Method of fabricating a molded package for micromechanical devices

• US 6,858,910 B2
• Filed: 10/16/2002
• Issued: 02/22/2005
• Est. Priority Date: 01/26/2000
• Status: Expired due to Term

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Coyle, Anthony L., Bednarz, George A.
• Primary Examiner(s): Chen, Jack
• Assistant Examiner(s): BEREZNY, NEMA O
• Application Number:
  US10/271,815
• Publication Number:
  US 20030045025A1
• Time in Patent Office: 860 Days
• Field of Search: 257/415, 257/417, 264/272.17, 438/51, 438/127
• US Class Current: 257/415
• CPC Class Codes: B29C 2045/14663 the mould cavity walls being lined with a film, e.g. release film
• CPC Class Codes: B29C 45/14655 connected to or mounted on a carrier, e.g. lead frame
• CPC Class Codes: B81C 1/00333 Aspects relating to packaging of MEMS devices, not covered by groups B81C1/00269 - B81C1/00325
• CPC Class Codes: B81C 2203/0154 Moulding a cap over the MEMS device
• CPC Class Codes: H01L 21/565 Moulds
• CPC Class Codes: H01L 2224/05568 the whole external layer protruding from the surface
• CPC Class Codes: H01L 2224/05573 Single external layer
• CPC Class Codes: H01L 2224/05599 Material
• CPC Class Codes: H01L 2224/05624 Aluminium [Al] as principal constituent
• CPC Class Codes: H01L 2224/05647 Copper [Cu] as principal constituent
• CPC Class Codes: H01L 2224/16245 the item being metallic
• CPC Class Codes: H01L 2224/45014 Ribbon connectors, e.g. rectangular cross-section
• CPC Class Codes: H01L 2224/45015 being circular
• CPC Class Codes: H01L 2224/45124 Aluminium (Al) as principal constituent
• CPC Class Codes: H01L 2224/45144 Gold (Au) as principal constituent
• CPC Class Codes: H01L 2224/45147 Copper (Cu) as principal constituent
• CPC Class Codes: H01L 2224/48091 Arched
• CPC Class Codes: H01L 2224/48227 connecting the wire to a bond pad of the item
• CPC Class Codes: H01L 23/3107 the device being completely enclosed
• CPC Class Codes: H01L 24/45 of an individual wire connector
• CPC Class Codes: H01L 24/48 : of an individual wire connector
• 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 2924/00013 : Fully indexed content
• 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 2924/01004 : Beryllium [Be]
• CPC Class Codes: H01L 2924/01015 : Phosphorus [P]
• CPC Class Codes: H01L 2924/01046 : Palladium [Pd]
• CPC Class Codes: H01L 2924/01047 : Silver [Ag]
• CPC Class Codes: H01L 2924/01078 : Platinum [Pt]
• CPC Class Codes: H01L 2924/01079 : Gold [Au]
• CPC Class Codes: H01L 2924/01087 : Francium [Fr]
• CPC Class Codes: H01L 2924/013 : Alloys
• CPC Class Codes: H01L 2924/01327 : Intermediate phases, i.e. intermetallics compounds
• CPC Class Codes: H01L 2924/10253 : Silicon [Si]
• CPC Class Codes: H01L 2924/12042 : LASER
• CPC Class Codes: H01L 2924/14 : Integrated circuits
• CPC Class Codes: H01L 2924/15311 : being a ball array, e.g. BGA
• CPC Class Codes: H01L 2924/15747 : Copper [Cu] as principal constituent
• CPC Class Codes: H01L 2924/181 : Encapsulation
• CPC Class Codes: H01L 2924/1815 : Shape
• CPC Class Codes: H01L 2924/206 : Length ranges
• CPC Class Codes: H01L 2924/20751 : larger or equal to 10 microns less than 20 microns
• CPC Class Codes: H01L 2924/20752 : larger or equal to 20 microns less than 30 microns
• CPC Class Codes: H01L 2924/20753 : larger or equal to 30 microns less than 40 microns

Abstract

A plastic land-grid array package, a ball-grid array package, and a plastic leaded package for micromechanical components are fabricated by a molding process characterized by lining the cavity surfaces of the top and bottom mold halves with a protective plastic film, which also protects the surfaces of the components during the molding phase, selectively encapsulating the bonding pads and coupling members of the chip while leaving empty space above the components, and attaching a lid over the components. A molding method as well as a molding apparatus are provided compatible with the sensitivity of the micromechanical devices, yet flexible with regard to the technique used to assemble the chip and the substrate. Furthermore, the method disclosed is flexible with regard to the material and the properties of the substrate.

