Abstract:
The present invention discloses a wafer level image sensor packaging structure and a manufacturing method for the same. The manufacturing method includes the following steps: providing a silicon wafer with image sensor chips, providing a plurality of transparent lids, allotting one said transparent lid on top of the corresponding image sensor chip, and carrying out a packaging process. The manufacturing method of the invention has the advantage of having a simpler process, lower cost, and higher production yield rate. The encapsulation compound arranges on the first surface of the image sensor chip and covers the circumference of the transparent lid to avoid the side light leakage as traditional chip scale package (CSP). Thus, the sensing performance of the wafer level image sensor packaging structure can be enhanced.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Technical Field 
         [0002]    The present invention relates to a wafer level image sensor packaging structure and a manufacturing method for the same. More particularly, the present invention discloses a wafer level image sensor packaging structure applicable to image sensor packaging structures made through batch manufacture and a manufacturing method for such wafer level image sensor packaging structure. 
         [0003]    2. Description of Related Art 
         [0004]    In recent years, bright prospects for digital image sensors have been promised by the developing global popularization of digital image products and the increasing demand for camera phones, digital still cameras, digital video cameras, and various other digital image products. 
         [0005]    Such digital image sensors, according to the manufacturing processes used, would be classified into two types, namely CCD (Charge-Coupled Device) and CMOS (Complementary Metal-Oxide-Semiconductor). While CCD is a mature technology that provides good image quality, the particular processing technique it involves requires higher costs. By comparison, CMOS technology is based on semiconductor chips and has the advantages of lower costs, simpler processes, resulting in more compact products, thus being especially suitable for applications where the dpi requirement is relatively compromised, such as camera phones. Therefore, CMOS and CCD are technologies that each has its market niche. 
         [0006]    The traditional packaging approaches for image sensors include COB (Chip On Board) and CSP (Chip Scale Package). The COB process is accomplished by adhering an image sensor chip onto a substrate, electrically connecting the substrate and the image sensor chip by means of metal wires, and carrying out a packaging procedure to package the image sensor chip. Hence, the resultant image sensor packaging structure is relatively large in size and has a significant height. On the other hand, the CSP process is more suitable for image sensor chips of low resolution. In high-resolution applications, CSP is less competitive in cost and its inherent glass structure further adds the height of the image sensor module in addition to the necessary lens module, while being inferior to COB packaging in sensing performance. Furthermore, the traditional CSP structure has the problem of side light leakage, and thus requires the additional procedures for setting shadow masks or coating shading material on the sides of the packaging structure for preventing the degradation of sensory performance or avoiding the generation of flares. 
       SUMMARY OF THE INVENTION 
       [0007]    The present invention provides a wafer level image sensor packaging structure and a manufacturing method for the same, wherein by adopting a TSV wafer as a silicon wafer, as compared with the traditional CSP process or COB process, the present invention dispenses with metal wires and any substrate so as to downsize the resultant image sensor packaging structure and reduce its height. 
         [0008]    The present invention provides a wafer level image sensor packaging structure and a manufacturing method for the same, wherein an opaque encapsulation compound covering the circumference of the transparent lid helps to prevent side light leakage for the image sensor packaging structure without using any additional shadow mask or shading layer. 
         [0009]    The present invention provides a wafer level image sensor packaging structure and a manufacturing method for the same, wherein the TSV wafer is adopted as the silicon wafer, so as to dispense with the use of any metal wire and substrate, and thus, as compared with the traditional process, the present invention saves materials and is suitable for mass manufacture which reduces costs, while the simplified manufacturing process improves the production yield rate. 
         [0010]    To achieve the foregoing effects, the present invention provides a manufacturing method for a wafer level image sensor packaging structure, comprising steps of: providing a silicon wafer, which has a plurality of image sensor chips, wherein each said image sensor chip has a photosensitive area; providing a plurality of transparent lids; allotting one said transparent lid over the photosensitive area of a respective said image sensor chip; and carrying out a packaging process by arranging an encapsulation compound on a first surface of the silicon wafer so that the encapsulation compound covers the circumferences of the transparent lids. 
