JP6444734B2 - Connectors and flexible wiring boards - Google Patents

Description

  The present invention relates to a connector and a flexible wiring board.

  Conventionally, various printed wiring boards of single side, double side or multilayer have been widely used in the field of industrial equipment or consumer equipment. In electronic devices, only one printed wiring board is rarely used. For example, a plurality of printed wiring boards divided by function are used. Usually, a plurality of wiring boards are connected by various connectors.

  Flexible wiring boards are composed of base materials such as polyimide, conductor materials, adhesives and coverlays, and are incorporated into mobile phones, video cameras and laptop computers in recent years as electronic devices become lighter and thinner. Yes. Since a flexible wiring board has low rigidity, it is generally mounted in a state where a reinforcing member (reinforcing plate) is attached to a mounting portion of an electronic component and a connector portion (for example, Patent Document 1).

  As the reinforcing plate of the flexible wiring board, a metal plate such as a polyester film, a stainless steel plate and an aluminum plate, ceramics, a glass cloth base material epoxy resin laminated plate, and the like are used. However, a thick polyimide film excellent in punching workability, heat resistance and workability has become the mainstream of the connector reinforcing plate. A reinforcement board is affixed on the base material on the surface side opposite to the wiring terminal arrange | positioned at one surface of a base material via an adhesive agent. (For example, refer nonpatent literature 1).

JP 2005-51177 A

Electronic materials, October 2004 issue

  However, in a connector having a polyethylene terephthalate film or a polyimide film described in Patent Document 1 and Non-Patent Document 1 as a reinforcing plate, it may not be possible to smoothly insert the connector into the mating connector.

  Therefore, an object of the present invention is to provide a connector having a smooth insertion property and a flexible wiring board provided with the connector.

  The present invention relates to an insertion-side connector used to connect a wiring by being inserted into a mating connector. The connector according to the present invention is flexible on the side opposite to the flexible base, the wiring terminal disposed on one side of the flexible base, and the wiring terminal of the flexible base. And a resin layer including a resin that is disposed on an end portion of the substrate and has a facing surface facing the flexible substrate. The end of the resin layer on the distal end side of the connector may have a surface forming a convex curved surface that curves from the facing surface toward the flexible substrate.

  The end of the resin layer on the distal end side of the connector has a surface forming a convex curved surface that curves from the facing surface facing the flexible substrate toward the flexible substrate. The feeling of resistance when the connector is inserted into the mating connector is reduced, and a sufficiently smooth insertion property can be obtained.

  The resin layer may further contain an inorganic filler. The inorganic filler may be silica particles, for example. The content of the inorganic filler in the resin layer may be 30 to 70% by volume with respect to the volume of the resin layer.

  The flexible substrate may be a polyester substrate or a polyimide substrate. The thickness of the flexible substrate may be 75 μm or less.

  The initial tensile elastic modulus at 25 ° C. of the resin layer may be 0.3 to 3.0 GPa. The resin layer may have a thickness of 50 to 500 μm.

  The present invention also relates to a flexible wiring board comprising the above connector, a circuit flexible substrate, and a circuit provided on the circuit flexible substrate and connected to a wiring terminal of the connector. The flexible substrate for the connector and the flexible substrate for the circuit may be the same substrate, or the flexible substrate for the connector and another flexible substrate for the circuit It may be connected.

  ADVANTAGE OF THE INVENTION According to this invention, the connector which has smooth insertion property, and a flexible wiring board provided with the same can be provided.

It is a mimetic diagram showing one embodiment of a connector. FIG. 2 is an end view taken along line II-II ′ of the connector shown in FIG. 1. It is an end view which shows the modification of the shape of a resin layer. It is an end view which shows other embodiment of a connector. It is an end view which shows other embodiment of a connector. It is an end view which shows other embodiment of a connector. It is process drawing which shows one Embodiment of the manufacturing method of a connector. It is a schematic explanatory drawing which shows the method of the durability test of a connector. It is an optical microscope photograph of the section of a connector. It is a scanning electron micrograph of the cross section of a resin layer.

  Hereinafter, preferred embodiments of the present invention will be described in detail. However, the present invention is not limited to the following embodiments. All the configurations described in the present specification can be arbitrarily combined without departing from the spirit of the present invention. For example, the upper and lower limits of the numerical ranges described in this specification, and numerical values arbitrarily selected from the numerical values described in the examples are used as the upper and lower limits, and the numerical ranges relating to various characteristics are defined. can do.

  FIG. 1 is a schematic view showing an embodiment of a connector. FIG. 2 is an end view taken along the line II-II 'of FIG. A connector 10 shown in FIGS. 1 and 2 includes a flexible substrate 2, a wiring terminal 1 disposed on one surface side of the flexible substrate 2, and a wiring terminal 1 of the flexible substrate 2. Is composed of a resin layer 3 disposed on the end of the flexible substrate 2 on the opposite surface side. The rigidity of the flexible substrate 2 is increased in the portion in contact with the resin layer 3 as compared with the case where the resin layer 3 is not formed. The connector 10 is a plug-in side connector that is used to connect a wiring by being plugged into a mating connector. By inserting the tip of the connector 10 into the mating connector, for example, a state in which transmission is possible by mechanical and electrical (electronic) connection is obtained. The connector 10 can be safely and easily detached and attached as necessary.

