Patent Description:
A flux used for soldering has an effect of chemically removing metal oxides present on a solder, and a metal surface of an object to be joined, which is a soldering target, thereby enabling the movement of metal elements at a boundary between two objects to be joined. Therefore, by performing soldering using the flux, an intermetallic compound is formed between the solder, and thereby, strong joining can be obtained. Such a flux generally contains a resin component, a solvent, an activator, a thixotropic agent, and the like.

A solder paste is a composite material obtained by mixing solder alloy powder and a flux. In soldering using the solder paste, first, the solder paste is printed on a substrate, and components are mounted on the substrate. Subsequently, the substrate on which the components are mounted is heated in a heating furnace referred to as a reflow furnace.

In the reflow furnace, preheating is performed, and then main heating for melting the solder alloy powder is performed. There is a case where the solder paste printed on the substrate softens during preheating and causes heating sagging. Heating sagging causes mounting defects such as solder balls and solder bridges.

In contrast, for example, a flux containing a hydride of an alcohol-modified dicyclopentadiene-based resin has been proposed in order to suppress heating sagging at a preheating temperature of <NUM> to <NUM> (refer to Patent Document <NUM>).

In soldering, in a case where the substrate has a large area, it is required to further increase the preheating temperature in order to suppress temperature variations in the substrate. However, in a case where the preheating temperature is set to <NUM> to <NUM>, for example, in the flux disclosed in Patent Document <NUM>, it is not possible to sufficiently suppress heating sagging. <CIT> relates to a thixotropic agent which contains a heat sagging inhibitor that has been made evenly and rapidly dispersible and as a result of this configuration, which, when added to a flux or solder paste, causes no thermal damage to the flux resin or the heat sagging inhibitor and which prevents the flux or solder paste from thermally sagging; and a flux and a solder paste each containing the thixotropic agent. <CIT> relates to a flow control agent for a non-aqueous coating material containing aliphatic polyamide wax, which is obtained by reacting an aliphatic primary diamine having <NUM> to <NUM> carbon atoms, <NUM>-hydroxystearic acid, and an aliphatic dicarboxylic acid having <NUM> to <NUM> carbon atoms. <CIT> relates to a solder composition for laser soldering containing (A) a rosin-based resin, (B) an activator, (C) a solvent and (D) a thixotropic agent, and (E) solder powder, the (A) component containing (A1) a polymerization rosin with a softening point of <NUM> or higher, and an acid value of <NUM> mgKOH/g or less.

Therefore, an object of the present invention is to provide a flux and a solder paste which are capable of sufficiently suppressing heating sagging during reflow.

In order to achieve the above-mentioned object, the present invention adopts the following constitution.

That is, a first aspect of the present invention is a flux containing: a rosin, a solvent, a thixotropic agent, and an activator, in which the thixotropic agent includes a polyamide (PA2), the PA2 is a condensate of an aliphatic carboxylic acid, a hydroxy group-containing aliphatic carboxylic acid, and an aliphatic amine having <NUM> to <NUM> carbon atoms, the aliphatic carboxylic acid includes an aliphatic dicarboxylic acid having <NUM> to <NUM> carbon atoms, the amount of the PA2 is <NUM>% by mass or more and <NUM>% by mass or less with respect to a total mass of the flux, and regarding an endothermic amount calculated from a peak area of a differential scanning calorific curve obtained by differential scanning calorimetry, in the PA2, a ratio of an endothermic amount in a range of <NUM> or higher and <NUM> or lower is <NUM>% or more with respect to a total endothermic amount in a range of <NUM> or higher and <NUM> or lower.

In the flux according to the first aspect, regarding the endothermic amount calculated from the peak area of the differential scanning calorific curve obtained by the differential scanning calorimetry, in the PA2, a ratio of an endothermic amount in a range of <NUM> or higher and <NUM> or lower is preferably <NUM>% or more with respect to the total endothermic amount in the range of <NUM> or higher and <NUM> or lower.

In addition, in the flux according to the first aspect, regarding the endothermic amount calculated from the peak area of the differential scanning calorific curve obtained by the differential scanning calorimetry, in the PA2, a ratio of an endothermic amount in a range of <NUM> or higher and <NUM> or lower is preferably <NUM>% or more with respect to the total endothermic amount in the range of <NUM> or higher and <NUM> or lower.

In addition, in the flux according to the first aspect, the amount of the rosin is preferably <NUM>% by mass or more and <NUM>% by mass or less with respect to a total mass of the flux.

In addition, a second aspect of the present invention is a solder paste containing solder alloy powder and the flux according to the first aspect.

According to the present invention, it is possible to provide a flux and a solder paste that are capable of sufficiently suppressing heating sagging during reflow.

A flux of the present embodiment contains rosin, a solvent, a thixotropic agent, and an activator. The embodiments of paragraphs [<NUM>] to [<NUM>] are not part of the present invention.

As the rosin, raw material rosin such as gum rosin, wood rosin, and tall oil rosin, and derivatives obtained from the raw material rosin are exemplary examples.

As the derivatives, purified rosin, hydrogenated rosin, disproportionated rosin, polymerized rosin, acid-modified rosin, acid-modified hydrogenated rosin, phenol-modified rosin, and α,β-unsaturated carboxylic acid-modified products (acrylated rosin, maleated rosin, fumarated rosin, and the like), and purified products, hydrides, and disproportionated products of the polymerized rosin, purified products, hydrides, and disproportionated products of the α,β-unsaturated carboxylic acid-modified products, and the like are exemplary examples.

For the rosin, one type may be used alone, or two or more types may be mixed together and used.

As the rosin, among these, it is preferable to use one or more selected from the group consisting of polymerized rosin, acid-modified hydrogenated rosin, and hydrogenated rosin.

As the acid-modified hydrogenated rosin, it is preferable to use acrylic acid-modified hydrogenated rosin.

The amount of the rosin in the flux is preferably <NUM>% by mass or more and <NUM>% by mass or less, more preferably <NUM>% by mass or more and <NUM>% by mass or less, and further more preferably <NUM>% by mass or more and <NUM>% by mass or less with respect to the total amount (<NUM>% by mass) of the flux.

In the flux of the present embodiment, as the solvent, water, alcohol solvent, glycol ether solvent, terpineol, and the like are exemplary examples.

As the alcohol solvent, isopropyl alcohol, <NUM>,<NUM>-butanediol, isobornyl cyclohexanol, <NUM>,<NUM>-diethyl-<NUM>,<NUM>-pentanediol, <NUM>,<NUM>-dimethyl-<NUM>,<NUM>-propanediol, <NUM>,<NUM>-dimethyl-<NUM>,<NUM>-hexanediol, <NUM>,<NUM>-dimethyl-<NUM>-hexyne-<NUM>,<NUM>-diol, <NUM>,<NUM>-dimethyl-<NUM>,<NUM>-butanediol, <NUM>-methylpentane-<NUM>,<NUM>-diol, <NUM>,<NUM>,<NUM>-tris(hydroxymethyl)propane, <NUM>-ethyl-<NUM>-hydroxymethyl-<NUM>,<NUM>-propanediol, <NUM>,<NUM>'-oxybis(methylene)bis(<NUM>-ethyl-<NUM>,<NUM>-propanediol), <NUM>,<NUM>-bis(hydroxymethyl)-<NUM>,<NUM>-propanediol, <NUM>,<NUM>,<NUM>-trihydroxyhexane, <NUM>-ethynyl-<NUM>-cyclohexanol, <NUM>,<NUM>-cyclohexanediol, <NUM>,<NUM>-cyclohexanedimethanol, <NUM>,<NUM>,<NUM>,<NUM>-tetramethyl-<NUM>-decyne-<NUM>,<NUM>-diol, and the like are exemplary examples.

As the glycol ether solvent, diethylene glycol mono-<NUM>-ethylhexyl ether, ethylene glycol monophenyl ether, diethylene glycol monohexyl ether, diethylene glycol dibutyl ether, triethylene glycol monobutyl ether, methyl propylene triglycol, butyl propylene triglycol, triethylene glycol butylmethyl ether, tetraethylene glycol dimethyl ether, and the like are exemplary examples.

As the solvent, it is preferable to use a glycol ether solvent, and more preferable to use diethylene glycol monohexyl ether.

For the solvent, one type may be used alone, or two or more types may be mixed together and used.

The amount of the solvent in the flux is preferably <NUM>% by mass or more and <NUM>% by mass or less, and more preferably <NUM>% by mass or more and <NUM>% by mass or less with respect to the total amount (<NUM>% by mass) of the flux.

In the flux of the present embodiment, the thixotropic agent contains a compound represented by General Formula (<NUM>) and a specific polyamide (PA1).

In the flux of the present embodiment, a compound represented by General Formula (<NUM>) is used.

[In the formula, R<NUM> represents a hydrocarbon group having <NUM> to <NUM> carbon atoms which may have a substituent. R0a represents a hydrocarbon group having <NUM> to <NUM> carbon atoms which may have a substituent or a hydrogen atom. R0b represents an n-valent hydrocarbon group having <NUM> to <NUM> carbon atoms which may have a substituent. R<NUM> represents an alkylene group having <NUM> to <NUM> carbon atoms. R0c represents an alkylene group having <NUM> to <NUM> carbon atoms or a single bond. n is <NUM> or <NUM>; When n is <NUM>, m is an integer of <NUM> to <NUM>. When n is <NUM>, m is <NUM>.

R0b is an n-valent hydrocarbon group having <NUM> to <NUM> carbon atoms, and this n-valent hydrocarbon group may have a substituent.

In General Formula (<NUM>), in a case where n is <NUM>, all of a plurality of R<NUM>, a plurality of R<NUM>, a plurality of R0a, and a plurality of R0c may be different or the same.

The compound represented by General Formula (<NUM>) may be a compound represented by General Formula (<NUM>) or General Formula (<NUM>).

In the compound represented by General Formula (<NUM>), in General Formula (<NUM>), n is <NUM>, R0a is -NH-C(=O)-R<NUM>, R0b is R0b1, and R0c is R<NUM>.

