Manufacturing Method For Micro-SD Flash Memory Card

Abstract

A method for fabricating MicroSD devices includes forming a PCB panel having multiple PCB regions arranged in parallel rows. Passive components are attached by conventional surface mount technology (SMT) techniques. IC chips, including a MicroSD controller chip and a flash memory chip, are attached to the PCB by wire bonding or other chip-on-board (COB) technique. A molded layer is then formed over the IC chips and passive components using a mold that prevents formation of plastic on the upper surface of each PCB. The panel is then singulated using one of a laser cutting method, an abrasive water jet cutting method, and a mechanical grinding method such that the resulting PCB substrate and plastic housing have the width, height and length specified by MicroSD specifications. A front edge chamfer process is then performed.

1 . A method for producing a plurality of memory card devices, having predefined width and height specifications, the method comprising:
 producing a printed circuit board (PCB) panel including a plurality of PCB regions;   attaching at least one passive component and at least one integrated circuit to each said PCB region;   forming a single-piece molded layer on the second surface of the PCB panel such that said at least one passive component and said at least one IC die of each PCB region are covered by thermal set plastic, wherein a combined thickness of said PCB panel and said single-piece molded layer is equal to said height specification; and   singulating said PCB panel and molded layer by cutting said PCB panel and said molded layer such that the PCB panel is separated into said plurality of memory card devices, wherein each memory card device includes a printed circuit board having a width that is equal to said predefined width specification.   
   
   
       2 . The method according to  claim 1 ,
 wherein producing said PCB panel comprises forming each said PCB region to include opposing first and second surfaces, a plurality of metal contacts disposed on the first surface, a plurality of first contact pads disposed on the second surface, a plurality of second contact pads disposed on the second surface, and a plurality of conductive traces formed on the PCB region such that each conductive trace is electrically connected to at least one of an associated metal contact, a first contact pad and a second contact pad; and   wherein attaching said at least one passive component and said at least one integrated circuit to each said PCB comprises:
 attaching said at least one passive component to the first contact pads using a surface mount technique, and 
 attaching said at least one unpackaged integrated circuit (IC) die to the second contact pads using a chip-on-board technique. 
   
   
   
       3 . The method of  claim 2 , wherein attaching said at least one passive component comprises:
 printing a solder paste on said first contact pads;   mounting said at least one component on said first contact pads; and   reflowing the solder paste such that said at least one component is fixedly soldered to said first contact pads.   
   
   
       4 . The method of  claim 2 , further comprising grinding a wafer including said at least one IC die such that a thickness of said wafer is reduced during said grinding, and then dicing said wafer to provide said at least one IC die. 
   
   
       5 . The method of  claim 4 , wherein attaching at least one IC die comprises bonding a first IC die to the second surface of the PCB and wire bonding the first IC die to said second contact pad. 
   
   
       6 . The method of  claim 5 , wherein attaching at least one IC die further comprises bonding a second IC die to the first IC die, and wire bonding wire bonding the second IC die to a third contact pad. 
   
   
       7 . The method according to  claim 1 , wherein forming said single-piece molded layer comprises disposing said PCB panel into a first molding die, said first molding die comprises a plurality of alignment poles, and wherein disposing said PCB panel comprises operably engaging said alignment poles into corresponding alignment holes defined in said PCB panel. 
   
   
       8 . The method according to  claim 1 , wherein singulating said PCB panel after forming said single-piece molded layer comprises cutting said PCB panel and said molded layer using one of a laser cutter, a water jet cutter, and a saw, whereby a PCB substrate is separated from said PCB panel, and a molded is separated from said molded layer. 
   
   
       9 . The method according to  claim 7 , further comprising mechanically grinding a peripheral edge of each of said plurality of memory card devices. 
   
   
       10 . The method according to  claim 1 , wherein said memory card devices comprise MicroSD devices, and wherein singulating comprising forming a peripheral edge of said PC substrate and peripheral walls of said molded housing such that both said peripheral edge and said peripheral walls define a width of 11 mm, and a combined thickness of said substrate and said molded housing is in the range of 0.7 mm to 1.0 mm. 
   
   
       11 . A MicroSD device comprising:
 a printed circuit board assembly (PCBA) including:
 a printed circuit board (PCB) having opposing first and second surfaces, and a peripheral edge extending between the first and second surfaces, 
 a plurality of metal contacts disposed on the first surface of the PCB, 
 at least one passive component mounted on the second surface of the PCB, 
 at least one unpackaged integrated circuit (IC) die mounted on the second surface of the PCB, and a plurality of conductive traces formed on the PCB such that each conductive trace is electrically connected to at least one of an associated metal contact, said at least one IC die and said at least one passive component; and 
   a single-piece molded housing formed on the second surface of the PCBA such that said at least one passive component and said at least one IC die are covered by said molded housing, and such that substantially all of the peripheral edge of the PCB is exposed,   wherein said peripheral edge of said PCB and peripheral walls of said molded housing are formed such that both said peripheral edge and said peripheral walls define a nominal width of approximately 11 mm, and a combined thickness of said PCB and said molded housing is in the range of 0.7 to 1.0 mm.