Resin composition for flux, solder paste, and mounting structure

Abstract

The present application provides a flux resin composition capable of achieving improvement in moisture resistance of a cured product of the flux resin composition. The flux resin composition of the present application contains an epoxy resin (A), a phenol resin (B), an imidazole compound (C), a thixotropic agent (D), and an active agent (E). The flux resin composition of the present application has at least one of the above-described epoxy resin (A) containing a low moisture absorption epoxy resin (A1) having a functional group equivalent of 200 or more and the above-described phenol resin (B) containing a low moisture absorption phenol resin (B1) having a functional group equivalent of 200 or more. When the total amount of organic solid components including the above-described epoxy resin (A), the above-described phenol resin (B), the above-described imidazole compound (C), the above-described thixotropic agent (D), and the above-described active agent (E) is set to 100 mass%, the content of the above-described active agent (E) is 4 mass% or more and 20 mass% or less, and the total content of the above-described low moisture absorption epoxy resin (A1) and the above-described low moisture absorption phenol resin (B1) is 10 mass% or more and 62 mass% or less.

Description

Technical Field

[0001] This invention relates to flux resin compositions, solder pastes, and mounting structures. More specifically, it relates to flux compositions containing epoxy resin and phenolic resin, solder pastes containing the flux resin compositions, and mounting structures having cured forms of the aforementioned flux resin compositions. Background Technology

[0002] Patent Document 1 describes a solder paste. This solder paste comprises solder powder and flux. The flux comprises an epoxy resin, a reactive diluent, a curing agent, an organic acid, and a rubber-modified epoxy resin. The reactive diluent comprises a compound having two or more epoxy groups, has a viscosity of 150 mPa·s or more and 700 mPa·s or less, and contains a total chlorine content of 0.5% by weight or less, comprising a proportion of 5% by weight or more and 45% by weight or less relative to the total weight of the flux.

[0003] In the invention described in Patent Document 1, the aim is to improve the moisture resistance and insulation of the cured flux by reducing the total chlorine content (amount of chloride ions) in the reactive diluent, rather than by improving the moisture resistance and insulation by focusing on the moisture absorption rate of other components such as epoxy resin.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2019-130568 Summary of the Invention

[0007] The object of the present invention is to provide a flux resin composition that can improve the moisture resistance and insulation of the cured flux.

[0008] In addition, the present invention aims to provide a solder paste and an mounting structure using the above-described flux resin composition.

[0009] One aspect of the flux resin composition of the present invention comprises an epoxy resin (A), a phenolic resin (B), an imidazole compound (C), a thixotropic agent (D), and an activator (E). Furthermore, it comprises at least one of the following: the epoxy resin (A) comprising a low-hygroscopic epoxy resin (A1) with a functional group equivalent of 200 or more, and the phenolic resin (B) comprising a low-hygroscopic phenolic resin (B1) with a functional group equivalent of 200 or more. When the total amount of the organic solid components comprising the epoxy resin (A), the phenolic resin (B), the imidazole compound (C), the thixotropic agent (D), and the activator (E) is set to 100% by mass, the content of the activator (E) is 4% by mass or more and 20% by mass or less, and the total content of the low-hygroscopic epoxy resin (A1) and the low-hygroscopic phenolic resin (B1) is 10% by mass or more and 62% by mass or less.

[0010] One embodiment of the solder paste of the present invention comprises the above-mentioned flux composition and solder powder.

[0011] One embodiment of the mounting structure of the present invention includes: a circuit board having a first conductor; an electronic component having a second conductor; solder bumps; and a reinforcement portion. The bumps are disposed between the first conductor and the second conductor, and electrically connect the first conductor and the second conductor. The reinforcement portion is a cured product of the flux resin composition and is located around the bumps. Attached Figure Description

[0012] Figure 1 This is a cross-sectional view showing one embodiment of the mounting structure of the present invention.

[0013] Figure 2 A to C in the diagram represent cross-sectional views of a portion of the manufacturing process of the aforementioned installation structure.

[0014] Figure 3 This is a cross-sectional view showing a portion of the manufacturing process of the aforementioned mounting structure. Detailed Implementation

[0015] (Implementation Method 1)

[0016] (1) Summary

[0017] The flux resin composition in this embodiment contains epoxy resin (A), phenolic resin (B), imidazole compound (C), thixotropic agent (D), and activator (E). For this flux composition, it is desirable to improve the moisture resistance and insulation properties of the cured product. For example, in Patent Document 1 mentioned above, the moisture resistance and insulation properties were studied with regard to the amount of chloride ions in the cured product.

[0018] Patent Document 1 describes a solder paste that, when cured at high temperatures, absorbs moisture. The presence of halogen ions, such as chloride ions, in the cured product can easily generate leakage current, sometimes leading to deterioration of the cured product's insulation. The primary cause of this deterioration is speculated to be the amount of halogen ions present in the epoxy resin cured product, particularly chloride ions, the moisture absorption rate of the cured product, and its adhesion to the circuit board. Furthermore, it was found that since the influence of these three factors is difficult to quantify individually, Patent Document 1 maintains the insulation of the cured product by limiting the total chloride content in the reactive diluent.

[0019] On the other hand, in this embodiment, the improvement of moisture-resistant insulation is achieved by focusing on the hygroscopicity of the resin component.

[0020] (2) Details

[0021] <Epoxy Resin (A)>

[0022] The flux composition (X) of this embodiment contains epoxy resin (A) as the main agent for the thermosetting reaction. Epoxy resin (A) preferably has two or more epoxy groups per molecule.

[0023] Epoxy resin (A) is preferably liquid at room temperature. If epoxy resin (A) is liquid at room temperature, it is suitable to mix epoxy resin (A) with other components to form a paste when formulating flux resin composition (X). It should be noted that being liquid at room temperature means having fluidity under atmospheric pressure and an ambient temperature of 5°C or higher and 28°C or lower (especially around 20°C). Epoxy resin (A) may consist only of components that are liquid at room temperature, or it may consist of components that are liquid at room temperature and components that are solid at room temperature. It should be noted that when reactive diluents, solvents, etc. are used in combination during the preparation of composition (X), epoxy resin (A) itself does not need to be liquid, as epoxy resin (A) becomes liquid at room temperature due to these reactive diluents, solvents, etc.

[0024] Epoxy resin (A) can include two types of epoxy resins: low-hygroscopic epoxy resin (A1) and epoxy resin (A2) other than epoxy resin (A1). Low-hygroscopic epoxy resin (A1) is epoxy resin with low hygroscopicity, while epoxy resin (A2) is epoxy resin with higher hygroscopicity than low-hygroscopic epoxy resin (A1).

[0025] As a low-hygroscopic epoxy resin (A1), an epoxy resin with a functional group equivalent of 200 or more can be cited. That is, an epoxy resin with an epoxy group equivalent (epoxy equivalent) of 200 or more can be used as a low-hygroscopic epoxy resin. Generally, if the epoxy group equivalent of an epoxy resin is low, it tends to be hygroscopic. Therefore, in this embodiment, an epoxy resin with a functional group equivalent of 200 or more is used as a low-hygroscopic epoxy resin. As a low-hygroscopic epoxy resin (A1), the following product numbers can be used. It should be noted that the unit of epoxy equivalent is [g / eq.].

[0026] Examples of epoxy resins from DIC Corporation include N690 (cresol-phenolic epoxy resin, epoxy equivalent 208), EXA-820D (epoxy equivalent 202 (low viscosity)), HP-820 (epoxy equivalent 209), HP-6000L (epoxy equivalent 215), N-655-EXP-S (cresol-phenolic epoxy resin, epoxy equivalent 200), and HP-7200L (dicyclopentadiene epoxy resin (DCPD), epoxy equivalent 242-252).

[0027] For Mitsubishi Chemical Corporation, examples include YX8000 (epoxy equivalent 205, liquid at room temperature, low viscosity), YX7700 (epoxy equivalent 260-285, softening point 65°C, solid at room temperature (low water absorption)), YX7105 (epoxy equivalent 440-520, liquid at room temperature, highly flexible), and 871 (epoxy equivalent 390-470, liquid at room temperature).

[0028] Examples from Nippon Kayaku Co., Ltd. include XD-1000 (epoxy equivalent 245, liquid at room temperature, low viscosity), NC-7300L (epoxy equivalent 207-221, low water absorption), and NC-3000L (biphenyl type epoxy resin, epoxy equivalent 261-282).

[0029] Among the above, one or both of NC-3000L and HP-7200L, which have excellent low moisture absorption, good curing properties, and good coatability, are preferred as low moisture absorption epoxy resins (Al). The structural formula of NC-3000L is represented by formula (1), and the structural formula of HP-7200L is represented by formula (2).

[0030] [Chemical Formula 1]

[0031] Equation (1)

[0032]

[0033] n represents an integer in the range of 1 to 10.

[0034] Equation (2)

[0035]

[0036] n represents an integer in the range of 1 to 10.

[0037] In this embodiment, the upper limit of the functional group equivalent of the low hygroscopic epoxy resin is not specifically set; 550 can be set as the upper limit.

[0038] <Phenolic Resin (B)>

[0039] The flux composition (X) of this embodiment comprises phenolic resin (B). Therefore, the phenolic resin (B) functions as a curing agent by reacting with the epoxy groups of the epoxy resin (A). Preferably, the phenolic resin (B) has two or more hydroxyl groups per molecule.

[0040] The phenolic resin (B) is preferably liquid at room temperature. If the phenolic resin (B) is liquid at room temperature, it is suitable to mix the phenolic resin (B) with other components to adjust it into a paste-like state when formulating the flux resin composition (X). The phenolic resin (B) may consist only of components that are liquid at room temperature, or it may consist of components that are liquid at room temperature and components that are not liquid at room temperature. It should be noted that when reactive diluents, solvents, etc. are used in combination when preparing the composition (X), the phenolic resin (B) itself does not need to be liquid, as the phenolic resin (B) is liquid at room temperature due to these reactive diluents, solvents, etc.

[0041] Phenolic resin (B) can include two types of phenolic resins: low-hygroscopic phenolic resin (B1) and phenolic resin (B2) other than phenolic resin (B1). Low-hygroscopic phenolic resin (B1) is a phenolic resin with low hygroscopicity, while phenolic resin (B2) is an epoxy resin with higher hygroscopicity than low-hygroscopic phenolic resin (B1).

[0042] As a low-hygroscopic phenolic resin (B1), phenolic resins with a functional group equivalent of 200 or more can be cited. That is, phenolic resins with a hydroxyl equivalent of 200 or more of the functional group of the phenolic resin can be used as low-hygroscopic phenolic resins. As a low-hygroscopic phenolic resin (B1), MEH-7851-SS (a phenolic resin with a biphenyl aryl backbone, hydroxyl equivalent of 201 to 205, and a softening point of 67°C) manufactured by Meiwa Chemical Co., Ltd. can be cited as an example. It should be noted that the unit of hydroxyl is [g / eq.]. The structural formula of MEH-7851-SS is shown in formula (3).

[0043] [Chemical Formula 2]

[0044] Equation (3)

[0045]

[0046] n represents an integer in the range of 1 to 10.

[0047] In this embodiment, the upper limit of the functional group equivalent of the low hygroscopic phenolic resin is not specifically set, and 500 can be used as the upper limit.

[0048] <Imidazole compound (C)>

[0049] The flux composition (X) of this embodiment contains an imidazole compound (C). The imidazole compound (C) acts as a curing accelerator for the epoxy resin (A), and by including the imidazole compound (C) in the flux resin composition (X), a cured product with high heat resistance can be obtained. That is, a cured product with a high glass transition temperature (Tg) can be obtained.

