High throughput manufacturing method for micro flash memory cards
According to certain embodiments of the invention, a flash memory card is manufactured using COB processes on a PCB panel with multiple micro cards PCB substrates. These micro memory cards are laid out in an array of 3×5 matrixes of micro cards PCB substrates. A method of molding over a PCBA is utilized, contrary to a conventional method of having two or more pieces of package components to tape together. This results in a simpler structure without the notch which enables easier singulation process and the package is moisture resistance. The final product is a single piece versus two or three pieces glued up pieces and would not separate from pieces. The final product has high water and moisture resistance, low cost and fast manufacturing throughput, no seam and aesthetically more appeasing, can stack more layers of flash memory die, and be maximized XY spaces to accommodate larger size flash memory die.
1. A method of fabricating micro flash memory cards using a combination of both surface mount technology (SMT) process and chip-on-board (COB) process, the method comprising:
providing a PCB (printed circuit board) substrate;
mounting and wire bonding a plurality of electrical components of a plurality of micro flash memory cards to the PCB substrate to form a PCB panel having the plurality of micro flash memory cards thereon;
molding a card body over the PCB panel to encapsulate the plurality of electrical components of each micro flash memory card in a thermal set plastic compound, wherein the molded PCB panel are designed such that only horizontal cuts are required to separate each micro flash memory card from the PCB panel followed by marking and testing to obtain final products of the micro flash memory cards;
providing the PCB panel having a plurality of individual micro flash memory substrate boards;
punching out a plurality of slots on the PCB panel corresponding a plurality ribs of a bottom pierce of a molding block respective;
placing a plurality of metal contacts on a top surface of each individual micro flash memory substrate board for a purpose of carrying power supply source and data signals;
mounting a plurality of passive components including a resistor and a capacitor on a bottom surface of each individual micro flash memory substrate board using a STM process;
attaching a plurality of active components including a controller chip and a flash memory chip on a designated location on each individual micro flash memory substrate board;
performing a wire bonding process from die pads to PCB fingers to establish electrical connections from chip to chip and chip to passive components via traces on the bottom surface of each individual micro flash memory substrate, wherein all electronic components are attached on the bottom surface of each individual micro flash memory substrate;
performing a transfer and injection molding process for encapsulating the electronic components on the bottom surface of the individual micro flash memory substrates, exposing the top surface with the plurality of metal contacts to make physical contacts with metal pads on a female micro flash memory card socket when inserted;
performing an encapsulation and outline forming process using a molding technique; and
performing a singulation process using a disc cut to separate individual micro flash memory cards from the PCB panel.
2. The method of claim 1 , wherein the plurality of micro flash memory substrates on the PCB panel enables a high throughput in the SMT process and the COB process.
3. The method of claim 1 , wherein the bottom pierce of the molding block includes a flat cavity floor with poles at three of a four corners to allow three index and alignment holes to fit in and hold in a precise position.
4. The method of claim 3 , wherein bottom pierce of the molding block further includes a plurality of ribs to fit into the corresponding slots of the PCB panel.
5. The method of claim 3 , wherein a depth of the bottom piece of the molding block defines a thickness of micro flash memory cards generated from the individual micro flash memory substrate boards.
6. The method of claim 1 , wherein a top piece of the molding block includes one set of run gates for each column of the micro flash memory cards.
7. The method of claim 6 , wherein the top piece of the molding block further includes an array of engraved depressions that define a shape and dimension of finger nail catch of each micro flash memory card.
8. The method of claim 1 , wherein the singulation process is performed using the disc saw straight cut to singulate a molded micro flash memory cards array block.
9. The method of claim 8 , further comprising chamfering off a front edge using a fixture and a grinding belt with fine abrading particles or grinder with disc grind stone to generate a finished piece.