Patent Document

CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present application is a continuation-in-part of U.S. patent application Ser. No. 13/783,557, entitled “Top Port MEMS Cavity Package and Method of Manufacture Thereof” and filed on Mar. 4, 2013, the entire contents of which are incorporated herein by reference. 
     
    
     BACKGROUND OF THE DISCLOSURE 
       [0002]    1. Field of the Disclosure 
         [0003]    Disclosed is a package to house a Micro-Electro-Mechanical Systems device, and more particularly to a method for manufacture of a top port package and the so manufactured. 
         [0004]    2. Description of the Related Art 
         [0005]    One Micro-Electro-Mechanical Systems (MEMS) device is an acoustic transducer used in a microphone chip for a personal electronic device (PED). These devices include, but are not limited to, cell phones, laptop computers, tablets and mobile digital devices such as the IPad® (Apple Inc., Cupertinio, Calif.). One acoustic transducer is disclosed in U.S. Pat. No. 5,870,482 to Loeppert et al., titled “Miniature Silicon Condenser Microphone.” The acoustic transducer is disclosed as having a frame with a silicon nitride diaphragm bonded to one side of the frame and extending cantilever style over the other side. A gap between the frame and the diaphragm forms a variable air gap capacitor. Deflection of the diaphragm by acoustic (sound) waves changes the gap spacing creating a measurable change in capacitance. U.S. Pat. No. 5,870,482 is incorporated by reference herein in its entirety. 
         [0006]    Demands on a package housing a MEMS device are stringent. The device must be protected from dirt, dust and mechanical damage. Electrical interconnection is required to transmit electrical signals between the device and other electrical components of the PED. Deflection of the diaphragm is against a fixed volume of air, requiring an air tight cavity adjacent one side of the device. Further, as cell phones and other electrical devices become smaller and more light weight, the package housing the MEMS device must contribute to those objectives. Likewise, cost constraints on the product require the package to be inexpensive and preferably not overly complex to assemble. 
         [0007]    Representative packages for housing MEMS devices are disclosed in U.S. Pat. No. 8,030,722 to Bolognia et al., titled “Reversible Top/Bottom MEMS Package” and in published United States Patent Application Publication No. 2011/0075875 by Wu et al. that is titled “MEMS Microphone Package.” Both U.S. Pat. No. 8,030,722 and U.S. 2011/0075875 are incorporated by reference herein in their entireties. 
         [0008]    U.S. Pat. No. 8,030,722 discloses a package for a MEMS device having a base and a cover formed from a printed circuit board material. Conductive sidewalls electrically interconnect the base and the cover. A MEMS device is mounted to either the base or the cover and wire bonds extending from the MEMS device contact circuit traces on both the cover and the base; electrically interconnecting the MEMS device to both. 
         [0009]    U.S. 2011/0075875 discloses a MEMS package having a MEMS device mounted to the package cover. The MEMS device is electrically interconnected to circuit traces that extend from the cover to conductive sidewalls to circuit traces formed in the base. An integrated circuit device, such as an amplifier or noise filter is electrically interconnected to the circuit traces formed in the base. 
         [0010]    Top and bottom port packages exist mainly due to the mechanical requirements of the end application. Top port packages are often preferred as bottom port packages require a corresponding hole in the application PCB to which the microphone is mounted. However, if the ratio of air behind the membrane is larger than that in front of it the package has improved technical performance particularly regarding signal to noise ratio (larger back volume of air than front volume of air). With a bottom port package where the MEMS die is connected directly to the package substrate it is easy to get this improved ratio of back to front volume by mounting the MEMS die over the sound port. For a top port package which many applications mechanically require, it is not possible with standard packaging to mount the MEMS die in such a way to get the improved technical performance. 
         [0011]    There are times when it is desirable to mount the MEMS device to the cover of the package encasing the device. However, forming circuit traces in the cover and electrically conductive sidewalls to transfer electric signals to and from the MEMS device, as in the disclosures referenced above, results in a complex package requiring accurate alignment which runs contrary to the objectives to simplify and reduce the cost of such a package. There remains a need for a robust package that enables mounting a MEMS device to a cover component of the package that does not have the disadvantages of complex assembly and high cost. 
       BRIEF SUMMARY 
       [0012]    Disclosed herein is a method to manufacture a package encasing a Micro-Electro-Mechanical Systems (MEMS) device. The method includes the steps of: (1) Providing a cover having a lid and sidewalls with a port extending through the lid. (2) Bonding a first base component to the sidewalls thereby defining an internal cavity having surfaces formed by the lid, the sidewalls and the first base component. This first base component further has an aperture extending therethrough. (3) Inserting the MEMS device through the aperture and bonding the MEMS device to the lid with the MEMS device at least partially overlapping the port. (4) And bonding a second base component to the first base component to seal the aperture. 
         [0013]    Also disclosed herein is method to manufacture a panel of packages to encase MEMS devices. This method includes the steps of: (1) Providing a panel having a matrix of first base components. Each first base component has an aperture extending there through. (2) Providing a cover for each first base component member of the matrix. Each cover has a lid and sidewalls with a port extending through the lid. (3) Bonding a first base component to the sidewalls thereby defining an internal cavity having surfaces formed by the lid, the sidewalls and the first base component. (4) Inserting a MEMS device through each aperture and bonding that MEMS device to the lid with the MEMS device at least partially overlapping the port. (5) Bonding a second base component to each first base component to seal the aperture. (6) And singulating the first panel to form a plurality of packages. 
         [0014]    Also disclosed are the packages so produced, which include a cover having a lid and sidewalls with a port extending through the lid. An aperture-containing first base component bonded to the sidewalls. A MEMS device bonded to the lid and electrically interconnected to electrically conductive features disposed on a surface of the first base component. A second base component is bonded to the first base component spanning the aperture. 
         [0015]    The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features, objects and advantages of the invention will be apparent from the description and drawings, and from the claims. 
     
    
     
       IN THE DRAWINGS 
         [0016]      FIG. 1  is a first intermediate assembly in the manufacture of a top port MEMS cavity package in accordance with a first embodiment. 
           [0017]      FIG. 2  is a second intermediate assembly in the manufacture of the top port MEMS cavity package in accordance with a first embodiment. 
           [0018]      FIG. 3  is a third intermediate assembly in the manufacture of the top port MEMS cavity package in accordance with the first embodiment. 
           [0019]      FIG. 4  is the top port MEMS cavity package manufactured in accordance with the first embodiment. 
           [0020]      FIG. 5  is a perspective view of a panel of first base components for used in the manufacture of a plurality of top port MEMS cavity packages. 
           [0021]      FIG. 6  is a first intermediate assembly in the manufacture of a top port MEMS cavity package in accordance with a second embodiment. 
           [0022]      FIG. 7  is a second intermediate assembly in the manufacture of the top port MEMS cavity package in accordance with the second embodiment. 
           [0023]      FIG. 8  is a third intermediate assembly in the manufacture of the top port MEMS cavity package in accordance with the second embodiment. 
           [0024]      FIG. 9  is the top port MEMS cavity package manufactured in accordance with the second embodiment. 
           [0025]      FIG. 10  illustrates an alternative substrate for the packages disclosed herein. 
           [0026]      FIG. 11  is a first intermediate assembly in the manufacture of a top port MEMS cavity package in accordance with a third embodiment. 
           [0027]      FIG. 12  is a second intermediate assembly in the manufacture of the top port MEMS cavity package in accordance with the third embodiment. 
           [0028]      FIG. 13  is a third intermediate assembly in the manufacture of the top port MEMS cavity package in accordance with the third embodiment. 
           [0029]      FIG. 14  is the top port MEMS cavity package manufactured in accordance with the third embodiment. 
           [0030]      FIG. 15  is a bottom perspective view of a cover for the packages disclosed herein. 
           [0031]      FIG. 16  is a bottom perspective view of an intermediate assembly for the packages disclosed herein. 
           [0032]      FIG. 17  is a bottom perspective view of an assembled package. 
           [0033]      FIG. 18  is a top perspective view of an assembled package. 
           [0034]      FIG. 19  is an alternative top port MEMS cavity package manufactured in accordance with the first embodiment. 
           [0035]    FIGS.  20 (A)-(B) are schematic side views of an embodiment package having a circuit device attached therein in a flip chip manner. 
