Solder connection material, method for producing connection structure, and connection structure

Abstract

To provide a film-like solder connection material capable of suppressing scattering of solder and having good handleability.SOLUTION: The solder connection material 21 contains film-forming resins, liquid epoxy resins, thermosetting agents, solder particles 20, and flux components, and has a maximum melt viscosity of 40 000Pa s or less at 170 °C or higher. The arithmetic mean of the weight average molecular weight of the film-forming resin is preferably 10,000 to 20,000.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present technology relates to, for example, a solder connection material for mounting surface-mounted components, a method for manufacturing a connection structure using this solder connection material, and a connection structure. [Background technology]

[0002] For example, mounting a surface mount device (SMD) on a rigid or flexible substrate generally involves printing or temporarily attaching solder paste or film to the substrate, placing the surface mount device on top of it, and then performing the mounting process using a reflow process.

[0003] Among these surface-mounted components, land grid array (LGA) type semiconductor chips, which are a type of semiconductor chip structure, have lands (electrodes) located underneath the chip. Therefore, when an LGA type semiconductor chip is used as a surface-mounted component, it is difficult to check the quality of the solder mounting or whether excess solder is scattered underneath the chip, compared to chip resistors, connectors, etc. Excess solder scattered between the lands underneath the chip can cause short circuits, for example.

[0004] For example, Patent Document 1 describes a paste-like anisotropic conductive material using solder particles. Patent Document 2 describes a film-like anisotropic conductive material using solder particles. However, Patent Documents 1 and 2 do not describe a film-like solder connection material that can suppress solder scattering and has good handleability even when used to mount surface-mounted components (e.g., LGA-type semiconductor chips). Furthermore, the method for manufacturing a circuit connection structure using an adhesive described in Patent Document 3 requires a thermocompression bonding step, and therefore has lower production efficiency than a manufacturing method that uses reflow. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2020-045463 [Patent Document 2] Japanese Patent Application Laid-Open No. 2016-127011 [Patent Document 3] International Publication No. 2025 / 057946 Summary of the Invention [Problem to be solved by the invention]

[0006] The present technology has been proposed in view of the above-mentioned conventional situation, and provides a solder connection material that can suppress scattering of solder and has good handleability when made into a film form. [Means for solving the problem]

[0007] The solder connection material according to this technology contains a film-forming resin, a liquid epoxy resin, a thermosetting agent, solder particles, and a flux component, and has a maximum melt viscosity of 40,000 Pa·s or less at 170°C or higher.

[0008] The method for manufacturing a connection structure according to the present technology joins a surface-mounted component to a wiring board via a solder connection material that contains a film-forming resin, a liquid epoxy resin, a thermosetting agent, solder particles, and a flux component, and has a maximum melt viscosity of 40,000 Pa·s or less at 170°C or higher.

[0009] The connection structure according to the present technology is formed by joining a surface-mounted component to a wiring board via a solder connection material that contains a film-forming resin, a liquid epoxy resin, a thermosetting agent, solder particles, and a flux component, and has a maximum melt viscosity of 40,000 Pa·s or less at 170°C or higher. [Effects of the Invention]

[0010] This technology can suppress scattering of solder and provide a solder connection material that is easy to handle when made into a film. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a cross-sectional view that schematically shows a state in which a solder connection material is provided on a terminal row of a wiring board. [Figure 2] FIG. 2 is a cross-sectional view that schematically shows a state in which the terminal row of the wiring board and the terminal row of the surface-mounted component are aligned. [Figure 3] FIG. 3 is a cross-sectional view that schematically shows a state in which the wiring board and the surface-mounted components are heated in a reflow furnace. [Figure 4] FIG. 4 is an example of an X-ray photograph taken from a planar direction of the evaluation sample obtained in the comparative example. [Figure 5] FIG. 5 is an example of an X-ray photograph taken from a planar direction of the evaluation sample obtained in the example. [Figure 6] FIG. 6 is a graph showing an example of the melt viscosity curve of a solder connection material in film form, where A1 is a graph showing an example of the melt viscosity curve of a solder connection material in film form of an example, and B1 is a graph showing an example of the melt viscosity curve of a solder connection material in film form of a comparative example. [Figure 7] Figure 7 is a graph showing an example of a storage modulus curve of a solder connection material in film form, where A2 is a graph showing an example of a storage modulus curve of a solder connection material in film form of an example, and B2 is a graph showing an example of a storage modulus curve of a solder connection material in film form of a comparative example. DETAILED DESCRIPTION OF THE INVENTION

[0012] <Solder connection materials> The solder connection material according to this embodiment contains a film-forming resin, a liquid epoxy resin, a thermosetting agent, solder particles, and a flux component, and has a maximum melt viscosity of 40,000 Pa·s or less at 170°C or higher. A maximum melt viscosity of 40,000 Pa·s or less at 170°C or higher means that the maximum melt viscosity at 170°C or higher on the melt viscosity curve is 40,000 Pa·s or less. A solder connection material having such a configuration can suppress solder scattering (spattering) when used to mount surface-mount components (e.g., LGA-type semiconductor chips), and is easy to handle when formed into a film.

[0013] Being able to suppress solder scattering means, for example, that scattering of solder (solder particles) into the spaces between terminals of a connection structure in which a surface-mounted component is joined to a wiring board via a solder connection material is unlikely to occur, and specifically includes the evaluation of solder scattering described in the examples below being ◯ (good) or △ (fair).

[0014] Good handling properties of a solder connection material means, for example, that the film properties of a film-shaped solder connection material are good, and specifically includes that the film properties of the film-shaped solder connection material described in the examples below are evaluated as ◯ (good) or △ (acceptable).

[0015] From the viewpoint of improving the handleability of the solder connection material, for example, the viscosity of the solder connection material at 25°C is preferably 2,500 Pa·s or more, may be 10,000 Pa·s or more, may be 15,000 Pa·s or more, may be 20,000 Pa·s or more, may be 25,000 Pa·s or more, may be 27,000 Pa·s or more, may be 30,000 Pa·s or more, may be 40,000 Pa·s or more, may be 45,000 Pa·s or more, may be 50,000 Pa·s or more, may be 60,000 Pa·s or more, may be 65,000 Pa·s or more, may be 70,000 Pa·s It may be equal to or greater than 80,000 Pa·s, may be equal to or greater than 90,000 Pa·s, may be equal to or greater than 100,000 Pa·s, may be equal to or greater than 110,000 Pa·s, may be equal to or greater than 120,000 Pa·s, may be equal to or greater than 130,000 Pa·s, may be equal to or greater than 140,000 Pa·s, may be equal to or greater than 200,000 Pa·s, may be equal to or greater than 270,000 Pa·s, may be equal to or greater than 280,000 Pa·s, may be equal to or greater than 290,000 Pa·s, may be equal to or greater than 300,000 Pa·s, may be equal to or greater than 400,000 Pa·s, or may be equal to or greater than 500,000 Pa·s. The upper limit of the viscosity of the solder connecting material at 25°C can be, for example, 600,000 Pa·s or less, or alternatively 500,000 Pa·s or less, 400,000 Pa·s or less, or 300,000 Pa·s or less. The viscosity of the solder connecting material at 25°C can be measured by the method described in the examples below.

[0016] The solder connecting material also has good solder fluidity. Good solder fluidity specifically includes a case where the solder fluidity of the film-shaped solder connecting material described in the examples below is evaluated as ◯ (good) or △ (fair).

