Adhesive and method for manufacturing circuit connection structure

Abstract

Provided is a thermosetting adhesive used when thermocompression bonding a pair of circuit members via a solder connection material in a method for manufacturing a circuit connection structure provided with the pair of circuit members, which are electrically connected by solder bonding, wherein the adhesive has a curing temperature Tc such that the difference (Tc − Tm) between the curing temperature Tc and the melting point Tm of the solder connection material is −20°C or higher, and the melt viscosity of the adhesive at the melting point Tm of the solder connection material is 5.0 × 105 Pa·s or lower.

Description

Adhesive and method for manufacturing circuit connection structure

[0001] The present disclosure relates to adhesives and methods for manufacturing circuit connection structures.

[0002] As a method for manufacturing a circuit connection structure such as a semiconductor device, a flip-chip mounting method is known in which a circuit component (such as a semiconductor chip) having solder bumps is directly mounted on another circuit component (such as a wiring circuit board) via the solder bumps. In this method, electrodes of opposing circuit components are electrically connected by solder bonding.

[0003] In the flip-chip mounting method, an underfill is formed using an adhesive to fill gaps between circuit components and seal connections. For example, a thermosetting adhesive is used as the adhesive for forming the underfill (see, for example, Patent Document 1).

[0004] Anisotropically conductive adhesives containing conductive particles such as solder particles have also attracted attention as adhesives for forming underfills (see, for example, Patent Document 2). Here, "anisotropically conductive" means that the adhesive is conductive in the direction of pressure application and is insulating in the direction of no pressure application. Anisotropically conductive adhesives can connect electrodes of opposing circuit components (between opposing electrodes) using conductive particles interposed between the electrodes without forming solder bumps in advance.

[0005] JP 2003-142529 A JP 2012-046756 A

[0006] When a connecting material containing solder (hereinafter referred to as a "solder connecting material") is used as an electrode connecting material, it has been confirmed that voids occur near the solder connections of a circuit connection structure obtained by thermocompression bonding circuit components together. The occurrence of such voids is particularly noticeable when multiple semiconductor chips are mounted together on a large-area circuit board.

[0007] An object of one aspect of the present disclosure is to suppress the occurrence of voids in the vicinity of solder connections in a circuit connection structure.

[0008] The present disclosure provides at least the following [1] to

[11] .

[0009] [1] In a manufacturing method of a circuit connection structure having a pair of circuit members electrically connected by soldering, a thermosetting adhesive is used when thermocompression bonding the pair of circuit members via a solder connecting material, the adhesive having a curing temperature Tc such that the difference (Tc - Tm) between the curing temperature Tc and the melting point Tm of the solder connecting material is -20°C or more, and the melt viscosity at the melting point Tm of the solder connecting material is 5.0 x 10 ５ An adhesive having a viscosity of Pa·s or less.

[0010] [2] The adhesive according to [1], wherein the curing temperature Tc is 100 to 200°C.

[0011] [3] Melt viscosity at 157 ° C. is 5.0 × 10 ５ The adhesive according to [1] or [2], which has a viscosity of Pa·s or less

[0012] [4] The adhesive according to any one of [1] to [3], comprising at least a thermosetting resin and a curing agent for the thermosetting resin, wherein the thermosetting resin includes an epoxy resin.

[0013] [5] The adhesive according to [4], wherein the curing agent includes an imidazole-based curing agent.

[0014] [6] The adhesive according to [4] or [5], wherein the curing agent includes a microcapsule-type latent curing agent.

[0015] [7] The adhesive according to any one of [1] to [6], which is insulating.

[0016] [8] The adhesive according to any one of [1] to [6], containing the solder connecting material.

[0017] [9] The adhesive according to any one of [1] to [8], which is in the form of a film.

[0018]

[10] The adhesive according to any one of [1] to [9], wherein at least one of the pair of circuit members has an electrode containing copper, gold, or a gold alloy on a surface that comes into contact with the solder connection material, and the solder connection material contains at least one selected from the group consisting of tin, a tin alloy, indium, and an indium alloy.

[0019]

[11] A method for manufacturing a circuit connection structure using a solder connection material, comprising: a step (a) of arranging a pair of circuit members so that their electrodes face each other; and a step (b) of thermocompression-bonding the pair of circuit members arranged opposite each other via a thermosetting adhesive, wherein the solder connection material is arranged on at least one electrode of the pair of circuit members, or the adhesive contains the solder connection material, the difference (Tc-Tm) between the hardening temperature Tc of the adhesive and the melting point Tm of the solder connection material is -20°C or more, and the melt viscosity of the adhesive at the melting point Tm of the solder connection material is 5.0 x 10 ５ A method for producing a circuit connection structure, wherein the electrical resistance is Pa·s or less.

[0020] According to one aspect of the present disclosure, it is possible to suppress the occurrence of voids near the solder connection portion of a circuit connection structure.

[0021] Fig. 1 is a schematic cross-sectional view showing one embodiment of a method for producing a circuit connection structure, and Fig. 2 is a schematic cross-sectional view showing another embodiment of a method for producing a circuit connection structure.

[0022] Unless otherwise specified, the materials exemplified herein may be used alone or in combination of two or more. Furthermore, a numerical range indicated using "to" indicates a range that includes the numerical values ​​before and after "to" as the minimum and maximum values, respectively. Furthermore, unless specifically stated otherwise, the units of the numerical values ​​before and after "to" are the same. In the numerical ranges described in stages in this specification, the upper or lower limit of a certain numerical range may be replaced with the upper or lower limit of a numerical range of another stage. Furthermore, in the numerical ranges described herein, the upper or lower limit of that numerical range may be replaced with a value shown in the examples. Furthermore, the upper and lower limits individually described can be combined in any combination.

[0023] Hereinafter, embodiments of the present disclosure will be described, but the present disclosure is not limited to these embodiments in any way.

[0024] <Adhesive> One embodiment of the present disclosure is an adhesive having a melt viscosity of 5.0 × 10 at a temperature Tx. ５The present invention relates to a thermosetting adhesive having a viscosity of Pa·s or less.

[0025] In this specification, the melt viscosity of an adhesive is a value measured using a melt viscosity measuring device under the following conditions: measurement temperature: 0 to 200°C, temperature rise rate: 10°C / min, frequency: 10 Hz, and strain: 1%.

[0026] The temperature Tx may be, for example, 100° C., or may be 120° C., 130° C., or 140° C. The temperature Tx may be, for example, 300° C., 200° C., 180° C., or 160° C.

[0027] The adhesive has a curing temperature Tc. In this specification, the curing temperature Tc of the adhesive refers to the peak temperature of the exothermic peak with the largest exothermic amount among the exothermic peaks observed in the obtained differential scanning calorimetry (DSC) curve when the adhesive is subjected to differential scanning calorimetry (DSC) measurement under conditions of a helium atmosphere (He gas flow), a temperature range of 40 to 300°C, and a temperature rise rate of 10°C / min, using a differential scanning calorimeter.

[0028] The curing temperature Tc is, for example, 100 to 200° C., preferably 105 to 195° C., and more preferably 110 to 185° C. The curing temperature Tc may be 120° C. or higher, 140° C. or higher, 160° C. or higher, or 180° C. or higher, or may be 120 to 185° C., 140 to 185° C., 160 to 185° C., or 180 to 185° C.

[0029] The transition initiation temperature (onset temperature) of the exothermic peak indicating the curing temperature Tc may be 90 to 200°C, 95 to 195°C, or 100 to 190°C.

