JP2011249710A - Connection structure for printed wiring board and camera module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a connection structure for printed wiring boards with a simple constitution where the printed wiring boards are not being delaminated even if a flexible substrate is largely warped, and a camera module having the connection structure for printed wiring boards.SOLUTION: The present invention relates to a connection structure for printed wiring boards, in which a first connection terminal provided over a rigid substrate and a second connection terminal provided over a flexible substrate are joined via a anisotropic conductive material, and a hole portion is provided on the rigid substrate side in vicinity of the end portion where the printed wiring boards are connected to tuck the flexible substrate beneath the hole. The present invention also relates to a camera module having the connection structure for printed wiring boards.

Description

  The present invention relates to a printed wiring board connection structure in which connection terminals respectively provided on two printed wiring boards are joined via an anisotropic conductive material, and a camera module having the printed wiring board connection structure.

  Conventionally, ultra-compact camera modules have been installed in small and thin mobile terminals such as mobile phones and PDAs (Personal Digital Assistants), thereby enabling image capture and image transmission as well as voice and email communication. It has become possible.

  An example of the camera module will be schematically described with reference to FIG. 6. FIG. 6A shows components before the camera module 60 is assembled, and FIG. 6B shows an assembled state.

  In FIG. 6A, the components are a camera head 63 in which a lens barrel 61 containing an imaging lens and the like is joined to a rigid printed wiring board 62 on which an image sensor such as a CCD or CMOS is mounted, and a camera head 63. A flexible printed wiring board 64 for electrically connecting a mobile terminal to a portable terminal, an anisotropic conductive film (also referred to as Anisotropic Conductive Film, ACF) for connecting the connection terminal 62a of the printed wiring board 62 and the connection terminal 64a of the printed wiring board 64. ) 65. The printed wiring board 62 and the printed wiring board 64 are thermocompression bonded with the anisotropic conductive film 65 sandwiched therebetween, whereby the camera module 60 is completed.

  In the present invention, a rigid printed wiring board is referred to as a rigid board, a flexible printed wiring board is referred to as a flexible board, and the two are collectively referred to as a printed wiring board. In addition, the printed wiring board is a wiring board having no electronic component in a narrow sense, but in the present invention, the printed wiring board including the printed circuit board on which the electronic component is mounted is referred to as a printed wiring board.

  In the figure, the aperture of the imaging lens is on the lower side, and light incident from the imaging lens is guided to an image sensor provided on the back surface of the rigid substrate 62 to form an image. The image data photoelectrically converted by the image sensor passes through the connection terminal 62a of the rigid substrate 62, the anisotropic conductive film 65, and the connection terminal 64a of the flexible substrate 64, and is sent from the connection terminal 64b on the free end side to the circuit of the portable terminal. . A reinforcing plate 64c is provided on the front surface side of the flexible substrate 64.

  Here, the anisotropic conductive film is a film for electrical joining having a thickness of 20 to 30 μm formed from a heat resistant resin. Inside the heat-resistant resin, a plurality of conductive particles are dispersed in the surface direction, and the conductive particles are formed in 3 to 5 μm spheres in which the resin is coated with nickel or the like. When the anisotropic conductive film disposed between the two printed wiring boards is thermocompression bonded, the connection terminals of the two printed wiring boards come into contact with the conductive particles, and therefore have conductivity in the thickness direction. Become. On the other hand, the conductive particles are dispersed in the heat-resistant resin at a ratio of approximately 10% or less, and since no pressure is applied in the surface direction, the conductive particles are not in contact with each other and the insulating property is maintained. Therefore, when joining a plurality of connection terminals provided on two printed wiring boards, the opposing connection terminals are conducted, and adjacent connection terminals are not conducted.

  The following patent documents are known as a method of thermocompression bonding a substrate using an anisotropic conductive film.

  Patent Document 1 discloses a thermocompression mounting method in which a plurality of film-like substrates on which an electrode pattern is arranged and an IC chip is mounted are thermocompression bonded to a single transparent substrate through an anisotropic conductive film. Yes. In this document, in order to prevent the film-like substrate from extending due to thermal expansion and causing a positional shift, a plurality of heating means are provided and the heating is controlled separately.

  Patent Document 2 discloses a method for connecting a semiconductor chip mounting film in which a plurality of semiconductor chip mounting films are thermocompression bonded to a single rectangular substrate via an anisotropic conductive film. According to this document, the inclination of the square substrate is detected, the semiconductor chip mounting films are temporarily bonded one by one in accordance with the inclination angle, and then the main bonding is performed simultaneously.

  In addition to the film type, a paste type is also known as an anisotropic conductive material, and both can be used in the present invention. Therefore, when both are collectively referred to as an anisotropic conductive material.

