JP2021150039A - Conductive composition, electronic apparatus, and method of manufacturing the same - Google Patents

Abstract

To provide a conductive composition which gives a cured product excellent in mechanical strength, flexibility and toughness.SOLUTION: The conductive composition for a wiring pattern contains: a flexible epoxy resin containing a ring structure having aromaticity; a dicyclopentadiene type epoxy resin; an amine curing agent; and a conductive material. The conductive material contains a filler having an aspect ratio of 2 or more.SELECTED DRAWING: Figure 1

Description

The present invention relates to elastic compositions and electronic devices.

With the expansion of applications of electronic devices, elasticity may be required for electronic devices. For example, in the field of sensing biological information, it is required to directly attach an electronic device to a flexible living body or to mount an electronic device on stretchable clothes. Therefore, Patent Documents 1 and 2 propose a resin composition containing a 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.

Patent Document 1 is a conductive film containing a conductive metal powder (A) and a resin (B), which has a specific resistance of ^{less than 1.0 × 10 -3} Ωcm and an original length in at least one direction. The resistivity increase ratio is less than 10 when the original length is 100% stretched in the state of a self-supporting film which is expandable by 36% or more and does not have a holding portion for holding the base material and the conductive film. We are proposing a conductive film characterized by being present.

Patent Document 2 contains at least one selected from a block copolymer and a functional group-containing elastomer, and a chained silver powder in which fine particles are aggregated to form aggregated particles. We have proposed a conductive composition characterized by having a tap density of 2.0 g / cm ^{3 or less.}

International Publication No. 2016/11278 Pamphlet International Publication No. 2017/026420 Pamphlet

With the resin (B), block copolymer or functional group-containing elastomer proposed in Patent Documents 1 and 2, it is difficult to sufficiently secure the flexibility and toughness required for the wiring pattern.

The present invention includes a flexible epoxy resin containing an aromatic ring structure, a dicyclopentadiene type epoxy resin, an amine curing agent, and a conductive material, and the conductive material has an aspect ratio of 2. The present invention relates to a conductive composition for a wiring pattern containing the above fillers.

The present invention also 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 is described above. The present invention relates to an electronic device containing a cured product of a conductive composition and having at least a part of the electrodes embedded in the wiring pattern.

Further, in the present invention, the step of preparing the conductive composition, the step of applying the conductive composition on the stretchable base material, and the contact between the applied conductive composition and the electrodes of the circuit member. As described above, the step of mounting the circuit member on the elastic base material and the applied conductive composition are heated to form a wiring pattern including a cured product of the conductive composition. The present invention relates to a method for manufacturing an electronic device, comprising a step of connecting an electrode and the wiring pattern.

According to the present invention, there is provided a conductive composition that provides a cured product having excellent strength, flexibility and toughness.

It is a side view which shows a part of the electronic device which concerns on one Embodiment of this invention typically. It is a side view which shows typically the main part of the electronic device which concerns on one Embodiment of this invention. It is a flowchart which shows the manufacturing method of the electronic device which concerns on one Embodiment of this invention. It is a schematic diagram of the wiring pattern made for evaluating the increase rate of a volume resistance value.

Various circuit members are usually mounted on the wiring pattern. The circuit member includes electrodes, and by connecting the electrodes to the wiring pattern, the circuit member functions. The connection between the circuit member and the wiring pattern is usually made by using solder. Generally, after printing the solder paste on a base material (board or the like), the circuit member is mounted on the base material. Finally, the solder is melted by the reflow process and the solder is solidified again, so that the electrodes of the circuit member and the wiring pattern of the substrate are electrically connected. When an elastic base material is used, the solidified solder is hard to be deformed, so that it may not be able to follow the expansion and contraction of the base material and may be peeled off from the electrode.

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

[Conductive composition]
The conductive composition for the wiring pattern according to the present embodiment includes a flexible epoxy resin containing an aromatic ring structure, a dicyclopentadiene type epoxy resin, an amine curing agent, and a conductive material. The conductive material contains a filler having an aspect ratio of 2 or more (hereinafter, also referred to as a flat filler). Such a conductive composition has appropriate fluidity and tackiness. Therefore, the conductive composition easily adheres to the base material, and the cured product obtained by curing the conductive composition also has high adhesion to the base material.

