Circuit board units and electronic devices

Abstract

This effectively suppresses unwanted radiated noise caused by the current flowing through the connector unit. [Solution] One embodiment of the circuit board unit of the present disclosure comprises a first circuit board having a first ground layer, a second circuit board having a second ground layer and arranged opposite to the first circuit board, a connector unit having a first connector attached to the first circuit board and a second connector attached to the second circuit board and connected to the first connector, and a metal member arranged between the first circuit board and the second circuit board to electrically connect the first ground layer and the second ground layer, wherein the metal member is arranged adjacent to the connector unit.

Description

Technical Field

[0001] The present disclosure relates to a circuit board unit and an electronic device.

Background Art

[0002] For example, an inter-board connector for connecting circuit boards as described in Patent Document 1 is known.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the above-described inter-board connector, when a signal such as a high-frequency signal flows from one circuit board to the other circuit board, unnecessary radiation noise, that is, electromagnetic noise is likely to occur, and it has been required to suppress the unnecessary radiation noise. In contrast, for example, in Patent Document 1, the connection between the GND patterns of the circuit boards is strengthened to attempt to suppress unnecessary radiation noise. However, there has been a problem that such a measure alone cannot sufficiently suppress unnecessary radiation noise.

Means for Solving the Problems

[0005] One embodiment of the circuit board unit of the present disclosure comprises: a first circuit board having a first ground layer; a second circuit board having a second ground layer and disposed opposite to the first circuit board; a connector unit having a first connector attached to the first circuit board and a second connector attached to the second circuit board and connected to the first connector; and a metal member disposed between the first circuit board and the second circuit board and electrically connecting the first ground layer and the second ground layer, wherein the metal member is disposed adjacent to the connector unit.

[0006] One embodiment of the electronic device of this disclosure is characterized by comprising the above-described circuit board unit. [Brief explanation of the drawing]

[0007] [Figure 1] This is a schematic diagram showing a projector according to the first embodiment. [Figure 2] This is a cross-sectional view showing a part of the circuit board unit of the first embodiment. [Figure 3] This is a cross-sectional view showing a part of the circuit board unit of the first embodiment, and it shows a different cross-section from that shown in Figure 2. [Figure 4] This is a plan view showing a part of the circuit board unit of the first embodiment. [Figure 5] This is a perspective view showing a part of the circuit board unit of the first embodiment. [Figure 6] This is a side view showing a part of the circuit board unit of the first embodiment. [Figure 7] This is a cross-sectional view showing a part of the circuit board unit of the second embodiment. [Figure 8] This is a perspective view showing a part of the circuit board unit of the second embodiment. [Figure 9] This is a cross-sectional view showing a part of the circuit board unit of the third embodiment. [Figure 10] This is a perspective view showing a part of the circuit board unit of the third embodiment. [Figure 11]This is a perspective view showing a part of the circuit board unit of the fourth embodiment. [Figure 12] This is a plan view showing a part of the circuit board unit of the fourth embodiment. [Modes for carrying out the invention]

[0008] Embodiments of this disclosure will be described below with reference to the drawings. In the following embodiments, a projector will be used as an example of an electronic device. The scope of this disclosure is not limited to the embodiments described below, and can be modified at will within the scope of the technical concept of this disclosure. Furthermore, in the following drawings, the scale and number of components in each structure may differ from the actual structure in order to make the configurations easier to understand.

[0009] <First Embodiment> Figure 1 is a schematic diagram showing the projector 1 as an electronic device in this embodiment. The projector 1 of this embodiment is a projection-type image display device that projects a color image onto a screen SCR. As shown in Figure 1, the projector 1 comprises a light source device 2, a uniform illumination optical system 40, a color separation optical system 3, an optical modulator 4R, an optical modulator 4G, an optical modulator 4B, a combining optical system 5, a projection optical system 6, and a control device 50. The light source device 2 emits illumination light WL toward the uniform illumination optical system 40.

[0010] The uniform illumination optical system 40 comprises an integrator optical system 31, a polarization conversion element 32, and a superposition optical system 33. The integrator optical system 31 comprises a first lens array 31a and a second lens array 31b. The uniform illumination optical system 40 homogenizes the intensity distribution of the illumination light WL emitted from the light source device 2 in the illuminated regions of the optical modulators 4R, 4G, and 4B. The illumination light WL emitted from the uniform illumination optical system 40 is incident on the color separation optical system 3.

[0011] The color separation optical system 3 separates white illumination light WL into red light LR, green light LG, and blue light LB. The color separation optical system 3 includes a first dichroic mirror 7a, a second dichroic mirror 7b, a first reflection mirror 8a, a second reflection mirror 8b, a third reflection mirror 8c, a first relay lens 9a, and a second relay lens 9b.

[0012] The first dichroic mirror 7a separates the illumination light WL from the light source device 2 into red light LR and other light, that is, green light LG and blue light LB. The first dichroic mirror 7a transmits the separated red light LR and reflects other light, that is, green light LG and blue light LB. On the other hand, the second dichroic mirror 7b separates the other light into green light LG and blue light LB. The second dichroic mirror 7b reflects the separated green light LG and transmits the blue light LB.

[0013] The first reflection mirror 8a is disposed in the optical path of the red light LR and reflects the red light LR transmitted through the first dichroic mirror 7a toward the optical modulation device 4R. On the other hand, the second reflection mirror 8b and the third reflection mirror 8c are disposed in the optical path of the blue light LB and reflect the blue light LB transmitted through the second dichroic mirror 7b toward the optical modulation device 4B. Also, the green light LG is reflected by the second dichroic mirror 7b toward the optical modulation device 4G.

[0014] The first relay lens 9a and the second relay lens 9b are disposed on the light emission side of the second dichroic mirror 7b in the optical path of the blue light LB. The first relay lens 9a and the second relay lens 9b correct the difference in the illumination distribution of the blue light LB caused by the fact that the optical path length of the blue light LB is longer than the optical path lengths of the red light LR and the green light LG.

[0015] The light modulation device 4R modulates the red light LR according to the image information and forms image light corresponding to the red light LR. The light modulation device 4G modulates the green light LG according to the image information and forms image light corresponding to the green light LG. The light modulation device 4B modulates the blue light LB according to the image information and forms image light corresponding to the blue light LB.

[0016] For the light modulation device 4R, the light modulation device 4G, and the light modulation device 4B, for example, a transmissive liquid crystal panel is used. In addition, polarizing plates (not shown) are respectively arranged on the incident side and the emission side of the liquid crystal panel, and only linearly polarized light in a specific direction can pass through.

[0017] Field lenses 10R, field lenses 10G, and field lenses 10B are respectively arranged on the incident sides of the light modulation device 4R, the light modulation device 4G, and the light modulation device 4B. The field lenses 10R, the field lenses 10G, and the field lenses 10B parallelize the principal rays of the red light LR, the green light LG, and the blue light LB incident on the respective light modulation devices 4R, 4G, and 4B.

[0018] The synthetic optical system 5 synthesizes the image light corresponding to the red light LR, the green light LG, and the blue light LB when the image light emitted from the light modulation device 4R, the light modulation device 4G, and the light modulation device 4B is incident, and emits the synthesized image light toward the projection optical device 6. For the synthetic optical system 5, for example, a cross dichroic prism is used.

[0019] The projection optical device 6 is composed of a plurality of projection lenses. The projection optical device 6 enlarges and projects the image light synthesized by the synthetic optical system 5 toward the screen SCR. Thereby, an image is displayed on the screen SCR.

[0020] Next, the control device 50 will be described. Figure 2 is a cross-sectional view showing a part of the circuit board unit 60 in the control device 50. Figure 3 is a cross-sectional view showing a part of the circuit board unit 60, but with a different cross-section than that shown in Figure 2. Figure 4 is a plan view showing a part of the circuit board unit 60. Figure 5 is a perspective view showing a part of the circuit board unit 60. Figure 6 is a side view showing a part of the circuit board unit 60.

[0021] Each diagram shows the X, Y, and Z axes as appropriate. The direction parallel to the X axis is called the "first horizontal direction X," the direction parallel to the Y axis is called the "second horizontal direction Y," and the direction parallel to the Z axis is called the "up and down direction Z." The first horizontal direction X, the second horizontal direction Y, and the up and down direction Z are all orthogonal to each other. The side of the up and down direction Z that the Z-axis arrow points to, i.e., the +Z side, is called the "up side," and the side of the up and down direction Z that is opposite to the side that the Z-axis arrow points to, i.e., the -Z side, is called the "down side." In the first horizontal direction X, the side in which the X-axis arrow points, i.e., the +X side, is called the "first horizontal direction one side," and the side opposite to the side in the first horizontal direction X, i.e., the -X side, is called the "first horizontal direction other side." In the second horizontal direction Y, the side in which the Y-axis arrow points, i.e., the +Y side, is called the "second horizontal direction one side," and the side opposite to the side in the second horizontal direction Y, i.e., the -Y side, is called the "second horizontal direction other side." The first horizontal direction X corresponds to the "predetermined direction," the second horizontal direction Y corresponds to the "orthogonal direction," and the vertical direction Z corresponds to the "connection direction."

[0022] Note that the vertical Z direction, the first horizontal X direction, and the second horizontal Y direction are merely names used to describe the relative positional relationships of each part, and the actual arrangement may differ from the arrangement indicated by these names.

[0023] The control device 50 is a main board that controls various parts of the projector 1, including the light source device 2. As shown in Figures 2 to 6, the control device 50 has a circuit board unit 60. As shown in Figure 2, the circuit board unit 60 includes a first circuit board 61, a second circuit board 62, and a connector unit 70. The first circuit board 61 and the second circuit board 62 are electrically connected to each other via the connector unit 70. The first circuit board 61 and the second circuit board 62 are connected in the vertical direction Z. The second circuit board 62 is positioned opposite the upper side of the first circuit board 61.

[0024] The first circuit board 61 and the second circuit board 62 are plate-shaped with their surfaces facing the vertical direction Z, and extend along the first horizontal direction X and the second horizontal direction Y. That is, in this embodiment, the first horizontal direction X and the second horizontal direction Y, which are orthogonal to each other, are the directions in which the first circuit board 61 and the second circuit board 62 extend. In this embodiment, the first circuit board 61 and the second circuit board 62 are printed circuit boards provided with wiring patterns made of copper foil. The first circuit board 61 and the second circuit board 62 are boards having the same structure, and are arranged inverted relative to each other in the vertical direction Z. In the following description, if the configuration of the second circuit board 62 is the same as that of the first circuit board 61 except for the inversion in the vertical direction Z, some descriptions of the second circuit board 62 may be omitted.