[In the formula, R<NUM> and R<NUM> each independently represent a hydrocarbon group having <NUM> to <NUM> carbon atoms which may have a substituent. R0b1 represents a hydrocarbon group having <NUM> to <NUM> carbon atoms which may have a substituent. R<NUM> and R<NUM> each independently represent an alkylene group having <NUM> to <NUM> carbon atoms. m represents an integer in a range of <NUM> to <NUM>.

In General Formula (<NUM>), R<NUM>, R<NUM>, and R0b1 may each be a saturated hydrocarbon group or an unsaturated hydrocarbon group. Each of R<NUM>, R<NUM>, and R0b1 is preferably a saturated hydrocarbon group.

R<NUM> and R<NUM> are each preferably a hydrocarbon group having <NUM> to <NUM> carbon atoms which may have a substituent, and more preferably a hydrocarbon group having <NUM> to <NUM> carbon atoms which may have a substituent.

In a case where R<NUM> or R<NUM> has a substituent, as the substituent, -CONH<NUM>, amino group (-NH<NUM>), carboxyl group, and the like are exemplary examples.

R0b1 is preferably a hydrocarbon group having <NUM> to <NUM> carbon atoms which may have a substituent, and more preferably a hydrocarbon group having <NUM> to <NUM> carbon atoms which may have a substituent.

In a case where R0b1 has a substituent, as the substituent, -CONH<NUM>, amino group (-NH<NUM>), carboxyl group, and the like are exemplary examples. The substituent that R0b1 may have is preferably -CONH<NUM>.

Each of R<NUM> and R<NUM> is preferably an alkylene group having <NUM> carbon atoms.

For the compound represented by General Formula (<NUM>), one type may be used alone, or two or more types may be mixed together and used.

The compound represented by General Formula (<NUM>) is preferably N,N-bis(<NUM>-stearamidoethyl)-azelicamide or N,N-bis(<NUM>-stearamidoethyl)-sebacamide.

In N,N-bis(<NUM>-stearamidoethyl)-azelicamide, in General Formula (<NUM>), R<NUM> and R<NUM> are each a linear alkyl group having <NUM> carbon atoms, R0b1 is -(CH<NUM>)<NUM>-CONH<NUM>, R<NUM> and R<NUM> are alkylene groups having <NUM> carbon atoms, and m is <NUM>.

In N,N-bis(<NUM>-stearamidoethyl)-sebacamide, in General Formula (<NUM>), R<NUM> and R<NUM> are each a linear alkyl group having <NUM> carbon atoms, R0b1 is -(CH<NUM>)<NUM>-CONH<NUM>, R<NUM> and R<NUM> are alkylene groups having <NUM> carbon atoms, and m is <NUM>.

In the compound represented by General Formula (<NUM>), in General Formula (<NUM>), n is <NUM>, m is <NUM>, and R0b is R0b2.

[In the formula, R<NUM> and R<NUM>' each independently represent a hydrocarbon group having <NUM> to <NUM> carbon atoms which may have a substituent. R0a and R0a' each independently represent a hydrocarbon group having <NUM> to <NUM> carbon atoms which may have a substituent or a hydrogen atom. R0b2 represents a hydrocarbon group having <NUM> to <NUM> carbon atoms which may have a substituent. R<NUM> and R<NUM>' each independently represent an alkylene group having <NUM> to <NUM> carbon atoms. R0c and R0c' each independently represent an alkylene group having <NUM> to <NUM> carbon atoms or a single bond.

In General Formula (<NUM>), R<NUM> and R<NUM>' may be each a saturated hydrocarbon group or an unsaturated hydrocarbon group. Each of R<NUM> and R<NUM>' is preferably a saturated hydrocarbon group.

Each of R<NUM> and R<NUM>' is preferably a hydrocarbon group having <NUM> to <NUM> carbon atoms which may have a substituent, and more preferably a hydrocarbon group having <NUM> to <NUM> carbon atoms which may have a substituent.

In a case where R<NUM> and R<NUM>' have a substituent, as the substituent, -CONH<NUM>, amino group (-NH<NUM>), carboxyl group, and the like are exemplary examples.

R0b2 may be a saturated hydrocarbon group or an unsaturated hydrocarbon group. R0b2 is preferably a saturated hydrocarbon group.

R0b2 is preferably a hydrocarbon group having <NUM> to <NUM> carbon atoms which may have a substituent, and more preferably a hydrocarbon group having <NUM> to <NUM> carbon atoms which may have a substituent.

In a case where R0b2 has a substituent, as the substituent, -CONH<NUM>, amino group (-NH<NUM>), carboxyl group, and the like are exemplary examples.

Each of R<NUM> and R<NUM>' is preferably an alkylene group having <NUM> carbon atoms.

Each of R0a and R0a' may be a saturated hydrocarbon group, and may be an unsaturated hydrocarbon group, or may be a hydrogen atom.

Each of R0a and R0a' is preferably a saturated hydrocarbon group or a hydrogen atom, and more preferably a hydrogen atom.

Each of R0c and R0c' is preferably a single bond.

R0c-R0a and R0c'-R0a' are preferably single bond-hydrogen atoms.

The compound represented by General Formula (<NUM>) is preferably N,N'-bis(<NUM>-stearamidoethyl)-azelicamide or N,N'-bis(<NUM>-stearamidoethyl)-sebacamide.

In N,N'-bis(<NUM>-stearamidoethyl)-azelicamide, in General Formula (<NUM>), R<NUM> and R<NUM>' are linear alkyl groups having <NUM> carbon atoms, R0a and R0a' are hydrogen atoms, R0b2 is -(CH<NUM>)<NUM>-, R0c and R0c' are single bonds, and R<NUM> and R<NUM>' are alkylene groups having <NUM> carbon atoms.

In N,N'-bis(<NUM>-stearamidoethyl)-sebacamide, in General Formula (<NUM>), R<NUM> and R<NUM>' are linear alkyl groups having <NUM> carbon atoms, and R0a and R0a' are hydrogen atoms, R0b2 is -(CH<NUM>)<NUM>-, R0c and R0c' are single bonds, and R<NUM> and R<NUM>' are alkylene groups having <NUM> carbon atoms.

The compound represented by General Formula (<NUM>) is preferably a compound represented by General Formula (<NUM>) or General Formula (<NUM>), and more preferably a compound represented by General Formula (<NUM>).

The amount of the compound represented by General Formula (<NUM>) in the flux is preferably <NUM>% by mass or more and <NUM>% by mass or less with respect to the total amount (<NUM>% by mass) of the flux.

A specific polyamide (PA1) is used in the flux of the present embodiment. The specific polyamide (PA1) is a condensate of one or more selected from the group consisting of an aliphatic carboxylic acid and a hydroxy group-containing aliphatic carboxylic acid, and an amine.

The specific polyamide (PA1) includes a "condensate of aliphatic carboxylic acids and amines", a "condensate of hydroxy group-containing aliphatic carboxylic acids and amines", and a "condensate of hydroxy group-containing aliphatic carboxylic acids, aliphatic carboxylic acids, and amines".

The endothermic peak temperature of the specific polyamide (PA1) by differential scanning calorimetry is <NUM> or higher and <NUM> or lower.

For the aliphatic carboxylic acid from which the specific polyamide (PA1) is derived, one type may be used alone or two or more types may be mixed together and used.

As the aliphatic carboxylic acid, monocarboxylic acid, dicarboxylic acid, tricarboxylic acid, and the like are exemplary examples. The aliphatic carboxylic acid is preferably monocarboxylic acid or dicarboxylic acid, and more preferably dicarboxylic acid.

The hydrocarbon group of the aliphatic carboxylic acid may be linear, branched, or cyclic. The hydrocarbon group is preferably linear or branched, and more preferably linear.

The hydrocarbon group may be a saturated hydrocarbon group or an unsaturated hydrocarbon group. The hydrocarbon group is preferably a saturated hydrocarbon group.

The number of carbon atoms in the aliphatic monocarboxylic acid is preferably <NUM> to <NUM>, more preferably <NUM> to <NUM>, and further more preferably <NUM> to <NUM>.

As the aliphatic monocarboxylic acid, lauric acid, myristic acid, pentadecyl acid, palmitic acid, margaric acid, stearic acid, nonadecanoic acid, arachidic acid, behenic acid, and the like are exemplary examples. The aliphatic monocarboxylic acid is preferably palmitic acid or stearic acid.

The number of carbon atoms in the aliphatic dicarboxylic acid is preferably <NUM> to <NUM>, more preferably <NUM> to <NUM>, and further more preferably <NUM> to <NUM>.

As the aliphatic dicarboxylic acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, tridecanedioic acid, tetradecanedioic acid, pentadecanedioic acid, and the like are exemplary examples. The aliphatic dicarboxylic acid is preferably suberic acid, azelaic acid, sebacic acid, undecanedioic acid, or dodecanedioic acid, and more preferably sebacic acid or dodecanedioic acid.

The aliphatic carboxylic acid may include one or more selected from the group consisting of sebacic acid and dodecanedioic acid, and one or more selected from the group consisting of palmitic acid and stearic acid.

For the hydroxy group-containing aliphatic carboxylic acid from which the specific polyamide (PA1) is derived, one type may be used alone or two or more types may be mixed together and used.

The hydrocarbon group of the hydroxy group-containing aliphatic carboxylic acid may be linear, branched, or cyclic. The hydrocarbon group is preferably linear or branched, and more preferably linear.

The number of carbon atoms in the hydroxy group-containing aliphatic carboxylic acid is preferably <NUM> to <NUM>, and more preferably <NUM> to <NUM>.

As the hydroxy group-containing aliphatic carboxylic acid, hydroxypentadecanoic acid, hydroxyhexadecanoic acid, hydroxyheptadecanoic acid, hydroxyoctadecanoic acid (hydroxystearic acid), hydroxyeicosanoic acid, hydroxyheneicosanoic acid, and the like are exemplary examples. The hydroxy group-containing aliphatic carboxylic acid is preferably hydroxystearic acid, and more preferably <NUM>-hydroxystearic acid.

For the amines from which the specific polyamide (PA1) is derived, one type may be used, or two or more types may be mixed together and used.

As the amine, aliphatic amine and aromatic amine are exemplary examples. The amine is preferably an aliphatic amine.

As the amine, monoamine, diamine, triamine, and tetraamine are exemplary examples. The amine is preferably a diamine.

