JP2015115437A - Flexible wiring board, and electronic apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a mechanism which allows for excellent impedance control, and efficient wiring while suppressing radiation noise, even when a flexible wiring board of hollow structure for wiring differential signal lines is used.SOLUTION: A flexible wiring board 3 has a flexible part 3e that is arranged while being bent in right angle. The flexible part 3e includes a patterning layer 3e1 where differential signal lines are wired, and a patterning layer 3e2 arranged to face the patterning layer 3e1 via a cavity E1, and where a ground pattern for controlling the impedance of the differential signal lines is wired. A mesh part having a plurality of openings is provided in the ground pattern, and the mesh part is formed so that the amount of a plurality of openings decreases gradually as the distance of the patterning layers 3e1 and 3e2 increases.

Description

  The present invention relates to a flexible wiring board on which a differential signal line is wired, and an electronic device such as a digital camera or a portable terminal including the flexible wiring board.

  In recent years, with the improvement of functions of electronic devices, higher-speed digital data transmission has been demanded, and examples of such transmission methods include LVDS (Low Voltage Differential Signaling) and USB (Universal Serial Bus) standards. LVDS is a high-speed (several hundred MBPS) transmission standard in which circuits and protocols can be designed relatively freely, and is widely used for signal transmission of imaging units and liquid crystal display devices such as digital cameras and mobile phones. In the differential transmission path, it is necessary to make the characteristic impedance of the paired differential transmission path uniform with a value determined by the standard.

  FIG. 8A is a perspective view showing the internal structure of a conventional imaging device having an LVDS transmission line, and FIG. 8B is an exploded view of the imaging device shown in FIG. It is a perspective view.

  In FIG. 8, a rigid flexible wiring board 703 has a rigid portion 703a on which an image sensor 702 is mounted, a rigid portion 703b on which a card connector 704 is mounted, and a rigid portion 703c on which a connector 706 is mounted. The flexible portions 703d and 703e electrically connect the rigid portions 703a to 703c.

  The connector 706 is electrically connected to the main wiring board 705 on which the image engine is mounted. Further, the image sensor 702 is disposed on the side surface of the apparatus main body that is orthogonal to the incident optical axis of the lens barrel 711.

  The lens barrel 711 has a bending optical system, and a light beam incident on the lens barrel 711 is bent at a right angle by a mirror (not shown) and guided to the image sensor 702 via the low-pass filter 708. The image sensor 702 is fixed to the sensor plate 707 by adhesion or the like, and the tilt of the image sensor 702 is adjusted by adjusting the tightening margins of the three screwing portions 707a to 707c of the sensor plate 707. The video signal output from the image sensor 702 is transmitted from the rigid flexible wiring board 703 to the main wiring board 705 via the connector 706 by LVDS, and is processed by an image engine mounted on the main wiring board 705.

  FIG. 9A is a diagram showing a differential line pattern of the flexible portion 703e, and FIG. 9B is a diagram showing a ground pattern of the flexible portion 703e. FIG. 10 is a cross-sectional view taken along the line AA of FIG. 8A in the mounting portion of the image sensor 702.

  A signal line transmitted by LVDS is made up of a plurality of pairs, although it depends on the specification of the image sensor. In FIG. 9A, three pairs of differential signal line groups 701 are wired on one surface of the flexible portion 703e, and the periphery thereof is surrounded by a ground pattern 702. As shown in FIG. 9B, a ground pattern 710 is wired on the other surface of the flexible portion 703e. The differential impedance is adjusted to be 100Ω by controlling the line width of the differential signal line, the clearance between the lines, the clearance on both sides of the differential signal line, and the mesh density of the ground pattern 710.

  However, in such a configuration, since many patterns are wired on the flexible portion 703e of the rigid flexible wiring substrate 703, the rigidity of the flexible portion 703e is increased and the reaction force at the time of deformation is increased. For this reason, the load acting on the rigid portion 703a during tilt adjustment of the image sensor 702 becomes large, which may make adjustment difficult. In addition, there is a problem in that the impact cannot be absorbed by the flexible portion 703e at the time of impact such as dropping, and the connector 706 connected to the main wiring board 705 is disconnected.

  Then, by making it the hollow structure flexible part which eliminated the adhesive bond layer between pattern formation layers, the flexibility of the flexible part which connects a rigid part is secured, and reaction force at the time of deformation is controlled. . For example, as shown in FIG. 9, a technique is proposed in which coplanar wiring is performed on the first pattern formation layer 703e1 of the flexible portion 703e and a ground pattern is wired on the second pattern formation layer 703e2 for impedance control. (Patent Document 1).