  In FIG. 2, the circuit flexible substrate 52 and the circuit 51 provided on the circuit flexible substrate 52 are shown together with the connector 10. The circuit 51 is connected to the wiring terminal 1 of the connector 10. The flexible wiring board 100 is configured by the connector 10, the circuit flexible substrate 52, and the circuit 51. The connector flexible substrate 2 and the circuit flexible substrate 52 may be the same single substrate or may be separate substrates connected to each other.

  The flexible substrate 2 is not particularly limited as long as it exhibits a foldable flexibility. From the viewpoint of toughness, the flexible substrate 2 is a polyester substrate (polyester film) or a polyimide substrate (polyimide film). The polyimide base material (polyimide film) may be sufficient from the point of toughness and heat resistance. The thickness of the flexible substrate 2 may be 75 μm or less from the viewpoint of bendability. The thickness of the flexible substrate 2 may be 10 μm or more.

  The wiring terminal 1 is a conductor layer formed from a conductor such as metal, for example. The thickness of the wiring terminal 1 may be 5 to 40 μm.

  The resin layer 3 usually contains a cured product of the curable resin composition as a resin. Details of the curable resin composition used to form the resin layer 3 will be described later.

  The resin layer 3 has a facing surface 6 facing the flexible substrate 2 as a surface located on the opposite side of the surface in contact with the flexible substrate 2. An end 3 a of the resin layer 3 on the distal end side of the connector 10 (side of the portion to be inserted into the mating connector) is curved from the facing surface 6 toward the flexible substrate 2 and directed toward the outside of the resin layer 3. It has the surface 7 which forms the convex curved surface which is convex. Since the surface 7 of the end portion 3a of the resin layer 3 forms a convex curved surface, the resistance at the time of inserting into the mating connector is reduced, and a smooth insertion property is obtained.

  In the connector according to the present embodiment, the end of the resin layer 3 opposite to the tip of the connector 10 also has a surface curved from the facing surface 6 toward the flexible substrate 2 to form a convex curved surface. Have. However, the surface of the end opposite to the tip of the connector 10 does not have to form a convex curved surface. Moreover, the edge part of the resin layer 3 of the side side of the connector 10 may have the surface which curves toward the flexible base material 2 from the opposing surface 6, and forms the convex curve.

  The surface of the end portion 3a of the resin layer 3 (the surface of the portion that is not in contact with the flexible base material 2) only needs to form a convex curved surface. The edge part 3a of the resin layer 3 may have the surface which forms the plane which follows the perpendicular of the main surface of a flexible base material like embodiment of FIG. (A), (b) of FIG. 3 is an end view which shows the modification of the shape of a resin layer. In the embodiment shown in FIG. 3B, the entire side surface of the end 3a of the resin layer 3 on the distal end side of the connector forms a convex curved surface.

  The thickness of the resin layer 3 may be 50 to 500 μm, 70 to 300 μm, or 75 to 200 μm. When the thickness of the resin layer 3 is within these ranges, the resin layer can be easily formed. In addition, since the resin layer 3 is not easily bent, particularly excellent connector shape retention is obtained. The length of the resin layer 3 in the connector insertion direction may be, for example, 3 to 30 mm. The resin layer 3 may be provided over the entire width direction of the flexible base material, or may be provided only in a partial region in the width direction as long as necessary rigidity is obtained.

  The initial tensile elastic modulus at 25 ° C. of the resin layer 3 may be 0.3 to 3.0 GPa, 0.5 to 2.5 GPa, or 1.0 to 2.2 GPa. When the initial tensile elastic modulus of the resin layer 3 is within these ranges, cracks in the resin layer 3 are unlikely to occur, and a further excellent insertion property can be obtained.

  The initial tensile elastic modulus at 25 ° C. of the resin layer 3 is obtained from the maximum value of the slope of the tangent of the stress-displacement curve obtained when a tensile stress is applied to the strip-shaped resin layer at a tensile speed of 50 mm / min. Can do. The strip-shaped resin layer can be prepared, for example, by cutting out from a plate-shaped resin layer formed by curing a curable resin composition described below. Details of the method of measuring the initial tensile elastic modulus will be described in detail in Examples described later.

  The initial tensile elastic modulus within the above numerical range can be achieved, for example, by a resin layer further containing an inorganic filler in addition to the resin.

  The inorganic filler in the resin layer 3 may be composed of one kind of particle or may be composed of a combination of two or more kinds of particles. The average particle diameter of the inorganic filler may be 1 to 100 μm, 1 to 50 μm, 1 to 20 μm, or 1.5 to 10 μm. The inorganic filler may be a mixture of plural kinds of fillers having different average particle diameters. Thereby, the space filling rate by an inorganic filler can be raised.

  The average particle diameter of the inorganic filler is an arithmetic average of the particle diameters (maximum diameters) of the plurality of inorganic fillers observed by observing the resin layer 3 with a scanning electron microscope at a magnification of, for example, 1000 times. . The number of inorganic fillers whose particle diameter is measured to determine the average particle diameter is, for example, 50 or more.

  The content of the inorganic filler in the resin layer 3 is 30 to 70% by volume, 40 to 65% by volume, or 50 to 65% by volume with respect to the volume of the resin layer 3 in terms of the strength of the resin layer and the initial tensile elastic modulus. There may be. The content of the inorganic filler in the resin layer 3 is 40 to 85% by mass, 45 to 80% by mass, or 50 to 80% by mass with respect to the mass of the resin layer 3 in terms of the strength of the resin layer and the initial tensile elastic modulus. %.

