PATENT DOCUMENT

Publication Number: US-9232302-B2
Application Number: US-201113149626-A
Country: US
Kind Code: B2

Title: Microphone assemblies with through-silicon vias

Abstract:
Microphone assemblies may be provided that have microelectromechanical systems microphones and associated application-specific integrated circuits mounted to printed circuit boards. The application-specific integrated circuits may contain amplifier circuitry for amplifying microphone signals from the microphone. One or more though-silicon vias may be formed in the application-specific integrated circuit that serve as an acoustic port through which sound may pass. The application-specific integrated circuit may be embedded in the printed circuit board and the microphone may be mounted to the upper surface of the printed circuit board, the application-specific integrated circuit and microphone may be stacked on the upper surface of the printed circuit board, or the microphone and application-specific integrated circuit may be mounted to the printed circuit board so that the microphone is received within an opening in the printed circuit board.

Claims:
What is claimed is: 
     
       1. A microphone assembly, comprising:
 a printed circuit board having a top surface, a bottom surface, and an opening passing through the bottom surface; 
 an integrated circuit having a top surface, a bottom surface, and at least one through-silicon via that forms an acoustic port through the top and bottom surfaces of the integrated circuit; and 
 a microphone, separate from the integrated circuit, that is mounted to a portion of the top surface of the integrated circuit so that the microphone receives sound through the acoustic port of the integrated circuit; 
 wherein the top surface of the integrated circuit is mounted to the bottom surface of the printed circuit board so that the microphone is positioned within the opening of the printed circuit board and the integrated circuit is positioned outside of the opening of the printed circuit board, 
 wherein the opening has at least one peripheral edge that is open and not surrounded by the printed circuit board. 
 
     
     
       2. The microphone assembly defined in  claim 1 , wherein the opening of the printed circuit board passes through the top surface of the printed circuit board and through the bottom surface of the printed circuit board. 
     
     
       3. The microphone assembly defined in  claim 1 , wherein the opening of the printed circuit board passes through the bottom surface of the printed circuit board and not through the top surface of the printed circuit board. 
     
     
       4. The microphone assembly defined in  claim 1 , wherein the microphone is positioned entirely within the opening of the printed circuit board. 
     
     
       5. The microphone assembly defined in  claim 1 , wherein the microphone is positioned only partly within the opening of the printed circuit board. 
     
     
       6. The microphone assembly defined in  claim 1 , further comprising solder with which the microphone is directly mounted to the integrated circuit. 
     
     
       7. The microphone assembly defined in  claim 1 , further comprising solder with which the integrated circuit is directly mounted to the printed circuit board. 
     
     
       8. The microphone assembly defined in  claim 1 , wherein the integrated circuit has a thickness in the range of 50 to 300 microns. 
     
     
       9. The microphone assembly defined in  claim 1 , wherein the integrated circuit comprises the through-silicon via layered with metal. 
     
     
       10. The microphone assembly defined in  claim 1 , wherein the microphone comprises a microelectromechanical systems microphone formed from a silicon substrate, wherein the microphone has a diaphragm, wherein the silicon substrate has a microphone opening aligned with the diaphragm, wherein the microphone opening is aligned with the acoustic port so that sound is received by the diaphragm through the acoustic port and the microphone opening. 
     
     
       11. The microphone assembly defined in  claim 1 , wherein the integrated circuit has at least some metal-filled through-silicon vias that form electrical paths between the top and bottom surfaces of the integrated circuit, the microphone assembly further comprising solder with which the microphone is soldered to the top surface of the integrated circuit and with which the integrated circuit is soldered to the printed circuit board. 
     
     
       12. The microphone assembly defined in  claim 1 , further comprising solder with which the integrated circuit is mounted to the printed circuit board and with which the microphone is mounted to the integrated circuit, wherein the integrated circuit has a thickness of 50 to 300 microns and wherein the integrated circuit includes amplifier circuitry that amplifies a microphone signal from the microphone. 
     
     
       13. The microphone assembly defined in  claim 2 , further comprising solder with which the microphone is mounted to the integrated circuit, solder with which the integrated circuit is mounted to the printed circuit board, wherein the microphone is positioned entirely within the opening of the printed circuit board, and wherein the integrated circuit has a thickness in the range of 50 to 300 microns. 
     
