Electrical component

Abstract

To provide a technique capable of suppressing a rise of a resistance value of a circuit via a low-temperature solder in an electrical component on which three-dimensional molding and insert molding are performed.SOLUTION: An electrical component 10 comprises a circuit component 12 and a resin molding part 70 on which insert molding is performed with the circuit component as an insert object. The circuit component includes a substrate layer 20, a conductive layer 30 which is provided in the substrate layer, and an electronic element 50 which is mounted in the conductive layer via a low-temperature solder 32. Three-dimensional molding is performed on the substrate layer and the conductive layer. The conductive layer is a coating formed by conductive past containing metallic fillers and thermosetting resin binders. The filler has a flake shape or a scale shape. An average particle diameter of the fillers is 6 μm or more to 20 μm or less. A mass percentage of the fillers in the coating is 90 wt.% or more to 97 wt.% or less.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present disclosure relates to electrical equipment. [Background technology]

[0002] Patent Document 1 discloses an electronic device in which a resin layer is formed by secondary molding on a circuit component in which electronic elements are mounted on a metal wiring pattern of a substrate via low-temperature solder. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-77663 Summary of the Invention [Problem to be solved by the invention]

[0004] In the electronic device described in Patent Document 1, the heat generated during secondary molding can cause the low-temperature solder to flow, which can increase the resistance of the circuit. Also, when the substrate and metal wiring pattern are three-dimensionally molded, the resistance of the circuit of the circuit component can increase.

[0005] Therefore, an object of the present invention is to provide a technology that can suppress an increase in the resistance value of a circuit via low-temperature solder in electrical equipment that has been processed by three-dimensional molding and insert molding. [Means for solving the problem]

[0006] The electrical equipment disclosed herein includes a base layer, a conductive layer provided on the base layer, a circuit component including an electronic element mounted on the conductive layer via low-temperature solder, and a resin molded portion insert-molded with the circuit component as an insert, wherein the base layer and the conductive layer are three-dimensionally molded, the conductive layer is a coating formed from a conductive paste containing a metal filler and a thermoplastic resin binder, the filler has a flake or scale shape, the average particle size of the filler is 6 μm or more and 20 μm or less, and the mass fraction of the filler in the coating is 90 wt% or more and 97 wt% or less. [Effects of the Invention]

[0007] According to the present disclosure, in electrical equipment that has been processed by three-dimensional molding and insert molding, an increase in the resistance value of a circuit via low-temperature solder can be suppressed. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a plan view showing an electrical component according to a first embodiment. [Figure 2] FIG. 2 is a side view showing the electrical equipment according to the first embodiment. [Figure 3] FIG. 3 is a cross-sectional view taken along line III-III in FIG. [Figure 4] FIG. 4 is an enlarged view of area A1 in FIG. [Figure 5] FIG. 5 is a diagram showing the process of manufacturing electrical equipment. [Figure 6] FIG. 6 is a diagram showing the process of manufacturing electrical equipment. [Figure 7] FIG. 7 is a diagram showing the process of manufacturing electrical equipment. [Figure 8] FIG. 8 is a diagram showing the process of manufacturing electrical equipment. [Figure 9] FIG. 9 shows the evaluation results of the samples. DETAILED DESCRIPTION OF THE INVENTION

[0009] [Description of the embodiments of the present disclosure] First, embodiments of the present disclosure will be listed and described.

[0010] The electrical equipment of the present disclosure is as follows.

[0011] (1) An electrical device comprising: a base layer; a conductive layer provided on the base layer; a circuit component including an electronic element mounted on the conductive layer via low-temperature solder; and a resin molded portion insert-molded with the circuit component as an insert; wherein the base layer and the conductive layer are three-dimensionally molded; the conductive layer is a coating formed from a conductive paste containing a metal filler and a thermoplastic resin binder; the filler has a flake or scale shape; the average particle size of the filler is 6 μm or more and 20 μm or less; and the mass fraction of the filler in the coating is 90 wt% or more and 97 wt% or less.

[0012] In the electrical equipment (1), the binder is made of a thermoplastic resin. When the coating is heated above the softening temperature of the thermoplastic resin during the solder mounting process, the coating softens, allowing the solder to penetrate into the coating, facilitating the formation of an alloy layer between the filler and the solder metal component. Furthermore, an average particle size of 20 μm or less prevents the conductive paste from clogging the nozzle when printing a conductive layer using the conductive paste. Furthermore, a filler loading of 97 wt% or less in the coating facilitates ensuring the flexibility of the coating and improving its three-dimensional processability (stretchability). Furthermore, the filler has a flake or scale shape, an average particle size of 6 μm or more, and a filler mass fraction of 90 wt% or more in the coating improves the coating's stretchability and solder wettability, preventing an increase in the circuit resistance via low-temperature soldering even after three-dimensional molding and insert molding.

[0013] (2) In the electrical equipment of (1), the filler may have an average particle size of 8 μm or more, which can further suppress an increase in resistance when the conductive layer is stretched by three-dimensional molding and improve solder wettability.