         [0011]    To achieve the foregoing effects, the present invention also provides a wafer level image sensor packaging structure, comprising: an image sensor chip, which has a plurality of photosensitive elements set in a photosensitive area on a first surface of the image sensor chip, a plurality of first contacts set on the first surface to surround the exterior the photosensitive area and electrically connected to the photosensitive elements, a plurality of conducting channels passing through the chip with one end thereof electrically connected to the first contacts, and a plurality of solder ball pads set on a second surface of the image sensor chip and electrically connected to the conducting channel; a transparent lid, which is correspondingly set over the photosensitive area so that an air chamber is defined between the transparent lid and the image sensor chip; and an encapsulation compound, which is arranged on the first surface and covers a circumference of the transparent lid. 
         [0012]    By implementing the present invention, at least the following progressive effects can be expected: 
         [0013]    1. The manufacturing process is simpler than the traditional CSP process or COB process, and the resultant image sensor packaging structure is made compact with reduced assembly height, thereby meeting the trend of compactness for electronic devices. 
         [0014]    2. The opaque encapsulation compound covering the circumference of the transparent lid helps to prevent side light leakage for the image sensor packaging structure. 
         [0015]    3. Since the overall use of material consumed is economized, the manufacturing cost is significantly reduced and the production yield rate is improved. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0016]    The invention as well as a preferred mode of use, further objectives and advantages thereof will be best understood by reference to the following detailed description of illustrative embodiments when acquired in conjunction with the accompanying drawings, wherein: 
           [0017]      FIG. 1  is a flowchart showing a manufacturing method for a wafer level image sensor packaging structure according to one embodiment of the present invention; 
           [0018]      FIG. 2  is a schematic view of a silicon wafer with image sensor chips according to one embodiment of the present invention; 
           [0019]      FIG. 3  is a schematic view of transparent lids according to one embodiment of the present invention; 
           [0020]      FIG. 4A  is a top schematic view of transparent lids with bank-shaped frames according to one embodiment of the present invention; 
           [0021]      FIG. 4B  is a perspective schematic view of the transparent lids with the bank-shaped frames; 
           [0022]      FIG. 5A  is a top schematic view of a silicon wafer having the transparent lids according to the present invention; 
           [0023]      FIG. 5B  is a schematic drawing showing the transparent lid correspondingly adhered to the image sensor chip according to the present invention; 
           [0024]      FIG. 6A  is a schematic drawing showing a silicon wafer placed in a mold according to one embodiment of the present invention; 
           [0025]      FIG. 6B  is a sectional view of the mold and the silicon wafer placed therein according to  FIG. 6A ; 
           [0026]      FIG. 6C  is a sectional view of a mold and a silicon wafer placed therein according to another embodiment of the present invention; 
           [0027]      FIG. 7A  is a top schematic view of a silicon wafer packaged by an encapsulation compound according to one embodiment of the present invention; 
           [0028]      FIG. 7B  is a sectional view of  FIG. 7A  taken along Line A-A; 
           [0029]      FIG. 8A  is a top schematic view of a silicon wafer packaged by an encapsulation compound according to another embodiment of the present invention; 
           [0030]      FIG. 8B  is a sectional view of  FIG. 8A  taken along Line B-B; 
           [0031]      FIG. 9  is a top schematic view of a silicon wafer with a dam according to one embodiment of the present invention; 
           [0032]      FIG. 10A  is a top schematic view of a silicon wafer with dam and cured encapsulation compound according to the present invention; 
           [0033]      FIG. 10B  is a sectional view of  FIG. 10A  taken along Line C-C; 
           [0034]      FIG. 11  is a schematic view of a silicon wafer with a ball grid array according to one embodiment of the present invention; and 
           [0035]      FIG. 12A  through  FIG. 14B  respectively show an embodiment of the image sensor packaging structure of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0036]    As shown in  FIG. 1 , the present embodiment provides a manufacturing method for a wafer level image sensor package structure. The manufacturing method comprises the following steps: providing a silicon wafer with image sensor chips (S 10 ); providing a plurality of transparent lids (S 20 ); allotting one said transparent lid on top of the corresponding image sensor chip (S 30 ); and carrying out a packaging process (S 40 ). 
