JP2019166550A - Thermosetting flux composition and method for manufacturing electronic substrate - Google Patents

Abstract

To provide a thermosetting flux composition having a high reinforcing effect by a cured product, excellent insulation properties of the cured product, and excellent solderability.SOLUTION: A thermosetting flux composition of the present invention is used when an electronic component having a solder bump made of a solder alloy having a melting point of 130°C or higher and 240°C or lower is bonded to an electronic substrate by reflow soldering or thermocompression bonding, and contains (A) an oxetane compound, (B) an activator, and (C) an inorganic filler, wherein the component (A) contains (A1) a bifunctional oxetane compound having two oxetane rings in one molecule, and wherein the component (B) contains (B1) an organic acid. When the temperature of the thermosetting flux composition is increased from 25°C at a rate of temperature rise of 5°C/min, the thermosetting flux composition exhibits a viscosity of 5 Pa s or less at 200°C, and a viscosity of 50 Pa s or more at 250°C.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

With the recent lead-free soldering, solder alloys having a high melting point (for example, a melting point of 200 ° C. or higher) have been used. However, when soldering a solder bump made of a high-melting-point solder alloy by the method using the adhesive described in Patent Document 1, the adhesive cures too much to inhibit the flow of molten solder. In addition, there is a problem that the solderability is impaired.
Moreover, in the method using the adhesive described in Patent Document 1, a cured product of the adhesive remains on the mounting substrate. For this reason, the cured product of the adhesive is also required to have insulating properties, as is the case with materials (such as solder resists) used for mounting substrates. Even if the solderability is improved by, for example, a method of reducing the curing rate of the adhesive, the insulation of the cured adhesive becomes a problem.
As described above, the insulation and solderability of the cured product are in a trade-off relationship, and it has been difficult to improve them together.
Further, from the viewpoint of reinforcing the joint portion, further improvement is required, and further improvement in the strength of the joint portion of the package component is required.

  Therefore, the present invention provides a thermosetting flux composition having a high reinforcing effect by a cured product, excellent insulation of the cured product, and excellent solderability, and a method for producing an electronic substrate using the same. Objective.

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 heat used when an electronic component having a solder bump made of a solder alloy having a melting point of 130 ° C. or higher and 240 ° C. or lower is joined to an electronic substrate by reflow soldering or thermocompression bonding. A curable flux composition comprising (A) an oxetane compound, (B) an activator, and (C) an inorganic filler, wherein the component (A) comprises (A1) two molecules in one molecule. Containing a bifunctional oxetane compound having an oxetane ring,
When the component (B) contains (B1) an organic acid and is heated at a temperature increase rate of 25 ° C./min from a temperature of 25 ° C., 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.

The thermosetting flux composition of the present invention may further contain (D) an epoxy resin.
In the thermosetting flux composition of the present invention, the component (C) is preferably at least one selected from the group consisting of a silica filler and an alumina filler.
In the thermosetting flux composition of the present invention, the component (C) is preferably surface-treated.
In the thermosetting flux composition of this invention, it is preferable that the compounding quantity of the said (C) component is 20 mass% or more and 70 mass% or less with respect to 100 mass% of said thermosetting flux compositions.

In the first method for producing an electronic substrate of the present invention, an application step of applying the thermosetting flux composition and an electronic component having solder bumps are mounted on a bonding land of the wiring substrate on the wiring substrate. A mounting step, a reflow step in which the solder bump is melted by heating the wiring substrate on which the electronic component is mounted, and the solder bump is bonded to the bonding land; and the thermosetting flux composition is heated. And a thermosetting step of curing.
According to a second method for producing an electronic substrate of the present invention, an application step of applying the thermosetting flux composition on a wiring substrate and an electronic component having solder bumps are mounted on a bonding land of the wiring substrate. It is a method comprising a mounting step, a thermocompression step for thermocompression bonding the electronic component to the wiring board, and a thermosetting step for heating and curing the thermosetting flux composition.
In the method for manufacturing an electronic substrate according to the present invention, it is preferable that a solder precoat is formed in advance on the bonding land.

