Abstract:
An image sensor without an opto-mechanical system. The image sensor comprises a substrate, a light source, an optical sensing device and a protective layer. The light source is disposed on the substrate and provides light for image capturing. The optical sensing device is disposed on the substrate and converts a light signal from the light source to an image signal. The protective layer is molded over the light source and the optical sensing device such that an optical path is created therein. No optical-mechanical component exists in the image sensor.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application is a Continuation-In-Part application of pending U.S. patent application Ser. No. 11/774,643, filed on Jul. 9, 2007 and entitled “Image Sensor Without Opto-Mechanical System And Manufacturing Method Thereof,” which claimed priority to China application 200610098610.5, filed on Jul. 7, 2006, and China application 20061011986.5, filed on Aug. 20, 2006. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The invention relates to an image sensor and, in particular, to an image sensor without an opto-mechanical system.  
         [0004]     2. Description of the Related Art  
         [0005]     For a conventional semiconductor optical image sensor, an optical-mechanical system is required to capture light beams or optical spots such that an image can be captured. Generally, the optical-mechanical system is very large, thus, making it difficult to shrink the conventional optical image sensor. In fact, the optical-mechanical system requires the largest volume of space in the conventional optical image sensor given current semiconductor manufacturing technology methods. Meanwhile, in addition to combining large-sized lenses, requirements for precise optical-mechanical structures and precise optical guides, make manufacturing of the optical image sensor relatively complicated.  
         [0006]      FIG. 1  is a flow chart of a manufacturing method for a conventional optical image sensor. The manufacturing method comprises disposing a light emitting device and a optical sensing device on a substrate (step  101 ), securing the periphery of the substrate with a plastic frame (step  102 ), injecting colloid in to the plastic frame (step  103 ), disposing a lens over the plastic frame and jointing the lens with the periphery with the colloid (step  104 ), and adjusting the height of the colloid for focusing (step  105 ).  
         [0007]      FIG. 2  is a cross sectional view of a conventional optical image sensor manufactured using the above-mentioned manufacturing method. The conventional optical image sensor comprises a light emitting unit  21  and an optical sensing device  22  on a substrate  23 . The periphery of the substrate  23  is secured within a plastic frame  24 . A lens  25  is disposed over the plastic frame  24  and jointed with the plastic frame  24  with a colloid  26 . Height of the colloid  26  is adjusted for focusing. The conventional optical image sensor is vulnerable to rework adjustments, for example, focus readjustment, due to height and volume limitations.  
         [0008]     A semiconductor optical image sensor typically comprises a specific light source. A specific light beam is guided to the optical sensing device along a specific optical path. Meanwhile, an optically designed structure usually has size problems. When light is guided to the optical sensing device, photoelectric conversion is carried out within the internal structure of the optical sensing device. With the specific light beam projected on a specific block of the optical sensing device, an image is captured thereby. Semiconductor optical image capturing methods have been frequently applied in VLSI processes and packaging technologies. Optical sensing devices commonly used are roughly classified into two types, CCD (Charge Coupled Device) and CMOS (Complementary Metal Oxide Semiconductor).  
         [0009]     Major packaging methods (the placement of the optical sensing device on a substrate or any other type of electrically conductive carrier) utilized for packaging optical image sensors are COB (Chip on Board) and DCA (Direct Chip Attachment) packaging methods.  
         [0010]     Production throughput is typically low due to the slower manufacturing process caused by utilization of large-sized packages. A slower manufacturing process results in excessive particles or precipitates on the optically sensing device, and abnormalities or damage to the optical sensing device during the slower manufacturing process.  
         [0011]     As a result, packaging technology for compact optical image sensors have been retarded due to the manufacturing process challenges, excessively large size of the final products or difficulties in photo coupling inherent in opto-mechanical system design. Eventually, space allocation for applied products must be enlarged, thus, hindering smaller-sized designs and causing inconvenience for users, producing an excessively large-sized final product.  
       BRIEF SUMMARY OF THE INVENTION  
       [0012]     An embodiment of an image sensor comprises a substrate, a light source, an optical sensing device and a protective layer. The light source is disposed on the substrate and provides light for image capturing. The optical sensing device is disposed on the substrate and converts a light signal from the light source to an image signal. The protective layer is molded over the light source and the optical sensing device such that an optical path is created therein. No optical-mechanical component exists in the image sensor.  
         [0013]     An embodiment of an image sensor comprises a substrate, a light source, an optical sensing device and a protective layer. The light source is disposed on the substrate and provides light for image capturing. The optical sensing device is disposed on the substrate and converts a light signal from the light source to an image signal. The protective layer is molded over the light source and the optical sensing device such that an optical path is created therein. The protective layer comprises epoxy.  
         [0014]     An embodiment of a manufacturing method of an image sensor without an opto-mechanical system comprises disposing a light source, an optical sensing device on a substrate, and performing insert molding to package a protective layer over the light source, and the optical sensing device.  
