JP2013229505A - Flexible printed circuit board, display device, and electronic apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To unfailingly remove static electricity and obtain a structure that is stable in terms of strength in a flexible printed circuit board where ESD measurements are taken by covering a surface with a tape using a metal foil.SOLUTION: A base film 61 side surface of a sheet member 70 is composed of: a conduction region including at least a part of a region corresponding to a ground pattern 62; and a non conduction region where a surface of a metal foil 71 is covered by an insulation film 72. At least a part of the conduction region of the sheet member 70 has a structure formed by folding the metal foil 71a and overlapping the two folded parts with each other, and a thickness of the sheet member 70 in the part of the conduction region is set so as to be equal to or larger than a thickness of the sheet member 70 in the non conduction region.

Description

  The present invention relates to a flexible printed wiring board, a display device including the flexible printed wiring board, and an electronic apparatus.

  The display device generally includes flexible printed circuit boards (hereinafter also referred to as “FPC”) as means for inputting a drive signal to a drive driver provided in the display panel. In the FPC, a circuit that controls a display panel by supplying a signal voltage is formed, and display is performed on the display panel based on a drive signal from the FPC.

  For inputting signals from the FPC to the liquid crystal driver, a high-speed interface capable of transmitting data at high speed (for example, a serial interface technology using differential signals such as LVDS (Low Voltage Differential Signaling)) is adopted. As the resolution of display devices in recent years increases, it is required to input interface signals at higher speeds.

  However, in a high-speed interface, a small amplitude signal is used and the data transfer rate is fast. For this reason, electromagnetic noise is likely to be generated from high-speed differential signals, and is also susceptible to noise generated by static electricity and other electronic components. Therefore, it is necessary to take measures to prevent other devices from malfunctioning due to the influence of the components of the other devices due to electromagnetic noise generated from high-speed signals. In addition, to prevent high-speed differential signals from being affected by noise from other electronic components, countermeasures against unwanted radiation (Electro Magnetic Interference: EMI), countermeasures against internal malfunctions, signal quality improvement due to internal interference, electrostatics (Electro It is necessary to take measures such as static discharge (ESD).

  Patent Document 1 discloses a liquid crystal display device in which a display panel, a light guide plate, and the like are housed in a metal frame (bezel) and a ground terminal is formed on a ground line in the vicinity of the metal frame of the FPC. In this liquid crystal display device, it is described that the ground of the display panel is strengthened by connecting the ground terminal of the FPC and the metal frame, thereby reducing EMI noise and improving ESD resistance.

  Further, as an ESD countermeasure, there is a method of attaching an electromagnetic wave absorbing sheet or a copper foil tape so as to cover FPC mounting components and wiring. When an unnecessary high-frequency current is generated in the FPC circuit, noise is radiated from a place where it can fly easily. If an electromagnetic wave absorbing sheet or copper foil tape is provided on the surface of the FPC, the high-frequency current is generated. Since it acts as a resistive impedance (magnetic loss) to the generated circuit and converts the high frequency current itself that causes noise into thermal energy, noise can be suppressed.

JP 2006-350243 A

  As a countermeasure against ESD, a ground pattern (GND) having a fixed potential is provided on the FPC, and an electroconductive region of an electromagnetic wave absorbing sheet or a copper foil tape is electrically connected to the ground pattern. Specifically, as shown in FIG. 21, a ground pattern 162 is formed on the surface of the base film 161 of the FPC 160, and a copper foil tape 171 provided on the base film 161 is provided. An insulating polyimide film 172 is bonded to the base film 161 side of the copper foil tape 171 with a conductive adhesive sheet 173, and the polyimide film 172 is bonded to the base film 161 with an insulating adhesive sheet 174. However, the polyimide film 172 is not provided in the region of the ground pattern 162 of the base film 161, and the ground pattern 162 and the copper foil tape 171 are electrically connected via the conductive adhesive sheet 173. The surface of the FPC 160 on the copper foil tape 171 side is in contact with a conductive member 152 (for example, a bezel of a mobile device body) in a non-conductive region where the polyimide film 172 is attached, and a ground pattern Static electricity is removed from 162 through member 152.