[0017] The solder connecting material has a maximum melt viscosity of 40,000 Pa·s or less at 170°C or higher. This prevents the solder from scattering, for example, between the lands below the LGA semiconductor chip, when a surface-mounted component (e.g., an LGA semiconductor chip) is joined to a wiring board via the solder connecting material using a reflow furnace set at a temperature equal to or higher than the melting point of the solder particles, as will be described in detail later. The maximum melt viscosity of the solder connecting material can be measured by the method described in the examples below.

[0018] The solder connection material may have a maximum melt viscosity at 170°C or higher of, for example, 39,000 Pa·s or less, 38,000 Pa·s or less, 37,000 Pa·s or less, 36,000 Pa·s or less, 35,000 Pa·s or less, 34,000 Pa·s or less, 30,000 Pa·s or less, 25,000 Pa·s or less, or 20,000 Pa·s or less. It may be 15,000 Pa·s or less, 10,000 Pa·s or less, 9,000 Pa·s or less, 8,500 Pa·s or less, 5,000 Pa·s or less, 3,000 Pa·s or less, 2,000 Pa·s or less, 1,100 Pa·s or less, 1,000 Pa·s or less, or 500 Pa·s or less.

[0019] Furthermore, the solder connection material may have a maximum melt viscosity at 170°C or higher of, for example, 30 Pa·s or more, 40 Pa·s or more, 100 Pa·s or more, 200 Pa·s or more, 300 Pa·s or more, 500 Pa·s or more, 1,000 Pa·s or more, 3,000 Pa·s or more, 5,000 Pa·s or more, 6,000 Pa·s or more, 7,000 Pa·s or more, 8,000 Pa·s or more, 9,000 Pa·s or more, 10,000 Pa·s or more, 15,000 Pa·s or more, 20,000 Pa·s or more, 25,000 Pa·s or more, 30,000 Pa·s or more, or 35,000 Pa·s or more.

[0020] The solder connection material may have a maximum melt viscosity at a temperature of 170° C. or higher and 270° C. or lower within the above-mentioned range.

[0021] The melt viscosity of the solder connection material at 230°C, 240°C, or 250°C may be, for example, 40,000 Pa·s or less, 35,000 Pa·s or less, 30,000 Pa·s or less, 29,000 Pa·s or less, 25,000 Pa·s or less, 20,000 Pa·s or less, 15,000 Pa·s or less, 10,000 Pa·s or less, 9,000 Pa·s or less, 8,000 Pa·s or less, 7,000 Pa·s or less, 5,000 Pa·s or less, 3,000 Pa·s or less, 2,000 Pa·s or less, 1,000 Pa·s or less, or 500 Pa·s or less. The melt viscosity of the solder connection material can be measured by the method described in the examples below.

[0022] Furthermore, the solder connection material may have a melt viscosity at 230°C, 240°C, or 250°C of, for example, 5 Pa·s or more, 10 Pa·s or more, 20 Pa·s or more, 30 Pa·s or more, 40 Pa·s or more, 50 Pa·s or more, 100 Pa·s or more, 200 Pa·s or more, 1,000 Pa·s or more, 3,000 Pa·s or more, 5,000 Pa·s or more, 7,000 Pa·s or more, 10,000 Pa·s or more, 15,000 Pa·s or more, 20,000 Pa·s or more, 25,000 Pa·s or more, or 28,000 Pa·s or more.

[0023] The solder connection material may have a melt viscosity at 230°C, 240°C and 250°C that falls within the above-mentioned range.

[0024] From the viewpoint of more effectively suppressing scattering of solder, the storage modulus of the solder connection material is preferably 3 MPa or less at 170°C. The storage modulus of the solder connection material can be measured by the method described in the Examples below. The storage modulus of the solder connection material at 170°C may be, for example, 2.9 MPa or less, 2.8 MPa or less, 2.7 MPa or less, or 2.6 MPa or less. The storage modulus of the solder connection material at 170°C may be, for example, 1.0 MPa or more, 1.5 MPa or more, 2.0 MPa or more, or 2.5 MPa or more. The storage modulus of the solder connection material at 230°C, 240°C, or 250°C may satisfy the above-mentioned range, or the storage moduli at 230°C, 240°C, and 250°C may satisfy the above-mentioned range.

[0025] The shear strength of the solder connecting material, which is a cured product of the components excluding solder particles from the solder connecting material (hereinafter also referred to as "the shear strength of the cured product of the resin component of the solder connecting material"), is preferably 4 to 6 MPa, but may be 4.14 to 5.55 MPa, or may be 4.14 to 4.91 MPa. If the shear strength of the cured product of the resin component of the solder connecting material is not too low, for example, the adhesive strength between a surface-mounted component (e.g., a connector) and a wiring board can be improved. Furthermore, if the shear strength of the cured product of the resin component of the solder connecting material is not too high, for example, repairability can be improved. The shear strength of the cured product of the resin component of the solder connecting material can be measured by the method described in the examples below.

[0026] The solder connection material of this embodiment may be in liquid or film form, but being in film form is preferred because it allows for a more uniform amount of solder particles and is easier to handle, thereby increasing work efficiency.

[0027] When formed into a film, the lower limit of the thickness of the solder connection material (thickness of the binder resin layer excluding the solder particles) is, for example, preferably 0.6 or more, more preferably 0.8 or more, and even more preferably 0.9 or more, relative to the average particle diameter of the solder particles. Furthermore, the upper limit of the thickness of the film-shaped solder connection material is, for example, preferably 3.0 or less, more preferably 2.0 or less, and even more preferably 1.5 or less, relative to the average particle diameter of the solder particles. When formed into a film, if the ratio of the average particle diameter of the solder particles to the thickness of the solder connection material (average particle diameter of solder particles / thickness of the film-shaped solder connection material) is large, the handling of the solder connection material when formed into a film may become difficult.

[0028] The thickness of the solder connection material in film form can be measured, for example, using a known micrometer or digital thickness gauge (e.g., Mitutoyo Corporation's MDE-25M, minimum display 0.0001 mm) that can measure to 1 μm or less, preferably 0.1 μm or less. The thickness of the solder connection material in film form can be determined, for example, by measuring at 10 or more locations and averaging the results. Note that when the thickness of the solder connection material in film form is smaller than the particle diameter of the solder particles, a contact-type thickness measuring device is not suitable, so it is preferable to use a laser displacement meter (e.g., Keyence Corporation's spectral interference displacement type SI-T series, etc.).

[0029] Next, an example of the composition of a solder connection material will be described below. As an example, a solder connection material will be described that is made of a thermal anionic polymerization resin composition containing a film-forming resin, a monofunctional epoxy resin and a bifunctional liquid epoxy resin as liquid epoxy resins, an epoxy resin curing agent as a heat curing agent, solder particles, and a flux component.

[0030] <Film-forming resin> The film-forming resin is, for example, a resin having a weight-average molecular weight (Mw) of 6,000 or more. From the viewpoint of film-forming properties and solder particle fluidity, it is preferable to use a mixture of two or more oligomers and / or polymers with different weight-average molecular weights. For example, a polymer and an oligomer with different weight-average molecular weights can be used in combination. When a mixture of two or more polymers and / or oligomers is used as the film-forming resin, the arithmetic average weight-average molecular weight of the film-forming resin is preferably 10,000 to 20,000, i.e., 10,000 or more and 20,000 or less. By having the arithmetic average weight-average molecular weight of the film-forming resin be 10,000 or more, for example, the handleability of the film-formed solder connection material can be improved. Furthermore, by having the arithmetic average weight-average molecular weight of the film-forming resin be 20,000 or less, for example, the handleability and solder fluidity of the film-formed solder connection material can be improved, and scattering of the solder can be more effectively suppressed.

