemical formulas (p1-3) and (p1-4), and copolymers having repeating units shown in the chemical formulas (p1-5) and (p2-4).

[0081] Among these, more preferably are copolymers having repeating units shown in the chemical formula (p1-3) and repeating units shown in the chemical formula (p1-4), and polymers having repeating units shown in the chemical formula (p1-5), and even more preferably copolymers having repeating units shown in the chemical formula (p1-3) and repeating units shown in the chemical formula (p1-4) (hereinafter also referred to as "copolymer (p34)").

[0082] As the copolymer (P34), it is preferred to be a copolymer having repeating units shown in the chemical formula (p1-4) as the main component, and more preferably a copolymer having a proportion of repeating units shown in the chemical formula (p1-4) exceeding 50 mol% relative to the total (100 mol%) of all repeating units constituting the copolymer (P34).

[0083] The (P) component used in this embodiment can be a synthetic substance or a commercially available product.

[0084] Commercially available products include: Nippon Seki polybutene (manufactured by ENEOS Corporation), indole polybutene (manufactured by INEOSOligomers Co., Ltd.), and Nippon Yu polybutene (registered trademark) (manufactured by Nippon Yu Corporation); liquid polybutadiene NISSO-PB (manufactured by Nippon Soda Co., Ltd.), and polybutadiene-type liquid polymer Poly bd. TM (Poly bd) (manufactured by Idemitsu Kosan Co., Ltd.), etc.

[0085] The weight-average molecular weight (Mw) of component (P) (based on polystyrene conversion standard using gel permeation chromatography (GPC)) is preferably 200 to 10,000, more preferably 250 to 9,000, and even more preferably 300 to 8,000.

[0086] The number average molecular weight (Mn) of component (P) (based on GPC polystyrene conversion) is preferably 200 to 7000, more preferably 250 to 6000, and even more preferably 300 to 5000.

[0087] When the Mw and Mn of the (P) component are within the above-mentioned preferred range, it is easy to suppress the precipitation of compounds with a benzotriazole skeleton in the flux, and the stability over time (accompanying the difficulty of precipitation over time) is improved.

[0088] The content of component (P) in the flux of this embodiment is preferably 1% or more and 15% or less relative to the total mass (100% by mass) of the flux, more preferably 2% or more and 10% or less by mass, and even more preferably 3% or more and 10% or less by mass.

[0089] When the content of component (P) is above the lower limit of the above preferred range, it is easy to suppress the precipitation of compounds with a benzotriazole skeleton in the flux and improve the stability over time (the difficulty of precipitation over time). When it is below the upper limit of the above preferred range, it is easy to improve the stability over time (the suppression of flux separation over time).

[0090] <Solvent> The flux in this embodiment contains a solvent.

[0091] Examples of solvents include water, alcohols, glycol ethers, and terpineols.

[0092] Examples of alcohol-based solvents include isopropanol, 1,2-butanediol, 1,3-butanediol, isobornylcyclohexanol, 2,4-diethyl-1,5-pentanediol, 2,2-dimethyl-1,3-propanediol, 2,5-dimethyl-2,5-hexanediol, 2,5-dimethyl-3-hexyn-2,5-diol, 2,3-dimethyl-2,3-butanediol, 2-methylpentane-2,4-diol, and 1,1,1-tris(hydroxymethyl) Propane, 2-ethyl-2-hydroxymethyl-1,3-propanediol, 2,2'-oxybis(methylene)bis(2-ethyl-1,3-propanediol), 2,2-bis(hydroxymethyl)-1,3-propanediol, 1,2,6-trihydroxyhexane, 1-ethynyl-1-cyclohexanol, 1,4-cyclohexanediol, 1,4-cyclohexanediol, 2,4,7,9-tetramethyl-5-decyn-4,7-diol, 2-hexyl-1-decanol, octanediol, etc.

[0093] Examples of glycol ether solvents include, for example, diethylene glycol mono-2-ethylhexyl ether, ethylene glycol monophenyl ether, diethylene glycol monohexyl ether (hexyl diethylene glycol: HeDG), diethylene glycol dibutyl ether, triethylene glycol monobutyl ether, triethylene glycol butyl methyl ether, tetraethylene glycol, tetraethylene glycol dimethyl ether, monoalkyl propylene glycol, etc.

[0094] Examples of terpineols include α-terpineol, β-terpineol, γ-terpineol, and mixtures of terpineols (i.e., mixtures whose main component is α-terpineol and which contain β-terpineol or γ-terpineol).

[0095] Other solvents include, for example, dioctyl sebacate and liquid paraffin.

[0096] In the flux of this embodiment, a single solvent may be used, or two or more solvents may be used together.

[0097] In the above, the solvent is preferably a glycol ether solvent, and more preferably a monoalkyl propylene glycol, from the viewpoint of easily suppressing the increase in viscosity of the solder paste.

[0098] As a monoalkyl propylene glycol, it preferably contains one or more selected from butylpropylene triethylene glycol, butylpropylene diethylene glycol and butylpropylene (mono) glycol, and more preferably contains one or more selected from butylpropylene triethylene glycol and butylpropylene diethylene glycol.

[0099] The solvent content in the flux of this embodiment is the remaining portion of the flux, determined based on the content of other components.

[0100] For example, the solvent content in the flux of this embodiment, relative to the total mass (100% by mass) of the flux, can be 30% or more and 70% or less by mass, 35% or more and 60% or less by mass, 35% or more and 55% or less by mass, or 40% or more and 50% or less by mass.

[0101] In the flux of this embodiment, when monoalkyl propylene glycol is selected as the solvent, the content of monoalkyl propylene glycol in the flux is preferably 5 to 50% by mass, more preferably 10 to 40% by mass, and even more preferably 15 to 35% by mass relative to the total mass (100% by mass) of the flux.

[0102] When the content of monoalkyl propylene glycol is above the lower limit of the above preferred range, it is easy to suppress the increase in viscosity of the solder paste. When it is below the upper limit of the above preferred range, it is easy to suppress the precipitation of compounds with a benzotriazole skeleton in the flux, thereby improving the stability over time (along with the difficulty of precipitation over time).

[0103] In the flux of this embodiment, from the viewpoint of stability over time (the difficulty of precipitation over time), the mixing ratio of the polymer (P) and the monoalkyl propylene glycol, expressed as a mass ratio of polymer (P) / monoalkyl propylene glycol, is preferably 0.05 or more, more preferably 0.10 or more and 3 or less.

[0104] When the mass ratio is within the preferred range described above, it is easier to suppress the precipitation of compounds with a benzotriazole skeleton in the flux, and the stability over time (as well as the difficulty of precipitation over time) is improved.

[0105] In the flux of this embodiment, from the viewpoint of balancing the suppression of viscosity increase of solder paste and stability over time (which is accompanied by the difficulty of precipitation over time), the mixing ratio of the polymer (P) to the monoalkyl propylene glycol, expressed as a mass ratio of polymer (P) / monoalkyl propylene glycol, is preferably 0.05 or more, more preferably 0.05 or more and 1.5 or less, further preferably 0.06 or more and 1.0 or less, and particularly preferably 0.10 or more and 0.50 or less.

[0106] When the mass ratio is above the lower limit of the above-mentioned preferred range, it is easy to suppress the precipitation of compounds with a benzotriazole skeleton in the flux, and the stability over time (accompanying the difficulty of precipitation over time) is improved. When it is below the upper limit of the above-mentioned preferred range, it is easy to suppress the increase in the viscosity of the solder paste.

[0107] <Thixotropic agent> The flux in this embodiment contains a thixotropic agent.

[0108] Examples of thixotropic agents include amide-based thixotropic agents, ester-based thixotropic agents, and sorbitol-based thixotropic agents.

[0109] Examples of amide-based thixotropic agents include monoamides, diamides, and polyamides.

[0110] Examples of monoamides include laurylamide, palmitamide, stearamide, behenamide, hydroxystearamide, saturated fatty acid amide, oleamide, erucamide, unsaturated fatty acid amide, 4-methylbenzamide (p-toluamide), p-toluenemethaneamide, aromatic amide, hexamethylene hydroxystearamide, substituted amide, hydroxymethylstearamide, hydroxymethylamide, fatty acid ester amide, etc.

[0111] Examples of diamides include ethylenedicarboxylic acid (C6-24 carbon atoms in fatty acids) amides, ethylenedihydroxycarboxylic acid (C6-24 carbon atoms in fatty acids) amides, hexamethylenedicarboxylic acid (C6-24 carbon atoms in fatty acids) amides, hexamethylenedihydroxycarboxylic acid (C6-24 carbon atoms in fatty acids) amides, and aromatic diamides. Examples of fatty acids used as raw materials for these diamides include stearic acid (C18 carbon atoms), oleic acid (C18 carbon atoms), and lauric acid (C12 carbon atoms).

