JP7378029B2 - Electronics - Google Patents

Description

TECHNICAL FIELD The present invention relates to a stretchable conductive composition and an electronic device.

As the uses of electronic devices expand, elasticity may be required for electronic devices.
Therefore, Patent Documents 1 and 2 propose resin compositions containing metal powder and a specific resin and having excellent elasticity. This resin composition is used, for example, to form a wiring pattern on a base material.

International Publication No. 2016/114278 pamphlet International Publication No. 2017/026420 pamphlet

Usually, a resin composition used to form a wiring pattern contains a solvent. Since the wiring pattern needs to be fixed quickly after being drawn, a highly volatile compound is used as the solvent. Therefore, the resin composition has almost no tackiness, and the adhesion between the wiring pattern and the circuit member to be mounted is low.

The present invention relates to a conductive composition including a polyol, a blocked isocyanate, and a conductive material, where the conductive material includes a filler having an aspect ratio of 2 or more.

Further, the present invention includes a stretchable base material, a wiring pattern formed on the surface of the stretchable base material, and a circuit member including an electrode connected to the wiring pattern, wherein the wiring pattern is Item 2. An electronic device comprising a cured product of the conductive composition according to Item 1, wherein at least a portion of the electrode is embedded in the wiring pattern.

According to the present invention, a conductive composition having excellent conductivity and tackiness is provided.

1 is a side view schematically showing a part of an electronic device according to an embodiment of the present invention. 1 is a side view schematically showing main parts of an electronic device according to an embodiment of the present invention. 1 is a flowchart showing a method for manufacturing an electronic device according to an embodiment of the present invention.

Various circuit members are usually mounted on the wiring pattern. The circuit member includes an electrode, and the circuit member functions by connecting the electrode to the wiring pattern. Connections between circuit members and wiring patterns are usually made using solder. Generally, after solder paste is printed on a base material (such as a board), circuit members are mounted on the base material. Finally, the electrodes of the circuit member and the wiring pattern of the board are electrically connected by melting the solder in a reflow process and solidifying the solder again. When using a stretchable base material, the solidified solder is difficult to deform, so it may not be able to follow the expansion and contraction of the base material and may peel off from the electrode.

In this embodiment, a conductive composition containing a raw material for a stretchable resin is used to form a wiring pattern and to electrically connect a circuit member and the wiring pattern. When the base material stretches, contracts, and/or bends (hereinafter simply referred to as "stretching"), the wiring pattern expands and contracts following the base material. Therefore, disconnection of the wiring pattern itself, separation between the base material and the wiring pattern, and further separation between the wiring pattern and the circuit member are suppressed. This embodiment includes an electronic device containing this conductive composition and a cured product thereof. The conductive composition according to this embodiment is particularly suitable for use in surface mount technology (SMT) such as flip-chip mounting technology.

[Conductive composition]
The conductive composition according to this embodiment includes a polyol, a blocked isocyanate, and a conductive material. The conductive material includes a filler having an aspect ratio of 2 or more (hereinafter referred to as a flat filler).

When the conductive composition is heated, the blocking agent dissociates from the blocked isocyanate to produce isocyanate, which reacts with the polyol to produce urethane resin. That is, the conductive composition of this embodiment contains not the urethane resin itself but the raw material of the urethane resin. Such a conductive composition has appropriate fluidity and tackiness. Therefore, the conductive composition easily adheres to the base material, and a composition containing a urethane resin and a conductive material obtained by curing it (hereinafter referred to as a cured product) also has high adhesion to the base material. has. The conductive composition contains a flat filler. As a result, conductivity is ensured even when the base material expands and contracts, and the electrical resistance of the cured product is maintained low.

For example, when the cured product is stretched in the first direction, the elongation rate of the cured product is when the electrical resistance value of the cured product after stretching becomes 120% of the electrical resistance value of the cured product before stretching in the first direction. , 5% or more. When the circuit member is joined to the cured product, the elongation rate of the cured product may be 4% or more.

