JP2001239395A - Thermosetting flux, soldering method, and substrate with electronic part - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide thermosetting flux, soldering method, and a substrate with electronic parts which has an ability to improve joint strength between electronic parts and the substrate even after soldering. SOLUTION: The soldering method uses thermosetting flux provided for soldering, which includes (A) a compound which has one more shadow carboxyl group in a molecule and (B) a compound which has two more reacting sensory groups able to be chemically bonded with carboxyl groups by heating in a molecule.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermosetting flux for soldering when components are mounted on a mounting board or the like. More specifically, the thermosetting flux of the present invention has good chemical performance and physical properties. It is characterized by having performance, especially adhesiveness, and also having excellent storage stability derived from a compound having a latent carboxyl group. Furthermore, the present invention relates to a soldering method using such a thermosetting flux, and an electronic component mounting board obtained by such a soldering method.

[0002]

2. Description of the Related Art Conventionally, as a mounting method for mounting an electronic component such as a chip component on an electronic circuit board, for example, a soldering technology (Tripps Co., Ltd., published on August 26, 1987), pp. 225- The method described on page 228 is generally known.

[0003] Briefly, this method is performed in the following steps. (1) A process of printing a solder cream (cream-like solder) on an electronic circuit board (on a chip component mounting electrode) using a solder mask. (2) A step of mounting a chip component to be mounted on the printed solder cream with a mounter or the like. (3) a step of passing the electronic circuit board on which the chip component is mounted through a solder reflow furnace and soldering the chip component to the electronic circuit board;

Further, when chip components and the like are mounted on both sides of an electronic circuit board, the chip components and the like to be mounted are fixed by an adhesive.

[0005] Flux is used for such soldering. Conventionally, the main purpose of the flux is to remove an oxide film from the surface of the substrate metal and the surface of the component terminal electrode to be mounted. However, some fluxes have a function as a temporary fixing agent before soldering the component, in addition to the purpose of removing the oxide film on the surface of the component to be joined to the substrate to improve the wettability of the solder.

The main component of the flux for removing the oxide film from the substrate is rosin, which is composed of an organic acid such as abietic acid. In some cases, a solvent, a plasticizer, and a flow control agent (thixotropic agent) are blended to obtain printability and temporary fixing strength.

[0007] The flux is R, which is specified in the mill standard.
MA (halogen-free) is mainly used, and the number of washing steps for flux and the like after reflow is reduced.

[0008] The non-cleaning type flux remains as a residue on the substrate after mounting, but hardly functions after soldering.

The bonding strength between the component and the board depends on the solder bonding area, and the bonding strength tends to decrease as the size of the component is reduced. As high-density mounting has progressed, miniaturization of components and narrowing of the pitch between components have become mainstream, and with this, the bonding area of the solder has been reduced, and the bonding strength between the substrate and the component has tended to decrease.

Conventionally, the bonding strength has been obtained by forming a solder fillet layer or the like to secure a larger solder bonding area between the component terminals and the board lands. It is also necessary to reduce the bonding area, and the bonding strength between the component and the substrate tends to decrease.

On the other hand, while Pb-free solder has become the mainstream in the future, no composition has been found that will replace high-temperature solder (eg, Pb-rich solder). For products that mount components on a board, such as module products, if conventional solder is used, when mounting the module product on the base board, problems such as shifting or falling off of the mounted components will occur. Occurs.

As a technique for coping with such recent high-density mounting, Japanese Patent Application Laid-Open No. 62-134194 discloses a cream solder in which a powdery solder is mixed with a high-viscosity flux to form a cream. It is described that a component can be mounted on a printed wiring board to which this has been applied and sent to a reflow soldering process to prevent a shift in terminal position.

Japanese Patent Application Laid-Open No. 11-121915 discloses an electronic component mounting device having a viscosity capable of temporarily fixing an electronic circuit board and an electronic component, comprising rosin as a main component and adjusting the viscosity with alcohol. A flux is disclosed.

However, it is still insufficient to respond to recent trends such as high-density mounting and miniaturization of components. In such a tendency, the bonding strength between the substrate and the components is increased, and There is a demand for a technique that does not cause problems such as shifting or falling off of parts.

[0015]

SUMMARY OF THE INVENTION It is an object of the present invention to improve the solder wettability, to secure the bonding strength between an electronic component and a substrate before a soldering step, and to maintain the electronic component even after soldering. The purpose of the present invention is to provide a thermosetting flux that has a function of improving the bonding strength between the substrate and the substrate and does not cause shifting or falling off of electronic components.
Another object of the present invention is to provide a soldering method and an electronic component mounting board using the same.

[0016]

Means for Solving the Problems The present inventors have conducted intensive studies to develop a thermosetting flux for soldering having the above-mentioned preferable properties. It has been found that the object can be achieved by the curable flux, and the present invention has been completed based on this finding. That is, the present invention is as follows. (1) (A) a compound having one or more latent carboxyl groups in one molecule; and (B) a reactive functional group capable of forming a chemical bond with a carboxyl group in one molecule by heating.
A thermosetting flux for soldering, comprising a compound having at least one compound. (2) The structure represented by the formula (1), wherein the compound having one or more latent carboxyl groups in one molecule of the component (A) has two or more latent carboxyl groups in one molecule. The thermosetting flux for soldering according to the above (1), which is a polyhemiacetal ester resin having units.

