CNF-dispersed resin composition-blended solder and method for manufacturing CNF-dispersed resin composition-blended solder

Abstract

To provide a CNF dispersion composition which can be uniformly dispersed in a resin without aggregation of CNF even if the CNF contains moisture, and a method for manufacturing the same.SOLUTION: A method for manufacturing a CNF dispersion composition performs a step of making a mixture composed of component (1): water, component (2): cellulose nanofiber and component (3): an organic solvent being azeotropic, removing the component (1) and the component (3), and obtaining a CNF dispersion composition, wherein an organic solvent weight ratio Or in the mixture is 56.8% or more.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a CNF dispersion composition and a method for producing the same. [Background technology]

[0002] Conventionally, resin composite materials using cellulose nanofibers (hereinafter sometimes referred to as CNF) or modified cellulose nanofibers as a resin reinforcing material have been known.

[0003] In this CNF / resin composite, it is important to uniformly disperse CNF in the resin in order to enable the CNF to function as a reinforcing material. However, CNF dispersed in water aggregates through hydrogen bonding to form strong aggregates when the water is removed, making it difficult to mix CNF uniformly into the resin in a nano-level dispersion state. Therefore, Patent Document 1 discloses a two-stage replacement method in which a hydrophilic organic solvent such as acetone is added to a CNF dispersion, followed by suction filtration to remove the water content and the hydrophilic organic solvent in the CNF dispersion, followed by adding a hydrophobic organic solvent to disperse the CNF, and then suction filtration to replace the organic solvent with a hydrophobic organic solvent. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-183153 [Non-patent literature]

[0005] [Non-Patent Document 1] "Fast Analysis of the Amount of Ingredients in Alcohol-Based Disinfectants Using FTIR," [online], [Retrieved September 14, 2021], Internet<URL:https: / / www.an.shimadzu.co.jp / aplnotes / ftir / an_a630.pdf> [Non-patent document 2] X-ray and electron microscope studies of the degradation of cellulose by sulphuric acid Mukherjee, SM; Woods, HJ: Biochim. Biophys. Acta, 10, 499501(1953) [Non-patent document 3] Characterization of Amphiphilic Janus-Type Surface in Cellulose Nanofibril Prepared by Aqueous Counter-CollisionTsubasa Tsuji, Kunio Tsuboi, Shingo Yokota, Satomi Tagawa, and Tetsuo KondoBiomacromolecules 2021, 22, 2, 620-628 Summary of the Invention [Problem to be solved by the invention]

[0006] However, in the method described in Patent Document 1, a thin film of CNF is formed on the filter cloth from the early stages of suction filtration, which blocks the passage of the solvent to be removed, requiring a long filtration time to obtain a CNF mat from which the solvent has been removed. Furthermore, a difference in moisture content occurs between the surface and the interior of the CNF mat, and the solids concentration tends to be higher on the surface side, which promotes aggregation due to hydrogen bonding, making it difficult to uniformly mix the CNF aqueous dispersion with the solvent.

[0007] Therefore, in consideration of the above circumstances, the present invention aims to provide a CNF dispersion composition that can uniformly disperse even water-containing CNFs in a resin without the CNFs agglomerating together, and a method for producing the same.

[0008] Furthermore, when adding other solvents to a CNF aqueous dispersion to form a mixture and calculating the weight ratio of the other solvents in the mixture to the water in the CNF dispersion, there was a question about measuring the amount of water in the CNF aqueous dispersion and calculating the weight ratio of the other solvents in the mixture from that amount of water and the weight of the other solvents.

[0009] Therefore, in consideration of the above circumstances, another object of the present invention is to provide a method for measuring the weight ratio of other solvents in a mixture when other solvents are added to a CNF aqueous dispersion. [Means for solving the problem]

[0010] In view of the above-mentioned problems, the present inventors have conducted extensive research and have found that a CNF dispersion composition obtained by adding a specific proportion of isopropyl alcohol to a CNF dispersion and azeotroping it can be uniformly dispersed in a resin without the CNFs agglomerating together.

[0011] Furthermore, in light of the above-mentioned problems, the inventors have conducted extensive research and have noticed that CNF is a fiber with extremely high water retention capacity, and therefore adsorbs a certain amount of moisture as fixed water, with only moisture above that amount remaining as free water, functioning as a solvent to ensure fluidity. This led to the discovery of a method for measuring the weight ratio of other solvents in a mixture. [Effects of the Invention]

[0012] According to the present invention, a CNF dispersion composition and a method for producing the same are provided, which can uniformly disperse even water-containing CNFs in a resin without the CNFs agglomerating together.

[0013] According to the present invention, a method is provided for measuring the weight ratio of another solvent in a mixture when another solvent is added to a CNF aqueous dispersion. [Brief explanation of the drawings]

[0014] [Figure 1] This is a vapor-liquid equilibrium curve for a mixed liquid of IPA and water. [Figure 2] 1 is a photograph showing the state in which CNF is uniformly dispersed in epoxy resin in Example 4. [Figure 3] 1 is a photograph showing a paste product containing 18% CNF in Example 13. [Figure 4] This is a photograph showing nylon resin in which 5% CNF is uniformly dispersed. [Figure 5] This is a photograph showing the CNF-dispersed rosin resin being spread on an iron plate in Example 15. [Figure 6] This is a photograph showing the process of cooling the CNF-dispersed rosin resin while continuing to stir after it reached approximately 150°C in Example 15. [Figure 7] FIG. 1 shows the results of differential scanning calorimetry. [Figure 8] This figure shows the state of diluted slurries with CNF contents of 1% (a), 2% (b), and 5% (c) after being left for 11 days. [Figure 9] 9 is an enlarged photograph of a part of FIG. 8. [Figure 10] This is a photograph of a board on which general-purpose small chip resistors are mounted. [Figure 11] FIG. 10 is a diagram showing the results of resistance value transition for a substrate on which a general-purpose small chip resistor is mounted. [Figure 12] FIG. 1 shows the bond after 800 cycles. [Figure 13] FIG. 10 is a diagram showing the transition of share strength. [Figure 14] FIG. 10 is a diagram showing the solder thickness below the ceramic capacitor component. [Figure 15] FIG. 1 shows FE-SEM images obtained by comparatively observing the states before and after a heat cycle test. [Figure 16] This is a schematic diagram of the effect of general Ag3Sn. [Figure 17] FIG. 10 is a diagram showing the results of elemental analysis using EDS to confirm the metal composition inside the solder. [Figure 18] FIG. 10 is a diagram showing the results of X-ray measurement performed using an X-ray diffraction device to confirm the orientation state of the composition inside the solder. [Figure 19]10 is a photograph showing a mounting board for productivity evaluation. [Figure 20] This is a diagram showing a calibration curve created from pure water and IPA. [Figure 21] A calibration curve was created from the CNF slurry and IPA and is shown in Figure 16. DETAILED DESCRIPTION OF THE INVENTION

[0015] Next, embodiments of the present invention will be described in detail. However, the following embodiments are provided to aid in understanding the invention and are not intended to limit the present invention.