[0014] (3) In the electrical equipment of (1) or (2), the mass fraction of the filler in the coating may be 94 wt % or more, which reduces the mass fraction of the binder in the coating, making it easier for the filler to form an alloy with the metal components of the low-temperature solder, and making it less likely for the low-temperature solder to aggregate.

[0015] (4) In the electrical equipment of any one of (1) to (3), the thermoplastic resin constituting the binder may have hydroxyl groups. This allows the hydroxyl groups to have good affinity with the metal filler, making it less likely for the binder and filler to break down at the interface even when the conductive layer is stretched during three-dimensional molding. Furthermore, the high reactivity of the hydroxyl groups also makes it easier to achieve good adhesion between the binder and the base layer.

[0016] [Details of the embodiments of the present disclosure] Specific examples of electrical equipment according to the present disclosure will be described below with reference to the drawings. Note that the present disclosure is not limited to these examples, but is defined by the claims, and is intended to include all modifications within the meaning and scope of the claims.

[0017] [Embodiment 1] The electrical equipment according to the first embodiment will be described below. Fig. 1 is a plan view showing the electrical equipment 10 according to the first embodiment. Fig. 2 is a side view showing the electrical equipment 10 according to the first embodiment. Fig. 3 is a cross-sectional view taken along line III-III in Fig. 1. Fig. 4 is an enlarged view of an area A1 in Fig. 3. Arrow A2 in Fig. 4 indicates the path of light emitted from the light source 50. Figs. 5 to 8 are diagrams showing the manufacturing process of the electrical equipment 10. Each figure shows three mutually orthogonal directions: X direction, Y direction, and Z direction.

[0018] The electrical equipment 10 includes a base layer 20, a conductive layer 30, an electrostatic switch electrode 40, a light source 50, a light guide layer 60, a reflective layer 72, and a light-shielding wall 74. The conductive layer 30 and the electrostatic switch electrode 40 are provided on the base layer 20. The light source 50 is mounted on the conductive layer 30. The light guide layer 60 is provided so as to cover the area from the light source 50 to the electrostatic switch electrode 40. The reflective layer 72 is provided on the side of the light guide layer 60 opposite the base layer 20. The light-shielding wall 74 surrounds the side of the light guide layer 60.

[0019] Here, the reflective layer 72 and the light-shielding wall 74 are configured by one resin part 70. Here, the resin part 70 is a resin molded part 70 that is insert-molded using the circuit part 12 including the base layer 20, the conductive layer 30, and the light source 50 as an insert. The light source 50 is an example of an electronic element, such as a light-emitting diode (LED). Hereinafter, the light source 50 may be referred to as an LED 50. Hereinafter, the light guide layer 60 is also referred to as an insert. The resin part 70 is a resin molded part 70 that is insert-molded using the circuit part 12 including the base layer 20, the conductive layer 30, the electrostatic switch electrode 40, the light source 50, and the light guide layer 60 as an insert.

[0020] The electrical component 10 is, for example, a touch panel device. The electrical component 10 is mounted on a vehicle such as an automobile. Here, the electrical component 10 is an interior component in which an electronic circuit for an automobile and a resin molded portion 70 are integrally molded. In the vehicle, the electrical component 10 may be mounted on, for example, an instrument panel. The resin molded portion 70 may constitute a part of the instrument panel.

[0021] The touch panel device includes an operation switch unit and a backlight illumination unit. The portion including the electrostatic switch electrode 40 constitutes the operation switch unit. The portion including the light source 50 constitutes the backlight illumination unit. As shown in FIG. 2, the outer surface of the operation switch unit constitutes an operation surface that a user touches with a finger UF or the like. The electrostatic switch electrode 40 is provided inside the operation surface. The backlight illumination unit illuminates the operation surface from the inside, making it easier for the user to see the operation surface. Here, as shown by arrow A2 in FIG. 4, the backlight illumination unit illuminates the operation switch unit by reflecting light emitted from the light source 50 toward the opposite side from the second surface 22 with the reflective layer 72. As shown in FIG. 1, indicators 14 (also referred to as icons, etc.) may be formed on the operation surface to indicate the location to be touched by the user and the function assigned to the electrostatic switch electrode 40. The backlight illumination unit may illuminate the indicators 14.

[0022] The base material layer 20 is formed in a film shape. The base material layer 20 has a first surface 21 and a second surface 22 facing opposite directions. A conductive layer 30, an electrostatic switch electrode 40, a light source 50, a light guide layer 60, and a resin part 70 are provided on the first surface 21. The second surface 22 is the surface facing the user.

