JP2011066093A - Imaging unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce warpage of a solid-state imaging element caused by the difference in thermal contraction after mounting, between a circuit board and the solid-state imaging element. <P>SOLUTION: The imaging unit 1 includes a solid-state imaging element 2, a printed board 3 and a protective glass 4. The protective glass 4 includes a plurality of conducting portions 4c connected electrically to the solid-state imaging element 2, to protect an element surface on a light-receiving portion 2a side of the solid-state imaging element 2, while the rigidity of the solid-state imaging element 2 is reinforced. On the printed board 3, the solid-state imaging element 2, to which the protective glass 4 is fitted, is flip-chip mounted. The thermal contraction force of the printed board 3 becomes weaker than the rigidity of the solid-state imaging element 2 that is reinforced by the protective glass 4. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an imaging unit including a solid-state imaging device such as a CCD or a CMOS, and more particularly to an imaging unit mounting structure capable of reducing warpage of the solid-state imaging device.

  2. Description of the Related Art Conventionally, various types of electronic imaging devices such as a digital camera and a digital video camera, an endoscope for observing the inside of an organ of a subject, and a mobile phone having an imaging function have appeared. An electronic imaging device includes an imaging unit including a solid-state imaging device such as a CCD or CMOS image sensor, and forms an optical image of a subject on a light-receiving portion of the solid-state imaging device by an optical system such as a lens. The image data of the subject is picked up by the photoelectric conversion process.

  A solid-state image sensor of such an image pickup unit is generally a bare chip state element in which metal bumps are respectively fixed on a plurality of electrode pads formed on a substrate on the light receiving unit side, and is heated on a circuit board by a heat treatment or the like. Are flip-chip mounted and electrically connected to the circuit wiring of the circuit board through the metal bumps. In addition, a protective glass is attached to the circuit board after mounting the solid-state image pickup device with an adhesive or the like so as to cover the light receiving portion of the solid-state image pickup device. As a result, the light receiving portion of the solid-state imaging device on the circuit board is sealed inside the protective glass.

  As a conventional example of such an imaging unit, a solid-state imaging device chip is mounted on a substrate having the same thermal expansion coefficient as that of a protective cap that protects the solid-state imaging device chip, and a solid state is provided between the protective cap and the substrate. There is a solid-state imaging device in which these are sealed with a sealing resin with an imaging element chip interposed therebetween (see Patent Document 1).

JP 2002-76313 A

  By the way, when a solid-state image sensor is mounted on a circuit board by a mounting technique such as flip-chip mounting, the circuit board and the solid-state image sensor are bonded together while thermally expanding by heat treatment in this mounting process. Thereafter, the circuit board and the solid-state imaging device in such a bonded state are both thermally contracted while the temperature is lowered to room temperature. However, there is a difference in thermal expansion coefficient between such a circuit board and a solid-state image sensor, resulting in a difference in thermal contraction between the two, resulting in warping of the solid-state image sensor after mounting. There is a problem of doing.

  The warp of the solid-state image sensor described above may cause a decrease in the imaging function of the solid-state image sensor, such as impairing the flatness of the light receiving unit of the solid-state image sensor and making it difficult to focus on the subject. In addition, problems caused by such warpage of the solid-state imaging device become more conspicuous as the solid-state imaging device becomes larger and thinner.

  In the solid-state imaging device described in Patent Document 1 described above, the wiring board and the solid-state imaging element chip are resin-sealed in a state of being in contact with each other via bumps for electrical joining. The contraction acts on the solid-state image sensor chip, and as a result, it is difficult to reduce the warpage of the solid-state image sensor chip due to the thermal contraction of the wiring board.

  The present invention has been made in view of the above circumstances, and provides an imaging unit capable of reducing the warpage of a solid-state image sensor due to a thermal contraction difference between a mounted circuit board and the solid-state image sensor. With the goal.

  In order to solve the above-described problems and achieve the object, an imaging unit according to the present invention includes a solid-state imaging device and a plurality of conductive portions electrically connected to the solid-state imaging device, and the solid-state imaging device. A protective glass that protects the element surface on the light receiving part side and reinforces the rigidity of the solid-state imaging element, and an opening corresponding to the light-receiving part of the solid-state imaging element is formed, and the light receiving part and the opening are opposed to each other A circuit board that is electrically connected to the solid-state imaging device via the plurality of conductive portions in a manner that is made to be, and the thermal contraction force of the circuit board is reinforced by the protective glass It is characterized in that it is weaker than the rigidity.