[0016] (Definition of terms) Here, the main terms used in the present invention will be defined. The term "CNF" as used herein includes both CNF and CNC and refers to cellulose fibers with an average thickness of 3 to 200 nm and an average length of 300 nm or more, including so-called single cellulose nanofibers with an average width of 3 to 4 nm, single cellulose nanofiber aggregates with an average width of 10 to 200 nm, which are formed by the aggregation of several single cellulose nanofibers into multiple layers, and cellulose nanocrystals (CNCs) from which the non-crystalline portion has been removed with sulfuric acid, etc. Furthermore, not only cellulose fibers that are unbranched in the longitudinal direction exist, but also those that are branched. The term "CNF dispersion composition" as used herein refers to a composition obtained by azeotroping a mixture of component (1) water, component (2) cellulose nanofibers, and component (3) organic solvent. In a broad sense, a CNF dispersion composition may also include a composition containing components (1), (2), and (3) that has not yet been azeotroped and has an organic solvent weight ratio Or (described below) of 56.8% or more, and a composition in which component (1) has evaporated to form components (2) and (3). The term "CNF-dispersed resin composition" as used herein refers to a composition obtained by azeotroping a mixture of component (1) water, component (2) cellulose nanofibers, component (3) organic solvent, and component (4) resin. The CNF-dispersed resin composition also includes a composition obtained by adding component (4) to the above-mentioned "CNF-dispersed composition" and a composition obtained by adding component (4) to component (2) after all the solvent has been removed. In this specification, the term "CNF-adhered water" refers to water that is strongly adsorbed to CNF due to the hydrogen bonding force or intermolecular forces of CNF. This is derived and defined by the following ideas. Even if a system consists of CNF and water, if it consists only of CNF and CNF-fixed water, the substance has no fluidity and behaves like a solid. Therefore, when a solvent is added to a CNF dispersion, CNF-fixed water exists between the solvent and the CNF. Therefore, when calculating the CNF solids concentration of a CNF dispersion after solvent addition, excluding the CNF-fixed water will be closer to the behavior of the actual CNF dispersion.

[0017] (Method for calculating the weight ratio Sr of the solvent in the mixture) In the present invention, the weight ratio Sr of the solvent in the mixture of the CNF dispersion and the solvent (excluding water) is calculated by the following calculation method. First, the solid content of CNF in the CNF dispersion, C n and the volume of water as solvent, V a Calculate. Next, CNF fixed water H C is calculated using the following formula (1). H C =C n × (100 - a) / a (1) (In equation (1), a is the CNF solids concentration at the point when some of the CNFs in the CNF aqueous dispersion begin to aggregate, and is the CNF solids concentration in the CNF-fixed water.) Next, the actual amount of water solvent in the CNF dispersion, V b is calculated using the following formula (2). V b =V a -H C ···(2) Finally, the weight of the solvent, V s and the actual water solvent volume V b Therefore, the weight ratio of the solvent S is calculated by the following formula (3): r Calculate. S r =V s / (V s +V b ) ···(3)

[0018] First, the CNF dispersion that can be used in the present invention will be described. For CNF dispersions, reference can be made to the method for producing fine fibers described in Japanese Patent No. 6867613, the cellulose nanofibers using cellulose as a natural polymer described in Japanese Patent No. 6704551, the preparation method described in Non-Patent Document 2, and the method for producing fine fibers derived from other raw materials described in each publication.

[0019] These raw materials for the CNF dispersion may be used alone or in combination of two or more. Furthermore, it is preferable to use pulp with an α-cellulose content of 60% to 99% by mass as the raw polysaccharide. A purity of 60% or more by mass of α-cellulose makes it easy to adjust the fiber diameter and length, and provides higher thermal stability and better color suppression than when an α-cellulose content of less than 60% by mass is used. On the other hand, when an α-cellulose content of 99% or more by mass is used, it becomes difficult to defibrate the fibers to the nano-level.

[0020] The crystallinity of CNF is preferably at least 50. The crystallinity can be measured by X-ray diffraction or the like, and if the crystallinity is less than 50, the properties of natural cellulose crystals cannot be fully utilized and there is a risk of deterioration over time during storage due to spoilage or the like.

[0021] The ACC method (underwater counter-impingement method) described in paragraph 0018 of Japanese Patent No. 6704551 allows for the production of CNFs with an average thickness of 3 to 200 nm and an average length of 0.1 μm or more. The average thickness and average fiber length are measured by observing and measuring the CNFs using an appropriate microscope, such as a scanning electron microscope (SEM) or a transmission electron microscope (TEM), selecting 20 or more fibers from the resulting photographs, and averaging the measurements. Alternatively, a fluorescence microscope observation method utilizing fluorescence amplification, as described in Non-Patent Document 3, may also be employed.

[0022] Next, solvents (excluding water) that can be used in the present invention will be described. In the present invention, any solvent other than water can be used, in other words, any substance that is in a liquid state can be used.

[0023] Next, we will explain how to calculate the amount of CNF Cn and the amount of water solvent Va in the CNF dispersion. The amount of CNF Cn and the amount of water solvent Va in the CNF dispersion can be measured and calculated using various known methods such as the dry weight method. Specifically, the weight of the CNF dispersion is measured, it is completely dried, and the residue is taken as CNF, and its weight is measured and designated as Cn. Next, the amount of water solvent, Va, is calculated by subtracting Cn from the weight of the CNF dispersion.

[0024] Next, CNF fixed water H C The method for calculating this using the following formula (1) will be explained. H C =C n × (100-a) / a (1) (In formula (1), a is the CNF solids concentration at the time when partial aggregation begins in the CNF system, and is the CNF solids concentration in the CNF-fixed water.) CNF Adherent Water H C is calculated using the above-mentioned a. CNF is a fiber with extremely strong water retention. This is supported by the following facts: Even when a CNF dispersion is dehydrated by applying very high pressure using a known hydraulic press or the like, it can only be dehydrated to a CNF solids concentration of approximately 30% at most. Furthermore, when a CNF dispersion is dehydrated using a general pneumatic press or the like, the CNF solids concentration generally reaches approximately 15%. On the other hand, if the CNF solids concentration exceeds approximately 18%, hydrogen bonding between the CNFs in the CNF dispersion begins, preventing them from existing as uniform CNFs. Therefore, it can be assumed that 15-19% exists as water adhering to the CNFs. This amount of water is referred to as the solids concentration in the CNF-adhered water, a. Therefore, it can be said that only water content above these values ​​functions as a solvent to ensure the fluidity of the CNF dispersion as free water in the CNF aqueous dispersion.

