Abstract:
This invention provides a sensor semiconductor package and a method for fabricating the same. The method includes: mounting on a substrate a sensor chip having a sensor area; electrically connecting the sensor chip and the substrate by means of bonding wires; forming on a transparent member an adhesive layer with an opening corresponding in position to the sensor area; and mounting the transparent member on the substrate via the adhesive layer while heating the substrate, such that the adhesive layer melts, to thereby encapsulate the periphery of the sensor chip and the bonding wires while exposing the sensor area from the adhesive layer. Thus, the sensor area is sealed by the transparent member cooperative with the adhesive layer, making the sensor semiconductor package thus-obtained dam-free, light, thin, and compact, and incurs low process costs. Also, the product reliability is enhanced since the bonding wires are encapsulated by the adhesive layer without severing concern.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates generally to semiconductor packages and methods for fabricating the same, and more particularly to a sensor semiconductor package and a method for fabricating the same. 
         [0003]    2. Description of Related Art 
         [0004]    In a conventional image sensor semiconductor package, a sensor chip is mounted to a chip carrier and electrically connected to the chip carrier through bonding wires, and the sensor chip is covered with a transparent member to allow image light to be captured by the sensor chip. Typically, the image sensor semiconductor package is installed in an external device such as a printed circuit board (PCB) so as to be applied in various electronic products such as digital still cameras (DSCs), digital videos (DVs), optical mice, mobile phones and so on. 
         [0005]      FIG. 1  is a diagram showing a sensor semiconductor package and a method for fabricating the same according to U.S. Pat. No. 5,534,725. Referring to  FIG. 1 , a sensor chip  12  having a sensor area  12   a  is mounted to the die pad  11   a  of a lead frame  11 , and bond pads  12   b  of the sensor chip  12  are electrically connected to leads  11   b  of the lead frame  11  through bonding wires  13 . Then, a transparent member  15  is adhered to the sensor chip  12  through an adhesive layer  14 , wherein the adhesive layer  14  is located between the sensor area  12   a  and the bond pads  12   b  so as to make the transparent member  15  sealingly cover the sensor area  12   a.  Subsequently, an encapsulant  16  is formed by molding to encapsulate the lead frame  11 , the bonding wires  13  and the periphery of the sensor chip  12 . Meanwhile, the transparent member  15  is exposed from the encapsulant  16 . 
         [0006]    However, during formation of the encapsulant  16 , since the transparent member  15  is directly abutted against the top of the inner wall of an upper mold, a molding press applied to the transparent member  15  may easily cause breakage of the transparent member  15  and even damage the sensor chip  12  located below the transparent member  15 . On the other hand, if the transparent member  15  and the inner wall of the upper mold are not tightly pressed together and spacing exists therebetween, the encapsulant  16  may overflow to the surface of the transparent member  15 . Also, since the sensor chip  12  needs a space reserved for disposing of the adhesive layer between the sensor area  12   a  and the bond pads  12   b,  size of the sensor area  12   a  must be reduced or size of the sensor chip  12  must be increased, which thus reduces the use efficiency of the sensor chip  12 . 
         [0007]    Accordingly, referring to  FIG. 2 , U.S. Pat. No. 5,962,810 discloses a sensor semiconductor package that has reduced size and prevents damage of the sensor chip thereof. Referring to  FIG. 2 , a sensor chip  22  is mounted to a substrate  21  and bond pads  22   b  of the sensor chip  22  are electrically connected to the substrate  21  through bonding wires  23 . A fluid adhesive is formed on the bonding wires  23  by dispensing so as to form a darn structure  24 . Further, a transparent adhesive material  25  is formed on the sensor area  22   a  of the sensor chip  22  so as to form a sensor semiconductor package with reduced size. 
         [0008]    However, the fluid adhesive has high fabrication cost and low reliability and cannot be widely applied in the industry. 