[0017]

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[In the formula (1), R ¹ and R ² are each a divalent organic group, and Y is an oxygen atom or a sulfur atom. (3) The reactive functional group capable of forming a chemical bond with the carboxyl group of the component (B) by heating is an epoxy group, and further contains an acid catalyst, a flow regulator or a solvent, if necessary. ) Or (2) a thermosetting flux for soldering. (4) When the total content of the component (A) and the component (B) is 100% by mass, the component (A) is 10 to 90% by mass,
The acid catalyst is added in an amount of 0 to the total solid content of the components (A) and (B).
10% by mass, 0 to 50% by mass of the solvent, 0 to
The thermosetting flux for soldering according to any one of the above (1) to (3), containing 50% by mass. (5) Furthermore, the above (1) to-containing solder powder
The thermosetting flux for soldering according to any of (4). (6) When the solder powder is Sn, Cu, Zn, Ag, Sb, Pb, In,
The thermosetting flux for soldering according to the above (5), which is a solder powder containing at least one selected from Bi and Ge. (7) The thermosetting flux for soldering according to any one of the above (1) to (6), which is in a liquid, paste or sheet form. (8) A soldering method using the thermosetting flux according to any one of (1) to (7). (9) The soldering method according to the above (8), which is performed when the electronic component is mounted on the electronic component mounting board. (10) An electronic component mounting board obtained by mounting an electronic component on the electronic component mounting substrate by the soldering method of (9).

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.
The thermosetting flux of the present invention comprises one or more, preferably two or more latent carboxyl groups in one molecule of the component (A).
And a compound having two or more reactive functional groups capable of forming a chemical bond with a carboxyl group in one molecule of the component (B), and optionally an acid catalyst and a flow regulator ( Thixotropic agent) and a solvent.

According to this, unlike the conventional flux, since it has adhesiveness after soldering, the bonding strength between the substrate and the electronic component is improved. For this reason, it is suitable for high-density mounting, and even when mounting is performed using Pb-free solder, shifting or falling off of the electronic component does not occur. Also, when mounting on both sides,
Since it has excellent adhesiveness, when mounting an electronic component on one side and then mounting an electronic component on the other side, special measures such as using an adhesive separately to prevent the mounted electronic component from peeling off There is no need to take measures. In addition, like a conventional flux, it has a function of removing an oxide film of an electronic component to be soldered, and has a low viscosity in a temperature range from room temperature (about 15 ° C.) to about 220 ° C. Therefore, it is possible to temporarily fix the substrate and the electronic component before soldering, and at the time of soldering, there is a self-alignment effect of correcting the mounting state of the electronic component by the surface tension of the melted solder.

Further, by appropriately selecting the component (A) and the component (B), it becomes possible to adjust the bonding temperature and the like, and the combination can be selected according to the purpose of use.

As described above, the thermosetting flux of the present invention differs from the conventional rosin-based flux which is generally used, after mounting electronic components on a substrate by heat (reflow).
It is characterized in that the flux has a function as an adhesive for fixing the mounting board and the electronic component.

The component (A), which is an essential component of the thermosetting flux of the present invention, is a compound containing one or more, preferably two or more latent carboxy groups in one molecule. By using such a compound, the thermosetting flux of the present invention has excellent storage stability.

Examples of such a latent carboxyl group include a tertiary butyl ester group, a trialkylsilyl ester group, and a hemiacetal ester group. Among them, a tertiary butyl ester group by-produces gaseous isobutene as a leaving group, and a trialkylsilyl ester group is sensitive to moisture, and thus a hemiacetal ester group is preferable. The compound of component) may be any compound having at least one such group, and among them, a polyhemiacetal ester resin having at least one structural unit represented by the following formula (1) is preferable. Particularly preferred is a polyhemiacetal ester resin having a repeating unit represented by the following formula (1).

[0025]

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In the formula (1), R ¹ and R ² are each a divalent organic group, and Y is an oxygen atom or a sulfur atom.

The divalent organic groups represented by R ¹ and R ² in the formula (1) may be the same or different.

Examples of the organic groups represented by R ¹ and R ² include an alkylene group such as trimethylene, a cycloalkylene group such as a cyclohexane residue (cyclohexylene) obtained by removing two hydrogen atoms from cyclohexane, and an alkenylene group such as vinylene. Polyoxyalkylene groups such as polyoxyethylene and polyoxypropylene, cycloalkenylene groups such as cyclohexene residues obtained by removing two hydrogen atoms from cyclohexene, divalent aromatic residues such as phenylene, biphenylene, and naphthylene, and polyalkynes Oxide residue, the following formula (2)

[0029]

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(Wherein R ³ and R ⁴ in the formula are divalent organic groups having 1 to 30 carbon atoms in the formula). Expression (2) will be described later.

The total carbon number of the organic group represented by R ¹ and R ² is
It is preferably from 2 to 30, and more preferably from 6 to 25.

These organic groups may be substituted with halogen atoms such as chlorine, bromine and iodine and other substituents.

Preferred among these organic groups are an alkylene group, a cycloalkylene group such as a cyclohexane residue, a divalent aromatic residue and an organic group of the formula (2).

The alkylene group may be a linear or branched 2
A hydrocarbon group, preferably an alkylene group having 1 to 10 carbon atoms, specifically, methylene, ethylene, trimethylene, methylmethylene, ethylmethylene, methylethylene, ethylethylene, 2-methyltrimethylene, tetramethyl Methylene, 1-methyltrimethylene, pentamethylene, 2,2-dimethyltrimethylene, 1-methylpentamethylene, 2-methylpentamethylene, 3-methylpentamethylene, hexamethylene, heptamethylene, octamethylene, nonamethylene, decamethylene, etc. Is mentioned.

As the cycloalkylene group, for example, a cyclopentane residue, a cyclohexane residue, a cycloheptane residue, and one or two bonds of these residues further include the above-mentioned alkylene groups such as a methylene group and an ethylene group. Bonded compounds and their alkyl-substituted compounds are preferred, and preferred are cyclohexane residues, cycloheptane residues, and their alkyl-substituted products. Total carbon number is 5
1818 is preferred.

