WO2006093377A1

WO2006093377A1 - Camera module without focusing adjustment and method of assembling thereof

Info

Publication number: WO2006093377A1
Application number: PCT/KR2006/000416
Authority: WO
Inventors: Hyun-Joo Jung; Sang-Eun Son
Original assignee: Hyun-Joo Jung; Sang-Eun Son
Priority date: 2005-03-04
Filing date: 2006-02-06
Publication date: 2006-09-08

Abstract

A camera module includes a lens holder having a receiving unit and a barrel that is combined with the receiving unit and includes a lens. A bottom portion of the receiving unit includes a reference face that is substantially horizontal to the optimal axis and makes contact with a surface of the substrate, and a bonding surface that is spaced apart from the surface of the substrate and makes contact with a bonding agent in a gap distance, A central portion of the lens includes a surface for guiding a light and a peripheral portion of the lens includes a spacer for separating neighboring lenses. The spacer includes a slope for aligning the neighboring lenses such that optical axes of the lenses coincide with each other. An IR cut film is coated on the lens. As a result, assembling error may be minimized and no focal distance adjustment is required.

Description

CAMERA MODULE WITHOUT FOCUSING ADJUSTMENT AND METHOD OF ASSEMBLING THEREOF

Technical Field The present invention relates to a camera module and a method of assembling the same, and more particularly, to a subminiature high-resolution camera module and a method of assembling the camera module.

Background Art Camera phones, which are cellular phones including internal digital cameras, were firstly launched into the market in the year 2000, and the digital cameras of the camera phones have been remarkably developed to have a 1.3 million-pixel resolution or higher, from the original 0.3 million-pixel resolution. Nowadays, camcorder phones are even being developed with built-in camcorders that can shoot videos. In addition, camera phones have also been making rapid progress with respect to function and quality by adopting such functions as a 2-megapixel or higher resolution, optical zoom and auto focus.

Recent trends toward development of lighter and smaller cellular phones and severe price competition has resulted in higher demand for smaller camera phone parts and reduced manufacturing costs.

In general, a camera module of the camera phone includes an image sensor, a lens, a printed circuit board (PCB), a connector and an infrared (IR) cut filter for blocking infrared light. So as to satisfy the recent trend toward smaller cellular phones, the image sensor has been bonded to the PCB not by a chiρ-on-board (COB) method but by a chip-on-flexible PCB (or film) (COF) method. While the COB method includes bonding the image sensor to the PCB through a wire, the COF method includes bonding the image sensor to the PCB using a flip-chip bonding process. The image sensor for the COF method includes a bump therein, and is bonded to the PCB through the bump. The bump in the image sensor may be either a gold bump or a solder bump.

The lens may comprise a plastic or a glass. A glass lens has critical disadvantages including high price and low productivity, despite particular advantages including high transparency and high heat resistance. As a result, a plastic lens is usually used in the camera phone. Further, the lens in the camera phone is mainly formed into a complicated lens rather than a single lens, so as to eliminate spherical aberration of the lens. In addition, the lens in the camera phone is also formed into an aspherical lens rather than a spherical lens, so as to reduce the number of the required lenses. However, the plastic lens may be deformed at a temperature above about 7O⁰C, which puts a limitation on subsequent thermal conditions after assembling the lens.

The IR-cut filter is positioned in front of the image sensor in the camera module, and prevents infrared light from passing through and allows visible light to pass through. As a result, the infrared light is sufficiently filtered by the IR-cut filter and only the visible light reaches the image sensor, thereby preventing noise from being generated in a digital image. Accordingly, the IR-cut filter is indispensable for obtaining a high quality and a high resolution digital image in the camera phone. The IR-cut filter is usually interposed between the lens and the image sensor in the conventional camera module of the camera phone. The reliability of the camera module is mainly dependent on a quality of mechanical assembly and electrical connections between the PCB and the image sensor, a quality of mechanical assembly between the PCB and the lens holder and a quality of optical assembly between the lens and the image sensor. Accordingly, the manufacturing costs and productivity of the camera module is varied in accordance with an assembly technology for the above mechanical and optical assemblies and the electrical connections.

FIG. 1 is a cross-sectional view illustrating a structure of a conventional camera module. Referring to FIG. 1, the conventional camera module includes a substrate 1, an image sensor 2, an IR-cut filter glass 4, a lens holder 6, a lens 8, a lens barrel 9, a spacer 11, a lens cover 12 and a connector 14.

All the above parts of the camera module are assembled with one another as follows, to thereby manufacture the camera module.

At first, the IR-cut filter glass 4 is adhered to an inner side of the lens holder 6 using an ultraviolet bonding agent 5. The lens 8 and the spacer 11 are received in the lens barrel 9, and the lens barrel 9 is covered with the lens cover 12, thereby completing a barrel assembly. A plurality of the substrates 1 is arranged on an array substrate 20, as shown in FIG. 2. The image sensor 2 is adhered to each of the substrates 1 on the array substrate 20 and the image sensor 2 is electrically connected to the substrate 1 through a gold wire 3 in an automatic assembler. An epoxy bonding agent 7 is spread out on a surface of the substrate 1, and the lens holder 6 is positioned on the substrate 1. Then, the lens holder 6 is pressed against the substrate 1, and is adhered to the substrate 1 due to the epoxy bonding agent 7.

Then, the array substrate 20 to which a plurality of lens holders 6 is adhered is baked at a predetermined temperature in an oven, thereby hardening the epoxy bonding agent 7. It is estimated whether the lens holder 6 is sufficiently adhered to the substrate 1 by measuring how much the epoxy bonding agent 7 is hardened. Then, when each of the lens holders 6 is sufficiently adhered to the substrate 1, the array substrate 20 is cut into individual substrates 1.

Then, the lens barrel 9 is assembled to the lens holder 6 by a screw joint, and a focal distance adjuster adjusts a distance between the lens 8 and a light-receiving face 2a of the image sensor 2, the distance being regulated by moving the lens barrel 9 forwardly and backwardly, thereby determining a focal distance between the lens 8 and the image sensor 2. Then, the lens barrel 9 is firmly adhered to the lens holder 6 by an ultraviolet bonding agent 10, thereby completing an image sensor module.

