JP7137097B2 - flux and solder paste - Google Patents

Description

The present invention relates to flux and solder paste using this flux.

Flux used for soldering chemically removes the metal surface of the object to be soldered and the metal oxide present in the solder, and has the effect of enabling the movement of metal elements at the boundary between the two. . Therefore, by performing soldering using flux, an intermetallic compound is formed between the two, and a strong bond can be obtained. Such fluxes generally contain resin components, solvents, activators, thixotropic agents, and the like.

Solder paste is a composite material obtained by mixing solder alloy powder and flux. In soldering using solder paste, first, solder paste is printed on a board, then components are mounted, and the board on which the components are mounted is heated in a heating furnace called a reflow furnace.

In the reflow furnace, main heating for melting the solder alloy powder is performed after preheating. The solder paste printed on the substrate may soften during preheating and cause heat dripping. Heat dripping 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 150° C. to 160° C. (see Patent Document 1). ).

JP 2009-154170 A

In soldering, when 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, when the preheating temperature is set to 180° C. to 190° C., for example, the flux described in Patent Document 1 cannot sufficiently suppress heating sagging.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a flux and a solder paste that can sufficiently suppress heat sagging during reflow.

In order to solve the above problems, the present invention employs the following configurations.
That is, the first aspect of the present invention contains a rosin, a solvent, a thixotropic agent, and an activator, and the thixotropic agent includes a compound and a polyamide represented by the following general formula (1), The polyamide is a condensate of one or more selected from the group consisting of aliphatic carboxylic acids and hydroxy group-containing aliphatic carboxylic acids and amines, and has an endothermic peak temperature of 120° C. or higher by differential scanning calorimetry. It is a flux that is 200° C. or less.

［式中、Ｒ^１１は、置換基を有してもよい炭素数１１～３０の炭化水素基を表す。Ｒ^０ａは、置換基を有してもよい炭素数１２～３１の炭化水素基又は水素原子を表す。Ｒ^０ｂは、置換基を有してもよい炭素数４～１２のｎ価の炭化水素基を表す。Ｒ^２１は、炭素数２～６のアルキレン基を表す。Ｒ^０ｃは、炭素数２～６のアルキレン基又は単結合を表す。ｎは、１又は２である。ｎが１のとき、ｍは、１～３の整数である。ｎが２のとき、ｍは、１である。］

[In the formula, R ¹¹ represents a hydrocarbon group having 11 to 30 carbon atoms which may have a substituent. R ^0a represents an optionally substituted hydrocarbon group having 12 to 31 carbon atoms or a hydrogen atom. R ^0b represents an optionally substituted n-valent hydrocarbon group having 4 to 12 carbon atoms. R ²¹ represents an alkylene group having 2 to 6 carbon atoms. R ^0c represents an alkylene group having 2 to 6 carbon atoms or a single bond. n is 1 or 2; When n is 1, m is an integer of 1-3. When n is 2, m is 1. ]

In the flux according to the first aspect, the polyamide is preferably a condensate of an aliphatic carboxylic acid, a hydroxy group-containing aliphatic carboxylic acid, and an amine.

Moreover, in the flux according to the first aspect, the aliphatic carboxylic acid preferably contains a dicarboxylic acid.

Moreover, in the flux according to the first aspect, the content of the compound represented by the general formula (1) is preferably 1% by mass or more and 10% by mass or less with respect to the total mass of the flux.

Moreover, in the flux according to the first aspect, the compound represented by the general formula (1) is preferably a compound represented by the following general formula (3).

［式中、Ｒ^１１及びＲ^１１’は、それぞれ独立に、置換基を有してもよい炭素数１１～３０の炭化水素基を表す。Ｒ^０ａ及びＲ^０ａ’は、それぞれ独立に、置換基を有してもよい炭素数１２～３１の炭化水素基又は水素原子を表す。Ｒ^０ｂ２は、置換基を有してもよい炭素数４～１２の炭化水素基を表す。Ｒ^２１及びＲ^２１’は、それぞれ独立に、炭素数２～６のアルキレン基を表す。Ｒ^０ｃ及びＲ^０ｃ’は、それぞれ独立に、炭素数２～６のアルキレン基又は単結合を表す。］

[In the formula, R ¹¹ and R ^11′ each independently represent a hydrocarbon group having 11 to 30 carbon atoms which may have a substituent. R ^0a and R ^0a′ each independently represent an optionally substituted hydrocarbon group having 12 to 31 carbon atoms or a hydrogen atom. R ^0b2 represents a hydrocarbon group having 4 to 12 carbon atoms which may have a substituent. R ²¹ and R ^21′ each independently represent an alkylene group having 2 to 6 carbon atoms. R ^0c and R ^0c′ each independently represent an alkylene group having 2 to 6 carbon atoms or a single bond. ]

Further, in the flux according to the first aspect, the compound represented by the general formula (3) is N,N'-bis(2-stearoamidoethyl)-sebacamide or N,N'-bis(2- Stearamidoethyl)-azelicamide is preferred.

Moreover, in the flux according to the first aspect, the rosin content is preferably 30% by mass or more and 50% by mass or less with respect to the total mass of the flux.

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 can sufficiently suppress heat sagging during reflow.

FIG. 3 is a diagram showing a DSC curve of polyamide contained in flux according to one embodiment of the present invention; 4 is a graph showing the DSC curve of the polyamide of Preparation Example 1. FIG. 4 is a graph showing the DSC curve of the polyamide of Preparation Example 2. FIG. 2 is a graph showing the relationship between the rate of endothermic amount of polyamide of Preparation Example 1 and temperature. 4 is a graph showing the relationship between the rate of endothermic amount of polyamide of Preparation Example 2 and temperature. 5 is a partially enlarged graph showing the relationship between the rate of endothermic amount of the polyamide of Preparation Example 1 and the temperature. FIG. 6 is a graph showing the relationship between the ratio of endothermic amount of polyamide of Preparation Example 2 and temperature, which is an enlarged part of FIG.

(flux)
The flux of this embodiment contains a rosin, a solvent, a thixotropic agent, and an activator.

<Rosin>
Rosins include, for example, raw rosins such as gum rosin, wood rosin and tall oil rosin, and derivatives obtained from the raw rosins.
Examples of the derivative include 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, etc.), purified products, hydrides and disproportions of said polymerized rosins, and purified products, hydrides and disproportions of said α,β unsaturated carboxylic acid-modified products, etc. .
One type of rosin may be used alone, or two or more types may be mixed and used.
As the rosin, among the above, 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 content of rosin in the flux is preferably 30% by mass or more and 50% by mass or less, more preferably 35% by mass or more and 50% by mass or less, relative to the total amount (100% by mass) of the flux. It is preferably 40% by mass or more and 50% by mass or less, more preferably.

<Solvent>
In the flux of the present embodiment, examples of solvents include water, alcohol solvents, glycol ether solvents, terpineols, and the like.
Examples of alcohol solvents include isopropyl alcohol, 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, 1,1,1-tris(hydroxymethyl)propane, 2-ethyl-2-hydroxymethyl-1,3-propanediol, 2,2′-oxybis(methylene)bis(2-ethyl-1,3 -propanediol), 2,2-bis(hydroxymethyl)-1,3-propanediol, 1,2,6-trihydroxyhexane, 1-ethynyl-1-cyclohexanol, 1,4-cyclohexanediol, 1, 4-cyclohexanedimethanol, 2,4,7,9-tetramethyl-5-decyne-4,7-diol and the like.
Examples of glycol ether solvents include diethylene glycol mono-2-ethylhexyl ether, ethylene glycol monophenyl ether, diethylene glycol monohexyl ether, diethylene glycol dibutyl ether, triethylene glycol monobutyl ether, methylpropylene triglycol, butylpropylene triglycol, triethylene glycol butyl methyl ether, tetraethylene glycol dimethyl ether and the like.
As the solvent, it is preferable to use a glycol ether solvent, and among these, it is preferable to use diethylene glycol monohexyl ether.
A solvent may be used individually by 1 type, and may be used in mixture of 2 or more types.

The content of the solvent in the flux is preferably 30% by mass or more and 60% by mass or less, more preferably 30% by mass or more and 45% by mass or less with respect to the total amount (100% by mass) of the flux. preferable.

<Thixotropic agent>
In the flux of the present embodiment, the thixotropic agent contains the compound represented by formula (1) and the specific polyamide (PA1).

<<Compound Represented by Formula (1)>>
A compound represented by the following general formula (1) is used in the flux of the present embodiment.

［式中、Ｒ^１１は、置換基を有してもよい炭素数１１～３０の炭化水素基を表す。Ｒ^０ａは、置換基を有してもよい炭素数１２～３１の炭化水素基又は水素原子を表す。Ｒ^０ｂは、置換基を有してもよい炭素数４～１２のｎ価の炭化水素基を表す。Ｒ^２１は、炭素数２～６のアルキレン基を表す。Ｒ^０ｃは、炭素数２～６のアルキレン基又は単結合を表す。ｎは、１又は２である。ｎが１のとき、ｍは、１～３の整数である。ｎが２のとき、ｍは、１である。］

[In the formula, R ¹¹ represents a hydrocarbon group having 11 to 30 carbon atoms which may have a substituent. R ^0a represents an optionally substituted hydrocarbon group having 12 to 31 carbon atoms or a hydrogen atom. R ^0b represents an optionally substituted n-valent hydrocarbon group having 4 to 12 carbon atoms. R ²¹ represents an alkylene group having 2 to 6 carbon atoms. R ^0c represents an alkylene group having 2 to 6 carbon atoms or a single bond. n is 1 or 2; When n is 1, m is an integer of 1-3. When n is 2, m is 1. ]

R ^0b is an n-valent hydrocarbon group having 4 to 12 carbon atoms, and this n-valent hydrocarbon group may have a substituent.