[0025] Using the solids concentration a in the CNF-fixed water derived based on this idea, the amount of water when CNF is taken as 100 can be calculated as 100 × (100 - a) / a. Here, if the CNF solids content is taken as Cn, then formula (1) can be derived.

[0026] Next, the actual amount of water solvent in the CNF dispersion, V b The method for calculating this using the following formula (2) will be explained. V b =V a -H C ···(2) From the water solvent volume Va of the CNF dispersion mentioned above, the CNF fixed water H C By subtracting the value of b Here, the actual volume of water solvent V b This means that it is possible to evaluate the amount of free water that contributes to the fluidity of each CNF dispersion according to the CNF content in each CNF aqueous dispersion.

[0027] Finally, the weight of the solvent Vs and the actual amount of water solvent V bTherefore, a method for calculating the weight ratio Sr of the entrained solvent using the following formula (3) will be described. S r =V s / (V s +V b ) ···(3) Weight of added solvent V s is the actual amount of water solvent in the CNF dispersion V b and the weight of the added solvent V s It is obtained by dividing by the sum of and.

[0028] The above method makes it possible to calculate the weight ratio of other solvents in the mixture when other solvents are added to a CNF aqueous dispersion. In addition, by taking into account the molecular weight using a similar method, it is also possible to calculate the molar ratio of other solvents in the mixture when other solvents are added to a CNF aqueous dispersion.

[0029] (Method of producing CNF dispersion composition) The method for producing a CNF dispersion composition according to the present invention is to remove the component (1) and the component (3) by carrying out an azeotropic distillation process while heating, mixing, and stirring a mixture of component (1): water, component (2): cellulose nanofibers, and component (3): an organic solvent, The weight ratio of the organic solvent in the mixture of component (3) is calculated by the method for calculating the weight ratio of the solvent (excluding water) in the mixture, and the weight ratio Or of the organic solvent in the mixture is 57% or more. In the method for calculating the weight ratio Sr of the solvent in the mixture, the weight ratio Or of the organic solvent when the solvent is the organic solvent is used.

[0030] In the present invention, components (1), (2), and (3) may be simultaneously added to form a mixture, followed by a step of azeotroping while heating, mixing, and stirring, to remove a portion of components (1) and (3) so that the organic solvent weight ratio Or is 57% or more. Alternatively, component (3) may be added while components (1) and (2) are heated, mixed, and stirred, followed by a step of azeotroping while heating, mixing, and stirring. Furthermore, a step of adding component (3) multiple times may be performed.

[0031] Examples of the means for heating, mixing and stirring include a method using a known heating device such as a mantle heater and a known stirring device such as a mixer.

[0032] (Component (1), Component (2)) In the present invention, components (1) and (2) can be used as components (1) and (2) by using the aforementioned CNF aqueous dispersion. Components (1) and (2) can also be used as components (1) and (2) by separately or simultaneously adding components (1) and (2) to the CNF aqueous dispersion.

[0033] The amount of component (2) used in the present invention, i.e., the CNF concentration in the CNF aqueous dispersion, is not particularly limited, but is preferably 1 to 18% by mass, more preferably 5 to 15% by mass. If it is less than 1% by mass, an excessive amount of component (3) will be required, increasing the burden of solvent recovery and increasing costs. If it is more than 18% by mass, some aggregation will occur, which may make it impossible to disperse without the application of strong energy, resulting in reduced uniformity and increased costs.

[0034] (Component (3)) Component (3) in the present invention is an organic solvent that forms an azeotrope with water. Component (3) is used to remove or reduce component (1) from the CNF dispersion by azeotroping with component (1). Component (3) may be used singly or in combination of two or more.

[0035] Specific examples of component (3) include alcohols, such as glycerol, methanol, ethanol, 2-propanol, n-propanol, butanol, isobutyl alcohol, secondary butyl alcohol, tert-butyl alcohol, 1,3-butanediol, and hexyl diglycol. Among these, ethanol, 2-propanol, and n-propanol are preferred, and 2-propanol is more preferred. The use of 2-propanol can lower the azeotropic temperature with component (1). Furthermore, the change in the gas phase ratio when the liquid phase ratio is changed is small, allowing the amount of solvent relative to water to be reduced, and component (1) can be easily and stably removed.

[0036] Other usable solvents include toluene, xylene, hexane, cyclohexane, octane, chlorobenzene, dioxane, tetrahydrofuran, anisole, and phenetole.

[0037] A CNF-dispersed resin composition can be obtained by adding a polymer resin that exists as a liquid under heating temperature conditions to the CNF-dispersed composition obtained as described above and stirring and mixing. From another perspective, the method for producing the CNF dispersion composition of the present invention can also be evaluated as a method for converting an aqueous CNF dispersion into an organic solvent.

[0038] (Method of producing CNF-dispersed resin composition) The method for producing a CNF-dispersed resin composition according to the present invention can be obtained in the same manner as in the method for producing a CNF-dispersed composition described above, except that component (4) resin is added. That is, a mixture of component (1): water, component (2): cellulose nanofibers, component (3): organic solvent, and component (4): resin is heated, mixed, and stirred while undergoing azeotropy, thereby removing component (1) and component (3), The weight ratio of the organic solvent in the mixture of component (3) is calculated by the method for calculating the weight ratio of the solvent (excluding water) in the mixture, and the weight ratio Or of the organic solvent in the mixture is 56.8% or more. In the method for calculating the weight ratio Sr of the solvent in the mixture, the weight ratio Or of the organic solvent when the solvent is the organic solvent is used.

[0039] In the present invention, components (1), (2), (3), and (4) may be added simultaneously to form a mixture, followed by a step of azeotroping while heating, mixing, and stirring. Alternatively, component (3) may be added while heating, mixing, and stirring components (1) and (2), followed by a step of azeotroping while heating, mixing, and stirring, followed by adding component (4). Furthermore, a step of adding component (3) multiple times may be performed.

[0040] In this case, the timing for adding component (4) must be such that component (3) remains in the system. If component (3) is not present, component (2) will begin to aggregate and will not be able to disperse. It is recommended to add component (4) when the concentration of component (2) relative to the total of components (1) and (3) is 1% to 18%, more preferably 2% to 15%, and even more preferably 5% to 10%. If the timing is less than 1%, the viscosity of the system will increase due to the viscosity of the resin being added, requiring strong stirring force, which may result in poor dispersion. Furthermore, the volume of the stirring vessel will be larger than necessary, resulting in excessive equipment and operating costs. If component (2) is added when the concentration is 18% or more, aggregation of component (2) will begin, which is likely to result in poor uniformity.

