JP7657614B2 - Imaging unit and imaging device - Google Patents

Description

The present invention relates to an imaging unit and an imaging device.

Patent Document 1 proposes a composite substrate structure having a connection structure between substrates. The composite substrate described in Patent Document 1 has a first flexible wiring board with a reinforcing plate laminated on a first surface, and a second flexible wiring board joined to a second surface of the first flexible wiring board. The reinforcing plate has a portion that protrudes beyond the end face of the first flexible wiring board so as to overlap the joint between the first and second flexible wiring boards. Patent Document 1 describes that the wiring patterns of the first and second flexible wiring boards are electrically connected to each other at the joint, and the reinforcing plate and the second flexible wiring board are fixed with an adhesive, thereby preventing breakage of the exposed portion of the wiring pattern due to bending stress.

However, when a flexible wiring board is connected to a moving body that moves finely, such as an image stabilization unit, the technology described in Patent Document 1 increases the rigidity of the entire system, which impairs the flexibility of the flexible wiring board. As a result, the technology described in Patent Document 1 impedes the driving of the moving body.

JP 2009-295821 A

According to one aspect of the present invention, there is provided an imaging unit having a printed wiring board having an imaging element and a first electrode on its surface, a base material having a first surface and a second surface, a conductor layer provided on the first surface, and an insulating layer provided on the conductor layer, the conductor layer further having a second electrode at one end portion of which the insulating layer is not provided, a conductive connecting material connecting the first electrode and the second electrode, and a reinforcing material provided on the second surface side of the base material, characterized in that the reinforcing material continuously covers an end portion of the insulating layer close to the second electrode and an end portion of the conductive connecting material connected to the second electrode close to the insulating layer.

According to another aspect of the present invention, there is provided an imaging device having a housing and an imaging unit inside the housing, the imaging unit being the imaging unit described above.

The present invention makes it possible to reduce the load on the connection between the flexible wiring board and the printed wiring board without compromising the flexibility of the flexible wiring board.

FIG. 2 is a top view showing a schematic configuration of the imaging unit according to the first embodiment. 1 is a schematic cross-sectional view showing a schematic configuration of an imaging unit according to a first embodiment. 4 is a schematic cross-sectional view showing an enlarged view of a connection portion between a flexible wiring board and a printed wiring board of the imaging unit according to the first embodiment. FIG. FIG. 11 is a top view showing a schematic configuration of an imaging unit according to a second embodiment. FIG. 11 is a schematic cross-sectional view showing a schematic configuration of an imaging unit according to a second embodiment. 13 is a schematic cross-sectional view showing an enlarged view of a connection portion between a flexible wiring board and a printed wiring board of an imaging unit according to a second embodiment. FIG. FIG. 13 is a top view showing a schematic configuration of an imaging unit according to a third embodiment. FIG. 13 is a schematic cross-sectional view showing a schematic configuration of an imaging unit according to a third embodiment. 13 is a schematic cross-sectional view of a connection portion between a flexible wiring board and a printed wiring board of an imaging unit according to a third embodiment. FIG. FIG. 13 is an explanatory diagram showing a schematic configuration of an imaging device as an example of an electronic device according to a fourth embodiment. FIG. 2 is a schematic diagram showing a three-dimensional structural analysis model according to Comparative Example 1. FIG. 11 is a schematic diagram showing a three-dimensional structural analysis model according to Comparative Example 2. FIG. 11 is a schematic diagram showing a three-dimensional structural analysis model according to Comparative Example 3. FIG. 13 is a schematic diagram showing a three-dimensional structural analysis model according to Comparative Example 4. FIG. 11 is a schematic diagram showing a three-dimensional structural analysis model according to a third embodiment. FIG. 1 is a diagram showing a comparison of the results of structural analysis of Comparative Examples 1, 2, 3, and 4 and Example 3. 1 is a graph showing the results of structure analysis of Examples 4, 5, and 6.

The following describes in detail the embodiments of the present invention with reference to the drawings. Note that the present invention is not limited to the following embodiments, and can be modified as appropriate without departing from the spirit of the invention. In the drawings described below, elements having the same functions are given the same reference numerals, and their description may be omitted or simplified.

[First embodiment]
The imaging unit according to the first embodiment will be described with reference to Figures 1, 2, and 3. Figure 1 is a schematic top view showing the general configuration of an imaging unit 400 according to this embodiment. Figure 2 is a schematic cross-sectional view showing the general configuration of the imaging unit 400 according to this embodiment, showing a cross section taken along line A-A' in Figure 1.

Figure 3 is a schematic cross-sectional view showing an enlarged view of the connection portion 19 between the flexible wiring board 4 and the printed wiring board 9 of the imaging unit 400 according to this embodiment, and shows an enlarged view of the cross section of the connection portion 19 in Figure 2.

As shown in Figures 1, 2 and 3, the imaging unit 400 has an imaging sensor module 14 having a printed wiring board 9, an image stabilization unit 410, and a flexible wiring board 4. The flexible wiring board 4 is connected to the printed wiring board 9 at a connection portion 19 via solder 11, as described below.

Here, the coordinate axes and directions of the X-axis, Y-axis, and Z-axis of the XYZ coordinate system, which is an orthogonal coordinate system used in the following description, are defined. First, the axis perpendicular to the main surface of the printed wiring board 9 is defined as the Z-axis. Also, the axis parallel to the main surface of the printed wiring board 9 and along a pair of parallel end sides of the printed wiring board 9 is defined as the X-axis. Also, the axis perpendicular to the X-axis and Z-axis is defined as the Y-axis. In the XYZ coordinate system in which the coordinate axes are defined in this way, the direction along the X-axis is defined as the X-direction, the direction from one end of the flexible wiring board 4 on the connection portion 19 side to the other end is defined as the +X-direction, and the direction opposite to the +X-direction is defined as the -X-direction. Also, the direction along the Y-axis is defined as the Y-direction, the direction from the right side to the left side of the +X-direction is defined as the +Y-direction, and the direction opposite to the +Y-direction is defined as the -Y-direction. The direction along the Z axis is defined as the Z direction, the direction from the imaging sensor element 15 of the imaging sensor module 14 toward the connection portion 19 is defined as the +Z direction, and the direction opposite to the +Z direction is defined as the -Z direction. The direction of rotation around the Z axis is defined as the θ direction.

