Abstract:
The present invention discloses an image sensor package structure. The image sensor package structure includes a substrate, a chip, a transparent lid, a first casing and a package material. The transparent lid covers a sensitization area of the chip and it also adheres to the chip which is deposed on the substrate. The first casing, which adheres to the transparent lid, forms an opening so that light can pass through the opening and the transparent lid to enter into the sensitization area. The package material covers around the chip and the transparent lid and fills between the substrate and the first casing. Because of the arrangement of adhesive layers placed between the first casing and the transparent lid and between the transparent lid and the chip, the blockage area from moisture is elongated. Therefore, the reliability of the image sensor package structure can be enhanced.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Technical Field 
         [0002]    The present invention relates to semiconductor packaging structures. More particularly, the present invention relates to an image sensor package structure with improved structural reliability. 
         [0003]    2. Description of Related Art 
         [0004]    With the rapid progress of technologies, popularization of multimedia devices is accelerated. In addition, when a large number of digital imaging apparatuses, such as digital still cameras, digital video cameras, and digital scanners, have been introduced to the market in recent years, image digitization has become an inevitable trend. One of the crucial elements that makes the digital imaging apparatuses work is the image sensor. It serves to receive and convert optical signals or image signals into electric signals, and transmit the electric signals to a circuit board for analysis, enabling a digital imaging apparatus to photograph. 
         [0005]    In order to meet the market demand for digital imaging apparatuses to be as compact as possible, the used image sensor nowadays is typically a CCD (Charge Coupled Device), a CMOS (Complementary Metal Oxide Semiconductor) image sensor, or the like. Therefore, the possibility of downsizing digital imaging apparatuses relies on the technology in packaging the image sensors into minimized image sensor package structures. 
         [0006]    Such packaging technology is preferably applicable to mass productions with lower material costs. In addition, the packaging technology should provide appropriate protection to the sensitization area on an image sensor that is extremely sensitive and might be adversely affected by external dust and moisture so as to improve the imaging performance of the image sensor and enhance the reliability of the resultant package structure. Moreover, the service life is maximized and the quality of the digital imaging apparatus is ensured. 
         [0007]    However, the liquid compound conventionally used by the traditional packaging technology to package image sensors for preventing moisture invasion is very expensive and leaves the overall material costs of the existing image sensor package structure high. Moreover, the constantly changing processing temperature during baking tends to cause the volatile gases in the liquid compound to burst or create crevices in the baked compound. As a result, the image sensor is likely to be invaded by moisture. When the image sensor package structure later receives a reliability test, the moisture will expand and increase the pressure inside the image sensor package structure, thus resulting in damage to the image sensor and significantly reducing the production yield and reliability of the image sensor package structure. 
       SUMMARY OF THE INVENTION 
       [0008]    The present invention provides an image sensor package structure wherein a transparent lid is peripherally covered by adhesive layers or a casing, so the blockage area from moisture is elongated, thereby preventing the image sensor package structure from external moisture invasion and improving the reliability of the image sensor package structure. 
         [0009]    The present invention provides an image sensor package structure wherein a casing is provided with at least one gas vent that allows volatile gases contained in the liquid compound to escape during compound dispensing or post mold cure, thereby improving the production yield of the image sensor package structure. 
         [0010]    The present invention provides an image sensor package structure wherein a casing serves to support the image sensor package structure, so the amount of expensive liquid compound used can be decreased, reducing material costs. 
         [0011]    The present invention provides an image sensor package structure wherein the casing and adhesive layers are stacked so as to enlarge the air cavity between a transparent lid and a chip in volume, thereby improving the imaging quality. 
         [0012]    To achieve the aforementioned effects, the image sensor package structure includes a substrate provided with a plurality of first conductive contacts; a chip including a first surface and a second surface opposite to the first surface, wherein the first surface is bound to the substrate while the second surface has a sensitization area and a plurality of second conductive contacts that surrounds the periphery of the sensitization area and is electrically connected with the first conductive contacts; a transparent lid having a third surface and a fourth surface opposite to the third surface, wherein the third surface adheres to the second surface for covering over the sensitization area to define an air cavity over the sensitization area; a first casing having a first board that is centrally formed with an opening and adheres to the fourth surface; and a package material covering around the chip, the transparent lid, and the first casing at peripheries thereof. 