  The inorganic filler may contain silica particles. The silica particles are not particularly limited, and may be, for example, spherical silica, crushed silica refined by pulverization, dry silica, or wet silica.

  When spherical silica particles are selected, the surface of the resin layer 3 becomes smooth, and a smooth insertion property is obtained. In addition, more excellent wear resistance and crack resistance can be obtained.

  The spherical silica particles can be obtained by, for example, a sol-gel method. The average particle diameter of the spherical silica particles may be 0.05 to 50 μm, 0.1 to 50 μm, 0.2 to 30 μm, or 0.5 to 20 μm.

  The spherical silica particles need only have a shape close to a sphere (see JIS Z2500: 2000), and are not necessarily spherical. The ratio of the major axis (DL) to the minor axis (DS) of the particles (DL) / (DS) (sometimes referred to as spherical coefficient or sphericity) may be 1.0 to 1.2. .

  As spherical silica particles, MSR-2212, MSR-SC3, MSR-SC4, MSR-3512, MSR-FC208 (trade name, manufactured by Tatsumori Corporation), Excelica (trade name, manufactured by Tokuyama Corporation), SO-E1 , SO-E2, SO-E3, SO-E5, SO-E6, SO-C1, SO-C2, SO-C3, SO-C5, SO-C6, SO-25R ), FB-5D, FB-12D, FB-20D, FB-105, FB-940, FB-9454, FB-950, FB-105FC, FB-870FC, FB-875FC, FB-9454FC, FB-950FC, FB-105FD, FB-970FD, FB-975FD, FB-950FD, FB-300FD, FB-300FD, FB-400 D, FB-400FE, FB-7SDC, FB-5SDC, FB-3SDC (or more, Denki Kagaku Kogyo trade names Co., Ltd.), and the like.

  Silica particles may be surface-treated. Examples of the surface treating agent used for surface treating silica particles include vinyltrimethoxysilane, vinyltriethoxysilane, 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, and 3-glycidoxypropylmethyldimethoxy. Silane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropyltriethoxysilane, p-styryltrimethoxysilane 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-acryloxypropyltrimeth Sisilane, n-2- (aminoethyl) -3-aminopropylmethyldimethoxysilane triethoxysilane, n-2- (aminoethyl) -3-aminopropyltrimethoxysilane, n-2- (aminoethyl) -3- Aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-triethoxysilyl-N- (1,3-dimethyl-butylidene) propylamine, N-phenyl-3-aminopropyl Trimethoxysilane, N- (vinylbenzyl) -2-aminoethyl-3-aminopropyltrimethoxysilane hydrochloride, 3-ureidopropyltriethoxysilane, 3-mercaptopropylmethyldimethoxysilane, 3-mercaptopropyltrimethoxysilane Bis (triethoxysilane) Propyl) tetrasulfide, 3-isocyanatopropyltriethoxysilane, polycondensate of dimethylsilane, polycondensate of diphenylsilane, and copolycondensate of dimethylsilane and diphenylsilane 2 or more types. Among these, N-phenyl-3-aminopropyltrimethoxysilane can be selected from the viewpoint of compatibility with the acrylic resin.

  The resin layer 3 may contain fumed silica as an inorganic filler. The fumed silica may be used to control the printability of a liquid composition to be described later used for forming the resin layer 3. Commercially available fumed silica includes hydrophilic silica such as Aerosil 50, 90G, 130, 200, 300, and 380, and R972, R972CF, R972V, R974, R9765, R140, RX50, NAX50, NX90G, RX200, RX300. , R812, R8200, and R200H, etc., and hydrophobic silica (trade name, Nippon Aerosil Co., Ltd.).

  FIG. 4 is an end view showing another embodiment of the connector. The flexible substrate 2 of the connector 10 shown in FIG. 4 includes a flexible substrate 40 and a cover film 41 provided on the main surface of the flexible substrate 40 on the resin layer 3 side. The cover film 41 can function as, for example, a film for protecting the wiring terminal 1 or a solder resist. The cover film 41 may be provided on the main surface of the flexible substrate 40 on the wiring terminal 1 side, or may be provided on both surfaces of the flexible substrate 40. As the flexible substrate 40, the same base material as the flexible base material 2 can be used.

  The cover film 41 can be formed using various thermosetting or photosensitive resin films. As a commercial product of the resin film used for forming the cover film 41, for example, Nikaflex CTSV, CISV, CISA, CKSE, CISG, CKSG (above, Nikkan Kogyo Co., Ltd. trade name), Piralux PC1000 (above , DuPont Co., Ltd. trade name), Raytec FR-7025, FR-7038, FR-7050, FZ-2520G, FZ-2525G, FZ-2530G, FZ-2535G (above, trade names made by Hitachi Chemical Co., Ltd.). It is done.

  FIG. 5 is also an end view showing another embodiment of the connector. The flexible base 2 of the connector shown in FIG. 5 is composed of a flexible substrate 40, a non-wiring metal layer 42 and a cover film 41 provided in this order on the main surface of the flexible substrate 40 on the resin layer 3 side. . As shown in FIG. 6, the flexible base 2 is composed of a flexible substrate 40 and a non-wiring metal layer 42 provided on the main surface of the flexible substrate 40 on the resin layer 3 side, and has a cover film 41. You don't have to.

