KR20070005150A - Flip-chip package for image sensor and compact camera module comprising the same - Google Patents

Abstract

A flip-chip package for an image sensor is provided to prevent a pixel region of an image sensor chip from being contaminated by liquid adhesive in a flip-chip bonding process of the image sensor chip and an FPCB(flexible printed circuit board) by including a dummy pattern in the outer part of a window of the FPCB. An image sensor pixel region(12) receives light and photoelectrically transforms the received light, formed in an image sensor chip(11). A plurality of bumps(13) for flip-chip bonding is formed on the upper surface of the periphery of the pixel region. The image sensor chip is mounted on a ductile substrate(15), and a window for exposing the image sensor pixel region is formed in the ductile substrate. A circuit pattern(16) is formed on at least the lower surface of the ductile substrate, functioning as an electrical path. Liquid adhesive(18) is deposited between the image sensor chip and the ductile substrate to bond the image sensor chip to the ductile substrate by a flip-chip bonding process. A dummy pattern(14) is interposed between the substrate and the image sensor chip to prevent the adhesive from invading a pixel region of the image sensor chip, positioned between the window of the substrate and the bump of the image sensor chip. The dummy pattern can be formed on one surface of the ductile substrate or on the image sensor chip.

Description

Flip-chip package for image sensor and compact camera module comprising the same}

1 is a view showing that a liquid adhesive invades and contaminates a pixel area of an image sensor chip in a flip chip package for a conventional image sensor.

2 is a vertical cross-sectional view of a compact camera module (CCM) according to an embodiment of the present invention.

3 is a plan view of a flip chip package for an image sensor according to an exemplary embodiment of the present invention.

4 is a plan view of a flip chip package for an image sensor according to another exemplary embodiment of the present invention.

Brief description of symbols for the main parts of the drawings

1, 11: image sensor chip 2, 12: pixel area

3, 13: chip bump 14, 24: dummy pattern

5, 15: flexible circuit board 6, 16: circuit pattern

8, 18: liquid adhesive 30: lens

32 IR: Filter 35: Barrel

The present invention relates to a flip chip package for an image sensor, and more particularly, to a Phillips chip package for an image sensor having a dummy pattern for preventing the liquid adhesive for flip chip bonding from invading the pixel region of the image sensor chip. will be.

The demand for camera phones in the mobile handset market is expected to grow explosively due to rapid technological developments and continuous replacement demand and new services.

The camera module, the core component of the camera phone, consists of an image sensor, a lens, an infrared filter, a flexible printed circuit board (FPCB), and a connector. The image sensor converts light incident through the lens into an electric video signal, and is responsible for format conversion and color correction.

The image sensor is divided into a CMOS (Complementary Metal Oxide Semiconductor) method and a high-pixel CCD (Charge Coupled Device) method. The lens functions to record and transmit still images or moving images by forming an external image onto an image sensor surface such as a CMOS or a CCD.

However, the CCD method has the advantage of realizing a high pixel, but in accordance with the trend of small size, low power consumption and low price of the mobile phone terminal, a System on Chip technology is possible, which is advantageous in multi-function integration and has a competitive price. Sensors are increasingly used.

This CMOS image sensor can also be packaged to connect the CMOS chip to an external lead.However, a chip on film (COF) that flip-chip bonds the image sensor onto the FPCB is used to secure space for miniaturization and multifunction of mobile phone terminals. It is used.

Flip chip bonding is a bonding method that inverts the chip for an image sensor and electrically and mechanically connects a bump of a chip and a circuit pattern of a substrate, particularly an FPCB.

Anisotropic conductive film (ACF) is mainly used for a chip on film (COF) method in which an image sensor is flip-chip pressed onto an FPCB. However, ACF is gradually changing to non-conducting paste (NCP) due to its reliability, productivity, and cost in terms of resistance to moisture absorption.

1 is a view showing that a liquid adhesive invades and contaminates a pixel area of an image sensor chip in a flip chip package for a conventional image sensor.

Referring to the drawings, the FPCB 5 is provided with a window portion for exposing the image sensor pixel region 2 to the upper portion, and the circuit pattern 6 is provided. In the image sensor chip 1 such as a CMOS chip, bumps 3 for flip chip bonding with the FPCB 5 are formed. An NCP 8 is applied therebetween for flip chip bonding of the image sensor chip 1 located below and the FPCB 5 located above.

However, the flip chip package technology using the NCP (8) requires precise NCP dispensing technology, and the process conditions are very demanding, resulting in difficulty in yield and workability. In particular, in the flip chip package structure using the NCP (8), the circuit pattern (6) of the FPCB (5) was composed only of a line for removing the bonding line to the connector terminal. As shown in FIG. 1 due to the fluidity of the NCP 8, the phenomenon that the NCP 8 invades the image sensor pixel region S of the chip often occurs.

SUMMARY OF THE INVENTION The present invention provides a flip chip package for an image sensor and a compact camera module including the same, having a dummy pattern in a form surrounding a pixel area of an image sensor chip on the outside of a window of an FPCB. There is a purpose.

In order to achieve the above object and various other objects, the present invention provides an image sensor chip for receiving light and photoelectric conversion, and an image sensor chip in which a plurality of bumps for flip chip bonding are formed on the upper surface of the pixel area. ; A flexible substrate having the image sensor chip mounted thereon and having a window for exposing the image sensor pixel region; A circuit pattern formed on at least a bottom surface of the flexible substrate and serving as an electrical passage; A liquid adhesive applied between the image sensor chip and the flexible substrate to flip chip bond the image sensor chip and the flexible substrate; And a dummy pattern interposed between the flexible substrate and the image sensor chip to prevent the adhesive from interfering with the pixel region of the image sensor chip, and located between the window of the flexible substrate and the image sensor chip bump. It provides a flip chip package for an image sensor having a.

The dummy pattern may be formed on one surface of the flexible substrate or on the image sensor chip.

When the dummy pattern is formed on one surface of the flexible substrate, the dummy pattern may be made of the same material and forming method as the circuit pattern of the flexible substrate, and when the dummy pattern is formed on the image sensor chip, It is characterized by being made of the same material and forming method as the electrode pads.

Here, the dummy pattern may have a form surrounding at least one corner portion of the window outer portion, and in particular, the dummy pattern may have a rectangular shape surrounding all of the window outer portion.

According to another aspect of the invention, the present invention is a flip chip package for the image sensor; A lens module for imaging light representing an image of a superficial body in a pixel region of the flip chip package for the image sensor; And a housing for supporting the image sensor and the lens module and blocking incidence of unnecessary light.

Hereinafter, with reference to the accompanying drawings, preferred embodiments of the present invention will be described in detail.

2 is a vertical cross-sectional view of a compact camera module (CCM) according to an embodiment of the present invention. 2, a camera module according to an exemplary embodiment of the present invention includes a lens 30 module, an infrared cutoff filter 32, a housing 35, and a flip chip package for an image sensor.

First, the overall function and operation of the camera module by the above configuration will be described.

The light representing the image of the subject enters through the lens 30 module, and forms an image on the pixel region 12 of the image sensor chip through an infrared cutoff filter 32 that removes light in the near infrared region to produce a color close to a natural color. do.

The formed light is converted into signal charge in a photodiode (not shown) arranged for each pixel of the image sensor, and the signal voltage at each pixel is sequentially read along the time axis, and the signal is input to the image processor (not shown). The image signal is processed to obtain a video signal.

Hereinafter, the configuration, function, and operation of each component will be described.

The lens 30 module is formed of at least one lens 30, and passes through light representing an image of a subject to form an image in the pixel region 12 of the image sensor.

The infrared filter 32 is positioned on the bottom surface of the lens 30 (the direction opposite to the direction in which the subject is positioned with respect to the lens 30), and removes light in the infrared region from the light passing through the lens 30. Do it. This is because the photodiode used in the pixel of the image sensor transmits to the infrared region to prevent the image from appearing red.

The housing 35 supports the lens 30 module and the infrared filter 32 and blocks light from entering an unwanted path from the outside. Lens 30, infrared filter 32, and housing 35 are already known to those of ordinary skill in the art, and are not a feature of the present invention, and no further description will be necessary.

3 is a plan view of a flip chip package for an image sensor according to an exemplary embodiment of the present invention. 2 and 3, in the flip chip package for the image sensor, the image sensor chip 11 and the FPCB 15 are flip chip bonded by NCP 18, which is a liquid adhesive.

The image sensor chip 11 is divided into a pixel region 12 in which incident light is formed and other portions thereof, and a plurality of chip bumps 13 for flip chip bonding are provided outside the pixel region 12. . Here, the image sensor has a CCD method and a CMOS method, but it is preferable to use a CMOS image sensor suitable for using the COF method for light and short reduction of the camera module by miniaturization and multifunction of the camera phone. However, the protection scope of the present invention is not necessarily limited thereto.

The image sensor chip 11 is mounted on the FPCB 15, and a window that is an opening for exposing the pixel region 12 of the image sensor is formed therein. In addition, a circuit pattern 16 serving as an electrical passage for transmitting the signal voltage of each pixel converted by the image sensor to a processing unit such as an image processor is formed. In the drawings, although the circuit pattern 16 is illustrated as being formed only on the bottom surface of the FPCB 15 in the preferred embodiment, the present invention is not limited thereto, and thus the circuit pattern 16 is formed on both surfaces. to be.

In addition, a dummy pattern 14 is formed in a rectangular shape on the window outer portion of the bottom surface of the FPCB 15. In order to flip-chip bond the image sensor chip 11 and the FPCB 15, a liquid adhesive (eg, NCP 18) is applied along the periphery of the chip bump 13, and the NCP 18 is applied. Due to its fluidity, pressing for flip chip bonding invades the image sensor pixel region 12 and contaminates it, resulting in deterioration of image quality. The dummy pattern 14 formed on the bottom surface of the FPCB 15 has an NCP ( This is because it prevents the intrusion into the image sensor pixel region 12 of 18).

Therefore, the position where the dummy pattern 14 is formed should be located between the chip bumps 13 and the edge of the pixel area 12 of the image sensor, as shown in FIG. 3.

Since the dummy pattern 14 is made together in the process of making the functional circuit pattern 16 in the FPCB 15, it is the same in the material, the manufacturing method, and the thickness to be formed with the functional circuit pattern 16. In order to form the dummy pattern 14, after forming the copper foil layer which is a conductor in the insulation film like PI, the surface of the copper foil layer is exposed to the photosensitive resin film using the film which the pattern of wiring was designed, and this photosensitive resin The circuit pattern 16 is formed by etching copper foil in a desired pattern using the characteristics of. Here, the method and material for forming the circuit pattern 16 in the FPCB 15 are already known to those of ordinary skill in the art and are obvious, and no further explanation thereof will be necessary.

In addition, since the functional circuit pattern 16 and the dummy pattern 14 are simultaneously formed in the same process, the thickness of the dummy pattern 14 is the same as the thickness of the functional circuit pattern 16.

In another embodiment of the present invention, the dummy pattern 14 may be formed on the image sensor chip 11. In this case, the dummy pattern 14 is formed from the electrode pads of the chip from the edge of the pixel region 12 of the image sensor in order to prevent the fluidized NCP 18 from invading and contaminating the image sensor pixel region 12. Not shown). Although not shown in the drawing, the electrode pads of the chip are positioned so as to be in surface contact with the lower surface of the chip bump 13.

Since the dummy pattern 14 in this embodiment is made together in the process of making an electrode pad of a chip, it is the same in an electrode pad and a material, a manufacturing method, and the thickness to be formed. Here, the method and material for forming the electrode pads on the chip 11 are already known to those of ordinary skill in the art and will be obvious, and description thereof will be unnecessary.

An NCP 18 is applied around the chip bumps 13 of the image sensor, and the chip bumps 13 of the image sensor are aligned with the circuit pattern 16 of the FPCB 15. Then, by pressing the FPCB 15, the top surface of the image sensor chip and the bottom surface of the FPCB 15 are flip chip bonded.

According to the embodiment of the present invention, the chip bump 13 has a thickness of about 18 μm, and the circuit pattern 16 is slightly thinner than the needle bump 13. When flip chip bonding, the ends of the chip bump 13 and the circuit pattern 16 are overlapped to be electrically energized. The overlapped portion is slightly thicker than the thickness of the portion on which the dummy pattern 14 is formed. Although the patterned portion may be slightly floating from the top surface of the image sensor chip, the dummy pattern is brought into contact with the bottom surface by pressing the flexible FPCB 15 entirely from above.

At this time, the process of applying the NCP 18 requires a very precise technique, the process conditions are difficult and the NCP 18 flows when pressed, so that the unwanted region 12 (for example, the pixel region 12 of the image sensor 12). It can invade)). However, the dummy pattern 14 formed outside the window of the FPCB 15 functions to prevent the NCP 18 from invading the pixel region 12 of the image sensor chip.

4 is a plan view of a flip chip package for an image sensor according to another exemplary embodiment of the present invention. Referring to the drawings, unlike the first embodiment illustrated in FIG. 3, the dummy pattern 24 is formed in a bent shape only on the window edge side of the FPCB 15.

This form can be used when it is difficult to print the dummy pattern 24 in the form surrounding the window as a whole because the arrangement of the functional circuit patterns 16 is made in a narrow space. The method, function, and operation of forming the dummy pattern 24 in the present embodiment are the same as those in the first embodiment, and reference may be made to the first embodiment.

According to the flip chip package for an image sensor and the compact camera module including the same according to the present invention, a dummy pattern is provided outside the window of the FPCB.

Accordingly, during the flip chip bonding between the image sensor chip and the FPCB, the liquid adhesive may be prevented from invading and contaminating the pixel area of the image sensor chip.

Although the present invention has been described with reference to the embodiments shown in the drawings, this is merely exemplary, and it will be understood by those skilled in the art that various modifications and equivalent other embodiments are possible. Therefore, the true technical protection scope of the present invention will be defined by the technical spirit of the appended claims.

Claims (8)

An image sensor chip for receiving light and performing photoelectric conversion and an image sensor chip having a plurality of bumps for flip chip bonding formed on an upper surface of the pixel area; A flexible substrate having the image sensor chip mounted thereon and having a window for exposing the image sensor pixel region; A circuit pattern formed on at least a bottom surface of the flexible substrate and serving as an electrical passage; A liquid adhesive applied between the image sensor chip and the flexible substrate to flip chip bond the image sensor chip and the flexible substrate; And A dummy pattern interposed between the flexible substrate and the image sensor chip to prevent the adhesive from interfering with the pixel region of the image sensor chip and between the window of the flexible substrate and the image sensor chip bump. Flip chip package for an image sensor provided. The method of claim 1, The dummy pattern is a flip chip package for an image sensor is formed on one surface of the flexible substrate. The method of claim 1, The dummy pattern is a flip chip package for an image sensor is formed on the image sensor chip. The method of claim 1, The dummy pattern is a flip chip package for an image sensor having a rectangular shape surrounding all of the window outer portion. The method of claim 1, The dummy pattern is a flip chip package for an image sensor that surrounds at least one corner portion of the window outer portion. The method of claim 2, And the dummy pattern is made of the same material and forming method as the circuit pattern of the flexible substrate. The method of claim 3, wherein The dummy pattern is a flip chip package for an image sensor made of the same material and forming method as the electrode pad of the image sensor chip. A flip chip package for an image sensor according to any one of claims 1 to 7; A lens module for imaging light representing an image of a superficial body in a pixel region of the flip chip package for the image sensor; And A compact camera module for supporting the image sensor and the lens module, and having a housing that blocks unnecessary light incident.

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