Abstract:
A structure and method for packaging flash memory cards is provided, including the steps of (a) placing a circuit board of said flash memory card inside a bottom plate; (b) placing a top plate on top of said bottom plate to cover said circuit board with only electrical connection parts of said circuit board exposed; and (c) using an insert molding process to form a covering layer on the circumference of said bottom plate and said top plate to form the shape of said flash memory card. The covering layer seals the seam of the bottom plate and the top plate to provide water-proof effect and reduce the defect rate and the manufacture cost.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention generally relates to a structure and a packaging method for flash memory cards, and more specifically to a structure and a packaging method for flash memory cards using insert molding.  
       BACKGROUND OF THE INVENTION  
       [0002]     As the digital products, such as digital camera, mobile phones, PDA, are becoming popular, the consumer demands on the flash memory cards increase. The current types of the flash memory cards include compact flash (CF), card, smart media card (SMC), multimedia card (MMC), secure digital (SD) card, memory stick (MS) card, and an even newer xD-picture card. As the capacity of the memory cards increases, the cost of the loss also increases if the memory card is broken or damaged and the precious data is lost. Therefore, the manufacturers aim to improve the structure of the memory cards so that not only the capacity of the memory cards is improved, but also the strength of the structure and the water-proof effect.  
         [0003]     Conventional memory cards are packed in a two-piece structure. That is, two pieces of thin plates sandwich the circuit board, and a high-frequency melting technique is then used to glue the two plates together to form a memory card structure. The drawback of this structure is that it is prone to breakage at the glued seam or creating small leakage gaps for humidity damaging the enclosed circuit board after a large number of repetitive insertions and ejections of the memory cards from the electronic devices. A number of techniques, such as U.S. patent application Ser. No. 11/146,545, are proposed for enhancing the structure. For further improvement, the present invention provides a structure and a method for packaging memory cards.  
       SUMMARY OF THE INVENTION  
       [0004]     The present invention has been made to overcome the aforementioned drawback of conventional structure and packaging methods. The primary object of the present invention is to provide a packaging structure that is cost-effective and has high yield rate, and a method of forming the same. The structure includes a covering layer that is made of a material used in the final insert molding to uniformly form a thin layer encompassing the outer structure of the memory card. This covering layer avoids the impact of the material on the circuit board during the insert molding so that yield rate is high. In case of defect, the structure can be disassembled, and the circuit board can be re-used to reduce the cost.  
         [0005]     Another object of the present invention is to provide a packaging structure that is water-proof, and a method of forming the same. As the covering layer of the structure is formed by insert molding, the sealing effect is good and the final structure is water-proof.  
         [0006]     Yet another object of the present invention is to provide a structure that is applicable to a wide range of memory cards, and a method of forming the same. The structure of the present invention is applicable to any memory cards that include a two-plate structure sandwiching a circuit board.  
         [0007]     To achieve the above object, the present invention provides a structure including a bottom plate, a circuit board, a top plate and a covering layer. The bottom plate includes a concave for housing the circuit board, and the top plate covers the bottom plate and the most of the circuit board so that only the electrical connection part of the circuit board is exposed. The covering layer is made of the material used in the insert molding process to form a thin layer to cover both the bottom plate and the top plate and the seam between the two plates. The covering layer gives the final structure a monolithic appearance so that the sealing is water-proof.  
         [0008]     The foregoing and other objects, features, aspects and advantages of the present invention will become better understood from a careful reading of a detailed description provided herein below with appropriate reference to the accompanying drawings. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]     The present invention can be understood in more detail by reading the subsequent detailed description in conjunction with the examples and references made to the accompanying drawings, wherein:  
         [0010]      FIG. 1  shows a flowchart of a packaging method of the present invention;  
         [0011]      FIG. 2  shows a schematic view of an embodiment of packaging an SD memory card according to the present invention;  
         [0012]      FIG. 3A  shows a schematic view of the circuit board being sandwiched by the bottom plate and the top plate before the covering layer according to the present invention;  
         [0013]      FIG. 3B  shows a cross-sectional view of  FIG. 3A ;  
         [0014]      FIG. 4A  shows a schematic view of the circuit board being sandwiched by the bottom plate and the top plate after the covering layer according to the present invention;  
         [0015]      FIG. 4B  shows a cross-sectional view of  FIG. 4A ;  
         [0016]      FIG. 5  shows a schematic view of another embodiment of the present invention;  
         [0017]      FIG. 6A  shows a schematic view of the circuit board being sandwiched by the bottom plate and the top plate before the covering layer of  FIG. 5 ;  
         [0018]      FIG. 6B  shows a schematic view of the circuit board being sandwiched by the bottom plate and the top plate after the covering layer of  FIG. 5 ; and  
         [0019]      FIG. 7  shows a schematic view of yet another embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0020]      FIG. 1  shows a flowchart of the present invention, including the following steps. Step  11  is to place a circuit board onto a bottom plate. The bottom plate includes a concave to house the circuit board. The electrical connection part of the circuit board is exposed for further electrical connection. Step  12  is to place a top plate on the circuit board to cover the circuit board except the exposed electrical connection part. Finally, step  13  is to use insert molding to form a covering layer to encompassing the seam where the bottom plate meets the top plate, the surrounding area of the electrical connection part of the circuit board while exposing the electrical connection part. The hardening of the molding material will slightly melt and glue the top and bottom plates tightly to form a water-proof seal and the final structure will have a monolithic appearance of a memory card with the electrical connection part exposed for electrical connection.  
