Plastic moldings and high-frequency devices

Abstract

To provide a resin-molded product for high-frequency equipment capable of improving design flexibility while reducing manufacturing costs, and high-frequency equipment.SOLUTION: The resin molded product for accommodating circuits that transmit and receive electromagnetic waves includes: a flat part including a scale-like first graphite filler; and a transmission part that is formed integrally with the flat part including a scale-like second graphite filler. The flat part has a flat plate shape that has a first plane and a second plane. The transmission part has an uneven shape formed with multiple first concavities that recess in a first direction and the cross-sectional area that decreases continuously in the first direction and multiple second concavities that recess in a second direction and the cross-sectional area that decreases continuously in the second direction. The first concavity has a side wall inclined at an angle greater than or equal to 65 degrees and less than 90 degrees with respect to the first plane, and the second concavity has a side wall inclined at an angle of 65 degrees or more and less than 90 degrees with respect to the second plane. The first graphite filler is placed along the shape of the flat part, and the second graphite filler is placed along multiple first concavity sidewalls or multiple second concavity sidewalls.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a resin molded product for use in high-frequency devices such as millimeter wave radar or quasi-millimeter wave radar, and to high-frequency devices. [Background technology]

[0002] In recent years, there has been an increasing demand for sensing devices aimed at improving automobile safety, autonomous driving, driving assistance, etc. Radar used in sensing devices is a high-frequency device capable of transmitting and receiving high-frequency signals such as millimeter waves.

[0003] In such high-frequency devices, various measures have been considered to ensure isolation between the high-frequency transmitting circuit and receiving circuit and improve reliability.

[0004] For example, Patent Document 1 discloses a high-frequency module that includes a case that selectively transmits electromagnetic waves and a case that absorbs electromagnetic waves. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2020-126939 A Summary of the Invention [Problem to be solved by the invention]

[0006] The high-frequency module described in Patent Document 1 still has room for improvement in terms of reducing manufacturing costs and improving design freedom.

[0007] The present disclosure provides a resin molded product for high-frequency devices and a high-frequency device that improves design freedom and reduces manufacturing costs. [Means for solving the problem]

[0008] A resin molded product according to one embodiment of the present disclosure includes: A resin molded product that houses a circuit for transmitting and receiving electromagnetic waves, A flat portion including a plurality of first graphite fillers having a scale shape; a transmission portion formed integrally with the flat portion and including a plurality of second graphite fillers having a scale shape; Equipped with The flat portion has a flat plate shape having a first surface and a second surface opposite to the first surface, the transmission portion has an uneven shape provided with a plurality of first recesses that are recessed in a first direction from the first surface toward the second surface and have a cross-sectional area that continuously decreases in the first direction, and a plurality of second recesses that are recessed in a second direction from the second surface toward the first surface and have a cross-sectional area that continuously decreases in the second direction, each of the first recesses has a sidewall that is inclined at an angle of 65 degrees or more and less than 90 degrees with respect to the first surface; each of the second recesses has a sidewall that is inclined at an angle of 65 degrees or more and less than 90 degrees with respect to the second surface; The plurality of first graphite fillers are arranged along the shape of the flat portion, The second graphite fillers are disposed along sidewalls of the first recesses or sidewalls of the second recesses.

[0009] A high-frequency device according to one aspect of the present disclosure includes: The above-mentioned resin molded product, A substrate accommodated in the resin molding; A circuit mounted on the substrate for transmitting and receiving electromagnetic waves; Equipped with. Effect of the Invention

[0010] According to the present disclosure, it is possible to provide a resin molded product for high-frequency devices and a high-frequency device that improves design freedom and reduces manufacturing costs. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a schematic plan view showing a high-frequency device according to a first embodiment; [Diagram 2] Cross-sectional view of high-frequency device 1 taken along line AA in FIG. [Diagram 3] Enlarged view of area Z1 in Figure 2 [Figure 4] A partially enlarged plan view of the transmission section [Diagram 5] A diagram showing an example of graphite filler [Figure 6] Flowchart showing the manufacturing method of resin molded products [Figure 7] Cross section B-B of Figure 5 [Figure 8] Cross section CC of Figure 5 [Figure 9] DD cross section of Fig. 5 [Figure 10] E-E cross section of Figure 5 [Figure 11] FIG. 1 is a schematic plan view of a high-frequency device according to a first modification of the first embodiment. [Figure 12] FF cross section of Figure 11 [Figure 13] FIG. 13 is a schematic diagram showing a part of a resin molded product according to a second modification of the first embodiment. [Figure 14] A graph showing the correlation between the angle of the graphite filler and the electromagnetic wave shielding rate DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] (Background to this disclosure) In recent years, the demand for sensing devices for the purpose of improving automobile safety, autonomous driving, and driving assistance has increased, and the distribution of vehicles equipped with these sensing devices has become more active. The radar used in the sensing devices is a high-frequency device capable of transmitting and receiving high-frequency signals such as millimeter waves.

[0013] In such high-frequency devices, a signal generated by a transmitting circuit is sent from an antenna, and the signal reflected by the target is received by a receiving circuit via the antenna. The receiving circuit compares the signal sent from the transmitting circuit via the circuit board with the signal received via the antenna to detect the target's position or distance.

[0014] Furthermore, the applications of high-frequency devices are becoming more diverse, such as transmitting individual vehicle information, receiving road condition information, etc. For this reason, high-frequency devices are required to selectively transmit and receive necessary signals.

[0015] Examples of applications of such high-frequency equipment include signal processing in a straight line to measure the distance to the vehicle ahead, signal processing that reflects off the bottom of the vehicle ahead to measure the distance to the vehicle ahead, and signal processing from above to send and receive data such as individual vehicle or road information.

[0016] On roads with heavy traffic, signals from sources other than the high-frequency device installed in the vehicle may cause problems such as a decrease in the detection accuracy of the target position or distance, or ghosting. Alternatively, the isolation between the transmitting circuit and the receiving circuit may deteriorate if a signal generated by the transmitting circuit in the high-frequency device is received by the receiving circuit via space rather than via wiring on the board.

[0017] For this reason, measures are being considered to prevent signals transmitted and received by one high-frequency device from affecting other high-frequency devices, such as signal phase conversion or using a case made of a composite of resin and functional material to selectively transmit electromagnetic waves, thereby improving the reliability of the high-frequency device.

[0018] An example of a high-frequency device that selectively transmits electromagnetic waves using a case made of a composite of resin and functional material is the high-frequency module described in Patent Document 1.

[0019] The high-frequency module described in Patent Document 1 improves reliability by selectively transmitting and absorbing electromagnetic waves.

[0020] However, in the high-frequency module described in Patent Document 1, the case that selectively transmits electromagnetic waves and the plate that absorbs electromagnetic waves are formed as separate parts or in two separate processes, making it difficult to reduce manufacturing costs. In addition, it is difficult to improve design freedom because the graphite filler inside the case is oriented in a specific direction relative to the circuit. In addition, a case that has an electromagnetic wave transmission function must be designed so that it does not receive signals from other devices.

[0021] Therefore, the present inventors have investigated a resin molded product for a high-frequency device and a high-frequency device that improves design freedom and reduces manufacturing costs, and have arrived at the following invention.

[0022] The resin molded product according to the first aspect of the present disclosure includes: A resin molded product that houses a circuit for transmitting and receiving electromagnetic waves, A flat portion including a plurality of first graphite fillers having a scale shape; a transmission portion formed integrally with the flat portion and including a plurality of second graphite fillers having a scale shape; Equipped with The flat portion has a flat plate shape having a first surface and a second surface opposite to the first surface, the transmission portion has an uneven shape provided with a plurality of first recesses that are recessed in a first direction from the first surface toward the second surface and have a cross-sectional area that continuously decreases in the first direction, and a plurality of second recesses that are recessed in a second direction from the second surface toward the first surface and have a cross-sectional area that continuously decreases in the second direction; each of the first recesses has a sidewall that is inclined at an angle of 65 degrees or more and less than 90 degrees with respect to the first surface; each of the second recesses has a sidewall that is inclined at an angle of 65 degrees or more and less than 90 degrees with respect to the second surface; The plurality of first graphite fillers are arranged along the shape of the flat portion, The second graphite fillers are disposed along sidewalls of the first recesses or sidewalls of the second recesses.

[0023] With such a configuration, it is possible to provide a resin molded product for high-frequency devices that improves the degree of design freedom and reduces the manufacturing cost.

[0024] In the resin molded product according to the second aspect of the present disclosure, the plurality of first recesses are constituted by a plurality of conical recesses, the plurality of second recesses are constituted by a plurality of conical recesses, when viewed from the first direction, the bottoms of the plurality of first recesses and the bottoms of the plurality of second recesses may be arranged at different positions from each other.

[0025] With such a configuration, the second graphite filler can be oriented at a desired angle, and furthermore, the manufacturing cost can be suppressed.

[0026] In the resin molded product according to the third aspect of the present disclosure, when viewed from the first direction, the plurality of first recesses and the plurality of second recesses may be arranged in a regular triangular lattice, respectively.

[0027] With such a configuration, the second graphite filler can be oriented at a desired angle, and furthermore, the manufacturing cost can be suppressed.

[0028] In the resin molded product according to the fourth aspect of the present disclosure, assuming that the thickness of the flat portion is t, the diameter of the opening of the plurality of first recesses is d1, the interval at which the plurality of first recesses are arranged is p1, and the inclination angle of the side wall of the plurality of first recesses with respect to the first surface is θ1, t×sinθ1≦d1≦2×t×sinθ1, and d1<p1≦1.5×d1 are satisfied, assuming that the thickness of the flat portion is t, the diameter of the opening of the plurality of second recesses is d2, the interval at which the plurality of second recesses are arranged is p2, and the inclination angle of the side wall of the plurality of second recesses with respect to the second surface is θ2, t×sinθ2≦d2≦2×t×sinθ2, and d2<p2≦1.5×d2 may be satisfied.

[0029] With this configuration, the resin molded product can be formed so that the transmitting portion transmits electromagnetic waves and the flat portion reflects electromagnetic waves.

[0030] In the resin molded product according to the fifth aspect of the present disclosure, The first recesses are formed of linear grooves, The second recesses are formed by a plurality of linear grooves, When viewed from the first direction, the plurality of first recesses and the plurality of second recesses may be aligned in parallel and in a staggered manner.

[0031] With this configuration, it is possible to provide a resin molded product for high frequency devices with improved design freedom and reduced manufacturing costs.

[0032] In the resin molded product according to the sixth aspect of the present disclosure, Bottoms of the plurality of first recesses may be located closer to the second surface than bottoms of the plurality of second recesses.

[0033] With this configuration, it is possible to provide a resin molded product for high-frequency devices that achieves both improved electromagnetic wave transmission characteristics in the transmission section and reduced manufacturing costs.

[0034] In the resin molded product according to the seventh aspect of the present disclosure, The second graphite fillers may have a basal surface that is inclined at an angle of 65 degrees or more and 90 degrees or less with respect to the first surface.

[0035] With this configuration, it is possible to provide the resin molded product with a portion that absorbs electromagnetic waves and a portion that transmits electromagnetic waves, thereby improving the reliability of the high frequency device.

[0036] In the resin molded product according to the eighth aspect of the present disclosure, the first graphite fillers have a basal surface, and an average value of a maximum length on the basal surface of the first graphite fillers is 1 μm or more and 100 μm or less and is 10 times or more an average value of a maximum thickness in a direction intersecting the basal surface of the first graphite fillers; The content of the first graphite fillers in the flat portion is 5% by weight or more and 30% by weight or less, an average value of a maximum length of the plurality of second graphite fillers on a basal plane is 1 μm or more and 100 μm or less, and is 10 times or more an average value of a maximum thickness of the plurality of second graphite fillers in a direction intersecting the basal plane; The content of the plurality of second graphite fillers in the transmission portion may be 5% by weight or more and 30% by weight or less.

[0037] With this configuration, it is possible to improve the electromagnetic wave transmission and absorption characteristics while maintaining the strength of the resin molded product.

[0038] A high-frequency device according to a ninth aspect of the present disclosure includes: A resin molded product according to any one of the first to eighth aspects; A substrate accommodated in the resin molding; A circuit mounted on the substrate for transmitting and receiving electromagnetic waves; Equipped with.

[0039] With this configuration, it is possible to provide a high-frequency device with improved reliability.

[0040] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In each drawing, each element is shown exaggerated for ease of explanation.

[0041] (Embodiment 1) [Overall configuration] Fig. 1 is a schematic plan view showing a high-frequency device 1 according to a first embodiment of the present invention. Fig. 2 is a cross-sectional view of the high-frequency device 1 taken along line AA in Fig. 1.

[0042] 1 and 2, the high-frequency device 1 is a device that includes a resin molded product 10, a substrate 2, and a circuit 3, and transmits and receives electromagnetic waves in a high-frequency band. The high-frequency device 1 can transmit and receive electromagnetic waves in a frequency band between 10 GHz and 300 GHz that is generally used in high-frequency devices. Note that the X, Y, and Z directions in the figures indicate the width, depth, and height directions of the high-frequency device 1, respectively.

[0043] <Substrate> 2, the substrate 2 is formed in a plate shape having a main surface 2a. A circuit 3 is mounted on the main surface 2a. An electronic circuit other than the circuit 3 may be mounted on the substrate 2.