The hydrocarbon group of the aliphatic amine may be linear, branched, or cyclic. The hydrocarbon group is preferably linear or branched, and more preferably linear. The number of carbon atoms in the aliphatic amine is preferably <NUM> to <NUM>, and more preferably <NUM> to <NUM>.

As the amine, ethylenediamine, <NUM>,<NUM>-propanediamine, <NUM>,<NUM>-butanediamine, hexamethylenediamine, methaxylenediamine, tolylenediamine, paraxylenediamine, phenylenediamine, isophoronediamine, <NUM>,<NUM>-decanediamine, <NUM>,<NUM>-dodecanediamine, <NUM>,<NUM>-diaminodicyclohexylmethane, <NUM>,<NUM>-diaminodiphenylmethane, butane-<NUM>,<NUM>,<NUM>,<NUM>-tetraamine, pyrimidine-<NUM>,<NUM>,<NUM>,<NUM>-tetraamine, and the like are exemplary examples. The amine is preferably hexamethylenediamine.

An endothermic peak temperature of polyamide is measured by DSC (Differential Scanning Calorimetry).

As a specific method of measuring an endothermic peak, there is a method of measurement by setting a temperature raising rate to <NUM>/min and raising a temperature of about <NUM> of polyamide from <NUM> to <NUM> in a nitrogen atmosphere. As a measuring apparatus, DSC7020 (manufactured by Hitachi High-Tech Science) can be used. In the present specification, the endothermic peak temperature means a peak top temperature.

The specific polyamide (PA1) used in the flux of the present embodiment has one or two or more endothermic peaks in a temperature range of <NUM> or higher and <NUM> or lower.

In a case where the number of endothermic peaks is one, the temperature of the endothermic peak is preferably <NUM> or higher and <NUM> or lower, more preferably <NUM> or higher and <NUM> or lower, further more preferably <NUM> or higher and <NUM> or lower, and particularly preferably <NUM> or higher and <NUM> or lower.

In a case where the number of endothermic peaks is <NUM> or more, for example, the lowest temperature of the endothermic peaks of the polyamide (PA1) may be in a range of <NUM> or higher and <NUM> or lower, the highest temperature of the endothermic peaks may be in a range of <NUM> or higher and <NUM> or lower, or all the endothermic peaks may be in a range of <NUM> or higher and <NUM> or lower.

The highest temperature of the endothermic peaks is preferably <NUM> or higher and <NUM> or lower, more preferably <NUM> or higher and <NUM> or lower, further more preferably <NUM> or higher and <NUM> or lower, and particularly preferably <NUM> or higher and <NUM> or lower.

In measurement by DSC of polyamide (PA1), the ratio of the endothermic amount in the range of <NUM> or higher and <NUM> or lower is preferably <NUM>% or more, more preferably <NUM>% or more, and further more preferably <NUM>% or more with respect to a total endothermic amount in the range of <NUM> or higher and <NUM> or lower.

An upper limit of the ratio of the endothermic amount is not particularly limited as long as the effect of the invention is exhibited, and may be <NUM>% or less, <NUM>% or less, or <NUM>% or less.

The ratio of the endothermic amount is preferably <NUM>% or more and <NUM>% or less, more preferably <NUM>% or more and <NUM>% or less, and further more preferably <NUM>% or more and <NUM>% or less. Alternatively, the ratio of the endothermic amount is preferably <NUM>% or more and <NUM>% or less, more preferably <NUM>% or more and <NUM>% or less, and further more preferably <NUM>% or more and <NUM>% or less.

In measurement by DSC of polyamide (PA1), the ratio of the endothermic amount in the range of <NUM> or higher and <NUM> or lower is the lower limit value or more, and thus it is possible to sufficiently suppress heating sagging during reflow. In particular, even in a case where a preheating temperature is raised, for example, even in a case where the preheating temperature is <NUM> or higher, or even <NUM> or higher, it is possible to suppress heating sagging.

In the present specification, the endothermic amount of the polyamide can be calculated from a peak area of the DSC curve of the polyamide.

In measurement by DSC of the polyamide (PA1), the ratio of the endothermic amount in the range of <NUM> or higher and <NUM> or lower is preferably <NUM>% or less, more preferably <NUM>% or less, and further more preferably <NUM>% or less with respect to the total endothermic amount in the range of <NUM> or higher and <NUM> or lower.

A lower limit of the ratio of the endothermic amount is not particularly limited as long as the effect of the invention is exhibited, and may be, for example, <NUM>% or more, <NUM>% or more, or <NUM>% or more.

In measurement by DSC of the polyamide (PA1), the ratio of the endothermic amount in a range of <NUM> or higher and <NUM> or lower is preferably <NUM>% or less, more preferably <NUM>% or less, and further more preferably <NUM>% or less with respect to the total endothermic amount in the range of <NUM> or higher and <NUM> or lower.

A lower limit of the ratio of the endothermic amount is not particularly limited as long as the effect of the invention is exhibited, and, for example, may be <NUM>% or more, <NUM>% or more, or <NUM>% or more.

A specific polyamide (PA1) contained in a flux of the present embodiment is preferably a condensate of an aliphatic carboxylic acid, a hydroxy group-containing monocarboxylic acid, and an amine, from a viewpoint of further enhancing the ability to suppress heating sagging.

The specific polyamide (PA1) contained in the flux of the present embodiment is more preferably a condensate of dicarboxylic acid, hydroxy group-containing monocarboxylic acid, and diamine. The specific polyamide (PA1) contained in the flux of the present embodiment is further more preferably a condensate of an aliphatic dicarboxylic acid having <NUM> to <NUM> carbon atoms, a hydroxy group-containing aliphatic monocarboxylic acid having <NUM> to <NUM> carbon atoms, and an aliphatic diamine having <NUM> to <NUM> carbon atoms.

Among these, the polyamide (PA1) is particularly preferably a condensate of a <NUM>-hydroxystearic acid, a hexamethylenediamine, and one or more selected from the group consisting of sebacic acid and dodecanedioic acid.

The polyamide (PA1) may be a condensate of a <NUM>-hydroxystearic acid, a hexamethylenediamine, one or more selected from the group consisting of sebacic acid and dodecanedioic acid, and one or more selected from the group consisting of palmitic acid and stearic acid.

In a case where the polyamide (PA1) is a condensate of an aliphatic dicarboxylic acid, a hydroxy group-containing aliphatic monocarboxylic acid, and an aliphatic diamine, the molar ratio of these raw materials preferably satisfies the following relational expression.

Here, the aliphatic dicarboxylic acid, the hydroxy group-containing aliphatic monocarboxylic acid, and the aliphatic diamine, which are used as raw materials of the polyamide (PA1), are denoted as X mole, Y mole, and Z mole, respectively.

A total number of moles of amino groups in the compound contained in the raw materials is equal to the total number of moles of carboxyl groups, or the total number of moles of amino groups in the compound contained in the raw materials is preferably less than the total number of moles of carboxyl groups. Specifically, it is preferable to satisfy 2Z ≤ 2X + Y.

The molar ratio relationship between the raw materials is preferably <NUM>. 2Y ≤ X ≤ 2Y, and more preferably <NUM>. 4Y ≤ X ≤ <NUM>.

The molar ratio relationship between the raw materials is preferably <NUM>. 5Y ≤ Z ≤ 2Y, and more preferably <NUM>. 8Y ≤ Z ≤ <NUM>.

The amount of the polyamide (PA1) in the flux is preferably <NUM>% by mass or more and <NUM>% by mass or less, more preferably <NUM>% by mass or more and <NUM>% by mass or less, and further more preferably <NUM>% by mass or more and <NUM>% by mass or less with respect to the total amount (<NUM>% by mass) of the flux.

The ratio of the compound represented by General Formula (<NUM>) to the total mass (<NUM>% by mass) of the compound represented by General Formula (<NUM>) and the specific polyamide (PA1) is preferably <NUM>% by mass or more and <NUM>% by mass or less, and more preferably <NUM>% by mass or more and <NUM>% by mass or less.

A thixotropic agent may include other thixotropic agents in addition to the compound represented by General Formula (<NUM>) and the polyamide (PA1).

As the other thixotropic agents, an amide-based thixotropic agent other than the above-mentioned ones, a wax-based thixotropic agent, and a sorbitol-based thixotropic agent are exemplary examples.

For the other thixotropic agents, one type may be used alone, or two or more types may be mixed together and used.

As the amide-based thixotropic agent other than the above-mentioned ones, a monoamide, a bisamide, and other polyamides are exemplary examples.

As the monoamide, lauric acid amide, palmitic acid amide, stearic acid amide, behenic acid amide, hydroxystearic acid amide, saturated fatty acid amide, oleic acid amide, erucic acid amide, unsaturated fatty acid amide, p-toluamide, p-toluenemethane amide, aromatic amide, hexamethylene hydroxystearic acid amide, substituted amide, methylol stearic acid amide, methylol amide, fatty acid ester amide, and the like are exemplary examples.

As the bisamide, methylene bisstearic acid amide, ethylene bislauric acid amide, ethylene bishydroxy fatty acid (the number of carbon atoms in the fatty acid: C6 to <NUM>) amide, ethylene bisstearic acid amide, ethylene bishydroxystearic acid amide, saturated fatty acid bisamide, methylene bisoleic acid amide, unsaturated fatty acid bisamide, m-xylylene bisstearic acid amide, aromatic bisamide, and the like are exemplary examples.

As the other polyamides, saturated fatty acid polyamide, unsaturated fatty acid polyamide, aromatic polyamide, tris <NUM>,<NUM>,<NUM>-propanetricarboxylate (<NUM>-methylcyclohexylamide), cyclic amide oligomer, acyclic amide oligomer, and the like are exemplary examples.

As the cyclic amide oligomer, an amide oligomer in which a dicarboxylic acid and a diamine are cyclically polycondensed, an amide oligomer in which a tricarboxylic acid and a diamine are cyclically polycondensed, an amide oligomer in which a dicarboxylic acid and a triamine are cyclically polycondensed, an amide oligomer in which a tricarboxylic acid and a triamine are cyclically polycondensed, an amide oligomer in which a dicarboxylic acid, a tricarboxylic acid, and a diamine are cyclically polycondensed, an amide oligomer in which a dicarboxylic acid, a tricarboxylic acid, and a triamine are cyclically polycondensed, an amide oligomer in which a dicarboxylic acid, a diamine, and a triamine are cyclically polycondensed, an amide oligomer in which a tricarboxylic acid, a diamine, and a triamine are cyclically polycondensed, an amide oligomer in which a dicarboxylic acid, a tricarboxylic acid, a diamine, and a triamine are cyclically polycondensed, and the like are exemplary examples.

