JP2018053056A - Thermosetting flux composition and method for manufacturing electronic substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thermosetting flux composition which has a sufficiently high glass transition point of a cured product and is excellent in solderability and self-alignment properties in reflow.SOLUTION: A thermosetting flux composition is used for a case in which an electronic component having a solder bump is joined to an electronic substrate by reflow soldering and contains (A) an epoxy resin, (B) a curing agent and (C) an activator, where the component (B) contains at least one selected from the group consisting of (B1) a polyamine-based curing agent having a melting point of 150°C or higher and (B2) an imidazole-based curing agent, and has viscosity at a temperature of 200°C of 5 Pa s or less and viscosity at a temperature of 250°C of 50 Pa s or more, when the temperature is raised from 25°C at a temperature-rising rate of 5°C/min.SELECTED DRAWING: None

Description

  The present invention relates to a thermosetting flux composition and an electronic substrate manufacturing method.

As electronic devices become smaller and thinner, package parts having solder balls (for example, a ball grid array package: BGA package) are used. Further, such a BGA package is also required to have a fine pitch. However, when a fine pitch BGA package is joined to a mounting substrate, there is a problem that the strength of the joint portion is weak only with solder balls. For this reason, usually, the joint portion is reinforced by filling and curing an underfill material between the BGA package and the mounting substrate. However, since it takes time to fill and cure the underfill material, there is a problem in terms of production cost.
On the other hand, a method has been proposed in which an adhesive containing a flux agent is printed in advance on a mounting substrate, and a package component is mounted on a printed portion (see Patent Document 1).

JP-A-4-280443

  In the method using the adhesive described in Patent Document 1, a cured product of the adhesive remains on the mounting substrate. Therefore, the cured product of this adhesive is also required to pass a durability test (for example, a thermal cycle test) similar to a material (such as a solder resist) used for a mounting substrate. However, since the cured product of the adhesive described in Patent Document 1 has a low glass transition point, the thermal cycle test fails.

  On the other hand, in order to increase the glass transition point of the cured product, there are a method of making the epoxy resin skeleton rigid and a method of increasing the curing rate of the epoxy resin. However, when such a method is used, there is a problem that the solderability and self-alignment property in reflow are impaired. In addition, as a technique for improving solderability and self-alignment in reflow, there are a method of making the epoxy resin skeleton flexible and a method of reducing the curing rate of the epoxy resin. However, when such a method is used, the glass transition point of the cured product is lowered. As described above, the glass transition point of the cured product, the reflow solderability and the self-alignment property are in a trade-off relationship, and it is difficult to improve both of them.

  Therefore, the present invention provides a thermosetting flux composition having a sufficiently high glass transition point of a cured product and excellent in reflow solderability and self-alignment property, and an electronic substrate manufacturing method using the same. The purpose is to do.

In order to solve the above problems, the present invention provides the following thermosetting flux composition and method for producing an electronic substrate.
That is, the thermosetting flux composition of the present invention is a thermosetting flux composition used when an electronic component having solder bumps is joined to an electronic substrate by reflow soldering, and (A) an epoxy resin; (B) a curing agent and (C) an activator, wherein the component (B) is selected from the group consisting of (B1) a polyamine curing agent having a melting point of 150 ° C. or higher and (B2) an imidazole curing agent. When the temperature is increased from a temperature of 25 ° C. to a temperature increase rate of 5 ° C./min, the viscosity at a temperature of 200 ° C. is 5 Pa · s or less, and the viscosity at a temperature of 250 ° C. is 50 Pa. -It is characterized by being more than s.