The reason why the thermosetting flux composition of the present invention has a high reinforcing effect by the cured product, excellent insulation of the cured product, and excellent solderability is not necessarily clear, but the present inventors have as follows. I guess.
That is, the thermosetting flux composition of the present invention uses (A) an oxetane compound that does not allow the thermosetting flux composition to cure so much in the reflow process. Therefore, since the fluidity of the molten solder is not hindered by the cured product of the thermosetting flux composition, the solderability can be maintained. 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 insulation of the cured product can be secured. Furthermore, since the thermosetting flux composition of the present invention contains (C) an inorganic filler, the difference between the linear thermal expansion coefficient between the cured product of the thermosetting flux composition and the electronic component can be reduced, Moreover, the elasticity modulus of the hardened | cured material of a thermosetting flux composition can be raised, and the reinforcement effect can be heightened. On the other hand, even if the (C) inorganic filler is blended, the solderability can be maintained if the thermosetting flux composition has a viscosity at a temperature of 200 ° C. of 5 Pa · s or less. As described above, the present inventors speculate that the effects of the present invention are achieved.

  ADVANTAGE OF THE INVENTION According to this invention, the reinforcement effect by hardened | cured material is high, can provide the thermosetting flux composition which is excellent in the insulation of hardened | cured material, and is excellent in solderability, and the manufacturing method of an electronic substrate using the same.

[Thermosetting flux composition]
First, the thermosetting flux composition of this embodiment will be described.
The thermosetting flux composition of the present embodiment is a thermosetting flux composition used when an electronic component having solder bumps is joined to an electronic substrate by reflow soldering or thermocompression bonding, and will be described below (A ) An oxetane compound, (B) an organic acid, and (C) an inorganic filler.

In the thermosetting flux composition of the present embodiment, the viscosity at a temperature of 200 ° C. is 5 Pa · s or less and the temperature is 250 ° C. when the temperature is increased from a temperature of 25 ° C. to a temperature increase rate of 5 ° C./min. It is necessary that the viscosity at is 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 thermosetting flux composition has insufficient curability, the insulation of the cured product becomes insufficient.
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”).

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 a solder composition in the range mentioned above.
The viscosity at 200 ° C. and 250 ° C. of the thermosetting flux composition can be adjusted, for example, by the following method.
(I) Changing the type of oxetane compound, organic acid, inorganic filler and the like.
(Ii) A combination of an oxetane compound and an epoxy resin.
(Iii) Use a curing agent.
(Iv) Changing the blending amount of the inorganic filler.

[(A) component]
As the (A) oxetane compound used in the present embodiment, a known oxetane compound can be appropriately used. Moreover, this (A) component needs to contain the bifunctional oxetane compound which has two oxetane rings in 1 molecule (A1).
Moreover, this (A) component may contain the monofunctional oxetane compound which has one oxetane ring in 1 molecule (A2). By containing this component (A2), the curing temperature of the thermosetting flux composition can be increased, and the curing temperature of the thermosetting flux composition can be adjusted.

As the component (A1), xylylene bisoxetane (“OXT-121” manufactured by Toagosei Co., Ltd.), 3-ethyl-3 {[(3-ethyloxetane-3-yl) methoxy] methyl} oxetane (Toagosei Co., Ltd.) "OXT-221" manufactured by the same company), and bifunctional oxetane compounds having a biphenyl skeleton ("ETERRNACOLL OXBP" manufactured by Ube Industries, Ltd.).
Examples of the component (A2) include 3-ethyl-3-hydroxymethyloxetane (“OXT-101” manufactured by Toagosei Co., Ltd.), 2-ethylhexyloxetane (“OXT-212” manufactured by Toagosei Co., Ltd.), and 3 -Ethyl-3- (methacryloyloxy) methyloxetane ("ETERNACOLL OXMA" manufactured by Ube Industries) is included.

  When the components (A1) and (A2) are used in combination, the mass ratio ((A1) / (A2)) of the component (A1) to the component (A2) is preferably 1 or more and 50 or less. It is more preferably 30 or less and particularly preferably 2 or more and 20 or less. If mass ratio is in the said range, the curing temperature of a thermosetting flux composition can be adjusted, maintaining the insulation of the hardened | cured material of a thermosetting flux composition.