[0023] The base layer 20 is three-dimensionally molded. Three-dimensional molding here refers to processing a member having a flat shape (2D shape) into a three-dimensional shape (3D shape). Three-dimensional molding is performed using a mold, for example, by vacuum molding, high-pressure molding, or vacuum / pressure molding. During three-dimensional molding, bending and stretching of the member may occur when processing from a flat shape to a three-dimensional shape. Therefore, the member processed three-dimensionally has flexibility that allows it to bend and stretch. Here, as shown in FIG. 5 , the base layer 20 is processed from a flat shape extending in the XY plane to a three-dimensional shape that also extends in the Z direction. Here, the base layer 20 includes a main body portion 23 and an extension portion 24. The main body portion 23 has a three-dimensional shape. The three-dimensional shape of the main body portion 23 is not particularly limited and can be set as appropriate. Here, the main body portion 23 is formed into a shape in which the first surface 21 is concave and the second surface 22 is convex. The extension portion 24 extends laterally (in the X direction or Y direction) from the outer edge of the main body portion 23. Here, the extension portion 24 is formed flat.

[0024] The base layer 20 includes a first region 25 and a second region 26. The first region 25 and the second region 26 are different regions. The first region 25 is a region where the conductive layer 30 is provided. The second region 26 is a region where the electrostatic switch electrode 40 is provided. The second region 26 is light-transmitting. The first region 25 may or may not be light-transmitting.

[0025] The base layer 20 includes a translucent base film layer 20A. As shown in FIG. 4, the base layer 20 may include a decorative layer 20B laminated on the base film layer 20A. The decorative layer 20B is provided, for example, on the first surface 21 side of the base film layer 20A. The decorative layer 20B may have light-blocking properties. The decorative layer 20B is formed by painting the base film layer 20A with a light-blocking paint or printing with a light-blocking ink. The decorative layer 20B may be a single layer or multiple layers with different colors. For example, the base film layer 20A may extend over the entire base layer 20, and the decorative layer 20B may be provided in a partial region of the base film layer 20A. The portion of the base layer 20 where the decorative layer 20B is not provided on the base film layer 20A forms a second region 26. Here, the first region 25 is the portion of the base layer 20 where the decorative layer 20B is provided. The first region 25 may be a portion of the base material layer 20 where the decorative layer 20B is not provided.

[0026] The thickness of the base film layer 20A is not particularly limited, but if the base film layer 20A is too thick, shape conformability will be poor, and if it is too thin, it may tear, wrinkle, etc. In consideration of these, the thickness of the base film layer 20A may be, for example, 0.025 mm or more and 1 mm or less.

[0027] The base film layer 20A preferably has a predetermined heat resistance. In the electrical equipment 10, the base film layer 20A is subjected to heat, for example, when the wiring pattern is cured or when the resin part 70 is insert-molded. If the heat resistance of the base film layer 20A is too low, the heat may cause tears, wrinkles, etc. in the base film layer 20A. By ensuring that the base film layer 20A has a predetermined heat resistance, tears, wrinkles, etc. caused by heat during manufacturing can be suppressed.

[0028] The heat shrinkage rate at 120°C for 30 minutes in an air atmosphere may be used as an index of heat resistance. The condition of 120°C for 30 minutes simulates the condition of the heat treatment applied to the base film layer 20A during the manufacturing process of the electrical component 10. The heat shrinkage rate of the base film layer 20A can be calculated by {(length of the base film layer 20A before heating - length of the base film layer 20A after heating) / length of the base film layer 20A before heating} × 100. The temperature before heating is room temperature. The length of the base film layer 20A after heating is the length of the base film layer 20A when it is returned to room temperature after being subjected to heat treatment at 120°C for 30 minutes. The predetermined heat resistance of the base film layer 20A is preferably such that the heat shrinkage rate is 5% or less. A heat shrinkage rate of 5% or less easily prevents damage to the base film layer 20A during the manufacturing process of the electrical component 10. More preferably, the predetermined heat resistance of the base film layer 20A is a heat resistance that satisfies the above-mentioned thermal shrinkage rate of 3% or less.

[0029] The base film layer 20A may be a directional film having anisotropic stretchability, such as a uniaxially stretched film, or may be a film having isotropic stretchability, such as a biaxially stretched film. When the base film layer 20A is made of a directional film, the heat shrinkage rate of the base film in both the MD (Machine Direction) and the TD (Transverse Direction) is preferably 5% or less, and more preferably 3% or less.

[0030] The surface of the base film layer 20A may be modified to improve adhesion to the conductive layer 30. Such surface modification may be performed by primer treatment, plasma irradiation, corona irradiation, UV irradiation, or the like.

[0031] The base film layer 20A is made of, for example, a resin, and the resin may include at least one selected from the group consisting of polyesters such as polyethylene terephthalate (PET), polycarbonate (PC), polystyrene (PS), syndiotactic polystyrene (SPS), liquid crystal polymer (LCP), polytetrafluoroethylene (PTFE), polyethylene naphthalate (PEN), nylons such as polyamide (PA), polyphenylene sulfide (PPS), polyphenylene ether (PPE), modified polyphenylene ether (m-PPE), cycloolefin polymer (COP), and acrylic (PMMA).