In the thermosetting flux composition of the present invention, the component (A) preferably contains (A1) a bisphenol A type epoxy resin and (A2) a naphthalene type epoxy resin.
In the thermosetting flux composition of the present invention, the component (B2) is 2-phenyl-4-methyl-5-hydroxymethylimidazole, 2-phenyl-4,5-dihydroxymethylimidazole, 2,4-diamino. -6- [2'-ethyl-4'-methylimidazolyl- (1 ')]-ethyl-s-triazine, 2,4-diamino-6- [2'-methylimidazolyl- (1')]-ethyl- s-triazine, 2,4-diamino-6- [2'-methylimidazolyl- (1 ')]-ethyl-s-triazine isocyanuric acid adduct, 1-cyanoethyl-2-phenylimidazole, 1-cyanoethyl-2- Phenylimidazolium trimellitate, 1-cyanoethyl-2-undecylimidazole, and 2,4-diamino-6- [2′-undecylimidazole - (1 ')] - is preferably at least one selected from the group consisting of ethyl -s- triazine.

In the thermosetting flux composition of this invention, it is preferable that the glass transition point of the hardened | cured material of the said thermosetting flux composition is 100 degreeC or more.
In the thermosetting flux composition of the present invention, the solder bump is preferably made of a solder alloy having a melting point of 200 ° C. or higher and 230 ° C. or lower.

  The method for producing an electronic substrate according to the present invention is a method for producing an electronic substrate using the thermosetting flux composition, wherein an application step of applying the thermosetting flux composition on a wiring board, and solder bumps are provided. A mounting step of mounting the electronic component on the bonding land of the wiring substrate; and heating the wiring substrate on which the electronic component is mounted to melt the solder bump, and the solder bump into the bonding land It is a method characterized by comprising a reflow process for bonding and a thermosetting process for heating and curing the thermosetting flux composition.

According to the thermosetting flux composition of the present invention, the glass transition point of the cured product is sufficiently high, and the reason why the reflow soldering property and the self-alignment property are excellent is not necessarily clear. Guesses as follows.
That is, in the reflow process, the thermosetting flux composition of the present invention uses (B) a curing agent that does not allow the thermosetting flux composition to cure so much. Therefore, since the fluidity of the molten solder is not hindered by the cured product of the thermosetting flux composition, it is possible to maintain reflow solderability and self-alignment properties. On the other hand, since the thermosetting flux composition of the present invention can be sufficiently cured in the thermosetting process after the reflow process, the glass transition point of the cured product can be sufficiently increased. As described above, the present inventors speculate that the effects of the present invention are achieved.

  According to the present invention, there is provided a thermosetting flux composition having a sufficiently high glass transition point of a cured product and excellent in reflow solderability and self-alignment property, and a method for producing an electronic substrate using the same. it can.

[Thermosetting flux composition]
First, the thermosetting flux composition of the present invention will be described.
The thermosetting flux composition of the present invention is a thermosetting flux composition used when an electronic component having solder bumps is joined to an electronic substrate by reflow soldering, and is described below as (A) an epoxy resin, (B) It contains a curing agent and (C) an activator.

In the thermosetting flux composition of the present invention, when the temperature is raised from a temperature of 25 ° C. to a rate of 5 ° C./min, the viscosity at a temperature of 200 ° C. is 5 Pa · s or less, and at a temperature of 250 ° C. The viscosity needs to be 50 Pa · s or more. When the viscosity at a temperature of 200 ° C. exceeds 5 Pa · s, the curing of the thermosetting flux composition proceeds too much, and the fluidity of the molten solder is hindered. descend. On the other hand, when the viscosity at a temperature of 250 ° C. is less than 50 Pa · s, since the curability of the thermosetting flux composition is insufficient, the glass transition point of the cured product is lowered.
Here, the viscosity can be measured by a rheometer. Specifically, the viscosity can be measured under predetermined conditions using a rheometer (manufactured by HAAKE, trade name “MARS-III”).