  In the imaging unit according to the present invention, the thermal expansion coefficient of the solid-state imaging device is the same as the thermal expansion coefficient of the protective glass.

  In the imaging unit according to the present invention as set forth in the invention described above, the protective glass is a glass member in which a concave portion that avoids contact with the light receiving portion is formed.

  In the imaging unit according to the present invention, in the above invention, the protective glass is formed with a plurality of through holes in which the plurality of conductive portions are arranged, and the conductive portions are filled in the plurality of through holes. A plurality of conductive filling members, and a plurality of protruding electrodes that electrically connect the conductive filling members and the circuit board.

  In the imaging unit according to the present invention, the protective glass is interposed between the solid-state imaging device and the circuit board.

  In the imaging unit according to the present invention, a protective glass having a plurality of conductive portions electrically connected to the solid-state imaging device and protecting the element surface on the light-receiving portion side of the solid-state imaging device is attached to the solid-state imaging device. Reinforcing the rigidity of the solid-state imaging device, the thermal contraction force of the circuit board that is electrically connected to the solid-state imaging device through the plurality of conductive portions in a mode in which the light receiving portion and the opening are opposed to each other, The rigidity of the solid-state imaging device reinforced by the protective glass is weakened. For this reason, there exists an effect that the curvature of the solid-state image sensor resulting from the thermal contraction difference of the circuit board after mounting and a solid-state image sensor can be reduced.

FIG. 1 is a schematic cross-sectional view illustrating a configuration example of an imaging unit according to an embodiment of the present invention. FIG. 2 is a flowchart illustrating an example of a manufacturing method of the imaging unit according to the embodiment of the present invention. FIG. 3 is a schematic diagram illustrating a state in which a protective glass is attached to the light receiving unit side element surface of the solid-state imaging element. FIG. 4 is a schematic diagram showing a state in which a plurality of conductive portions are formed on the protective glass attached to the solid-state imaging device. FIG. 5 is a schematic diagram showing a state in which a solid-state imaging device with a protective glass is flip-chip mounted on a printed circuit board. FIG. 6 is a schematic diagram illustrating a state in which the warpage of the solid-state image sensor is reduced by reinforcing the rigidity of the solid-state image sensor with the protective glass. FIG. 7 is a schematic diagram illustrating a cross-section of the main part of Modification Example 1 of the conductive part in the imaging unit according to the embodiment of the present invention. FIG. 8 is a schematic diagram illustrating a cross-section of the main part of Modification Example 2 of the conductive part in the imaging unit according to the embodiment of the present invention.

  Hereinafter, embodiments of an imaging unit according to the present invention will be described in detail with reference to the drawings. Hereinafter, as an example of the imaging unit according to the present invention, an imaging unit including a solid-state imaging device flip-chip mounted on a circuit board is illustrated, but the present invention is not limited to this embodiment.

(Embodiment)
FIG. 1 is a schematic cross-sectional view illustrating a configuration example of an imaging unit according to an embodiment of the present invention. As shown in FIG. 1, an imaging unit 1 according to this embodiment includes a solid-state imaging device 2 that captures an image of a subject, a printed circuit board 3 on which the solid-state imaging device 2 is flip-chip mounted, and the solid-state imaging device 2. A protective glass 4 that reinforces the rigidity and protects the light receiving portion 2 a and an adhesive 5 that reinforces the mounting strength between the solid-state imaging device 2 and the printed circuit board 3 are provided.

  The solid-state imaging device 2 is a bare chip-shaped semiconductor device exemplified by a CCD or CMOS image sensor and has an imaging function of receiving light from a subject and capturing an image of the subject. Specifically, the solid-state imaging device 2 includes a light receiving unit 2a that receives light from a subject on a chip substrate such as a substrate, and a drive circuit unit 2b in which a drive circuit for performing an imaging operation is formed. And a plurality of electrode pads 2c electrically connected to the drive circuit portion 2b.

  The light receiving unit 2a is realized using a pixel group and a microlens that are arranged in a predetermined shape such as a lattice shape, and is formed on the chip substrate of the solid-state imaging device 2. The drive circuit unit 2b is formed around the light receiving unit 2a. The plurality of electrode pads 2 c are electrically connected to the drive circuit unit 2 b via wiring (not shown) formed on the chip substrate of the solid-state imaging device 2. The plurality of electrode pads 2c are formed around the drive circuit portion 2b (for example, two or four sides facing each other). Such a plurality of electrode pads 2c are electrically connected to the printed circuit board 3 via a conductive portion 4c of a protective glass 4 described later.