When the conductive composition is heated, the flexible epoxy resin and the dicyclopentadiene type epoxy resin react with the amine curing agent to produce a cured product having a three-dimensional network structure. Since the flexible epoxy resin contains a ring structure having a soft component and an aromatic property, it imparts flexibility and toughness to the cured product. Further, the dicyclopentadiene type epoxy resin imparts mechanical strength and toughness to the cured product. In addition, the amine curing agent imparts elasticity and toughness to the cured product. Therefore, the cured product has excellent flexibility and toughness as well as excellent strength. For example, in a tensile test according to JIS K 6251 of a cured product of a conductive composition, the elongation at the maximum point of stress can be achieved to be 3% or more, and further 4% or more.

In addition, 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 kept small. For example, when the cured product is stretched in the first direction, the elongation rate of the cured product when the electrical resistance value of the cured product after stretching becomes 115% of the electrical resistance value of the cured product before stretching in the first direction is It can be 5% or more. When the circuit member is bonded to the cured product, the elongation rate of the cured product may be 4% or more.

Furthermore, when the flexible epoxy resin and the dicyclopentadiene type epoxy resin react with the amine curing agent, the volume of the conductive composition shrinks slightly. Therefore, the adhesion to the base material is further enhanced, and the conductive materials dispersed in the cured product are easily brought into contact with each other, and the conductivity is also enhanced. Even if only the flexible epoxy resin is used as the epoxy resin, the shrinkage during curing is small, and it is difficult to sufficiently secure the contact between the conductive materials. On the other hand, when the dicyclopentadiene type epoxy resin is used in combination, the volume shrinkage becomes large, and the conductive composition exhibits sufficient conductivity.

Since the conductive composition has fluidity and tackiness, when the wiring is drawn with the conductive composition and the circuit member is mounted on the wiring, at least a part of the electrodes of the circuit member is wired (conductive composition). ) Can be buried in it and adhere to it in that state. When the conductive composition is heated in this state, a wiring pattern (cured product) is formed with at least a part of the electrodes buried. That is, the wiring pattern is not only the wiring of the electronic device but also functions as a joining material that adheres the circuit member and the wiring and electrically connects them.

As described above, when the conductive composition according to the present embodiment is used, the wiring pattern is formed and the circuit member and the wiring pattern are electrically connected, so that the man-hours can be reduced and the electronic device can be used. Productivity can be improved. Furthermore, it can be expected that the manufacturing cost will be reduced by reducing the man-hours. Further, by electrically connecting the circuit member and the wiring pattern using the conductive composition, the reflow step and the thermocompression bonding step can be omitted. Therefore, as the base material, a material having not so high heat resistance can be used. Many elastic materials do not have very high heat resistance.

A. Flexible Epoxy Resin The flexible epoxy resin containing an aromatic ring structure is an epoxy resin having a rigid skeleton containing an aromatic ring structure and a flexible skeleton in the molecule. Gives the cured product flexibility and toughness. When the flexible epoxy resin contains an aromatic ring structure, the ring structure acts like a cross-linking point of rubber, and exhibits excellent mechanical strength as well as flexibility and toughness. For example, in a tensile test based on JIS K 6251 of a cured product of a conductive composition, the maximum stress is large and the elongation at the maximum point of stress is large. The cured product of such a conductive composition can easily follow the expansion and contraction of the elastic base material and can firmly hold the circuit member.

The ring structure having aromaticity is not particularly limited, and may be a condensed aromatic ring structure or a heterocyclic structure. The ring structure having an aromatic property may be, for example, at least one such as a benzene ring, a naphthalene ring, an anthracene ring, a pyrene ring, a fluorene ring, a pyrrole ring, a thiophene ring, a biphenyl ring, a bisphenol structure, and a cardo structure.

The flexible skeleton of the flexible epoxy resin is not particularly limited, and for example, the flexible epoxy resin includes a group consisting of an aliphatic modified epoxy resin, a polyether-modified epoxy resin, a urethane-modified epoxy resin, and a rubber-modified epoxy resin. At least one selected can be used. Aliphatic modified epoxy resins have flexible aliphatic groups. The polyether-modified epoxy resin has a flexible polyoxyalkylene group and the like. The urethane-modified epoxy resin is a combination of a flexible urethane prepolymer and an epoxy resin. The rubber-modified epoxy resin is a rubber-like polymer obtained by polymerizing isoprene, butadiene, styrene, acrylonitrile, etc., bonded to the epoxy resin.

