Abstract:
A carrier including a bottom plate, an intermediate cover, and a top cover for manufacturing a memory device is introduced herein. A printed circuit board is disposed on the bottom plate, and memory elements are arranged and disposed on the PCB. The intermediate cover is used to press peripheral regions of the printed circuit board, and to expose the regions where the memory elements are formed on the printed circuit board. The printed circuit board is closely attached to a surface of the bottom plate by fixing the intermediate cover. The top cover is used to cover the memory elements formed on the printed circuit board after some manufacturing processes, and by exerting an external force, the formed memory elements are clamped down, so as to protect the memory elements from being affected by the printed circuit board in the following thermal process due to the thermal stress deformation.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims the priority benefit of Taiwan application serial no. 96113187, filed on Apr. 14, 2007. All disclosure of the Taiwan application is incorporated herein by reference. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to a carrier for manufacturing a memory device, a method using the same, and a portable memory device using the manufacturing method. 
         [0004]    2. Description of Related Art 
         [0005]    In recent years, the technology and material of an electronic integrated circuit have been developed rapidly, and the volume of a chip is increasingly reduced, but the function becomes increasingly powerful and the applications thereof have been gradually reached anywhere. Therefore, the products manufactured by using the electronic integrated circuit gradually becomes light, thin, short, and small, such as electronic dictionaries, digital cameras, and various other digital products. Furthermore, because of the gradually mature chip packaging technology, in the current market, a single chip or multiple chips are packaged into a quite slim card, to form a removable memory with a volume smaller than that of an existed magnetic recording medium by utilizing the characteristic that the chip may store a large amount of data. Such electronic media are all called memory card. 
         [0006]    Currently, SD (secure digital) memory card is one of the most commonly used memory cards. The SD memory card uses a standard of a flash memory, for example, and is applied in portable devices, such as digital cameras, personal digital assistants (PDA), and multi-media players. The technology of the SD memory card is formed based on a format of a multi-media card (i.e., so-called MMC), but the SD memory card is slightly thicker than the MMC. The SD memory card has a high data transmission rate and the standard with which the SD memory card uses is updated continually. The profile of the common SD memory card is about 32 mm×24 mm×2.1 mm. 
         [0007]    In recent years, as the demand for data storage capacity is increased, and the development trends of electronic devices towards light weight, thinness, shortness, and smallness, the substrate area of the memory card is gradually reduced. A miniSD specification was also introduced for the SD cards in the year of 2003, so as to reduce the size of the memory card, for example, the size is about 20 mm×21.5 mm×1.4 mm. 
         [0008]    However, as the size of the memory card is increasingly reduced, the size of the memory dies in the memory card is also reduced accordingly, and the used printed circuit board also becomes much thinner and smaller. Under this circumstance, a carrier used in the manufacturing process plays a crucial role. How to ensure the efficiency of the memory card and to protect the components in the memory card from being damaged becomes a topic deserving further consideration. 
         [0009]    For example, the memory card meeting the miniSD specification requirement is only 1.4 mm in thick, so the thickness of the employed printed circuit board (PCB) must be lower than 0.16 mm. If such a specification is adopted, during the process of manufacturing the memory cards, PCB manufacturers cannot overcome the problem of the bending of the PCB, i.e., the bowing problem in the field, which also causes the problem that the components cannot be installed successfully by using the Surface Mounted Technology (SMT), or deformation occurs during the reflow process. Accordingly, the problem of empty soldering occurs during a soldering process, and as a result, the flash memory may suffer a short circuit problem. This is also one of the reasons why the yield rate of the manufacturers of the miniSD memory card cannot break through 60%. 
         [0010]    Some PCB manufacturers have suggested amending the layout of the PCB to connect the plate edges, i.e., through the manner of the edge connector of gold fingers, which however cannot overcome the aforementioned problems, so the yield rate cannot be enhanced efficiently. 
         [0011]    In addition, some SMT manufacturers also employ a two-piece manufacturing carrier, including a bottom plate and a top cover, in which the top cover is used to press each flash memory, so as to overcome the bowing problem of the PCB. However, the conventional method is merely to add the top cover in the reflow process, which can only avoid thermal deformation occurring in the reflow process, but cannot overcome the bowing problem that has already occurred before the material of the PCB is purchased. Therefore, the two-piece manufacturing carrier only may enhance the yield rate by 10%-15%, but the additional operation steps wastes some extra working hours. 