  As shown in FIG. 1, the solid-state imaging device 2 having the above-described configuration includes the opening 3 a and the light receiving unit 2 a of the printed circuit board 3 in a state where the light receiving unit 2 a and the drive circuit unit 2 b are protected by the protective glass 4. Are flip-chip mounted on the printed circuit board 3. By this flip chip mounting, the plurality of electrode pads 2 c of the solid-state imaging device 2 are electrically connected to the wiring layer 3 b of the printed circuit board 3 through the conductive portion 4 c of the protective glass 4. In the solid-state imaging device 2 thus mounted on the printed circuit board 3, the light receiving unit 2a receives light from the subject that has passed through the opening 3a and the protective glass 4 of the printed circuit board 3, and photoelectrically converts the received light. Process. The drive circuit unit 2b generates an image signal of a subject based on the signal photoelectrically processed by the light receiving unit 2a, and the generated image signal is transmitted to the wiring layer 3b of the printed circuit board 3 through the plurality of electrode pads 2c and the like. Output to.

  The printed board 3 is a multilayer circuit board on which a circuit for realizing the imaging function of the solid-state imaging device 2 described above is formed. Specifically, as shown in FIG. 1, the printed circuit board 3 includes a wiring layer 3 b in which circuit wiring and the like necessary for realizing the imaging function of the solid-state imaging device 2 are patterned. Further, in the multilayer structure of the printed circuit board 3, an opening 3 a corresponding to the light receiving portion 2 a of the solid-state imaging device 2 described above is formed.

  The opening 3a has an opening dimension designed to correspond to the light receiving part 2a of the solid-state imaging device 2, and allows light from a subject to enter the light receiving part 2a. The wiring layer 3b is a conductive layer in which circuit wiring and the like necessary for realizing the imaging function of the solid-state imaging device 2 are patterned as described above. Although not particularly shown in FIG. 1, a plurality of electrode pads corresponding to the plurality of conductive portions 4 c in the protective glass 4 on the solid-state imaging device 2 are formed on the wiring layer 3 b. The protruding electrodes 4e of the plurality of conductive parts 4c are connected to the electrode pads of the wiring layer 3b by a thermocompression bonding technique or an ultrasonic connection technique, respectively.

  The printed circuit board 3 having the multilayer structure as described above may be a flexible flexible circuit board that can be easily deformed by application of external force, or a rigid circuit board that is not easily deformed as compared with the flexible circuit board. There may be. FIG. 1 shows a part of the imaging unit 1 according to this embodiment, specifically, the solid-state imaging device 2 and the vicinity thereof. That is, the external shape of the printed circuit board 3 described above is designed to have a desired external shape such as a plate shape or a belt shape.

  The protective glass 4 protects the element surface on the light receiving unit 2a side of the solid-state imaging device 2 mounted on the printed circuit board 3 and reinforces the rigidity of the solid-state imaging device 2 (more specifically, a transparent member). Glass member) and seals the light-receiving portion 2a of the solid-state image pickup device 2 without impairing the translucency to the light-receiving portion 2a of the solid-state image pickup device 2 and the electrical connection between the solid-state image pickup device 2 and the printed circuit board 3. Specifically, the protective glass 4 has a plurality of conductive portions 4 c that are electrically connected to the solid-state imaging device 2. Further, the protective glass 4 is formed with a recess 4a that avoids contact with the light receiving portion 2a of the solid-state imaging device 2, and a plurality of through holes 4b for forming the plurality of conductive portions 4c.

  The concave portion 4a is formed in the protective glass 4 in order to avoid contact between the protective glass 4 fixed to the solid-state imaging device 2 and the light receiving portion 2a. Here, in the solid-state imaging device 2 described above, the light receiving portion 2a and the drive circuit portion 2b are slightly projected on the silicon substrate, for example, as shown in FIG. The formation size of the recess 4a is set in consideration of the protrusion range and the protrusion height of the light receiving portion 2a and the drive circuit portion 2b. When the protective glass 4 having such a recess 4a is attached to the element surface of the solid-state imaging device 2 on the light receiving portion 2a side, as shown in FIG. 1, the light receiving portion 2a and the drive circuit portion 2b are placed inside the recess 4a. To avoid contact with both. In this case, the light receiving unit 2 a and the drive circuit unit 2 b of the solid-state imaging device 2 are hermetically sealed in the recess 4 a of the protective glass 4.

  The through-hole 4b is for arranging a conductive portion 4c that electrically connects the solid-state imaging device 2 and the printed board 3, and arrangement of electrode pads (not shown) on the wiring layer 3b of the printed board 3 A plurality of protective glasses 4 are formed correspondingly. The plurality of through holes 4 b communicate with the plurality of electrode pads 2 c in the solid-state imaging device 2 when the protective glass 4 is fixed to the element surface on the light receiving unit 2 a side of the solid-state imaging device 2.

  The conductive portion 4c is for electrically connecting the solid-state imaging device 2 and the printed circuit board 3, and is provided on the protective glass 4 corresponding to the plurality of through holes 4b described above. Specifically, as shown in FIG. 1, each of the plurality of conductive portions 4c includes a conductive filler 4d filled in the through hole 4b and a protruding electrode 4e joined to the wiring layer 3b.

  The conductive filler 4 d is a conductive member exemplified by a metal paste such as silver, and is filled in each through-hole 4 b of the protective glass 4 attached to the solid-state imaging device 2. In this case, the conductive filler 4d embeds the electrode pad 2c of the solid-state imaging device 2 forming the bottom of the through-hole 4b in the through-hole 4b and forms a recess in the through-hole 4b that is larger than the outer size of the protruding electrode 4e. Filled to the extent that it does not. The conductive filler 4d electrically connects the protruding electrode 4e attached on the exposed surface and the electrode pad 2c of the solid-state imaging device 2.

  The plurality of protruding electrodes 4e are fixed to the exposed surfaces of the respective conductive fillers 4d filled in the plurality of through holes 4b of the protective glass 4 as described above, and electrically connect the conductive fillers 4d and the printed board 3 to each other. Connect to. Specifically, the plurality of protruding electrodes 4e are bonded to a plurality of electrode pads (not shown) formed on the wiring layer 3b of the printed circuit board 3, and the wiring layer 3b and the conductive filler 4d are electrically connected. Connect to. The protruding electrode 4e may be a gold or copper stud bump formed by a wire bonding method, or a metal bump such as gold, silver, copper, indium or solder formed by a plating method. Also good. Further, the protruding electrode 4e may be a metal ball or a resin ball having a surface plated with metal, or a conductive adhesive patterned by printing or the like.

  Here, the protective glass 4 having such a configuration is a glass member having silicon oxide or the like as a main component formed in a predetermined thickness, and a solid-state imaging device 2 that is a semiconductor chip having silicon as a main component. Have approximately the same coefficient of thermal expansion. Such a protective glass 4 is attached to the light receiving unit 2a side element surface of the solid-state imaging device 2 as shown in FIG. 1, thereby causing a thermal expansion coefficient difference (thermal expansion difference and The rigidity of the solid-state imaging device 2 is reinforced without causing a difference in heat shrinkage. In this case, the protective glass 4 reinforces the rigidity of the solid-state imaging device 2 to be stronger than the thermal contraction force of the printed circuit board 3. That is, the thermal contraction force of the printed circuit board 3 described above is weaker than the rigidity of the solid-state imaging device 2 reinforced by the protective glass 4. Note that the rigidity of the solid-state imaging element 2 reinforced by the protective glass 4 is a total rigidity obtained by adding the rigidity of the solid-state imaging element 2 and the rigidity of the protective glass 4.

  Further, as shown in FIG. 1, the protective glass 4 is interposed between the solid-state imaging device 2 and the printed circuit board 3, and the light of the subject incident through the opening 3 a of the printed circuit board 3, that is, the solid-state imaging device 2. The light to be received by the light receiving unit 2a is transmitted to the light receiving unit 2a side. Furthermore, the protective glass 4 prevents foreign matter from entering the light receiving unit 2a side of the solid-state imaging device 2. The protective glass 4 may be adhered to the element surface of the solid-state imaging element 2 on the light receiving portion 2a side by an adhesive, or may be welded by a metallized heat treatment formed in advance on both contact surfaces. . Hereinafter, the solid-state imaging device 2 in a state where the protective glass 4 is fixed to the element surface on the light receiving unit 2a side as described above is referred to as a solid-state imaging device 2 with protective glass.