[0041] (Component (4)) The fluid resin (component (4)) used in the present invention can be any material that exhibits fluidity when mixed. If it is soluble in a solvent, it can be used as is. If it softens when heated, it can be used while heating the system. For example, thermosetting resins include phenolic resin, epoxy resin, melamine resin, urea resin, unsaturated polyester resin, alkyd resin, silicone resin, polyurethane resin, thermosetting polyimide resin, etc., and thermoplastic resins include nylon resin, polypropylene resin, polyethylene resin, polyvinyl chloride, polyvinylidene chloride, polystyrene, polyvinyl acetate, polyurethane, polytetrafluoroethylene, ABS resin, AS resin, acrylic resin, etc. In the case of thermoplastic resins, the resin can be softened and dispersed uniformly by dispersing it in a high-boiling point solvent such as glycerin. Furthermore, component (4) is not limited to resins; solvents with boiling points higher than the manufacturing temperature can also be used. Examples include hydrocarbons with 8 or more carbon atoms, such as terpineol and octane, alcohols with 4 or more carbon atoms, such as propylene glycol and pentanol, dihydric or higher alcohols, such as ethylene glycol and glycerin, phenol, xylene, pyridine, isopentyl acetate, glycol ethers with 3 or more carbon atoms, such as 2-methoxyethanol, 2,6-lutidine, formamide, 2-butoxyethanol acetate, dimethyl sulfoxide, N,N-dimethylformamide, butyl carbitol acetate, and cresol.

[0042] The amount of component (4) used in the present invention is not particularly limited, but the CNF solids content in the CNF-dispersed resin composition is preferably 1 to 20 mass %, more preferably 2 to 15 mass %. If it is less than 1 mass %, the final required amount of CNF cannot be supplied. If it is more than 20 mass %, the viscosity becomes too high, making it difficult to handle.

[0043] CNF-dispersed resin compositions can be used in solder (solder paste). powderThe following effects were confirmed when a CNF-dispersed resin composition was added to a solder paste made of 89% resin and rosin-based resin and epoxy-based resin: prevention of high-temperature sagging, improved wettability, improved cohesion, reduction of voids (defects) inside the solder, improved strength due to the refinement of the internal structure of the solder metal, homogenization of the solder alloy due to improved copper dispersion, and energy savings due to a reduction in the amount of heat absorbed during melting. These results can help reduce quality control and production management costs, as well as improve joint reliability.

[0044] (Method for quantifying organic solvent in CNF dispersion composition and CNF dispersion resin composition) When ethanol or isopropyl alcohol is used as the organic solvent, these values ​​in the CNF dispersion composition and CNF dispersion resin composition can be calculated using the method shown in Non-Patent Document 1 using a Fourier transform infrared spectrophotometer (FT-IR) according to the following procedure. 1. Using a standard sample, create a calibration curve in the concentration range of 0 to 100%. 2. The CNF dispersion composition and the CNF dispersion resin composition are filtered to separate the CNF and water adhering to the CNF. 3. The obtained filtrate is measured using FT-IR. [Example]

[0045] The present invention will be described below based on examples, but the present invention is not limited to these examples.

[0046] (Examples 1 to 3, Comparative Example 1) A 1% aqueous CNF dispersion (nanoforest-S BB-C, manufactured by Chuetsu Pulp Industry Co., Ltd.) and isopropyl alcohol (2-propanol, manufactured by Kishida Chemical Co., Ltd.) were prepared in the amounts shown in Table 1 below. Next, while heating and stirring the CNF aqueous dispersion, isopropyl alcohol was added in several batches, and the mixture was heated and stirred to obtain a CNF dispersion composition. Next, an epoxy resin (Rikaresin, New Japan Chemical Co., Ltd.) was added in an amount such that the CNF solids concentration in the epoxy resin became 4%, and a CNF dispersion resin composition was obtained. The end point was the point at which steam could no longer be visually confirmed. The obtained CNF-dispersed resin composition was visually evaluated using the following evaluation criteria. The results are shown in Table 1. The viscosity was evaluated by rheometer measurement. ◎: No agglomerates and high viscosity is achieved. ◯: No agglomerates and viscosity is imparted. △: Viscosity was imparted, but some aggregates were observed. ×: Most of the CNFs are aggregated.

[0047] [Table 1]

[0048] (Examples 4 to 5, Comparative Examples 2 and 3) A 5% aqueous CNF dispersion (nanoforest-S BB-C manufactured by Chuetsu Pulp Industry Co., Ltd.) and isopropyl alcohol (2-propanol manufactured by Kishida Chemical Co., Ltd.) were prepared in the amounts shown in Table 2 below. Next, the amounts listed in Table 2 and an amount that would result in a 3% CNF solids concentration in epoxy resin (Rikaresin, New Japan Chemical Co., Ltd.) were all added to a 1-L beaker, and azeotropic distillation was performed while heating and stirring to obtain a CNF-dispersed resin composition. The end point was when steam could no longer be visually observed and the temperature reached 150°C. The obtained CNF-dispersed resin composition was visually evaluated using the above-mentioned evaluation criteria. The results are shown in Table 2. Figure 2 is a photograph showing the state of CNF uniformly dispersed in the epoxy resin in Example 4.

[0049] [Table 2]

[0050] Examples 6 to 9 A 10% aqueous CNF dispersion (nanoforest-S BB-C, manufactured by Chuetsu Pulp Industry Co., Ltd.) and isopropyl alcohol (2-propanol, manufactured by Kishida Chemical Co., Ltd.) were prepared in the amounts shown in Table 3 below. Next, the amounts listed in Table 3 and amounts that would result in CNF solids concentrations of 5% and 4% in epoxy resin (Rikaresin, New Japan Chemical Co., Ltd.) were all placed in a 300 ml beaker, and azeotroped while heating and stirring to obtain CNF-dispersed resin compositions. The end point was the point at which steam could no longer be visually confirmed. The viscosity of Example 6 was too high to measure with a rheometer, so the other epoxy resins contained 4% CNF. The obtained CNF-dispersed resin composition was evaluated visually and by rheometer measurement using the above-mentioned evaluation criteria. The results are shown in Table 3 below.

[0051] [Table 3]

[0052] It is clear from Tables 1 to 3 that a good CNF-dispersed resin composition can be obtained by setting the weight ratio Or of IPA to 56.8% or more. From this, it became clear that a good CNF-dispersed resin composition can be obtained by mixing components (1), (2), and (3) so that the organic solvent weight ratio Or is 56.8% or more to form a CNF-dispersed composition, and then adding a resin to this and azeotroping it while heating, mixing, and stirring. It was also revealed that a good CNF-dispersed resin composition can be obtained by adjusting components (1), (2), and (3) so that the organic solvent weight ratio Or is 56.8% or more, adding component (3) multiple times to a CNF aqueous dispersion containing only components (1) and (2), and then adding component (4) at any timing. In other words, it has become clear that it is possible to obtain a CNF dispersion composition in which even CNFs containing moisture can be uniformly dispersed in a resin without the CNFs agglomerating, and a CNF dispersion resin composition in which CNFs are uniformly dispersed in a resin.

[0053] Examples 10 to 12 Examples 10 to 12 are examples relating to the behavior of components (1) and (3) of a CNF dispersion composition when the value of the organic solvent weight ratio Or is changed, while taking into account the fact that a good CNF dispersion resin composition can be obtained when a CNF dispersion composition having an organic solvent weight ratio Or of 56.8% or more is used, as was made clear in Examples 1 to 9 and Comparative Examples 1 to 3.

[0054] Figure 1 shows a vapor-liquid equilibrium curve in which the horizontal axis represents the liquid phase composition of IPA in a liquid mixture of IPA and water, and the vertical axis represents the vapor phase composition of IPA in the vapor mixture of IPA and water vapor produced when the liquid mixture is evaporated. Equation (4) was obtained by plotting the values ​​of the IPA gas phase composition corresponding to the IPA liquid phase composition of 0.05 to 0.9 on a graph from Figure 1. The values ​​read are shown in Table 4.

[0055] y = 0.6543x 3 - 0.5245x 2 + 0.4005x + 0.4462 (4)

[0056] [Table 4]

[0057] CNF aqueous dispersion (nanoforest-S BB-C manufactured by Chuetsu Pulp Industry Co., Ltd.) and isopropyl alcohol (2-propanol manufactured by Kishida Chemical Co., Ltd.) were prepared in the amounts listed in Table 5 below.

[0058] Next, the remaining amount of IPA when the water was assumed to have evaporated was calculated using Figure 1 and formula (4), and the CNF concentration in the CNF dispersion composition was calculated using the following method. Table 5 shows the CNF concentration in the CNF dispersion composition, and Tables 6 to 8 show the calculation results for Examples 10 to 12. 1. The liquid molar ratio of IPA in the CNF dispersion composition is substituted into equation (4) to calculate the gas phase ratio of IPA. 2. Calculate the water vapor ratio from the IPA vapor ratio. 3. Calculate the weight ratio from these values ​​and the molecular weights of water and IPA. 4. Calculate the weight ratio from these values. 5. Calculate the amount of IPA that has evaporated when all the water has evaporated. 6. If IPA remains, divide the CNF solid content Cn by the sum of Cn and the remaining amount of IPA to determine the CNF concentration in the CNF dispersion composition.

[0059] [Table 5]

[0060] [Table 6]

[0061] [Table 7]

[0062] [Table 8]

[0063] Next, the amounts described in Examples 10 to 12 were placed in a beaker, and an epoxy resin (Rikaresin, New Japan Chemical Co., Ltd.) was added in an amount that resulted in a CNF concentration of 4%, and azeotropy was performed while heating and mixing and stirring to obtain a CNF-dispersed resin composition. The obtained CNF-dispersed resin composition was in a high-viscosity paste state with the CNFs uniformly dispersed. Furthermore, the amounts described in Examples 10 to 12 were placed in a beaker and azeotropically distilled while being heated, mixed and stirred to obtain a CNF dispersion composition with a CNF concentration of about 10%. Next, a portion of each of the CNF dispersion compositions (Examples 11 and 12) was filtered, and the resulting filtrate and a 100% IPA standard were measured using FT-IR. The vibration absorption spectra at 1131 cm-1 were compared, revealing similar intensities. This result revealed that the resulting CNF dispersion composition did not contain water. This demonstrates that a CNF dispersion composition consisting of CNF and IPA was obtained. Next, a portion of the CNF dispersion composition (Example 10) was filtered, and the filtrate was subjected to FT-IR analysis in the same manner, confirming that the peak intensity had decreased. It was also revealed that CNF dispersion compositions with an organic solvent weight ratio Or of 56.8% or more were CNF dispersion compositions containing water, CNF, and IPA.

[0064] Example 13 In a 1-L beaker, 300 g of a 10% aqueous CNF dispersion (nanoforest-S BB-C, manufactured by Chuetsu Pulp Industries Co., Ltd.) and 400 g of isopropyl alcohol (2-propanol, manufactured by Kishida Chemical Co., Ltd.) were added and mixed in three separate portions. After the first addition, azeotropy was initiated by heating with a lower heater while stirring with a glass rod, and when about half of the solvent had evaporated, the second addition of isopropanol was added. Furthermore, a paste containing 18% CNF was prepared by dispersing it in isopropanol and glycerin with the addition of food grade glycerin. The calculated weight values, assuming that all of the water solvent except for the adhering water had evaporated, are shown in Table 9. A photograph of the paste containing 18% CNF is shown in Figure 2.

[0065] [Table 9]

[0066] Next, 5.2 g of the paste containing 18% CNF was mixed with 61 g of food grade glycerin, stirred, and heated to 200°C. Next, 17 g of nylon resin PA-66 (POTICON Otsuka Chemical Co., Ltd.) was added to dissolve the entire nylon resin. At this point, the viscosity was estimated to be in the range of 100-1,000 cp based on manual mixing. After dissolving, the mixture was heated to 300°C to evaporate the food-grade glycerin, then poured onto a steel plate and cooled, yielding a nylon resin with 5% CNF uniformly dispersed therein, as shown in Figure 3.

[0067] Comparative Example 4 Using the paste containing 18% CNF used in Example 11, dispersion in the same nylon resin was examined. First, 54g of nylon resin was evenly spread across the bottom of a beaker and heated to 400°C. By pressing down on the pellets with a medicine spoon, heat was transferred to the nylon at the bottom of the beaker, gradually softening it. Approximately 80% of the nylon softened, but it was still fluid. The above-mentioned CNF paste was then added. The moment it was added, some of it began to burn on contact with the bottom of the beaker, emitting white smoke. The fluidity of the nylon also decreased further, making it impossible to mix. An additional 20g of glycerin was then added. As the nylon dissolved, the transparent glycerin turned black, but only a portion of the nylon immersed in the glycerin dissolved. It was found that a sufficient amount of glycerin was needed to completely dissolve the nylon resin, and that uniform heat transfer and dissolution were important.