           [0036]    FIGS.  21 (A)-(B) are schematic side views of an embodiment package having an embedded circuit device. 
           [0037]    FIGS.  22 (A)-(B) are schematic side views of an embodiment package having a passive component attached therein. 
           [0038]    FIGS.  23 (A)-(B) are schematic side views of an embodiment package having an embedded passive component. 
           [0039]    FIGS.  24 (A)-(B) are schematic side views of an embodiment package in which a MEMS device is attached in a flip chip manner. 
           [0040]    FIGS.  25 (A)-(B) are schematic side views of an embodiment package in which a MEMS device is attached in a flip chip manner and there is an embedded circuit device. 
           [0041]    FIGS.  26 (A)-(B) are schematic side views of an embodiment package in which a MEMS device is attached in a flip chip manner and there is an attached passive component. 
           [0042]    FIGS.  27 (A)-(B) are schematic side views of an embodiment package in which a MEMS device is attached in a flip chip manner and there is an embedded passive component. 
       
    
    
     DETAILED DESCRIPTION 
       [0043]      FIGS. 1 through 4  illustrate in cross-sectional representation a first assembly process for the manufacture of a top port MEMS cavity package (reference numeral  100  in  FIG. 4 ). In  FIG. 1 , a first intermediate assembly  10  includes a cover  12  and a first base component  14 . While “cover” and “top” are used interchangeably, it is recognized that the package may be flipped over and the cover be the bottom. As such, the word cover should be broadly construed to be the non-substrate side of the package. 
         [0044]    The cover  12  has a lid  13  and sidewalls  15 . A port  16  extends through the lid  13  and is sized to permit acoustic waves to interact with a MEMS device (reference numeral  18  in  FIG. 2 ). The port  16  may be an open cavity or sealed with a fibrous material or polymer film to protect the MEMS device. The cover  12  is formed from any suitable material such as a metal, ceramic, liquid crystal polymer or other molded polymer. The first base component  14  forms a portion of the substrate (reference numeral  20  in  FIG. 4 ). The first base component  14  is formed from an electrical dielectric as is typically used in the manufacture of printed circuit boards, for example, FR-4 or a ceramic. Wire bond attach sites  22  and conductive circuit traces  24  are formed on and in the first base component. A metallized bond pad  26  may be formed on an exterior surface  28  of the first base component  14  to facilitate electrical interconnection to an electrically conductive via  30  formed in a second base component  32  ( FIG. 4 ). 
         [0045]    Sidewalls  15  of the cover  12  are bonded to first base component  14  with an adhesive  34  or other sealant thereby defining an internal cavity  60  having surfaces formed by the lid  13 , sidewalls  15  and first base component  14 . As electrical interconnection between circuit traces in the cover  12  and circuit traces in the first base components  14  is not necessary, adhesive  34  need not be electrically conductive, and is preferably a dielectric material such as an epoxy, that may be applied by any suitable process, such as printed, dispensed or dipped. Further, precise alignment of the cover  12  and first base component  14  to align circuit traces is not required. 
         [0046]    With reference to  FIG. 2 , a MEMS device  18 , such as described in U.S. Pat. No. 5,870,482, is attached to an interior surface  36  of the cover  12  by insertion through an aperture  38  that extends through the first base component  14 . The aperture  38  is sufficiently large to enable the MEMS devise  18  to be inserted there through with sufficient precision to align the MEMS device over the port  16  to at least partially overlap the port. Accurate insertion may be obtained using standard production die attach equipment using fiducials and alignment features on the substrate  14  for alignment. The MEMS device is then bonded, such as with adhesive  40 , to the cover  12 . Electrical interconnection between the MEMS device  18  and circuitry, if any, on the cover  12  is not required and the MEMS device is preferably electrically isolated from the cover  12 . 
         [0047]    Referring to  FIG. 3 , bond wires  42  are attached to wire bond sites  44  on the MEMS device  18 . A distance, D, between the exterior surface  28  of the first base component  14  and the wire bond sites  44  is on the order of from 0 to 500 μm, within the capability of a standard wire bond machines. Opposing ends of the bond wires  42  are bonded to the wire bond attach sites  22 . 