[0025] As shown in Figure 3, the first circuit board 61 includes a first base portion 61a, a pair of first ground layers 61b and 61c, and a pair of first resist layers 61d and 61e. The first base portion 61a may consist of only one layer or multiple layers. The first ground layer 61b is laminated on the underside of the first base portion 61a. The first ground layer 61c is laminated on the upper side of the first base portion 61a. The first resist layer 61d is laminated on the underside of the first ground layer 61c. The first resist layer 61e is laminated on the upper side of the first ground layer 61c.

[0026] The lower surface of the first resist layer 61d constitutes the lower surface of the first circuit board 61. The upper surface of the first resist layer 61e constitutes the upper surface of the first circuit board 61. The upper surface of the first circuit board 61 is the mounting surface on which electronic components and the like are attached. The first ground layers 61b and 61c are layers whose potential becomes the reference potential in the circuit board unit 60. The first ground layers 61b and 61c are composed of, for example, solid patterns made of copper foil. The first ground layers 61b and 61c are also called reference planes.

[0027] The first ground layers 61b and 61c have first ground pad portions 61g and 61i. The first ground pad portion 61g is the portion exposed on the underside of the first circuit board 61 through an opening 61f formed in the first resist layer 61d. Although not shown in the figure, the first ground pad portion 61g is circular in shape when viewed in the vertical direction Z. The first ground pad portion 61i is the portion exposed on the upper side of the first circuit board 61 through an opening 61h formed in the first resist layer 61e. As shown in Figure 5, in this embodiment, the first ground pad portion 61i is rectangular in shape when viewed in the vertical direction Z, with the length elongated in the second horizontal direction Y.

[0028] As shown in Figure 4, the first circuit board 61 has a wiring layer 61p. The wiring layer 61p is a layer composed of multiple wiring patterns made of copper foil. Although not shown in the figure, the wiring layer 61p is provided between the first ground layer 61c and the first resist layer 61e. An insulating layer is provided between the wiring layer 61p and the first ground layer 61c. Note that the first resist layer 61e is not shown in Figure 4.

[0029] The wiring pattern of wiring layer 61p includes a plurality of signal lines 77 and a plurality of signal lines 78 arranged in the first horizontal direction X. The plurality of signal lines 77 and the plurality of signal lines 78 are electrically connected to the first connector 71, which will be described later. The plurality of signal lines 77 are located on one side of the first connector 71 in the second horizontal direction. The plurality of signal lines 78 are located on the other side of the first connector 71 in the second horizontal direction.

[0030] The multiple signal lines 77 include a first signal line 77a and a second signal line 77b. The frequency of the signal flowing through the second signal line 77b is higher than the frequency of the signal flowing through the first signal line 77a. Multiple first signal lines 77a and multiple second signal lines 77b are provided. In this embodiment, two second signal lines 77b are provided. The signal lines 77 other than the two second signal lines 77b among the multiple signal lines 77 are first signal lines 77a. The number of second signal lines 77b is less than the number of first signal lines 77a. The second signal lines 77b are located one side in the first horizontal direction, i.e., on the +X side, than the multiple first signal lines 77a. In this embodiment, the two signal lines 77b are the signal line 77 located furthest to the one side in the first horizontal direction among the multiple signal lines 77, and the signal line 77 located second from the one side in the first horizontal direction among the multiple signal lines 77. The signal flowing through the second signal line 77b is a high-frequency signal. The frequency of the signal flowing through the second signal line 77b is, for example, 20 MHz or higher.

[0031] The multiple signal lines 78, like the multiple signal lines 77, include a first signal line 78a and a second signal line 78b. The first signal line 78a has the same configuration as the first signal line 77a, except that it is located on the other side of the second horizontal direction relative to the first connector 71, i.e., the -Y side. The second signal line 78b has the same configuration as the second signal line 77b, except that it is located on the other side in the second horizontal direction relative to the first connector 71.

[0032] As shown in Figure 3, the second circuit board 62 has a second base portion 62a, a pair of second ground layers 62b and 62c, and a pair of second resist layers 62d and 62e. Although not shown, the second circuit board 62 has wiring layers, similar to the first circuit board 61. The second base portion 62a may consist of only one layer or multiple layers. The second ground layer 62b is laminated on the upper side of the second base portion 62a. The second ground layer 62c is laminated on the lower side of the second base portion 62a. The second resist layer 62d is laminated on the upper side of the second ground layer 62b. The second resist layer 62e is laminated on the lower side of the second ground layer 62b.

[0033] The lower surface of the second resist layer 62e constitutes the lower surface of the second circuit board 62. The lower surface of the second circuit board 62 is the mounting surface on which electronic components and the like are attached. The upper surface of the second resist layer 62d constitutes the upper surface of the second circuit board 62. The second ground layers 62b and 62c are layers whose potential becomes the reference potential in the circuit board unit 60. The second ground layers 62b and 62c are composed of, for example, solid patterns made of copper foil. The second ground layers 62b and 62c are also called reference planes.

[0034] The second ground layers 62b and 62c have second ground pad portions 62g and 62i. The second ground pad portion 62g is the portion exposed on the upper side of the second circuit board 62 through an opening 62f formed in the second resist layer 62d. Although not shown in the figures, the second ground pad portion 62g is circular in shape when viewed in the vertical direction Z. The second ground pad portion 62i is the portion exposed on the lower side of the second circuit board 62 through an opening 62h formed in the second resist layer 62e. Although not shown in the figures, in this embodiment the second ground pad portion 62i is rectangular in shape, elongated in the second horizontal direction Y.

[0035] The connector unit 70 relays signal transmission between the first circuit board 61 and the second circuit board 62. As shown in Figure 4, in this embodiment, the connector unit 70 has a shape that is elongated in the first horizontal direction X when viewed in the vertical direction Z. In this embodiment, the connector unit 70 has a rectangular shape that is elongated in the first horizontal direction X when viewed in the vertical direction Z. Figures 3 to 6 show the connector unit 70 schematically.

[0036] As shown in Figure 2, the connector unit 70 includes a first connector 71 and a second connector 72. The first connector 71 is mounted on the upper surface of the first circuit board 61. The second connector 72 is mounted on the lower surface of the second circuit board 62. The first connector 71 and the second connector 72 are connected in the vertical direction Z. In other words, in this embodiment, the connection direction between the first connector 71 and the second connector 72 is the vertical direction Z.

[0037] In this embodiment, the first connector 71 is a male connector, and the second connector 72 is a female connector. The first connector 71 and the second connector 72 are mated in the vertical direction Z and are electrically connected to each other. In other words, in this embodiment, the mating direction between the first connector 71 and the second connector 72 is the vertical direction Z.

[0038] The first connector 71 includes a first housing 73, a plurality of first connectors 75a, and a plurality of first connectors 75b. The first housing 73 is a resin component that holds the plurality of first connectors 75a and the plurality of first connectors 75b. The first housing 73 is made, for example, by insert molding, with the plurality of first connectors 75a and the plurality of first connectors 75b as insert components. The first housing 73 is a roughly rectangular box shape with an opening on the top.

[0039] The first housing 73 has a bottom wall portion 73a that constitutes the lower wall portion, a peripheral wall portion 73b that protrudes upward from the outer peripheral edge of the bottom wall portion 73a, and a convex portion 73c that protrudes upward from the bottom wall portion 73a on the inside of the peripheral wall portion 73b. As shown in Figure 4, the peripheral wall portion 73b is a rectangular frame shape that is long in the first horizontal direction X. The convex portion 73c is a rectangular parallelepiped shape that extends in the first horizontal direction X. The outer surface of the protrusion 73c is positioned away from the inner surface of the peripheral wall 73b over its entire circumference. As shown in Figure 2, the first housing 73 is positioned above the top surface of the first circuit board 61, separated by a gap.

[0040] Multiple first connectors 75a and multiple first connectors 75b are held in the first housing 73. A portion of each first connector 75a, 75b is embedded in the first housing 73. The first connectors 75a, 75b are elongated, plate-like members made of metal. Multiple first connectors 75a are held in one portion of the first housing 73 in the second horizontal direction. Multiple first connectors 75b are held in the other portion of the first housing 73 in the second horizontal direction, i.e., the -Y side.

[0041] As shown in Figure 4, multiple first connectors 75a are arranged side by side with spacing along the first horizontal direction X. Multiple first connectors 75b are arranged side by side with spacing along the first horizontal direction X. Each first connector 75b is positioned so as to sandwich the protrusion 73c between itself and each first connector 75a in the second horizontal direction Y. The first connectors 75a and 75b are members having similar shapes. The first connectors 75a and 75b are arranged symmetrically to each other in the second horizontal direction Y with the protrusion 73c in between.

[0042] As shown in Figure 2, the first connector 75a has a first extension portion 75c, a second extension portion 75d, a third extension portion 75e, and a substrate connection portion 75f. The first extension portion 75c extends in the vertical direction Z. The lower end of the first extension portion 75c is embedded in the bottom wall portion 73a. The portion of the first extension portion 75c above the lower end protrudes upward from the bottom wall portion 73a and is exposed from the first housing 73, and is electrically connected to the first extension portion 76c, which will be described later. The portion of the first extension portion 75c above the lower end is located on the inside of the peripheral wall portion 73b, on one side in the second horizontal direction relative to the convex portion 73c.

[0043] The second extension 75d extends from the lower end of the first extension 75c to one side in the second horizontal direction, i.e., to the +Y side. The end of the second extension 75d on one side in the second horizontal direction protrudes from the side of the first housing 73 to one side in the second horizontal direction and is exposed from the first housing 73. The portion of the second extension 75d excluding the end on one side in the second horizontal direction is embedded in the bottom wall portion 73a.

[0044] The third extension portion 75e extends downward and diagonally to the second horizontal direction from the second horizontal end of the second extension portion 75d, i.e., the +Y side end. The lower end of the third extension portion 75e is located below the first housing 73. The board connection portion 75f extends to the second horizontal direction from the lower end of the third extension portion 75e. The board connection portion 75f is electrically connected to the first circuit board 61. As shown in Figure 4, the board connection portions 75f of the multiple first connectors 75a are electrically connected to the multiple signal lines 77, respectively. More specifically, the board connection portion 75f contacts the portion of the signal line 77 that is exposed on the upper surface of the first circuit board 61 and is electrically connected to the signal line 77.