  The blending amount of the component (A) is preferably 20% by mass or more and 75% by mass or less, and 22% by mass or more and 70% by mass or less, in terms of solid content, with respect to 100% by mass of the thermosetting flux composition. More preferably, it is more preferably 25% by mass or more and 60% 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)]
Examples of the (B) activator used in this embodiment include organic acids, organic acid amine salts, non-dissociative activators composed of non-dissociable halogenated compounds, and amine-based activators. These activators may be used individually by 1 type, and may mix and use 2 or more types. Moreover, this (B) component needs to contain (B1) organic acid. In the reflow process, since the curing reaction between the organic acid and the oxetane compound does not proceed so much, the curing temperature of the thermosetting flux composition can be adjusted to an appropriate range.

Examples of the component (B1) include other organic acids in addition to monocarboxylic acid and dicarboxylic acid. These may be used alone or in combination of two or more.
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, and diglycolic acid. Among these, glutaric acid, adipic acid, pimelic acid, and suberic acid are preferable from the viewpoint of physical properties of the cured product of the thermosetting flux composition.
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.

  The blending amount of the component (B1) is preferably 1% by mass or more and 35% by mass or less, preferably 2% by mass or more and 25% by mass or less, in terms of solid content, with respect to 100% by mass of the thermosetting flux composition. It is more preferable that it is 3 mass% or more and 15 mass% or less. If the blending amount of the component (B1) is equal to or greater than the lower limit, it is possible to more reliably prevent solder bonding defects. Moreover, if the compounding quantity of (B1) component is below the said upper limit, the insulation of a thermosetting flux composition is securable.

The component (B) may contain an activator other than the component (B1) (component (B2)) as necessary. Examples of the component (B2) include organic acid amine salts, non-dissociative activators composed of non-dissociable halogenated compounds, and amine-based activators.
The organic acid amine salt is an amine salt of the component (B1). As the amine, a known amine can be appropriately used. Such an amine may be an aromatic amine or an aliphatic amine. These may be used alone or in combination of two or more. As such an amine, from the viewpoint of the stability of the organic acid amine salt, it is preferable to use an amine having 3 to 13 carbon atoms, and it is more preferable to use a primary amine having 4 to 7 carbon atoms. preferable.
Aromatic amines include benzylamine, aniline, 1,3-diphenylguanidine and the like. Of these, benzylamine is particularly preferred.
Examples of the aliphatic amine include propylamine, butylamine, pentylamine, hexylamine, heptylamine, octylamine, cyclohexylamine, and triethanolamine.

  Examples of the non-dissociable activator comprising a non-dissociable halogenated compound 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. 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, And 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 compound similar to these is mentioned. Examples of the halogenated carboxyl include 2-iodobenzoic acid, 3-iodobenzoic acid, 2-iodopropionic acid, 5-iodosalicylic acid, 5-iodoanthranilic acid, and the like, 2-chlorobenzoic acid, and 3- Examples thereof include carboxyl chloride such as chloropropionic acid, brominated carboxyl such as 2,3-dibromopropionic acid, 2,3-dibromosuccinic acid, and 2-bromobenzoic acid, and similar compounds.

  Examples of amine activators include amines (such as polyamines such as ethylenediamine), amine salts (such as ethylamine, diethylamine, trimethylolamine, cyclohexylamine, and amines such as diethylamine and organic acid salts such as amino alcohols and inorganic acid salts (hydrochloric acid). , Sulfuric acid, hydrobromic acid, etc.)), amino acids (glycine, alanine, aspartic acid, glutamic acid, valine, etc.), amide compounds, and the like. Specifically, ethylamine hydrobromide, diphenylguanidine hydrobromide, cyclohexylamine hydrobromide, diethylamine salts (such as hydrochloride, succinate, adipate, and sebacate), tris Examples include ethanolamine, monoethanolamine, and hydrobromides of these amines.

  (B) As a compounding quantity of a component, it is preferable that they are 1 mass% or more and 35 mass% or less with respect to 100 mass% of thermosetting flux compositions in conversion of solid content, and 2 mass% or more and 25 mass% or less. It is more preferable that it is 3 mass% or more and 15 mass% or less. If the blending amount of the component (B) is equal to or greater than the lower limit, it is possible to more reliably prevent solder bonding defects. Moreover, if the compounding quantity of (B) component is below the said upper limit, the insulation of a thermosetting flux composition is securable.