Furthermore, when the polyol and isocyanate react, the volume of the conductive composition shrinks slightly. Therefore, the adhesion to the base material is further increased, and the conductive materials dispersed in the cured product are more likely to come into contact with each other, thereby increasing the conductivity.

Since the conductive composition has fluidity and tackiness, when wiring is drawn using the conductive composition and a circuit member is mounted on the wiring, at least a part of the electrode of the circuit member is ) and can remain in close contact with it. When the conductive composition is heated in this state, a wiring pattern (cured product) is formed with at least a portion of the electrode buried. In other words, the wiring pattern is the wiring of the electronic device, and also functions as a bonding material that adheres and electrically connects the circuit member and the wiring.

As described above, when the conductive composition according to the present embodiment is used, the wiring pattern is formed and the electrical connection between the circuit member and the wiring pattern is made, so it is possible to reduce the number of man-hours and improve the performance of electronic devices. Productivity can be improved. Furthermore, a reduction in manufacturing costs can be expected due to the reduction in man-hours. Furthermore, by electrically connecting the circuit member and the wiring pattern using the conductive composition, a reflow process and further a thermocompression bonding process can be omitted. Therefore, a material that is not very heat resistant can be used as the base material. Many stretchable materials do not have very high heat resistance.

A. Polyol Polyol is one of the raw materials for urethane resin and has two or more hydroxyl groups in one molecule.
Examples of polyols include polyether polyols, polyester polyols, polycarbonate polyols, polyurethane polyols, and acrylic polyols. These may be used alone or in combination of two or more. The content of the polyol may be, for example, 30% by mass or more and 80% by mass or less of the nonvolatile components in the conductive composition. Hereinafter, the nonvolatile components in the conductive composition may be referred to as solid content. The mass of non-volatile components in the conductive composition is calculated by subtracting the mass of the solvent from the prepared conductive composition. Moreover, the mass of the conductive composition after drying and after curing may be regarded as the mass of the nonvolatile component in the conductive composition.

Among these, polyester polyols are preferred because the flexibility and stretchability of the resulting urethane resin can be easily improved. A polyester polyol is obtained, for example, by a condensation reaction between a polyhydric alcohol and a polyhydric carboxylic acid. 80 equivalent percent or more of the total polyols may be polyester polyols.

The polyhydric alcohol is not particularly limited, and includes ethylene glycol, 1,2-propanediol, 1,3-propanediol, 2-methyl-1,3-propanediol, 2-butyl-2-ethyl-1,3- Propanediol, 1,4-butanediol, neopentyl glycol, 3-methyl-2,4-pentanediol, 2,4-pentanediol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, 2-Methyl-2,4-pentanediol, 2,4-diethyl-1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 3,5-heptanediol, 1,8-octane Diol, aliphatic diol such as 2-methyl-1,8-octanediol, 1,9-nonanediol, 1,10-decanediol; alicyclic diol such as cyclohexanedimethanol, cyclohexanediol; trimethylolethane, trimethyl Trihydric or higher polyhydric alcohols such as methylolpropane, hexitols, pentitols, glycerin, polyglycerin, pentaerythritol, dipentaerythritol, and tetramethylolpropane can be mentioned. These may be used alone or in combination of two or more.

Polycarboxylic acids are not particularly limited, and include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, dodecanedioic acid, 2-methylsuccinic acid, and 2-methyladipine. acids, 3-methyladipic acid, 3-methylpentanedioic acid, 2-methyloctanedioic acid, 3,8-dimethyldecanedioic acid, 3,7-dimethyldecanedioic acid, hydrogenated dimer acid, fats such as dimer acid group dicarboxylic acids; aromatic dicarboxylic acids such as phthalic acid, terephthalic acid, isophthalic acid, and naphthalene dicarboxylic acid; alicyclic dicarboxylic acids such as cyclohexanedicarboxylic acid; tricarboxylic acids such as trimellitic acid, trimesic acid, and trimers of castor oil fatty acids ; Examples include tetracarboxylic acids such as pyromellitic acid. These may be used alone or in combination of two or more.