In the general formula (1), when n is 2, the plurality of R ¹¹ , the plurality of R ²¹ , the plurality of R ^0a , and the plurality of R ^0c may be different or the same can be anything.

The compound represented by the general formula (1) may be a compound represented by the following general formula (2) or the following general formula (3).

[Compound represented by general formula (2)]
In the compound represented by the following general formula (2), in the above general formula (1), n is 1, R ^0a is -NH-C(=O)-R ¹² , R ^0b is R ^0b1 Yes, and R ^0c is R ²² .

［式中、Ｒ^１１及びＲ^１２は、それぞれ独立に、置換基を有してもよい炭素数１１～３０の炭化水素基を表す。Ｒ^０ｂ１は、置換基を有してもよい炭素数４～１２の炭化水素基を表す。Ｒ^２１及びＲ^２２は、それぞれ独立に、炭素数２～６のアルキレン基を表す。ｍは、１～３の整数である。］

[In the formula, R ¹¹ and R ¹² each independently represent a hydrocarbon group having 11 to 30 carbon atoms which may have a substituent. R ^0b1 represents a hydrocarbon group having 4 to 12 carbon atoms which may have a substituent. R ²¹ and R ²² each independently represent an alkylene group having 2 to 6 carbon atoms. m is an integer of 1-3. ]

In general formula (2) above, R ¹¹ , R ¹² and R ^0b1 may each be a saturated hydrocarbon group or an unsaturated hydrocarbon group. Each of R ¹¹ , R ¹² and R ^0b1 is preferably a saturated hydrocarbon group.

R ¹¹ and R ¹² are each preferably a hydrocarbon group having 14 to 25 carbon atoms which may have a substituent, and a hydrocarbon group having 14 to 20 carbon atoms which may have a substituent. It is more preferable to have
When R ¹¹ or R ¹² has a substituent, examples of the substituent include —CONH ₂ , amino group (—NH ₂ ), carboxyl group and the like.

R ^0b1 is preferably an optionally substituted hydrocarbon group having 5 to 10 carbon atoms, more preferably an optionally substituted hydrocarbon group having 6 to 9 carbon atoms. .
When R ^0b1 has a substituent, examples of the substituent include —CONH ₂ , an amino group (—NH ₂ ), a carboxyl group, and the like. Among these, the substituent that R ^0b1 may have is preferably —CONH ₂ .

Each of R ²¹ and R ²² is preferably an alkylene group having 2 carbon atoms.
m is preferably one.

The compounds represented by the general formula (2) may be used singly or in combination of two or more.
The compound represented by the general formula (2) is preferably N,N-bis(2-stearoamidoethyl)-azelicamide or N,N-bis(2-stearoamidoethyl)-sebacamide.

In N,N-bis(2-stearamidoethyl)-azelicamide, R ¹¹ and R ¹² are each a linear alkyl group having 17 carbon atoms, and R ^0b1 is -( CH ₂ ) ₇ —CONH ₂ , R ²¹ and R ²² are alkylene groups having 2 carbon atoms, and m is 1;

N,N-bis(2-stearamidoethyl)-sebacamide is represented by the above general formula (2), wherein R ¹¹ and R ¹² are each a linear alkyl group having 17 carbon atoms, and R ^0b1 is -( CH ₂ ) ₈ —CONH ₂ , R ²¹ and R ²² are alkylene groups having 2 carbon atoms, and m is 1;

[Compound represented by general formula (3)]
In the compound represented by the following general formula (3), n is 2, m is 1, and R ^0b is R ^0b2 in the above general formula (1).

［式中、Ｒ^１１及びＲ^１１’は、それぞれ独立に、置換基を有してもよい炭素数１１～３０の炭化水素基を表す。Ｒ^０ａ及びＲ^０ａ’は、それぞれ独立に、置換基を有してもよい炭素数１２～３１の炭化水素基又は水素原子を表す。Ｒ^０ｂ２は、置換基を有してもよい炭素数４～１２の炭化水素基を表す。Ｒ^２１及びＲ^２１’は、それぞれ独立に、炭素数２～６のアルキレン基を表す。Ｒ^０ｃ及びＲ^０ｃ’は、それぞれ独立に、炭素数２～６のアルキレン基又は単結合を表す。］

[In the formula, R ¹¹ and R ^11′ each independently represent a hydrocarbon group having 11 to 30 carbon atoms which may have a substituent. R ^0a and R ^0a′ each independently represent an optionally substituted hydrocarbon group having 12 to 31 carbon atoms or a hydrogen atom. R ^0b2 represents a hydrocarbon group having 4 to 12 carbon atoms which may have a substituent. R ²¹ and R ^21′ each independently represent an alkylene group having 2 to 6 carbon atoms. R ^0c and R ^0c′ each independently represent an alkylene group having 2 to 6 carbon atoms or a single bond. ]

In general formula (3) above, R ¹¹ and R ^11′ may each be a saturated hydrocarbon group or an unsaturated hydrocarbon group. Each of R ¹¹ and R ^11′ is preferably a saturated hydrocarbon group.
Each of R ¹¹ and R ^11′ is preferably an optionally substituted hydrocarbon group having 14 to 25 carbon atoms, and an optionally substituted hydrocarbon group having 14 to 20 carbon atoms. is more preferable.
When R ¹¹ and R ^11′ have a substituent, examples of the substituent include —CONH ₂ , amino group (—NH ₂ ), carboxyl group and the like.

R ^0b2 may be a saturated hydrocarbon group or an unsaturated hydrocarbon group. R ^0b2 is preferably a saturated hydrocarbon group.
R ^0b2 is preferably an optionally substituted hydrocarbon group having 5 to 10 carbon atoms, more preferably an optionally substituted hydrocarbon group having 6 to 9 carbon atoms. .
When R ^0b2 has a substituent, examples of the substituent include —CONH ₂ , an amino group (—NH ₂ ), a carboxyl group, and the like.

Each of R ²¹ and R ^21′ is preferably an alkylene group having 2 carbon atoms.

Each of R ^0a and R ^0a′ may be a saturated hydrocarbon group, an unsaturated hydrocarbon group, or a hydrogen atom.
Each of R ^0a and R ^0a′ is preferably a saturated hydrocarbon group or a hydrogen atom, more preferably a hydrogen atom.

Each of R ^0c and R ^0c' is preferably a single bond.

R ^0c -R ^0a and R ^0c' -R ^0a' are preferably single bond-hydrogen atoms.

The compound represented by the general formula (3) is N,N'-bis(2-stearoamidoethyl)-azelicamide or N,N'-bis(2-stearoamidoethyl)-sebacamide. preferable.

N,N'-Bis(2-stearamidoethyl)-azelicamide is represented by the above general formula (3), wherein R ¹¹ and R ^11' are linear alkyl groups having 17 carbon atoms, and R ^0a and R ^0a′ is a hydrogen atom, R ^0b2 is —(CH ₂ ) ₇ —, R ^0c and R ^0c′ are single bonds, and R ²¹ and R ^21′ are alkylene groups having 2 carbon atoms.

N,N'-Bis(2-stearamidoethyl)-sebacamide is represented by the above general formula (3), wherein R ¹¹ and R ^11' are linear alkyl groups having 17 carbon atoms, and R ^0a and R ^0a′ is a hydrogen atom, R ^0b2 is —(CH ₂ ) ₈ —, R ^0c and R ^0c′ are single bonds, and R ²¹ and R ^21′ are alkylene groups having 2 carbon atoms.

The compounds represented by the general formula (1) may be used singly or in combination of two or more.
The compound represented by the general formula (1) is preferably a compound represented by the general formula (2) or the general formula (3), and is a compound represented by the general formula (3). is more preferable.
The content of the compound represented by the general formula (1) in the flux is preferably 1% by mass or more and 10% by mass or less with respect to the total amount (100% by mass) of the flux.

《Polyamide (PA1)》
A specific polyamide (PA1) is used in the flux of this embodiment. The specific polyamide (PA1) is a condensate of one or more selected from the group consisting of aliphatic carboxylic acids and hydroxy group-containing aliphatic carboxylic acids and amines.
The specific polyamide (PA1) is a "condensate of an aliphatic carboxylic acid and an amine", a "condensate of a hydroxy group-containing aliphatic carboxylic acid and an amine", and a "hydroxyl group-containing aliphatic carboxylic acid, Condensates of aliphatic carboxylic acids and amines”.
The endothermic peak temperature of the specific polyamide (PA1) measured by differential scanning calorimetry is 120° C. or higher and 200° C. or lower.