JP-A-8-204329 Japanese Patent Laid-Open No. 5-144889

  FIG. 6C is a side view of the camera module 60. As described above, the rigid substrate 62 and the flexible substrate 64 are bonded via the anisotropic conductive film 65. The flexible substrate 64 has a connection terminal 64b for connecting to the circuit of the portable terminal on the free end side. When the connection terminal 64b is connected to a circuit of a mobile terminal, or when the camera module 60 is incorporated into a mobile phone or the like or transported, the free end side may be warped upward in the drawing. is there. The flexible substrate 64 is vulnerable to such an external force in the turning direction and has a problem of peeling off.

  As a means for preventing such a problem, it is conceivable that the side wall of the rigid substrate 62 and the lower portion of the flexible substrate 64 are bonded with an adhesive at a position indicated by an arrow, but this method uses an adhesive bonding step or a solidifying step. Is necessary and increases the cost, which is not preferable. For example, when bonding with a thermosetting resin, a heating time of about 60 minutes is required. In addition, in order to bond with an ultraviolet curable resin, it is necessary to protect the ultraviolet irradiation equipment and workers from harmful ultraviolet rays.

  The present invention has been made in view of the problems as described above, and has a printed wiring board connection structure that does not peel off even when the flexible substrate is largely warped with a simple configuration, and a connection structure for the printed wiring board. An object of the present invention is to provide a camera module.

  The above object is achieved by limiting the force acting on the flexible substrate to only shear stress. Restricting the working force only to shear stress is to prevent peeling stress or splitting stress from being applied to the flexible substrate even if the external force described above is applied. For this purpose, a hole is provided on the rigid substrate side. Is made to pass through the hole.

In particular,
1. In the connection structure of the printed wiring board in which the first connection terminal provided on the rigid board and the second connection terminal provided on the flexible board are bonded via an anisotropic conductive material,
A printed wiring board connection structure, wherein a hole is provided on the rigid board side in the vicinity of an end position where both printed wiring boards are connected, and a free end side of the flexible board is passed through the hole.
2. 2. The printed wiring board connection structure according to claim 1, wherein the hole is provided in a side portion of the rigid board.
3. 2. The printed wiring board connection structure according to claim 1, wherein the hole is provided in a member connected to the rigid board.
4). 2. The printed wiring board connection structure according to claim 1, wherein the hole is a hole formed in a frame surrounding the rigid board.
5). 5. The printed wiring board connection structure according to any one of 1 to 4, wherein the width of the hole is formed substantially equal to the width of the flexible substrate.
6). 6. The printed wiring board connection structure according to any one of 1 to 5, wherein the flexible substrate is provided with at least one crease so as to be along the inner surface of the hole.
7). 7. A camera module comprising the printed wiring board connection structure according to any one of 1 to 6 above.

  In the present invention, when connecting the flexible substrate to the rigid substrate, the flexible substrate is passed through the hole provided on the rigid substrate side. Therefore, even if an external force is applied to the flexible substrate, the external force is applied in the peeling direction or the splitting direction. Therefore, it is possible to provide a printed wiring board connection structure in which a flexible substrate is not peeled off and a camera module having the printed wiring board connection structure.

Sectional drawing (a) and top view (b) which show embodiment of the camera module of this invention. The schematic diagram which shows the effect | action of the external force which acts on the junction part of the anisotropic conductive film 5. FIG. Sectional drawing which shows the 1st modification of this invention. Sectional drawing which shows the 2nd modification of this invention. Sectional drawing (a) and a top view (b) which show the 2nd modification of this invention. FIG. 10 is a schematic diagram illustrating a method for creating a camera module according to a conventional technique.

  FIG. 1 is a cross-sectional view (a) and a top view (b) showing an embodiment of a camera module of the present invention. In the figure, the camera module 1 includes a camera head 2, a rigid substrate 3, a flexible substrate 4, and an anisotropic conductive film 5 that joins the rigid substrate 3 and the flexible substrate 4.

  The camera head 2 has an imaging lens 22 fixedly disposed in a lens barrel 21, and further includes a diaphragm plate 23, an infrared cut filter 24, and the like.

  A rigid substrate 3 having an image sensor 31 such as a CCD or CMOS mounted on the back surface thereof is bonded to the upper surface of the camera head 2 by a known method.

  The rigid substrate 3 has a shape slightly extending in the free end direction of the flexible substrate 4, and a hole 32 is formed in this portion, and the flexible substrate 4 is bonded to the upper portion of the rigid substrate 3 by the anisotropic conductive film 5. However, it extends through the hole 32 in the horizontal direction from below the hole 32. It is desirable that the anisotropic conductive film 5 is provided up to the edge of the hole 32.

  Here, the free end of the flexible substrate 4 extends in the horizontal direction. This is because the flexible substrate 4 is preliminarily provided with creases along the upper and lower edges of the hole 32. It can be in such a state. Folding is not always necessary, but it is suitable when the flexible substrate 4 extends in the horizontal direction depending on the connection position with the circuit of the mobile terminal and is convenient for connection work.