[0112] Examples of polyamides include saturated fatty acid polyamides, unsaturated fatty acid polyamides, aromatic polyamides, 1,2,3-propanetricarboxylic acid tris(2-methylcyclohexylamide), cyclic amide oligomers, and non-cyclic amide oligomers.

[0113] Examples of cyclic amide oligomers include amide oligomers obtained by condensing dicarboxylic acids and diamines into a cyclic form, amide oligomers obtained by condensing tricarboxylic acids and diamines into a cyclic form, amide oligomers obtained by condensing dicarboxylic acids and triamines into a cyclic form, amide oligomers obtained by condensing tricarboxylic acids and triamines into a cyclic form, amide oligomers obtained by condensing dicarboxylic acids and tricarboxylic acids and diamines into a cyclic form, amide oligomers obtained by condensing dicarboxylic acids and tricarboxylic acids and triamines into a cyclic form, amide oligomers obtained by condensing dicarboxylic acids and diamines and triamines into a cyclic form, and amide oligomers obtained by condensing dicarboxylic acids and tricarboxylic acids and diamines and triamines into a cyclic form.

[0114] Furthermore, examples of acyclic amide oligomers include those obtained by the condensation polymerization of monocarboxylic acids with diamines and / or triamines to form acyclic amide oligomers, and those obtained by the condensation polymerization of dicarboxylic acids and / or tricarboxylic acids with monoamines to form acyclic amide oligomers. When the amide oligomer contains a monocarboxylic acid or a monoamine, the monocarboxylic acid or monoamine functions as terminal molecules, resulting in acyclic amide oligomers with reduced molecular weight. Additionally, in the case of amide compounds obtained by the condensation polymerization of dicarboxylic acids and / or tricarboxylic acids with diamines and / or triamines to form acyclic amide compounds, the acyclic amide oligomer becomes an acyclic polymeric amide polymer. Furthermore, acyclic amide oligomers also include those obtained by the condensation polymerization of monocarboxylic acids and monoamines to form acyclic amide oligomers.

[0115] Examples of ester-based thixotropic agents include, for example, ester compounds, specifically hydrogenated castor oil and ethyl myristate.

[0116] Examples of sorbitol-based thixotropic agents include, for example, dibenzylidene-D-sorbitol, di(4-methylbenzylidene)-D-sorbitol, (D-)sorbitol, monobenzylidene(-D-)sorbitol, and mono(4-methylbenzylidene)-(D-)sorbitol.

[0117] In the flux of this embodiment, a thixotropic agent may be used alone or in combination with two or more.

[0118] In the above, the thixotropic agent preferably contains one or more selected from amide-based thixotropic agents and ester-based thixotropic agents, and more preferably contains one or more selected from amide-based thixotropic agents.

[0119] Among amide-based thixotropic agents, polyamides are preferred, especially from the viewpoint of easily improving stability over time (suppressing flux separation that occurs over time). It is particularly effective to select polyamides with a high content of the (P) component (e.g., 10% or more relative to the total mass of flux (100% by mass)).

[0120] In this embodiment, the content of thixotropic agent in the flux is preferably 2% or more and 15% or less relative to the total mass (100% by mass) of the flux, more preferably 4% or more and 12% or less, and even more preferably 5% or more and 9% or less.

[0121] When the content of thixotropic agent is above the lower limit of the above-mentioned preferred range, it is easy to improve the stability over time (suppress flux separation that occurs over time). On the other hand, when the content of thixotropic agent is below the upper limit of the above-mentioned preferred range, it is easy to suppress the initial viscosity of the solder paste from being too high.

[0122] Dicarboxylic acid The flux of this embodiment contains dicarboxylic acid. By selecting dicarboxylic acid as an organic acid, the cohesiveness of the solder alloy powder is improved (suppressing the formation of solder balls) during reflow soldering when the solder alloy powder melts.

[0123] As a dicarboxylic acid, examples include dicarboxylic acids, which can be aliphatic or aromatic.

[0124] Preferred dicarboxylic acids include compounds represented by the following general formula (c1).

[0125] [Chemical Formula 7]

[0126] [In the formula, R represents an alkylene group, a phenylene group, or a single bond with 1 to 10 carbon atoms. The methylene group constituting the alkylene group may also be substituted with an oxygen atom.] In the formula (c1), the alkylene group in R preferably has 2 to 8 carbon atoms. The alkylene group in R can be linear or branched, but is preferably linear.

[0127] Examples of dicarboxylic acids include succinic acid, glutaric acid, diethylene glycol, adipic acid, sebacic acid, dodecanoic acid, phthalic acid, isophthalic acid (1,3-phthalic acid), and terephthalic acid (1,4-phthalic acid).

[0128] In the flux of this embodiment, dicarboxylic acid can be used alone or in combination with two or more.

[0129] In the above, the dicarboxylic acid is preferably an aliphatic dicarboxylic acid, more preferably a dicarboxylic acid in which R in formula (c1) is an alkylene dicarboxylic acid with 2 to 8 carbon atoms, and further preferably glutaric acid or adipic acid, especially adipic acid.

[0130] The content of dicarboxylic acid in the flux of this embodiment is preferably 0.5% or more and 7.5% or less relative to the total mass (100% by mass) of the flux, more preferably 1% or more and 6% or less, and even more preferably 2% or more and 4% or less.

[0131] When the content of dicarboxylic acid is above the lower limit of the above-mentioned preferred range, the cohesiveness of the solder alloy powder is easily improved during reflow soldering. On the other hand, when it is below the upper limit of the above-mentioned preferred range, the increase in the viscosity of the solder paste is easily suppressed.

[0132] <Compounds with a benzotriazole skeleton> The flux of this embodiment contains a compound having a benzotriazole skeleton (hereinafter also referred to as the "(AZ1) component"). By containing the (AZ1) component, the blackening of flux residues can be suppressed.

[0133] In this specification, "compounds having a benzotriazole skeleton" refers to compounds in which a hetero-five-membered ring containing three nitrogen atoms and a benzene ring form a fused ring.

[0134] As components of (AZ1), for example, the compounds described in formula (AZ1-1) and the compounds shown in formula (AZ1-2) can be cited.

[0135] [Chemical Formula 8]

[0136] [In the formula, R] 11 It can be an organic group or a hydrogen atom. R 12 For substituents. n1 represents an integer from 0 to 4. R 21 It can be an organic group or a hydrogen atom. R 22 [This is a substituent. n2 represents an integer from 0 to 4.] Regarding compounds represented by general formula (AZ1-1) R 11 It can be an organic group or a hydrogen atom, preferably a hydrogen atom.

[0137] R 11 When the organic group is an organic group, examples of such organic groups include, for example, a chain hydrocarbon group having 1 to 40 carbon atoms that may have substituents, an alicyclic hydrocarbon group having 3 to 40 carbon atoms that may have substituents, and -R 101 -N(R 102a (R) 102b )wait.

[0138] Examples of substituents include carboxyl, carbonyl, hydroxyl, amino, and halogen atoms.

[0139] R 11When the hydrocarbon group is a chain, it can be straight-chain or branched, preferably branched. The chain hydrocarbon group can be saturated or unsaturated, preferably saturated.

[0140] R 11 When the alicyclic hydrocarbon group is used, it can be a polycyclic group or a monocyclic group. As a monocyclic alicyclic hydrocarbon group, it is preferably a group formed by removing one or more hydrogen atoms from a monocyclic alkane. As a polycyclic alicyclic hydrocarbon group, it is preferably a group formed by removing one or more hydrogen atoms from a polycyclic alkane.

[0141] R 11 -R 101 -N(R 102a (R) 102b When R 101 For example, it can be a hydrocarbon group with 1 to 5 carbon atoms. As R... 101 The hydrocarbon group in the hydrocarbon group can be, for example, aliphatic hydrocarbon groups that are straight-chain or branched, and the number of carbon atoms is preferably 1 to 10, more preferably 1 to 6, further preferably 1 to 4, and most preferably 1 to 3.

[0142] As R 101 The linear aliphatic hydrocarbon group in the form of the alkyl group is preferred to be linear alkylene group. Specifically, examples include methylene [-CH2-], ethylene [-(CH2)2-], trimethylene [-(CH2)3-], tetramethylene [-(CH2)4-], pentamethylene [-(CH2)5-], etc.