         [0009]    U.S. Pat. No. 5,950,074, No. 6,060,340, No. 6,262,479, No. 6,384,472, and No. 6,590,269 disclose another kind of sensor semiconductor package. Referring to  FIG. 3A , a dam structure  34  is formed on a substrate  31 , and a sensor chip  32  having a sensor area  32   a  is mounted on the substrate  31  and received in the dam structure  34 . Bond pads  32   b  of the sensor chip  32  are electrically connected to the substrate  31  through bonding wires  33 . Further, a transparent member  35  is mounted on the dam structure  34  so as to cover the sensor chip  32 . 
         [0010]    Referring to  FIG. 3B , U.S. Pat. No. 6,545,332 discloses a similar sensor semiconductor package. A lead frame  310  having a die pad  310   a  and a plurality of leads  310   b  is provided, and a first encapsulant  36  is formed between the die pad  310   a  and the leads  310   b.  A sensor chip  32  having a sensing area  32   a  is mounted on the die pad  310   a  and bond pads  32   b  of the sensor chip  32  are electrically connected to the leads  310   b  of the lead frame  310  through bonding wires  33 . A dam structure  34  is further formed on the leads  310   b  to enclose the sensor chip  32  and the bonding wires  33 . Then, a second encapsulant  37  is formed between the sensor chip  32  and the dam structure  34  by dispensing to encapsulate part of the bonding wires  33  connected to the leads  310   b,  the die pad  310   a  and the leads  310   b.  Finally, a transparent member  35  is disposed on the dam structure  34  to cover the sensor chip  32 . Alternatively, the dam structure  34  is formed on the leads  310   b  before mounting of the sensor chip  32  and formation of the bonding wires  33 . 
         [0011]    In the above-described techniques, the dam structure  34  is applied to prevent the transparent member  35  from directly contacting the sensor chip  32 , thereby preventing damage of the sensor chip  32 . However, the integral planar size of the package comprises chip size, wire bonding space and the width of the dam structure  34 . Particularly, space required by the dam structure  34  prevents the packages from becoming lighter, thinner, smaller and shorter. 
         [0012]    Referring to  FIG. 4A , U.S. Pat. No. 6,995,462 discloses a sensor semiconductor package without dam structure. A substrate  41  having a concave portion  41   a  is provided. A sensor chip  42  having a sensor area  42   a  is mounted to the concave portion  41   a,  and bond pads  42   b  of the sensor chip  42  are electrically connected to the substrate  41  through bonding wires  43 . A transparent member  45  is adhered to the sensor chip  42  through an adhesive layer  44  which encapsulates part of the bonding wires  43 . Thus, the transparent member  45  covers, but does not contact, the sensor area  42   a  of the sensor chip  42 . Then, a liquid mold compound (LMC) is deposited in the concave portion  41   a  of the substrate  41  by dispensing so as to form an encapsulant  46  which encapsulates part of the bonding wires  43  while exposing the transparent member  45 . 
         [0013]    However, as shown in  FIG. 4B , since the encapsulant  46  made of a liquid mold compound has poor adhesion with the adhesive layer  44 , delamination is easy to occur therebetween, which may further lead to breakage  43   a  of the bonding wires  43  encapsulated by both the encapsulant  46  and the adhesive layer  44 . 
         [0014]    Therefore, how to provide a sensor semiconductor package and a method for fabricating the same to overcome the above-described drawbacks has become urgent. 
       SUMMARY OF THE INVENTION 
       [0015]    According to the above drawbacks, the present invention is to provide a sensor semiconductor package and a method for fabricating the same so as to prevent delamination, eliminate the requirement of a dispensing process, simplify fabrication processes, and reduce the fabrication costs. 
         [0016]    Accordingly, the present invention provides a sensor semiconductor package, which comprises: a substrate; a sensor chip, having a sensor area, mounted on the substrate and electrically connected to the substrate via bonding wires; an adhesive layer encapsulating a periphery of the sensor chip and the bonding wires without contacting the sensor area of the sensor chip; and a transparent member mounted to the substrate via the adhesive layer for hermetically sealing the sensor area. 
