WO2011152033A1 - Printed wiring board connecting structure, and camera module - Google Patents

Abstract

Disclosed is a technology of suppressing, with a simple configuration, peeling of a flexible substrate due to warping of the flexible substrate. In a disclosed printed wiring board connecting structure, connecting terminals provided on a rigid substrate and connecting terminals provided on the flexible substrate are connected with an anisotropic conductive material therebetween. A resist region formed of a porous material is provided on a part of the rigid substrate and/or the flexible substrate surface on the connecting terminal side, said part having at least no connecting terminal. The anisotropic conductive material is provided such that the anisotropic material partially overlaps the resist region. The rigid substrate and the flexible substrate are connected to each other with the resist region and the anisotropic conductive material therebetween.

Description

Printed wiring board connection structure and camera module

The present invention relates to a printed wiring board connection structure and a camera module having the same.

In recent years, small and thin mobile terminals such as mobile phones and PDAs (Personal Digital Assistants) have become widespread. Some of such portable terminals are equipped with a small camera module. As a result, not only communication by voice or e-mail (character string) but also image capture and transmission became possible.

An example of a conventional camera module will be described with reference to FIGS. 8A to 8C. FIG. 8A shows the components of the camera module 60. FIG. 8B shows the configuration of the camera module 60.

As shown in FIG. 8A, the camera module 60 has a camera head 63, a flexible printed wiring board 64, and an anisotropic conductive film (also referred to as Anisotropic Conductive Film, ACF) 65. The camera head 63 is formed by joining a lens barrel 61 to a rigid printed wiring board 62. The lens barrel 61 houses an imaging lens and the like. An image sensor such as a CCD or CMOS is mounted on the printed wiring board 62. The printed wiring board 64 electrically connects the camera head 63 to the portable terminal. The anisotropic conductive film 65 connects the connection terminal 62 a of the printed wiring board 62 and the connection terminal 64 a of the printed wiring board 64. The printed wiring board 62 and the printed wiring board 64 are joined by thermocompression bonding with the anisotropic conductive film 65 interposed therebetween. Thereby, the camera module 60 is completed.

In this specification, a rigid printed wiring board may be called a rigid board, and a flexible printed wiring board may be called a flexible board. Moreover, what put these together may be called a printed wiring board. The printed wiring board generally refers to a wiring board having no electronic component in a narrow sense, but in this specification, the printed wiring board including the printed circuit board on which the electronic component is mounted is referred to as a printed wiring board.

Now, in the figure, the aperture of the imaging lens is on the lower side. 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 sensor detects imaged light and performs photoelectric conversion to generate image data. This image data is sent from the connection terminal 64b on the free end side to the circuit of the portable terminal via the connection terminal 62a of the rigid board 62, the anisotropic conductive film 65, and the connection terminal 64a of the flexible board 64. A reinforcing plate 64 c is provided on the front side of the free end of the flexible substrate 64.

The anisotropic conductive film 65 is an electrical bonding film having a thickness of 20 to 30 μm formed of a heat resistant resin. A plurality of conductive particles are dispersed in the surface direction inside the heat resistant resin. The conductive particles are formed as 3 to 5 μm spheres in which a resin is coated with nickel or the like. When the anisotropic conductive film disposed between the two printed wiring boards 62 and 64 is thermocompression bonded, the connection terminals 62a and 64a of the printed wiring boards 62 and 64 are in contact with the conductive particles, respectively. Realizes conductivity in the thickness direction. On the other hand, the conductive particles are dispersed at a ratio of approximately 10% or less in the inside of the heat-resistant resin, and no pressure is applied in the surface direction, so that the conductive particles are not in contact with each other so that insulation is maintained. It has become. Therefore, in a state where the plurality of connection terminals 62a and 64a are joined via the anisotropic conductive film 65, the opposing connection terminals 62a and 64a are conductive, and the adjacent connection terminals 62a and 64a are conductive. Absent.

Patent Documents 1 and 2 are known as methods for thermocompression bonding of a substrate using an anisotropic conductive film 65.

In the thermocompression bonding method disclosed in Patent Document 1, a plurality of film-like substrates on which an electrode pattern is arranged and an IC chip is mounted are thermocompression bonded to one transmissive substrate through an anisotropic conductive film. To do. In this method, a plurality of heating means are provided and individually controlled for heating in order to prevent the film-like substrate from extending due to thermal expansion and causing a positional shift.

Further, Patent Document 2 discloses a method in which a plurality of semiconductor chip mounting films are thermocompression bonded to a single rectangular substrate via an anisotropic conductive film. In this method, 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 simultaneously performed.

