News Column

Patent Issued for Camera Module Lens Holder

September 3, 2014



By a News Reporter-Staff News Editor at Journal of Engineering -- From Alexandria, Virginia, VerticalNews journalists report that a patent by the inventor Hirooka, Shohgo (Osaka, JP), filed on March 9, 2012, was published online on August 19, 2014.

The patent's assignee for patent number 8810722 is Sharp Kabushiki Kaisha (Osaka-Shi, Osaka, JP).

News editors obtained the following quote from the background information supplied by the inventors: "A camera module mounted on a portable phone or the like has a structure including (i) a solid-state image sensor, (ii) a glass substrate, (iii) a wired board with terminals, (iv) a lens, and (v) a holder (lens holder) for holding the lens. The solid-state image sensor is, for example, CCD (Charge Coupled Device) or CMOS (Complementary Metal Oxide Semiconductor) image sensor.

"Recently, the solid-state image sensor has been further miniaturized. Thus, if there is a foreign material present in a light receiving portion of the solid-state image sensor, in an optical path in which light to enter the solid-state image sensor travels on the glass substrate, or in the like position, shadow of the foreign material would be possibly captured on a screen on which a captured image is displayed. On the screen, the shadow of the foreign material appears as a black spot, or stain, thereby causing defection in the image captured by the camera module. In the following, such a foreign material is referred to as 'dust'. Furthermore, if the dust is of such a minute size that it has a size of 30 .mu.m or less, or about 20 .mu.m, the dust not only causes the shadow or black spot on the screen, but also is difficult to remove from the camera module because the dust can enter gaps formed in non-flat portions in a micro lens arrays.

"Here, the dust contaminating the inside the camera module can be classified generally into two types: process-origin dust; and material-origin dust.

"Examples of the process-origin dust encompass ones generated by wearing of devices used in a manufacturing process of the camera module, ones (hair and the like) derived from a body of a worker in the manufacturing process, and the like dust. The material-origin dust is relatively large (to be visible by human eyes) and is easy to find and remove by inspections or the like.

"Examples of the material-origin dust encompass (i) ones carried by components of the camera module when the components are shipped in, (ii) exfoliation (such as filler) fallen off from a molded resin or an adhesive agent, (iii) dust worn off from an auto focusing or zooming operating mechanism or component during its operation, and (iv) the like. The material origin dust often very small in size, because it would be minute resin pieces, a fallen-off filler, or the like.

"If dust of a visible size is present on the glass substrate, it is easy to remove the dust from the glass substrate. However, if minute dust is attached to a wall surface of the lens holder, a surface of the wiring board, etc. other than the light receiving portion (micro lens array) of the solid-state image sensor, it is difficult to detect the dust by inspection or the like. Failure of detecting the dust would lead to shipping out a defective camera module having a risk of causing defective image capturing. If the dust is moved to the light receiving portion (micro lens array) of the solid-state image sensor by vibration and/or impact during transportation or delivery, the camera module is impaired at a dealer or a user.

"The glass substrate is not only a component having optical functions such as a function as an optical filter as described above, but also a component for preventing dust from contaminating the light receiving portion (micro lens array) of the solid-state image sensor, the wall surface of the lens holder, the surface of the wired board, etc.

"Patent Literatures 1 to 3 discloses techniques as to assembling structures that such a glass substrate has for the purpose of preventing the dust contamination.

"The object of the technique disclosed in Patent Literature 1 is to accurately determine a distance between an optical system of an image capturing device lb and an image capturing surface 211, and a tilting of the optical system with respect to the image capturing surface 211. In order to attain the object, the Patent Literature 1 discloses the following technical feature. From above an electrically conductive adhesive agent (such as silver paste) applied on an electrode on a steric circuit substrate 3, a glass substrate 22 is pressed against the steric circuit substrate 3 via a ball bump 221b. By deforming the ball bump 221b by a force of the pressing, the glass substrate 22 is adhered to a mounding reference surface 351 in such a state that the glass substrate 22 is abutted against the mounting reference surface 351, which is a top edge of a protrusion section 35b (see FIG. 25).