[0068] Example 14 Using the paste containing 18% CNF used in Example 11, dispersion in the same nylon resin was examined using a different method. First, 44.5 g of nylon resin was placed in a simple kneader (manufactured by Imoto Manufacturing Co., Ltd.) and softened at 270°C, after which 2.5 g of the above paste was added in four separate batches. After each addition, the mixture was kneaded for at least 5 minutes. After the final fourth addition, the kneaded resin was removed and hot-pressed into a sheet. The aggregates were evaluated by filtration, but no aggregates were visible. It was found that nylon can be used to obtain a CNF-dispersed resin composition using a kneading extruder or similar device without dissolving it in a solvent.

[0069] Example 15 A CNF slurry was obtained by adding and mixing 100 g of isopropyl alcohol (2-propanol, Kishida Chemical Co., Ltd.) to 40 g of an 11.14% CNF aqueous dispersion (nanoforest-S BB-C, manufactured by Chuetsu Pulp Industry Co., Ltd.). Next, 115 g of rosin resin (Hydrogenated Rosin Hyper Pale, Arakawa Chemical Industries, Ltd.) was added to 387 g of isopropanol and dissolved by stirring at room temperature to prepare a rosin solution in which the rosin was completely dissolved. The rosin solution was added to the CNF slurry, and the mixture was heated and stirred to azeotropically evaporate isopropanol and water. The rosin solution was added in four portions, 112 g, 110 g, 101 g, and 104 g of the remaining liquid, each time approximately 100 cc of the reaction solution evaporated by azeotropy. After the rosin solution was finally added, the liquid temperature rose as the solvent evaporated, and once the free water had finished evaporating at around 105°C, the boiling rate decreased. At 130°C, the solid water had completely evaporated and steam could no longer be detected. After the temperature reached around 150°C, the mixture was cooled with continued stirring, yielding a rosin resin with 3.7% CNF dispersed in it, with the CNF uniformly dispersed. The obtained CNF-dispersed rosin resin was in a viscous paste state at about 100°C, but was transferred to an iron plate and cooled to room temperature to become a solid rosin resin. Figure 5 shows a photograph of the resulting CNF-dispersed rosin resin being spread on an iron plate, and Figure 6 shows a photograph of the resin being cooled with continued stirring after reaching approximately 150°C.

[0070] Example 16 A CNF slurry was obtained by adding and mixing 103 g of isopropyl alcohol (2-propanol, Kishida Chemical Co., Ltd.) to 50 g of an 11.14% CNF aqueous dispersion (nanoforest-S BB-C, manufactured by Chuetsu Pulp Industry Co., Ltd.). Next, while stirring, 100 g of terpineol (product code RCI-YS-0130, serial number YSCHEM354-3, 100% concentration, manufactured by Yasuhara Chemical Co., Ltd.) was added. This slurry was heated and stirred while undergoing azeotropy, evaporating the isopropanol and water. As the solvent evaporated, the liquid temperature rose, and at approximately 135°C, the free and bound water had completely evaporated, and the mixture was heated and stirred until no more steam was visible. After that, the mixture was cooled while continuing to stir, yielding 92 g of 5% CNF-dispersed terpineol in which the CNFs were uniformly dispersed. During the heating and stirring process, an aroma was detected, which suggested that some terpineol had evaporated in addition to the azeotropic reaction between water and isopropanol. Terpineol was then added to dilute the slurry to prepare samples with a CNF content of 1% (a) and 2% (b). Figure 8 shows the state after 11 days, and a magnified photograph is shown in Figure 9. These figures confirm that the 5% CNF terpineol slurry (c) remained stable even after 11 days. On the other hand, some oil separation occurred in the 2% CNF slurry, while the 1% CNF slurry clearly separated oil and settled to the bottom. Using this technology, the CNFs were dispersed in the terpineol without agglomeration. However, the hydroxyl groups on the CNF surface are natural cellulose without chemical modification or other functional group introduction, and therefore cannot adsorb oil present in excess of the oil adsorption capacity. The excess terpineol, with a specific gravity of 0.934, floated to the surface.

[0071] Example 17 A CNF aqueous dispersion (nanoforest-S BB-C, manufactured by Chuetsu Pulp Industries Co., Ltd., 6.45%, 400 g) was placed in a planetary mixer (PLM-2, manufactured by Inoue Seisakusho Co., Ltd.) and stirred at 64 rpm (low speed). IPA (2-propanol, manufactured by Kishida Chemical Co., Ltd., 700 g) was gradually added in four portions (IPA molar ratio 35.9%, organic solvent weight ratio Sr = 75.4%). Next, 230 g of epoxy resin (Rikaresin, New Japan Chemical Co., Ltd.) was added, the temperature was set to 90°C, and heating began. When the actual temperature reached 70°C, pressure was reduced and the maximum temperature was 110°C and the pressure was 0.099 MPa to completely volatilize the water, yielding a CNF-dispersed resin composition containing 10% CNF.

[0072] (Examples 18 to 21) Next, the obtained CNF-dispersed resin compositions were added to the solder paste formulations shown in Table 10 so that the dry solid weights per 500 g of solder paste were 0.005 g, 0.01 g, 0.05 g, and 0.1 g (Table 11), and the mixtures were stirred for 2 minutes using a planetary centrifugal mixer (UM-102, manufactured by Japan Unix Corporation) at a revolution of 1000 rpm and a rotation of 250 rpm. Note that this process raised the temperature of the solder paste from 10°C to approximately 25°C.

[0073] [Table 10]

[0074] [Table 11]

[0075] (Thermal properties of solder paste) Using Examples 18 and 20 and Comparative Example 5, differential scanning calorimetry (DSC-60, Shimadzu Corporation) was performed in a nitrogen gas atmosphere (30 ml / min). The results are shown in Figure 7. The results in Figure 7 reveal that in the process of applying heat to the solder paste, the temperature at which it begins to melt increases and the total amount of heat absorbed is kept low. This is thought to be because heat is transmitted along the CNF fiber axis, increasing the heat transfer rate and resulting in a uniform temperature throughout the solder paste. In other words, in the case of Comparative Example 5, it is presumed that the temperature of the surface portion rises first, causing the surface to melt, with the interior melting later. Furthermore, the results of Comparative Example 5 revealed that in the process of cooling and solidifying the solder paste, in the absence of CNF, supercooling occurs and crystallization begins, with heat dissipation occurring at this time. This indicates that the addition of CNF suppresses supercooling and allows crystallization to proceed smoothly. This is thought to be because heat is transferred along the CNF fiber axis and released.