[0050] Examples of imidazole compounds (C) include 2-phenyl-4,5-dihydroxymethylimidazolium (manufactured by Shikoku Kasei Corporation, product number: 2PHZ-PW, melting point 230°C), 2-phenyl-4-methyl-5-hydroxymethylimidazolium (manufactured by Shikoku Kasei Corporation, product number: 2P4MHZ-PW, melting point 191-195°C), 2-phenylimidazolium (manufactured by Shikoku Kasei Corporation, product numbers: 2PZ, 2PZ-PW, melting point 137-147°C), and 2,4-diamino-6-[2'-methylimidazolyl-(1')]-ethyl-triazine isocyanuric acid adduct (manufactured by Shikoku Kasei Corporation, product numbers: 2MA-OK, 2MAOK-PW, melting point 260°C).

[0051] <Thixotropic Agent (D)>

[0052] The flux composition (X) of this embodiment contains a thixotropic agent (D). The thixotropic agent (D) is a compound that imparts thixotropic properties to the flux resin composition (X). Here, "thixotropy" refers to the property of a substance to decrease in viscosity under shear stress. Thixotropy is quantified by a thixotropic ratio, for example, by measuring two viscosities at a certain temperature by changing the rotational speed of a rotary viscometer, and then taking the ratio of these two viscosities. The rotational speed of the rotary viscometer is, for example, 0.25 rpm and 2.5 rpm at 25°C. The flux resin composition (X) containing the thixotropic agent (D) easily maintains its shape after printing and coating, with minimal reduction in continuous printability and coating properties.

[0053] Thixotropic agents (D) can be selected from one or more of the following: 1,3:2,4-bis-O-benzyl-D-glucol (dibenzyl sorbitol) (manufactured by New Japan Rika Co., Ltd., product name: GEL ALL D), 1,3:2,4-bis-O-(4-methylbenzyl)-D-sorbitol (manufactured by New Japan Rika Co., Ltd., product name: GEL ALL MD), and N,N'-methylenebis(stearamide) (manufactured by Mitsubishi Chemical Co., Ltd., product name: Bisamide LA).

[0054] <Active Agent (E)>

[0055] The flux composition (X) of this embodiment contains an activator (E). The activator (E) has the function of removing metal oxide films. Therefore, the flux resin composition (X), by containing the activator (E), can exhibit flux action. Here, "flux action" refers to the reducing effect of removing the oxide film generated on the metal surface coated with solder, and the effect of reducing the surface tension of the molten solder to promote the wettability of the solder to the bonding metal surface.

[0056] The activator (E) preferably comprises at least one of an organic acid (E1) with a carboxyl equivalent of 40 g / mol to 400 g / mol and a melting point below 220°C, and an amine (E2) with a nitrogen atom equivalent of 10 g / mol to 300 g / mol and a melting point below 220°C. By making the melting point of the activator (E) below 220°C, even when using solder with a melting point around or above 200°C, the oxide film on the solder can be removed before the solder melts. It should be noted that "carboxyl equivalent" here refers to the value expressed as molar molecular weight (g) / number of carboxyl groups per molecule (mol), and "nitrogen atom equivalent" refers to the value expressed as molar molecular weight (g) / number of nitrogen atoms per molecule (mol).

[0057] The organic acid (E1) may include, for example, at least one selected from rosin components, adipic acid, glutaric acid, succinic acid, malonic acid, citric acid, cork acid, sebacic acid, and pimelic acid. Particularly preferred organic acids (E1) include succinic acid (carboxyl equivalent: 59 g / mol), glutaric acid (carboxyl equivalent: 66 g / mol), adipic acid (carboxyl equivalent: 73 g / mol), cork acid (carboxyl equivalent: 87 g / mol), sebacic acid (carboxyl equivalent: 101 g / mol), and Tsunodyme 395 (carboxyl equivalent: 288 g / mol).

[0058] The amine (E2) is not particularly limited to any amine used as a flux, and may include at least one selected from various amine salts, alkanolamines, and guanidines. Particularly preferred amines (E2) include diethanolamine (nitrogen equivalent: 105 g / mol), triethanolamine (TEA) (nitrogen equivalent: 149 g / mol), triisopropanolamine (nitrogen equivalent: 191 g / mol), 1,3-diphenylguanidine (nitrogen equivalent: 70 g / mol), and 1,3-di-o-tolylguanidine (nitrogen equivalent: 80 g / mol).

[0059] Surfactant (E) may contain components other than organic acids (E1) and amines (E2). Surfactant (E) may also contain organic acids or amines with melting points exceeding 220°C.

[0060] <Solvent(F)>

[0061] The flux composition (X) of this embodiment contains a solvent (F) as needed. The solvent (F) is used to adjust the viscosity of the flux resin composition (X). Preferably, the solvent has a boiling point of 200°C or higher; for example, glycol ether-based solvents can be used, among which diethylene glycol dibutyl ether (DBDG), diethylene glycol diethyl ether (DEDG), and diethylene glycol monohexyl ether (HeDG) are suitable. The flux resin composition (X) containing solvent (F) easily ensures printability and coatability, and is less prone to degradation of moisture resistance and insulation.

[0062] <Resin Compositions for Flux>

[0063] The flux resin composition (X) of this embodiment contains epoxy resin (A), phenolic resin (B), imidazole compound (C), thixotropic agent (D), and activator (E) as organic solid components. Furthermore, the flux resin composition (X) of this embodiment may further contain the aforementioned solvent (F) as needed. Moreover, the flux resin composition (X) has at least one composition: epoxy resin (A1) comprising a low-hygroscopic epoxy resin with a functional group equivalent of 200 or more, and phenolic resin (B1) comprising a low-hygroscopic phenolic resin with a functional group equivalent of 200 or more. That is, the flux resin composition (X) of this embodiment contains one or both of a low-hygroscopic epoxy resin (A1) with a functional group equivalent of 200 or more and a low-hygroscopic phenolic resin (B1) with a functional group equivalent of 200 or more.