         [0017]    The substrate is a LGA (Land Grid Array) substrate. The height of the adhesive layer is greater than that of a wire loop of each of the bonding wires. The adhesive layer is made of a material that has low viscosity when heated, which is a resin material in the form of a tape at room temperature. The transparent member is made of glass material. 
         [0018]    The present invention further provides a method for fabricating a sensor semiconductor package, comprising: mounting on a substrate a sensor chip having a sensor area and electrically connecting the sensor chip to the substrate via bonding wires; and mounting on the substrate a transparent member pre-adhered with an adhesive layer in a manner that the adhesive layer is interposed between the substrate and the transparent member for encapsulating the bonding wires and a periphery of the sensor chips, and that the sensor area of the sensor chip is exposed from an opening formed in the adhesive layer, so as to allow the sensor area to be hermetically isolated from the atmosphere by the transparent member cooperative with the adhesive layer. 
         [0019]    Another method for fabricating a sensor semiconductor package comprises: mounting on a batch-type substrate a plurality of sensor chips each having a sensor area and electrically connecting the sensor chips to the substrate through bonding wires; mounting on the batch-type substrate a plurality of transparent members each pre-adhered with an adhesive layer in a manner that the adhesive layer is interposed between the batch-type substrate and a corresponding one of the transparent members for encapsulating the bonding wires and a periphery of a corresponding one of the sensor chips while the sensor area of the corresponding one of the sensor chips is exposed from an opening formed in the adhesive layer, so as to allow the sensor area to be hermetically isolated from the atmosphere by the transparent member cooperative with the adhesive layer; and performing a singulation process to form a plurality of sensor semiconductor packages. 
         [0020]    Another method for fabricating a sensor semiconductor package comprises: mounting on a batch-type substrate a plurality of sensor chips each having a sensor area and electrically connecting the sensor chips to the substrate via bonding wires; mounting on the batch-type substrate a sheet of transparent member pre-adhered with an adhesive layer having a plurality of openings formed corresponding in position to the sensor areas, in a manner that the adhesive layer is interposed between the sheet of the transparent member and the batch-type substrate for encapsulating the bonding wires and peripheries of the sensor chips, and the sensor areas of the sensor chips are exposed from the openings of the adhesive layer so as to allow the sensor areas to be hermetically isolated from the atmosphere by the sheet of the transparent member cooperative with the adhesive layer; and performing a singulation process to form a plurality of sensor semiconductor packages. According to another embodiment, the adhesive layer is further formed with a plurality of through openings in positions corresponding to cutting lines for performing the singulation process. 