       SUMMARY OF THE INVENTION 
       [0012]    The present invention is directed to a carrier for manufacturing a memory device, a method using the same, and a portable memory device using the manufacturing method, capable of efficiently overcoming the bowing problem of the PCB and significantly enhancing the yield rate. 
         [0013]    The present invention is directed to a carrier for manufacturing a memory device, a method using the same, and a portable memory device using the manufacturing method, capable of efficiently solving the problems that, during an SMT process, the pieces cannot be assembled successfully, an integrated circuit (IC) to be adhered is offset, or empty soldering or a short circuit occurs, so as to greatly enhance the yield rate. 
         [0014]    The present invention provides a carrier for manufacturing a memory device, which includes a bottom plate, an intermediate cover, and a top cover. A PCB is placed and fixed on the bottom plate, which is used for forming a plurality of memory elements. The intermediate cover is used to press peripheral regions of the PCB and to expose regions where the memory elements are formed on the PCB, such that the PCB may be closely attached to the surface of the bottom plate by fixing the intermediate cover. The top cover is used to cover the memory elements formed on the PCB, and the memory elements are clamped by an external force, so as to protect the memory elements from being affected by the PCB due to thermal stress deformation. 
         [0015]    The present invention provides a manufacturing method using a carrier for manufacturing a memory device, in which the carrier for manufacturing a memory device includes a bottom plate, an intermediate cover, and a top cover. The manufacturing method includes the steps as follows. Firstly, the PCB is fixed on the bottom plate, which is used for forming a plurality of memory elements. Next, a solder paste printing process is performed. After that, the intermediate cover is placed on the bottom plate and the PCB, which presses peripheral regions of the PCB and exposes regions where the memory elements are formed on the PCB; and the printed circuit board is closely attached onto the surface of the bottom plate by fixing the intermediate cover. Thereafter, the assembling process of the SMT is performed. Then, the top cover is placed on the intermediate cover to press the memory elements and clamp the memory elements by an external force, so as to protect the memory elements from being affected by the PCB due to thermal stress deformation. 
         [0016]    The present invention provides a portable memory device using the above manufacturing method, which is an NAND flash memory device meeting the miniSD specification requirement, and the method of manufacturing the same includes the steps as follows. Firstly, a PCB with a thickness lower than 0.2 mm is fixed on the bottom plate, which is used for forming a plurality of memory elements meeting the miniSD specification. Then, a solder paste printing process is performed. After that, the intermediate cover is placed on the bottom plate and the PCB to press peripheral regions of the PCB and expose regions where the memory elements are formed on the PCB; and the PCB is closely attached onto the surface of the bottom plate by fixing the intermediate cover. Thereafter, the assembling process of the SMT is performed. Then, the top cover is placed to press each memory element, and the memory elements are clamped by an external force, so as to protect the memory elements from being affected by the PCB due to thermal stress deformation. 
         [0017]    In order to make the aforementioned and other objects, features and advantages of the present invention comprehensible, preferred embodiments accompanied with figures are described in detail below. 
         [0018]    It is to be understood that both the foregoing general description and the following detailed description are exemplary, and are intended to provide further explanation of the invention as claimed. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0019]    The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention. 
           [0020]      FIGS. 1A-1C  and  2 A- 2 C respectively show a carrier for manufacturing a memory device according to a preferred embodiment of the present invention, in which  FIGS. 1A ,  1 B, and  1 C are schematic top views of a bottom plate, an intermediate cover, and a top cover respectively, and  FIGS. 2A ,  2 B, and  2 C are side views of the bottom plate, the intermediate cover, and the top cover respectively. 
           [0021]      FIG. 3  is a detailed flow chart of a manufacturing method using the carrier for manufacturing a memory device according to the present invention. 