It is an aspect of the present invention to be applicable to a variety of different semiconductor micromechanical devices, for instance actuators, motors, sensors, spatial light modulators, and deformable mirror devices. In all applications, the invention achieves technical advantages as well as significant cost reduction and yield increase.

Claims

1. A packaged micromechanical device, comprising:

a substrate having a first surface and a second surface, said first surface having a first plurality of terminals thereon, and said second surface having a second plurality of terminals thereon, selected ones of said first plurality of terminals coupled to selected ones of said second plurality of terminals;

an integrated circuit comprising micromechanical components in a central region and bond pads in a peripheral region, said integrated circuit mounted on said first surface of said substrate in proximity to said first plurality of terminals;

bond wires connecting said bond pads to selected ones of said first plurality of terminals;

encapsulation material disposed over a portion of said first surface of said substrate and said integrated circuit covering said bond pads, said bond wires, and said selected ones of said first plurality of terminals to which said bond wires are connected, said micromechanical components being uncovered by said encapsulation material, and

a visible light permeable cover disposed over said encapsulation material and spaced from the central region of said micromechanical device, said encapsulation material extending sufficiently above said central region to permit uninhibited movement of said micromechanical components beneath said cover.

2. The packaged micromechanical device of claim 1, wherein said encapsulation material surrounds said micromechanical components.

3. The packaged micromechanical device of claim 2, wherein said encapsulation material comprises a flat top surface and a molded protrusion extending toward said micromechanical components, said molded protrusion having a top surface lower than said flat top surface.

4. The packaged micromechanical device of claim 3, further comprising a passivant releasing chemical compound on said molded protrusion.

5. The packaged micromechanical device of claim 1, wherein said cover is glass.

6. A packaged micromechanical device, comprising:

a leadframe comprising leads having inner sections and outer sections arranged around a central chip pad;

an integrated circuit comprising micromechanical components in a central region and bond pads in a peripheral region, said integrated circuit mounted on said chip pad;

bond wires connecting selected ones of said bond pads to selected ones of said inner sections of said leads;

encapsulation material disposed over said inner sections of said leads and said integrated circuit covering said bond pads and said bond wires, said micromechanical components being uncovered by said encapsulation material, and

a visible light permeable cover disposed over said encapsulation material and spaced from the central region of said micromechanical device, said encapsulation material extending sufficiently above said central region to permit uninhibited movement of said micromechanical components beneath said cover.

7. The packaged micromechanical device of claim 6, wherein said encapsulation material surrounds said micromechanical components.

8. The packaged micromechanical device of claim 7, wherein said encapsulation material comprises a flat top surface and a molded protrusion extending toward said micromechanical components, said molded protrusion having a top surface lower than said flat top surface.

9. The packaged micromechanical device of claim 8, further comprising a passivant releasing chemical compound on said molded protrusion.

10. The packaged micromechanical device of claim 6, wherein said cover is glass.

11. A packaged micromechanical device, comprising:

a leadframe comprising leads having inner sections and outer sections arranged around a central area;

an integrated circuit comprising micromechanical components in a central region and bond pads in a peripheral region, said integrated circuit mounted over said central area of said leadframe, selected ones of said bond pads attached to selected ones of said inner sections of said leads;

encapsulation material disposed over said inner sections of said leads and said integrated circuit covering said bond pads and said inner sections of said leads, said micromechanical components being uncovered by said encapsulation material, and

a visible light permeable cover disposed over said encapsulation material and spaced from the central region of said micromechanical device, said encapsulation material extending sufficiently above said central region to permit uninhibited movement of said micromechanical components beneath said cover.

12. The packaged micromechanical device of claim 11, wherein said integrated circuit comprises a back side opposite the side of said integrated circuit comprising micromechanical components, and further wherein said back side is not covered by said encapsulation material.

13. The packaged micromechanical device of claim 11, wherein said encapsulation material surrounds said micromechanical components.

14. The packaged micromechanical device of claim 13, wherein said encapsulation material comprises a flat top surface and a molded protrusion extending toward said micromechanical components, said molded protrusion having a top surface lower than said flat top surface.

15. The packaged micromechanical device of claim 14, further comprising a passivant releasing chemical compound on said molded protrusion.

16. The packaged micromechanical device of claim 11, wherein said cover is glass.