         [0048]    As shown in  FIG. 4 , the top port MEMS cavity package  100  is completed by bonding the second base component  32  to the first base component  14  sealing aperture  38  to make an air tight seal for internal cavity  60  and to form electrical interconnections. 
         [0049]      FIG. 19  illustrates an alternative top port MEMS cavity package  120  manufactured in accordance with the first embodiment. In this alternative, the combined height, H, of the MEMS device  18  and adhesive  40  is greater than the length, L, of the sidewalls  45  of the cover  12 . A portion of the MEMS device  18  is accommodated in the aperture  38  of the first base component  14 . Bond wires  42  fit within a clearance  47  between the first base component  14  and the second base component  32 . 
         [0050]    While the top port MEMS cavity package  100  may be assembled in singular form as illustrated in  FIGS. 1-4 , package assembly is particularly amendable to automated assembly of an array of package units.  FIG. 5  is a perspective view of a panel  50  having a matrix of first base components  14 , each matrix member having apertures  38  for use in the manufacture of a plurality of top port MEMS cavity packages. The assembly steps shown in  FIGS. 1-4 , or other embodiments described below, are performed using either individual covers or a second panel having a matrix of covers for bonding to the matrix of first base components. After insertion and wirebonding of the MEMS devices and other device components, the package units are singulated by cutting along saw lines  52 . The second base component may be added to create an air tight seal and electrical interconnection in either panel form, as a third panel before singulation, or as individual components subsequent to singulation. While the panel  50  is illustrated for twelve packages, much larger matrices, for example, containing up to 1000 package units may be utilized. A typical panel contains from 75 to 100 units. 
         [0051]      FIGS. 6-9  illustrate an assembly process in accordance with a second embodiment. As shown in  FIG. 6 , an integrated circuit device  54 , such as an amplifier or a noise filter, is attached to a surface  56  of the first base component  14  and electrically interconnected to electrically conductive features, such as conductive traces on a surface  56 , of first base component  14 , such as by wire bonds  58  and also electrically interconnected to the MEMS device. 
         [0052]    Referring to  FIG. 7 , cover  12  is then bonded to the first base component  14 , such as with adhesive  34 . Next, as shown in  FIG. 8 , the MEMS device  18  is bonded to interior surface  36  of the cover  12 , forming an air tight seal around the port  16 . Bond wires  42  electrically interconnect the MEMS device  18  to wire bond attach sites  22 . The package is then completed by bonding of second base component  32 , as illustrated in  FIG. 9 . 
         [0053]    Each MEMS package disclosed herein has an internal cavity  60  that undergoes changes in volume and pressure when a membrane  62  of the MEMS device  18  is displaced by acoustic waves. The volume of this internal cavity  60  may be changed, changing the sensitivity of the package, such as by addition of a blind cavity  64  formed in the second base component  32 , as shown in  FIG. 10 . This blind cavity  64  is aligned with the internal cavity  60  to be in fluid communication therewith. Attachment of the MEMS device  18  requires a seal completely around the base of the MEMS device so that there is no leakage or alternate routes for sound waves to travel. 
         [0054]      FIGS. 11-14  illustrate an assembly process in accordance with a second embodiment. As shown in  FIG. 11 , the aperture  38  in the first base component  14  is enlarged to facilitate insertion of both an integrated circuit device  54  and the MEMS device  18  ( FIG. 12 ). With reference to  FIG. 13 , wire bond  58  then electrically interconnects the integrated circuit device  54  and the MEMS device  18 . Wire bonds  42  electrically interconnect these devices  54 ,  18  to wire bond attach sites  22  on the first base component  14 . Second base component  32  then seals the package forming internal cavity  60 . In any of the embodiments herein, secondary cavity  64  may extend over the metallized bond pads  26  to accommodate bond wires  42 . 
         [0055]      FIG. 15  is a perspective view of the inside of a cover  12  illustrating the port  16 .  FIG. 16  is a perspective view of an intermediate assembly showing wire bonds  42  extending from an integrated circuit device  54  to conductive circuit traces (not visible) on the first base component  14 . The conductive circuit traces terminate at metallized bond pads  26 .  FIG. 17  illustrates the completed package with electrically conductive vias  30  extending to an exterior surface of the second base component  32  for providing electrical interconnection between the enclosed devices and external circuitry and devices.  FIG. 18  is a top perspective view of the assembled package. 