         [0021]    Therefore, the present invention pre-disposes an adhesive layer to a transparent member and mounts the transparent member with the adhesive layer on a substrate such that the adhesive layer encapsulates the periphery of the sensor chip and the bonding wires, thereby saving space for disposing of the adhesive layer between the sensor area and the bond pads as in the prior art and increasing the sensor area ratio of the sensor chip. Meanwhile, the whole planar size of the package only comprises the chip size and the space for wire bonding, thereby saving the space for disposing of a dam structure as in the prior art and facilitating fabrication of lighter, thinner, shorter and smaller packages. Further, the present invention eliminates the need of a dam structure, the dispensing process and formation of several kinds of encapsulants as in the prior art. Instead, the present invention uses only one kind of encapsulants in the process, thereby simplifying the fabrication process, saving the fabrication cost and time, and preventing the delamination problem occurring between different kinds of the encapsulants as in the prior art and accordingly increasing the product yield. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0022]      FIG. 1  is a sectional diagrams of a sensor semiconductor package disclosed by U.S. Pat. No. 5,534,725; 
           [0023]      FIG. 2  is a sectional diagram of a sensor semiconductor package disclosed by U.S. Pat. No. 5,962,810; 
           [0024]      FIG. 3A  is a sectional diagram of a conventional sensor semiconductor package; 
           [0025]      FIG. 3B  is a sectional diagram of a conventional sensor semiconductor package disclosed by U.S. Pat. No. 6,545,332; 
           [0026]      FIG. 4A  is a sectional diagram of a conventional sensor semiconductor package disclosed by U.S. Pat. No. 6,995,462; 
           [0027]      FIG. 4B  is a locally enlarged view of  FIG. 4A , showing a delamination phenomenon occurring between different encapsulants; 
           [0028]      FIGS. 5A to 5C  are sectional diagrams of a sensor semiconductor package according to a first embodiment of the present invention; 
           [0029]      FIGS. 6A to 6D  are sectional diagrams of a sensor semiconductor package according to a second embodiment of the present invention; 
           [0030]      FIGS. 7A to 7D  are sectional diagrams of a sensor semiconductor package according to a third embodiment of the present invention; and 
           [0031]      FIGS. 8A to 8D  are sectional diagrams of a sensor semiconductor package according to a fourth embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0032]    The following illustrative embodiments are provided to illustrate the disclosure of the present invention, these and other advantages and effects can be apparent to those skilled in the art after reading the disclosure of this specification. 
         [0033]    The following embodiments are described in sufficient detail to enable those skilled in the art to make and use the invention. It is to be understood that other embodiments would be evident based on the present disclosure, and that proves or mechanical changes may be made without departing from the scope of the present invention. 
         [0034]    In the following description, numerous specific details are given to provide a thorough understanding of the invention. However, it will be apparent that the invention may be practiced without these specific details. In order to avoid obscuring the present invention, some well-known configurations and process steps are not disclosed in detail. 
         [0035]    Likewise, the drawings showing embodiments of the structure are semi-diagrammatic and not to scale and, particularly, some of the dimensions are for the clarity of presentation and are shown greatly exaggerated in the drawing FIGS. Similarly, although the views in the drawings for ease of description generally show similar orientations, this depiction in the FIGs. is arbitrary for the most part. Generally, the invention can be operated in any orientation. 
         [0036]    For expository purposes, the term “horizontal” as used herein is defined as a plane parallel to the plane or surface of the substrate, regardless of its orientation. The term “vertical” refers to a direction perpendicular to the horizontal as just defined. Terms, such as “on”, “above”, “below”, “bottom”, “top”, “side” (as in “sidewall”), “higher”, “lower”, “upper”, “over”, and “under”, are defined with respect to the horizontal plane. 
       First Embodiment 
       [0037]      FIGS. 5A to 5C  are diagrams showing a sensor semiconductor package and a method for fabricating the same according to a first embodiment of the present invention. 
         [0038]    As shown in  FIG. 5A , a substrate  51  such as an LGA (Land Grid Array) substrate is provided. A sensor chip  52  having a sensor area  52   a  and a plurality of bond pads  52   b  is mounted on the substrate  51  and the bond pads  52   b  are electrically connected to the substrate  51  through bonding wires  53 . A transparent member  55 , such as glass, provided for an adhesive layer  54  to be applied thereon around the periphery of the transparent member  55 . In order to prevent the transparent member  55  from being interfered with the bonding wires  53 , the adhesive layer  54  is required to have a height greater than that of a wire loop of each of the bonding wires  53 . In addition, the adhesive layer  54  is made of a resin material in the form of a tape at room temperature, such as an epoxy tape, and the adhesive layer  54  is formed with an opening  54   a  corresponding in position to the sensor area  52   a.    