  The adhesive 5 is for securely fixing such a solid-state imaging device 2 with a protective glass and the printed board 3. Specifically, the adhesive 5 is an insulating adhesive such as epoxy, phenol, silicon, urethane, or acrylic. As shown in FIG. 1, the adhesive 5 does not enter the region between the light receiving portion 2 a of the solid-state imaging device 2 and the opening 3 a of the printed circuit board 3, so that the solid-state imaging with protective glass after flip chip mounting is performed. The gap between the element 2 and the printed board 3 is filled. In addition, the adhesive 5 forms a skirt shape around the periphery of the solid-state imaging device 2 with the protective glass on the printed circuit board 3, in practice, along the periphery of the protective glass 4 on the solid-state imaging device 2. It is applied until. As a result, the adhesive 5 closes the gap between the solid-state imaging device 2 with the protective glass and the printed board 3. The adhesive 5 thus filled and applied is cured by heat treatment or ultraviolet irradiation treatment. As a result, the adhesive 5 adheres the solid-state image pickup device 2 with the protective glass and the printed circuit board 3 to the mounting strength between the solid-state image pickup device 2 with the protective glass and the printed circuit board 3, that is, each protrusion of the protective glass 4. The bonding strength between the electrode 4e and the wiring layer 3b of the printed board 3 is reinforced. Further, the adhesive 5 prevents foreign matter from entering the upper surface of the protective glass 4 and the incidence of unnecessary light on the light receiving portion 2a through the gap between the solid-state imaging device 2 with the protective glass and the printed board 3.

  Note that the adhesive 5 is not limited to the insulating adhesive described above, and may be an anisotropic conductive adhesive. In this case, the adhesive 5 adheres the solid-state imaging device 2 with protective glass and the printed circuit board 3 in the above-described flip-chip mounting of the solid-state imaging device 2 with protective glass, and the protective glass with the flip-chip mounting. Each protruding electrode 4e of the attached solid-state imaging device 2 and the wiring layer 3b of the printed circuit board 3 are electrically connected to each other. On the other hand, when the adhesive 5 is an anisotropic conductive adhesive, the conductive filler 4d in each through-hole 4b and the adhesive 5 may be brought into direct contact without using the protruding electrode 4e described above. In this case, the adhesive 5 electrically connects the conductive filler 4d in each through-hole 4b of the solid-state imaging device 2 with protective glass and the wiring layer 3b of the printed board 3 respectively. The adhesive 5 is not limited to the thermosetting type described above, but may be an ultraviolet curable adhesive.

  Next, a method for manufacturing the imaging unit 1 according to the embodiment of the present invention will be described. FIG. 2 is a flowchart illustrating an example of a manufacturing method of the imaging unit according to the embodiment of the present invention. FIG. 3 is a schematic diagram illustrating a state in which a protective glass is attached to the light receiving unit side element surface of the solid-state imaging element. FIG. 4 is a schematic diagram showing a state in which a plurality of conductive portions are formed on the protective glass attached to the solid-state imaging device. FIG. 5 is a schematic diagram showing a state in which a solid-state imaging device with a protective glass is flip-chip mounted on a printed circuit board. The imaging unit 1 according to the embodiment of the present invention prepares the solid-state imaging device 2, the printed circuit board 3, and the protective glass 4 in advance as components of the imaging unit 1, and each of these using an adhesive 5 or the like. Manufactured by combining components.

  That is, as shown in FIG. 2, first, the protective glass 4 is attached to the solid-state imaging device 2 (step S101). In this step S101, as shown in FIG. 3, in the protective glass 4, the light receiving part 2a and the drive circuit part 2b of the solid-state image sensor 2 are accommodated in the recesses 4a, and each electrode pad 2c of the solid-state image sensor 2 passes through each of them. It is bonded or welded to the element surface of the solid-state imaging device 2 on the light receiving portion 2a side in a mode of being accommodated in the hole 4b. At this time, the light receiving unit 2 a and the drive circuit unit 2 b of the solid-state imaging device 2 are hermetically sealed in the recess 4 a of the protective glass 4. Subsequently, the conductive filler 4d is filled in each through-hole 4b of the protective glass 4 attached to the solid-state imaging device 2, and then the conductive filler 4d in each through-hole 4b as shown in FIG. The protruding electrode 4e is attached to each by heat treatment or ultrasonic treatment. As a result, a plurality of conductive portions 4c are formed on the protective glass 4 on the solid-state imaging device 2, and the solid-state imaging device 2 with the protective glass is manufactured.