[0031] Here, the arithmetic mean of the weight average molecular weight of the film-forming resin refers to the value expressed by the following formula 1, for example, when the film-forming resin consists of two component resins (for example, a first film-forming resin and a second film-forming resin).

[0032] Equation 1: ((Mw1×X1) / (X1+X2))+((Mw2×X2) / (X1+X2)) (In formula 1, Mw1 is the weight average molecular weight of the first film-forming resin, Mw2 is the weight average molecular weight of the second film-forming resin, X1 is the number of parts of the first film-forming resin, and X2 is the number of parts of the second film-forming resin.

[0033] Examples of film-forming resins include phenoxy resin, epoxy resin oligomer, polyester resin, polyurethane resin, polyester urethane resin, acrylic resin, polyimide resin, and butyral resin. One type of film-forming resin may be used alone, or two or more types may be used in combination. Among these, from the viewpoints of film formation state, connection reliability, and the like, it is preferable to use a phenoxy resin (polymer) and an epoxy resin oligomer. For example, a mixture of a phenoxy resin having a fluorene skeleton and a solid epoxy resin oligomer may be used. Specific examples of phenoxy resins include FX-293, FX280, and YP-50 (manufactured by Nippon Steel Chemical & Material Co., Ltd.). Specific examples of epoxy resin oligomers include TOPR-300 (manufactured by Nippon Steel Chemical & Material Co., Ltd.), EHPE-3150 (manufactured by Daicel Corporation), JER4010, and JER4007 (manufactured by Mitsubishi Chemical Corporation).

[0034] The upper limit of the weight-average molecular weight of the phenoxy resin is, for example, preferably 100,000 or less, more preferably 60,000 or less, and even more preferably 50,000 or less, while the lower limit of the weight-average molecular weight of the phenoxy resin is, for example, preferably 10,000 or more, more preferably 25,000 or more, and even more preferably 35,000 or more.

[0035] The upper limit of the weight average molecular weight of the epoxy resin oligomer is, for example, preferably 20,000 or less, more preferably 14,000 or less, and even more preferably 8,000 or less.The lower limit of the weight average molecular weight of the epoxy resin oligomer is, for example, preferably 2,000 or more, more preferably 5,000 or more, and even more preferably 6,000 or more.

[0036] The content of the film-forming resin is not particularly limited, but can be, for example, 48% by mass to 60% by mass, or 48% by mass to 55% by mass, based on the total resin content. In this specification, the total resin content refers to the total mass of the film-forming resin and the liquid epoxy resin. The film-forming resin may be used alone or in combination of two or more types. When two or more film-forming resins are used in combination, it is preferable that the total amount of the film-forming resins satisfies the above range.

[0037] <Monofunctional epoxy resin> The monofunctional epoxy resin is not particularly limited as long as it is a monofunctional epoxy resin that is liquid at room temperature. Room temperature refers to, for example, the range of 15 to 25°C as specified in JIS K 0050:2019 (General Rules for Chemical Analysis Methods). Examples of monofunctional epoxy resins include p-tert-butylphenyl glycidyl ether, 2-ethylhexyl glycidyl ether, 2-phenylphenol glycidyl ether, phenyl glycidyl ether, ethylene oxide-modified phenyl glycidyl ether, glycidyl ethers of long-chain alcohols, glycidyl ethers of ethylene oxide-modified long-chain alcohols, and N-glycidyl phthalimide.

[0038] A specific example of p-tert-butylphenyl glycidyl ether is "Denacol EX-146" manufactured by Nagase ChemteX Corporation. A specific example of 2-ethylhexyl glycidyl ether is "Epiol EH-N" manufactured by NOF Corporation. A specific example of 2-phenylphenol glycidyl ether is "OPP-G" manufactured by Sankosha. A specific example of phenyl glycidyl ether is "Epiol P" manufactured by NOF Corporation. A specific example of ethylene oxide-modified phenyl glycidyl ether is "Denacol EX-145" manufactured by Nagase ChemteX Corporation. A specific example of a glycidyl ether of a long-chain alcohol is "Denacol EX-192" manufactured by Nagase ChemteX Corporation. A specific example of a glycidyl ether of an ethylene oxide-modified long-chain alcohol is "Denacol EX-172" manufactured by Nagase ChemteX Corporation. A specific example of N-glycidylphthalimide is "Denacol EX-731" manufactured by Nagase ChemteX Corp. One type of monofunctional epoxy resin may be used alone, or two or more types may be used in combination.

[0039] The inclusion of a monofunctional epoxy resin in the solder connection material can suppress scattering of solder, and improves the handleability of the solder connection material when it is made into a film. For example, the inclusion of a monofunctional epoxy resin in the film-shaped solder connection material can suppress scattering of solder below a semiconductor chip when the semiconductor chip is mounted by reflow using the solder connection material, and when the solder connection material is made into a film, the solder connection material can be handled without breaking when it is attached to the semiconductor chip mounting portion.

[0040] The content of the monofunctional epoxy resin is preferably more than 10% by mass and less than 47% by mass of the total resin content. When the content of the monofunctional epoxy resin exceeds 10% by mass of the total resin content, scattering of the solder can be more effectively suppressed. Furthermore, when the content of the monofunctional epoxy resin is less than 47% by mass of the total resin content, the handleability of the solder connection material, for example, in the form of a film, can be improved.

[0041] The content of the monofunctional epoxy resin may be, for example, 15% by mass or more, 20% by mass or more, 25% by mass or more, 30% by mass or more, 32% by mass or more, 36% by mass or more, 39% by mass or more, 40% by mass or more, 42% by mass or more, or 45% by mass or more, based on the total resin content. The content of the monofunctional epoxy resin may be, for example, 47% by mass or less, 45% by mass or less, or less than 45% by mass, 42% by mass or less, 40% by mass or less, 39% by mass or less, 36% by mass or less, 32% by mass or less, or 30% by mass or less, based on the total resin content. When two or more monofunctional epoxy resins are used in combination, it is preferable that the total amount of the monofunctional epoxy resins satisfy the above range.

[0042] <Bifunctional liquid epoxy resin> The bifunctional liquid epoxy resin is not particularly limited as long as it is liquid at room temperature and is a bifunctional epoxy resin. The combined use of a bifunctional epoxy resin with a monofunctional epoxy resin improves the strength of the solder connection material film when formed into a film, improving its handleability. The bifunctional liquid epoxy resin may have a viscosity of 2,000 to 6,000 mPa·s at 25°C, for example, from the viewpoints of suppressing scattering of solder particles beneath the chip, assisting film formation, and adjusting the crosslink density after curing.

[0043] Examples of bifunctional liquid epoxy resins that can be used include bisphenol A epoxy resins, bisphenol F epoxy resins, and urethane-modified epoxy resins. More specifically, examples of bifunctional liquid epoxy resins that can be used include hydrogenated bisphenol A epoxy resins, bisphenol F epoxy resins, and polyethylene oxide-modified bisphenol A epoxy resins. One type of bifunctional epoxy resin may be used alone, or two or more types may be used in combination.