[0044] <Circuit> The circuit 3 includes a transmission circuit that transmits electromagnetic waves, a reception circuit that receives the electromagnetic waves, and an arithmetic circuit. The transmission circuit of the circuit 3 generates a high-frequency signal, such as a millimeter wave or a microwave, and transmits the high-frequency signal as an electromagnetic wave toward a target. The reception circuit of the circuit 3 receives, of the electromagnetic waves transmitted from the transmission circuit, those that are reflected back from the target. The arithmetic circuit of the circuit 3 performs arithmetic processing based on the electromagnetic waves received by the reception circuit. For example, the arithmetic circuit of the circuit 3 compares the electromagnetic waves transmitted from the transmission circuit with the electromagnetic waves received by the reception circuit, and calculates the position of the target and the distance to the target.

[0045] <Resin molded products> The resin molded product 10 is a housing that houses a circuit 3 that transmits and receives radio waves. The resin molded product 10 is made of a matrix material in which a plurality of scaly graphite fillers 5 are dispersed. The matrix material is a material formed from a thermoplastic resin or an elastomer. The resin molded product 10 includes a flat portion 30 and a transparent portion 20 that is formed integrally with the flat portion 30.

[0046] The flat portion 30 includes a plurality of first graphite fillers 5a each having a scale shape. The flat portion 30 has a plate shape having a first surface 30a and a second surface 30b opposite to the first surface 30a.

[0047] In this embodiment, the resin molded product 10 has a side wall 31 arranged so as to surround the second surface 30b of the flat portion 30, and is formed in a box shape. That is, the resin molded product 10 is a housing having the flat portion 30 and the side wall 31 and formed in a concave shape. An opening 10a is formed in the resin molded product 10. In the resin molded product 10, the substrate 2 is arranged on the opening 10a side, and the substrate 2 and the circuit 3 are housed so that the flat portion 30 and the main surface 2a of the substrate 2 face each other. That is, the flat portion 30 of the resin molded product 10 is arranged at a position facing the main surface 2a of the substrate 2.

[0048] The transmissive portion 20 is formed integrally with the flat portion 30. In the present embodiment, the transmissive portion 20 is formed at a position overlapping the circuit 3 when viewed from a direction perpendicular to the first surface 30a of the flat portion 30. The transmissive portion 20 includes a plurality of flake-like second graphite fillers 5b.

[0049] In the resin molded product 10, the transmitting portion 20 transmits electromagnetic waves transmitted from the transmitting circuit of the circuit 3 and traveling in the second direction A2 (see FIG. 3), and electromagnetic waves traveling in the first direction A1 (see FIG. 3) and received by the receiving circuit. On the other hand, the flat portion 30 and the side portion 31, excluding the transmitting portion 20, are regions that absorb electromagnetic waves. In other words, the flat portion 30 and the side portion 31 function to absorb electromagnetic waves, and the transmitting portion 20 functions to transmit electromagnetic waves.

[0050] Absorbing electromagnetic waves means that the electromagnetic waves irradiated to the flat portion 30 and the side portion 31 are taken into the flat portion 30 and the side portion 31 and are not allowed to exit from the flat portion 30. Although there are electromagnetic waves that are reflected by the flat portion 30 and the side portion 31 and exit, the proportion of such waves is very small, and therefore, for the sake of simplification, a description thereof will be omitted. On the other hand, transmitting electromagnetic waves means that the electromagnetic waves irradiated on one side (the first surface 30a side) of the transmitting portion 20 are emitted from the other side (the second surface 30b side), or that the electromagnetic waves irradiated on the other side are emitted to one side. Since the electromagnetic waves can pass through the transmitting portion 20, the electromagnetic waves that have passed through the transmitting portion 20 can reach the substrate 2 and the circuit 3.

[0051] The resin molded product 10 is made of a matrix material in which a plurality of flaky graphite fillers 5 (first graphite filler 5a and second graphite filler 5b) are dispersed.

[0052] As described below, in the flat portion 30 of the resin molded product 10, the first graphite filler 5a is arranged along the first surface 30a or the second surface 30b of the flat portion 30. Arrangement of the first graphite filler 5a along the first surface 30a or the second surface 30b means that the first graphite filler 5a is arranged substantially parallel to the first surface 30a or the second surface 30b. Therefore, the flat portion 30 can absorb electromagnetic waves from the first direction A1 (see FIG. 3).

[0053] On the other hand, in the transmitting portion 20, the second graphite filler 5b is arranged along the side wall 21a of the first recess 21 or the side wall 22a of the second recess 22 (see FIG. 3). Therefore, the second graphite filler 5b is arranged at an angle to the first surface 30a or the second surface 30b of the flat portion 30. Therefore, the transmitting portion 20 can transmit electromagnetic waves from the first direction A1.

[0054] Fig. 3 is an enlarged view of a region Z1 in Fig. 2. Fig. 4 is an enlarged plan view of a part of the transmission section 20. The transmission section 20 will be described with reference to Figs. 3 and 4.

[0055] 1, the transmissive portion 20 is formed in a portion of the flat portion 30 of the resin molded product 10 that overlaps with the circuit 3 when viewed from a direction perpendicular to the main surface 2a of the substrate 2. As shown in FIG. 3, the transmissive portion 30 has an uneven shape in which a plurality of first recesses 21 and a plurality of second recesses 22 are provided.

[0056] The first recesses are recessed in a first direction A1 from the first surface 30a to the second surface 30b of the flat portion 30, and the cross-sectional areas become smaller continuously in the first direction A1. The second recesses 22 are recessed in a second direction A2 from the second surface 20b to the first surface 30a of the flat portion 30, and the cross-sectional areas become smaller continuously in the second direction A2. Here, the cross-sectional areas of the first recesses 21 and the second recesses 22 indicate the areas of the openings of the first recesses 21 and the second recesses 22 when cut along the XY plane.

[0057] The resin molded product 10 can be formed, for example, by injection molding. In this embodiment, the first recesses 21 and the second recesses 22 are formed by using a mold having a plurality of convex shapes on its surface.

[0058] In this embodiment, the first recess 21 is formed so that the cross section thereof is circular when viewed from the first direction A1 (see FIG. 4). Here, the cross section of the first recess 21 indicates the opening of the first recess 21 when cut along the XY plane. The multiple first recesses 21 are composed of multiple cone-shaped recesses. Also, in this embodiment, the first recess 21 is formed so that the cross-sectional area becomes smaller toward the second surface 30b. The first recess 21 has a sidewall 21a that is inclined at an angle θ1 of 65 degrees or more and less than 90 degrees with respect to the first surface 30a of the flat portion 30.