         [0037]    In the step of providing the silicon wafer (S 10 ), as shown in  FIG. 2 , the silicon wafer  10  has a plurality of image sensor chips  11 , and each said image sensor chip  11  has a photosensitive area  12 . 
         [0038]    For further illustration, the silicon wafer  10  may be a TSV (Through-Silicon Vias) wafer. Referring to  FIG. 12A  in connection with  FIG. 1 , by dicing the TSV wafer, the TSV wafer is subdivided into a plurality of image sensor chips  11 . Each said image sensor chip  11  has a first surface  13  and a second surface  14 , wherein the first surface  13  and the second surface  14  are also the first surface  13  and the second surface  14  of the silicon wafer  10 . 
         [0039]    Referring to the sectional view of the TSV wafer as shown in  FIG. 12A , the wafer is preformed with vias, and conducting channels  18  are provided in the vias, so as to electrically connect the conducting channel  18  with the first contacts  16  on the first surface  13  of the silicon wafer  10 . The conducting channels  18  may be extended to the second surface  14 . 
         [0040]    In addition, a re-distribution layer (not shown) may be formed on the second surface  14 . The re-distribution layer may be electrically connected to solder ball pads  30 , which are also electrically connected to the conducting channel  18  and arranged as an LGA (Land Grid Array), so as to arrange intervals between the solder ball pads  30  by the re-distribution layer. 
         [0041]    In the step of providing the plurality of transparent lids (S 20 ), as shown in  FIG. 3 , the transparent lids  20  may be formed by cutting a transparent panel  21  which is placed on a carrier film  22  on which a frame  23  is provided to surround edges of the transparent panel  21 . The frame  23  facilitates the positioning of the transparent panel  21  during the cutting procedure. 
         [0042]    Referring to  FIG. 4A  and  FIG. 4B , before the cutting procedure, there may be further provided a plurality of bank-shaped frames  25  on the transparent panel  21 . In the cutting procedure, the transparent panel  21  is cut along each cutting lines  40   a  on one of the bank-shaped frames  25 , so that each of the separated transparent lids  20  has a supporting frame  24  edgewise (referring to  FIG. 5B  as well). In addition, the bank-shaped frame  25  may be formed through a screen printing process, a transfer molding process, or an injection molding process. 
         [0043]    In the step of allotting one said transparent lid on top of the corresponding image sensor chip (S 30 ), as shown in  FIG. 5A  and  FIG. 5B , each said transparent lid  20  is correspondingly set on top of the photosensitive area  12  of the corresponding image sensor chip  11 . Referring to  FIG. 12A ,  FIG. 13A  and  FIG. 14A  all together, the transparent lid  20  has a third surface  26  and a fourth surface  27 , and the first surface  13  may be provided with an adhesive so that the adhesive corresponds to the edges of the fourth surface  27  and serves to adhere the transparent lid  20  to the image sensor chip  11  such that an air chamber  17  is defined over the photosensitive area  12  of the image sensor chip  11 . 
         [0044]    Referring to  FIG. 5B , the transparent lid  20  with the supporting frame  24  is adhered to the image sensor chip  11  by the supporting frame  24  to make the photosensitive area  12  edgewise surrounded by the supporting frame  24 . 
         [0045]    In the step of carrying the packaging process (S 40 ), as shown in  FIG. 7B ,  FIG. 8B  and  FIG. 10B , an encapsulation compound  60  is deposited on the first surface  13  of the silicon wafer  10  to make the encapsulation compound  60  cover the circumference of the transparent lids  20 . Since the encapsulation compound  60  may be of an opaque material, the image sensor packaging structure can avoid the side light leakage without the use of additional shadow masks or shading material. 
         [0046]    Two different packaging processes are disclosed in the present embodiment, namely molding packaging process and dispensing packaging process. 
         [0047]    The molding packaging process is first illustrated, wherein the encapsulation compound  60  used is a mold compound. 
         [0048]    As shown in  FIG. 6A  and  FIG. 6B , the silicon wafer  10  with the transparent lids  20  is placed in a mold  50 . The mold  50  comprises an upper mold member  51  and a lower mold member  52 . Therein, the upper mold member  51  is configured to abut against the third surfaces  26  of the transparent lids  20 , and the lower mold member  52  is configured to carry the silicon wafer  10  while abutting against the second surface  14  of the silicon wafer  10 . 