Among them, an aliphatic modified epoxy resin, a polyether modified epoxy resin, and the like are desirable because they have high flexibility. For example, the flexible epoxy resin is at least selected from the group consisting of an alkylene group having 1 to 8 carbon atoms (preferably 3 to 7) and a polyoxyalkylene group having 1 to 8 carbon atoms (preferably 3 to 7). It is desirable to have one.

The flexible epoxy resin containing an aromatic ring structure is, for example, a copolymer (or polycondensation) containing an epoxy resin unit having an aromatic ring structure and an epoxy resin unit having a flexible skeleton. It may be a body). Among the epoxy resins having an aromatic ring structure, for example, the bisphenol type epoxy resin is easy to handle, and among them, the bisphenol F type epoxy resin is suitable for introducing the bisphenol structure into the flexible epoxy resin. .. Further, among the epoxy resins having a flexible skeleton, for example, an aliphatic modified epoxy resin is suitable, and among them, an alkylene glycol diepoxy resin having an alkylene group having 3 to 7 carbon atoms is suitable.

The flexible epoxy resin containing an aromatic ring structure has, for example, a structure represented by the following formula (1). In the formula (1), A is an alkylene group, X represents _two CR groups, and R independently represents a hydrogen atom, a methyl group, a phenyl group, or the like.

The epoxy equivalent of the flexible epoxy resin may be, for example, 800 g / eq or more and 1400 g / eq or less. The flexible epoxy resin having an epoxy equivalent in the above range has a large proportion of the flexible skeleton, suppresses the cured product from becoming excessively hard and brittle, and imparts flexibility to the cured product. On the other hand, by combining the flexible epoxy resin and the dicyclopentadiene type epoxy resin, sufficient mechanical strength of the cured product is also ensured.

The content of the flexible epoxy resin is, for example, 30% by mass or more and 70% by mass or less of the balance (hereinafter, also referred to as a resin component) obtained by removing the conductive material from the non-volatile component in the conductive composition. It's okay. The mass of the non-volatile component in the conductive composition is calculated by subtracting the mass of the solvent from the prepared conductive composition. Further, the mass of the conductive composition after drying and curing may be regarded as the mass of the non-volatile component in the conductive composition. It is not necessary to use a solvent.

B. Dicyclopentadiene type epoxy resin The dicyclopentadiene type epoxy resin refers to an epoxy resin having a plurality of epoxy groups and a dicyclopentadiene skeleton in the molecule. Since the dicyclopentadiene type epoxy resin has a bulky structure, it imparts excellent toughness while imparting appropriate mechanical strength to the cured product. The combination of the flexible epoxy resin and the dicyclopentadiene type epoxy resin makes the physical characteristic balance of the cured product more suitable for the wiring pattern formed on the stretchable base material.

The dicyclopentadiene type epoxy resin may have, for example, a novolak structure as represented by the following formula (2).

The epoxy equivalent of the dicyclopentadiene type epoxy resin may be, for example, 150 g / eq or more and 200 g / eq or less. A dicyclopentadiene type epoxy resin having an epoxy equivalent in the above range is preferable because it has a low viscosity, is excellent in reactivity, and can improve the printability of the conductive composition.

The amount of the dicyclopentadiene type epoxy resin may be, for example, 30 to 110 parts by mass or 50 to 100 parts by mass with respect to 100 parts by mass of the flexible epoxy resin.

The conductive composition may contain an epoxy resin other than the above epoxy resin in a small amount, but the amount is preferably 10 parts by mass or less with respect to 100 parts by mass of the flexible epoxy resin. .. Examples of such optional component epoxy resins include bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol AD type epoxy resin, bisphenol S type epoxy resin, fluorene type epoxy resin, naphthalene type epoxy resin, biphenyl type epoxy resin, and glycidyl. Amine type epoxy resin, alicyclic epoxy resin, polyether type epoxy resin, novolak type epoxy resin and the like can be used. These may be used alone or in combination of two or more.