In addition, as an anisotropic conductive material, a paste type or the like is known in addition to a film type. In the present specification, any type including these is collectively referred to as an anisotropic conductive material.

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

FIG. 8C 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. In addition, a connection terminal 64b connected to a circuit of the mobile terminal is provided on the free end side of the flexible substrate 64. When the connection terminal 64b is connected to the circuit of the mobile terminal, the camera module 60 is incorporated into the mobile terminal, or the camera module 60 is transported, the free end may warp upward in the figure. Since the flexible substrate 64 is weak against such an external force in the turning direction, there is a possibility that the flexible substrate 64 may be peeled off due to the curvature of the free end.

As a means for preventing this problem, it is conceivable to bond the side wall of the rigid substrate 62 and the lower portion of the flexible substrate 64 with an adhesive at a position indicated by an arrow in FIG. 8C. However, this method requires a step of bonding with an adhesive and a step of solidifying the adhesive, which increases the cost. Therefore, this method is not preferable in practice. For example, when bonding with a thermosetting resin, a heating time of about 60 minutes is required. In addition, when bonding with an ultraviolet curable resin, equipment for irradiating ultraviolet rays and equipment for protecting workers from harmful ultraviolet rays are required.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a technique capable of suppressing peeling due to warping of a flexible substrate with a simple configuration.

To achieve the above object, according to a first aspect of the present invention, there is provided a print in which a connection terminal provided on a rigid board and a connection terminal provided on a flexible board are joined via an anisotropic conductive material. In the wiring board connection structure, a resist region of a porous body is provided on at least a portion of the surface of the rigid substrate and / or the flexible substrate on the connection terminal side where the connection terminal is not disposed, and the anisotropic The conductive conductive material is provided so as to partially overlap the resist region, and the rigid substrate and the flexible substrate are bonded via the resist region and the anisotropic conductive material. .
In the first aspect, the resist region is provided in the vicinity of an extended portion of the flexible substrate for connecting the flexible substrate to an external circuit in a connection region between the rigid substrate and the flexible substrate. May be.
In the first aspect, the porous body may be a solder resist material.
In order to achieve the above object, according to a second aspect of the present invention, a first connection terminal provided on a rigid board and a second connection terminal provided on a flexible board are interposed via an anisotropic conductive material. In the connection structure of the printed wiring boards joined together, the flexible substrate has a connection portion with the rigid substrate, and an extending portion extending from the connection portion to the free end side in order to connect to an external circuit, A narrow portion narrower than the connection portion is provided at least in the vicinity of the connection portion in the extension portion.
In the second aspect, the flexible substrate has a plurality of signal lines extending from the second connection terminal to the extending portion, and is provided at an edge of the narrow portion of the plurality of signal lines. The nearest signal line may be formed thicker than other signal lines.
Moreover, the said 2nd aspect WHEREIN: The said narrow part may be provided over substantially the whole of the said extension part.
Moreover, the said 2nd aspect WHEREIN: The said narrow part may be formed of the notch provided in the vicinity of the said connection part.
Moreover, the said 2nd aspect WHEREIN: The depth of the hollow of the said narrow part with respect to the said connection part may be formed substantially the same as the width | variety of the said 2nd connection terminal.
A camera module according to the present invention is characterized by having a printed wiring board connection structure according to the first aspect, the second aspect, or a modification thereof.

According to the printed wiring board connection structure according to the first aspect of the present invention, at least a portion of the rigid substrate and / or flexible substrate on the connection terminal side where the connection terminal is not disposed is a porous resist. A region is provided, the anisotropic conductive material is provided so as to partially overlap the resist region, and the rigid substrate and the flexible substrate are bonded via the resist region and the anisotropic conductive material. Therefore, it is possible to improve the bonding force between the two substrates, and it is possible to suppress peeling due to the warping of the flexible substrate with a simple configuration.

According to the printed wiring board connection structure according to the second aspect of the present invention, the flexible substrate includes a connection portion with the rigid substrate, and an extending portion extending from the connection portion to the free end side in order to connect to an external circuit. And a narrow portion having a width narrower than that of the connection portion is provided at least in the vicinity of the connection portion of the extended portion. Therefore, even if an external force in the turning direction is applied, the external force is dispersed and the strength against turning is improved. Therefore, it is possible to suppress peeling due to warping of the flexible substrate with a simple configuration.

Since the connection structure of the printed wiring board according to the first or second aspect of the present invention is applied to the camera module according to the present invention, it is possible to suppress peeling due to warping of the flexible substrate with a simple configuration. It is.