  Next, the solid-state imaging device 2 with the protective glass manufactured by the process of step S101 is flip-chip mounted on the printed circuit board 3 (step S102). In step S102, the solid-state imaging device 2 with protective glass is flip-chip mounted on the printed circuit board 3 as shown in FIG. Specifically, the printed circuit board 3 makes the light receiving portion 2a and the opening 3a of the solid-state image pickup device 2 face each other through the protective glass 4, and the protruding electrodes 4e of the solid-state image pickup device 2 with the protective glass and the wiring. Each electrode pad in the layer 3b is positioned. Subsequently, the protruding electrodes 4e thus positioned and the wiring layer 3b are temporarily attached, and the temporarily mounted solid-state image pickup device 2 with the protective glass and the printed circuit board 3 are temporarily attached to a reflow furnace or the like. It puts into a predetermined heating apparatus, and this temporary mounting body is heat-treated by this heating apparatus. By this heat treatment of the temporary mounting body, each protruding electrode 4e of the solid-state imaging device 2 with the protective glass is welded and joined to the wiring layer 3b of the printed circuit board 3, and as a result, the solid-state imaging device 2 with the protective glass and the printed circuit board. Flip chip mounting with 3 is achieved. In this case, the solid-state imaging device 2 with the protective glass is electrically connected to the wiring layer 3b of the printed board 3 with the opening 3a and the light receiving part 2a of the printed board 3 facing each other with the protective glass 4 interposed therebetween. The

  In the provisional mounting of the solid-state imaging device 2 with protective glass and the printed circuit board 3 in step S102, a pressing process or ultrasonic waves is applied to the solid-state imaging device 2 with protective glass and the printed circuit board 3 after positioning. The protruding electrodes 4e of the solid-state imaging device 2 with a protective glass may be temporarily joined to the wiring layer 3b of the printed circuit board 3 by further processing.

  Here, in the state after the flip chip mounting, the solid-state imaging device 2 with the protective glass opposes the thermal contraction force of the printed circuit board 3 due to the rigidity reinforced by the protective glass 4. As a result, the solid-state imaging device 2 with the protective glass corrects the warp against the thermal contraction force of the printed circuit board 3 and maintains the light receiving portion 2a in a flat state.

  After that, the adhesive 5 is filled between the solid-state imaging device 2 with protective glass and the printed circuit board 3 after the flip chip mounting process in step S102 (step S103). In this step S103, the adhesive 5 does not enter the region between the light receiving portion 2a and the opening 3a of the printed circuit board 3, so that the solid-state imaging device 2 with the protective glass and the printed circuit board 3 after the flip chip mounting are disposed. The gap is filled. Subsequently, it is applied in a skirt shape along the periphery of the protective glass 4 on the solid-state image sensor 2 until the gap between the solid-state image sensor 2 with the protective glass 2 and the printed circuit board 3 is closed (see FIG. 1). . By the filling process of the adhesive 5, the bonding strength between the protruding electrodes 4e of the solid-state imaging device 2 with the protective glass and the wiring layer 3b of the printed board 3 is reinforced. The adhesive 5 may be cured at room temperature by UV irradiation or the like, or may be cured by heat treatment.

  The imaging unit 1 having the configuration shown in FIG. 1 can be manufactured by sequentially performing the manufacturing steps of steps S101 to S103 described above. The imaging unit 1 manufactured in this manner is used in various types of electronic imaging devices such as a digital camera and a digital video camera, an endoscope for observing the inside of an organ of a subject, and a mobile phone having an imaging function. Can be built in.

  Next, the warp reducing action of the solid-state imaging device 2 with the protective glass will be described. FIG. 6 is a schematic diagram illustrating a state in which the warpage of the solid-state image sensor is reduced by reinforcing the rigidity of the solid-state image sensor with the protective glass. The solid-state imaging device 2 with the protective glass in the imaging unit 1 according to this embodiment is temporarily mounted on the wiring layer 3b of the printed board before the thermal expansion of the printed board 3 in step S102 shown in FIG. The Thereafter, the solid-state imaging device 2 with the protective glass after the temporary mounting is flip-chip mounted on the printed circuit board 3 by heat treatment.

  In this step S102, the printed circuit board 3 is thermally expanded by such heat treatment, and then thermally contracts while the temperature is lowered to room temperature. In this state, the solid-state imaging device 2 with the protective glass on the printed circuit board 3 receives the thermal expansion force of the printed circuit board 3, and then receives the thermal contraction force F1 of the printed circuit board 3 as shown in FIG. . Here, the protective glass 4 has a rigidity higher than that of the printed circuit board 3 and, as described above, reinforces the rigidity of the solid-state imaging device 2 to be stronger than the heat shrinkage force F1 of the printed circuit board 3. To do. Such a protective glass 4 causes the reaction force F2 based on its own rigidity to act on the solid-state imaging device 2 against the thermal contraction force F1 of the printed circuit board 3. The reaction force F2 is a force that opposes the thermal contraction force F1 of the printed circuit board 3 applied to the solid-state imaging device 2 with protective glass.