  In the above FPC, there is a difference in thickness of, for example, about 50 μm between the non-conductive region provided with the polyimide film and the conductive region for conducting the ground pattern depending on the presence or absence of polyimide. Therefore, the copper foil tape 171 in the conductive region cannot directly contact the ground pattern 162 or the member 152. The ground pattern is conducted through the conductive adhesive sheet 173 as described above. On the other hand, the member 152 is electrically connected by a non-conductive region of the copper foil tape 171. Therefore, there is a problem that the conduction stability is not sufficient.

  Further, the conductive region of the copper foil tape 171 is thinner than the other regions, and when the member 152 is overlaid, a space is created between the FPC 160 and the member 152, thereby increasing strength. There is also a problem that the stability becomes low.

  An object of the present invention is to reliably remove static electricity and obtain a stable structure in terms of strength in an FPC in which ESD countermeasures are taken with a tape using a metal foil.

  The FPC of the present invention that solves the above problem is provided so as to cover a base film on which one of the surfaces of the circuit including the ground pattern is formed and the surface of the base film on which the ground pattern is formed, A sheet member having a metal foil as a base, wherein the surface of the sheet member on the base film side includes a conduction region including at least a part of a region corresponding to the ground pattern, and the metal foil. The surface is configured by a non-conductive region covered with an insulating film, and at least a part of the conductive region of the sheet member has a configuration in which two metal foils are folded and stacked, and the thickness of the sheet member is It is more than the thickness of the sheet member in the said non-conduction area | region.

  According to the above configuration, two folded metal foils are stacked in the conductive region of the sheet member, and the thickness thereof is equal to or greater than the thickness of the non-conductive region. The bottom surface of the foil is in direct contact with the ground pattern of the base film. Therefore, the ground pattern and the metal foil can be made conductive without using another configuration such as an adhesive material, and static electricity can be reliably removed from the ground pattern to the outside.

  In addition, according to the above configuration, by folding the metal foil in the conductive region of the sheet member and stacking two sheets, the level difference formed on the sheet member at the boundary between the conductive region and the non-conductive region is reduced. An FPC having a stable structure can be obtained.

  In the FPC of the present invention, it is preferable that the thickness of the sheet member in the conductive region is equal to the thickness in the non-conductive region.

  According to the above configuration, the step is not formed on the sheet member at the boundary between the conduction region and the non-conduction region of the sheet member, so that the FPC can have a more stable structure.

  In the FPC of the present invention, in the non-conduction region, the insulating film may be a polyimide film bonded to the surface of the metal foil via an adhesive sheet.

  Moreover, the FPC of this invention WHEREIN: The insulating adhesive sheet adhere | attached on the surface of the said metal foil may be sufficient as the said insulating film in the said non-conduction area | region.

  In the FPC of the present invention, the metal foils stacked in the conductive region are preferably bonded to each other with an insulating adhesive sheet.

  According to said structure, since two metal foil is adhere | attached with the insulating adhesive sheet, the structural stability of FPC is improved more. At this time, even if the metal foil is bonded with the insulating pressure-sensitive adhesive sheet, since both are folded and overlapped, stable conduction can be obtained.

  In the FPC of the present invention, the metal foil may be a copper foil tape.

  The display device of the present invention includes the FPC of the present invention, a display panel on which the FPC is mounted, and a current-carrying member electrically connected to the ground pattern via the metal foil.

  In the display device of the present invention, the energization member may be a metal frame that encloses a display panel.

  The display device of the present invention is suitably used when mounted on an electronic device.

  According to the present invention, it is possible to reliably remove static electricity and obtain a structure that is stable in terms of strength in an FPC that has been subjected to ESD countermeasures with a tape that uses a metal foil.