[0044] Specific examples of hydrogenated bisphenol A epoxy resins include "YX8000" (hydrogenated BPA epoxy resin) manufactured by Mitsubishi Chemical Corporation. Specific examples of bisphenol F epoxy resins include "YL983U" and "JER807" manufactured by Mitsubishi Chemical Corporation. Furthermore, other bifunctional liquid epoxy resins can be used, such as polypropylene oxide-modified bisphenol A epoxy resins with a viscosity at 25°C in the range of 2,000 to 6,000 mPa·s. Specific examples of such polypropylene oxide-modified bisphenol A epoxy resins include "EP-4003" and "EP-4000" manufactured by ADEKA Corporation.

[0045] The content of the bifunctional liquid epoxy resin is preferably 3% by mass or more and less than 45% by mass of the total resin content. When the content of the bifunctional liquid epoxy resin is 3% by mass or more of the total resin content, the handleability of the film-shaped solder connection material can be improved. Furthermore, when the content of the bifunctional liquid epoxy resin is less than 45% by mass of the total resin content, scattering of the solder can be more effectively suppressed.

[0046] The content of the bifunctional liquid epoxy resin may be, for example, 4% by mass or more, 5% by mass or more, 6% by mass or more, 10% by mass or more, 15% by mass or more, 20% by mass or more, 25% by mass or more, 30% by mass or more, 32% by mass or more, 35% by mass or more, or 40% by mass or more, based on the total resin content. The content of the bifunctional liquid epoxy resin may be, for example, 40% by mass or less, 35% by mass or less, 32% by mass or less, 30% by mass or less, 25% by mass or less, 20% by mass or less, 15% by mass or less, or 10% by mass or less, based on the total resin content. When two or more bifunctional liquid epoxy resins are used in combination, it is preferable that the total amount of the bifunctional liquid epoxy resins satisfy the above range.

[0047] When a monofunctional epoxy resin and a bifunctional liquid epoxy resin are used in combination, it is also preferable that the content of the bifunctional liquid epoxy resin in the solder connecting material is 3% by mass or more but less than 45% by mass of the total resin content, and the content of the monofunctional epoxy resin is less than 45% by mass of the total resin content. By adopting such a configuration, the film-forming properties of the solder connecting material when made into a film are further improved, the handleability is further improved, and scattering of the solder can be more effectively reduced.

[0048] Furthermore, when a monofunctional epoxy resin and a bifunctional liquid epoxy resin are used in combination, the mass ratio of the monofunctional epoxy resin to the bifunctional liquid epoxy resin in the solder connection material (bifunctional liquid epoxy resin / monofunctional epoxy resin) can be, for example, 0.07 or more and 1.60 or less, or may be 0.11 or more, 0.15 or more, 0.24 or more, 0.63 or less, or 0.24 or less.

[0049] [Epoxy resin hardener] The epoxy resin curing agent is not particularly limited as long as it is a heat-curing agent that initiates curing by heat. Examples of epoxy resin curing agents include anionic curing agents such as amines and imidazoles, and cationic curing agents such as sulfonium salts. The epoxy resin curing agent may be microencapsulated to improve resistance to solvents used in film formation and to improve latency. Examples of anionic curing agents include "2P4MHZ-PW" (2-phenyl-4-methyl-5-hydroxymethylimidazole), "2MA-OK-PW" (isocyanuric acid adduct of 2,4-diamino-6-[2'-imidazolyl-(1')]-ethyl-S-triazine), and "2MZ-A-PW" (2,4-diamino-6-[2'-imidazolyl-(1')]-ethyl-S-triazine), all manufactured by Shikoku Chemical Industries, Ltd., because they have excellent storage stability and can appropriately control the solder fluidity and curing speed when the solder connection material is used in a reflow process. Examples of suitable epoxy resin curing agents include imidazole-based epoxy resin curing agents such as 2-(2'-imidazolyl-(1')-ethyl-S-triazine) and 2-(2'-imidazolyl-(1')-ethyl-S-triazine. The epoxy resin curing agents may be used alone or in combination of two or more. The imidazole-based epoxy resin curing agent is preferably a fine powder having a volume average particle size of about 1 to 10 μm, from the viewpoints of not interfering with the solder bonding of the substrate (wiring board) or electronic components (surface-mounted components) to be mounted and of controlling the solder fluidity.

[0050] The content of the epoxy resin curing agent can be, for example, 0.1 to 20 parts by mass, or alternatively 1 to 20 parts by mass, 1 to 15 parts by mass, 2 to 15 parts by mass, 1 to 10 parts by mass, or 2 to 10 parts by mass, when the total amount of the resin components is 100 parts by mass. When two or more types of epoxy resin curing agents are used in combination, it is preferable that the total amount of the epoxy resin curing agents falls within the above range.

[0051] [Solder particles] The solder particles can be appropriately selected from, for example, Sn-Pb, Pb-Sn-Sb, Sn-Sb, Sn-Pb-Bi, Bi-Sn, Sn-Cu, Sn-Pb-Cu, Sn-In, Sn-Ag, Sn-Pb-Ag, Pb-Ag, etc., as specified in JIS Z 3282-1999, depending on the electrode material, connection conditions, etc. Among these, the solder particles are preferably one or more selected from the group consisting of Sn-Bi-Cu alloy, Sn-Bi-Ag alloy, Sn-Bi alloy, Sn-Pb-Bi alloy, and Sn-In alloy. Specific examples of solder particles include Sn59.9Bi40Cu0.1, Sn30Bi0.5Cu, Sn30Bi, Sn40Bi, Sn50Bi, Sn58Bi, Sn40Bi0.1Cu, Sn43Pb14Bi, Sn20In, etc. This allows for excellent connection reliability.

[0052] The lower limit of the melting point of the solder particles is, for example, preferably 110°C or higher, more preferably 120°C or higher, and even more preferably 130°C or higher. The upper limit of the melting point of the solder particles may be, for example, 250°C or lower, preferably 200°C or lower, more preferably 180°C or lower, and even more preferably 160°C or lower. In addition, a flux component may be directly bonded to the surface of the solder particles for the purpose of activating the surface. Activating the surface of the solder particles can promote metal bonding with the electrode portion.

[0053] The average particle diameter of the solder particles is, for example, preferably 0.5 times or less, more preferably 0.3 times or less, and even more preferably 0.2 times or less, the minimum inter-terminal distance (space distance) between the terminal row of the surface-mounted component and the terminal row of the wiring board. This relationship between the space distance and the average particle diameter of the solder particles allows the terminal row of the surface-mounted component and the terminal row of the wiring board to be more reliably joined, for example, using a reflow furnace. If the average particle diameter of the solder particles is, for example, greater than 0.5 times the minimum inter-terminal distance between the terminal row of the surface-mounted component and the terminal row of the wiring board, the likelihood of a short circuit occurring increases.

[0054] The lower limit of the average particle size of the solder particles is, for example, preferably 0.5 μm or more, more preferably 3 μm or more, and even more preferably 5 μm or more. The upper limit of the average particle size of the solder particles may be, for example, 50 μm or less, or 30 μm or less, preferably 25 μm or less, and more preferably 20 μm or less. This allows for a good solder joint state and high reliability.

