Abstract:
A card-type electronic apparatus such as an SD card, a CF card, a Memory Stick card, or a USB flash drive is formed from an upper and lower cover that are bonded together at an interior seam formed using ultrasonic joining. Lower sidewalls on the lower cover create an installation pocket for the upper cover. The installation pocket not only simplifies alignment between the upper and lower covers, but also contains any bonder material overflow that might otherwise affect the external dimensions of the apparatus housing. The lower sidewalls can completely surround the upper cover, for drop in installation. Alternatively, the lower sidewalls can partially surround the upper cover, so that the upper cover can be slid into place during assembly.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The invention relates to the field of electronic devices, and in particular, to a method and structure for accurately and neatly assembling a card-type electronic apparatus. 
   2. Related Art 
   A card-type electronic apparatus (such as a flash memory card or a PCMCIA card) is a computer component that can be used, for example, as a storage element, a communications interface, or an authentication device. A card-type electronic apparatus typically includes a small printed circuit board assembly (PCBA) encased in a durable housing. The PCBA can include various types of integrated circuits (ICs), such as flash memory or communications controllers. 
   The form factors of the different card-type electronic apparatus housings are typically defined by a formal specification that provides detailed size, shape, and connectivity requirements. Card-type electronic apparatus housings must therefore be carefully controlled to ensure compatibility with related products. 
   A card-type electronic apparatus is typically formed in a sandwich fashion, with two rigid plastic device covers enclosing the PCBA. Typically, those plastic covers are ultrasonically welded together, thereby ensuring a permanent encapsulation of the PCBA. 
     FIGS. 1A and 1B  depict a conventional assembly process for a standard Secure Digital (SD) card  100 . This process is similar to that described in U.S. Pat. No. 6,381,143, issued to Nakamura on Apr. 30, 2002. In  FIG. 1A , an upper cover  110  is positioned above a lower cover  120 . A PCBA  130  (that includes an IC  131  mounted on a PCB  132 ) is affixed to upper cover  110 . PCBA  130  includes an IC  131  mounted on a printed circuit board (PCB)  132 . 
   Upper cover  110  includes upper sidewalls  111  that run along the perimeter of upper cover  110 . Multiple ultrasonic bonders  141  are mounted on mating surfaces  119  of upper sidewalls  111 . Upper sidewalls  111  are sized and positioned such that mating surfaces  119  match up with corresponding mating surfaces  129  on lower sidewalls  121  that run along the perimeter of lower cover  120 . Ideally, when upper sidewalls  111  and lower sidewalls  121  are clamped together and ultrasonic vibrations are applied to bonders  141 , upper cover  110  and lower cover  120  are permanently joined to form a rigid enclosure for PCBA  130 , as shown in  FIG. 1B . 
   Unfortunately, the SD card  100  formed using conventional upper cover  110  and lower cover  120  can exhibit problematic deviations from the optimal SD card form factor. For example, because upper sidewalls  111  and lower sidewalls  121  must be aligned using a die (jig) or some other external alignment mechanism, misalignment can occur between upper cover  110  and lower cover  120 . This misalignment can increase the overall width W 1  of SD card  100  and cause SD card  100  to not fit properly into all SD card sockets. 
   Furthermore, because the height Hi of SD card  100  is determined by the combined heights of upper sidewalls  111  and lower sidewalls  121  (and any residual bonding material between the two), accurately achieving a specific value for height Hi can be difficult. In addition, the flow of bonders  141  as they melt during the ultrasonic joining process can cause form factor problems. Because joining occurs at an external seam of SD card  100  (i.e., mating surfaces  119  and  129  form a joint on the exterior of SD card  100 ), bonder overflow  142  can reach the exterior of SD card  100 . This bonder overflow  142  can then harden, and like misalignment between upper cover  110  and lower cover  120 , can cause fit problems for SD card  100 . 
   What is needed is a card-type electronic apparatus housing that ensures good form factor integrity. 
   SUMMARY OF THE INVENTION 
   The present invention is directed to a card-type electronic apparatus that is formed from upper and lower covers that are joined at a seam that is internal to the apparatus housing. This internal joining beneficially prevents bonding material from overflowing to the exterior of the apparatus, and also minimizes the chances of misalignment between the upper and lower covers (and at the same time eliminating the need for high-precision alignment tooling for assembly). The invention can be applied to any card-type electronic apparatus, including Secure Digital (SD) cards, CompactFlash (CF) cards, Memory Stick cards, and USB flash drives, among others. 