[0076] (Examples 22 to 25, Comparative Example 6) (Electronic packaging substrate manufacturing and reliability and productivity evaluation) (i) Fabrication of electronic mounting board Drawings of mounting boards for evaluating the productivity and reliability of the solder pastes obtained in Examples 18 to 21 and Comparative Example 5 were designed using CAD, and production specifications were prepared. Electronic component mounting boards were then fabricated, with those corresponding to Examples 18 to 21 being Examples 22 to 25 and Comparative Example 6. Next, reliability evaluation and productivity evaluation were carried out using the obtained electronic component mounting boards. (ii) Reliability evaluation The reliability evaluation was carried out by a heat cycle test of 1000 cycles using the following two types of substrates ((A) and (B)). (A) These differences were evaluated by measuring electrical resistance using a board mounted with a general-purpose small chip resistor (Figure 10 (lower)). (B) The second evaluation was performed by measuring the shear strength using a board mounted with a large ceramic capacitor (Figure 10 (top)).

[0077] (Results of reliability evaluation by electrical resistance measurement) Figure 11 shows the results of the resistance value transition for (A) above. As can be seen from Figure 11, no clear difference was confirmed in the electrical resistance measurement using a general-purpose small chip resistor. Furthermore, since there was not a single chip in which insulation breakdown occurred at the bonding surface due to cracking, it became clear that there was no significant deterioration of the solder joint.

[0078] (Results of reliability evaluation based on shear strength measurement) Figures 12 and 13 show the joint after 800 cycles and the change in shear strength over time for the above (B) test, respectively. Figure 12 shows that visually observable cracks appeared at the component joint of the board mounted with a large ceramic capacitor at 800 cycles. Figure 13 also shows that the shear strength declined more slowly in Examples 22 to 25, which contained CNF. This suggests that the presence of CNF improved the reliability evaluation. In particular, the CNF addition rates of 0.01% (Example 20) and 0.002% (Example 19) showed excellent results, surpassing the 800-cycle non-additive test piece (Comparative Example 5) at the end of 1000 cycles. Next, the solder thickness under the ceramic capacitor component was investigated. The results are shown in Figure 14. After the heat cycle test, cross-sections of two points on both sides of the ceramic capacitor component were observed and the average thickness was calculated. It was clear that the thickness was thinner in Examples 22 to 25 than in Comparative Example 5, and that the thickness became thinner as the addition rate increased. From these results, the following can be inferred. First, the premise is that solder paste is applied to a board, and ceramic capacitor components are placed on top of it (placed without being fixed), and then melted in a reflow furnace. During this thermal melting, the components move due to their own weight and wettability, resulting in changes in thickness. This results in variations in the thickness of each joined component. Next, we will consider the possibility of thinner solder thickness under ceramic capacitor components depending on whether or not CNF is added, focusing on the viscosity of molten solder. The solder paste of the example contains CNF, which has thixotropy, a property in which viscosity gradually decreases when subjected to continued shear stress, gradually increases when stationary, and finally becomes solid. It is thought that imparting this property to the solder paste causes thinner solder thickness under ceramic capacitor components. This is supported by the fact that when observing the state of the solder melting with a camera installed in a reflow simulator, convection motion was observed. It is thought that when this thermal motion continues to apply shear stress to the molten solder, the viscosity decreases. It can be inferred that this makes it easier for the ceramic capacitor parts to sink due to gravity, resulting in thinning. Next, the influence of the solder thickness on the results of the reliability evaluation is presumed as follows. Under heat cycle testing conditions, shear strain occurs in the solder joints between ceramic capacitor components, which exhibit little thermal expansion and contraction, and large resin substrates. More precisely, in addition to plastic strain, there is also nonlinear, time-dependent creep strain, and although it is not a simple linear equation, thinner thickness means greater shear strain, which can be interpreted as indicating that thinner substrates are being evaluated under more stringent conditions. Therefore, if the solder paste formulation can be modified to maintain joint thickness while also utilizing the strength-enhancing effects of CNF, it is expected to produce significant improvements in the reliability of electronic substrates. It also becomes possible to use additives that increase viscosity when added, broadening the formulation range.

[0079] (Cross-section observation after heat cycle test) The difference in thermal fatigue between the presence and absence of CNF was evaluated by observing the cross sections before and after the heat cycle test using Example 25 and Comparative Example 6. FE-SEM images comparing the states before and after the heat cycle test are shown in Figure 15 (left: Comparative Example 6, right: Example 25). It is generally believed that within solder, the Ag3Sn eutectic region, which exists in a network around the grain boundaries of β-Sn, prevents the initiation and propagation of cracks (Figure 16).Then, thermal cycling causes the β-Sn to become finer and the Ag3Sn to diffuse and recrystallize, reducing the crack propagation prevention effect of this network. The observation results (Example 25) before the heat cycle test (no cooling cycle treatment) revealed that the growth of columnar crystal zones due to directional solidification was prominent, dendritic crystals grew from dendritic cells, and secondary arms also clearly grew. This supports the effect of suppressing supercooling and promoting smooth crystallization during the cooling process after solder melting, which was revealed by the differential thermal analysis results mentioned above. On the other hand, the results after the heat cycle test (1000 cooling cycles) confirmed that the occurrence of cracks, which are precursors to cracks, may have been suppressed in electron microscope observations after the heat cycle test. Furthermore, the results of Comparative Example 5 showed that thermal fatigue caused minute cracks, likely due to differences in expansion and contraction between the β-Sn crystals and the surrounding Ag3Sn eutectic regions, resulting in deep grooves separating the β-Sn crystals. Furthermore, the refinement of the β-Sn and the scattering of Ag3Sn within the β-Sn crystal grains were confirmed. The degree of this cracking was reduced by the addition of CNF, suggesting that the presence of CNF leads to improved reliability.

[0080] In order to confirm the metal composition inside the solder in the samples joined using solder paste, elemental analysis was performed on the fracture surface after the shear test using EDS (ProX, manufactured by Rhenom), and the results are shown in Figure 17. From Figure 17, it was confirmed that the shape of the Ag3Sn intermetallic compound structure changed from needle-like to granular, becoming finer, due to the addition of CNF. Next, to confirm the composition of the interior of the solder, such as the orientation of the fracture surface after the shear test, X-ray measurements were performed using an X-ray diffractometer (Ultim IV, manufactured by Rigaku Corporation). The results are shown in Figure 18. Figure 18 shows a clear difference in the Ag3Sn composition, with the peaks for the (200), (101), and (211) planes becoming smaller, while the peak for the (220) plane becoming larger, confirming that the addition of CNFs results in an orientation of the (220) plane of the Ag3Sn composition. This suggests that the (220) plane may have been oriented during bonding, or that the (220) plane may have been oriented as a result of shear deformation. The X-ray diffraction results suggest that adding cellulose has the effect of aligning the crystal orientation during solidification, and that the (220) plane may be oriented when voids are removed. It is thought that the (220) plane orientation may have improved the bonding strength.