The molecular weight of the polyol is not particularly limited. From the viewpoint of handleability, flexibility and elasticity of the obtained cured product, the weight average molecular weight of the polyol may be 300 or more and 5,000 or less, or 300 or more and 3,000 or less.

The hydroxyl value of the polyol is also not particularly limited. The hydroxyl value of the polyol may be, for example, 40 mgKOH/g or more and 800 mgKOH/g or less, or 40 mgKOH/g or more and 600 mgKOH/g or less.

B. Blocked Isocyanate Blocked isocyanate is one of the raw materials for urethane resins, and is obtained by the reaction between an isocyanate compound and a blocking agent that protects the isocyanate groups contained therein. The blocking agent is dissociated by heating to produce isocyanate. The conductive composition according to this embodiment can be prepared as a one-component type.

The isocyanate compound is not particularly limited, and includes aliphatic polyisocyanates such as ethylene diisocyanate and 1,6-hexamethylene diisocyanate; alicyclic polyisocyanates such as isophorone diisocyanate, cyclohexane 1,3-diisocyanate, and cyclohexane 1,4-diisocyanate: 2 , 4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, polymeric diphenylmethane diisocyanate, xylylene diisocyanate, naphthalene diisocyanate, and other aromatic isocyanates. The isocyanate compound may be a copolymer, an isocyanurate, an adduct, or a biuret of these. Isocyanate compounds may be included as prepolymers reacted with the polyols described above. These may be used alone or in combination of two or more.

Blocking agents are not particularly limited, and include phenol-based, alcohol-based, oxime-based, β-carbonyl compound, lactam-based, amine-based, imine-based, amine-imide-based, nitrile carbonate-based, pyrazole-based, active methylene-based, mercaptan-based, imidazole-based , carbamic acid type, triazole type, etc.

Among these, active methylene-based blocking agents, pyrazole-based blocking agents, and the like are preferred from the viewpoint of lowering the reaction temperature. The reaction temperature (curing temperature) between the polyol and the blocked isocyanate may be, for example, 150°C or lower, or 140°C or lower. When the reaction temperature is within this range, the heating temperature can be set low, and deterioration of the substrate to be coated can be easily suppressed.

Examples of pyrazole blocking agents include pyrazole, 3,5-dimethylpyrazole, 3-methylpyrazole, 4-benzyl-3,5-dimethylpyrazole, 4-nitro-3,5-dimethylpyrazole, 4-bromo-3 , 5-dimethylpyrazole, 3-methyl-5-phenylpyrazole and the like.

Examples of active methylene blocking agents include Meldrum's acid; dimethyl malonate, diethyl malonate, dibutyl malonate, di2-ethylhexyl malonate, methyl butyl malonate, ethyl butyl malonate, diethyl methyl malonate, dibenzyl malonate, and malonate. Dialkyl malonates such as diphenyl acid, benzylmethyl malonate, ethylphenyl malonate, butylphenyl malonate, etc.: methyl acetoacetate, ethyl acetoacetate, n-propyl acetoacetate, isopropyl acetoacetate, butyl acetoacetate, benzyl acetoacetate, acetoacetate Examples include alkyl acetoacetates such as phenyl acetate; 2-acetoacetoxyethyl methacrylate; acetylacetone; and ethyl cyanoacetate.

The content of NCO groups (including NCO groups protected by a blocking agent) in the blocked isocyanate is not particularly limited. The effective NCO group content of the blocked isocyanate may be, for example, 5% by mass or more and 20% by mass or less.

The blending ratio of polyol and blocked isocyanate is not particularly limited. The equivalent ratio of the active hydrogen group that the polyol has and the NCO group that the blocked isocyanate has (NCO group/active hydrogen group) may be 1 or more and 10 or less, or 1 or more and 5 or less. When the NCO group/active hydrogen group is within this range, side reactions of isocyanate are easily suppressed, and the flexibility and elasticity of the resulting urethane resin are likely to be improved.