         [0039]    As shown in  FIG. 5B , the transparent member  55  is mounted to the substrate  51  via the adhesive layer  54  such that the adhesive layer  54  is interposed between the transparent member  55  and the substrate  51 . Before the mounting of the transparent member  55  onto the substrate  51  via the adhesive layer  54 , the substrate is heated  51  so as to melt the adhesive layer  54  to a low viscosity state eligible for encapsulating the bonding wires  53  and a periphery of the sensor chip  52 , while exposing the sensor area  52   a  of the sensor chip  52  and leaving the sensor area  52   a  of the sensor chip  52  uncovered by the adhesive layer  54 . 
         [0040]    As shown in  FIG. 5C , after the heating of the substrate  51  is determined, the adhesive layer  54  is cooled and cured to securely attach the transparent member  55  to the substrate  51  via the adhesive layer  54 . As a result, a sensor semiconductor package  50  is formed and capable of hermetically isolating the sensor area  52   a  of the sensor chip  52  from the atmosphere by the transparent member  55  cooperative with the adhesive layer  54 . 
         [0041]    It should be noted that the bonding wires  53 , which are conventional gold wires, are merely encapsulated by the adhesive layer  54  rather than two different adhesives as in the prior arts, whereby the severing of the bonding wires  53  can be prevented and the product reliability can be accordingly improved. In addition, since the adhesive layer  54  is used to encapsulate the bonding wires  53  and attach the transparent member  55 , the package size of the finished semiconductor package can be desirably reduced to meet industrial requirements and the fabrication cost can be lowered. Moreover, interfaces among various elements are reduced, and delamination issues can thus be effectively prevented. 
         [0042]    The substrate  51  is an LGA substrate. The adhesive layer  54  has a height greater than that of a wire loop of each of the bonding wires  53 . The adhesive layer  54  may be such as an epoxy tape, which has a low viscosity when heated. The transparent member  55  is made of glass material. 
       Second Embodiment 
       [0043]      FIGS. 6A to 6D  are sectional diagrams showing a method for fabricating a sensor semiconductor package according to a second embodiment of the present invention. The present embodiment is mostly similar to the first embodiment, a main difference from the first embodiment is a plurality of sensor chips is mounted and electrically connected to a batch-type substrate, and a plurality of transparent members with an adhesive layer is mounted on the substrate, and further a singulation process is performed to form a plurality of packages. 
         [0044]    As shown in  FIG. 6A , a batch-type substrate  61  having a plurality of substrate units is provided for mounting a plurality of sensor chips  62  each having a sensor area  62   a  and a plurality of bond pads  62   b  thereon, and the bond pads  62   b  are electrically connected to the substrate  61  via a plurality of bonding wires  63 . A plurality of transparent members  65  are provided for the adhesive layer  64  to be applied to a peripheral area of each of the transparent members  65 , and the adhesive layer  64  is formed within an opening  64   a  corresponding in position to the sensor area  62   a.    
         [0045]    As shown in  FIG. 6B , the transparent members  65  are attached onto the substrate  61  via the adhesive layers  64 , such that the adhesive layers  64  are interposed between the corresponding transparent members  65  and the substrate  61 . Before the attachment of the transparent members  65  to the substrate  61  via the adhesive layers  64 , the substrate  61  is heated so as to melt the adhesive layers  64  to a low viscosity state good for encapsulating the peripheries of the sensor chips  62  and the bonding wires  63  while exposing the sensor area  62   a  of each of the sensor chips  62  and leaving the sensor area  62   a  of each of the sensor chips  62  uncovered by the adhesive layers  64 . 
         [0046]    As shown in  FIG. 6C , after the heating of the substrate  61  is terminated, the adhesive layers  64  are cooled and then cured, such that the transparent members  65  are allowed to be securely attached to the substrate  61  via the adhesive layers  64 . It thus allows the sensor area  62   a  of each of the sensor chips  62  to be hermetically isolated from the atmosphere by the corresponding transparent members  65  cooperative with the adhesive layers  64 . 
         [0047]    As shown in  FIG. 6D , a singulation process is performed to form a plurality of sensor semiconductor packages  60 . 