[0064] In the flux resin composition (X) of this embodiment, when the total amount of organic solid components of composition (X) is set to 100% by mass, the total content of epoxy resin (A) and phenolic resin (B) is preferably 70% by mass or more and 90% by mass or less. This ensures appropriate curability of composition (X). The lower limit of the total content of epoxy resin (A) and phenolic resin (B) is more preferably 75% by mass, and even more preferably 78% by mass. The upper limit of the total content of epoxy resin (A) and phenolic resin (B) is set according to the balance of appropriate proportions with other components. For example, when the proportions of other components are balanced to a greater extent, the upper limit may be set to 87% by mass, or even more preferably 85% by mass. In addition, the ratio of epoxy resin (A) to phenolic resin (B) is preferably in the range of (A):(B) = 20:1 to 1:1, preferably 20:1 to 2:1, and more preferably 20:1 to 3:1. The content of epoxy resin (A) relative to the total amount of the above-mentioned organic solid components in the composition (X) is preferably 40% by mass or more and 85% by mass or less, more preferably 45% by mass or more and 80% by mass or less, and even more preferably 50% by mass or more and 75% by mass or less. In the flux resin composition (X) of this embodiment, the content of phenolic resin (B) relative to the total amount of the composition (100% by mass) is preferably 5% by mass or more and 40% by mass or less, more preferably 5% by mass or more and 25% by mass or less, and even more preferably 5% by mass or more and 15% by mass or less.

[0065] In this embodiment, the total content of the low-moisture-absorbing epoxy resin (A1) and the low-moisture-absorbing phenolic resin (B1) is preferably 10% by mass or more and 62% by mass or less of the total organic solid components (100% by mass) of the composition (X). The lower limit of the total content of the low-moisture-absorbing epoxy resin (A1) and the low-moisture-absorbing phenolic resin (B1) can also be set to 15% by mass or more, or 20% by mass or more. The upper limit of the total content of the low-moisture-absorbing epoxy resin (A1) and the low-moisture-absorbing phenolic resin (B1) can be set to 60% by mass or less, more preferably 58% by mass or less. This facilitates the improvement of the moisture resistance and insulation properties of the cured flux resin composition (X). Among the low-moisture-absorbing epoxy resin (A1) and the low-moisture-absorbing phenolic resin (B1), the flux resin composition (X) preferably contains at least the low-moisture-absorbing epoxy resin (A1). In addition, it is also preferable to include both low moisture-absorbing epoxy resin (A1) and low moisture-absorbing phenolic resin (B1).

[0066] In the flux resin composition (X) of this embodiment, the content of imidazole compound (C) is preferably 0.01% by mass or more and 5% by mass or less, more preferably 0.01% by mass or more and 3% by mass or less, and even more preferably 0.05% by mass or more and 2% by mass or less, of the total amount of organic solid components (100% by mass) of the composition (X). This facilitates the curing of epoxy resin (A) and improves the storage stability of the flux resin composition (X). Furthermore, in this embodiment, since phenolic resin (B) is used as the curing agent for epoxy resin (A), the content of imidazole compound (C) can be reduced. If a large amount of imidazole compound (C) is used, there is a tendency for voids to easily form in the cured flux resin composition (X), but in this embodiment, the content of imidazole compound (C) can be suppressed, thus reducing the likelihood of void formation.

[0067] In the flux resin composition (X) of this embodiment, the content of the thixotropic agent (D) is preferably 1% to 5% by mass or less of the total amount (100% by mass) of the organic solid components of the composition (X), more preferably 1.5% to 4% by mass or less, and even more preferably 2% to 3% by mass or less. This allows for easy adjustment of the thixotropic properties of the flux resin composition (X), making it readily adaptable to supply methods such as printing, transfer printing, and dispensers.

[0068] In the flux resin composition (X) of this embodiment, the content of the activator (E) is preferably 4% by mass or more and 20% by mass or less of the total amount (100% by mass) of the organic solid components of the composition (X), more preferably 8% by mass or more and 18% by mass or less, and even more preferably 10% by mass or more and 15% by mass or less. This makes it easy for the flux resin composition (X) to possess flux properties and enables good storage stability of the flux resin composition (X).

[0069] It should be noted that the flux resin composition (X) of this embodiment may contain a solvent (F) depending on the necessity of adjusting fluidity, etc. The solvent (F) is not required, but when the solvent (F) is contained, for example, the solvent (F) may be incorporated in amounts of 20% by mass or less relative to the total amount (100% by mass) of the organic solid components of the composition (X).

[0070] The flux resin composition (X) of this embodiment can melt and solidify at low temperatures. Therefore, the flux resin composition (X) can be applied, for example, to low-temperature soldering processes. Typically, when using high-temperature solder (e.g., Sn-Ag-Cu alloy solder, melting point 219°C), the reflow soldering temperature is around 240°C, but the flux resin composition (X) of this embodiment can also be used in low-temperature soldering processes with reflow soldering temperatures below 240°C. Therefore, by changing from a high-temperature soldering process to a low-temperature soldering process, it is possible to reduce power consumption and carbon dioxide emissions. For example, when using low-temperature solder (Sn-Bi alloy solder, melting point 139°C), the reflow soldering temperature is around 160°C, but the flux resin composition (X) of this embodiment melts and solidifies at a low reflow soldering temperature of 160°C. Furthermore, the flux resin composition (X) of this embodiment acts as a flux when melting and, after solidification, it covers the area around the solder joint, thereby providing reinforcement. Therefore, the flux resin composition (X) of this embodiment can compensate for the brittleness of low-temperature solder by utilizing its cured product.

[0071] (Implementation Method 2)

[0072] The solder paste of this embodiment has a composition comprising the flux resin composition (X) of Embodiment 1 and solder powder. Hereinafter, the same symbols are used for the same components as in Embodiment 1, and descriptions are omitted where appropriate. The composition described in Embodiment 2 can be appropriately combined with the composition described in Embodiment 1.

[0073] The solder paste (Y) of this embodiment contains the flux resin composition (X) and solder powder (G) disclosed in Embodiment 1. That is, the solder paste (Y) is a mixture of the flux resin composition (X) and the solder powder (G).

[0074] There are no particular limitations on the solder powder (G). The chemical composition of the solder powder (G) includes lead-free solder and lead-containing solder. From an environmental protection point of view, the chemical composition of the solder powder (G) is preferably lead-free solder.