C. Conductive Material The conductive material includes a flat filler. This ensures conductivity during expansion and contraction of the cured product. Examples of flat fillers include flaky fillers, scale fillers, and fibrous fillers (metal nanowires, metal nanotubes, etc.).

The aspect ratio of the flat filler may be 3 or more, 10 or more, or 20 or more. The aspect ratio of the flaky filler and the scale-like filler is the ratio of the average length in the thickness direction to the average length in the surface direction. The aspect ratio of the fibrous filler is the ratio of the average length in the longitudinal direction to the average length in the lateral direction. The average length in the surface direction may be the diameter of a circle having the same area as the surface. Other average lengths are average values of 10 fillers.

The aspect ratio may be determined from a cross section in the thickness direction of the dried conductive composition or its cured product (wiring pattern). For example, an arbitrary cross section in the thickness direction of the wiring pattern is photographed at a magnification of 100 times or more using a scanning electron microscope (SEM) or a transmission electron microscope (TEM). An arbitrary plurality of fillers (for example, 20 fillers) are selected from within the observation field of this image, and the major axis and minor axis are measured. A filler in which the ratio of the major axis to the minor axis is 2 or more is referred to as a flat filler. In this way, 10 flat fillers are selected, the ratio of the major axis to the minor axis of each is calculated, and the average value thereof is taken as the aspect ratio of the flat filler. Aspect ratios of other fillers are determined in the same manner.

The average particle diameter of the flat filler may be, for example, 1 μm or more and 20 μm or less, or 1 μm or more and 10 μm or less. When the average particle diameter of the flat filler is within the above range, conductivity during expansion and contraction of the cured product is easily ensured.

The average particle size is the particle size at 50% cumulative volume (D50; the same applies hereinafter) in a volume-based particle size distribution. The average particle size may be determined from a cross section in the thickness direction of the dried conductive composition or its cured product (wiring pattern). For example, it can be determined by calculating the particle diameters of a plurality of flat fillers (for example, 10) selected as described above and averaging them. The diameter of a circle having the same area as the cross-sectional area of the flat filler may be taken as the particle diameter of the flat filler. The average particle diameters of other fillers are determined in the same manner.

The content of the conductive material may be, for example, 30 volume% or more and 80 volume% or less, and 50 volume% or more and 80 volume% or less, with the total of the polyol, blocked isocyanate, and conductive material being 100 volume%. It's good to be there. When the content of the conductive material is within the above range, reliability of electrical connection is easily ensured.

The content (volume ratio) of the conductive material can be calculated by considering the specific gravity of each mass of the polyol, blocked isocyanate, and conductive material. The content of the conductive material may be determined from a cross section in the thickness direction of the conductive composition after drying or its cured product (wiring pattern). For example, the SEM image or TEM image obtained as described above is divided into polyol, blocked isocyanate (organic component), and conductive material and binarized. Within the observation field of the binarized image, the area ratio occupied by the organic component and the conductive material is calculated. The volume ratio (content) of the conductive material may be calculated by regarding these area ratios as the volume ratio of each component in the organic component and the conductive material.

Elements contained in the flat filler include silver, copper, gold, aluminum, magnesium, tungsten, cobalt, zinc, nickel, brass, molybdenum, tantalum, niobium, iron, platinum, tin, chromium, lead, titanium, manganese, and ruthenium. , rhodium, palladium, cadmium, osmium, iridium and the like. The flat filler may contain these elements as an alloy. These may be used alone or in combination of two or more. Among these, from the viewpoint of electrical conductivity, it is preferable that the flat filler contains silver.

The conductive composition may further include a filler having an aspect ratio of less than 2 (hereinafter referred to as spherical filler) as the conductive material. The average particle size of the spherical filler is not particularly limited, but it may be smaller than the average particle size of the flat filler.This allows it to easily enter the gaps between the flat fillers, making it easier to maintain conductivity during expansion and contraction of the cured product. Become. The average particle diameter of the spherical filler may be, for example, 1 μm or more and 20 μm or less, or 1 μm or more and 10 μm or less. Examples of elements contained in the spherical filler include the same elements as in the flat filler.