   According to an embodiment of the invention, a card-type electronic apparatus includes an upper cover and a lower cover that enclose a PCBA. The lower cover includes two or more sidewalls that define an internal region (“pocket”) within the lower cover that is sized to accept corresponding portions of the upper cover. The upper cover is placed into this pocket region, where it is bonded to the lower cover. 
   Bonding between the upper cover and lower cover takes place within this pocket region, so that the sidewalls of the lower cover beneficially prevent melted bonding material from flowing to the exterior of the apparatus. In addition, since the sides of the card-type electronic apparatus can be formed from just the sidewalls of the lower cover (rather than from a combination of sidewalls from both the upper and lower covers), control over the dimensional integrity of the apparatus can be more easily maintained. 
   According to an embodiment of the invention, the sidewalls of the lower cover can be a slip fit with the upper cover, thereby simple assembly and re-assembly prior to ultrasonic bonding. According to another embodiment of the invention, the sidewalls of the lower cover can be an interference fit with the upper cover, thereby providing improved bonding between the upper and lower covers for enhanced durability. 
   According to an embodiment of the invention, the sidewalls of the lower cover completely surround the upper cover, thereby providing total positioning and alignment of the upper cover relative to the lower cover. According to another embodiment of the invention, the sidewalls of the lower cover only partially surround the upper cover, thereby enabling greater assembly flexibility. 
   The invention will be more fully understood in view of the following description of the exemplary embodiments and the drawings thereof. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIGS. 1A and 1B  are a cross-sectional view of conventional SD card components being assembled into an SD card. 
       FIGS. 2A ,  2 B, and  2 C are cross-sectional views of card-type electronic apparatus components according to an embodiment of the invention being assembled. 
       FIG. 2D  is a cross-sectional view of a card-type electronic apparatus according to another embodiment of the invention. 
       FIGS. 3A ,  3 B, and  3 C are cross sectional views of card-type electronic apparatus having various sidewall configurations, in accordance with various embodiments of the invention. 
       FIG. 4  is a flow diagram of a card-type electronic apparatus assembly procedure in accordance with an embodiment of the invention. 
       FIG. 5A  is a partial exploded isometric view of a card-type electronic apparatus in accordance with an embodiment of the invention. 
       FIG. 5B  is an isometric assembled view of the card-type electronic apparatus shown in  FIG. 5A . 
       FIG. 6  is a top plan view of the assembled card-type electronic apparatus shown in  FIG. 2C . 
       FIGS. 7A ,  7 B, and  7 C are cross-sectional views of the card-type electronic apparatus of  FIG. 6 , showing an assembly procedure according to another embodiment of the invention being assembled. 
       FIGS. 8A and 8B  are top plan views of card-type electronic apparatus according to various other embodiments of the invention. 
   

   DETAILED DESCRIPTION 
     FIGS. 2A ,  2 B, and  2 C show an assembly process for a card-type electronic apparatus, according to an embodiment of the invention. As depicted in  FIG. 2A , the card-type electronic apparatus includes an upper cover  210 , a lower cover  220 , and a PCBA  230 . PCBA  230  includes one or more ICs  231  and/or other electronic components mounted on a PCB  232 . Upper cover  210  includes upper sidewalls  211  that extend substantially perpendicularly away from a substantially planar upper (external) surface  210 -S of upper surface  210 . Sidewalls  211  run along at least two edges of upper cover  210 , and multiple ultrasonic bonders  241  are attached to various locations on mating surfaces  219  of sidewalls  211 . Meanwhile, lower cover  220  includes lower sidewalls  221  that extend substantially perpendicularly from a substantially planar lower (external) surface  220 -S of lower cover  220 . Sidewalls  221  run along at least two edges of lower cover  220 . 
   Unlike in conventional card-type device housings (such as depicted in  FIGS. 1A-1B ), lower sidewalls  221  are not designed to be directly attached to upper sidewalls  211 . Instead, lower sidewalls  221  are sized and positioned to define a pocket  229  that is larger than the outer dimension of upper sidewalls  211  (i.e., the external surface-to-external surface distance WU 2  between sidewalls  211 ). Meanwhile, lower cover  220  also includes mating features  223  that are inboard of sidewalls  221  (i.e., are within pocket  229 ). 
   According to an embodiment of the invention, the bottom of pocket  229  can include various interior support structures  222 . As is described in greater detail below, interior support structures  222  can improve the structural rigidity and durability of the final assembled device. 
