Fluxing agents and assembly manufacturing methods

Abstract

The invention relates to a flux containing rosin (P), compound (SA), an activator (provided that the compound corresponding to compound (SA) is excluded), and a solvent (provided that the compound corresponding to compound (SA) is excluded). Compound (SA) is a compound of the general formula (sa). In formula (sa), R11 is a hydrocarbon group which may contain a hydroxyl group. Each R12 and R13 is an independent hydrocarbon group of 5 or fewer carbon atoms which may contain a substituent, a hydroxyl group, or a hydrogen atom. m is a positive integer. In addition, the invention relates to a method for producing an assembly using the flux according to the invention.

Description

Flux and method for manufacturing joint body

[0001] The present invention relates to a flux and a method for manufacturing a joint. This application claims priority based on Japanese Patent Application No. 2021-199990, filed on December 9, 2021, the contents of which are incorporated herein by reference.

[0002] Fixing components to a substrate and electrically connecting the components to the substrate are generally performed by soldering. Soldering uses flux, solder, and a solder paste made by mixing flux and solder. Flux chemically removes metal oxides present in the solder and the metal surfaces of the objects to be soldered, allowing the migration of metal elements at the interface between the two. Therefore, soldering using flux forms an intermetallic compound between the two, resulting in a strong bond.

[0003] In soldering, methods such as flow soldering and reflow soldering are used depending on the size of the objects to be joined. In flow soldering, flux is first applied to a board on which components are mounted. Then, while the board on which components are mounted is being transported, molten solder is jetted from below and brought into contact with the surface to be soldered, thereby performing soldering. In reflow soldering, solder paste is first printed on the board. Next, components are mounted on the board, and the board on which components are mounted is heated in a heating furnace called a reflow furnace, thereby performing soldering.

[0004] Fluxes used in soldering generally contain a resin component, a solvent, an activator, a thixotropic agent, etc. For example, an example of Patent Document 1 describes a flux used in flow soldering that contains rosin as a resin component and an organic acid, an organic halogen compound, or an amine hydrohalide as an activator.

[0005] Patent No. 6617848

[0006] Recently, lead-free solder has been used in consideration of its adverse effects on the environment. Because lead-free solder has a high melting point, it must be heated to a higher temperature during soldering. The higher the temperature of the molten solder, the more likely it is to produce oxides (called dross).

[0007] In particular, solder containing Sn and Bi may generate dross in a molten state because Bi is easily oxidized. In addition, when solder containing Sn and Bi is used, the generated dross is likely to adhere to the substrate. The dross that adheres to the substrate may cause short circuits, a decrease in insulation properties, etc.

[0008] The flux described in Patent Document 1 may easily cause dross to adhere to the surface of a substrate. Therefore, an object of the present invention is to provide a flux and a method for manufacturing a joined body that can suppress the adhesion of dross to the surface of a substrate during soldering.

[0009] In order to solve the above problems, the present invention employs the following configuration: That is, a first aspect of the present invention is a flux containing rosin (P), a compound (SA) represented by the following general formula (sa), an activator (excluding one corresponding to the compound (SA)), and a solvent (excluding one corresponding to the compound (SA)).

[0010] [In formula (sa), R １１ represents a hydrocarbon group which may have a hydroxy group. １２ and R １３ are each independently a hydrocarbon group having 5 or less carbon atoms which may have a substituent, a hydroxy group, or a hydrogen atom; and m is a positive integer.

[0011] In the flux according to the first aspect, the rosin (P) preferably contains a rosin (PA) having a softening point of more than 100°C and a rosin (PB) having a softening point of 100°C or lower.

[0012] In the flux according to the first aspect, the mixing ratio of the rosin (PA) to the rosin (PB), expressed as a mass ratio of (PA) / (PB), is preferably (PA) / (PB)=5 / 5 to 9 / 1.

[0013] In the flux according to the first aspect, it is preferable that the rosin (PA) contains at least one type of rosin (P1) selected from the group consisting of acrylic acid-modified hydrogenated rosin and polymerized rosin, and the rosin (PB) contains hydrogenated rosin.

[0014] In the flux according to the first aspect, the content of the compound (SA) is preferably 1 to 60 parts by mass per 100 parts by mass of the rosin (P).

[0015] In the flux according to the first aspect, the activator preferably contains a compound represented by the following general formula (a1):

[0016] [In formula (a1), R １ , R ２ , R ３ and R ４ each independently represents a hydrocarbon group, a hydroxy group, a halogen atom, or a hydrogen atom.

[0017] In the flux according to the first aspect, the activator preferably includes an alkanolamine.

[0018] In the flux according to the first aspect, the solvent preferably contains at least one selected from the group consisting of ethanol and 2-propanol.

[0019] In the flux according to the first aspect, the solid content concentration is preferably 20 mass % or less.

[0020] A second aspect of the present invention is a method for producing a bonded body, comprising the step of soldering a solder alloy to a surface of a substrate that has been treated with the flux according to the first aspect, to obtain a bonded body.

[0021] In the method for joining a joined body according to the second aspect, the solder alloy is preferably a solder alloy containing Sn and Bi.

[0022] According to the present invention, it is possible to provide a flux and a method for manufacturing a bonded body that can suppress adhesion of dross to the surface of a substrate during soldering.

[0023] (Flux) The flux according to the first aspect can be used for both flow soldering and reflow soldering, but is preferably used for flow soldering.

[0024] Hereinafter, an embodiment in which the flux according to the first aspect is applied to a flux for flow soldering will be described. The flux of the embodiment contains rosin (P), compound (SA), an activator (excluding those corresponding to the compound (SA)), and a solvent (excluding those corresponding to the compound (SA)). The compound (SA) will be described later.

[0025] In this specification, the solid content of the flux means all components remaining after excluding only the solvent from the flux.

[0026] <Rosin> The flux of this embodiment contains rosin (P). In the present invention, "rosin" encompasses natural resins containing abietic acid as a main component, including a mixture of abietic acid and its isomers, and chemically modified natural resins (sometimes referred to as rosin derivatives).

[0027] The total content of abietic acid and abietic acid isomers in the natural resin is, for example, 40% by mass or more and 80% by mass or less relative to the natural resin. In this specification, the term "main component" refers to a component that constitutes a compound and whose content in the compound is 40% by mass or more.

[0028] Representative isomers of abietic acid include neoabietic acid, palustric acid, levopimaric acid, etc. The structure of abietic acid is shown below.

[0029]

[0030] ​Examples of the "natural resin" include gum rosin, wood rosin, and tall oil rosin.

[0031] In the present invention, the term "chemically modified natural resin (rosin derivative)" includes the "natural resin" that has been subjected to one or more treatments selected from the group consisting of hydrogenation, dehydrogenation, neutralization, alkylene oxide addition, amidation, dimerization, oligomerization, esterification, and Diels-Alder cycloaddition.

[0032] Examples of rosin derivatives include purified rosin, modified rosin, etc. Modified rosins include hydrogenated rosin, polymerized rosin, polymerized hydrogenated rosin, disproportionated rosin, acid-modified rosin, rosin ester, 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, fumarated rosin, etc.), as well as purified products, hydrogenated products, and disproportionated products of the polymerized rosin, purified products, hydrogenated products, and disproportionated products of the α,β-unsaturated carboxylic acid-modified products, rosin alcohol, rosin amine, hydrogenated rosin alcohol, rosin ester, hydrogenated rosin ester, rosin soap, hydrogenated rosin soap, and acid-modified rosin soap.

[0033] Examples of rosin amines include dehydroabietylamine and dihydroabietylamine. Rosin amine refers to so-called disproportionated rosin amine. The structures of dehydroabietylamine and dihydroabietylamine are shown below.

[0034]

[0035] ​The rosin (P) may be used singly or in a mixture of two or more. The rosin (P) preferably contains a rosin derivative, more preferably contains one or more selected from the group consisting of acid-modified rosin, polymerized rosin, hydrogenated rosin, acid-modified hydrogenated rosin, and rosin ester, still more preferably contains one or more selected from the group consisting of acid-modified hydrogenated rosin, polymerized rosin, hydrogenated rosin, and rosin ester, and particularly preferably contains one or more selected from the group consisting of acid-modified hydrogenated rosin and hydrogenated rosin. As the acid-modified hydrogenated rosin, acrylic acid-modified hydrogenated rosin is preferred.

[0036] The rosin (P) preferably contains a rosin (PA) having a softening point of more than 100°C and a rosin (PB) having a softening point of 100°C or lower.

[0037] The softening point of rosin can be measured by the ring and ball method. Examples of the ring and ball method include the method described in JIS K 5902. Specifically, the softening point can be measured by the following procedure. First, the sample to be measured is quickly melted at the lowest possible temperature and carefully filled into a ring placed on a flat metal plate, avoiding the formation of bubbles. After cooling, the raised portion of the ring, including the top edge, is cut off using a slightly heated knife. Next, a holder (ring stand) is placed in a glass container (heating bath) with a diameter of at least 85 mm and a height of at least 127 mm, and a heating medium is poured in to a depth of at least 90 mm. Next, a steel ball (diameter 9.5 mm, weight 3.5 g) and the ring filled with the sample are immersed in the heating medium without touching each other, and the temperature of the heating medium is maintained at 20°C ± 5°C for 15 minutes. Next, the steel ball is placed in the center of the surface of the sample in the ring and placed in its fixed position on the holder. Next, maintain a distance of 50 mm from the top of the ring to the heat transfer surface, place a thermometer, and align the center of the thermometer's mercury bulb with the center of the ring. Heat the container. The flame of the Bunsen burner used for heating should be aimed midway between the center and edge of the bottom of the container to ensure uniform heating. After heating begins and reaching 40°C, the bath temperature should increase at a rate of 5.0 ± 0.5°C per minute. The sample gradually softens, flows down the ring, and finally touches the bottom plate. The temperature is read and considered the softening point. Two or more softening point measurements are taken simultaneously, and the average value is used. If the softening point of the sample is 80°C or lower, water is used as the heat transfer medium. If the softening point of the sample is higher than 80°C, glycerin is used as the heat transfer medium.

[0038] When the rosin (P) contains the rosin (PA), the stickiness of the flux residue can be more easily reduced.

[0039] The softening point of the rosin (PA) is preferably 110° C. or higher, more preferably 115° C. or higher, even more preferably 120° C. or higher, particularly preferably 125° C. or higher, and most preferably 130° C. or higher. When the softening point of the rosin (PA) is equal to or higher than the lower limit, the stickiness of the flux residue can be more easily reduced.

[0040] The softening point of the rosin (PA) is preferably 170°C or lower, more preferably 160°C or lower, and even more preferably 150°C or lower.

[0041] The softening point of the rosin (PA) may be higher than 100°C and lower than 170°C, preferably higher than 110°C and lower than 160°C, more preferably higher than 115°C and lower than 160°C, even more preferably higher than 120°C and lower than 160°C, particularly preferably higher than 125°C and lower than 160°C, and most preferably higher than 130°C and lower than 160°C. Alternatively, the softening point of the rosin (PA) is preferably higher than 110°C and lower than 150°C, more preferably higher than 115°C and lower than 150°C, even more preferably higher than 120°C and lower than 150°C, particularly preferably higher than 125°C and lower than 150°C, and most preferably higher than 130°C and lower than 150°C. When the softening point of the rosin (PA) is within the above range, the stickiness of the flux residue can be more easily reduced.

[0042] When the rosin (P) contains the rosin (PB), the fluidity of the flux is more likely to be increased, which makes it easier to suppress soldering defects.

[0043] The softening point of the rosin (PB) is preferably 96° C. or lower, and more preferably 93° C. or lower. When the softening point of the rosin (PB) is equal to or lower than the upper limit, the fluidity of the flux is more easily increased, which makes it easier to suppress soldering defects.

[0044] The softening point of the rosin (PB) is preferably 60°C or higher, more preferably 65°C or higher, and even more preferably 70°C or higher.

[0045] The softening point of the rosin (PB) may be 60°C or higher and 100°C or lower, preferably 60°C or higher and 96°C or lower, more preferably 65°C or higher and 96°C or lower, and even more preferably 70°C or higher and 96°C or lower. Alternatively, the softening point of the rosin (PB) is preferably 60°C or higher and 93°C or lower, more preferably 65°C or higher and 93°C or lower, and even more preferably 70°C or higher and 93°C or lower. When the softening point of the rosin (PB) is within the above range, the fluidity of the flux is more easily increased. This makes it easier to suppress soldering defects.

[0046] The rosin (PA) may be used alone or in combination of two or more. The rosin (PA) preferably contains at least one rosin (P1) selected from the group consisting of acid-modified hydrogenated rosin and polymerized rosin, and may consist solely of the rosin (P1).

[0047] The rosin (PB) may be used alone or in combination of two or more. Examples of the rosin (PB) include hydrogenated rosin and rosin ester. From the viewpoint of improving the fluidity of the flux, the rosin (PB) preferably contains hydrogenated rosin, or may consist solely of hydrogenated rosin. From the viewpoint of improving the heat resistance of the flux, the rosin (PB) preferably contains rosin ester.

[0048] The content of the rosin (P) in the flux is preferably 2% by mass or more and 30% by mass or less, more preferably 4% by mass or more and 20% by mass or less, and even more preferably 6% by mass or more and 15% by mass or less, relative to the total amount (100% by mass) of the flux. When the rosin (P) contains the rosin (PA), the content of the rosin (PA) is preferably 2% by mass or more and 30% by mass or less, more preferably 4% by mass or more and 20% by mass or less, even more preferably 5% by mass or more and 15% by mass or less, particularly preferably 6% by mass or more and 15% by mass or less, and most preferably 8% by mass or more and 15% by mass or less, relative to the total amount (100% by mass) of the flux. When the rosin (P) contains the rosin (PB), the content of the rosin (PB) is preferably more than 0 mass% and not more than 15 mass%, more preferably more than 0 mass% and not more than 10 mass%, even more preferably more than 0 mass% and not more than 6 mass%, particularly preferably more than 0 mass% and not more than 4 mass%, and most preferably more than 0 mass% and not more than 2 mass%, relative to the total amount (100 mass%) of the flux.

[0049] In the solid content of the flux, the content of the rosin (P) is preferably 15% by mass or more and 95% by mass or less, more preferably 30% by mass or more and 90% by mass or less, and even more preferably 45% by mass or more and 90% by mass or less, relative to the total amount (100% by mass) of the solid content. When the rosin (P) contains the rosin (PA), the content of the rosin (PA) in the solid content of the flux is preferably 15% by mass or more and 95% by mass or less, more preferably 20% by mass or more and 90% by mass or less, even more preferably 30% by mass or more and 90% by mass or less, particularly preferably 40% by mass or more and 90% by mass or less, and most preferably 50% by mass or more and 90% by mass or less, relative to the total amount (100% by mass) of the solid content. When the rosin (P) contains the rosin (PB), the content of the rosin (PB) in the solid content of the flux is preferably more than 0 mass% and not more than 50 mass%, more preferably more than 0 mass% and not more than 40 mass%, even more preferably more than 0 mass% and not more than 30 mass%, particularly preferably more than 0 mass% and not more than 20 mass%, and most preferably more than 0 mass% and not more than 10 mass%, relative to the total amount (100 mass%) of the solid content.

[0050] When the rosin (P) contains the rosin (PA) and the rosin (PB), the mixing ratio of the rosin (PA) to the rosin (PB) is preferably 4 / 6 to 9 / 1, more preferably 5 / 5 to 9 / 1, and even more preferably 6 / 4 to 9 / 1, as a mass ratio expressed as (PA) / (PB). When the mass ratio is within the above-mentioned preferred range, the stickiness of the flux residue can be more easily reduced.

[0051] <Compound (SA)> The flux of the present embodiment contains a compound (SA) represented by the following general formula (sa).

[0052] [In formula (sa), R １１ represents a hydrocarbon group which may have a hydroxy group. １２ and R １３each independently represents a hydrocarbon group having 5 or less carbon atoms which may have a substituent, a hydroxy group, or a hydrogen atom; and m represents a positive integer.

[0053] R １１ The hydrocarbon group in may be an aliphatic hydrocarbon group or an aromatic hydrocarbon group. The aliphatic hydrocarbon group may be saturated or unsaturated, and is usually preferably saturated. More specific examples of the aliphatic hydrocarbon group include linear or branched aliphatic hydrocarbon groups, and aliphatic hydrocarbon groups containing a ring in the structure. The linear or branched aliphatic hydrocarbon group preferably has 1 to 10 carbon atoms, more preferably 1 to 6 carbon atoms, even more preferably 1 to 4 carbon atoms, and most preferably 1 to 3 carbon atoms.

[0054] R １１ The linear aliphatic hydrocarbon group in is preferably a linear alkylene group, specifically a methylene group [—CH ２ -], ethylene group [-(CH ２ ) ２ -], trimethylene group [-(CH ２ ) ３ -], tetramethylene group [-(CH ２ ) ４ -], pentamethylene group [-(CH ２ ) ５ -], and an ethylene group [-(CH ２ ) ２ -] is preferred. １１ The branched aliphatic hydrocarbon group in is preferably a branched alkylene group, specifically, —CH(CH ３ ) -, -CH ２ -CH(CH ３ ) -, -CH(CH ２ CH ３ ) -, -C(CH ３ ) ２ -, -C(CH ３ ) (CH ２ CH ３ ) -, -C(CH ３ ) (CH ２ CH ２ CH ３ ) -, -C(CH ２ CH３ ) ２ alkylmethylene groups such as -; -CH(CH ３ ) CH ２ -, -CH(CH ３ ) CH(CH ３ ) -, -C(CH ３ ) ２ CH ２ -, -CH(CH ２ CH ３ ) CH ２ -, -C(CH ２ CH ３ ) ２ -CH ２ alkylethylene groups such as -; -CH(CH ３ ) CH ２ CH ２ -, -CH ２ CH (CH ３ ) CH ２ alkyltrimethylene groups such as -; -CH(CH ３ ) CH ２ CH ２ CH ２ -, -CH ２ CH (CH ３ ) CH ２ CH ２ and alkyl alkylene groups such as alkyl tetramethylene groups, such as —CH ２ -CH(CH ３ )- is preferred. The alkyl group in the alkylalkylene group is preferably a straight-chain alkyl group having 1 to 5 carbon atoms. Examples of the aliphatic hydrocarbon group containing a ring in the structure include alicyclic hydrocarbon groups (groups in which two hydrogen atoms have been removed from an aliphatic hydrocarbon ring), groups in which an alicyclic hydrocarbon group is bonded to the end of a straight-chain or branched-chain aliphatic hydrocarbon group, and groups in which an alicyclic hydrocarbon group is interposed in the middle of a straight-chain or branched-chain aliphatic hydrocarbon group. Examples of the straight-chain or branched-chain aliphatic hydrocarbon group include the same as the straight-chain aliphatic hydrocarbon group or the branched-chain aliphatic hydrocarbon group.

[0055] The alicyclic hydrocarbon group preferably has 3 to 20 carbon atoms, and more preferably 3 to 12 carbon atoms. The alicyclic hydrocarbon group may be polycyclic or monocyclic. The monocyclic alicyclic hydrocarbon group is preferably a group in which two hydrogen atoms have been removed from a monocycloalkane. The monocycloalkane is preferably one having 3 to 6 carbon atoms, and specific examples thereof include cyclopentane and cyclohexane. The polycyclic alicyclic hydrocarbon group is preferably a group in which two hydrogen atoms have been removed from a polycycloalkane, and the polycycloalkane is preferably one having 7 to 12 carbon atoms, and specific examples thereof include adamantane, norbornane, isobornane, tricyclodecane, and tetracyclododecane.

[0056] R １１The aromatic hydrocarbon group as the divalent hydrocarbon group in the formula (I) is a hydrocarbon group having an aromatic ring. The aromatic hydrocarbon group preferably has 3 to 30 carbon atoms, more preferably 5 to 30 carbon atoms, even more preferably 5 to 20 carbon atoms, particularly preferably 6 to 15 carbon atoms, and most preferably 6 to 10 carbon atoms. However, the number of carbon atoms does not include the number of carbon atoms in the substituents. Specific examples of the aromatic ring contained in the aromatic hydrocarbon group include aromatic hydrocarbon rings such as benzene, biphenyl, fluorene, naphthalene, anthracene, and phenanthrene; aromatic heterocycles in which a portion of the carbon atoms constituting the aromatic hydrocarbon ring is substituted with a heteroatom; and fused rings in which an aromatic hydrocarbon ring and an aromatic heterocycle are fused. Examples of heteroatoms in the aromatic heterocycle include an oxygen atom, a sulfur atom, and a nitrogen atom. Specific examples of the aromatic hydrocarbon group include a group in which two hydrogen atoms have been removed from the aromatic hydrocarbon ring (an arylene group); a group in which one hydrogen atom has been removed from the aromatic hydrocarbon ring (an aryl group), in which one hydrogen atom has been substituted with an alkylene group (for example, a group in which one hydrogen atom has been further removed from the aryl group in an arylalkyl group, such as a benzyl group, a phenethyl group, a 1-naphthylmethyl group, a 2-naphthylmethyl group, a 1-naphthylethyl group, or a 2-naphthylethyl group). The number of carbon atoms in the alkylene group (the alkyl chain in the arylalkyl group) is preferably 1 to 4, more preferably 1 or 2, and particularly preferably 1.

[0057] R １１ R may be the above-mentioned hydrocarbon group in which a hydrogen atom is substituted with a hydroxy group. １１ may have a substituent other than a hydroxy group. Examples of the substituent other than a hydroxy group include a carbonyl group, a carboxy group, an amino group, and a halogen atom. Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom. R having a hydroxy group １１ As the group, -CH ２ -CH(OH)-CH ２ - is preferred.

[0058] In compound (SA), a plurality of R １１may be the same as or different from each other.

[0059] In the general formula (sa), R １２ is R １２ is a hydrocarbon group having 5 or less carbon atoms which may have a substituent, R １２ is R １２１ It is preferably O-. １２１ represents a hydrocarbon group having 5 or less carbon atoms which may have a substituent. １２１ The hydrocarbon group in may be an aliphatic hydrocarbon group. The aliphatic hydrocarbon group may be saturated or unsaturated, and is usually preferably saturated. More specifically, the aliphatic hydrocarbon group may be a linear or branched aliphatic hydrocarbon group, or an aliphatic hydrocarbon group containing a ring in its structure. R １２１ The hydrocarbon group in R preferably has 1 to 3 carbon atoms, more preferably 1 to 2 carbon atoms, and most preferably 1 carbon atom. １２ is preferably a hydroxy group.

[0060] In the general formula (sa), R １３ is R １３ is a hydrocarbon group having 5 or less carbon atoms which may have a substituent, R １３ is -C(=O)-R １３１ It is preferable that R １３１ represents a hydrocarbon group having 5 or less carbon atoms which may have a substituent. １３１ The hydrocarbon group in R １２１ The hydrocarbon groups in R １３１ The hydrocarbon group in R preferably has 1 to 3 carbon atoms, more preferably 1 to 2 carbon atoms, and most preferably 1 carbon atom. １３ is preferably a hydrogen atom.

[0061] In the above general formula (sa), m is not particularly limited as long as the effects of the present invention are exhibited, but may be 1 to 300, preferably 1 to 200, more preferably 2 to 100, even more preferably 2 to 70, particularly preferably 2 to 40, and most preferably 2 to 20.

[0062] In the above general formula (sa), R １１ When m is an ethylene group, m is not particularly limited as long as the effects of the present invention are achieved, but is preferably 2 to 100, more preferably 2 to 70, still more preferably 2 to 40, and particularly preferably 2 to 20.

[0063] In the above general formula (sa), R １１ Ga-CH ２ -CH(CH ３ )-, m is not particularly limited as long as the effects of the present invention are exhibited, but is preferably 2 to 100, more preferably 2 to 70, even more preferably 2 to 40, and particularly preferably 2 to 20.

[0064] In the above general formula (sa), R １１ Ga-CH ２ -CH(OH)-CH ２ When m is -, it is not particularly limited as long as the effects of the present invention are exhibited, but is preferably 1 to 15, more preferably 1 to 7, and even more preferably 1 to 3.

[0065] The flux according to the present embodiment may contain a single compound (SA) or may contain two or more compounds (SA) having different m. When the flux according to the present embodiment contains two or more compounds (SA), the average molecular weight of the compounds (SA) may be as follows:

[0066] As used herein, the term "average molecular weight" refers to a weight-average molecular weight obtained by gel permeation chromatography (GPC). The term "average molecular weight" as used herein refers to a PEG-equivalent molecular weight. The average molecular weight measured by this method is a weight-average molecular weight calculated based on all compounds (SA) contained in the flux.

[0067] The average molecular weight of the compound (SA) is preferably from 100 to 4,000, more preferably from 100 to 3,600, even more preferably from 100 to 1,600, and particularly preferably from 100 to 800.

[0068] R １１ is an ethylene group, R １１The average molecular weight of the compound (SA) in which is an ethylene group is preferably 100 to 4000, more preferably 100 to 2000, still more preferably 100 to 1000, and particularly preferably 100 to 800. When the average molecular weight is within the above range, adhesion of dross to the surface of the substrate can be more easily suppressed, and the stickiness of the flux residue can be more easily reduced.

[0069] R １１ Ga-CH ２ -CH(CH ３ )-, then R １１ Ga-CH ２ -CH(CH ３ The average molecular weight of the compound (SA) in the formula (I)- is preferably from 100 to 4,000, more preferably from 300 to 4,000.

[0070] R １１ Ga-CH ２ -CH(OH)-CH ２ -, then R １１ Ga-CH ２ -CH(OH)-CH ２ The average molecular weight of the compound (SA) is preferably 100 to 1,000, more preferably 200 to 600, and even more preferably 200 to 350.

[0071] Examples of the compound (SA) include polyethylene glycol, polypropylene glycol, polyglycerin, polyethylene glycol-polypropylene glycol copolymer, ethylene oxide-resorcinol copolymer, etc. The copolymer may be any of an alternating copolymer, a random copolymer, and a block copolymer.

[0072] When compound (SA) is polyethylene glycol, the freezing point of compound (SA) is preferably −100° C. or higher and 60° C. or lower, more preferably −70° C. or higher and 60° C. or lower, even more preferably −70° C. or higher and 48° C. or lower, particularly preferably −70° C. or higher and 30° C. or lower, and most preferably −70° C. or higher and 25° C. or lower.

[0073] The compound (SA) may be used singly or in a mixture of two or more. The compound (SA) preferably contains one or more selected from the group consisting of polyethylene glycol, polypropylene glycol, and polyglycerin, and more preferably contains one or more selected from the group consisting of polyethylene glycol and polypropylene glycol. When the compound (SA) contains one or more selected from the group consisting of polyethylene glycol and polypropylene glycol, adhesion of dross to the surface of the substrate is more easily suppressed and the stickiness of the flux residue is more easily reduced.