[0059] In this embodiment, the second recess 22 is formed so that the cross section is circular when viewed from the second direction A2 (see FIG. 4). Here, the cross section of the first recess 21 shows the opening of the second recess 22 when cut along the XY plane. The multiple second recesses 22 are composed of multiple cone-shaped recesses. Also, in this embodiment, the second recess 22 is formed so that the cross-sectional area becomes smaller toward the first surface 30a. The second recess 22 has a sidewall 22a that is inclined at an angle θ2 of 65 degrees or more and less than 90 degrees with respect to the second surface 30b of the flat portion 30.

[0060] When the angle θ1 of the side wall 21a relative to the first surface 30a and the angle θ2 of the side wall 22a relative to the second surface 30b are 65 degrees or more and less than 90 degrees, the mold releasability is improved in the molding process of the resin molded product 10, and the productivity of the resin molded product 10 can be improved. When the angle θ1 and the angle θ2 are 65 degrees or more and less than 90 degrees, the graphite filler 5 is less likely to reflect electromagnetic waves, and the electromagnetic wave transmission characteristics of the transmission portion 20 can be improved. More preferably, the angle θ1 and the angle θ2 are 75 degrees or more and less than 90 degrees. In this case, the electromagnetic wave transmission characteristics of the transmission portion 20 and the productivity of the resin molded product 10 can be further improved.

[0061] 3, the bottom 21b of the first recess 21 and the bottom 22b of the second recess 22 are disposed at different positions. That is, the bottom 21b of the first recess 21 and the bottom 22b of the second recess 22 are disposed so as not to overlap with each other when viewed from a direction perpendicular to the main surface 2a of the substrate 2. The bottom 21b of the first recess 21 indicates the deepest part of the first recess 21, and the bottom 22b of the second recess 22 indicates the deepest part of the second recess 22.

[0062] Moreover, the first recesses 21 are arranged in a regular triangular lattice pattern when viewed from the first direction A1, as shown in Fig. 4. Arranged in a regular triangular lattice pattern means that when the first recesses 21 are arranged in a plurality of rows, the first recesses 21 in adjacent rows are arranged in a staggered pattern. The second recesses 22 are also arranged in a regular triangular lattice pattern as shown in Fig. 5. In this embodiment, the first recesses 21 and the second recesses 22 are arranged such that the bottom 21b of the first recess 21 is located midway between the bottoms 22b of two adjacent second recesses 22, as shown in Fig. 3.

[0063] In addition, when viewed from the first direction A1, the bottom 21b of the first recess 21 is disposed closer to the second surface 30b of the flat portion 30 than the bottom 22b of the second recess 22. Conversely, when viewed from the first direction A1, the bottom 22b of the second recess 22 is disposed closer to the first surface 30a of the flat portion 230 than the bottom 21b of the first recess 21. With this configuration, the first recess 21 and the second recess 22 can be made to have a complicated shape. With the first recess 21 and the second recess 22 in a complicated state, the second graphite filler 5b can be easily oriented along the side wall 21a or the side wall 21b, and the transmission characteristic of the electromagnetic wave in the transmission portion 20 can be improved.

[0064] In this embodiment, the relationship expressed by formula (1) holds between the width d1 of the opening of first recess 21, the thickness t of flat portion 30, and angle θ1.

[0065]

number

[0066] When the width d1 of the opening of the first recess 21 is within the range of formula (1), it is possible to improve the productivity during molding of the resin molded product 10 while improving the electromagnetic wave transmission characteristics of the transmission section 20. When the width d1 of the opening of the first recess 21 is below the lower limit of formula (1) or exceeds the upper limit of formula (1), it is not possible to set the angle θ1 of the side wall 21a of the first recess 21 with respect to the first surface 30a to an appropriate value, and the electromagnetic wave transmission characteristics of the transmission section 20 may deteriorate.

[0067] Similarly, the relationship of formula (2) holds between the width d2 of the opening of the second recess 22, the thickness t of the flat portion 30, and the angle θ2.

[0068]

number

[0069] When the width d2 of the opening of the second recess 22 is within the range of formula (2), it is possible to improve the productivity during molding of the resin molded product 10 while improving the electromagnetic wave transmission characteristics of the transmission section 20. When the width d2 of the opening of the second recess 22 is below the lower limit value of formula (2) or exceeds the upper limit value of formula (2), it is not possible to set the angle θ2 of the side wall 22a of the second recess 22 with respect to the second surface 30b to an appropriate value, and the electromagnetic wave transmission characteristics of the transmission section 20 may deteriorate.

[0070] Furthermore, the relationship of formula (3) is established between the width d1 of the opening of the first recess 21 and the interval p1 at which adjacent first recesses 21 are arranged.

[0071]

number

[0072] If the interval p1 is below the lower limit of formula (3), the convex portion of the mold that forms the first recess 21 and the convex portion of the mold that forms the second recess 22 may interfere with each other when molding the resin molded product 10, which may result in reduced productivity. If the interval p1 is above the upper limit of formula (3), the electromagnetic wave transmission characteristics will be reduced.

[0073] Similarly, the relationship of formula (4) is established between the width d2 of the opening of the second recess 22 and the interval p2 at which adjacent second recesses 22 are arranged.

[0074]

number

[0075] If the distance p2 is below the lower limit of formula (4), the convex portion of the mold that forms the first recess 21 and the convex portion of the mold that forms the second recess 22 may interfere with each other when molding the resin molded product 10, which may result in reduced productivity. If the distance p2 is above the upper limit of formula (4), the electromagnetic wave transmission characteristics will be reduced.

[0076] <Matrix material> The matrix material can be made of a thermoplastic resin or an elastomer, or may be made of a mixture of a thermoplastic resin having no elasticity and an elastomer having elasticity.

[0077] Examples of the thermoplastic resin include styrene-based polymers such as styrene-acrylonitrile copolymer, styrene-maleic anhydride copolymer, and (meth)acrylic acid ester-styrene copolymer; rubber-reinforced resins such as ABS resin and AES resin; olefin-based polymers such as polyethylene, polypropylene, ethylene-vinyl acetate copolymer, ethylene-vinyl alcohol copolymer, and chlorinated polyethylene; vinyl chloride-based polymers such as polyvinyl chloride, ethylene-vinyl chloride polymer, and polyvinylidene chloride; (meth)acrylic acid ester-based polymers such as polymethyl methacrylate; imide-based polymers such as polyamide, polyimide, polyamideimide, and polyetherimide; polyester-based polymers such as polyethylene terephthalate and polybutylene terephthalate; fluororesins such as polyacetal, polycarbonate, polyarylate, polyphenylene ether, polyphenylene sulfide, polytetrafluoroethylene, and polyvinylidene fluoride; ketone-based polymers such as polyether ketone and polyether ether ketone; sulfone-based polymers such as polysulfone and polyether sulfone; urethane-based polymers; and polyvinyl acetate. The matrix material may be formed by using any one of these materials alone, or may be formed by combining two or more of these materials.