         [0013]    To achieve the aforementioned effects, the image sensor package structure alternatively includes a substrate provided with a plurality of first conductive contacts; a chip including a first surface and a second surface opposite to the first surface, wherein the first surface is bound to the substrate while the second surface has a sensitization area and a plurality of second conductive contacts that surrounds the periphery of the sensitization area and is electrically connected with the first conductive contacts; a transparent lid having a third surface and a fourth surface opposite to the third surface, wherein the third surface covers over the sensitization area to define an air cavity over the sensitization area; a second casing having a second board that is adhesively sandwiched between the second surface and the third surface, a third board that has one edge connected with one edge of the second board, and a fourth board that is parallel to the second board and connected with an opposite edge of the third board; and a package material covering around the chip and the second casing at peripheries thereof. 
         [0014]    To achieve the aforementioned effects, the image sensor package structure alternatively includes a substrate provided with a plurality of first conductive contacts; a chip including a first surface and a second surface opposite to the first surface, wherein the first surface is bound to the substrate while the second surface has a sensitization area and a plurality of second conductive contacts that surrounds the periphery of the sensitization area and is electrically connected with the first conductive contacts; a transparent lid having a third surface and a fourth surface opposite to the third surface, wherein the third surface covers over the sensitization area to define an air cavity over the sensitization area; a third casing having a fifth board that adheres to the second surface, a sixth board that has one edge connected with one edge of the fifth board, a seventh board that is parallel to the fifth board and connected with an opposite edge of the sixth board so that the fifth, sixth, and seventh boards jointly form a transverse U-shaped structure for locking in the transparent lid, and an eighth board that extends from the seventh board outward from the third casing; and a package material covering around the chip and the third casing at peripheries thereof. 
         [0015]    By implementing the present invention, at least the following progressive effects can be achieved: 
         [0016]    1. By virtue of the adhesive layers or the casing covering around the transparent lid, the blockage area from moisture is elongated so that the image sensor package structure is prevented from external moisture invasion. 
         [0017]    2. Since the casing serves to support the image sensor package structure, the amount of the expensive liquid compound used can be reduced, leading to reduced material costs. 
         [0018]    3. The stacked casing and adhesive layers help to enlarge the air cavity between the transparent lid and the chip in volume, thereby improving imaging quality. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0019]    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 read in conjunction with the accompanying drawings, wherein: 
           [0020]      FIG. 1  is a cross-sectional view of an image sensor package structure according to a first embodiment of the present invention; 
           [0021]      FIG. 2  is a bottom oblique view of a first casing according to the first embodiment of the present invention; 
           [0022]      FIG. 3  is a cross-sectional view of an image sensor package structure according to a second embodiment of the present invention; 
           [0023]      FIG. 4  is a cross-sectional view of an image sensor package structure according to a third embodiment of the present invention; 
           [0024]      FIG. 5 , according to a first concept of the present invention, shows soldering pads formed on the lower surface of the substrate; and 
           [0025]      FIG. 6 , according to a second concept of the present invention, shows soldering pads formed on the lower surface of the substrate. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     First Embodiment 
       [0026]    Referring to  FIG. 1 , the present embodiment is an image sensor package structure  100 , including: a substrate  110 , a chip  120 , a transparent lid  130 , a first casing  140 , and a package material  150 . 
         [0027]    As shown in  FIG. 1 , the substrate  110  may be a circuit substrate and provided thereon with at least one first conductive contact  111 . 
         [0028]    The chip  120  has a first surface  121  and a second surface  122 , referring to the lower surface and the upper surface of the chip  120 , respectively. Therein, the first surface  121  is combined with the substrate  110 , so as to adhere the chip  120  to the substrate  110 . Additionally, a glue layer  112  may be provided between the chip  120  and the substrate  110  for enhancing the combination between the chip  120  and the substrate  110 . The second surface  122  of the chip  120  is formed with at least one second conductive contact  123  and a sensitization area  124 . The sensitization area  124  includes therein a plurality of photosensitive elements and one or more said second conductive contacts  123  surrounding the periphery of the sensitization area  124  in electrical connection with the photosensitive elements in the sensitization area  124 . 
