JPH05175472A - Solid-state image sensing device - Google Patents

Abstract

PURPOSE:To provide a small-sized face down-based solid-state image sensing device which is free of image effects induced by the reflection of light on its side no matter how large a board is adopted and no matter what focal distance is adopted for a lens. CONSTITUTION:In a solid state-image sensing device which is provided with a glass board 10 where a thick film wiring 11 is installed based on a screen print on a main plane and a solid-state image sensing element 20 where a light received plane side is mounted on the main plane where the thick film wiring 11 of the board 10 is formed by way of a soldered bump 31, the sides of the board 10 which exclude its light incident plane and light emission plane, are machined unevenly so that a center line average roughness Ra of the sides is set to the range of 0.05<=Ra<=5mum.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid-state image pickup device used for a video camera, an electronic still camera and the like, and more particularly to a solid-state image pickup device with improved mounting technology for a solid-state image pickup element chip.

[0002]

2. Description of the Related Art Conventionally, in this type of solid-state image pickup device, a solid-state image pickup element chip 2 is arranged in a ceramic package 1 as shown in FIG. 6, and electrical connection is made by a bonding wire 3. In addition, the solid-state image sensor chip 2
In order to protect the above, the cover glass 4 is generally adhered and fixed on the package 1 with an adhesive or the like, and then sealed.

However, in the above method, the pad portion for wire bonding and the portion for fixing the cover glass are indispensable, and these have determined the size of the entire package. Therefore, when compared in the image pickup plane direction, the package has to be considerably larger than the solid-state image pickup element chip, and the whole solid-state image pickup device becomes large.

To solve these problems, Japanese Unexamined Patent Publication No.
2-8664 and Japanese Unexamined Patent Publication No. 62-8665 disclose a method of mounting a solid-state image sensor chip on a light-transmissive substrate face down using bumps and connecting it to an external circuit on the side surface of the substrate. Proposed.

FIG. 7 shows a sectional view of an example of a solid-state image pickup device by face-down mounting. Solid-state image sensor chip 20
Are connected to the thick film wiring 11 provided on the glass substrate 10 using the bumps 31, and the thick film wiring 1
Reference numeral 1 surrounds the side surface of the glass substrate 10 and is connected to the flexible printed circuit board 32. The space between the chip 20 and the glass substrate 10, and also the back surface of the chip 20 are sealed with a silicone resin 33.

According to this method, since a pad for wire bonding and a portion for fixing the cover glass are not required unlike the conventional solid-state image pickup device using a ceramic package, a large size reduction can be realized. In particular, when compared in the direction of the image pickup surface, the chip can be mounted in the same size as the solid-state image pickup element chip.

However, this method has the following difficult problems. In the structure as shown in FIG. 6, the image pickup surface of the solid-state image pickup element chip and the cover glass are separated from each other, and most of the reflected light from the side surface of the cover glass is blocked by the ceramic package. It was relatively rare for the light reflected by the above to enter the image pickup surface of the solid-state image pickup element chip. However, in the case of the solid-state imaging device by face-down mounting as shown in FIG. 7, since the distance between the imaging surface of the solid-state imaging element chip and the glass substrate is short, the light reflected by the side surface reaches the imaging surface,
It may affect the image. This is a phenomenon that appears more often as the outer diameter of the glass substrate on which the solid-state imaging device chip is mounted is smaller and the thickness thereof is thicker and the focal length of the lens used is shorter.

When the light from the side surface is incident on the image pickup surface, since the light is different from the image light to be obtained, it appears as bright lines or bright spots on the image screen, and the solid-state image pickup device is defective. Cause of. Although a method of suppressing the incidence of light on the side surface from the beginning by using a mask or the like can be considered, it is not suitable because the size and the position of the mask require considerable accuracy, and the cost is increased to realize it.

[0009]

As described above, when it is attempted to realize a small solid-state image pickup device by the face-down method, the image quality is affected by the reflected light from the side surface of the light transmissive substrate for mounting. There was a problem of deterioration. Further, in order to suppress the reflected light from the side surface, there is a problem that the size of the substrate and the focal length of the lens are restricted.

The present invention has been made in consideration of the above circumstances. An object of the present invention is to achieve light transmission regardless of the size of the light transmissive substrate, the focal length of the lens, etc. even though the face down mounting is performed. An object of the present invention is to provide a small-sized solid-state imaging device that can prevent an image from being adversely affected by the reflection of light on the side surface of the flexible substrate and that has a high image quality.

[0011]

The essence of the present invention is to scatter the light incident on the side surface in order to suppress the influence of the reflected light from the side surface of the light transmissive substrate excluding the light entrance surface and the exit surface. It is in.

That is, the present invention provides a solid-state image sensor having a light-transmissive substrate having a conductor pattern on one main surface, and a solid-state image sensor having a light-receiving surface side attached to the main surface of the substrate on which the conductor pattern is formed. The image pickup device is characterized in that the side surface of the light transmissive substrate excluding the light incident surface and the light emitting surface is processed to be uneven.

The following are preferred embodiments of the present invention. (1) The center line average roughness Ra of the side surface of the light transmissive substrate is 0.0
Set to 5 μm or more. (2) Center line average roughness Ra of the side surface of the light transmissive substrate is 5 μm
Set as follows. (3) The center line average roughness Ra of the side surface of the light transmissive substrate is set to 0.
The thickness is set to 05 ≦ Ra ≦ 5 μm, a conductor pattern made of thick film wiring is formed on this side surface by a screen printing method, and the wiring board is electrically connected to the conductor pattern on the side surface.

[0014]

According to the present invention, the side surface of the light transmissive substrate on which the solid-state image sensor chip is mounted except for the light incident surface and the light emitting surface is processed to have irregularities so that the light incident on the side surface is irregularly reflected by the side surface. Therefore, it does not reach the image pickup surface of the solid-state image pickup element chip. In particular, the center line average roughness Ra of the side surface is set to 0.
If the thickness is 05 μm or more, it is possible to almost ignore the influence of the reflection on the side surface. Therefore, even if the light-transmissive substrate has substantially the same size as the solid-state image pickup element chip, even if a lens having a short focal length is used, reflected light from the side surface does not affect the image.

When a conductor pattern made of thick film wiring or the like is formed not only on the main surface of the light transmissive substrate but also on the side surface,
If Ra is 0.05 μm or more, there is also an advantage that the adhesion strength between the conductor pattern on the side surface and the light transmissive substrate is improved. In order to prevent disconnection of the conductor pattern on the side surface, it is desirable that the center line average roughness Ra of the side surface be 5 μm or less.

[0016]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view showing the schematic arrangement of a solid-state image pickup device according to an embodiment of the present invention. In the figure, 10 is a glass substrate (light transmissive substrate), and a thick film wiring (conductor pattern) 11 is formed on one main surface of the substrate 10 by printing and firing a gold paste. A part of the thick film wiring 11 is formed so as to surround one side surface of the glass substrate 10. Reference numeral 20 denotes a CCD type solid-state image pickup element chip, and an image pickup section 21 and an electrode pad 22 around the image pickup section 21 are formed on one main surface of the chip 20.

The electrode pads 22 of the solid-state image pickup device chip 20 are connected to the thick film wiring 11 formed on the main surface of the glass substrate 10 via solder bumps 31. A flexible printed circuit board 32 is connected to the thick film wiring 11 that extends around the side surface of the glass substrate 10. The space between the glass substrate 10 and the solid-state imaging device chip 20 and the back surface of the chip 20 are sealed with a silicone resin 33.

The basic structure up to this point is the same as that of the conventional apparatus shown in FIG. 7, but in addition to this, in this embodiment, incident light is incident on the side surfaces of the glass substrate 10 excluding the light incident surface and the light emitting surface. It has an uneven surface that causes irregular reflection. That is, the center line average roughness Ra of the side surface of the glass substrate 10 is 0.05 to 5.
It was processed to have a thickness of, for example, 1 μm. Specifically, there are a method of polishing the side surface of the glass substrate 10 with an abrasive material of about # 1000, a method of protecting the light incident surface and the light emitting surface with a resist, and a method of mixing with a powder having a diameter of 1 μm or less. can give.

As shown in FIG. 2, the center line average roughness Ra represents the cross-sectional shape as a roughness curve f (x), and the center line is set so that the upper and lower areas of the roughness curve f (x) are equal. Let's decide, let this be the x-axis, and let the measurement length be L,

[0021]

[Equation 1]

Is defined by This is the distance from the center of the straight line formed when the curve formed by folding back the valley portion of the roughness curve at the center line is smoothed, and is the average absolute deviation of f (x). Further, there is a relation of Rmax ≦ 4 · Ra between the maximum heights Rmax and Ra.

FIG. 3 shows an example of the relationship between the incidence rate of reflected light from the side surface to the image pickup surface of the solid-state image pickup element chip and the centerline average roughness Ra. It can be seen that when Ra is 0.05 μm or less, that is, in a state close to the mirror surface, a considerable amount of light reflected on the side surface reaches the imaging surface. Therefore, it can be said that Ra is preferably 0.05 μm or more in order to suppress the influence of reflected light from the side surface.

In this embodiment, as described above, the thick film wiring 11 of gold is formed on the surface by screen printing, and the thick film wiring 11 is connected to the electrode pad 21 of the solid-state image pickup device chip 20 by the solder bump 31. did. Further, the thick film wiring 11 wraps around one of the side surfaces, and is connected to an external circuit using the flexible printed board 32 on the side surface.

Generally, it is difficult to increase the adhesion strength of the wiring to the glass substrate, not limited to the thick film, and a defect may occur due to the peeling of the wiring film. However, for the wiring formed on the surface, the sealing resin is used. Since the sealing is performed by 33, a large force is not applied directly to the wiring, and a defect is unlikely to occur. However, as in this example, wiring on the side surface,
When the printed circuit board 32 is connected, a force such as shearing or pulling is directly applied to the side wiring. Therefore, stronger adhesion strength is required.

FIG. 4 shows an example of the relationship between the adhesion strength of the side wiring and the center line average roughness Ra. As in the case of the incident rate of reflected light, the adhesion strength increases when Ra is 0.05 μm or more. Therefore, the thick film wiring 1 is formed on the side surface of the glass substrate 10.
When forming 1 and connecting the printed circuit board 32 to this, Ra of the connecting surface is preferably 0.05 μm or more.

FIG. 5 shows an example of the relationship between the incidence of defective connection of thick film wiring and the average roughness Ra of the center line. The connection failure occurrence rate indicates an occurrence rate of open or increase in connection resistance due to disconnection of wiring. From this, it can be seen that when Ra becomes 5 μm or more, the occurrence of defects rapidly increases. Generally, the film thickness of the thick film wiring is about several μm to 20 μm, and when Ra is 5 μm or more, the maximum height Rmax is 20 μm.
Therefore, it is fully conceivable that the cross section due to the unevenness of the surface or the wiring film becomes thin. Therefore, when wiring is provided on the side surface, Ra does not have to be simply large, and Ra must be suppressed to 5 μm or less in order to prevent disconnection of the wiring.

As described above, according to the present embodiment, the concavo-convex processing is performed on the side surfaces of the glass substrate 10 excluding the light incident surface and the light emitting surface so that the center line average roughness Ra is 0.05 to 5 μm, for example, 1 μm. By performing the above, it is possible to realize a small-sized and lightweight solid-state imaging device that does not affect the image by the reflection of light on the side surface, regardless of the size of the substrate or the focal length of the lens. Further, since the center line average roughness Ra of the side surface is set to 0.05 μm or more, the adhesion strength of the thick film wiring 11 formed on the side surface can be sufficiently increased, and the thick film wiring 11 can be prevented from peeling off. further,
Since Ra is set to 5 μm or less, disconnection of the thick film wiring 11 can be prevented.

The present invention is not limited to the above embodiment. Although the glass substrate is used as the mounting substrate in the embodiments, the present invention is not limited to this, and any light transmissive substrate capable of forming a conductor pattern on the main surface can be used. The conductor pattern is not limited to a thick film formed by screen printing, and may be a thick film formed by another method or a thin film formed by vapor deposition, sputtering or the like. In addition, various modifications can be made without departing from the scope of the present invention.

[0030]

As described above in detail, according to the present invention, the solid-state image pickup device chip is mounted on the glass substrate having the center line average roughness Ra of the side surface excluding the light incident surface and the light emitting surface of 0.05 μm or more and 5 μm or less. By flip-chip connection, it is possible to realize a small and lightweight solid-state imaging device that does not affect the image due to the reflection of light on the side surface, regardless of the size of the substrate or the focal length of the lens. Becomes

[Brief description of drawings]

FIG. 1 is a sectional view showing a schematic configuration of a solid-state imaging device according to an embodiment of the present invention,

FIG. 2 is a schematic diagram for explaining the definition of centerline average roughness Ra,

FIG. 3 is a characteristic diagram showing a relationship between an incident rate of reflected light and a centerline average roughness Ra in an example,

FIG. 4 is a characteristic diagram showing the relationship between wiring adhesion strength and centerline average roughness Ra in the example,

FIG. 5 shows the defect occurrence rate and center line average roughness R in the example.
a characteristic diagram showing the relationship with a,

FIG. 6 is a sectional view showing a schematic configuration of a conventional solid-state imaging device by wire bonding,

FIG. 7 is a cross-sectional view showing a schematic configuration of a conventional flip-chip mounted solid-state imaging device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Glass substrate (light transmissive substrate), 11 ... Thick film wiring (conductor pattern), 20 ... Solid-state image sensor chip, 21 ... Imaging part, 22 ... Electrode pad, 31 ... Solder bump, 32 ... Flexible printed circuit board (wiring) Substrate), 33 ... Sealing resin.

Claims (2)

[Claims] 1. A solid-state imaging device comprising: a light-transmissive substrate having a conductor pattern on one main surface; and a solid-state image sensor chip having a light-receiving surface side attached to the main surface of the substrate on which the conductor pattern is formed. The solid-state imaging device according to claim 1, wherein side surfaces of the light-transmissive substrate, excluding a light-incident surface and a light-emitting surface, are processed to have an uneven surface. 2. The center line average roughness Ra of the side surface of the light transmissive substrate is 0.05 ≦ Ra ≦ 5 μm, and a conductor pattern made of thick film wiring is formed on the side surface, and the conductor pattern on the side surface is formed. The solid-state imaging device according to claim 1, wherein a wiring board is electrically connected to the.