     
       14. The microphone assembly defined in  claim 2 , further comprising solder with which the microphone is mounted to the integrated circuit, solder with which the integrated circuit is mounted to the printed circuit board, wherein the microphone is positioned only partly within the opening of the printed circuit board, and wherein the integrated circuit has a thickness in the range of 50 to 300 microns. 
     
     
       15. The microphone assembly defined in  claim 3 , further comprising solder with which the microphone is mounted to the integrated circuit, solder with which the integrated circuit is mounted to the printed circuit board, wherein the microphone is positioned entirely within the opening of the printed circuit board, and wherein the integrated circuit has a thickness in the range of 50 to 300 microns. 
     
     
       16. The microphone assembly defined in  claim 3 , further comprising solder with which the microphone is mounted to the integrated circuit, solder with which the integrated circuit is mounted to the printed circuit board, wherein the microphone is positioned only partly within the opening of the printed circuit board, and wherein the integrated circuit has a thickness in the range of 50 to 300 microns. 
     
     
       17. The microphone assembly defined in  claim 1 , further comprising solder with which the microphone is mounted to the integrated circuit, solder with which the integrated circuit is mounted to the printed circuit board, and wherein the integrated circuit has a thickness in the range of 50 to 300 microns. 
     
     
       18. A process for making a microphone assembly, comprising:
 forming a stacked die assembly by mounting a microphone to a top surface of an integrated circuit having at least one through-silicon via that forms an acoustic port so that the microphone is capable of receiving sound through the acoustic port; 
 inserting the microphone into an opening of a printed circuit board so that the microphone is positioned within the opening, wherein the printed circuit board has a top surface and a bottom surface and has at least one peripheral edge that is open and not surrounded by the printed circuit board; and 
 mounting the stacked die assembly to the printed circuit board by attaching the top surface of the integrated circuit to the bottom surface of the printed circuit board so that the integrated circuit is positioned outside of the opening of the printed circuit board. 
 
     
     