[0143] As R 101 The branched aliphatic hydrocarbon group in the form of a branched alkylene group is preferred. Specifically, examples include: alkylmethylene groups such as -CH(CH3)-, -CH(CH2CH3)-, -C(CH3)2-, -C(CH3)(CH2CH3)-, -C(CH3)(CH2CH2CH3)-, and -C(CH2CH3)2-; alkylethylene groups such as -CH(CH3)CH2-, -CH(CH3)CH(CH3)-, -C(CH3)2CH2-, -CH(CH2CH3)CH2-, and -C(CH2CH3)2-CH2-; alkyltrimethylene groups such as -CH(CH3)CH2CH2- and -CH2CH(CH3)CH2-; and alkylalkylene groups such as alkyltetramethylene groups such as -CH(CH3)CH2CH2CH2- and -CH2CH(CH3)CH2CH2-.

[0144] R 102a and R 102bEach of the substituents can be, for example, a chain-like hydrocarbon group or a hydrogen atom having 1 to 20 carbon atoms. Examples of the substituents described above are possible examples.

[0145] R 102a and R 102b When the hydrocarbon group is a chain, it can be straight-chain or branched. The chain hydrocarbon group can be saturated or unsaturated, preferably saturated.

[0146] R in the general formula (AZ1-1) 12 For example, examples include hydrocarbon groups, carboxyl groups, hydroxyl groups, amino groups, and halogen atoms with 1 to 5 carbon atoms.

[0147] R 12 When the hydrocarbon group has 1 to 5 carbon atoms, the hydrocarbon group can be either straight-chain or branched. Furthermore, the hydrocarbon group can be a saturated hydrocarbon group or an unsaturated hydrocarbon group, with a saturated hydrocarbon group being preferred.

[0148] As R 12 The hydrocarbon group in the form of methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, isopentyl, sec-pentyl, tert-pentyl, neopentyl, etc., with methyl being preferred.

[0149] As R 12 Halogen atoms in the atom can be fluorine, chlorine, bromine, or iodine.

[0150] When n1 is 2 or more, there are multiple R 12 They can be the same or different. n1 is preferably 0 or 1.

[0151] Examples of compounds represented by the general formula [AZ1-1] include 1,2,3-benzotriazole, 5-methylbenzotriazole, 1-[N,N-bis(2-ethylhexyl)aminomethyl]benzotriazole, carboxybenzotriazole, and 1-[N,N-bis(2-ethylhexyl)aminomethyl]methylbenzotriazole, among which one or more are preferably selected from 1,2,3-benzotriazole and 5-methylbenzotriazole, and more preferably 1,2,3-benzotriazole.

[0152] Regarding compounds represented by general formula (AZ1-2) R 21 It can be an organic group or a hydrogen atom. R 21 When the organic group is an organic group, examples of such organic groups include aromatic hydrocarbon groups that may have substituents, chain hydrocarbon groups with 1 to 40 carbon atoms that may have substituents, and alicyclic hydrocarbon groups with 3 to 40 carbon atoms that may have substituents, with aromatic hydrocarbon groups being preferred.

[0153] R 21 The explanation of chain hydrocarbon groups and alicyclic hydrocarbon groups in the above R is the same as that of R. 11 The descriptions of chain hydrocarbon groups and alicyclic hydrocarbon groups are the same.

[0154] The aromatic hydrocarbon group is a hydrocarbon group having at least one aromatic ring. Examples include aromatic hydrocarbon rings of benzene, naphthalene, anthracene, phenanthrene, etc.; aromatic heterocycles in which a portion of the carbon atom constituting the aromatic hydrocarbon ring is replaced by a heteroatom; and fused rings formed by the condensation of aromatic hydrocarbon rings and aromatic heterocycles.

[0155] R 21 When the aromatic hydrocarbon group in the compound has a substituent, examples of substituents include hydrocarbon groups with 1 to 20 carbon atoms, aromatic hydrocarbon groups, carboxyl groups, hydroxyl groups, amino groups, halogen atoms, etc., with hydrocarbon groups or hydroxyl groups being preferred. When the substituent is a hydrocarbon group, examples of hydrocarbon groups include those related to R... 11 The same hydrocarbon group as the one in the text. When the substituent is an aromatic hydrocarbon group, the aforementioned aromatic hydrocarbon groups can be cited as examples of such aromatic hydrocarbon groups.

[0156] R in the above general formula (AZ1-2) 22 Examples of R in the above general formula (AZ1-1) can be cited. 12 The same group.

[0157] The compounds represented by general formula (AZ1-2) can have multiple benzotriazole skeletons. Here, "multiple" means, for example, 2 to 5, preferably 2.

[0158] Examples of compounds represented by the above general formula (AZ1-2) include 2-(2'-hydroxy-5'-methylphenyl)benzotriazole, 2-(2'-hydroxy-3'-tert-butyl-5'-methylphenyl)-5-chlorobenzotriazole, 2-(2'-hydroxy-3',5'-di-tert-pentylphenyl)benzotriazole, 2-(2'-hydroxy-5'-tert-octylphenyl)benzotriazole, 2,2'-methylenebis[6-(2H-benzotriazol-2-yl)-4-tert-octylphenol], 6-(2-benzotriazolyl)-4-tert-octyl-6'-tert-butyl-4'-methyl-2,2'-methylenebisphenol, etc., among which 2-(2'-hydroxy-5'-methylphenyl)benzotriazole is preferred.

[0159] In the flux of this embodiment, the (AZ1) component can be used alone or in combination with two or more components.

[0160] In the above, the (AZ1) component is preferably selected from one or more of 1,2,3-benzotriazole, 5-methylbenzotriazole and 2-(2'-hydroxy-5'-methylphenyl)benzotriazole, and more preferably contains at least 1,2,3-benzotriazole.

[0161] The (AZ1) component used in the flux of this embodiment can be 1,2,3-benzotriazole alone, 5-methylbenzotriazole alone, 2-(2'-hydroxy-5'-methylphenyl)benzotriazole alone, a combination of 1,2,3-benzotriazole and 5-methylbenzotriazole, or a combination of 1,2,3-benzotriazole and 2-(2'-hydroxy-5'-methylphenyl)benzotriazole. More preferably, it can be 1,2,3-benzotriazole alone, a combination of 1,2,3-benzotriazole and 5-methylbenzotriazole, or a combination of 1,2,3-benzotriazole and 2-(2'-hydroxy-5'-methylphenyl)benzotriazole.

[0162] The content of the compound having a benzotriazole skeleton in the flux of this embodiment is preferably 1% or more and 10% or less relative to the total mass (100% by mass) of the flux, more preferably 1% or more and 6% or less by mass, and even more preferably 3% or more and 5% or less by mass.

[0163] When the content of the compound having a benzotriazole skeleton is above the lower limit of the above-mentioned preferred range, it is easy to suppress the blackening of flux residues. On the other hand, when it is below the upper limit of the above-mentioned preferred range, the wetting and spreading properties of the solder paste on the pads become better.

[0164] In this embodiment, the rosin content in the flux is preferably 15% by mass or more, more preferably 20% by mass or more, relative to the total mass of the flux (100% by mass), and the content of the compound having a benzotriazole skeleton is preferably 6% by mass or less, more preferably 5% by mass or less, so that the wetting and spreading properties of the solder paste on the pads are more likely to be better.

[0165] In the flux of this embodiment, the mixing ratio of the dicarboxylic acid and the compound having a benzotriazole skeleton, expressed as a mass ratio of dicarboxylic acid / compound having a benzotriazole skeleton, is preferably 0.2 or more and 3 or less, more preferably 0.4 or more and 2 or less, further preferably 0.5 or more and 1.5 or less, and particularly preferably more than 0.5 and less than 1.5.

[0166] When the mass ratio is above the lower limit of the above-mentioned preferred range, the cohesiveness of the solder alloy powder during reflow soldering is easily improved; when it is below the upper limit of the above-mentioned preferred range, the blackening of flux residue is easily suppressed.

[0167] <Other Ingredients> In addition to the rosin, polymer (P), solvent, thixotropic agent, dicarboxylic acid, and compound with a benzotriazole skeleton mentioned above, the flux of this embodiment may also contain other ingredients as needed.

[0168] Other components that can be listed include surfactants, resins other than rosin, metal passivators, surfactants, silane coupling agents, antioxidants, and colorants.

[0169] Surfactants Examples of active agents include organic acids other than amines and dicarboxylic acids, as well as halogenated compounds.

[0170] Regarding amines Examples of amines include, for example, rosin amines, azoles, guanidines, alkylamine compounds, and amino alcohol compounds. Among the rosin amines, the rosin amines exemplified in the above section on <Rosin> can be cited.