[0045] The first connector 75b, like the first connector 75a, has a first extension, a second extension, a third extension, and a substrate connection portion. Each part of the first connector 75b has the same shape as each of the parts with the same names in the first connector 75a, except that it is symmetrical with respect to the second horizontal direction Y. The substrate connection portions of the multiple first connectors 75b are electrically connected to each of the multiple signal lines 78.

[0046] As shown in Figure 2, the second connector 72 includes a second housing 74, a plurality of second connectors 76a, and a plurality of second connectors 76b. The second housing 74 is a resin component that holds the plurality of second connectors 76a and the plurality of second connectors 76b. The second housing 74 is manufactured, for example, by insert molding, with the plurality of second connectors 76a and the plurality of second connectors 76b as insert components.

[0047] The second housing 74 is a roughly rectangular box shape with an opening on the bottom. The second housing 74 has a top wall portion 74a that constitutes the upper wall portion, and a peripheral wall portion 74b that protrudes downward from the center of the top wall portion 74a. The peripheral wall portion 74b is a rectangular frame shape that is long in the first horizontal direction X. The outer peripheral edge of the peripheral wall portion 74b is located further inward than the outer peripheral edge of the top wall portion 74a. The top wall portion 74a and the peripheral wall portion 74b form a recess that is recessed on the upper side. The second housing 74 is positioned below the lower surface of the second circuit board 62, separated by a gap.

[0048] The second housing 74 is fitted to the first housing 73 in the vertical direction Z. In this embodiment, the peripheral wall portion 74b of the second housing 74 is fitted from above to the inside of the peripheral wall portion 73b of the first housing 73. The lower end of the peripheral wall portion 74b is positioned opposite the upper side of the bottom wall portion 73a of the first housing 73 with a gap in between. The portion of the top wall portion 74a of the second housing 74 that is located outside the peripheral wall portion 74b is in contact with the upper end of the peripheral wall portion 73b of the first housing 73. A protrusion 73c is inserted inside the peripheral wall portion 74b of the second housing 74. The upper end of the protrusion 73c is located below the top wall portion 74a.

[0049] Multiple second connectors 76a and multiple second connectors 76b are held in the second housing 74. A portion of each second connector 76a, 76b is embedded in the second housing 74. The second connectors 76a, 76b are elongated, plate-shaped members made of metal. Multiple second connectors 76a are held in one portion of the second horizontal direction of the second housing 74. Multiple second connectors 76b are held in the other portion of the second horizontal direction of the second housing 74.

[0050] Although not shown in the diagram, multiple second connectors 76a are arranged side by side with spacing along the first horizontal direction X. Multiple second connectors 76b are arranged side by side with spacing along the first horizontal direction X. Each second connector 76b is positioned opposite each second connector 76a on the other side of the second horizontal direction with spacing between them. The second connectors 76a and 76b are members with similar shapes. The second connectors 76a and 76b are arranged symmetrically with respect to each other in the second horizontal direction Y.

[0051] The second connector 76a is a component having substantially the same shape as the first connector 75a. The second connector 76a is positioned in a position inverted in the vertical direction Z relative to the first connector 75a. The second connector 76b is a component having substantially the same shape as the first connector 75b. The second connector 76b is positioned in a position inverted in the vertical direction Z relative to the first connector 75b.

[0052] The second connector 76a has a first extension portion 76c, a second extension portion 76d, a third extension portion 76e, and a substrate connection portion 76f. The first extension portion 76c extends in the vertical direction Z. The upper end of the first extension portion 76c is embedded in the top wall portion 74a. The portion of the first extension portion 76c below the upper end protrudes downward from the top wall portion 74a and is exposed from the second housing 74, and is electrically connected to the portion of the first extension portion 75c of the first connector 75a that protrudes upward from the bottom wall portion 73a.

[0053] The second extension 76d extends from the upper end of the first extension 76c to one side in the second horizontal direction. The end of the second extension 76d on one side in the second horizontal direction protrudes from the side of the second housing 74 to one side in the second horizontal direction and is exposed from the second housing 74. The portion of the second extension 76d excluding the end on one side in the second horizontal direction is embedded in the top wall portion 74a.

[0054] The third extension 76e extends upward and diagonally to the second horizontal direction from one end of the second extension 76d. The upper end of the third extension 76e is located above the second housing 74. The board connection portion 76f extends to the second horizontal direction from the upper end of the third extension 76e. The board connection portion 76f is electrically connected to the second circuit board 62.

[0055] The second connector 76b, like the second connector 76a, has a first extension portion, a second extension portion, a third extension portion, and a substrate connection portion. Each part of the second connector 76b has the same shape as each of the parts of the second connector 76a that have the same name, except that they are symmetrical in the second horizontal direction Y.

[0056] As shown in Figure 3, the circuit board unit 60 includes a metal member 80 positioned between the first circuit board 61 and the second circuit board 62. The metal member 80 electrically connects the first ground layer 61c and the second ground layer 62c. As shown in Figures 3 and 5, in this embodiment, the metal member 80 is a sheet metal member. The material constituting the metal member 80 is not particularly limited as long as it is a metal. In addition, a conductive material such as carbon may be used instead of the metal member 80.

[0057] As shown in Figures 4 to 6, the metal member 80 is positioned adjacent to the connector unit 70. In this embodiment, the metal member 80 is located on one side of the connector unit 70 in the first horizontal direction. That is, in this embodiment, the metal member 80 is positioned adjacent to the connector unit 70 in the first horizontal direction X. As shown in Figure 4, the metal member 80 is positioned on the same side as the second signal lines 77b and 78b are positioned relative to the first signal lines 77a and 78a in the first horizontal direction X, i.e., on the +X side. As a result, in this embodiment, the second signal lines 77b and 78b are positioned closer to the metal member 80 than the first signal lines 77a and 78a in the first horizontal direction X.

[0058] As shown in Figure 5, in this embodiment, the metal member 80 has a main body portion 83, a first connecting portion 81, and a second connecting portion 82. The main body portion 83 extends in the connection direction, i.e., the vertical direction Z, to which the first connector 71 and the second connector 72 are connected. In this embodiment, the main body portion 83 is plate-shaped with its surface facing the second horizontal direction Y. The main body portion 83 is rectangular. The main body portion 83 is located on one side of the connector unit 70 in the first horizontal direction. Of the sides of the main body portion 83, the side 83a on the other side in the first horizontal direction is positioned opposite the connector unit 70 with a gap between them. In this embodiment, the main body portion 83 is positioned in the same position as the center of the connector unit 70 in the second horizontal direction Y.

[0059] The first connecting portion 81 protrudes from one end of the main body portion 83 in the vertical direction Z, i.e., from the lower end of the main body portion 83 to one side in the second horizontal direction. The first connecting portion 81 is a substantially rectangular plate with its surface facing the vertical direction Z. The first connecting portion 81 is in contact with the first ground pad portion 61i of the first ground layer 61c from above. The lower surface of the first connecting portion 81 is the first connecting surface 81f, which is electrically connected to the first ground layer 61c. The first connecting surface 81f is in contact with the first ground pad portion 61i. As a result, the metal member 80 is in contact with the first ground layer 61c on the surface of the first circuit board 61 facing the second circuit board 62, i.e., the upper surface. The first connecting surface 81f extends along the first ground layer 61c in a direction perpendicular to the vertical direction Z.

[0060] The first connecting portion 81 has a plate-shaped portion 81a, a cylindrical portion 81b, and engaging claw portions 81d and 81e. The plate-shaped portion 81a is a rectangular plate-shaped part. The lower surface of the plate-shaped portion 81a is the first connecting surface 81f. The cylindrical portion 81b protrudes upward from the plate-shaped portion 81a. The cylindrical portion 81b is cylindrical with an opening on the upper side. The engaging claw portion 81d protrudes downward from one edge of the plate-shaped portion 81a in the second horizontal direction. As shown in Figure 3, the engaging claw portion 81d is inserted from above into an engaging hole portion 61k formed in the first circuit board 61. The engaging hole portion 61k penetrates the first circuit board 61 in the vertical direction Z. As shown in Figure 5, the engaging claw portion 81e protrudes downward from one edge of the plate-shaped portion 81a in the first horizontal direction. The engaging claw portion 81e is inserted from above into the engaging hole portion 61m formed in the first circuit board 61. The engaging hole portion 61m penetrates the first circuit board 61 in the vertical direction Z.

[0061] As shown in Figure 3, a female screw hole 81c is formed in the first connecting portion 81. The female screw hole 81c penetrates the first connecting portion 81 in the vertical direction Z. More specifically, the female screw hole 81c penetrates the plate-shaped portion 81a and the cylindrical portion 81b in the vertical direction Z. The inner circumferential surface of the cylindrical portion 81b constitutes a part of the inner circumferential surface of the female screw hole 81c. A female screw portion is formed on the inner circumferential surface of the female screw hole 81c.

[0062] A metal bolt 91 is tightened into the female screw hole 81c to secure the first connection part 81 to the first circuit board 61. The bolt 91 is passed through a through hole 61j formed in the first circuit board 61 from below. The through hole 61j penetrates the first circuit board 61 in the vertical direction Z. The inner diameter of the through hole 61j is larger than the inner diameter of the female threaded hole 81c.

[0063] The bolt 91 has a bolt body portion 91a and a bolt head portion 91b. The bolt body portion 91a is cylindrical and extends in the vertical direction Z. A male thread portion is formed on the outer circumferential surface of the bolt body portion 91a that engages with the female thread portion formed on the inner circumferential surface of the female thread hole 81c. The bolt body portion 91a is passed through the through hole 61j from below, protruding above the first circuit board 61, and is tightened into the female thread hole 81c. In this way, the bolt body portion 91a is tightened into the metal member 80. In this embodiment, the upper end of the bolt body portion 91a protrudes above the cylindrical portion 81b.

[0064] The bolt head 91b is provided at one end of the bolt body 91a, i.e., the lower end. The bolt head 91b extends from the lower end of the bolt body 91a in a direction perpendicular to the vertical direction Z. The outer diameter of the bolt head 91b is larger than the outer diameter of the bolt body 91a. The outer diameter of the bolt head 91b is larger than the inner diameter of the through hole 61j. The bolt head 91b is in contact with the first gland pad portion 61g of the first gland layer 61b from below. As a result, the bolt head 91b is in contact with the first gland layer 61b on the side of the first circuit board 61 opposite to the side facing the second circuit board 62, i.e., the lower surface.

