MEMS packaging method for enhanced EMI immunity using flexible substrates
A MEMS package and methods for its embodiment are described. The MEMS package has at least one MEMS device mounted on a flexible and foldable substrate. A metal cap structure surrounds the at least one MEMS device wherein an edge surface of the metal cap structure is attached to the flexible substrate and wherein a portion of the flexible substrate is folded under itself thereby forming the MEMS package. A meshed metal environmental hole underlying the at least one MEMS device provides enhanced EMI immunity.
1. A MEMS package comprising:
at least one MEMS device;
a flexible substrate having at least one metal layer on a top side of which said at least one MEMS device is mounted;
a rigid conductive plate having a top side attached to a bottom side of said flexible substrate and underlying said at least one MEMS device wherein a portion of said flexible substrate is folded and attached to a bottom side of said rigid conductive plate;
a passage hole in said flexible substrate underlying said at least one MEMS device;
a plurality of via holes in said flexible substrate;
a metal cap structure surrounding said at least one MEMS device wherein an edge surface of said metal cap structure is attached and electrically connected to said folded flexible substrate and to said rigid conductive plate through said via holes in said flexible substrate wherein said metal cap structure and said at least one metal layer in said flexible substrate together provide EMI shielding of said at least one MEMS device;
at least one punched opening in said rigid conductive plate and underlying said passage hole in said flexible substrate wherein said at least one punched opening and said passage hole provide a back chamber for said at least one MEMS device; and
an environmental hole in said metal cap structure.
2. The package according to claim 1 wherein said flexible substrate comprises a core film with a copper layer on a top side of said core film or copper layers on both sides of said core film wherein said core film comprises polyimide, polyethylene polyimide, poly tetra fluoro ethylene, or liquid crystal polymer.
3. The package according to claim 1 wherein said at least one metal layer in said flexible substrate comprises a copper metal layer with a surface finish of nickel and gold.
4. The package according to claim 1 wherein said metal cap structure encapsulates said at least one MEMS device and may comprise a copper, a copper alloy, an aluminum alloy, an iron alloy with solderable metal finish, a plastic with a metal finish formed by either electroless plating or painting, or a conductive composite material formed by either injection molding or transfer molding.
5. The package according to claim 1 wherein said environmental hole permits interaction between said MEMS device and the environment outside said package.
6. The package according to claim 1 wherein said rigid conductive plate comprises a metal plate or a FR-4 PCB.
7. The package according to claim 1 wherein said metal cap structure is attached and electrically connected to said at least one metal layer in said flexible substrate and a top portion of said rigid conductive plate through said via holes in said flexible substrate at said edge surface of said metal cap structure by a conductive adhesive, or soldering, or a combination of conductive adhesive or soldering and a non-conductive adhesive, or by a combination of a conductive adhesive or solder with a non-conductive adhesive.
8. The package according to claim 1 further comprising one or more electronic components located on said flexible substrate and within said metal cap structure.
9. The package according to claim 8 further comprising wire bonding connections among said one or more electronic components, said at least one MEMS device, and said flexible substrate.