D. Others A solvent, a catalyst, a chain extender, a binder, a coupling agent, a conductive aid, an inorganic filler, an organic filler, etc. may be further added to the conductive composition.

The chain extender is not particularly limited, and known ones can be used. Examples of the chain extender include polyamine compounds, polyols having active hydrogen, and the like. The catalyst is not particularly limited, and any known catalyst used when synthesizing urethane resins can be used. Examples of the catalyst include tin-based catalysts, amine-based catalysts, organometallic compound-based catalysts, and the like.

The conductive aid is not particularly limited, and any known conductive aid can be used. Examples of the conductive aid include conductive polymers, ionic liquids, carbon black, acetylene black, and carbon nanotubes. These may be used alone or in combination of two or more.

The binder is not particularly limited, and any known binder can be used. As the binder, a polymer having a high expansion/contraction rate and containing no unsaturated bonds in the molecule is preferable. Specific examples include urethane resin, urethane rubber, acrylic resin, acrylic rubber, butyl rubber, chlorosulfonated rubber, fluororubber, and silicone. The urethane resin and urethane rubber may be of a solvent evaporation type or a thermosetting type. These may be used alone or in combination of two or more.

[Electronics]
The electronic device according to this embodiment includes a stretchable base material, a wiring pattern formed on the surface of the stretchable base material, and a circuit member including an electrode connected to the wiring pattern. The wiring pattern includes a cured product of the above-mentioned conductive composition. Therefore, when the base material expands and contracts, the wiring pattern deforms following the stretchable base material, thereby suppressing disconnection of the wiring pattern itself and separation of the base material and the cured product. Furthermore, at least a portion of the electrode is buried in the stretchable wiring pattern. That is, the bottom surface of the electrode is in contact with the wiring pattern, and at least a portion of the side surface is also in contact with the wiring pattern. Therefore, even if the base material expands and contracts, peeling between the cured product and the circuit member is also suppressed. Therefore, the electronic device according to this embodiment has high connection reliability while being flexible and/or stretchable.

Electronic devices perform electrical input/output, calculation, communication, etc. The electronic device according to this embodiment is particularly suitable as a wearable device that is used close to or in close contact with the body. Such wearable devices are used, for example, by being attached to clothing by sewing or thermal adhesion, or by being attached to the body with an adhesive.

When the bonding material that adheres the circuit member and the wiring pattern and the wiring pattern are made of different stretchable materials, the stress applied to each material due to the expansion and contraction of the base material and the stress that remains in each material. Stress is different. Therefore, the electrical characteristics, wearing comfort, etc. of the electronic device are likely to deteriorate. In the electronic device according to this embodiment, the wiring pattern also functions as a bonding material, so that the above-mentioned problems are unlikely to occur.

FIG. 1 is a side view schematically showing a part of the electronic device according to the present embodiment. FIG. 2 is a side view schematically showing main parts of the electronic device according to the present embodiment.

The electronic device 100 includes a stretchable base material 10, a wiring pattern 20 formed on the surface of the stretchable base material 10, and a circuit member 30 including an electrode 31 connected to the wiring pattern 20. The wiring pattern 20 includes a cured product of the above-mentioned conductive composition. At least a portion of the electrode 31 is buried in the wiring pattern 20. That is, at least a portion of the bottom surface 31a and side surface 31b of the electrode 31 is in contact with the wiring pattern 20.

The base material is not particularly limited. In addition to conventionally known glass substrates, resin substrates, ceramic substrates, silicon substrates, etc. used as wiring boards, substrates that have elasticity and/or bending properties such as flexible substrates and stretchable substrates can be used as base materials. Can be mentioned. The conductive composition according to this embodiment is also suitable for other stretchable and/or bendable base materials. These stretchable and/or bendable base materials are collectively referred to as stretchable base materials.