Moreover, it is preferable that the glass transition point of the hardened | cured material of the thermosetting flux composition of this invention is 100 degreeC or more, It is more preferable that it is 120 degreeC or more, It is especially preferable that it is 130 degreeC or more. If the glass transition point is equal to or higher than the lower limit, it is possible to sufficiently suppress solder cracks in the thermal cycle test.
Here, the glass transition point can be measured using a dynamic viscoelasticity measuring device (DMA). Specifically, using a dynamic viscoelasticity measuring device “DMS6100” manufactured by Seiko Instruments Inc., a cured product of a thermosetting flux composition (thickness: 100 μm, length: 20 mm, width: 4 mm) was used as a sample. Measurement is performed under the condition of a temperature rate of 5 ° C./min, and the peak value of tan δ can be measured as the glass transition point. In addition, about the magnitude | size of a sample, if it is larger than the said conditions, it can measure.

In addition, the following methods are mentioned as a method of adjusting the viscosity in 200 degreeC and 250 degreeC of a thermosetting flux composition, and the glass transition point of hardened | cured material to the range mentioned above.
The viscosity at 200 ° C. and 250 ° C. of the thermosetting flux composition can be adjusted by changing the type of epoxy resin and curing agent (particularly, the type of curing agent). For example, the viscosity at 200 ° C. and 250 ° C. can be adjusted by adjusting the reactivity of the curing agent with the epoxy resin.
The glass transition point of hardened | cured material can be adjusted by changing kinds and compounding quantities, such as an epoxy resin and a hardening | curing agent. For example, the glass transition point can be adjusted by adjusting the combination of the epoxy resin and the curing agent.

[(A) component]
As (A) epoxy resin used for this invention, a well-known epoxy resin can be used suitably. Examples of such epoxy resins include bisphenol A type, bisphenol F type, biphenyl type, naphthalene type, cresol novolak type, phenol novolak type and the like. These epoxy resins may be used individually by 1 type, and may mix and use 2 or more types. Moreover, it is preferable that these epoxy resins are rubber-modified from the viewpoint of impact resistance of the cured product. Further, these epoxy resins preferably contain a liquid at normal temperature, and when a solid is used at normal temperature, it is preferably used in combination with a liquid at normal temperature.

  The component (A) preferably contains (A1) a bisphenol A type epoxy resin and (A2) a naphthalene type epoxy resin from the viewpoint of increasing the glass transition point of the cured product or improving the impact resistance. . In such a case, the mass ratio (A1 / A2) of the component (A1) and the component (A2) is preferably 1/4 or more and 4/1 or less, and more preferably 1/2 or more and 2/1 or less. More preferred.

  The blending amount of the component (A) is preferably 40% by mass to 95% by mass and more preferably 60% by mass to 92% by mass with respect to 100% by mass of the thermosetting flux composition. It is particularly preferably 70% by mass or more and 90% by mass or less. If the blending amount of the component (A) is within the above range, sufficient curability can be ensured and the solder joint between the electronic component and the electronic substrate can be sufficiently reinforced.

[Component (B)]
The (B) curing agent used in the present invention contains at least one selected from the group consisting of (B1) a polyamine curing agent having a melting point of 150 ° C. or higher and (B2) an imidazole curing agent. When these components (B1) and (B2) are used, it is possible to prevent the thermosetting flux composition from curing so much in the reflow process, and in the thermosetting process after the reflow process, thermosetting is performed. The magnetic flux composition can be sufficiently cured.
Moreover, as this (B) component, you may use well-known epoxy resin hardening | curing agents other than (B1) component and (B2) component in the range which does not inhibit the effect of this invention. However, it is preferable not to use dicyandiamide (DICY) and derivatives thereof, or melamine and derivatives thereof, because the thermosetting flux composition is excessively cured in the reflow process. Moreover, when using well-known epoxy resin hardening | curing agents other than (B1) component and (B2) component, it is preferable that the compounding quantity is 10 mass% or less with respect to 100 mass% of (B) component, More preferably, it is 5 mass% or less.

As the component (B1), those having a melting point of 150 ° C. or higher (more preferably 160 ° C. or higher) can be selected from those commercially available as polyamine epoxy curing agents.
As a commercial item of the said (B1) component, the modified | denatured aliphatic polyamine type | system | group hardening | curing agent of Adeka Hardener EH series etc. (made by ADEKA) is mentioned.