  In the connector 10, for example, the step of providing the wiring terminal 1 on one surface side of the flexible base material 2 and the resin layer 3 on the surface side opposite to the wiring terminal 1 of the flexible base material 2 are formed. And a process including the steps. The wiring terminal 1 may be provided before the resin layer 3 is formed, or may be provided after the resin layer 3 is formed.

  The resin layer 3 can be formed, for example, by a method including a step of applying a curable resin composition and a liquid composition (liquid ink) containing an inorganic filler as necessary to a flexible substrate. According to the method using such a liquid composition, a rigid resin layer can be formed by a simple process. The thickness of the resin layer can be easily and precisely controlled by a method such as printing. Therefore, products with different thickness specifications can be efficiently manufactured. In addition, according to a method such as printing, a resin layer can be formed very efficiently at any position on the flexible substrate without manual operation. Furthermore, a resin layer excellent in reflow resistance can be formed.

  FIG. 7 is a process diagram showing an embodiment of a method for forming the resin layer 3 using the liquid composition 5. First, a liquid composition 5 containing a curable resin composition and a metal mask 4 having an opening 4a are prepared (see FIG. 7A). The liquid composition 5 may contain a solvent in which the curable resin composition is dissolved or dispersed.

  Next, the liquid composition 5 is filled in the opening 4a of the metal mask 4 and printed on the flexible substrate 2 (see FIG. 7B). The method of applying the liquid composition can be appropriately selected from screen printing, bar coater and the like in addition to printing using a metal mask.

  If necessary, the solvent is removed from the coated liquid composition 5 by a method such as heating to form an uncured resin layer 3 (see FIG. 7C). By curing the curable resin composition in the uncured resin layer 3, the resin layer 3 containing a cured product of the curable resin composition as a resin is formed. Curing of the curable resin composition can be performed, for example, by heating or light irradiation. The metal mask 4 can be removed, for example, after application of the curable resin composition. According to the method in which the liquid composition is applied and cured, it is possible to easily form a resin layer having an end portion on which a convex curved surface is formed.

  The removal (drying) and curing temperature of the solvent may be 50 to 250 ° C, 80 to 200 ° C, or 100 to 190 ° C.

  For example, the resin layer 3 can be disposed on the end of the flexible substrate 2 by punching the flexible substrate 2 (see FIG. 7D).

  The liquid composition 5 may contain, for example, a curable resin composition, the above-described inorganic filler, and a solvent. A curable resin composition is comprised from components other than a solvent and an inorganic filler among the liquid compositions 5, for example, contains the curable resin hardened | cured with a heat | fever and / or light, and a thermoplastic resin. The curable resin includes, for example, one kind or two or more kinds of epoxy resins. A thermoplastic resin contains 1 type, or 2 or more types of acrylic resins (polymer of an acrylic monomer), for example.

  The epoxy resin is, for example, a polyglycidyl ether obtained by reacting a polyhydric phenol such as bisphenol A, a novolac type phenol resin and an orthocresol novolac type phenol resin, or a polyhydric alcohol such as 1,4-butanediol and epichlorohydrin. Polyglycidyl ester obtained by reacting polybasic acid such as phthalic acid and hexahydrophthalic acid with epichlorohydrin, N-glycidyl derivative of compound having amino group, amide group, or heterocyclic nitrogen base, and alicyclic ring Selected from the formula epoxy resins. Since it has high compatibility with the acrylic resin, a biphenyl aralkyl type epoxy resin can be selected.

  The curable resin may contain an epoxy resin curing agent. The curing agent can be selected from, for example, dicyandiamide, diaminodiphenylmethane, diaminodiphenylsulfone, phthalic anhydride, pyromellitic anhydride, and polyfunctional phenols (phenolic resins) such as phenol novolac and cresol novolac.

  The phenol resin may contain a phenol resin of a phenol type, a bisphenol A type, a cresol novolac type, or an aminotriazine novolac type. One or both of the cresol novolak type and aminotriazine novolak type phenol resins can be selected from the viewpoint of compatibility with the acrylic resin. The aminotriazine novolac type phenolic resin has a structural unit represented by the following structural formula (I).

[In formula (I), R shows a hydrogen atom or a methyl group, and n shows the integer of 1-30. ]

  The curable resin may contain a high molecular weight component for the purpose of improving the heat resistance of the resin layer. However, the molecular weight of the component constituting the curable resin is usually 3000 or less.

  The curable resin may contain an accelerator for the purpose of accelerating the curing reaction. The kind and compounding quantity of an accelerator are not specifically limited. For example, one or more selected from imidazole compounds, organophosphorus compounds, tertiary amines, quaternary ammonium salts and the like are used.

  The acrylic resin is generally a copolymer containing a polymerizable monomer containing two or more acrylic monomers having an acrylic group or a methacryl group as a monomer unit. The acrylic resin can be manufactured at low cost by selecting various combinations from commercially available acrylic monomers according to desired properties. The acrylic resin is excellent in that it can easily dry the printed liquid composition because it has good solubility in a low-boiling ketone solvent.