JP 2008-288516 A

  However, as shown in FIG. 10, when the rigid portion 703b is arranged substantially orthogonal to the rigid portion 703a, there is a problem that good impedance control cannot be performed due to the difference in the path of the pattern forming layers 703e1 and 703e2 of the flexible portion 703e. is there. That is, the gap interval between the pattern formation layers 703e1 and 703e2 varies due to the difference in the path between the inner pattern formation layer 703e1 and the outer pattern formation layer 703e2, and the impedance varies. Further, if impedance control is to be performed only on one side without using a ground pattern, it is necessary to increase the line width of the differential signal line and there is a concern about the influence of radiation noise.

  Therefore, the present invention enables good impedance control and efficient wiring even when using a flexible wiring board having a hollow structure on which differential signal lines are wired, and suppresses radiation noise. The purpose is to provide a mechanism that can do this.

  In order to achieve the above object, the present invention provides a flexible wiring board having a flexible portion arranged to be bent, wherein the flexible portion includes a first pattern forming layer on which a differential signal line is wired, A second pattern forming layer disposed opposite to the first pattern forming layer via a gap and to which a ground pattern is wired, and the ground pattern has a mesh-shaped portion having a plurality of openings The mesh-shaped portion is formed such that the opening amounts of the plurality of openings are gradually reduced as the distance between the first pattern formation layer and the second pattern formation layer increases. Features.

  According to the present invention, even when a flexible wiring board having a hollow structure on which differential signal lines are wired is used, good impedance control can be performed and efficient wiring can be achieved, and radiation noise can be suppressed. it can.

(A) is a perspective view which shows the internal structure of the digital camera as an example of an electronic device provided with the rigid flexible wiring board which is 1st Embodiment of the flexible wiring board of this invention, (b) is the digital shown to (a). It is the perspective view which decomposed | disassembled a part which looked at the camera from the back side. It is sectional drawing which shows the layer structure of a rigid flexible wiring board. It is the sectional view on the AA line of FIG. 1 in the mounting part of an image pick-up element. (A) is a figure which shows the wiring pattern of the differential signal line of the 1st layer of a rigid flexible wiring board, (b) is a figure which shows the wiring pattern of the differential signal line of the 2nd layer of a rigid flexible wiring board. (A) is a figure which shows the wiring pattern of the 3rd layer differential signal line of a rigid flexible wiring board, (b) is a figure which shows the wiring pattern of the 4th layer differential signal line of a rigid flexible wiring board. (A) is the elements on larger scale of FIG.4 (b), (b) is the elements on larger scale of Fig.5 (a). It is principal part sectional drawing of the mounting part of the image pick-up element in the digital camera as an example of an electronic device provided with the rigid flexible wiring board which is 2nd Embodiment of the flexible wiring board of this invention. (A) is a perspective view which shows the internal structure of the conventional imaging device which has a LVDS transmission line, (b) is the perspective view which decomposed | disassembled one part which looked at the imaging device shown to (a) from the back side. (A) is a figure which shows the pattern of the differential line of a flexible part, (b) is a figure which shows the ground pattern of a flexible part. It is the sectional view on the AA line of Fig.8 (a) in the mounting part of an image pick-up element.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(First embodiment)
FIG. 1A is a perspective view showing an internal structure of a digital camera as an example of an electronic apparatus including a rigid flexible wiring board according to the first embodiment of the flexible wiring board of the present invention. FIG. 1B is an exploded perspective view of a part of the digital camera shown in FIG.

  The digital camera shown in FIG. 1 includes a rigid flexible wiring board 3 having an LVDS wiring structure. The rigid flexible wiring board 3 includes a rigid portion 3a on which the imaging device 2 is mounted, a rigid portion 3b on which the card connector 4 is mounted, and a rigid portion 3c on which the connector 6 is mounted.

  The connector 6 is electrically connected to the main wiring board 5 on which the image engine is mounted, and transmits a signal to the main wiring board 5. The image sensor 2 is disposed on the left side surface when the camera is viewed from the front side (subject side). The rigid portion 3a and the rigid portion 3b are electrically connected by the flexible portion 3e, and the rigid portion 3b and the rigid portion 3c are electrically connected by the flexible portion 3d. Here, the rigid portion 3a corresponds to an example of the first rigid portion of the present invention, and the rigid portion 3b corresponds to an example of the second rigid portion of the present invention.