  The protective glass 4 suppresses the thermal contraction deformation of the solid-state imaging device 2 due to the thermal contraction deformation of the printed circuit board 3 when the temperature is lowered by the reaction force F2 that opposes the thermal contraction force F1 of the printed circuit board 3 described above. The stress resulting from the thermal contraction of the solid-state imaging device 2 is sufficiently absorbed. As a result, the protective glass 4 reduces the warpage of the solid-state imaging device 2 caused by such stress. In this way, the protective glass 4 corrects the warp of the light receiving portion 2a of the solid-state imaging device 2 after the heat treatment, specifically after the flip chip mounting on the printed circuit board 3, thereby making the light receiving portion 2a Keep it flat.

  On the other hand, as described above, the protective glass 4 is a glass member that has a predetermined thickness (for example, a thickness larger than that of the solid-state imaging device 2) and that has silicon oxide or the like as a main component. It has substantially the same thermal expansion coefficient as the solid-state imaging device 2 which is a semiconductor chip. For this reason, the protective glass 4 attached to the solid-state imaging device 2 as described above has a difference in thermal expansion coefficient (difference in thermal expansion and thermal contraction) that is peeled off from the mounting surface, that is, the element surface on the light receiving portion 2a side. The rigidity of the solid-state imaging device 2 can be reinforced without being generated between the solid-state imaging device 2.

  The protective glass 4 is similarly applied to the printed circuit board 3 before and after the heat treatment (for example, thermosetting treatment of the adhesive 5) after the flip-chip mounting process of the solid-state imaging device 2 with the protective glass described above. The warpage of the solid-state imaging device 2 can be corrected against the thermal contraction force, and as a result, the warpage of the light receiving portion 2a of the solid-state imaging device 2 due to the thermal contraction of the printed circuit board 3 can be reduced.

  As described above, in the embodiment of the present invention, a protective glass including a plurality of conductive portions that are electrically connected to the solid-state imaging device is attached to the element surface on the light-receiving portion side of the solid-state imaging device. While protecting the light receiving part side element surface of a solid-state image sensor, it comprised so that the rigidity of this solid-state image sensor might be reinforced. For this reason, the rigidity of the solid-state imaging device can be reinforced by a heat treatment so that it is stronger than the thermal contraction force of the circuit board on which the solid-state imaging device is mounted, and the reaction force based on the reinforced rigidity is used. In addition, it is possible to sufficiently absorb the stress caused by the thermal contraction of the solid-state image sensor while suppressing the thermal contraction deformation of the solid-state image sensor due to the thermal contraction deformation of the circuit board. As a result, it is possible to reduce the warpage of the solid-state image sensor due to the thermal contraction difference between the circuit board after mounting by heat treatment and the solid-state image sensor.

  In addition, since the thermal expansion coefficient of the protective glass described above and the thermal expansion coefficient of the solid-state image sensor are set to be approximately the same, the heat that is large enough to peel off the protective glass attached to the light receiving unit side element surface of the solid-state image sensor. The rigidity of the solid-state imaging device can be reinforced by the protective glass without causing a difference in expansion coefficient between the solid-state imaging device and the protective glass.

  In the above-described embodiment, in order to form the conductive portion 4c that electrically connects the solid-state imaging device 2 and the printed circuit board 3, the through holes 4b of the protective glass 4 are filled with the conductive filler 4d. However, the present invention is not limited to this. FIG. 7 is a schematic diagram illustrating a cross-section of the main part of Modification Example 1 of the conductive part in the imaging unit according to the embodiment of the present invention. FIG. 8 is a schematic diagram illustrating a cross-section of the main part of Modification Example 2 of the conductive part in the imaging unit according to the embodiment of the present invention.