C. Amine curing agent As the amine curing agent, polyamines such as aliphatic (including alicyclic) polyamines and aromatic polyamines, hydrazines, unsaturated diamines such as diallylamine compounds and the like can be used. The aliphatic polyamines include ethylenediamine, diethylenetriamine, triethylenetetramine, dipropylenetriamine, tetraethylenepentamine, dimethylaminopropylamine, bishexamitylenetriamine, cyclohexylaminopropylamine, aminoethylethanolamine, monohydroxyethyldiethylenetriamine, and bis. Hydroxyethyldiethylenetriamine, N- (2-hydroxypropyl) ethylenediamine, hexamethylenediamine, diethyleneglycolbis (3-aminopropyl) ether, diethylaminopropylamine, 3,9-bis (3-aminopropyl) -2,4,8, Examples thereof include 10-tetraspoxaspiro [5,5] undecane, mensendiamine, isophoronediamine, bis (4-amino-3-methylcyclohexyl) methane, N-aminoethylpiperazine and the like. Aromatic polyamines include phenylenediamine, diaminodiphenylmethane, diaminoanisole, toluenediamine, xylylenediamine (eg, metaxylylenediamine), diaminodiphenylsulfone (eg, 4,4'-diaminodiphenylsulfone), 3,3'-dichloro. Examples thereof include −4,4′-diaminodiphenylmethane, 4,4′-methylenebis (phenylamine), 4,4′-diaminodiphenyl ether and the like. Of these, m-xylylenediamine is preferable because it has excellent mechanical strength and toughness.

The amount of the amine curing agent may be 20 to 60 parts by mass with respect to 100 parts by mass of the total amount of the epoxy resin including the flexible epoxy resin and the dicyclopentadiene type epoxy resin, for example, 25 to 40 parts by mass. It may be. The equivalent ratio of active hydrogen groups (NH group / epoxy group) of the amine curing agent to the epoxy group (epoxy equivalent) of the total amount of the epoxy resin including the flexible epoxy resin and the dicyclopentadiene type epoxy resin is Considering the balance between the curing time and the pot life of the conductive composition, for example, 1 or more and 2 or less are preferable.

D. Conductive material The conductive material contains a flat filler. As a result, the conductivity of the cured product during expansion and contraction is ensured. Examples of the flat filler include flake-like fillers, scaly fillers, and fibrous fillers (metal nanowires, metal nanotubes, etc.).

The aspect ratio of the flat filler may be 3 or more, 10 or more, and 20 or more. The aspect ratio of the flake-like filler and the scaly filler is the ratio of the average length of the maximum diameter in the thickness direction to the average length in the plane 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 plane direction may be the diameter of a circle having the same area as the area of the plane. Other average lengths are average values of 10 fillers.

The aspect ratio may be determined from the cross section of the dried conductive composition or its cured product (wiring pattern) in the thickness direction. For example, an arbitrary cross section in the thickness direction of the wiring pattern is photographed with a scanning electron microscope (SEM) or a transmission electron microscope (TEM) at a magnification of 100 times or more. Arbitrary plurality of (for example, 20) fillers are selected from the observation field of view of this image, and the major axis and the minor axis are measured. The major axis is the maximum diameter, and the minor axis is the maximum diameter in the direction perpendicular to the maximum diameter. A filler having a ratio of a major axis to a minor axis of 2 or more is defined as a flat filler. In this way, 10 flat fillers are selected, the ratio of each major axis to the minor axis is calculated, and the average value of these is used as the aspect ratio of the flat filler. The aspect ratios of other fillers are also obtained in the same manner.

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

The average particle size is the particle size (D50; the same applies hereinafter) at a cumulative volume of 50% in the volume-based particle size distribution. D50 can be measured by a laser diffraction type particle size distribution measuring device. Alternatively, the average particle size may be determined from the cross section of the dried conductive composition or its cured product (wiring pattern) in the thickness direction. For example, it can be obtained by calculating the particle size of a plurality of (for example, 10) flat fillers 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 defined as the particle size of the flat filler. The average particle size of the other fillers is also determined in the same manner.

The content of the conductive material is, for example, 30% by volume or more, 80, where the total amount of the epoxy resin including the flexible epoxy resin and the dicyclopentadiene type epoxy resin and the total of the amine curing agent and the conductive material is 100% by volume. It may be 50% by volume or less, and may be 50% by volume or more and 80% by volume or less. When the content of the conductive material is in the above range, the reliability of the electrical connection can be easily ensured.

The content (volume ratio) of the conductive material can be calculated by considering the specific gravity of each epoxy resin, amine curing agent and conductive material. The content of the conductive material may be determined from the cross section of the dried conductive composition or its cured product (wiring pattern) in the thickness direction. For example, the SEM image or TEM image obtained as described above is divided into an organic component and a conductive material and binarized. The area ratios occupied by the organic component and the conductive material in the observation field of view of the binarized image are calculated respectively. The volume ratio (content) of the conductive material may be calculated by regarding these area ratios as the volume ratios of 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 them, from the viewpoint of conductivity, the flat filler preferably contains silver.