  The lens barrel 1 is disposed on the front side of the camera and has a bending optical system. The light beam incident on the lens barrel 1 is bent at a right angle by a mirror (not shown) and guided to the image sensor 2 through the low-pass filter 8.

  The image sensor 2 is fixed to the sensor plate 7 by adhesion or the like, and the tilt of the image sensor 2 is adjusted by adjusting the tightening margins of the three screw fixing portions 7a to 7c of the sensor plate 7. The screw stoppers 7a to 7c are provided with rubber bushes 9 for preventing the image sensor 2 from being shielded from light and preventing dust from entering. The video signal output from the image sensor 2 is transmitted from the rigid flexible wiring board 3 to the main wiring board 5 via the connector 6 by LVDS, and is processed by the image engine mounted on the main wiring board 5.

  FIG. 2 is a cross-sectional view showing the layer structure of the rigid flexible wiring board 3. In FIG. 2, the rigid portions 3a and 3b and the flexible portion 3e that electrically connects the rigid portion 3a and the rigid portion 3b will be described as an example.

  As shown in FIG. 2, the rigid portions 3a and 3b have a four-layer structure from the first conductor layer P1 to the fourth conductor layer P4, and have a layer configuration in which two double-sided flexible wiring boards are bonded together. It has become.

  The conductor layer P1 is attached to the surface side (upper surface side in the figure) of the base material B12 made of polyimide or the like, and the conductor layer P2 is attached to the rear surface side (lower surface side in the figure) of the base material B12. A solder resist R1 is applied to the surface side of the conductor layer P1. A coverlay film C2 made of polyimide or the like is attached to the back side of the conductor layer P2.

  Similarly, the conductor layer P3 is affixed to the front surface side of the base material B34 made of polyimide or the like, and the conductor layer P4 is affixed to the back surface side of the base material B34. A coverlay film C3 made of polyimide or the like is attached to the front surface side of the conductor layer P3, and a solder resist R4 is applied to the back surface side of the conductor layer P4. The image sensor 2 is mounted on the conductor layer P4 side.

  A glass epoxy resin F1 is disposed between the coverlay film C2 and the coverlay film C3. The glass epoxy resin F1 is adhesively fixed to the cover lay film C2 via the adhesive A2, and is also adhesively fixed to the cover lay film C3 via the adhesive A3. In addition, the connection between the rigid portions 3a and 3b is made through the through holes TH2 and TH1.

  The flexible part 3e is drawn out from the second and third layers of the rigid parts 3a and 3b and is electrically connected to the rigid parts 3a and 3b. That is, the flexible part 3e is composed of the pattern forming layer 3e1 having the conductor layer P2, the base material B12 and the cover lay film C2, and the pattern forming layer 3e2 having the conductor layer P3, the base material B34 and the cover lay film C3. .

  The pattern forming layer 3e2 is disposed opposite to the pattern forming layer 3e1, and there is no adhesive layer between the cover lay film C2 of the pattern forming layer 3e1 and the cover lay film C3 of the pattern forming layer 3e2, and the gap E1 is formed. It is formed.

  Thus, by setting it as the flexible part 3e of the hollow structure which provided the space | gap part E1, the softness | flexibility of the flexible part 3e is ensured and the reaction force at the time of a deformation | transformation is suppressed. Thereby, the flexibility of the flexible part 3e is improved and the load concerning the rigid part 3a in which the image pick-up element 2 is mounted, and the connector 6 connected to the main wiring board 5 is reduced. Here, the pattern formation layer 3e1 corresponds to an example of the first pattern formation layer of the present invention, and the pattern formation layer 3e2 corresponds to an example of the second pattern formation layer of the present invention.

  3 is a cross-sectional view taken along line AA of FIG. As shown in FIG. 3, the rigid portion 3a and the rigid portion 3b of the rigid flexible wiring board 3 are arranged so as to be substantially perpendicular to each other. Therefore, the flexible part 3e that connects the rigid part 3a and the rigid part 3b is bent at a substantially right angle.

  The pattern forming layer 3e2 on the inner side is away from the pattern forming layer 3e1 due to the difference in the path between the pattern forming layer 3e1 on the outer side and the pattern forming layer 3e2 on the inner side of the flexible part 3e bent at a substantially right angle. Bend.

  Here, in this embodiment, the spacer T is attached so as to be inserted between the pattern formation layer 3e1 and the pattern formation layer 3e2, so that the interval T1 between the pattern formation layer 3e1 and the pattern formation layer 3e2 is regulated to a specific value. Has been.

  4A is a diagram showing a wiring pattern of the first differential signal line of the rigid flexible wiring board 3, and FIG. 4B is a wiring pattern of the second differential signal line of the rigid flexible wiring board 3. FIG. FIG. 5A shows a wiring pattern of the third layer differential signal line of the rigid flexible wiring board 3, and FIG. 5B shows a wiring pattern of the fourth layer differential signal line of the rigid flexible wiring board 3. FIG. FIG. 6 (a) is a partially enlarged view of FIG. 4 (b), and FIG. 6 (b) is a partially enlarged view of FIG. 5 (a).

  As shown in FIG. 4, a differential signal line group 401 is wired from the image sensor 2 to the connector 6 on the rigid flexible wiring board 3. The differential signal uses one pair of differential signal lines for one signal. In this embodiment, three pairs of differential signal lines 402p and 402n, differential signal lines 403p and 403n, and differential signal lines are used. A differential signal line group 401 is constituted by 404p and 404n (see FIG. 6A). Each pair of differential signal lines has an opposite phase signal and detects a differential signal based on the difference. Further, the differential impedance of the differential signal is controlled to be 100Ω.

  The differential signal line group 401 has a different wiring pattern because the distance to the ground pattern, the dielectric constant of the substrate, and the like differ depending on the layer to be wired. When the differential signal line group 401 is wired to the first conductor layer P1 (FIG. 2) of the rigid portions 3a and 3b, the entire ground pattern is wired to the second conductor layer P2 immediately below. When the differential signal line group 401 is wired to the second conductor layer P2 of the rigid portions 3a and 3b, the entire ground pattern is wired to the first conductor layer P1, and the third conductor layer The entire ground pattern is wired to the fourth conductor layer P4 without wiring to P3.

  When the differential signal line group 401 is wired to the conductor layer P2 of the pattern forming layer 3e1 of the flexible portion 3e, if the ground pattern is wired to the conductor layer P3 of the pattern forming layer 3e2, the gap E1 is provided. Differential impedance is reduced. For this reason, in this embodiment, the impedance is controlled by providing a plurality of types of mesh-shaped portions having a plurality of openings on the entire ground pattern.

  Specifically, as shown in FIG. 6B, the entire ground pattern of the conductor layer P3 of the pattern forming layer 3e2 of the flexible portion 3e includes three types of mesh-shaped portions 405a and 405e and mesh-shaped portions 405b and 405d. , And a mesh-shaped portion 405c.

  The mesh shape portion 405a is disposed adjacent to the rigid portion 3a, and the mesh shape portion 405e is disposed adjacent to the rigid portion 3b. The mesh-shaped part 405c is disposed in the middle part of the flexible part 3e. The mesh shape portion 405b is disposed between the mesh shape portion 405a and the mesh shape portion 405c, and the mesh shape portion 405d is disposed between the mesh shape portion 405e and the mesh shape portion 405c.

  And the opening amount of the some opening part of mesh shape part 405a, 405e is the largest, and the opening amount of several opening part becomes small in order of mesh shape part 405b, 405d and mesh shape part 405c.

  When there is no gap between the pattern forming layer 3e1 and the pattern forming layer 3e2 of the flexible portion 3e, the differential impedance is set to 100Ω with the opening amounts of the plurality of openings of the mesh-shaped portions 405a and 405e. Yes.

  As described in FIG. 3, when the flexible portion 3e is bent and disposed, the pattern forming layer 3e2 is away from the pattern forming layer 3e1 with respect to the pattern forming layer 3e1 on which the differential signal line group 401 is wired. To curve. As the distance between the differential signal line group 401 and the ground pattern increases, the differential impedance increases.

  For this reason, as the pattern forming layer 3e2 moves away from the pattern forming layer 3e1, the openings of the mesh-shaped portions 405b and 405d and the mesh-shaped portion 405c are gradually reduced to reduce the differential impedance. Yes. That is, as the distance between the pattern formation layer 3e2 and the pattern formation layer 3e1 increases, the opening amounts of the plurality of openings in the mesh-shaped portion are reduced stepwise.

  In the present embodiment, as described above, the spacer 10 is inserted between the pattern formation layer 3e1 and the pattern formation layer 3e2, and the interval T1 between the pattern formation layer 3e1 and the pattern formation layer 3e2 is regulated to a specific value. ing.