Examples of the form of the stretchable base material include fiber structures such as woven fabrics, knitted fabrics, and nonwoven fabrics, rubber, and resin films. The material of the base material is not particularly limited. The fiber structure includes, for example, synthetic fibers such as polyester, nylon, acrylic, urethane, and polyvinyl alcohol; regenerated cellulose fibers such as rayon and cupro; natural fibers such as cotton, hemp, wool, and silk; and composite fibers thereof. It's okay to be there. Rubbers may include styrene butadiene rubber, butadiene rubber, chloroprene rubber, isoprene rubber, isobutylene isoprene rubber, ethylene propylene rubber, acrylonitrile butadiene rubber, silicone rubber, fluororubber, acrylic rubber, urethane rubber, and the like. The resin film may include, for example, polyester, polypropylene, polycarbonate, polyethylene sulfone, urethane, silicone, and the like. These may be used alone or in combination of two or more.

When the base material is a rubber or resin film, if the elongation at break measured according to JIS K 7126 or JIS K 7127 is 3% or more, it can be evaluated as a stretchable base material.
When the base material is a fibrous structure, if the elongation rate measured in accordance with JIS L 1096 tensile strength and elongation rate A method (strip method) is 3% or more, it is a stretchable base material. It can be evaluated that there is.

The thickness of the stretchable base material is not particularly limited, and may be appropriately set depending on the purpose and the like.

The electronic device can be manufactured, for example, by the following method.
The electronic device according to the present embodiment includes (1) a step (S1) of preparing a conductive composition containing a polyol, a blocked isocyanate, and a conductive material containing a filler with an aspect ratio of 2 or more; a step (S2) of applying a conductive composition onto the stretchable base material, and (3) mounting the circuit member on the stretchable base material so that the applied conductive composition and the electrodes of the circuit member are in contact with each other. (S3), and a step (S4) of heating the applied conductive composition to form a wiring pattern containing a conductive material and a reaction product of a polyol and a blocked isocyanate. manufactured by the method. FIG. 3 is a flowchart showing a method for manufacturing an electronic device according to this embodiment.

(1) Preparation step of conductive composition The conductive composition is prepared by mixing the above-mentioned conductive material, polyol, blocked isocyanate, and other additives using, for example, a mixer.

(2) Step of applying conductive composition The method of applying the conductive composition to the base material is not particularly limited. Examples of the application method include coating methods using an applicator, wire bar, comma roll, gravure roll, etc.; printing methods using a screen, flat plate offset, flexo, inkjet, stamping, dispenser, etc.

The amount of the conductive composition to be applied is not particularly limited, and may be appropriately set depending on the use of the electronic device, the average particle size of the conductive material, the circuit member to be mounted, and the like. In order to make it easier to bury the electrode, the conductive composition may be applied thickly to the portion that comes into contact with the electrode.

(3) Circuit member mounting process The conductive composition applied to the stretchable base material before heating has fluidity and tackiness. Therefore, when a circuit member is mounted on the conductive composition, at least a portion of the electrode of the circuit member is buried in the conductive composition and is in close contact with the conductive composition.

The circuit member is not particularly limited as long as it has an external terminal on the surface facing the base material. Examples of circuit members include bare chip components such as IC chips, package components including interposers, electronic component modules, chip components such as passive elements, and laminated semiconductors having through electrodes.

(4) Heating step By heating the conductive composition, the blocking agent of the blocked isocyanate is dissociated, and the isocyanate component and the polyol react. As a result, the wiring pattern (cured material) is formed while at least a portion of the electrode remains buried, and the electrode and the wiring pattern are connected. In other words, the wiring pattern is not only the wiring of the electronic device, but also a bonding material that electrically connects the circuit member and the wiring. In other words, the conductive composition is a material for forming wiring and a material for bonding. Therefore, it is not necessary to consider the compatibility of each material, the difference in physical properties, etc., and concerns about peeling between the materials are also eliminated.

The heating process forms the wiring pattern and electrically connects the circuit member and the wiring pattern, so it is possible to reduce the number of man-hours and improve the productivity of electronic devices. Furthermore, a reduction in manufacturing costs can be expected due to the reduction in man-hours. Since the materials used are also limited, manufacturing costs can be further reduced.