[0074] The content of compound (SA) in the flux is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, and even more preferably 1% by mass or more, relative to the total mass (100% by mass) of the flux. The content of compound (SA) in the solid content of the flux is preferably 0.7% by mass or more, more preferably 3.4% by mass or more, and even more preferably 6.7% by mass or more, relative to the total amount (100% by mass) of the solid content. By having the content of compound (SA) equal to or greater than the lower limit, adhesion of dross to the surface of a substrate during soldering can be more easily suppressed.

[0075] The content of compound (SA) in the flux is preferably 6% by mass or less, more preferably 5% by mass or less, even more preferably 4% by mass or less, particularly preferably 3% by mass or less, most preferably 2% by mass or less, and may be 1.5% by mass or less, relative to the total mass (100% by mass) of the flux. The content of compound (SA) in the flux is preferably 30% by mass or less, more preferably 26% by mass or less, even more preferably 22% by mass or less, particularly preferably 17% by mass or less, most preferably 12% by mass or less, and may be 9.7% by mass or less, relative to the total amount (100% by mass) of the solids. By having the content of compound (SA) equal to or less than the upper limit, the stickiness of the flux residue is more easily reduced.

[0076] The content of the compound (SA) in the flux is preferably 0.1% by mass to 6% by mass, more preferably 0.5% by mass to 4% by mass, even more preferably 1% by mass to 3% by mass, particularly preferably 1% by mass to 2% by mass, and most preferably 1% by mass to 1.5% by mass, relative to the total mass (100% by mass) of the flux. The content of the compound (SA) in the flux is preferably 0.7% by mass to 30% by mass, more preferably 3.4% by mass to 22% by mass, even more preferably 6.7% by mass to 22% by mass, particularly preferably 6.7% by mass to 17% by mass, and most preferably 6.7% by mass to 9.7% by mass, relative to the total mass (100% by mass) of the solids. When the content of the compound (SA) is equal to or greater than the lower limit of the above-mentioned preferred range, adhesion of dross to the surface of the substrate can be more easily suppressed, and when the content is equal to or less than the upper limit of the above-mentioned preferred range, stickiness of the flux residue can be more easily reduced.

[0077] The content of the compound (SA) in the flux is preferably 1 part by mass or more, more preferably 5 parts by mass or more, and even more preferably 10 parts by mass or more, per 100 parts by mass of the rosin (P). When the content of the compound (SA) is equal to or more than the lower limit, adhesion of dross to the surface of the board during soldering can be more easily suppressed.

[0078] The content of the compound (SA) in the flux is preferably 60 parts by mass or less, more preferably 50 parts by mass or less, even more preferably 40 parts by mass or less, particularly preferably 30 parts by mass or less, most preferably 20 parts by mass or less, and may be 15 parts by mass or less, 10 parts by mass or less, 5 parts by mass or less, or 1 part by mass or less, relative to 100 parts by mass of the rosin (P). When the content of the compound (SA) is equal to or less than the upper limit, the stickiness of the flux residue can be more easily reduced.

[0079] The content of compound (SA) in the flux is preferably 1 to 60 parts by mass, more preferably 5 to 40 parts by mass, even more preferably 10 to 30 parts by mass, particularly preferably 10 to 20 parts by mass, and most preferably 10 to 15 parts by mass, per 100 parts by mass of rosin (P). When the content of compound (SA) is at least the lower limit of the preferred range, adhesion of dross to the surface of the board during soldering is more easily suppressed, and when the content is at most the upper limit of the preferred range, stickiness of the flux residue is more easily reduced.

[0080] <Activator> The flux according to this embodiment contains an activator (excluding those corresponding to the compound (SA)). Examples of the activator include organic acids, amines, and halogen compounds.

[0081] <Organic Acid> Examples of the organic acid include carboxylic acids and organic sulfonic acids. Examples of the carboxylic acid include aliphatic carboxylic acids and aromatic carboxylic acids. Examples of the aliphatic carboxylic acids include aliphatic monocarboxylic acids and aliphatic dicarboxylic acids. Examples of aliphatic monocarboxylic acids include caproic acid, enanthic acid, caprylic acid, pelargonic acid, isopelargonic acid, capric acid, caproleic acid, lauric acid (dodecanoic acid), undecanoic acid, linderic acid, tridecanoic acid, myristoleic acid, pentadecanoic acid, isopalmitic acid, palmitoleic acid, hiragonic acid, hydnocarpic acid, margaric acid, isostearic acid, elaidic acid, petroselinic acid, moroctic acid, eleostearic acid, talic acid, vaccenic acid, riminoleic acid, vernolic acid, sterculic acid, nonadecanoic acid, eicosanoic acid, stearic acid, 12-hydroxystearic acid, oleic acid, linoleic acid, linolenic acid, myristic acid, 2,2-bis(hydroxymethyl)propionic acid, 2,2-bis(hydroxymethyl)butanoic acid, and the like. Examples of aliphatic dicarboxylic acids include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, dodecanedioic acid, eicosanedioic acid, and tartaric acid. Examples of aromatic carboxylic acids include salicylic acid, dibutylaniline diglycolic acid, terephthalic acid, parahydroxyphenylacetic acid, phenylsuccinic acid, phthalic acid, benzoic acid, 2,3-dihydroxybenzoic acid, 2,4-diethylglutaric acid, 2-quinolinecarboxylic acid, 3-hydroxybenzoic acid, and p-anisic acid. Examples of carboxylic acids include tris(2-carboxyethyl) isocyanurate and 1,3-cyclohexanedicarboxylic acid.

[0082] Examples of the carboxylic acid include dimer acid, trimer acid, hydrogenated dimer acid, which is a hydrogenated product of dimer acid with hydrogen added, and hydrogenated trimer acid, which is a hydrogenated product of trimer acid with hydrogen added. Examples of dimer acids and trimer acids include dimer acids which are reaction products of oleic acid and linoleic acid, trimer acids which are reaction products of oleic acid and linoleic acid, dimer acids which are reaction products of acrylic acid, trimer acids which are reaction products of acrylic acid, dimer acids which are reaction products of methacrylic acid, trimer acids which are reaction products of methacrylic acid, dimer acids which are reaction products of acrylic acid and methacrylic acid, trimer acids which are reaction products of acrylic acid and methacrylic acid, dimer acids which are reaction products of oleic acid, trimer acids which are reaction products of oleic acid, dimer acids which are reaction products of linoleic acid, trimer acids which are reaction products of linolenic acid, trimer acids which are reaction products of linolenic acid, dimer acids which are reaction products of acrylic acid and oleic acid, trimer acids which are reaction products of acrylic acid and oleic acid, dimer acids which are reaction products of acrylic acid and linoleic acid, acrylic Examples of the dimer acid include a trimer acid which is a reaction product of acrylic acid and linoleic acid, a dimer acid which is a reaction product of acrylic acid and linoleic acid, a dimer acid which is a reaction product of methacrylic acid and oleic acid, a trimer acid which is a reaction product of methacrylic acid and linoleic acid, a dimer acid which is a reaction product of methacrylic acid and linoleic acid, a dimer acid which is a reaction product of methacrylic acid and linoleic acid, a dimer acid which is a reaction product of methacrylic acid and linoleic acid, a dimer acid which is a reaction product of methacrylic acid and linoleic acid, a dimer acid which is a reaction product of oleic acid and linolenic acid, a dimer acid which is a reaction product of linoleic acid and linolenic acid, a trimer acid which is a reaction product of linoleic acid and linolenic acid, a hydrogenated dimer acid which is a hydrogenated product of each of the above dimer acids, and a hydrogenated trimer acid which is a hydrogenated product of each of the above trimer acids. For example, dimer acid, which is a reaction product of oleic acid and linoleic acid, is a dimer with 36 carbon atoms. Also, trimer acid, which is a reaction product of oleic acid and linoleic acid, is a trimer with 54 carbon atoms.

[0083] Examples of the carboxylic acid include compounds represented by the following general formula (a1).

[0084] [In formula (a1), R １ , R ２ , R ３ and R ４ each independently represents a hydrocarbon group, a hydroxy group, a halogen atom, or a hydrogen atom.

[0085] R １ , R ２ , R ３ and R ４ Examples of the hydrocarbon group in R include a chain hydrocarbon group having 1 to 20 carbon atoms which may have a substituent, an alicyclic hydrocarbon group having 3 to 20 carbon atoms which may have a substituent, an amino group, a hydroxy group, a carboxy group, etc. The chain hydrocarbon group may be linear or branched. The chain hydrocarbon group is a saturated hydrocarbon group or an unsaturated hydrocarbon group, and is preferably a saturated hydrocarbon group. The alicyclic hydrocarbon group may be a polycyclic group or a monocyclic group. A monocyclic alicyclic hydrocarbon group is preferably a group in which one or more hydrogen atoms have been removed from a monocycloalkane. A polycyclic alicyclic hydrocarbon group is preferably a group in which one or more hydrogen atoms have been removed from a polycycloalkane. R １ , R ２ , R ３ and R ４ Examples of the substituent that the hydrocarbon group in the formula (I) may have include an amino group, a hydroxy group, a carboxy group, an acyl group, an alkoxy group, a carbonyl group, and a halogen atom.