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

E. In addition, a solvent (solvent), a catalyst, a chain extender, a binder, a coupling agent, a conductive auxiliary agent, an inorganic filler, an organic filler and the like may be further added to the conductive composition.

The solvent is appropriately used for adjusting the viscosity of the conductive composition. Examples of the catalyst include tin-based catalysts, amine-based catalysts, organometallic compound-based catalysts and the like.

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

The binder is not particularly limited, and a known binder can be used. As the binder, a polymer having a high stretch ratio and containing no unsaturated bond in the molecule is preferable. Specific examples thereof include urethane resin, urethane rubber, acrylic resin, acrylic rubber, butyl rubber, chlorosulphonized rubber, fluororubber, and silicone. The urethane resin and urethane rubber may be 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 the present embodiment includes a stretchable base material, a wiring pattern formed on the surface of the stretchable base material, and a circuit member including electrodes connected to the wiring pattern. The wiring pattern includes a cured product of the above conductive composition. Therefore, when the base material expands and contracts, the wiring pattern deforms following the elastic base material, and the disconnection of the wiring pattern itself and the peeling of the base material and the cured product are suppressed. Further, at least a part of the electrodes is embedded in a stretchable wiring pattern. That is, the bottom surface of the electrode is in contact with the wiring pattern, and at least a part of the side surface is also in contact with the wiring pattern. Therefore, even when the base material expands and contracts, peeling between the cured product and the circuit member is suppressed. Therefore, the electronic device according to the present embodiment has high connection reliability while being flexible and / or stretchable.

Electronic devices perform electrical input / output, calculation, communication, and the like. The electronic device according to the present embodiment is particularly suitable as a wearable device used in close proximity to or in close contact with the body. Such wearable devices are used, for example, by being attached to clothes by sewing or heat bonding, 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 formed of different elastic materials, the stress applied to each material due to the expansion and contraction of the base material and the stress remaining on each material remain. The stress is different. Therefore, the electrical characteristics and wearing feeling of the electronic device are likely to deteriorate. In the electronic device according to the present embodiment, since the wiring pattern also functions as a joining material, 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 a main part 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 conductive composition. At least a part of the electrode 31 is buried in the wiring pattern 20. That is, at least a part of the bottom surface 31a and the side surface 31b of the electrode 31 is in contact with the wiring pattern 20.

The base material is not particularly limited. As the base material, in addition to conventionally known glass substrates, resin substrates, ceramic substrates, silicon substrates and the like used as wiring boards, elastic and / or flexible substrates such as flexible substrates and stretchable substrates can be used. Can be mentioned. The conductive composition according to this embodiment is also suitable for other stretchable and / or flexible substrates. These stretchable and / or flexible 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 non-woven fabrics, rubber, resin films and the like. 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 cupra; natural fibers such as cotton, linen, wool and silk; and composite fibers thereof. You can go out. The rubber may include styrene butadiene rubber, butadiene rubber, chloroprene rubber, isoprene rubber, isoprene isoprene rubber, ethylene propylene rubber, acrylonitrile butadiene rubber, silicone rubber, fluororubber, acrylic rubber, urethane rubber and the like. The resin film may contain, 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, it can be evaluated as a stretchable base material when the elongation at break measured according to JIS K 7126 or JIS K 7127 is 3% or more.

When the base material is a fiber structure, when the tensile strength and elongation rate measured according to the JIS L 1096 A method (strip method) is 3% or more, it is considered to be a stretchable base material. Can be evaluated.

The thickness of the stretchable base material is not particularly limited, and may be appropriately set according to the intended use.

The electronic device can be manufactured, for example, by the following method.
The electronic device according to the present embodiment is (1) conductive including a flexible epoxy resin containing an aromatic ring structure, a dicyclopentadiene type epoxy resin, an amine curing agent, and a filler having an aspect ratio of 2 or more. A step (S1) of preparing a conductive composition containing a conductive material, (2) a step of applying the conductive composition on a stretchable substrate (S2), and (3) a applied conductive composition. The step (S3) of mounting the circuit member on the elastic base material so that the electrodes of the circuit member come into contact with each other, and the wiring containing the cured product of the conductive composition by heating the applied conductive composition. It is manufactured by a method comprising a step of forming a pattern (S4). FIG. 3 is a flowchart showing a method of manufacturing an electronic device according to the present embodiment.

