LEADFRAME PACKAGE FOR MEMS MICROPHONE ASSEMBLY

• US 20090263937A1
• Filed: 05/28/2009
• Published: 10/22/2009
• Est. Priority Date: 01/03/2007
• Status: Active Grant

• Current Assignee: Stats Chippac Pte. Lte.
• Original Assignee: Stats Chippac Incorporated (JCET Group Co., Ltd.)
• Inventors: Chow, Seng Guan, Ramakrishna, Kambhampati
• Granted Patent: US 7,795,078 B2
• Time in Patent Office: Days
• US Class Current: 438/123
• CPC Class Codes: B81B 2201/0257 Microphones or microspeakers
• CPC Class Codes: B81B 7/0061 suitable for fluid transfer from the MEMS out of the package or vice versa, e.g. transfer of liquid, gas, sound
• CPC Class Codes: H01L 2224/32225 the item being non-metallic, e.g. insulating substrate with or without metallisation
• CPC Class Codes: H01L 2224/48091 Arched
• CPC Class Codes: H01L 2224/48137 the bodies being arranged next to each other, e.g. on a common substrate
• CPC Class Codes: H01L 2224/48227 connecting the wire to a bond pad of the item
• CPC Class Codes: H01L 2224/73265 Layer and wire connectors
• CPC Class Codes: H01L 24/73 Means for bonding being of different types provided for in two or more of groups H01L24/10, H01L24/18, H01L24/26, H01L24/34, H01L24/42, H01L24/50, H01L24/63, H01L24/71
• CPC Class Codes: H01L 2924/00 Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• CPC Class Codes: H01L 2924/00012 Relevant to the scope of the group, the symbol of which is combined with the symbol of this group
• CPC Class Codes: H01L 2924/00014 the subject-matter covered by the group, the symbol of which is combined with the symbol of this group, being disclosed without further technical details
• CPC Class Codes: H01L 2924/01046 Palladium [Pd]
• CPC Class Codes: H01L 2924/01078 Platinum [Pt]
• CPC Class Codes: H01L 2924/01079 Gold [Au]
• CPC Class Codes: H01L 2924/14 Integrated circuits
• CPC Class Codes: H01L 2924/1461 MEMS
• CPC Class Codes: H01L 2924/19041 being a capacitor
• CPC Class Codes: H04R 1/04 Structural association of microphone with electric circuitry therefor in deaf-aid sets H04R25/00
• CPC Class Codes: H04R 1/2869 Reduction of undesired resonances, i.e. standing waves within enclosure, or of undesired vibrations, i.e. of the enclosure itself
• CPC Class Codes: H04R 19/005 using semiconductor materials
• CPC Class Codes: H04R 31/006 : Interconnection of transducer parts of diaphragm and outer suspension by moulding H04R31/003

Abstract

A cavity semiconductor package has a pre-molded leadframe construction. The leadframe is formed by molding around a die pad, and plural terminal lands. The leadframe has a hole for an acoustic port, such that the package can be soldered on a back side of a printed circuit board and have air access to a sensor die in the package from a front side of the printed circuit board via the acoustic port. The leadframe may also have a hollow or concave recess that defines an acoustic cavity in conjunction with the sensor die or printed circuit board.

Claims

1. A method of manufacturing a pre-molded leadframe for use in a cavity semiconductor package, the method comprising:

providing a die pad and a plurality of terminal lands;

molding a material about the die pad and the terminal lands to form a substrate having an outer frame portion, a top surface and a bottom surface;

leaving portions of the die pad and terminal lands exposed to the top surface and the bottom surface; and

providing an acoustic opening configured to permit through-air sound transmission through one or both of the molding material and the die pad, the acoustic opening extending between the top surface and the bottom surface.

2. The method of claim 1, further comprising providing a recessed region in one or both of the top surface and the bottom surface, the recessed region adjoining the acoustic opening.

3. The method of claim 1, wherein the acoustic opening is configured to permit through-air sound transmission to a semiconductor die being mounted to the die pad.

4. The method of claim 1, wherein the acoustic opening extends through the die pad.

5. The method of claim 1, wherein the acoustic opening extends through the outer frame portion.

6. The method of claim 1, wherein the acoustic opening is centrally located relative to the substrate.

7. The method of claim 1, wherein the acoustic opening is located off-center of the substrate.

9. The method of claim 1, further comprising plating an area of the bottom surface adjacent the acoustic opening with a metal for use in soldering the substrate to a printed circuit board, wherein said soldering is capable of forming an air-tight seal between the substrate and the printed circuit board, and adjacent the acoustic opening and a corresponding hole in the printed circuit board being aligned therewith.

10. The method of claim 9, further comprising leaving an unplated area on the bottom surface immediately adjacent the acoustic opening for reducing or substantially eliminating solder contamination and obstruction of the acoustic opening when the substrate is soldered to the printed circuit board.

11. The method of claim 1, wherein the die pad has an inwardly hollowed surface adjoining the acoustic opening for defining a portion of an acoustic cavity.

12. The method of claim 11, wherein the inwardly hollowed surface is recessed from the top surface for defining an acoustic cavity between the substrate and a semiconductor die mounted thereto.

13. The method of claim 11, wherein the inwardly hollowed surface is recessed from the bottom surface for defining an acoustic cavity between the substrate and a printed circuit board to which the substrate is soldered.

14. The method of claim 1, further comprising:

coupling a conductive lid to the substrate for enclosing a semiconductor die mounted thereto.

15. The method of claim 14, wherein the conductive lid defines a second acoustic opening for through-air transmission of acoustic energy.

16. A method of manufacturing a pre-molded leadframe substrate, the method comprising:

positioning a die pad and a plurality of terminal lands in a substantially common plane within a mold so as to define one or more interstitial volumes among the die pad and terminal lands;

flowing a material into at least one of the one or more interstitial volumes, wherein the material, die pad and terminal lands define a substantially planar substrate having a top surface and a bottom surface; and

forming an acoustic opening extending between the top surface and the bottom surface for through-air transmission of sound,

wherein, subsequent to the act of flowing the material, at least a portion of the die pad and a portion of one or more of the terminal lands are exposed to one or both of the top surface and the bottom surface and free of the material.

17. The method of claim 16, wherein the act of positioning a die pad comprises positioning a plurality of die pads.

18. The method of claim 17, wherein the act of flowing the material into at least one of the one or more interstitial volumes comprises flowing the material into a plurality of interstitial volumes, each of the interstitial volumes corresponding to a respective die pad, thereby forming a panel of pre-molded lead frame substrates.

19. A method of assembling a cavity semiconductor package, the method comprising:

providing a pre-molded leadframe substrate comprising a top surface and a bottom surface, a die pad and a plurality of exposed terminal lands arranged in a substantially common plane between the top surface and the bottom surface, and a molding material, wherein the pre-molded leadframe substrate defines an acoustic opening for through-air transmission of acoustic energy, the acoustic opening extending between the top surface and the bottom surface;

coupling a semiconductor die being responsive to through-air transmission of acoustic energy to the pre-molded leadframe substrate, wherein said act of coupling comprises positioning the semiconductor die so as to receive at least a portion of any through-air transmission of acoustic energy passing through the acoustic opening.

20. The method of claim 19, further comprising coupling a lid to the leadframe substrate.