[0030] The curing temperature Tc (and onset temperature) of the adhesive can be adjusted, for example, by the type of thermosetting resin and curing agent contained in the adhesive (for example, by using a microcapsule-type latent curing agent), the mixing ratio of these, etc.

[0031] The difference (Tc-Tx) between the curing temperature Tc and the temperature Tx is, for example, -20°C or higher, and may be -15°C or higher, -10°C or higher, 0°C or higher, 10°C or higher, or 20°C or higher, and may be 50°C or lower, 40°C or lower, or 30°C or lower, or may be -20 to 50°C, -15 to 40°C, -10 to 30°C, 0 to 30°C, 10 to 30°C, or 20 to 30°C.

[0032] Tc and melt viscosity are 5.0 × 10 ５ The difference (Tc-Ty) between the temperature Ty at which the viscosity becomes Pa s is, for example, -20°C or higher, and may be -15°C or higher or -10°C or higher, or may be 50°C or lower, 40°C or lower, or 30°C or lower, or may be -20 to 50°C, -15 to 40°C, or -10 to 30°C.

[0033] The adhesive is a thermosetting adhesive used, for example, in a method for manufacturing a circuit connection structure having a pair of circuit components electrically connected by solder bonding, when the pair of circuit components are thermocompression bonded via a solder connection material.

[0034] The adhesive has a hardening temperature Tc such that the difference (Tc-Tm) between the hardening temperature Tc and the melting point Tm of the solder connecting material is -20°C or more, and the melt viscosity at the melting point Tm of the solder connecting material is 5.0 x 10 ５ It is less than Pa·s.

[0035] In this specification, the melting point Tm of a solder connecting material means the peak temperature of the lowest temperature endothermic peak observed in the obtained differential scanning calorimetry (DSC) curve when the solder connecting material is subjected to differential scanning calorimetry (DSC) measurement using a differential scanning calorimeter under conditions of a helium atmosphere (He gas flow), a temperature range of 40 to 300°C, and a temperature rise rate of 10°C / min.

[0036] The adhesive described above can suppress the occurrence of voids near the solder connection portions of the circuit connection structure. The reason for this is presumed to be as follows. First, when a solder connection material is used to connect circuit components, a phenomenon occurs in which the solder connection material melts due to heating during thermocompression bonding, and then a portion of the melted solder connection material diffuses into the electrodes of the circuit components. At this time, if the adhesive is curing, it is thought that the space (where the solder connection material was previously located) created by the diffusion of the solder connection material is not filled with the adhesive, resulting in the occurrence of voids. Meanwhile, the adhesive has a curing temperature Tc whose difference from the melting point Tm of the solder connection material (Tc - Tm) is -20°C or more, and the curing temperature Tc is 5.0 x 10 at the melting point Tm of the solder connection material. ５ Because the adhesive has a melt viscosity of Pa s or less, it can remain sufficiently fluid even at temperatures at which the solder connection material melts, and even if the solder connection material diffuses into the electrode, the adhesive flows into the space created by the diffusion of the solder connection material. Therefore, it is presumed that the adhesive can suppress the generation of voids near the solder connection portion of the circuit connection structure.

[0037] The adhesive contains, for example, at least a thermosetting resin (hereinafter also referred to as "component (A)") and a curing agent for the thermosetting resin (hereinafter also referred to as "component (B)"). The adhesive may further contain a thermoplastic resin (hereinafter also referred to as "component (C)"), a non-conductive filler (hereinafter also referred to as "component (D)"), an organic acid component (hereinafter also referred to as "component (E)"), etc.

[0038] The adhesive may be conductive (e.g., anisotropically conductive) or insulating (non-conductive). Here, "conductive" means containing a conductive material, and "insulating" means not containing a conductive material. The conductive material may be any metal having conductivity, such as gold, silver, palladium, ruthenium, iridium, nickel, tungsten, molybdenum, copper, tin, solder, etc. The conductive material (e.g., conductive particles) may be a solder connecting material (e.g., solder particles). That is, the adhesive may contain a solder connecting material. Hereinafter, the solder connecting material contained in the adhesive will be referred to as "component (F)," and components contained in the adhesive other than the solder connecting material will be referred to as "adhesive components."

[0039] [Component (A): Thermosetting Resin] Component (A) is not particularly limited as long as it has adhesive properties upon curing. However, from the viewpoint of more significantly achieving the effects of the present disclosure (void suppression effect), an epoxy resin may be used. Examples of epoxy resins that can be used include known epoxy resins (e.g., those described in Epoxy Resin Handbook (edited by Masaki Shinbo, Nikkan Kogyo Shimbun, 1987)). Examples of component (A) include bifunctional epoxy resins such as bisphenol A epoxy and bisphenol F epoxy, novolac epoxy resins such as phenol novolac epoxy resin and cresol novolac epoxy resin, and trisphenolmethane epoxy resin. Component (A) can be generally known resins such as multifunctional epoxy resins, glycidylamine epoxy resins, heterocycle-containing epoxy resins, and alicyclic epoxy resins.

[0040] From the viewpoint of maintaining the heat resistance and adhesiveness of the adhesive after curing and exhibiting high reliability, the content of component (A) may be 40 to 95 parts by mass, 50 to 90 parts by mass, 60 to 85 parts by mass, or 70 to 80 parts by mass, relative to 100 parts by mass of the total amount of component (A) and component (C), which will be described later. When the content of component (A) is 40 parts by mass or more, even higher connection reliability tends to be easily obtained. When the content of component (A) is 95 parts by mass or less, the adhesive layer tends to easily retain its shape.

[0041] [Component (B): Curing Agent] Examples of the component (B) include imidazole-based curing agents, phenolic resin-based curing agents, acid anhydride-based curing agents, amine-based curing agents, phosphine-based curing agents, etc. Among these, by using an imidazole-based curing agent in combination with an epoxy resin (component (A)), the effect of the present disclosure (void suppression effect) tends to be more pronounced.

[0042] Examples of imidazole-based curing agents include 2-phenylimidazole, 2-phenyl-4-methylimidazole, 1-benzyl-2-methylimidazole, 1-benzyl-2-phenylimidazole, 1-cyanoethyl-2-undecylimidazole, 1-cyano-2-phenylimidazole, 1-cyanoethyl-2-undecylimidazole trimellitate, 1-cyanoethyl-2-phenylimidazolium trimellitate, 2,4-diamino-6-[2'-methylimidazolyl-(1')]-ethyl-s-triazine, 2,4-diamino-6 -[2'-undecylimidazolyl-(1')]-ethyl-s-triazine, 2,4-diamino-6-[2'-ethyl-4'-methylimidazolyl-(1')]-ethyl-s-triazine, 2,4-diamino-6-[2'-methylimidazolyl-(1')]-ethyl-s-triazine isocyanuric acid adduct, 2-phenylimidazole isocyanuric acid adduct, 2-phenyl-4,5-dihydroxymethylimidazole, 2-phenyl-4-methyl-5-hydroxymethylimidazole, adducts of epoxy resins and imidazoles, etc. Among these, the imidazole-based curing agent may be 2,4-diamino-6-[2'-methylimidazolyl-(1')]-ethyl-s-triazine isocyanuric acid adduct from the viewpoint of excellent curing properties.