[0086] The hydrocarbon group is preferably a chain hydrocarbon group having 1 to 5 carbon atoms, which may have a substituent, or a carboxy group. Examples of the chain hydrocarbon group include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, an n-pentyl group, an isopentyl group, a sec-pentyl group, a tert-pentyl group, and a neopentyl group. The hydrocarbon group is preferably a carboxy group. Examples of the compound represented by general formula (a1) above include picolinic acid, dipicolinic acid, and 3-hydroxypicolinic acid.

[0087] The compound represented by the general formula (a1) is preferably picolinic acid. １ , R ２ , R ３ and R ４ is a hydrogen atom.

[0088] Alternatively, the compound represented by the general formula (a1) may be R １ , R ２ , R ３ , R ４ are each independently preferably a hydroxy group, and more preferably 3-hydroxypicolinic acid. 3-hydroxypicolinic acid is a compound represented by the general formula (a1) above, １ is a hydroxy group, and R ２ , R ３ and R ４ is a hydrogen atom.

[0089] Examples of organic sulfonic acids include aliphatic sulfonic acids, aromatic sulfonic acids, etc. Examples of aliphatic sulfonic acids include alkanesulfonic acids, alkanolsulfonic acids, etc.

[0090] Examples of alkane sulfonic acids include methanesulfonic acid, ethanesulfonic acid, 1-propanesulfonic acid, 2-propanesulfonic acid, 1-butanesulfonic acid, 2-butanesulfonic acid, pentanesulfonic acid, hexanesulfonic acid, decanesulfonic acid, dodecanesulfonic acid, etc. Examples of alkanol sulfonic acids include 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. Examples of aromatic sulfonic acids include 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.

[0091] The organic acid may be used alone or in combination of two or more. The organic acid preferably includes one or more selected from the group consisting of aliphatic carboxylic acids and compounds represented by the general formula (a1). The aliphatic carboxylic acid preferably includes one or more selected from the group consisting of aliphatic monocarboxylic acids and aliphatic dicarboxylic acids. The compound represented by the general formula (a1) is preferably one or more selected from the group consisting of picolinic acid and dipicolinic acid, and more preferably picolinic acid.

[0092] The total content of the organic acids in the flux is preferably 1% by mass or more and 10% by mass or less, more preferably 2% by mass or more and 8% by mass or less, and even more preferably 3% by mass or more and 6% by mass or less, relative to the total mass (100% by mass) of the flux.

[0093] In the solid content of the flux, the content of the organic acid is preferably 5% by mass or more and 50% by mass or less, more preferably 10% by mass or more and 40% by mass or less, and even more preferably 15% by mass or more and 35% by mass or less, relative to the total amount (100% by mass) of the solid content.

[0094] The content of the compound represented by the general formula (a1) in the flux is preferably 0.05 mass % or more and 1 mass % or less, more preferably 0.1 mass % or more and 0.5 mass % or less, and even more preferably 0.1 mass % or more and 0.3 mass % or less, relative to the total mass (100 mass %) of the flux.

[0095] In the solid content of the flux, the content of the compound represented by general formula (a1) is preferably 0.3 mass % or more and 7 mass % or less, more preferably 0.5 mass % or more and 3 mass % or less, and even more preferably 0.5 mass % or more and 2 mass % or less, relative to the total amount (100 mass %) of the solid content.

[0096] <Amine> Examples of the amine include rosin amine, azoles, guanidines, alkylamine compounds, amino alcohol compounds, etc. Examples of the rosin amine include those exemplified in <Rosin>.

[0097] Examples of azoles include 2-methylimidazole, 2-ethylimidazole, 2-undecylimidazole, 2-heptadecylimidazole, 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, and 1-cyanoethyl-2-ethylimidazole. ethyl-4-methylimidazole, 1-cyanoethyl-2-phenylimidazole, 1-cyanoethyl-2-undecylimidazolium trimellitate, 1-cyanoethyl-2-phenylimidazolium trimellitate, 2,4-diamino-6-[2'-methylimidazolyl-(1')]-ethyl-s-triazine, 2,4-diamino-6-[2'-undecylimidazolyl-(1')]-ethyl-s-triazine, 2,4-diamino-6-[2'-ethyl-4'-methylimidazolyl-(1')]-ethyl- s-Triazine, 2,4-diamino-6-[2'-methylimidazolyl-(1')]-ethyl-s-triazine isocyanuric acid adduct, 2-phenylimidazole isocyanuric acid adduct, 2-phenyl-4,5-dihydroxymethylimidazole, 2-phenyl-4-methyl-5-hydroxymethylimidazole, 2,3-dihydro-1H-pyrrolo[1,2-a]benzimidazole, 1-dodecyl-2-methyl-3-benzylimidazolium chloride, 2-methylimidazoline, 2-phenylimidazo Phosphorus, 2,4-diamino-6-vinyl-s-triazine, 2,4-diamino-6-vinyl-s-triazine isocyanuric acid adduct, 2,4-diamino-6-methacryloyloxyethyl-s-triazine, epoxy-imidazole 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-amylphenyl)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-benzotriazolyl 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]bisethanol, 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, and the like.

[0098] Examples of guanidines include 1,3-diphenylguanidine, 1,3-di-o-tolylguanidine, 1-o-tolylbiguanide, 1,3-di-o-cumenylguanidine, and 1,3-di-o-cumenyl-2-propionylguanidine.

[0099] Examples of alkylamine compounds include ethylamine, triethylamine, ethylenediamine, triethylenetetramine, cyclohexylamine, hexadecylamine, and stearylamine.

[0100] Examples of the amino alcohol compound include alkanolamines such as 1-amino-2-propanol and N,N,N',N'-tetrakis(2-hydroxypropyl)ethylenediamine.

[0101] The amine may be used alone or in combination of two or more. The amine is preferably an aminoalcohol compound, more preferably an alkanolamine, and further preferably 1-amino-2-propanol.

[0102] The amine content in the flux is preferably 0.05% by mass or more and 2% by mass or less with respect to the total amount (100% by mass) of the flux. The amine content in the solid content of the flux is preferably 0.5% by mass or more and 10% by mass or less with respect to the total amount (100% by mass) of the solid content.

[0103] <Halogen Compound> Examples of the halogen compound include amine hydrohalides and organic halogen compounds other than amine hydrohalides.

[0104] Amine hydrohalides are compounds obtained by reacting amines with hydrogen halides. Examples of amines include aliphatic amines, azoles, and guanidines. Examples of hydrogen halides include chlorine, bromine, and iodine hydrides. Examples of aliphatic amines include ethylamine, diethylamine, triethylamine, and ethylenediamine. Examples of guanidines and azoles include those described above in the section "Amines."

[0105] More specifically, examples of amine hydrohalides include cyclohexylamine hydrobromide, hexadecylamine hydrobromide, stearylamine hydrobromide, ethylamine hydrobromide, diphenylguanidine hydrobromide, ethylamine hydrochloride, stearylamine hydrochloride, diethylaniline hydrochloride, diethanolamine hydrochloride, 2-ethylhexylamine hydrobromide, pyridine hydrobromide, isopropylamine hydrobromide, diethylamine hydrobromide, dimethyl ...methylamine hydrobromide, methylamine hydrobromide, methylamine hydrobromide, methyl Benzylamine hydrochloride, rosinamine hydrobromide, 2-ethylhexylamine hydrochloride, isopropylamine hydrochloride, cyclohexylamine hydrochloride, 2-pipecoline hydrobromide, 1,3-diphenylguanidine hydrochloride, dimethylbenzylamine hydrochloride, hydrazine hydrate hydrobromide, dimethylcyclohexylamine hydrochloride, trinonylamine hydrobromide, diethylaniline hydrobromide, 2-diethylaminoethanol hydrobromide, 2-diethylaminoethanol hydrochloride, ammonium chloride, diallylamine hydrochloride, diarylamine hydrochloride Aminomethylamine hydrobromide, diethylamine hydrochloride, triethylamine hydrobromide, triethylamine hydrochloride, hydrazine monohydrochloride, hydrazine dihydrochloride, hydrazine monohydrobromide, hydrazine dihydrobromide, pyridine hydrochloride, aniline hydrobromide, butylamine hydrochloride, hexylamine hydrochloride, n-octylamine hydrochloride, dodecylamine hydrochloride, dimethylcyclohexylamine hydrobromide, ethylenediamine dihydrobromide, rosinamine hydrobromide, 2-phenylimidazole hydrobromide, 4-benzyl Examples of the hydrofluoric acid salt include pyridine hydrobromide, L-glutamic acid hydrochloride, N-methylmorpholine hydrochloride, betaine hydrochloride, 2-pipecoline hydroiodide, cyclohexylamine hydroiodide, 1,3-diphenylguanidine hydrofluoride, diethylamine hydrofluoride, 2-ethylhexylamine hydrofluoride, cyclohexylamine hydrofluoride, ethylamine hydrofluoride, rosinamine hydrofluoride, cyclohexylamine tetrafluoroborate, and dicyclohexylamine tetrafluoroborate.