In addition, as the acyclic amide oligomer, a case of an amide oligomer in which a monocarboxylic acid, a diamine, and/or a triamine are acyclically polycondensed, a case of an amide oligomer in which a dicarboxylic acid and/or a tricarboxylic acid, and a monoamine are acyclically polycondensed, and the like are exemplary examples. In the case of an amide oligomer containing a monocarboxylic acid or a monoamine, the monocarboxylic acid and the monoamine function as terminal molecules, thereby resulting in an acyclic amide oligomer having a reduced molecular weight. In addition, in a case where the acyclic amide oligomer is an amide compound in which a dicarboxylic acid and/or a tricarboxylic acid, and a diamine and/or a triamine are acyclically polycondensed, the acyclic amide oligomer is an acyclic polymer-based amide polymer. In addition, the acyclic amide oligomer also includes an amide oligomer in which a monocarboxylic acid and a monoamine are acyclically condensed.

The total amount of the amide-based thixotropic agent in the flux is preferably <NUM>% by mass or more and <NUM>% by mass or less, more preferably <NUM>% by mass or more and <NUM>% by mass or less, and further more preferably <NUM>% by mass or more and <NUM>% by mass or less with respect to the total amount (<NUM>% by mass) of the flux.

As the wax-based thixotropic agent, an ester compound is an exemplary example, and hardened castor oil is a specific exemplary example.

The amount of the wax-based thixotropic agent in the flux is preferably <NUM>% by mass or more and <NUM>% by mass or less, more preferably <NUM>% by mass or more and <NUM>% by mass or less, and further more preferably <NUM>% by mass or more and <NUM>% by mass or less with respect to the total amount (<NUM>% by mass) of the flux.

As the sorbitol-based thixotropic agent, dibenzylidene-D-sorbitol, bis(<NUM>-methylbenzylidene)-D-sorbitol, (D-)sorbitol, monobenzylidene (-D-)sorbitol, mono(<NUM>-methylbenzylidene)-(D-)sorbitol, and the like are exemplary examples.

The amount of the sorbitol-based thixotropic agent in the flux is preferably <NUM>% by mass or more and <NUM>% by mass or less, and more preferably <NUM>% by mass or more and <NUM>% by mass or less with respect to the total amount (<NUM>% by mass) of the flux.

The total amount of the thixotropic agent in the flux is preferably <NUM>% by mass or more and <NUM>% by mass or less, more preferably <NUM>% by mass or more and <NUM>% by mass or less, and further more preferably <NUM>% by mass or more and <NUM>% by mass or less with respect to the total amount (<NUM>% by mass) of the flux.

The amount of other thixotropic agents in the flux is preferably <NUM>% by mass or more and <NUM>% by mass or less, and more preferably <NUM>% by mass or more and <NUM>% by mass or less with respect to the total amount (<NUM>% by mass) of the flux.

The ratio of the other thixotropic agents in the flux is preferably <NUM>% by mass or more and <NUM>% by mass or less, more preferably <NUM>% by mass or more and <NUM>% by mass or less, and further more preferably <NUM>% by mass or more and <NUM>% by mass or less with respect to the total mass (<NUM>% by mass) of the thixotropic agents.

As the activator, an organic acid, a halogen-based activator, an amine, and the like are exemplary examples.

As the organic acid, glutaric acid, adipic acid, azelaic acid, eicosanedioic acid, citric acid, glycolic acid, succinic acid, salicylic acid, diglycolic acid, dipicolinic acid, dibutylaniline diglycolic acid, suberic acid, sebacic acid, thioglycolic acid, dithioglycolic acid, terephthalic acid, dodecanedioic acid, parahydroxyphenylacetic acid, picolinic acid, phenylsuccinic acid, phthalic acid, fumaric acid, maleic acid, malonic acid, lauric acid, benzoic acid, tartaric acid, tris(<NUM>-carboxyethyl)isocyanurate, glycine, <NUM>,<NUM>-cyclohexanedicarboxylic acid, <NUM>,<NUM>-bis(hydroxymethyl)propionic acid, <NUM>,<NUM>-bis(hydroxymethyl)butanoic acid, <NUM>,<NUM>-dihydroxybenzoic acid, <NUM>,<NUM>-diethylglutaric acid, <NUM>-quinolinecarboxylic acid, <NUM>-hydroxybenzoic acid, propionic acid, malic acid, p-anisic acid, stearic acid, <NUM>-hydroxystearic acid, oleic acid, linoleic acid, linolenic acid, palmitic acid, pimelic acid, dimer acid, trimer acid, hydrogenated dimer acid, which is a hydrogenated product obtained by adding hydrogen to dimer acid, hydrogenated trimer acid, which is a hydrogenated product obtained by adding hydrogen to trimer acid, and the like are exemplary examples.

For the organic acid, one type may be used alone, or two or more types may be mixed together and used.

The organic acid is preferably a dicarboxylic acid.

The dicarboxylic acid is preferably one or more selected from the group consisting of glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, and sebacic acid, and more preferably one or more selected from the group consisting of glutaric acid, adipic acid, and azelaic acid.

The total amount of the organic acid in the flux is preferably <NUM>% by mass or more and <NUM>% by mass or less, and more preferably <NUM>% by mass or more and <NUM>% by mass or less with respect to the total amount (<NUM>% by mass) of the flux.

As the halogen-based activator, halogenated aliphatic compound, amine hydrohalic acid salt, and the like are exemplary examples.

For the halogen-based activator, one type may be used alone, or two or more types may be mixed together and used.

As the halogenated aliphatic compound, <NUM>-bromo-<NUM>-propanol, <NUM>-bromo-<NUM>-propanol, <NUM>-bromo-<NUM>,<NUM>-propanediol, <NUM>-bromo-<NUM>-butanol, <NUM>,<NUM>-dibromo-<NUM>-propanol, <NUM>,<NUM>-dibromo-<NUM>-propanol, <NUM>,<NUM>-dibromo-<NUM>-butanol, <NUM>,<NUM>-dibromo-<NUM>,<NUM>-butanediol, trans-<NUM>,<NUM>-dibromo-<NUM>-butene-<NUM>,<NUM>-diol, and the like are exemplary examples.

The amine hydrohalic acid salt is a compound obtained by reacting amines with hydrogen halides, as the amine, ethylamine, diethylamine, triethylamine, ethylenediamine, <NUM>,<NUM>-diphenylguanidine, <NUM>,<NUM>-di-o-tolylguanidine, <NUM>-o-tolylbiguanide, and the like are exemplary examples, and as the hydrogen halide, hydrides of chlorine, bromine, and iodine, and the like are exemplary examples.

The flux of the present embodiment preferably contains a halogen-based activator.

The flux of the present embodiment preferably contains a halogenated aliphatic compound.

The halogenated aliphatic compound is preferably trans-<NUM>,<NUM>-dibromo-<NUM>-butene-<NUM>,<NUM>-diol.

The total amount of the halogen-based activator in the flux is preferably <NUM>% by mass or more and <NUM>% by mass or less with respect to the total amount (<NUM>% by mass) of the flux.

As the amine, ethylamine, triethylamine, ethylenediamine, triethylenetetramine, <NUM>-methylimidazole, <NUM>-undecylimidazole, <NUM>-heptadecylimidazole, <NUM>,<NUM>-dimethylimidazole, <NUM>-ethyl-<NUM>-methylimidazole, <NUM>-phenylimidazole, <NUM>-phenyl-<NUM>-methylimidazole, <NUM>-benzyl-<NUM>-methylimidazole, <NUM>-benzyl-<NUM>-phenylimidazole, <NUM>-cyanoethyl-<NUM>-methylimidazole, <NUM>-cyanoethyl-<NUM>-undecylimidazole, <NUM>-cyanoethyl-<NUM>-ethyl-<NUM>-methylimidazole, <NUM>-cyanoethyl-<NUM>-phenylimidazole, <NUM>-cyanoethyl-<NUM>-undecylimidazolium trimellitate, <NUM>-cyanoethyl-<NUM>-phenylimidazolium trimellitate, <NUM>,<NUM>-diamino-<NUM>-[<NUM>'-methylimidazolyl-(<NUM>')]-ethyl-s-triazine, <NUM>,<NUM>-diamino-<NUM>-[<NUM>'-undecylimidazolyl-(<NUM>')]-ethyl-s-triazine, <NUM>,<NUM>-diamino-<NUM>-[<NUM>'-ethyl-<NUM>'-methylimidazolyl-(<NUM>')]-ethyl-s-triazine, <NUM>,<NUM>-diamino-<NUM>-[<NUM>'-methylimidazolyl-(<NUM>')]-ethyl-s-triazine isocyanuric acid adduct, <NUM>-phenylimidazole isocyanuric acid adduct, <NUM>-phenyl-<NUM>,<NUM>-dihydroxymethylimidazole, <NUM>-phenyl-<NUM>-methyl-<NUM>-hydroxymethylimidazole, <NUM>,<NUM>-dihydro-<NUM>-pyrrolo[<NUM>,<NUM>-a]benzimidazole, <NUM>-dodecyl-<NUM>-methyl-<NUM>-benzylimidazolium chloride, <NUM>-methylimidazoline, <NUM>-phenylimidazoline, <NUM>,<NUM>-diamino-<NUM>-vinyl-s-triazine, <NUM>,<NUM>-diamino-<NUM>-vinyl-s-triazine isocyanuric acid adduct, <NUM>,<NUM>-diamino-<NUM>-methacryloyloxyethyl-s-triazine, epoxy-imidazole adduct, <NUM>-methylbenzimidazole, <NUM>-octylbenzimidazole, <NUM>-pentylbenzimidazole, <NUM>-(<NUM>-ethylpentyl)benzimidazole, <NUM>-nonylbenzimidazole, <NUM>-(<NUM>-thiazolyl)benzimidazole, benzimidazole, <NUM>-(<NUM>'-hydroxy-<NUM>'-methylphenyl)benzotriazole, <NUM>-(<NUM>'-hydroxy-<NUM>'-tert-butyl-<NUM>'-methylphenyl)-<NUM>-chlorobenzotriazole, <NUM>-(<NUM>'-hydroxy-<NUM>',<NUM>'-di-tert-amylphenyl)benzotriazole, <NUM>-(<NUM>'-hydroxy-<NUM>'-tert-octylphenyl)benzotriazole, <NUM>,<NUM>'-methylenebis[<NUM>-(<NUM>-benzotriazol-<NUM>-yl)-<NUM>-tert-octylphenol], <NUM>-(<NUM>-benzotriazolyl)-<NUM>-tert-octyl-<NUM>'-tert-butyl-<NUM>'-methyl-<NUM>,<NUM>'-methylenebisphenol, <NUM>,<NUM>,<NUM>-benzotriazole, <NUM>-[N,N-bis(<NUM>-ethylhexyl)aminomethyl]benzotriazole, carboxybenzotriazole, <NUM>-[N,N-bis(<NUM>-ethylhexyl)aminomethyl]methylbenzotriazole, <NUM>,<NUM>'-[[(methyl-<NUM>-benzotriazol-<NUM>-yl)methyl]imino]bisethanol, <NUM>-(<NUM>',<NUM>'-dicarboxyethyl)benzotriazole, <NUM>-(<NUM>,<NUM>-dicarboxypropyl)benzotriazole, <NUM>-[(<NUM>-ethylhexylamino)methyl]benzotriazole, <NUM>,<NUM>-bis[(<NUM>-benzotriazol-<NUM>-yl)methyl]-<NUM>-methylphenol, <NUM>-methylbenzotriazole, <NUM>-phenyltetrazole, and the like are exemplary examples.