The above conventional assembling process and the camera module by the same process have the following problems:

1) The conventional assembling process necessarily requires the focal distance to be adjusted at each assembling step.

According to the conventional assembling process, the substrate 1 and the lens holder 6 are assembled to each other by an epoxy bonding agent 7, the lens barrel 9 and the lens holder 6 are not formed as one body and are different from each other, and a plurality of lenses 8 and spacers 11 are utilized in the camera module. As a result, the focal distance between the lens 8 and the image sensor 2 usually increases far off from an allowable error range. In addition, assembling errors may be generated at each of the unit steps of the conventional assembling process, so that the focal distance is necessarily adjusted just after each of the unit steps of the assembling process. 2) A plurality of the lenses 8 and the image sensors is necessarily arranged, such that each common optical axis commonly penetrates each pair of the lens 8 and the image sensor 2. Every optical axis of each lens 8 is slightly different from each other due to an aberration of each lens 8 in the lens barrel 9. In addition, an outer diameter of the lens barrel 9 may be slightly different from an inner diameter thereof. For those reasons, the lenses 8 and the image sensors 2 are necessarily adjusted in a view of the optical axis thereof after the assembling process.

3) The substrate 1 and the lens holder 6 require being bonded to each other using an epoxy bonding agent 7, because the epoxy bonding agent 7 can sufficiently firmly bond the lens holder 6 to the substrate 1 while simultaneously sealing off the image sensor from surroundings. When minute particles and dust are positioned on the light-receiving face 2a of the image sensor 2 that is disposed in a receiving space defined by the lens holder 6 and the substrate 1, an image defect is generated in the camera module due to the minute particles and dust, thereby causing a defect of the camera phone. Accordingly, the inside of the lens holder 6 requires being sealed off from surroundings as well as being firmly adhered to the substrate 1, and the epoxy bonding agent 7 most satisfies the above requirements. As a result, the epoxy bonding agent 7 is indispensable for the conventional assembling process.

4) The epoxy bonding agent 7 is hardened at a temperature of about 100⁰C to about 120⁰C. The lens barrel 9 integrated with the lens holder 6 as one body cannot be used when the lens 8 comprises a plastic that may be easily deformed at a high temperature. Physical and optical characteristics of the plastic lens 8 may be indeterminate at a temperature above about 85°C. For those reasons, the lens barrel 9 and the lens holder 6 are formed into a separated structure, and are assembled to each other by a screw joint, so as to adjust the focal distance of the lens 8.

5) There are many limitations in reducing a length of the camera module. A thickness of the epoxy bonding agent 7, a thickness of the IR-cut filter glass, a bottom thickness of the lens barrel 9 and a minimum height for the focal distance adjustment may put limitations on how much the camera module can be shortened.

The conventional camera module of the camera phone is difficult to reduce in size, and manufacturing costs are difficult to reduce due to the above-mentioned problems, and has low productivity caused by the focal distance adjustment.

Korean Patent Laid-Open Publication No. 2005-26487 discloses a lens holder of which a reference surface makes contact with a top surface of the image sensor. However, the above lens holder has a problem in that a crack is easily generated on the top surface of the image sensor when variable forces are applied on the image sensor.

As described above, the assembly process for the camera module of the camera phone includes very complicated connections, such as mechanical and electrical connections, as well as a complex optical assembly, so that an improvement of one part of the camera module or one unit step of the assembly process requires satisfying relationships with other parts of the camera module or unit steps of the assembly process.

Disclosure of the Invention Technical Problem

The present invention provides a camera module having improved endurance and productivity caused by an improved assembly process for assembling the camera module.

The present invention also provides a camera module capable of accurately forming an image on the light-receiving face of an image sensor.

The present invention still also provides a method of assembling a camera module of a camera phone without a focal distance adjustment step.

Technical Solution

A camera module, according to an example embodiment of the present invention, includes a substrate to which a lens holder and an image sensor are installed. The lens holder includes at least one lens and the image sensor receives light through the lens. The lens holder includes a barrel in which the lens is installed, and a box-shaped receiving unit that is combined together with the barrel as one body and is bonded to a top surface of the substrate, thereby providing a space for receiving the image sensor. In such a structure, one of an inner or outer edge portion of a bottom surface of the receiving unit is arranged vertically with respect to an optical axis of the lens and makes contact with an edge portion of a top surface of the substrate, to thereby function as a reference face for a focal distance between the lens and a light-receiving surface of the image sensor, and the other of the inner or outer edge portion of the bottom surface of the receiving unit is spaced apart from the top surface of the substrate by a predetermined gap distance. A bonding agent is filled into the gap distance, to thereby bond the lens holder to the substrate, and to seal off the space of the receiving unit, in which the image sensor is received, from surroundings.

Accordingly, a lower structure of the lens holder is improved in such a way that an epoxy bonding agent is coated along an edge portion of the lens holder, so that the lens holder is firmly bonded to the substrate and is sealed off from surroundings. In addition, the lens holder is bonded to a predetermined position spaced apart from the reference face by a given distance, so that no focal distance adjustment is required in the present embodiment. A central portion of the lens includes a spherical or an aspherical surface for guiding a light, and a peripheral portion of the lens includes a spacer for separating neighboring lenses adjacent to each other. The spacer includes at least one slope at an edge portion thereof, and the slope aligns the neighboring lenses in such a way that optical axes of the lenses coincide with each other. Accordingly, the spacer combined together with the lens as one body removes additional spacers from the lens holder, so that the assembly errors due to the assembly of the additional spacer to the lens holder may be minimized. The upper lens and the lower lens are horizontally self-aligned with each other due to a combination of the slopes of each spacer. The lens includes a combination of a plastic lens and a glass lens, or a single plastic lens.

When the lens includes a combination of the plastic lens and the glass lens, an infrared (IR) cut film may be coated on a surface of the glass lens, to thereby substitute for the conventional IR-cut filter glass. When the lens includes a plastic lens, the lens holder is bonded to the substrate using a low-temperature hardening bonding agent. An example of the low-temperature hardening epoxy bonding agent includes LPD-4391 (a product made by Loctite Co., Ltd. in the U.S.A.)