[0171] Examples of azoles include, for instance, 2-methylimidazole, 2-ethylimidazole, 2-undecylimidazole, 2-heptadecanylimidazole, 1,2-dimethylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, 2-phenyl-4-methylimidazole, 1-benzyl-2-methylimidazole, 1-benzyl-2-phenylimidazole, 1-cyanoethyl-2-methylimidazole, 1-cyanoethyl-2-undecylimidazole, 1-cyanoethyl-2-ethyl-4-methylimidazole, 1-cyanoethyl-2-phenylimidazole, 1-cyanoethyl-2-undecylimidazole trimellitate, 1-cyanoethyl-2-phenylimidazole trimellitate, and 2,4-diamino-6-[2'-methylimidazole-(1')]-ethyltrimethylimidazole. Azine, 2,4-diamino-6-[2'-undecylimidazolyl-(1')]-ethyltriazine, 2,4-diamino-6-[2'-ethyl-4'-methylimidazolyl-(1')]-ethyltriazine, 2,4-diamino-6-[2'-methylimidazolyl-(1')]-ethyltriazine isocyanuric acid adduct, 2-phenylimidazolyl isocyanuric acid adduct, 2-phenyl-4,5-dihydroxymethylimidazolium, 2-phenyl-4-methyl-5-hydroxymethylimidazolium, 2,3-dihydro-1H-pyrrolo[1,2-a]benzimidazole, 1-dodecyl-2-methyl-3-benzylimidazolium chloride, 2-methylimidazoline, 2-phenylimidazoline, 2,4-diamino-6-vinyltriazine, 2,4-Diamino-6-vinyltriazine isocyanuric acid adduct, 2,4-diamino-6-methacryloyloxyethyltriazine, epoxy-imidazolium adduct, 2-methylbenzimidazole, 2-octylbenzimidazole, 2-pentylbenzimidazole, 2-(1-ethylpentyl)benzimidazole, 2-nonylbenzimidazole, 2-(4-thiazolyl)benzimidazole, benzimidazole, 1,2,4-triazole, 2-(2'-hydroxy-5'-methylphenyl)benzotriazole, 2-(2'-hydroxy-3'-tert-butyl-5'-methylphenyl)-5-chlorobenzotriazole, 2-(2'-hydroxy-3',5'-di-tert-pentylphenyl)benzotriazole, 2-(2'-hydroxy-5'-tert-octylphenyl)benzotriazole, 2, 2'-Methylenebis[6-(2H-benzotriazol-2-yl)-4-tert-octylphenol], 6-(2-benzotriazolyl)-4-tert-octyl-6'-tert-butyl-4'-methyl-2,2'-methylenebisphenol, 1,2,3-benzotriazole, 1-[N,N-bis(2-ethylhexyl)aminomethyl]benzotriazole, carboxybenzotriazole, 1-[N,N-bis(2-ethylhexyl)aminomethyl]methylbenzotriazole, 2,2'-[[(methyl-1H-benzotriazol-1-yl)methyl]imino]diethanol, 1-(1',2'-dicarboxyethyl)benzotriazole, 1-(2,3-dicarboxypropyl)benzotriazole, 1-[(2-ethylhexylamino)methyl]benzotriazole, 2,6-Bis[(1H-benzotriazol-1-yl]methyl]-4-methylphenol, 5-methylbenzotriazole, 5-phenyltetrazole, etc.

[0172] Examples of guanidines include, for example, 1,3-diphenylguanidine, 1,3-di-o-tolylguanidine, 1-o-tolylguanidine, 1,3-di-o-isopropylphenylguanidine, and 1,3-di-o-isopropylphenyl-2-propionylguanidine.

[0173] Examples of alkylamine compounds include, for example, ethylamine, triethylamine, ethylenediamine, triethylenetetramine, cyclohexylamine, hexadecylamine, stearylamine, etc.

[0174] Examples of amino alcohol compounds include alkyl alcohol amines such as 1-amino-2-propanol and N,N,N',N'-tetra(2-hydroxypropyl)ethylenediamine.

[0175] When using amines, one type can be used alone, or two or more types can be used in combination.

[0176] Among the aforementioned substances, azoles and guanidines are preferred as amines. Among azoles, particularly from the viewpoint that the increase in solder paste viscosity is more easily suppressed, phenyl-substituted imidazoles are preferred, with 2-phenyl-4-methylimidazolium being especially preferred. Among guanidines, 1,3-di-o-tolylguanidine is particularly preferred.

[0177] The amine used in the flux of this embodiment is preferably a combination of azoles and guanidines. For example, a combination of 2-phenyl-4-methylimidazole and 1,3-di-o-tolylguanidine is preferred.

[0178] When using amines other than those with a benzotriazole skeleton as described above, the content of amines (excluding amines equivalent to those with a benzotriazole skeleton as described above) in the flux relative to the total amount of the flux (100% by mass) is preferably 4% by mass or more and 15% by mass or less, more preferably 5% by mass or more and 12% by mass or less, and even more preferably 6% by mass or more and 10% by mass or less.

[0179] When the amine content is above the lower limit of the above-mentioned preferred range, it is easy to suppress the increase in the viscosity of the solder paste. On the other hand, when it is below the upper limit of the above-mentioned preferred range, it is easy to improve the cohesiveness of the solder alloy powder during reflow soldering.

[0180] Regarding organic acids other than dicarboxylic acids Examples of organic acids other than dicarboxylic acids include carboxylic acids and organic sulfonic acids. Examples of carboxylic acids include aliphatic carboxylic acids and aromatic carboxylic acids. Examples of aliphatic carboxylic acids include aliphatic monocarboxylic acids.

[0181] Examples of aliphatic monocarboxylic acids include, for example, hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid, isononanoic acid, decanoic acid, decenoic acid, lauric acid (dodecanoic acid), undecanoic acid, icosanoic acid, tridecanoic acid, myristone acid, pentadecanoic acid, isopalmitic acid, palmitoleic acid, hexadecanetrienoic acid, cyclopentene undecanoic acid, heptadecanic acid, isostearic acid, transoleic acid, phellandrenic acid, stearatetraenoic acid, tungsten acid, tarric acid, octadecano-11-enoic acid, ricinoleic acid, piperidinic acid, styracidin, nonadecanic acid, eicosanoic acid, stearic acid, 12-hydroxystearic acid, oleic acid, linoleic acid, linolenic acid, myristic acid, 2,2-bis(hydroxymethyl)propionic acid, and 2,2-bis(hydroxymethyl)butyric acid.

[0182] Examples of aromatic carboxylic acids include, for example, salicylic acid, p-hydroxyphenylacetic acid, benzoic acid, 2,3-dihydroxybenzoic acid, 2-quinoline carboxylic acid, 3-hydroxybenzoic acid, p-anisic acid; pyridinecarboxylic acid, 3-hydroxypyridinecarboxylic acid, etc.

[0183] Examples of organic sulfonic acids include, for example, aliphatic sulfonic acids and aromatic sulfonic acids. Examples of aliphatic sulfonic acids include, for example, alkane sulfonic acids and alkanolic sulfonic acids.

[0184] Examples of alkane sulfonic acids include, for example, methane sulfonic acid, ethane sulfonic acid, 1-propane sulfonic acid, 2-propane sulfonic acid, 1-butane sulfonic acid, 2-butane sulfonic acid, pentane sulfonic acid, hexane sulfonic acid, decane sulfonic acid, dodecane sulfonic acid, etc.

[0185] Examples of alkanol sulfonic acids include, for example, 2-hydroxyethane-1-sulfonic acid, 2-hydroxypropane-1-sulfonic acid, 2-hydroxybutane-1-sulfonic acid, 2-hydroxypentane-1-sulfonic acid, 1-hydroxypropane-2-sulfonic acid, 3-hydroxypropane-1-sulfonic acid, 4-hydroxybutane-1-sulfonic acid, 2-hydroxyhexane-1-sulfonic acid, 2-hydroxydecane-1-sulfonic acid, and 2-hydroxydodecane-1-sulfonic acid.

[0186] Examples of aromatic sulfonic acids include, for example, 1-naphthalenesulfonic acid, 2-naphthalenesulfonic acid, p-toluenesulfonic acid, xylenesulfonic acid, p-phenolsulfonic acid, cresolsulfonic acid, sulfosalicylic acid, nitrobenzenesulfonic acid, sulfobenzoic acid, and diphenylamine-4-sulfonic acid.

[0187] When using organic acids other than dicarboxylic acid, one can be used alone or two or more can be used in combination. However, in the flux of this embodiment, the effect of dicarboxylic acid is sufficiently high. From the viewpoint of reducing flux residue, it is preferable that the flux does not contain organic acids other than dicarboxylic acid.