[0065] The bolt body 91a is tightened into the first connecting portion 81, which contacts the first gland pad portion 61i of the first gland layer 61c, and the bolt head 91b contacts the first gland pad portion 61g of the first gland layer 61b. As a result, the pair of first gland layers 61b and 61c, which are provided in different layers, are electrically connected to each other via the bolt 91 and the first connecting portion 81.

[0066] The second connecting portion 82 protrudes from the other end of the main body portion 83 in the vertical direction Z, that is, from the upper end of the main body portion 83 to the other side in the second horizontal direction. In other words, the second connecting portion 82 protrudes from the other end of the main body portion 83 in a direction different from the direction in which the first connecting portion 81 protrudes. In this embodiment, the direction in which the second connecting portion 82 protrudes relative to the main body portion 83 is opposite to the direction in which the first connecting portion 81 protrudes relative to the main body portion 83.

[0067] The second connection portion 82 is a roughly rectangular plate with its surface facing the vertical direction Z. The second connection portion 82 is in contact with the second ground pad portion 62i of the second ground layer 62c from below. The upper surface of the second connection portion 82 is the second connection surface 82f, which is electrically connected to the second ground layer 62c. The second connection surface 82f is in contact with the second ground pad portion 62i. As a result, the metal member 80 is in contact with the second ground layer 62c on the surface of the second circuit board 62 facing the first circuit board 61, i.e., the lower surface. The second connection surface 82f extends along the second ground layer 62c in a direction perpendicular to the vertical direction Z.

[0068] The second connecting portion 82 has a plate-like portion 82a and a cylindrical portion 82b. The plate-like portion 82a is a substantially rectangular plate-shaped part. The upper surface of the plate-like portion 82a is the second connecting surface 82f. The cylindrical portion 82b protrudes downward from the plate-like portion 82a. The cylindrical portion 82b is cylindrical with an opening on the downward side.

[0069] A female screw hole 82c is formed in the second connecting portion 82. The female screw hole 82c penetrates the second connecting portion 82 in the vertical direction Z. More specifically, the female screw hole 82c penetrates the plate-shaped portion 82a and the cylindrical portion 82b in the vertical direction Z. The inner circumferential surface of the cylindrical portion 82b constitutes a part of the inner circumferential surface of the female screw hole 82c. A female screw portion is formed on the inner circumferential surface of the female screw hole 82c.

[0070] A metal bolt 92 is tightened into the female screw hole 82c to secure the second connector 82 to the second circuit board 62. The bolt 92 is passed through a through hole 62j formed in the second circuit board 62 from above. The through hole 62j penetrates the second circuit board 62 in the vertical direction Z. The inner diameter of the through hole 62j is larger than the inner diameter of the female threaded hole 82c.

[0071] The bolt 92 has a bolt body 92a and a bolt head 92b. The bolt body 92a is cylindrical and extends in the vertical direction Z. A male thread is formed on the outer circumferential surface of the bolt body 92a that engages with the female thread formed on the inner circumferential surface of the female thread hole 82c. The bolt body 92a is passed through the through hole 62j from above, protruding below the second circuit board 62, and is tightened into the female thread hole 82c. In this way, the bolt body 92a is tightened into the metal member 80. In this embodiment, the lower end of the bolt body 92a protrudes below the cylindrical portion 82b.

[0072] The bolt head 92b is provided at one end, i.e., the upper end, of the bolt body 92a. The bolt head 92b extends from the upper end of the bolt body 92a in a direction perpendicular to the vertical direction Z. The outer diameter of the bolt head 92b is larger than the outer diameter of the bolt body 92a. The outer diameter of the bolt head 92b is larger than the inner diameter of the through hole 62j. The bolt head 92b is in contact with the second gland pad portion 62g of the second gland layer 62b from above. As a result, the bolt head 92b is in contact with the second gland layer 62b on the side of the second circuit board 62 opposite to the side facing the first circuit board 61, i.e., the upper surface.

[0073] The bolt body 92a is tightened into the second connecting portion 82, which contacts the second gland pad portion 62i of the second gland layer 62c, and the bolt head 92b contacts the second gland pad portion 62g of the second gland layer 62b, thereby electrically connecting the pair of second gland layers 62b and 62c, which are provided in different layers, to each other via the bolt 92 and the second connecting portion 82.

[0074] As shown in Figure 6, the first distance L1a between adjacent metal members 80 and the connector unit 70 is smaller than the second distance L2 between the opposing first circuit board 61 and second circuit board 62. The first distance L1a is the shortest distance along the first horizontal direction X between the side surface 83a of the main body portion 83 of the metal member 80 and the connector unit 70. The second distance L2 is the shortest distance along the vertical direction Z between the upper surface of the first circuit board 61 and the lower surface of the second circuit board 62. In this embodiment, the first distance L1a is less than or equal to half of the second distance L2. The first distance L1a is, for example, about 0.5 mm or more and 20 mm or less. The first distance L1a is preferably, for example, less than 10 mm. The second distance L2 is, for example, about 10 mm or more and 30 mm or less. The first distance L1a is smaller than the dimension of the connector unit 70 in the second horizontal direction Y.

[0075] According to this embodiment, the circuit board unit 60 includes a first circuit board 61 having a first ground layer 61c, a second circuit board 62 having a second ground layer 62c and positioned opposite the first circuit board 61, a connector unit 70 having a first connector 71 attached to the first circuit board 61 and a second connector 72 attached to the second circuit board 62 and connected to the first connector 71, and a metal member 80 positioned between the first circuit board 61 and the second circuit board 62, electrically connecting the first ground layer 61c and the second ground layer 62c. The metal member 80 is positioned adjacent to the connector unit 70.

[0076] Therefore, the metal member 80 can provide a return path through which the return current flows between the first circuit board 61 and the second circuit board 62. Since the metal member 80 is positioned adjacent to the connector unit 70, the metal member 80 can be positioned close to the connector unit 70. This makes it easier to pass the return current corresponding to the current flowing through the connector unit 70 through the metal member 80. Consequently, the electromagnetic field generated by the return current flowing through the metal member 80 can suitably cancel out the electromagnetic field generated by the current flowing through the connector unit 70. Therefore, unwanted radiation noise caused by the current flowing through the connector unit 70 connecting the first circuit board 61 and the second circuit board 62 can be suitably suppressed. In other words, the energy of the current flowing through the connector unit 70 and the return current are balanced, and excess energy is less likely to be generated, thus suitably suppressing unwanted radiation noise caused by such excess energy. The current flowing through the connector unit 70 includes the current flowing through the first connector 75a and the second connector 76a, and the current flowing through the first connector 75b and the second connector 76b.

[0077] Furthermore, the metal member 80 allows for the electrical connection between the first ground layer 61c of the first circuit board 61 and the second ground layer 62c of the second circuit board 62, thereby enabling more favorable stabilization of the potential of each ground layer. This allows for more favorable suppression of unwanted radiated noise caused by currents flowing along signal lines 77, 78, etc., along each ground layer.

[0078] Furthermore, the metal member 80 provides return current paths for the connector unit 70, such as the first ground layers 61b, 61c and the second ground layers 62b, 62c. Therefore, even if each connector of the connector unit 70 is separated from each circuit board, the metal member 80 provides a return current path for each connector that is separated from each circuit board. This shortens the return current paths for each connector and each wiring layer on each circuit board compared to the case where the metal member 80 is not provided. Therefore, the design of the return current path for each connector can be made easier, and the degradation of signal quality flowing through each connector can be suppressed.

[0079] Furthermore, the structure with the metal member 80 is simpler than the structure in which the connector unit 70 having the first connector 71 and the second connector 72 is surrounded from the outside by a shielding member. Therefore, the complexity of the circuit board unit 60 structure can be suppressed compared to a structure in which the connector unit 70 is surrounded by a shielding member. Consequently, the increase in the manufacturing cost of the circuit board unit 60 can be suppressed.

[0080] Furthermore, according to this embodiment, the first distance L1a between adjacent metal members 80 and the connector unit 70 is smaller than the second distance L2 between the opposing first circuit board 61 and second circuit board 62. Therefore, the metal members 80 can be brought more favorably closer to the connector unit 70. This makes it easier to favorably pass the return current corresponding to the current flowing through the connector unit 70 to the metal members 80. Consequently, the electromagnetic field generated by the return current flowing through the metal members 80 can more favorably cancel out the electromagnetic field generated by the current flowing through the connector unit 70. Therefore, unwanted radiation noise caused by the current flowing through the connector unit 70 connecting the first circuit board 61 and the second circuit board 62 can be more favorably suppressed.

[0081] Furthermore, according to this embodiment, the connector unit 70 has a shape that is elongated in the first horizontal direction X when viewed in the connection direction, i.e., the vertical direction Z, in which the first connector 71 and the second connector 72 are connected. The metal member 80 is positioned adjacent to the connector unit 70 in the first horizontal direction X. When the connector unit 70 has a shape that is elongated in one direction, as in this embodiment, each connector of the connector unit 70 is often arranged in line along the longitudinal direction of the connector unit 70. In this case, the signal lines 77 and 78 tend to be positioned on both sides of the connector unit 70 in the short direction, i.e., the second horizontal direction Y. Therefore, by positioning the metal member 80 adjacent to the connector unit 70 in the longitudinal direction of the connector unit 70, i.e., the predetermined direction, the first horizontal direction X, interference between the metal member 80 and the signal lines 77 and 78 can be suppressed, while the metal member 80 can be positioned suitably close to the connector unit 70.

[0082] Furthermore, according to this embodiment, the first circuit board 61 has a plurality of signal lines 77, 78 arranged in a first horizontal direction X and electrically connected to the first connector 71. The plurality of signal lines 77, 78 include first signal lines 77a, 78a and second signal lines 77b, 78b through which signals with a higher frequency than the signals flowing through the first signal lines 77a, 78a flow. The second signal lines 77b and 78b are positioned closer to the metal member 80 than the first signal lines 77a and 78a in the first horizontal direction X. Here, unwanted radiated noise caused by the current flowing through the connector unit 70 tends to increase as the frequency of the current flowing through the connector unit 70 increases. Therefore, by positioning the second signal lines 77b and 78b, which carry relatively high-frequency signals, closer to the metal member 80, the metal member 80 can be positioned more favorably closer to the connectors of the connector unit 70 to which the second signal lines 77b and 78b are connected. This makes it easier to favorably channel the return current corresponding to the relatively high-frequency current flowing through each connector of the connector unit 70 into the metal member 80. Consequently, unwanted radiated noise caused by the current flowing through the connector unit 70 can be more favorably suppressed.