[Component (C)]
As the inorganic filler (C) used in the present embodiment, a known inorganic filler can be used as appropriate. The component (C) is preferably subjected to a surface treatment from the viewpoint that the blending amount in the thermosetting flux composition can be increased. (C) As a component, a silica filler, an alumina filler, etc. are mentioned. These may be used alone or in combination of two or more.
The average particle size of the component (C) is preferably 0.01 μm or more and 15 μm or less, more preferably 0.1 μm or more and 10 μm or less, from the viewpoint of ease of blending into the thermosetting flux composition. preferable. The average particle size can be measured with a dynamic light scattering type particle size measuring device.

  (C) As a compounding quantity of a component, it is preferable that it is 20 mass% or more and 70 mass% or less with respect to 100 mass% of thermosetting flux compositions in conversion of solid content, and 22 mass% or more and 60 mass% or less. It is more preferable that it is 25 mass% or more and 55 mass% or less. If the blending amount of the component (C) is equal to or greater than the lower limit, the solder joint reinforcing effect can be further improved. Moreover, if the compounding quantity of (C) component is below the said upper limit, the viscosity of a thermosetting flux composition can be made lower.

  The thermosetting flux composition of the present embodiment is selected from the group consisting of (D) an epoxy resin and (E) a curing agent in addition to the component (A) to the component (C) as necessary. You may further contain at least 1 sort.

[(D) component]
As (D) epoxy resin used for this embodiment, a well-known epoxy resin can be used suitably. By this (D) component, the glass transition point of hardened | cured material can be raised or impact resistance can be improved. Moreover, the curing temperature of a thermosetting flux composition can be adjusted with this (D) component.
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 (D) is more preferably a bisphenol A type epoxy resin or a naphthalene type epoxy resin from the viewpoint of increasing the glass transition point of the cured product and increasing the impact resistance.

  When the component (D) is used, the blending amount is preferably 1% by mass or more and 30% by mass or less, and preferably 2% by mass or more and 25% by mass or less in terms of solid content with respect to 100% by mass of the thermosetting flux composition. The content is more preferably at most 3 mass%, particularly preferably at least 3 mass% but at most 20 mass%. If the compounding quantity of (D) component is in the said range, the intensity | strength of the hardened | cured material of a thermosetting flux composition can be improved, without making the hardening temperature of a thermosetting flux composition too low.

[(E) component]
As the (E) curing agent used in the present embodiment, a known curing agent can be used as appropriate. With this component (E), the curing temperature of the thermosetting flux composition can be adjusted. As the component (E), for example, a cationic polymerization initiator can be used. The cationic polymerization initiator is one that generates an acid by heat or light. In this embodiment, it is preferable to use a thermal cationic polymerization initiator that generates an acid by heat.
Examples of the thermal cationic polymerization initiator include aryl diazonium salts, aryl iodonium salts, aryl sulfonium salts, allene-ion complexes, quaternary ammonium salts, aluminum chelates, and boron trifluoride amine complexes. Among these, arylsulfonium salts are preferable from the viewpoint of adjusting the curing temperature of the thermosetting flux composition to an appropriate range.

  When the component (E) is used, the blending amount is preferably 0.01% by mass or more and 10% by mass or less with respect to 100% by mass of the thermosetting flux composition in terms of solid content. It is more preferably from 5% by mass to 5% by mass, and particularly preferably from 0.05% by mass to 3% by mass. If the compounding quantity of (E) component is more than the said minimum, the sclerosis | hardenability of a thermosetting flux composition can be improved. On the other hand, if the amount of component (E) is not more than the above upper limit, the storage stability of the thermosetting flux composition can be ensured.

[Other ingredients]
The thermosetting flux composition of the present embodiment, if necessary, in addition to the component (A) to the component (E), a thixotropic agent, a surfactant, a coupling agent, an antifoaming agent, and a powder surface treatment An additive such as an agent, a reaction inhibitor, 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 in conversion of solid content, 0.05 mass% or more More preferably, it is 5 mass% or less. Moreover, the thermosetting flux composition of the present embodiment may contain a solvent from the viewpoint of adjustment of applicability. When using a solvent, the compounding quantity is not particularly limited.