[0188] • About halogen compounds Examples of halogen compounds include, for example, hydrohalates and other organic halogen compounds.

[0189] Amino halides are compounds formed by reacting amines with hydrogen halides. Examples of amines include aliphatic amines, azoles, and guanidines. Examples of hydrogen halides include, for example, hydrides of chlorine, bromine, and iodine.

[0190] Examples of aliphatic amines include ethylamine, diethylamine, triethylamine, and ethylenediamine.

[0191] Examples of guanidines and azoles can be found in the description of the amines above.

[0192] Other than amine hydrohalides, organohalogen compounds include, for example, halogenated aliphatic compounds. A halogenated aliphatic hydrocarbon group is a group in which some or all of the hydrogen atoms constituting the aliphatic hydrocarbon group are replaced by halogen atoms.

[0193] Examples of halogenated aliphatic compounds include halogenated fatty alcohols and halogenated heterocyclic compounds.

[0194] When using halogen compounds, one type can be used alone, or two or more types can be used in combination. However, in the flux of this embodiment, from the viewpoint of easily suppressing the increase in the viscosity of the solder paste, it is preferable to use a flux that does not contain halogen compounds.

[0195] Resin components other than rosin As resin components other than rosin-based resins, examples include terpene resins, modified terpene resins, terpene phenol resins, modified terpene phenol resins, styrene resins, modified styrene resins, xylene resins, modified xylene resins, acrylic resins, polyethylene resins, acrylic-polyethylene copolymer resins, epoxy resins, etc.

[0196] Examples of modified terpene resins include aromatic modified terpene resins, hydrogenated terpene resins, and hydrogenated aromatic modified terpene resins. Examples of modified terpene phenol resins include hydrogenated terpene phenol resins. Examples of modified styrene resins include styrene acrylic resins and styrene maleic acid resins. Examples of modified xylene resins include phenol modified xylene resins, alkylphenol modified xylene resins, phenol-modified methylphenolic resin-type xylene resins, polyol modified xylene resins, and polyoxyethylene addition xylene resins.

[0197] Metal passivating agents Examples of metal passivating agents include hindered phenolic compounds and nitrogen compounds.

[0198] The "metal passivating agent" mentioned here refers to a compound that has the property of preventing metals from deteriorating due to contact with a certain compound.

[0199] Hindered phenolic compounds are phenolic compounds that have a large substituent (such as a branched chain or cyclic alkyl group such as tert-butyl) at at least one ortho position of phenol.

[0200] Nitrogen compounds used as metal passivating agents include, for example, hydrazide nitrogen compounds, amide nitrogen compounds, triazole nitrogen compounds, and melamine nitrogen compounds.

[0201] Surfactants Examples of surfactants include nonionic surfactants and cationic surfactants. Examples of nonionic surfactants include fatty alcohol polyoxyethylene adducts, aromatic alcohol polyoxyethylene adducts, polyol polyoxyethylene adducts, fatty alcohol polyoxypropylene adducts, aromatic alcohol polyoxypropylene adducts, and polyol polyoxypropylene adducts. Examples of cationic surfactants include terminal diamine polyethylene glycol, terminal diamine polyethylene glycol-polypropylene glycol copolymers, aliphatic amine polyoxyethylene adducts, aromatic amine polyoxyethylene adducts, and polyamine polyoxypropylene adducts.

[0202] As explained above, the flux of this embodiment, in addition to rosin, solvent, thixotropic agent, dicarboxylic acid, and compounds having a benzotriazole skeleton, also uses a polymer (P) having repeating units shown in the general formula (p1). By using this polymer (P), although the reason is uncertain, it is possible to provide a flux with high cohesiveness of solder alloy powder during reflow soldering, suppression of blackening of flux residue, difficulty in generating precipitation over time, and good stability over time.

[0203] In another embodiment of the flux, a solvent containing monoalkyl propylene glycol is included. By using this flux, viscosity changes (thickening) of the solder paste are suppressed.

[0204] Furthermore, by controlling the mixing ratio of monoalkyl propylene glycol to polymer (P), it is possible to easily suppress both the precipitation of compounds with a benzotriazole backbone in the flux and the increase in the viscosity of the solder paste.

[0205] (Solder paste) One embodiment of the solder paste contains solder alloy powder and flux as described in the above embodiments.

[0206] As the solder alloy constituting the solder alloy powder, a solder alloy with a known composition can be used.

[0207] Solder alloys can be Sn monomer solders, or Sn-Ag, Sn-Cu, Sn-Ag-Cu, Sn-Bi, Sn-In, etc., or solder alloys with added Sb, Bi, In, Cu, Zn, As, Ag, Cd, Fe, Ni, Co, Au, Ge, P, etc.

[0208] Solder alloys can also be Sn-Pb based, or Sn-Pb based solder alloys with added Sb, Bi, In, Cu, Zn, As, Ag, Cd, Fe, Ni, Co, Au, Ge, P, etc.

[0209] The solder alloy is preferably a Pb-free solder alloy, and more preferably a solder alloy containing Sn and Bi.

[0210] The welding conditions in the welding process can be appropriately set according to the melting point of the solder alloy. For example, when using a Sn-Ag-Cu based solder alloy, the molten solder temperature is preferably 230~280℃, more preferably 250~270℃. Alternatively, when using a Sn-Bi based solder alloy (a solder alloy containing Sn and Bi), the molten solder temperature is preferably 170~220℃, more preferably 180~200℃.

[0211] Flux content: In the solder paste of this embodiment, the flux content is preferably 5 to 30% by mass, more preferably 5 to 15% by mass, relative to the total mass of the solder paste.

[0212] The solder paste of this embodiment described above uses the flux of the above embodiment, resulting in high cohesion of solder alloy powder during reflow (suppressing the generation of solder balls), and the blackening of flux residue is suppressed.

[0213] Furthermore, the solder paste according to this embodiment exhibits improved wetting and spreading properties on the pads, suppressed viscosity changes (tackification), and enhanced stability over time (accompanied by suppression of flux separation over time).

[0214] Furthermore, since the solder paste of this embodiment uses the flux of the above embodiment, it is particularly preferable to use a solder alloy containing Sn and Bi (so-called low-temperature solder) as a solder alloy powder.

[0215] As another embodiment of flux and solder paste, the following configuration may also be adopted.

[0216]

[21] A flux comprising rosin, a polymer (P) having repeating units as shown in the following general formula (p1), a solvent, a thixotropic agent containing polyamide, a dicarboxylic acid as shown in the following general formula (c1), and a compound having a benzotriazole skeleton selected from the compounds shown in the following general formula (AZ1-1) and the compounds shown in the following general formula (AZ1-2).

[0217] [Chemical Formula 9]

[0218] [In the formula, R] 1 It can be a methyl group or a hydrogen atom. R 2 It consists of a hydrocarbon group with 1 to 2 carbon atoms or a hydrogen atom. [Chemical Formula 10]

[0219] [In the formula, R represents an alkylene group, a phenylene group, or a single bond with 1 to 10 carbon atoms. The methylene group constituting the alkylene group may also be substituted with an oxygen atom.] [Chemical Formula 11]

[0220] [In the formula, R] 11 It can be an organic group or a hydrogen atom. R 12 For substituents. n1 represents an integer from 0 to 4. R 21 It can be an organic group or a hydrogen atom. R 22 [This is a substituent. n2 represents an integer from 0 to 4.]

[22] According to the flux described in

[21] above, wherein the weight-average molecular weight of the polymer (P) is 300 to 8000.

[0221]

[23] According to the flux described in

[21] or

[22] above, wherein the content of the polymer (P) is 1% by mass or more and 15% by mass or less relative to the total mass of the flux.

[0222]

[24] The flux according to any one of

[21] to

[23] above, wherein the solvent contains monoalkyl propylene glycol.

[0223]

[25] According to the flux described above

[24] , wherein the monoalkyl propylene glycol contains at least one selected from butylpropylene triethylene glycol and butylpropylene diethylene glycol.

[0224]

[26] According to the flux described in

[24] or

[25] above, wherein the content of the monoalkyl propylene glycol is 5% by mass or more and 50% by mass or less relative to the total mass of the flux.

[0225]

[27] The flux according to any one of

[24] to

[26] above, wherein the mixing ratio of the polymer (P) to the monoalkyl propylene glycol is 0.05 or more by mass ratio of polymer (P) / monoalkyl propylene glycol.

[0226]

[28] The flux according to any one of

[21] to

[27] above, wherein the content of the dicarboxylic acid is 0.5% by mass or more and 7.5% by mass or less relative to the total mass of the flux.