It is sectional drawing which shows the camera module which concerns on 1st Embodiment. It is a top view which shows the camera module which concerns on 1st Embodiment. It is an expanded view which shows the state before joining of 1st Embodiment. It is a schematic diagram which shows the manufacturing process of the camera module which concerns on 1st Embodiment. It is a schematic diagram which shows the manufacturing process of the camera module which concerns on 1st Embodiment. It is a schematic diagram which shows the manufacturing process of the camera module which concerns on 1st Embodiment. It is sectional drawing which shows the camera module which concerns on 2nd Embodiment. It is a top view which shows the camera module which concerns on 2nd Embodiment. It is a schematic diagram which shows the effect | action of 2nd Embodiment. It is a schematic diagram which shows the effect | action of 2nd Embodiment. It is a schematic diagram which shows the effect | action of 2nd Embodiment. Sectional drawing which shows the modification of 2nd Embodiment. The schematic diagram which shows the effect | action of the modification of 2nd Embodiment. It is a schematic diagram which shows the creation method of the conventional camera module. It is a schematic diagram which shows the creation method of the conventional camera module. It is a schematic diagram which shows the creation method of the conventional camera module.

<First Embodiment>
The configuration of the camera module according to the first embodiment is shown in FIGS. 1A and 1B. As shown in FIG. 1A, the camera module 1 includes a camera head 2, a rigid substrate 3, a flexible substrate 4, an anisotropic conductive film 5, and resist films 6a and 6b. The anisotropic conductive film 5 joins the rigid substrate 3 and the flexible substrate 4. The resist films 6a and 6b may be collectively referred to as a resist film 6.

In the lens barrel 21 of the camera head 2, an imaging lens 22 is fixedly arranged. A diaphragm plate 23 is joined to the lower end of the lens barrel 21. An infrared cut filter 24 is provided in the opening of the diaphragm plate 23. A rigid substrate 3 is bonded to the upper surface of the camera head 2. An image sensor 31 is mounted on the back surface of the rigid substrate 3. That is, the image sensor 31 is provided at the upper end portion in the lens barrel 21. The image sensor 31 is, for example, a CCD or a CMOS.

As shown in FIGS. 1B and 2, the rigid board 3 is provided with connection terminals 3a, and the flexible board 4 is provided with connection terminals 4a. The connection terminal 3 a and the connection terminal 4 a are joined via the anisotropic conductive film 5. As shown in FIG. 1B, the area of the bonding surface of the anisotropic conductive film 5 is wider than the area of the connection terminals 3a and 4a. The resist film 6 is provided so as to overlap the anisotropic conductive film 5 in a portion where the connection terminals 3a and 4a are not disposed. In FIG. 1B, only the resist film 6b on the flexible substrate 4 side is shown. 1B is a portion where the resist film 6b and the anisotropic conductive film 5 overlap each other.

The installation position of the resist film 6 will be described in more detail with reference to FIG. A resist film 6a is provided on the entire surface of the rigid substrate 3 where the connection terminals 3a are not disposed. In addition, the resist film 6b is provided in a connection portion that overlaps the rigid substrate 3 in the flexible substrate 4 and is not provided with the connection terminal 4a. Further, the resist film 6b is provided at least in the vicinity of the extension portion side in the connection portion. This is because an external force in the turning direction is applied to this position.

Specific examples of the resist film include a solder resist and a screen printing resist. It is desirable that the resist film has at least a porous surface and has a sufficient adhesion to the substrate. The surface of the resist film is porous having fine irregularities or fine pores. Therefore, when the resist film and the anisotropic conductive film are overlapped and thermocompression bonded, the material of the anisotropic conductive film enters the concave portion of the resist film and increases the bonding force. In other words, the resist film exhibits an anchor effect.

Usually, the resist film is provided for the purpose of protecting the circuit of the printed circuit board and the wiring of the printed wiring board. On the other hand, in the camera module 1 of this embodiment, since the module itself is housed in a highly confidential casing such as a portable terminal, a resist film is not always necessary. This embodiment is characterized in that a resist film is used to increase the bonding force between the substrate and the anisotropic conductive film.

In addition, when requesting the production of a substrate from a substrate maker, it is possible to form a resist film using equipment normally possessed by the substrate maker. It can also be manufactured by the manufacturer that manufactures the camera module.

The resist film 6 is desirably provided both between the rigid substrate 3 and the anisotropic conductive film 5 and between the flexible substrate 4 and the anisotropic conductive film 5. However, even when the resist film is provided only between the flexible substrate 4 and the anisotropic conductive film 5, the effect is exhibited.