  For this reason, even if the pattern formation layer 3e2 is curved in a direction away from the pattern formation layer 3e1, it is easy to change the opening amounts of the plurality of openings of the mesh shape portions 405a to 405e in accordance with the interval T1. It becomes possible to control the differential impedance.

  Moreover, since the change of differential impedance can be made small by changing the opening amount of the some opening part of the mesh-shaped parts 405a-405e in steps, discharge | emission of radiation noise can be suppressed. Note that the spacer 10 does not necessarily have to be inserted in the entire width direction of the flexible portion 3e, but may be inserted into a region where the differential signal lines are wired.

  Since the flexible portion 3e is bent at a substantially right angle by the mesh-shaped portion 405e having the largest opening amount of the plurality of openings, the flexible portion 3e is easily bent as compared with a normal full-surface ground pattern. For this reason, the load with respect to the rigid part 3b can be made small. Moreover, since the part of the mesh-shaped part 405e is easy to bend at the time of assembly, it is easy to assemble and can be used as a bending index.

  As described above, in this embodiment, even when the rigid flexible wiring board 3 having a hollow structure is used, good impedance control can be performed, efficient wiring can be performed, and radiation noise can be suppressed. .

  In the present embodiment, the opening shape of the mesh-shaped portion is a rectangular shape, but is not limited thereto, and may be an opening shape such as a circle or a rhombus, and the opening shapes of the plurality of opening portions are different from each other. Also good.

(Second Embodiment)
Next, with reference to FIG. 7, a digital camera as an example of an electronic apparatus including a rigid flexible wiring board according to a second embodiment of the flexible wiring board of the present invention will be described. FIG. 7 is a cross-sectional view of the main part of the mounting portion of the image sensor 2. In addition, about the part which overlaps with the said 1st Embodiment, the same code | symbol is attached | subjected to a figure and only a different point is demonstrated.

  In the first embodiment, the spacer 10 is used to regulate the interval T1 between the pattern formation layer 3e1 and the pattern formation layer 3e2 to a specific value.

  On the other hand, in the present embodiment, the pattern forming layer 3e1 and the pattern forming layer 3e2 are brought into contact with the sensor plate 7 by extending the sensor plate 7 to which the imaging device 2 is fixed and contacting the curved pattern forming layer 3e2. The interval T2 is regulated to a specific value. The sensor plate 7 is made of a material having a lower dielectric constant than a metal such as a resin material because the sensor plate 7 affects the impedance of the differential signal when the metal is used. Thereby, the number of parts at the time of an assembly can be reduced. Other configurations and operational effects are the same as those in the first embodiment.

  The configuration of the present invention is not limited to those exemplified in the above embodiments, and the material, shape, dimensions, form, number, arrangement location, and the like are appropriately changed without departing from the gist of the present invention. Is possible.

3 Rigid flexible wiring boards 3a, 3b Rigid portion 3e Flexible portions 3e1, 3e2 Pattern forming layer 7 Sensor plate 10 Spacer 401 Differential signal line group 405a-405e Ground pattern E1 Gap

Claims (8)

A flexible wiring board having a flexible portion arranged to be bent,
The flexible part includes a first pattern forming layer to which a differential signal line is wired, and a second pattern in which a ground pattern arranged to face the first pattern forming layer via a gap is wired. And a forming layer,
The ground pattern is provided with a mesh-shaped portion having a plurality of openings,
The mesh-shaped portion is formed in such a manner that opening amounts of the plurality of opening portions are gradually reduced as the distance between the first pattern forming layer and the second pattern forming layer is increased. Wiring board.   The flexible wiring board according to claim 1, further comprising a first rigid portion and a second rigid portion that are electrically connected to each other by the flexible portion.   An electronic apparatus comprising the flexible wiring board according to claim 1.   An electronic apparatus comprising the flexible wiring board according to claim 2, wherein the first rigid portion and the second rigid portion are disposed substantially at right angles.   5. The apparatus according to claim 3, further comprising a regulating unit that regulates a distance between the first pattern forming layer and the second pattern forming layer when the flexible part is bent and disposed. Electronic equipment.   6. The electronic apparatus according to claim 5, wherein the restricting unit is disposed at least in a region where the differential signal line is wired.   The electronic apparatus according to claim 5, wherein the restricting unit is a sensor plate to which an imaging element is fixed.   The electronic device according to claim 7, wherein the sensor plate is made of a resin material.