"The technique disclosed in Patent Literature 1, an image capturing device 21 is mounted on the steric circuit substrate 3 with the highly-flat glass substrate 22 imposed therebetween. This makes it possible to mount the image capturing device 21 on the steric circuit substrate 3 easily and accurately. Furthermore, the glass substrate 22 has a thermal expansion coefficient (about 8.times.10.sup.-6/.degree. C.) smaller than that (about 25.times.10.sup.-6/.degree. C.) of a resin substrate. This reduces a heat stress applied on a position (connection portion) at which the image capturing device 21 and the glass substrate 22 are connected with each other, thereby giving a better connection reliability to the image capturing device 21.

"Patent Literature 2 discloses the following technical feature. On an upper surface of a ring-shaped connection section 34 of a frame-shaped member 30, a thermally-curing adhesive agent 40 (illustrated by hatching with oblique lines) is applied. The adhesive agent 40 is applied selectively on a region other than a groove region B, which is that part of the upper surface of the ring-shaped connection section in which grooves 36 are provided (see FIG. 26).

"Patent Literature 3 discloses the following technical feature. A camera module has a pedestal portion having an abutting section positioned apart from side walls, and connection sections positioned at corners between adjacent side walls, and a bank section. The abutting section is not for bonding with a glass cover but is for abutting against the glass cover so as to determine position of the glass cover with respect to a mounding surface of the pedestal portion, and to determine a tilting angle of the glass cover. The abutting section and the bank section further have a function of banking up an adhesive agent to prevent the adhesive agent from flooding into an image capturing region. By this, a good image capturing quality is ensured meanwhile a wide-spreading of a connection region is prevented. Like the abutting section, the bank section also abuts against the glass cover in bonding the pedestal portion and the glass cover with each other. Meanwhile, the connection section is lower than the abutting section, so that the connection section will not touch the glass cover in bonding the pedestal portion and the glass cover with each other. Thus, the bonding the pedestal portion and the glass cover with each other crease a gap between the connection section and the glass cover. The bonding between the connection section and the glass cover is carried out in the gap."

As a supplement to the background information on this patent, VerticalNews correspondents also obtained the inventor's summary information for this patent: "Technical Problem

"The technique disclosed in Patent Literature 1 requires that the bonding between the steric circuit substrate 3 and the glass substrate 22 need providing, therebetween, the ball bump 221b higher than the mounting reference surface 351, and deforming the ball bump 221b by pressing. If the force of the pressing is not strong enough, the deformation of the ball bump 221b becomes insufficient. This causes the glass substrate 22 to abut against the mounding reference surface 351 insufficiently, thereby creating a risk that the distance between the steric circuit substrate 3 and the glass substrate 22, and the tilting angle of the glass substrate are deviated from desired distance and tilting angle, respectively. This also causes insufficient abutting of the ball bump 221b against the steric circuit substrate, thereby creating a risk that electric conduction between the ball bump 221b and the steric circuit substrate 3 becomes defective. On the contrary, if the force of the pressing is excessively strong, the glass substrate 22 will strongly press the mounting reference surface 351, thereby creating a risk that the mounting reference surface 351 is deformed and/or the glass substrate 22 is broken. Further, the deformation of the mounting reference surface 351 would create a risk that the distance between the steric circuit substrate 3 and the glass substrate 22, and the tilting angle of the glass substrate are deviated from desired distance and tilting angle, respectively.

"Moreover, the technique disclosed in Patent Literature 1 is such that the glass substrate 22 has a thermal expansion coefficient (about 8.times.10.sup.-6/.degree. C.) much smaller than that (about 25.times.10.sup.-6/.degree. C.) of the steric circuit substrate 3, which is a resin substrate. As a result, if thermal expansion occurs in the glass substrate 22 and the steric circuit substrate 3 bonded together, the steric circuit substrate 3 is extended further than the glass substrate, thereby applying a stress on the connection portion or the glass substrate 22. Moreover, because the ball bump 221b and the steric circuit substrate 3 are bonded tightly, it is difficult to buffer the stress at the connection portion at which the bonding bump 221b and the steric circuit substrate 3 are bonded. Consequently, the stress would be a cause of peeling or breaking of the glass substrate 22.