[0032] The conductive layer 30 is laminated on the decorative layer 20B of the base material layer 20. The conductive layer 30 has an LED pattern and an electrostatic switch electrode pattern. The conductive layer 30 may have a pattern for a purpose other than the LED pattern and the electrostatic switch electrode pattern.

[0033] The electrostatic switch electrode 40 is light-transmitting. The electrostatic switch electrode 40 is laminated on the base film layer 20A of the base layer 20. A portion of the electrostatic switch electrode 40 extends to the first region 25 and is connected to the electrostatic switch electrode pattern. The electrostatic switch electrode 40 may be made of a conductive polymer such as PEDOT:PSS (polyethylenedioxythiophene:polystyrenesulfonate). The electrostatic switch electrode 40 may be adjacent to the LED 50 in the direction along the second surface 22, or may be spaced apart from the LED 50.

[0034] The LED 50 is mounted on an LED pattern in the conductive layer 30. Light from the LED 50 passes through the electrostatic switch electrode 40 and the second region 26 and exits the electrical component 10. Here, the conductive layer 30 and the decorative layer 20B are located closer to the second surface 22 than the LED 50, and therefore the light emitted from the LED 50 is prevented from directly passing through the electrostatic switch electrode 40 and the second region 26. The light emitted from the LED 50 is reflected by the reflective layer 72 and exits the electrical component 10 after passing through the electrostatic switch electrode 40 and the second region 26.

[0035] The LED 50 is mounted on the conductive layer 30 via a bonding layer 32. Here, the bonding layer 32 is a low-temperature solder 32. Therefore, the conductive layer 30 has good solder wettability. The electrical equipment 10 may also include electronic elements other than the LED 50. Such electronic elements may be, for example, resistors, capacitors, or control IC chips. It is preferable that such electronic elements are mounted using the same mounting method as the LED 50.

[0036] The low-temperature solder 32 is a solder with a melting point of 184 degrees Celsius or lower. The low-temperature solder 32 is, for example, Sn-Bi based. When the bonding layer 32 is made of low-temperature solder 32, the heat applied to the base layer 20 during soldering can be reduced. The heating method for the low-temperature solder 32 is not particularly limited and can be set as appropriate. The heating method for the low-temperature solder 32 is preferably an instantaneous local heating method using an infrared laser. As a result, the heat applied to the base layer 20 is instantaneous and localized only at the mounting location, thereby suppressing damage to the base layer 20 due to heating (warping, tearing, etc.).

[0037] The conductive layer 30 is a coating formed from a conductive paste. The conductive paste is provided on the base layer 20 by printing. The printing method is not particularly limited, and may be, for example, screen printing, flexographic printing, clavier printing, clavier offset printing, inkjet printing, or dispenser printing. The conductive paste printed on the base layer 20 is heated and cured to form a coating. The method for curing the paste coating is not particularly limited, and may be, for example, drying in a hot air oven.

[0038] The conductive paste contains a metal filler and a thermoplastic resin binder. The metal type of the filler is, for example, silver, copper, or silver-coated copper powder. The filler and binder remain in the coating even after the conductive paste is heat-cured.

[0039] The conductive paste material may contain, in addition to filler and binder, solvent, additives, etc. The conductive paste may consist of filler, binder, solvent, and additive. Because the solvent volatilizes when a coating is formed by heating, the mass fraction of the solvent in the coating is smaller than the mass fraction of the solvent in the conductive paste. The entire amount of solvent may volatilize, and no solvent may remain in the coating. Due to the reduction of the solvent during heat curing, the mass fraction of the filler in the coating may change from the mass fraction of the filler in the conductive paste before heat curing, and may usually become larger.

[0040] The solvent enhances the fluidity of the conductive paste. Examples of the solvent include glycols, glycol ethers, glycol esters, and ketones. The solvent preferably contains at least one selected from the group consisting of glycols, glycol ethers, glycol esters, and ketones.

[0041] The additives may be, for example, a thixotropic agent, an anti-settling agent, an antioxidant, etc. The thixotropic agent is added to prevent sagging of the conductive paste and ensure smooth application. The anti-settling agent prevents the filler from settling. The antioxidant prevents the filler from oxidizing.

[0042] Here, the conductive layer 30 is three-dimensionally molded together with the base layer 20. Therefore, the conductive layer 30 also has flexibility that allows it to be bent and stretched. Regarding the thickness of the coating after the conductive paste has hardened, if the film is too thin, resistance is likely to increase due to insufficient contact of the filler. Furthermore, if the film is too thick, costs increase and shape conformability during three-dimensional molding decreases. In view of these factors, the thickness of the coating is preferably, for example, 5 μm or more and 100 μm or less, and more preferably 10 μm or more and 50 μm or less.

[0043] Here, the LED 50 is mounted on the conductive layer 30 using low-temperature solder 32. Therefore, the conductive layer 30 has good solder wettability. The filler and binder in the conductive paste are blended to ensure good three-dimensional molding processability and solder wettability.