         [0048]    Therefore, such a method implements mass production and simplifies the fabrication process. 
       Third Embodiment 
       [0049]      FIGS. 7A to 7D  are sectional diagrams showing a method for fabricating a sensor semiconductor package according to a third embodiment of the present invention. The present embodiment is mostly similar to the first embodiment, a main difference from the first embodiment is a plurality of sensor chips is mounted and electrically connected to a batch-type substrate, a sheet of a transparent member pre-adhered with an adhesive layer is mounted on the substrate, and the adhesive layer has a plurality of openings formed corresponding in position to the sensor areas respectively. 
         [0050]    As shown in  FIG. 7A , a batch-type substrate  71  is provided. A plurality of sensor chips  72  each having a sensor area  72   a  and bond pads  72   b  is mounted on the substrate  71 , and the bond pads  72   b  are electrically connected to the substrate  71  through bonding wires  73 . Meanwhile, a sheet of the transparent member  75  is mounted on the batch-type substrate  71 . An adhesive layer  74  is formed on the transparent members  75  and the adhesive layer  74  has a plurality of openings  74   a  formed corresponding in position to the sensor areas  72   a.    
         [0051]    As shown in  FIG. 7B , the transparent member  75  is mounted on the substrate  71  via the adhesive layer  74 , and the substrate  71  is heated so as to melt the adhesive layer  74  to a low viscosity state eligible for encapsulating the bonding wires  73  and the periphery of the sensor chips  72  while exposing the sensor area  72   a  of each of the sensor chips  72 . 
         [0052]    As shown in  FIG. 7C , after the heating of the substrate is terminated, the adhesive layer  74  is cured to securely attach the transparent member  75  to the substrate  71  via the adhesive layer  74 . 
         [0053]    As shown in  FIG. 7D , a singulation process is performed to form a plurality of sensor semiconductor packages  70 . 
         [0054]    Therefore, mass production is implemented and the fabrication process is simplified. 
       Fourth Embodiment 
       [0055]      FIGS. 8A to 8D  are sectional diagrams showing a method for fabricating a sensor semiconductor package according to a fourth embodiment of the present invention. 
         [0056]    The present embodiment is mostly similar to the first embodiment, a main difference from the first embodiment is a plurality of sensor chips  82  having sensor areas  82   a  is mounted on and electrically connected to a batch-type substrate  81 , a transparent member  85  with an adhesive layer  84  is mounted on the substrate  81 , and the adhesive layer  84  is further formed with a plurality of openings  84   a  in positions corresponding to the sensor areas  82   a  and a plurality of through openings  84   b  in positions corresponding to cutting lines for performing a singulation process so as to save material of the adhesive layer  84 . 
         [0057]    Therefore, the present invention pre-disposes an adhesive layer to a transparent member and mounts the transparent member with the adhesive layer on a substrate such that the adhesive layer encapsulates the periphery of the sensor chip and the bonding wires, thereby saving space for disposing of the adhesive layer between the sensor area and the bond pads as in the prior art and increasing the sensor area ratio of the sensor chip. Meanwhile, the whole planar size of the package only comprises the chip size and the space for wire bonding, thereby saving the space for disposing of a dam structure as in the prior art and facilitating fabrication of lighter, thinner, shorter and smaller packages. Further, the present invention eliminates the need of a dam structure, the dispensing process and formation of several kinds of encapsulants as in the prior art. Instead, the present invention uses only one kind of encapsulant in the process, thereby simplifying the fabrication process, saving the fabrication cost and time, and preventing the delamination problem occurring between different kinds of the encapsulants as in the prior art and accordingly increasing the product yield. 
         [0058]    The above-described descriptions of the detailed embodiments are only to illustrate the preferred implementation according to the present invention, and it is not to limit the scope of the present invention, Accordingly, all modifications and variations completed by those with ordinary skill in the art should fall within the scope of present invention defined by the appended claims.