[0106] Furthermore, examples of halogen compounds include amine and tetrafluoroboric acid (HBF ４ ), and salts obtained by reacting amines with boron trifluoride (BF ３ ) can also be used. Examples of the complex include boron trifluoride piperidine.

[0107] Examples of organic halogen compounds other than amine hydrohalides include halogenated aliphatic compounds. A halogenated aliphatic hydrocarbon group refers to an aliphatic hydrocarbon group in which some or all of the hydrogen atoms constituting the group have been substituted with halogen atoms. Examples of halogenated aliphatic compounds include halogenated aliphatic alcohols and halogenated heterocyclic compounds.

[0108] Examples of halogenated aliphatic alcohols include 1-bromo-2-propanol, 3-bromo-1-propanol, 3-bromo-1,2-propanediol, 1-bromo-2-butanol, 1,3-dibromo-2-propanol, 2,3-dibromo-1-propanol, 1,4-dibromo-2-butanol, and trans-2,3-dibromo-2-butene-1,4-diol.

[0109] Examples of the halogenated heterocyclic compound include compounds represented by the following general formula (1H).

[0110] R ６１ - (R ６２ ) ｎ (1H) [wherein, R ６１ represents an n-valent heterocyclic group. ６２ represents a halogenated aliphatic hydrocarbon group.

[0111] R ６１ In the above, the heterocyclic ring of the n-valent heterocyclic group includes a ring structure in which some of the carbon atoms constituting an aliphatic hydrocarbon or aromatic hydrocarbon ring are substituted with heteroatoms. Examples of heteroatoms in this heterocyclic ring include oxygen atoms, sulfur atoms, and nitrogen atoms. This heterocyclic ring is preferably a 3- to 10-membered ring, and more preferably a 5- to 7-membered ring. Examples of this heterocyclic ring include an isocyanurate ring. R ６２The halogenated aliphatic hydrocarbon group in R preferably has 1 to 10 carbon atoms, more preferably 2 to 6 carbon atoms, and even more preferably 3 to 5 carbon atoms. ６２ is preferably a brominated aliphatic hydrocarbon group or a chlorinated aliphatic hydrocarbon group, more preferably a brominated aliphatic hydrocarbon group, and further preferably a brominated saturated aliphatic hydrocarbon group. Examples of halogenated heterocyclic compounds include tris-(2,3-dibromopropyl)isocyanurate.

[0112] Examples of organic halogen compounds other than amine hydrohalides include iodinated carboxyl compounds such as 2-iodobenzoic acid, 3-iodobenzoic acid, 2-iodopropionic acid, 5-iodosalicylic acid, and 5-iodoanthranilic acid; chlorinated carboxyl compounds such as 2-chlorobenzoic acid and 3-chloropropionic acid; and brominated carboxyl compounds such as 2,3-dibromopropionic acid, 2,3-dibromosuccinic acid, and 2-bromobenzoic acid. One halogen-based activator may be used alone, or two or more may be used in combination.

[0113] <Solvent> The solvent contained in the flux according to this embodiment does not fall under the category of the compound (SA). Examples of the solvent include water, alcohol-based solvents, glycol ether-based solvents, and terpineols. Examples of the alcohol-based solvent include ethanol, 1-propanol, 2-propanol, 1,2-butanediol, isobornylcyclohexanol, 2,4-diethyl-1,5-pentanediol, 2,2-dimethyl-1,3-propanediol, 2,5-dimethyl-2,5-hexanediol, 2,5-dimethyl-3-hexyne-2,5-diol, 2,3-dimethyl-2,3-butanediol, 2-methylpentane-2,4-diol, and 1,1,1-tris(hydroxybenzoates). Examples of glycol ether solvents include diethylene glycol mono-2-ethylhexyl ether, ethylene glycol monophenyl ether, diethylene glycol monohexyl ether (hexyl diglycol), diethylene glycol dibutyl ether, triethylene glycol monobutyl ether, methyl propylene triglyceride, butyl propylene triglyceride, triethylene glycol butyl methyl ether, and tetraethylene glycol dimethyl ether.

[0114] The solvent may be used alone or in combination of two or more. From the viewpoint of increasing volatility during preheating, the solvent preferably includes a solvent having a boiling point of 100°C or less. The boiling point of the solvent having a boiling point of 100°C or less may be 50°C or more, 60°C or more, or 70°C or more. From the viewpoint of solubility of the specific activator, the solvent having a boiling point of 100°C or less is preferably an alcohol-based solvent. The alcohol-based solvent preferably includes one or more selected from the group consisting of ethanol and 2-propanol.

[0115] The content of the solvent in the flux is preferably 60% by mass or more and 95% by mass or less, more preferably 70% by mass or more and 95% by mass or less, and even more preferably 80% by mass or more and 95% by mass or less, relative to the total amount (100% by mass) of the flux.

[0116] <Other Components> The flux in this embodiment may contain other components as needed in addition to the rosin, activator, and solvent. Examples of other components include a thixotropic agent, a resin component other than rosin, a metal deactivator, a surfactant, a silane coupling agent, an antioxidant, and a colorant.

[0117] <<Resin Components Other Than Rosin>> Examples of resin components other than rosin-based resins include terpene resins, modified terpene resins, terpene phenolic resins, modified terpene phenolic resins, styrene resins, modified styrene resins, xylene resins, modified xylene resins, acrylic resins, polyethylene resins, acrylic-polyethylene copolymer resins, and epoxy resins. Examples of modified terpene resins include aromatic modified terpene resins, hydrogenated terpene resins, and hydrogenated aromatic modified terpene resins. Examples of modified terpene phenolic resins include hydrogenated terpene phenolic 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 resol-type xylene resins, polyol-modified xylene resins, and polyoxyethylene-added xylene resins.

[0118] <<Metal Deactivator>> Examples of metal deactivators include hindered phenol compounds, nitrogen compounds, etc. The term "metal deactivator" used herein refers to a compound that has the ability to prevent metals from deteriorating due to contact with certain compounds.

[0119] The hindered phenol compound refers to a phenol compound having a bulky substituent (for example, a branched or cyclic alkyl group such as a t-butyl group) at least on one of the ortho positions of the phenol. The hindered phenol compound is not particularly limited, and examples thereof include bis[3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionic acid][ethylenebis(oxyethylene)], N,N'-hexamethylenebis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propanamide], 1,6-hexanediol bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], 2,2'-methylenebis[6-(1-methylsilyl ... cyclohexyl)-p-cresol], 2,2'-methylenebis(6-tert-butyl-p-cresol), 2,2'-methylenebis(6-tert-butyl-4-ethylphenol), triethylene glycol-bis[3-(3-tert-butyl-5-methyl-4-hydroxyphenyl)propionate], 1,6-hexanediol-bis-[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], 2,4-bis-(n-octylthio)-6-(4-hydroxyphenyl)propionate N,N'-Hexamethylenebis(3,5-di-t-butyl-4-hydroxyphenyl)propionate, ... di-hydrocinnamamide), 3,5-di-tert-butyl-4-hydroxybenzylphosphonate-diethyl ester, 1,3,5-trimethyl-2,4,6-tris(3,5-di-tert-butyl-4-hydroxybenzyl)benzene, N,N'-bis[2-[2-(3,5-di-tert-butyl-4-hydroxyphenyl)ethylcarbonyloxy]ethyl]oxamide, 2,6-di-tert-butyl-4-methylphenol, and compounds represented by the following chemical formula:

[0120] (wherein Z is an optionally substituted alkylene group. R ８１ and R ８２ R is each independently an optionally substituted alkyl group, aralkyl group, aryl group, heteroaryl group, cycloalkyl group, or heterocycloalkyl group. ８３ and R ８４ are each independently an optionally substituted alkyl group.

[0121] Examples of the nitrogen compound in the metal deactivator include hydrazide-based nitrogen compounds, amide-based nitrogen compounds, triazole-based nitrogen compounds, and melamine-based nitrogen compounds.

[0122] The hydrazide nitrogen compound may be any nitrogen compound having a hydrazide skeleton, and examples thereof include dodecanedioic acid bis[N2-(2-hydroxybenzoyl)hydrazide], N,N'-bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl]hydrazine, decanedicarboxylic acid disalicyloylhydrazide, N-salicylidene-N'-salicylhydrazide, m-nitrobenzhydrazide, 3-aminophthalhydrazide, phthalic acid dihydrazide, adipic acid hydrazide, oxalobis(2-hydroxy-5-octylbenzylidenehydrazide), N'-benzoylpyrrolidonecarboxylic acid hydrazide, and N,N'-bis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl)hydrazine.