[0078] Examples of the elastomer include, but are not limited to, chloroprene rubber, isoprene rubber, natural rubber, styrene-butadiene rubber, butadiene rubber, butyl rubber, ethylene-propylene rubber, ethylene-propylene-diene rubber (EPDM), nitrile rubber, urethane rubber, acrylic rubber, silicone rubber, fluororubber, hydrogenated nitrile rubber, etc. The matrix material may be formed by using one of these materials alone. Alternatively, the matrix material may be formed by combining two or more of these materials.

[0079] <Graphite filler> The graphite filler 5 is formed in a scale shape. In this specification, the term "scale shape" refers to a shape such as a flat plate or curved plate, in which the area when observed from a specific angle (when viewed in plan) is larger than the area when observed from an angle perpendicular to the observation direction.

[0080] 5 is a diagram showing an example of graphite filler 5. The term "flake-like" refers not only to a scale-like shape but also to an elliptical shape, a circular shape, a polygonal shape, or an irregular shape obtained by pulverizing a thin film. In the present embodiment, graphite filler 5 has, for example, a major axis of 1 μm or more and 100 μm or less, and an average major axis / thickness ratio of 10 or more.

[0081] The relative dielectric constant of graphite filler 5 is preferably 7 or more and 17 or less. When the relative dielectric constant of graphite filler 5 is 7 or more and 17 or less, the transmittance of electromagnetic waves incident in first direction A1 at flat portion 30 can be made less than 10%. When the relative dielectric constant of graphite is less than 7, absorption of electromagnetic waves due to multiple reflections is insufficient, and the transmittance of electromagnetic waves becomes 10% or more. On the other hand, when the relative dielectric constant of the graphite sheet exceeds 17, reflection of electromagnetic waves becomes dominant, and even unwanted radiation inside is reflected, which may reduce the reliability of high-frequency devices.

[0082] A method for producing graphite filler 5 will be described. Graphite filler 5 can be obtained, for example, by pulverizing artificial graphite or natural graphite. Graphite filler 5 may be produced using natural flake graphite powder. Graphite filler 5 may be produced by mixing multiple types of graphite filler as long as the conditions that the long diameter is 1 μm or more and 100 μm or less on average and the long diameter / thickness ratio is 10 or more on average are satisfied.

[0083] Artificial graphite can be obtained by heat treating a polymer film under an inert gas at a high temperature of 2400°C or more, preferably 2600°C to 3300°C. The heat treatment may be performed in one step, or may be divided into two or more steps with different temperatures for each step. The inert gas is not particularly limited, but nitrogen gas or argon gas is inexpensive and preferable. The heat treatment time is not particularly limited, but is preferably, for example, 2 hours to 10 hours.

[0084] The thickness of the polymer film before graphitization can be appropriately selected, but is, for example, 400 μm or less, and is preferably 1 μm or more and 150 μm or less. Even when a relatively thick polymer film is used, peeling occurs between the graphite layers when the graphite film is crushed, so that thinner flake-like graphite filler 5 can be obtained. If the polymer film is 400 μm or more thick, it becomes difficult to apply heat evenly within the film, and the crystallinity of the graphite decreases. Also, if it is thinner than 1 μm, it will be destroyed by heat treatment.

[0085] Preferred examples of the polymer film include polyimide, polyamideimide, polyoxadiazole, polybenzothiazole, polybenzobisthiazole, polybenzoxazole, polybenzobisthiazole, poly(p-phenyleneisophthalamide), poly(m-phenylenebenzimidazole), poly(phenylenebenzobisimidazole), polythiazole, and polyparaphenylenevinylene.

[0086] The method for producing the graphite filler 5 is not limited to the above. These materials may be used alone or in combination. For example, different types of films may be graphitized and pulverized, and then mixed. Alternatively, multiple materials may be compounded or alloyed in advance, formed into a film, and the film may be graphitized. The resulting graphite film is pulverized to obtain multiple graphite fillers 5 formed in a scale shape.

[0087] The pulverization method is not particularly limited, but a jet mill method in which graphite filler 5 is collided with itself or graphite filler 5 is physically collided with a hard substance is preferred. Other methods include a ball mill method, a nanomizer method, and freeze pulverization. The thickness of the graphite film to be pulverized may be appropriately selected depending on the desired thickness of the flake-like graphite filler 5.

[0088] The content of the first graphite filler 5a in the matrix material forming the resin molded product 10 may be, for example, 5% by weight or more and 30% by weight or less. When the content of the first graphite filler 5a is within this range, the electromagnetic wave absorption characteristics of the flat portion 30 can be improved. When the content of the graphite filler 5 in the matrix material is less than 5% by weight, multiple reflections are unlikely to occur, and the electromagnetic wave absorption characteristics are degraded. When the content of the first graphite filler 5a in the matrix material is more than 30% by weight, not only is it difficult to maintain the strength of the resin molded product 10, but the number of paths for the electromagnetic waves is reduced, making it difficult for multiple reflections to occur, and thus degrading the electromagnetic wave absorption characteristics.

[0089] The content of the second graphite filler 5b in the matrix material forming the resin molded product 10 may be, for example, 5% by weight or more and 30% by weight or less. When the content of the second graphite filler 5b is within this range, the electromagnetic wave transmission characteristics of the transmission part 20 can be improved. When the content of the graphite filler 5 in the matrix material is less than 5% by weight, multiple reflections are unlikely to occur, and the electromagnetic wave absorption characteristics are degraded. When the content of the second graphite filler 5b in the matrix material is more than 30% by weight, not only is it difficult to maintain the strength of the resin molded product 10, but the number of paths for the electromagnetic waves is reduced, making it difficult for multiple reflections to occur, and thus degrading the electromagnetic wave absorption characteristics.

[0090] <Graphite filler placement> With reference to FIG. 3, the arrangement of the graphite filler 5 inside the matrix material will be described.

[0091] The graphite filler 5 includes first graphite filler 5 a arranged in the flat portion 30 and second graphite filler 5 b dispersed in the transparent portion 20 .

[0092] 3, the first graphite filler 5a is arranged along the shape of the flat portion 30. More specifically, the first graphite filler 5a is arranged so that the average value of the angle α1 between the basal plane BP1 of the first graphite filler 5a and the first surface 30a of the flat portion 30 is 0 degrees or more and 25 degrees or less. More preferably, the average value of the angle α1 is 0 degrees. The basal plane BP1 refers to a plane in the benzene ring direction of the first graphite filler 5a.