The aliphatic carboxylic acid from which the specific polyamide (PA1) is derived may be used alone or in combination of two or more.
Examples of the aliphatic carboxylic acid include monocarboxylic acid, dicarboxylic acid and tricarboxylic acid. The aliphatic carboxylic acid is preferably monocarboxylic acid or dicarboxylic acid, 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, 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 12-22, more preferably 14-22, and even more preferably 16-22.
Examples of the aliphatic monocarboxylic acid include lauric acid, myristic acid, pentadecyl acid, palmitic acid, margaric acid, stearic acid, nonadecanic acid, arachidic acid, and behenic acid. The aliphatic monocarboxylic acid is preferably palmitic acid or stearic acid.
The number of carbon atoms in the aliphatic dicarboxylic acid is preferably 2-20, more preferably 6-16, and even more preferably 8-14.
Examples of the aliphatic dicarboxylic acids include adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, tridecanedioic acid, tetradecanedioic acid, and pentadecanedioic acid. The aliphatic dicarboxylic acid is preferably suberic acid, azelaic acid, sebacic acid, undecanedioic acid or dodecanedioic acid, 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. .

The hydroxy group-containing aliphatic carboxylic acid from which the specific polyamide (PA1) is derived may be used alone or in combination of two or more.
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, 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 hydroxy group-containing aliphatic carboxylic acid is preferably 10-25, more preferably 15-21.
Examples of the hydroxy group-containing aliphatic carboxylic acid include hydroxypentadecanic acid, hydroxyhexadecanoic acid, hydroxyheptadecanoic acid, hydroxyoctadecanoic acid (hydroxystearic acid), hydroxyeicosanoic acid, and hydroxyheneicosanoic acid. The hydroxy group-containing aliphatic carboxylic acid is preferably hydroxystearic acid, more preferably 12-hydroxystearic acid.

The amines from which the specific polyamide (PA1) is derived may be used singly or in combination of two or more.
Examples of the amine include aliphatic amines and aromatic amines. Preferably, the amine is an aliphatic amine.
Examples of the amine include monoamine, diamine, triamine, and tetraamine. Preferably, the amine is a diamine.
The hydrocarbon group of the aliphatic amine may be linear, branched or cyclic. The hydrocarbon group is preferably linear or branched, more preferably linear. The number of carbon atoms in the aliphatic amine is preferably 3-10, more preferably 4-8.
The hydrocarbon group may be a saturated hydrocarbon group or an unsaturated hydrocarbon group. The hydrocarbon group is preferably a saturated hydrocarbon group.
Examples of the amine include ethylenediamine, 1,3-propanediamine, 1,4-butanediamine, hexamethylenediamine, metaxylenediamine, tolylenediamine, paraxylenediamine, phenylenediamine, isophoronediamine, and 1,10-decane. diamine, 1,12-dodecanediamine, 4,4-diaminodicyclohexylmethane, 4,4-diaminodiphenylmethane, butane-1,1,4,4-tetramine, pyrimidine-2,4,5,6-tetraamine and the like. be done. Preferably, the amine is hexamethylenediamine.

The endothermic peak temperature of polyamide is measured by DSC (Differential Scanning Calorimetry).
As a specific method for measuring the endothermic peak, about 10 mg of polyamide is heated from 25° C. to 350° C. at a rate of 20° C./min in a nitrogen atmosphere. DSC7020 (manufactured by Hitachi High-Tech Science) can be used as a measuring instrument. As used herein, the endothermic peak temperature means the peak top temperature.

The specific polyamide (PA1) used in the flux of the present embodiment has one or more endothermic peaks in the temperature range of 120°C or higher and 200°C or lower.
When the number of endothermic peaks is one, the temperature of the endothermic peak is preferably 150° C. or higher and 200° C. or lower, more preferably 160° C. or higher and 200° C. or lower, and 170° C. or higher and 200° C. or lower. is more preferable, and 180° C. or more and 200° C. or less is particularly preferable.
When the number of endothermic peaks is 2 or more, the polyamide (PA1) may have, for example, the lowest endothermic peak at 120°C or higher and 200°C or lower, or the highest endothermic peak at 120°C. It may be in the range of 120° C. or higher and 200° C. or lower, or all the endothermic peaks may be in the range of 120° C. or higher and 200° C. or lower.
The temperature of the highest endothermic peak is preferably 150°C or higher and 200°C or lower, more preferably 160°C or higher and 200°C or lower, even more preferably 170°C or higher and 200°C or lower, and 180°C. It is particularly preferable that the temperature is above 200°C and below.

DSC measurement of the polyamide (PA1) shows that the ratio of the endothermic amount in the range of 160°C to 200°C is preferably 30% or more of the total endothermic amount in the range of 50°C to 200°C. It is more preferably 40% or more, and even more preferably 45% or more.
When the ratio of heat absorption in the range of 160° C. to 200° C. measured by DSC of the polyamide (PA1) is equal to or higher than the lower limit, heat sagging during reflow can be sufficiently suppressed. In particular, even when the preheating temperature is raised, for example, 190° C. or higher, or even 200° C. or higher, heating droop can be suppressed.
In this specification, the endothermic amount of polyamide can be calculated from the peak area of the DSC curve of polyamide.

DSC measurement of the polyamide (PA1) shows that the ratio of the endothermic amount in the range of 50°C to 150°C is preferably 80% or less of the total endothermic amount in the range of 50°C to 200°C. It is more preferably 60% or less, even more preferably 50% or less.
DSC measurement of the polyamide (PA1) shows that the ratio of the endothermic amount in the range of 50° C. or higher and 180° C. or lower is preferably 95% or less of the total endothermic amount in the range of 50° C. or higher and 200° C. or lower. It is more preferably 90% or less, even more preferably 85% or less.

The specific polyamide (PA1) contained in the flux of the present embodiment is a condensate of an aliphatic carboxylic acid, a hydroxy group-containing monocarboxylic acid, and an amine, from the viewpoint of further enhancing the ability to suppress heat sagging. preferable.
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 comprises an aliphatic dicarboxylic acid having 8 to 14 carbon atoms, a hydroxy group-containing aliphatic monocarboxylic acid having 15 to 21 carbon atoms, and More preferably, it is a condensate with an aliphatic diamine in which is 4-8.
Among these, the polyamide (PA1) is particularly preferably a condensate of one or more selected from the group consisting of sebacic acid and dodecanedioic acid, 12-hydroxystearic acid, and hexamethylenediamine.
Polyamide (PA1) is one or more selected from the group consisting of sebacic acid and dodecanedioic acid, one or more selected from the group consisting of palmitic acid and stearic acid, 12-hydroxystearic acid, and hexamethylene. Condensates with diamines may also be used.

When the polyamide (PA1) is a condensation product 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, X mol of aliphatic dicarboxylic acid, Y mol of hydroxy group-containing aliphatic monocarboxylic acid, and Z mol of aliphatic diamine, which are used as raw materials for the polyamide (PA1).
The total number of moles of amino groups in the compound contained in the raw material 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 material is equal to the total number of moles of carboxyl groups. preferably less than Specifically, it is preferable to satisfy 2Z≦2X+Y.
The molar ratio relationship between the raw materials is preferably 0.2Y≦X≦2Y, more preferably 0.4Y≦X≦1.5Y.
The molar ratio relationship between the raw materials is preferably 0.5Y≦Z≦2Y, more preferably 0.8Y≦Z≦1.8Y.

The content of the polyamide (PA1) in the flux is preferably 1% by mass or more and 15% by mass or less, more preferably 2% by mass or more and 10% by mass or less with respect to the total amount (100% by mass) of the flux. It is preferably 3% by mass or more and 6% by mass or less.
The ratio of the compound represented by the general formula (1) to the total mass (100% by mass) of the compound represented by the general formula (1) and the specific polyamide (PA1) is 10% by mass or more and 90% by mass. % or less, more preferably 15 mass % or more and 75 mass % or less.

《Other thixotropic agents》
The thixotropic agent may contain other thixotropic agent in addition to the compound represented by the general formula (1) and the polyamide (PA1).
Other thixotropic agents include, for example, amide-based thixotropic agents, wax-based thixotropic agents, sorbitol-based thixotropic agents, and the like.
Other thixotropic agents may be used singly or in combination of two or more.

Amide-based thixotropic agents other than the above include, for example, monoamides, bisamides, and other polyamides.
Examples of monoamides include 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- Toluenemethanamide, aromatic amide, hexamethylene hydroxystearic acid amide, substituted amide, methylolstearic acid amide, methylolamide, fatty acid ester amide and the like.
Examples of bisamides include methylenebisstearic acid amide, ethylenebislauric acid amide, ethylenebishydroxy fatty acid (C6-C24 fatty acid) amide, ethylenebisstearic acid amide, ethylenebishydroxystearic acid amide, saturated fatty acid bisamide, methylenebis Oleic acid amide, unsaturated fatty acid bisamide, m-xylylenebisstearic acid amide, aromatic bisamide and the like.
Other polyamides include saturated fatty acid polyamides, unsaturated fatty acid polyamides, aromatic polyamides, 1,2,3-propanetricarboxylic acid tris(2-methylcyclohexylamide), cyclic amide oligomers, non-cyclic amide oligomers, and the like.