For the amine, one type may be used alone, or two or more types may be mixed together and used.

The amine is preferably one or more selected from the group consisting of <NUM>-phenylimidazole and <NUM>-phenyl-<NUM>-methylimidazole.

The amount of the amine in the flux is preferably more than <NUM>% by mass and <NUM>% by mass or less, more preferably more than <NUM>% by mass and <NUM>% by mass or less, further more preferably more than <NUM>% by mass and <NUM>% by mass or less, and particularly preferably more than <NUM>% by mass and <NUM>% by mass or less with respect to the total amount (<NUM>% by mass) of the flux.

In addition, the flux of the present embodiment may further include other components in addition to rosin, a solvent, a thixotropic agent, and an activator.

As the other components, a surfactant, a silane coupling agent, a colorant, and the like are exemplary examples.

As the surfactant, a nonionic surfactant, a weak cationic surfactant, and the like are exemplary examples.

As the nonionic surfactant, polyethylene glycol, a polyethylene glycol-polypropylene glycol copolymer, an aliphatic alcohol polyoxyethylene adduct, an aromatic alcohol polyoxyethylene adduct, a polyhydric alcohol polyoxyethylene adduct, and the like are exemplary examples.

As the weak cationic surfactant, diamine-terminated polyethylene glycol, a diamine-terminated polyethylene glycol-polypropylene glycol copolymer, an aliphatic amine polyoxyethylene adduct, an aromatic amine polyoxyethylene adduct, a polyvalent amine polyoxyethylene adduct, and the like are exemplary examples.

As the surfactant other than the above examples, polyoxyalkylene acetylene glycols, polyoxyalkylene glyceryl ethers, polyoxyalkylene alkyl ethers, polyoxyalkylene esters, polyoxyalkylene alkylamines, polyoxyalkylene alkylamides, and the like are exemplary examples.

In addition, an antioxidant may be used for the purpose of suppressing oxidation of solder alloy powder in the flux of the present embodiment. As the antioxidant, a hindered phenol-based antioxidant such as <NUM>,<NUM>'-methylenebis[<NUM>-(<NUM>-methylcyclohexyl)-p-cresol] may be used.

An additive such as a matting agent and an anti-foaming agent may be further added to the flux of the present embodiment.

The flux of the present embodiment described above uses a combination of the specific amide compound represented by General Formula (<NUM>) and the specific polyamide as the thixotropic agent, and thus it is possible to sufficiently suppress heating sagging during reflow. In particular, in a case where a preheating temperature is raised, for example, even in a case where the preheating temperature is <NUM> or higher, or even <NUM> or higher, it is possible to suppress heating sagging by applying this combination.

A solder paste of the present embodiment contains solder alloy powder and the above-mentioned flux.

The solder alloy powder may be constituted of solder powders of Sn single body, or solder alloy powder obtained by adding Sb, Bi, In, Cu, Zn, As, Ag, Cd, Fe, Ni, Co, Au, Ge, P, and the like to Sn-Ag-based, Sn-Cu-based, Sn-Ag-Cu-based, Sn-Bi-based, and Sn-In-based powders, or alloys of these.

The solder alloy powders may be constituted of solder alloy powders obtained by adding Sb, Bi, In, Cu, Zn, As, Ag, Cd, Fe, Ni, Co, Au, Ge, and P to the Sn-Pb-based powders, or Sn-Pb-based powders.

The solder alloy powder is preferably Pb-free solders.

The amount of the flux in a solder paste is preferably <NUM>% to <NUM>% by mass, and more preferably <NUM>% to <NUM>% by mass with respect to the total mass of the solder paste.

Since the solder paste of the present embodiment contains the above-described flux, it is possible to sufficiently suppress heating sagging.

In addition, the flux of the present embodiment may have other embodiments than those described above. In such other embodiments, the flux contains rosin, a solvent, a specific thixotropic agent, and an activator.

As rosin used in the flux of such other embodiments, those described above are exemplary examples.

The amount of the rosin in the flux of other embodiments is preferably <NUM>% by mass or more and <NUM>% by mass or less, and more preferably <NUM>% by mass or more and <NUM>% by mass or less with respect to the total amount (<NUM>% by mass) of the flux.

As the solvents used in the flux of such other embodiments, those described above are exemplary examples.

The amount of the solvent in the flux of such other embodiments is preferably <NUM>% by mass or more and <NUM>% by mass or less, and more preferably <NUM>% by mass or more and <NUM>% by mass or less with respect to the total amount (<NUM>% by mass) of the flux.

The flux of such other embodiments includes a polyamide (PA2) as a specific thixotropic agent.

The polyamide (PA2) is a condensate of an aliphatic amine having <NUM> to <NUM> carbon atoms and an aliphatic carboxylic acid and hydroxy group-containing aliphatic carboxylic acid.

That is, the polyamide (PA2) is obtained by specifying amine which is a raw material of the polyamide (PA1) as an aliphatic amine having <NUM> to <NUM> carbon atoms.

For the aliphatic carboxylic acid from which the polyamide (PA2) is derived, one type may be used alone, or two or more types may be mixed together and used.

The aliphatic carboxylic acid is dicarboxylic acid.

The number of carbon atoms in the aliphatic dicarboxylic acid is <NUM> to <NUM>, preferably <NUM> to <NUM>, and further more preferably <NUM> to <NUM>.

As the aliphatic dicarboxylic acid, dodecanedioic acid, tridecanedioic acid, tetradecanedioic acid, pentadecanedioic acid, and the like are exemplary examples. The aliphatic dicarboxylic acid is preferably dodecanedioic acid.

The aliphatic carboxylic acid may include dodecanedioic acid and one or more selected from the group consisting of palmitic acid and stearic acid.

For the hydroxy group-containing aliphatic carboxylic acid from which the polyamide (PA2) is derived, one type may be used alone or two or more types may be mixed together and used.

The amine from which polyamide (PA2) is derived is an aliphatic amine having <NUM> to <NUM> carbon atoms. For the amine from which the polyamide (PA2) is derived, one type may be used alone, or two or more types may be mixed together and used.

As the aliphatic amine, monoamine, diamine, triamine, tetraamine, and the like are exemplary examples. The amine is preferably a diamine.

The hydrocarbon group of the aliphatic amine may be linear, branched, or cyclic. The hydrocarbon group is preferably linear or branched, and more preferably linear. The number of carbon atoms in the aliphatic amine is preferably <NUM> to <NUM>.

As the aliphatic amine, <NUM>,<NUM>-propanediamine, <NUM>,<NUM>-butanediamine, hexamethylenediamine, butane-<NUM>,<NUM>,<NUM>,<NUM>-tetraamine, and the like are exemplary examples. The aliphatic amine is preferably hexamethylenediamine.

The polyamide (PA2) is more preferably a condensate of an aliphatic dicarboxylic acid having <NUM> to <NUM> carbon atoms, a hydroxy group-containing monocarboxylic acid having <NUM> to <NUM> carbon atoms, and an aliphatic diamine having <NUM> to <NUM> carbon atoms.

Among these, the polyamide (PA2) is further more preferably a condensate of dodecanedioic acid, <NUM>-hydroxystearic acid, and hexamethylenediamine.

The polyamide (PA2) may be a condensate of <NUM>-hydroxystearic acid, hexamethylenediamine, and one or more selected from the group consisting of dodecanedioic acid, palmitic acid, and stearic acid.

The polyamide (PA2) has the following properties.

In measurement by DSC of the polyamide (PA2), an endothermic amount in a range of <NUM> or higher and <NUM> or lower is preferably <NUM>% or more, more preferably <NUM>% or more, and further more preferably <NUM>% or more with respect to the total endothermic amount in a range of <NUM> or higher and <NUM> or lower.

The ratio of the endothermic amount is preferably as high as possible. An upper limit of the ratio of the endothermic amount is not particularly limited as long as the effect of the invention is exhibited, and may be, for example, <NUM>%.

The ratio of the endothermic amount is preferably <NUM>% or more and <NUM>% or less, more preferably <NUM>% or more and <NUM>% or less, and further more preferably <NUM>% or more and <NUM>% or less.

As the ratio of the endothermic amount is equal to or higher than the lower limit, the ability to suppress void generation is likely to be enhanced.

In measurement by DSC of the polyamide (PA2), the endothermic amount in a range of <NUM> or higher and <NUM> or lower is preferably <NUM>% or more, more preferably <NUM>% or more, and further more preferably <NUM>% or more with respect to the total endothermic amount in a range of <NUM> or higher and <NUM> or lower.