Alkenylene groups are straight-chain or branched
A divalent hydrocarbon group, preferably an alkenylene group having 1 to 10 carbon atoms, specifically cis-vinylene, trans-
Vinylene, propenylene, 2-butenylene, 1-methylpropenylene, 3-methyl-2-butenylene, 3,3-dimethylpropenylene, 2-pentenylene, 3-methyl-2-butenylene, 3-methyl-3-butenylene, 2-hexenylene, 3-heptenylene, 4-octenylene, 3-nonenylene, 3-decenylene and the like can be mentioned.

Examples of the polyoxyalkylene group include polyoxyethylene, polyoxypropylene and polyoxybutylene. The total carbon number is preferably 4 to 30.

As the cycloalkenylene group, for example, a cyclopentene residue, a cyclohexene residue, a cycloheptene residue, and one or two bonds of these residues further bonded with the above-mentioned alkylene group such as a methylene group or an ethylene group And the alkyl-substituted products thereof, preferably a cyclopentene residue and a cyclohexene residue. Preferably, the total carbon number is 5-18.

The divalent aromatic residue is a residue obtained by removing two hydrogen atoms from an aromatic compound, and specific examples thereof include, for example, phenylene, biphenylene, naphthylene, oxonaphthylene, and divalent anthracene residue. Group, 2
Divalent anthraquinone residue, alkane diphenylene, carbonyl diphenylene, sulfonyl diphenylene and their alkyl substituents, and one or two bonds of these residues further have the above alkylene group such as a methylene group or an ethylene group. Examples thereof include those bonded and substituted with a halogen atom such as chlorine, bromine and iodine.

Preferred of these aromatic residues are phenylene, naphthylene, alkanediphenylene,
Oxonaphthylene residues and their alkyl substituents. The total carbon number is preferably 6-20.

Examples of the alkyl group substituted on the cycloalkyl ring, cycloalkenyl ring or aromatic ring include, for example, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl, isopentyl, neopentyl Tert-pentyl, 2-methylbutyl, n-hexyl, isohexyl, 3-methylpentyl, ethylbutyl, n-heptyl, 2-methylhexyl, n-octyl, 3-methylheptyl, n-nonyl,
Methyl octyl, ethyl heptyl, n-decyl, n-undecyl, n-dodecyl, n-tetradecyl, n-heptadecyl, n-octadecyl, cyclohexyl and the like, preferably an alkyl group having 1 to 8 carbon atoms, Specifically, for example, methyl, ethyl, n-propyl, n-
Octyl and the like. The number of the alkyl groups substituted on the cycloalkyl ring, cycloalkenyl ring or aromatic ring may be one, or two or more.

The phenylene and its alkyl-substituted product include, for example, o-phenylene, m-phenylene, p-
Isomers of tolylene such as -phenylene, 4-methyl-o-phenylene, 5-methyl-m-phenylene, 5-methyl-p-phenylene, 3,4-dimethyl-o-phenylene, 4,5-dimethyl- Each isomer of xylylene such as m-phenylene, 2,5-dimethyl-p-phenylene, 4-ethyl-o-phenylene, 4-ethyl-m-phenylene, 2
-Ethylphenylene isomers such as -ethyl-p-phenylene, n-propylphenylene isomers, isopropylphenylene isomers, n-butylphenylene isomers, t-butylphenylene isomers, amyl Each isomer of phenylene, each isomer of hexylphenylene, each isomer of nonylphenylene, and the like, with preferable ones being o-phenylene, m-phenylene, p-phenylene, 4-methyl-o-phenylene, 5 -Methyl-m
-Phenylene, 5-methyl-p-phenylene.

Examples of naphthylene and its alkyl-substituted product include 1,2-naphthylene, 1,3-naphthylene, 1,4
-Naphthylene, 1,5-naphthylene, 1,6-naphthylene, 1,
7-naphthylene, 1,8-naphthylene, 2,3-naphthylene,
2,6-naphthylene, 2,7-naphthylene and their methyl-substituted isomers, dimethyl-substituted isomers, ethyl-substituted isomers, isopropyl-substituted isomers,
Examples include isomers of n-butyl substituents, and preferred are 1,2-naphthylene, 1,3-naphthylene, 1,4
-Naphthylene, 1,5-naphthylene, 1,6-naphthylene, 1,
7-naphthylene, 1,8-naphthylene, 2,3-naphthylene,
Examples include 2,6-naphthylene and 2,7-naphthylene.

Oxonaphthylene and its alkyl-substituted product include, for example, 1,2-naphthoquinone-5,8-position residue,
4-naphthoquinone-5,8-position residue, 2,6-naphthoquinone-5,8
Residue and their methyl-substituted isomers, ethyl-substituted isomers, isopropyl-substituted isomers, n
Each isomer of -butyl substituent, and the like, preferably
1,2-naphthoquinone-5,8-position residue, 1,4-naphthoquinone-
Residues at 5,8 and 2,6-naphthoquinone-5,8 are listed.

The divalent anthracene residue is a residue obtained by removing two hydrogen atoms from anthracene, and specific examples of the anthracene residue and its alkyl-substituted product include:
For example, 1,2-anthracene residue, 1,3-anthracene residue, 1,4-anthracene residue, 1,5-anthracene residue,
1,6-anthracene residue, 1,7-anthracene residue, 1,8
-Anthracene residue, 2,3-anthracene residue, 2,6-anthracene residue, 2,7-anthracene residue, and their methyl-substituted isomers, ethyl-substituted isomers, and isopropyl substitution Isomers, n-butyl-substituted isomers and the like, and preferably 1,2-anthracene residue, 1,3-anthracene residue, 1,4-anthracene residue, 1,5- Anthracene residue, 1,6-anthracene residue, 1,7-anthracene residue, 1,8-anthracene residue,
2,3-anthracene residue, 2,6-anthracene residue, 2,7
-Anthracene residues.