(1) Preparation Step of Conductive Composition In the conductive composition, the above-mentioned conductive material, flexible epoxy resin, dicyclopentadiene type epoxy resin, amine curing agent and other additives are mixed, for example, with a mixer or the like. Prepared by

(2) Coating Step of Conductive Composition The method of applying the conductive composition to the substrate is not particularly limited. Examples of the coating method include a coating method using an applicator, a wire bar, a comma roll, a gravure roll and the like: a printing method using a screen, a flat plate offset, a flexo, an inkjet, a stamping, a dispenser and the like.

The amount of the conductive composition applied is not particularly limited, and may be appropriately set according to the application of the electronic device, the average particle size of the conductive material, the circuit member to be mounted, and the like. In order to facilitate the burial of the electrode, a thick conductive composition may be applied to the portion in contact with the electrode.

(3) Mounting Step of Circuit Member The conductive composition before heating applied to the stretchable base material has fluidity and tackiness. Therefore, when the circuit member is mounted on the conductive composition, at least a part of the electrodes of the circuit member is buried in the conductive composition and adheres to the conductive composition in that state.

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, each epoxy resin reacts with the amine curing agent. As a result, a wiring pattern (cured product) is formed while at least a part of the electrode is buried, and the electrode and the wiring pattern are connected to each other. That is, the wiring pattern is not only the wiring of the electronic device but also the joining 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 joining. Therefore, it is omitted to consider the compatibility of each material and the difference in physical properties between the materials, and the concern about peeling between the materials is also eliminated.

By the heating process, the wiring pattern is formed and the circuit member and the wiring pattern are electrically connected, so that the man-hours can be reduced and the productivity of the electronic device is improved. Furthermore, it can be expected that the manufacturing cost will be reduced by reducing the man-hours. Since the materials used are also limited, the manufacturing cost can be further reduced.

The heating temperature is appropriately determined according to the reaction temperature of each epoxy resin and the amine curing agent, the melting point of the base material, and the like. The heating temperature may be, for example, 100 ° C. to 150 ° C., and may be 110 ° C. to 140 ° C. The heating time is not particularly limited, but may be 60 minutes or less, 45 minutes or less, and 30 minutes or less.

[Examples 1 to 7, Comparative Examples 1 to 3]
Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to the following examples.

(I) Preparation of Conductive Composition Each component is mixed in the blending amount shown in Table 1, kneaded with a rotation / revolution mixer, and paste-like conductive compositions A1 to A7 and Comparative Examples of Examples 1 to 7. Conductive compositions B1 to B3 of 1 to 3 were prepared.

The components used in Examples 1 to 7 and Comparative Examples 1 to 3 are as follows.

1st epoxy resin (flexible epoxy resin): aliphatic modified bisphenol F type epoxy resin, epoxy equivalent about 1000, product name: jERYX7110B80, 2nd epoxy resin (dicyclopentadiene type epoxy resin) manufactured by Mitsubishi Chemical Co., Ltd .: Epoxy equivalent about 165, product name: EP-4088L, manufactured by ADEKA Co., Ltd. Third epoxy resin (bisphenol A type epoxy resin): epoxy equivalent about 190, product name: jER828, manufactured by Mitsubishi Chemical Co., Ltd. Hardener (amine curing) Agent): ST12 (metaxylylene diamine), manufactured by Mitsubishi Chemical Co., Ltd. Conductive material: flaky silver powder, product name: AgC-2351, average particle size (D50) 6.95 μm, Fukuda Metal Epoxy Co., Ltd. Made, Aspect ratio: 2.2 or more

(Ii) Preparation of Electronic Equipment The prepared conductive composition was applied on an elastic base material (urethane film, manufactured by Nihon Matai Co., Ltd., Esmer URS) in the pattern shown in FIG.

The conductive composition was formed by printing using a mesh screen. The wiring pattern 20 includes four wirings 21 having a width of 0.3 mm extending in the first direction, four terminal portions 22A to 22D having a size of 2.0 mm × 1.0 mm for measuring resistance values, and two 1s. It is composed of a chip component mounting portion 23 having a size of 0.0 mm × 1.25 mm. The total length of the wiring pattern 20 in the first direction is 25 mm. A chip component (0Ω chip resistor) 30 (2125 size) is mounted so as to straddle the two mounting portions 23 of the coating film of the conductive composition before curing, and the two electrodes of the chip component are respectively attached. It was brought into contact with the mounting portion 23. In this state, heating was performed at 120 ° C. for 30 minutes to form a wiring pattern 20 and mount a circuit member to obtain an electronic device.

[evaluation]
The following evaluations were performed on the conductive composition, wiring pattern and electronic device.
(1) Volume resistance value After applying the prepared conductive composition on a glass plate, it is heated under the above conditions to form a 60 mm × 10 mm rectangular film (cured product of the conductive composition) on the glass plate. It was formed and the resistance value in the longitudinal direction of the film was measured. Using the measured resistance value, the volume resistivity value (specific resistance value) of the film was calculated by the following formula.

Volume resistance value R = (resistance value x film thickness x length in the lateral direction of the film / length in the longitudinal direction of the film) x 100

The resistance value was measured by the 4-terminal method according to JIS K 7194. The measurement temperature was 25 ° C., and the correction of the resistance value by the temperature was omitted. The following resistance values were also measured in the same manner.

The volume resistance value R was evaluated by the following index.
⊚: less than 1.0 mΩ ・ cm ○: 1.0 to 2.0 mΩ ・ cm
×: Larger than 2.0 mΩ · cm

(2) Mechanical properties A conductive composition is applied onto a silicone sheet using a dumbbell-shaped printing mask, and heated at 120 ° C. for 30 minutes to obtain a dumbbell-shaped No. 6 test piece conforming to JIS K 6251. It was prepared and subjected to a tensile test. As the test device, A & D Co., Ltd.'s Tensilon universal material tester RTC series was used. The maximum stress and the elongation (strain) at the maximum point were measured.

The maximum stress was evaluated by the following indexes.
⊚: greater than 4.5 N / mm ² ○: 3.0 to 4.5 N / mm ²
×: Less than 3.0 N / mm ²

Growth was evaluated using the following indicators.
⊚: greater than 3.5% ○: 3.0 to 3.5%
×: Less than 3.0%

(3) Rate of increase in resistance of cured product at 5% elongation (ΔRA)
The predetermined terminals of the tester are connected to the four terminal portions 22A to 22D of the wiring pattern 20 of the electronic device obtained in (ii) above, and the initial resistance value ER ₀ is set at 25 ° C. by the same four-terminal method as described above. It was measured. The internal resistance of the chip resistor is added to this resistance value.

Next, both ends of the urethane film are sandwiched and the wiring pattern is stretched in the first direction (left-right direction in FIG. 4), and the electric resistance value ER between the wiring patterns when the stretch ratio of the urethane film is 5% is 25 ° C. The rate of increase ΔRA of the resistance value from the initial resistance value ER _{0 was calculated.} At this time, if the rate of increase is less than 15%, it can be said that the rate of elongation is 5% or more when the electric resistance value of the cured product of the conductive composition after stretching reaches 115% before stretching.

The stretch rate of the urethane film can be regarded as the stretch rate of the wiring pattern.

ΔRA was evaluated by the following indicators.
⊚: less than 10% ○: 10 to 15%
×: Greater than 15%

(4) Rate of increase in resistance of cured product during stretching ΔRB
Of the four terminal portions of the wiring pattern 20 of the electronic device obtained in (ii) above, the predetermined terminals of the tester are connected to the two terminal portions 22A and 22B, and the initial resistance value PR ₀ is set by the two-terminal method. It was measured at 25 ° C. The internal resistance of the chip resistor is not added to this resistance value.

Next, both ends of the urethane film are sandwiched and the wiring pattern is stretched in the first direction (left-right direction in FIG. 4), and the electric resistance value PR between the wiring patterns when the stretch ratio of the urethane film is 5% is 25 ° C. The rate of increase ΔRB of the resistance value from the initial resistance value PR _{0 was calculated.} At this time, if the rate of increase is less than 15%, it can be said that the rate of elongation is 5% or more when the electric resistance value of the cured product of the conductive composition after stretching reaches 115% before stretching.

ΔRB was evaluated by the following indexes.
⊚: less than 15% ○: 15-20%
×: Greater than 20%

The cured products of the conductive compositions prepared in Examples 1 to 7 had low initial resistance values and high evaluations of resistance increase rates ΔRA and ΔRB. This indicates that the resistance value is unlikely to increase even if the cured product is stretched. The resistance increase rate ΔRA is also highly evaluated, and the electrical resistance of the chip is kept small even when the stretchable base material is stretched. Since the conductive composition has a high tack property, it can be seen that the chip is firmly adhered to the cured product. Looking at the electronic devices manufactured when evaluating the resistance increase rate ΔRA, a part of the electrodes was buried in the cured product.