[0083] Furthermore, according to this embodiment, the metal member 80 has a first connection surface 81f that extends along the first ground layer 61c and is electrically connected to the first ground layer 61c, and a second connection surface 82f that extends along the second ground layer 62c and is electrically connected to the second ground layer 62c. Therefore, the contact area between the metal member 80 and the first ground layer 61c, and the contact area between the metal member 80 and the second ground layer 62c can be suitably increased. This makes it easier to suitably increase the amount of return current flowing between the first ground layer 61c and the second ground layer 62c via the metal member 80. Consequently, unwanted radiated noise caused by the current flowing through the connector unit 70 can be more suitably suppressed. In addition, the metal member 80 can suitably connect the first ground layer 61c and the second ground layer 62c, and the potential of each ground layer can be suitably stabilized.

[0084] Furthermore, according to this embodiment, the metal member 80 has a main body portion 83 extending in the connection direction, i.e., the vertical direction Z, in which the first connector 71 and the second connector 72 are connected; a first connection portion 81 having a first connection surface 81f and protruding from one end of the main body portion 83 in the connection direction, i.e., the lower end; and a second connection portion 82 having a second connection surface 82f and protruding from the other end of the main body portion 83 in the connection direction, i.e., the upper end, in a direction different from the direction in which the first connection portion 81 protrudes. The main body portion 83 is plate-shaped, and its side surface 83a is positioned opposite to the connector unit 70. Therefore, the positions of the first connection surface 81f and the second connection surface 82f can be made different in the direction perpendicular to the vertical direction Z. As a result, the position in which the first connection surface 81f is connected to the first circuit board 61 and the position in which the second connection surface 82f is connected to the second circuit board 62 can be made different in the direction perpendicular to the vertical direction Z. Therefore, the position to which each connection surface is connected can be easily adjusted according to the arrangement of electronic components on the mounting surface of each circuit board, thereby improving the degree of freedom in the arrangement of electronic components on each circuit board. Furthermore, by positioning the side surface 83a of the main body 83 opposite the connector unit 70, a return path can be suitably created by the metal member 80. In addition, while making it easier to manufacture the metal member 80 as a sheet metal member, a structure can be suitably adopted in which the position of the first connection surface 81f and the position of the second connection surface 82f differ in a direction perpendicular to the vertical direction Z.

[0085] Furthermore, according to this embodiment, the first circuit board 61 has a pair of first ground layers 61b and 61c provided on different layers. The pair of first ground layers 61b and 61c are electrically connected to each other. Therefore, the potential of the pair of first ground layers 61b and 61c can be stabilized. In addition, it is possible to more favorably pass a return current through the metal member 80 that is electrically connected to the first ground layers 61b and 61c.

[0086] In this embodiment, the second circuit board 62 is also provided with a pair of second ground layers 62b and 62c, and the pair of second ground layers 62b and 62c are electrically connected to each other. Therefore, the potential of the pair of second ground layers 62b and 62c can be stabilized. In addition, it is possible to more favorably pass a return current through the metal member 80 that is electrically connected to the second ground layers 62b and 62c.

[0087] Furthermore, according to this embodiment, the first circuit board 61 has a through hole 61j that penetrates the first circuit board 61. A metal bolt 91 is passed through the through hole 61j. The bolt 91 has a bolt body portion 91a that is passed through the through hole 61j and tightened into a metal member 80, and a bolt head portion 91b provided at one end of the bolt body portion 91a. The metal member 80 is in contact with one of the pair of first ground layers 61b, 61c on the surface of the first circuit board 61 facing the second circuit board 62. The bolt head 91b is in contact with the other of the pair of first ground layers 61b, 61c on the surface of the first circuit board 61 opposite to the surface facing the second circuit board 62. Therefore, by fixing the metal member 80 to the first circuit board 61 with the bolt 91, the pair of first ground layers 61b, 61c can be easily and suitably electrically connected to each other via the bolt 91 and the metal member 80. Furthermore, the bolts 91 allow the metal member 80 to be stably fixed to the first circuit board 61.

[0088] In this embodiment, the pair of second ground layers 62b and 62c are also electrically connected to each other via bolts 92. Therefore, the pair of second ground layers 62b and 62c can be easily and suitably electrically connected to each other. In addition, the metal member 80 can be stably fixed to the second circuit board 62 by bolts 92.

[0089] Furthermore, according to this embodiment, the metal member 80 has engaging claws 81d and 81e inserted into engaging holes 61k and 61m formed in the first circuit board 61. Therefore, when the bolt 91 is tightened into the metal member 80, the engaging claws 81d and 81e catch on the inner surfaces of the engaging holes 61k and 61m, preventing the metal member 80 from rotating relative to the first circuit board 61. This makes it easier to tighten the bolt 91 into the metal member 80 and to fix the metal member 80 to the first circuit board 61 with the bolt 91.

[0090] Furthermore, by fixing the metal member 80 to the first circuit board 61 with bolts 91, and then fixing the metal member 80 to the second circuit board 62 with bolts 92, it is possible to suppress the rotation of the metal member 80 relative to the second circuit board 62 when fixing the metal member 80 to the second circuit board 62 with bolts 92. Therefore, as in this embodiment, even if the second connecting portion 82 is not provided with an engaging claw portion, it is possible to easily fix the metal member 80 to the second circuit board 62 with bolts 92.

[0091] <Second Embodiment> In this embodiment, the shape of the metal member 280 differs from that of the first embodiment. Figure 7 is a cross-sectional view showing a part of the circuit board unit 260 of this embodiment. Figure 8 is a perspective view showing a part of the circuit board unit 260 of this embodiment. Note that in Figures 7 and 8, the connector unit 70 is schematically shown. In the following description, components similar to those in the above-described embodiment may be omitted from description by using the same reference numerals as appropriate.

[0092] As shown in Figure 7, in the circuit board unit 260 of this embodiment, the first circuit board 261 differs from the first embodiment in that it does not have engagement holes 61k, 61m and through holes 61j. The second circuit board 262 differs from the first embodiment in that it has an engagement hole 262k. The engagement hole 262k penetrates the second circuit board 262 in the vertical direction Z.

[0093] As shown in Figures 7 and 8, the metal member 280 in this embodiment is a sheet metal member and is arranged adjacent to one side of the connector unit 70 in the first horizontal direction. The metal member 280 has a main body portion 283, a first connecting portion 281, and a second connecting portion 282. The main body portion 283 extends in the connection direction, i.e., the vertical direction Z, to which the first connector 71 and the second connector 72 are connected. In this embodiment, the main body portion 283 is a substantially rectangular plate shape with its plate surface facing the first horizontal direction X. The plate surface 283b of the main body portion 283 on the other side in the first horizontal direction is arranged opposite to one side of the connector unit 70 in the first horizontal direction. The distance in the first horizontal direction X between the plate surface 283b and the connector unit 70 is the first distance L1b between adjacent metal members 280 and the connector unit 70, and is smaller than the second distance L2 between the opposing first circuit board 261 and second circuit board 262.

[0094] The first connecting portion 281 protrudes from one end of the main body portion 283 in the vertical direction Z, that is, from the lower end of the main body portion 283 to one side in the first horizontal direction. In other words, the first connecting portion 281 protrudes from the lower end of the main body portion 283 in a direction away from the connector unit 70. The first connecting portion 281 is a rectangular plate shape with its plate surface facing the vertical direction Z. In this embodiment, the first connecting portion 281 consists only of a substantially rectangular plate-shaped portion 281a.

[0095] As shown in Figure 7, the first connection portion 281 is in contact with the first ground pad portion 61i of the first ground layer 61c via a conductive member 293. The conductive member 293 is a conductive and elastically deformable member. The conductive member 293 is, for example, a conductive gasket. The lower surface of the conductive member 293 is in contact with the first ground pad portion 61i. As a result, the conductive member 293 is in contact with the first ground layer 61c. The upper surface of the conductive member 293 is in contact with the lower surface of the first connection portion 281. As a result, the metal member 280 is electrically connected to the first ground layer 61c via the conductive member 293. The lower surface of the first connection portion 281 is the first connection surface 281f, which is electrically connected to the first ground layer 61c via the conductive member 293. The first connection surface 281f extends along the first ground layer 61c in a direction perpendicular to the vertical direction Z. The conductive member 293 is pressed down from above by the metal member 280, and is in a state of compressive elastic deformation in the vertical direction Z.

[0096] The second connecting portion 282 protrudes from the other end of the main body portion 283 in the vertical direction Z, that is, from the upper end of the main body portion 283, to one side in the first horizontal direction. In other words, the second connecting portion 282 protrudes from the other end of the main body portion 283 in the vertical direction Z in the same direction as the first connecting portion 281 protrudes. The second connecting portion 282 is a substantially rectangular plate with its plate surface facing the vertical direction Z. The second connecting portion 282 is positioned opposite the first connecting portion 281 with a gap between them, above it. The second connecting portion 282 is in contact with the second ground pad portion 62i of the second ground layer 62c. The upper surface of the second connecting portion 282 is the second connecting surface 282f, which is electrically connected to the second ground layer 62c. The second connecting surface 282f is in contact with the second ground pad portion 62i. As a result, the metal member 280 is in contact with the second ground layer 62c on the surface of the second circuit board 262 facing the first circuit board 261, i.e., the lower surface. The second connecting surface 282f extends along the second ground layer 62c in a direction perpendicular to the vertical direction Z. The second connecting portion 282 is fixed to the second circuit board 262 by bolts 92, similar to the first embodiment.

[0097] The second connecting portion 282 has a plate-shaped portion 282a, a cylindrical portion 82b, and engaging claw portions 282d and 282e. The plate-shaped portion 282a is a substantially rectangular plate-shaped part. As shown in Figure 8, the dimension of the plate-shaped portion 282a in the second horizontal direction Y is smaller than the dimension of the plate-shaped portion 281a of the first connecting portion 281 in the second horizontal direction Y. The engaging claw portion 282d protrudes upward from one edge of the plate-shaped portion 282a in the first horizontal direction. The engaging claw portion 282e protrudes upward from the other edge of the plate-shaped portion 282a in the second horizontal direction. As shown in Figure 7, the engaging claw portion 282d is inserted from below into an engaging hole portion 262k formed in the second circuit board 262. Although not shown, the engaging claw portion 282e is inserted from below into another engaging hole portion formed in the second circuit board 262.

[0098] The other configurations of the first circuit board 261 are the same as those of the first circuit board 61 in the first embodiment. The other configurations of the second circuit board 262 are the same as those of the second circuit board 62 in the first embodiment. The other configurations of the metal member 280 are the same as those of the metal member 80 in the first embodiment. The other configurations of the circuit board unit 260 are the same as those of the circuit board unit 60 in the first embodiment.