It is a schematic perspective view of the smart phone of this embodiment. It is a disassembled perspective view of the liquid crystal display device of this embodiment. 2 is a rear view of the liquid crystal display device according to Embodiment 1. FIG. 6 is a rear view of a liquid crystal display device according to a modification of Embodiment 1. FIG. 4 is a plan view showing a sheet member of the FPC according to Embodiment 1. FIG. It is a top view which shows metal foil among the sheet | seat members of FPC which concerns on Embodiment 1. FIG. It is a top view which shows a polyimide film among the sheet | seat members of FPC which concerns on Embodiment 1. FIG. It is sectional drawing of FPC containing the cross section in the AA of FIG. 5 of a sheet | seat member. It is sectional drawing of FPC containing the cross section in the BB line of FIG. 5 of a sheet | seat member. It is a principal part enlarged view of the cross section of the liquid crystal display device containing the cross section in the AA of FIG. 5 of a sheet | seat member. It is sectional drawing of FPC of Embodiment 2. FIG. It is sectional drawing of FPC of the modification 1. FIG. It is sectional drawing of FPC of the modification 1. FIG. 10 is a plan view showing an FPC sheet member according to Modification 2. FIG. It is a top view which shows metal foil among the sheet | seat members of FPC which concerns on the modification 2. FIG. It is a top view which shows a polyimide film among the sheet | seat members of FPC which concerns on the modification 2. FIG. 10 is a plan view showing an FPC sheet member according to Modification 3. FIG. It is a top view which shows metal foil among the sheet | seat members of FPC which concerns on the modification 3. FIG. It is a top view which shows a polyimide film among the sheet | seat members of FPC which concerns on the modification 3. It is sectional drawing of FPC which concerns on the modification 4. It is a principal part enlarged view of the cross section of the liquid crystal display device of a prior art example.

  The case where the display device on which the FPC that is the subject of the present invention is mounted is mounted on, for example, an electronic device of a smartphone will be described in detail. Hereinafter, embodiments of the present invention will be described with reference to the drawings.

Embodiment 1
1 to 10 show a liquid crystal display device, an electronic apparatus, and an FPC according to this embodiment.

  FIG. 1 is a perspective view of a smartphone 10 according to the present embodiment. As shown in FIG. 1, the smartphone 10 includes a thin housing 30 whose upper side in the drawing is rectangular. And the smart phone 10 is provided with the liquid crystal display device 20 (refer FIG. 2) so that the display area D may be exposed from the opening part inside the housing | casing 30, and an image display may be performed in the display area D. FIG. Here, as shown in FIG. 1, a sensor area S whose touch position can be detected is defined so as to overlap the display area D and an outer portion along one short side (lower left side in the figure) of the display area D. The touch panel is configured.

  FIG. 2 is an exploded perspective view of the liquid crystal display device 20 constituting the smartphone 10. As shown in FIG. 2, the liquid crystal display device 20 has a configuration in which a display panel 40, a light guide plate (not shown), and the like are housed in a front metal frame 51 and a back metal frame 52. The display panel 40 has a configuration in which a liquid crystal layer (not shown) is sandwiched between an active matrix substrate 41 and a counter substrate 42. The active matrix substrate 41 has a liquid crystal driving driver (not shown) mounted in a terminal area. In the terminal region of the active matrix substrate 41, an FPC 60 for connecting a liquid crystal driving driver (not shown) and the active matrix substrate 41 and transmitting a driving signal to the driver is mounted.

  The display panel 40, the light guide plate, the front metal frame 51, the back metal frame 52, and the like generally have the same configuration as a known one. The front metal frame 51 and the back metal frame 52 are made of, for example, SUS.

  As shown in FIG. 2, the FPC 60 has a configuration in which a sheet member 70 is laminated on a base film 61. As shown in FIG. 3, the FPC 60 is folded back on the back surface of the active matrix substrate 41 of the display panel 40. Then, the sheet member 70 of the FPC 60 is accommodated in the back metal frame 52 so as to cover them and come into contact with the back metal frame 52. Note that the FPC 60 may protrude outside the back metal frame 52, and in that case, the FPC 60 is folded back to the back side of the back metal frame 52 as shown in FIG. 4. At this time, the FPC 60 is folded twice so that the sheet member 70 contacts the back metal frame 52. Further, in the case of protruding outside the rear metal frame 52, the sheet member 70 may be provided on the surface of the FPC 60 opposite to FIG. In this case, the sheet member 70 can be brought into contact with the surface of the back metal frame 52 without turning the FPC 60 twice.