   In  FIG. 2B , PCBA  230  is mounted on upper cover  210 , between sidewalls  211 . However, note that according to various other embodiments of the invention, PCBA  230  could be attached to lower cover  220 . According to various other embodiments of the invention, PCBA  230  separate from both upper cover  210  and lower cover  220 , in which case PCBA  230  would be held in place by the assembly of covers  210  and  220 . 
   To complete the assembly process, upper cover  210  is inserted into pocket  229  (with bonders  241  being pressed into receiving features  223 ), and a compressive (clamping) load is applied to force upper cover  210  towards lower cover  220  while ultrasonic vibrations are applied to bonders  241 . The ultrasonic vibrations cause bonders  241  to melt, thereby joining upper cover  210  with lower cover  220  to form the final card-type electronic apparatus  200 , as shown in  FIG. 2C . Card-type electronic apparatus  200  can be any type of card-type electronic apparatus, including an SD card, a CF card, a Memory Stick card, a USB flash drive, or a flash memory hard drive, among others. 
   Because upper cover  210  “fits into” lower cover  220 , the external form factor of apparatus  200  can be controlled to a large degree by lower sidewalls  221 . As shown in  FIG. 2C , the width WL 2  of card-type electronic apparatus  200  is defined by the external surfaces of sidewalls  221  of lower cover  220 . Lower cover  220  can similarly define the length of card-type electronic apparatus  200 . Note also that while the top surface  210 -S of upper cover  210  is positioned above the plane P 2  (shown in  FIG. 2B ) defined by the top surfaces  221 -T of lower sidewalls  221  for exemplary purposes, according to another embodiment of the invention, top surface  210 -S could be positioned at or below plane P 2 . 
   For example,  FIG. 2D  shows a card-type electronic apparatus  200 - 1  that is substantially similar to card-type electronic apparatus  200  of  FIG. 2C , except that the top surface  210 -S 1  of upper cover  210 - 1  is at the same level as (i.e., coplanar with) the top surfaces  221 -T 1  of lower sidewalls  221 - 1  of lower cover  220 - 1 . Therefore, the height of card-type electronic apparatus  200 - 1  is determined by the height HL 2  of lower sidewalls  221 - 1 . 
   Another benefit provided by the mating features  223  of lower cover  220  being inboard of sidewalls  221  is that sidewalls  221  can provide alignment of upper cover  210  as it is being inserted into pocket  229 . Consequently, the assembly of card-type electronic apparatus  200  is greatly simplified over the assembly of conventional card-type electronic apparatus  100  shown in  FIGS. 1A-1B . 
   According to an embodiment of the invention, pocket  229  can have a slip fit interface with upper sidewalls  211 , so that upper cover  210  can be easily placed into lower cover  220  prior to the ultrasonic joining operation. According to another embodiment of the invention, pocket  229  can provide an interference fit with sidewalls  211 , thereby providing additional joint strength when apparatus  200  is fully assembled. 
   Note that because the actual bonding between upper cover  210  and lower cover  220  is performed at an interior seam  245  (i.e., a joint inboard of sidewalls  221 ), any bonder overflow  242  is contained within apparatus  200 , thereby preventing the overflow material from causing (external) dimensional problems. Optional receiving features  223  can further minimize the possibility of external bonding material overflow by providing specific regions into which bonder overflow  242  can flow. 
   Note further that, as indicated in  FIG. 2C , optional support structure  222  can improve the strength and durability of apparatus  200  by providing an interface contour that is similar to that of PCBA  230 . In particular, the raised support structures  222  meet the unpopulated regions of PCBA  230  (i.e., the portions of PCBA  230  that do not include components such as IC  231 , such as regions  232 -U indicated in  FIG. 2A ), thereby minimizing the possibility of crush-type damage to IC  231 . 
   Note also that while the sidewalls  211  and  221  are depicted as having simple rectangular cross sections for exemplary purposes, any sidewall (and mating surface/feature) profile can be used that allows an internal seam to be formed. For example,  FIG. 3A  shows a card-type electronic apparatus  200 ( 1 ) that is substantially similar to electronic apparatus  200  shown in  FIG. 2C , except that the mating surfaces of the upper sidewalls of upper cover  210  include a “tongue” feature  216  that mates with a “groove” feature  226  in lower cover  220  to form an interior seam  245 ( 1 ). This tongue and groove interface can improve the strength of the bond between upper cover  210  and lower cover  220 . 