Examples of the component (B2) include 2-phenyl-4-methyl-5-hydroxymethylimidazole, 2-phenyl-4,5-dihydroxymethylimidazole, 2,4-diamino-6- [2′-ethyl-4 ′. -Methylimidazolyl- (1 ')]-ethyl-s-triazine, 2,4-diamino-6- [2'-methylimidazolyl- (1')]-ethyl-s-triazine, 2,4-diamino-6 -[2'-methylimidazolyl- (1 ')]-ethyl-s-triazine isocyanuric acid adduct, 1-cyanoethyl-2-phenylimidazole, 1-cyanoethyl-2-phenylimidazolium trimellitate, 1-cyanoethyl- 2-undecylimidazole and 2,4-diamino-6- [2′-undecylimidazolyl- (1 ′)]-ethyl-s-triazine It is below. Among these, 2-phenyl-4-methyl-5-hydroxymethylimidazole, 2,4-diamino-6- [2′-methylimidazolyl- (1 ′)]-ethyl-s-triazine isocyanuric acid adduct, and It is preferable to use 1-cyanoethyl-2-phenylimidazolium trimellitate or the like. These may be used alone or in combination of two or more.
Commercially available products of the component (B2) include 2P4MHZ, 2PHZ-PW, 2E4MZ-A, 2MZ-A, 2MA-OK, 2PZ-CN, 2PZCNS-PW, C11Z-CN, and C11Z-A (Shikoku Chemical Industries, Ltd.) Product name).

  In the present invention, in order to adjust the viscosity at 200 ° C. and 250 ° C. of the thermosetting flux composition and the glass transition point of the cured product to the above-described ranges, as the component (B), the component (B1) and ( It is preferable to use only at least one selected from the group consisting of B2) components.

  The blending amount of the component (B) is preferably 0.1% by mass or more and 10% by mass or less, and 0.2% by mass or more and 5% by mass or less with respect to 100% by mass of the thermosetting flux composition. More preferably, it is more preferably 0.5% by mass or more and 3% by mass or less. If the compounding quantity of (B) component is more than the said minimum, the sclerosis | hardenability of a thermosetting flux composition is securable. On the other hand, if the blending amount of the component (B) is not more than the above upper limit, the storage stability of the thermosetting flux composition can be ensured.

[Component (C)]
Examples of the (C) activator used in the present invention include organic acids, non-dissociative activators composed of non-dissociable halogenated compounds, and amine-based activators.

Examples of the organic acid include other organic acids in addition to monocarboxylic acid and dicarboxylic acid.
Monocarboxylic acids include formic acid, acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, enanthic acid, capric acid, lauric acid, myristic acid, pentadecylic acid, palmitic acid, margaric acid, stearic acid, tuberculostearic acid Arachidic acid, behenic acid, lignoceric acid, glycolic acid and the like.
Examples of the dicarboxylic acid include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, fumaric acid, maleic acid, tartaric acid, diglycolic acid and the like.
Examples of other organic acids include dimer acid, levulinic acid, lactic acid, acrylic acid, benzoic acid, salicylic acid, anisic acid, citric acid, and picolinic acid.

  Examples of the non-dissociative activator include non-salt organic compounds in which halogen atoms are bonded by a covalent bond. The halogenated compound may be a compound formed by covalent bonding of chlorine, bromine and fluorine, such as chlorinated, brominated and fluoride, but any two or all of chlorine, bromine and fluorine may be used. The compound which has the following covalent bond may be sufficient. In order to improve the solubility in an aqueous solvent, these compounds preferably have a polar group such as a hydroxyl group or a carboxyl group such as a halogenated alcohol or a halogenated carboxyl compound. Examples of the halogenated alcohol include 2,3-dibromopropanol, 2,3-dibromobutanediol, trans-2,3-dibromo-2-butene-1,4-diol, 1,4-dibromo-2-butanol, Brominated alcohols such as tribromoneopentyl alcohol, chlorinated alcohols such as 1,3-dichloro-2-propanol and 1,4-dichloro-2-butanol, fluorinated alcohols such as 3-fluorocatechol, and the like Compounds. Examples of the halogenated carboxyl compound include 2-iodobenzoic acid, 3-iodobenzoic acid, 2-iodopropionic acid, 5-iodosalicylic acid, 5-iodoanthranilic acid, and the like, 2-chlorobenzoic acid, 3-chloro Examples thereof include carboxylated carboxyl compounds such as chloropropionic acid, brominated carboxyl compounds such as 2,3-dibromopropionic acid, 2,3-dibromosuccinic acid and 2-bromobenzoic acid, and the like.