[0093] The first graphite fillers 5a are arranged in the flat portion 30 such that the basal plane BP1 is substantially perpendicular to the first direction A1. When an electromagnetic wave travels in the first direction A1 and reaches the flat portion 30, the electromagnetic wave collides with the basal plane BP1 of the first graphite filler 5a and is reflected. The reflected electromagnetic wave collides with the basal plane BP1 of another first graphite filler 5a and is further reflected. In this manner, the electromagnetic wave is multiple-reflected by the first graphite fillers 5a, and is attenuated. Therefore, the electromagnetic wave is absorbed in the flat portion 30.

[0094] The basal surface BP1 of the first graphite filler 5a is arranged along the first surface 30a or the second surface 30b of the flat portion 30. This is because the resin molded product 10 is obtained by molding, such as injection molding, in which a matrix material is injected into a mold. Specifically, this is because the matrix material hardens in a state in which the basal surface BP1 of the first graphite filler 5a is pressed against the wall surface (the first surface 30a or the second surface 30b) by shear pressure due to the molten flow.

[0095] As shown in FIG. 3, the second graphite filler 5b is disposed along the side walls 21a of the first recesses 21 or the side walls 22a of the second recesses. More specifically, the average value of the angle α2 between the basal plane BP2 of the second graphite filler 5a and the side walls 21a of the first recesses 21 or the side walls 22a of the second recesses 22 may be 0 degrees or more and 10 degrees or less. More preferably, the average value of the angle α2 may be 0°. By disposing the second graphite filler 5b along the side walls 21a or 21b, the angle between the basal plane BP2 of the second graphite filler 5b and the first surface 30a of the flat portion 30 is 65 degrees or more and 90 degrees or less. The basal plane BP2 refers to a plane in the benzene ring direction of the second graphite filler 5b.

[0096] Since the basal planes BP2 of the plurality of second graphite fillers 5b are arranged along the side walls 21a or 22a, multiple reflections are less likely to occur in the transmitting portion 20 compared to the flat portion 30. For this reason, in the transmitting portion 20, the electromagnetic waves are not reflected by the plurality of second graphite fillers 5b and are transmitted through the transmitting portion 20. For this reason, the electromagnetic waves that have passed through the transmitting portion 20 reach the circuit mounted on the substrate 2. When the angle between the basal planes BP2 of the plurality of second graphite fillers 5b and the first surface 30b of the flat portion 30 is 65 degrees or more and 90 degrees or less, the transmittance of the electromagnetic waves in the transmitting portion 20 can be made 85% or more.

[0097] As described above, the basal surface BP2 of the second graphite filler 5b is disposed along the side wall 21a of the first recess 21 and the side wall 22a of the second recess 22. This is because, as described later, the resin molded product 10 is obtained by molding, such as injection molding, in which a matrix material is injected into a mold. Specifically, the matrix material hardens in a state in which the basal surface BP2 of the second graphite filler 5b is pressed against the wall surface (side wall 21a or side wall 22a) by shear pressure caused by the flow of the matrix material. The angle α2 in the transmission portion 20 can be measured, for example, by observing a cross section of the cut surface of the resin molded product 10 as shown in FIG. 4.

[0098] The average value of angle α2 can be calculated by measuring angle α2 of basal plane BP2 of 20 or more second graphite fillers 5b dispersed inside the matrix material. Angle α2 can be measured by measuring the angle between a line extending from basal plane BP2 of second graphite filler 5b and a line extending from side wall 21a of first recess 21 or side wall 22a of second recess 22. When two extended lines intersect, there are two angles, and the smaller angle is used as angle α2.

[0099] 2, in side portion 31 of resin molded product 10, the basal surface of graphite filler 5 is disposed along side surface 31a. Specifically, in side portion 31 of resin molded product 10, the basal surface of graphite filler 5 is disposed substantially parallel to side surface 31. Furthermore, in the vicinity of end surface 31b of side portion 31, the basal surface of graphite filler 5 is disposed along end surface 31b. Specifically, in the vicinity of end surface 31b of side portion 31 of resin molded product 10, the basal surface of graphite filler 5 is disposed substantially parallel to end surface 31b.

[0100] <Manufacturing method of resin molded products> A method for producing the resin molded product 10 will be described with reference to Fig. 6. Fig. 6 is a flow chart illustrating the method for producing the resin molded product 10.

[0101] First, a matrix material kneaded with graphite filler 5 is prepared (step S11). Next, the matrix material kneaded with graphite filler 5 is weighed and melted (step S12). Next, the matrix material is injected and filled into a mold by injection molding (step S13).

[0102] The mold for filling the matrix material has a fixed mold and a movable mold that is movable relative to the fixed mold. The fixed mold and the movable mold are provided with a plurality of convex portions for forming the first recess 21 and the second recess 22. In the fixed mold and the movable mold, the plurality of convex portions are formed in a cone shape. In the fixed mold and the movable mold, the plurality of convex portions are arranged in a regular triangular lattice shape. When the fixed mold and the movable mold are clamped together, the cone-shaped apex of the plurality of convex portions provided in the fixed mold and the cone-shaped apex of the plurality of convex portions provided in the movable mold are disposed at different positions.

[0103] The mold filled with the matrix material is pressure-maintained and cooled (step S14), and then removed from the mold (step S15), completing the resin molded product 10.

[0104] <Flow of matrix material and arrangement of graphite filler during injection and filling> The flow of the matrix material injected and filled into the mold will be described with reference to Figs. 7 to 10. Fig. 7 is a cross-sectional view taken along line BB in Fig. 5. Fig. 8 is a cross-sectional view taken along line CC in Fig. 5. Fig. 9 is a cross-sectional view taken along line DD in Fig. 5. Fig. 10 is a cross-sectional view taken along line EE in Fig. 5. For ease of explanation, graphite filler 5 is omitted from Figs. 7 to 10, and the flow of the matrix material is indicated by arrows. Also, in Figs. 7 to 10, the mold for injection molding is indicated by hatching. Also, the matrix material flows in the direction of arrow A1 in Fig. 5.

[0105] After the movable die is clamped against the fixed die, the matrix material flowing into the die reaches the first convex portions C1 of the die corresponding to the first concave portions 21 and the second convex portions D1 of the die corresponding to the second concave portions 22, as shown in Fig. 7. The matrix material that reaches the first convex portions C1 and the second convex portions D1 flows around and follows the shapes of the convex portions C1 and D1. After going around 1 / 4 of a turn between the convex portions C1 and D1, the matrix material reaches the next convex portions C2 and D2, as shown in Fig. 8, and flows around and follows the convex portions C2 and D2.