The heating temperature is appropriately determined depending on the reaction temperature of the polyol and the blocked isocyanate, the melting point of the base material, and the like. The heating temperature may be, for example, 100°C to 150°C, or 110°C to 140°C. The heating time is not particularly limited, but may be 60 minutes or less, 45 minutes or less, or 30 minutes or less.

[Examples 1 to 6, Comparative Example 1]
EXAMPLES Hereinafter, the present invention will be explained in more detail with reference to examples, but the present invention is not limited to the following examples.

(i) Preparation of conductive composition The components were mixed in the amounts shown in Table 1 and kneaded using a rotation/revolution mixer to prepare a paste-like conductive composition.

The components used in Examples 1 to 6 and Comparative Example 1 are as follows.
Polyol A : Polyester polyol, number average molecular weight 500, product name P-520, manufactured by Kuraray Co., Ltd., hydroxyl value 224
Polyol B : Polyester polyol, number average molecular weight 2000, product name P-2010, manufactured by Kuraray Co., Ltd., hydroxyl value 56
Polyol C : Polyester polyol, number average molecular weight 300, product name F-510, manufactured by Kuraray Co., Ltd., hydroxyl value 336
Polyurethane resin : Product name AR Binder GS, manufactured by Matsui Shiki Kagaku Kogyo Co., Ltd.
Blocked isocyanate A : Blocking agent active methylene type, product name Duranate MF-K60B, manufactured by Asahi Kasei Corporation
Blocked isocyanate B : Blocking agent pyrazole type, product name Duranate SBN-70D, manufactured by Asahi Kasei Corporation
Conductive material : flaky silver powder, product name AgC-2351, average particle size (D50) 6.95 μm, manufactured by Fukuda Metal Foil and Powder Industries Co., Ltd.

(ii) Production of electronic device The prepared conductive composition was applied in a rectangular shape onto a stretchable base material (urethane film, manufactured by Nippon Matai Co., Ltd., Esmer URS). The conductive composition was applied at two locations on the same straight line. The chip component was mounted so as to straddle the conductive compositions at two locations, and as shown in FIG. 1, the two electrodes of the chip component were brought into contact with the respective conductive compositions. In this state, it was heated under the conditions shown below to form a rectangular wiring pattern and to mount circuit members to obtain an electronic device.

(Heating conditions)
Example using blocked isocyanate A: 120°C, 30 minutes Example using blocked isocyanate B: 140°C, 30 minutes

[evaluation]
The conductive composition, wiring pattern, and electronic device were evaluated as follows.
(1) Volume resistance value After applying the prepared conductive composition onto a glass plate, it is heated under the above conditions to form a rectangular film (cured product of the conductive composition) on the glass plate, The resistance value of the film in the longitudinal direction was measured. Using the measured resistance value, the volume resistance value (specific resistance value) of the film was calculated using the following formula.
Volume resistance value = (resistance value x film thickness x length of film in transverse direction/length of film in longitudinal direction) x 100

The resistance value was measured by a four-terminal method according to JIS C 2525. The measurement temperature was 25° C., and correction of the resistance value due to temperature was omitted. The following resistance values were also measured in the same manner.

(2) Tackiness After applying the prepared conductive composition in two spots on a glass plate, it was allowed to stand for 60 seconds. The area of each spot is smaller than the mounting area of the chip component. After that, the chip component was mounted so that the entire surfaces of the two spots were in contact with one chip component (2.0 mm x 1.25 mm), and a bond tester (DAGE Bond Tester Series 4000 manufactured by Nordson Advanced Technology) was used. ) was used to measure the shear strength. The shear strength was evaluated as A when it was 70 mN or more, B when it was 50 mN or more but less than 70 mN, and C when it was less than 50 mN. The higher the shear strength, the better the tackiness.

(3) Resistance value characteristic A of cured product during stretching
After applying the prepared conductive composition on a stretchable base material (urethane film, Esmar URS, manufactured by Nippon Matai Co., Ltd.), it is heated under the above conditions to form a rectangular wiring pattern ( A cured product of the conductive composition was formed. Thereafter, the initial resistance value PR ₀ in the longitudinal direction of the wiring pattern was measured.