  On one surface of the base film 61, wiring connected to the drive driver is formed. The base film 61 is made of, for example, polyimide and has a thickness of 50 to 100 μm. On the base film 61, GND wiring (not shown) is provided for each drive driver. In the ground pattern 62, a part of each GND wiring becomes a GND terminal. The ground pattern 62 is exposed on the surface of the base film 61 of the FPC 60. The wiring such as the GND wiring including the ground pattern 62 is formed by, for example, gold plating.

  Here, FIG. 5 is a plan view of the sheet member 70. FIG. 6 is a plan view of the metal foil 71 constituting the sheet member 70. FIG. 7 is a plan view of the insulating film 72 constituting the sheet member 70. 8 and 9 are cross-sectional views of the FPC 60, and show portions including cross-sections of the sheet member 70 taken along lines AA and BB in FIG. 5, respectively.

  The surface of the base film 61 on which the wiring is provided is covered with a sheet member 70 having a metal foil 71 as a base. The sheet member 70 is provided so as to cover at least the ground pattern 62 on the base film 61. The metal foil 71 serving as a base of the sheet member 70 is, for example, a copper foil, and has a thickness of 18 to 35 μm, for example.

  On the surface of the sheet member 70 that is bonded to the base film 61, a region including a region corresponding to the ground pattern 62 is a conductive region, and the other region is a non-conductive region.

  In the non-conduction region, an insulating film 72 is bonded to the surface of the metal foil 71 as shown in FIG. The insulating film 72 is formed of a polyimide film having a thickness of 15 to 70 μm, for example. The insulating film 72 is bonded to the metal foil 71 with an insulating adhesive sheet 73. The surface of the insulating film 72 opposite to the metal foil 71 is bonded to the base film 61 with an insulating adhesive sheet 74.

  As shown in FIG. 6, the metal foil 71 is cut into a shape having a region 71 a that protrudes from the shape of the sheet member 70. This region 71a is a folded portion 71a that is folded back toward the surface to which the insulating film 72 is bonded. And the folding | returning part 71a is folded by the main area | region of the metal foil 71, and as shown in FIG.8 and 9, two sheets are piled up and become a conduction | electrical_connection area | region.

  In the conduction region, the sheet member 70 has a thickness obtained by stacking two metal foils 71. On the other hand, in the non-conducting region, the thickness of the sheet member 70 is a thickness obtained by adding the metal foil 71, the insulating film 72, and the adhesive sheets 73 and 74 thereto. As shown in FIG. 8, both thicknesses are set to be equal. For example, a copper foil having a thickness of 35 μm is used as the metal foil 71, a polyimide film having a thickness of 25 μm (for example, “Kapton (registered trademark)” manufactured by Toray DuPont Co., Ltd.), and thick adhesive sheets 73 and 74 are used. By using a double-sided tape having a thickness of 5 μm, it is possible to realize a sheet member 70 having a completely flat surface even at the boundary portion between the conductive region and the non-conductive region.

  FIG. 10 is a cross-sectional view showing a connection state between the back metal frame 52 and the FPC 60. Since the surface of the back metal frame 52 is in contact with the surface of the sheet member 70 of the FPC 60, that is, the metal foil 71, the back metal frame 52 and the ground pattern 62 in contact with the metal foil 71 are electrically connected.

  Next, a method for manufacturing the FPC 60 of this embodiment will be described.

  First, a base film 61 having a ground pattern 62 and the like is prepared by a known method. On the other hand, as shown in FIGS. 6 and 7, the metal foil 71 and the polyimide film 72 are respectively cut out and bonded together with an adhesive sheet 73, and further, the folded portion 71 a of the metal foil is folded in the conductive region, Get 70. And the FPC 60 of said structure is obtained by adhere | attaching the sheet | seat member 70 on the base film 61 with the adhesive sheet 74. FIG.