In addition, a light-blocking material may be coated around the lens and an additional light-blocking plate may be installed to the lens holder. In the same way as the spacer of the lens, a slope may be formed at an edge portion of the light-blocking plate, so that optical axes of the stacked lenses may be self-aligned with one another. The lens may include a lens combination having a plurality of lenses and a single lens of which a surface is aspherical.

The image sensor is bonded to the substrate by a flip-chip bonding process. For example, an ultrasonic wave is applied to a gold bump and a gold pad, so that the gold bump is bonded to the gold pad by a metal thermal bonding process. Otherwise, a non-conductive paste (NCP) is interposed between the gold bump of the image sensor and the gold pad of the substrate and the gold bump is pressed onto the gold pad. As a result, the gold bump is strongly bonded to the gold pad due to the NCP, and the gold bump is also electrically connected to the gold pad via the NCP. An example of the NCP includes NEX-181, which is a product name of an NCP manufactured by Nippon Steel Chemical Co., Ltd. (NSC) in Japan.

A bonding apparatus for the flip-chip bonding process can be operated only in a clean room, so that defects caused by foreign matter, such as dust, may be sufficiently reduced as compared with a conventional surface mounting technology (SMT) that is mainly utilized at a location where a clean room cannot be installed. In addition, a defect such as a deficient amount or a short circuit is less generated with the gold bump than with the conventional soldering bump, and an overall size of the camera module may be reduced by utilizing the gold bump in place of the soldering bump. A glass is positioned on a light-receiving surface of the image sensor and an IR-cut material may be coated on the glass.

The substrate may include a flexible substrate of which a mechanical strength is reinforced by a supplementary plate. In such a case, a receiving hole for receiving the image sensor is formed at a central portion of the flexible substrate and the supplementary plate, thereby reducing an overall size of the camera module.

In an example embodiment of the present invention, the camera module is assembled as follows. A gold bump is formed on an image sensor, and an insulation paste is coated on a substrate including a gold pad. The gold bump of the image sensor is pressed onto the gold pad of the substrate by a flip-chip bonding process, so that the gold bump is electrically connected to the gold pad. Then, the insulation paste is hardened while the gold bump is pressed against the gold pad. A lens is installed into a barrel of a lens holder. The lens holder includes a reference face at a portion of a bottom surface and a bonding surface stepped away from the bottom surface. A bonding agent is coated along a peripheral portion of the substrate, and the lens holder is combined with the substrate, so that the reference face of the lens holder makes contact with a top surface of the substrate and the bonding surface of the lens holder makes contact with the bonding agent. The bonding agent is hardened while the bonding surface of the lens holder makes contact with the bonding agent, to thereby bond the lens holder to the substrate.

A camera module, according to another example embodiment of the present invention, includes a substrate to which a lens holder and an image sensor are installed. The lens holder includes at least one lens and the image sensor receiving light through the lens. The lens holder includes a barrel in which the lens is installed, and a box-shaped receiving unit that is combined together with the barrel as one body and is bonded to a top surface of the substrate, thereby providing a space for receiving the image sensor. An inner edge portion of a bottom surface of the receiving unit is arranged vertically with respect to an optical axis of the lens and makes contact with an edge portion of a top surface of the substrate, to thereby function as a reference face for a focal distance between the lens and a light-receiving surface of the image sensor. An extension wall downwardly extends from an outer edge portion of the bottom surface of the receiving unit adjacent to the inner edge portion of the bottom surface of the receiving unit and makes contact with a side surface of the substrate, to thereby seal off the space of the receiving unit from surroundings. A plurality of protrusions downwardly extends from the inner edge portion of a bottom surface of the receiving unit to a length larger than a thickness of the substrate, so that the protrusion penetrates the substrate and an end portion of the protrusion is protruded from a bottom surface of the substrate. A plurality of insertion holes is formed at the edge portion of the substrate, and the protrusion of the lens holder is inserted into the insertion hole. The protruded end portion of the protrusion is thermally pressed against the bottom surface of the substrate, to thereby bond the lens holder to the substrate.

Accordingly, the lens holder of the present invention may be bonded to the substrate without an epoxy bonding agent, so that a plastic lens tends to be easily utilized in the camera module of the present invention even though the camera module may be assembled at a high temperature at which physical and optical characteristics of the plastic lens may be easily changed.

In another example embodiment of the present invention, the camera module is also assembled as follows. A gold bump is formed on an image sensor, and an insulation paste is coated on a substrate including a gold pad. The gold bump of the image sensor is pressed onto the gold pad of the substrate by a flip-chip bonding process, so that the gold bump is electrically connected to the gold pad. The insulation paste is hardened while the gold bump is pressed against the gold pad. A lens is installed into a barrel of a lens holder. A protrusion of the lens holder is inserted into an insertion hole of an edge portion of the substrate, and an end portion of the protrusion, which is protruded from a bottom surface of the substrate, is thermally pressed against the bottom surface of the substrate, so that a size of the end portion of the protrusion is larger than a diameter of the insertion hole.

A camera module, according to still another example embodiment of the present invention, includes a substrate of which a top surface is substantially horizontal with respect to an optical axis and on which a gold pad is positioned, a lens holder including a box-shaped receiving unit and a barrel combined together with the receiving unit as one body, at least one lens installed in the barrel of the lens holder, and an image sensor positioned in a sealed space between the receiving unit and the substrate and connected to a top surface of the substrate. A bottom portion of the receiving unit includes a reference face that is substantially horizontal with respect to the optimal axis and makes direct contact with a top surface of the substrate, and a bonding surface that is spaced apart from the top surface of the substrate by a predetermined gap distance and makes direct contact with a bonding agent in the gap distance. A central portion of the lens includes a spherical or an aspherical surface for guiding light and a peripheral portion of the lens includes a spacer for separating neighboring lenses adjacent to each other. The spacer includes at least one slope at an edge portion so as to align the neighboring lenses in such a way that optical axes of the neighboring lenses coincide with each other, and an infrared light-cut film is coated on the at least one lens. Accordingly, no focal distance adjustment is required after the assembling process.

Effect of the Invention According to the present invention, the lens holder may be directly bonded to the substrate, so that an overall size of the camera module may be reduced and no focal distance adjustment is required after the assembling process. No focal distance adjustment means that an assembly time for the camera module is reduced, and labor costs for the focal distance adjustment are saved, thereby reducing manufacturing costs and improving productivity of the camera module.