[0075] As a lead-free solder, there are no special limitations. For example, it may contain Sn, and may also contain one or more elements selected from Bi, Sb, Cu, Ag, Zn, In, Ni, P, Ga and Ge. That is, examples of lead-free solders include Sn-Bi based solders, Sn-Sb based solders, Sn-Cu based solders, Sn-Ag based solders, Sn-Zn based solders, Sn-In based solders, Sn-Ag-Cu based solders, Sn-Cu-Ni based solders, Sn-Zn-Bi based solders, Sn-Ag-Cu-In based solders, Sn-Bi-Cu-In based solders, Sn-Ag-Bi-Cu based solders, Sn-In-Ag-Bi based solders, Sn-Cu-Ag-P-Ga based solders, Sn-Cu-Ni-P-Ga based solders, Sn-Ag-Cu-Ni-Ge based solders, and Sn-Bi-Ag-Cu-In based solders. In particular, Sn-Bi based solders are preferred because they have a low melting point and good wettability. In addition, Sn-Ag-Cu solders have high reliability and good wettability, and are therefore preferred.

[0076] In the solder paste (Y), the melting point of the solder powder (G) is preferably 80°C or higher. Therefore, a wide variety of solder powders (G) can be used. There is no particular limitation on the upper limit of the melting point of the solder powder; for example, it can be the heat resistance temperature of the component (surface mount component). Specifically, the upper limit of the melting point of the solder powder is, for example, 300°C.

[0077] In the solder paste (Y), the content of solder powder (G) is 75% by mass or more and 90% by mass or less of the total amount of solder paste (Y) (100% by mass), preferably 77% by mass or more and 88% by mass or less, and more preferably 80% by mass or more and 85% by mass or less. By making the content of solder powder (G) 75% by mass or more, the conductivity of the solder joint is less likely to be impaired, and by making the content of solder powder (G) 90% by mass or less, the reinforcing effect brought about by the cured product of the flux resin composition (X) can be improved.

[0078] (Modified Example)

[0079] This embodiment discloses a solder paste, but a silver paste can also be made using the flux resin composition of Embodiment 1. In this case, the silver paste contains silver powder and the flux resin composition of Embodiment 1.

[0080] (Implementation Method 3)

[0081] The mounting structure 1 of this embodiment is constructed using the flux resin composition (X) of Embodiment 1 or the solder paste (Y) of Embodiment 2. Hereinafter, the same symbols are used for the same configurations as in Embodiment 1 or 2, and descriptions are omitted where appropriate. The configuration described in Embodiment 3 can be applied in appropriate combinations with the configurations described in Embodiment 1 or 2 (including variations).

[0082] <Case where flux resin composition (X) is used>

[0083] like Figure 1 As shown, the mounting structure 1 of this embodiment includes a circuit board 2, electronic components 3, bumps 32 and reinforcement 4.

[0084] The circuit board 2 is, for example, a mother substrate, a packaging substrate, or an interposer substrate. The circuit board 2 is, for example, an insulating substrate made of glass epoxy, polyimide, polyester, ceramic, or other materials. A first conductor 21 is formed on the surface of the circuit board 2. Therefore, the circuit board 2 includes a first conductor 21. The first conductor 21 is not particularly limited; for example, it may be a wiring formed by a conductor containing a metal such as copper or a copper alloy. Furthermore, the first conductor 21 may have a plating layer such as a nickel plating layer, a nickel-gold plating layer, or a gold plating layer on its surface.

[0085] Electronic component 3 is, for example, a semiconductor chip, and more specifically, a flip-chip type chip such as BGA (Ball Grid Array), LGA (Large Grid Array), or CSP (Chip Scale Package). Electronic component 3 can also be a PoP (PoP) type chip. A second conductor 31 is formed on the surface of electronic component 3. Therefore, electronic component 3 includes a second conductor 31. The second conductor 31 is not particularly limited, and for example, it can be an electrode pad formed of a conductor containing a metal such as copper or a copper alloy. In addition, the second conductor 31 may have a plating layer such as a nickel plating layer, a nickel-gold plating layer, or a gold plating layer on its surface.

[0086] A bump 32 is fixed between the first conductor 21 of the circuit board 2 and the second conductor 31 of the electronic component 3. The bump 32 electrically connects the first conductor 21 and the second conductor 31. The bump 32 can be formed of solder. In this case, the type of solder is not particularly limited; for example, it can be SAC solder (lead-free solder), tin-bismuth based solder, or the material constituting the solder powder described in Embodiment 2 can be used to form the solder bump 32.

[0087] The reinforcing part 4 is a cured product of the flux resin composition (X). In the mounting structure 1, the reinforcing part 4 is attached to the outside of the joint 20 between the bump 32 and the first conductor 21. Therefore, the reinforcing part 4 strengthens the bump 32, the first conductor 21, and the joint 20 between the bump 32 and the first conductor 21, thereby improving the connection reliability of the mounting structure 1. It should be noted that if the connection reliability is low, repeated application of stress caused by changes in ambient temperature, etc., may sometimes lead to fatigue failure.

[0088] It should be noted that, in Figure 1 In the mounting structure 1 shown, the reinforcement 4 is attached to the outer side (outer surface) of the joint 20 between the first conductor 21 and the bump 32 of the circuit board 2, but is not limited thereto. For example, the reinforcement 4 may also be attached to the outer side of the joint between the second conductor 31 and the bump 32 of the electronic component 3. Alternatively, for example, the reinforcement 4 may be attached to both the outer side of the joint between the first conductor 21 and the bump 32 of the circuit board 2 and the outer side of the joint between the second conductor 31 and the bump 32 of the electronic component 3.

[0089] The following is for reference Figure 2 A to C pairs Figure 1 The manufacturing method of the mounting structure 1 shown will be described. First, a circuit board 2 having a first conductor 21 is prepared, and a flux resin composition (X) is arranged to cover the first conductor 21 (see reference). Figure 2 (A) The method for preparing the flux resin composition (X) is not particularly limited; for example, it can be done by printing, transfer, coating, etc.

[0090] Next, an electronic component 3 having a second conductor 31 is prepared. A bump 32 is provided on the second conductor 31, and the second conductor 31 is electrically connected to the bump 32. This electronic component 3 is disposed on the circuit board 2 such that the bump 32 contacts the flux resin composition (X) (see reference). Figure 2 (B in the middle).

[0091] Next, the bump 32 and the flux resin composition (X) are heated. The heating method is not particularly limited; for example, heating using a low-temperature reflow oven can be employed. The flux resin composition (X) is maintained at a low viscosity until the bump 32 melts. Furthermore, even after the bump 32 begins to melt, the viscosity of the flux resin composition (X) does not immediately increase, but rises sharply after a period of time. Therefore, the flux resin composition (X) can be cured after covering the outer side of the joint 20 between the first conductor 21 and the bump 32. This allows for a good connection between the first conductor 21 and the bump 32, suppressing poor conductivity between them. Additionally, the cured flux resin composition (X) can be fixed to the outer side of the joint 20 between the first conductor 21 and the bump 32. Therefore, the reinforcing part 4 can be used to reinforce the joint 20 between the first conductor 21 and the bump 32.

[0092] It should be noted that in the manufacturing method of the mounting structure 1 described above, a bump 32 is provided on the second conductor 31, but this is not a limitation. For example, a bump 32 may also be provided on the first conductor 21. In this case, when the flux resin composition (X) is disposed to cover the second conductor 31 to connect the second conductor 31 and the bump 32, the flux resin composition (X) can be cured after covering the outside of the joint 20 between the second conductor 31 and the bump 32. In this case, the outside of the joint 20 between the second conductor 31 and the bump 32 can be reinforced by the reinforcing part 4.

[0093] <Case using solder paste (Y)>

[0094] The mounting structure 1 can also be formed using the solder paste (Y) disclosed in Embodiment 2 instead of the flux resin composition (X). In this case, the bonding portion between the circuit board 2 and the electronic component 3 has Figure 3 The structure is as shown. Specifically, the bump 32, electrically connected to the second conductor 31, is joined to the first conductor 21 via a joint 5. A reinforcing portion 4 is formed on the outer side of the joint 51 between the bump 32 and the joint 5, and on the outer side of the joint 52 between the joint 5 and the first conductor 21. The joint 5 is a cured product formed by the hardening or solidification of solder powder (G) contained in the solder paste (Y) after melting. The reinforcing portion 4 is a cured product of the flux resin composition (X) contained in the solder paste (Y).

[0095] When manufacturing the mounting structure 1 using solder paste (Y), solder paste (Y) can be used instead of flux resin composition (X), and... Figure 2 The methods shown in A, B, and C are performed in the same way.

[0096] Furthermore, since the mounting structure 1 of this embodiment has a cured product of flux resin composition (X) as a reinforcing part 4, the moisture resistance and insulation of the reinforcing part (cured product of flux resin composition (X)) 4 can be improved.

[0097] (Summarize)

[0098] As described above, the flux resin composition of the present invention has the following characteristics.

[0099] The flux resin composition of the first embodiment contains an epoxy resin (A), a phenolic resin (B), an imidazole compound (C), a thixotropic agent (D), and an activator (E). The composition (X) comprises at least one of the following: the epoxy resin (A) comprising a low-hygroscopic epoxy resin (A1) with a functional group equivalent of 200 or more, and the phenolic resin (B) comprising a low-hygroscopic phenolic resin (B1) with a functional group equivalent of 200 or more. When the total amount of the organic solid components comprising the epoxy resin (A), the phenolic resin (B), the imidazole compound (C), the thixotropic agent (D), and the activator (E) is set to 100% by mass, the content of the activator (E) is 4% by mass or more and 20% by mass or less, and the total content of the low-hygroscopic epoxy resin (A1) and the low-hygroscopic phenolic resin (B1) is 10% by mass or more and 62% by mass or less.

[0100] According to the first method, it has the advantage of improving the moisture resistance and insulation of the cured flux resin composition.

[0101] The second aspect relates to the flux resin composition of the first aspect, wherein the total content of the epoxy resin (A) and the phenolic resin (B) is 70% by mass or more and 90% by mass or less relative to the total amount of the organic solid components, and the ratio of the epoxy resin (A) to the phenolic resin (B) is in the range of (A):(B) = 20:1 to 1:1.

[0102] According to the second method, suitable curability of the flux resin composition can be achieved.

[0103] The third method relates to the flux resin composition of the first or second method, which at least comprises the aforementioned low moisture absorption epoxy resin (A1).

[0104] According to the third method, it has the advantage of improving the moisture resistance and insulation of the cured flux resin composition.

[0105] The fourth method relates to a flux resin composition of any of the methods 1 to 3, comprising both the aforementioned low-moisture-absorbing epoxy resin (A1) and the aforementioned low-moisture-absorbing phenolic resin (B1).

[0106] According to the fourth method, it has the advantage of improving the moisture resistance and insulation of the cured flux resin composition.

[0107] The fifth method relates to a flux resin composition of any of the methods 1 to 4, wherein the aforementioned low moisture-absorbing epoxy resin (A1) comprises either a biphenyl aralkyl type epoxy resin or a dicyclopentadiene type epoxy resin.

[0108] According to the fifth method, it has the advantage of being able to further improve the moisture resistance and insulation of the cured flux resin composition.

[0109] The sixth method relates to a flux resin composition of any of the methods 1 to 5, which further comprises a glycol ether-based solvent.

[0110] According to the sixth method, it has the advantage of easily obtaining a flux resin composition with excellent printability.

[0111] The seventh method relates to a flux resin composition of any of the methods 1 to 6, wherein the moisture absorption rate of the cured product is 3.0% or less.

[0112] According to the seventh method, it has the advantage of being able to further improve the moisture resistance and insulation of the cured resin composition for flux.

[0113] The solder paste of the eighth method contains the flux composition and solder powder described in any of the methods 1 to 7.

[0114] According to method 8, it has the advantage of improving the moisture resistance and insulation of the cured solder paste.

[0115] The ninth method relates to the solder paste of the eighth method, wherein the content of the solder powder is 70% by mass or more and 95% by mass or less relative to the total amount of the paste.

[0116] According to the ninth method, it has the advantages of improving the moisture resistance and insulation of the cured solder paste, and also easily ensuring conductivity.

[0117] The mounting structure (1) of the tenth type includes a circuit board (2), an electronic component (3), a solder bump (32), and a reinforcement (4). The circuit board (2) includes a first conductor (21). The electronic component (3) includes a second conductor (31). The bump (32) is disposed between the first conductor (21) and the second conductor (31) and electrically connects the first conductor (21) and the second conductor (31). The reinforcement (4) is a cured product of a flux resin composition of any of the first to seventh types and is located around the bump (32).

[0118] According to the 10th method, it has the advantage of being able to obtain an installation structure (1) with excellent moisture resistance and insulation.

[0119] Example

[0120] (Examples 1-1 to 14, Comparative Examples 1-1 to 3)

[0121] Tables 1-3 show Examples 1-1-14 and Comparative Examples 1-1-3 corresponding to the flux resin composition (X) in Embodiment 1.

[0122] (1) Materials used in each embodiment and comparative example.

[0123] Biphenyl aryl epoxy resin

[0124] NC-3000-L (Nippon Kayaku Co., Ltd., low moisture absorption epoxy resin, epoxy equivalent 261-282)

[0125] Dicyclopentadiene type epoxy resin

[0126] HP-7200L (DIC Corporation, low moisture absorption epoxy resin, epoxy equivalent 242-252)

[0127] Bisphenol type epoxy resin

[0128] YD8125 (NIPPON STEEL Chemical & Material Co., Ltd., epoxy equivalent 168-178)

[0129] YDF8170 (NIPPON STEEL Chemical & Material Co., Ltd., epoxy equivalent 155-165)

[0130] ·Imidazole compounds

[0131] 2PHZ-PW (Shikoku Chemical Industry Co., Ltd., 2-Phenyl-4,5-dihydroxymethylimidazolium, melting point 230°C)

[0132] 2P4MHZ-PW (Shikoku Chemical Industry Co., Ltd., 2-Phenyl-4-methyl-5-hydroxymethylimidazolium, melting point 191℃~195℃)

[0133] 2MAOK-PW (Shikoku Chemical Industry Co., Ltd., 2,4-diamino-6-[2'-methylimidazolyl-(1')]-ethyl-triazine isocyanuric acid adduct, melting point 260°C)

[0134] Phosphate

[0135] TPP-K (Registered Trademark, Hokuko Chemical Industry Co., Ltd., tetraphenylphosphonium tetraphenylborate (Japanese: テ卜ラフエ二ルホスホ二ウ厶テ卜ラフエ二ルボレ一卜))

[0136] ·Active agent

[0137] Adipic acid (Tokyo Chemical Industry Co., Ltd.)

[0138] Glutaric acid (Tokyo Chemical Industry Co., Ltd.)

[0139] Sebacic acid

[0140] ·Phenolic resin

[0141] MEH-8000H (Meiwa Kasei Co., Ltd., hydroxyl equivalent 141)

[0142] MEH-7851SS (Low moisture absorption phenolic resin, Meiwa Kasei Co., Ltd., hydroxyl equivalent 201 to 205)

[0143] MEH-7841-4S (Meiwa Kasei Co., Ltd., hydroxyl equivalent 164 to 168)

[0144] ·Thixotropic agent

[0145] GEL ALL D (Registered Trademark, New Japan Chemical Co., Ltd., 1,3:2,4-bis-O-benzylidene-D-glucitol)

[0146] GEL ALL MD (Registered Trademark, New Japan Chemical Co., Ltd., bis(4-methylbenzylidene)sorbitol)

[0147] ·Solvent

[0148] DEDG (Nippon Emulsifier Co., Ltd., diethylene glycol diethyl ether)

[0149] DBDG (Nippon Emulsifier Co., Ltd., dibutylene glycol diethyl ether)

[0150] HEDG (Nippon Emulsifier Co., Ltd., diethylene glycol monohexyl ether)

[0151] (2) Evaluation

[0152] Table 1 shows the evaluation results of each example and each comparative example. The evaluation items are as follows.

[0153] ·Printability (SP80V)

[0154] Regarding printability, the flux resin composition of each example and each comparative example was printed onto a substrate having Ni-Pd-Au pads (conductors) with Φ300μm and 0.5mmP by a printing machine, and the printing state was observed through a microscope for judgment.

[0155] A: There is no shape problem.

[0156] B: There are bridging and gaps, but there are no practical problems.

[0157] C: Many bridging and gaps.

[0158] • 85% (moisture absorption rate) at 85℃

[0159] The flux resin compositions of each embodiment and comparative example were heat-treated according to a specified temperature profile to obtain cured products. The cured products were placed in a high-temperature and high-humidity bath at 85°C and 85% RH for 24 hours. Then, using the mass M1 of the cured product before placement and the mass M2 of the cured product after placement, the moisture absorption rate was calculated according to {(M2-M1) / M1}×100 (%).

[0160] A: Moisture absorption rate below 2.3%

[0161] B: Moisture absorption rate greater than 2.3% and less than 2.5%

[0162] C: Moisture absorption rate greater than 2.5%

[0163] • Wetting spread (on copper plates)

[0164] In the flux resin compositions of each embodiment and comparative example, the wetting spread rate was calculated using the diameter D of the solder ball before reflow soldering on the copper plate and the height H of the solder ball after reflow soldering, based on {(DH) / D}×100(%). It should be noted that the wetting spread rate was calculated according to the method in JIS Z 3198-3.

[0165] A: More than 60%.

[0166] B: 50% or more but less than 60%.

[0167] C: Less than 50%.

[0168] • Lifetime (rate of viscosity increase)

[0169] In the flux resin compositions of each embodiment and comparative example, the lifespan is defined as the time from the start of storage to the end of storage. That is, the lifespan is calculated as (viscosity after storage / viscosity at the start of storage) × 100 (%), and is judged by the time it takes to reach 120% (storage temperature: 25°C). Viscosity (Pa·s) was measured at 25°C and 2.5 rpm. Viscosity was measured using an E-type viscometer (manufactured by Toki Sangyo Co., Ltd., product number: RE-215U).

[0170] A: More than 24 hours.

[0171] B: More than 20 hours but less than 24 hours.

[0172] C: Less than 20 hours.

[0173] • THB (Moisture-resistant Insulation)

[0174] The flux resin compositions of each embodiment and comparative example were supplied to a JIS II type comb substrate by printing, and heat-treated by reflow soldering at a specified temperature profile to obtain an evaluation substrate. The evaluation substrate was then placed in a high-temperature, high-humidity bath at 85°C and 85% RH, and after being subjected to a 50V bias voltage for 24 hours, its resistance value was measured. The resistance values ​​were classified according to the following evaluation criteria to evaluate the moisture resistance insulation.

[0175] A: The resistance value is 1×10 8 Ω and above

[0176] C: Resistance value is less than 1×10 8 Q

[0177] Overall evaluation

[0178] In the comprehensive evaluation, the evaluation results of printability, moisture absorption, wetting spread, lifespan and THB were evaluated according to the following criteria.

[0179] A: In the evaluations of printability, moisture absorption, wetting spread, lifespan, and THB, all were rated A.

[0180] B: In the evaluation of printability, moisture absorption, wetting spread, lifespan, and THB, there is more than one B evaluation, and no C evaluation.

[0181] C: In the evaluation of printability, moisture absorption, wetting spread, lifespan, and THB, C has a score of more than one.

[0182] [Table 1]

[0183]

[0184] [Table 2]

[0185]

[0186] [Table 3]

[0187]

[0188] (Examples 2-1 to 14, Comparative Examples 2-1 to 3)

[0189] Tables 4-6 show Examples 2-1-14 and Comparative Examples 2-1-3 corresponding to the solder paste (Y) in Embodiment 2.

[0190] Sn-Bi based solder (Sn42Bi58, melting point 139°C) was used as the solder powder. Other materials were the same as described above.

[0191] In addition to the items shown in Tables 1-3, the following items were also evaluated.

[0192] • Area of ​​insufficient wetting

[0193] A 10mm × 10mm QFN component (Amkor, model: A-MLF68 10mm-.5mm DC Sn TR J) was placed on a solder composition printed on a substrate. Then, using a reflow soldering apparatus, the substrate and QFN component were bonded at 160°C with a trapezoidal profile for 6 minutes. This formed a solder joint and a reinforcement. The surface of the solder joint where the substrate and QFN component were bonded was photographed using an X-ray imaging device (Hitachi, Ltd., model: MF100C). The obtained images were binarized, and the percentage (%) of the area of ​​the insufficiently wetted portion relative to the total area was determined. Evaluation was performed according to the following criteria.

[0194] A: The area of ​​the insufficiently wetted part accounts for less than 20% of the total area.

[0195] B: The area of ​​the insufficiently moistened part accounts for more than 20% but less than 25% of the total area.

[0196] C: The area of ​​the insufficiently moistened part accounts for more than 25% of the total area.

[0197] Overall evaluation

[0198] In the comprehensive evaluation, the evaluation results of printability, moisture absorption rate, area of ​​insufficient wetting, lifespan, and THB are evaluated according to the following criteria.

[0199] A: In the evaluations of printability, moisture absorption, area of ​​insufficient wetting, lifespan, and THB, all received an A rating.

[0200] B: In the evaluation of printability, moisture absorption, area of ​​insufficient wetting, lifespan, and THB, there is more than one B rating, and no C rating.

[0201] C: In the evaluation of printability, moisture absorption, area of ​​insufficient wetting, lifespan, and THB, C has a score of more than one.

[0202] [Table 4]

[0203]

[0204] [Table 5]

[0205]

[0206] [Table 6]

[0207]

[0208] Explanation of reference numerals in the attached figures

[0209] 1: Installation structure

[0210] 2: Circuit board

[0211] 21: First Conductor

[0212] 3: Electronic components

[0213] 31: Second conductor

[0214] 32: Bump

[0215] 4: Enhancement Department

Claims

1. A flux resin composition comprising an epoxy resin (A), a phenolic resin (B), an imidazole compound (C), a thixotropic agent (D), and an activator (E). The epoxy resin (A) comprises a low-hygroscopic epoxy resin (A1) with a functional group equivalent of 200 or more. The phenolic resin (B) comprises a low-hygroscopic phenolic resin (B1) with a functional group equivalent of 200 or more. When the total amount of the organic solid components comprising the epoxy resin (A), the phenolic resin (B), the imidazole compound (C), the thixotropic agent (D), and the surfactant (E) is set to 100% by mass, The content of the active agent (E) is 4% by mass or more and 20% by mass or less. The total content of the low-hygroscopic epoxy resin (A1) and the low-hygroscopic phenolic resin (B1) is 10% by mass or more and 62% by mass or less.

2. The flux resin composition according to claim 1, wherein, The total content of the epoxy resin (A) and the phenolic resin (B) relative to the total amount of the organic solid components is 70% by mass or more and 90% by mass or less, and the ratio of the epoxy resin (A) to the phenolic resin (B) is in the range of (A):(B) = 20:1 to 1:

1.

3. The flux resin composition according to claim 1, wherein, The low-hygroscopic epoxy resin (A1) comprises either a biphenyl aryl epoxy resin or a dicyclopentadiene epoxy resin.

4. The flux resin composition according to claim 1, further comprising a glycol ether solvent.

5. The flux resin composition according to claim 1, wherein the cured product has a moisture absorption rate of 3.0% or less.

6. A solder paste comprising a flux resin composition according to any one of claims 1 to 5 and solder powder.

7. The solder paste according to claim 6, wherein, The content of the solder powder relative to the total paste is 70% by mass or more and 95% by mass or less.

8. An installation structure comprising: A circuit board having a first conductor; An electronic component that has a second conductor; A solder bump is disposed between the first conductor and the second conductor, and electrically connects the first conductor and the second conductor; and A reinforcing portion, which is formed from the cured product of the flux resin composition according to any one of claims 1 to 5, is located around the bump.

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