[0227]

[29] The flux according to any one of

[21] to

[28] above, wherein the content of the compound having a benzotriazole skeleton is 1% by mass or more and 10% by mass or less relative to the total mass of the flux.

[0228]

[30] The flux according to any one of

[21] to

[29] above, wherein the mixing ratio of the dicarboxylic acid to the compound having a benzotriazole skeleton is 0.2 or more and 3 or less by mass ratio of dicarboxylic acid to compound having a benzotriazole skeleton.

[0229]

[31] The flux according to any one of

[21] to

[30] above, wherein the rosin content is 10% by mass or more and 40% by mass or less relative to the total mass of the flux.

[0230]

[32] The flux according to any one of

[21] to

[31] above, wherein the rosin contains at least one selected from acrylic acid modified hydrogenated rosin, hydrogenated rosin and polymerized rosin.

[0231]

[33] The flux according to any one of

[21] to

[32] above, wherein the content of the thixotropic agent is 2% by mass or more and 15% by mass or less relative to the total mass of the flux.

[0232]

[34] According to the flux described in

[21] above, wherein, relative to the total mass (100% by mass) of the flux, the content of the rosin is 10% by mass or more and 40% by mass or less, the content of the polymer (P) is 1% by mass or more and 15% by mass or less, the content of the thixotropic agent is 2% by mass or more and 15% by mass or less, the content of the dicarboxylic acid is 0.5% by mass or more and 7.5% by mass or less, and the content of the compound having a benzotriazole skeleton is 1% by mass or more and 10% by mass or less.

[0233]

[35] According to the flux described above

[34] , wherein the weight-average molecular weight of the polymer (P) is 300 to 8000.

[0234]

[36] The flux according to

[34] or

[35] above, wherein the solvent contains monoalkyl propylene glycol.

[0235]

[37] According to the flux described above

[36] , wherein the monoalkyl propylene glycol contains at least one selected from butylpropylene triethylene glycol and butylpropylene diethylene glycol.

[0236]

[38] According to the flux described in

[36] or

[37] above, wherein the content of the monoalkyl propylene glycol is 5% by mass or more and 50% by mass or less relative to the total mass of the flux.

[0237]

[39] The flux according to any one of

[36] to

[38] above, wherein the mixing ratio of the polymer (P) to the monoalkyl propylene glycol is 0.05 or more by mass ratio of polymer (P) / monoalkyl propylene glycol.

[0238]

[40] The flux according to any one of

[34] to

[39] above, wherein the mixing ratio of the dicarboxylic acid and the compound having a benzotriazole skeleton is 0.2 or more and 3 or less by mass ratio of dicarboxylic acid / compound having a benzotriazole skeleton.

[0239]

[41] The flux according to any one of

[34] to

[40] above, wherein the rosin contains at least one selected from acrylic acid modified hydrogenated rosin, hydrogenated rosin and polymerized rosin.

[0240]

[42] The flux according to any one of

[21] to

[41] above, wherein the flux further contains a phenyl-substituted imidazole.

[0241]

[43] The flux according to any one of

[21] to

[42] above, wherein the flux does not contain halogen compounds.

[0242]

[44] A solder paste comprising solder alloy powder and any one of the fluxes described in

[21] to

[43] above.

[0243]

[45] According to the solder paste described above

[44] , wherein the solder alloy powder is composed of a solder alloy containing Sn and Bi.

[0244] Example The present invention will be described below through embodiments, but the present invention is not limited to the following embodiments.

[0245] <Preparation of Flux> (Examples 1-174, Comparative Examples 1-12) The fluxes of the embodiments and comparative examples with the compositions shown in Tables 1 to 31 are prepared.

[0246] In the table, the content of each raw material is expressed as a percentage (mass%) relative to the total mass (100% mass) of the flux.

[0247] The raw materials used are shown below.

[0248] ·rosin Use acrylic-modified hydrogenated rosin, hydrogenated rosin, and polymerized rosin.

[0249] • Polymers (P) having repeating units as shown in the general formula (p1) The copolymers having repeating units shown in the above chemical formulas (p1-3) and (p1-4) are respectively polybutenes (P1) to (P6). Polybutenes (P1) to (P6) are copolymers having a molecular structure with isobutene as the main component and a portion of n-butene as a long-chain hydrocarbon after reaction.

[0250] In addition, a polymer having repeating units shown in the above chemical formulas (p1-5) is used, namely polybutadiene (P7). Polybutadiene (P7) is a homopolymer with more than 90% repeating units shown in chemical formulas (p1-5) and less than 10% repeating units shown in chemical formulas (p2-4).

[0251] Polybutene (P1): Weight average molecular weight 3370, number average molecular weight 1558, manufactured by ENEOS Co., Ltd., trade name "GradeHV-300" Polybutene (P2): Weight average molecular weight 345, number average molecular weight 332, manufactured by ENEOS Co., Ltd., trade name "GradeLV-7" Polybutene (P3): Weight average molecular weight 1130, number average molecular weight 689, manufactured by ENEOS Co., Ltd., trade name "GradeHV-15" Polybutene (P4): weight average molecular weight 2114, number average molecular weight 944, manufactured by ENEOS Co., Ltd., trade name "GradeHV-50". Polybutene (P5): Weight average molecular weight 2578, number average molecular weight 1136, manufactured by ENEOS Co., Ltd., trade name "GradeHV-100" Polybutene (P6): Weight average molecular weight 7773, number average molecular weight 4808, manufactured by ENEOS Co., Ltd., trade name "GradeHV-1900" Polybutadiene (P7): weight average molecular weight 3991, number average molecular weight 2778, manufactured by Nippon Soda Co., Ltd., trade name "NISSO-PB B-2000". [Methods for determining the molecular weight of polymer (P)] The weight-average molecular weight and number-average molecular weight (converted from polystyrene) of the polymer (P) were determined by diluting the analytical sample in tetrahydrofuran (THF) and using gel permeation chromatography (GPC). The determination conditions are as follows.

[0252] Analytical apparatus: Waters e2695 Mobile phase: THF Column: Tosoh TSKguardcolumn HXL (protective column) +Tosoh TSKgel G3000 HXL +Tosoh TSKgel G2000 HXL Column temperature: 40℃ Flow rate: 1.0 (mL / min) Detector: RI detector, Po (+), Res (1.0s) Injection volume: 50μL Standard reference material: Tosoh's "Standard Polystyrene Reagent Kit for GPC PStQuick F" was used. The analytical results were converted to polystyrene.

[0253] Solvent Use butylpropylene triethylene glycol, butylpropylene diethylene glycol, butylpropylene (mono) glycol, and tetraethylene glycol dimethyl ether.

[0254] ·Thixotropic agents Polyamide and hydrogenated castor oil were used.

[0255] dicarboxylic acid Use adipic acid, glutaric acid, diglycolic acid, succinic acid, sebacic acid, dodecanedioic acid, and phthalic acid.

[0256] Monocarboxylic acids Use stearic acid.

[0257] Compounds with a benzotriazole skeleton Use 1,2,3-benzotriazole, 5-methylbenzotriazole, or 2-(2'-hydroxy-5'-methylphenyl)benzotriazole.

[0258] Other ingredients As amines, azoles and guanidines are used.

[0259] 2-Ethylimidazole, 2-Ethyl-4-methylimidazole, and 2-Phenyl-4-methylimidazole were used as the azole compounds.

[0260] The guanidine used is 1,3-di-o-tolylguanidine.

[0261] <Preparation of solder paste> Solder pastes were prepared by separately mixing each flux and the solder alloy powder described below. The prepared solder pastes contained 10.5% flux by mass and 89.5% solder alloy powder by mass.

[0262] Solder alloy powder: A powder formed from a solder alloy of 58% by mass Bi and the balance Sn. The solidus temperature of the solder alloy is 139°C, and the liquidus temperature is 141°C.

[0263] The size of the solder alloy powder is the size (particle size distribution) that meets the notation 4 in the classification of powder sizes in JIS Z3284-1:2014 (Table 2).

[0264] <Evaluation> As shown below, the evaluations were conducted on wetting spread, cohesiveness of solder alloy powder (difficulty in solder ball formation), stability over time (difficulty in precipitation over time), viscosity change of solder paste (inhibition of thickening), inhibition of blackening of flux residue, and stability over time (inhibition of flux separation over time). The results of these evaluations are shown in Tables 1-31.

[0265] Figure 1 The distribution of reflux in the evaluation of this embodiment is shown.

[0266] Regarding the temperature inside the reflux furnace, the heating rate for 50~130℃ is 1.3~2.2℃ / second. Maintain the temperature at 130~150℃ for 60~90 seconds. The heating rate for 150~170℃ is 0.4~1℃ / second. After reaching 170℃, maintain the temperature under natural cooling conditions for 30~90 seconds.