[0106] 9 and 10, the matrix material that has flowed along the convex portions C1 and D1 next flows along the convex portions C2 and D2 when it reaches the convex portions C2 and D2, and further flows along the convex portions C3 and D3 when it reaches the convex portions C3 and D3. In this manner, the matrix material passes between the multiple first convex portions and the multiple second convex portions. By repeatedly flowing along the first convex portions and the second convex portions and passing between the first convex portions and the second convex portions, the matrix material is filled between the first convex portions and the second convex portions in the mold.

[0107] In this manner, the matrix material repeatedly branches and merges, whereby the graphite filler contained in the matrix material is arranged along the side walls 21 a, 22 a of the recesses 21, 22.

[0108] Generally, additives such as filler or fiber kneaded into a matrix material are oriented along the wall surface of the mold, but for example, the vicinity of the center in the thickness direction of the resin molded product 10 is cooled and solidified later than the vicinity of the surface, so that orientation along the wall surface may not occur. In this embodiment, since the distance between the first convex portion and the second convex portion in the mold is small, the flow rate of the matrix material during molding increases, and additives such as filler or fiber are likely to be arranged along the wall surface of the mold.

[0109] Therefore, by adjusting the inclination angles of the conical shapes of the first convex portion and the second convex portion, it is possible to adjust the angles θ1, θ2 (see FIG. 4) of the side walls 21a, 22a of the recesses 21, 22. By adjusting the angles θ1, θ2 of the side walls 21a, 22a of the recesses 21, 22, the arrangement of the first graphite filler 5a, i.e., the angle α2 between the basal plane BP2 and the side wall 21a or the side wall 22a, can be set to a desired angle.

[0110] In this embodiment, the matrix material flows in a direction intersecting the direction in which the multiple protrusions C1 to D3 of the mold are arranged. This is because if the matrix material is flowed along the direction in which the multiple protrusions are arranged, there may be areas where the matrix material is difficult to split and join.

[0111] [effect] According to the above-described embodiment, the resin molded product 10 includes a flat portion 30 and a transmissive portion 20. The flat portion 30 includes a plurality of first graphite fillers 5a in a scale-like shape, and has a flat plate shape having a first surface 30a and a second surface 30b. The transmissive portion 20 is formed integrally with the flat portion 30, and has an uneven shape provided with a plurality of first recesses 21 and a plurality of second recesses 22. The plurality of first recesses 21 are recessed in a first direction A1 from the first surface 30a toward the second surface 30b, and the cross-sectional area continuously decreases toward the first direction A1. The plurality of recesses 22 are recessed in a second direction from the second surface 30b toward the first surface 30a, and the cross-sectional area continuously decreases toward the second direction A2. The plurality of first recesses 21 each have a sidewall 21a inclined at an angle of 65 degrees or more and less than 90 degrees with respect to the first surface 30a. The second recesses 22 each have a sidewall 22a that is inclined at an angle of 65 degrees or more and less than 90 degrees with respect to the second surface 30b. The first graphite fillers 5a are arranged along the shape of the flat portion 30. The second graphite fillers 5b are arranged along the sidewalls 21a of the first recesses 21 or the sidewalls 22a of the second recesses 22.

[0112] With this configuration, first graphite filler 5a arranged in transmitting portion 20 can be arranged at a different angle from second graphite filler 5b arranged in flat portion 30. Therefore, flat portion 30 absorbs electromagnetic waves, while transmitting portion 20 transmits electromagnetic waves. Furthermore, since transmitting portion 20 and flat portion 30 are integrally formed, manufacturing costs can be reduced and design freedom can be improved.

[0113] By using the resin molded product 10 according to the above-described embodiment, it is possible to provide a high-frequency device 1 having a wide range of electromagnetic wave transmission and absorption characteristics.

[0114] Moreover, the transmitting portion 20 and the flat portion 30 can be molded together by injection molding. Furthermore, since the function of transmitting electromagnetic waves can be imparted within the range of the general thickness of the molded product, this contributes to miniaturization of the high-frequency device 1 and improves the design freedom. Furthermore, since the recess 21 of the transmitting portion 20 can be visually confirmed, inspection from the outside is also easy.

[0115] In the above-described embodiment, the resin molded product 10 is used in a high-frequency device that transmits and receives electromagnetic waves in a high-frequency band, but the present invention is not limited to this. The resin molded product 10 can also be used in devices that transmit and receive electromagnetic waves in bands other than the high-frequency band.

[0116] [Variations] Fig. 11 is a schematic plan view of a high-frequency device 1A according to a first modification of the first embodiment, and Fig. 12 is a cross-sectional view taken along line FF of Fig. 11 .

[0117] As shown in FIG. 11 and FIG. 12, the transmissive portion 120 of the resin molded product 110 may be formed by a plurality of linear grooves. Specifically, the plurality of first recesses 121 may be formed by a plurality of linear grooves. Furthermore, the plurality of second recesses 122 may also be formed by a plurality of linear grooves. Moreover, when viewed from the first direction A1, the plurality of first recesses 121 and the plurality of second recesses 122 are arranged in parallel and alternately. Therefore, the transmissive portion 120 is formed with a corrugated cross-sectional shape when cut on the XZ plane. With this configuration, the resin molded product 110 can be formed with a mold having a simpler shape, and therefore the manufacturing cost can be reduced.

[0118] FIG. 13 is a schematic diagram showing a part of resin molded product 210 according to Modification 2 of Embodiment 1. As shown in FIG. 13, bottom 221c of first recess 221 and bottom 222c of second recess 222 may have a fillet shape of 0.1 mm or less. The fillet shape means that bottoms 221c, 222c of recesses 221, 222 are rounded as shown in FIG. 14. The size of the fillet shape refers to the width of the rounded portion. The size of the fillet shape is preferably 0.1 mm or less. More preferably, it is 0.05 mm. If the size of the fillet shape is smaller than 0.05 mm, moldability may decrease. Conversely, if the size of the fillet shape is larger than 0.1 mm, second graphite filler 5b is not arranged at a desired angle, and the transmission characteristics of electromagnetic waves decrease.

[0119] Moreover, the top 221d of the first recess 221 and the top 222d of the second recess 222 have a fillet shape of 0.3 mm or less. The top 221d is a convex portion defined by two adjacent first recesses 221, and the top 222d is a concave portion defined by two adjacent second recesses 222. The size of the fillet shape is preferably 0.3 mm or less. More preferably, it is 0.1 mm. When the size of the fillet shape is within this range, the moldability of the resin molded product 10 can be improved. When the size of the fillet shape is smaller than 0.1 mm, the moldability may be reduced. Conversely, when the size of the fillet shape is larger than 0.3 mm, the second graphite filler 5b is not arranged at a desired angle, and the transmission characteristics of the electromagnetic wave are reduced.

[0120] In addition, when the first recess 221 and the second recess 222 are hollowed out in a conical shape as in embodiment 1, if the size of the fillet shape of the top 221d of the first recess 221 and the top 222d of the second recess 222 is 0.2 mm or less, the moldability in injection molding can be improved.