[0044] Specifically, the filler has a flake or scale shape. The flake shape is, for example, a thin, flat plate shape. The scale shape is a shape in which the main surface of the flake shape is curved. In addition to the flake or scale shape, spherical shapes may also be mixed into the filler.

[0045] Regarding the average particle size of the filler, if the average particle size of the filler is too small, it is difficult to obtain good three-dimensional molding processability and solder wettability. The larger the average particle size of the conductive paste filler, the easier it is for the fillers to maintain contact with each other even when the conductive layer 30 is stretched during three-dimensional molding process, and the increase in resistance can be suppressed. Furthermore, the larger the average particle size of the filler, the more likely the filler will appear on the coating surface, resulting in good solder wettability. Furthermore, if the average particle size of the filler is too large, it will easily clog the nozzle during printing, resulting in poor printability. The smaller the average particle size of the filler, the less likely it is to clog the nozzle during printing.

[0046] The average particle size of the multiple fillers can be determined by observing the cross section of the conductive layer 30 under a microscope. The cross section of the conductive layer 30 is, for example, a cross section along the stacking direction of the base layer 20 and the conductive layer 30. Five or more microscopic images are obtained from the cross section of the conductive layer 30. Each microscopic image is binarized to determine the particle size of all fillers in the image. The measured particle size of the filler is the maximum dimension of each filler in the cross section. The average value of the particle sizes of all fillers is the average particle size of the multiple fillers.

[0047] Considering these two conflicting conditions, the average particle size of the filler should be 6 μm or more and 20 μm or less. When the average particle size of the filler is 6 μm or more, good three-dimensional molding processability and solder wettability are easily obtained. When the average particle size of the filler is 8 μm or more, even better three-dimensional molding processability and solder wettability are easily obtained. When the average particle size is 20 μm or less, the filler is less likely to clog the nozzle during printing. Therefore, the conductive paste can be printed well even with inkjet printing and dispenser printing.

[0048] The binder is made of a thermoplastic resin. Such a thermoplastic resin preferably has a hydroxyl group as a functional group. The presence of a highly reactive hydroxyl group improves the affinity between the binder and the filler, making it less likely for the interfacial breakdown between the binder and the filler to occur even when the cured coating is stretched. Furthermore, the binder also provides excellent adhesion to the base layer 20. Furthermore, during the solder mounting process, when the coating is heated to above the softening temperature of the thermoplastic resin during localized instantaneous heating, the coating softens, allowing the solder to penetrate into the coating, and the filler and the metal component of the solder tend to form an alloy layer.

[0049] Such thermoplastic resins may be, for example, phenoxy resin, hydroxy polyurethane resin, polyvinyl alcohol resin, polyvinyl acetal resin, vinyl chloride-vinyl acetate-hydroxyalkyl acrylate copolymer resin, or the like.

[0050] The hydroxyl groups may be urethane-modified by reacting with isocyanate. This imparts rubber elasticity to the cured coating, improving stretchability. A blocked isocyanate compound is preferred as the isocyanate. Because the urethane reaction does not occur below the dissociation temperature of the blocking agent, the storage stability of the conductive paste at room temperature is excellent. From the perspective of the drying and curing temperature of the conductive paste, the blocked isocyanate compound is preferably 3,5-dimethylpyrazole (DMP), diethyl malonate (DEM), or a DMP / DEM hybrid, which has a blocking agent dissociation temperature of 120°C or less. The isocyanate is preferably trimer hexamethylene diisocyanate or biuret hexamethylene diisocyanate, which have excellent flexibility, and more preferably biuret hexamethylene diisocyanate.

[0051] Regarding the mass fraction of the filler in the coating, if the mass fraction of the filler in the coating is too low, the resin component of the binder becomes too high, making it difficult for the filler and the metal component of the solder to form an alloy, and the solder becomes more likely to clump. If the mass fraction of the filler in the coating is too high, the resin component of the binder becomes too low, reducing flexibility and making it difficult to achieve flexibility that can withstand three-dimensional molding. In light of these factors, for low-temperature solder 32 mounting, the mass fraction of the filler in the coating is preferably 90 wt% or more and 97 wt% or less. This allows for both good solder wettability and flexibility that can withstand three-dimensional molding. Specifically, if the mass fraction of the filler in the coating is 90 wt% or more, the filler and the metal component of the solder easily form an alloy, making it difficult for the solder to clump, and making it easier to achieve good solder wettability. Furthermore, if the filler loading in the coating is 97 wt% or less, the resin component of the binder easily provides flexibility that can withstand three-dimensional molding. More preferably, the mass fraction of the filler in the coating is 94 wt % or more, which makes it easier to obtain better solder wettability.