[0043] The content of the imidazole curing agent may be 0.1 to 40 parts by mass per 100 parts by mass of component (A). (When the content of the imidazole curing agent is 0.1 part by mass or more, a sufficient curing reaction rate tends to be easily obtained. When the content of the imidazole curing agent is 40 parts by mass or less, good heat resistance and adhesiveness tend to be easily maintained.) The content of the imidazole curing agent may be 1 to 30 parts by mass, 3 to 20 parts by mass, or 5 to 10 parts by mass per 100 parts by mass of component (A).

[0044] Examples of phenolic resin-based curing agents include various polyfunctional phenolic resins such as phenol novolac resin, cresol novolac resin, phenol aralkyl resin, cresol naphthol formaldehyde polycondensate, triphenylmethane-type polyfunctional phenolic resin, etc. The equivalent ratio of the phenolic resin-based curing agent to component (A) (phenolic hydroxyl groups of the phenolic resin-based curing agent / epoxy groups of component (A) (molar ratio)) may be 0.3 to 1.5, 0.4 to 1.0, or 0.5 to 1.0.

[0045] Examples of acid anhydride curing agents include methylcyclohexanetetracarboxylic dianhydride, trimellitic anhydride, pyromellitic anhydride, benzophenonetetracarboxylic dianhydride, ethylene glycol bisanhydrotrimellitate, etc. The equivalent ratio of the acid anhydride curing agent to component (A) (acid anhydride groups of the acid anhydride curing agent / epoxy groups of component (A) (molar ratio)) may be 0.3 to 1.5, 0.4 to 1.0, or 0.5 to 1.0.

[0046] Examples of amine-based curing agents include dicyandiamide, etc. The equivalent ratio of the amine-based curing agent to component (A) (amino groups of the amine-based curing agent / epoxy groups of component (A) (molar ratio)) may be 0.3 to 1.5, 0.4 to 1.0, or 0.5 to 1.0.

[0047] Examples of phosphine-based curing agents include triphenylphosphine, tetraphenylphosphonium tetraphenylborate, tetraphenylphosphonium tetra(4-methylphenyl)borate, tetraphenylphosphonium(4-fluorophenyl)borate, etc. The amount of the phosphine-based curing agent may be 0.1 to 10 parts by mass or 0.1 to 5 parts by mass per 100 parts by mass of component (A).

[0048] As component (B), a latent curing agent (microcapsule-type latent curing agent) in which the above-mentioned curing agent is microencapsulated can also be used. The use of a microcapsule-type latent curing agent makes it easier to adjust the reaction temperature (peak temperature of the exothermic peak) of the adhesive. For example, the thicker the capsule film thickness of the microcapsule-type latent curing agent, the higher the reaction temperature (peak temperature of the exothermic peak) of the adhesive tends to be, making it less likely to gel (when the mounting temperature is fixed, the gel time becomes longer, and when the gel time is fixed, the gel temperature becomes higher). The gel time of the microcapsule-type latent curing agent alone at 100°C may be 1 minute or more (e.g., 1 to 180 minutes), 2 minutes or more, or even 30 minutes or more. The more difficult it is to gel, the more likely it is to improve storage stability. The microcapsule-type latent curing agent may be, for example, a latent curing agent in which an imidazole-based curing agent is microencapsulated.

[0049] The microcapsule-type latent curing agent may be, for example, a commercially available product as a mixture with a thermosetting resin. Examples of commercially available products containing a microcapsule-type latent curing agent include "HX-3042HP," "HXA4982HP," and "HXA9382HP" (all manufactured by Asahi Kasei Corporation).

[0050] The content of component (B) may be 0.1 to 40 parts by mass per 100 parts by mass of component (A). When the content of component (B) is 0.1 part by mass or more, a sufficient curing reaction rate tends to be easily obtained. When the content of component (B) is 40 parts by mass or less, good heat resistance and adhesiveness tend to be easily maintained. The content of component (B) may be 1 to 30 parts by mass, 3 to 20 parts by mass, or 5 to 10 parts by mass per 100 parts by mass of component (A).

[0051] [Component (C): Thermoplastic Resin] Component (C) contributes to improving the film-forming properties of the adhesive. Examples of component (C) include polyester resins, polyether resins, polyamide resins, polyamideimide resins, polyimide resins, polyvinyl butyral resins, polyvinyl formal resins, phenoxy resins, polyhydroxypolyether resins, acrylic resins, polystyrene resins, butadiene resins, acrylonitrile-butadiene copolymers, acrylonitrile-butadiene-styrene resins, styrene-butadiene copolymers, and acrylic acid copolymers. Among these, component (C) may contain polyimide resins or phenoxy resins because of their excellent heat resistance and mechanical strength.

[0052] The weight average molecular weight of component (C) may be 10,000 to 800,000, 15,000 to 500,000, or 20,000 to 200,000. When the weight average molecular weight is within this range, not only does the adhesive have good strength and flexibility when formed into a film, but the adhesive also has good flow properties, tending to provide excellent circuit filling (embedding) properties. In this specification, the weight average molecular weight refers to a value measured by gel permeation chromatography and converted using a standard polystyrene calibration curve.

[0053] The glass transition temperature of component (C) may be 20 to 170°C or 25 to 120°C. When the glass transition temperature of component (C) is 20°C or higher, the adhesive tends to maintain a film state at room temperature (25°C). When the glass transition temperature of component (C) is 170°C or lower, better connection reliability tends to be obtained.

[0054] The content of component (C) may be 5 to 60 parts by mass, 10 to 50 parts by mass, 15 to 40 parts by mass, or 20 to 30 parts by mass, relative to 100 parts by mass of the total amount of components (A) and (C). When the content of component (C) is within such range, the adhesive tends to have better film-forming properties, and tends to have better flowability and resin expulsion properties during thermocompression bonding.

[0055] [Component (D): Non-conductive Filler] The component (D) is used, for example, to adjust the linear expansion coefficient and elastic modulus of the adhesive within desired ranges, and to adjust the fluidity during thermocompression bonding, the elastic modulus after thermocompression bonding, etc.

[0056] The component (D) may be an inorganic filler or an organic filler.

[0057] Examples of inorganic fillers include metal oxide particles such as silica particles, alumina particles, silica-alumina particles, titania particles, and zirconia particles; metal nitride particles, etc. These may be used alone or in combination of two or more.

[0058] Examples of organic fillers include silicone particles, methacrylate-butadiene-styrene particles, acrylic-silicone particles, polyamide particles, polyimide particles, etc. These may be used alone or in combination of two or more.

[0059] From the viewpoint of improving the film-forming properties of the adhesive and the reliability of the connection structure, component (D) may be an inorganic filler. This effect tends to be more pronounced when the inorganic filler is silica particles. The silica particles may be crystalline silica particles or amorphous silica particles. These silica particles may be synthetic products. The silica particles may be synthesized by a dry method or a wet method. The silica particles may include at least one type selected from the group consisting of fumed silica particles and sol-gel silica particles.

[0060] The silica particles may be surface-treated silica particles from the viewpoint of excellent dispersibility in the adhesive.The surface-treated silica particles may be, for example, silica particles surface-treated with a silane compound such as an alkoxysilane compound, a disilazane compound, or a siloxane compound, or may be silica particles surface-treated with a silane coupling agent.The surface-treated silica particles are, for example, silica particles whose surface hydroxyl groups are hydrophobized with a silane compound or a silane coupling agent.