  Examples of the amine activator include amines (polyamines such as ethylenediamine), amine salts (amines such as trimethylolamine, cyclohexylamine, diethylamine, and organic acid salts such as amino alcohols and inorganic acid salts (hydrochloric acid, sulfuric acid, odors). Hydroacid, etc.)), amino acids (glycine, alanine, aspartic acid, glutamic acid, valine, etc.), amide compounds and the like. Specifically, diphenylguanidine hydrobromide, cyclohexylamine hydrobromide, diethylamine salt (hydrochloride, succinate, adipate, sebacate, etc.), triethanolamine, monoethanolamine, etc. And the hydrobromide of the amine.

  The blending amount of the component (C) is preferably 1% by mass or more and 25% by mass or less, and preferably 2% by mass or more and 20% by mass or less with respect to 100% by mass of the thermosetting flux composition. More preferably, the content is 3% by mass or more and 15% by mass or less. If the compounding amount of the component (C) is equal to or more than the lower limit, it is possible to prevent the solder joint failure more reliably. Moreover, if the compounding quantity of (C) component is below the said upper limit, the insulation of a thermosetting flux composition is securable.

  The thermosetting flux composition of the present invention may further contain (D) a thixotropic agent in addition to the component (A), the component (B) and the component (C).

[(D) component]
Examples of the thixotropic agent (D) used in the present invention include hardened castor oil, amides, kaolin, colloidal silica, organic bentonite, and glass frit. These thixotropic agents may be used alone or in combination of two or more.

  When the component (D) is used, the blending amount is preferably 0.1% by mass or more and 5% by mass or less, and 0.5% by mass or more and 2% by mass with respect to 100% by mass of the thermosetting flux composition. It is more preferable that the amount is not more than mass%. If the compounding quantity of (D) component is more than the said minimum, sufficient thixotropy will be acquired and dripping can fully be suppressed. Moreover, if the compounding quantity of (D) component is below the said upper limit, thixotropy will be too high and it will not become a printing defect.

[Other ingredients]
The thermosetting flux composition of the present invention, if necessary, in addition to the component (A) to the component (D), a surfactant, a coupling agent, an antifoaming agent, a powder surface treatment agent, a reaction inhibitor. An additive such as an agent, an anti-settling agent and a filler may be contained. As a compounding quantity of these additives, it is preferable that it is 0.01 mass% or more and 10 mass% or less with respect to 100 mass% of thermosetting flux compositions, and 0.05 mass% or more and 5 mass% or less. More preferably.

[Method for producing thermosetting flux composition]
The thermosetting flux composition of this invention can be manufactured by mix | blending the said (A) component-(D) component etc. in the said predetermined ratio, and stirring and mixing.

[Electronic substrate manufacturing method]
Next, the manufacturing method of the electronic substrate of this invention is demonstrated. In addition, the usage method of the thermosetting flux composition of this invention is not necessarily limited to the manufacturing method of the electronic substrate of this invention.
The method for producing an electronic substrate of the present invention is a method using the above-described thermosetting flux composition of the present invention, and includes a coating process, a mounting process, a reflow process, and a thermosetting process described below.