[0267] In all evaluations, the cohesiveness of the solder alloy powder (difficulty in solder ball formation) was assessed in an atmosphere with an oxygen concentration of 1000 ppm. Other evaluations were conducted in an atmospheric atmosphere.

[0268] [Evaluation of wetting and spreading properties] In the evaluation of wetting spread, the substrate used was a Cu-OSP treated glass epoxy board. The number of pads was set to 41, the pad width to be 0.27 mm, and the solder resist width to be 0.37 mm.

[0269] Figure 2 This diagram illustrates the wetting and spreading evaluation method in this embodiment.

[0270] like Figure 2As shown, solder paste 20 is printed with a single character on the top of pads 26 (light green area) and solder resist 28 (dark green area) formed on the substrate, with a length of 0.3 mm and a mask thickness of 0.15 mm, and then reflow soldering is performed. After reflow soldering, the length of solder alloy 22 that wets and spreads on pads 26 is measured. Wetting spread is evaluated based on the following criteria.

[0271] Judgment Criteria Grade 1: The average length of solder alloy 22 that wets and spreads on pad 26 is over 700 μm.

[0272] Grade 2: The average length of the solder alloy 22 that wets and spreads on pad 26 is 650 to less than 700 μm.

[0273] Level 3: The average length of the solder alloy 22 that wets and spreads on pad 26 is 600 to less than 650 μm.

[0274] Grade 4: The average length of solder alloy 22 wetted and extended on pad 26 is less than 600 μm.

[0275] Evaluation of the cohesiveness of solder alloy powder (difficulty in producing solder balls) The following describes the evaluation of the cohesiveness of solder alloy powder.

[0276] Solder paste was printed on a ceramic plate with a diameter of 6.5 mm and a mask thickness of 0.20 mm, and then reflow soldering was performed. After reflow soldering, the state of solder ball formation was checked. The cohesiveness of the solder alloy powder (difficulty in solder ball formation) was evaluated based on the following criteria.

[0277] Judgment Criteria Grade 1: After the solder alloy powder melts, it agglomerates into a large sphere. Less than 15 solder alloy particles with a diameter of less than 150 μm are identified around this large sphere.

[0278] Level 2: After the solder alloy powder melts, it agglomerates into a large sphere. More than 15 but less than 30 solder alloy particles with a diameter of less than 150 μm are identified around this large sphere.

[0279] Level 3: After the solder alloy powder melts, it agglomerates into a large sphere. More than 30 but less than 40 solder alloy particles with a diameter of less than 150 μm are identified around this large sphere.

[0280] Level 4: After the solder alloy powder melts, it agglomerates into a large sphere. More than 40 solder alloy particles with a diameter of less than 150 μm, or solder alloy particles with a diameter of more than 150 μm, or unagglomerated particles are identified around the periphery of this large sphere.

[0281] [Evaluation of stability over time (difficulty of precipitation occurring over time)] Evaluate the stability over time (the difficulty of precipitation occurring over time) in the following ways.

[0282] The flux was stored at 25°C and 50% relative humidity. For each flux stored for 1 week, 1 month, 2 months, and 3 months, flux was printed on a glass slide with a thickness of 100 μm to identify precipitates. The stability over time (the difficulty of precipitation occurring over time) was evaluated based on the following criteria.

[0283] Judgment Criteria Level 1: No precipitates were identified after 3 months of storage.

[0284] Level 2: No precipitates were identified after 2 months of storage.

[0285] Level 3: No precipitates were identified after one month of storage.

[0286] Level 4: After 1 week of storage, precipitates are confirmed (i.e., precipitates are generated within 1 week).

[0287] [Evaluation of viscosity change (tickling inhibition) of solder paste] The viscosity change of the solder paste was evaluated in accordance with JIS Z3284-3:2014 "4.2 Viscosity Characteristics Test".

[0288] The viscometer used is a Malcom PCU-205.

[0289] The measurement conditions were: temperature 25℃, rotation speed 10 rpm, and initial viscosity was the viscosity 30 minutes after the start of the measurement.

[0290] The viscosity change (tack inhibition) of solder paste is evaluated based on the following criteria.

[0291] Judgment Criteria Grade 1: The viscosity 24 hours after the start of the test is less than 1.05 times the initial viscosity.

[0292] Grade 2: The viscosity 12 hours after the start of the test is less than 1.05 times the initial viscosity.

[0293] Level 3: The viscosity 8 hours after the start of the test is less than 1.05 times the initial viscosity.

[0294] Level 4: The viscosity 8 hours after the start of the measurement is more than 1.05 times the initial viscosity.

[0295] [Evaluation of the inhibition of blackening of flux residue] The following is an evaluation of the inhibition of blackening of flux residues.

[0296] Solder paste was printed on a Cu-OSP substrate with a diameter of 5.0 mm and a mask thickness of 0.15 mm, and then left to stand for 2 hours at 25°C and 50% relative humidity. Reflow soldering was then performed, and the blackening state of flux residues was confirmed by binarization. The blackening inhibition of flux residues was evaluated based on the following criteria.

[0297] Figure 3 The image shows the blackened state of flux residue 34 remaining on the outer periphery of solder alloy 32 after reflow soldering.

[0298] Judgment Criteria In the top view, Grade 1: Of the surface area of ​​flux residue 34, the area of ​​blackening is greater than 0% and less than 10%.

[0299] Grade 2: Of the surface area of ​​flux residue 34, the area of ​​blackening is more than 10% and less than 30%.

[0300] Grade 3: Of the surface area of ​​flux residue 34, the area of ​​blackening is more than 30% but less than 50%.

[0301] Grade 4: In the surface area of ​​flux residue 34, the area of ​​blackening is more than 50%.

[0302] [Evaluation of stability over time (accompanied by flux separation over time)] Evaluate the stability over time (accompanied by flux separation over time) in the following manner.

[0303] The container uses an opening area of ​​24 cm². 2 A container with an opening diameter of approximately 5.5 cm.

[0304] Fill the container with 500g of solder paste and store it at 25°C and 50% relative humidity for 7 days. Then, determine the area of ​​flux that floats (separates) on the surface of the solder paste (the proportion of separated flux to the container opening: area ratio). Evaluate the stability over time (accompanying flux separation over time) based on the following criteria.

[0305] Figure 4 The diagram shows the state in which flux 44 floats (separates) on the surface of solder paste 42 after the solder paste filled in container 40 has been stored for a predetermined time.

[0306] Judgment Criteria Grade 1: No separation of flux 44.

[0307] Level 2: There is separation of flux 44, and the separated flux 44 accounts for more than 0% and less than 10% of the area of ​​the container opening.

[0308] Level 3: There is separation of flux 44, and the separated flux 44 accounts for more than 10% but less than 30% of the area of ​​the container opening.

[0309] Level 4: Flux 44 is separated, and the separated flux 44 accounts for more than 30% of the area of ​​the container opening.

[0310] [Table 1]

[0311] The results shown in Table 1 confirm that when using the flux of Example 1 of the present invention, the solder alloy powder has high cohesion (difficulty in generating solder balls) during reflow soldering, which inhibits the blackening of flux residues and makes it difficult to produce precipitation over time, resulting in good stability over time.

[0312] On the other hand, when using the flux of Comparative Example 1 which lacks dicarboxylic acid, the evaluation of the cohesiveness of the solder alloy powder was poor.

[0313] When the flux of Comparative Example 4, which contains monocarboxylic acid instead of dicarboxylic acid, was used, the evaluation of the cohesiveness of the solder alloy powder was also poor.

[0314] When using the flux of Comparative Example 2, which lacks a compound with a benzotriazole skeleton, the evaluation of flux residue blackening inhibition was poor.

[0315] When using the flux of Comparative Example 3, which lacks polymer (P), the evaluation of stability over time (accompanied by the difficulty of precipitation over time) was poor.

[0316] [Table 2]

[0317] Table 2 shows the results of using the flux of Comparative Example 5, which confirms that dicarboxylic acid, as an activator in the flux, is effective in improving the cohesiveness of solder alloy powder, while conversely, it is poor in suppressing the blackening of flux residue.

[0318] The results from using the flux of Comparative Example 6 confirm that compounds with a benzotriazole framework are effective for blackening flux residues, and conversely, have poor evaluation of stability over time (accompanied by the difficulty of precipitation over time).

[0319] In contrast, the results from using the fluxes of Examples 1 and 15 confirm that by further using polymer (P), the cohesiveness of the solder alloy powder, the inhibition of blackening of flux residues, and the evaluation of time stability (accompanying the difficulty of precipitation over time) all become good.