[0052] The light guide layer 60 is partially provided in the switch illumination area of ​​the base layer 20, including the LED 50. The light guide layer 60 is made of transparent resin. This resin is a UV-curable resin or a thermosetting resin. The light guide layer 60 allows light to be emitted not only near the LED 50 but also over a wide area. The light guide layer 60 also increases the distance between the reflective layer 72 and the operation switch, thereby reducing brightness unevenness. The thickness of the light guide layer 60 is greater than the thickness of the LED mounting portion and the thickness of the electrostatic switch electrode 40. The light guide layer 60 surrounds the LED 50 on all four sides and below (the side opposite the base layer 20). The light guide layer 60 surrounds the electrostatic switch electrode 40 on all four sides and below (the side opposite the base layer 20). The light guide layer 60 has a portion that contacts the base layer 20.

[0053] Here, insert molding is performed after the LEDs 50 are mounted. The light guide layer 60 is provided after the LEDs 50 are mounted but before insert molding. The light guide layer 60 is interposed between the LEDs 50 and the resin part 70. During insert molding, molding heat and molding pressure are typically applied to the insert. The light guide layer 60 prevents the low-temperature solder 32 from melting due to the molding heat and molding pressure. This prevents the electronic elements including the LEDs 50 from peeling off from the conductive layer 30. The light guide layer 60 also protects the electronic elements including the LEDs 50 from the molding heat and molding pressure.

[0054] The reflective layer 72 reflects, toward the inside of the light-guiding layer 60, light emitted from the LEDs 50 that passes through the light-guiding layer 60 and strikes the surface of the reflective layer 72. Here, the light-shielding wall 74 is also formed of the same material as the reflective layer 72. Therefore, like the reflective layer 72, the light-shielding wall 74 also reflects, toward the inside of the light-guiding layer 60, light that passes through the light-guiding layer 60 and strikes the surface of the light-shielding wall 74.

[0055] The resin material of the resin parts 70 forming the reflective layer 72 and the light-shielding walls 74 preferably includes at least one selected from the group consisting of polypropylene resin (PP), polystyrene resin (PS), acrylonitrile butadiene styrene resin (ABS), polycarbonate resin (PC), polyvinyl chloride resin (PVC), and acrylic resin (PMMA). Furthermore, the resin parts 70 forming the reflective layer 72 and the light-shielding walls 74 are preferably white or translucent. It is more preferable that the resin parts 70 be made of white resin. When the resin parts 70 are white, the reflectivity is likely to be increased, improving the luminous efficiency.

[0056] The resin part 70, which forms the reflective layer 72 and the light-shielding walls 74, surrounds the light guide layer 60. This reduces uneven light emission and suppresses light leakage to the outside due to the light reflection effect at the interface between the light guide layer 60 and the resin part 70. Here, the light guide layer 60 is covered on all four sides by the light-shielding walls 74. Furthermore, one main surface of the light guide layer 60 is covered by a reflective wall. Here, the entire portion of the light guide layer 60 in contact with the surface opposite the base layer 20 is made of a reflective layer 72 made of a white or translucent resin. Here, the light guide layer 60 is formed of a uniform material, and the surface material of the light guide layer 60 is also uniform. Similarly, the resin part 70 is formed of a uniform material, and the surface material of the resin part 70 is also uniform. Therefore, the combination of materials at the contact portion between the light guide layer 60 and the resin part 70 is uniform.

[0057] The resin part 70 is provided so as to fill the concave surface on the first surface 21 of the base layer 20. The resin part 70 also functions as a housing for the electrical component 10. As shown in FIG. 4 , the base layer 20 here has a third region 27 in contact with the light guide layer 60 and a fourth region 28 in contact with the resin part 70.

[0058] <Manufacturing method> A method for manufacturing the electrical component 10 will now be described.

[0059] First, as shown in Fig. 5, a base material layer 20 is prepared, which is provided with a base material film layer 20A and a decorative layer 20B. At this time, the base material layer 20 is in the form of a flat film having an area larger than that when used as the electrical equipment 10. Then, a conductive paste is applied in a predetermined pattern to a first region 25 of the first surface 21 of the base material layer 20, where the decorative layer 20B is provided, and the pattern is heated and cured to form a coating that becomes the conductive layer 30. Furthermore, an electrostatic switch electrode 40 is formed in a second region 26 of the first surface 21 of the base material layer 20, where the decorative layer 20B is not provided.

[0060] Next, as shown in FIG. 6, the base layer 20 and the conductive layer 30 are three-dimensionally formed. The three-dimensional forming is performed by vacuum forming, high-pressure forming, or vacuum / pressure forming. Here, the base layer 20 is three-dimensionally formed so that it has a main body portion 23 and an extension portion 24, and the first surface 21 of the main body portion 23 is concave and the second surface 22 is convex. The portion of the conductive layer 30 that overlaps the main body portion 23 is also three-dimensionally formed. After that, excess portions of the base layer 20 are cut off by Thomson punching or press punching.

[0061] Next, as shown in Fig. 7, electronic components (LEDs 50, resistors, capacitors, control IC chips, etc.) are mounted on the conductive layer 30 with low-temperature solder 32. Here, the LEDs 50 are mounted on the LED pattern with low-temperature solder 32. Mounting with low-temperature solder 32 is performed by a localized instantaneous heating method using an infrared laser or the like. This forms the circuit components 12.

