Abstract:
A MEMS microphone module includes a substrate and a conducting lid covered on the substrate to define a chamber therebetween for accommodation of a MEMS chip and an ASIC chip. A ground layer of the substrate is electrically coupled to a protrusion of the conductive lid to form an EMI shielding structure. By this way, an EMI shielding effect can be applied by the EMI shielding structure to the MEMS chip and the ASIC chip.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention The present invention relates generally to a micro-electro-mechanical system (hereinafter referred to as “MEMS”) microphone and more particularly, to a MEMS microphone module that has a simple structure and low manufacturing cost. 
         [0002]    2. Description of the Related Art 
         [0003]    With the advance of the science and the technology, MEMS microphones having great advantages of small size and powerful function have been widely developed and used. When the MEMS microphone is used to receive the external sounds, it may be easily interfered by external factors (such as electromagnetic waves) which may cause poor signal quality or errors, resulting in lower added value of electrical products equipped with the conventional MEMS microphone. Thus, how to enhance an electromagnetic interference (hereinafter referred to as “EMI”) shielding effect of the MEMS microphone is the most important concern for manufacturing industries. 
         [0004]    Taiwan Patent No. 1299961 discloses a MEMS microphone and a method of manufacturing the same. The MEMS microphone includes a substrate and a lid covered on the substrate and having a third conducting layer electrically coupled to a second conducting layer, which is formed of a conductive sliver glue, of the substrate. Further, an EMI shielding structure is created by the electrical connection among a first conducting layer of a frame, the second conducting layer of the substrate, the third conducting layer of the lid, and a grounding device for providing an EMI shielding to an IC chip. However, this prior art design has a disadvantage of high material cost and needs to address a manufacturing challenge that the conductive sliver glue has to be contacted with both of the first and third conducting layers, resulting in increase of manufacturing cost. 
         [0005]    Taiwan Patent Publication No. 201101851 discloses a MEMS acoustic sensor package. In the second embodiment of this prior art design, the upper and middle plates of the lid are attached to each other through an conductive adhesive, the middle plate of the lid and the support plate are attached to each other through an electrically insulating adhesive, and the lid and the support plate are electrically coupled to each other through an elastic sheet for providing an EMI shielding effect. However, it is difficult to control the dimension of the elastic sheet and the process of connecting the upper plate of the lid to the support plate is a little bit complicated, so that this prior art design has the disadvantage of high manufacturing cost. 
       SUMMARY OF THE INVENTION 
       [0006]    The present invention has been accomplished in view of the above-noted circumstances. It is therefore the primary objective of the present invention to provide a MEMS microphone module, which can simplify structure and reduce manufacturing cost. 
         [0007]    To achieve the above-mentioned objective, the micro-electro-mechanical system (MEMS) microphone module provided by the present invention comprises a substrate, a MEMS chip mounted with the substrate, an application-specific integrated circuit (ASIC) chip mounted with the substrate and electrically coupled to the MEMS chip, and a conducting lid covered on the substrate to define a chamber therebetween for accommodation of the MEMS chip and the ASIC ship. The conducting lid has an acoustic hole communicated with the chamber and a protrusion at a bottom side thereof electrically coupled to a ground layer of the substrate to create an EMI shielding structure for applying an EMI shielding effect to the MEMS chip and the ASIC chip. 
         [0008]    By means of this design, the MEMS microphone module of the present invention is assembled by the attachment of the substrate and the conducting lid, and provided with the EMI shielding structure by the electrical connection of the ground layer of the substrate and the protrusion of the conducting lid, such that the MEMS microphone module of the present invention can attain the purpose of simplifying the overall structure and reducing the manufacturing cost. 
         [0009]    Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]    The present invention will become more fully understood from the detailed description given herein below and the accompanying drawings which are given by way of illustration only, and thus are not limitative of the present invention, and wherein: 
           [0011]      FIG. 1  is a cross-sectional view of a MEMS microphone module in accordance with a first embodiment of the present invention; 
           [0012]      FIG. 2  is a cross-sectional view of a MEMS microphone module in accordance with a second embodiment of the present invention; 
           [0013]      FIG. 3  is a cross-sectional view of a MEMS microphone module in accordance with a third embodiment of the present invention; and 
           [0014]      FIG. 4  is a cross-sectional view of a MEMS microphone module in accordance with a forth embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0015]    Referring to  FIG. 1 , a micro-electro-mechanical system (MEMS) microphone module  10  provided by a first embodiment of the present invention comprises a substrate  20 , a MEMS chip  30 , an application-specific integrated circuit (hereinafter referred to as “ASIC”) chip  40 , and a conducting lid  50 . 