In Comparative Example 1 in which the conductive composition did not contain the dicyclopentadiene type epoxy resin, the volume resistance was large and the rate of increase in resistance during elongation was also large. It is considered that this is because the shrinkage of the conductive composition during curing is small and it is difficult to obtain contact points between the conductive materials. Further, in Comparative Example 2 in which the conductive composition did not contain the flexible epoxy resin, the elongation was very small in the tensile test, and the resistance increase rate at the time of elongation could not be measured. Further, in Comparative Example 3 in which the bisphenol A type epoxy resin was used instead of the dicyclopentadiene type epoxy resin, the resistance increase rate at the time of elongation was considerably increased. It is considered that this is because the mechanical strength of the cured product was insufficient and the wiring pattern was finely broken, and the adhesion between the wiring pattern and the chip component was reduced.

The conductive composition of the present invention has conductivity and tackiness, and the cured product thereof has conductivity and elasticity, and is excellent in flexibility and toughness. Therefore, the conductive composition of the present invention can be preferably used as a material and a joining material for forming wiring of an electronic device having a stretchable base material. Since the electronic device of the present invention has elasticity, flexibility, and high connection reliability, it is suitably used for products in the field of high-performance electronics 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)
21 Wiring 22A to 22D Terminal part 23 Mounting part 30 Circuit member (chip part)
31 Electrode 31a Bottom surface 31b Side surface

Claims (12)

Flexible epoxy resin containing an aromatic ring structure,
Dicyclopentadiene type epoxy resin and
Amine hardener and
Including conductive materials,
The conductive material is a conductive composition for a wiring pattern, which contains a filler having an aspect ratio of 2 or more. The conductive composition for a wiring pattern 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 wiring pattern. The flexible epoxy resin is at least one selected from the group consisting of an aliphatic modified epoxy resin, a polyether-modified epoxy resin, a urethane-modified epoxy resin, and a rubber-modified epoxy resin, according to claim 1 or 2. A conductive composition for wiring patterns. Any one of claims 1 to 3, wherein the flexible epoxy resin has at least one selected from the group consisting of an alkylene group having 1 to 8 carbon atoms and a polyoxyalkylene group having 1 to 8 carbon atoms. The conductive composition for the wiring pattern described in 1. The conductive composition for a wiring pattern according to any one of claims 1 to 4, wherein the epoxy equivalent of the flexible epoxy resin is 800 g / eq or more and 1400 g / eq or less. The conductive composition for a wiring pattern according to any one of claims 1 to 5, wherein the amine curing agent is at least one selected from the group consisting of aliphatic polyamines and aromatic polyamines. The conductivity for a wiring pattern according to any one of claims 1 to 6, wherein the amount of the dicyclopentadiene type epoxy resin is 30 parts by mass or more and 110 parts by mass or less with respect to 100 parts by mass of the flexible epoxy resin. Sex composition. Any of claims 1 to 7, wherein the amount of the amine curing agent is 20 parts by mass or more and 60 parts by mass or less with respect to 100 parts by mass of the total amount of the flexible epoxy resin and the epoxy resin containing the dicyclopentadiene type epoxy. The conductive composition for the wiring pattern according to item 1. The wiring pattern according to any one of claims 1 to 8, wherein the elongation at the maximum stress point is 3% or more in a tensile test according to JIS K 6251 of the cured product of the conductive composition. Conductive composition. When the cured product of the conductive composition is stretched in the first direction, the electrical resistance value of the cured product after stretching at 25 ° C. is the electrical resistance value of the cured product before stretching at 25 ° C. in the first direction. The conductive composition for a wiring pattern according to any one of claims 1 to 9, wherein the elongation rate of the cured product when it reaches 115% is 5% or more. With elastic base material
The wiring pattern formed on the surface of the elastic base material and
A circuit member including electrodes connected to the wiring pattern, and
The wiring pattern includes a cured product of the conductive composition according to claim 1.
An electronic device in which at least a part of the electrodes is embedded in the wiring pattern. The step of preparing the conductive composition according to claim 1 and
The step of applying the conductive composition on the stretchable base material and
A step of mounting the circuit member on the stretchable base material so that the coated conductive composition and an electrode of the circuit member come into contact with each other.
Manufacture of an electronic device including a step of heating the applied conductive composition to form a wiring pattern containing a cured product of the conductive composition, and connecting the electrode and the wiring pattern. Method.

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