1. Field of the Invention
The present invention relates to an optical device and a method for manufacturing the same. In particular, it relates to a resin-sealed optical device and a method for manufacturing the same.
2. Description of Related Art
Electronic devices such as mobile phones and terminal units incorporate semiconductor devices therein. In the semiconductor devices, IC chips perform specified processing in response to external voltage applied thereto. The IC chips are mounted on a substrate provided with internal and external terminals. The internal terminals are connected to electrode terminals of the IC chips via thin conductive wires. The external terminals are solder balls, for example, and electrically connected to the internal terminals and external voltage is applied thereto. In recent years, reduction in size and thickness of the electronic devices has been demanded and a study has been actively made to meet the demand. Some of the achievements of the study are described below.
Patent Publication W098/35382 discloses a technique of forming a conductive film as an external terminal on part of the rear surface of the substrate. As the solder balls serving as the external terminals are replaced with the conductive film, the obtained semiconductor device is thinned down by the diameter of the solder balls.
Patent Publication U.S. Pat. No. 6,586,824B1 discloses a semiconductor device without a substrate. This semiconductor device is fabricated in the following manner. First, IC chips and internal terminals are implemented on polyamide tape and sealed in a resin. Then, the tape is peeled off to form the solder balls on the surface from which the tape is peeled off. Due to the inexistence of the substrate, the obtained semiconductor device is thinned down by the thickness of the substrate.
An optical device of the present invention includes: a substrate; an optical element mounted on one of the surfaces of the substrate to receive or emit light; a plate-shaped translucent component whose bottom surface is bonded to a top surface of the optical element; a plurality of terminals provided on the periphery of said one of the surfaces of the substrate and electrically connected to the optical element; and a sealant provided on said one of the surfaces of the substrate to seal the optical element therein, wherein the sealant is located lower than a top surface of the translucent component and a top surface of the translucent component is exposed out of the sealant a side surface of the translucent component is covered with the sealant.
Since the translucent component is bonded to the optical element, there is no need of forming ribs for keeping the translucent component separated from the optical element.
Further, as the side surface of the sealant is covered with the sealant, stray light is prevented from entering the optical element through the side surface.
A method according to the present invention is a method for manufacturing an optical device including an optical element for receiving or emitting light. The method includes the steps of: (a) providing a plurality of terminals on the periphery of one of the surfaces of a substrate; (b) fixing the optical element onto said one of the surfaces of the substrate; (c) bonding a bottom surface of a plate-shaped translucent component to a top surface of the optical element; (d) electrically connecting the plurality of terminals and the optical element to provide a first intermediate structure; (e) laying a sealing film extending substantially parallel to the substrate on a top surface of the translucent component; (f) injecting resin between the sealing film laid on the translucent component and the substrate to seal the optical element therein; and (g) removing the sealing film from the translucent component after the step (f).
According to this method, the optical element and the translucent component are stacked on the substrate and fixed thereto. This makes it possible to fabricate the optical device without the step of forming ribs for keeping the translucent component separated from the optical element.
Further, in the sealing step, the resin is injected between the sealing film laid on the translucent component and the substrate. Therefore, the resin does not flow onto the surface of the translucent component, while all the side surface of the translucent component is covered with the resin.
Optical devices such as light-emitting devices and image pickup devices are examples of the semiconductor devices. In addition to the reduction in size and thickness, these optical devices are also required to achieve improvement in sensitivity to light. From this aspect, the present invention provides an optical device which achieves both of the reduction in size and thickness and the improvement in sensitivity to light, as well as a method for manufacturing the same.
Hereinafter, explanation of embodiments of the present invention will be provided with reference to the drawings. However, the invention is not limited thereto.
In the first embodiment of the invention, an image pickup element and an image pickup device are taken as examples of the optical element and the optical device, respectively. Explanation of the structure of the image pickup device and a method for manufacturing the same are provided below.
The image pickup device 1 of the present embodiment includes a substrate 11, an image pickup element 21, a plurality of first terminals (terminals) 13, a plurality of second terminals 15, a translucent component 27 and a sealant 29. In the image pickup device 1, an optical signal received by the image pickup element 21 is converted into an electrical signal to perform image analysis upon application of external voltage to the second terminals 15.