         [0021]      FIG. 2  shows an embodiment of packaging an SD card according to the present invention. However, the present invention is not limited to the application of SD cards. Any other equivalent types of memory cards are also within the scope of the present invention. As shown in  FIG. 2 , a bottom plate  2  and the top plate  3  are formed with an injection molding process in advance. The top surface of bottom plate  2  includes a concave  21 . The shape of concave  21  matches the shape of a circuit board  4 . Concave  21  further includes at least a deep housing cave  211  a plurality of shallow housing caves  212 . Deep housing cave  211  is for housing a memory chip  41  on circuit board  4 , and shallow housing caves  212  are for housing other smaller chips  42  and solder points  43 ,  44  of circuit board  4 . The shape of each shallow housing cave  212  should accommodate the corresponding elements on circuit board  4 . When circuit board  4  is placed onto bottom plate  2 , the circuitry and the solder points on circuit board  4  are not interfered. The other side of circuit board  4  includes a plurality of electrical connection parts  45 , so-called gold-fingers, as shown in  FIG. 3A . The total thickness of bottom plate  2  and top plate  3  is equal to the standard thickness of an SD card. As a covering layer is formed with the material during the insert molding process to cover the seam of bottom plate  2  and top plate  3 , the size of bottom plate  2  should be slightly smaller than the standard size of SD cards. Furthermore, the circumference of bottom plate  2  should include a slanted slope  22  on at least two sides, and the circumference of top plate  3  should include a slanted slope  31  on at least two sides to increase the attachment during the gluing process. Top plate  3  is shorter than bottom plate  2 , so that when placed on bottom plate  2 , electrical connection parts  45  of circuit board  4  are exposed.  
         [0022]      FIGS. 3A and 3B  show a schematic view of the circuit board being sandwiched by the bottom plate and the top plate before the covering layer according to the present invention, which corresponds to the view after step  12  of  FIG. 1 . As shown in  FIGS. 3A and 3B , circuit board  4  has only the electrical connection parts exposed, and top plate  3  covers both circuit board  4  and bottom plate  2 . The purpose of top plate  3  is to shoulder the pressure on circuit board  4  during the insert molding process to prevent the damage to circuit board  4 .  
         [0023]      FIGS. 4A and 4B  show a schematic view of the circuit board being sandwiched by the bottom plate and the top plate after the covering layer according to the present invention, which correspond to the view after step  13  of  FIG. 1 . As shown in  FIGS. 4A and 4B , a covering layer A is made of the same material used for bottom plate  2  and top plate  3 . Therefore, after covering layer A is hardened, covering layer A will form a tight seal with bottom plate  2  and top plate  3 . In addition, slanted slopes  22  on bottom plate  2  and slanted slopes  31  on top plate  3  also increase the strength of the bonding. As shown, covering layer A covers the circumferences of bottom plate  2  and top plate  3 , and the surrounding of exposed electrical connection parts  45  of circuit board  4 . The final appearance after forming covering layer A (step  13  of  FIG. 1 ) is a complete seal memory card with electrical connection parts exposed. Because an insert molding process is used to form covering layer A, the seal at the seam of bottom plate  2  and top plate  3  is water-proof.  
         [0024]     In summary of the aforementioned embodiment, the structure of the present invention includes a bottom plate, a circuit board, a top plate and a covering layer. The bottom plate includes a concave for housing the circuit board, and the top plate covers the bottom plate and the most of the circuit board so that only the electrical connection part of the circuit board is exposed. Both the bottom plate and the top plate have a slanted slope on at least two sides of their circumference. The covering layer is made of the material used in the insert molding process to form a thin layer to cover both the bottom plate and the top plate and the seam between the two plates. The covering layer covers the slanted slopes of both plates to enhance the water-proof seal. The covering layer gives the final structure a monolithic appearance so that the sealing is water-proof.  
         [0025]      FIG. 5  shows a schematic view of another embodiment of the present invention. In this embodiment, the shape of top plate  3  includes a protruding block  32 . The shape of protruding block  32  corresponds to the shape of concave  21  of bottom plate. As shown in  FIG. 6A , protruding block  32  of top plate  3  is inside concave  21  of bottom plate  2  when top plate  3  is placed into bottom plate  2 . The purpose of having protruding block  3  fitting inside concave  21  is to ensure that top plate will not shift due to the impact of material during the insert molding process. In addition, protruding block can also prevent the leakage of the molding material into the seam of bottom plate  2  and top plate  3 . This will improve the yield rate.  FIG. 6B  shows a cross-sectional view of the final structure.  
         [0026]      FIG. 7  shows a schematic view of yet another embodiment of the present invention. In this embodiment, one side of bottom plate  2  is attached to one side of top plate  3 . The thickness of this attachment is very thin so that when top plate  3  covers bottom plate  2 , an insert molding process can still be applied to form a covering layer on the attachment to form a memory card. The advantage of this embodiment is that bottom plate  2  and top plate  3  are monolithic and the subsequent packaging process is easier and less expensive.  
         [0027]     Although the present invention has been described with reference to the preferred embodiments, it will be understood that the invention is not limited to the details described thereof. Various substitutions and modifications have been suggested in the foregoing description, and others will occur to those of ordinary skill in the art. Therefore, all such substitutions and modifications are intended to be embraced within the scope of the invention as defined in the appended claims.