The acrylic monomer used for producing the acrylic resin is not particularly limited. Examples of the acrylic resin include acrylonitrile, methyl acrylate, ethyl acrylate, n-propyl acrylate, i-propyl acrylate, n-butyl acrylate, i-butyl acrylate, t-butyl acrylate, pentyl acrylate, N-hexyl acrylate, 2-ethylhexyl acrylate, n-octyl acrylate, dodecyl acrylate, octadecyl acrylate, butoxyethyl acrylate, phenyl acrylate, benzyl acrylate, naphthyl acrylate, cyclohexyl acrylate, isobornyl acrylate , Norbornylmethyl acrylate, tricycloacrylate [5.2.1. ^O2,6 ] dec-8-yl (dicyclopentanyl acrylate), tricycloacrylate [5.2.1. ^O2,6 ] dec-4-methyl, adamantyl acrylate, isobornyl acrylate, norbornyl acrylate, tricyclohexyl acrylate [5.2.1. ^O2,6 ] dec-8-yl, tricyclohexyl acrylate [5.2.1. ^O2,6 ] dec-4-methyl, and acrylic esters such as adamantyl acrylate, and ethyl methacrylate, n-propyl methacrylate, i-propyl methacrylate, n-butyl methacrylate, i-butyl methacrylate T-butyl methacrylate, pentyl methacrylate, n-hexyl methacrylate, 2-ethylhexyl methacrylate, n-octyl methacrylate, dodecyl methacrylate, octadecyl methacrylate, butoxyethyl methacrylate, phenyl methacrylate, naphthyl methacrylate, Cyclopentyl methacrylate, cyclohexyl methacrylate, methyl cyclohexyl methacrylate, tricyclohexyl methacrylate, norbornyl methacrylate, norbornyl methyl methacrylate, isobornyl methacrylate, Acrylic acid bornyl, menthyl methacrylate, adamantyl methacrylate, tricyclo [5.2.1. ^O2,6 ] dec-8-yl (dicyclopentanyl methacrylate) and tricyclomethacrylate [5.2.1. One or two or more acrylic monomers selected from methacrylic acid esters such as O ^2,6 ] deca 4-methyl are included as monomer units.

  From the viewpoint of heat resistance and adhesiveness of the resin layer according to this embodiment, the acrylic monomer constituting the acrylic resin may contain a monomer having a functional group. The monomer having a functional group includes at least one functional group selected from the group consisting of a carboxyl group, a hydroxyl group, an acid anhydride group, an amino group, an amide group, and an epoxy group, and at least one polymerizable carbon-carbon 2. It may have a double bond. Specific examples of the monomer having a functional group include carboxyl group-containing monomers such as acrylic acid, methacrylic acid, and itaconic acid, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, and 2-hydroxypropyl acrylate. , 2-hydroxypropyl methacrylate and N-methylolmethacrylamide, hydroxyl group-containing monomers such as (o-, m-, p-) hydroxystyrene, acid anhydride group-containing monomers such as maleic anhydride, diethylaminoacrylate Amino group-containing monomers such as ethyl and diethylaminoethyl methacrylate, and glycidyl acrylate, glycidyl α-ethyl acrylate, glycidyl α-n-propyl acrylate, acrylic acid-3,4-epoxybutyl, methacrylic acid-3, 4-epoxybutyl Acrylic acid-4,5-epoxypentyl, acrylic acid-6,7-epoxyheptyl, methacrylic acid-6,7-epoxyheptyl, acrylic acid-3-methyl-4-epoxybutyl, methacrylic acid-3-methyl- 3,4-epoxybutyl, 4-methyl-4,5-epoxypentyl acrylate, 4-methyl-4,5-epoxypentyl methacrylate, 5-methyl-5,6-epoxyhexyl acrylate, acrylic Acid-β-methylglycidyl, methacrylate-β-methylglycidyl, α-ethylacrylic acid-β-methylglycidyl, acrylate-3-methyl-3,4-epoxybutyl, methacrylate-3-methyl-3,4 -Epoxy butyl, 4-methyl-4,4-epoxy acrylate, 4-methyl-4,5-epoxy methacrylate Pentyl, methyl-5-acrylic acid, 6-epoxy-hexyl, and include epoxy group-containing monomers such as methacrylic acid methyl-5,6-epoxy-hexyl. These can be used alone or in combination of two or more.

  When the acrylic resin has a glycidyl group, the heat resistance of the resin layer is further enhanced. Therefore, the acrylic resin may contain glycidyl methacrylate or glycidyl acrylate as a monomer unit. Even if the content ratio of glycidyl methacrylate or glycidyl acrylate is 0.5 to 10% by mass, 1 to 8% by mass, or 2 to 5% by mass, based on the amount of all polymerizable monomers constituting the acrylic resin. Good.

  The acrylic resin may contain alkyl acrylate as a monomer from the viewpoint of adhesion between the flexible substrate and the resin layer. 1-12 or 2-10 may be sufficient as carbon number of the alkyl group of alkylacrylate. Based on the amount of all polymerizable monomers constituting the acrylic resin, the content ratio of the alkyl acrylate may be 50 to 99 mass%, 60 to 98 mass%, or 70 to 96 mass%. The alkyl acrylate is selected from, for example, ethyl acrylate and butyl acrylate.

  The acrylic resin may contain acrylonitrile or methacrylonitrile as a monomer unit from the viewpoint of toughness and adhesiveness. Even if the content ratio of acrylonitrile or methacrylonitrile is 0.5 to 10% by mass, 1 to 8% by mass, or 2 to 5% by mass, based on the amount of all polymerizable monomers constituting the acrylic resin. Good.