[0099] According to this embodiment, the metal member 280 has a main body portion 283 extending in the connection direction, i.e., the vertical direction Z, to which the first connector 71 and the second connector 72 are connected; a first connection portion 281 having a first connection surface 281f and projecting away from the connector unit 70 from one end of the main body portion 283 in the connection direction; and a second connection portion 282 having a second connection surface 282f and projecting from the other end of the main body portion 283 in the connection direction in the same direction as the projection of the first connection portion 281. The main body portion 283 is plate-shaped, and its plate surface 283b is positioned facing the connector unit 70. Therefore, the entire main body portion 283 can be positioned suitably close to the connector unit 70. This makes it easier to suitably pass the return current corresponding to the current flowing through the connector unit 70 to the metal member 280. Therefore, the electromagnetic field generated by the return current flowing through the metal member 280 can more suitably cancel out the electromagnetic field generated by the current flowing through the connector unit 70. Therefore, unwanted radiated noise caused by the current flowing through the connector unit 70 connecting the first circuit board 261 and the second circuit board 262 can be effectively suppressed.

[0100] Furthermore, according to this embodiment, the circuit board unit 260 includes an elastically deformable conductive member 293. The conductive member 293 is in contact with the first ground layer 61c. The metal member 280 is electrically connected to the first ground layer 61c via the conductive member 293. Therefore, even if there is variation in the vertical Z dimension of the metal member 280, this variation in dimension can be absorbed by the elastic deformation of the conductive member 293. As a result, the metal member 280, which is placed between the first circuit board 261 and the second circuit board 262, can be suitably electrically connected to the first ground layer 61c of the first circuit board 261 and the second ground layer 62c of the second circuit board 262, regardless of variations in the vertical Z dimension of the metal member 280. Furthermore, by compressing and elastically deforming the conductive member 293, the restoring force of the conductive member 293 can press the metal member 280 against the second circuit board 262, allowing the metal member 280 to be suitably fixed and positioned between the first circuit board 261 and the second circuit board 262. In addition, the portion of the metal member 280 that is fixed to the first circuit board 261, i.e., the first connection portion 281, can be fixed to the first circuit board 261 more easily than when it is fixed to the first circuit board 261 with bolts.

[0101] <Third Embodiment> In this embodiment, the shape of the metal member 380 differs from that of the first embodiment. Figure 9 is a cross-sectional view showing a part of the circuit board unit 360 of this embodiment. Figure 10 is a perspective view showing a part of the circuit board unit 360 of this embodiment. Note that the connector unit 70 is schematically shown in Figures 9 and 10. In the following description, components similar to those in the above-described embodiment may be omitted from description by using the same reference numerals as appropriate.

[0102] As shown in Figure 9, in the circuit board unit 360 of this embodiment, a pair of through holes 361j are formed in the first circuit board 361. The pair of through holes 361j penetrate the first circuit board 361 in the vertical direction Z. The pair of through holes 361j are spaced apart in the first horizontal direction X.

[0103] As shown in Figures 9 and 10, the metal member 380 in this embodiment is arranged adjacent to one side of the connector unit 70 in the first horizontal direction. In this embodiment, the metal member 380 has a main body 381 and a connecting portion 382. The main body 381 is columnar in shape and extends in the connection direction, i.e., the vertical direction Z, through which the first connector 71 and the second connector 72 are connected. In this embodiment, the main body 381 is cylindrical in shape and extends in the vertical direction Z. The main body 381 is arranged opposite the connector unit 70 in the first horizontal direction X. The distance in the first horizontal direction X between the main body 381 and the connector unit 70 is the first distance L1c between adjacent metal members 380 and the connector unit 70, and is smaller than the second distance L2 between the opposing first circuit board 361 and second circuit board 62.

[0104] A female screw hole 381a is formed on the upper surface of the main body 381, recessed on the lower side. As shown in Figure 9, the bolt body 92a of the bolt 92 is screwed into the female screw hole 381a. As a result, the main body 381 is fixed to the second circuit board 62 by bolts 92. The upper surface of the main body 381 is in contact with the second ground pad portion 62i of the second ground layer 62c of the second circuit board 62. A female screw hole 381b that is recessed upwards is formed on the lower surface of the main body 381. The lower surface of the main body 381 is located above the upper surface of the first circuit board 361.

[0105] The connecting portion 382 is connected to the lower side of the main body portion 381. The connecting portion 382 is an angular U-shaped member that opens downwards when viewed in the second horizontal direction Y. The connecting portion 382 has a base portion 382a, a pair of legs 382b and 382c, and a male threaded portion 382d. The base portion 382a is a rectangular plate with its surface facing the vertical direction Z. The upper surface of the base portion 382a is in contact with the lower surface of the main body portion 381. The base portion 382a is positioned separately above the first circuit board 361. The male threaded portion 382d protrudes upward from the upper surface of the main body portion 381. The male threaded portion 382d is screwed into the female threaded hole 381b of the main body portion 381 from below. This fixes the main body portion 381 and the connecting portion 382 to each other.

[0106] A pair of legs 382b and 382c protrude downward from each of the edges on both sides of the base 382a in the first horizontal direction X. The pair of legs 382b and 382c are rectangular plates with their surface facing the first horizontal direction X. Leg 382b is inserted from above into one of a pair of through holes 361j and passes through in the vertical direction Z. Leg 382c is inserted from above into the other of a pair of through holes 361j and passes through in the vertical direction Z. The pair of legs 382b and 382c protrude below the first circuit board 361 through each of the through holes 361j. Each of the pair of legs 382b and 382c is electrically connected by solder 394 to the lower surface of the first ground pad portion 61g of the first ground layer 61b and to the upper surface of the first ground pad portion 61i of the first ground layer 61c, respectively. As a result, the first ground layer 61b and the first ground layer 61c are electrically connected via a pair of legs 382b and 382c.

[0107] The other configurations of the first circuit board 361 are the same as those of the first circuit board 61 in the first embodiment. The other configurations of the metal member 380 are the same as those of the metal member 80 in the first embodiment. The other configurations of the circuit board unit 360 are the same as those of the circuit board unit 60 in the first embodiment.

[0108] According to this embodiment, the metal member 380 has a columnar main body portion 381 that extends in the connection direction, i.e., the vertical direction Z, through which the first connector 71 and the second connector 72 are connected. The main body portion 381 is positioned opposite the connector unit 70. By positioning the columnar main body portion 381 opposite the connector unit 70, the amount of return current flowing through the main body portion 381 in response to the current flowing through the connector unit 70 can be suitably increased compared to the case where the main body portion 381 is plate-shaped. As a result, the electromagnetic field generated by the return current flowing through the metal member 380 can more suitably cancel out the electromagnetic field generated by the current flowing through the connector unit 70. Therefore, unwanted radiation noise caused by the current flowing through the connector unit 70 connecting the first circuit board 361 and the second circuit board 62 can be suitably suppressed.

[0109] <Fourth Embodiment> This embodiment differs from the third embodiment in the arrangement of the metal member 480 relative to the connector unit 70. Figure 11 is a perspective view showing a part of the circuit board unit 460 of this embodiment. Figure 12 is a plan view showing a part of the circuit board unit 460 of this embodiment. Note that the connector unit 70 is schematically shown in Figures 11 and 12. In the following description, components similar to those in the above-described embodiment may be omitted from description by using the same reference numerals as appropriate.

[0110] As shown in Figure 11, in the circuit board unit 460 of this embodiment, the portion of the first circuit board 461 located on one side of the connector unit 70 in the second horizontal direction does not have a signal line 77. The plurality of signal lines 478 provided on the portion of the first circuit board 461 located on the other side of the connector unit 70 in the second horizontal direction are arranged in a line in the first horizontal direction X. The plurality of signal lines 478, similar to the plurality of signal lines 78 in the first embodiment, include a first signal line 478a and a second signal line 478b through which a signal with a higher frequency than the signal frequency flowing through the first signal line 478a flows. There are multiple first signal lines 478a and multiple second signal lines 478b. There are two second signal lines 478b. The two second signal lines 478b are signal lines 478 located in the center of the first horizontal direction X among the multiple signal lines 478.

[0111] In this embodiment, the metal member 480 is positioned adjacent to one side of the connector unit 70 in the second horizontal direction. That is, in this embodiment, the metal member 480 is positioned adjacent to the connector unit 70 in the second horizontal direction Y, which is perpendicular to the first horizontal direction X. As shown in Figure 12, when viewed from above, the metal member 480 is positioned on the opposite side of the connector unit 70 from the plurality of signal lines 478, with the connector unit 70 in the second horizontal direction Y. That is, the plurality of signal lines 478 are positioned on the first side of the second horizontal direction Y, i.e., the -Y side, relative to the connector unit 70, and the metal member 480 is positioned on the second side of the second horizontal direction Y, i.e., the +Y side, relative to the connector unit 70.

[0112] The position of the metal member 480 in the first horizontal direction X is the same as the position of the connector unit 70 in the first horizontal direction X at its central part. The position of the metal member 480 in the first horizontal direction X includes the position of the second signal line 478b in the first horizontal direction X. That is, when the metal member 480 is viewed from the second horizontal direction Y, and the first part of the metal member 480 located furthest to the first side and the second part located furthest to the second side in the first horizontal direction X are projected onto a position along the vertical direction Z of the second signal line 478b, the position of the second signal line 478b in the first horizontal direction X is located between the first part and the second part. When viewed in the vertical direction Z, the metal member 480 is positioned to sandwich the connector unit 70 in the second horizontal direction Y between it and the second signal line 478b. The shape of the metal member 480 is the same as the shape of the metal member 380 in the third embodiment. In this embodiment, the shape of the metal member may be the same as the shape of the metal member 80 in the first embodiment or the shape of the metal member 280 in the second embodiment.

[0113] The other configurations of the first circuit board 461 are the same as those of the first circuit board 361 in the third embodiment. The other configurations of the metal member 480 are the same as those of the metal member 380 in the third embodiment. The other configurations of the circuit board unit 460 are the same as those of the circuit board unit 360.