Further, an epoxy bonding agent is no longer required due to the thermal bonding of the lens holder to the substrate, so that a lens assembly process may be performed prior to bonding of the lens holder to the substrate. In addition, when a low-temperature hardening epoxy bonding agent is used as the bonding agent for bonding the lens holder to the substrate, the lens assembly process may also be performed prior to bonding of the lens holder to the substrate.

The image sensor is bonded to the substrate by a flip-chip bonding process, so that a contamination on a light-receiving window of the image sensor is minimized because the flip-chip bonding process is performed in a clean room.

When a high resolution lens combination including a plurality of lenses is utilized in the camera module, optical axes of the lenses are self-aligned to a common optical axis of the lens combination due to a slope at an edge portion of each of the lenses.

Brief Description of the Drawings

The above and other advantages of the present invention will become more apparent by describing in detail example embodiments thereof with reference to the accompanying drawings, in which: FIG. 1 is a cross-sectional view illustrating a structure of a conventional camera module assembled by a wire bonding process;

FIG. 2 is a view illustrating an individual substrate separated from an array substrate;

FIG. 3 is a front view illustrating a camera module according to a first example embodiment of the present invention;

FIG. 4 is a bottom view illustrating a camera module according to the first example embodiment of the present invention;

FIG. 5 is a cross-sectional view taken along the line A-A' of FIG. 4;

FIG. 6 is an exploded perspective view illustrating a camera module according to the first example embodiment of the present invention;

FIG. 7 is a view illustrating a structure of an automatic aligning lens system according to an example embodiment of the present invention;

FIG. 8 is a flow chart illustrating a method of assembling the camera module of the first embodiment of the present invention; FIG. 9 is an exploded perspective view illustrating a camera module according to a second example embodiment of the present invention;

FIG. 10 is a cross-sectional view illustrating the camera module shown in FIG. 9; FIG. 11 is a cross-sectional view illustrating a modified lens holder of the camera module of the second embodiment of the present invention;

FIG. 12 is a flow chart illustrating a method of assembling the camera module of the second embodiment of the present invention;

FIG. 13 is an exploded perspective view illustrating a camera module having an auto-focusing system according to a third example embodiment of the present invention; and

FIG. 14 is a cross-sectional view illustrating the camera module shown in FIG. 13.

Best Mode for Carrying Out the Invention

It should be understood that the example embodiments of the present invention described below may be varied modified in many different ways without departing from the inventive principles disclosed herein, and the scope of the present invention is therefore not limited to these particular following embodiments. Rather, these embodiments are provided so that this disclosure will be through and complete, and will fully convey the concept of the invention to those skilled in the art by way of example and not of limitation.

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

Thermal adhesion type lens holder without an epoxy bonding agent and a focal distance adjustment

FIG. 3 is a front view illustrating a camera module according to a first example embodiment of the present invention, and FIG. 4 is a bottom view illustrating a camera module according to a first example embodiment of the present invention. FIG. 5 is a cross-sectional view taken along the line A-A' of FIG. 4, and FIG. 6 is an exploded perspective view illustrating a camera module according to the first example embodiment of the present invention.

Referring to FIGS. 3 to 6, the camera module 100 according to the first example of the present invention includes a lens holder 110, a rigid substrate 150, a flexible substrate 152 and a connector 154.

The lens holder 110 includes a box-shaped receiving unit 112 and a barrel 114 mounted on the receiving unit 112. As an example embodiment, the lens holder 110 is formed into a two-stepped tower structure through an injection molding process, so that the receiving unit 112 is formed simultaneously with the barrel 114 as one body. A bottom surface of the receiving unit 112 includes a reference face 112a. The reference face 112a is substantially horizontal with respect to an optical axis 102, and makes contact with a top surface 150a of an edge portion of the rigid substrate 150. An adjustment for a back-focus is performed on a basis of the reference face 112a.

An extension wall 112b downwardly extends from an edge portion of the receiving unit 112 adjacent to the reference face 112a, and a side surface 150c of the rigid substrate 150 makes surface contact with the extension wall 112b. As an example embodiment, the extension wall 112b has a length substantially identical to a thickness of the rigid substrate 150.

A plurality of protrusions 112c downwardly extends from the reference face 112a to a length larger than the thickness of the rigid substrate 150, so that the protrusion 112c penetrates the rigid substrate 150, and an end portion of the protrusion 112c is protruded from a bottom surface of the rigid substrate 150. The protrusion 112c is thermally pressed against the bottom surface of the rigid substrate 150, to thereby be flattened on the bottom surface of the rigid substrate 150. Accordingly, the lens holder 110 is firmly bonded to the rigid substrate 150. As a result, the top surface 150a of the rigid substrate 150 makes close contact with the reference face 112a of the lens holder 110, so that foreign matter, such as dust, is prevented from being supplied into the lens holder 110. The foreign matter is firstly prevented from being supplied into the lens holder 110 by the extension wall 112b making contact with the sidewall of the rigid substrate 150. The extension wall 112b also prevents horizontal shifting of the rigid substrate 150, to thereby align the rigid substrate 150 in a horizontal direction together with the protrusion 112c. The above-described adhesion of the rigid substrate 150 and the lens holder 110 ensures a high degree of sealing and an improved endurance even though a bonding agent such as an epoxy bonding agent is not interposed between the rigid substrate 150 and the lens holder 110. Furthermore, no bonding agent between the rigid substrate 150 and the lens holder 110 means that assembly errors, due to the bonding agent when assembling the lens holder 110 to the rigid substrate 150, may be eliminated, so that a focal distance adjustment tends to be much less required in the lens holder 110.

The barrel 114 is formed through an injection molding process together with the lens holder 112, and a light-receiving hole 114b is formed on a top surface 114a of the barrel 114. The light-receiving hole 114b has an inner diameter smaller than a diameter of the lens. A group of lenses is inserted into the barrel 114, and is bonded to the barrel 114 using an ultraviolet adhesive 118.