       19. The process of  claim 18 , wherein the microphone is positioned entirely within the opening.

Description:
BACKGROUND 
     This relates to assemblies of electrical and mechanical components for electronic devices, and, more particularly, to assemblies including acoustic components such as microphones. 
     Electronic devices often include acoustic components. For example, speakers may be used to produce sound for a user. Microphones may be used to gather audio input signals. In devices such as noise cancelling headphones, microphones may be used to gather ambient noise signals. Microphones may also be used to collect a user&#39;s voice or other sound input. For example, microphones may be used in cellular telephone headsets to gather a user&#39;s voice during a telephone call. 
     Space-constrained accessories such as headsets and other electronic equipment may benefit from compact microphones. It can be challenging, however, to reduce the size of conventional microphones. If care is not taken, acoustic quality will be degraded or microphone assemblies will not be sufficiently compact. 
     It would therefore be desirable to be able to provide improved microphone assemblies. 
     SUMMARY 
     Microphone assemblies may be provided that have microelectromechanical systems microphones, associated application-specific integrated circuits, and printed circuit boards. The application-specific integrated circuits may contain amplifier circuitry for amplifying microphone signals from the microphone. The microelectromechanical systems microphones may contain microphone openings that allow sound to reach associated diaphragms. 
     One or more though-silicon vias may be formed in the application-specific integrated circuit that serve as an acoustic port through which sound may pass. The application-specific integrated circuit may be thinned prior to through-silicon via formation. In the microphone assembly, the a microphone may be aligned with respect to the application-specific integrated circuit so that sound passes through the acoustic port and reaches the microphone diaphragm through the microphone opening. 
     With one illustrative arrangement, the application-specific integrated circuit may be embedded in the printed circuit board and the microphone may be mounted to the upper surface of the printed circuit board. With another illustrative arrangement, the application-specific integrated circuit and microphone may be stacked on the upper surface of the printed circuit board. With another illustrative arrangement, the microphone and application-specific integrated circuit may be mounted to the printed circuit board so that the microphone is received within an opening in the printed circuit board. 
     Further features of the invention, its nature and various advantages will be more apparent from the accompanying drawings and the following detailed description of the preferred embodiments. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a cross-sectional side view of an illustrative microphone assembly with an application-specific integrated circuit that has through-silicon vias that serve as an acoustic port and that has been embedded in a printed circuit board under a microelectromechanical systems microphone in accordance with the embodiment of the present invention. 
         FIG. 2  is a cross-sectional side view of a portion of the illustrative microphone assembly of  FIG. 2  in the vicinity of a via in accordance with an embodiment of the present invention. 
         FIG. 3  is a cross-sectional side view of an illustrative microphone assembly that includes an application-specific integrated circuit with through-silicon vias that serve as an acoustic port mounted on the surface of a printed circuit board under a microelectromechanical systems microphone in accordance with an embodiment of the present invention. 
         FIG. 4  is a cross-sectional side view of an illustrative microphone assembly in which a microelectromechanical systems microphone has been mounted in an opening in a printed circuit board and in which an application-specific integrated circuit with through-silicon vias that serve as an acoustic port has been mounted under the microelectromechanical systems microphone in accordance with an embodiment of the present invention. 
         FIG. 5  is a top view of a microphone assembly of the type shown in  FIG. 4  in accordance with an embodiment of the present invention. 
         FIG. 6  is an exploded cross-sectional side view of a microphone assembly of the type shown in  FIGS. 4 and 5  showing how the microphone assembly may be assembled in accordance with an embodiment of the present invention. 
         FIG. 7  is a top view of an illustrative microphone assembly in which a microelectromechanical systems microphone has been mounted in a corner opening in a printed circuit board in accordance with an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     This relates to assemblies that include acoustic components such as microphones and speakers. Illustrative arrangements in which the assemblies are formed from microphones are sometimes described herein as examples, but arrangements that use speakers, combinations of speakers and microphones, or other configurations may be used if desired. 
     An illustrative microphone assembly is shown in  FIG. 1 . As shown in  FIG. 1 , microphone assembly  10  may be formed by mounting a microphone such as microphone  12  and an associated application-specific integrated circuit such as integrated circuit  32  to a common substrate such as printed circuit board  24 . One or more openings in application-specific integrated circuit  32  such as one or more through-silicon vias  34  may serve as an acoustic port for assembly  10 . With this arrangement, sound from the surrounding environment may enter microphone opening  14  in microphone  12  through the acoustic port formed from vias  34 . 