[Method for producing thermosetting flux composition]
The thermosetting flux composition of the present embodiment can be produced by blending the component (A) to the component (C) at the predetermined ratio and stirring and mixing.

[Electronic substrate manufacturing method]
Next, the manufacturing method of the electronic substrate of this embodiment is demonstrated. In addition, the usage method of the thermosetting flux composition of this embodiment is not necessarily limited to the manufacturing method of the electronic substrate of this embodiment.
The manufacturing method of the 1st electronic substrate of this embodiment is a method using the thermosetting flux composition of this embodiment mentioned above, Comprising: The coating process, mounting process, reflow process, and thermosetting process which are demonstrated below are provided. .

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 (such as methyl ethyl ketone and cyclohexanone), aromatic hydrocarbons (such as toluene and xylene), alcohols (such as methanol, isopropanol and cyclohexanol), and alicyclic hydrocarbons (such as cyclohexane and methylcyclohexane). Petroleum solvents (such as petroleum ether and petroleum naphtha), cellosolves (such as cellosolve and butylcellosolve), carbitols (such as carbitol and 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, and Ethylene glycol monoethyl 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 made of a solder alloy having a melting point of 130 ° C. or higher and 240 ° 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 130 ° C. or higher and 150 ° C. or lower include Sn—Bi solder alloys. Moreover, as a solder alloy whose melting | fusing point is 200 degreeC or more and 240 degrees C or less, solder alloys, such as Sn-Ag-Cu type and Sn-Ag type, are mentioned.
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. Note that a solder precoat is preferably formed in advance on the bonding lands. The solder precoat is a solder thin film provided on the bonding land for the purpose of preventing oxidation of copper or the like of the bonding land, for example. By this solder pre-coating, the joint strength at the joint can be further improved. Examples of the method for forming the solder precoat include (i) a method in which a solder composition is printed on a bonding land and a reflow treatment is performed, (ii) a method by solder plating, and (iii) a method by hot air leveler. .

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—Ag—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 from 10 minutes to 3 hours, more preferably from 20 minutes to 90 minutes, and particularly preferably from 30 minutes to 60 minutes. 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 manufacturing method of the 1st electronic board as mentioned above, the junction part by a solder bump can be reinforced with the hardened | cured material of a thermosetting flux composition.

  Next, the manufacturing method of the 2nd electronic substrate of this embodiment is demonstrated. However, since the manufacturing method of the second electronic substrate is the same as the manufacturing method of the first electronic substrate described above except that the reflow process is changed to the thermocompression bonding process, the description other than the thermocompression bonding process is omitted.

In the thermocompression bonding step, the electronic component is thermocompression bonded to the wiring board.
The temperature at the time of thermocompression bonding is preferably a temperature higher than the melting point of the solder (more preferably a temperature higher by 10 ° C. or more). If the temperature during thermocompression bonding is higher than the melting point of the solder, the solder can be sufficiently melted.
For example, when using a Sn—Ag—Cu-based solder alloy, the temperature during thermocompression bonding is preferably 200 ° C. or higher and 250 ° C. or lower.
Although the pressure at the time of thermocompression bonding is not particularly limited, it is preferably 0.05 MPa or more and 4 MPa or less, more preferably 0.1 MPa or more and 2 MPa or less from the viewpoint of the balance between solderability and stress on the substrate. Preferably, it is particularly preferably 0.3 MPa or more and 1 MPa or less.
The time for thermocompression bonding is not particularly limited, but is preferably 1 second or longer and 60 seconds or shorter, more preferably 2 seconds or longer and 20 seconds or shorter, and particularly preferably 3 seconds or longer and 15 seconds or shorter.

According to the manufacturing method of the second electronic substrate as described above, the joint portion by the solder bump can be reinforced by the cured product of the thermosetting flux composition.
Note that the thermosetting flux composition of this embodiment and the method for producing an electronic substrate are not limited to the above-described embodiments, and modifications, improvements, etc. within a range that can achieve the object of the present invention are included in the present invention. It is included.