  Specifically, the conductive portion that electrically connects the solid-state imaging device 2 and the printed board 3 may be realized by patterning internal wiring in each through-hole 4 b of the protective glass 4. For example, as shown in FIG. 7, the through hole 4 b of the protective glass 4 in Modification 1 of the present invention is a via hole or a through hole for electrically connecting the protruding electrode 4 e and the electrode pad 2 c of the solid-state imaging device 2. It is formed. In such a through hole 4b, the internal wiring 4f is patterned so as to be electrically connected to the electrode pad 2c and to expose one wiring portion outside the through hole 4b. The protruding electrode 4e described above is arranged in a part of the internal wiring 4f exposed to the outside of the through hole 4b in this way. The conductive portion 14c of the imaging unit according to the modification 1 is formed by such a protruding electrode 4e and the internal wiring 4f, and the solid-state imaging device 2 and the print are formed in the same manner as the conductive portion 4c in the above-described embodiment. The substrate 3 is electrically connected.

  On the other hand, the conductive portion that electrically connects the solid-state imaging device 2 and the printed circuit board 3 may be realized by patterning external wiring along the outer wall of the protective glass 4. For example, as shown in FIG. 8, in the protective glass 4 in Modification 2 of the present invention, the protruding electrode 4e and the electrode pad 2c of the solid-state imaging device 2 are electrically connected without forming the above-described through hole 4b. The external wiring 4g for forming a pattern along the outer shape of the protective glass 4. The protruding electrode 4e described above is arranged in one wiring portion of the external wiring 4g thus patterned. The conductive portion 15c of the imaging unit according to the second modification is formed by such a protruding electrode 4e and the external wiring 4g. Similarly to the case of the conductive portion 4c in the above-described embodiment, the solid-state imaging device 2 and the print unit 15c are printed. The substrate 3 is electrically connected.

  In the above-described embodiment, the protective glass 4 is first attached to the solid-state imaging device 2, and then the solid-state imaging device 2 with the protective glass is flip-chip mounted on the printed circuit board 3. However, the present invention is not limited to this. The protective glass 4 on which the conductive portion 4c is formed in advance may be mounted on the printed circuit board 3, and then the solid-state imaging device 2 may be attached to the protective glass 4 on the printed circuit board 3.

  In the above-described embodiment, the case where the solid-state imaging device 2 with protective glass is flip-chip mounted on the printed circuit board 3 is exemplified. However, the present invention is not limited thereto, and the solid-state imaging device 2 with protective glass is mounted on the printed circuit board 3. Die bonding mounting may be performed using an adhesive such as a silver paste material, and the printed circuit board 3 and the solid-state imaging device 2 with a protective glass may be electrically connected by a metal wire bonding technique.

  In the above-described embodiment, the printed circuit board 3 which is a multilayer circuit board is illustrated. However, the circuit board in the imaging unit according to the embodiment of the present invention is not limited to this, and the circuit board has a single-layer structure. It may be.

  As described above, the imaging unit according to the present invention is useful for an imaging unit including a solid-state imaging device such as a CCD or a CMOS, and particularly reduces the warpage of the solid-state imaging device due to thermal contraction of the circuit board. Suitable for imaging units that can

DESCRIPTION OF SYMBOLS 1 Imaging unit 2 Solid-state image sensor 2a Light-receiving part 2b Drive circuit part 2c Electrode pad 3 Printed circuit board 3a Opening part 3b Wiring layer 4 Protective glass 4a Recessed part 4b Through-hole 4c, 14c, 15c Conductive part 4d Conductive filler 4e Projection electrode 4f Internal wiring 4g External wiring 5 Adhesive

Claims (5)

A solid-state image sensor;
A protective glass having a plurality of conductive portions electrically connected to the solid-state imaging device, protecting the element surface on the light-receiving portion side of the solid-state imaging device and reinforcing the rigidity of the solid-state imaging device;
A circuit in which an opening corresponding to the light receiving portion of the solid-state imaging device is formed and electrically connected to the solid-state imaging device through the plurality of conductive portions in a mode in which the light receiving portion and the opening are opposed to each other A substrate,
And the thermal contraction force of the circuit board is weaker than the rigidity of the solid-state imaging device reinforced by the protective glass.   The imaging unit according to claim 1, wherein a thermal expansion coefficient of the solid-state imaging device is the same as a thermal expansion coefficient of the protective glass.   The imaging unit according to claim 1, wherein the protective glass is a glass member in which a concave portion that avoids contact with the light receiving unit is formed. In the protective glass, a plurality of through holes for arranging the plurality of conductive portions are formed,
The conductive part is
A plurality of conductive filling members filled in the plurality of through holes;
A plurality of protruding electrodes that electrically connect the conductive filling member and the circuit board;
The imaging unit according to claim 1, further comprising:   The imaging unit according to claim 1, wherein the protective glass is interposed between the solid-state imaging device and the circuit board.

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