           [0022]      FIGS. 4A-4E  are detailed flow charts of a manufacturing method using the carrier for manufacturing a memory device according to the present invention. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0023]    The carrier for manufacturing a memory device, the method using the same, and the portable memory device using the manufacturing method provided by the present invention is capable of efficiently overcoming the bowing problem of the printed circuit board (PCB) and also efficiently solving the problems that, during a surface mounted technology (SMT) process, pieces cannot be assembled successfully, an integrated circuit (IC) to be adhered is offset, or the empty soldering or short circuit problem occurs, so as to greatly enhance the yield rate of the manufacturing process. 
         [0024]    The carrier for manufacturing a memory device provided by the present invention is a three-piece carrier, which includes a bottom plate, an intermediate cover, and a top cover.  FIGS. 1A ,  1 B, and  1 C are schematic top views of the bottom plate, the intermediate cover, and the top cover, and  FIGS. 2A ,  2 B, and  2 C are side views of the bottom plate, the intermediate cover, and the top cover. In order to illustrate clearly, the present invention will be described below with reference to  FIGS. 1A-1C  and  2 A- 2 C. 
         [0025]      FIGS. 1A and 2A  are respectively a schematic top view and a side view of a bottom plate  110  of the carrier for manufacturing a memory device according to an embodiment of the present invention. The bottom plate  110  has four pillars  112  respectively disposed at four corners where the printed circuit board (PCB) of a flash memory will be fixed, such that the locating holes of the PCB are engaged with the pillars  112 . The bottom plate  110  has a plurality of louvers  114  at four edges. In addition, the position  116 , where the PCB of the flash memory will be placed, also has a plurality of louvers for dissipating heats generated during the manufacturing process. Additionally, in order to make the direction of the carrier be consistent, each piece in the three-piece carrier provided by the present invention has a direction mark, such that the pieces will not be placed incorrectly during the manufacturing process, for example, the bottom plate  110  in  FIG. 1  has a direction mark  118  facing a predetermined direction  150 . 
         [0026]      FIGS. 1B and 2B  are respectively a schematic top view and a side view of an intermediate cover  120  of the carrier for manufacturing a memory device according to an embodiment of the present invention. The intermediate cover  120  has two holes  122  disposed in the upside and downside for exposing the flash memory of the PCB and a plurality of grooves  124  for carrying the top cover, and further has a direction mark  126  to prevent the intermediate cover  120  from being placed incorrectly during the manufacturing process. In addition, a plurality of protruding portions  128  is formed at positions of the holes  122  for exposing the flash memory, which is used to further fix the PCB. 
         [0027]      FIGS. 1C and 2C  are respectively a schematic top view and a side view of the top cover  130  of the carrier for manufacturing a memory device according to an embodiment of the present invention. The top cover  130  includes a plurality of holes  132  disposed in upside and downside for exposing the flash memory and a plurality of protruding portions  134  for being placed in the grooves of the intermediate cover, and further has a direction mark  136  to prevent the top cover  130  from being placed incorrectly during the manufacturing process. The holes  132  may serve as louvers for dissipating heats generated by the flash memory. 
         [0028]      FIG. 3  shows a detailed flow chart of the method using the carrier for manufacturing a memory device according to the present invention. Firstly, in Step  310 , the bottom plate is placed on a crosser or another insulating manufacturing base. Next, in Step  320 , the PCB is placed on the bottom plate, and the four locating holes of the PCB are engaged with the four pillars, so that the PCB is fixed thereon. Then, in Step  330 , a solder paste printing process is performed to form a solder paste between the elements that should be adhered during the SMT process and the PCB. Then, in Step  340 , the intermediate cover provided by the present invention is placed on the bottom plate and the PCB. Furthermore, it is confirmed whether the intermediate cover presses the PCB or not, and the PCB should be flattened. In an embodiment, for example, a strong magnet may be used on the intermediate cover, such that the intermediate cover may be combined with the bottom plate under a force, and the PCB may be flattened as expected. 
         [0029]    Next, in Step  350 , an SMT assembling process is performed to mount the necessary elements to be adhered. Then, in Step  360 , a top cover is placed to press each memory. Subsequently, in Step  370 , for example, the strong magnet is used to clamp the memories tightly. In this manner, the memories are protected from being offset or suffering from an empty soldering or a short circuit, when the thermal stress deformation occurs due to the reflow process of the PCB. 