The cyclic amide oligomer includes an amide oligomer obtained by cyclic polycondensation of dicarboxylic acid and diamine, an amide oligomer obtained by cyclic polycondensation of tricarboxylic acid and diamine, an amide oligomer obtained by cyclic polycondensation of dicarboxylic acid and triamine, and tricarboxylic acid. amide oligomer obtained by cyclic polycondensation of and triamine, amide oligomer obtained by cyclic polycondensation of dicarboxylic acid or tricarboxylic acid and diamine, amide oligomer obtained by cyclic polycondensation of dicarboxylic acid or tricarboxylic acid and triamine, dicarboxylic acid and diamine and cyclic polycondensation of triamine, amide oligomers of cyclic polycondensation of tricarboxylic acid and diamine and triamine, amide oligomers of cyclic polycondensation of dicarboxylic acid and tricarboxylic acid and diamine and triamine, and the like. .

When the non-cyclic amide oligomer is an amide oligomer obtained by acyclic polycondensation of a monocarboxylic acid and a diamine and/or triamine, an amide obtained by acyclic polycondensation of a dicarboxylic acid and/or tricarboxylic acid and a monoamine For example, it may be an oligomer. In the case of an amide oligomer containing monocarboxylic acid or monoamine, the monocarboxylic acid or monoamine functions as terminal molecules, resulting in a non-cyclic amide oligomer with a reduced molecular weight. When the non-cyclic amide oligomer is an amide compound obtained by non-cyclic polycondensation of dicarboxylic acid and/or tricarboxylic acid and diamine and/or triamine, it becomes a non-cyclic high-molecular-weight amide polymer. Furthermore, non-cyclic amide oligomers include amide oligomers in which a monocarboxylic acid and a monoamine are condensed acyclically.

The total content of the amide-based thixotropic agent in the flux is preferably 3% by mass or more and 30% by mass or less, and 4% by mass or more and 20% by mass or less with respect to the total amount (100% by mass) of the flux. is more preferably 5.5% by mass or more and 14.5% by mass or less.

Examples of wax-based thixotropic agents include ester compounds, and specific examples include hydrogenated castor oil.
The content of the wax-based thixotropic agent in the flux is preferably 0% by mass or more and 10% by mass or less, and is 0% by mass or more and 5% by mass or less with respect to the total amount (100% by mass) of the flux. is more preferable, and more preferably 0% by mass or more and 3% by mass or less.

Examples of sorbitol-based thixotropic agents include dibenzylidene-D-sorbitol, bis(4-methylbenzylidene)-D-sorbitol, (D-) sorbitol, monobenzylidene (-D-) sorbitol, and mono(4-methylbenzylidene). -(D-) sorbitol and the like.
The content of the sorbitol-based thixotropic agent in the flux is preferably 0% by mass or more and 5.0% by mass or less with respect to the total amount (100% by mass) of the flux, and 0% by mass or more and 3.5% by mass. % or less is more preferable.

The total content of the thixotropic agent in the flux is preferably 2% by mass or more and 30% by mass or less with respect to the total amount (100% by mass) of the flux, and more preferably 4% by mass or more and 20% by mass or less. It is preferably 5% by mass or more and 15% by mass or less.
The content of other thixotropic agents in the flux is preferably 0% by mass or more and 10% by mass or less, more preferably 0% by mass or more and 5% by mass or less, relative to the total amount (100% by mass) of the flux. preferable.
The ratio of the other thixotropic agent to the total mass (100% by mass) of the thixotropic agent in the flux is preferably 0% by mass or more and 50% by mass or less, and is 0% by mass or more and 30% by mass or less. is more preferable, and more preferably 0% by mass or more and 20% by mass or less.

<Activator>
Examples of activators include organic acids, halogen-based activators, and amines.

Organic acid:
Examples of organic acids include 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, p-hydroxyphenylacetic acid, picolinic acid, phenylsuccinic acid, phthalic acid, fumaric acid, maleic acid, malonic acid, lauric acid, benzoic acid, tartaric acid, tris isocyanurate (2-carboxyethyl), glycine, 1,3-cyclohexanedicarboxylic acid, 2,2-bis(hydroxymethyl)propionic acid, 2,2-bis(hydroxymethyl)butanoic acid, 2,3-dihydroxybenzoic acid, 2 , 4-diethylglutaric acid, 2-quinolinecarboxylic acid, 3-hydroxybenzoic acid, propionic acid, malic acid, p-anisic acid, stearic acid, 12-hydroxystearic acid, oleic acid, linoleic acid, linolenic acid, palmitic acid , pimelic acid, dimer acid, trimer acid, hydrogenated dimer acid which is hydrogenated dimer acid, and hydrogenated trimer acid which is hydrogenated trimer acid.

An organic acid may be used individually by 1 type, and may mix and use 2 or more types.
Preferably, the organic acid is 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 is selected from the group consisting of glutaric acid, adipic acid and azelaic acid. It is more preferable that it is one or more kinds.

The total content of organic acids in the flux is preferably 3% by mass or more and 10% by mass or less, more preferably 5% by mass or more and 8% by mass or less, relative to the total amount (100% by mass) of the flux. preferable.

Halogen activator:
Halogenated activators include, for example, halogenated aliphatic compounds, amine hydrohalides, and the like.
Halogen-based activators may be used singly or in combination of two or more.

Halogenated aliphatic compounds 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, 2,3-dibromo-1,4-butanediol, trans-2,3-dibromo-2-butene-1, 4-diol and the like.
Amine hydrohalides are compounds obtained by reacting amines with hydrogen halides. Examples of amines include ethylamine, diethylamine, triethylamine, ethylenediamine, 1,3-diphenylguanidine, and 1,3-di-o-tolylguanidine. , 1-o-tolylbiguanide and the like, and hydrogen halides include hydrides of chlorine, bromine and iodine.

The flux of this embodiment preferably contains a halogen-based activator.
The flux of this embodiment preferably contains a halogenated aliphatic compound.
Preferably, the halogenated aliphatic compound is trans-2,3-dibromo-2-butene-1,4-diol.

The total content of the halogen-based activator in the flux is preferably 0% by mass or more and 5% by mass or less with respect to the total amount (100% by mass) of the flux.

Amine:
Amines include ethylamine, triethylamine, ethylenediamine, triethylenetetramine, 2-methylimidazole, 2-undecylimidazole, 2-heptadecylimidazole, 1,2-dimethylimidazole, 2-ethyl-4-methylimidazole, 2-phenyl imidazole, 2-phenyl-4-methylimidazole, 1-benzyl-2-methylimidazole, 1-benzyl-2-phenylimidazole, 1-cyanoethyl-2-methylimidazole, 1-cyanoethyl-2-undecylimidazole, 1- Cyanoethyl-2-ethyl-4-methylimidazole, 1-cyanoethyl-2-phenylimidazole, 1-cyanoethyl-2-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 isocyanurate, 2-phenylimidazole isocyanurate, 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-phenylimidazoline, 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-methyl benzimidazole, 2-octylbenzimidazole, 2-pentylbenzimidazole, 2-(1-ethylpentyl)benzimidazole, 2-nonylbenzimidazole, 2-(4-thiazolyl)benzimidazole, benzimidazole, 2-(2'-hydroxy-5'-methylphenyl)benzotriazole,2-(2'-hydroxy-3'-tert-butyl-5'-methylphenyl)-5-chlorobe zotriazole, 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-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'-dicarboxy ethyl)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.
Amines may be used singly or in combination of two or more.
The amine is preferably one or more selected from the group consisting of 2-phenylimidazole and 2-phenyl-4-methylimidazole.

The content of amine in the flux is preferably more than 0% by mass and 20% by mass or less, and more than 0% by mass and 10% by mass or less with respect to the total amount (100% by mass) of the flux. More preferably, it is more than 0% by mass and 3% by mass or less, and particularly preferably more than 0% by mass and 1% by mass or less.

<Other ingredients>
Moreover, the flux of the present embodiment may further contain other components in addition to the rosin, solvent, thixotropic agent and activator.
Other components include, for example, surfactants, silane coupling agents, and colorants.

Examples of surfactants include nonionic surfactants and weak cationic surfactants.
Examples of nonionic surfactants include polyethylene glycol, polyethylene glycol-polypropylene glycol copolymers, aliphatic alcohol polyoxyethylene adducts, aromatic alcohol polyoxyethylene adducts, polyhydric alcohol polyoxyethylene adducts, and the like. mentioned.
Examples of weak cationic surfactants include terminal diamine polyethylene glycol, terminal diamine polyethylene glycol-polypropylene glycol copolymer, aliphatic amine polyoxyethylene adduct, aromatic amine polyoxyethylene adduct, polyvalent amine polyoxy Ethylene adducts can be mentioned.

Examples of surfactants other than the above-exemplified surfactants include polyoxyalkylene acetylene glycols, polyoxyalkylene glyceryl ethers, polyoxyalkylene alkyl ethers, polyoxyalkylene esters, polyoxyalkylene alkylamines, polyoxyalkylene alkyl and amides.

Moreover, an antioxidant may be used in the flux of the present embodiment for the purpose of suppressing oxidation of the solder alloy powder. As the antioxidant, a hindered phenolic antioxidant such as 2,2'-methylenebis[6-(1-methylcyclohexyl)-p-cresol] may be used.