Next, the two ends of the urethane film are held and stretched in the longitudinal direction of the wiring pattern, and the stretching rate of the urethane film is determined when the electrical resistance value PR of the wiring pattern becomes 120% of the initial resistance value _PR0 . was calculated. The elongation rate of the urethane film can be regarded as the elongation rate of the wiring pattern.

(4) Resistance characteristic B of cured product during stretching
The initial resistance value ER ₀ between the two wiring patterns of the electronic device obtained in (ii) above was measured. This resistance value also takes into account the internal resistance of the chip components.
Next, both ends of the urethane film are held and stretched in the linear direction of the wiring pattern (horizontal direction in FIG. 1), and the urethane film is stretched when the electrical resistance value ER between the wiring patterns becomes 120% of the initial resistance value _ER0. The elongation rate of the film was calculated.

The cured products of the conductive compositions prepared in Examples 1 to 6 all had low initial resistance values and were highly evaluated in resistance value characteristic A. This shows that even if the cured product is stretched, the resistance value is difficult to increase. Furthermore, the evaluation of resistance value characteristic B is high, and the electrical resistance of the chip is maintained low even when the stretchable base material is stretched. Since the tackiness of the conductive composition is also high, it can be seen that the chip is firmly adhered to the cured product. Looking at the sample prepared when evaluating resistance value characteristic B, a part of the electrode was buried in the cured material.

In Comparative Example 1, although the evaluation of resistance value characteristic A was high, when the urethane film was stretched to evaluate resistance value characteristic B, the chip fell off. Therefore, it was not possible to evaluate the resistance value characteristic B. Comparative Example 1 also had a low evaluation of tackiness. Looking at the sample prepared when evaluating resistance value characteristic B, the electrode was not buried in the cured material.

The conductive composition of the present invention has conductivity and tackiness, and the cured product thereof has conductivity and stretchability. Therefore, the conductive composition of the present invention can be preferably used as a material and bonding material for forming wiring of electronic devices having a stretchable base material. Since the electronic device of the present invention has stretchability, flexibility, and high connection reliability, it can be suitably used in products in the high-performance electronics field, such as healthcare products, various displays, solar cells, and RFID.

100 Electronic equipment 10 Stretchable base material 20 Wiring pattern (cured product of conductive composition)
30 circuit member 31 electrode 31a bottom surface 31b side surface

Claims (8)

a stretchable base material;
a wiring pattern formed on the surface of the stretchable base material;
a circuit member including an electrode connected to the wiring pattern,
The wiring pattern includes a cured product of a conductive composition,
The conductive composition is
polyol and
Blocked isocyanate,
a conductive material;
The conductive material includes a filler with an aspect ratio of 2 or more,
An electronic device, wherein at least a portion of the electrode is buried in the wiring pattern. The electronic device according to claim 1, wherein the content of the conductive material is 30% by volume or more and 80% by volume or less of the total of the polyol, the blocked isocyanate, and the conductive material. The electronic device according to claim 1 or 2, wherein the polyol has a weight average molecular weight of 300 or more and 5,000 or less. The electronic device according to any one of claims 1 to 3, wherein the polyol has a hydroxyl value of 40 mgKOH/g or more and 800 mgKOH/g or less. The electronic device according to any one of claims 1 to 4, wherein the polyol is a polyester polyol. The electronic device according to any one of claims 1 to 5, wherein the reaction temperature between the polyol and the blocked isocyanate is 150°C or less. When the cured product of the conductive composition is stretched in a first direction, the electrical resistance value of the cured product after stretching becomes 120% of the electrical resistance value of the cured product before stretching in the first direction. The electronic device according to any one of claims 1 to 6, wherein the elongation rate of the cured product is 5% or more. The electronic device according to any one of claims 1 to 7, wherein the conductive material further includes a filler having an aspect ratio of less than 2.

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