[0121] When the top 221d of the first recess 221 and the top 222d of the second recess 222 are provided with a fillet shape, it is preferable to set an appropriate size of the fillet shape so that the thickness of the transmitting portion 220 does not become thin.

[0122] [Example] The electromagnetic shielding factor was measured according to the angle of the graphite filler 5. Specifically, the electromagnetic shielding factor of the resin molded product 10 of the first embodiment was measured by electromagnetic field simulation analysis. The frequency of the electromagnetic wave used in the measurement was 70 GHz or more and 110 GHz or less, and the electromagnetic wave was incident on the resin molded product 10 from the Z direction in FIG. 2. The sum of the reflectance and absorptance of the electromagnetic wave was defined as the shielding factor. The shielding factor indicates the ratio of the difference between the total amount of the emitted electromagnetic wave and the electromagnetic wave transmitted through the resin molded product to the total amount.

[0123] Polypropylene resin was used as the matrix material. The amount of graphite filler mixed into the matrix material was 30% by weight. The size of the graphite filler was 0.02 mm in length and 0.001 mm in thickness.

[0124] The electromagnetic wave shielding rate was measured when the angle between the basal plane of the graphite filler and first surface 30a of flat portion 30 (angle of the graphite filler) was changed from 0 degrees to 90 degrees at intervals of 15 degrees.

[0125] FIG. 14 is a graph showing the correlation between the angle of the graphite filler 5 and the electromagnetic wave shielding rate.

[0126] Therefore, in order to absorb electromagnetic waves, it is preferable that the flat portion 30 of the resin molded product 10 has a shielding rate of 85% or more. Therefore, it is preferable that the basal surface BP1 of the first graphite filler 5a is arranged so as to be at an angle of 0 degree or more and 25 degree or less with respect to the first surface 30a.

[0127] On the other hand, in order to transmit electromagnetic waves, the shielding rate of the transmitting portion 20 of the resin molding 10 is preferably 15% or less. Therefore, the basal surface BP2 of the second graphite filler 5b is preferably arranged to be at an angle of 65 degrees or more and 90 degrees or less with respect to the first surface 30a. [Industrial Applicability]

[0128] The resin molded product and high-frequency device disclosed herein have parts that absorb and transmit electromagnetic waves, and are applicable to fields such as in-vehicle devices, electronic devices, and industrial equipment that use high-frequency devices that transmit and receive electromagnetic waves. [Explanation of symbols]

[0129] 1. 1A high frequency equipment 2. Board 2a Main surface 3 Circuit 5. Graphite Filler 5a 1st graphite filler 5b Second graphite filler 10, 110, 210 Resin molded products 20, 120, 220 Transparent part 21, 121, 221 First recess 21a side wall 21b, 221c bottom 221d top 22, 122, 222 Second recess 22a side wall 22b, 222c bottom 222d Top 30, 230 flat area 30a, 230a 1st page 30b, 230b 2nd side BP1 Basal surface BP2 Basal surface

Claims

1. A resin molded product that houses a circuit for transmitting and receiving electromagnetic waves, a flat portion including a plurality of first graphite fillers having a scale shape; a transmission portion formed integrally with the flat portion and including a plurality of second graphite fillers having a scale shape; Equipped with The flat portion has a plate shape having a first surface and a second surface opposite to the first surface, the transmitting portion has an uneven shape provided with a plurality of first recesses that are recessed in a first direction from the first surface toward the second surface and have a cross-sectional area that continuously decreases in the first direction, and a plurality of second recesses that are recessed in a second direction from the second surface toward the first surface and have a cross-sectional area that continuously decreases in the second direction, each of the first recesses has a sidewall inclined at an angle of 65 degrees or more and less than 90 degrees with respect to the first surface; each of the second recesses has a sidewall inclined at an angle of 65 degrees or more and less than 90 degrees with respect to the second surface; the plurality of first graphite fillers are arranged along the shape of the flat portion, the second graphite fillers are disposed along sidewalls of the first recesses or sidewalls of the second recesses; Resin molded product.

2. The plurality of first recesses are constituted by a plurality of conical recesses, The plurality of second recesses are constituted by a plurality of conical recesses, When viewed from the first direction, bottoms of the first recesses and bottoms of the second recesses are disposed at different positions from each other. The resin molded product according to claim 1.

3. When viewed from the first direction, the first recesses and the second recesses are each arranged in a regular triangular lattice pattern. The resin molded product according to claim 2.

4. Let t be the thickness of the flat portion, d1 be the diameter of the openings of the plurality of first recesses, p1 be the interval at which the plurality of first recesses are arranged, and θ1 be the inclination angle of the sidewalls of the plurality of first recesses with respect to the first surface. t × sin θ1 ≦ d1 ≦ 2 × t × sin θ1 and d1 < p1 ≦ 1.5 × d1 are satisfied, If the thickness of the flat portion is t, the diameter of the openings of the second recesses is d2, the interval at which the second recesses are arranged is p2, and the inclination angle of the sidewalls of the second recesses with respect to the second surface is θ2, then: t × sin θ2 ≦ d2 ≦ 2 × t × sin θ2 and d2 < p2 ≦ 1.5 × d2 are satisfied. The resin molded product according to claim 2 or 3.

5. The first recesses are formed by a plurality of linear grooves, The second recesses are formed by a plurality of linear grooves, When viewed from the first direction, the first recesses and the second recesses are aligned in parallel and in a staggered manner. The resin molded product according to claim 1.

6. bottoms of the first recesses are disposed closer to the second surface than bottoms of the second recesses; The resin molded product according to any one of claims 1 to 5.

7. the second graphite fillers have a basal surface inclined at an angle of 65 degrees or more and 90 degrees or less with respect to the first surface; The resin molded product according to any one of claims 1 to 6.

8. the first graphite fillers have a basal surface, and an average value of a maximum length on the basal surface of the first graphite fillers is 1 μm or more and 100 μm or less and is 10 times or more an average value of a maximum thickness in a direction intersecting the basal surface of the first graphite fillers; The content of the first graphite fillers in the flat portion is 5% by weight or more and 30% by weight or less, an average value of a maximum length on a basal plane of the plurality of second graphite fillers is 1 μm or more and 100 μm or less, and is 10 times or more an average value of a maximum thickness in a direction intersecting the basal plane of the plurality of second graphite fillers; The content of the second graphite fillers in the transmission portion is 5% by weight or more and 30% by weight or less. The resin molded product according to any one of claims 1 to 7.

9. A resin molded product according to any one of claims 1 to 8, A substrate accommodated in the resin molding; A circuit mounted on the substrate for transmitting and receiving electromagnetic waves; Equipped with High frequency equipment.

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