[0123] The amide nitrogen compound may be any nitrogen compound having an amide skeleton, and examples thereof include N,N'-bis{2-[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyloxyl]ethyl}oxamide.

[0124] The triazole-based nitrogen compound may be any nitrogen compound having a triazole skeleton, and examples thereof include N-(2H-1,2,4-triazol-5-yl)salicylamide, 3-amino-1,2,4-triazole, and 3-(N-salicyloyl)amino-1,2,4-triazole.

[0125] The melamine-based nitrogen compound may be any nitrogen compound having a melamine skeleton, such as melamine and melamine derivatives. More specific examples include trisaminotriazine, alkylated trisaminotriazine, alkoxyalkylated trisaminotriazine, melamine, alkylated melamine, alkoxyalkylated melamine, N2-butylmelamine, N2,N2-diethylmelamine, and N,N,N',N',N'',N''-hexakis(methoxymethyl)melamine. One type of metal deactivator may be used alone, or two or more types may be used in combination.

[0126] <<Surfactants>> Examples of surfactants include nonionic surfactants and cationic surfactants. Examples of nonionic surfactants include aliphatic alcohol polyoxyethylene adducts, aromatic alcohol polyoxyethylene adducts, polyhydric alcohol polyoxyethylene adducts, aliphatic alcohol polyoxypropylene adducts, aromatic alcohol polyoxypropylene adducts, and polyhydric alcohol polyoxypropylene adducts. Examples of cationic surfactants include diamine-terminated polyethylene glycol, diamine-terminated polyethylene glycol-polypropylene glycol copolymers, aliphatic amine polyoxyethylene adducts, aromatic amine polyoxyethylene adducts, polyvalent amine polyoxyethylene adducts, and polyvalent amine polyoxypropylene adducts.

[0127] Examples of surfactants other than those mentioned above include polyoxyalkylene acetylene glycols, polyoxyalkylene glyceryl ethers, polyoxyalkylene alkyl ethers, polyoxyalkylene esters, polyoxyalkylene alkylamines, polyoxyalkylene alkylamides, etc. One type of surfactant may be used alone, or two or more types may be used in combination.

[0128] The solid content of the flux is preferably 20% by mass or less, more preferably 5% by mass or more and 20% by mass or less, and even more preferably 10% by mass or more and 20% by mass or less, relative to the total amount (100% by mass) of the flux. By having the solid content within the above range, the flux can be easily used in flow soldering.

[0129] The flux according to one embodiment described above contains rosin, a compound (SA), an activator, and a solvent, and is suitable for flow soldering. In flow soldering, molten solder is likely to produce oxides (dross). When the molten solder is brought into contact with a substrate, this dross may adhere to the substrate. The flux according to this embodiment can prevent dross from adhering to the surface of the substrate after soldering in flow soldering.

[0130] In particular, when solder containing Sn and Bi is used, Bi is easily oxidized, and therefore dross is likely to form on the surface of the molten solder. The flux according to this embodiment can suppress the adhesion of dross to the surface of the substrate after soldering, even when solder containing Bi is used. In addition, by performing soldering using the flux according to this embodiment, a bonded body with good insulation reliability can be obtained.

[0131] The flux according to the above embodiment contains the compound (SA) and rosin in combination, and thus can suppress adhesion of dross to the surface of the board after soldering and can reduce the stickiness of flux residue.

[0132] (Method for manufacturing a bonded body) A method for manufacturing a bonded body according to the second aspect includes a step of soldering a solder alloy to the surface of a substrate treated with the flux according to the first aspect to obtain a bonded body. One embodiment of the method for manufacturing a bonded body according to the second aspect will be described below. The method for manufacturing a bonded body according to this embodiment is a method that includes, in this order, a component mounting step, a flux application step, a preheating step, and a soldering step.

[0133] In the component mounting process, components are mounted on a substrate, such as a printed wiring board, and components include integrated circuits, transistors, diodes, resistors, and capacitors.

[0134] In the flux application step, the flux of the above embodiment is applied to the soldering surface of the board on which the components are mounted. Examples of flux application devices include spray fluxers and foaming fluxers. Among these, spray fluxers are preferred from the viewpoint of the stability of the amount of application. From the viewpoint of solderability, the amount of application of flux is 30 to 180 mL / m. ２ is preferably 40 to 150 mL / m ２ More preferably, it is 50 to 120 mL / m ２ It is particularly preferred that:

[0135] In the preheating step, the substrate on which the components are mounted is preheated. The temperature to which the substrate is heated in the preheating step is preferably 80 to 130°C, and more preferably 90 to 120°C.

[0136] In the soldering process, the soldering surface of a substrate carrying components is brought into contact with molten solder, which is a melted solder alloy. The method for bringing the molten solder into contact with the surface to be soldered is not particularly limited as long as it allows the molten solder to come into contact with the substrate. Examples of such methods include the jet method and the immersion method. The jet method is a method in which the soldering surface of the substrate carrying components is brought into contact with a jet of molten solder. The immersion method is a method in which the soldering surface of the substrate carrying components is brought into contact with the liquid surface of stationary molten solder.

[0137] The solder alloy may have a known composition. The solder alloy may be a solder containing only Sn, or may be an Sn—Ag, Sn—Cu, Sn—Ag—Cu, Sn—Bi, or Sn—In alloy, or may be an alloy of these with Sb, Bi, In, Cu, Zn, As, Ag, Cd, Fe, Ni, Co, Au, Ge, or P added thereto. The solder alloy may be an Sn—Pb alloy, or an Sn—Pb alloy with Sb, Bi, In, Cu, Zn, As, Ag, Cd, Fe, Ni, Co, Au, Ge, or P added thereto. The solder alloy is preferably a Pb-free solder alloy, and more preferably a Sn and Bi solder alloy.

[0138] The soldering conditions in the soldering step may be appropriately set depending on the melting point of the solder. For example, when a Sn—Ag—Cu solder alloy is used, the molten solder temperature is preferably 230 to 280° C., and more preferably 250 to 270° C. Alternatively, when a Sn—Bi solder alloy (a solder alloy containing Sn and Bi) is used, the molten solder temperature is preferably 170 to 220° C., and more preferably 180 to 200° C.

[0139] According to the manufacturing method of the bonded body of the present embodiment described above, it is possible to suppress the adhesion of dross to the surface of the substrate after soldering. According to the manufacturing method of the bonded body of the present embodiment, it is possible to suppress the adhesion of dross to the surface of the substrate even when a solder alloy containing Sn and Bi is used. Therefore, it is possible to manufacture a bonded body with increased bonding strength. In addition, it is possible to manufacture a bonded body that is less likely to cause short circuits and deterioration of insulation properties.

[0140] The present invention will be described below with reference to examples, but the present invention is not limited to the following examples.

[0141] <Preparation of Flux> (Examples 1 to 27, Comparative Examples 1 to 6) Each flux of the examples and comparative examples was prepared according to the composition shown in Tables 2 to 7. The raw materials used are shown below.

[0142] The types and softening points of the rosins used are as follows: Rosin (P): Acrylic acid modified hydrogenated rosin (softening point 130°C) Polymerized rosin (softening point 139°C) Hydrogenated rosin (softening point 74°C) Rosin ester (softening point 90°C)

[0143] The softening point of the rosin was measured using the ring and ball method described in JIS K 5902. Specifically, the sample to be measured was first melted as quickly as possible at the lowest possible temperature and then carefully filled into a ring placed on a flat metal plate, taking care to avoid the formation of bubbles. After cooling, the raised portion of the ring, including the top edge, was cut off with a slightly heated knife. Next, a holder (ring stand) was placed in a glass container (heating bath) with a diameter of at least 85 mm and a height of at least 127 mm, and a heating medium was poured into it to a depth of at least 90 mm. Next, a steel ball (diameter 9.5 mm, weight 3.5 g) and the ring filled with the sample were immersed in the heating medium without touching each other, and the temperature of the heating medium was maintained at 20°C ± 5°C for 15 minutes. Next, the steel ball was placed in the center of the surface of the sample in the ring and placed in its fixed position on the holder. Next, a thermometer was placed at a distance of 50 mm from the top of the ring to the heating medium surface, with the center of the thermometer's mercury bulb at the same height as the center of the ring, and the container was heated. The flame of the Bunsen burner used for heating was aimed midway between the center and edge of the bottom of the container to ensure uniform heating. The rate of increase in bath temperature after reaching 40°C from the start of heating was set at 5.0 ± 0.5°C per minute. The temperature at which the sample gradually softened, flowed down the ring, and finally touched the bottom plate was read and recorded as the softening point. Rosins with softening points of 80°C or less were measured in a water bath using water as the heating medium. Rosins with softening points above 80°C were measured in a glycerin bath using glycerin as the heating medium. Measurements were performed twice for each rosin. The softening point values ​​given above are the average of the two measurements.

[0144] Compound (SA): Polyethylene glycol (PEG), polypropylene glycol (PPG), and polyglycerin were used. PEG is a compound represented by the general formula (sa): １１ O is -(CH ２ ) ２ In general formula (sa), PPG is１１ O is -CH ２ -CH(CH ３ )-O-. In the general formula (sa), R １１ O is -CH ２ -CH(OH)-CH ２ In PEG, PPG and polyglycerin, R １２ is a hydroxy group, and R １３ is a hydrogen atom.