The divalent anthraquinone residue is a residue obtained by removing two hydrogen atoms from anthraquinone, and specific examples of the anthraquinone residue and its alkyl-substituted product include, for example, 9,10-anthraquinone-5,8 Residue, 9,10
-Anthraquinone-1,5-position residue, 1,2-anthraquinone-
6,9-position residue, 1,4-anthraquinone-6,9-position residue and their methyl-substituted isomers, ethyl-substituted isomers, isopropyl-substituted isomers, n-butyl substitution And the like, preferably 9,10-anthraquinone-5,8-position residue, 9,10-anthraquinone-1,5-position residue, 1,2-anthraquinone-6,9-position residue , 1,4-anthraquinone-6,9-position residues.

The alkanediphenylene and its alkyl-substituted product include, for example, propane-2,2-diphenylene, 2-methylpropane-3,3-diphenylene, methylcyclohexylmethane-diphenylene, and isomers of these methyl-substituted products. Examples include ethyl-substituted isomers, isopropyl-substituted isomers, and n-butyl-substituted isomers, and preferred is propane-2,2-diphenylene.

Examples of the sulfonyldiphenylene and its alkyl-substituted product include sulfonyldiphenylene and their methyl-substituted isomers, ethyl-substituted isomers, isopropyl-substituted isomers, n-butyl-substituted isomers. Each isomer of the compound is preferable, and sulfonyl diphenylene is preferable.

Y represents an oxygen atom or a sulfur atom, preferably an oxygen atom.

R ³ and R ⁴ in the formula (2) are each a divalent organic group. R ³ and R ^{4 on} the left and right in the formula are
Each may be the same or different. Specific examples of R ³ and R ⁴ include, among the above R ¹ and R ² ,
The same organic groups as the organic groups other than the organic group of (2) can be mentioned.

The polyhemiacetal ester resin which is preferred as an essential component of the present invention has a repeating unit represented by the above formula (1), but only one of the repeating units represented by the formula (1) Or may have two or more kinds, and may include a repeating unit other than the repeating unit represented by the above formula (1).

The other repeating unit contained in the polyhemiacetal ester resin used in the present invention includes, for example, a repeating unit that forms a polyester resin,
Examples of the repeating unit include a urethane resin.

The weight-average molecular weight of the polyhemiacetal ester resin is not particularly limited, but is usually
In the range of 500-100,000, preferably 800-20,
000 range.

The polyhemiacetal ester resin having a repeating unit represented by the formula (1) used in the present invention is represented by the formula (3)

[0055]

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(Wherein R ¹ is a divalent organic group) and a dicarboxylic acid compound represented by the formula (4):

[0057]

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(Wherein R ² is a divalent organic group and Y is an oxygen atom or a sulfur atom), which can be easily obtained by an addition reaction with a divinyl ether compound or a divinyl thioether compound. Can be. In addition,
R ¹ and R ^{2 in the} formulas (3) and (4) have the same meanings as those in the formula (1).

The dicarboxylic acid compound represented by the formula (3) used in the production of the polyhemiacetal ester resin used in the present invention includes, for example, maleic acid, fumaric acid, mesaconic acid, citraconic acid, itaconic acid, Chlorinated maleic acid, heptic acid, succinic acid, adipic acid, azelaic acid, sebacic acid, aliphatic dicarboxylic acids having 2 to 30 carbon atoms such as decamethylenedicarboxylic acid, phthalic acid, isophthalic acid, terephthalic acid, dichlorophthalic acid Aromatic dicarboxylic acids such as dichloroisophthalic acid, tetrachlorophthalic acid, tetrachloroisophthalic acid, tetrachloroterephthalic acid, tetrahydrophthalic acid, hexahydrophthalic acid, methylhexahydrophthalic acid, hexahydroisophthalic acid, hexahydroterephthalic acid, etc. An alicyclic dicarboxylic acid, and 2 R ¹ and R ² which are organic groups
And a dicarboxylic acid in which a carboxyl group has been introduced into the divalent residue.

In place of this dicarboxylic acid, a half-ester of dicarboxylic acid obtained by an addition reaction of 1 mol of diol and 2 mol of acid anhydride can be used. Such diols include, for example, ethylene glycol, diethylene glycol, 1,2- and 1,3
-Propylene glycol, 1,3-butanediol, 1,4-
Butanediol, 2,3-butanediol, 1,6-hexanediol, pentanediol, dimethylbutanediol, hydrogenated bisphenol A, bisphenol A, neopentyl glycol, 1,8-octanediol, 1,4-cyclohexanediol, Examples thereof include 1,4-cyclohexanedimethanol and 2-methyl-1,3-propanediol. As the acid anhydride used for the half ester compound,
For example, succinic, glutaric, phthalic, maleic,
Acid anhydrides of dicarboxylic acids such as dichlorophthalic acid, tetrachlorophthalic acid, tetrahydrophthalic acid, methyl hexahydrophthalate and hexahydrophthalic acid.
In addition, any compound having a dicarboxylic acid structure, such as a terminal dicarboxylic acid having a polyester structure or a polybutadiene structure, can be used.

Specific examples of the divinyl ether compound represented by the above formula (4) used for producing the polyhemiacetal ester resin used in the present invention include, for example, trimethylene glycol divinyl ether, 1,4- Bisvinyloxymethyl cyclohexene, ethylene glycol divinyl ether, polyethylene glycol divinyl ether, butanediol divinyl ether, pentanediol divinyl ether, hexanediol divinyl ether, 1,4-cyclohexanedimethanol divinyl ether, 1,4-benzenedivinyl ether, bisphenol a divinyl ether, R ¹ is a bisphenol F divinyl ether, and divinyl thioethers, and 2,2-bis (vinylthio) propane, and divalent organic group described above their corresponding Etc. and divinyl ethers to introduce a vinyl ether group or vinyl thioether group divalent residue of R ² or divinyl thioethers and the like.