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)
Bifunctional oxetane compound: Trade name “ETERRNACOLL OXBP”, manufactured by Ube Industries, Ltd. (component (B1))
Activator: Adipic acid (component (C))
Inorganic filler A: Silica filler (surface treatment is vinyl treatment, average particle size is 7 μm), trade name “5 μm SV-E6”, manufactured by Admatex, Inc. Inorganic filler B: Silica filler (surface treatment is vinyl treatment, average particle size is 0) 0.5 μm), trade name “SC2500-SVJ”, inorganic filler C manufactured by Admatechs: silica filler (surface treatment is vinyl treatment, average particle size is 0.3 μm), trade name “0.3 μm SV-C5”, Admatechs Inorganic filler D: silica filler (surface treatment is trimethyl treatment, average particle size is 0.5 μm), trade name “0.5 μm ST-E2”, Admatex inorganic filler E: alumina filler (surface treatment is phenylamino Treatment, average particle diameter is 0.6 μm), trade name “AC2500-SXQ”, Admatechs inorganic filler F: Silica filler (no surface treatment, average particle size is 0.6 μm), trade name “SPH507-05”, manufactured by Micron (component (D))
Epoxy resin A: heat-resistant epoxy resin, trade name “NC-7000L”, Nippon Kayaku's epoxy resin B: bisphenol A type epoxy resin, trade name “EPICLON EXA-850CRP”, DIC's epoxy resin C: naphthalene type Epoxy resin, trade name “EPICLON HP-4032D”, manufactured by DIC (component (E))
Curing agent A: Cationic polymerization initiator, trade name “SAN-AID SI-B4”, Sanshin Chemical Co., Ltd. hardener B: 2-phenyl-4-methyl-5-hydroxymethylimidazole, trade name “2P4MHZ”, Made by Shikoku Chemicals

[Example 1]
25% by mass of a bifunctional oxetane compound, 15% by mass of an activator and 60% by mass of inorganic filler A are charged into a container, and are pulverized, mixed and dispersed in a pulverizer / mixer (three rolls) to obtain a thermosetting flux composition. Obtained.
Next, a substrate (number of pads: 30, pad diameter: 130 μm, pad pitch: 180 μm) on which chip components can be mounted is prepared, and solder paste (SAC, manufactured by Tamura Seisakusho Co., Ltd.) is formed on the electrodes of this substrate by screen printing. System solder paste) was applied, reflowed to form a solder precoat, and then washed.
And the thermosetting flux composition was printed on the obtained board | substrate using the metal mask (opening: 2 mm x 2 mm, thickness: 0.5 mm). Next, a chip component (silicon chip, solder alloy: Sn-Ag3.0-Cu0.5, solder melting point: 217 ° C. to 220 ° C.) having solder bumps is placed on the bonding lands of the substrates after the coating film is formed. It was mounted and heated while observing the reflow conditions with a high temperature observation device (SMT scope SK5000, manufactured by Sanyo Seiko Co., Ltd.). 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 250 ° C. Thereafter, the substrate after reflowing was put into a heating furnace and subjected to a heat treatment at a temperature of 200 ° C. for 3 hours to produce an evaluation substrate.