[0055] The average particle size is the average major axis diameter of particles measured, for example, at N=20 or more, preferably N=50 or more, and more preferably N=200 or more, in observation images using a metallurgical microscope, optical microscope, or electron microscope such as a scanning electron microscope (SEM). In the case of spherical particles, it is the average diameter of the particles. It may also be measured using known image analysis software (such as "WinROOF" from Mitani Shoji Co., Ltd. or "Azo-kun (registered trademark)" from Asahi Kasei Engineering Co., Ltd.) or using an image-based particle size distribution analyzer (e.g., FPIA-3000 (Malvern Instruments)) (N=1000 or more). The average particle size determined from observation images or an image-based particle size distribution analyzer can be the average maximum length of the particles. When preparing a solder connection material, manufacturer values ​​such as the particle size (D50) at which the cumulative frequency in the particle size distribution determined by a laser diffraction / scattering method reaches 50% or the arithmetic mean diameter (preferably on a volume basis) may be used.

[0056] The solder particles are preferably dispersed in the binder, and may be arranged randomly or according to a certain rule. The solder particles may also be in the form of aggregates in which a plurality of solder particles are aggregated.

[0057] The content of solder particles in the solder connection material can be determined appropriately based on the pitch of the terminal rows of the surface-mounted components and the wiring board. For example, for a terminal row pitch of 0.1 to 0.4 mm for the surface-mounted components and the wiring board, it is preferably 10 to 60 volume %. For example, when the pitch is 0.4 mm, it is preferably 20 to 58 volume %, when the pitch is 0.35 mm, it is preferably 20 to 58 volume %, when the pitch is 0.2 mm, it is preferably 20 to 48 volume %, when the pitch is 0.15 mm, it is preferably 15 to 48 volume %, and when the pitch is 0.1 mm, it is preferably 10 to 38 volume %. If the solder particle content is too low, excellent conductivity, heat dissipation, and adhesion cannot be obtained. If the solder particle content is too high, anisotropy is easily impaired, making it difficult to obtain excellent conductivity reliability.

[0058] The solder particles may be used alone or in combination of two or more types. When two or more types of solder particles are used in combination, it is preferable that the total amount of the solder particles satisfies the above range.

[0059] [Flux components] Flux components are compounds used to remove foreign matter and oxide films from electrode surfaces, prevent oxidation of the electrode surface, and reduce the surface tension of molten solder. Examples of flux components include carboxylic acid compounds such as levulinic acid, maleic acid, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, and sebacic acid. Among these, glutaric acid is preferred because of its excellent ability to remove oxide films. Flux components may be used alone or in combination of two or more.

[0060] The content of the flux component can be, for example, 0.1 to 20 parts by mass when the total amount of the resin component is 100 parts by mass. When two or more types of flux components are used in combination, it is preferable that the total amount of the flux components satisfies the above range.

[0061] [Additives] In addition to the above-mentioned components, the solder connection material may contain various additives conventionally used in adhesives, as long as the effects of the present technology are not impaired. If the additive is incompatible with the resin component of the solder connection material, the particle size of the additive is not particularly limited as long as it does not impede inter-electrode bonding, but is preferably smaller than the average particle size of the solder particles.

[0062] From the viewpoint of improving film formability and handling properties when made into a film, the solder connecting material preferably has an arithmetic average weight-average molecular weight of the entire resin of 7,000 to 10,000. Here, the arithmetic average weight-average molecular weight of the entire resin refers to the value expressed by the following formula 2, for example, when the film-forming resin is composed of two resin components (for example, a first film-forming resin and a second film-forming resin).

[0063] Formula 2: ((Mw1×X1) / (X1+X2+X3+X4))+((Mw2×X2) / (X1+X2+X3+X4))+((Mw3×X3) / (X1+X2+X3+X4))+((Mw4×X4) / (X1+X2+X3+X4)) (In formula 2, Mw1 is the weight average molecular weight of the first film-forming resin, Mw2 is the weight average molecular weight of the second film-forming resin, Mw3 is the molecular weight of the monofunctional epoxy resin, Mw4 is the molecular weight of the bifunctional liquid epoxy resin, X1 is the number of parts of the first film-forming resin, X2 is the number of parts of the second film-forming resin, X3 is the number of parts of the monofunctional epoxy resin, and X4 is the number of parts of the bifunctional liquid epoxy resin.

[0064] Next, an example of a method for producing a solder connection material will be described. When the solder connection material is formed into a film, for example, a resin component, solder particles, and flux components are mixed in a solvent, and the mixture is applied to a release-treated film to a predetermined thickness using a bar coater, followed by drying to volatilize the solvent. Alternatively, the mixture may be applied to a release-treated film using a bar coater and then pressurized to a predetermined thickness. To improve the dispersibility of the solder particles, a high shear force may be applied while the material contains the solvent. For example, a known batch-type planetary stirring device may be used. When the solder connection material is formed into a film, the amount of residual solvent in the material is, for example, preferably 2% or less, more preferably 1% or less.

[0065] The method for producing the solder connection material is not limited to the above-mentioned examples, and for example, the resin component, solder particles, and flux component may be mixed at room temperature or under heated and melted conditions to produce a paste-like, syrup-like, or semi-solid solder connection material.

[0066] <Method of manufacturing the connection structure> The method for manufacturing a connection structure according to this embodiment bonds a surface-mounted component to a wiring board via the above-mentioned solder connection material, for example, a film-like solder connection material containing a film-forming resin, a liquid epoxy resin, a thermosetting agent, solder particles, and a flux component, and having a maximum melt viscosity of 40,000 Pa s or less at 170°C or higher. Bonding refers to joining two materials or members together.

[0067] The solder connecting material has the same meaning as the solder connecting material described above, and the preferred range is also the same, so detailed description will be omitted.

[0068] The surface mount component is not particularly limited, and examples thereof include a component having a first terminal row and a second terminal row arranged in parallel, a component having a first terminal row and a second terminal row arranged in parallel, and a third terminal row and a fourth terminal row arranged in parallel and perpendicular to the first terminal row and the second terminal row. A terminal row refers to a configuration in which terminals (electrodes) are arranged in a predetermined direction at a predetermined interval (pitch). The predetermined direction in which the terminals are arranged is called the row direction of the terminal row, and the direction perpendicular to the row direction is called the width direction of the terminal row.

[0069] Specific examples of surface-mounted components include, but are not limited to, semiconductor chips, connectors, LEDs (Light Emitting Diodes), switches, etc. For example, connectors include SMT (Surface Mount) connectors that have a first terminal row in which multiple pins (lead frames) extending outward on one side of the short side are arranged in the longitudinal direction, and a second terminal row in which multiple pins (lead frames) extending outward on the other side of the short side are arranged in the longitudinal direction. Furthermore, for example, semiconductor chip package configurations include surface-mounted lead types such as SOP (Small Outline Package) and SOJ (Small Outline J-leaded) that have terminal rows on two opposing rectangular sides, QFP (Quad Flat Package) and QFN (Quad Flat No-leaded package) that have terminal rows on four rectangular sides, and LGA (Large Grid Array) that have terminal lands arranged in a grid pattern on the bottom surface of the package.

[0070] In the method for manufacturing a connection structure according to this embodiment, by using the above-described solder connection material, it is possible to prevent solder from scattering between lands below the chip, even when an LGA-type semiconductor chip is used as the surface-mount component, for which it is difficult to check the quality of solder mounting and the scattering of excess solder below the chip, compared to chip resistors, connectors, etc. Furthermore, in the method for manufacturing a connection structure, even when a connector, for example, is used as the surface-mount component, it is possible to prevent solder from scattering by using the above-described solder connection material.