[0145] Specifically, the following were used: PEG: PEG200 (manufactured by Sanyo Chemical Industries, Ltd.), PEG400 (manufactured by Sanyo Chemical Industries, Ltd.), PEG600 (manufactured by Sanyo Chemical Industries, Ltd.), PEG1500 (manufactured by Sanyo Chemical Industries, Ltd.), PEG1540 (manufactured by Sanyo Chemical Industries, Ltd.), PEG4000S (manufactured by Sanyo Chemical Industries, Ltd.); PPG: PPG400 (manufactured by Wako Pure Chemical Industries, Ltd.), PPG1000 (manufactured by Wako Pure Chemical Industries, Ltd.), PPG3000 (manufactured by Wako Pure Chemical Industries, Ltd.); and polyglycerin: a mixture of 3- to 6-mers.

[0146] Comparative compounds: polyoxyethylene behenyl ether, polyethylene glycol stearate, diglycerin monoester, sorbitan monolaurate, sorbitan monostearate The chemical formulas of each comparative compound are as follows, and do not fall under general formula (sa).

[0147] Polyoxyethylene behenyl ether is a compound represented by the following formula (1).

[0148] [In formula (1), n1 is 25 to 35.]

[0149] Polyethylene glycol stearate is a compound represented by the following formula (2).

[0150] [In formula (2), n2 is 100 to 150.

[0151] Diglycerin monoester is a compound represented by the following formula (3).

[0152]

[0153] Sorbitan monolaurate is a compound represented by the following formula (4).

[0154]

[0155] Sorbitan monostearate is a compound represented by the following formula (5).

[0156]

[0157] Activators: picolinic acid, 1-amino-2-propanol, adipic acid

[0158] Solvent: 2-propanol, ethanol

[0159] The average molecular weights of the above Compound (SA) and the comparative compounds were measured by gel permeation chromatography (GPC). The average molecular weights are molecular weights converted into PEG. The instruments and conditions used in the GPC measurements were as follows. The measurement results are shown in Table 1. In Table 1, Mw represents the weight average molecular weight. The freezing point of each PEG is also shown.

[0160] Analytical apparatus: EcoSEC HLC-8320GPC manufactured by Tosoh Mobile phase: tetrahydrofuran Column: TSKguard column HXL manufactured by Tosoh, TSKgel G2000HXL manufactured by Tosoh, TSKgel G1000HXL manufactured by Tosoh Column temperature: 40°C Flow rate: 1.0 (mL / min), reference 1 / 3 Detector: RI, Pol(+), Res(0.5s) Injection volume: 50 μl

[0161]

[0162] <Preparation of Molten Solder> An ingot made of an alloy containing 58 mass % of Bi and the remainder of Sn was prepared as a master alloy, and was melted to prepare a molten solder.

[0163] According to the evaluation methods described in the following <Evaluation>, the <Evaluation of the ability to inhibit dross adhesion> and the <Evaluation of the stickiness of flux residue> were carried out. The results of these evaluations are shown in Tables 2 to 7.

[0164] <Evaluation> <Evaluation of Dross Adhesion Suppression Ability> (1) Evaluation Method 0.15 mL of each flux was applied to a glass substrate (50 mm × 50 mm, 0.7 mm thick). The obtained substrate was heated and dried at 100°C for 5 minutes to obtain a pretreated substrate. Next, the pretreated substrate was immersed in molten solder in a small jet soldering bath in an air atmosphere for 5 seconds. The presence or absence of dross on the substrate was visually confirmed, and evaluation was performed based on the following criteria.

[0165] (2) Evaluation criteria A: No dross was observed. B: A slight amount of dross was observed. C: A small amount of dross was observed. D: A large amount of dross was observed. In the evaluation results, the amount of dross adhering to the substrate increases in the order from A to D. Fluxes with evaluation results A to C were deemed to have passed, and fluxes with evaluation results D were deemed to have failed.

[0166] <Evaluation of Stickiness of Flux Residue> Evaluation Method: 0.15 mL of each flux was applied to a glass epoxy substrate (50 mm × 50 mm, thickness 1 mm), and then heated and dried to obtain a pretreated substrate. For each pretreated substrate, the stickiness of the flux residue was measured according to the following procedure.

[0167] The pretreated substrate was left standing on a pedestal heated to 60°C for 3 minutes, and then the stickiness was measured. The stickiness measurement was carried out using the following equipment under the following conditions. In Tables 2 to 7, the unit of the stickiness measurement is gf. Here, 1 [gf] = 9.8 × 10 －３ [N]. Apparatus: Tackiness tester (Malcom, model number: TK-1) Pressing method: Constant pressure penetration method Pressing time: 0.2 sec Pressing pressure: 50 gf Penetration speed: 2.0 mm / sec Peeling speed: 10 mm / sec

[0168]

[0169]

[0170]

[0171]

[0172]

[0173]

[0174] It was confirmed that the fluxes of Examples 1 to 27 containing rosin, compound (SA), an activator, and a solvent had a higher ability to suppress dross adhesion than the fluxes of Comparative Examples 1 to 6 not containing compound (SA).

[0175] The reason why such an effect is obtained is not clear, but is presumed as follows. １２ and R １３ However, all of these compounds are hydrocarbon groups, hydroxyl groups, or hydrogen atoms having 5 or fewer carbon atoms, and are therefore less hydrophobic and less compatible with rosin. Therefore, the rosin and compound (SA) separate, and a layer of compound (SA) is more likely to form on top of the rosin layer. This makes it easier for the dross present on the surface of the molten solder to flow into the solder bath along with the layer of compound (SA). On the other hand, the comparative compound has an alkyl group having 6 or more carbon atoms, is highly hydrophobic, and is more compatible with rosin. Therefore, the rosin and compound (SA) are more likely to be compatible, and a layer of the comparative compound is less likely to form. This makes it easier for the dross present on the surface of the molten solder to remain attached to the flux applied to the board.

[0176] The results of Examples 1, 2, 4, 5, and 27 show that when rosin (PB) and rosin (PA) are used in combination as the rosin (P), the mixing ratio of rosin (PA) having a softening point of more than 100°C to rosin (PB) having a softening point of 100°C or less is expressed as (PA) / (PB), and the stickiness of the flux residue is further reduced when (PA) / (PB) is 4 / 6 or more, the stickiness of the flux residue is further reduced when (PA) / (PB) is 5 / 5 or more, and the stickiness of the flux residue is particularly reduced when (PA) / (PB) is 8 / 2 or more.

[0177] According to the present invention, it is possible to provide a flux and a method for manufacturing a bonded body that can suppress adhesion of dross to the surface of a substrate during soldering. This flux is suitable for flow soldering. It is also suitable for flow soldering using lead-free solder.

Claims

1. A flux containing: rosin (P); a compound (SA) represented by the following general formula (sa); an activator (excluding those corresponding to the compound (SA)); and a solvent (excluding those corresponding to the compound (SA)). [wherein R １１ represents a hydrocarbon group which may have a hydroxy group. １２ and R １３ each independently represents a hydrocarbon group having 5 or less carbon atoms which may have a substituent, a hydroxy group, or a hydrogen atom; and m represents a positive integer.

2. The flux according to claim 1, wherein the rosin (P) includes a rosin (PA) having a softening point of more than 100°C and a rosin (PB) having a softening point of 100°C or less.

3. The flux according to claim 2, wherein the mixing ratio of the rosin (PA) to the rosin (PB), expressed as a mass ratio of (PA) / (PB), is (PA) / (PB) = 5 / 5 to 9 / 1.

4. The flux according to claim 2 or 3, wherein the rosin (PA) contains at least one type of rosin (P1) selected from the group consisting of acrylic acid-modified hydrogenated rosin and polymerized rosin, and the rosin (PB) contains hydrogenated rosin.

5. The flux according to any one of claims 1 to 4, wherein the content of the compound (SA) is 1 to 60 parts by mass per 100 parts by mass of the rosin (P).

6. The flux according to any one of claims 1 to 5, wherein the activator contains a compound represented by the following general formula (a1): [In formula (a1), R １ , R ２ , R ３ and R ４ each independently represents a hydrocarbon group, a hydroxy group, a halogen atom, or a hydrogen atom.

7. The flux according to any one of claims 1 to 6, wherein the activator comprises an alkanolamine.

8. The flux according to any one of claims 1 to 7, wherein the solvent includes at least one selected from the group consisting of ethanol and 2-propanol.

9. A flux according to any one of claims 1 to 8, wherein the solid content is 20 mass% or less.

10. A method for producing a bonded body, comprising the step of soldering a solder alloy to the surface of a substrate that has been treated with the flux according to any one of claims 1 to 9 to obtain a bonded body.

11. The method for manufacturing a joint body according to claim 10, wherein the solder alloy comprises a solder alloy containing Sn and Bi.