In the coating step, the thermosetting flux composition is coated on the wiring board.
Examples of the wiring board include a printed wiring board and a silicon substrate provided with wiring.
Examples of the coating apparatus include a spin coater, a spray coater, a bar coater, an applicator, a dispenser, and a screen printer. In addition, when using a spin coater, a spray coater, etc. as a coating device, it is preferable to dilute and use a thermosetting flux composition with a solvent.
Solvents include ketones (eg, methyl ethyl ketone, cyclohexanone), aromatic hydrocarbons (eg, toluene, xylene), alcohols (eg, methanol, isopropanol, cyclohexanol), alicyclic hydrocarbons (eg, cyclohexane) , Methylcyclohexane), petroleum-based solvents (eg, petroleum ether, petroleum naphtha), cellosolves (eg, cellosolve, butylcellosolve), (eg, carbitol, butylcarbitol), and esters (eg, ethyl acetate, Butyl acetate, cellosolve acetate, butyl cellosolve acetate, carbitol acetate, butyl carbitol acetate, ethyl diglycol acetate, diethylene glycol monomethyl ether acetate, diethylene glycol Roh ether acetate) and the like. These may be used individually by 1 type, and may mix and use 2 or more types.
The thickness of the coating film (coating film thickness) can be set as appropriate.

In the mounting step, an electronic component having solder bumps is mounted on the bonding land of the wiring board.
Examples of electronic components having solder bumps include BGA packages and chip size packages.
The solder bump is preferably made of a solder alloy having a melting point of 200 ° C. or higher and 230 ° C. or lower. The solder bump may have a surface plated with a solder alloy. Examples of the solder alloy having a melting point of 200 ° C. or higher and 230 ° C. or lower include Sn—Ag—Cu based and Sn—Ag based solder alloys.
As a device used in the mounting process, a known chip mount device can be used as appropriate.
As a material for the bonding land, a known conductive material (copper, silver, etc.) can be used as appropriate.

In the reflow process, the wiring board on which the electronic component is mounted is heated to melt the solder bump, and the solder bump is joined to the joining land.
As an apparatus used here, a well-known reflow furnace can be used suitably.
What is necessary is just to set reflow conditions suitably according to melting | fusing point of solder. For example, when using a Sn—Au—Cu-based solder alloy, preheating may be performed at a temperature of 150 to 180 ° C. for 60 to 120 seconds, and a peak temperature may be set to 220 to 260 ° C.

In the thermosetting step, the thermosetting flux composition is heated and cured.
As heating conditions, the heating temperature is preferably 150 ° C. or higher and 220 ° C. or lower, and more preferably 180 ° C. or higher and 200 ° C. or lower. When the heating temperature is within the above range, the thermosetting flux composition can be sufficiently cured, and there is little adverse effect on the electronic components mounted on the electronic substrate.
The heating time is preferably 10 minutes or more and 3 hours or less, and more preferably 30 minutes or more and 90 minutes or less. When the heating time is within the above range, the thermosetting flux composition can be sufficiently cured, and there is little adverse effect on the electronic component mounted on the electronic substrate.

According to the method for manufacturing an electronic substrate as described above, the joint portion by the solder bump can be reinforced by the cured product of the thermosetting flux composition.
In addition, the manufacturing method of the electronic substrate of this invention is not limited to the said embodiment, The deformation | transformation in the range which can achieve the objective of this invention, improvement, etc. are included in this invention.

EXAMPLES Next, although an Example and a comparative example demonstrate this invention further in detail, this invention is not limited at all by these examples. In addition, the material used in the Example and the comparative example is shown below.
((A1) component)
Epoxy resin A: bisphenol A type epoxy resin, trade name “EPICLON EXA-850CRP”, manufactured by DIC (component (A2))
Epoxy resin B: Naphthalene type epoxy resin, trade name “EPICLON HP-4032D”, manufactured by DIC (component (B1))
Curing agent A: Modified aliphatic polyamine curing agent, trade name “ADEKA HARDNER EH”, manufactured by ADEKA (component (B2))
Curing agent B: 2-phenyl-4-methyl-5-hydroxymethylimidazole, trade name “2P4MHZ”, manufactured by Shikoku Kasei Kogyo Co., Ltd. (component (C))
Activator A: Adipic acid Activator B: Benzylamine adipate (component (D))
Thixo: Brand name “Gelall D”, manufactured by Shin Nippon Rika Co., Ltd. (other ingredients)
Curing agent C: Dicyandiamide curing agent D: Melamine