The flexible wiring board 4 has a flexible base material 1, a flexible wiring layer 2, and a coverlay 3. The flexible wiring board 4 has one or more conductor layers as the flexible wiring layer 2, and is configured by stacking the conductor layers as insulating layers via the flexible base material 1. Note that in this embodiment, a case where the wiring layer in the flexible wiring board 4 is a single layer will be described, but it is not limited to a single layer, and the wiring layer may be multiple layers.

The flexible substrate 1 is an insulating substrate made of resin or the like, for example in the form of a sheet or film, and has plasticity and flexibility. Therefore, the flexible wiring board 4 can be deformed, such as by bending. The insulator constituting the flexible substrate 1 only needs to have electrical insulation properties. For example, polyimide, polyethylene terephthalate, etc. are used as the insulator constituting the flexible substrate 1. The flexible substrate 1 has a front surface, which is the first surface, and a back surface, which is the second surface. Layers and members are provided on the front surface and back surface of the flexible substrate 1 as follows.

The flexible wiring layer 2 is a conductor layer made of copper foil, other metal foil, etc. The flexible wiring layer 2 has a wiring pattern. The flexible wiring layer 2 is formed on one or both of the front and back surfaces of the flexible substrate 1. The flexible wiring layer 2 may be formed directly on the front or back surface of the flexible substrate 1, or may be formed on the front or back surface of the flexible substrate 1 via a layer structure such as an insulating layer. The conductor constituting the flexible wiring layer 2 is a material having higher electrical conductivity and thermal conductivity than an insulator, such as a metal such as copper, silver, or gold. The flexible wiring layer 2 may be formed on at least one surface of the flexible substrate 1. For example, the flexible wiring layer 2 is provided on the surface of the flexible substrate 1 facing the printed wiring board 9.

The coverlay 3 is an insulating layer that protects the wiring pattern of the flexible wiring layer 2. The coverlay 3 is formed of a cover film, an overcoat, etc. The coverlay 3 is provided on the surface of the flexible wiring board 4, and is formed on the surface of the flexible base material 1 that includes the flexible wiring layer 2 so as to cover the flexible wiring layer 2. For example, the coverlay 3 is provided on the flexible wiring layer 2 provided on the surface of the flexible base material 1.

On the side of the coverlay 3 provided on the surface of the flexible substrate 1 of the flexible wiring board 4, the coverlay 3 is not formed on one end of the flexible wiring board 4, and the flexible wiring layer 2 is exposed. The exposed portion of the flexible wiring layer 2 constitutes the first electrode 5. That is, the flexible wiring layer 2 provided on the surface of the flexible substrate 1 has a first electrode 5 on one end where the coverlay 3 is not provided. In addition, the first electrode 5 may be plated with gold or the like. The first electrodes 5 made of the exposed flexible wiring layer 2 are arranged in a row, for example, at a predetermined pitch. In this way, the first electrode 5 is formed by the flexible wiring layer 2 exposed at the end of the flexible wiring board 4. One end of the flexible wiring board 4 where the first electrode 5 is formed is an electrode part where the first electrode 5 is exposed. Although not shown, the other end of the flexible wiring board 4 is an insertion terminal on which an electrode is formed.

At the connection 19 between the printed wiring board 9 and the flexible wiring board 4 of the imaging sensor module 14, the first electrode 5 exposed at one end of the flexible wiring board 4 is connected to the second electrode 10 of the printed wiring board 9 via the solder 11. It is desirable that a gap is formed between the coverlay 3 of the flexible wiring board 4 connected to the printed wiring board 9 at the connection 19 and the solder 11, and that an exposed portion 24 where the flexible wiring layer 2 is exposed is secured. In other words, it is desirable that the flexible wiring layer 2 is exposed between the end of the solder 11 on the coverlay 3 side and the end of the coverlay 3 on the solder 11 side. The exposed portion 24 is a portion where the first electrode 5 is exposed between the end of the coverlay 3 close to the first electrode 5 and the solder 11. When the exposed portion 24 is secured, the end of the coverlay 3 close to the first electrode 5 is not in contact with the solder 11. By ensuring the exposed portion 24, the loss of flexibility of the flexible wiring board 4 caused by the reinforcing material 21 described below can be minimized, while the reinforcing material 21 can reinforce the connection portion 19 between the flexible wiring board 4 and the printed wiring board 9.

Although not shown in the figure, the insertion terminal at the other end of the flexible wiring board 4 is inserted into a connector mounted on the printed wiring board of the image processing unit. In this way, the flexible wiring board 4 electrically connects the imaging unit 400 and the image processing unit to each other.

The imaging sensor module 14 has a printed wiring board 9, an imaging sensor element 15, a frame 17, and a cover glass 16. The printed wiring board 9 is adhered and fixed to the metal frame 22 with an adhesive such as an ultraviolet-curable resin. The imaging sensor module 14 is supported by the image stabilization unit 410 so as to be movable relative to the image stabilization unit 410, as described below.

On one side of the printed wiring board 9 to which the flexible wiring substrate 4 is connected, a second electrode 10 is provided on the surface layer, as described below. A frame 17 is attached and disposed on the peripheral edge of the other side of the printed wiring board 9. The cover glass 16 is attached to the frame 17 so as to be parallel to the printed wiring board 9.