         [0056]    FIGS.  20 (A)-(B) illustrate an embodiment package  2001 , that in many respects is similar to certain other embodiments described above. Circuit device  2002  is connected to first base component  14  in a flip chip manner. Connectors  2003  electrically link circuit device  2002  to connection points  2004 . Connectors  2003  may be any suitable material, such as solder or gold. Connection points  2004  may be metallized pads. It should be understood that flip chip connection methods are known to those of skill in the art to which the present application pertains. Circuit device  2002  becomes disposed within the internal cavity of package  2001  when first base component  14  and sidewalls  15  are bonded. In the production of packages as disclosed in the present application, circuit device  2002  may be attached to first base component  14  in a flip chip manner before the bonding of sidewalls  15  and first base component  14 .  FIG. 20B  illustrates the use of alternate cover  2005 . 
         [0057]    FIGS.  21 (A)-(B) illustrate embodiment package  2101 . Second base component  2102  has embedded in it circuit device  2103 . Bond wires  2104  electrically connect circuit device  2103  to bond wire attachment sites  2105 .  FIG. 21B  illustrates the use of alternate cover  2106 . In the production of packages as disclosed in the present application, circuit device  2103  may be embedded prior to assembly of the package  2101 . 
         [0058]    FIGS.  22 (A)-(B) illustrate embodiment package  2201 . Passive component  2202  is attached to first base component  14 . Passive component  2202  is attached in such a manner that it is disposed within the internal cavity of the package when first base component  14  and side walls  15  are bonded. In the production of packages as disclosed in the present application, circuit device  2202  may be attached to first base component  14  before the bonding of sidewalls  15  and first base component  14 .  FIG. 22B  illustrates the use of alternate cover  2203 . 
         [0059]    FIGS.  23 (A)-(B) illustrate embodiment package  2301 . Second base component  2302  has embedded in it passive component  2303 .  FIG. 23B  illustrates the use of alternate cover  2304 . In the production of packages as disclosed in the present application, passive component  2303  may be embedded prior to assembly of the package. 
         [0060]    FIGS.  24 (A)-(B) illustrate embodiment package  2401 . MEMS device  18  is attached to second base component  32  in a flip chip manner. Connectors  2402  electronically connect first and second connection points  2403  and  2404 , respectively, thus electrically connecting MEMS device  18  to first connection points  2403 . Package  2401  may be produced, in part, by electrically connecting MEMS device  18  to second base component  32  in a flip chip manner during the step of bonding second base component  32  to first base component  14 .  FIG. 24B  illustrates the use of alternate cover  2405 . 
         [0061]    FIGS.  25 (A)-(B) illustrate embodiment package  2501 . MEMS device  18  is attached to second base component  2502  in a flip chip manner. Circuit device  2503  is embedded in second base component  2502 . Bond wires  2504  electrically connect circuit device  2503  to bond wire connection sites  2505 . In the production of packages as disclosed in the present application, circuit device  2503  may be embedded prior to assembly of the package.  FIG. 25B  illustrates the use of alternate cover  2506 . 
         [0062]    FIGS.  26 (A)-(B) illustrate embodiment package  2601 . MEMS device  18  is attached to second base component  32  in a flip chip manner. Passive component  2602  is attached to first base component  14 . Passive component  2602  is attached in such a manner that it is disposed within the internal cavity of the package when first base component  14  and side walls  15  are bonded. In the production of packages as disclosed in the present application, passive component  2602  may be attached to first base component  14  before the bonding of sidewalls  15  and first base component  14 .  FIG. 26B  illustrates the use of alternate cover  2603 . 
         [0063]    FIGS.  27 (A)-(B) illustrate embodiment package  2701 . MEMS device  18  is attached to second base component  2702  in a flip chip manner. Second base component  2702  has embedded in it passive component  2703 .  FIG. 27B  illustrates the use of alternate cover  2704 . In the production of packages as disclosed in the present application, passive component  2703  may be embedded prior to assembly of the package. 
         [0064]    One or more embodiments of the present invention have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the invention. Accordingly, other embodiments are within the scope of the following claims.

Technology Category: 7