  The acrylic resin may further contain another monomer copolymerized with the acrylic monomer. Other monomers include, for example, 4-vinylpyridine, 2-vinylpyridine, α-methylstyrene, α-ethylstyrene, α-fluorostyrene, α-chlorostyrene, α-bromostyrene, fluorostyrene, chlorostyrene, bromostyrene Aromatic vinyl compounds such as methylstyrene, methoxystyrene, and styrene, and N-methylmaleimide, N-ethylmaleimide, N-propylmaleimide, Ni-propylmaleimide, N-butylmaleimide, Nii-butylmaleimide , Nt-butylmaleimide, N-laurylmaleimide, N-cyclohexylmaleimide, N-benzylmaleimide, and N-phenylmaleimide and at least one compound selected from N-substituted maleimides.

  The weight average molecular weight of the acrylic resin may be 150,000 to 1,800,000, 400,000 to 1,500,000, or 500,000 to 1,400,000. When the weight average molecular weight of the acrylic resin is 150,000 or more, the viscosity of the liquid composition is high and the liquid composition can exhibit thixotropy. When the weight average molecular weight of the acrylic resin is 1.8 million or less, the solubility in a solvent is improved, and the concentration of solid content in the liquid composition is easily increased. When the concentration of the solid content of the liquid composition is high, it is less necessary to consider the control of the film thickness of the coated liquid composition and the reduction of the film pressure due to drying shrinkage.

The glass transition temperature (Tg) of the acrylic resin may be −50 to 100 ° C., −45 to 20 ° C., or −40 ° C. to 5 ° C. Tg of the acrylic resin composed of n kinds of monomers can be calculated by the following calculation formula (FOX formula).
Tg (° C.) = {1 / (W ₁ / Tg ₁ + W ₂ / Tg ₂ +... + W _i / Tg _i +... + W _n / Tg _n )}-273
In the FOX equation, _Tg i (K) shows a glass transition temperature of the homopolymer of each monomer, _{W i} represents the weight fraction of each _{monomer, W 1 + W 2 + ...} + W i + ... W n = 1.

For example, the glass transition temperature (Tg) of an acrylic resin obtained by copolymerizing 5% by mass of glycidyl methacrylate, 5% by mass of acrylonitrile, 85% by mass of ethyl acrylate, and 5% by mass of butyl acrylate is as follows: Is calculated as follows.
Tg = {1 / (0.05 / 319 + 0.05 / 498 + 0.85 / 251 + 0.05 / 219)}-273 = −14.7 ° C.

  Based on the total mass of the thermoplastic resin (for example, acrylic resin), the curable resin (for example, epoxy resin) and the curing agent (for example, phenol resin), the content of the thermoplastic resin is 40 to 90% by weight, 50 to 85% by weight. %, Or 60 to 80% by weight. At this time, the total of the glycidyl group of the acrylic resin and the epoxy group of the epoxy resin and the amount of the hydroxyl group of the phenol resin may be substantially equivalent.

  The liquid composition 5 can be prepared, for example, by a method in which each component constituting the curable resin composition and, if necessary, a solvent are mixed and stirred. When the liquid composition 5 contains an inorganic filler, the liquid composition may be prepared using a slurry obtained by dispersing the inorganic filler in an organic solvent containing a surface treating agent in advance. Moreover, the liquid composition can also be obtained by preparing in advance a mixture of components of a curable resin composition containing a curable resin, and mixing this mixture with an inorganic filler slurry.

  The solvent used for dissolving or dispersing the curable resin composition and the inorganic filler is selected from, for example, ketone solvents such as methyl ethyl ketone and cyclohexanone. From the viewpoint of printability, cyclohexanone can be selected.

  Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to these.

Production Example 1
After dissolving 3.0 g of N-phenyl-3-aminopropyltrimethoxysilane (KBM573, trade name manufactured by Shin-Etsu Silicon Co., Ltd.) in 129 g of cyclohexanone, Admafine SO-25R (product of Admatech Co., Ltd.) is used as spherical silica particles. Name) 300 g was added with stirring, and after adding the entire amount, the mixture was further stirred at room temperature for 1 hour. 27.6 g of cyclohexanone solution (solid content 50 mass%) of NC-3000H (trade name, manufactured by Nippon Kayaku Co., Ltd.) as an epoxy resin, and propylene glycol monomethyl of LA-3018 (trade name, manufactured by Dainippon Ink Co., Ltd.) as a phenol resin After adding 18.7 g of ether solution (solid content 60 mass%) and 0.42 g of 2-ethyl-4-methylimidazole (2E4MZ, trade name, manufactured by Shikoku Kasei Co., Ltd.), the mixture was further stirred for 30 minutes, and then glycidyl as an acrylic resin. Add 301 g of a cyclohexanone solution (solid content 24.9% by mass) of a copolymer of methacrylate, acrylonitrile, ethyl acrylate and butyl acrylate (weight average molecular weight 610,000, epoxy equivalent 2869) and stir and mix in a ball mill for 12 hours to obtain a liquid composition Got.