The ratio of the endothermic amount is preferably as high as possible. The upper limit of the ratio of the endothermic amount is not particularly limited as long as the effect of the invention is exhibited, and may be, for example, <NUM>%.

In measurement by DSC of the polyamide (PA2), the ratio of the endothermic amount in a range of <NUM> or higher and <NUM> or lower is preferably <NUM>% or more, more preferably <NUM>% or more, and furthermore preferably <NUM>% or more with respect to the total endothermic amount in a range of <NUM> or higher and <NUM> or lower.

The ratio of the endothermic amount is preferably <NUM>% or more and <NUM>% or less, more preferably <NUM>% or more and <NUM>% or less, and further more preferably <NUM>% or more and <NUM>% or less. Alternatively, the ratio of the endothermic amount is preferably <NUM>% or more and <NUM>% or less, more preferably <NUM>% or more and <NUM>% or less, and further more preferably <NUM>% or more and <NUM>% or less. In measurement by DSC of the polyamide (PA2), as the ratio of the endothermic amount in a range of <NUM> or higher and <NUM> or lower is equal to or more than the lower limit, it is possible to sufficiently suppress heating sagging during reflow. In particular, even in a case where a preheating temperature is raised, for example, even in a case where the preheating temperature is <NUM> or higher, or even <NUM> or higher, it is possible to suppress heating sagging.

In measurement by DSC of the polyamide (PA2), the ratio of the endothermic amount in a range of <NUM> or higher and <NUM> or lower is preferably <NUM>% or less, more preferably <NUM>% or less, and further more preferably <NUM>% or less with respect to the total endothermic amount in the range of <NUM> or higher and <NUM> or lower.

The lower limit of the ratio of the endothermic amount is not particularly limited as long as the effect of the invention is exhibited, and may be, for example, <NUM>% or more, <NUM>% or more, or <NUM>% or more.

In measurement by DSC of the polyamide (PA2), the ratio of the endothermic amount in a range of <NUM> or higher and <NUM> or lower is preferably <NUM>% or less, more preferably <NUM>% or less, and further more preferably <NUM>% or less with respect to the total endothermic amount in a range of <NUM> or higher and <NUM> or lower.

The lower limit of the ratio of the endothermic amount is not particularly limited as long as the effect of the invention is exhibited, and, for example, may be <NUM>% or more, <NUM>% or more, or <NUM>% or more.

The polyamide (PA2) has one or two or more endothermic peaks in a temperature range of <NUM> or higher and <NUM> or lower as measured by DSC.

In a case where the number of endothermic peaks is <NUM> or more, for example, the lowest temperature of the endothermic peaks of the polyamide (PA2) may be in a range of <NUM> or higher and <NUM> or lower, the highest temperature of the endothermic peaks may be in a range of <NUM> or higher and <NUM> or lower, and all the endothermic peaks may be in a range of <NUM> or higher and <NUM> or lower.

The temperature of the highest temperature of the endothermic peaks is preferably <NUM> or higher and <NUM> or lower, more preferably <NUM> or higher and <NUM> or lower, further more preferably <NUM> or higher and <NUM> or lower, and particularly preferably <NUM> or higher and <NUM> or lower.

In a DSC curve, the polyamide (PA2) preferably has three endothermic peaks consisting of a first endothermic peak, a second endothermic peak, and a third endothermic peak.

A temperature of the first endothermic peak is preferably less than <NUM>, more preferably <NUM> or higher and <NUM> or lower, further more preferably <NUM> or higher and <NUM> or lower, and particularly preferably <NUM> or higher and <NUM> or lower.

The temperature of the second endothermic peak is preferably <NUM> or higher, more preferably <NUM> or higher and <NUM> or lower, further more preferably <NUM> or higher and <NUM> or lower, and particularly preferably <NUM> or higher and <NUM> or lower.

The temperature of the third endothermic peak is preferably <NUM> or higher, more preferably <NUM> or higher and <NUM> or lower, further more preferably <NUM> or higher and <NUM> or lower, and particularly preferably <NUM> or higher and <NUM> or lower.

In a case where the polyamide (PA2) is a condensate of an aliphatic dicarboxylic acid, a hydroxy group-containing aliphatic monocarboxylic acid, and an aliphatic diamine, the molar ratio of these raw materials preferably satisfies the following relational expression.

Here, the aliphatic dicarboxylic acid, the hydroxy group-containing aliphatic monocarboxylic acid, and the aliphatic diamine, which are used as raw materials of the polyamide (PA2), are denoted as X mole, Y mole, and Z mole, respectively.

The molar ratio relationship between the raw materials is preferably <NUM>. 5Y ≤ Z ≤ 2Y, and more preferably <NUM>. 8Y ≤ Z ≤ <NUM>.

The amount of the polyamide (PA2) is <NUM>% by mass or more and <NUM>% by mass or less, preferably <NUM>% by mass or more and <NUM>% by mass or less, particularly preferably <NUM>% by mass or more and <NUM>% by mass or less, and most preferably <NUM>% by mass or more and <NUM>% by mass or less with respect to the total amount (<NUM>% by mass) of the flux.

In addition, the flux of such other embodiments may further include other components in addition to the rosin, the solvent, the specific thixotropic agent, and the activator.

As the other components, a thixotropic agent other than the polyamide (PA2), a surfactant, a silane coupling agent, a colorant, and the like are exemplary examples.

As the other thixotropic agents, an amide-based thixotropic agent other than the polyamide (PA2), a wax-based thixotropic agent, a sorbitol-based thixotropic agent, and the like are exemplary examples.

The amount of the wax-based thixotropic agent in the flux is preferably <NUM>% by mass or more and <NUM>% by mass or less, more preferably <NUM>% by mass or more and <NUM>% by mass or less, further more preferably <NUM>% by mass or more and <NUM>% by mass or less with respect to the total amount (<NUM>% by mass) of the flux.

The amount of the wax-based thixotropic agent in the flux is preferably <NUM>% by mass or more and <NUM>% by mass or less, more preferably <NUM>% by mass or more and <NUM>% by mass or less, further more preferably <NUM>% by mass or more and <NUM>% by mass or less, and particularly preferably <NUM>% by mass or more and <NUM>% by mass or less with respect to the total amount (<NUM>% by mass) of the amide-based thixotropic agent and the wax-based thixotropic agent.

In the flux of such other embodiments, since the polyamide (PA2) contained in the flux melts at <NUM> and <NUM> and has sufficiently high fluidity, it is possible to sufficiently suppress generation of voids.

In addition, in the flux of such other embodiments, since the polyamide (PA2) contained in the flux does not partially melt at <NUM> and <NUM>, it is possible to sufficiently suppress heating sagging. In particular, even in a case where a preheating temperature is raised, for example, even in a case where the preheating temperature is <NUM> or higher, or even <NUM> or higher, it is possible to suppress heating sagging.

Other embodiments of the solder paste contain solder alloy powder and the flux of such other embodiments.

In the solder paste of the other embodiments, the amount of the flux is preferably <NUM>% to <NUM>% by mass, and more preferably <NUM>% to <NUM>% by mass with respect to a total mass of the solder paste.

Since the solder paste of the present embodiment contains the flux of such other embodiments, it is possible to sufficiently suppress heating sagging. In addition, it is possible to suppress generation of voids.

Hereinafter, the present invention will be described with reference to examples, but the present invention is not limited to the following examples. (The examples according to paragraphs [<NUM>] to [<NUM>] are not part of the present invention).

As the rosin, acrylic acid-modified hydrogenated rosin, polymerized rosin, and hydrogenated rosin were used.

As the thixotropic agent, a thixotropic agent A, a thixotropic agent B, a bisamide, and a polyamide were used.

Thixotropic agent A: N,N'-bis(<NUM>-stearamidoethyl)-azelicamide.

The thixotropic agent A is a compound represented by the following chemical formula (<NUM>-<NUM>).

Thixotropic agent B: N,N'-bis(<NUM>-stearamidoethyl)-sebacamide.

The thixotropic agent B is a compound represented by the following chemical formula (<NUM>-<NUM>).

As the polyamide, one obtained by the following method (polyamide (PA1)) was used.

<NUM>-Hydroxystearic acid and dodecanedioic acid were added and heated to about <NUM>, then hexamethylenediamine was added thereto and heated to about <NUM>, and held for <NUM> hours to obtain a polyamide of Preparation Example <NUM>.

Dodecanedioic acid, <NUM>-hydroxystearic acid, and hexamethylenediamine, used as raw materials, are denoted as X mole, Y mole, and Z mole, respectively. The number of moles of raw materials satisfied a relationship of 2Z = 2X + Y.

<NUM>-Hydroxystearic acid and sebacic acid were added and heated to about <NUM>, then hexamethylenediamine was added thereto and heated to about <NUM>, and held for <NUM> hours to obtain a polyamide of Preparation Example <NUM>.

Sebacic acid, <NUM>-hydroxystearic acid, and hexamethylenediamine, used as raw materials, are denoted as X mole, Y mole, and Z mole, respectively. The number of moles of raw materials satisfied a relationship of 2Z = 2X + Y.

The temperature of the endothermic peak of the obtained polyamide was measured by DSC (Differential Scanning Calorimetry).

As a more specific method of measuring an endothermic peak, a temperature raising rate was set to <NUM>/min, and a temperature of about <NUM> of polyamide was raised from <NUM> to <NUM> under a nitrogen atmosphere. As a measuring apparatus, DSC7020 (manufactured by Hitachi High-Tech Science) was used. The measurement results are shown in <FIG> is a diagram showing a DSC curve of the obtained polyamide preparation example <NUM>. The temperature of a peak top was defined as the temperature of the endothermic peak.

The obtained polyamide had the temperature of the peak top of all endothermic peaks of <NUM> or higher and <NUM> or lower.

As the bisamide, ethylene bis stearamide (product name: Slipax E) was used.

As an organic acid, an adipic acid, an azelaic acid, and a glutaric acid were used.

As a halogen-based activator, trans-<NUM>,<NUM>-dibromo-<NUM>-butene-<NUM>,<NUM>-diol was used.