  According to the present embodiment, the folded portion 71a of the metal foil 71 is folded and overlapped in the conductive region of the sheet member 70, and the thickness of the sheet member 70 is equal to the thickness in the non-conductive region. In the conduction region of the sheet member 70, the surface of the folded portion 71 a of the metal foil 71 is in direct contact with the ground pattern 62 of the base film 61. Therefore, the ground pattern 62 and the metal foil 71 can be conducted without any other configuration such as an adhesive material, and the static electricity can be reliably removed from the ground pattern 62 to the back metal frame 52 in contact with the metal foil 71. It can be carried out.

  In addition, according to the present embodiment, by folding the metal foil in the conductive region of the sheet member and stacking two sheets, there is no step on the sheet member 70 at the boundary between the conductive region and the non-conductive region, so that it becomes completely flat. Even with the thin liquid crystal display device 20, excellent strength can be obtained.

  In addition to the conventional FPC manufacturing method, the FPC having the configuration of the present embodiment is manufactured very simply by cutting the metal foil 71 into a shape including the folded portion 71a in addition to the sheet member 70 and folding it. be able to.

<< Embodiment 2 >>
11 and 12 show a cross section of the FPC 60 according to the second embodiment. The FPC 60 is mounted on the liquid crystal display device 20 mounted on an electronic device such as the smartphone 10 as in the first embodiment.

  As in the first embodiment, the FPC 60 has a configuration in which the sheet member 70 is laminated on the base film 61. This FPC 60 is different from the first embodiment in that two metal foils 71 (main region and folded portion 71a) overlapped in the conductive region of the sheet member 70 are bonded to each other with an insulating adhesive sheet 73. ing.

  The insulating adhesive sheet 73 is the same as that in which the metal foil 71 and the insulating film 72 are bonded in the first embodiment. Here, the adhesive sheet 73 is pasted not on the insulating film 72 side but on the metal foil 71 side including the folded portion 71a, and then the insulating film 72 is pasted and the folded portion 71a is folded. The FPC 60 having the configuration can be obtained.

  According to the present embodiment, in addition to the effects obtained in the first embodiment, the folded portion 71a of the metal foil 71 is bonded to the upper layer of the metal foil 71, whereby a more stable structure can be obtained. At this time, since the folded portion 71a of the metal foil 71 is provided by folding the metal foil 71, the adhesive sheet 73 is not required to have conductivity because it is integrated with the upper layer portion of the metal foil 71, An insulating adhesive sheet can be used, and the cost of the adhesive sheet 73 can be suppressed.

<< Other Embodiments >>
In Embodiment 1 and 2 demonstrated above, although the insulating film 72 which comprises the non-conduction area | region of the sheet | seat member 70 was demonstrated as a polyimide film, as shown as the modification 1 in FIG. The insulating adhesive sheet 75 itself may be used as the insulating film. In this case, the surface of the sheet member 70 can be made flat by using the adhesive sheet 75 having the same thickness as the metal foil 71.

  The shape of the conduction region and the non-conduction region of the sheet member 70 of the present invention is not limited to the case described in FIGS. 5 to 7 of the first embodiment described above, and the conduction region of the sheet member 70 is formed on the base film 61. It is sufficient that at least a part of the ground pattern 62 is provided so as to overlap. Another example of the shape of the conductive region and the non-conductive region of the sheet member 70 is shown in Modifications 2 and 3.

  FIGS. 14, 15 and 16 are plan views showing the sheet member 70 according to the second modification, the metal foil 71 constituting the sheet member 70, and the insulating film 72, respectively. Here, the folded portion 71 a is formed in the metal foil 71 so as to cover a part of the ground pattern 62, and therefore the conduction region is also formed corresponding to a part of the ground pattern 62 instead of the whole. Yes. The insulating film 72 is bonded so as to cover a region of the ground pattern 62 where the folded portion 71a of the metal foil 71 does not exist, so that the sheet member 70 can be provided at the boundary between the conductive region and the conductive region. It has a structure with no steps.

  FIGS. 17, 18 and 19 are plan views showing the sheet member 70 according to the third modification, the metal foil 71 constituting the sheet member 70, and the insulating film 72, respectively. Modification 3 shows an example in which two ground patterns 62 are provided on the base film 61. In this case, conductive regions are formed in the sheet member 70 so as to correspond to the respective ground patterns 62. That is, as shown in FIG. 18, the metal foil is cut out so that the metal foil 71 has two folded portions 71a.