"The technique disclosed in Patent Literature 2 does not perform the determination of the position and tilting of the glass cap 50 with respect to the frame-shaped component 30.

"Moreover, the technique disclosed in Patent Literature has the following drawback. If the frame-shaped component 30 and the glass cap 50 are connected via their contact surfaces which are too flat, a gap between their surfaces will be too narrow to bent out swelling air. On the other hand, if the frame-shaped component 30 and the glass cap 50 are connected via their contact surfaces, at least one of which is not flat, bending out the swelling air can be performed but the gap become so wide to face the risk that foreign materials enter into the gap.

"In addition, if the frame-shaped component 30 and the glass cap 50 are connected via contact surfaces of a large contact (bonding) area, the contact surfaces cannot maintain desired smoothness necessary for performing the bonding highly accurately. That is, it is necessary to have a small bonding area between the contact surfaces of the frame-shaped component 30 and the glass cap 50. Furthermore, downsizing of portable devices such as portable phones etc. requires that a region to which the adhesive agent is to be applied should be limited even within a region in which components to be bonded overlap each other in assembling the camera module.

"Conventionally, in order to bond a glass substrate (glass cap 50) to a lens holder (frame-shaped component 30), an adhesive agent is applied on a flat surface of the lens holder (frame-shaped component 30) by using a dispenser (applying device). However, the dispenser has a difficulty in dispensing the adhesive agent in a constant direction under influence of various forces applied on the dispenser according to (i) a speed at which the adhesive agent is pushed out from the dispenser and (ii) a moving speed etc. of the dispenser. As a result, it is difficult to apply the adhesive agent straightly (in a non-staggered manner), and the adhesive agent is applied in a staggered manner to have a staggered trace.

"In the technique disclosed in Patent Literature 2, it is necessary to spare a region to allow the adhesive agent to be applied with the staggered trace and a region to allow the adhesive agent to be extended in bonding. This inhibits downsizing of the camera module. In the technique disclosed in Patent Literature 1, the adhesive agent is applied pointedly to points at which the ball bump 221b and the steric circuit substrate 3 are to be bonded. Thus, the technique disclosed in Patent Literature 1 does not relate to the aforementioned drawback regarding the downsizing of the camera module.

"In the technique disclosed in Patent Literature 3, the abutting section functions to bank up the adhesive agent in bonding the connection sections and the glass cover, thereby preventing the connection region from being widely spread. The abutting section according to Patent Literature 3 prevents the wide-spreading of the connection region by causing the adhesive agent to attach to the abutting section.

"When the adhesive agent is attached to the abutting section in bonding the connection section and the cover glass, there is a risk that the abutting section is bonded to the cover glass. In case where the abutting section is bonded to the glass cover, the abutting section is fixedly bonded to the glass cover, thereby causing the glass cover to be firmly fixed.

"In the technique disclosed in Patent Literature 3, the firm fixing of the glass cover by the abutting section makes it difficult to absorb the stress caused due to the thermal expansion of the pedestal section and/or the glass cover and applied on the glass cover or the bonding portion at which the pedestal section and the glass cover is bonded. The stress would possibly damage the glass cover.

"Moreover, the technique disclosed in Patent Literature 3 is such that the gap between the abutting section and the glass cover in bonding the connection section and the glass cover is smaller than a diameter of a filler and a curing agent contained in the adhesive agent, but the adhesive agent can enter the gap. Thus, the gap at which the abutting section and the glass cover abut causes only a main component of the adhesive agent to enter and spread therein. In the technique disclosed in Patent Literature 3, this results in quality deterioration of the adhesive agent or causes post-bonding curing to be insufficient in some parts. This leads to a risk of lowering accuracy of bonding of the pedestal section and the glass cover.