Additives such as a matting agent and an antifoaming 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 the general formula (1) and the specific polyamide as the thixotropic agent, so that heat sag during reflow is sufficiently reduced. can be suppressed to In particular, even when the preheating temperature is raised, for example, 190° C. or higher, or even 200° C. or higher, heat sagging can be suppressed by applying this combination.

(solder paste)
The solder paste of this embodiment contains solder alloy powder and the flux described above.

The solder alloy powder is a solder powder of single Sn, Sn--Ag-based, Sn--Cu-based, Sn--Ag--Cu-based, Sn--Bi-based, Sn--In-based, etc., or alloys thereof containing Sb , Bi, In, Cu, Zn, As, Ag, Cd, Fe, Ni, Co, Au, Ge, P or the like may be added to the solder alloy powder.
The solder alloy powder is a Sn--Pb system or a solder alloy obtained by adding Sb, Bi, In, Cu, Zn, As, Ag, Cd, Fe, Ni, Co, Au, Ge, P, etc. to the Sn--Pb system. powder.
The solder alloy powder is preferably a Pb-free solder.

Flux content:
The flux content in the solder paste is preferably 5 to 30% by mass, more preferably 5 to 15% by mass, based on the total mass of the solder paste.

Since the solder paste of the present embodiment contains the above-described flux, heat sagging is sufficiently suppressed.

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

<Rosin>
Rosins used in the flux of such other embodiments include those described above.
One type of rosin may be used alone, or two or more types may be mixed and used.
The content of rosin in the flux of another embodiment is preferably 30% by mass or more and 50% by mass or less, more preferably 30% by mass or more and 40% by mass or less with respect to the total amount (100% by mass) of the flux. It is more preferable to have

<Solvent>
Solvents used in the flux of such other embodiments include those described above.
A solvent may be used individually by 1 type, and may be used in mixture of 2 or more types.
The content of the solvent in the flux of such another embodiment is preferably 30% by mass or more and 60% by mass or less, and 35% by mass or more and 55% by mass or less with respect to the total amount (100% by mass) of the flux. is more preferable.

<Specific thixotropic agents>
Such other embodiment fluxes contain polyamide (PA2) as a specific thixotropic agent.
Polyamide (PA2) is a condensation product of one or more selected from the group consisting of aliphatic carboxylic acids and hydroxy group-containing aliphatic carboxylic acids and aliphatic amines having 3 to 10 carbon atoms.
That is, the polyamide (PA2) is obtained by specifying an aliphatic amine having 3 to 10 carbon atoms as the amine which is the raw material of the polyamide (PA1).

The aliphatic carboxylic acid from which the polyamide (PA2) is derived may be used alone or in combination of two or more.
Examples of the aliphatic carboxylic acid include monocarboxylic acid, dicarboxylic acid and tricarboxylic acid. The aliphatic carboxylic acid is preferably monocarboxylic acid or dicarboxylic acid, 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, 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 12-22, more preferably 14-22, and even more preferably 16-22.
Examples of the aliphatic monocarboxylic acid include lauric acid, myristic acid, pentadecyl acid, palmitic acid, margaric acid, stearic acid, nonadecanic acid, arachidic acid, and behenic acid. The aliphatic monocarboxylic acid is preferably palmitic acid or stearic acid.
The number of carbon atoms in the aliphatic dicarboxylic acid is preferably 11-20, more preferably 12-18, even more preferably 12-16.
Examples of the aliphatic dicarboxylic acid include dodecanedioic acid, tridecanedioic acid, tetradecanedioic acid, and pentadecanedioic acid. Preferably, the aliphatic dicarboxylic acid is 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.

The hydroxy group-containing aliphatic carboxylic acid from which the polyamide (PA2) is derived may be used alone or in combination of two or more.
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, 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 hydroxy group-containing aliphatic carboxylic acid is preferably 10-25, more preferably 15-21.
Examples of the hydroxy group-containing aliphatic carboxylic acid include hydroxypentadecanic acid, hydroxyhexadecanoic acid, hydroxyheptadecanoic acid, hydroxyoctadecanoic acid (hydroxystearic acid), hydroxyeicosanoic acid, and hydroxyheneicosanoic acid. The hydroxy group-containing aliphatic carboxylic acid is preferably hydroxystearic acid, more preferably 12-hydroxystearic acid.

Amines from which polyamide (PA2) is derived are aliphatic amines having 3 to 10 carbon atoms.
The amines from which the polyamide (PA2) is derived may be used singly or in combination of two or more.
Examples of the aliphatic amines include monoamines, diamines, triamines and tetraamines. Preferably, the amine is a diamine.
The hydrocarbon group of the aliphatic amine may be linear, branched or cyclic. The hydrocarbon group is preferably linear or branched, more preferably linear. The number of carbon atoms in the aliphatic amine is preferably 4-8.
The hydrocarbon group may be a saturated hydrocarbon group or an unsaturated hydrocarbon group. The hydrocarbon group is preferably a saturated hydrocarbon group.
Examples of the aliphatic amine include 1,3-propanediamine, 1,4-butanediamine, hexamethylenediamine, butane-1,1,4,4-tetraamine and the like. Preferably, the aliphatic amine is hexamethylenediamine.

Polyamide (PA2) is preferably a condensate of an aliphatic carboxylic acid, a hydroxy group-containing monocarboxylic acid, and an aliphatic diamine having 3 to 10 carbon atoms.
Polyamide (PA2) is a condensation of an aliphatic dicarboxylic acid having 12 to 20 carbon atoms, a hydroxy group-containing monocarboxylic acid having 15 to 21 carbon atoms, and an aliphatic diamine having 4 to 8 carbon atoms. It is more preferable to be a thing.
Among these, the polyamide (PA2) is more preferably a condensate of dodecanedioic acid, 12-hydroxystearic acid and hexamethylenediamine.
Polyamide (PA2) may be a condensate of dodecanedioic acid, one or more selected from the group consisting of palmitic acid and stearic acid, 12-hydroxystearic acid, and hexamethylenediamine.

Polyamide (PA2) has the following properties.
DSC measurement of the polyamide (PA2) shows that the endothermic amount in the range of 50°C to 190°C is preferably 90% or more, more preferably 90% or more, of the total endothermic amount in the range of 50°C to 200°C. It is 92% or more, more preferably 94% or more.
DSC measurement of the polyamide (PA2) shows that the heat absorption in the range of 50°C to 195°C is preferably 96% or more, more preferably 96% or more, of the total heat absorption in the range of 50°C to 200°C. It is 98% or more, more preferably 99% or more.

DSC measurement of the polyamide (PA2) shows that the ratio of the endothermic amount in the range of 160°C to 200°C is preferably 30% or more of the total endothermic amount in the range of 50°C to 200°C. It is more preferably 40% or more, and even more preferably 45% or more.
When the ratio of heat absorption in the range of 160° C. to 200° C. measured by DSC of the polyamide (PA2) is equal to or higher than the lower limit, heat sagging during reflow can be sufficiently suppressed. In particular, even when the preheating temperature is raised, for example, 190° C. or higher, or even 200° C. or higher, heating droop can be suppressed.
In this specification, the endothermic amount of polyamide can be calculated from the peak area of the DSC curve of polyamide.

DSC measurement of the polyamide (PA2) shows that the ratio of the endothermic amount in the range of 50°C to 150°C is preferably 80% or less of the total endothermic amount in the range of 50°C to 200°C. It is more preferably 60% or less, even more preferably 50% or less.
DSC measurement of the polyamide (PA2) shows that the ratio of the endothermic amount in the range of 50°C or higher and 180°C or lower is preferably 95% or less of the total endothermic amount in the range of 50°C or higher and 200°C or lower. It is more preferably 90% or less, even more preferably 85% or less.

Polyamide (PA2) has one or more endothermic peaks in the temperature range of 120° C. or higher and 200° C. or lower as measured by DSC.
When the number of endothermic peaks is one, the temperature of the endothermic peak is preferably 150° C. or higher and 200° C. or lower, more preferably 160° C. or higher and 200° C. or lower, and 170° C. or higher and 200° C. or lower. is more preferable, and 180° C. or more and 200° C. or less is particularly preferable.
When the number of endothermic peaks is 2 or more, the polyamide (PA2) may have, for example, the lowest endothermic peak at 120°C or higher and 200°C or lower, or the highest endothermic peak at 120°C. It may be in the range of 120° C. or higher and 200° C. or lower, or all the endothermic peaks may be in the range of 120° C. or higher and 200° C. or lower.
The temperature of the highest endothermic peak is preferably 150°C or higher and 200°C or lower, more preferably 160°C or higher and 200°C or lower, even more preferably 170°C or higher and 200°C or lower, and 180°C. It is particularly preferable that the temperature is above 200°C and below.

The polyamide (PA2) preferably has three endothermic peaks in the DSC curve, consisting of a first endothermic peak, a second endothermic peak and a third endothermic peak.
The temperature of the first endothermic peak is preferably less than 150°C, more preferably 120°C or higher and 140°C or lower, even more preferably 125°C or higher and 135°C or lower, and 125°C or higher and 130°C or lower. is particularly preferred.
The temperature of the second endothermic peak is preferably 150°C or higher, more preferably 155°C or higher and 175°C or lower, even more preferably 160°C or higher and 170°C or lower, and 162°C or higher and 167°C or lower. is particularly preferred.
The temperature of the third endothermic peak is preferably 150°C or higher, more preferably 180°C or higher and 196°C or lower, even more preferably 183°C or higher and 195°C or lower, and 185°C or higher and 193°C or lower. is particularly preferred.