     FIG. 3B  shows a card-type electronic apparatus  200 ( 2 ) that is substantially similar to card-type electronic apparatus  200  shown in  FIG. 2C , except that upper sidewalls  211 ( 2 ) include “step” features that mate with lower sidewalls  221 ( 2 ). Note, however, that an interior seam  245 ( 2 ) can still be formed, since the top “steps” of upper sidewalls  211 ( 2 ) extend into the pocket defined by lower sidewalls  221 ( 2 ). 
     FIG. 3C  shows a card-type electronic apparatus  200 ( 3 ) that is substantially similar to card-type electronic apparatus  200  shown in  FIG. 2C , except that upper sidewalls  211 ( 3 ) and lower sidewalls  221 ( 3 ) include inclined mating surfaces  211 -S and  221 -S, respectively. Inclined mating surface  211 -S slopes away from upper cover  210  (i.e., the slope of surface  211 -S diverges from upper cover  210 ), while inclined mating surface  221 -S slopes towards lower cover  220  (i.e., the slope of surface  221 -S intersects lower cover  220 ). Therefore, inclined mating surfaces  211 -S and  221 -S provide self-alignment capability between upper cover  210  and lower cover  220 , while still allowing an interior seam  245 ( 3 ) to be formed (inboard of lower sidewalls  221 ( 3 )). Note that the sidewall configurations shown in  FIGS. 3A and 3B  can also provide self-alignment capabilities, but to a lesser degree than the inclined mating surfaces  211 -S and  221 -S in  FIG. 3C . 
     FIG. 4  shows a flow diagram for a card-type electronic apparatus that is substantially similar to the assembly procedure shown in  FIGS. 2A-2C , according to an embodiment of the invention. In a “LOWER COVER IN DIE” step  410 , the lower cover ( 220 ) is placed in an assembly die or jig. Then, in a “MOUNT PCBA” step  420 , the PCBA ( 240 ) is attached to the upper cover ( 210 ). Once the PCBA has been mounted, accessories such as switches or LED indicators can be installed in an optional “INSTALL ACCESSORIES” step  425 . 
   Next, in an “ALIGN UPPER AND LOWER COVERS” step  430 , the upper and lower covers are placed in a position relative to one another that is appropriate for the assembly procedure being used. For example, if the sidewalls ( 221 ) of the lower cover form a pocket ( 229 ) that completely surrounds the mating features ( 223 ) in the lower cover, then the upper cover would be positioned directly above (i.e., facing) the lower cover. However, if the sidewalls of the lower cover form a pocket that only partially surrounds the mating features, the upper cover could be positioned beside the lower cover to allow the upper cover to be “slid” in to the pocket (as described in greater detail below with respect to FIGS.  6  and  7 A- 7 C). 
   After step  430 , the upper cover is placed into the pocket formed by the sidewalls of the lower cover in a “PLACE UPPER COVER INTO LOWER COVER” step  440 . Finally, a clamping load and ultrasonic vibrations are applied to join the upper and lower covers in a “BOND UPPER AND LOWER COVERS” step  450 . If necessary, accessories such as switches can be installed in an optional “INSTALL ACCESSORIES” step  455  to complete the assembly of the card-type electronic apparatus ( 200 ). 
     FIG. 5A  shows a partially exploded isometric view of the card-type electronic apparatus  200  shown in  FIG. 2C , in accordance with an embodiment of the invention. An upper cover  210  includes upper sidewalls  211 (A),  211 (B), and  211 (C), which run along three edges of upper cover  210 , and a plurality of contact slots  215 . Multiple ultrasonic bonders  241  are attached to the mating surfaces of upper sidewalls  211 (A)- 211 (C). 
   A PCBA  230  is sized to fit into the region of upper cover  210  defined by upper sidewalls  211 (A)- 211 (C). PCBA  230  includes ICs  231 (A) and  231 (B) and contacts  233 , which are all mounted on (the reverse side of) a PCB  232 . When PCBA  230  is mounted in upper cover  210 , access to contacts  233  is provided via contact slots  215 . 
   Finally, a lower cover  220  includes lower sidewalls  221 (A),  221 (B), and  221 (C), which run along three edges of lower cover  220 , and multiple internal support structures  222  in the region of lower cover  220  defined by sidewalls  221 (A)- 221 (C). Lower sidewalls  221 (A)- 221 (C) are sized and positioned such that upper sidewalls  211 (A)- 211 (C) fit within the region defined by lower sidewalls  221 (A)- 221 (C). 