     Microphone  12  may be a microelectromechanical systems (MEMs) microphone formed from a silicon substrate or may be a microphone that is implemented using other suitable microphone technologies. As shown in  FIG. 1 , microphone  12  may have a diaphragm such as diaphragm  16 . Diaphragm  16  may be located within microphone opening  14  in the lower surface of microphone  12 . An acoustic cavity for microphone  12  may be formed within the same silicon substrate as diaphragm  16  (see, e.g., cavity  18 ). Arrangements in which cavity  18  is formed within the silicon substrate from which the microphone diaphragm is formed are sometimes referred to as “back volume in die” arrangements. In configurations of the type shown in  FIG. 1  in which microphone  12  is mounted efficiently in assembly  10 , there may be an increased amount of space available in microphone  12  for forming cavity  18 . Increasing the space used for back volume cavity space  18  may help improve microphone performance (e.g., signal-to-noise ratio). Other acoustic cavity configurations may be used for microphone  12  if desired. The use of back volume in die MEMs microphones is merely illustrative. 
     Application-specific integrated circuit  32  may include circuitry for supporting the operations of microphone  12 . For example, application-specific integrated circuit  32  may contain audio amplifier circuitry that amplifies microphone signals from microphone  12  (i.e., application-specific integrated circuit  32  may be an audio integrated circuit with microphone amplifier circuitry). Application-specific integrated circuit  32  may also include ancillary circuitry such as circuits for converting analog microphone signals to digital signals, etc. 
     For satisfactory operation, it is generally desirable for application-specific integrated circuit  32  to be mounted in the vicinity of microphone  12 . In the illustrative configuration of  FIG. 1 , application-specific integrated circuit  32  is embedded within printed circuit board  24  under MEMs microphone  12  (e.g., by forming a cavity within one or more of the dielectric layers that make up printed circuit board  24  and by mounting circuit  32  in the cavity during the process of forming printed circuit board  24 ). Printed circuit board  24  may be a rigid printed circuit board (e.g., a fiberglass-filled epoxy printed circuit board such as an FR-4 printed circuit board) or a flexible printed circuit board. 
     One or more through-silicon vias  34  (i.e., openings that pass through the silicon die used to form application-specific integrated circuit  32 ) may be used to form an acoustic port (i.e., a passageway that allows sound to pass through integrated circuit  32 ). Vias  34  may be formed by etching (e.g., dry and/or wet etching). To facilitate via formation, application-specific integrated circuit  32  may be thinned before vias  34  are etched. For example, application-specific integrated circuit  32  may be thinned to a thickness of about 50-300 microns (e.g., 100-200 microns) by polishing (e.g., using chemical-mechanical polishing operations). 
     Opening  36  in printed circuit board  24  may pass through printed circuit board from lower surface  38  to upper surface  40  and may be aligned with the acoustic port in integrated circuit  32  formed from through-silicon vias  34 . This allows sound to pass through opening  36  and the acoustic port in application-specific integrated circuit  32  to reach microphone opening  14  of microphone  12  and diaphragm  16 . 
     Diaphragm  16  and the audio circuitry on application-specific integrated circuit  32  may be interconnected using solder, conductive traces, and other suitable interconnect paths. As shown in  FIG. 1 , for example, solder balls  26  may be used to mount microphone  12  to upper surface  40  of printed circuit board  24 . Vias such as via  28  (e.g., laser vias or other suitable vias) may be formed in printed circuit board  24  to connect solder bumps  26  to circuitry on application-specific integrated circuit (shown by the interconnect of via  28  and trace  30  on application-specific integrated circuit  32  in the  FIG. 1  example). 
     If desired, an encapsulant layer such as layer  20  (e.g., an epoxy layer or other suitable material) may be used to form an environmental seal for microphone  12 . Shield  22  may help to reduce electrical interference and may help protect microphone  12  from environmental exposure. 
       FIG. 2  is a cross-sectional side view of via  28  of  FIG. 1 . As shown in  FIG. 2 , via  28  may have metal  44  that is formed within via opening  42 . Metal  44  may interconnect solder ball  26  to trace  30  on application-specific integrated circuit  32 . Microphone  12  may have traces such as pad  43 . Pad  43  may be electrically coupled to diaphragm  16  ( FIG. 1 ). When mounting microphone  12 , solder ball  26  may interconnect pad  43  to via metal  44  in via  28 . Printed circuit  24  may contain traces that interconnect microphone  12  and application specific integrated circuit to wires and other circuitry in an electrical device. 
     If desired, microphone  12  and application-specific integrated circuit  32  may be mounted on upper surface  40  of printed circuit board  24 . As shown in  FIG. 3 , for example, application-specific integrated circuit  32  may be a double-sided integrated circuit that has solder pads on both its upper and lower surfaces. Active circuitry may be formed on one of the two surfaces of application-specific integrated circuit  32  (e.g., the upper surface). Through-silicon vias such as vias  49  that are filled with metal may be used in forming interconnects that route signals from the upper surface of application-specific integrated circuit  32  to the lower surface of application-specific integrated circuit. 