[0320] [Table 3]

[0321] Table 3 shows that the comparison between Example 1 and Example 34 confirms that by using monoalkyl propylene glycol as a solvent, the viscosity change of the solder paste can be further reduced (improving the effect of inhibiting thickening).

[0322] When the flux of Comparative Example 7, which lacks both polymer (P) and monoalkyl propylene glycol, is used, the evaluation of its stability over time (the difficulty of precipitation over time) and the viscosity change of the solder paste (tack inhibition) are both poor.

[0323] [Table 4]

[0324] [Table 5]

[0325] The results shown in Tables 4-5 confirm that when using the fluxes of Examples 1-15 of the present invention, the solder alloy powder exhibits high cohesion during reflow soldering, suppresses the blackening of flux residues, and is less prone to precipitation over time, resulting in good stability over time.

[0326] A comparison of Examples 1, 5, and 7 confirms that by using a monoalkyl propylene glycol selected from butylpropylene triethylene glycol and butylpropylene diethylene glycol as a solvent, the viscosity change of the solder paste can be further reduced (improving the effect of inhibiting thickening).

[0327] [Table 6]

[0328] [Table 7]

[0329] [Table 8]

[0330] [Table 9]

[0331] [Table 10]

[0332] [Table 11]

[0333] [Table 12]

[0334] The results shown in Tables 6-12 confirm that when the content of monoalkyl propylene glycol is 5% by mass or more, preferably 10% by mass or more, and more preferably more than 10% by mass, the viscosity change of the solder paste can be further reduced (the effect of inhibiting thickening is improved).

[0335] The results shown in Tables 6-12 confirm that when the mass ratio of polymer (P) to monoalkyl propylene glycol is 0.05 or higher, it is easier to suppress the precipitation of compounds with a benzotriazole skeleton in the flux, and the stability over time (accompanying the difficulty of precipitation over time) is improved.

[0336] [Table 13]

[0337] [Table 14]

[0338] When using the fluxes of Examples 59-70 of the present invention, it can be confirmed that the solder alloy powder has high cohesion (difficulty in generating solder balls) during reflow soldering, inhibits the blackening of flux residues, and is difficult to produce precipitation over time, resulting in good stability over time.

[0339] When using the flux of Comparative Example 8, which lacks dicarboxylic acid, the evaluation of the cohesiveness of the solder alloy powder was poor.

[0340] [Table 15]

[0341] When using the fluxes of Examples 71-76 of the present invention, it can be confirmed that the solder alloy powder has high cohesion (difficulty in generating solder balls) during reflow soldering, inhibits the blackening of flux residues, and is difficult to produce precipitation over time, resulting in good stability over time.

[0342] When using the flux of Comparative Example 9, which lacks a compound with a benzotriazole skeleton, the evaluation of flux residue blackening inhibition was poor.

[0343] [Table 16]

[0344] When using the flux of Examples 77-80 of the present invention, it can be confirmed that the solder alloy powder has high cohesion (difficulty in generating solder balls) during reflow soldering, inhibits the blackening of flux residue, and is difficult to produce precipitation over time, with good stability over time.

[0345] [Table 17]

[0346] When using the fluxes of Examples 81-90 of the present invention, it can be confirmed that the solder alloy powder has high cohesion (difficulty in generating solder balls) during reflow soldering, inhibits the blackening of flux residues, and is difficult to produce precipitation over time, resulting in good stability over time.

[0347] When using the flux of Comparative Example 10, which lacks polymer (P), the evaluation of stability over time (accompanied by the difficulty of precipitation over time) was poor.

[0348] [Table 18]

[0349] [Table 19]

[0350] [Table 20]

[0351] [Table 21]

[0352] [Table 22]

[0353] [Table 23]

[0354] [Table 24]

[0355] When using the fluxes of Examples 91 to 133 of the present invention, it can be confirmed that the solder alloy powder has high cohesion (difficulty in generating solder balls) during reflow soldering, inhibits the blackening of flux residues, and is difficult to produce precipitation over time, resulting in good stability over time.

[0356] When using the flux of Comparative Example 11, which lacks polymer (P), the evaluation of stability over time (accompanied by the difficulty of precipitation over time) was poor.

[0357] [Table 25]

[0358] [Table 26]

[0359] [Table 27]

[0360] [Table 28]

[0361] [Table 29]

[0362] [Table 30]

[0363] [Table 31]

[0364] When using the fluxes of Examples 134 to 174 of the present invention, it can be confirmed that the solder alloy powder has high cohesion (difficulty in generating solder balls) during reflow soldering, inhibits the blackening of flux residues, and is difficult to produce precipitation over time, resulting in good stability over time.

[0365] When using the flux of Comparative Example 12, which lacks polymer (P), the evaluation of stability over time (accompanied by the difficulty of precipitation over time) was poor.

[0366] The preferred embodiments of the present invention have been described above, but the present invention is not limited to these embodiments. Additions, omissions, substitutions, and other modifications to the structure are possible without departing from the spirit of the present invention. The present invention is not limited by the foregoing description, but only by the scope of the appended claims.

[0367] Explanation of symbols 20 Solder paste, 22 Solder alloy, 26 Pad, 28 Solder resist, 32 Solder alloy, 34 Flux residue, 40 Container, 42 Solder paste, 44 Flux.

Claims

1. A flux containing a rosin, a polymer (P) having a repeating unit represented by the following general formula (Pl), a solvent, a thixotropic agent containing a polyamide, a dicarboxylic acid represented by the following general formula (cl), and a compound having a benzotriazole skeleton selected from a compound represented by the following general formula (AZ1-1) and a compound represented by the following general formula (AZ1-2), [Chemical Formula 1] wherein R 1 is a methyl group or a hydrogen atom; R 2 is a hydrocarbon group having 1 to 2 carbon atoms or a hydrogen atom, [Chemical Formula 2] In the formula, R represents an alkylene group having 1 to 10 carbon atoms, a phenylene group, or a single bond; wherein, The methylene group constituting the alkylene group can also be substituted with an oxygen atom, [Chemical Formula 3] wherein R 11 is an organic group or a hydrogen atom; R 12 is a substituent; n1 represents an integer of 0 to 4; R 21 is an organic group or a hydrogen atom; R 22 is a substituent; n2 represents an integer of 0 to 4.

2. The flux according to claim 1, wherein, The weight average molecular weight of the polymer (P) is 300 to 8000.

3. The flux according to claim 1, wherein The content of the polymer (P) is 1 mass% or more and 15 mass% or less with respect to the total mass of the flux.

4. The flux according to claim 1, wherein, The solvent contains a monoalkyl propylene glycol.

5. The flux according to claim 4, wherein, The monoalkyl propylene glycol contains at least one selected from butylpropylene glycol triethylene glycol and butylpropylene glycol diethylene glycol.

6. The flux according to claim 4, wherein The content of the monoalkyl propylene glycol is 5 mass% or more and 50 mass% or less with respect to the total mass of the flux.

7. The flux according to claim 4, wherein The mixing ratio of the polymer (P) and the monoalkyl propylene glycol is 0.05 or more in terms of the mass ratio of polymer (P) / monoalkyl propylene glycol.

8. The flux according to claim 1, wherein The content of the dicarboxylic acid is 0.5 mass% or more and 7.5 mass% or less with respect to the total mass of the flux.

9. The flux according to claim 1, wherein The content of the compound having a benzotriazole skeleton is 1 mass% or more and 10 mass% or less with respect to the total mass of the flux.

10. The flux according to claim 1, wherein The mixing ratio of the dicarboxylic acid and the compound having a benzotriazole skeleton is 0.2 or more and 3 or less in terms of the mass ratio of dicarboxylic acid / compound having a benzotriazole skeleton.

11. The flux according to claim 1, wherein The content of the rosin is 10 mass% or more and 40 mass% or less with respect to the total mass of the flux.

12. The flux according to claim 1, wherein The rosin contains at least one selected from an acrylic-modified hydrogenated rosin, a hydrogenated rosin, and a polymerized rosin.

13. The flux according to claim 1, wherein The content of the thixotropic agent is 2 mass% or more and 15 mass% or less with respect to the total mass of the flux.

14. The flux according to claim 1, wherein The flux further contains a phenyl-substituted imidazole.

15. The flux according to claim 1, wherein The flux does not contain a halogen compound.

16. A solder paste containing a solder alloy powder and the flux according to any one of claims 1 to 15.

17. The solder paste of claim 16, wherein, The solder alloy powder is composed of a solder alloy containing Sn and Bi. The solder alloy powder is composed of a solder alloy containing Sn and Bi.

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