When the polyamide (PA2) is a condensation product 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, X mol of the aliphatic dicarboxylic acid, Y mol of the hydroxy group-containing aliphatic monocarboxylic acid, and Z mol of the aliphatic diamine are used as raw materials for the polyamide (PA2).
The total number of moles of amino groups in the compound contained in the raw material 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 material is equal to the total number of moles of carboxyl groups. preferably less than Specifically, it is preferable to satisfy 2Z≦2X+Y.
The molar ratio relationship between the raw materials is preferably 0.2Y≦X≦2Y, more preferably 0.4Y≦X≦1.5Y.
The molar ratio relationship between the raw materials is preferably 0.5Y≦Z≦2Y, more preferably 0.8Y≦Z≦1.8Y.

The content of the polyamide (PA2) is preferably 0.5% by mass or more and 20% by mass or less, more preferably 1% by mass or more and 20% by mass or less, relative to the total amount (100% by mass) of the flux. , more preferably 2% to 20% by mass, particularly preferably 5% to 20% by mass, and most preferably 15% to 20% by mass.

<Other ingredients>
Also, the flux of such other embodiments may contain other ingredients in addition to the rosin, solvent, certain thixotropic agents and activators.
Other components include, for example, thixotropic agents other than polyamide (PA2), surfactants, silane coupling agents, and colorants.
Other thixotropic agents include, for example, amide-based thixotropic agents other than polyamide (PA2), wax-based thixotropic agents, sorbitol-based thixotropic agents, and the like.
Other thixotropic agents may be used singly or in combination of two or more.

The total content of the amide-based thixotropic agent in the flux is preferably 0.5% by mass or more and 30% by mass or less with respect to the total amount (100% by mass) of the flux, and is 0.5% by mass or more. It is more preferably 20% by mass or less, and even more preferably 5% by mass or more and 20% by mass or less.

The content of the wax-based thixotropic agent in the flux is preferably 0% by mass or more and 10% by mass or less, and is 2% by mass or more and 7% by mass or less with respect to the total amount (100% by mass) of the flux. is more preferable, and more preferably 3% by mass or more and 6% by mass or less.
The content of the wax-based thixotropic agent in the flux is preferably 12% by mass or more and 100% by mass or less with respect to the total amount (100% by mass) of the amide-based thixotropic agent and the wax-based thixotropic agent, and is 18% by mass. % or more and 100 mass % or less, more preferably 33 mass % or more and 100 mass % or less, and particularly preferably 60 mass % or more and 100 mass % or less.

The content of the sorbitol-based thixotropic agent in the flux is preferably 0% by mass or more and 5.0% by mass or less with respect to the total amount (100% by mass) of the flux, and 0% by mass or more and 3.5% by mass. % or less is more preferable.

In the flux of such another embodiment, the polyamide (PA2) contained in the flux melts at 190° C. and 195° C. and has sufficiently high fluidity, so voids can be sufficiently suppressed.
Moreover, in the flux of such another embodiment, the polyamide (PA2) contained in the flux does not partially melt at 150° C. and 180° C., so heat sagging can be sufficiently suppressed. In particular, even when the preheating temperature is raised, for example, 190° C. or higher, or even 200° C. or higher, heating droop can be suppressed.

(solder paste)
Other embodiments of solder pastes contain solder alloy powders and fluxes of such other embodiments.

The solder alloy powder is a solder powder of single Sn, Sn--Ag-based, Sn--Cu-based, Sn--Ag--Cu-based, Sn--Bi-based, Sn--In-based, etc., or alloys thereof containing Sb , Bi, In, Cu, Zn, As, Ag, Cd, Fe, Ni, Co, Au, Ge, P or the like may be added to the solder alloy powder.
The solder alloy powder is a Sn--Pb system or a solder alloy obtained by adding Sb, Bi, In, Cu, Zn, As, Ag, Cd, Fe, Ni, Co, Au, Ge, P, etc. to the Sn--Pb system. powder.
The solder alloy powder is preferably a Pb-free solder.

Flux content:
The flux content in the solder paste of another embodiment is preferably 5 to 30% by mass, more preferably 5 to 15% by mass, based on the total mass of the solder paste.

Since the solder paste of the present embodiment contains the flux of the other embodiment, heat sagging is sufficiently suppressed. Moreover, generation of voids is sufficiently suppressed.

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

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

<Thixotropic agent>
As thixotropic agents, thixotropic agent A, thixotropic agent B, bisamide and polyamide were used.
Thixotropic agent A: N,N'-bis(2-stearoamidoethyl)-azelicamide The thixotropic agent A is a compound represented by the following chemical formula (3-1).

Thixotropic agent B: N,N'-bis(2-stearoamidoethyl)-sebacamide The thixotropic agent B is a compound represented by the following chemical formula (3-2).

As the polyamide, one obtained by the following method (polyamide (PA1)) was used.
(Polyamide Preparation Example 1)
12-Hydroxystearic acid and dodecanedioic acid were added and heated to about 100° C., then hexamethylenediamine was added and heated to about 220° C. and held for 3 hours to obtain a polyamide of Preparation Example 1.
Let X mol of dodecanedioic acid, Y mol of 12-hydroxystearic acid, and Z mol of hexamethylenediamine be used as raw materials. The number of moles of raw materials satisfied the relationship of 2Z=2X+Y.
(Polyamide Preparation Example 2)
12-Hydroxystearic acid and sebacic acid were added and heated to about 100°C, then hexamethylenediamine was added and heated to about 220°C and maintained for 3 hours to obtain a polyamide of Preparation Example 2.
X mol of sebacic acid, Y mol of 12-hydroxystearic acid, and Z mol of hexamethylenediamine used as raw materials. The number of moles of raw materials satisfied the relationship of 2Z=2X+Y.

The endothermic peak temperature of the obtained polyamide was measured by DSC (Differential Scanning Calorimetry).
As a more specific method for measuring the endothermic peak, about 10 mg of polyamide was heated from 25° C. to 350° C. under a nitrogen atmosphere at a temperature elevation rate of 20° C./min. DSC7020 (manufactured by Hitachi High-Tech Science) was used as a measuring instrument. The measurement results are shown in FIG. FIG. 1 is a diagram showing the DSC curve of the obtained polyamide preparation example 1. FIG. The peak top temperature was defined as the endothermic peak temperature.
The resulting polyamide had a peak top temperature of all endothermic peaks of 120° C. or higher and 200° C. or lower.

Ethylene bis stearamide (trade name: Slipax E) was used as the bisamide.

<Activator>
Adipic acid, azelaic acid, and glutaric acid were used as organic acids.
Trans-2,3-dibromo-2-butene-1,4-diol was used as the halogen-based activator.
2-phenylimidazole and 2-phenyl-4-methylimidazole were used as amines.

<Solvent>
Diethylene glycol monohexyl ether was used as the solvent.

<Preparation of Flux>
(Examples 1 to 15, Comparative Examples 1 to 4)
Fluxes of Examples and Comparative Examples were prepared according to the compositions shown in Tables 1 to 3 below.
The content of each component in Tables 1 to 3 is mass % when the total mass of the flux is 100 mass %, and a blank means 0 mass %.

<Preparation of Solder Paste>
A solder paste was prepared by mixing the flux of each example and the following solder alloy powder.
As the solder alloy powder, a Sn--Ag--Cu solder alloy containing 3.0% by mass of Ag, 0.5% by mass of Cu, and the balance of Sn was used.
The solder alloy powder used had a size (particle size distribution) satisfying symbol 4 in the powder size classification (Table 2) in JIS Z 3284-1:2014.
All of the prepared solder pastes contained 11% by mass of flux and 89% by mass of solder alloy powder.

<Evaluation of print droop>
The drooping of the solder paste during printing was evaluated. The results are shown in Tables 1-3.

Measuring method:
The resulting solder paste was evaluated for printing sagging according to the method described in JIS Z 3284-3:2014, "Test for sagging during printing." Solder paste was printed using a metal mask having patterned holes shown in FIG. The test boards were evaluated for the minimum spacing at which all of the printed solder paste did not come together.

<Evaluation of heating sauce>
A solder paste obtained by mixing a flux and a solder alloy powder was evaluated for drooping during heating. The results are shown in Tables 1-3.

Measuring method:
Heat sagging was evaluated for the obtained solder paste according to the method described in JIS Z 3284-3:2014, "Test for sagging during heating". First, solder paste was printed using a metal mask having patterned holes shown in I (hole size 3.0×0.7) in FIG. rice field. The obtained test plate was heated to 200° C. in an air circulation heating furnace. After heating, the test board was evaluated for the minimum spacing at which all of the printed solder paste did not come together.

<Evaluation of Heat Sagging Suppression Ability>
criterion:
Good: The evaluation value of heat smear is 0.5 mm or less, or the difference between the evaluation value of heat smear and the evaluation value of print smear is 0.2 mm or less.
x: The evaluation value of heat smear is 0.6 mm or more, or the difference between the evaluation value of heat smear and the evaluation value of print smear is 0.3 mm or more.

As shown in Example 1, acrylic acid-modified hydrogenated rosin is included as rosin, thixotropic agent A and polyamide (Preparation Example 1) are included as thixotropic agent, and adipic acid, azelaic acid, trans-2,3- Flux containing dibromo-2-butene-1,4-diol, 2-phenylimidazole and 2-phenyl-4-methylimidazole and containing diethylene glycol monohexyl ether as a solvent should have sufficient ability to suppress heat sagging. was made.

As shown in Example 2, the type of rosin was changed to include polymerized rosin, thixotropic agent A and polyamide (Preparation Example 1) were included as thixotropic agents, and adipic acid, azelaic acid, trans-2, trans-2, A flux containing 3-dibromo-2-butene-1,4-diol, 2-phenylimidazole and 2-phenyl-4-methylimidazole and containing diethylene glycol monohexyl ether as a solvent has a sufficient ability to suppress heat sagging. We were able to.

As shown in Example 3, the type of rosin was changed to include hydrogenated rosin, thixotropic agent A and polyamide (Preparation Example 1) were included as thixotropic agents, and adipic acid, azelaic acid and trans-2 were used as active agents. ,3-dibromo-2-butene-1,4-diol, 2-phenylimidazole and 2-phenyl-4-methylimidazole, and diethylene glycol monohexyl ether as a solvent have sufficient heat sag suppression ability. I was able to

As shown in Example 4, acrylic acid-modified hydrogenated rosin is included as rosin, the content of thixotropic agent A is reduced, polyamide (Preparation Example 1) is included, and activators are adipic acid, azelaic acid, trans-2, A flux containing 3-dibromo-2-butene-1,4-diol, 2-phenylimidazole and 2-phenyl-4-methylimidazole and containing diethylene glycol monohexyl ether as a solvent has a sufficient ability to suppress heat sagging. We were able to.

As shown in Example 5, acrylic acid-modified hydrogenated rosin is contained as rosin, the content of thixotropic agent A is increased, polyamide (Preparation Example 1) is contained, and adipic acid, azelaic acid, trans-2, trans-2, A flux containing 3-dibromo-2-butene-1,4-diol, 2-phenylimidazole and 2-phenyl-4-methylimidazole and containing diethylene glycol monohexyl ether as a solvent has a sufficient ability to suppress heat sagging. We were able to.

As shown in Example 6, acrylic acid-modified hydrogenated rosin is included as rosin, the type of thixotropic agent is changed to include thixotropic agent B and polyamide (Preparation Example 1), and adipic acid, azelaic acid, and adipic acid are used as activators. A flux containing trans-2,3-dibromo-2-butene-1,4-diol, 2-phenylimidazole and 2-phenyl-4-methylimidazole and containing diethylene glycol monohexyl ether as a solvent has an ability to suppress heat sagging. was able to suffice.

As shown in Example 7, acrylic acid-modified hydrogenated rosin is contained as rosin, the content of thixotropic agent B is reduced, polyamide (Preparation Example 1) is contained, and activators are adipic acid, azelaic acid, trans-2, A flux containing 3-dibromo-2-butene-1,4-diol, 2-phenylimidazole and 2-phenyl-4-methylimidazole and containing diethylene glycol monohexyl ether as a solvent has a sufficient ability to suppress heat sagging. We were able to.

As shown in Example 8, acrylic acid-modified hydrogenated rosin is included as rosin, the content of thixotropic agent B is increased, polyamide (Preparation Example 1) is included, and adipic acid, azelaic acid, trans-2, A flux containing 3-dibromo-2-butene-1,4-diol, 2-phenylimidazole and 2-phenyl-4-methylimidazole and containing diethylene glycol monohexyl ether as a solvent has a sufficient ability to suppress heat sagging. We were able to.

As shown in Example 9, the content of acrylic acid-modified hydrogenated rosin was reduced, thixotropic agent A and polyamide (Preparation Example 1) were included as thixotropic agents, and adipic acid, azelaic acid and trans-2,3 were used as active agents. Flux containing dibromo-2-butene-1,4-diol, 2-phenylimidazole and 2-phenyl-4-methylimidazole and containing diethylene glycol monohexyl ether as a solvent has sufficient ability to suppress heat sagging. I was able to

As shown in Example 10, the content of acrylic acid-modified hydrogenated rosin was increased, thixotropic agent A and polyamide (Preparation Example 1) were included as thixotropic agents, and adipic acid, azelaic acid and trans-2,3 were used as active agents. Flux containing dibromo-2-butene-1,4-diol, 2-phenylimidazole and 2-phenyl-4-methylimidazole and containing diethylene glycol monohexyl ether as a solvent has sufficient ability to suppress heat sagging. I was able to

As shown in Example 11, acrylic acid-modified hydrogenated rosin is included as rosin, thixotropic agent A, thixotropic agent B and polyamide (Preparation Example 1) are included as thixotropic agents, and thixotropic agent A and thixotropic agent B are contained in total. Adipic acid, azelaic acid, trans-2,3-dibromo-2-butene-1,4-diol, 2-phenylimidazole and 2-phenyl-4-methylimidazole as active agents and diethylene glycol as solvent. A flux containing monohexyl ether was able to achieve a sufficient ability to suppress heat sagging.

As shown in Example 12, an acrylic acid-modified hydrogenated rosin is included as a rosin, and thixotropic agent A, thixotropic agent B and polyamide (Preparation Example 1) are included as thixotropic agents, and the total content of thixotropic agent A and thixotropic agent B is included. increased amounts to include adipic acid, azelaic acid, trans-2,3-dibromo-2-butene-1,4-diol, 2-phenylimidazole and 2-phenyl-4-methylimidazole as activators and diethylene glycol as solvent A flux containing monohexyl ether was able to achieve a sufficient ability to suppress heat sagging.

As shown in Example 13, acrylic acid-modified hydrogenated rosin is included as rosin, thixotropic agent A, bisamide and polyamide (Preparation Example 1) are included as thixotropic agents, and adipic acid, azelaic acid, trans-2, trans-2, A flux containing 3-dibromo-2-butene-1,4-diol, 2-phenylimidazole and 2-phenyl-4-methylimidazole and containing diethylene glycol monohexyl ether as a solvent has a sufficient ability to suppress heat sagging. We were able to.

As shown in Example 14, acrylic acid-modified hydrogenated rosin is included as rosin, thixotropic agent A and polyamide (Preparation Example 1) are included as thixotropic agents, and glutaric acid and trans-2,3-dibromo-2 are used as active agents. A flux containing -butene-1,4-diol, 2-phenylimidazole and 2-phenyl-4-methylimidazole and containing diethylene glycol monohexyl ether as a solvent was able to achieve a sufficient ability to suppress heat sagging. .

As shown in Example 15, acrylic acid-modified hydrogenated rosin is included as rosin, thixotropic agent A and polyamide (Preparation Example 2) are included as thixotropic agents, and adipic acid, azelaic acid, trans-2,3- Flux containing dibromo-2-butene-1,4-diol, 2-phenylimidazole and 2-phenyl-4-methylimidazole and containing diethylene glycol monohexyl ether as a solvent should have sufficient ability to suppress heat sagging. was made.

The fluxes of Examples 1 to 14 contained the compound represented by the above general formula (1) and the polyamide (Preparation Example 1), and were able to achieve a sufficient ability to suppress heating sagging at 200°C.
Since the flux of Example 15 contained the compound represented by the above general formula (1) and polyamide (Preparation Example 2), it was possible to achieve a sufficient ability to suppress heating sagging at 200°C.
On the other hand, the fluxes of Comparative Examples 1 and 4 did not contain the thixotropic agent A and the thixotropic agent B, and had an insufficient ability to suppress heating sagging at 200°C.
In addition, the fluxes of Comparative Examples 2 and 3 did not contain polyamide (Preparation Example 1) and polyamide (Preparation Example 2), and had insufficient ability to suppress heating sagging at 200°C.
From these results, it has been clarified that by including the compound represented by the general formula (1) and the polyamide, it is possible to obtain a sufficient ability to suppress heat sagging.

As shown below, the polyamide of Preparation Example 1 and the polyamide of Preparation Example 2 were prepared. Using these polyamides, flux and solder paste were prepared and evaluated for heat sagging and void generation.

As the polyamide, one obtained by the following method (polyamide (PA2)) was used.
(Polyamide Preparation Example 1)
12-Hydroxystearic acid and dodecanedioic acid were added and heated to about 100° C., then hexamethylenediamine was added and heated to about 220° C. and held for 3 hours to obtain a polyamide of Preparation Example 1.
Let X mol of dodecanedioic acid, Y mol of 12-hydroxystearic acid, and Z mol of hexamethylenediamine be used as raw materials. The number of moles of raw materials satisfied the relationship of 2Z=2X+Y.
(Polyamide Preparation Example 2)
12-Hydroxystearic acid and sebacic acid were added and heated to about 100°C, then hexamethylenediamine was added and heated to about 220°C and maintained for 3 hours to obtain a polyamide of Preparation Example 2.
X mol of sebacic acid, Y mol of 12-hydroxystearic acid, and Z mol of hexamethylenediamine used as raw materials. The number of moles of raw materials satisfied the relationship of 2Z=2X+Y.