A plurality of gold pads 150d to which an image sensor 160 is bonded is formed on the top surface 150a of the rigid substrate 150, and an adhesive 164 is spread out on a predetermined area (defined by a dotted line in FIG. 6) in which the gold pads are arranged. A plurality of insertion holes 150b is formed at the edge portion of the rigid substrate 150, and the protrusion 112c of the lens holder 110 is inserted into the insertion hole 150b. A terminal (not shown) is formed on the bottom surface of the rigid substrate 150, and the rigid substrate 150 is electrically connected to the flexible substrate 152 through the terminal. The terminal is also electrically connected to the gold pad 15Od on the top surface of the rigid substrate 150 through a conductive pattern that is formed at the rigid substrate 150.

The image sensor 160 includes a light-receiving window 160a on a top surface thereof, and a gold bump 160b is protruded from a bottom surface of the image sensor 160. A bonding pad of the image sensor 160 is electrically connected to the gold bump 160b in a chip-packaging process. The gold bump 160b is firmly bonded to the gold pad 15Od of the rigid substrate 150 by a non-conductive paste (NCP, for example, NEX-181, which is a product name of an NCP manufactured by Nippon Steel Chemical Co., Ltd. (NSC), Japan) as the adhesive 164, so that the gold bump 160b is also electrically connected to the gold pad 150d via the NCP. The image sensor 160 and the rigid substrate 150 are assembled to each other using the NCP, so that assembly errors between the image sensor 160 and the rigid substrate 150 may be minimized as compared with a conventional solder bump. The conventional solder bump has a problem in that the image sensor is spaced apart from the rigid substrate by a gap of about 0.2mm to about 0.3mm after soldering balls are completely hardened. However, the image sensor 160 and the rigid substrate 150 are mechanically assembled to each other by the NCP, and the electrical connection between the image sensor 160 and the rigid substrate 150 is completed by a direct contact of the gold bump 160b and the gold pad 15Od, so that the image sensor 160 is not spaced apart from the rigid substrate 150, even though the NCP is sufficiently hardened. Furthermore, an attractive force is applied to each other between the gold bump 160b and the gold pad 150d when hardening the adhesive 164, so that the contact between the gold bump 160b and the gold pad 15Od is much more improved, to thereby much more improve the electrical connection between the gold bump 160b and the gold pad 150d.

A cover glass 162 is disposed on the top surface of the image sensor 160, so that the light receiving window 160a is protected by the cover glass 162. As an example embodiment, an infrared light-blocking material may be coated on the cover glass 162, to thereby form an infrared light-blocking layer on the cover glass and to omit an IR-cut filter glass from the camera module 100.

FIG. 7 is a view illustrating a structure of an automatic aligning lens system according to an example embodiment of the present invention. Optical axes of the lenses in the automatic aligning lens system automatically coincide with one another.

Referring to FIG. 7, the automatic aligning lens system of the present example embodiment includes a lens combination 200 having first, second and third lenses 202, 204 and 206 formed through a plastic injection molding process. The first and third lenses 202 and 206 include central portions 202a and 206a having a convex surface, respectively, and peripheral portions 202b and 206b functioning as a spacer, respectively. The second lens 204 includes a central portion 204a having a convex surface and a peripheral portion 204b functioning as a spacer. The first, second and third lenses are spaced apart from one another by a predetermined distance due to the peripheral portions 202b, 204b and 206b of the lenses functioning as a spacer, to thereby reduce assembly errors as compared with the conventional individual spacer structure.

A first slope 202c is protruded from a lower edge portion of the peripheral portion 202b of the first lens 202, and a second slope 204c is formed at an upper edge portion of the peripheral portion 204b of the second lens 204. The first slope 202c and the second slope 204c are slanted at the same grade and make surface contact with each other. A third slope 204d is formed at a lower edge portion of the peripheral portion 204b of the second lens 204, and a fourth slope 206c is protruded from an upper edge portion of the peripheral portion 206b of the third lens 206. The third slope 204d and the fourth slope 206c are slanted at the same grade and make surface contact with each other. The first, second, third and fourth slopes 202c, 204c, 204d and 206c guide the first, second and third lenses 202, 204 and 206, to align the first, second and third lenses 202, 204 and 206 with respect to a common central axis, so that an optical axis of each of the lenses 202, 204 and 206 automatically coincides with one another.

As an example embodiment, first, second and third light shielding layers

202d, 204e and 206d may be further formed on the peripheral portions 202b, 204b and 206b of each of the lenses 202, 204 and 206, so that noise due to scattered light may be prevented, by preventing the scattered light from passing through the peripheral portions 202b, 204b and 206b.

In addition, an infrared light-blocking layer 204f is formed on a bottom surface of the central portion 204a of the second lens 204. Otherwise, the infrared light-blocking layer 204f may be formed on cover glass 162 of the image sensor 160 in place of the lens combination 200. The infrared light-blocking layer 204f may substitute for the conventional IR-cut glass, to thereby reduce a length of the lens combination 200. As a result, the size of the camera module may be reduced and the light-receiving window 160a of the image sensor 160 may be sufficiently prevented from being contaminated by a conventional adhesion structure including the IR-cut glass disposed in front of the image sensor.

Method of assembling the camera module of the first embodiment of the present invention FIG. 8 is a flow chart illustrating a method of assembling the camera module of the first embodiment of the present invention.

Referring to FIG. 8, the gold bump is formed on a die on which the image sensor is formed in a clean room (step S 102), and the non-conductive paste (NCP) is coated on the gold pad of the rigid substrate (step S 104). Then, the die including the gold bump is positioned on the rigid substrate in a flip-chip bonding apparatus (step S 106), and is thermally pressed against the rigid substrate with heat, to thereby harden the NCP (step S 108). As a result, the NCP between the gold bump and the gold pad is extracted out, and the gold bump makes direct contact with the gold pad while the NCP is hardened by the heat. The hardening of the NCP causes the gold bump to make closer contact with the gold pad, thereby improving an electrical connection between the gold bump and the gold pad.

Meanwhile, the lens combination is installed in the barrel of the lens holder (step Sl 10), and an ultraviolet bonding agent is spread out at a boundary area of the lens combination and the barrel (step Sl 12). Then, an ultraviolet light is irradiated onto the ultraviolet bonding agent, and the ultraviolet bonding agent is hardened between the lens combination and the barrel (step Sl 14), to thereby complete a lens assembly process. The lenses in the lens combination are automatically aligned with one another so that the optical axes of the lenses automatically coincide to the same axis. As a result, the lens combination has an automatically aligned optical axis.

The lens holder including the lens combination is combined with the rigid substrate to which the die is bonded (step Sl 16), and the protrusions of the lens holder, which penetrates the rigid substrate and is protruded from a bottom surface of the rigid substrate, are thermally pressed against the bottom surface of the rigid substrate (step Sl 18). As a result, the protrusions are flattened and spread out on the bottom surface of the rigid substrate, thereby firmly bonding the lens holder to the rigid substrate. The above-mentioned assembly process causes the reference surface of the lens holder to make very close contact with the top surface of the rigid substrate to such a degree that a gap distance between the lens combination and the rigid substrate is no more than about 2±0.1mm. Accordingly, the focal distance between the image sensor and the light-receiving window is set to be within an allowable design range, so that no focal distance adjustment is required according to the present example embodiment.

When the lens holder is sufficiently bonded to the rigid substrate, a plurality of individual substrates is separated from the array substrate (step S120). Various parts such as a connector are installed to the flexible substrate (step S 122), and the flexible substrate is connected to the rigid substrate by the connector (step S 124), thereby completing the camera module.

A module test is performed on the completed camera module (step S 126), and camera quality, such as display quality and electrical connections, is checked in the module test. The camera module not satisfying a desired camera quality is flagged as a defect and is discarded.

The above-mentioned assembling method of the lens holder and the rigid substrate does not require the epoxy bonding agent, so that a high-temperature thermal treatment, for example, in a range of about 100⁰C to about 120⁰C, may be omitted in the present example embodiment. Accordingly, a plastic lens, which is easily deformed by heat, may be utilized as a member of the lens combination in the lens holder even though the lens combination including a plurality of lenses is installed into the lens holder before the lens holder is bonded to the rigid substrate.

Lens holder bonded by an epoxy bonding agent without a focal distance adjustment FIG. 9 is an exploded perspective view illustrating a camera module according to a second example embodiment of the present invention, and FIG. 10 is a cross-sectional view illustrating the camera module shown in FIG. 9.

The camera module of the present embodiment is the same as in

Embodiment 1 except that the lens holder is bonded to the rigid substrate using an epoxy bonding agent. Accordingly, in FIGS. 9 and 10, the same reference numerals denote the same elements in FIGS. 3 to 8; thus, the detailed descriptions of the same elements will be omitted.

Referring to FIGS. 9 and 10, a box-shaped receiving unit 112 of the lens holder 110 in the camera module of the present embodiment includes a reference face 112f on the bottom surface thereof. The reference face 112f is substantially horizontal with respect to an optical axis 102, and makes contact with a top surface 150a of an edge portion 150f of the rigid substrate 150. An adjustment for a back-focus is performed on a basis of the reference face 112f.

A bonding surface 112g is formed on inner sidewalls of the receiving unit 112 upwardly stepped from the reference face 112f, so that the bonding surface 112g is higher than the reference face 112f by a predetermined gap distance. The bonding surface 112g makes contact with an epoxy bonding agent 156 that is coated on a bonding area 15Og (represented as a dotted line in FIG. 9) of a top surface 150a of the rigid substrate 150, and the gap distance between the reference face 112f and the bonding surface 112g corresponds to a thickness of the epoxy bonding agent 156.

The epoxy bonding agent 156 is coated along an inner edge portion of the bonding area 150g of the rigid substrate 150, and is pressed down upon by the bonding surface 112g of the lens holder 110. Therefore, the epoxy bonding agent 156 is spread out from the inner edge portion of the bonding area 150g to an outer edge portion of the bonding area 150g. The spreading of the epoxy bonding agent 156 is adjusted in such a way that the epoxy bonding agent 156 is not interposed between the reference face 112f and the edge portion 150f of the rigid substrate 150.

In the present example embodiment, the epoxy bonding agent 156 comprises a low-temperature hardening epoxy that tends to be hardened at a temperature below about 80⁰C, so that a thermal effect on the plastic lenses in the lens combination, which have been already installed in the barrel 114 of the lens holder 110 before the epoxy bonding agent 156, may be minimized during a hardening process for the epoxy bonding agent 156. An example of the low-temperature hardening epoxy bonding agent includes LPD-4391 (a product made by Loctite Co., Ltd. in the U.S.A.)

According to the present embodiment, the reference face of the lens holder functions as a base for a process without a focal distance adjustment, and the lens holder is firmly bonded to the rigid substrate by the low-temperature hardening epoxy bonding agent without any thermal effect on the plastic lenses in the lens holder. In addition, the lens holder may be more closely sealed off from surroundings due to the epoxy bonding agent, so that the contamination of the light-receiving window due to foreign matter, such as dust, is sufficiently prevented by the epoxy bonding agent. That is, the present example embodiment satisfies the desired three factors for a camera module: no focal distance adjustment, a firm bondage of the lens holder and the substrate, and a superior sealing of the lens holder from surroundings.

Modification of Embodiment 2

Lens holder bonded by an epoxy bonding agent without a focal distance adjustment

FIG. 11 is a cross-sectional view illustrating a modified lens holder of the camera module of the second embodiment of the present invention. Referring to FIG. 11, the modified lens holder shown in FIG. 11 is the same as the lens holder of the second embodiment except that a reference face 112m is formed at an inner portion of the bottom surface of the lens holder 110, and a bonding surface 112n is formed at an outer portion of the bottom surface of the lens holder 110. Accordingly, the epoxy bonding agent 158 is coated along the edge portion 150f of the rigid substrate 150, and is pressed down upon by the bonding surface 112n of the lens holder 110. Therefore, the epoxy bonding agent 158 is spread out from the outer portion of the bottom surface into the inner portion of the lens holder 110. In the same way as in Embodiment 2, the spreading of the epoxy bonding agent 158 is adjusted in such a way that the epoxy bonding agent 158 is not interposed between the reference face 112m and the edge portion 15Of of the rigid substrate 150.

According to the modification of Embodiment 2, a sidewall of the rigid substrate 150 is also covered with the epoxy bonding agent 158, thereby improving a bonding strength of the lens holder 110 with respect to the rigid substrate 150.

Method of assembling the camera module of the second embodiment of the present invention

FIG. 12 is a flow chart illustrating a method of assembling the camera module of the second embodiment of the present invention.

The method of assembling the camera module of the present embodiment is the same as in Embodiment 1 except for a step of bonding the lens holder to the rigid substrate. Accordingly, in FIG. 12, the same reference numerals denote the same steps in FIG 9; thus, the detailed descriptions of the same steps will be omitted.

Referring to FIG. 12, the lens assembly process is completed through the same steps S 102 to Sl 14 as described with reference to FIG. 9, and the low-temperature hardening epoxy bonding agent is coated on the edge portion 150f of the rigid substrate 150 (step S 130). As an example embodiment, the low-temperature hardening epoxy bonding agent is spread out to such an amount that the epoxy bonding agent is not interposed between the reference face of the lens holder and the edge portion of the rigid substrate. Then, the lens holder including the lens combination is combined with the rigid substrate on which the epoxy bonding agent is coated (step S 132), and heat is transferred to the epoxy bonding agent in an oven at a temperature below about 8O⁰C, thereby hardening the epoxy bonding agent (step S 134). According to the above-mentioned method of assembling the camera module, the reference face of the lens holder makes much closer contact with the top surface of the rigid substrate, and the focal distance between the lens and the light-receiving window of the image sensor is set to be within an allowable design range, so that no focal distance adjustment is required in the lens assembly process.

Lens holder bonded to a flexible substrate by an epoxy bonding agent without a focal distance adjustment and with an auto-focusing system

FIG. 13 is an exploded perspective view illustrating a camera module having an auto-focusing system according to a third example embodiment of the present invention, and FIG. 14 is a cross-sectional view illustrating the camera module shown in FIG. 13. Referring to FIGS. 13 and 14, the auto-focusing camera module 300 of the present example embodiment includes an auto-focusing barrel 310, a lens holder 320, a flexible substrate 330, an image sensor 340 and a supplementary plate 350.

The auto-focusing barrel 310 includes an operation barrel 312, in which a lens is installed, and a driving unit 314. The driving unit 314 includes a step motor, a hydraulic motor, a micro electromechanical motor operated by a Piezo method, an actuator operated in a magnetic field and a solenoid operated in an electromagnetic field such as an electromagnet. The auto-focusing barrel 310 is installed into the lens holder 310 and performs an optical zoom feature in the camera module 300.

The lens holder 320 includes a receiving portion for receiving the auto-focusing barrel 310 and a bonding portion to which the flexible substrate 330 is bonded. As an example embodiment, a lower portion of the bonding portion includes the same structure as the lens holder in Embodiment 2, so that the bonding portion includes a two-stepped structure of a reference face 322 and a bonding surface 324.

The flexible substrate 330 includes a die portion 332, a bridge portion 334 and a connector portion 336. A light-passing hole 332a is formed at a central portion of the die portion 332, and a low-temperature hardening epoxy bonding agent 338 is coated on a peripheral portion 332b (represented as a doted line in

FIG. 13) of the die portion 332.

An image sensor 340 is bonded to a bottom surface of the flexible substrate 330 through a flip-chip bonding process in such a way that a light-receiving window 342 of the image sensor 340 is aligned with the light-passing hole 332a. A non-conductive paste (NCP) is interposed between a plurality of gold pads on the bottom surface of the flexible substrate 330 and a plurality of gold bumps arranged around the light-receiving window 342, so that the gold pad is electrically connected to the gold bump 342 through the NCP and the image sensor 340 is strongly adhered to the flexible substrate 330 due to the NCP. The image sensor 340 is received into a receiving hole 352 of the supplementary plate 350, and a sealing agent such as an epoxy bonding agent is spread around the image sensor 340, thereby sealing off the image sensor from surroundings. The supplementary plate 350 is bonded to the bottom surface of the flexible substrate 330, thereby reinforcing a mechanical strength of the flexible substrate 330.

A connector 360 is positioned on the connector portion 336, and a conductive pattern is positioned on the bridge portion 334. Accordingly, the die portion 332 is electrically connected to the connector portion 336 through the conductive pattern on the bridge portion 334.

According to the third embodiment of the present invention, the image sensor is received in a space of which a height is substantially identical to a thickness summation of the flexible substrate 330 and the supplementary plate 350, so that a height of the bonding portion of the lens holder 320 may be sufficiently reduced. Accordingly, an overall size of the camera module 300 may be sufficiently reduced due to the reduction of the size of the lens holder 320.

A method of assembling the auto-focusing camera module 300 is described hereinafter. At first, the image sensor is bonded to the flexible substrate by a flip-chip bonding process and the supplementary plate is bonded to the flexible substrate. Then, a sealing agent such as an epoxy bonding agent is filled into a gap space between the image sensor and the supplementary plate, to thereby seal off the image sensor from surroundings. A connector is combined to the flexible substrate and an epoxy bonding agent is spread out on a bonding area of the top surface of the flexible substrate. The lens holder is combined to the bonding area of the flexible substrate and the epoxy bonding agent is hardened, so that the lens holder is strongly bonded to the flexible substrate in such a way that the reference face of the lens holder makes contact with the top surface of the flexible substrate. Accordingly, the resultant size of the image sensor and the flexible substrate may be set to be within an allowable design range.

Thereafter, the auto-focusing barrel is positioned in the receiving portion of the lens holder, to thereby complete the auto-focusing camera module for a camera phone.

This invention has been described with reference to the example embodiments. It is evident, however, that many alternative modifications and variations will be apparent to those having skill in the art in light of the foregoing description. Accordingly, the present invention embraces all such alternative modifications and variations as fall within the spirit and scope of the appended claims. For example, various modifications would be allowable at the various parts of the camera module of the present invention, such as a bonding structure of the lens holder and the substrate, an IR-cut coating structure for protecting the lens and the image sensor, lens combinations, a structure of the flexible substrate and the supplementary plate and auto-focusing lens combinations. In addition, an aspherical single lens may be utilized in place of the lens combinations in the lens holder, as would be known to one of ordinary skill in the art.

Industrial Applicability

As described above, the camera module for a cellular phone may be formed into a subminiature size and to have a high performance without a focal distance adjustment, thereby improving productivity and reducing manufacturing costs of the camera module.