[0071] The wiring board is not particularly limited as long as it has wiring, and may be, for example, a board that can be broadly defined as a so-called printed wiring board (PWB) provided with electrodes on which surface-mounted components can be mounted, and may be either a rigid board or a flexible board (FPC: Flexible Printed Circuits). Examples of substrates based on the type of base material include glass substrates, ceramic substrates, and plastic substrates.

[0072] The upper limit of the pitch of the terminal rows of the surface-mounted components and the wiring board is preferably 2 mm or less, more preferably 1 mm or less, and even more preferably 0.5 mm or less, and the lower limit of the pitch of the terminal rows is preferably 0.06 mm or more, more preferably 0.08 mm or more, and even more preferably 0.1 mm or more.

[0073] Hereinafter, with reference to Figures 1 to 3, we will explain process A of providing a solder connection material on the terminal row of the wiring board, process B of fixing surface-mounted components on the solder connection material, and process C of joining the terminal row of the wiring board and the terminal row of the surface-mounted components using a reflow furnace.

[0074] [Process A] 1 is a cross-sectional view showing a state in which a solder connection material is provided on a terminal row of a wiring board. As shown in FIG. 1, in step A, for example, a solder connection material 21 containing solder particles 20 is provided on a terminal row 11 of a wiring board 10.

[0075] If the solder connection material 21 is in film form, process A may be a temporary attachment process in which the solder connection material 21 is attached to the terminal row 11 of the wiring board 10 at low temperature and low pressure, or may be a lamination process in which the solder connection material 21 is laminated onto the terminal row 11 of the wiring board 10.

[0076] [Process B] 2 is a cross-sectional view showing a state in which the terminal row of the wiring board and the terminal row of the surface-mounted component are aligned. As shown in FIG. 2, in step B, for example, the terminal row 11 of the wiring board 10 and the terminal row 31 of the surface-mounted component 30 are aligned, and the surface-mounted component 30 is fixed onto the solder connecting material 21.

[0077] In step B, for example, a tool is used to align the terminal row 11 with the terminal row 31 of the surface mount component 30. The tool preferably includes, for example, a suction mechanism for suctioning the surface mount component. In step B, for example, temporary pressure bonding may be performed by pressing the surface mount component 30 from the side using the tool.

[0078] [Process C] 3 is a cross-sectional view schematically illustrating a state in which a wiring board and a surface-mounted component are heated in a reflow furnace. As shown in FIG. 3, in step C, the terminal row 11 of the wiring board 10 and the terminal row 31 of the surface-mounted component 30 are joined with solder 41 using a reflow furnace set at a temperature equal to or higher than the melting point of the solder particles 20. This allows the solder particles 20 in the solder connection material 21 to aggregate with the terminal row 11 of the wiring board 10 and the terminal row 31 of the surface-mounted component 30.

[0079] Examples of reflow furnaces include atmospheric pressure reflow, vacuum reflow, atmospheric pressure ovens, and autoclaves (pressure ovens). Among these, vacuum reflow and autoclaves are preferred, as they can eliminate air bubbles trapped in the joints. A reflow furnace heats and bonds the components without applying mechanical pressure or load. That is, a reflow furnace can be used to bond the surface mount components 30 to the wiring board 10 without applying load, thereby reducing damage to the wiring board 10 and the surface mount components 30. Here, "without load" refers to a state in which no mechanical pressure is applied.

[0080] The lower limit of the peak temperature (maximum temperature reached) in the reflow furnace should be equal to or higher than the temperature at which the solder particles 20 melt and the temperature at which the solder connection material 21 begins to harden, and is preferably 150°C or higher, or may be 170°C or higher, or 180°C or higher, or may be 200°C or higher. The upper limit of the peak temperature in the reflow furnace is 300°C or lower, more preferably 290°C or lower, or may be 280°C or lower, or may be 270°C or lower. This results in solder bonding between the terminal row 11 of the wiring board 10 and the terminal row 31 of the surface-mounted component 30. Furthermore, the terminals are bonded together except for the solder-bonded portions by the cured product 40 of the thermosetting binder. Here, solder bonding refers to connecting the terminals (electrodes) of opposing electronic components by melting solder.

[0081] According to the manufacturing method of the connection structure of this embodiment, by using the solder connection material 21, it is possible to obtain appropriate resin fluidity, and the solder particles can be efficiently aggregated on the electrode even after aging, when the self-aggregation performance of the solder decreases.

[0082] In the above-described method for manufacturing a connection structure, in step C, a reflow furnace is used to join the terminal row of the wiring board and the terminal row of the surface-mounted component, but this is not limited to this. For example, joining may be performed using a heating and pressurizing tool within a range that does not prevent the solder particles from agglomerating onto the terminals.

[0083] Furthermore, the solder connection material 21 may be used to join multiple terminal rows 11 of the wiring board 10 to multiple terminal rows 31 of the surface-mounted component 30. In addition, in the case of a wiring board 10 having multiple terminal rows 11, the solder connection material 21 may be provided for each terminal row 11. This, for example, limits the movement of the solder particles 20 between the terminal rows 11 due to the self-alignment effect during heating, and allows only the solder particles 20 in a predetermined solder connection material 21 to aggregate with a predetermined terminal row 11.

[0084] As described above, in the manufacturing method of the connection structure according to this embodiment, by using the solder connection material 21, even when an LGA-type semiconductor chip is used as the surface-mounted component 30, it is possible to prevent the solder (solder balls) made of solder particles 20 from scattering between the lands below the chip (for example, between the multiple terminal rows 31 of the surface-mounted component 30).

[0085] <Connection structure> The connection structure according to this embodiment is obtained, for example, by the above-described method for manufacturing a connection structure, and is formed by joining a surface-mounted component 30 to a wiring board 10 via the above-described solder connection material 21. A connection structure refers to an electrical connection between two materials or members. By using the solder connection material 21, the connection structure according to this embodiment can prevent solder consisting of solder particles 20 from scattering between lands below the chip (for example, between multiple terminal rows 31 of the surface-mounted component 30) even when an LGA-type semiconductor chip is used as the surface-mounted component 30. This can prevent short circuits from occurring. [Example]

[0086] Examples of the present technology will be described below. In these examples, a solder connection material was prepared in a film form to form a film-like solder connection material, and the film properties of this film-like solder connection material were evaluated. The film-like solder connection material was also attached to a substrate, and the solder flow in the evaluation sample after reflow was evaluated. The film-like solder connection material was then attached to a substrate, the substrate was mounted on the film-like solder connection material, and the solder scattering in the evaluation sample after reflow was evaluated. Note that the present technology is not limited to these examples.

[0087] [Preparation of film-type solder connection material] The following materials were prepared.

[0088] <Film-forming resin> Fluorene-type phenoxy resin (solid type), Mw: 44,000 Cycloaliphatic solid epoxy resin oligomer, Mw: 6,500

[0089] <Liquid epoxy resin> YL983U (Mitsubishi Chemical Corporation): Bisphenol F epoxy resin (liquid type), molecular weight: 312.36 Denacol EX-146P (Nagase ChemteX Corporation): p-tert-butylphenyl glycidyl ether, molecular weight: 206.3

[0090] <Thermal curing agent> 2P4MHZ-PW (Shikoku Chemicals Corporation): 2-phenyl-4-methyl-5-hydroxymethylimidazole

[0091] <Flux components> Glutaric acid (Tokyo Chemical Industry Co., Ltd.)