  In the first and second embodiments described above, the sheet member 70 has been described as having a completely flat configuration without a step at the boundary between the conductive region and the non-conductive region. However, as illustrated in FIG. The thickness may be larger than the thickness in the non-conducting region. In this case, the step formed at the boundary between the conducting region and the non-conducting region does not become a complete flat surface, but the folded portion 71a of the metal foil 71 is folded to constitute the conducting region. An effect of reliably removing static electricity without using a material or the like can be obtained. Moreover, in the modification 4, since the conduction | electrical_connection area | region is twice the thickness of the metal foil 71, since the magnitude | size of this level | step difference becomes smaller than the level | step difference formed in a prior art example as shown in FIG. A strength superior to that of the prior art can be obtained. However, if the step formed at the boundary between the conductive region and the non-conductive region is too large, the structural stability of the FPC 60 is lowered and the strength is lowered. Therefore, the step is preferably 10 μm or less.

  In Embodiments 1 and 2 described above, the ground pattern 62 is connected to the back metal frame 52 via the metal foil 71 to eliminate static electricity. However, a conductive energizing member other than the back metal frame 52 is used. And may be connected. Examples of the conductive member other than the back metal frame 52 include a conductive connector.

  In the first and second embodiments, the FPC 60 is mounted on the liquid crystal display device 20 and a driver for driving the liquid crystal is connected. However, the FPC may be used for other purposes. Further, the FPC 60 may be mounted on a display device other than the liquid crystal display device 20, for example, an organic EL display device or an inorganic EL display device. Moreover, although the smart phone 10 was demonstrated to the example as an electronic device which mounts the liquid crystal display device 20, it may be a liquid crystal display device mounted in the display of other portable devices, for example, and is mounted as a display of television or PC. Or a liquid crystal display device.

  The present invention is useful for a flexible printed wiring board, a display device including the flexible printed wiring board, and an electronic apparatus.

10 Smartphone (electronic equipment)
20 Liquid crystal display device (display device)
40 Display panel
52 Back metal frame
60 FPC
61 Base film
62 Ground pattern
70 Sheet material
71 metal foil
72 Insulation film (polyimide film)
73 Insulating adhesive sheet

Claims (9)

A base film in which a circuit including a ground pattern is formed on one surface;
A sheet member provided so as to cover the surface of the base film on which the ground pattern is formed, and having a metal foil as a base;
A flexible printed wiring board having
The surface on the base film side of the sheet member is composed of a conduction region including at least a part of a region corresponding to the ground pattern, and a non-conduction region in which the surface of the metal foil is covered with an insulating film,
At least a part of the conductive region of the sheet member has a configuration in which two metal foils are folded and stacked, and the thickness of the sheet member is equal to or greater than the thickness of the sheet member in the non-conductive region. A flexible printed wiring board characterized by that. In the flexible printed wiring board according to claim 1,
The flexible printed wiring board, wherein a thickness of the sheet member in the conductive region is equal to a thickness of the non-conductive region. In the flexible printed wiring board according to claim 1 or 2,
In the non-conduction region, the insulating film is a polyimide film bonded to the surface of the metal foil via an adhesive sheet. In the flexible printed wiring board according to claim 1 or 2,
In the non-conduction region, the insulating film is an insulating adhesive sheet bonded to the surface of the metal foil. In the flexible printed wiring board as described in any one of Claims 1-4,
The flexible printed wiring board, wherein the metal foils stacked in the conductive region are bonded to each other with an insulating adhesive sheet. In the flexible printed wiring board as described in any one of Claims 1-5,
The flexible printed wiring board, wherein the metal foil is a copper foil. The flexible printed wiring board according to any one of claims 1 to 6,
A display panel mounted with the flexible printed wiring board;
A current-carrying member electrically connected to the ground pattern via the metal foil;
A display device. The display device according to claim 7,
The display device according to claim 1, wherein the energizing member is a metal frame including the flexible printed wiring board and the display panel.   An electronic device equipped with the display device according to claim 7 or 8.

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