Claims

1. A camera module including a substrate to which a lens holder and an image sensor are installed, the lens holder including at least one lens and the image sensor receiving light through the lens, the lens holder comprising: a barrel in which the lens is installed; and a box-shaped receiving unit that is combined together with the barrel as one body and is bonded to a top surface of the substrate, thereby providing a space for receiving the image sensor, wherein, one of an inner or outer edge portion of a bottom surface of the receiving unit is arranged vertically with respect to an optical axis of the lens and makes contact with an edge portion of a top surface of the substrate, to thereby function as a reference face for a focal distance between the lens and a light-receiving surface of the image sensor, and a remaining portion of the inner or outer edge portion of the bottom surface of the receiving unit is spaced apart from the top surface of the substrate by a predetermined gap distance and a bonding agent is filled into the gap distance, to thereby bond the lens holder to the substrate and to seal off the space of the receiving unit in which the image sensor is received from surroundings.

2. The camera module of claim 1, wherein the lens is inserted into the barrel through the receiving unit combined together with the barrel as one body, and is bonded to the barrel.

3. The camera module of claim 1, wherein a central portion of the lens includes a spherical or an aspherical surface for guiding a light, and a peripheral portion of the lens includes a spacer for separating neighboring lenses adjacent to each other.

4. The camera module of claim 3, wherein the spacer includes at least one slope at an edge portion thereof, the slope aligning the neighboring lenses in such a way that optical axes of the lenses coincide with each other.

5. The camera module of claim 1, wherein the lens includes a plastic lens and the bonding agent for bonding the lens holder to the substrate includes a low-temperature hardening bonding agent.

6. The camera module of claim 1, wherein at least one lens includes at least one aspherical lens.

7. The camera module of claim 1, wherein the image sensor is bonded to the substrate by a flip-chip bonding process.

8. The camera module of claim 1, wherein a non-conductive paste is interposed between a gold bump of the image sensor and a gold pad of the substrate, and the gold bump is bonded to the gold pad due to the non-conductive paste when the gold bump is pressed against the gold pad, so that the gold bump is electrically connected to the gold pad through the non-conductive paste.

9. The camera module of claim 1, wherein the substrate includes a flexible substrate and a supplementary plate for reinforcing a mechanical strength of the flexible substrate.

10. The camera module of claim 9, wherein the supplementary plate includes a receiving hole for receiving the image sensor at a central portion.

11. A method of assembling a camera module, comprising: forming a gold bump on an image sensor; coating a non-conductive paste on a substrate including a gold pad ; pressing the gold bump of the image sensor onto the gold pad of the substrate by a flip-chip bonding process, so that the gold bump is electrically connected to the gold pad; hardening the non-conductive paste while the gold bump is pressed against the gold pad; installing a lens into a barrel of a lens holder, the lens holder including a reference face at a portion of a bottom surface and a bonding surface stepped away from the bottom surface; coating a bonding agent along a peripheral portion of the substrate; combining the lens holder with the substrate, so that the reference face of the lens holder makes contact with a top surface of the substrate and the bonding surface of the lens holder makes contact with the bonding agent; and hardening the bonding agent while the bonding surface of the lens holder makes contact with the bonding agent, to thereby bond the lens holder to the substrate.

12. A camera module including a substrate to which a lens holder and an image sensor are installed, the lens holder including at least one lens and the image sensor receiving light through the lens, the lens holder comprising: a barrel in which the lens is installed; and a box-shaped receiving unit that is combined together with the barrel as one body and is bonded to a top surface of the substrate, thereby providing a space for receiving the image sensor, wherein, an inner edge portion of a bottom surface of the receiving unit is arranged vertically with respect to an optical axis of the lens and makes contact with an edge portion of a top surface of the substrate, to thereby function as a reference face for a focal distance between the lens and a light-receiving surface of the image sensor; an extension wall downwardly extending from an outer edge portion of the bottom surface of the receiving unit adjacent to the inner edge portion of the bottom surface of the receiving unit and making contact with a side surface of the substrate, to thereby seal off the space of the receiving unit from surroundings; a plurality of protrusions downwardly extending from the inner edge portion of a bottom surface of the receiving unit to a length larger than a thickness of the substrate, so that the protrusion penetrates the substrate and an end portion of the protrusion is protruded from a bottom surface of the substrate; and a plurality of insertion holes being formed at the edge portion of the substrate, and the protrusion of the lens holder being inserted into the insertion hole, wherein, the protruded end portion of the protrusion is thermally pressed against the bottom surface of the substrate, to thereby bond the lens holder to the substrate.

13. A method of assembling a camera module, comprising: forming a gold bump on an image sensor; coating an insulation paste on a substrate including a gold pad; pressing the gold bump of the image sensor onto the gold pad of the substrate by a flip-chip bonding process, so that the gold bump is electrically connected to the gold pad; hardening the insulation paste while the gold bump is pressed against the gold pad; installing a lens into a barrel of a lens holder; inserting a protrusion of the lens holder into an insertion hole of an edge portion of the substrate; and thermally pressing an end portion of the protrusion, which is protruded from a bottom surface of the substrate, against the bottom surface of the substrate, so that a size of the end portion of the protrusion is larger than a diameter of the insertion hole.

14. A camera module comprising: a substrate of which a top surface is substantially horizontal with respect to an optical axis and on which a gold pad is positioned; a lens holder including a box-shaped receiving unit and a barrel combined together with the receiving unit as one body; at least one lens installed in the barrel of the lens holder; and an image sensor positioned in a sealed space between the receiving unit and the substrate and connected to a top surface of the substrate, wherein, a bottom portion of the receiving unit includes a reference face that is substantially horizontal with respect to the optimal axis and makes direct contact with a top surface of the substrate, and a bonding surface that is spaced apart from the top surface of the substrate by a predetermined gap distance and makes direct contact with a bonding agent in the gap distance; wherein a central portion of the lens includes a spherical or an aspherical surface for guiding light, and a peripheral portion of the lens includes a spacer for separating neighboring lenses adjacent to each other; and wherein the spacer includes at least one slope at an edge portion thereof for aligning the neighboring lenses in such a way that optical axes of the lenses coincide with each other, and an infrared light-cut film is coated on the at least one lens, so that no focal distance adjustment is required after an assembling process.