Manufacturing method for memory card
A portable memory card including a molded plastic casing formed over a memory device and other circuits mounted on a substrate such that the molding material extends over side edges of the substrate to provide accurate width and thickness dimensions. Contact pads are formed on a lower surface of the PCBA substrate, which is exposed through a bottom of the casing. The PCBA is fabricated on a substrate carrier, then positioned inside of a mold assembly. During the molding process, a rod extends from an upper portion of the mold assembly and pushes the substrate against the lower surface. A vacuum is then applied to hold the substrate against the lower surface of the mold, and the rod is subsequently withdrawn from the mold cavity during injection of the molten molding material. A single cavity mold assembly provides molding material extends over front and back edges of the memory card.
1. A method for manufacturing a memory card comprising:
forming a printed circuit board assembly (PCBA) including a substrate having a plurality of IC components mounted on an upper surface thereof and a plurality of contact pads exposed on a bottom surface thereof, wherein the substrate has a continuous peripheral edge extending around an entire perimeter thereof and excludes tie bars that extends from the peripheral edge away from the substrate;
positioning the PCBA inside of a cavity defined by a mold assembly, the mold assembly having a lower mold portion having a lower surface for receiving the PCBA, and an upper mold portion mounted over the PCBA, wherein the cavity extends over the continuous peripheral edge of the substrate such that a portion of the lower surface is exposed around the entire perimeter of the substrate;
securing the substrate to the lower surface of the mold assembly such that the bottom surface of the substrate is held against the lower surface of the lower mold portion; and
injecting molten material into the cavity such that the molten material forms a casing over the IC components, whereby molten material flows over the continuous peripheral edge of the substrate and contacts the exposed portion of the lower surface of the lower mold portion, thereby forming casing portions that cover the continuous peripheral edge of the substrate and extend over the entire perimeter of the substrate, wherein the substrate is secured during said injecting such that molten material is prevented from forming on the bottom surface of the substrate.
2. The method according to claim 1 , wherein forming the PCBA comprises:
fabricating a substrate carrier including the substrate integrally formed with a carrier frame, wherein the carrier frame includes a first frame portion connected to a first end of the substrate, and a second frame portion integrally connected to a second end of the substrate; and
mounting said plurality of IC components onto the substrate to form a printed circuit board assembly (PCBA).
3. The method according to claim 2 ,
wherein the plurality of IC components includes a rectangular memory device defining a long axis, and
wherein mounting the IC components comprises aligning the long axis of the memory device in a width direction of the substrate.
4. The method according to claim 2 ,
wherein the plurality of IC components includes a rectangular memory device defining a long axis, and
wherein mounting the IC components comprises aligning the long axis of the memory device in a length direction of the substrate.
5. The method according to claim 2 , wherein fabricating the substrate comprises forming at least one slot between the carrier frame and each substrate.
6. The method according to claim 2 , wherein fabricating the substrate comprises forming slots between adjacent contact pads.
7. The method according to claim 2 , wherein forming the PCBA further comprises separating the PCBA from the carrier frame by cutting along the first and second ends of the substrate.
8. The method according to claim 1 , wherein positioning the PCBA inside the mold assembly comprises:
placing a positioning block inside of the mold assembly;
inserting the PCBA into a central cutout region defined by the positioning block, wherein the central cutout region is aligned with a predetermined desired position of the PCBA; and
removing the positioning block from the mold assembly.
9. The method according to claim 1 , wherein positioning the PCBA inside the mold assembly comprises:
deploying a plurality of positioning rods such that the positioning rods protrude into a lower cavity region of the mold assembly;
inserting the PCBA into a central region defined by the plurality of positioning rods, wherein the central region is aligned with a predetermined desired position of the PCBA; and
retracting the positioning rods such that the positioning rods are positioned outside of the lower cavity region.
10. The method according to claim 1 , wherein positioning the PCBA inside the mold assembly comprises:
deploying a plurality of L-shaped corner blocks such that the corner blocks protrude into a lower cavity region of the mold assembly;
inserting the PCBA into a central region defined by the corner blocks, wherein the central region is aligned with a predetermined desired position of the PCBA; and
retracting the corner blocks such that the corner blocks are positioned outside of the lower cavity region.
11. The method according to claim 1 , wherein positioning the PCBA inside the mold assembly comprises utilizing a pick-and-place machine to place the PCBA into a predetermined desired position inside a lower mold portion of the mold assembly.
12. The method according to claim 1 , wherein positioning the PCBA inside the mold assembly comprises interposing a release film between an upper mold portion of the mold assembly and the PCBA.
13. The method according to claim 1 , wherein securing the PCBA comprises inserting a rod into the cavity such that the rod contacts the upper surface of the substrate at a point opposite to the contact pads.
14. The method according to claim 13 , wherein securing the PCBA inside the mold assembly further comprises applying a vacuum force to the bottom surface of the substrate, thereby holding the substrate against the lower surface of the lower mold portion.
15. The method according to claim 14 , further comprising retracting the rod from the cavity during injection of the molten material into the cavity.
16. The method according to claim 1 , wherein securing the PCBA inside the mold assembly comprises applying a vacuum force to the bottom surface of the substrate, thereby holding the substrate against the lower surface of the lower mold portion.
17. The method according to claim 1 , further comprising removing the memory card from the mold assembly, and performing at least one of testing the memory card and labeling the memory card.
18. The method according to claim 1 , wherein forming the PCBA comprises mounting on an upper surface of the substrate a controller device and a memory device formed in at least one of a Very Very Thin Small Outline Package (WSOP), a Ball Grid Array (BGA) package, and a Thin Small Outline Package (TSOP).
19. The method according to claim 1 , wherein forming the PCBA comprises the substrate with one of seven, nine, and eleven contact pads.