CAP FOR A MICROELECTROMECHANICAL SYSTEM DEVICE WITH ELECTROMAGNETIC SHIELDING, AND METHOD OF MANUFACTURE

• US 20130322039A1
• Filed: 05/31/2012
• Published: 12/05/2013
• Est. Priority Date: 05/31/2012
• Status: Active Grant

• Current Assignee: STMicroelectronics International N.V. (STMicroelectronics NV)
• Original Assignee: Stmicroelectronics Pte Limited (STMicroelectronics NV)
• Inventors: Teysseyre, Jerome, de los Reyes, Glenn, Lim, Wee Chin Judy
• Granted Patent: US 8,987,871 B2
• Time in Patent Office: Days
• US Class Current: 361/753
• CPC Class Codes: H05K 9/003 made from non-conductive materials comprising an electro-conductive coating H05K9/0031 takes precedence

Abstract

A cap for a microelectromechanical system device includes a first layer of, e.g., Bismaleimide Triazine (BT) resin material in which a through-aperture is formed, laminated to a second layer of BT resin material that closes the aperture in the first layer, forming a cavity. The first and second layers are laminated with a thermosetting adhesive that is sufficiently thick to encapsulate particles that may remain from a routing operation for forming the apertures. The interior of the cavity, including exposed portions of the adhesive, and the exposed face of the first layer are coated with an electrically conductive paint. The cap is adhered to a substrate over the MEMS device using an electrically conductive adhesive, which couples the conductive paint layer to a ground plane of the substrate. The layer of conductive paint serves as a shield to prevent or reduce electromagnetic interference acting on the MEMS device.

Claims

1. A device, comprising:

a body of polymeric material having a substantially planar face;

a cavity extending into the body from the face, the cavity having side walls and a back wall; and

an electrically continuous layer of conductive paint extending on the side walls and back wall of the cavity and on the face of the body.

2. The device of claim 1 wherein the body comprises:

a first layer of polymeric material having a first face and a second face, opposite the first face;

an aperture extending through the first layer from the first face to the second face;

a second layer of polymeric material positioned on the first face of the first layer and covering an opening of the aperture on the first face to form the cavity; and

a layer of adhesive positioned between the first face of the first layer and the second layer and coupling the first layer to the second layer;

3. The device of claim 2 wherein the polymeric material of the first and second layers is Bismaleimide Triazine Resin.

4. The device of claim 2 wherein a portion of the layer of adhesive extends from between the first and second layers and forms a bead around the back wall of the cavity, and wherein the layer of conductive paint extends over the bead of adhesive.

5. The device of claim 1, comprising:

a package substrate mechanically coupled to the face of the body;

a wiring circuit in the package substrate and having a circuit ground electrically coupled to the conductive paint extending on the face of the body;

a microelectromechanical systems device coupled to a face of the package substrate inside the cavity.

6. The device of claim 5, comprising:

a conductive land on the face of the package substrate, in electrical contact with the circuit ground of the wiring circuit, and in a position corresponding to the face of the body; and

conductive adhesive positioned between the conductive land and the face of the body and electrically coupling the conductive paint extending on the face of the body and the conductive land.

7. A Method of manufacture, comprising:

positioning a layer of adhesive on a first face of a first sheet of polymeric material;

forming a plurality of apertures extending through the first sheet of thermosetting material and through the layer of adhesive;

positioning a second sheet of polymeric material on the first face of the first sheet of thermosetting material in contact with the layer of adhesive, closing one side of the plurality of apertures and forming a plurality of cavities;

depositing a layer of electrically conductive paint over the second face of the first sheet of polymeric material, over side walls and end walls of the plurality of cavities, and over an exposed portion of the layer of adhesive.

8. The method of claim 7 wherein positioning the second sheet of polymeric material on the first face of the first sheet of polymeric material comprises applying compressive force between the first and second sheets.

9. The method of claim 8 wherein the applying compressive force comprises applying a compressive force of more than 10 kg/cm² and less than 20 kg/cm².

10. The method of claim 8 wherein the applying compressive force comprises forming a bead of adhesive around the back walls of the plurality of cavities, and wherein the depositing the layer of electrically conductive paint comprises depositing the conductive paint over the beads of adhesive.

11. The method of claim 7 wherein the positioning a layer of adhesive comprises positioning a layer of adhesive film that includes a protective liner.

12. The method of claim 7 wherein the positioning a layer of adhesive comprises positioning a layer of adhesive having a thickness of more than 20 μ

m and less than 30 μ

m.

13. A method, comprising:

forming a cavity extending into a body of polymeric material from a face thereof; and

applying an electrically continuous layer of conductive paint to side and back walls of the cavity, and to the face of the body.

14. The method of claim 13 wherein forming the cavity comprises:

forming an aperture in a first sheet of polymeric material; and

coupling a second sheet of polymeric material to a face of the first sheet and covering one side of the aperture, forming a cavity.

15. The method of claim 14, comprising positioning adhesive on one of the first or second sheets of material before the coupling the second sheet, and wherein the coupling the second sheet comprises coupling the second sheet of polymeric material to the face of the first sheet with the adhesive positioned between the first and second sheets.

16. The method of claim 13 wherein:

the forming the cavity comprises forming a plurality of cavities extending into the body of polymeric material from the face thereof; and

applying the electrically continuous layer comprises applying an electrically continuous layer of conductive paint to side and back walls of each of the plurality of cavities, and to the face of the body.