[0061] The average particle size of component (D) may be, for example, 7 nm to 20 μm, where the average particle size of component (D) is the average primary particle size measured using a flow particle image analyzer (for example, FPIA-3000S manufactured by CIMEX Co., Ltd.).

[0062] The content of component (D) may be 10 to 80 mass%, 15 to 70 mass%, or 20 to 60 mass%, based on the total mass of the adhesive components. When the content of component (D) is 10 mass% or more, an increase in the linear expansion coefficient and a decrease in the elastic modulus of the adhesive are suppressed, making it easier to achieve excellent connection reliability. When the content of component (D) is 80 mass% or less, the melt viscosity of the adhesive does not become too high, and the occurrence of voids tends to be further suppressed.

[0063] [Component (E): Organic Acid Component] Component (E) functions as a fluxing agent, i.e., component (E) has a melting point lower than that of the solder connecting material, and after melting, component (E) removes oxides from the surfaces of the solder connecting material and the metal surfaces of electrodes, etc., thereby improving solder wettability.

[0064] As component (E), organic acids and organic acid esters known as fluxing agents can be used. Examples of organic acids include succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, malic acid, propionic acid, and dimethylolpropionic acid. Examples of organic acid esters include succinic acid diester, glutaric acid diester, adipic acid diester, pimelic acid diester, suberic acid diester, malic acid diester, phthalic acid diester, isophthalic acid diester, and terephthalic acid diester.

[0065] The content of component (E) may be 0.1 to 20 mass % or 0.5 to 10 mass % based on the total mass of the adhesive components. When the content of component (E) is within this range, good solder wettability is easily ensured.

[0066] [Component (F): Solder Connection Material] Component (F) is a connection material containing solder. Component (F) may contain at least one solder selected from the group consisting of tin, a tin alloy, indium, and an indium alloy. When component (F) contains these solder components, the solder connection material is more likely to diffuse into the electrode, which tends to significantly improve the effect of the present disclosure (void suppression effect).

[0067] Examples of tin alloys that can be used include In—Sn alloys, In—Sn—Ag alloys, Sn—Au alloys, Sn—Bi alloys, Sn—Bi—Ag alloys, Sn—Ag—Cu alloys, Sn—Cu alloys, etc. Specific examples of these tin alloys include the following: In-Sn (In 52% by mass, Sn 48% by mass, melting point 118°C) In-Sn-Ag (In 20% by mass, Sn 77.2% by mass, Ag 2.8% by mass, melting point 175°C) Sn-Bi (Sn 43% by mass, Bi 57% by mass, melting point 138°C) Sn-Bi (Sn 42% by mass, Bi 58% by mass, melting point 138°C) Sn-Bi (Sn 72% by mass, Bi 28% by mass, melting point 138°C) Sn-Bi-Ag (Sn 42% by mass, Bi 57% by mass, Ag 1% by mass, melting point 139°C) Sn-Ag-Cu (Sn 96.5% by mass, Ag 3% by mass, Cu 0.5% by mass, melting point 217°C) ・Sn-Cu (99.3% by mass of Sn, 0.7% by mass of Cu, melting point 227°C) ・Sn-Au (21.0% by mass of Sn, 79.0% by mass of Au, melting point 278°C)

[0068] Examples of indium alloys that can be used include In-Bi alloys and In-Ag alloys. Specific examples of these indium alloys include the following: In-Bi (66.3% by mass of In, 33.7% by mass of Bi, melting point 72°C) In-Bi (33.0% by mass of In, 67.0% by mass of Bi, melting point 109°C) In-Ag (97.0% by mass of In, 3.0% by mass of Ag, melting point 145°C) The above-mentioned indium alloys containing tin are classified as tin alloys.

[0069] Among the above, when a solder connecting material containing at least one selected from the group consisting of an Sn—Bi alloy and indium is used as the (F) component, the effect of the present disclosure (void suppression effect) tends to be more pronounced.

[0070] The content of solder in component (F) (for example, the total amount of tin, tin alloy, indium, and indium alloy) may be 90 mass % or more, 95 mass % or more, or 99 mass % or more. The solder connecting material may consist only of solder, excluding impurities that are inevitably mixed in.

[0071] The (F) component is, for example, solder particles. From the viewpoint of excellent dispersibility and conductivity, the average particle diameter of the (F) component may be 1.0 μm or more, 2.0 μm or more, 2.5 μm or more, or 5.0 μm or more. From the viewpoint of ensuring insulation between adjacent electrodes, the average particle diameter of the (F) component may be 30.0 μm or less, 25.0 μm or less, 20.0 μm or less, 15.0 μm or less, 10.0 μm or less, 8.0 μm or less, or 5.0 μm or less. From these viewpoints, the average particle diameter of the (F) component may be 1.0 to 30.0 μm, 2.0 to 20.0 μm, 2.5 to 20.0 μm, or 5.0 to 20.0 μm. The average particle diameter of the (F) component is the average particle diameter obtained by measuring the particle diameter of 300 solder particles contained in the adhesive by observation using a scanning electron microscope (SEM). When the solder particles are not spherical, the particle diameter of the solder particles is defined as the diameter of a circle circumscribing the solder particles in an image observed by SEM.

[0072] The content of the (F) component may be 3% by mass or more, 5% by mass or more, or 8% by mass or more, based on the total mass of the adhesive, from the viewpoint of obtaining better connection resistance. The content of the (F) component may be 30% by mass or less, 20% by mass or less, or 15% by mass or less, based on the total mass of the adhesive, from the viewpoint of ensuring insulation between adjacent electrodes. From these viewpoints, the content of the (F) component may be 3 to 30% by mass, 5 to 20% by mass, or 8 to 15% by mass, based on the total mass of the adhesive. The content of the (F) component may even be 0% by mass. In this case, the solder connection material may be, for example, a solder bump disposed on an electrode of at least one of a pair of circuit members. Even when the solder connection material is a solder bump, the preferred aspects of the solder connection material (such as the type of solder, the solder content, and the melting point) are the same as those described above.

[0073] From the viewpoint of further suppressing the generation of voids, the difference (Tc - Tm) between the curing temperature Tc of the adhesive and the melting point Tm of the solder connecting material is preferably -15°C or higher, more preferably -10°C or higher, and may be 0°C or higher, 10°C or higher, or 20°C or higher. The difference (Tc - Tm) may be, for example, 50°C or lower, 40°C or lower, or 30°C or lower, or may be -20 to 50°C, -15 to 40°C, -10 to 30°C, 0 to 30°C, 10 to 30°C, or 20 to 30°C.

[0074] The melting point Tm of the solder connecting material is, for example, 100° C. or higher, and may be 120° C. or higher, 130° C. or higher, or 140° C. or higher. The melting point Tm of the solder connecting material is, for example, 300° C. or lower, and may be 200° C. or lower, 180° C. or lower, 160° C. or lower, or 140° C. or lower. That is, the melting point Tm of the solder connecting material may be, for example, 100 to 300° C., 120 to 200° C., 130 to 180° C., 140 to 160° C., or 100 to 140° C.