         [0029]    Moreover, the second conductive contact  123  may be electrically connected to the first conductive contact  111  of the substrate  110  through a metal conducting wire  10  formed by wiring. The chip  120  may be a CMOS (Complementary Metal Oxide Semiconductor) image sensor or a CCD (Charge Coupled Device) for sensing light. 
         [0030]    As can be seen in  FIG. 1 , the transparent lid  130  has a third surface  131  and a fourth surface  132 , referring to the lower surface and the upper surface of the transparent lid  130 , respectively. The transparent lid  130  covers the sensitization area  124  of the chip  120  for protecting the sensitization area  124  of the chip  120  from contaminants that may otherwise adversely affect the imaging quality of the sensed image. Also, the transparent lid  130  allows light to pass therethrough and enter into the sensitization area  124  of the chip  120 . 
         [0031]    The third surface  131  of the transparent lid  130  adheres to the second surface  122  of the chip  120  by means of a first adhesive layer  160 , which may be made of epoxy resin. Since the first adhesive layer  160  is settled between the sensitization area  124  and the second conductive contact  123 , the first adhesive layer  160  does not cover the sensitization area  124 , and thus the chip  120  is ensured with the optimal light-sensing effect. As a result of the first adhesive layer  160 , an air cavity  170  is formed between the transparent lid  130  and the sensitization area  124  of the chip  120 . 
         [0032]    Referring to  FIG. 2 , the first casing  140  has a first board  141 , which may be a quadrilateral board centrally formed with an opening  143 . The first casing  140  may further include a flange  142  that is defined by a vertically extended peripheral portion of the first board  141 , so that the first casing  140  has a stepped inner periphery. 
         [0033]    As shown in  FIG. 1 , the first board  141  has a fifth surface  144  adhering to the fourth surface  132  of the transparent lid  130  by means of a second adhesive layer  180 . In other words, the peripheral surface of the opening  143  of the first board  141  is adhesively attached to the transparent lid  130 , while the second adhesive layer  180  extends and covers lateral sides of the transparent lid  130  for enhancing the combination between the first casing  140  and the transparent lid  130 . The second adhesive layer  180  may also be made of epoxy resin. 
         [0034]    Again in  FIG. 1 , the opening  143  of the first board  141  is positioned corresponding to the sensitization area  124  of the chip  120 , so as to allow light to pass through the opening  143  and pierce through the transparent lid  130  to enter into the sensitization area  124  of the chip  120 , thereby enabling the sensitization area  124  to receive light and conduct its sensing function. 
         [0035]    The first casing  140  may be made of a heat-resistant plastic material or a metal material. When the first casing  140  is made of the metal material, the first casing  140  provides additional heat-dissipation effect to the image sensor package structure  100 . Furthermore, the first casing  140  and the transparent lid  130  may be adhesively combined beforehand by means of the second adhesive layer  180 , and then jointly adhered to the chip  120  by means of the first adhesive layer  160 . 
         [0036]    Also in  FIG. 1 , the package material  150  is formed by injecting liquid compound or mold compound to cover around the chip  120 , the transparent lid  130 , and the first casing  140  at peripheries thereof so that the chip  120  and metal conducting wires  10  are protected by the package material  150  from damage that may be otherwise caused by external force or moisture. 
         [0037]    For dissipation of volatile gases contained in the liquid compound during compound dispensing, the first casing  140  or the flange  142  of the first casing  140  may further have at least one gas vent  145 . The gas vent  145  penetrates through the first casing  140  or the flange  142  so as to allow the volatile gases in the liquid compound to instantly dissipate through the gas vent  145  during compound dispensing or baking. It prevents formation of air bubbles otherwise incurred by such volatile gases in the package material  150 , and ensures the production yield of the image sensor package structure  100 . 
         [0038]    Still referring to  FIG. 1 , in the image sensor package structure  100 , the first adhesive layer  160  and the second adhesive layer  180  adhere the transparent lid  130  to the chip  120  and adhere the first casing  140  to the transparent lid  130 , respectively. The fourth surface  132  of the transparent lid  130  is peripherally covered by the second adhesive layer  180  while the first board  141  covers thereon. Consequently, the transparent lid  130  has its edges covered and sealed by the first casing  140  and the second adhesive layer  180 , thereby elongating the blockage area from moisture seeping into the air cavity  170  and in turn effectively enhancing the reliability of the image sensor package structure  100 . 
         [0039]    The first casing  140  in the image sensor package structure  100  not only advantageously provides structural support but also decreases the volume of the package material  150 , which reduces the amount of liquid compound used in the image sensor package structure  100 , and thereby lowering material costs. 
       Second Embodiment 
       [0040]    Referring to  FIG. 3 , in an image sensor package structure  200  of the present embodiment, the first casing  140  of the first embodiment is replaced by a second casing  210 . While the remainder has been described in detailed in the first embodiment, related explanation is omitted herein. The second casing  210  is combined with the transparent lid  130  in a different way. The second casing  210  has a second board  211 , a third board  212 , and a fourth board  213 . 
         [0041]    According to  FIG. 3 , the second board  211  and the fourth board  213  of the second casing  210  are parallel to each other while the third board  212  serves to connect edges of the second board  211  and the fourth board  213 , so that the second casing  210  has a stepped shape. Moreover, the third board  212  may be perpendicular to the second board  211  and the fourth board  213 , or be connected to either boards (second board  211  and fourth board  213 ) at angles other than 90 degrees. The second board  211  has a sixth surface  214  adhering to the second surface  122  of the chip  120  by means of a third adhesive layer  220 , so as to adhere the second casing  210  to the chip  120 . 
         [0042]    The second board  211  further has a seventh surface  215  adhering to the third surface  131  of the transparent lid  130  by means of a fourth adhesive layer  230 . Both the third adhesive layer  220  and the fourth adhesive layer  230  may be made of epoxy resin. The transparent lid  130  and the second board  211  may be formed through an injection molding process as a whole before the second casing  210  is adhered to the chip  120  by means of the third adhesive layer  220 . 
         [0043]    Also in  FIG. 3 , the fourth board  213  of the second casing  210  may further have at least one gas vent  216 . The gas vent  216  penetrates through the second casing  210  so as to allow the volatile gases in the liquid compound to instantly dissipate through the gas vent  216  during compound dispensing or baking. It prevents formation of air bubbles otherwise incurred by volatile gases in the package material  150  and ensures the production yield of the image sensor package structure  200 . The package material  150  is arranged between the substrate  110  and the second casing  210  for covering the periphery of the second casing  210 , the metal conducting wires  10  and the chip  120 . In addition, since the second casing  210  directly adheres to the chip  120 , it may be made of a heat-resistant plastic material, enduring a temperature as high as 260 or more. 
         [0044]    In the image sensor package structure  200 , since the chip  120  and transparent lid  130  jointly sandwich therebetween the third adhesive layer  220 , the second board  211  and the fourth adhesive layer  230 , a distance between the transparent lid  130  and the chip  120  is enlarged, in turn widening the air cavity  170  in volume, preventing ghost images that are otherwise caused by multiple reflection or diffraction of light, thereby improving the imaging quality of the image sensor. 
         [0045]    In addition, the second casing  210  in the image sensor package structure  200  not only advantageously provides structural support but also reduces the volume of the package material  150 , which also decreases the amount of liquid compound used in the image sensor package structure  200 , thereby lowering material costs. 
       Third Embodiment 
       [0046]    Referring to  FIG. 4 , in an image sensor package structure  300  of the present embodiment, the second casing  210  of the second embodiment is replaced by a third casing  310 . Since the remainder has been described in detailed in the first embodiment, related explanation is omitted herein. The third casing  310  has a fifth board  311 , a sixth board  312 , a seventh board  313 , and an eighth board  314 . 
         [0047]    According to  FIG. 4 , the fifth board  311  and the seventh board  313  are parallel to each other while the sixth board  312  serves to connectedges of the fifth board  311  and the seventh board  313 , so that the fifth board  311 , the sixth board  312 , and the seventh board  313  jointly form a transverse U-shaped structure. In addition, the eighth board  314  is defined by an extended peripheral portion of the seventh board  313  extending transversely outward from the third casing  310 . 
         [0048]    As can be seen in  FIG. 4 , the fifth board  311  has an eighth surface  315  adhering to the second surface  122  of the chip  120  by means of a fifth adhesive layer  320 , so as to fixedly fasten the third casing  310  to the chip  120 . The opening defined by the transverse U-shaped structure of the third casing  310  locking in the transparent lid  130  so that the periphery of the transparent lid  130  is fully covered by the third casing  310 . Similarly, the transparent lid  130  and the third casing  310  may be formed through an injection molding process as a whole before adhering to the chip  120  by means of the fifth adhesive layer  320 . 
         [0049]    Also in  FIG. 4 , the eighth board  314  may further have at least one gas vent  316 . The gas vent  316  penetrates through the eighth board  314  so as to allow the volatile gases in the liquid compound to instantly dissipate through the gas vent  316  during compound dispensing or baking, in turn preventing formation of air bubbles otherwise incurred by such volatile gases in the package material  150 , and ensuring the production yield of the image sensor package structure  300 . The package material  150  is arranged between the substrate  110  and the third casing  310  for covering the periphery of the third casing  310 , the metal conducting wires  10  and the chip  120 . In addition, since the third casing  310  directly adheres to the chip  120 , it may be made of a heat-resistant plastic material, enduring a temperature as high as 260 or more. 
         [0050]    In the image sensor package structure  300 , since the chip  120  and transparent lid  130  jointly sandwich between them the fifth board  311  and the fifth adhesive layer  320 , the distance between the transparent lid  130  and the chip  120  is enlarged, in turn increasing the air cavity  170  in volume, thereby improving the imaging quality of the image sensor. In addition, the third casing  310  in the image sensor package structure  300  not only advantageously provides structural support but also reduces the volume of the package material  150 , which also decreases the amount of liquid compound used in the image sensor package structure  300 , thereby reducing material costs. 
         [0051]    In the image sensor package structures  100 ,  200 ,  300 , the presence of the gas vents  145 ,  216 ,  316  effectively ensures dissipation of volatile gases during the compound dispensing or baking process. Furthermore, in the image sensor package structure  100  or  300 , the transparent lid  130  is peripherally covered by the second adhesive layer  180  or the seventh board  313 , which elongating the blockage area of moisture entering into the air cavity  170  and thus preventing moisture invasion that may otherwise occur in the air cavity  170 . 
         [0052]    In each of the above embodiments, a plurality of solder balls  20  may be attached to the lower surface  113  of the substrate  110 . The solder balls  20  may be electrically connected to the first conductive contacts  111  on the substrate  110  by means of the circuit structure of the substrate  110  so that the solder balls  20  allow the image sensor package structure  100 ,  200  or  300  to electrically connect with external circuit devices. 
         [0053]    Furthermore, referring to  FIGS. 5 and 6 , in addition to the solder balls  20 , soldering pads  30  may be formed on the lower surface  113  of the substrate  110 . The soldering pads  30  may also be electrically connected to the circuit structure of the substrate  110 , and also be in electrical connection to the first conductive contacts  111  on the substrate  110 . Thus, the soldering pads  30  allow the image sensor package structure  100 ,  200  or  300  to electrically connect with external circuit devices. Preferably, the soldering pads  30  may be formed along the periphery of the lower surface  113 , as shown in  FIG. 5 , or may be formed into an array, as shown in  FIG. 6 . 
         [0054]    The embodiments described above are intended only to demonstrate the technical concept and features of the present invention so as to enable a person skilled in the art to understand and implement the contents disclosed herein. It is understood that the disclosed embodiments are not to limit the scope of the present invention. Therefore, all equivalent changes or modifications based on the concept of the present invention should be encompassed by the appended claims.