<Measurement of endothermic peak>
The endothermic peak temperatures of the polyamides of Preparation Examples 1 and 2 were measured by DSC (Differential Scanning Calorimetry).
As a more specific method for measuring the endothermic peak, about 7 mg of each of the polyamides of Preparation Examples 1 and 2 was heated from 30° C. to 220° C. at a rate of 20° C./min under a nitrogen atmosphere. It was measured by heating. DSC7020 (manufactured by Hitachi High-Tech Science) was used as a measuring instrument. The peak top temperature was defined as the endothermic peak temperature.
Measurement results are shown in FIGS.
2 shows the endothermic peak of the polyamide of Preparation Example 1, and FIG. 3 shows the endothermic peak of the polyamide of Preparation Example 2. FIG.

<Evaluation of heat absorption ratio>
For the polyamides of Preparation Examples 1 and 2, the ratio of endothermic amount at a certain specific temperature was calculated as follows.
The endothermic amount of polyamide was calculated from the peak area of the DSC curve of polyamide.
Here, the "ratio of heat absorption at a specific temperature" means the heat absorption in the range of 50°C or higher and the specific temperature or lower with respect to the total heat absorption in the range of 50°C or higher and 200°C or lower.
The results are shown in Figures 4-7.
4 is a graph showing the relationship between the heat absorption rate and temperature of the polyamide of Preparation Example 1, and FIG. 5 is a graph showing the relationship between the heat absorption rate and temperature of the polyamide of Preparation Example 2.
FIG. 6 is a graph showing the relationship between the heat absorption ratio of the polyamide of Preparation Example 1 and the temperature, which is an enlarged part of FIG.
FIG. 7 is a graph showing the relationship between the heat absorption ratio of the polyamide of Preparation Example 2 and the temperature, which is an enlarged part of FIG.

The polyamide of Preparation Example 1 had an endothermic rate of 90% or more at 190°C and an endothermic rate of 98% or more at 195°C.
In contrast, the polyamide of Preparation Example 2 had an endothermic rate of less than 90% at 190°C and an endothermic rate of less than 98% at 195°C.
It was found that the ratio of the endothermic amount of the polyamide of Preparation Example 1 at 195° C. or higher and 200° C. or lower was smaller than that of the polyamide of Preparation Example 2 at 195° C. or higher and 200° C. or lower.

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

<Thixotropic agent>
As thixotropic agents, the polyamides of Preparation Examples 1 and 2, hexamethylenebishydroxystearic acid amide, and hydrogenated castor oil were used.

<Activator>
Adipic acid, suberic acid, and hydrogenated dimer acid were used as organic acids.
Trans-2,3-dibromo-2-butene-1,4-diol was used as the halogen-based activator.
2-phenylimidazole was used as the amine.

<Solvent>
Diethylene glycol monohexyl ether was used as the solvent.

<Preparation of Flux>
(Test Examples 1 to 14)
Each flux of the test example was prepared with the composition shown in Table 4 below.
The fluxes of Test Examples 1-13 contain rosin, solvent, polyamide (PA2), and activator.
The flux of Test Example 14 contains rosin, solvent, and activator, but does not contain polyamide (PA2).
The content of each component in Table 4 is mass % when the total mass of the flux is 100 mass %, and a blank means 0 mass %.

<Preparation of Solder Paste>
A solder paste was prepared by mixing the flux of each example and the following solder alloy powder.
As the solder alloy powder, a Sn--Ag--Cu solder alloy containing 3.0% by mass of Ag, 0.5% by mass of Cu, and the balance of Sn was used.
The solder alloy powder used had a size (particle size distribution) satisfying symbol 4 in the powder size classification (Table 2) in JIS Z 3284-1:2014.
All of the prepared solder pastes contained 11% by mass of flux and 89% by mass of solder alloy powder.

<Evaluation of heating sauce>
A solder paste obtained by mixing a flux and a solder alloy powder was evaluated for drooping during heating.

Measuring method:
Heat sagging was evaluated for the obtained solder paste according to the method described in JIS Z 3284-3:2014, "Test for sagging during heating". First, patterns shown in I (hole size 3.0×0.7) in FIG. 6 and II (hole size 3.0×1.5) in FIG. A test board was obtained by printing a solder paste using a metal mask with holes. The obtained test plates were heated to 150° C. or 200° C. in an air circulation heating furnace. The test board after heating was evaluated for the minimum distance (unit: mm) at which all the printed solder pastes were not integrated. The results are shown in Table 4.

<Evaluation of void generation>
Using a metal mask (opening diameter 0.30 mm, mask thickness 0.12 mm), solder paste is printed on the substrate (Cu-OSP treated glass epoxy substrate), LGA (Land Grid Array: terminal processing Au flash, pitch: 0 .5 mm, φ: 0.3 mm, number of bumps: 160).
Subsequently, by atmospheric reflow, the temperature was raised from 40 to 150°C at a rate of 3 to 4°C/sec, held at 150 to 175°C for 80 to 90 seconds, and then raised to 175 to 240°C at a rate of 1 to 2°C/sec. , and held at 220° C. or higher for 35 to 45 seconds.
Subsequently, the LGA mounting part was imaged using an X-ray observation device (TUX-3200 manufactured by Mars Thoken Solution). Data were similarly acquired for 3 LGAs (480 bumps total).
For each of the 480 bumps, the ratio of the total area of voids to the land area of the bump was calculated. The average value of the obtained ratios was calculated and used as the void area ratio. The results are shown in Table 4.
Also, the ratio of the number of bumps having no void to the total number of bumps (480) was calculated, and this was taken as the non-void generation rate. The results are shown in Table 4.

Judgment criteria for void area ratio:
○: The void area ratio is 1.2% or less.
x: The void area ratio is more than 1.2%.

Criteria for non-void occurrence rate:
○: The void non-occurrence rate is 35% or more.
x: The void non-occurrence rate is less than 35%.

Test Examples 1 to 6 and 8 to 13 contained the polyamide of Preparation Example 1, and had a sufficient ability to suppress heating sagging at 200°C.
Test Example 14 did not contain polyamide, and had an insufficient ability to suppress heat drooping at 200°C.
Test Examples 1 to 12 contained the polyamide of Preparation Example 1, and had a sufficient ability to suppress the generation of voids.
Test Example 13 contained the polyamide of Preparation Example 2, and was insufficient in suppressing the generation of voids.

The polyamide of Preparation Example 1 was prepared using dodecanedioic acid having 12 carbon atoms as a starting material.
The polyamide of Preparation Example 2 was prepared using sebacic acid having 10 carbon atoms as a starting material.
In general, organic compounds such as lipids have a higher melting point as the number of carbon atoms increases.
Surprisingly, in the polyamide of Preparation Example 1, the ratio of the amount of heat absorption at 50° C. or higher and 190° C. or lower and the ratio of the amount of heat absorption at 50° C. or higher and 195° C. or lower are sufficiently high. was sufficient to suppress the
In addition, the polyamide of Preparation Example 2 does not have a sufficiently high ratio of the amount of heat absorbed at 50°C or higher and 190°C or lower and the ratio of the amount of heat absorbed at 50°C or higher and 195°C or lower. was insufficient.

Since the polyamide of Preparation Example 1 has sufficiently high fluidity at 190° C. and 195° C., it is presumed that Test Examples 1 to 12 had sufficient ability to suppress the generation of voids.
Since the polyamide of Preparation Example 2 does not have sufficiently high fluidity at 190° C. and 195° C., it is presumed that Test Example 13 was insufficient in suppressing the generation of voids.

According to the present invention, it is possible to provide a flux and a solder paste that can sufficiently suppress heat sagging during reflow. This flux and solder paste can be suitably used for soldering a substrate having a large area.

Claims (3)

containing a rosin, a solvent, a thixotropic agent and an activator;
The thixotropic agent contains a compound and a polyamide represented by the following general formula (3),
The polyamide is a condensate of an aliphatic carboxylic acid, a hydroxy group-containing aliphatic carboxylic acid, and an amine, and has an endothermic peak temperature of 120° C. or higher and 200° C. or lower by differential scanning calorimetry,
The aliphatic carboxylic acid includes a dicarboxylic acid,
The content of the rosin is 30% by mass or more and 50% by mass or less with respect to the total mass of the flux,
The content of the compound represented by the following general formula (3) is 1% by mass or more and 10% by mass or less with respect to the total mass of the flux,
The flux, wherein the content of the polyamide is 1% by mass or more and 15% by mass or less with respect to the total mass of the flux.

[In the formula, R ¹¹ and R ^11′ each independently represent a hydrocarbon group having 14 to 20 carbon atoms. R ^0a and R ^0a' each represent a hydrogen atom. R ^0b2 represents a hydrocarbon group having 6 to 9 carbon atoms. R ²¹ and R ^21′ each independently represent an alkylene group having 2 to 6 carbon atoms. R ^0c and R ^0c' each represent a single bond. ] wherein the compound represented by the general formula (3) is N,N'-bis(2-stearamidoethyl)-sebacamide or N,N'-bis(2-stearoamidoethyl)-azelicamide; Item 1. The flux according to item 1. A solder paste containing solder alloy powder and the flux according to claim 1 or 2 .

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