The substrate 11 may be a resin substrate made of glass epoxy resin, amide resin, polyimide resin or acrylic resin and the thickness thereof is preferably not less than 60 μm and not more than 200 μm. A mount region 11a is defined in the middle of the top surface of the substrate 11 (one of the surfaces of the substrate), to which the image pickup element 21 is fixed. In part of the substrate 11 outside the mount region 11a, a plurality of conductive parts 17 penetrating the substrate 11 are arranged to be spaced from each other. The first terminals 13 extend from the conductive parts 17 toward the middle of the top surface of the substrate 11, but not in contact with the mount region 11a.
On the bottom surface of the substrate 11 (the other surface of the substrate), the second terminals 15 extend from the conductive parts 17. To be more specific, the first terminals 13 and the second terminals 15 are electrically connected to each other via the conductive parts 17, respectively. A resist film 19 is formed on the bottom surface of the substrate 11 to prevent short circuit from occurring between the second terminals 15.
The mount region 11a, the first terminals 13, the second terminals 15 and the conductive parts 17 are made of a stack of copper foil, a copper plating layer, a nickel plating layer and a gold plating layer formed in this order. The copper foil and the plating layers are preferably not less than 10 μm and not more than 50 μm in thickness, respectively.
The image pickup element 21 may be an image sensor (CMOS or CCD). A plurality of electrode terminals 21b are provided on the periphery of the top surface of the image pickup element 21 and electrically connected to the first terminals 13 via thin conductive wires 23, respectively.
The image pickup element 21 includes an image pickup region 21a. As shown in
The translucent component 27 may be a glass plate or a transparent resin plate for optical use and it is bonded to the top surface of the image pickup element 21 with a translucent adhesive 25. Since the entire bottom surface of the translucent component 27 is bonded to the top surface of the image pickup element 21, there is no need of providing ribs for keeping the bottom surface of the translucent component 27 separated from the top surface of the image pickup element 21. This makes it possible to reduce the size and thickness of the image pickup device 1.
The sealant 29 is made of resin which is poor in optical transmittance. The sealant 29 is provided above the top surface of the substrate 11 such that it is located closer to the substrate 11 than a top surface 27a of the translucent component 27. In a region of the sealant 29 around the translucent component 27, a distance between the top surface of the sealant 29 and the substrate 11 becomes smaller in part of the sealant 29 at a larger distance from the translucent component 27. In other words, in the region of the sealant 29 around the translucent component 27, the thickness of the sealant 29 is slightly smaller in part of the sealant 29 at a larger distance from the translucent component 27.
A recess 29a is formed in the top surface of the sealant 29 to surround the translucent component 27. The top surface of the sealant 29 shows arithmetic average roughness smaller than that of the side surface of the sealant 29. The recess 29a and the difference in arithmetic average roughness will be described later in the explanation of a method for manufacturing the image pickup device 1.
Now, the optical sensitivity of the image pickup device will be explained.
The inventors of the present application have tried to improve the optical sensitivity of the image pickup device by optimizing the relative positions of the translucent component and the sealant. Before the explanation of matters considered by the inventors, a cause of reduction in optical sensitivity of the image pickup device will be described first.
As described above, the image pickup device 1 converts light incident on the image pickup element 21 into an electrical signal and performs analysis such as image analysis based on the electrical signal. Therefore, it is preferred that only the light required for the analysis enters the image pickup device 1 while the entrance of other light (stray light) is prevented. If the stray light enters the image pickup element 21, the analysis cannot be performed properly, resulting in deterioration in performance of the image pickup device 1.
In general, the image pickup device is designed to perform analysis using light incident on the top surface of the translucent component and incorporated into optical equipment or the like such that the light required for the analysis properly enters through the top surface of the translucent component. Therefore, the light required for the analysis hardly enters through the side surfaces of the translucent component. However, in some cases, the stray light may enter the image pickup device through the side surfaces of the translucent component because the translucent component is a glass plate as described above. Therefore, if the stray light passing through the side surfaces of the translucent component is blocked, the unwanted entrance of the stray light into the image pickup device is prevented while the light required for the analysis is not blocked.
In order to prevent the stray light from entering the image pickup device through the side surfaces of the translucent component, the inventors have studied on image pickup devices shown in
For example, as shown in
On the other hand, if a sealant 229 is provided to be located higher than the top surface of the translucent component 27 as shown in
In the image pickup device 1 of the present embodiment, as shown in
In other words, when the image pickup device 1 of the present embodiment is observed from above, the top surface 27a of the translucent component 27 is exposed almost in the middle of the device and surrounded by the sealant 29 provided in close contact with the translucent component 27. When the image pickup device 1 is observed from the side, the sealant 29 is provided in close contact with the substrate 11. As a result, the light required for the analysis surely enters the image pickup element 21 without decreasing its intensity, while light which may possibly cause erroneous analysis results and light unnecessary for the analysis are prevented from entering the image pickup element 21 to the greatest possible extent. Thus, the image pickup device 1 is improved in optical sensitivity.