In the polyhemiacetal ester resin used in the present invention, the dicarboxylic acid compound represented by the formula (3) or the half ester compound and the compound represented by the formula (4)
Or a plurality of divinyl ether compounds represented by In addition, a monofunctional carboxylic acid compound, a phenol or a monoalcohol may be used in addition to the dicarboxylic acid compound or the half ester in order to adjust the molecular weight and physical properties of the coating film. Examples of such compounds include synthetic resin acids having 1 to 20 carbon atoms, natural fatty acids having 10 to 32 carbon atoms, rosin, phenols having 1 to 25 carbon atoms, alcohols and the like.

The reaction between the above-mentioned dicarboxylic acid compound or half-ester and the divinyl ether compound is usually carried out without a solvent or in a suitable solvent at a temperature in the range of room temperature (about 20 ° C.) to 200 ° C.

The component (B) used in the thermosetting composition of the present invention has a reactive functional group capable of forming a chemical bond by reacting with a free carboxyl group regenerated by heating the component (A). A compound having two or more, preferably 2 to 50 in one molecule.

Examples of such a reactive functional group include an epoxy group, an oxazoline residue, a silanol residue, an alkoxysilane residue, a hydroxyl group, an amino group, an imino group, an isocyanate group, a blocked isocyanate group, a cyclocarbonate group, Examples include a vinyl ether group, a vinyl thioether group, an aminomethylol group, an alkylated aminomethylol group, an acetal residue, and a ketal residue.

Of these, the epoxy group undergoes an addition reaction with a carboxyl group generated by thermal decomposition of the polyhemiacetal ester resin as the component (A) to form a strong β-hydroxyethyl ester bond, and Divinyl ether by-produced by the thermal decomposition reaction of the above-mentioned polyhemiacetal ester resin further reacts with the hydroxyl group of β-hydroxyethyl ester to form an acetal bond,
It is particularly preferable because it is advantageous for improving the physical properties of the cured product.

Specific examples of the compound of the component (B) include bisphenol type epoxy resin, phenol novolak type epoxy resin, phenol cresol type epoxy resin, biphenyl type epoxy resin, cyclopentadiene type epoxy resin, alicyclic epoxy type Resin, glycidyl acrylate, glycidyl methacrylate, 3,4-epoxycyclohexylmethyl acrylate, homopolymer or copolymer such as 3,4-epoxycyclohexylmethyl methacrylate, a copolymer of glycidyl allyl ether and vinylidene fluoride and vinyl ether, Polyglycidyl compound obtained by reacting polycarboxylic acid or polyol with epichlorohydrin and silicone oil containing epoxy group, for example, Epicoat 828, 8
Epoxy resins such as 72, 1001, 1004 (all trade names, manufactured by Yuka Shell Epoxy Co., Ltd.), KF-101, KF-10
3, epoxy group-containing compounds such as KF-105 and X-22-169AS (all trade names, manufactured by Shin-Etsu Chemical Co., Ltd.).

In the thermosetting composition of the present invention,
The content ratio of the component (A) and the component (B) is such that the equivalent ratio of the latent carboxyl group of the component (A) to the epoxy group of the component (B) is 0.2: 1.0 to 1.0: 0.2. It is desirable to include each component. The polyhemiacetal ester resin of the component (A) can regenerate the original free carboxyl group simply by heating, but the carboxyl group can be rapidly regenerated by the presence of the acid catalyst.

As such an acid catalyst, a Bronsted acid or a Lewis acid can be used. When a one-part type thermosetting composition is intended for the final purpose, a heat-latent acid catalyst component which becomes active only when heated, And / or compounds that generate an acid upon irradiation with light are preferred. Examples of the heat-latent acid catalyst component exhibiting activity for the first time upon heating include a compound obtained by neutralizing a Bronsted acid or a Lewis acid with a Lewis base, a mixture of a Lewis acid and a trialkyl phosphate, a sulfonate, a phosphate, and an onium. Compounds, and (i) a compound having an epoxy group, (ii) a sulfur-containing compound and (iii) a Lewis acid as essential components, and optionally a compound comprising (iv) a carboxylic acid compound and / or a carboxylic anhydride compound are preferred. No.

The above acid catalysts may be used alone or in combination of two or more.

The amount of the heat-latent acid catalyst component is not particularly limited, but is usually 0 to 10% by mass relative to the total solid content of the thermosetting composition containing the polyhemiacetal ester resin of the present invention. More preferably, it is in the range of 0.1 to 10% by mass.

As the flow regulator (thixo agent) optionally used in the present invention, inorganic silica powder and resin powder of organic polyamide, silicone, phenol and the like are desirable. The compounding amount is effectively in the range of 0 to 50% by mass, and more preferably 0.1 to 50% by mass, based on the total solid content of the thermosetting composition.

The solvent optionally used in the present invention is not particularly limited, but may be an aromatic solvent, an ester solvent,
Ether type, ketone type, amide type, sulfoxide type,
Phosphate-based solvents are preferred. The solvent is preferably in the range of 0 to 50% by mass based on the total solid content of the thermosetting composition.

The type of the solder metal powder used in the present invention includes a composition containing at least one element of Sn, Pb, Cu, Zn, Ag, Sb, In, Bi, and Ge, and a melting solder temperature, In order to obtain the target bonding strength, the metal compounding ratio can be set arbitrarily. The solder metal powder is usually used in a range of 20 to 100% by mass based on the resin solid content. There is no particular limitation on the particle size of the solder powder, but the average particle size is 10 to 30μ
m.