[0062] 8, the mounting portion of the LED 50 and the backlight display area formed by the LED 50 are molded with a transparent resin (thermosetting resin or UV-curable resin) to form the light guide layer 60. Here, the light guide layer 60 is provided in a portion including the periphery of the LED 50 and the periphery of the electrostatic switch electrode 40. In this way, the circuit component 12 with the light guide layer 60 is formed.

[0063] Next, the circuit component 12 with the light guide layer 60 is placed in a mold as an insert. Then, a fluid resin is poured into the mold to form the resin molded portion 70 that forms the light-shielding wall 74 and the reflective layer 72. This completes the electrical equipment 10 shown in FIG. 1.

[0064] As shown in FIG. 1 , for example, the electrical component 10 is connected to a device 92 via a connection wiring 90. In the electrical component 10, a connection portion with the connection wiring 90 is provided on the extension portion 24. The connection portion may be provided at a position other than the extension portion 24. The connection wiring 90 is, for example, a flexible printed circuit board (FPC). The connection wiring 90 may be wiring other than an FPC. The device 92 is, for example, a control device such as an electronic control unit (ECU). The device 92 may be a device other than a control device.

[0065] Figure 9 shows the evaluation results of the samples. Nine samples were evaluated in Figure 9. The nine samples were formed as follows: Silver paste and PEDOT:PSS were screen-printed onto a transparent substrate film to form a conductive layer 30 and electrostatic switch electrodes 40. Next, three-dimensional molding was performed using high-pressure molding, followed by Thomson punching. Next, LEDs 50 were mounted on the conductive layer 30 with low-temperature solder 32 using an infrared laser method. Next, LEDs 50 and electrostatic switch electrodes 40 were provided using transparent UV-curable resin to form a light-guiding layer 60. Next, a resin molded section 70 was formed using insert molding with a white PC resin and a circuit component 12 with a light-guiding layer 60 as an insert. The nine samples were designed to differ from one another in at least one of the following characteristics: the shape of the filler in the silver paste, the filler content, or the average particle size of the filler, but all other conditions were the same.

[0066] In Figure 9, the A-rated area is shown with fine sand, the B-rated area is shown with coarse sand, and the C-rated area is shown with no color. These A, B, and C-rated areas are evaluations of solderability. A, B, and C-rated areas are in order of superior solderability. The B-rated sample exhibited superior solderability than the C-rated sample. The A-rated sample exhibited superior solderability than the B-rated sample. The A-rated sample exhibited particularly superior solderability among the samples tested. The boundaries between the A-rated, B-rated, and C-rated areas were drawn based on the evaluation results of the samples.

[0067] As shown in Figure 9, six samples with flake-shaped fillers, filler contents of 90 wt% or more, and average filler particle diameters of 6 μm or more were rated B or higher. Of these, three samples with flake-shaped fillers, filler contents of 94 wt% or more, and average filler particle diameters of 8 μm or more were rated A. Two samples with spherical fillers, filler contents of 97 wt%, and average filler particle diameters of less than 6 μm, and two samples with flake-shaped fillers, filler contents of 84 wt%, and average filler particle diameters of 6 μm or more were rated C.

[0068] <Effects, etc.> In the electrical equipment 10 configured as described above, the binder is made of a thermoplastic resin. During the solder mounting process, the coating is heated above the softening temperature of the thermoplastic resin, softening the coating. This allows the solder to penetrate the coating, facilitating the formation of an alloy layer between the filler and the solder metal component. Furthermore, the average particle size is 20 μm or less, which prevents the conductive paste from clogging the nozzle when printing the conductive layer 30 using the conductive paste. Furthermore, the filler loading amount in the coating is 97 wt% or less, which facilitates ensuring the flexibility of the coating and improving its three-dimensional processability (stretchability). Furthermore, the filler has a flake or scale shape, an average particle size of 6 μm or more, and a filler mass fraction in the coating of 90 wt% or more improves the stretchability and solder wettability of the coating, thereby preventing an increase in the resistance of the circuit via the low-temperature solder 32, even after three-dimensional molding and insert molding.

[0069] The average particle size of the filler is 8 μm or more, which makes it possible to further suppress an increase in resistance when the conductive layer 30 is stretched by three-dimensional molding, and also improves solder wettability.

[0070] The mass fraction of the filler in the coating is 94 wt % or more, which reduces the mass fraction of the binder in the coating, making it easier for the filler to form an alloy with the metal components of the low-temperature solder 32, making it less likely for the low-temperature solder 32 to aggregate.

[0071] The thermoplastic resin constituting the binder also contains hydroxyl groups. As a result, the hydroxyl groups have a good affinity with the metal filler, so that even if the conductive layer 30 is stretched during three-dimensional molding, the interface between the binder and the filler is less likely to break down. Furthermore, the hydroxyl groups are highly reactive, so good adhesion between the binder and the base layer 20 is easily achieved.