  In the configuration as described above, the action of external force acting on the joint portion of the anisotropic conductive film 5 will be described with reference to FIG. FIG. 2 is a schematic view showing only the rigid substrate 3, the flexible substrate 4, and the anisotropic conductive film 5. When force is applied in the opposite direction as shown in FIG. The force acting on the joint portion becomes a peeling stress. Alternatively, when a force is applied in the direction in which the rigid substrate 3 and the flexible substrate 4 are peeled off at the joint end as shown in FIG. The joint part of the anisotropic conductive film 5 is weak to such a force, and the flexible substrate 4 will be peeled off.

  The present invention has a structure in which the force acting on the joint portion of the anisotropic conductive film 5 is limited to only shear stress. That is, as shown in FIG. 2C, the force acting on the joint portion of the anisotropic conductive film 5 is restrained by the hole 32 regardless of the direction of F1, F2, F3 or the like acting on the flexible substrate 4. Thus, a force F in the shear direction parallel to the bonding plane of the anisotropic conductive film 5 is obtained. As a result, a force in the turning direction does not act on the flexible substrate 4 and does not peel off.

  Next, a first modification of the present invention will be described with reference to FIG. In the first modification, the folds of the flexible substrate 4 are provided in two stages. That is, in FIG. 3, the flexible substrate 4 is provided with the crease 4a once again after passing through the hole 32 in addition to the crease in FIG. This modification is advantageous when the connection portion with the mobile terminal is in the same plane as the flexible substrate 4.

  FIG. 4 is a cross-sectional view showing a second modification. In this modification, the hole 25 is provided in the upper part of the lens barrel 21. Also in this case, the crease may be the one-stage crease shown in FIG. 1 or the two-stage crease shown in FIG. In any case, the effect of the present invention is exhibited by providing a hole in a member near the flexible substrate and passing the flexible substrate through the hole.

  FIG. 5 is a cross-sectional view (a) and a top view (b) showing a third modification. In this modification, a frame 50 is fitted on the outer periphery of the rigid substrate 3, and a hole 51 is provided in the frame 50. In the plan view of FIG. 5B, the shape of the frame body 50 is shown by dot hatching so that the shape can be easily understood.

  The frame 50 is actually a four-frame frame, and a stepped portion 52 is formed at the inner corner on the extending portion side of the flexible substrate 4. Therefore, when the frame body 50 is fitted, the three sides of the frame body 50 surround the rigid substrate 3, and the remaining one side has a gap. This gap becomes the hole 51. A hole may be formed on the remaining one side.

  The width of the hole 51 is made slightly larger than the width of the flexible substrate 4 and slightly smaller than the width of the rigid substrate 3 (vertical direction in FIG. 5B). As a result, a stepped portion 52 that hits the corner of the rigid substrate 3 can be formed on the side of the hole 51, and the frame 50 can hold the rigid substrate 3 firmly.

  In this modified example, since the rigid substrate 3 and the flexible substrate 4 are joined with the anisotropic conductive film 5 and then the frame body 50 is simply fitted, the operation is simplified.

  In the embodiment and the modification shown and described above, the width of the hole portion is shown to be substantially the same as the width of the flexible substrate. However, when the free end side of the flexible substrate is wider than the side to be joined to the rigid substrate For example, the hole may have a large width. The width of the hole can be determined as appropriate according to the structure of the flexible substrate and how the process is assembled.

DESCRIPTION OF SYMBOLS 1 Camera module 2 Camera head 3 Rigid board 4 Flexible board 5 Anisotropic conductive film (anisotropic conductive material)
21 Lens barrel 25, 32, 41 Hole 40 Frame

Claims (7)

In the connection structure of the printed wiring board in which the first connection terminal provided on the rigid board and the second connection terminal provided on the flexible board are bonded via an anisotropic conductive material,
A printed wiring board connection structure, wherein a hole is provided on the rigid board side in the vicinity of an end position where both printed wiring boards are connected, and a free end side of the flexible board is passed through the hole.   The printed wiring board connection structure according to claim 1, wherein the hole is provided in a side portion of the rigid board.   The printed wiring board connection structure according to claim 1, wherein the hole is provided in a member connected to the rigid board.   The printed wiring board connection structure according to claim 1, wherein the hole is a hole formed in a frame surrounding the rigid board.   5. The printed wiring board connection structure according to claim 1, wherein a width of the hole is formed substantially equal to a width of the flexible substrate.   The printed wiring board connection structure according to claim 1, wherein the flexible substrate is provided with at least one crease so as to be along an inner surface of the hole.   A camera module comprising the printed wiring board connection structure according to claim 1.

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