The temperature and the time required for curing the thermosetting composition containing the polyhemiacetal ester resin of the present invention are determined by the temperature at which free carboxyl groups are regenerated from the polyhemiacetal ester resin represented by the above formula (1). Although it depends on the type of the reactive functional group, the presence or absence of the acid catalyst, the type, and the like, it is preferable to design so as to sufficiently cure in the solder reflow step (normally at a temperature of about 230 ° C. to 270 ° C.).

The form of the thermosetting flux of the present invention includes a solvent-added liquid type diluted with a solvent, and a solvent-free liquid type (solder powder is added), which is used without solvent and contains 100% active ingredient without solvent. ) And a paste-like mold obtained by adding a solder powder to these pastes, and any form is possible. Further, it is also possible to take the form of a sheet-shaped mold obtained by processing the above-mentioned thermosetting composition into a sheet.

The thermosetting flux of the present invention is summarized as follows, including those already described.

A-1) The thermosetting flux of the present invention imparts a function as an adhesive to the conventional flux, and gives the flux after soldering an adhesive property for fixing the substrate and the component, and provides an impact or heat. A non-cleaning flux containing a thermosetting resin and a curing agent, which has an effect of preventing components from falling due to stress and improving reliability of a solder joint interface.

A-2) As a method of increasing the mounting density of the mounted components on the mounting board, there is a method of making the pattern of the substrate land smaller than the component shape. Since it was not formed, the fixing strength of the component could not be obtained and it was not employed. However, when the above-mentioned thermosetting flux is used, a sufficient fixing strength can be ensured even without a fillet, and the mounting density of mounted components can be improved.

The above-mentioned thermosetting flux is from room temperature to about 220
Since it exhibits low viscosity up to the temperature range of ° C., it does not cause joining defects and has the same joining properties and self-alignment properties as those of the conventional method.

A-3) Pb-free solder compositions have been actively developed at present, but it has become difficult to develop Pb-free solders at high temperatures. The general composition of high temperature solder is
It is determined by the amount of Pb and the amounts of Cu and Sb added. The semi-solid temperature on the phase diagram in the above composition is about 220 ° C to 235 ° C.

The Pb-free solders currently being developed are:
The melting point is around 220 ° C, about 40 ° C higher than that of eutectic solder, and the practical reflow temperature is said to be 240 ° C to 260 ° C, which reaches the semi-solid temperature range of high-temperature solder.

The conventional application of high-temperature solder has been used for mounting components such as module substrate components. When the module substrate component is mounted on the set substrate again, a high-temperature solder that does not re-melt (semi-solid temperature) through a reflow furnace and does not shift the mounted component is used.
However, when the Pb-free solder is introduced, the reflow temperature rises, and the high-temperature solder may be re-melted, and the components mounted on the module substrate may come off the substrate land. As a countermeasure, if the mounted component is fixed with a thermosetting flux, since the flux fixes the component even if the solder is re-melted, no problem such as detachment occurs.

A-4) In the case of a double-sided mounting board, there are cases where components are temporarily fixed or high-temperature solder is used as the first surface solder so that the components mounted on the first surface do not fall off during reflow of the second surface. General. In the above double-sided mounting board, since the thermosetting flux fixes the component, the solder on the first and second surfaces is not changed, and the components are not changed on the first and second surfaces under the same conditions on both the first and second surfaces without using a temporary fixing agent. It can be implemented.

B) The thermosetting flux is prepared by mixing a thermosetting epoxy resin with an organic acid or solvent having a reducing action, and removing the oxide film from the organic acid or solvent in the same manner as the conventional flux. After heat (reflow) is passed through the resin, the resin functions to provide an adhesive action. Each has a separate function in the soldering process. As the curing agent in the flux, a polyhemiacetal ester resin is preferably used, and the action of the flux and the curing of the thermosetting resin are used in combination. There is also a method in which microcapsules containing a curing agent are mixed and allowed to act.

The resin system for imparting adhesiveness is preferably a thermosetting epoxy resin, and can be arbitrarily mixed depending on the temperature range in which adhesiveness is desired. The working temperature can also be changed by changing the dicarboxylic acid compound or divinyl ether compound which is a component of the curing agent polyhemiacetal ester resin.

The soldering method of the present invention is carried out by using the above-mentioned thermosetting flux, and is preferably carried out when an electronic component is mounted on an electronic component mounting substrate. Various electronic components and substrates can be used. The specific method of soldering is as usual. For example, there is a method of pre-coating solder on an electrode of an electronic component and / or a substrate.

The electronic component mounting board (electronic component mounting board) of the present invention thus obtained is compatible with high-density mounting, and has a sufficient bonding strength between the component and the board.
There is no problem such as shifting or dropping of mounted components.

As a specific mounting method, there is a method shown in the embodiment.

[0090]

Next, the present invention will be described in more detail by way of examples. First, a production example of a synthetic intermediate and a polyhemiacetal ester resin of the component (A) will be described.

Production Example 1 Production of Dicarboxylic Acid Compound Half-Ester Form α In a four-necked flask equipped with a thermometer, a reflux condenser, and a stirrer, a mixture having the composition shown in Table 1 was charged, and the temperature was adjusted.
The mixture was stirred while being kept at 120 to 140 ° C. The reaction was terminated when the reaction rate of the mixture reached 98%. After washing with xylene, it was dried under reduced pressure to obtain a dicarboxylic acid half ester α, which is a half ester compound of a diol and an acid anhydride.

