JP4362931B2 - Solid-state imaging device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a solid-state imaging device, and more particularly to a solid-state imaging device in which a hollow portion is provided on an imaging region.
[0002]
[Prior art]
In general, in a solid-state imaging device, an on-chip lens is provided on a light receiving surface in an imaging region in order to improve sensitivity, and incident light is concentrated on the light receiving surface so as to efficiently collect light. In such a solid-state imaging device, the upper part of the imaging region has a hollow structure in order to maintain sensitivity during imaging.
[0003]
As such a solid-state imaging device, conventionally, for example, the one shown in the plan view of FIG. 4A and the cross-sectional view of FIG. 4B is known. The solid-state imaging device shown in these drawings includes an element substrate 1, a flexible printed circuit board (hereinafter referred to as a flexible substrate) 2, and a transparent substrate 3.
[0004]
The element substrate 1 has an imaging region (for example, a CCD area sensor) 11 in which light receiving sensors are arrayed on the surface side, and electrode pads 12 are arrayed around the imaging region 11. A protruding electrode 13 (shown only in a sectional view) such as an Au (gold) ball bump is formed thereon.
[0005]
Further, the flexible substrate 2 is provided with a wiring 21 (shown only in a sectional view) on a flexible insulating film, and particularly has an opening 22 corresponding to the imaging region 11 of the element substrate 1. Yes. The wiring 21 is formed by, for example, performing Ni (nickel) plating or Au plating on a Cu wiring. This flexible substrate 2 is in a state where one end of the wiring 21 is electrically and mechanically connected to the protruding electrode 13 via a conductive paste 4 (shown only in a sectional view) such as a thermosetting Ag paste, for example. The opening 22 is disposed to face the imaging region 11. In addition, one end side of the flexible substrate 2 extends outside the element substrate 1, and the other end side of the wiring 21 serves as an external lead for connection with an external circuit substrate that performs signal processing. Is also extended outward.
[0006]
The transparent substrate 3 is disposed so as to face the imaging region 11 of the element substrate 1 so as to close the opening 22 of the flexible substrate 2, thereby forming a hollow portion a on the imaging region 11. The transparent substrate 3 is made of, for example, optical glass, and is attached to the entire surface excluding the opening 22 of the flexible substrate 2 via an adhesive (for example, a thermosetting epoxy resin) 5.
[0007]
Furthermore, in order to seal the hollow part a formed between the element substrate 1 and the transparent substrate 3, the entire periphery of the opening 22 is sealed between the element substrate 1 and the flexible substrate 2. Resin (for example, thermosetting epoxy resin) 6 is filled, and further, the sealing resin 6 is filled on the transparent substrate 3 so as to cover the outer periphery of the flexible substrate 2.
[0008]
In the solid-state imaging device configured as described above, since the inside of the hollow portion a is sealed, it is possible to prevent the occurrence of condensation due to the ingress of moisture into the hollow portion a.
[0009]
[Problems to be solved by the invention]
However, in the solid-state imaging device having the configuration described with reference to FIG. 4, due to changes in the external environment (for example, increase in temperature and humidity), the internal pressure of the hollow portion a in the sealed state increases and the sealing resin 6 is heated. Inflate. As a result, as indicated by the arrows in the cross-sectional view, stress is applied to the element substrate 1 and the transparent substrate 3 in the direction of pushing them outward. (Hereinafter referred to as peeling stress) occurs.
[0010]
In particular, as shown in the enlarged cross-sectional view of the main part of FIG. 5, the connection area between the protruding electrode 13 and the wiring 21 that is usually formed to have a diameter of about 60 μm to 80 μm has a small adhesion area between the conductive paste 4 and Peeling is likely to occur when the peeling stress is repeatedly applied. In particular, between the conductive paste 4 and the wiring 21, the surface of the copper wiring is subjected to Ni plating or Au plating as compared with the wettability of the conductive paste 4 to the protruding electrode 13 such as an Au bump. For the reason that the wettability of the conductive paste 4 with respect to the wiring 21 is inferior, peeling is likely to occur when the peeling stress is applied.