First, as shown in
Subsequently, in each region of the mother board 111, an image pickup element 21 is bonded to the mount region 11a with a conductive adhesive (not shown) (step (b)) and then the bottom surface of a translucent component 27 is bonded to the top surface of the image pickup element 21 with a translucent adhesive 25 (step (c)). For prevention of complex illustration, the image pickup region 21a is not depicted in
Then, as shown in
Then, as shown in
Then, as shown in
The sealing film 31 is removed after the resin is solidified (step (g)). When the sealing film 31 is removed, a recess 29a is formed in the top surface of part of the sealant 29 to surround the translucent component 27.
Then, as shown in
In the method of the present embodiment, the lower die of the molding dies 37 may be shifted upward after the sealing film 31 of the second intermediate structure 35 is brought into contact with the inner surface of the upper die of the molding dies 37.
In the present embodiment, the image pickup device shown in
Specifically, the first intermediate structure 33 shown in
Then, as shown in
After the resin is solidified, the mother board 111 is taken out of the molding dies 37 and divided by the regions.
The image pickup device 3 of the present embodiment is different from the image pickup device described in the first and second embodiments in that the periphery portion of the bottom surface of a translucent component 47 is bonded to the image pickup element 21 with an adhesive 45, while the middle portion of the bottom surface of the translucent component 47 is not bonded to the image pickup element 21.
Specifically, the translucent component 47 of the present embodiment has a recess 47b in the middle of the bottom surface thereof. The recess 47b is positioned to correspond with the image pickup region 21a of the image pickup element 21. As described in the first embodiment, the microlenses 24 are provided on the top surface of the image pickup region 21a (not shown in
Since the translucent component 47 has the recess 47b and the recess 47b is not filled with the adhesive, the translucent component 47 is bonded to the image pickup element 21 without applying the adhesive to the image pickup region 21a of the image pickup element 21. Accordingly, the light passed through the translucent component 47 enters the image pickup region 21a without passing through the adhesive. Therefore, other adhesives than the translucent adhesive may be used as the adhesive 45. The image pickup device of the present embodiment may be manufactured by the method according to the first or second embodiment described above.
The image pickup device 4 of the present embodiment has a substrate different from those described in the first to third embodiment.
Specifically, a substrate 51 of the present embodiment is a lead frame filled with resin 56. The lead frame includes a die pad 51a, a hanging lead (not shown) for supporting the die pad 51a, a plurality of first terminals 53 and a plurality of second terminals 55. As the lead frame is filled with the resin 56, electrical insulation between the die pad 51a and the first terminals 53 is maintained.
For example, the lead frame is made of a Ni layer, a Pd layer and an Au layer stacked in this order on a Cu frame. An image pickup element 21 is bonded onto the die pad 51a. The top surface of the lead frame functions as the first terminals 53 and the bottom surface of the lead frame opposite to the first terminals 53 functions as the second terminals 55.
The image pickup device 4 of the present embodiment may include the translucent component described in the third embodiment instead of the translucent component described in the first embodiment.
The image pickup device 4 of the present embodiment may be manufactured by the method described in the first or second embodiment after the substrate 51 is prepared. The substrate 51 may be obtained by attaching sealing films (not shown) on the bottom and top surfaces of the lead frame, respectively, and injecting the resin 56 in the cavities formed between the lead frame and the sealing films.
The above-described embodiments may be modified in the following manner.
In the above-described embodiments, the image pickup element is taken as an example of the optical element. However, the present invention is not limited to the light receiving elements and light emitting elements (e.g., lasers and light emitting diodes) may also be applicable.
The optical device of the present invention is not limited to the image pickup device and a light emitting device may also be used.
The substrate of the present invention is not limited to the resin substrate and the lead frame used in the above-described embodiments.
In the above-described embodiments, a plurality of optical devices are manufactured simultaneously using a mother board. However, the optical devices may be manufactured one by one.
Number | Date | Country | Kind |
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2006-059525 | Mar 2006 | JP | national |
Number | Date | Country | |
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Parent | 11708472 | Feb 2007 | US |
Child | 12970407 | US |