   Note that according to various embodiments of the invention, sidewalls need not be continuous structures. For example, lower sidewalls  221 (A) and  221 (C) can include optional gaps  224  and  225  that could be used as an interface feature and a switch opening, respectively. 
     FIG. 5B  shows an assembled isometric view of card-type electronic apparatus  200 , which shows upper cover  210  within the region defined by lower sidewalls  221 (A)- 221 (C). Note that while three lower sidewalls on three edges of lower cover  220  are depicted for exemplary purposes, according to various other embodiments of the invention, lower cover  220  could include more or fewer sidewalls  221 . 
     FIG. 6  shows a top view of a card-type electronic apparatus  600  according to an embodiment of the invention. Apparatus  600  includes an upper cover  610  that is bonded to a lower cover  620  (the location of enclosed PCBA  630  and possible locations for bonders  641  are depicted for exemplary purposes). Like lower cover  520  shown in  FIGS. 5A and 5B , lower cover  620  includes three lower sidewalls  621 (A),  621 (B), and  621 (C), which bound upper cover  610  on three sides. Optional interface feature  624  and switch opening  625  are shown in lower sidewalls  621 (A) and  621 (C), respectively, for reference purposes. 
   Because upper cover  610  is only partially surrounded by lower sidewalls  621 (A)- 621 (C), upper cover  610  need not be inserted into lower cover  620  in the vertical direction (i.e., the direction substantially perpendicular to the plane of covers  610  and  620 ). Instead, upper cover  610  can be slid into place in the horizontal direction (i.e., parallel to the plane of covers  610  and  620 ). 
   For example,  FIGS. 7A-7C  show an assembly procedure for card-type electronic apparatus  600  (taken through cross-section AA in  FIG. 6 ), according to an embodiment of the invention. Though not part of cross-section AA, ultrasonic bonders  641  and lower sidewall  621 (A) are shown for reference.  FIG. 7A  depicts upper cover  610  (with PCBA  630  installed) separated from lower cover  620 . As indicated by the dashed arrow, upper cover  610  is placed next to the unwalled edge of lower cover  620 . Upper cover  610  can then be slid into place over lower cover  620 , with lower sidewalls  621 (A) and  621 (C) (not shown) acting as guides. Lower sidewall  621 (B) sets the end of travel for the slide operation. 
   Once upper cover  610  is properly positioned over lower cover  620 , as shown in  FIG. 7B , a clamping force is applied to covers  610  and  620 , and ultrasonic energy is applied to bonders  641 , as indicated by the large arrows. Bonders  641  melt under those bonding conditions, thereby joining upper cover  610  and lower cover  620  to form card-type electronic apparatus  600 . 
   Note that according to another embodiment of the invention, lower sidewall  621 (B) (in  FIGS. 6 and 7C ) can be removed, and some other means (e.g., external tooling, manual inspection) can be used to set the end position of upper cover  610  relative to lower cover  620 .  FIG. 8A  shows a top view of a card-type electronic apparatus  800 - 1  that is substantially similar to card-type electronic apparatus  600  shown in  FIGS. 6 and 7C , except that lower cover  620 - 1  includes only two sidewalls  621 (A) and  621 (C), and upper cover  610 - 1  extends all the way to the front and rear edges S- 627  of lower cover  620 - 1 . 
     FIG. 8B  shows a top view of a card-type electronic apparatus  800 - 2  according to another embodiment of the invention. Card-type electronic apparatus  800 - 2  is substantially similar to the card-type electronic apparatus  600  shown in  FIGS. 6 and 7C , except that lower cover  620 - 2  of apparatus  800 - 2  includes sidewalls  621 (A),  621 (B),  621 (C), and  621 (D) that run along the entire perimeter of lower cover  620 - 2 . Sidewalls  621 (A)- 621 (D) completely surround upper cover  610 - 2 , thereby providing total alignment between upper cover  610 - 2  and lower cover  620 - 2 . Note that a vertical assembly process would be required for card-type electronic apparatus  800 - 2  (i.e., upper cover  610 - 2  would be positioned above lower cover  620 - 2  and then lowered into the pocket formed by lower sidewalls  621 (A)- 621 (D). 
   The various embodiments of the structures and methods of this invention that are described above are illustrative only of the principles of this invention and are not intended to limit the scope of the invention to the particular embodiments described. Thus, the invention is limited only by the following claims and their equivalents.