         [0049]    Moreover, a vacuum absorbed buffer layer  53  may be provided on the inner surface of the upper mold member  51 . The buffer layer  53  directly presses on the transparent lids  20  to prevent the third surfaces  26  of the transparent lids  20  from being contacted by the bleeding resin during injection of the encapsulation compound. It is therefore provided between the transparent lids  20  and the upper mold member  51  for abutting against the third surfaces  26  of the transparent lids  20  so as to prevent contamination caused by resin bleeding. 
         [0050]    As shown in  FIG. 6C , for the encapsulation compound  60  to cover the circumference of the third surfaces  26  but not to cover the entire third surfaces  26 , an alternative structure of the upper mold member indicated by the numeral  51   a  may be used. The upper mold member  51   a  has a plurality of bulges  51   b  each abutting against the center portion of the corresponding third surface  26 . Meantime, there is also a vacuum absorbed buffer layer  53  provided between the upper mold member  51   a  and the transparent lids  20  for abutting against the third surfaces  26  and thereby preventing contamination caused by resin bleeding. 
         [0051]    After the silicon wafer  10  with the transparent lids  20  is placed into the mold  50 , the packaging process can be commenced. In the packaging process, vacuum is applied to make the upper mold member  51  and the lower mold member  52  closely contact the transparent lids  20  and the silicon wafer  10  by the vacuum absorbed buffer layer  53 , and thereby a mold cavity is formed (referring to  FIG. 6B  as well). The encapsulation compound  60  is then injected into the mold cavity, so that the encapsulation compound  60  covers the circumference of each said transparent lid  20  but does not cover the entire third surface  26  of each transparent lid  20  (as shown in  FIG. 6B ), or the encapsulation compound  60  covers edges of the third surfaces  26  (as shown in  FIG. 6C ), as long as the photosensitive area  12  is not covered. 
         [0052]    The mold  50  is pressurized to transform the encapsulation compound  60 , and the mold  50  is open before a post-mold baking process is carried out for curing the encapsulation compound  60 . What is illustrated in  FIG. 7A  and  FIG. 7B  is the image sensor packaging structure made with the mold  50  of  FIG. 6B  and through the post-mold baking process, which is to be further cut. From the sectional view of  FIG. 7B , it is clear that the encapsulation compound  60  covers the circumference of the transparent lids  20  but leaves the third surface  26  exposed. 
         [0053]    On the other hand,  FIG. 8A  and  FIG. 8B  depict the image sensor packaging structure made with the mold  50  of  FIG. 6C  and through the post-mold baking process, which is to be further cut. Therein, the encapsulation compound  60  covers the edges of each said third surface  26 , so the transparent lids  20  shown in  FIG. 8A  are relatively small in area. 
         [0054]    In addition, please refer to  FIG. 9  and  FIG. 10A , the dispensing packaging process may implement a dam  70  provided at the periphery of the first surface  13  of the silicon wafer  10 , so as to form a circular structure enclosing the silicon wafer  10  and in turn the image sensor chips  11  with the transparent lids  20 . The dam  70  may be made of epoxy resin, while the height of the dam  70  is equal to or smaller than the overall height of the image sensor packaging structure composed of the transparent lids  20  and the image sensor chip  11 . 
         [0055]    Referring to  FIG. 10B , the technique of dispensing is used to apply the encapsulation compound  60  onto the first surface  13  so that the encapsulation compound  60  is filled between the dam  70  and the transparent lids  20  to the full while the encapsulation compound  60  is used to the extent that the height thereof is not greater than that of the transparent lid  20 . Therefore, it can ensure that the encapsulation compound  60  covers the circumference of the transparent lids  20  without covering the third surfaces  26  of the transparent lids  20  (as shown in  FIG. 10B ). The encapsulation compound  60  adopted is a liquid compound. 
         [0056]    As shown in  FIG. 11 , after the packaging process, the silicon wafer  10  is overturned in order to place solder balls  81  on the second surface  14 . The solder balls  81  are in fact placed on solder ball pads  30  and arrayed as a ball grid array  80 , so that the image sensor chip  11  is electrically connected to an external device (such as a circuit substrate) by way of the first contacts  16 , the conducting channel  18 , the solder ball pads  30  and the solder balls  81 . At last, by dicing the silicon wafer  10  along the cutting lines  40   b , a plurality of image sensor package structures can be obtained. 
         [0057]    The separate image sensor packaging structure may be any one depicted in  FIG. 12A ,  FIG. 12B ,  FIG. 13A ,  FIG. 13B ,  FIG. 14A  and  FIG. 14B . To sum up, the image sensor packaging structure made through the manufacturing method may be as the six shown embodiments. 
         [0058]    Therein, the wafer level image sensor packaging structure comprises an image sensor chip  11 , a transparent lid  20 , and an encapsulation compound  60 . 
         [0059]    The image sensor chip  11  has a first surface  13  and a second surface  14 , which are respectively the upper surface and the lower surface of the image sensor chip  11 . The first surface  13  is provided with a plurality of photosensitive elements  15 , which are arranged into an array in the photosensitive area  12  on the first surface  13 , for sensing light. 
         [0060]    The first surface  13  is provided with a plurality of first contacts  16 , which surround outside the photosensitive area  12  and are electrically connected to the photosensitive elements  15  through the inner circuit configuration of the image sensor chip  11 . 
         [0061]    The image sensor chip  11  comprises a plurality of conducting channels  18 , and each conducting channel passes through the image sensor chip  11 . The conducting channel  18  has one end electrically connected to the first contacts  16 , and the other end electrically connected to the solder ball pads  30  on the second surface  14 , thus acting as a channel that electrically connects the photosensitive elements  15  to the exterior. 
         [0062]    On the second surface  14  of the image sensor chip  11 , there may further be solder balls  81 , which are electrically connected to the solder ball pads  30  and form a ball grid array  80  on the second surface  14  (seeing  FIG. 11  as well). The solder balls  81  are not only electrically connected to solder ball pads  30 , but also electrically connected to the conducting channel  18  through the solder ball pads  30 , thus acting as an interface that electrically connects the photosensitive elements  15  to the exterior. 
         [0063]    As shown in  FIG. 12A ,  FIG. 13A  and  FIG. 14A , the transparent lid  20  is positioned over the photosensitive area  12  and adhered to the first surface  13  such that an air chamber  17  is defined between the transparent lid  20  and the image sensor chip  11 . 
         [0064]    Referring to  FIG. 12B ,  FIG. 13B  and  FIG. 14B , the transparent lid  20  has a third surface  26  and a fourth surface  27 . A supporting frame  24  may be further provided at edges of the fourth surface  27 , so that the transparent lid  20  is adhered to the first surface  13  via the supporting frame  24  while the supporting frame  24  surrounds the exterior of the photosensitive area  12 . Therein, the supporting frame  24  may be made of a resin material or a plastic material. 
         [0065]    As shown in  FIG. 12A ,  FIG. 12B ,  FIG. 14A  and  FIG. 14B , the encapsulation compound  60  is arranged on the first surface  13  and covers the circumference of the transparent lid  20  and the supporting frame  24  (as shown in  FIG. 12B ,  FIG. 13B  and  FIG. 14B ). In addition, the encapsulation compound  60  may be of an opaque material, so as to prevent light from entering the sides of the transparent lid  20 , thereby reducing noise caused by stray light. Furthermore, as shown in  FIG. 13A  and  FIG. 13B , the encapsulation compound  60  may further extend to cover the edges of the third surface  26  of the transparent lid  20 , without covering the photosensitive area  12 , so as to further shade the lateral of the transparent lid  20  from incoming light. The encapsulation compound  60  may be a mold compound or a liquid compound. 
         [0066]    The present invention has been described with reference to the preferred embodiments and it is understood that the embodiments are not intended to limit the scope of the present invention. Moreover, as the contents disclosed herein should be readily understood and can be implemented by a person skilled in the art, all equivalent changes or modifications which do not depart from the concept of the present invention should be encompassed by the appended claims.