[0092] <Solder particles> Solder particles (Sn59.9Bi40Cu0.1) with an average particle size of 20 μm

[0093] A binder was prepared by mixing the film-forming resin, liquid epoxy resin, thermosetting agent, and flux components using a planetary mixer to obtain the composition (parts by mass) shown in Table 1. 115.75 parts by mass of the resulting binder were combined with 460 parts by mass of solder particles (38% by volume of the binder and solder particle mixture), and the resulting mixture was mixed using a planetary mixer to prepare a mixed solution. The resulting mixed solution was applied to a base film (50 μm thick PET film) using a bar coater and dried at 50°C for 5 minutes and then at 80°C for 5 minutes, yielding a 30 μm-thick sheet-like composition (film-like solder connection material). A film from which the solder particles had been removed (hereinafter also referred to as the "film without solder particles") was also prepared for shear strength evaluation.

[0094] [Viscosity and melt viscosity of film-type solder connecting material] The melt viscosity of the film-type solder connecting material was measured using a rotational rheometer (manufactured by Thermo Fisher Scientific) under the following conditions: measurement pressure 1N, temperature range 25-270°C, heating rate 10°C / min, measurement frequency 1Hz, and measurement plate diameter 8mm. The film-type solder connecting material was then evaluated for viscosity at 25°C and maximum melt viscosity at 170°C or higher. The results are shown in Table 1. In Table 1, a diagonal line (\) indicates that the measurement was not performed.

[0095] [Storage modulus of film-type solder connecting material] The storage modulus of the film-type solder connecting material was measured using a reflow simulator (Sanyo Seiko Co., Ltd., SMT Scope Light SL-1) by heating the film-type solder connecting material from room temperature (25°C) at a rate of 3°C / s to 180°C, holding it at 180°C for 120 seconds to cure, then slowly cooling to room temperature and cutting it into a 2 mm wide, 20 mm long sample. This sample was then placed in a dynamic viscoelasticity measuring device (A&D Co., Ltd., Rheovibron) and measured over a temperature range of 30 to 270°C, at a heating rate of 3°C / min, and at a frequency of 1 Hz. The storage modulus was then evaluated at 170°C, 230°C, 240°C, and 250°C. The results are shown in Table 1. In Table 1, a diagonal line (\) indicates that the measurement was not performed. In addition, in Table 1, "impossible to measure" indicates that, for example, the sample was brittle and broke when attached to the measuring device, making it impossible to actually measure, but this does not pose a practical problem as a film-type solder connecting material.

[0096] [Evaluation of film properties of film-type solder connecting materials] The film properties of the film-like solder connecting material were evaluated according to the following criteria. From a practical standpoint, an evaluation of ◯ (good) or △ (fair) is preferable, with an evaluation of ◯ (good) being more preferable. The results are shown in Table 1. ○ (Good): The film-type solder connecting material can be attached to the object, and the film shape can be maintained even after the base film is peeled off. △ (Acceptable): The film-type solder connection material can be attached to the object, but the film shape cannot be maintained when the base film is peeled off. × (Not possible): The film-type solder connecting material is liquid and cannot be attached to the target object.

[0097] [Evaluation of solder flow] An LGA mock-up board (gold-plated wiring, pad diameter: 0.245 mm, spacing: 0.105 mm, number of pads: 20 x 20 = 400) was prepared as the substrate. A film-type solder connecting material was temporarily attached to the pads of the LGA mock-up board at 50°C, 1.0 MPa, and 10 seconds, and reflow was performed under the following reflow conditions without mounting components, to produce evaluation sample A. Reflow conditions: Heating rate 3°C / sec → Preheat 175°C - 90 sec → Heating rate 3°C / sec → 250°C - 20 sec

[0098] An X-ray photograph of evaluation sample A was taken using an X-ray photography device, and the number of solder balls present other than the pads was counted. Evaluation sample A was then evaluated according to the following criteria. In practical terms, an evaluation of ◯ (good) or △ (fair) is preferable, with an evaluation of ◯ (good) being more preferable. The results are shown in Table 1. ○ (Good): 0 solder balls other than the terminals (pads) △ (Acceptable): There are 1 to 3 solder balls other than the terminals (pads) × (Not acceptable): There are four or more solder balls other than the terminal (pad).

[0099] [Evaluation of solder scattering] An LGA mock-up board (gold-plated wiring, pad diameter: 0.245 mm, spacing: 0.105 mm, number of pads: 20 x 20 = 400) was prepared as the substrate. A film-type solder connecting material was temporarily attached to the pads of the LGA mock-up board at 50°C, 1.0 MPa, and 10 seconds. Glass was placed on the temporarily attached film-type solder connecting material, and reflow was performed under the following reflow conditions to produce evaluation sample B. Reflow conditions: Heating rate 3°C / sec → Preheat 175°C - 90 sec → Heating rate 3°C / sec → 250°C - 20 sec

[0100] An X-ray photograph of evaluation sample B was taken using an X-ray imaging device, and the number of solder balls present in the space was counted. Evaluation sample B was then evaluated according to the following criteria. In practice, an evaluation of ◯ (good) or △ (fair) is preferable, with an evaluation of ◯ (good) being more preferable. The results are shown in Table 1. In Table 1, a diagonal line (\) indicates that the measurement was not performed. ○ (Good): 0 solder in the space △(Acceptable): 1 to 3 solder spaces × (Not acceptable): There are 4 or more solder spaces.

[0101] [Evaluation of shear strength of cured resin components of solder connection materials] A PWB substrate (gold-plated wiring, pitch: 0.35 mm, wiring width: 0.175 mm, spacing: 0.175 mm) was prepared as the substrate. A connector (Hirose Electric Co., Ltd., BM23FR0.6-20DS-0.35V, gold-plated wiring, pitch: 0.35 mm, number of terminals: 20) was prepared as the mounted component. A film with solder particles removed was temporarily attached to the wiring of the PWB substrate at 40°C, and the connector was mounted on the temporarily attached film and reflowed under the following reflow conditions to create an evaluation sample.

[0102] Reflow conditions: Heating rate 3°C / sec → Preheat 175°C - 90 sec → Heating rate 3°C / sec → 250°C - 20 sec

[0103] After reflow, the connector was cooled slowly to room temperature (25°C), and then a bond tester (TRY Precision) was used to apply a load to the longitudinal side of the connector at a test speed of 200 μm / s, and the shear strength of the cured resin component of the solder connecting material when the connector peeled off from the board was measured. The results are shown in Table 1.

[0104] [comprehensive evaluation] For the evaluation of film quality, solder flow, and solder scattering, if all were rated as ○ (good) or there was one or less △ (fair), the overall evaluation was OK; otherwise, the overall evaluation was NG. The results are shown in Table 1.

[0105] [Table 1]

[0106] The film-like solder connecting materials used in Examples 1 to 9 contained a film-forming resin, a liquid epoxy resin, a thermosetting agent, solder particles, and a flux component, and had a maximum melt viscosity of 40,000 Pa·s or less at 170°C or higher, so the overall evaluation was found to be ◯ (good) or △ (fair). In other words, it was found that the film-like solder connecting materials used in Examples 1 to 9 could suppress solder scattering, had good handleability, and also had good solder fluidity.

[0107] Furthermore, it was found that the film-shaped solder connecting materials used in Examples 1 to 9 were evaluated as OK (good) in overall evaluation. That is, it was found that the film-shaped solder connecting materials used in Examples 1 to 9 could suppress scattering of solder, had good handling properties, and also had good solder fluidity.