[0092]

[Table 1]

Production Examples 2 to 4 Production of Polyhemiacetal Ester Resins A to C A monomer having the composition shown in Table 2 was charged into a four-necked flask equipped with a thermometer, a reflux condenser, and a stirrer. To
The mixture was stirred while keeping the temperature at 100 ° C to 120 ° C. The point at which the infrared absorption spectrum at 3543 cm ^-1 due to the hydroxyl value is 5 or less or the disappearance of the infrared absorption spectrum attributable to the hydroxyl group is regarded as the end point of the reaction.
A solution was obtained.

[0094]

[Table 2]

Example 1 (1) Preparation of a thermosetting composition Using the thermosetting epoxy resin and the curing agent polyhemiacetal ester resin shown in Table 3, a thermosetting composition was prepared at each mixing ratio. A preliminary evaluation of the physical properties of the cured film was performed.

(2) Evaluation of test sample 2 g of the sample was applied on a Cu plate, and the film after passing through a heat (reflow furnace) was observed. The reflow temperature was in the range of 230 ° C to 270 ° C mainly used for mounting electronic components.

The evaluation criteria were x for an uncured film, Δ for a gel-like film, ● for an elastic film after curing, and を for a hard film after curing. Table 3 shows the results.

[0098]

[Table 3]

In the reflow temperature range of 230 ° C. to 270 ° C., almost a cured film was formed. The physical properties of the film, from a hard film to an elastic film, could be easily adjusted by the mixing ratio of the thermosetting resin.

The evaluation of the properties of the cured film was made at 260 ° C.
The film hardening time at a constant temperature was also compared. Table 4 shows the results.

[0101]

[Table 4]

It can be seen that the curing speed of the thermosetting resin film depends on the compounding ratio of the resin and the molecular weight of the curing agent. By setting this mixing ratio arbitrarily, a cured film can be formed in a target temperature range.

Example 2 In the thermosetting flux prepared in Example 1, 65% by mass of solder powder (Sn-3.5Ag-0.7Cu: numerical value is mass ratio: average particle diameter 1)
5 μm) to form a solder paste. In order to confirm the bonding effect (adhesion of parts) of the thermosetting flux, we used a prototype solder paste and a conventional solder paste with rosin flux.
Lateral pressing strength values after mounting the chip component (1005 chip capacitor) on the board were compared. The results are shown in FIG. 1 in relation to the thermosetting resin compounding ratio. Here, the thermosetting flux containing solder is referred to as a solder paste for convenience. FIG. 2 shows a mounting method.

As shown in FIG. 2, the electronic component mounting substrate 1
Was used in which solder was previously formed on the electronic component mounting land 2 [FIG. 2 (a)]. A solder paste 3 is applied on the land 2 [FIG. 2 (b)], and a 1005 chip capacitor 4 as an electronic component is placed on the land 2 so that the terminal electrodes 41 and 42 for board bonding are mounted on the land 2. [FIG. 2 (c)] and passed through a reflow furnace. The reflow temperature was 230 ° C to 270 ° C. Thus, an electronic component mounting board was obtained. The joining terminal electrodes 41 and 42 of the chip capacitor 4 may be further pre-coated with solder.

As for the test method of the lateral pressing strength,
As shown in FIG. 3, a weight is applied from the front side of the mounted 1005 chip capacitor 4, and the strength value at the time when the terminal electrodes 41 and 42 of the mounted 1005 chip capacitor 4 are separated from the substrate 1, that is, the chip component and The shear fracture value between the mounting substrates was measured, and the average value (g) was obtained.

In all of the compounding compositions, the lateral pressing strength value (average value Ave) mounted with a conventional rosin-based flux was used.
= 500 g). The change in strength in the composition of the resin is represented by the thermosetting resins 1001 and 1004 (Epicoat 1001: an abbreviated name of bisphenol A type epoxy resin manufactured by Yuka Shell Epoxy Co., Ltd., hereinafter abbreviated as 1001. (Abbreviated name of bisphenol A type epoxy resin manufactured by the company, hereinafter abbreviated as 1004.)
With respect to the compounding ratio of 15 to 50% by mass, the component lateral pressing strength 2.5 times that of the current rosin solder-containing paste was obtained. In FIG. 1, the mixing ratio of the thermosetting resin is as follows.
2 (Epicoat 872: Abbreviation of dimer acid-modified epoxy resin manufactured by Yuka Shell Epoxy Co., Ltd .; hereinafter abbreviated as 872); the entire thermosetting resin (872 and 1001 or 872 and 1004: 872 and 1
Expressed as 001/1004. ) Is shown by the mixing ratio (% by mass). In addition to Example 1, the case of 1004 alone is also shown.

Example 3 In the thermosetting flux prepared in Example 1, 65% by mass of solder powder (Sn-3.5Ag-0.7Cu: numerical value is mass ratio: average particle size 15)
μm) was dispersed to prepare a solder paste. Using the prototype solder paste, a 1005 chip capacitor was mounted on the mounting board by heat (reflow), and the bonding properties between the chip component terminals and the mounting board were compared based on the number of defective products (pieces). FIG. 4 shows the results.

In the combination of 872 and 1001, 1001
When the compounding ratio of is high, good bonding properties are shown. In the combination of the thermosetting resins 872 and 1004, the blending ratio of 1004 takes a small value at 25% by mass. When the solvent cyclohexanone was added by 20% by mass to the solder paste as a post-addition to the blending sample No. 10 of Example 1 in order to reduce the joining defect, no joining defect occurred. In order to obtain the reliability of the bonding interface, the bonding property is improved by lowering the viscosity of the thermosetting resin with a solvent. This is considered to have the effect of reducing the absolute viscosity of the resin, exhibiting good fluidity, and extruding the adhesive resin in the solder to the periphery of the solder. The results are also shown in FIG.