[Examples 2 to 9 and Comparative Examples 1 to 3]
A thermosetting flux composition and an evaluation substrate 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 at 200 ° C. and 250 ° C., reflow bondability, shear strength, impact resistance, insulation of the thermosetting flux composition) 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) Reflow Bondability For the evaluation substrate, the resistance value between the electrodes was measured using a digital multimeter (“34401A” manufactured by Agilent, measurement voltage: 15 V), and the presence or absence of conduction was confirmed. Moreover, the X-ray inspection apparatus (made by Nordson DAGE) observed the solder joint part, and confirmed the presence or absence of solder joint. The reflow bondability was evaluated according to the following criteria.
○: Conductivity was obtained and solder joint was confirmed.
(Triangle | delta): Although conduction | electrical_connection was taken, the solder joint with a bad shape was confirmed partially.
X: Conductivity cannot be obtained.
(3) Shear strength The silicon chip on the evaluation substrate was peeled off with a bond tester (manufactured by Nordson Advanced Technology), and the shear strength (unit: N) at that time was measured. And shear strength was evaluated according to the following reference | standard. In Comparative Examples 2 and 3, since the evaluation of the reflow bondability was “x”, the shear strength was not evaluated.
○: The shear strength is 20 N or more.
(Triangle | delta): Shear strength is 10N or more and less than 20N.
X: Shear strength is less than 10N.
(4) Impact resistance The evaluation substrate was dropped from a height of 100 cm, and it was determined whether or not the soldering breakage occurred on the evaluation substrate. When the resistance value between the soldered electrodes is measured using a digital multimeter (“34401A” manufactured by Agilent, measurement voltage: 15 V), and the resistance value becomes 1000Ω or more due to a drop impact, the solder It was determined that the ball was destroyed. Then, the number of drops until the solder ball was broken was measured, and the impact resistance was evaluated according to the following criteria. In Comparative Examples 2 and 3, since the evaluation of the reflow bondability was “x”, the impact resistance was not evaluated.
○: The number of drops is 10 or more.
(Triangle | delta): The frequency | count of dropping is 5 times or more and less than 10 times.
X: The number of drops is less than 5.
(5) Insulation 50% by mass of thermosetting flux composition and 50% by mass of solder powder (solder alloy: Sn-Ag3.0-Cu0.5, average particle size: 20 μm, particle size distribution: 10-40 μm) Were mixed to obtain a solder composition.
About the obtained solder composition, the insulation resistance value was measured based on the insulation resistance test of 8.5.3 of JIS Z3284-1 and JIS Z3197. That is, a skewer electrode substrate (conductor width: 0.318 mm, conductor interval: 0.318 mm, size: 30 mm × 30 mm), metal mask (processed into a slit shape in accordance with the skewer electrode pattern, thickness: 100 μm ) Was used to print the solder composition. Then, reflow was performed under conditions of preheating 150 ° C. for 60 seconds, temperature 250 ° C. and melting time 30 seconds, and a test substrate was produced. This test substrate was put into a high-temperature and high-humidity tester set at a temperature of 85 ° C. and a relative humidity of 95%, and the insulation resistance value after 500 hours was measured. And insulation was evaluated according to the following reference | standard.
A: The insulation resistance value is 1.0 × 10 ⁹ or more.
X: The insulation resistance value is less than 1.0 × 10 ⁹ .

  As is apparent from the results shown in Table 1, when the thermosetting flux composition of the present invention is used (Examples 1 to 9), reflow bondability, shear strength, impact resistance and insulation are good. It was confirmed that. Therefore, according to this invention, it was confirmed that the reinforcement effect by hardened | cured material is high, it is excellent in the insulation of hardened | cured material, and excellent in solderability.

  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 (8)

A thermosetting flux composition used when an electronic component having a solder bump made of a solder alloy having a melting point of 130 ° C. or higher and 240 ° C. or lower is bonded to an electronic substrate by reflow soldering or thermocompression bonding,
(A) an oxetane compound, (B) an activator, and (C) an inorganic filler,
The component (A) contains (A1) a bifunctional oxetane compound having two oxetane rings in one molecule;
The component (B) contains (B1) an organic acid,
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,
(D) A thermosetting flux composition characterized by further containing an epoxy resin. In the thermosetting flux composition according to claim 1 or claim 2,
The component (C) is at least one selected from the group consisting of a silica filler and an alumina filler. In the thermosetting flux composition according to any one of claims 1 to 3,
The thermosetting flux composition, wherein the component (C) is surface-treated. In the thermosetting flux composition according to any one of claims 1 to 4,
The compounding quantity of the said (C) component is 20 mass% or more and 70 mass% or less with respect to 100 mass% of the said thermosetting flux compositions. The thermosetting flux composition characterized by the above-mentioned. An application step of applying the thermosetting flux composition according to any one of claims 1 to 5 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: An application step of applying the thermosetting flux composition according to any one of claims 1 to 5 on the wiring board;
A mounting step of mounting electronic components having solder bumps on the bonding lands of the wiring board;
A thermocompression bonding step of thermocompression bonding the electronic component to the wiring board;
And a thermosetting step of heating and curing the thermosetting flux composition. An electronic substrate manufacturing method comprising: In the manufacturing method of the electronic substrate of Claim 6 or Claim 7,
A solder precoat is formed in advance on the bonding lands.