[0114] According to this embodiment, the connector unit 70 has a shape that is elongated in the first horizontal direction X when viewed in the connection direction, i.e., the vertical direction Z, in which the first connector 71 and the second connector 72 are connected. The metal member 480 is positioned adjacent to the connector unit 70 in an orthogonal direction perpendicular to the first horizontal direction X, i.e., in the second horizontal direction Y. Therefore, compared to the case where the metal member 480 is adjacent to the connector unit 70 in the first horizontal direction X, it is easier to increase the degree of freedom in positioning the metal member 480 relative to the connector unit 70. Specifically, it is possible to adjust the position of the metal member 480 relative to the connector unit 70 in the first horizontal direction X, and the position of the metal member 480 can be suitably set according to the current flowing through the connector unit 70. Therefore, a suitable return current can be flowed through the metal member 480, and unwanted radiated noise caused by the current flowing through the connector unit 70 can be suitably suppressed.

[0115] Furthermore, according to this embodiment, the first circuit board 461 has a plurality of signal lines 478 formed thereon, arranged in a first horizontal direction X and electrically connected to the first connector 71. The plurality of signal lines 478 include a first signal line 478a and a second signal line 478b through which a signal with a higher frequency than the signal flowing through the first signal line 478a flows. The plurality of signal lines 478 are arranged in a second horizontal direction Y with respect to the connector unit 70. The metal member 480 is arranged on the opposite side of the connector unit 70 from the plurality of signal lines 478. The position of the metal member 480 in the first horizontal direction X includes the position of the second signal line 478b in the first horizontal direction X. Therefore, the metal member 480 can be positioned suitably close to the connector of the connector unit 70 to which the second signal line 478b is connected. This makes it easier to suitably flow the return current corresponding to the relatively high-frequency current among the currents flowing through each connector of the connector unit 70 to the metal member 480. Therefore, unwanted radiated noise caused by the current flowing through the connector unit 70 can be more effectively suppressed.

[0116] The embodiments of this disclosure are not limited to those described above, and the following configurations and methods may also be adopted. The metal member may have any configuration as long as it is placed between the first circuit board and the second circuit board, electrically connects the first ground layer and the second ground layer, and is placed adjacent to the connector unit. The metal member may be placed adjacent to the connector unit in any direction. The metal member may have any shape.

[0117] For example, in the third embodiment described above, the main body 381 of the metal member 380 may be a columnar shape other than cylindrical, such as a polygonal prism. Also, in the third embodiment, the legs 382b and 382c of the metal member 380 do not have to penetrate the first circuit board 361, and may only be connected to the first ground layer 61c on the upper surface of the first circuit board 361. Furthermore, in the metal member 380 of the third embodiment, the main body 381 and the connecting portion 382 may be fixed to each other by a bolt inserted from below into a hole penetrating the first circuit board 361. Also, in the third embodiment, a conductive gasket may be provided between the base 382a of the metal member 380 and the first circuit board 361.

[0118] The connector unit may have any configuration as long as it has a first connector and a second connector connected to each other. The first circuit board and the second circuit board may have any configuration as long as they each have a ground layer and are arranged facing each other.

[0119] Furthermore, while the first embodiment described above illustrates an example of applying the present disclosure to a transmissive projector, the present disclosure can also be applied to a reflective projector. Here, "transmissive" means that the liquid crystal light bulb, including a liquid crystal panel, transmits light. "Reflective" means that the liquid crystal light bulb reflects light. Note that the light modulation device is not limited to a liquid crystal panel, but may also be a light modulation device using, for example, a micromirror.

[0120] Furthermore, while the first embodiment described above provided an example of a projector 1 using three optical modulators 4R, 4G, and 4B, this disclosure is also applicable to projectors using only one optical modulator, or projectors using four or more optical modulators. Furthermore, the electronic devices on which the circuit board is mounted and the electronic devices on which the circuit board unit is mounted are not limited to projectors, but may be other electronic devices. Furthermore, the configurations and methods described herein can be combined as appropriate, provided they are not inconsistent with each other.

[0121] [Summary of this disclosure] A summary of this disclosure is provided below.

[0122] (Note 1) A first circuit board having a first ground layer, A second circuit board having a second ground layer and positioned opposite the first circuit board, A connector unit having a first connector attached to the first circuit board and a second connector attached to the second circuit board and connected to the first connector, A metal member disposed between the first circuit board and the second circuit board, electrically connecting the first ground layer and the second ground layer, Equipped with, The circuit board unit is characterized in that the metal member is arranged adjacent to the connector unit.

[0123] This configuration allows a return path to be provided between the first and second circuit boards by a metal component, through which the return current flows. Since the metal component is positioned adjacent to the connector unit, it can be positioned close to the connector unit. This makes it easier to pass the return current corresponding to the current flowing through the connector unit through the metal component. Therefore, the electromagnetic field generated by the return current flowing through the metal component can effectively cancel out the electromagnetic field generated by the current flowing through the connector unit. As a result, unwanted radiated noise caused by the current flowing through the connector unit connecting the first and second circuit boards can be effectively suppressed.

[0124] Furthermore, since the first ground layer of the first circuit board and the second ground layer of the second circuit board can be electrically connected by a metal component, the potential of each ground layer can be more effectively stabilized. This allows for more effective suppression of unwanted radiated noise caused by currents flowing along signal lines and the like along each ground layer.

[0125] Furthermore, metal components can be used to provide return current paths, such as the first and second ground layers, to the connector unit. Therefore, even if each connector of the connector unit is separated from each circuit board, the metal components can provide return current paths to each connector that is separated from each circuit board. This shortens the return current paths for each connector and each wiring layer on each circuit board compared to the case where metal components are not provided. Consequently, the design of the return current paths for each connector can be simplified, and deterioration of the signal quality flowing through each connector can be suppressed.

[0126] Furthermore, the structure using metal components is simpler than the structure in which the connector unit having the first and second connectors is surrounded from the outside by a shielding member. Therefore, the complexity of the circuit board unit structure can be suppressed compared to a structure in which the connector unit is surrounded by a shielding member. Consequently, the increase in the manufacturing cost of the circuit board unit can be suppressed.

[0127] (Note 2) The circuit board unit according to Appendix 1, wherein the first distance between adjacent metal members and the connector unit is smaller than the second distance between the opposing first circuit board and the second circuit board.

[0128] This configuration allows the metal component to be brought more favorably closer to the connector unit. This makes it easier to favorably pass the return current corresponding to the current flowing through the connector unit through the metal component. Therefore, the electromagnetic field generated by the return current flowing through the metal component can more favorably cancel out the electromagnetic field generated by the current flowing through the connector unit. As a result, unwanted radiated noise caused by the current flowing through the connector unit connecting the first circuit board and the second circuit board can be more favorably suppressed.

[0129] (Note 3) In the connection direction in which the first connector and the second connector are connected, the connector unit has a shape that is elongated in a predetermined direction. The aforementioned metal member is arranged adjacent to the connector unit in the predetermined direction, as described in Appendix 1 or Appendix 2, in the circuit board unit described in Appendix 1 or Appendix 2.

[0130] This configuration allows the metal components to be positioned conveniently close to the connector unit while suppressing interference between the metal components and the signal lines provided on each circuit board.

[0131] (Note 4) The first circuit board has a plurality of signal lines formed thereon, which are arranged in the predetermined direction and electrically connected to the first connector. The plurality of signal lines include a first signal line and a second signal line through which a signal with a higher frequency than the signal flowing through the first signal line flows. The circuit board unit as described in Appendix 3, wherein the second signal line is positioned closer to the metal member than the first signal line in the predetermined direction.

[0132] With this configuration, by positioning the second signal line, which carries a relatively high-frequency signal, close to the metal member, the metal member can be positioned more favorably close to the connector to which the second signal line is connected among the connectors of the connector unit. This makes it easier to favorably channel the return current corresponding to the relatively high-frequency current among the currents flowing through each connector of the connector unit to the metal member. Therefore, unwanted radiated noise caused by the current flowing through the connector unit can be more favorably suppressed.

[0133] (Note 5) In the connection direction in which the first connector and the second connector are connected, the connector unit has a shape that is elongated in a predetermined direction. The circuit board unit according to Appendix 1 or Appendix 2, wherein the metal members are arranged adjacent to the connector unit in an orthogonal direction perpendicular to the predetermined direction.

[0134] This configuration allows for greater flexibility in the placement of metal components relative to the connector unit compared to the case where the metal components are adjacent to the connector unit in a predetermined direction. Specifically, it is possible to adjust the position of the metal components relative to the connector unit in a predetermined direction, and the placement of the metal components can be suitably set according to the current flowing through the connector unit. Therefore, a suitable return current can be supplied to the metal components, and unwanted radiated noise caused by the current flowing through the connector unit can be suitably suppressed.

[0135] (Note 6) The first circuit board has a plurality of signal lines formed thereon, which are arranged in the predetermined direction and electrically connected to the first connector. The plurality of signal lines include a first signal line and a second signal line through which a signal with a higher frequency than the signal flowing through the first signal line flows. The plurality of signal lines are arranged in the direction perpendicular to the connector unit. The metal member is positioned on the opposite side of the connector unit from the plurality of signal lines. The circuit board unit as described in Appendix 5, wherein the position of the metal member in the predetermined direction includes the position of the second signal line in the predetermined direction.

[0136] This configuration allows the metal component to be positioned more favorably close to the connector to which the second signal line is connected among the connector units. This makes it easier to favorably route the return current corresponding to the relatively high-frequency currents flowing through each connector of the connector unit to the metal component. Therefore, unwanted radiated noise caused by the current flowing through the connector unit can be more favorably suppressed.

[0137] (Note 7) The aforementioned metal member is A first connection surface extending along the first ground layer and electrically connected to the first ground layer, A second connection surface extending along the second ground layer and electrically connected to the second ground layer, A circuit board unit having any one of the specifications described in Appendix 1 to Appendix 6.

[0138] This configuration allows for a favorable increase in the contact area between the metal member and the first ground layer, and between the metal member and the second ground layer. This makes it easier to favorably increase the amount of return current flowing between the first and second ground layers via the metal member. Therefore, unwanted radiated noise caused by the current flowing through the connector unit can be more favorably suppressed. Furthermore, the metal member allows for a more favorable connection between the first and second ground layers, and the potential of each ground layer can be more favorably stabilized.

[0139] (Note 8) The aforementioned metal member is A main body portion extending in the connection direction to which the first connector and the second connector are connected, Having the first connecting surface, the first connecting portion protrudes from one end of the main body in the connecting direction, The second connecting portion has the second connecting surface and protrudes from the other end of the main body in the connection direction in a direction different from the direction in which the first connecting portion protrudes, It has, The circuit board unit as described in Appendix 7, wherein the main body is plate-shaped and its side is positioned opposite the connector unit.

[0140] This configuration allows the positions of the first and second connection surfaces to be different in a direction perpendicular to the connection direction. This makes it possible to make the position where the first connection surface is connected to the first circuit board and the position where the second connection surface is connected to the second circuit board different in a direction perpendicular to the connection direction. Therefore, it is possible to easily adjust the position to which each connection surface is connected according to the arrangement of electronic components on the mounting surface of each circuit board, thereby improving the degree of freedom in the arrangement of electronic components on each circuit board. Furthermore, by positioning the side of the main body opposite the connector unit, a return path can be suitably created using a metal member. In addition, it is possible to suitably adopt the structure in which the positions of the first and second connection surfaces are different in a direction perpendicular to the connection direction, while making it easier to manufacture the metal member as a sheet metal member.

[0141] (Note 9) The aforementioned metal member is A main body portion extending in the connection direction to which the first connector and the second connector are connected, Having the first connection surface, the first connection portion protrudes from one end of the main body in the connection direction toward the connector unit, The second connecting portion has the second connecting surface and protrudes from the other end of the main body in the connection direction in the same direction as the protruding first connecting portion, It has, The circuit board unit as described in Appendix 7, wherein the main body is plate-shaped and its plate surface is positioned opposite the connector unit.

[0142] This configuration allows the entire main body to be positioned conveniently close to the connector unit. This facilitates the flow of the return current corresponding to the current flowing through the connector unit through the metal component. Consequently, the electromagnetic field generated by the return current flowing through the metal component can more effectively cancel out the electromagnetic field generated by the current flowing through the connector unit. Therefore, unwanted radiation noise caused by the current flowing through the connector unit connecting the first and second circuit boards can be effectively suppressed.

[0143] (Note 10) The metal member has a columnar main body portion that extends in the connection direction in which the first connector and the second connector are connected. The main body is a circuit board unit according to any one of the appendices 1 to 9, which is positioned opposite the connector unit.

[0144] With this configuration, by arranging the columnar main body opposite the connector unit, the amount of return current flowing to the main body in response to the current flowing to the connector unit can be suitably increased compared to when the main body is plate-shaped. As a result, the electromagnetic field generated by the return current flowing through the metal member can more effectively cancel out the electromagnetic field generated by the current flowing through the connector unit. Therefore, unwanted radiation noise caused by the current flowing through the connector unit connecting the first circuit board and the second circuit board can be suitably suppressed.

[0145] (Note 11) The circuit board unit according to any one of the appendices 1 to 10, wherein the first circuit board has a pair of first ground layers provided on different layers from each other, and the pair of first ground layers are electrically connected to each other.

[0146] This configuration allows for stabilization of the potential of the pair of first ground layers. Furthermore, it facilitates the flow of return current more effectively through the metal components electrically connected to the first ground layers.

[0147] (Note 12) The first circuit board has through holes formed therein. A metal bolt is passed through the aforementioned through hole. The aforementioned bolt is The bolt body portion is passed through the through hole and fastened to the metal member, A bolt head provided at one end of the bolt body, It has, The metal member contacts one of the pair of first ground layers on the surface of the first circuit board facing the second circuit board. The circuit board unit as described in Appendix 11, wherein the bolt head is in contact with the other of the pair of first ground layers on the surface of the first circuit board opposite to the surface facing the second circuit board.

[0148] With this configuration, by fixing the metal member to the first circuit board with bolts, a pair of first ground layers can be easily and suitably electrically connected to each other via the bolts and the metal member. Furthermore, the metal member can be stably fixed to the first circuit board with bolts.

[0149] (Note 13) The circuit board unit as described in Appendix 12, wherein the metal member has an engaging claw portion inserted into an engaging hole formed in the first circuit board.

[0150] With this configuration, when the bolt is tightened into the metal member, the engaging claw catches on the inner surface of the engaging hole, preventing the metal member from rotating relative to the first circuit board. This makes it easier to tighten the bolt into the metal member and to fix the metal member to the first circuit board with the bolt.

[0151] (Note 14) Equipped with an elastically deformable conductive member, The conductive member is in contact with the first ground layer, The circuit board unit according to any one of the appendices 1 to 13, wherein the metal member is electrically connected to the first ground layer via the conductive member.

[0152] With this configuration, even if there are variations in the dimensions of the metal members, these variations can be absorbed by the elastic deformation of the conductive member. As a result, the metal member placed between the first circuit board and the second circuit board can be electrically connected to the first ground layer of the first circuit board and the second ground layer of the second circuit board, regardless of variations in the dimensions of the metal members. Furthermore, by putting the conductive member in a state of compressive elastic deformation, the restoring force of the conductive member can press the metal member against the second circuit board, allowing the metal member to be fixed and positioned between the first and second circuit boards. In addition, the portion of the metal member that is fixed to the first circuit board can be fixed to the first circuit board more easily than when it is fixed to the first circuit board with bolts.

[0153] (Note 15) An electronic device characterized by comprising a circuit board unit as described in any one of the appendices 1 to 14.

[0154] This configuration effectively suppresses unwanted radiated noise caused by the current flowing through the connector unit in electronic devices. [Explanation of symbols]

[0155] 1…Projector (electronic device), 60,260,360,460…Circuit board unit, 61,261,361,461…First circuit board, 61b,61c…First ground layer, 61j,62j,361j…Through hole, 61k,61m,262k…Engagement hole, 62,262…Second circuit board, 62b,62c…Second ground layer, 70…Connector unit, 71…First connector, 72…Second connector, 77,78,478…Signal line, 77a,78a,478a…First signal line, 77b,78b,478b…Second signal line, 80,280, 380, 480…Metal member, 81, 281…First connection part, 81d, 81e, 282d, 282e…Engaging claw part, 81f, 281f…First connection surface, 82, 282…Second connection part, 82f, 282f…Second connection surface, 83, 283, 381…Main body part, 83a…Side side, 91, 92…Bolt, 91a, 92a…Bolt body part, 91b, 92b…Bolt head, 283b…Plate surface, 293…Conductive member, L2…Second distance, L1a, L1b, L1c…First distance, X…First horizontal direction (determined direction), Y…Second horizontal direction (orthogonal direction), Z…Up and down direction (connection direction)

Claims

1. A first circuit board having a first ground layer, A second circuit board having a second ground layer and positioned opposite the first circuit board, A connector unit having a first connector attached to the first circuit board and a second connector attached to the second circuit board and connected to the first connector, A metal member disposed between the first circuit board and the second circuit board, electrically connecting the first ground layer and the second ground layer, Equipped with, The circuit board unit is characterized in that the metal member is arranged adjacent to the connector unit.

2. The circuit board unit according to claim 1, wherein the first distance between adjacent metal members and the connector unit is smaller than the second distance between the opposing first circuit board and the second circuit board.

3. Viewed in the connection direction in which the first connector and the second connector are connected, the connector unit has a shape that is elongated in a predetermined direction. The circuit board unit according to claim 1, wherein the metal members are arranged adjacent to the connector unit in the predetermined direction.

4. The first circuit board has a plurality of signal lines formed thereon, which are arranged in the predetermined direction and electrically connected to the first connector. The plurality of signal lines include a first signal line and a second signal line through which a signal with a higher frequency than the signal flowing through the first signal line flows. The circuit board unit according to claim 3, wherein the second signal line is positioned closer to the metal member than the first signal line in the predetermined direction.

5. Viewed in the connection direction in which the first connector and the second connector are connected, the connector unit has a shape that is elongated in a predetermined direction. The circuit board unit according to claim 1, wherein the metal members are arranged adjacent to the connector unit in an orthogonal direction perpendicular to the predetermined direction.

6. The first circuit board has a plurality of signal lines formed thereon, which are arranged in the predetermined direction and electrically connected to the first connector. The plurality of signal lines include a first signal line and a second signal line through which a signal with a higher frequency than the signal flowing through the first signal line flows. The plurality of signal lines are arranged in the direction perpendicular to the connector unit. The metal member is positioned on the opposite side of the connector unit from the plurality of signal lines. The circuit board unit according to claim 5, wherein the position of the metal member in the predetermined direction includes the position of the second signal line in the predetermined direction.

7. The aforementioned metal member is A first connection surface extending along the first ground layer and electrically connected to the first ground layer, A second connection surface extending along the second ground layer and electrically connected to the second ground layer, A circuit board unit according to any one of claims 1 to 6, having the following features.

8. The aforementioned metal member is A main body portion extending in the connection direction to which the first connector and the second connector are connected, A first connecting portion having the first connecting surface and protruding from one end of the main body in the connecting direction, The second connecting portion has the second connecting surface and protrudes from the other end of the main body in the connection direction in a direction different from the direction in which the first connecting portion protrudes, It has, The circuit board unit according to claim 7, wherein the main body is plate-shaped and its side is positioned opposite the connector unit.

9. The aforementioned metal member is A main body portion extending in the connection direction to which the first connector and the second connector are connected, Having the first connection surface, the first connection portion protrudes from one end of the main body in the connection direction toward the connector unit, The second connecting portion has the aforementioned second connecting surface and protrudes from the other end of the main body in the connection direction in the same direction as the protruding first connecting portion, It has, The circuit board unit according to claim 7, wherein the main body is plate-shaped and its plate surface is positioned opposite the connector unit.

10. The metal member has a columnar main body portion that extends in the connection direction in which the first connector and the second connector are connected. The circuit board unit according to any one of claims 1 to 6, wherein the main body is arranged opposite to the connector unit.

11. The circuit board unit according to any one of claims 1 to 6, wherein the first circuit board has a pair of first ground layers provided on different layers from each other, and the pair of first ground layers are electrically connected to each other.

12. The first circuit board has through holes formed therein. A metal bolt is passed through the aforementioned through hole. The aforementioned bolt is The bolt body portion is passed through the through hole and fastened to the metal member, A bolt head provided at one end of the bolt body, It has, The metal member contacts one of the pair of first ground layers on the surface of the first circuit board facing the second circuit board. The circuit board unit according to claim 11, wherein the bolt head is in contact with the other of the pair of first ground layers on the surface of the first circuit board opposite to the surface facing the second circuit board.

13. The circuit board unit according to claim 12, wherein the metal member has an engaging claw portion inserted into an engaging hole formed in the first circuit board.

14. Equipped with an elastically deformable conductive member, The conductive member is in contact with the first ground layer, The circuit board unit according to any one of claims 1 to 6, wherein the metal member is electrically connected to the first ground layer via the conductive member.

15. An electronic device comprising a circuit board unit according to any one of claims 1 to 6.

Images