[Example 1]
44 parts by mass of epoxy resin A, 44 parts by mass of epoxy resin B, 2 parts by mass of curing agent A, 5 parts by mass of activator A, 5 parts by mass of activator B, and 1 part by mass of thixotropic agent are put into a container and pulverized and mixed in a pulverizer. And dispersed to obtain a thermosetting flux composition.
Further, 10 parts by mass of a solvent (propylene glycol monomethyl ether acetate) was added to 100 parts by mass of the obtained thermosetting flux composition to prepare a spin coater coating solution.
Next, a substrate on which chip components can be mounted is prepared, and a solder paste (SAC solder paste, manufactured by Tamura Corporation) is applied onto the electrodes of this substrate by screen printing, followed by reflow treatment, and solder bumps are applied. Formed and then washed.
And the coating liquid for spin coaters was apply | coated on the obtained board | substrate using the spin coater. The coating film thickness of the coating film was 30 μm. Next, a chip component (1005 chip, solder alloy: Sn—Au3.0-Cu0.5, melting point of solder: 217 ° C. to 220 ° C.) is mounted on the bonding land of the substrate after the coating film is formed and reflowed. Heated through a furnace (Tamura Seisakusho). The reflow conditions here are a preheat temperature of 150 to 180 ° C. (60 seconds), a temperature of 220 ° C. or higher for 50 seconds, and a peak temperature of 230 ° C. Thereafter, the substrate after reflowing was put into a heating furnace and subjected to a heat treatment for 1 hour at a temperature of 200 ° C., thereby producing a substrate for a thermal cycle test.

[Example 2, Comparative Examples 1 and 2]
A thermosetting flux composition, a spin coater coating solution, and a substrate for a thermal cycle test were obtained in the same manner as in Example 1 except that each material was blended according to the composition shown in Table 1.

<Evaluation of thermosetting flux composition>
Evaluation of the thermosetting flux composition (viscosity of the thermosetting flux composition at 200 ° C. and 250 ° C., glass transition point of the cured product, solder meltability, cooling cycle test) was performed by the following methods. The obtained results are shown in Table 1.
(1) Viscosity of thermosetting flux composition Using a rheometer (manufactured by HAAKE, trade name “MARS-III”), the temperature is raised from a temperature of 25 ° C. to the melting point of the solder at a rate of 5 ° C./min. While measuring the viscosity of the thermosetting flux composition. From the obtained results, (i) viscosity at a temperature of 200 ° C. and (ii) viscosity at a temperature of 250 ° C. were determined. And about the viscosity, it divided according to the following reference | standard.
A: The viscosity is 5 Pa · s or less.
B: The viscosity is more than 5 Pa · s and less than 50 Pa · s.
C: The viscosity is 50 Pa · s or more.
(2) Glass transition point of cured product Using a dynamic viscoelasticity measuring device “DMS6100” manufactured by Seiko Instruments Inc., a cured product of a thermosetting flux composition (curing condition: 200 ° C. for 1 hour, thickness: 100 μm, long The measurement was performed under the condition of a temperature rising rate of 5 ° C./min using a sample of 20 mm in width and 4 mm in width. From the obtained graph, the peak value of tan δ was read as the glass transition point.
(3) Solder meltability 50% by mass of thermosetting flux composition and 50% by mass of solder powder (solder alloy: Sn-Au3.0-Cu0.5, particle size distribution: 20 to 40 μm) are mixed, A mixed sample was obtained. The obtained mixed sample was formed on a substrate (surface material: copper) by a screen printing method to form a coating film having a diameter of 1 cm and a thickness of 50 μm, and heated on a hot plate set at a temperature of 250 ° C. for 30 seconds. And the molten state of the solder was observed visually and the solder meltability was evaluated according to the following criteria.
○: Solder melted.
X: Solder did not melt.
(4) Thermal cycle test The substrate for the thermal cycle test is put in a thermal cycle tester, left at a temperature of −40 ° C. for 10 minutes and then left at a temperature of 125 ° C. for 10 minutes, which is 2000 cycles. A repeated cooling / heating cycle test was performed (according to the cooling / heating cycle test of the in-vehicle solder paste). The substrate after the thermal cycle test was observed with a microscope, the presence or absence of solder cracks in the chip components was confirmed, and the resistance to the thermal cycle test was evaluated according to the following criteria.
○: The location where solder cracks occurred is less than 90%.
X: The location where the solder crack occurred is 90% or more.