[0108] In examples other than Examples 5 to 7 and 9, the handling properties were improved. This is thought to be due in part to the fact that the liquid epoxy resin in the film-shaped solder connecting material contains a monofunctional epoxy resin and a bifunctional liquid epoxy resin, the content of the bifunctional liquid epoxy resin being 3% by mass or more and less than 45% by mass of the total resin content, and the content of the monofunctional epoxy resin being less than 45% by mass of the total resin content.

[0109] Furthermore, in examples other than Examples 1 and 2, the scattering of solder was more effectively suppressed. This is thought to be due in part to the fact that the film-type solder connecting materials used in Examples 3 to 9 have a lower maximum melt viscosity at 170°C or higher than the film-type solder connecting materials used in Examples 1 and 2.

[0110] In Examples 1 to 9, the shear strength of the cured product of the binder component, excluding the solder particles from the solder connection material consisting of the film-forming component, liquid epoxy resin, thermosetting agent, flux component, and solder particles, was found to be 4.14 to 5.55 MPa (approximately 4 to 6 MPa).From these results, it was found that the film-like solder connection materials used in Examples 1 to 9 can, for example, improve repairability because the shear strength of the cured product of the binder component is not too high.

[0111] It was found that the overall evaluation of the film-shaped solder connecting materials used in Comparative Examples 1 to 5 was NG. For example, it was found that the film-shaped solder connecting materials used in Comparative Examples 1 to 5 had difficulty in suppressing scattering of solder or did not have good handleability.

[0112] Specifically, it was found that the film-like solder connecting material used in Comparative Example 1 did not have good handleability. One of the reasons for this is thought to be that the arithmetic mean of the weight-average molecular weight of the film-forming resin was less than 10,000.

[0113] It was found that it was difficult to suppress scattering of solder with the film-like solder connecting materials used in Comparative Examples 2 to 4. One reason for this is thought to be that the film-like solder connecting materials used in Comparative Examples 2 to 4 did not satisfy the maximum melt viscosity of 40,000 Pa s or less at 170°C or higher.

[0114] The film-like solder connecting material used in Comparative Example 5 could not be evaluated for solder splashing because the solder flow result was △ (fair). One reason for this is thought to be that the Mw (arithmetic mean of weight-average molecular weight) of the film-forming resin in the film-like solder connecting material of Comparative Example 5 exceeded 20,000.

[0115] Fig. 4 is an example of an X-ray photograph taken from a planar direction of evaluation sample B obtained in comparative examples 2 to 4. Fig. 5 is an example of an X-ray photograph taken from a planar direction of evaluation sample B obtained in examples 1 to 9. In Fig. 4, region 50 indicates a region in evaluation sample B where solder is scattered into space 53 of the LGA mock board. Also, in Fig. 4, region 51 indicates a pad 52 among multiple pads 52 where solder is insufficient.

[0116] In Examples 1 to 9, the number of solders present in the space 53 was 0, as shown in Fig. 5, and the evaluation of solder scattering was found to be good. In contrast, in Comparative Examples 2 to 4, the number of solders 54 present in the space 53 was 4 or more, as shown in Fig. 4, and the evaluation of solder scattering was found to be poor.

[0117] 6 is a graph showing an example of the melt viscosity curve of a film-like solder connecting material, where A1 is a graph showing an example of the melt viscosity curve of a film-like solder connecting material of an example, and B1 is a graph showing an example of the melt viscosity curve of a film-like solder connecting material of a comparative example. It was found that the film-like solder connecting materials used in Examples 1 to 9 had a maximum melt viscosity of 40,000 Pa·s or less at 170°C or higher, as shown in graph A1 in FIG. 6. On the other hand, it was found that the film-like solder connecting materials used in Comparative Examples 2 to 4 had a maximum melt viscosity of more than 40,000 Pa·s at 170°C or higher, as shown in graph B1 in FIG. 6.

[0118] 7 is a graph showing an example of the storage elastic modulus curve of a film-like solder connecting material, where A2 is a graph showing an example of the storage elastic modulus curve of a film-like solder connecting material of an example, and B2 is a graph showing an example of the storage elastic modulus curve of a film-like solder connecting material of a comparative example. It was found that the film-like solder connecting materials used in Examples 1 to 9 had a storage elastic modulus of 3 MPa or less at 170°C, as shown in graph A2 in FIG. 7. On the other hand, it was found that the film-like solder connecting materials used in Comparative Examples 2 to 4 had a storage elastic modulus of more than 3 MPa at 170°C, as shown in graph B2 in FIG. [Explanation of symbols]

[0119] 10 wiring board, 11 terminal row, 20 solder particles, 21 solder joint materials, 30 surface mount components, 31 terminal row, 40 Cured product of thermosetting binder, 41 Solder, 50 Areas with solder scattering into space, 51 Pads with insufficient solder, 52 pads, 53 spaces, 54 Solder

Claims

1. a film-forming resin; A liquid epoxy resin; A heat curing agent; Solder particles and and a flux component, A solder connection material having a maximum melt viscosity of 40,000 Pa·s or less at 170°C or higher.

2. 2. The solder connecting material according to claim 1, wherein the film-forming resin has an arithmetic mean weight-average molecular weight of 10,000 to 20,000.

3. 3. The solder connection material according to claim 2, wherein a cured product of the solder connection material, excluding the solder particles, has a shear strength of 4 to 6 MPa.

4. 3. The solder connecting material according to claim 2, wherein the film-forming resin is a mixture of a phenoxy resin and an epoxy resin.

5. The liquid epoxy resin contains a monofunctional epoxy resin, 3. The solder connecting material according to claim 1, wherein the content of the monofunctional epoxy resin is more than 10 mass % and less than 47 mass % of the total resin content.

6. The liquid epoxy resin further contains a bifunctional liquid epoxy resin, the content of the bifunctional liquid epoxy resin is 3% by mass or more and less than 45% by mass of the total resin content, 6. The solder connecting material according to claim 5, wherein the content of the monofunctional epoxy resin is less than 45 mass % of the total resin content.

7. 7. The solder connecting material according to claim 6, wherein the bifunctional liquid epoxy resin is a bisphenol F type epoxy resin or a hydrogenated bisphenol A type epoxy resin.

8. 2. The solder connecting material according to claim 1, wherein the thermal curing agent is an imidazole-based thermal curing agent.

9. 2. The solder connecting material according to claim 1, which has a storage modulus at 170°C of 3 MPa or less.

10. the liquid epoxy resin contains a monofunctional epoxy resin and a bifunctional liquid epoxy resin, 2. The solder connecting material according to claim 1, wherein the mass ratio of the monofunctional epoxy resin to the difunctional liquid epoxy resin (difunctional liquid epoxy resin / monofunctional epoxy resin) is 0.07 or more and less than 0.

63.

11. The solder connecting material according to claim 1 or 2, which is in the form of a film.

12. A method for manufacturing a connection structure, comprising joining a surface-mounted component to a wiring board via the solder connection material according to claim 1.

13. The method for manufacturing a connection structure according to claim 12, wherein the surface-mounted component is bonded to the wiring board without applying any weight using a reflow furnace.

14. The method for manufacturing a connection structure according to claim 12 or 13, wherein the surface-mounted component is a land grid array type semiconductor chip.

15. A connection structure in which a surface-mounted component is joined to a wiring board via the solder connection material according to claim 1 or 2.

Images