"Moreover, the technique disclosed in Patent Literature 3 is such that the connection sections are provided at the corners of adjacent side walls, and the adhesive agent is provided in the gap on the top of the connection sections. Moreover, in the technique disclosed in Patent Literature 3, the glass cover abuts the side walls. Glass processing (dicing etc.) is generally carried out at most with accuracy needing allowance of about +/-0.05 mm. Moreover, in general, it is necessary to have a gap (clearance) between the glass cover and the side wall in order to absorb the allowance. Thus, there is a slight gap between the glass cover and the side wall. There is a risk that the adhesive agent may enter into the gap, thereby being extended, along a reverse side of the glass cover, out of the region in which the adhesive agent supposed to remain for bonding. This leads to a risk that the bonding between the connection section and the glass cover becomes insufficient in the technique disclosed in Patent Literature 3.

"The present invention was accomplished in view of the aforementioned problem, and one object of the present invention is to provide a camera module a camera module and a production method thereof, each of which makes it possible to perform bonding of a glass substrate to a lens holder in such a way to achieve (i) high accuracy in bonding and glass substrate positioning, (ii) reduction in damaging the glass substrate, and (iii) miniaturization.

"Solution to Problem

"In order to attain the object, a camera module according to the present invention is a camera module including a lens holder for holding a lens, and a glass substrate bonded to the lens holder, wherein: the lens holder includes (i) an abutting section for abutting the glass substrate in order to determine a position of the glass substrate, and (ii) a protrusion section configured to be bonded with the glass substrate via an adhesive agent; the abutting section is not bonded with the glass substrate; and the protrusion section has a top portion that is positioned apart from the glass substrate.

"With this configuration, the position of the glass substrate can be determined by abutting the glass substrate to the abutting section. Therefore, it is possible to perform the positioning of the glass substrate in bonding the glass substrate to the lens holder.

"With this configuration, it is not necessary that the lens holder or the glass substrate should have a component higher than the abutting section in order to perform the bonding of the glass substrate to the lens holder. That the camera module according to the present invention does not need pressing the lens holder or the glass substrate in abutting the glass substrate to the abutting section. Therefore, it is possible to reduce the risk that the distance between the lens holder and the glass substrate, and the tilting angle of the glass substrate are deviated from the desired distance or tilting angle. Moreover, it is possible to reduce the factor for causing disconnection in the glass substrate.

"According to the arrangement, the abutting section, which is a portion with which the lens holder abuts the glass substrate, is not bonded to the glass substrate, meanwhile the protrusion section, lower than the abutting section, is bonded to the glass substrate. This makes it possible that the glass substrate and the protrusion section do not touch each other when the glass substrate abuts the abutting section. This allows the adhesive agent to interpose between the glass substrate and the protrusion section. Unless the adhesive agent is not an adhesive agent having a very large adhesive strength (very small flexibility), the behavior of the adhesive agent can absorb the stress caused by the thermal expansion/shrinkage of the lens holder and/or the glass substrate. Thus, the camera module can reduce the peeling or cracking of the glass substrate.

"With this configuration, the adhesive agent, applied to the top portion of the protrusion section by an applying device such as the dispenser or the like, abuts the top portion of the protrusion section, and the adhesive agent as abutted thereto adheres to the top portion of the protrusion section. Therefore, the adhesive agent can be applied in a non-staggered manner by abutting the protrusion section at the top portion thereof, even if the adhesive agent is not ejected in a constant direction from the applying device. As described above, the protrusion section has a guiding function for applying the adhesive agent on the lens holder in a non-staggered manner. Thus, the camera module does not need a space for allowing to apply the adhesive agent with the staggered trace. This makes it possible to downsize the camera module.

"In this Description, what is meant by the term 'top portion' is an upper edge portion of a given member, and the upper edge portion may be a point, a line, or a surface.

"With this configuration, the camera module is configured such that the glass substrate will not be bonded with the abutting section. Thus, the adhesive agent will not flow to the region where the glass substrate abuts the abutting section. Therefore, it will not happen that only the main component of the adhesive agent is spread, by wetting, to the region where the glass substrate abuts the abutting section. This makes it possible to reduce the risk that a portion at which curing of the adhesive agent is insufficient or the accuracy in the bonding of the lens holder and the glass substrate is reduced.