[0075] The melt viscosity of the adhesive at the melting point Tm of the solder connecting material is set to 4.0×10 ５ Pa・s or less, 1.0×10 ５ Pa・s or less, 5.0×10 ４ Pa・s or less, 1.0×10 ４Pa s or less or 5.0 x 10 ３ The lower limit of the melt viscosity at the melting point Tm of the solder connecting material may be, for example, 1.0×10 ３ Pa s, 1.0 × 10 ４ Pa s or 2.0 x 10 ４ That is, the melt viscosity at the melting point Tm of the solder connecting material may be, for example, 1.0×10 ３ ~5.0 x 10 ５ Pa s, and 1.0 × 10 ３ ~4.0 x 10 ５ Pa・s, 1.0×10 ３ ~1.0 x 10 ５ Pa・s, 1.0×10 ３ ~5.0 x 10 ４ Pa・s, 1.0×10 ３ ~1.0 x 10 ４ Pa s or 1.0 x 10 ３ ~5.0 x 10 ３ The melt viscosity of the adhesive can be adjusted by, for example, increasing the curing temperature Tc of the adhesive using the above-mentioned method, or by changing the type of thermosetting resin, thermoplastic resin, non-conductive filler, etc.

[0076] In one embodiment, the melt viscosity of the adhesive at 157°C is 5.0 x 10 ５ The melt viscosity of the adhesive at 157°C may be 5.0 x 10 Pa s or less from the viewpoint of further suppressing the generation of voids. ５ It is preferable that the viscosity is 4.0×10 Pa s or less. ５ Pa・s or less, 1.0×10 ５ Pa・s or less, 5.0×10 ４ Pa・s or less, 1.0×10 ４ Pa s or less or 5.0 x 10 ３ The lower limit of the melt viscosity at 157°C may be, for example, 1.0 x 10 ３ Pa s, 1.0 × 10 ４ Pa s or 2.0 x 10 ４ That is, the melt viscosity at 157°C may be, for example, 1.0 x 10 ３ ~5.0 x 10 ５Pa s, and 1.0 × 10 ３ ~4.0 x 10 ５ Pa・s, 1.0×10 ３ ~1.0 x 10 ５ Pa・s, 1.0×10 ３ ~5.0 x 10 ４ Pa・s, 1.0×10 ３ ~1.0 x 10 ４ Pa s or 1.0 x 10 ３ ~5.0 x 10 ３ It may be Pa·s.

[0077] In one embodiment, the melt viscosity of the adhesive at 138°C is 5.0 x 10 ５ The melt viscosity of the adhesive at 138°C may be 5.0 x 10 Pa s or less from the viewpoint of further suppressing the generation of voids. ５ It is preferable that the viscosity is 4.0×10 Pa s or less. ５ Pa・s or less, 1.0×10 ５ Pa・s or less, 5.0×10 ４ Pa・s or less, 1.0×10 ４ Pa s or less or 5.0 x 10 ３ The lower limit of the melt viscosity at 138°C may be, for example, 1.0 x 10 ３ Pa s, 1.0 × 10 ４ Pa s or 2.0 x 10 ４ That is, the melt viscosity at 138°C may be, for example, 1.0 x 10 ３ ~5.0 x 10 ５ Pa s, and 1.0 × 10 ３ ~4.0 x 10 ５ Pa・s, 1.0×10 ３ ~1.0 x 10 ５ Pa・s, 1.0×10 ３ ~5.0 x 10 ４ Pa・s, 1.0×10 ３ ~1.0 x 10 ４ Pa s or 1.0 x 10 ３ ~5.0 x 10 ３ It may be Pa·s.

[0078] The difference (Tc-Tp) between the adhesive curing temperature Tc and the thermocompression bonding temperature Tp may be -30 to 120°C, -25 to 60°C, or -20 to 30°C, from the viewpoint of further suppressing the generation of voids.

[0079] From the viewpoint of excellent handleability, the adhesive is preferably in the form of a film (i.e., an adhesive film). The thickness of the film may be, for example, 5 μm or more or 10 μm or more, and may be 40 μm or less, 30 μm or less, or 20 μm or less.

[0080] The adhesive film can be prepared, for example, by the following method. First, the above-mentioned components are dissolved or dispersed by stirring and mixing in an organic solvent to prepare a varnish (varnish-like adhesive). Next, the obtained varnish is applied to a release-treated substrate using a knife coater, roll coater, applicator, comma coater, die coater, or the like to form a coating film. Next, the organic solvent in the coating film is volatilized by heating. This allows an adhesive film to be formed on the substrate. At this time, the thickness of the adhesive film can be adjusted by adjusting the amount of varnish applied.

[0081] The organic solvent used in preparing the varnish is not particularly limited as long as it has the property of being able to dissolve or disperse each component substantially uniformly. Examples of such organic solvents include toluene, acetone, methyl ethyl ketone, methyl isobutyl ketone, ethyl acetate, propyl acetate, and butyl acetate. These organic solvents can be used alone or in combination of two or more. The stirring, mixing, or kneading in preparing the varnish can be performed using, for example, a mixer, a grinder, a three-roll mill, a ball mill, a bead mill, a homodisper, or the like.

[0082] The substrate is not particularly limited as long as it has heat resistance that can withstand the heating conditions when volatilizing the organic solvent. Examples of such substrates include substrates (e.g., films) made of oriented polypropylene (OPP), polyethylene terephthalate (PET), polyethylene naphthalate, polyethylene isophthalate, polybutylene terephthalate, polyolefin, polyacetate, polycarbonate, polyphenylene sulfide, polyamide, polyimide, cellulose, ethylene-vinyl acetate copolymer, polyvinyl chloride, polyvinylidene chloride, synthetic rubber, liquid crystal polymer, etc.

[0083] The heating conditions for volatilizing the organic solvent from the varnish applied to the substrate can be appropriately set depending on the organic solvent used, etc. The heating conditions may be, for example, 40 to 120°C for 0.1 to 10 minutes.

[0084] A portion of the solvent may remain in the adhesive without being removed. The content of the solvent in the adhesive may be, for example, 0 to 10 mass % based on the total mass of the adhesive.

[0085] The adhesive described above is used when thermocompression bonding a pair of circuit members together via a solder connecting material. More specifically, it is used to bond a pair of circuit members together in a method for manufacturing a circuit connection structure, which will be described later.

[0086] <Method for manufacturing a circuit connection structure> In one embodiment of the method for manufacturing a circuit connection structure, when a pair of circuit members are thermocompression-bonded via a solder connecting material, the adhesive of the above embodiment is interposed between the pair of circuit members. Hereinafter, one of the pair of circuit members will be referred to as the first circuit member, and the other will be referred to as the second circuit member. In addition, the electrode (connection portion) of the first circuit member will be referred to as the first electrode, and the electrode (connection portion) of the second circuit member will be referred to as the second electrode.

[0087] The method for manufacturing a circuit connection structure includes, for example, a step (a) of arranging a pair of circuit members (a first circuit member having a first electrode and a second circuit member having a second electrode) so that their electrodes (the first electrode and the second electrode) face each other, and a step (b) of thermocompression bonding the pair of circuit members (the first circuit member and the second circuit member) that are arranged facing each other via an adhesive. The solder connection material is, for example, arranged on at least one electrode of the pair of circuit members, or is contained in the adhesive as a component (F).

[0088] The adhesive is, for example, the adhesive of the above embodiment, and the difference (Tc-Tm) between the hardening temperature Tc of the adhesive and the melting point Tm of the solder connecting material is -20°C or more, and the melt viscosity of the adhesive at the melting point Tm of the solder connecting material is 5.0 x 10 ５ It is less than Pa·s.