  As is apparent from the results shown in Table 1, when the thermosetting flux composition of the present invention is used (Examples 1 and 2), the solder meltability is good and the glass transition point of the cured product is sufficient. It was confirmed that the resistance to the thermal cycle test was good. Moreover, since it has solder melting property, it was confirmed that the reflow solderability and the self-alignment property are excellent.

  The thermosetting flux composition of the present invention can be particularly suitably used as a technique for mounting an electronic component on an electronic substrate such as a printed wiring board of an electronic device.

Claims (6)

A thermosetting flux composition used when an electronic component having solder bumps is joined to an electronic substrate by reflow soldering,
(A) an epoxy resin, (B) a curing agent, and (C) an activator,
The component (B) contains at least one selected from the group consisting of (B1) a polyamine curing agent having a melting point of 150 ° C. or higher and (B2) an imidazole curing agent,
When the temperature is raised from 25 ° C. at a rate of 5 ° C./min, the viscosity at a temperature of 200 ° C. is 5 Pa · s or less, and the viscosity at a temperature of 250 ° C. is 50 Pa · s or more. A thermosetting flux composition. In the thermosetting flux composition according to claim 1,
The component (A) contains (A1) a bisphenol A type epoxy resin and (A2) a naphthalene type epoxy resin. A thermosetting flux composition, wherein: In the thermosetting flux composition according to claim 1 or claim 2,
The component (B2) is 2-phenyl-4-methyl-5-hydroxymethylimidazole, 2-phenyl-4,5-dihydroxymethylimidazole, 2,4-diamino-6- [2′-ethyl-4′- Methylimidazolyl- (1 ′)]-ethyl-s-triazine, 2,4-diamino-6- [2′-methylimidazolyl- (1 ′)]-ethyl-s-triazine, 2,4-diamino-6 [2′-Methylimidazolyl- (1 ′)]-ethyl-s-triazine isocyanuric acid adduct, 1-cyanoethyl-2-phenylimidazole, 1-cyanoethyl-2-phenylimidazolium trimellitate, 1-cyanoethyl-2 Consisting of -undecylimidazole and 2,4-diamino-6- [2'-undecylimidazolyl- (1 ')]-ethyl-s-triazine Thermosetting flux composition which is characterized in that at least one selected from the. In the thermosetting flux composition according to any one of claims 1 to 3,
The thermosetting flux composition characterized by the glass transition point of the hardened | cured material of the said thermosetting flux composition being 100 degreeC or more. In the thermosetting flux composition according to any one of claims 1 to 4,
The said solder bump consists of a solder alloy whose melting | fusing point is 200 degreeC or more and 230 degrees C or less. The thermosetting flux composition characterized by the above-mentioned. A method for producing an electronic substrate using the thermosetting flux composition according to any one of claims 1 to 5,
An application step of applying the thermosetting flux composition on the wiring board;
A mounting step of mounting electronic components having solder bumps on the bonding lands of the wiring board;
A reflow step of heating the wiring board on which the electronic component is mounted to melt the solder bump and bonding the solder bump to the bonding land;
And a thermosetting step of heating and curing the thermosetting flux composition. An electronic substrate manufacturing method comprising: