Abstract:
A manufacturing method for molding an image sensor package structure and the image sensor package structure thereof are disclosed. The manufacturing method includes following steps of providing a half-finished image sensor for packaging, arranging a dam on the peripheral of a transparent lid of the half-finished image sensor, positioning the half-finished image sensor within a mold, and injecting a mold compound into the mold cavity of the mold. The dam is arranged on the top surface of the transparent lid and the inner surface of the mold can exactly contact with the top surface of dam so that the mold compound injected into the mold cavity is prevented from overflowing to the transparent lid by the dam. Furthermore, the arrangement of the dam and the mold compound can increase packaged areas and extend blockage to invasive moisture so as to enhance the reliability of the image sensor package structure.

Description:
BACKGROUND OF THE INVENTION 
     1. Technical Field 
     The present invention relates to semiconductor packaging structures. More particularly, the present invention relates to a manufacturing method for molding image sensor package structure and an image sensor package structure made through the method. 
     2. Description of Related Art 
     Conventionally, an image sensor package is made by placing an image sensor chip on a substrate, connecting the image sensor chip and the substrate by means of metal conducting wires, and mounting a transparent lid (e.g. glass) upon the image sensor chip so as to allow light to pass through the transparent lid and get acquired by the sensor chip. The resultant image sensor package is for a system manufacturer to integrate to an external device, such as a printed circuit board, or to apply to any of various electronic products such as a DSC (Digital Still Camera), a DV (Digital Video), a security monitoring system, a mobile phone, or a vehicle image sensing module. 
     In traditional image sensor package, the transparent lid is adhered beforehand to the image sensor chip for protecting the chip against foreign pollutant particles. After the transparent lid is installed, the metal conducting wires are arranged so as to electrically connect the image sensor chip with the substrate or a carrier. Then, a macromolecular liquid compound is used to cover the metal conducting wires. However, the macromolecular liquid compound is quite costly and needs to be arranged through a time-consuming dispensing process. Consequently, the traditional technology of such image sensor package is disadvantageous in its prolonged processing cycle and high cost. 
     In addressing the above problems, U.S. Pat. No. 7,312,106 has proposed a method for encapsulating a chip having a sensitive surface. The known method comprises mounting a chip having a sensitive chip surface and contact pads on a carrier having carrier contact pads; bonding the chip contact pads to the carrier contact pads; applying a closed dam around the sensitive chip surface, which defines an open space inside the dam; positioning a lid, which closes the open space inside the dam; positioning the chip and the carrier into a mould; introducing package material into the mould for transfer molding; and conducting a post mold cure process so as to complete encapsulation of the chip. 
     The upper half of the mould could have an inward-extending section facing the sensitive chip surface so as to facilitate the package material in fully covering around the lid without covering the central upper surface of the lid, thereby protecting the periphery of the lid. However, the inward-extending section could significantly increase the cost for making the upper mould half, and is unfavorable to the purpose of reducing the overall cost of the image sensor package. Although the prior art method might also be accomplished by using a different upper mould half without the inward-extending section, it otherwise requires an additional elastic material settled between the upper mould half and the lid so as to protect the lid from the pressure exerted by the direct application of the upper mould. Even when the elastic material is used, the known method for encapsulating a chip still puts the image sensor in risk from damage, thus leading to a decreased yield rate. 
     SUMMARY OF THE INVENTION 
     The present invention provides a manufacturing method for molding image sensor package structure and an image sensor package structure made through the method, wherein by virtue of a dam arranged on a transparent lid, the transparent lid is free from being directly pressed by a mold, thus leading to an improved yield rate. 
     The present invention provides a manufacturing method for molding image sensor package structure and an image sensor package structure made through the method, wherein by virtue of a dam arranged on a transparent lid, a mold compound is allowed to cover around the chip, the transparent lid and the dam, thereby extending of the blockage to invasive moisture. 
     The present invention provides a manufacturing method for molding image sensor package structure and an image sensor package structure made through the method, wherein by virtue of a dam that facilitates extending blockage to invasive moisture, the reliability of the image sensor package structure is improved. 
     The present invention provides a manufacturing method for molding image sensor package structure and an image sensor package structure made through the method, wherein the image sensor package structure is produced by means of molding so as to significantly shorten processing cycle time and increase throughput. 
     The present invention provides a manufacturing method for molding image sensor package structure and an image sensor package structure made through the method, wherein batch-type production of the image sensor package structure is achieved by means of molding so as to reduce processing costs. 
     The present invention provides a manufacturing method for molding image sensor package structure and an image sensor package structure made through the method, wherein the disadvantages of the known technology related to the costly liquid compound and the time-consuming dispensing process are eliminated. 
     To achieve the aforementioned effects, the manufacturing method for molding image sensor package structure of the present invention includes the following steps: providing a half-finished image sensor for packaging, wherein the half-finished image sensor has a substrate including a carrying surface provided with a plurality of first conductive contacts; at least one chip including a first surface, a second surface, and a plurality of second conductive contacts, wherein the first surface is coupled to the carrying surface and the second surface has a sensitization area peripherally surrounded by the second conductive contacts that are electrically connected with the first conductive contacts; and at least one transparent lid settled on the second surface and covering over the sensitization area to define an air cavity over the sensitization area; arranging a dam extending along the upper periphery of the transparent lid; positioning the half-finished image sensor within a mold, wherein the mold includes an upper mold half contacting the upper surface of the dam and a lower mold half contacting the lower surface of the substrate, wherein a mold cavity between the upper mold half and the lower mold half is defined; injecting a mold compound into the mold cavity; and molding the image sensor package structure, opening the mold, and conducting a post mold cure process. 
     To achieve the aforementioned effects, the image sensor package structure of the present invention includes a substrate having a carrying surface provided with a plurality of first conductive contacts; a chip with a first surface coupled to the carrying surface, a second surface having a sensitization area and a plurality of second conductive contacts surrounding the sensitization area peripherally and electrically connected with the first conductive contacts; a transparent lid settled on the second surface and covering over the sensitization area to define an air cavity over the sensitization area; a dam extending along the upper periphery of the transparent lid; and a mold compound covering around the chip, the transparent lid and the dam at peripheries thereof. 
     By implementing the present invention, at least the following progressive effects can be achieved: 
     1. By virtue of the dam arranged on the transparent lid, the transparent lid is free from being directly pressed and damaged by the mold, thus leading to an improved yield rate of the image sensor package structure. 
     2. By virtue of the dam arranged on the transparent lid, there is no need to make the mold with a custom-made inward-extending section for varying lid dimensions, which significantly reduces costs for preparing the mold. 
     3. The dam on the transparent lid allows the mold compound to cover around the chip, the transparent lid, and the dam, thereby extending the blockage to invasive moisture. 
     4. The existence of the dam allows the mold to depress against the top of the dam and allows the mold compound protect the periphery of the transparent lid to prevent moisture from invading the air cavity underneath the transparent lid, thereby improving the reliability of the image sensor package structure. 
     5. The image sensor package structure is produced by means of molding so as to significantly shorten processing cycle time and increase throughput. 
     6. The molding formation and batch-type production of the image sensor package structure facilitate the reduction of the processing costs of the image sensor package structure. 
     7. The disadvantages of the known technology related to the costly liquid compound and the time-consuming dispensing process are eliminated. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       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: 
         FIG. 1  is a flowchart of a first embodiment of a method for molding an image sensor package structure according to the present invention; 
         FIG. 2  is a schematic structural drawing of a half-finished image sensor for packaging according to the present invention; 
         FIG. 3A , according to a first embodiment of the present invention, shows the half-finished image sensor for packaging provided with a dam; 
         FIG. 3B  is a top view of the half-finished image sensor of  FIG. 3A ; 
         FIG. 4A , according to the first embodiment of the present invention, shows the half-finished image sensor having the dam enclosed by a mold; 
         FIG. 4B , according to the first embodiment of the present invention, shows injection of a mold compound into a mold cavity of the mold; 
         FIG. 4C , according to the first embodiment of the present invention, shows the resultant image sensor package structure after the mold is opened; 
         FIG. 5A , according to a second embodiment of the present invention, shows the half-finished image sensors for packaging provided with dams; 
         FIG. 5B , according to the second embodiment of the present invention, shows the half-finished image sensors having the dams enclosed by a mold; 
         FIG. 5C , according to the second embodiment of the present invention, shows injection of a mold compound into a mold cavity of the mold; 
         FIG. 5D , according to the second embodiment of the present invention, shows the resultant image sensor package structure after the mold of  FIG. 5C  is opened; 
         FIG. 5E , according to the second embodiment of the present invention, shows the package structure of  FIG. 5D  cut into individuals; 
         FIG. 6A , according to a first concept of the present invention, shows soldering pads arranged on a lower surface of the substrate; and 
         FIG. 6B , according to a second concept of the present invention, shows soldering pads arranged on the lower surface of the substrate. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to  FIG. 1 , the present embodiment is a method (S 100 ) for molding an image sensor package structure. The method (S 100 ) includes the following steps: providing a half-finished image sensor for packaging (S 10 ); arranging a dam on a transparent lid (S 20 ); positioning the half-finished image sensor within a mold (S 30 ); injecting a mold compound into the mold cavity of the mold (S 40 ); and molding the image sensor package structure, opening the mold and conducting a post mold cure process (S 50 ). 
     In the step of providing a half-finished image sensor for packaging (S 10 ), as shown in  FIG. 2 , a half-finished image sensor  10  for packaging is provided. The half-finished image sensor  10  has a substrate  11 , at least one chip  12 , and at least one transparent lid  13 . Alternatively, as shown in  5 A, multiple said chips  12  are provided on the same substrate  11  for producing multiple said image sensor package structures simultaneously. 
     The substrate  11  may be one conventionally used in a normal image sensor, and may be a circuit substrate. The substrate  11  has a carrying surface  111  for carrying the chip  12 . In addition, a plurality of first conductive contacts  112  is formed on the carrying surface  111 , as shown in  FIG. 3B . 
     The chip  12  has a first surface  121  coupled to the carrying surface  111  of the substrate  11  so that the chip  12  is mounted on the substrate  11 . Furthermore, a glue layer  113  may be provided between the chip  12  and the substrate  11  for adhering the chip  12  onto the substrate  11 . The chip  12  may be a CMOS (Complementary Metal Oxide Semiconductor) image sensing chip or a CCD (Charge Coupled Device) for sensing light. In addition, the chip  12  has a plurality of photosensitive elements and a plurality of second conductive contacts  124 , as can be seen in FIG.  3 B. Therein, the photosensitive elements are settled on a second surface  122  of the chip  12  so as to form a sensitization area  123 . The second conductive contacts  124  are arranged to surround the sensitization area  123  and are electrically connected with the photosensitive elements. Moreover, the second conductive contacts  124  on the chip  12  and the first conductive contacts  112  on the substrate  11  may be electrically connected with each other through metal conducting wires  15  formed by wiring. The first surface  121  of the chip  12  refers to the lower surface of the chip  12  while the second surface  122  of the chip  12  refers to the upper surface of the chip  12 . 
     The transparent lid  13  serves to protect the sensitization area  123  on the chip  12  against contaminants while allowing light to pass therethrough and enter into the sensitization area  123  of the chip  12 . An adhesive layer  14  attaches the transparent lid  13  to the second surface  122  of the chip  12  so that the transparent lid  13  covers over the sensitization area  123  and so that an air cavity is defined between the transparent lid  13  and the chip  12 . The adhesive layer  14  may be made of epoxy resin. Since the adhesive layer  14  is sandwiched between the sensitization area  123  and the second conductive contacts  124 , it does not overlap with the sensitization area  123 , and thus the chip  12  is ensured with the optimal light-sensing effect. 
     In the step of arranging a dam on a transparent lid (S 20 ), referring to  FIGS. 3A and 5A , a dam  20  is set on the transparent lid  13  in such a way that it extends along an upper periphery of the transparent lid  13  while keeping away from the sensitization area  123  of the chip  12 , as shown in  FIG. 3B . Thereby, light is still allowed to pass through the transparent lid  13  and enter into the sensitization area  123  of the chip  12  without any complications. The dam  20  may be made of epoxy resin or a film. The epoxy resin or film are prearranged at a predetermined location and treated with ultraviolet or baked to a semi-cured state for being properly elastic and then receives a post mold cure process to become completely cured. 
     In the step of positioning the half-finished image sensor within a mold (S 30 ), referring to  FIGS. 4A and 5B , the mold comprises a lower mold half  31  and an upper mold half  32 . Therein the lower mold half  31  is settled at the lower surface  114  of the substrate  11  and contacts the lower surface  114  of the substrate  11 , while the upper mold half  32  has its lateral wall  321  mounted on the upper surface of the substrate  11  so that the substrate  11  has its carrying surface  111  and lower surface  114  sandwiched between the upper mold half  32  and the lower mold half  31 . Additionally, the upper mold half  32  has a planar inner upper surface for contacting the upper surface of the dam  20  so as to define a mold cavity  33  between the upper mold half  32  and the lower mold half  31 . 
     In the step of injecting a mold compound into the mold cavity of the mold (S 40 ), as shown in  FIGS. 4B and 5C , the mold compound  40  is injected into the mold cavity  33  formed between the upper mold half  32  and the lower mold half  31  so that the mold compound  40  encapsulates the metal conducting wires  15  therein and covers around the chip  12 , the transparent lid  13  and the dam  20  at peripheries thereof. Since the dam  20  acts as a barricade between the transparent lid  13  and the upper mold half  32 , the mold compound  40  is blocked outside the transparent lid  13  from overflowing into the central region of the transparent lid  13 . Furthermore, the upper mold half  32  directly presses upon the dam  20  so as not to directly contact the transparent lid  13 , thereby protecting the transparent lid  13  from damage or surface contamination. 
     In the step of molding the image sensor package structure, opening the mold and conducting the post mold cure process (S 50 ), the upper mold half  32  and the lower mold half  31  help the mold compound  40  to undergo transfer molding. After the mold is opened, a post mold cure process is conducted as to produce an image sensor package structure as shown in  FIG. 4C . During the progress of post mold cure, the dam  20  also becomes completely cured. 
     The disclosed method may further include a step of placing solder balls. Referring to  FIGS. 4C and 5D , solder balls  50  may be attached to the lower surface  114  of the substrate  11 . The solder balls  50  are also electrically connected to the first conductive contacts  112  on the carrying surface  111  by way of the circuit structure of the substrate  11 , which allows the image sensor package structure to electrically connect with external circuit devices. 
     Since the mold compound  40  is more inexpensive than the conventionally used liquid compound, substitution of liquid compound with the mold compound  40  helps to significantly reduce material costs for packaging. Furthermore, coating of the conventionally used liquid compound requires the known dispensing process that prolongs the processing cycle. On the other hand, the transfer molding process of the mold compound  40  achieves the purpose of forming in a significantly reduced cycle time, thereby improving throughput and in turn lowering the overall manufacturing costs. Moreover, the dam  20  additionally mounted on the transparent lid  13  serves as a mount for the mold compound to seal off the transparent lid and prevent invasive moisture from seeping into the chip  12 , thereby vastly improving the reliability of the image sensor package structure. 
     Furthermore, as shown in  FIGS. 5A through 5E , the above method (S 100 ) for molding the image sensor package structure may be applied to producing multiple said image sensor package structure at the same time. In this alternative application, the substrate  11  carrying multiple said chips  12  is positioned within a mold, as shown in  FIG. 5B . The mold compound  40  is injected into the mold cavity  33  of the mold, as shown in  FIG. 5C , so that the mold compound  40  later undergoes transfer molding, mold opening and the post mold cure process. Additionally, placement of solder balls  50  may be conducted after the post mold cure. The solder balls  50  may be electrically connected to the first conductive contacts  112  on the carrying surface  111  by way of the circuit structure of the substrate  11  so that the solder balls  50  allow the image sensor package structure to electrically connect with external circuit devices. At last, as illustrated by  FIGS. 5D and 5E , the finished image sensor package structure, after the post mold cure and placement of the solder balls  50 , may be cut by means of any existing cutting technology to become plural image sensor package structures, as package individuals, so as to improve efficiency of the throughput. 
     Referring to  FIGS. 6A and 6B , in addition to the solder balls  50 , soldering pads  60  may be arranged on the lower surface  114  of the substrate  11 . The soldering pads  60  are electrically connected to the first conductive contacts  112  of the circuit structure of the substrate  11  so that the soldering pads  60  allow the image sensor package structure to electrically connect with external circuit devices. Preferably, the soldering pads  60  may be arranged along the lower periphery of the lower surface  114 , as shown in  FIG. 6A , or may be arranged into an array, as shown in  FIG. 6B . 
     The molded image sensor package structure is thus suitable for vehicle image sensors to give the advantage of effectively blocking moisture invasion. 
     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.