[0089] According to this method, the first and second circuit members are thermocompression-bonded with the solder connecting material interposed between them, so that the first and second electrodes are electrically connected by solder bonding. Furthermore, because the adhesive of the above embodiment is used to bond the first and second circuit members to each other, the occurrence of voids near the solder connection, i.e., near the solder-bonded first and second electrodes, is suppressed.

[0090] The circuit members (first circuit member and second circuit member) may be circuit boards, semiconductor wafers, or semiconductor chips. Examples of circuit boards include glass substrates or plastic substrates (plastic substrates made of organic materials such as polyimide, polycarbonate, polyethylene terephthalate, and cycloolefin polymer) on which circuit electrodes are formed; printed wiring boards; ceramic wiring boards; and flexible wiring boards. Examples of semiconductor chips include driving IC chips and micro LED chips. The combination of the first circuit member and the second circuit member is not particularly limited. The first circuit member and the second circuit member may be the same or different. For example, both the first circuit member and the second circuit member may be semiconductor chips, with one being a circuit board or semiconductor wafer and the other being a semiconductor chip.

[0091] The electrodes (first electrode and second electrode) are formed on a substrate that constitutes a circuit member. The electrodes may be electrodes containing metals such as gold, silver, tin, ruthenium, rhodium, palladium, osmium, iridium, platinum, copper, aluminum, molybdenum, titanium, or nickel, or oxides such as indium tin oxide (ITO), indium zinc oxide (IZO), or indium gallium zinc oxide (IGZO). The electrodes may be electrodes formed by stacking layers composed of these metals and oxides. In this case, the electrodes may have a two-layer structure or a three-layer or more structure.

[0092] Preferably, at least one of the pair of circuit members has an electrode containing copper, gold, or a gold alloy on the surface that contacts the solder connection material. In this case, the solder connection material is likely to diffuse into the electrode, which tends to significantly enhance the effect of the present disclosure (void suppression effect). Furthermore, as described above, diffusion of the solder connection material into the electrode is particularly likely when the solder connection material contains at least one selected from the group consisting of tin, tin alloys, indium, and indium alloys. Therefore, when at least one of the pair of circuit members has an electrode containing copper, gold, or a gold alloy on the surface that contacts the solder connection material, and the solder connection material contains at least one selected from the group consisting of tin, tin alloys, indium, and indium alloys, the effect of the present disclosure tends to be more pronounced. The electrode containing copper, gold, or a gold alloy on the surface that contacts the solder connection material may be an electrode formed of copper, gold, or a gold alloy, or may be an electrode including a plating layer formed of copper, gold, or a gold alloy.

[0093] Next, the method for manufacturing the circuit connection structure of the above embodiment will be described in more detail with reference to FIGS.

[0094] Fig. 1 is a schematic cross-sectional view showing a method for manufacturing a circuit connection structure 100A using an adhesive that does not contain a solder connection material. Fig. 2 is a schematic cross-sectional view showing a method for manufacturing a circuit connection structure 100B using an adhesive that contains a solder connection material. In the method of Fig. 1, solder bumps 10A are used as the solder connection material, and adhesive 1A that does not contain a solder connection material is used as the adhesive. In the method of Fig. 2, solder particles 10B are used as the solder connection material, and adhesive 1B that contains a solder connection material (solder particles) is used as the adhesive.

[0095] In step (a), for example, first, an adhesive layer is formed on the first circuit member 11 (on the surface on which the first electrode 11a is formed) using adhesive 1A or adhesive 1B. Next, the second circuit member 12 is placed on the first circuit member 11 so that the first electrode 11a and the second electrode 12a face each other (see FIGS. 1A and 2A).

[0096] The method for forming the adhesive layer on the first circuit member 11 may be, for example, a method using a liquid adhesive or a method using a film-like adhesive (adhesive film). When a liquid adhesive is used, the adhesive layer can be formed in the same manner as the above-mentioned method for producing an adhesive film. Examples of methods using an adhesive film include hot pressing, roll lamination, and vacuum lamination. Lamination can be performed, for example, under temperature conditions of 0 to 80°C.

[0097] Since alignment is required when placing the second circuit component 12 on the first circuit component 11, a crimping machine such as a flip-chip bonder is generally used. Although not shown, in step (a), heat and pressure may be applied when placing the second circuit component 12 on the first circuit component 11. This step is generally referred to as pre-bonding, and when pre-bonding is performed, the thermocompression bonding in step (b) is referred to as full-compression bonding. Pre-bonding may be performed using a heat and pressure tool (a crimping head) of the crimping machine. The heating temperature (pre-bonding temperature) during pre-bonding is adjusted so that the maximum temperature (e.g., the maximum temperature of the adhesive) is less than the melting point Tm of the solder connecting material and less than the curing temperature Tc of the adhesive, so that the solder connecting material does not melt and the adhesive does not lose its thermal fluidity. If the first circuit component is placed on a heatable stage, pre-bonding may be performed while the stage is heated.

[0098] In step (b), the first circuit member 11 and the second circuit member 12 are thermocompression bonded via the adhesive 1A or adhesive 1B. The thermocompression bonding can be performed using a heating and pressurizing tool 15, as shown in Fig. 2(b). Specifically, the first circuit member 11 and the second circuit member 12 are thermocompression bonded together by heating the second circuit member 12 while pressing it against the first circuit member 11 using the heating and pressurizing tool 15 (while applying pressure in the direction indicated by the arrow in Fig. 2(b)).

[0099] During thermocompression bonding, in the method of Fig. 1, solder bumps 10A are interposed between the first electrode 11a and the second electrode 12a, while in the method of Fig. 2, solder particles 10B are interposed between the first electrode 11a and the second electrode 12a. These solder connection materials (solder bumps 10A or solder particles 10B) melt during the thermocompression bonding (heating and pressure) and solidify upon cooling, forming a solder connection 13 between the first electrode 11a and the second electrode 12a. This electrically connects the first electrode 11a and the second electrode 12a. In addition, the heating hardens the adhesive components in the adhesive, forming an underfill 14 in the gap between the first circuit member 11 and the second circuit member 12. In this way, the first circuit member 11 and the second circuit member 12 are bonded (fixed) together, and the solder connection portion 13 is sealed, thereby obtaining a circuit connection structure (100A or 100B) (see Figures 1(b) and 1(c) and Figures 2(b) and 2(c)).

[0100] The thermocompression bonding temperature Tp is higher than the melting point Tm of the solder connecting material, for example, 130 to 240°C. From the viewpoint of the curing property of the adhesive, the thermocompression bonding temperature Tp is preferably 140°C or higher, and more preferably 150°C or higher. From the viewpoint of the melting of the solder after thermocompression bonding, the thermocompression bonding temperature Tp is preferably 200°C or lower, and more preferably 190°C or lower. Here, the thermocompression bonding temperature Tp is the maximum temperature reached during thermocompression bonding, and is determined, for example, by the maximum temperature reached by the adhesive.

[0101] Thermocompression bonding may be performed by pressing a heating and pressurizing tool heated to a temperature near the thermocompression bonding temperature Tp (for example, [Tp-10]°C to Tp°C) against the circuit member, or by pressing an unheated heating and pressurizing tool heated to a temperature sufficiently lower than the thermocompression bonding temperature Tp (for example, a temperature lower than the melting point Tm of the solder connecting material) against the circuit member. That is, the heating start temperature for thermocompression bonding may be [Tp-10]°C to Tp°C, or may be a temperature lower than the melting point Tm of the solder connecting material.