[0011]
For this reason, the connection state between the electrode pad 12 of the element substrate 1 and the wiring 21 of the flexible substrate 2 becomes unstable under a severe use environment, and there is a problem that long-term reliability of the solid-state imaging device cannot be obtained. .
[0012]
Accordingly, an object of the present invention is to provide a solid-state imaging device that can ensure a stable connection state between an electrode pad of an element substrate and a wiring on a flexible substrate for a long period of time regardless of an external environment.
[0013]
[Means for Solving the Problems]
In order to achieve such an object, the solid-state imaging device of the present invention has a wiring between an element substrate provided with an electrode pad around the imaging region and a transparent substrate arranged facing the imaging region side. A flexible substrate on which is formed is sandwiched. The flexible substrate disposed in a state where the wiring is connected to the electrode pads of the element substrate is provided with an opening facing the imaging region, thereby forming a hollow portion in the opening. Further, the flexible substrate and the transparent substrate are bonded by an adhesive, and a sealing resin is filled between the element substrate and the transparent substrate around the opening. In particular, the adhesive between the flexible substrate and the transparent substrate is characterized in that it is provided on the outer peripheral side with respect to the pad region where the electrode pads are arranged.
[0014]
In the solid-state imaging device having such a configuration, only the flexible substrate portion corresponding to the outer peripheral side of the pad region in the element substrate is bonded to the transparent substrate by the adhesive, and the flexible substrate portion corresponding to the opening side from the pad region is the transparent substrate. It is in a state of being bonded only to the element substrate side without being bonded to the element. For this reason, due to a change in the external environment, the internal pressure of the hollow portion formed between the element substrate and the transparent substrate increases or the sealing resin expands, causing a stress that pushes the element substrate and the transparent substrate outward. In this case, the flexible substrate is curved so that the flexible substrate portion corresponding to the pad region follows the element substrate side. Then, the peeling stress applied to the portion corresponding to the pad region is released by this curvature. Therefore, no peeling stress is applied to the connection portion between the wiring on the flexible substrate and the electrode pad on the surface of the element substrate, and the connection state between the wiring and the electrode pad is ensured.
[0015]
In the solid-state imaging device having the above-described configuration, the flexible substrate may be provided with a cut portion along the pad region from the inner peripheral side of the opening.
[0016]
By providing such a cut portion, the flexibility of the flexible substrate portion corresponding to the pad region is improved.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the solid-state imaging device of the present invention will be described in detail with reference to the drawings. In addition, the same code | symbol is attached | subjected to the same structural member demonstrated using FIG.4 and FIG.5 in the prior art, and the overlapping description is abbreviate | omitted.
[0018]
(First embodiment)
FIG. 1A is a plan view in which a part of the solid-state imaging device of the first embodiment is cut out, and FIG. 1B is a cross-sectional view corresponding to the AA ′ portion. FIG. 2 is an enlarged cross-sectional view of a main part in the cross-sectional view of FIG.
[0019]
The solid-state imaging device shown in FIG. 1 and FIG. 2 includes an element substrate 1 having an electrode pad 12 and a protruding electrode 13 around the imaging region 11, a wiring 21, and an opening 22, as in the conventional solid-state imaging device. A flexible substrate 2 and a transparent substrate 3 are provided, and a hollow portion a is provided on the imaging region 11. Further, the protruding electrode 13 and the wiring 21 are electrically and mechanically connected by the conductive paste 4, and the flexible substrate 2 and the transparent substrate 3 are bonded by an adhesive 5 ′. Further, a seal is formed on the transparent substrate 3 so as to cover the periphery of the opening 22 between the element substrate 1 and the transparent substrate 3, that is, between the element substrate 1 and the flexible substrate 2 and the outer periphery of the flexible substrate 2. A stop resin 6 is filled.
[0020]
The difference between the solid-state imaging device shown in these drawings and the solid-state imaging device shown in FIGS. 4 and 5 is the arrangement state of the adhesive 5 ′. That is, the adhesive 5 ′ for bonding the flexible substrate 2 and the transparent substrate 3 is provided on the outer peripheral side of the pad region 14 where the electrode pads 12 of the element substrate 1 are provided. The pad region 14 is a region in which a plurality of electrode pads are arranged.
[0021]
For example, as shown in the plan view of FIG. 1A, when a plurality of electrode pads 12 are arranged on each side of the imaging region 11, one side of each of the imaging region 11 is defined as a pad region 14. The adhesive 5 ′ is continuously provided between the transparent substrate 3 and the flexible substrate 2 over the entire periphery of the opening a on the outer peripheral side of the pad region 14. That is, the flexible substrate 2 portion extending from the inner periphery of the opening a to the pad region 14 is bonded only to the element substrate 1 side by the sealing resin 6 and the conductive paste 4 without being bonded to the transparent substrate 3. Will be. However, it is assumed that the width of each part of the adhesive 5 ′ is maintained to such an extent that the adhesive force between the transparent substrate 3 and the flexible substrate 2 is ensured.
[0022]
Further, this solid-state imaging device is designed so that the planar space W between the electrode pad 12 and the adhesive 5 ′ is maintained at about 100 μm. Make sure that the agent 5 'does not overlap.
[0023]
According to the solid-state imaging device having such a configuration, only the portion of the flexible substrate 2 corresponding to the outer peripheral side of the pad region 14 where the electrode pad 12 is disposed is bonded to the transparent substrate 3 by the adhesive 5 ′. The flexible substrate 2 corresponding to the opening 22 side is bonded only to the element substrate 1 side. For this reason, the internal pressure of the hollow part a rises due to a change in the external environment or the sealing resin 6 is thermally expanded, so that the element substrate 1 and the transparent substrate 3 are pushed outward as indicated by arrows in the sectional view. When a large stress is generated, the flexible substrate 2 is curved so that the flexible substrate 2 corresponding to the pad region 14 follows the element substrate 1 side as shown in FIG.
[0024]
Therefore, in the portion corresponding to the pad region 14, the peeling stress applied to each member due to the generation of the stress is released due to the bending of the flexible substrate 2, and the conductive paste 4 having a small adhesion area and a weak adhesion force. It is possible to prevent peeling stress from being applied. As a result, the connection state between the wiring 21 and the protruding electrode 13 connected via the conductive paste 4 is stabilized, and the connection state between the flexible substrate 2 and the element substrate 1 can be secured.
[0025]
In particular, the conductive paste 4 is inferior in the wettability of the conductive paste 4 to the protruding electrode 13 such as an Au bump for the wiring 21 in which the surface of the copper wiring is subjected to Ni plating or Au plating. -Separation was likely to occur between the wirings 21 due to the above-described peeling stress. However, since the peeling stress is prevented from being applied to the conductive paste 4, the connection state between the conductive paste 4 and the wiring 21 can be secured, and as a result, the connection state between the wiring 21 and the electrode pad 12 is stabilized. It becomes possible. As a result, it is possible to improve the long-term reliability of the solid-state imaging device regardless of the use environment.
[0026]
(Second Embodiment)
FIG. 3 is a partially cutaway plan view showing the configuration of the solid-state imaging device of the second embodiment. The difference between the solid-state imaging device shown in this figure and the solid-state imaging device of the first embodiment is in the configuration of the flexible substrate 2 ′, and the other configurations are the same.
[0027]
That is, the flexible substrate 2 ′ of the solid-state imaging device shown in this figure has a configuration in which the cut portion 23 is provided in the flexible substrate (2) of the first embodiment. The cut portion 23 is provided with a length that reaches the portion where the adhesive 5 ′ is provided along the pad region 14 from the inner peripheral side of the opening 22. For this reason, a total of four cut portions 23 are provided on each end of each of the two rows of pad regions 14 in the flexible substrate 2 ′.
[0028]
The cut portion 23 may have a width or may not have a width.
[0029]
In the solid-state imaging device having such a configuration, by providing the cut portion 23 along the pad area 14, the flexibility of the flexible substrate 2 ′ corresponding to the pad area 14 is improved. For this reason, when compared with the solid-state imaging device of the first embodiment, the hollow portion a and the sealing resin 6 expand due to a change in the external environment, resulting in a stress that pushes the element substrate 1 and the transparent substrate 3 outward. The peeling stress applied to the portion corresponding to the pad region 14 can be more easily released. Therefore, it is possible to stabilize the connection state between the element substrate 1 and the flexible substrate 2 more reliably than in the first embodiment.
[0030]
In the first embodiment and the second embodiment described above, the case where the pad areas 14 are provided on both sides of the imaging area 11 has been described. However, the solid-state imaging device of the present invention is not limited to this. For example, the solid-state imaging device in which the pad area 14 is arranged over the entire circumference of the imaging area 11 or the pad area 14 on one side of the imaging area 11. The present invention can also be widely applied to solid-state imaging devices in which are arranged. In this case, the adhesive 5 ′ is provided outside the pad regions 14, and when the cut portions 23 are provided, the cut portions 23 are provided in the respective portions along the pad regions 14.
[0031]
【The invention's effect】
As described above, according to the solid-state imaging device of the present invention, in the solid-state imaging device provided with the hollow portion on the imaging region, the element substrate is formed by increasing the internal pressure of the hollow portion or expanding the surrounding sealing resin. When the stress that pushes the substrate and the transparent substrate to the outside occurs, the flexible substrate can be curved so that the flexible substrate portion corresponding to the pad area of the element substrate follows the element substrate side. It is possible to prevent the peeling stress from being applied between the electrode pad on the surface of the element substrate and the connection between the wiring and the electrode pad. As a result, it is possible to ensure a stable connection state between the electrode pads of the element substrate and the wiring of the flexible substrate regardless of the external environment, and it is possible to provide a solid-state imaging device with high long-term reliability even under severe use environments. .
[Brief description of the drawings]
1A and 1B are a plan view and a cross-sectional view illustrating a configuration of a solid-state imaging device according to a first embodiment.
FIG. 2 is an enlarged cross-sectional view of a main part for explaining the configuration of the solid-state imaging device according to the embodiment.
FIG. 3 is a plan view for explaining a configuration of a solid-state imaging apparatus according to a second embodiment.
4A and 4B are a plan view and a cross-sectional view for explaining a configuration of a conventional solid-state imaging device.
FIG. 5 is an enlarged cross-sectional view of a main part for explaining a conventional problem.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Element substrate 2, 2 '... Flexible substrate, 3 ... Support substrate, 5 ... Adhesive, 6 ... Sealing resin, 11 ... Imaging region, 12 ... Electrode pad, 14 ... Pad region, 21 ... Wiring, 22 ... Opening, 23 ... notch, a ... hollow

Claims (4)

An element substrate provided with an electrode pad around the imaging region;
A flexible printed wiring board having an opening facing the imaging region in a state where the wiring on the front side is connected to the electrode pad; and
A transparent substrate that is disposed facing the imaging region side of the element substrate in a state of making the inside of the opening hollow and is attached to the back side of the flexible printed wiring board via an adhesive;
A sealing resin filled between the element substrate and the transparent substrate around the opening ;
The adhesive between the flexible printed wiring board and the transparent substrate is provided, et al is on the outer peripheral side of the electrode pads are disposed pad area,
A solid-state imaging device, wherein the flexible printed wiring board is provided with a cut portion along the pad region from an inner peripheral side of the opening .   The cut portion is provided on both end sides of the pad region.
  The solid-state imaging device according to claim 1.   Protruding electrodes are provided on the electrode pads in the element substrate,
  The wiring of the flexible printed wiring board and the protruding electrode are electrically and mechanically connected by a conductive paste.
  The solid-state imaging device according to claim 1 or 2.   A sealing resin is filled between the element substrate and the flexible printed circuit board around the opening of the flexible printed circuit board.
  The solid-state imaging device according to claim 1.

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