[0072] Furthermore, the electrical equipment 10 has the following effect. As shown by arrow A2 in FIG. 4 , light emitted from the light source 50 is reflected by the reflective layer 72 and reaches a user outside the electrical equipment 10 through the light guide layer 60, the electrostatic switch electrode 40, and the second region 26 of the base layer 20. The user's recognition of this light makes it easier to recognize the position of the electrostatic switch electrode 40. By providing the light-shielding wall 74 in the electrical equipment 10, it is possible to prevent light emitted from the light source 50 and passing through the light guide layer 60 from leaking to the sides of the light guide layer 60. This allows the light emitted from the light source 50 to illuminate a more appropriate range in the electrical equipment 10 that includes an electrostatic switch.

[0073] Here, if the switches installed in a vehicle are conventional mechanical switches, each switch requires the wiring of a covered electrical wire. In contrast, if the switches installed in a vehicle are touch panel devices such as electrical equipment 10, multiple switch functions can be integrated into a single electrostatic film sensor, resulting in weight reduction and space savings. Some touch panel devices have LEDs 50 mounted on the base layer 20, but rather have a PCB board with LEDs 50 laminated on the light-guiding layer 60. Compared to touch panel devices that have a PCB board with LEDs 50, the electronic device of the present disclosure can be made thinner by mounting LEDs 50 on the base layer 20.

[0074] The reflective layer 72 is made of resin, which allows the dimensions of the electrical component 10 in the stacking direction to be smaller than when an air layer serving as the reflective layer 72 and a resin layer covering the air layer are provided separately.

[0075] Furthermore, the entire portion of the light guide layer 60 that is in contact with the surface opposite to the base layer 20 side is the reflective layer 72. This makes it easier for the reflective layer 72 to diffusely reflect light, making it less likely that unevenness will occur in the light that passes through the second region 26. This makes it easier for the second region 26 to emit clear surface light.

[0076] Furthermore, the light-shielding wall 74 and the reflective layer 72 are formed from one resin part 70. This allows the number of parts to be reduced compared to when the light-shielding wall 74 and the reflective layer 72 are formed from different resin parts 70.

[0077] Furthermore, the resin part 70 is a resin molded part 70 that is insert-molded using the circuit part 12, which has the base material layer 20, the conductive layer 30, the electrostatic switch electrode 40, the light source 50, and the light guide layer 60, as an insert. This makes it easier to form the surface of the resin part 70 that faces the light guide layer 60 into a shape that conforms to the light guide layer 60, compared to when the resin part 70 is a separately molded part. In particular, when three-dimensional molding is performed, a curved surface may be formed on the surface that comes into contact with the resin part 70. Because the resin part 70 is an insert-molded resin molded part 70, it is easy to achieve a state in which the resin part 70 is in contact with the curved surface as a whole.

[0078] Furthermore, the conductive layer 30 is a coating formed from a conductive paste, and the light source 50 is mounted on the conductive layer 30 with low-temperature solder 32. This reduces the resistance value applied to the circuit of the light source 50 compared to when the light source 50 is mounted with a conductive adhesive.

[0079] [Note] In the first embodiment, the electrical component 10 is described as being a touch panel device, but this is not a required configuration. The electrical component 10 may be a device other than a touch panel device. In this case, the electrical component does not need to include an LED and a light guide layer. If the electrical component does not include an LED, it may include an electronic element other than an LED.

[0080] The configurations described in the above embodiments and modifications can be combined as appropriate as long as they are not mutually contradictory. [Explanation of symbols]

[0081] 10 Electrical equipment 12 Circuit Components 20 Base material layer 20A Base film layer 20B Decorative layer 21 Page 1 22 Side 2 23 Main body 24 Extension 25 First area 26 Second area 27 Third area 28 4th area 30 Conductive layer 32 Bonding layer (low temperature solder) 40 Electrostatic switch electrode 50 LED (light source, electronic element) 60 Light guide layer 70 Resin parts (plastic molded parts) 72 Reflective layer 74 Blackout Wall 90 Connection wiring 92 Control equipment UF finger

Claims

1. a circuit component including a base layer, a conductive layer provided on the base layer, and an electronic element mounted on the conductive layer via low-temperature solder; a resin molded portion that is insert-molded with the circuit component as an insert; Equipped with the base layer and the conductive layer are three-dimensionally molded, the conductive layer is a coating formed from a conductive paste containing a metal filler and a thermoplastic resin binder, The filler has a flake or scale shape, The average particle size of the filler is 6 μm or more and 20 μm or less, The electrical component, wherein the mass fraction of the filler in the coating is 90 wt % or more and 97 wt % or less.

2. The electrical equipment according to claim 1, The electrical component, wherein the average particle size of the filler is 8 μm or more.

3. The electrical equipment according to claim 1 or 2, The electrical component, wherein the mass fraction of the filler in the coating is 94 wt % or more.

4. The electrical equipment according to claim 1 or 2, The thermoplastic resin constituting the binder has a hydroxyl group.

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