[0102] When using a heating and pressing tool that is unheated or heated to a temperature sufficiently lower than the thermocompression bonding temperature Tp, the heating start temperature (e.g., the temperature of the heating and pressing tool 15 at the start of pressing) may be 20 to 100°C, and the temperature rise rate may be 7 to 11°C / min.

[0103] When a heating and pressing tool heated to a temperature near the thermocompression bonding temperature Tp is used, the thermocompression bonding time (the time from the start of heating to the end of heating) is preferably 180 seconds or less (e.g., 5 to 160 seconds), more preferably 5 to 160 seconds, even more preferably 5 to 140 seconds, and particularly preferably 5 to 120 seconds, from the viewpoint of further suppressing the generation of voids. When a heating and pressing tool that is unheated or heated to a temperature sufficiently lower than the thermocompression bonding temperature Tp is used, the thermocompression bonding time is preferably 15 minutes or less (e.g., 0.1 to 15 minutes), more preferably 0.1 to 13 minutes, and even more preferably 0.1 to 10 minutes, from the viewpoint of further suppressing the generation of voids.

[0104] If the first circuit member is placed on a heatable stage, the thermocompression bonding may be performed while the stage is heated, but the heating temperature of the stage is preferably lower than the melting point Tm of the solder connecting material.

[0105] The pressure applied during thermocompression bonding is set appropriately depending on the size and number of circuit components to be connected. The pressure may be, for example, above atmospheric pressure and 1 MPa or less. From the viewpoint of improving connectivity, a higher pressure is preferable, and from the viewpoint of suppressing fillets, a lower pressure is preferable. The pressure may be, for example, 0.1 to 100 MPa.

[0106] Cooling after thermocompression bonding may be carried out by natural cooling (for example, to 20 to 30° C.).

[0107] Although the method for manufacturing the circuit connection structure of the embodiment has been described above using the method shown in FIGS. 1 and 2 as an example, the method for manufacturing the circuit connection structure is not limited to the above example.

[0108] For example, in step (a), a layer of adhesive may be formed on the second circuit member. However, from the viewpoint of thermocompression bonding, it is preferable to form a layer of adhesive on the circuit member on which the solder bumps are formed. This is because the thermocompression bonding tool is often pressed against the second circuit member, which promotes curing of the layer of adhesive. In addition, in step (b), the first circuit member and the second circuit member may be thermocompression bonded to each other by applying heat while pressing the first circuit member against the second circuit member using a heating and pressure tool.

[0109] 1 and 2, the number of first circuit members and the number of second circuit members are one each, but the number of first circuit members and the number of second circuit members are not limited to 1. For example, the method of this embodiment also includes a mode in which multiple semiconductor chips are mounted collectively on a large-area circuit board.

[0110] When multiple semiconductor chips are mounted on a circuit board at once, it is preferable to perform thermocompression bonding by pressing a heating and pressure tool that is unheated or heated to a temperature sufficiently lower than the thermocompression bonding temperature Tp against the circuit members in order to uniformly harden the adhesive. This method tends to require a long heating time, and conventional methods tend to significantly increase the amount of voids that occur, but the method of this embodiment can suppress the occurrence of voids.

[0111] The present disclosure will be specifically described below with reference to examples, but the present disclosure is not limited to the following examples.

[0112] <Material Preparation> The materials shown below were prepared as materials used in the following examples. Note that the gel times of AB-2 to AB-4 refer to the gel times of the microencapsulated imidazole curing agent alone. Furthermore, C-1 was diluted with a solvent (a mixed solvent of toluene and ethyl acetate (ratio 1:1)) to a solids concentration of 40% by mass.

[0113] (Thermosetting components) AB-1: HXA4982HP (thermosetting mixture containing 60 to 70 mass% of epoxy resin and 30 to 40 mass% of microencapsulated imidazole curing agent (capsule film thickness: extra thick), manufactured by Asahi Kasei Corporation, product name) AB-2: HXA9382HP (thermosetting mixture containing 60 to 70 mass% of epoxy resin and 30 to 40 mass% of microencapsulated imidazole curing agent (capsule film thickness: extra thick, gel time at 100°C: >30 minutes), manufactured by Asahi Kasei Corporation, product name) AB-3: HXA3042HP (thermosetting mixture containing 60 to 70 mass% of epoxy resin and 30 to 40 mass% of microencapsulated imidazole curing agent (capsule film thickness: thick, gel time at 100°C: 2.0 minutes), manufactured by Asahi Kasei Corporation, product name) AB-4: HXA3941HP (thermosetting mixture containing 60 to 70% by mass of epoxy resin and 30 to 40% by mass of microencapsulated imidazole curing agent (capsule film thickness: extra thick, gel time at 100°C: 2.5 minutes), product name, manufactured by Asahi Kasei Corporation) A-1: ​​jER1032H60 (triphenolmethane skeleton-containing multifunctional solid epoxy, product name ("jER" is a registered trademark) manufactured by Mitsubishi Chemical Corporation) A-2: HTR-P3-TEA (butyl acrylate / ethyl acrylate / acrylonitrile / glycidyl methacrylate (mass ratio 40 / 30 / 30 / 3) copolymer, Mw 850,000, manufactured by Nagase ChemteX Corporation)

[0114] (Thermoplastic resin) C-1: FX293 (biphenylfluorene type phenoxy resin, weight average molecular weight: 45,000, glass transition temperature: 158°C, product name, manufactured by Nippon Steel Chemical & Material Co., Ltd.) C-2: PKHC (phenoxy resin, manufactured by Union Carbide Corporation)

[0115] (Non-conductive filler) D-1: R805 (hydrolysis product of trimethoxyoctylsilane and silica (silica fine particles), manufactured by Evonik Industries AG, diluted with an organic solvent to a non-volatile content of 10% by mass)

[0116] (Organic acid components) E-1: dimethyl glutarate (manufactured by Tokyo Chemical Industry Co., Ltd.)

[0117] (Solder particles) F-1: In powder (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., product name, average particle size: 50 μm, melting point: 157°C) F-2: Sn42Bi58 solder particles (Sn42Bi58 Type 5, manufactured by Mitsui Kinzoku Co., Ltd., the number of particles with a particle size of 15 to 25 μm is 80% or more of the total, melting point: 138°C)

[0118] Examples 1a to 5a and Comparative Example 1a (Preparation of Adhesive Film) The materials shown in Table 1 were mixed with an organic solvent, and the resulting mixture (varnish-like adhesive) was then coated onto a release-treated PET (polyethylene terephthalate) film. A mixed solvent of toluene and ethyl acetate was used as the organic solvent. The materials shown in Table 1 were blended in the amounts (non-volatile content, units: parts by mass) shown in Table 1. Coating was carried out so that the thickness of the film-like adhesive (adhesive film) obtained after drying would be 30 μm. The organic solvent was then removed by drying to obtain the adhesive films of Examples 1a to 5a and Comparative Example 1a.

[0119] (DSC Measurement) DSC measurement of the adhesive film obtained above was carried out under the following conditions to determine the curing temperature Tc of the adhesive film and the transition start temperature (onset temperature) of the exothermic peak indicating the curing temperature Tc. The results are shown in Table 1. [Conditions] - Apparatus: Differential scanning calorimeter (DSC2500, manufactured by TA Instruments) - Measurement atmosphere: Helium atmosphere (flow rate: 25 ml / min) - Measurement temperature range: 40 to 300°C - Heating rate: 10°C / min

[0120] (Preparation of Connection Structure) Using the adhesive films of Examples 1a to 5a and Comparative Example 1a obtained above, circuit connection structures of Examples 1a to 5a and Comparative Example 1a were prepared, respectively.

[0121] Specifically, first, a PWB (with Cu, Ni, and Au plating) (circuit member A) and an FPC (with Cu, Ni, and Au plating) (circuit member B) were prepared as circuit members. Next, solder bumps, which are solder connection materials, were formed on the electrodes of the circuit member A to obtain a circuit member with solder bumps. In Examples 1a to 4a and Comparative Example 1a, In solder bumps (solder connection material) were used, and the solder bump thickness was set to 25 μm. In Example 5a, Sn—Bi solder (72% by mass Sn, 28% by mass Bi, melting point 138°C) was used, and the solder bump thickness was set to 15 μm.

[0122] A connection structure was produced using the above-mentioned circuit member with solder bumps as the first circuit member and the above-mentioned circuit member B as the second circuit member. Specifically, an adhesive film was placed on the electrode side of the above-mentioned circuit member with solder bumps, and then the circuit member with solder bumps and circuit member B were aligned so that their electrodes faced each other. Next, the opposed circuit member with solder bumps and second circuit member B were thermocompression bonded using a heating and pressurizing tool to obtain a circuit connection structure. The thermocompression bonding conditions for each example are shown below.

[0123] [Thermocompression bonding conditions for Examples 1a to 4a and Comparative Example 1a] Heating start temperature: 40°C Heating rate: 14°C / min Thermocompression bonding temperature Tp (maximum temperature reached by adhesive): shown in Table 1 Thermocompression bonding time (time from heating start to heating end): 10 minutes Pressure: 25 MPa

[0124] [Thermocompression bonding conditions for Example 5a] Heating start temperature: 40°C Heating rate: 13.75°C / sec Thermocompression bonding temperature Tp (maximum temperature reached by adhesive): shown in Table 1 Thermocompression bonding time (time from heating start to heating end): 8 seconds Pressure: 1 MPa

[0125] (Void Evaluation) The presence or absence of voids near the soldered connections of the produced circuit connection structures was evaluated by the following method. The results are shown in Table 1. A: No voids relative to the cross-sectional area of ​​the solder B: Void area is more than 0% and not more than 5% relative to the cross-sectional area of ​​the solder C: Void area is more than 5% and less than 20% relative to the cross-sectional area of ​​the solder D: Void area is 20% or more relative to the cross-sectional area of ​​the solder

[0126] Examples 1b to 5b and Comparative Example 1b The materials shown in Table 2 were mixed with an organic solvent, and the resulting mixture (varnish-like adhesive) was then coated onto a release-treated PET (polyethylene terephthalate) film. A mixed solvent of toluene and ethyl acetate was used as the organic solvent. The materials shown in Table 2 were blended in the amounts (non-volatile content, units: parts by mass) shown in Table 2. Coating was carried out so that the thickness of the film-like adhesive (adhesive film) obtained after drying would be 30 μm. The organic solvent was then removed by drying, yielding adhesive films (1b to 6b) of Examples 1b to 5b and Comparative Example 1b.

[0127] (Preparation of connection structure) As circuit members, a PWB (with Cu, Ni, and Au plating) (circuit member A) and an FPC (with Cu, Ni, and Au plating) (circuit member B) were prepared. Next, the circuit connection structures of Examples 1b to 5b and Comparative Example 1b were each prepared in the same manner as Examples 1a to 5a and Comparative Example 1a, except that the adhesive films of Examples 1b to 5b and Comparative Example 1b obtained above were used as the adhesive films, and the thermocompression bonding conditions were changed as shown below, and voids in the circuit connection structures were evaluated. The results are shown in Table 2.

[0128] [Thermocompression bonding conditions for Examples 1b to 4b and Comparative Example 1b] Heating start temperature: 40°C Heating rate: 14°C / min Thermocompression bonding temperature Tp (maximum temperature reached by adhesive): shown in Table 2 Thermocompression bonding time (time from heating start to heating end): 10 minutes Pressure: 25 MPa

[0129] [Thermocompression bonding conditions for Example 5b] Heating start temperature: 40°C Heating rate: 3.67°C / sec Thermocompression bonding temperature Tp (maximum temperature reached by adhesive): shown in Table 2 Thermocompression bonding time (time from heating start to heating end): 30 seconds Pressure: 1 MPa

[0130]

[0131]

[0132] In Tables 1 and 2 above, "melt viscosity" refers to the melt viscosity of the adhesive film at the melting point Tm of the solder connecting material, and is a value measured under the following conditions: [Conditions] Apparatus: Melt viscosity measuring apparatus (ARES-G2, manufactured by TA Instruments Co., Ltd.) Measurement temperature: 0 to 200°C Heating rate: 10°C / min Frequency: 10 Hz Strain: 1%

[0133] 1A, 1B...adhesive, 10A...solder bump (solder connecting material), 10B...solder particle (solder connecting material), 11...first circuit member, 11a...first electrode, 12...second circuit member, 12a...second electrode, 13...solder connection portion, 14...underfill, 15...heat and pressure tool, 100A, 100B...circuit connection structure.

Claims

1. In a method for manufacturing a circuit connection structure having a pair of circuit members electrically connected by soldering, a thermosetting adhesive is used when thermocompressing the pair of circuit members via a solder connecting material, the adhesive having a curing temperature Tc such that the difference (Tc-Tm) between the curing temperature Tc and the melting point Tm of the solder connecting material is -20°C or more, and a melt viscosity at the melting point Tm of the solder connecting material is 5.0 x 10 ５ An adhesive having a viscosity of less than Pa·s.

2. The adhesive according to claim 1, wherein the curing temperature Tc is 100 to 200°C.

3. Melt viscosity at 157°C is 5.0 x 10 ５ The adhesive according to claim 1 or 2, having a viscosity of Pa·s or less.

4. The adhesive according to claim 1 or 2, comprising at least a thermosetting resin and a curing agent for said thermosetting resin, said thermosetting resin including an epoxy resin.

5. The adhesive of claim 4, wherein the curing agent comprises an imidazole-based curing agent.

6. The adhesive of claim 4, wherein the hardener comprises a microencapsulated latent hardener.

7. The adhesive according to claim 1 or 2, which is insulating.

8. The adhesive according to claim 1 or 2, containing the solder connecting material.

9. The adhesive according to claim 1 or 2, which is in the form of a film.

10. The adhesive according to claim 1 or 2, wherein at least one of the pair of circuit members has an electrode containing copper, gold or a gold alloy on a surface that comes into contact with the solder connecting material, and the solder connecting material contains at least one material selected from the group consisting of tin, tin alloys, indium and indium alloys.

11. A method for manufacturing a circuit connection structure using a solder connecting material, comprising: a step (a) of arranging a pair of circuit members so that their electrodes face each other; and a step (b) of thermocompressing the pair of circuit members arranged opposite each other via a thermosetting adhesive, wherein the solder connecting material is arranged on at least one electrode of the pair of circuit members, or the adhesive contains the solder connecting material, the difference (Tc-Tm) between the hardening temperature Tc of the adhesive and the melting point Tm of the solder connecting material is -20°C or more, and the melt viscosity of the adhesive at the melting point Tm of the solder connecting material is 5.0 x 10 ５ A method for producing a circuit connection structure, wherein the viscosity is less than Pa·s.

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