The imaging sensor element 15 is an imaging element formed, for example, of a semiconductor element. Specifically, the imaging sensor element 15 is, for example, a solid-state imaging element such as a CMOS (Complementary Metal Oxide Semiconductor) image sensor or a CCD (Charge Coupled Device) image sensor. The imaging sensor element 15 is attached to the printed wiring board 9 in a hollow portion surrounded by the printed wiring board 9, the cover glass 16, and the frame 17 so as not to come into contact with the cover glass 16. The imaging sensor element 15 is electrically connected to a wire pad 23 of the printed wiring board 9 through a metal wire 18. The wire pad 23 is, for example, Au-plated.

The image stabilization unit 410 supports the metal frame 22 so that the image sensor module 14 fixed to the metal frame 22 can move in the X and Y directions and rotate in the θ direction. The image stabilization unit 410 can correct camera shake by moving or rotating the image sensor module 14 in response to camera shake. The image stabilization unit 410 is configured to have, for example, an L-shape and support the metal frame 22, which has a rectangular outer shape, from two adjacent sides of the metal frame 22.

In this embodiment, the case where the frame 17 is attached is described, but the location of the frame 17 is not limited to the peripheral portion of the printed wiring board 9. Also, the location of the image sensor element 15 may be within a hollow portion of the printed wiring board 9 that has a recess, such as a cavity board.

The printed wiring board 9 on which the image sensor element 15 is provided has a printed wiring substrate 6, a wiring layer 7, and a solder resist layer 8. The printed wiring board 9 is configured by stacking a plurality of wiring layers 7 via the printed wiring substrate 6. Unlike the flexible wiring board 4, the printed wiring board 9 is a rigid wiring board.

For example, the printed wiring board 9 may be made of a glass epoxy material or a ceramic substrate. It is also possible to use a printed circuit board in which the image sensor element 15 is disposed on a ceramic substrate, and the ceramic substrate and the printed wiring board 9 are connected by a pair of electrodes via solder 11. For example, an LGA (Land Grid Array) type or CLCC (Ceramic Leadless Chip Carrier) type image sensor unit can also be used.

In this embodiment, the wiring layer 7 in the printed wiring board 9 is described as having four layers, but is not limited to four layers. The wiring layer 7 in the printed wiring board 9 may be a single layer or multiple layers, i.e., four or less layers or four or more layers.

Although not shown, the printed wiring board 9 is also equipped with the minimum number of components required for the operation of the imaging unit 400.

The printed wiring substrate 6 is, for example, a board-shaped insulating substrate made of a hard composite material. Unlike the flexible substrate 1, the printed wiring substrate 6 is hard. The insulator constituting the printed wiring substrate 6 only needs to have electrical insulation properties. For example, the printed wiring substrate 6 may be a resin substrate made of a hardened resin such as an epoxy resin, or a ceramic substrate made of ceramic.

The wiring layer 7 is a conductor layer made of copper foil or other metal foil. The wiring layer 7 has a wiring pattern. The wiring layer 7 is formed on one or both sides of the printed wiring substrate 6. One or more layers of the wiring layer 7 are also formed inside the printed wiring substrate 6. Figures 2 and 3 show a case where a total of four wiring layers 7 are formed on both sides and inside the printed wiring substrate 6. Also, vias 13 are formed inside the printed wiring substrate 6 to electrically connect the wiring layers 7. Conductors such as the wiring layer 7 and the vias 13 are materials that have higher electrical conductivity and thermal conductivity than insulators, such as metals such as copper and gold.

The solder resist layer 8 is an insulating protective film that protects the circuit formed by the wiring layer 7. The solder resist layer 8 is formed of a hardened liquid solder resist, a film-like solder resist, or the like. The solder resist layer 8 is formed so as to cover the wiring layer 7 on one side of the printed wiring board 9 to which the flexible wiring substrate 4 is connected. The solder resist layer 8 is also formed so as to cover the wiring layer 7 on the other side of the printed wiring board 9 to which the image sensor element 15 is attached.

The solder resist layer 8 has an opening through which the wiring layer 7 is exposed. The exposed portion of the wiring layer 7 forms the second electrode 10. The second electrodes 10 are arranged, for example, in a row at a predetermined pitch. The second electrodes 10 are arranged, for example, in the center of the printed wiring board 9. In this way, the second electrode 10 made of the wiring layer 7 is provided on the surface layer of the printed wiring board 9. The second electrode 10 provided on the surface layer is electrically connected to the first electrode 5 of the flexible wiring board 4 via solder 11, which is a conductive connecting material.

When connecting the first electrode 5 and the second electrode 10 using solder 11, the first electrode 5 and the second electrode 10 can be connected by adhering the connecting material having the solder 11 to the solder 11 while the connecting material is heated to a temperature equal to or higher than the melting point of the solder 11. The solder 11 may be, for example, Sn-3.0Ag-0.5Cu solder or Sn-58Bi solder mixed with flux to form a paste. Instead of the solder 11, a conductive adhesive or the like may be used as the conductive connecting material that connects the first electrode 5 and the second electrode 10.

As described above, a reinforcing material 21 that reinforces the connection 19 is provided at the connection 19 between the flexible wiring board 4 and the printed wiring board 9, where the first electrode 5 and the second electrode 10 are connected. The reinforcing material 21 is provided on the back surface of the flexible substrate 1, which is the surface opposite to the surface on which the first electrode 5 of the flexible wiring board 4 is exposed. The reinforcing material 21 provided on the back surface of the flexible substrate 1 may be provided on the back surface of the flexible substrate 1, or may be provided on the back surface of the flexible substrate 1 via a layer such as a wiring layer or an insulating layer.

As shown in FIG. 1, the reinforcing material 21 is provided on both ends in the width direction (short direction) of the flexible wiring board 4 along the Y direction at the tip of the flexible substrate 1 of the flexible wiring board 4 on the connection portion 19 side. Note that the reinforcing material 21 may be provided on both ends of the flexible substrate 1 in the width direction of the flexible wiring board 4, or may be provided across the width direction of the flexible wiring board 4 as in the third embodiment described below.

As shown in FIG. 3, the reinforcing material 21 is provided on the flexible substrate 1 so as to continuously cover both the end of the solder 11 on the coverlay 3 side and the end of the coverlay 3 on the solder 11 side via the flexible substrate 1 and the flexible wiring layer 2. That is, the reinforcing material 21 continuously covers the end of the coverlay 3 on the side closer to the first electrode 5 and the end of the part of the solder 11 connected to the first electrode 5 on the side closer to the coverlay 3.

The reinforcing material 21 is not particularly limited, but may be, for example, a cured resin such as an ultraviolet (UV) curable resin or a thermosetting resin. In addition to being a cured resin, the reinforcing material 21 may also be a reinforcing film attached to the same location on the surface of the flexible substrate 1.

Here, the flexible wiring board 4 connected to the printed wiring board 9 includes a fixed portion 4a, which is a portion where the first electrode 5 is connected and fixed to the second electrode 10 via the solder 11, and a non-fixed portion 4b, which is a portion other than the fixed portion 4a. The non-fixed portion 4b can bend in a direction away from the printed wiring board 9 with respect to the fixed portion 4a. The reinforcing material 21 provided as described above is provided across the fixed portion 4a and the non-fixed portion 4b. Due to the presence of such reinforcing material 21, the angle θb at which the non-fixed portion 4b bends with respect to the fixed portion 4a is maintained at an obtuse angle. The reinforcing material 21 can be formed with a material, thickness, area, shape, etc. that can be deformed within a range in which the angle θb at which the non-fixed portion 4b bends with respect to the fixed portion 4a can be maintained at an obtuse angle.
In this manner, the imaging unit 400 according to the present embodiment is configured.

In recent years, digital cameras have been equipped with image stabilization units that move the image sensor itself to correct camera shake. Image stabilization units are subject to not only conventional static loads, but also superimposed dynamic loads in the planar XY directions and the rotational θ direction during image stabilization, such as vibration. For this reason, the flexible wiring board connecting the rigid wiring board mounting the image sensor and the rigid wiring board mounting the image processing LSI is required to have flexibility that does not impede the operation of the image stabilization unit, and to have bonding strength that can withstand repeated loads.

In contrast, in the imaging unit 400 according to the present embodiment, as described above, the reinforcing material 21 is provided in the connection portion 19 so as to continuously cover both the end portion of the solder 11 on the coverlay 3 side and the end portion of the coverlay 3 on the solder 11 side. The reinforcing material 21 thus provided can locally increase the rigidity of the connection portion 19 between the flexible wiring board 4 and the printed wiring board 9. Therefore, in this embodiment, the deformation behavior in the vicinity of the connection portion 19 caused when the image stabilization unit 410 is driven can be suppressed to a small value. At the same time, in this embodiment, the bending angle θb of the flexible wiring board 4 during driving can be maintained at an obtuse angle, so that the load on the connection portion 19 can be reduced. Furthermore, in this embodiment, the connection portion 19 is only locally increased in rigidity and reinforced, and the entire flexible wiring board 4 is not reinforced, so that the flexibility of the flexible wiring board 4 is not impaired. Therefore, according to this embodiment, it is possible to reduce the load on the connection portion 19 without impeding the operation of the image stabilization unit 410.

In this way, according to this embodiment, it is possible to reduce the load generated at the connection portion 19 between the flexible wiring board 4 and the printed wiring board 9 without compromising the flexibility of the flexible wiring board 4.

Note that, although FIG. 1 shows a case where the reinforcing material 21 is provided only on both ends in the width direction along the Y direction of the flexible wiring board 4, this is not limited to this. The reinforcing material 21 may be provided over the entire width direction, or may be provided so as to extend from the flexible wiring board 4 onto the printed wiring board 9 in the width direction of the flexible wiring board 4.

2 and 3 show a case where the reinforcing material 21 is provided to cover the end portion of the solder 11 on the coverlay 3 side, but this is not limited to the case. The reinforcing material 21 may be provided to cover one end portion of the flexible wiring board 4, or may be provided to extend from the flexible wiring board 4 onto the solder resist layer 8 of the printed wiring board 9.

[Second embodiment]
Next, an imaging unit 400 according to a second embodiment will be described with reference to Figures 4, 5, and 6. Figure 4 is a schematic top view showing the general configuration of the imaging unit 400 according to this embodiment. Figure 5 is a schematic cross-sectional view showing the general configuration of the imaging unit 400 according to this embodiment, showing a cross section along line B-B' in Figure 4. Figure 6 is a schematic cross-sectional view showing an enlarged view of a connection portion 19 between the flexible wiring board 4 and the printed wiring board 9 of the imaging unit 400 according to this embodiment, showing an enlarged view of the connection portion 19 in Figure 5.

In this embodiment, the manner in which the flexible wiring board 4 is arranged relative to the printed wiring board 9 is different from that of the first embodiment. The rest of the configuration is the same as in the first embodiment, so a description of the similar configuration will be omitted.

In the first embodiment, the flexible wiring board 4 was arranged so that its other end, opposite to the end on the connection portion 19 side, extended without bending in the +X direction on the side of the image processing unit (not shown), which is the connection destination to which the other end is connected.

In contrast, in this embodiment, the flexible wiring board 4 is arranged to extend from the connection portion 19 in the -X direction opposite to the +X direction of the image processing unit (not shown) to which the other end is connected. Furthermore, the flexible wiring board 4 extending in the -X direction is bent on the printed wiring board 9 in the +X direction of the image processing unit.

That is, in this embodiment, as shown in FIG. 4, FIG. 5, and FIG. 6, the first electrode 5 of the flexible wiring board 4 is connected to the second electrode 10 via the solder 11 so that one end of the flexible wiring board 4 faces the +X direction opposite to that of the first embodiment, and is connected to the printed wiring board 9. Furthermore, the flexible wiring board 4 is in a bent state in which it is folded back once from the side opposite the image stabilization unit 410 to the side of the image stabilization unit 410 so that the other end of the flexible wiring board 4 is located on the side of the image stabilization unit 410 and the image processing unit to which it is connected. Thus, in this embodiment, the flexible wiring board 4 is folded back and bent from the side opposite the image stabilization unit 410 and the image processing unit to the side of the image stabilization unit 410 and the image processing unit.

In this embodiment, the reinforcing material 21 is provided on the flexible wiring board 4 folded back as described above, similarly to the first embodiment.
In this manner, in the present embodiment, the flexible wiring board 4 is in a bent state. In the present embodiment, the reinforcing material 21 is provided on the flexible wiring board 4 in a bent state, as in the first embodiment. Therefore, according to the present embodiment as well, it is possible to reduce the load acting on the connection portion 19 between the flexible wiring board 4 and the printed wiring board 9 without impairing the flexibility of the flexible wiring board 4.

Note that, although FIG. 4 shows a case where the reinforcing material 21 is provided only on both ends in the width direction along the Y direction of the flexible wiring board 4, this is not limited to this. The reinforcing material 21 may be provided over the entire width direction, or may be provided so as to extend from the flexible wiring board 4 onto the printed wiring board 9 in the width direction of the flexible wiring board 4.

5 and 6 show a case where the reinforcing material 21 is provided to cover the end portion of the solder 11 on the coverlay 3 side, but this is not limited to the case. The reinforcing material 21 may be provided to cover one end portion of the flexible wiring board 4, or may extend from the flexible wiring board 4 onto the solder resist layer 8 of the printed wiring board 9.

In this embodiment, the number of flexible wiring boards 4 may be two or more, not just one. Furthermore, the connection position between the flexible wiring board 4 and the printed wiring board 9 is not limited to the center of the printed wiring board 9, but may be an edge of the printed wiring board 9. Furthermore, when multiple flexible wiring boards 4 are mounted, their positions may be, for example, one at the center of the printed wiring board 9 and one at an edge of the printed wiring board 9.

[Third embodiment]
Next, an imaging unit 400 according to a third embodiment will be described with reference to Figures 7, 8, and 9. Figure 7 is a schematic top view showing the general configuration of the imaging unit 400 according to this embodiment. Figure 8 is a schematic cross-sectional view showing the general configuration of the imaging unit 400 according to this embodiment, showing a cross section along line CC' in Figure 7. Figure 8 is a schematic cross-sectional view showing an enlarged view of a connection portion 19 between the flexible wiring board 4 and the printed wiring board 9 of the imaging unit 400 according to this embodiment, showing an enlarged view of the connection portion 19 in Figure 7.

In this embodiment, the area where the reinforcing material 21 is provided is different from that of the second embodiment. The rest of the configuration is the same as that of the second embodiment, so a description of the similar configuration will be omitted.

That is, in this embodiment, as shown in FIG. 7, the reinforcing material 21 is provided in an area wider than the width of the flexible wiring board 4 across the entire width (short side) of the flexible wiring board 4 along the Y direction. That is, the reinforcing material 21 is provided protruding from above the flexible base material 1 of the flexible wiring board 4 onto the solder resist layer 8 of the printed wiring board 9 in the width direction of the flexible wiring board 4.

In this embodiment, as shown in Figures 7, 8, and 9, the reinforcing material 21 is applied in the longitudinal direction of the flexible wiring board 4 along the X direction, beyond one end of the connection portion 19 side of the flexible wiring board 4, and onto the solder resist layer 8. That is, the reinforcing material 21 is provided so as to extend from the flexible base material 1 of the flexible wiring board 4 onto the solder resist layer 8 of the printed wiring board 9 in the longitudinal direction of the flexible wiring board 4.

In this embodiment, the reinforcing material 21 provided as described above can reduce the load on the connection 19 between the flexible wiring board 4 and the printed wiring board 9 without impairing the flexibility of the flexible wiring board 4. By changing the area in which the reinforcing material 21 is provided, the degree of localized stiffness of the connection 19 can be adjusted, and the load on the connection 19 can be reduced according to the flexibility required for the flexible wiring board 4.

In the first embodiment, the reinforcing material 21 can be provided in the same area as in this embodiment.

The reinforcing material 21 may extend from above the flexible base material 1 of the flexible wiring board 4 to above the solder resist layer 8 of the printed wiring board 9 in either the width direction or the length direction of the flexible wiring board 4.

[Fourth embodiment]
Next, an electronic device according to a fourth embodiment will be described with reference to Fig. 10. Fig. 10 is a schematic diagram showing a schematic configuration of an image capture device as an example of an electronic device according to this embodiment.

A digital camera (camera) 100 serving as an imaging device, which is an example of an electronic device according to this embodiment, is, for example, a digital single-lens reflex camera. As shown in FIG. 10, the camera 100 comprises a camera body 200 and an interchangeable lens 300 (lens barrel) 300 that is detachable from the camera body 200. In FIG. 10, the interchangeable lens 300 is attached to the camera body 200. Below, a case where the interchangeable lens 300 is attached to the camera body 200 to constitute the camera 100 serving as an imaging device will be described.

The camera body 200 includes a housing 201, and a mirror 222, a shutter 223, an imaging unit 400 which is a printed circuit board, and an image processing circuit 224, which are arranged inside the housing 201. The camera body 200 also includes a liquid crystal display 225 which is fixed to the housing 201 so as to be exposed to the outside.

The imaging unit 400 has the configuration described in the first to third embodiments above, and includes an image stabilization unit 410, an imaging sensor module 14 with a printed wiring board 9, and a flexible wiring board 4.

The interchangeable lens 300 has a housing 301, which is an interchangeable lens housing, and an imaging optical system 311. The imaging optical system 311 is disposed inside the housing 301, and forms a light image on the imaging sensor module 14 when the housing 301 (interchangeable lens 300) is attached to the housing 201. The imaging optical system 311 is configured to have multiple lenses.

The housing 301 of the interchangeable lens 300 has a lens side mount 301a with an opening formed therein. On the other hand, the housing 201 of the camera body 200 has a camera side mount 201a with an opening formed therein. The interchangeable lens 300 (housing 301) is attached to the camera body 200 (housing 201) by fitting the lens side mount 301a and the camera side mount 201a together. Note that the direction of the arrow X shown in FIG. 10 is the optical axis direction of the imaging optical system 311.

Light traveling in the direction of the arrow X by the imaging optical system 311 is guided into the housing 201 through an opening in the lens side mount 301a in the housing 301 and an opening in the camera side mount 201a in the housing 201. Inside the housing 201, a mirror 222, a shutter 223, etc. are provided in front of the imaging unit 400 in the direction of the arrow X along the arrow X.

The imaging sensor element 15 in the imaging sensor module 14 is a solid-state imaging element such as a CMOS image sensor or a CCD image sensor that photoelectrically converts the optical image formed by the imaging optical system 311.

The above constitutes the camera 100, which is an imaging device including the imaging unit 400.

As described above, according to this embodiment, even when the digital single-lens reflex camera 100 is dropped or otherwise impacted, the load on the connection 19 between the flexible wiring board 4 and the printed wiring board 9 can be reduced, thereby improving performance.

In this embodiment, the case where the interchangeable lens 300 is attached to the camera body 200 has been described, but this is not limited to the case. When there is only the camera body 200 without the interchangeable lens 300 attached, the camera body 200 is the imaging device.

In addition, in this embodiment, the camera 100 is described as being separated into the camera body 200 and the interchangeable lens 300, but the camera 100 may be an integrated type in which the lens is built into the camera body 200.

Furthermore, in this embodiment, the camera 100 is described as an imaging device that is an electronic device, but this is not limited to this.

[Example 1]
As the imaging unit of Example 1, an imaging unit 400 according to the first embodiment shown in Figures 1, 2 and 3 was manufactured. In the imaging unit 400 of Example 1, the frame 17 was made of resin and had a thickness of 2 mm. The imaging sensor element 15 was a CMOS image sensor having a rectangular planar shape of 30 mm x 20 mm. The cover glass 16 was a rectangular planar shape of 28 mm x 38 mm.

The flexible wiring board 4 used had a flexible base material 1 and coverlay 3 made of polyimide, and a flexible wiring layer 2 and first electrode 5 made of Cu. The flexible base material 1 had a thickness of 25 μm, the coverlay 3 had a thickness of 12 μm, and the flexible wiring layer 2 had a thickness of 18 μm.

The printed wiring board 9 had a rectangular outer shape of 30 mm x 40 mm, the printed wiring substrate 6 was made of glass epoxy material, and the wiring layer and second electrode 10 were made of Cu. The wiring layer 7 and second electrode 10 had a thickness of about 30 μm, and the solder resist layer 8 had a thickness of about 25 μm. A UV-curable resin was used as the adhesive for fixing the printed wiring board 9 to the metal frame 22. The metal frame 22 had an outer shape of 50 mm x 60 mm.

The first electrode 5 of the flexible wiring board 4 and the second electrode 10 of the printed wiring board 9 were connected by solder 11. The second electrodes 10 had a pitch of 0.2 mm, an electrode width of 0.15 mm, and 80 wires. The opening in the solder resist layer 8 through which the second electrodes 10 were exposed had a size of 1.1 mm x 20 mm. On the other hand, the first electrodes 5 had a pitch of 0.2 mm, an electrode width of 0.15 mm, and 80 wires. The width of the flexible wiring board 4 was 22 mm, which is larger than the opening width of 20 mm in the solder resist layer 8. The electrode pitch, electrode width, width between electrodes, and number of electrodes were appropriately set according to the specifications of the imaging sensor module 14.

The length in the X direction of the exposed portion 24 in the gap between the coverlay 3 and the solder 11 was 1 mm. The solder 11 was made of Sn-3.0-Ag-0.5Cu. The image stabilization unit 410 was an L-shaped unit with a 70 mm x 55 mm rectangle cut out of an 85 mm x 70 mm rectangle.

A UV-curable resin was used as the reinforcing material 21. The reinforcing material 21 had a thickness of 0.5 mm. The reinforcing material 21 was provided at both ends in the width direction of the flexible wiring board 4 when viewed from above. The reinforcing material 21 covered the gap between the coverlay 3 and the solder 11, and was provided so as to cover 0.5 mm from the end of the coverlay 3 in the direction opposite the connection part 19 of the flexible wiring board 4. The reinforcing material 21 was provided so as to cover 0.5 mm from the joint between the flexible wiring layer 2 and the solder 11 in the direction of the connection part 19.

The completed imaging device equipped with the imaging unit 400 of Example 1 was able to fully guarantee the optical performance of the built-in CMOS image sensor.

[Example 2]
As the imaging unit of Example 2, an imaging unit 400 according to the third embodiment shown in Fig. 7, Fig. 8 and Fig. 9 was manufactured. In the imaging unit 400 of Example 2, the flexible wiring board 4 was pulled out to the side opposite the image stabilization unit 410 as shown in Fig. 7 and folded back once. Also, as shown in Fig. 8, the reinforcing region where the reinforcing material 21 was provided was a region wider than the width of the flexible wiring board 4. Furthermore, as shown in Fig. 9, the reinforcing material 21 was applied beyond the tip of the connection portion 19 of the flexible wiring board 4 and onto the solder resist layer 8.

The flexible wiring board 4 used was the same as in Example 1. The printed wiring board 9 used was the same as in Example 1. The reinforcing material 21 used was the same UV-curable resin as in Example 1.

The completed imaging device equipped with the imaging unit 400 of Example 2 was able to fully guarantee the optical performance of the built-in CMOS image sensor. Furthermore, in Example 2, even in a bent state, the flexibility of the flexible wiring board 4 was maintained, and the load generated at the connection portion 19 between the flexible wiring board 4 and the printed wiring board 9 was reduced. Furthermore, in Example 2, the reinforcing material 21 was provided in an area wider than the width of the flexible wiring board 4, so that the load generated not only at the connection portion 19 but also at the flexible base material 1 was reduced.

[Evaluation by structural analysis]
In order to confirm the effect of the present invention, an example will be shown in which a structure including a flexible wiring board 4 and a printed wiring board 9 was simplified and subjected to a structural analysis.

As shown in Figures 11 to 15, structural analysis was performed on Comparative Example 1, in which no reinforcing material 21 was placed on the flexible substrate 1, and Comparative Examples 2, 3, 4, and Example 3, in which the reinforcing material 21 was placed in different locations on the flexible substrate 1.

That is, FIG. 11 is a schematic diagram showing a structure in which a flexible wiring board 4 is connected to a printed wiring board 9 using solder 11 as Comparative Example 1. FIG. 12 is a schematic diagram showing a structure in which, in addition to Comparative Example 1, a reinforcing material 21 is arranged at a location including the end of the solder 11 on the coverlay 3 side and not including the end of the coverlay 3 on the solder 11 side. FIG. 13 is a schematic diagram showing a structure in which, in addition to Comparative Example 1, a reinforcing material 21 is arranged at a location including the end of the solder 11 on the coverlay 3 side and not including the end of the coverlay 3 on the solder 11 side. FIG. 14 is a schematic diagram showing a structure in which, in addition to Comparative Example 1, a reinforcing material 21 is arranged intermittently at a location including the end of the solder 11 on the coverlay 3 side and at a location including the end of the coverlay 3 on the solder 11 side.

On the other hand, FIG. 15 is a schematic diagram showing a structure of Example 3 in which, in contrast to Comparative Example 1, the reinforcing material 21 is continuously arranged at a location including the end of the solder 11 on the coverlay 3 side and at a location including the end of the coverlay 3 on the solder 11 side.

The structural analysis method used in the evaluation is explained below. The structural analysis software used was ANSYS Mechanical Enterprise Version 19.1. The structural analysis was performed in three dimensions.

The dimensions used in the structural analysis are explained below. The printed wiring board 9 was 2.5 mm long, 1 mm wide, and 0.8 mm thick. The solder 11 was 1 mm long from a point 0.75 mm from the end face of the printed wiring board 9 in the X direction, and 0.1 mm long from a point 0.45 mm from the end face of the printed wiring board 9 in the Y direction, and the solder height in the Z direction was 50 μm. The flexible wiring board 4 was modeled for each layer. The flexible wiring layer 2 was 2 mm long from the end face of the solder 11 in the X direction, 0.1 mm long in the Y direction like the solder 11, and 20 μm thick in the Z direction. The flexible substrate 1 was stacked in the +Z direction with respect to the flexible wiring layer 2, and the thickness in the Z direction was 20 μm. The coverlay 3 is laminated in the -Z direction relative to the flexible wiring layer 2, has a length of 0.9 mm from a point 1.1 mm from the end face of the flexible wiring layer 2 in the X direction, and has a thickness of 20 μm in the -Z direction. In other words, the length in the X direction of the exposed portion 24 of the flexible wiring layer 2, which is the gap between the solder 11 and the coverlay 3, is 0.1 mm.

The reinforcing material 21 is a cured product of epoxy resin, laminated on the flexible substrate 1, and has a thickness of 20 μm. In Comparative Example 2, the length of the reinforcing material 21 in the X direction is 10 μm in each of the ±X directions, totaling 20 μm, with the end of the solder 11 on the coverlay 3 side as the center, and the length in the Y direction is the same as that of the solder 11. In Comparative Example 3, the length of the reinforcing material 21 in the X direction is 10 μm in each of the ±X directions, totaling 20 μm, with the end of the solder 11 on the coverlay 3 as the center, and the length in the Y direction is the same as that of the solder 11. In Comparative Example 4, the reinforcing material 21 is disposed at the same location as Comparative Examples 2 and 3 at the same time. In Example 3, the length of the reinforcing material 21 in the X direction is 0.12 mm, from a position 10 μm in the -X direction from the end of the solder 11 on the coverlay 3 side to a position 10 μm in the +X direction from the end of the solder 11 on the coverlay 3 side, and the length in the Y direction is the same as that of the solder 11.

The conditions for the structural analysis are as follows. In the printed wiring board 9, the nodal displacement on the back surface, which is the surface in the -Z direction that is not connected to the flexible wiring board 4, was set to 0 in all of the X, Y, and Z directions. Furthermore, the end opposite the connection portion 19 of the flexible wiring board 4 was set to area A, and the plane of area A was set to a displacement of 0.1 mm in the +Z direction. Structural analysis was performed under the above conditions for all of the comparative examples 1, 2, 3, 4, and example 3.

The evaluation standard was the maximum value of equivalent stress in the non-covered area of the flexible wiring layer 2, which is the area where the solder 11 and the coverlay 3 are not connected. A structural analysis was performed under the above conditions, and the stress values generated in the flexible wiring layer 2 were compared. Figure 16 shows the results of the stress analysis by the structural analysis. In Figure 16, the evaluation axis is the stress ratio, where the stress value of Comparative Example 1 is set to a reference value of 100%.

As shown in FIG. 16, in Example 3, the stress can be reduced by about 20% compared to Comparative Examples 1, 2, 3, and 4. From the results shown in FIG. 16, it can be seen that if the reinforcing material 21 is placed in a location that includes only the end portion of the solder 11 on the coverlay 3 side, as in Comparative Example 2, the reinforcing material 21 does not have a reinforcing effect. It can also be seen that if the reinforcing material 21 is placed in a location that includes only the end portion of the coverlay 3 on the solder 11 side, as in Comparative Example 3, the reinforcing material 21 does not have a reinforcing effect. Furthermore, it can be seen that even if the reinforcing material 21 is placed in a location that includes both end portions, as in Comparative Example 4, the reinforcing material 21 is placed intermittently, and the reinforcing material 21 does not have a reinforcing effect.

Next, in order to confirm the effect of the covering length of the reinforcing material 21 of the present invention, the longitudinal length L1 of the coverlay 3 and the covering length L2 of the reinforcing material 21 in FIG. 15 were changed and structural analysis was performed. The longitudinal length L1 of the coverlay 3 is the length from one end of the coverlay 3 on the solder 11 side to the opposite end in the longitudinal direction of the flexible wiring board 4 along the X direction. The covering length L2 of the reinforcing material 21 is the length of the portion of the reinforcing material 21 that continuously covers the end of the solder 11 on the coverlay 3 side and the end of the coverlay 3 on the solder 11 side in the longitudinal direction, covering the coverlay 3 in the +X direction from one end of the coverlay 3 on the solder 11 side.

As shown in Table 1 below, the effect of reinforcement when length L1 and covering length L2 were changed was verified by structural analysis. The units of length L1 and covering length L2 in Table 1 are mm. Table 1 also shows the coverage ratio L2/L1, which is the ratio of covering length L2 to length L1. The structural analysis method and evaluation criteria are the same as those described above. In addition, when comparing stress values, the stress value when reinforcing material 21 was not placed in Examples 4, 5, and 6 was set to 100% of the reference value. The results are shown in Figure 17. As a result of performing structural analysis under these conditions, in Examples 4, 5, and 6, the effect of reinforcement was obtained regardless of the value of coverage ratio L2/L1, but a particularly significant effect of reinforcement was obtained when coverage ratio L2/L1 was less than 0.4.

From the above, it has been confirmed that the present invention can reduce the load generated at the connection portion 19 between the flexible wiring board 4 and the printed wiring board 9 without impairing the flexibility of the flexible wiring board 4.

REFERENCE SIGNS LIST 1 Flexible substrate 2 Flexible wiring layer 3 Coverlay 4 Flexible wiring board 5 First electrode 6 Printed wiring substrate 7 Wiring layer 8 Solder resist layer 9 Printed wiring board 10 Second electrode 11 Solder 13 Via 14 Image sensor module 15 Image sensor element 16 Cover glass 17 Frame 18 Metal wire 19 Connection portion 21 Reinforcement material 22 Metal frame 23 Wire pad 24 Exposed portion 400 Image sensor unit

Claims (20)

a printed wiring board on which an imaging element is provided and which has a first electrode on a main surface;
a flexible wiring board having a base material having a first surface and a second surface, a conductor layer provided on the base material on the side of the first surface, and an insulating layer provided on the conductor layer, the conductor layer having a first region between the base material and the insulating layer, the conductor layer further having a second electrode that is not provided between the base material and the insulating layer;
a conductive connecting member connecting the first electrode and the second electrode and contacting a second region of the second electrode;
a reinforcing member provided on the base material on the second surface side,
the reinforcing material continuously covers a first portion of the flexible wiring board and a second portion of the flexible wiring board, the first portion includes the second region of the second electrode, and the second portion includes the first region of the conductor layer,
an imaging unit, characterized in that the first portion and the second portion overlap the main surface of the printed wiring board in a direction perpendicular to the main surface , and the second portion is bent in a direction away from the printed wiring board relative to the first portion. The imaging unit according to claim 1 , wherein the angle at which the second portion is bent with respect to the first portion is an obtuse angle. 3 . The imaging unit according to claim 1 , wherein the second electrode is exposed between an end portion of the insulating layer close to the second electrode and the conductive connecting material. 4 . The imaging unit according to claim 1 , wherein the reinforcing material is provided on both ends of the base material in a short-side direction of the flexible wiring board. 5. The imaging unit according to claim 1, wherein the reinforcing material is provided so as to protrude from above the base material onto above the printed wiring board in the longitudinal direction of the flexible wiring board. The imaging unit according to claim 1 , wherein the reinforcing material is provided so as to protrude from above the base material onto the printed wiring board in the short-side direction of the flexible wiring board. 7. The imaging unit according to claim 1, wherein a ratio of a length of the portion of the reinforcing material that covers the insulating layer to a length in a longitudinal direction of the insulating layer is smaller than 0.4. an image sensor module having the printed wiring board;
8. The imaging unit according to claim 1, further comprising: an image stabilization unit that movably supports the imaging sensor module. The imaging unit according to any one of claims 1 to 8, characterized in that the flexible wiring board extends in a second direction opposite to a first direction on a connection destination side to which the other end portion is connected with respect to a connection portion where the first electrode and the second electrode are connected by the conductive connecting material, and then is bent in the first direction. 10. The imaging unit according to claim 1, wherein the reinforcing material is a hardened product of an epoxy resin, an ultraviolet-curable resin, or a thermosetting resin. 11. The imaging unit according to claim 1 , wherein the insulating layer has a portion located between the reinforcing material and the printed wiring board . 12. The imaging unit according to claim 1, wherein the reinforcing material covers an end portion of the insulating layer closer to the second electrode and an end portion of the conductive connecting material closer to the insulating layer. The imaging unit according to claim 1 , wherein the reinforcing material is a resin that is in contact with the base material. The imaging unit according to claim 1 , wherein the reinforcing material is in contact with the conductive connecting material. 15. The imaging unit according to claim 1, wherein the conductive connecting material is solder. 16. The imaging unit according to claim 1, wherein the printed wiring board has a solder resist layer on the main surface, and the reinforcing material is in contact with the solder resist layer. 17. The imaging unit according to claim 1, wherein the first portion of the flexible wiring board is disposed between a third portion of the flexible wiring board and the main surface of the printed wiring board. 18. The imaging unit according to claim 17, wherein the third portion includes the first region of the conductor layer, and the third portion is not disposed between the reinforcing material and the main surface of the printed wiring board. An imaging device including a housing and an imaging unit inside the housing,
19. An imaging device, wherein the imaging unit is an imaging unit according to claim 1. The imaging device according to claim 19 , wherein the flexible wiring board has a portion that does not overlap the main surface in a direction perpendicular to the main surface of the printed wiring board .

Images