     Solder pads on the upper surface of application-specific integrated circuit  32  may be soldered to corresponding solder pads on the lower surface of microphone  12  using solder  46 . Solder pads on the lower surface of application-specific integrated circuit  32  may be soldered to corresponding solder pads on upper surface  40  of printed circuit board  24  using solder  48 . 
     Application-specific integrated circuit  32  may have one or more through-silicon vias  34  that form an acoustic port. Opening  36  in printed circuit board  24  may pass through printed circuit board  24  from lower surface  38  to opposing upper surface  40  and may be aligned with the acoustic port. Sound may travel through opening  36 , the acoustic port formed from through-silicon vias  34 , and opening  14  in microphone  12  to reach diaphragm  16 . As shown by dashed acoustic cavity line  18 , microphone  12  may have a back volume in die configuration. Microphone  12  and application-specific integrated circuit  32  may be covered with encapsulant  20 . 
     In the illustrative arrangement of  FIG. 4 , microphone  12  has been mounted in opening  360  in printed circuit board  24 . Opening  360  may pass entirely through printed circuit board  24  or may pass only partly through printed circuit board  24  (e.g., to form a cavity that receives all or part of microphone  12 ). 
     Application-specific integrated circuit  32  may have one or more through-silicon vias  34  that form an acoustic port. This allows sound to pass through application-specific integrated circuit  32  to reach opening  14  and diaphragm  16  of microphone  12 . 
     Microphone  12  may be mounted on the upper surface of application-specific integrated circuit  12  using solder balls  52 . Application-specific integrated circuit  32  may be mounted to the underside of printed circuit board  24  using solder balls  50 . 
     In the illustrative configurations of  FIGS. 1 and 4 , application-specific integrated circuit  32  may be a single-sided circuit (i.e., a circuit that contains active circuitry and interconnect traces only on one surface without through-silicon vias for forming back-side connections). 
     A top view of the microphone assembly of  FIG. 4  is shown in  FIG. 5 . As shown in  FIG. 5 , opening  360  may have a rectangular outline for receiving microphone  12 . Solder balls  50  may be arranged around the periphery of microphone  12  on the underside of printed circuit board  24  to mount application-specific integrated circuit  32  to the underside of printed circuit board  24 . 
     Microphone assembly  10  of  FIGS. 4 and 5  may be formed using a process of the type illustrated in  FIG. 6 . As shown in  FIG. 6 , microphone  12  may be mounted on application-specific integrated circuit  32  using solder balls  52  to form stacked die assembly  54 . Following formation of stacked die assembly  54 , stacked die assembly  54  may be moved in direction  56  to insert microphone  12  into opening  360  of printed circuit board  24 . Once microphone  12  has been inserted into opening  360 , stacked die assembly  54  may be mounted to the lower surface of printed circuit board  24  by attaching application-specific integrated circuit  32  to printed circuit board  24  with solder  50 . 
       FIG. 7  is a top view of an illustrative microphone assembly in which opening  360  in printed circuit board  24  has been formed in a corner of printed circuit board  24 . Solder  50  may be used to mount application-specific integrated circuit  32  to the underside of printed circuit board  24  within opening  360 . In the configuration of  FIG. 7 , opening  360  has the shape of a notch that is open on at least some edges (e.g., the upper and right edges in the  FIG. 7  example). In general, opening  360  may have any suitable shape (e.g., a closed opening with a periphery that is completely surrounded by portions of printed circuit board  24  or other suitable substrates, a slot-shaped opening that has an open side and that is otherwise closed, a notch-shaped corner opening of the type shown in  FIG. 7 , openings that pass through the entire thickness of printed circuit board  24 , openings that pass only partway through printed circuit board  24 , etc.). Shapes such as these may, if desired, be used for the cavity in printed circuit board  24  that encloses (or partially encloses) application-specific integrated circuit  32  of  FIG. 1  and openings such as openings  36  of  FIG. 1  and  FIG. 3 . 
     Although sometimes described in connection with solder connections, the electrical and mechanical connections that are formed in microphone assembly  10  may be formed using any suitable connection mechanisms. For example, connections may be formed using conductive springs, conductive screws, welds, conductive adhesive, or other suitable conductive materials. The use of solder joints in electrically and mechanically connecting the components of microphone assembly  10  to each other is merely illustrative. 
     The foregoing is merely illustrative of the principles of this invention and various modifications can be made by those skilled in the art without departing from the scope and spirit of the invention.

Metadata:
Filing Date: 20110531
Publication Date: 20160105
Grant Date: 20160105
Priority Date: 20110531
Inventors: MINOO JAHAN
SEROFF NICHOLAS C.
Assignee: APPLE INC
CPC Classifications: [{"code": "H04R19/005", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04R1/086", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04R1/342", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04R1/342", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04R1/086", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04R19/005", "inventive": false, "first": false, "tree": "[]"}]
Family ID: 47261702