         [0030]    The detailed manufacturing method using the carrier for manufacturing a memory device provided by the present invention is further described below. 
         [0031]      FIGS. 4A-4E  are detailed flow charts of the manufacturing method using the carrier for manufacturing a memory device according to the present invention. Firstly, as shown in  FIG. 4A , the bottom plate  420  is placed on the crosser  410 . Next, as shown in  FIG. 4B , the PCB  430  is placed on the bottom plate  420 , and the four locating holes of the PCB  430  are engaged with the four pillars  422 , so that the PCB is fixed thereon. Then, the solder paste printing process is performed to form the solder paste between the elements that should be adhered during the subsequent SMT process and the PCB. Then, as shown in  FIG. 4C , the intermediate cover  440  is placed on the bottom plate  420  and the PCB  430 , and the direction mark  442  of the intermediate cover  440  must be consistent with the direction mark  424  of the bottom plate  420 . 
         [0032]    Subsequently, as shown in  FIG. 4D , after the SMT assembling process, as shown in  FIG. 4E , the top cover  450  is pressed to press each memory, for example, a strong magnet is used to clamp the memories tightly. In this manner, the memories are protected from being offset or suffering from an empty soldering or a short circuit problem, when the thermal stress deformation of the PCB  430  occurs during the subsequent reflow process of the PCB  430 . 
         [0033]    The carrier for manufacturing a memory device and the manufacturing method provided by the present invention is capable of efficiently overcoming the bowing problem of the PCB and also efficiently solving the problems that, during the surface mounted technology (SMT) process, pieces cannot be assembled successfully, an integrated circuit (IC) to be adhered is offset, or the empty soldering or short circuit occurs, which thus greatly enhancing the yield rate. 
         [0034]    If the carrier for manufacturing a memory device and the manufacturing method are applied in manufacturing an NAND flash memory device meeting the miniSD specification (referred as miniSD memory card below), the NAND flash memories are arranged in a form of “pages”, and each page has a storage space of 256 or 512 bytes and an assistant storage capacity of 8-16 bytes. Recently, an NAND memory with each page having a main storage space of 2048 bytes and an assistant storage space of 64 bytes has been introduced. The assistant storage space is mainly used to store error correction codes (ECCs), damaged memory marks, and data about file systems. These pages constitute a block. The NAND flash memory is read and written “page” by “page”; and the data is deleted “block” by “block”. 
         [0035]    At this time, the size of the miniSD memory card is about 20 millimeter (mm)×21.5 mm×1.4 mm. Since the thickness of the miniSD memory card is merely 1.4 mm, the thickness of the employed PCB must be lower than 0.2 mm. However, such a thin PCB may suffer from serious problems in the conventional process, and the yield rate cannot be enhanced efficiently. However, through the carrier for manufacturing a memory device and the manufacturing method provided by the present invention, the yield rate may be increased to over 90-95%. 
         [0036]    In addition, it takes about 80 seconds to manufacture one panel of a flash memory, including the SMT assembling, visual inspection, changing the top cover, and clamping it out by using a clip and so on. However, if the carrier for manufacturing a memory device and the manufacturing method provided by the present invention are used, since the strong magnet is used for adsorption, for example, and the time in changing the top cover is saved, a visual inspector may have sufficient time to correct the offset of the SMT assembling process. Therefore, it only takes 45-55 seconds to manufacture one panel of the flash memory under the same quantity conditions, so as to enhance both the yield rate and the efficiency. 
         [0037]    The carrier for manufacturing a memory device and the manufacturing method provided by the present invention may also be applied in manufacturing a memory card requiring a quite thin PCB, for example, with a thickness of lower than 0.2 mm, such as, a compact flash (CF) memory card, a memory stick (MS) card, a memory stick duo (MS Duo), a multi media card (MMC), a reduced size multi media card (RS MMC), a secure digital (SD) card, a mini secure digital (Mini SD) card, a μ card, a reduced size μ (RS μ) card, and other small memory cards with similar functions. 
         [0038]    It will be apparent to those skilled in the art that various modifications and variations can be made to the structure of the present invention without departing from the scope or spirit of the invention. In view of the foregoing, it is intended that the present invention cover modifications and variations of this invention provided they fall within the scope of the following claims and their equivalents.