Production Examples 2-7
A liquid composition was obtained in the same manner as in Production Example 1 except that the materials shown in Tables 1 and 2 were used in the mixing ratios shown in the table. The acrylic resin compounding amount, the epoxy resin compounding amount, and the phenol resin compounding amount shown in Tables 1 and 2 are ratios based on the total amount of the acrylic resin, the epoxy resin, and the phenol resin.

The weight average molecular weight of the acrylic resin was converted from a calibration curve using standard polystyrene by gel permeation chromatography (GPC). The calibration curve was prepared by approximating with a cubic equation using 5 standard polystyrene sample sets (PStQuick MP-H, PStQuick B [trade name, manufactured by Tosoh Corporation]). The GPC conditions are shown below.
Apparatus: (Pump: L-2130 type [manufactured by Hitachi High-Technologies Corporation]),
(Detector: L-2490 type RI [manufactured by Hitachi High-Technologies Corporation]),
(Column oven: L-2350 [manufactured by Hitachi High-Technologies Corporation])
Column: Gelpack GL-A100M (trade name, manufactured by Hitachi Chemical Co., Ltd.)
Column size: 10.7 mmI. D x 300mm
Eluent: Tetrahydrofuran Sample concentration: 10 mg / 2 mL
Injection volume: 200 μL
Flow rate: 2.05 mL / min Measurement temperature: 25 ° C

Details of each material shown in Table 1 and Table 2 are as follows.
1. 1. Acrylic resin / GMA / AN / EA / BA: copolymer of glycidyl methacrylate, acrylonitrile, ethyl acrylate and butyl acrylate Epoxy resin / NC-3000H: biphenyl aralkyl type epoxy resin (trade name, epoxy equivalent 290, manufactured by Nippon Kayaku Co., Ltd.)
3. Phenol resin / LA-3018: Aminotriazine novolak type phenol resin (trade name, hydroxyl equivalent 151, nitrogen content 18%, manufactured by Dainippon Ink Co., Ltd.)
4). Silica particles / F05-12: crushed silica, trade name of Fukushima Ceramics Co., Ltd./SO-25R: spherical silica, trade name of Admatechs Co., Ltd. Surface treatment agent (silane coupling agent)
KBM573: N-phenyl-3-aminopropyltrimethoxysilane, trade name manufactured by Shin-Etsu Silicon Co., Ltd.

(Mechanical properties of the resin layer)
The liquid composition was applied to a release-treated PET (polyethylene terephthalate) film using a bar coater so that the thickness after drying was 125 μm. The applied liquid composition was dried by heating at 130 ° C. for 10 minutes, and then cured by heating at 185 ° C. for 30 minutes. After removing the release-treated PET film, the cured product was punched out to a width of 10 mm and a length of 100 mm to obtain a test piece. The test piece was subjected to a tensile test using a EZ tester (Autograph EZ-S manufactured by Shimadzu Corporation) at a tensile speed of 50 mm / min to obtain a stress-displacement curve. The maximum value of the slope of the tangent line of the stress-displacement curve at the initial rise after starting the stress load was determined, and the initial tensile elastic modulus was determined from the value according to the following formula.
Initial tensile modulus (Pa) = maximum value of slope of tangent line of stress-displacement curve (N / m) × [displacement (m) / cross-sectional area of cured product (m ² )]

Example 1
A copper foil of a polyimide substrate (thickness 25 μm) / copper foil (thickness 18 μm) laminate (Espanex, trade name, manufactured by Nippon Steel Chemical Co., Ltd.) was processed by photolithography to form a wiring terminal pattern. . The liquid composition of Production Example 1 was printed on the surface of the polyimide substrate opposite to the wiring terminals using a metal mask. The printed liquid composition is dried by heating at 130 ° C. for 10 minutes, and further cured by heating at 185 ° C. for 60 minutes to form a resin layer having a length of 30 mm from the end of the polyimide substrate and a thickness of 75 μm. Thus, a connector test piece (width 10 mm, length 100 mm) having a resin layer was obtained. The edge part of the resin layer which has a substantially rectangular main surface had the surface which forms the convex curve which curves toward the polyimide base material from the opposing surface which opposes a polyimide base material.

Examples 2-12
A connector having a resin layer in the same manner as in Example 1 except that the liquid composition of each production example was used and the thickness of the polyimide base material or the thickness of the resin layer was changed as shown in Tables 3 and 4. A test piece was prepared. In any of the test pieces, the end portion of the resin layer had a surface forming a convex curved surface that curves toward the polyimide base material from the facing surface facing the polyimide base material.

Comparative Example 1
Similar to the example, a wiring terminal pattern was formed on a polyimide substrate (thickness 50 μm). A polyimide film (UPILEX 75S, Ube Industries, Ltd. product name) with a thickness of 75 μm on a surface opposite to the wiring terminal of the polyimide substrate via a 30 μm-thick adhesive film (Hybon 10-850, product name, manufactured by Hitachi Chemical Co., Ltd.) ) Was cut out into a strip shape having a width of 10 mm and a length of 100 mm to obtain a test piece of a connector for comparison. The end of the polyimide film affixed to the polyimide substrate has a facing surface facing the polyimide substrate and a side surface along the perpendicular of the polyimide substrate, and the facing surface and the side surface intersect at a right angle. It was.

(Evaluation)
(Bendability)
A load of 490 mN (50 gf) was applied from the end by pressing the end of a 10 mm wide test piece against the balance. When a load was applied, the case where the test piece did not bend was determined as “A”, and the case where the test piece was bent or the resin layer was broken was determined as “C”.