[0081] (Productivity evaluation results) We confirmed productivity by evaluating the solder void area ratio using a mounting board for productivity evaluation. The mounting board for productivity evaluation is shown in Figure 19. Solder voids: In accordance with JISC61191-6 (Table A.4 - Void evaluation criteria for LGA solder joints), X-ray CT observation was performed, and the image of the solder layer alone was binarized and evaluated using the void area value obtained. Internal voids reduce the bonding area, resulting in reduced bonding strength; heat generation due to increased electrical resistance caused by reduced electrical flow paths; and noise generation due to current disturbances, ultimately leading to instability of electrical signals. The results are shown in Table 12. It was confirmed that the void area ratio tends to decrease with increasing CNF content. Example 25, with a CNF content of 0.02 wt%, achieved a 23% reduction in void generation. Table 13 also shows the results of investigating changes in void generation ratio using components of different sizes and various solder pastes. While the reduction in internal voids varied, it was clear that a maximum reduction of 50% was achieved. This is thought to be due to mechanisms such as improved fluidity allowing volatile gases to escape or the CNFs carrying the gases and floating them away. We also checked for blowholes. Here, blowholes are voids formed by gas generated within the solder that open to the surface. These are holes resembling golf ball dimples on the solder surface (interface). Blowholes disappear when the gas inside the molten solder completely escapes, but if the gas escapes slowly, they remain. In severe cases, they can even be observed visually. Depending on the operating environment, blowholes can cause cracks that prevent the mounted components from functioning properly, increasing the likelihood of problems in the market. Furthermore, blowholes on the surface can easily be detected using an inline camera, leading to complaints and production losses. Using the boards of Reference Example 2 prepared in Table 13, we performed a blowhole inspection using a 2D visual inspection device and visual evaluation (50x magnification). We confirmed that blowholes, which previously occurred at a frequency of more than 5%, had been eliminated.

[0082] [Table 12]

[0083] [Table 13]

[0084] (Creating a calibration curve) Pure water and IPA were mixed at the concentrations shown in Table 14 below, and then the absorbance was measured using a Fourier transform infrared spectrophotometer (Spectrum One, manufactured by PerkinElmer). -1 and 1075cm -1 The absorbance value (I 1127 + and I 1075 ) using the following formula: 1127cm -1 The absorbance ratio was calculated. Formula I 1127 / ( I 1127 + I 1075 ) × 100 These values ​​were then used to generate a calibration curve, the results of which are shown in Figure 20.

[0085] [Table 14]

[0086] The correlation coefficient for the calibration curve with the lowest IPA concentration, up to No. 5, was 0.9469. On the other hand, the correlation coefficient for the calibration curve with an IPA concentration of 37 wt% (2.2 mol%) or higher was 0.989. These results confirmed that there is a high correlation.

[0087] A 1.2% CNF slurry and IPA were mixed at the concentrations shown in Table 15 below, and similar measurements were performed using a Fourier transform infrared spectrophotometer. The results are shown in Figure 21. Figures 20 and 21 confirm that even in solutions containing CNF, the curve is nearly identical to the calibration curve in Figure 20. Therefore, even if the CNF cannot be completely removed in step 2 of the "Method for Quantifying Organic Solvent in CNF-Dispersed Compositions and CNF-Dispersed Resin Compositions" described above, the IPA content in the solvent can be determined.

[0088] [Table 15]

Claims

1. a step of azeotropically distilling a mixture of component (1): water, component (2): cellulose nanofiber, component (3): isopropyl alcohol, and component (4): resin to obtain a CNF-dispersed resin composition; a method for producing a solder paste containing a CNF-dispersed resin composition, the method comprising the steps of: mixing the obtained CNF-dispersed resin composition into a solder paste; A method for producing a solder paste containing a CNF-dispersed resin composition, comprising a step of confirming that the isopropyl alcohol weight ratio Or of the component (3) is 56.8% or more, as calculated by the following calculation method. Method for calculating the weight ratio Or of organic solvent in a mixture of CNF aqueous dispersion and organic solvent (excluding water) First, the amount of CNF Cn and the amount of water solvent Va in the CNF dispersion are calculated. Next, CNF fixed water H Ｃ is calculated by the following formula (1). H C =C n × (100 - a) / a (1) (where a (15 ≤ a ≤ 19) is the weight-based CNF solids concentration (%) at which no aggregation of CNF occurs in the CNF aqueous dispersion.) Next, the actual amount of water solvent Vb in the CNF dispersion is calculated using the following formula (2). V b =V ａ -H C ・・・(2) Next, the weight V of the organic solvent s and the actual water solvent volume V b From this, the weight ratio Or of the organic solvent is calculated by the following formula (3). Or=V s / (V s +V b )・・・(3)

2. a step of azeotropically distilling a mixture of component (1): water, component (2): cellulose nanofiber, component (3): isopropyl alcohol, and component (4): resin, and removing component (1) and component (3) to obtain a CNF-dispersed resin composition in which component (2) is uniformly dispersed in component (4); a method for producing a solder paste containing a CNF-dispersed resin composition, the method comprising the steps of: mixing the obtained CNF-dispersed resin composition into a solder paste; A method for producing a solder paste containing a CNF-dispersed resin composition, comprising a step of confirming that the isopropyl alcohol weight ratio Or of the component (3) is 56.8% or more, as calculated by the following calculation method. Method for calculating the weight ratio Or of organic solvent in a mixture of CNF aqueous dispersion and organic solvent (excluding water) First, the amount of CNF Cn and the amount of water solvent Va in the CNF dispersion are calculated. Next, CNF fixed water H Ｃ is calculated by the following formula (1). H C =C n × (100 - a) / a (1) (where a (15 ≤ a ≤ 19) is the weight-based CNF solids concentration (%) at which no aggregation of CNF occurs in the CNF aqueous dispersion.) Next, the actual amount of water solvent Vb in the CNF dispersion is calculated using the following formula (2). V b =V ａ -H C ・・・(2) Next, the weight V of the organic solvent s and the actual water solvent volume V b From this, the weight ratio Or of the organic solvent is calculated by the following formula (3). Or=V s / (V s +V b )・・・(3)

3. A method for manufacturing an electronic circuit board, comprising a step of forming a joint on the electronic circuit board using a solder paste containing the CNF-dispersed resin composition described in claim 1 or claim 2.

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