         [0016]    The substrate  20  has a first concavity  21  at the top side thereof, a second concavity  22  at the top side thereof spaced from the first concavity  21 , and a ground layer  23 . The ground layer  23  has a first section  232  arranged at the top side of the substrate  20 , a second section  234  connected with the first section  232  and vertically arranged inside the substrate  20 , and a third section  236  connected with the second section  234  and horizontally arranged inside the substrate  20 . 
         [0017]    The MEMS chip  30  and the ASIC chip  40  are disposed in the first and second concavities  21  and  22  of the substrate  20 . The ASIC chip  40  is electrically coupled to the first section  232  of the ground layer  23  of the substrate  20  and the MEMS chip  30  through two wires  60  respectively. 
         [0018]    The conducting lid  50  is made of metal, including a top wall  51  and a lateral wall  52  extending from a periphery of the top wall  51  and attached to the top side of the substrate  20  through an adhesive  53  (such as an insulating adhesive or conductive adhesive), such that a chamber  54  is define between the conducting lid  50  and the substrate  20  for accommodation of the MEMS chip  30  and the ASIC chip  40 . An acoustic hole  512  is provided at the top wall  51  of the conducting lid  50  and communicated with the outsides for enabling the MEMS chip  30  to receive the external sounds therethrough. Further, a protrusion  55  extends integrally from the bottom side of the top wall  51  of the conducting lid  50  and is electrically contacted with the first section  232  of the ground layer  23  of the substrate  20 , such that an EMI shielding structure  70  is created by the electrical connection of the protrusion  55  of the conducting lid  50  and the ground layer  23  of the substrate  20  for providing an EMI shielding effect to the MEMS chip  30  and the ASIC chip  40 . 
         [0019]    To deserve to be mentioned, if the insulating adhesive is used between the substrate  20  and the conducting lid  50 , the conducting lid  50  and the substrate  20  are electrically coupled to each other through the contact between the protrusion  55  of the conducting lid  50  and the ground layer  23  of the substrate  20 . On the other hand, if the conductive adhesive is used between the substrate  20  and the conducting lid  50 , the electrical connection (especially in ground connection) between the conducting lid  50  and the substrate  20  can be ensured by the contact between the protrusion  55  of the conducting lid  50  and the ground layer  23  of the substrate  20 . Besides, the protrusion  55  of the conducting lid  50  can be electrically coupled to the ground layer  23  of the substrate  20  through a conductive adhesive for ensuring the electrical connection between the protrusion  55  and the ground layer  23 . 
         [0020]    When compared with the conducting member (such as the conductive sliver glue or the elastic sheet) of the prior art design, the MEMS microphone module  10  of the present invention has a relatively simpler structure adopting the cooperation of the ground layer  23  of the substrate  20  and the protrusion  55  of the conducting lid  50  to offer the desired EMI shielding effect. Further, as stated above, the conductive adhesive can be used between the ground layer  23  of the substrate  20  and the protrusion  55  of the conducting lid  50  if the protrusion  55  is not long enough to touch the ground layer  23 . Accordingly, the MEMS microphone module  10  of the present invention has the advantage of simplifying overall structure and reducing manufacturing cost. 
         [0021]    To deserve to be mentioned, the protrusion  55  of the conducting lid  50  can be electrically coupled to the ground layer  23  of the substrate  20  through a conducting member, such as a metal wire  80  shown in  FIG. 2  or a metal elastic sheet  90  shown in  FIG. 3 , for creating the EMI shielding structure  70 . Further, as shown in  FIG. 4 , the protrusion  55  can be forced to protrude from the bottom side of the top wall  51  of the conducting lid  50  by stamping process or other processes, and therefore a recess  56  will be formed at the top side of the conducting lid  50  and arranged opposite to the protrusion  55 . 
         [0022]    The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.