"Furthermore, this configuration, which makes it possible to apply the adhesive agent in a non-staggered manner by the function of the protrusion section, allows to reduce the region to which the adhesive agent is applied. This reduces the risk that the adhesive agent flows into the gap between the glass substrate and the side wall of the lens holder. This makes it possible to suppress the risk that the bonding between the lens holder and the glass substrate is insufficient.

"In order to attain the object, a production method according to the present invention is a production method for producing a camera module including a lens holder for holding a lens, and a glass substrate bonded to the lens holder, wherein the lens holder includes (i) an abutting section for abutting the glass substrate in order to determine a position of the glass substrate, and (ii) a protrusion section configured to be bonded with the glass substrate via an adhesive agent, the abutting section is not bonded with the glass substrate; and the protrusion section has a top portion that is positioned apart from the glass substrate, the method comprising: applying the adhesive agent on the protrusion section, so that a top portion of the adhesive agent applied on the protrusion section protrudes beyond a top portion of the abutting section in height level; and abutting the glass substrate to the abutting section, so as to bond the glass substrate and the protrusion section together via the adhesive agent.

"In order to attain the object, a production method according to the present invention is a production method for producing a camera module including a lens holder for holding a lens, and a glass substrate bonded to the lens holder, wherein the lens holder includes (i) an abutting section for abutting the glass substrate in order to determine a position of the glass substrate, and (ii) a protrusion section configured to be bonded with the glass substrate via an adhesive agent, the abutting section is not bonded with the glass substrate; and the protrusion section has a top portion that is positioned apart from the glass substrate, the method comprising: applying the adhesive agent on the protrusion section, so that a height of the adhesive agent applied on the protrusion section is greater than a level difference between the abutting section and the protrusion section; and abutting the glass substrate to the abutting section, so as to bond the glass substrate and the protrusion section together via the adhesive agent.

"In order to attain the object, a production method according to the present invention is a production method for producing a camera module including a lens holder for holding a lens, and a glass substrate bonded to the lens holder, wherein the lens holder includes (i) an abutting section for abutting the glass substrate in order to determine a position of the glass substrate, and (ii) a protrusion section configured to be bonded with the glass substrate via an adhesive agent, the abutting section is not bonded with the glass substrate; and the protrusion section has a top portion that is positioned apart from the glass substrate, the method comprising: abutting the glass substrate to the abutting section; and applying the adhesive agent to a gap between the protrusion section and the glass section abutted to the abutting section.

"Each of these methods makes it possible to realize the bonding structure of the camera module according to the present invention for bonding the lens holder and glass substrate

"Advantageous Effects of Invention

"As described above the present invention is arranged such that a camera module includes a lens holder for holding a lens, and a glass substrate bonded to the lens holder, wherein: the lens holder includes (i) an abutting section for abutting the glass substrate in order to determine a position of the glass substrate, and (ii) a protrusion section configured to be bonded with the glass substrate via an adhesive agent; the abutting section is not bonded with the glass substrate; and the protrusion section has a top portion that is positioned apart from the glass substrate.

"Thus, the present invention makes it possible to perform highly accurately the bonding and positioning of the glass substrate in bonding the glass substrate to the lens holder, to prevent the glass substrate from being damaged, and to down size the camera module."

For additional information on this patent, see: Hirooka, Shohgo. Camera Module Lens Holder. U.S. Patent Number 8810722, filed March 9, 2012, and published online on August 19, 2014. Patent URL: http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO1&Sect2=HITOFF&d=PALL&p=1&u=%2Fnetahtml%2FPTO%2Fsrchnum.htm&r=1&f=G&l=50&s1=8810722.PN.&OS=PN/8810722RS=PN/8810722

Keywords for this news article include: Sharp Kabushiki Kaisha.

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Source: Journal of Engineering


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