Example 4 As shown in FIG. 5, a sample of the thermosetting flux 12 (that is, a sample of the adhesive flux blended in Example 1)
No. 7), using a squeegee 13 on the release sheet 11,
It was formed to a thickness of 50 μm by the doctor blade method [Fig.
(a), (b), (c)]. After drying in a dryer at 80 ° C for 30 minutes,
The thermosetting flux 12 was peeled off from the release sheet 11 to form a sheet-shaped thermosetting flux 12 (FIG. 5D).

FIG. 6 shows a mounting method using the sheet-like thermosetting flux 12. As shown in FIG. 6, the sheet-like thermosetting flux 12 is attached to the electronic component mounting substrate 1 in which the solder is formed on the electronic component mounting lands 2 in advance [FIGS. 6 (a), (b), (c). )] And an electronic component 4 (1
005 chip capacitor) on the land 2 with the terminal electrode 41,
42 (see FIGS. 6 (d) and 6 (e)) and passed through heat (reflow) [FIG. 6 (f)].

The bonding state between the substrate and the electronic components after the furnace was well bonded via the thermosetting flux.

[0112]

By imparting the function of securely bonding the component and the substrate to the flux, the fixing strength of the component can be improved or maintained even in a mounting board pad on which a fillet layer cannot be formed. Further, the same effect can be obtained by using a solder paste using a thermosetting flux. By arbitrarily changing the curing temperature of the thermosetting flux, designing from a eutectic composition to a Pb-free solder composition and a melting point range becomes possible. With respect to the mixing ratio of the solder paste, the amount of solder can be reduced, and the flux can fix the component, with the flux content ranging from about 10% by mass to the maximum of 45% by mass. By increasing the content of the flux, the factors for studying the printing conditions when mounting high-density components can be significantly reduced. Further, by using the adhesive flux, the adhesive flux fixes the components even on the double-sided mounting board, so that problems such as component standing and shifting do not occur.

As described above, the present invention is characterized by using a thermosetting flux which has more adhesive strength than a conventional rosin flux and can fix a mounted component. It can be used as a flux alone, a method of using the flux in a solder paste form, or as an underfill substitute for a chip size package (CSP).

[Brief description of the drawings]

FIG. 1 is a graph showing the relationship between the composition of a flux containing solder and the lateral pressing strength.

FIG. 2 is a schematic view illustrating a mounting method for mounting an electronic component on a substrate.

FIG. 3 is a schematic diagram showing a test method of a lateral pressing strength.

FIG. 4 is a graph showing the relationship between the composition of a solder-containing flux and the number of defects.

FIG. 5 is a schematic view showing a method for producing a sheet-like thermosetting flux.

FIG. 6 is a schematic view illustrating a mounting method for mounting an electronic component on a substrate.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 board 2 mounting land 3 solder paste 4 1005 chip capacitor 11 template sheet 12 thermosetting flux 13 squeegee

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C08L 67/00 C08L 67/00 101/08 101/08 H05K 3/34 503 H05K 3/34 503A 504 504B 507 507C (72) Inventor Atsushi Sato 447-1 Shimokuratacho, Totsuka-ku, Yokohama, Kanagawa Prefecture (72) Inventor Shun 473 Shimokuratacho, Totsuka-ku, Yokohama-shi, Kanagawa F term (reference) 4J002 CC033 CD02X CD05X CD06X CD19X CF00W CK03W CL003 CN01W CP033 DA108 DA118 DJ017 EW066 EW176 FD206 FD207 GQ05 4J036 AB07 AD07 AD08 AF06 AK01 AK11 FA02 FA05 FB13 FB16 GA19 GA20 GA22 JA10 5E319 AA03 AB05 AC01 BB05 BB08 CC36 CC61 CD15 CD21 CD26 GG09

Claims (10)

[Claims] (A) a compound having one or more latent carboxyl groups in one molecule; and (B) a reactive functional group capable of forming a chemical bond with a carboxyl group in one molecule by heating. A thermosetting flux for soldering, comprising a compound having at least one compound. 2. The compound represented by the formula (1) wherein the compound having one or more latent carboxyl groups in one molecule of the component (A) has two or more latent carboxyl groups in one molecule. The thermosetting flux for soldering according to claim 1, wherein the flux is a polyhemiacetal ester resin having a structural unit. Embedded image [In the formula (1), R ¹ and R ² are each a divalent organic group, and Y is an oxygen atom or a sulfur atom. ] 3. The reactive functional group capable of forming a chemical bond with the carboxyl group of the component (B) by heating is an epoxy group, and further contains an acid catalyst, a flow regulator or a solvent as required. 1 or 2 thermosetting flux for soldering. 4. The total content of component (A) and component (B) is 1
When the amount is 00% by mass, the component (A) is 10 to 90% by mass, the acid catalyst is 0 to 10% by mass, and the solvent is 0 to 50% by mass based on the total solid content of the components (A) and (B). The thermosetting flux for soldering according to any one of claims 1 to 3, wherein the flux contains 0 to 50% by mass of a flow modifier. 5. The method according to claim 1, further comprising a solder powder.
4. A thermosetting flux for soldering according to any one of (1) to (4). 6. The solder powder is composed of Sn, Cu, Zn, Ag, Sb, P
The thermosetting flux for soldering according to claim 5, which is a solder powder containing at least one selected from b, In, Bi, and Ge. 7. The thermosetting flux for soldering according to claim 1, which is in a liquid, paste or sheet form. 8. A soldering method using the thermosetting flux according to claim 1. 9. The soldering method according to claim 8, which is performed when mounting an electronic component on an electronic component mounting board. 10. An electronic component mounting board obtained by mounting an electronic component on an electronic component mounting board by the soldering method according to claim 9.