As an amine, <NUM>-phenylimidazole and <NUM>-phenyl-<NUM>-methylimidazole were used.

As a solvent, diethylene glycol monohexyl ether was used.

Each flux of examples and comparative examples was blended using the compositions shown in Tables <NUM> to <NUM> below.

The amount of each component in Tables <NUM> to <NUM> is % by mass in a case where the total mass of the flux is <NUM>% by mass, and blanks mean <NUM> % by mass.

Each flux of examples and the following solder alloy powder were mixed to blend a solder paste.

As the solder alloy powder, a Sn-Ag-Cu-based solder alloy containing <NUM>% by mass of Ag, <NUM>% by mass of Cu, and the balance of Sn was used.

As the solder alloy powder, a powder of a size (particle size distribution) satisfying symbol <NUM> in the powder size classification (Table <NUM>) in JIS Z <NUM>-<NUM>:<NUM> was used.

In all the blended solder pastes, the flux was <NUM>% by mass, and the solder alloy powder was <NUM>% by mass.

Sagging of the solder paste during printing was evaluated. The results were shown in Tables <NUM> to <NUM>.

Regarding the obtained solder paste, print sagging was evaluated according to the method described in "Test for sagging during printing" of JIS Z <NUM>-<NUM>:<NUM>. The solder paste was printed by using a metal mask arranged with pattern holes shown in I (hole size <NUM> × <NUM>) in <FIG> of "Test for sagging during printing" to obtain a test plate. Regarding the test plate, a minimum interval at which all the printed solder pastes were not coincident was evaluated.

Sagging during heating of a solder paste obtained by mixing a flux and solder alloy powder was evaluated. The results were shown in Tables <NUM> to <NUM>.

Regarding the obtained solder paste, heating sagging was evaluated according to the method described in "Test for sagging during heating" of JIS Z <NUM>-<NUM>:<NUM>. First, the solder paste was printed by using a metal mask arranged with pattern holes shown in I (hole size <NUM> × <NUM>) in <FIG> of "Test for sagging during printing" to obtain a test plate. The obtained test plate was heated to <NUM> in an air circulation heating furnace. Regarding the test plate after heating, a minimum interval at which all the printed solder pastes were not coincident was evaluated.

As shown in Example <NUM>, a flux, in which acrylic acid-modified hydrogenated rosin is included as rosin, a thixotropic agent A and polyamide (Preparation Example <NUM>) are included as thixotropic agents, an adipic acid, an azelaic acid, a trans-<NUM>,<NUM>-dibromo-<NUM>-butene-<NUM>,<NUM>-diol, <NUM>-phenylimidazole, and <NUM>-phenyl-<NUM>-methylimidazole are included as activators, and diethylene glycol monohexyl ether is included as a solvent, could have sufficient ability to suppress heating sagging.

As shown in Example <NUM>, a flux, in which the type of the rosin is changed, polymerized rosin is included, a thixotropic agent A and polyamide (Preparation Example <NUM>) are included as thixotropic agents, an adipic acid, an azelaic acid, a trans-<NUM>,<NUM>-dibromo-<NUM>-butene-<NUM>,<NUM>-diol, <NUM>-phenylimidazole, and <NUM>-phenyl-<NUM>-methylimidazole are included as activators, and diethylene glycol monohexyl ether is included as a solvent, could have a sufficient ability to suppress heating sagging.

As shown in Example <NUM>, a flux, in which the type of the rosin is changed, hydrogenated rosin is included, a thixotropic agent A and polyamide (Preparation Example <NUM>) are included as thixotropic agents, an adipic acid, an azelaic acid, a trans-<NUM>,<NUM>-dibromo-<NUM>-butene-<NUM>,<NUM>-diol, <NUM>-phenylimidazole, and <NUM>-phenyl-<NUM>-methylimidazole are included as activators, and diethylene glycol monohexyl ether is included as a solvent, could have sufficient ability to suppress heating sagging.

As shown in Example <NUM>, a flux, in which acrylic acid-modified hydrogenated rosin is included as rosin, the amount of a thixotropic agent A is reduced, and polyamide (Preparation Example <NUM>) is included, an adipic acid, an azelaic acid, a trans-<NUM>,<NUM>-dibromo-<NUM>-butene-<NUM>,<NUM>-diol, <NUM>-phenylimidazole, and <NUM>-phenyl-<NUM>-methylimidazole are included as activators, and diethylene glycol monohexyl ether is included as a solvent, could have sufficient ability to suppress heating sagging.

As shown in Example <NUM>, a flux, in which acrylic acid-modified hydrogenated rosin is included as rosin, the amount of the thixotropic agent A is increased, polyamide (Preparation Example <NUM>) is included, an adipic acid, an azelaic acid, a trans-<NUM>,<NUM>-dibromo-<NUM>-butene-<NUM>,<NUM>-diol, <NUM>-phenylimidazole, and <NUM>-phenyl-<NUM>-methylimidazole are included as activators, and diethylene glycol monohexyl ether is included as a solvent, could have sufficient ability to suppress heating sagging.

As shown in Example <NUM>, a flux, in which acrylic acid-modified hydrogenated rosin is included as rosin, the type of the thixotropic agent is changed, a thixotropic agent B and polyamide (Preparation Example <NUM>) are included, an adipic acid, an azelaic acid, a trans-<NUM>,<NUM>-dibromo-<NUM>-butene-<NUM>,<NUM>-diol, <NUM>-phenylimidazole, and <NUM>-phenyl-<NUM>-methylimidazole are included as activators, and diethylene glycol monohexyl ether is included as a solvent, could have sufficient ability to suppress heating sagging.

As shown in Example <NUM>, a flux, in which acrylic acid-modified hydrogenated rosin is included as rosin, the amount of the thixotropic agent B is reduced, polyamide (Preparation Example <NUM>) is included, an adipic acid, an azelaic acid, a trans-<NUM>,<NUM>-dibromo-<NUM>-butene-<NUM>,<NUM>-diol, <NUM>-phenylimidazole, and <NUM>-phenyl-<NUM>-methylimidazole are included as activators, and diethylene glycol monohexyl ether is included as a solvent, could have sufficient ability to suppress heating sagging.

As shown in Example <NUM>, a flux, in which acrylic acid-modified hydrogenated rosin is included as rosin, the amount of the thixotropic agent B is increased, polyamide (Preparation Example <NUM>) is included, an adipic acid, an azelaic acid, a trans-<NUM>,<NUM>-dibromo-<NUM>-butene-<NUM>,<NUM>-diol, <NUM>-phenylimidazole, and <NUM>-phenyl-<NUM>-methylimidazole are included as activators, and diethylene glycol monohexyl ether is included as a solvent, could have sufficient ability to suppress heating sagging.

As shown in Example <NUM>, a flux, in which the amount of the acrylic acid-modified hydrogenated rosin is reduced, a thixotropic agent A and polyamide (Preparation Example <NUM>) are included as thixotropic agents, an adipic acid, an azelaic acid, a trans-<NUM>,<NUM>-dibromo-<NUM>-butene-<NUM>,<NUM>-diol, <NUM>-phenylimidazole, and <NUM>-phenyl-<NUM>-methylimidazole are included as activators, and diethylene glycol monohexyl ether is included as a solvent, could have sufficient ability to suppress heating sagging.

As shown in Example <NUM>, a flux, in which the amount of the acrylic acid-modified hydrogenated rosin is included, a thixotropic agent A and polyamide (Preparation Example <NUM>) are included as thixotropic agents, an adipic acid, an azelaic acid, a trans-<NUM>,<NUM>-dibromo-<NUM>-butene-<NUM>,<NUM>-diol, <NUM>-phenylimidazole, and <NUM>-phenyl-<NUM>-methylimidazole are included as activators, and diethylene glycol monohexyl ether is included as a solvent, could have sufficient ability to suppress heating sagging.

As shown in Example <NUM>, a flux, in which acrylic acid-modified hydrogenated rosin is included as rosin, a thixotropic agent A, thixotropic agent B, and polyamide (Preparation Example <NUM>) are included as thixotropic agents, the total amount of the thixotropic agent A and the thixotropic agent B is reduced, an adipic acid, an azelaic acid, a trans-<NUM>,<NUM>-dibromo-<NUM>-butene-<NUM>,<NUM>-diol, <NUM>-phenylimidazole, and <NUM>-phenyl-<NUM>-methylimidazole are included as activators, and diethylene glycol monohexyl ether is included as a solvent, could have sufficient ability to suppress heating sagging.

As shown in Example <NUM>, a flux, in which acrylic acid-modified hydrogenated rosin is included as rosin, a thixotropic agent A, a thixotropic agent B, and polyamide (Preparation Example <NUM>) are included as thixotropic agents, the total amount of the thixotropic agent A and thixotropic agent B is increased, an adipic acid, an azelaic acid, a trans-<NUM>,<NUM>-dibromo-<NUM>-butene-<NUM>,<NUM>-diol, <NUM>-phenylimidazole, and a <NUM>-phenyl-<NUM>-methylimidazole are included as activators, and diethylene glycol monohexyl ether is included as a solvent, could have sufficient ability to suppress heating sagging.

As shown in Example <NUM>, a flux, in which acrylic acid-modified hydrogenated rosin is included as rosin, a thixotropic agent A, bisamide, and polyamide (Preparation Example <NUM>) are included as thixotropic agents, an adipic acid, an azelaic acid, a trans-<NUM>,<NUM>-dibromo-<NUM>-butene-<NUM>,<NUM>-diol, <NUM>-phenylimidazole, and <NUM>-phenyl-<NUM>-methylimidazole are included as activators, and diethylene glycol monohexyl ether is included as a solvent, could have sufficient ability to suppress heating sagging.

As shown in Example <NUM>, a flux, in which acrylic acid-modified hydrogenated rosin is included as rosin, a thixotropic agent A and polyamide (Preparation Example <NUM>) are included as thixotropic agents, a glutaric acid, a trans-<NUM>,<NUM>-dibromo-<NUM>-butene-<NUM>,<NUM>-diol, <NUM>-phenylimidazole, and <NUM>-phenyl-<NUM>-methylimidazole are included as activators, diethylene glycol monohexyl ether is included as a solvent, could have sufficient ability to suppress heating sagging.

As shown in Example <NUM>, a flux, in which acrylic acid-modified hydrogenated rosin is included as rosin, a thixotropic agent A and polyamide (Preparation Example <NUM>) are included as thixotropic agents, an adipic acid, an azelaic acid, a trans-<NUM>,<NUM>-dibromo-<NUM>-butene-<NUM>,<NUM>-diol, <NUM>-phenylimidazole, and <NUM>-phenyl-<NUM>-methylimidazole and are included, and diethylene glycol monohexyl ether is included as a solvent, could have sufficient ability to suppress heating sagging.

The fluxes of Examples <NUM> to <NUM> include a compound represented by General Formula (<NUM>) and polyamide (Preparation Example <NUM>), and thus could have sufficient ability to suppress heating sagging at <NUM>.

The flux of Example <NUM> includes a compound represented by General Formula (<NUM>) and polyamide (Preparation Example <NUM>), and thus could have sufficient ability to suppress heating sagging at <NUM>. On the other hand, the fluxes of Comparative Examples <NUM> and <NUM> did not contain the thixotropic agent A and the thixotropic agent B, and had insufficient ability to suppress heating sagging at <NUM>.

In addition, the fluxes of Comparative Examples <NUM> and <NUM> did not contain polyamide (Preparation Example <NUM>) and polyamide (Preparation Example <NUM>), and had insufficient ability to suppress heating sagging at <NUM>.

From these results, it has been clarified that by including the compound represented by General Formula (<NUM>) and the polyamide, it is possible to obtain sufficient ability to suppress heating sagging.

As shown below, the polyamide of Preparation Example <NUM> and the polyamide of Preparation Example <NUM> were prepared. Using these polyamides, a flux and a solder paste were prepared and evaluated for heating sagging and generation of voids.

As the polyamide, one obtained by the following method (polyamide (PA2)) was used.

The endothermic peak temperatures of the polyamides of Preparation Examples <NUM> and <NUM> were measured by DSC (Differential Scanning Calorimetry).

As a more specific method of measuring an endothermic peak, measurement was performed by setting a temperature raising rate to <NUM>/min, and raising a temperature of about <NUM> of each of the polyamides of Preparation Examples <NUM> and <NUM> was raised from <NUM> to <NUM> under a nitrogen atmosphere. As a measuring apparatus, DSC7020 (manufactured by Hitachi High-Tech Science) was used. A temperature of a peak top was defined as the temperature of the endothermic peak.

Measurement results are shown in <FIG> and <FIG>.

<FIG> shows an endothermic peak of the polyamide of Preparation Example <NUM>, and <FIG> shows an endothermic peak of the polyamide of Preparation Example <NUM>.

For the polyamides of Preparation Examples <NUM> and <NUM>, the ratio of an endothermic amount at a certain specific temperature was calculated as follows.

The endothermic amount of the polyamide was calculated from a peak area of the DSC curve of the polyamide.

Here, the "ratio of an endothermic amount at a certain specific temperature" means an endothermic amount in a range of <NUM> or higher and a specific temperature or lower with respect to a total endothermic amount in a range of <NUM> or higher and <NUM> or lower. The results are shown in <FIG>.

<FIG> is a graph showing a relationship between the ratio of an endothermic amount of the polyamide and a temperature of Preparation Example <NUM>, and <FIG> is a graph showing a relationship between the ratio of an endothermic amount of the polyamide and a temperature of Preparation Example <NUM>. <FIG> is a graph showing the relationship between the ratio of the endothermic amount of the polyamide and the temperature of Preparation Example <NUM>, which is a partially enlarged one of <FIG>.

<FIG> is a graph showing the relationship between the ratio of the endothermic amount of the polyamide and the temperature of Preparation Example <NUM>, which is a partially enlarged one of <FIG>.

The polyamide of Preparation Example <NUM> had the ratio of an endothermic amount of <NUM>% or more at <NUM> and the ratio of an endothermic amount of <NUM>% or more at <NUM>.

On the other hand, the polyamide of Preparation Example <NUM> had the ratio of an endothermic amount of less than <NUM>% at <NUM> and the ratio of an endothermic amount of less than <NUM>% at <NUM>.

It was clarified that the ratio of the endothermic amount of the polyamide of Preparation Example <NUM> at <NUM> or higher and <NUM> or lower was smaller than that of the ratio of the endothermic amount of the polyamide of Preparation Example <NUM> at <NUM> or higher and <NUM> or lower.

As a thixotropic agent, the polyamides of Preparation Examples <NUM> and <NUM>, hexamethylenebishydroxystearic acid amide, and hardened castor oil were used.

As an organic acid, an adipic acid, a suberic acid, and a hydrogenated dimer acid were used.

As an amine, <NUM>-phenylimidazole was used.

Each flux of the test example was blended with the composition shown in Table <NUM> below.

The fluxes of Test Examples <NUM> to <NUM> contain rosin, a solvent, a polyamide (PA2), and an activator.

The flux of Test Example <NUM> contains rosin, a solvent, and an activator, but does not contain a polyamide (PA2).

The amount of each component in Table <NUM> is % by mass in a case where the total mass of the flux is <NUM>% by mass, and blanks mean <NUM>% by mass.

Sagging during heating of a solder paste obtained by mixing a flux and solder alloy powder was evaluated.

Regarding the obtained solder paste, heating sagging was evaluated according to the method described in "Test for sagging during heating" of JIS Z <NUM>-<NUM>:<NUM>. First, the solder paste was printed by using a metal mask arranged with pattern holes shown in I (hole size <NUM> × <NUM>) in <FIG> and II (hole size <NUM> × <NUM>) in <FIG> of "Test for sagging during printing" to obtain a test plate. The obtained test plate was heated to <NUM> or <NUM> in an air circulation heating furnace. Regarding the test plate after heating, a minimum interval (unit is mm) at which all the printed solder pastes were not coincident was evaluated. The results were shown in Table <NUM>.

A solder paste was printed on a substrate (CU-OSP-treated glass epoxy substrate) using a metal mask (opening diameter <NUM>, mask thickness <NUM>), and LGA (Land Grid Array: terminal-treated Au flash, pitch: <NUM>, ϕ: <NUM>, number of bumps: <NUM>) was mounted.

Subsequently, a temperature was raised from <NUM> to <NUM> at <NUM> to <NUM>/sec by atmospheric reflow, the solder paste was held at <NUM> to <NUM> for <NUM> to <NUM> seconds, then the temperature was raised to <NUM> to <NUM> at <NUM> to <NUM>/sec, and held at <NUM> or higher for <NUM> to <NUM> seconds.

Subsequently, an LGA mounting portion was imaged using an X-ray observation device (TUX-<NUM> manufactured by Mars Tohken Solution Co. Data were similarly acquired for <NUM> LGAs (a total of <NUM> bumps).

Regarding each of the <NUM> bumps, the ratio of the total area of voids to the land area of the bumps was calculated. An average value of the obtained ratios was calculated and used as a void area ratio. The results were shown in Table <NUM>.

In addition, the ratio of the number of bumps having no void with respect to the total number of bumps (<NUM>) was calculated, and this was used as a void non-generation ratio. The results were shown in Table <NUM>.

Determination criteria of void area ratio:.

Determination criteria of void non-generation ratio:.

Test Examples <NUM> to <NUM> and <NUM> to <NUM> contained a polyamide of Preparation Example <NUM>, and had sufficient ability to suppress heating sagging at <NUM>. Comparative Example <NUM> did not contain a polyamide, and had insufficient ability to suppress heating sagging at <NUM>. Test Examples <NUM> to <NUM> and <NUM> to <NUM> contained the polyamide of Preparation Example <NUM>, and had sufficient ability to suppress the generation of voids. Comparative Example <NUM> contained the polyamide of Preparation Example <NUM>, and had insufficient ability to suppress generation of voids.

The polyamide of Preparation Example <NUM> was prepared using dodecanedioic acid having <NUM> carbon atoms as a raw material.

The polyamide of Preparation Example <NUM> was prepared using sebacic acid having <NUM> carbon atoms as a raw material.

In general, organic compounds such as lipid have a high melting point as the number of carbon atoms increases.

Surprisingly, in the polyamide of Preparation Example <NUM>, since the ratio of an endothermic amount at <NUM> or higher and <NUM> or lower and the ratio of an endothermic amount at <NUM> or higher and <NUM> or lower were sufficiently high, Test Examples <NUM> to <NUM> had sufficient ability to suppress generation of voids.

In addition, in the polyamide of Preparation Example <NUM>, since the ratio of an endothermic amount at <NUM> or higher and <NUM> or lower and the ratio of an endothermic amount at <NUM> or higher and <NUM> or lower were not sufficiently high, Comparative Example <NUM> had insufficient ability to suppress generation of voids.

In the polyamide of Preparation Example <NUM>, fluidity was sufficiently high at <NUM> and <NUM>, it is presumed that Test Examples <NUM> to <NUM> and <NUM> to <NUM> had sufficient ability to suppress generation of voids.

In the polyamide of Preparation Example <NUM>, fluidity was not sufficiently high at <NUM> and <NUM>, it is presumed that Comparative Example <NUM> had insufficient ability to suppress generation of voids.

Claim 1:
A flux comprising:
a rosin;
a solvent;
a thixotropic agent; and
an activator,
wherein the thixotropic agent includes a polyamide (PA2),
the PA2 is a condensate of an aliphatic carboxylic acid, a hydroxy group-containing aliphatic carboxylic acid, and an aliphatic amine having <NUM> to <NUM> carbon atoms,
the aliphatic carboxylic acid includes an aliphatic dicarboxylic acid having <NUM> to <NUM> carbon atoms,
the amount of the PA2 is <NUM>% by mass or more and <NUM>% by mass or less with respect to a total mass of the flux,
regarding an endothermic amount calculated from a peak area of a differential scanning calorific curve obtained by differential scanning calorimetry, in the PA2, a ratio of an endothermic amount in a range of <NUM> or higher and <NUM> or lower is <NUM>% or more with respect to a total endothermic amount in a range of <NUM> or higher and <NUM> or lower, and
the endothermic peak of the PA2 is measured by setting a temperature raising rate to <NUM>/min and raising a temperature of about <NUM> of the PA2 from <NUM> to <NUM> under a nitrogen atmosphere.