(Reflow resistance)
A conveyor type with a heating profile in which the maximum temperature of the substrate surface is 260 ° C. and the temperature is maintained for 10 seconds while the test piece of the connector is sandwiched between two wire meshes and moved at a speed of 1.2 m / min. The test piece was processed three times by the reflow test. After the treatment, the presence or absence of blistering and peeling between the polyimide base material / resin layer was confirmed by visual inspection. The case where no blistering and peeling occurred was determined as “A”, and the case where blistering and / or peeling occurred was determined as “C”.

(Durability test of connectors)
FIG. 8 is a schematic explanatory view showing a method of a durability test of the connector. The mirror finished aluminum plates 31 and 32 having a thickness of 1 mm fixed to the spindle 21 and the anvil 22 which are measurement parts of the digital micrometer 20 (MDC-25SB manufactured by Mitutoyo Corporation) with an adhesive are used for evaluating the insertion and removal durability. Used as a jig. The test was performed by setting the gap between the two aluminum plates 31 and 32 facing each other to be equal to the thickness of the test piece, −15 μm, or +15 μm by the digital micrometer 20. After inserting about 10 mm of the test piece 10 into the gap in the direction A parallel to the aluminum plate, the operation of pulling out was repeated up to 30 times. The abnormality of the test piece 10 was visually observed, and the number of times until an abnormality such as peeling, cracking, or bending occurred was recorded.

(Adhesiveness between polyimide substrate and resin layer)
The liquid composition was applied to a polyimide film (Upilex 50S, Ube Industries, Ltd. product name) using a bar coater so that the thickness after drying was 125 μm. The applied liquid composition was dried by heating at 130 ° C. for 10 minutes and then cured by heating at 185 ° C. for 30 minutes to obtain a sample for adhesion evaluation. In the resin layer of the sample, 10 grids of 2 mm width were cut with a cutter knife, and 10 grids with a width of 2 mm were made so as to intersect at right angles. Cellotape (registered trademark) was stretched there, and then peeled off to confirm whether the resin layer was peeled off. The case where peeling did not occur was determined as “A”, and the case where peeling occurred was determined as “C”.

(result)
The evaluation results are shown in Tables 3 and 4. In Examples, the polyimide base material and the resin layer were good, and there was no problem with reflow resistance. Regarding the bendability of the connector, in any of the examples, the test piece did not bend against a load of 490 mN (50 gf).
Regarding the durability test of the connector, in the example, the test piece could be smoothly inserted and removed, and no abnormality was observed even after 30 insertions and removals. In the case of the comparative example, when the resistance of insertion / extraction of the test piece was strong and the gap was equal to that of the test piece (173 μm) or −15 μm (158 μm), the occurrence of abnormality was observed at the time of insertion / removal less than 30 times.

  FIG. 9 is a photomicrograph of the cross section of the connector produced in Example 1. Microscopic observation also confirmed that the end of the resin layer 3 has a surface that forms a convex curved surface that curves toward the polyimide substrate 2 from the facing surface that faces the polyimide substrate. FIG. 10 is a scanning micrograph (10,000 magnifications) of the resin layer of the connector produced in Example 1. It was confirmed that spherical silica particles were contained in the resin layer.

  DESCRIPTION OF SYMBOLS 1 ... Wiring terminal, 2 ... Flexible base material, 3 ... Resin layer, 3a ... End part of resin layer 3, 4 ... Metal mask, 4a ... Opening part, 5 ... Liquid composition, 6 ... Opposite surface, 7 ... Surface forming convex curved surface, 10 ... connector, 20 ... digital micrometer, 21 ... spindle, 22 ... anvil, 31, 32 ... aluminum plate, 40 ... flexible substrate, 41 ... cover film, 42 ... non-wiring metal layer, 51 ... Circuit, 52 ... Flexible substrate for circuit, 100 ... Flexible wiring board.

Claims (5)

A connector on the plug-in side that is used to connect the wiring by plugging into the connector on the mating side,
A flexible substrate;
A wiring terminal disposed on one surface side of the flexible substrate;
A resin layer containing a resin, which is disposed on an end portion of the flexible substrate on a surface opposite to the wiring terminal of the flexible substrate, and has a facing surface facing the flexible substrate. When,
With
The end of the resin layer on the tip side of the connector has a surface that forms a convex curved surface that curves from the facing surface toward the flexible substrate,
The resin layer further includes an inorganic filler, and the content of the inorganic filler in the resin layer is 70 to 80% by mass with respect to the mass of the resin layer,
The resin layer has a thickness of 50 to 500 μm, and the flexible substrate has a thickness of 75 μm or less.
connector.   The connector according to claim 1, wherein the inorganic filler is silica particles.   The connector according to claim 1 or 2, wherein the flexible substrate is a polyester substrate or a polyimide substrate.   The connector as described in any one of Claims 1-3 whose initial stage tensile elasticity modulus in 25 degreeC of the said resin layer is 0.3-3.0 GPa. The connector according to any one of claims 1 to 4,
A flexible substrate for circuits;
A circuit provided on the flexible substrate for the circuit and connected to a wiring terminal of the connector;
With
The flexible substrate for the connector and the flexible substrate for circuit are the same substrate, or the flexible substrate for circuit different from the flexible substrate for the connector And a flexible wiring board.