In the above-described embodiment, a resist film is applied as a material interposed between the substrate and the anisotropic conductive film, but this material is not limited to the resist film. This material can be selected arbitrarily as long as it has minute irregularities or minute holes on the surface and has sufficient adhesion to the substrate. In the present specification, a material having such a property is referred to as a porous body. The porous body does not need to be completely porous having pores penetrating from the front surface to the back surface, and may be any material that has a recess or a hole that allows an anisotropic conductive material to enter and exert an anchor effect. .

As the anisotropic conductive material, for example, an arbitrary material such as a film type or a paste type can be applied.

Next, the process of assembling the camera module 1 will be described with reference to FIGS. 3A to 3C. It is assumed that the resist film 6 shown in FIG. 2 has already been formed on the rigid substrate 3 and the flexible substrate 4.

First, the anisotropic conductive film 5 is provided on the rigid substrate 3. The anisotropic conductive film 5 usually has a configuration in which a layer of an anisotropic conductive material is formed on a base film via a release layer, and is provided in a state of being wound on a reel.

As shown in FIG. 3A, the anisotropic conductive film 5 wound around the reels L1 and L2 is pressed against the rigid substrate 3, and the base film and the release layer are peeled off from the anisotropic conductive material. The base film and the release layer peeled off from the anisotropic conductive material are wound on reels L3 and L4. As a result, the anisotropic conductive material is adhered to a predetermined position of the rigid substrate 3.

In addition, in this embodiment, since the connection terminals are arranged on both sides, the process of providing two sets of reels and working simultaneously is shown, but an anisotropic conductive material may be attached one by one. Furthermore, an anisotropic conductive material having a width substantially equal to the width of the substrate may be attached to the entire surface of the substrate.

Next, as shown in FIG. 3B, the rigid substrate 3 to which the anisotropic conductive material 5 is adhered and the flexible substrate 4 are subjected to a thermocompression bonding machine HP to join them together. According to such a joining method, as shown in FIG. 3C, since the anisotropic conductive material 5 enters the recesses of the resist films 6a and 6b, the joining strength can be increased like an anchor.

When the joining state was examined by applying an external force in the turning direction to the flexible substrate of the camera module of this embodiment, the joining strength was higher than that of the conventional one.

<Second Embodiment>
The configuration of the camera module according to the second embodiment is shown in FIGS. 4A and 4B. 4A is a cross-sectional view, and FIG. 4B is a top view. In addition, the camera module 10 to which the same code | symbol is attached | subjected about the component similar to 1st Embodiment has the camera head 2, the rigid board | substrate 3, the flexible substrate 4, and the anisotropic conductive film 5. FIG. . The anisotropic conductive film 5 joins the rigid substrate 3 and the flexible substrate 4.

In the lens barrel 21 of the camera head 2, an imaging lens 22 is fixedly arranged. A diaphragm plate 23 is joined to the lower end of the lens barrel 21. An infrared cut filter 24 is provided in the opening of the diaphragm plate 23. A rigid substrate 3 is bonded to the upper surface of the camera head 2. An image sensor 31 is mounted on the back surface of the rigid substrate 3. That is, the image sensor 31 is provided at the upper end portion in the lens barrel 21. The image sensor 31 is, for example, a CCD or a CMOS.

A flexible substrate 4 is bonded to the rigid substrate 3 via an anisotropic conductive film 5. As shown in FIG. 4B, the connection terminal 3 a of the rigid substrate 3 and the connection terminal 4 a of the flexible substrate 4 overlap with each other with an anisotropic conductive film 5 interposed therebetween. In FIG. 4B these are indicated by broken lines.

The portion where the flexible substrate 4 and the rigid substrate 3 overlap is referred to as a connection portion, and the free end side of the connection portion is referred to as an extension portion. Cuts 41 are provided on both sides of the extended portion in the vicinity of the connecting portion. A narrow portion 42 is formed between the cuts 41. A reinforcing plate 4c is provided at the tip of the extended portion.

The shape of the edge of the cut 41 is preferably a smooth curved surface such as an arc shown in FIG. 4B, for example, and an acute cut is inappropriate. The depth A of the notch 41 is substantially the same as the width B of the connection terminals 3 a and 4 a in the connection direction of the flexible substrate 4.

A large number of signal lines are printed on the flexible substrate 4. Of these signal lines, the signal line 4b closest to the notch 41 is thicker than the other signal lines. The signal line 4b is, for example, a ground line. In practice, the signal line and the connection terminal are connected by a relatively thin signal line, but since the figure is schematically shown, details are omitted.

The operation of this embodiment will be described with reference to FIGS. 5A to 5C. 5A and 5B show a conventional flexible substrate 4 '. The flexible substrate 4 'is not provided with a narrow portion. FIG. 5A shows a case where an external force is uniformly applied to the flexible substrate 4 ′ in the turning direction. When such an external force is applied to the flexible substrate 4 ′, a force indicated by an arrow in FIG. 5A works, and the flexible substrate 4 ′ is peeled off from the rigid substrate 3. FIG. 5B shows a case where an external force in the twisting direction is applied in addition to the turning direction. Even in this case, stress is applied to the flexible substrate 4 'in the turning direction. However, since the stress is generated particularly on the side where the twist is applied, the flexible substrate 4' is peeled off from this side.

On the other hand, FIG. 5C shows the flexible substrate 4 of this embodiment, and a narrow portion 42 is provided. When an external force in the turning direction and twisting direction similar to FIG. 5B is applied to the flexible substrate 4, stress concentrates on the portion of the notch 41 and the stress in the turning direction applied to the connection portion decreases. Therefore, according to this embodiment, resistance to the external force in the turning direction is improved, and the possibility that the flexible substrate 4 is peeled off is reduced.

FIG. 6 is a top view showing a modification of this embodiment. In this modification, the narrow portion 42 is formed over the entire extending portion from the position near the connection portion to the reinforcing plate 4c. The depth A of the recess 43 forming the narrow portion 42 is substantially the same as the width B of the connection terminals 3a and 4a in the connection direction of the flexible substrate 4 as in the above embodiment. The width of the reinforcing plate 4c is arbitrarily set according to the connection form with the external circuit, and may be the same width as the narrow portion 42, or may be wider or narrower than this.

FIG. 7 shows a state in which an external force is applied in the turning direction to the flexible substrate 4 of this modification. Even in this case, since the stress applied to the connection portion is dispersed by the narrow portion 42, the flexible substrate 4 is difficult to peel off.

When an external force was applied in the turning direction to the flexible substrate of the camera module according to this embodiment and the modified example to examine the bonding state between the flexible substrate 4 and the rigid substrate, the bonding strength was higher than that of the conventional product.

DESCRIPTION OF SYMBOLS 1, 10 Camera module 2 Camera head 3 Rigid board 3a Connection terminal 4 Flexible board 4a Connection terminal 4b Signal line 4c Reinforcement board 5 Anisotropic conductive film (anisotropic conductive material)
6, 6a, 6b Resist film 41 Notch 42 Narrow part 43 Recess

Claims (9)

In the connection structure of the printed wiring board in which the connection terminal provided on the rigid board and the connection terminal provided on the flexible board are bonded via an anisotropic conductive material,
In the rigid substrate and / or the surface of the flexible substrate on the side of the connection terminal, at least a portion where the connection terminal is not disposed is provided with a porous resist region,
The anisotropic conductive material is provided so as to partially overlap the resist region,
The rigid substrate and the flexible substrate are bonded via the resist region and the anisotropic conductive material,
A printed wiring board connection structure characterized by that. The resist region is provided in a vicinity of an extended portion of the flexible substrate for connecting the flexible substrate to an external circuit in a connection region between the rigid substrate and the flexible substrate. The printed wiring board connection structure described in 1. 3. The printed wiring board connection structure according to claim 1, wherein the porous body is a solder resist material. 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,
The flexible substrate has a connection portion with the rigid substrate, and an extending portion extending from the connection portion to the free end side in order to connect to an external circuit,
A narrow portion narrower than the connection portion is provided at least in the vicinity of the connection portion of the extension portion,
A printed wiring board connection structure characterized by that. The flexible substrate has a plurality of signal lines extending from the second connection terminal to the extension portion,
The signal line closest to the edge of the narrow part among the plurality of signal lines is formed thicker than the other signal lines.
The printed wiring board connection structure according to claim 4, wherein: The printed wiring board connection structure according to claim 4 or 5, wherein the narrow portion is provided over substantially the whole of the extending portion. The printed wiring board connection structure according to claim 4 or 5, wherein the narrow portion is formed by a notch provided in the vicinity of the connection portion. The printed wiring board according to any one of claims 4 to 7, wherein a depth of the recess of the narrow portion with respect to the connection portion is formed to be substantially the same as a width of the second connection terminal. Connection structure. 9. A camera module comprising the printed wiring board connection structure according to claim 1.

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