         [0015]     A detailed description is given in the following embodiments with reference to the accompanying drawings. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0016]     The invention can be more fully understood by reading the subsequent detailed description and examples with references made to the accompanying drawings, wherein:  
         [0017]      FIG. 1  is a flow chart of a manufacturing method for a conventional optical image sensor;  
         [0018]      FIG. 2  is a cross sectional view of a conventional optical image sensor manufactured using the above-mentioned manufacturing method;  
         [0019]      FIGS. 3A, 3B  and  4  are respectively cross sectional views and a perspective view of an optical image sensor without an optical-mechanical system according to an embodiment of the invention; and  
         [0020]      FIG. 5  is a schematic diagram of an optical image sensor with an additional light source according to an embodiment of the invention; and  
         [0021]      FIG. 6  is a flow chart of a manufacturing method of the disclosed optical image sensor according to an embodiment of the invention.  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0022]     The following description is of the best-contemplated mode of carrying out the invention. This description is made for the purpose of illustrating the general principles of the invention and should not be taken in a limiting sense. The scope of the invention is best determined by reference to the appended claims.  
         [0023]      FIGS. 3A, 3B  and  4  are respectively a cross sectional view and a perspective view of an optical image sensor without an optical-mechanical system according to an embodiment of the invention. The optical image sensor  3  comprises a substrate  31 , an LED  32 , an optical sensing device  34 , and a protective block  33 . The substrate  31  is used to carry the LED  32 , the optical sensing device  34  and the protective block  33 .  
         [0024]     The LED  32  is disposed on the substrate  31  to provide high quality light required for capturing image. Alternatively, a directional light source of multi-mode or single-mode may be used as the light source. The protective block  33  protects the optical sensing device  34  from direct light projection from the LED  32  and also optimizes incident angle of light such that performance of the optical image sensor is improved. The optical sensing device  34  is also disposed on the substrate  31  and receives signals from the specific light source, wherein the signals are converted to digital signals such that an image of the detected object is captured. More specifically, the optical sensing device  34  is a charge coupled device (CCD) or a complementary metal oxide semiconductor (CMOS) sensing device. Alternatively, a plated film or a thin film that blocks permeable specific light source may be printed into the optical sensing device to capture image. The LED  32  and the optical sensing device  34  are packaged on the substrate  31  using welding wires  37  (die up or flip chip). An optical path for a specific light source is formed with a protective layer  36  (made up of high density chemical material) and a conductor  35  which allows transmission of a light source with a specific spectrum and blocks light beams whose frequencies are not in the specific spectrum. The conductor  35  is essentially made up of an optical material such as a high density polymer to provide an optical path specifically designed for the light source such that the optical sensing device  34  can capture the image produced by the specific light source. The protective layer  36  is made up of a high density polymer and blocks the specific light source and any light which is not specifically designed for image capturing such that misjudgment or failure in image capturing of the optical sensing device  34  is avoided. Preferably, the protective layer  36  comprises epoxy. In addition, the protection layer  36  may have a step  38  between the LED  32  and the optical sensing device  34  as shown in  FIG. 3A . The step  38  may be helpful for optimizing the optical path and improving performance of the optical image sensor  3 . Preferably, the step  38  has a slope such that top surface of the protection layer  36  on a side of the optical sensing device  34  is lower than that on a side of the LED  32 , as shown in  FIG. 3B .  
         [0025]     Embodiments of the invention utilize a high-density chemical material to cover an LED  32  such that an optical path for a specific light source is formed. The light source can be a variable light source or an external light source to provide light required for image capturing. The light source is usually connected directly to the substrate  31  through welding wires  37 . Light signals are transmitted via the conductor  35  to the optical sensing device (CCD or CMOS sensor)  34  where the signals are converted to digital signals for image capturing of the detected object.  
         [0026]      FIG. 5  is a schematic diagram of an optical image sensor with an additional light source according to an embodiment of the invention. The LED in the optical image sensor of the disclosed embodiments of the invention in  FIGS. 3A and 3B  is replaced by an external light source  5 . As a result, a user is allowed put a finger  6  on a surface of the protective layer  36  for image display without relying upon a lens. Accordingly, size of the packaging structure can be significantly reduced and flattened with the ratio between the captured image and the object approximately at 1:1.  
         [0027]      FIG. 6  is a flow chart of a manufacturing method for the disclosed optical image sensor according to an embodiment of the invention. The manufacturing method comprises disposing a light source, an optical sensing device on a substrate (step  601 ), and performing insert molding to package a protective layer over the light source, and the optical sensing device (step  602 ). As disclosed previously, an LED, an optical sensing device, and a protective block for blocking specific light source are placed on the substrate. Subsequently, a protective layer which allows transmission of a light source with specific spectrum is integrated with the substrate by insert molding technology to form an independent optical image sensor.  
         [0028]     The protective layer is made up of a high-density chemical material and a conductor that allows transmission by a light source with a specific spectrum to define a specific optical path. To obtain the optimal optical path, the protective layer comprised of a high density chemical material has a refraction index not less than 1.5 and a transmission rate greater than 40%. The thickness of the protective layer above the optical sensing device ranges from 5 to 70 μm and that above the LED device ranges from 0.15 to 0.8 mm. The spacing between the optical sensing device and the LED ranges from 0.7 to 2.8 mm.  
         [0029]     While the invention has been described by way of example and in terms of preferred embodiment, it is to be understood that the invention is not limited thereto. To the contrary, it is intended to cover various modifications and similar arrangements as would be apparent to those skilled in the Art. Therefore, the scope of the appended claims should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements.