Abstract:
A miniaturized microphone maintaining the properties of a microphone chip and achieving a smaller mounting area. The microphone includes a package which includes a first and second member. At least one of the first second members includes a recess. The microphone also includes a circuit element installed on an inner surface of the first member. Additionally, the microphone includes a microphone chip arranged on a surface on an opposite side of an installing surface of the circuit element.

Description:
BACKGROUND OF THE INVENTION 
     1. Technical Field 
     One or more embodiments of the present invention relate to microphones, and specifically, to a microphone in which a microphone chip (acoustic sensor) is accommodated in a package. 
     2. Related Art 
     For example, U.S. Pat. No. 7,166,910 describes a MEMS (Micro Electro Mechanical Systems) microphone manufactured using the MEMS technique. In the microphone described in FIG. 1 of U.S. Pat. No. 7,166,910, a package is configured by a substrate and a cover, a microphone chip and a circuit element are arranged side by side on an upper surface of the substrate, and an acoustic perforation is opened in the cover. Furthermore, in the microphone described in FIG. 31 of U.S. Pat. No. 7,166,910, the microphone chip and the circuit element are arranged side by side on the upper surface of the substrate, and the acoustic perforation is opened in the substrate at the lower surface of the microphone chip. Moreover, in the microphone described in FIG. 32 of U.S. Pat. No. 7,166,910, the microphone chip and the circuit element are arranged side by side on the upper surface of the substrate, and the acoustic perforation is opened in the substrate at a position deviated from the microphone chip. 
     Miniaturization is demanded on electronic devices particularly portable devices, and to this end, components such as a microphone need to be mounted at high density on a small circuit substrate. However, in all the MEMS microphones described in U.S. Pat. No. 7,166,910, it is difficult to miniaturize the microphone and in particular, it is difficult to reduce the occupying area at the time of mounting (hereinafter referred to as the mounting area) because the microphone chip and the circuit element are arranged side by side on the upper surface of the substrate or the lower surface of the cover. 
     It is effective to miniaturize the microphone chip and the circuit element themselves in order to miniaturize the microphone, but the sensitivity lowers if the microphone chip is miniaturized. Therefore, it is desired to reduce the dimension while maintaining the properties and to reduce the mounting area in the microphone, but these are difficult in conventional microphones. 
     SUMMARY OF INVENTION 
     One or more embodiments of the present invention have been devised to miniaturize the microphone while maintaining the properties of the microphone chip, and in particular, to achieve smaller area of the mounting area. 
     A first microphone according to one or more embodiments of the present invention includes a package including a cover and a substrate, at least one of which having a recess, a circuit element installed on an inner surface of the cover, and a microphone chip arranged on a surface on an opposite side of an installing surface of the circuit element; wherein the microphone further includes: a microphone terminal arranged on the microphone chip and a plurality of input/output terminals arranged on the circuit element, wherein the microphone terminal and some of the plurality of input/output terminals are connected by a wire wiring, wherein the remaining input/output terminals arranged on the circuit element and a pad portion arranged on a surface facing the substrate of the cover are connected by a wire wiring, and wherein the pad portion arranged on the cover and a pad portion arranged on the substrate are joined by a conductive material. 
     This is a configuration for a case where the circuit element and the microphone chip are mounted on the inner surface of the cover with the microphone chip mounted on the circuit element. In the first microphone of one or more embodiments of the present invention, the microphone can be miniaturized by effectively using the vertical space in the package because the circuit element and the microphone chip are accommodated in the package with the microphone chip stacked on the circuit element. In particular, the bottom area of the package can be reduced compared to the case where the circuit element and the microphone chip are arranged side by side, so that the mounting area of the microphone can be reduced. Furthermore, the performance of the microphone does not lower because the microphone chip and the circuit element themselves do not need to be reduced in size to miniaturize the microphone. 
     Further, in the first microphone according to one or more embodiments of the present invention, the cover can be joined to the substrate after the wiring task by the wire wiring is completed in only the cover. Even if the circuit element and the microphone chip are mounted on the cover, the circuit element and the microphone chip can be connected to the substrate by joining the pad portion of the cover and the pad portion of the substrate with the conductive material. Therefore, the assembly task of the microphone can be easily carried out. Furthermore, higher reliability and lower cost of the microphone can be achieved because the structure is simple. 
     A second microphone according to one or more embodiments of the present invention includes a package including a cover and a substrate, at least one of which having a recess, a microphone chip installed on an inner surface of the cover, and a circuit element arranged on a surface on an opposite side of an installing surface of the microphone chip; wherein the microphone further includes: a microphone terminal arranged on the microphone chip and a plurality of input/output terminals arranged on the circuit element, wherein the microphone terminal and some of the plurality of input/output terminals are connected by a wire wiring, wherein the remaining input/output terminals arranged on the circuit element and a pad portion arranged on a surface facing the substrate of the cover are connected by a wire wiring, and the pad portion arranged on the cover and a pad portion arranged on the substrate are joined by a conductive material. 
     This is a configuration for a case where the microphone chip and the circuit element are mounted on the inner surface of the cover with the circuit element mounted on the microphone chip. In the second microphone of one or more embodiments of the present invention, the microphone can be miniaturized by effectively using the vertical space in the package because the circuit element and the microphone chip are accommodated in the package with the circuit element stacked on the microphone chip. In particular, the bottom area of the package can be reduced compared to the case where the circuit element and the microphone chip are arranged side by side, so that the mounting area of the microphone can be reduced. Furthermore, the performance of the microphone does not lower because the microphone chip and the circuit element themselves do not need to be reduced in size to miniaturize the microphone. 
     Further, in the second microphone according to one or more embodiments of the present invention, the cover can be joined to the substrate after the wiring task by the wire wiring is completed in only the cover. Even if the circuit element and the microphone chip are mounted on the cover, the circuit element and the microphone chip can be connected to the substrate by joining the pad portion of the cover and the pad portion of the substrate with the conductive material. Therefore, the assembly task of the microphone can be easily carried out. Furthermore, higher reliability and lower cost of the microphone can be achieved because the structure is simple. 
     A third microphone according to one or more embodiments of the present invention includes a package including a cover and a substrate, at least one of which having a recess, a circuit element installed on an inner surface of the cover, and a microphone chip arranged on a surface on an opposite side of an installing surface of the circuit element; wherein the microphone further includes: a microphone terminal arranged on the microphone chip and a plurality of input/output terminals arranged on the circuit element, wherein the microphone terminal and some of the plurality of input/output terminals are connected by a through-wiring arranged in the microphone chip, and the remaining input/output terminals arranged on the circuit element and a pad portion arranged on a surface facing the substrate of the cover are connected by a wire wiring, and the pad portion arranged on the cover and a pad portion arranged on the substrate are joined by a conductive material. 
     This is a configuration for a case where the circuit element and the microphone chip are mounted on the inner surface of the cover with the microphone chip mounted on the circuit element. 
     In the third microphone of one or more embodiments of the present invention, the microphone can be miniaturized by effectively using the vertical space in the package because the circuit element and the microphone chip are accommodated in the package with the microphone chip stacked on the circuit element. In particular, the bottom area of the package can be reduced compared to the case where the circuit element and the microphone chip are arranged side by side, so that the mounting area of the microphone can be reduced. Furthermore, the performance of the microphone does not lower because the microphone chip and the circuit element themselves do not need to be reduced in size to miniaturize the microphone. 
     Further, in the third microphone according to one or more embodiments of the present invention, the cover can be joined to the substrate after the wiring task by the wire wiring or the through-wiring is completed in only the cover. Even if the circuit element and the microphone chip are mounted on the cover, the circuit element and the microphone chip can be connected to the substrate by joining the pad portion of the cover and the pad portion of the substrate with the conductive material. Therefore, the assembly task of the microphone can be easily carried out. Furthermore, higher reliability and lower cost of the microphone can be achieved because the structure is simple. 
     A fourth microphone according to one or more embodiments of the present invention includes a package including a cover and a substrate, at least one of which having a recess, a microphone chip installed on an inner surface of the cover, and a circuit element arranged on a surface on an opposite side of an installing surface of the microphone chip; wherein the microphone further includes: a microphone terminal arranged on the microphone chip and a plurality of input/output terminals arranged on the circuit element, wherein the microphone terminal and some of the plurality of input/output terminals are connected by a through-wiring arranged in the circuit element, wherein the remaining input/output terminals arranged on the circuit element and a pad portion arranged on a surface facing the substrate of the cover are connected by a wire wiring, and the pad portion arranged on the cover and a pad portion arranged on the substrate are joined by a conductive material. 
     This is a configuration for a case where the circuit element and the microphone chip are mounted on the inner surface of the cover with the circuit element mounted on the microphone chip. 
     In the fourth microphone of one or more embodiments of the present invention, the microphone can be miniaturized by effectively using the vertical space in the package because the circuit element and the microphone chip are accommodated in the package with the circuit element stacked on the microphone chip. In particular, the bottom area of the package can be reduced compared to the case where the circuit element and the microphone chip are arranged side by side, so that the mounting area of the microphone can be reduced. Furthermore, the performance of the microphone does not lower because the microphone chip and the circuit element themselves do not need to be reduced in size to miniaturize the microphone. 
     Further, in the fourth microphone according to one or more embodiments of the present invention, the cover can be joined to the substrate after the wiring task by the wire wiring or the through-wiring is completed in only the cover. Even if the circuit element and the microphone chip are mounted on the cover, the circuit element and the microphone chip can be connected to the substrate by joining the pad portion of the cover and the pad portion of the substrate with the conductive material. Therefore, the assembly task of the microphone can be easily carried out. Furthermore, higher reliability and lower cost of the microphone can be achieved because the structure is simple. 
     The input/output terminal of one or more embodiments of the present invention may function as both an input terminal and an output terminal, may function as an input terminal, or may function as an output terminal (the same is true hereinafter). 
     The acoustic perforation for transmitting the acoustic vibration into the package may be arranged in the member in which the microphone chip and the circuit element are arranged out of the cover and the substrate (namely, the cover), or may be arranged in a different member (namely, the substrate). The acoustic perforation may adopt various aspects described below. First, the acoustic perforation may be arranged in the cover. This is the case of arranging the acoustic perforation in the member in which the microphone chip and the circuit element are arranged. 
     In another aspect, in the first or third microphone in which the circuit element is mounted on the cover and the microphone chip is arranged on the front surface thereof, the acoustic perforation is arranged in continuation to the cover and the circuit element, so that the opening of the acoustic perforation at the outer surface side of the cover and the opening of the acoustic perforation at the inner surface side of the circuit element may at least partially overlap when viewed from the direction perpendicular to the bottom surface of the package. According to such an aspect, the acoustic vibration can be easily transmitted to the package. 
     In still another aspect, in the first or third microphone in which the circuit element is mounted on the cover and the microphone chip is arranged on the front surface thereof, the acoustic perforation is arranged in continuation to the cover and the circuit element, so that the opening of the acoustic perforation at the outer surface side of the cover and the opening of the acoustic perforation at the inner surface side of the circuit element may not overlap when viewed from the direction perpendicular to the bottom surface of the package. According to such an acoustic perforation, foreign substances can be prevented from entering the package or the microphone chip from the acoustic perforation, and environmental factors such as light or moisture can be prevented from entering from the acoustic perforation so that the microphone chip and the circuit element are less likely to be affected. 
     In yet another aspect, in the first or third microphone in which the circuit element is mounted on the cover, and the microphone chip is arranged on the front surface thereof, the acoustic perforation is arranged in continuation to the cover and the circuit element, so that the acoustic perforation may be bent so that the opening on the inner surface side of the circuit element is not linearly viewed from the opening on the outer surface side of the cover. According to such an acoustic perforation, foreign substances can be prevented from entering the package or the microphone chip from the acoustic perforation, and environmental factors such as light or moisture can be prevented from entering from the acoustic perforation so that the microphone chip and the circuit element are less likely to be affected. 
     In yet another aspect, in the second or fourth microphone in which the microphone chip is mounted on the cover and the circuit element is arranged on the front surface thereof, the acoustic perforation for transmitting the acoustic vibration to the package may be arranged in the cover so that at least one part faces the diaphragm of the microphone chip when viewed from the direction perpendicular to the bottom surface of the package. According to such an aspect, the acoustic vibration can be easily transmitted to the diaphragm, so that the sensitivity of the microphone can be enhanced. 
     The acoustic perforation may be formed in the substrate. This is a case in which the acoustic perforation is formed in a member different from the member on which the microphone chip and the circuit element are arranged. 
     Further, in such an aspect, the acoustic perforation may be bent so that the opening on the inner surface side of the substrate cannot be linearly viewed from the opening on the outer surface side of the substrate. According to such an acoustic perforation, foreign substances can be prevented from entering the package or the microphone chip from the acoustic perforation, and environmental factors such as light or moisture can be prevented from entering from the acoustic perforation so that the microphone chip and the circuit element are less likely to be affected. 
     At least one of the cover or the substrate is desirably configured by at least one type of material including copper laminated stacked plate, glass epoxy, ceramic, plastic, metal, or carbon nano tube. 
     One or more embodiments of the present invention has a characteristic of appropriately combining the configuring elements described above, and the one or more embodiments of the present invention enables a great number of variations by the combination of the configuring elements. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  is a perspective view from an upper surface side of a microphone according to a first embodiment of the present invention, and  FIG. 1B  is a perspective view from a lower surface side of the microphone of the first embodiment; 
         FIG. 2A  is a plan view showing a substrate of the microphone of the first embodiment, and  FIG. 2B  is a cross-sectional view of the microphone of the first embodiment taken along a portion corresponding to line X 1 -X 1  in  FIG. 2A ; 
         FIG. 3A  is a perspective view from an upper surface side of a microphone according to a second embodiment of the present invention, and  FIG. 3B  is a perspective view from a lower surface side of the microphone of the second embodiment; 
         FIG. 4A  is a plan view showing a substrate of the microphone of the second embodiment, and  FIG. 4B  is a cross-sectional view of the microphone of the second embodiment taken along a portion corresponding to line X 2 -X 2  in  FIG. 4A ; 
         FIG. 5A  is a bottom view showing a cover of a microphone according to a third embodiment of the present invention, and  FIG. 5B  is a cross-sectional view of the microphone of the third embodiment taken along a portion corresponding to line X 3 -X 3  in  FIG. 5A ; 
         FIG. 6A  is a bottom view showing a cover of a microphone according to a fourth embodiment of the present invention, and  FIG. 6B  is a cross-sectional view of the microphone of the fourth embodiment taken along a portion corresponding to line X 4 -X 4  in  FIG. 6A ; 
         FIG. 7A  is a plan view showing a substrate of a microphone according to a fifth embodiment of the present invention, and  FIG. 7B  is a cross-sectional view of the microphone of the fifth embodiment taken along a portion corresponding to line X 5 -X 5  in  FIG. 7A ; 
         FIG. 8A  is a bottom view showing a cover of a microphone according to a sixth embodiment of the present invention, and  FIG. 8B  is a cross-sectional view of the microphone of the sixth embodiment taken along a portion corresponding to line X 6 -X 6  in  FIG. 8A ; 
         FIG. 9A  is a plan view showing a substrate of a microphone according to a seventh embodiment of the present invention, and  FIG. 9B  is a cross-sectional view of the microphone of the seventh embodiment taken along a portion corresponding to line X 7 -X 7  in  FIG. 9A ; 
         FIG. 10  is a plan view of the circuit element used in the seventh embodiment; 
         FIG. 11A  is a plan view showing the substrate of a microphone according to an eighth embodiment of the present invention, and  FIG. 11B  is a cross-sectional view of the microphone of the eighth embodiment taken along a portion corresponding to line X 8 -X 8  in  FIG. 11A ; 
         FIG. 12A  is a plan view showing the substrate of a microphone according to a ninth embodiment of the present invention, and  FIG. 12B  is a cross-sectional view of the microphone of the ninth embodiment taken along a portion corresponding to line X 9 -X 9  in  FIG. 12A ; 
         FIG. 13A  is a plan view showing the substrate of a microphone according to a tenth embodiment of the present invention, and  FIG. 13B  is a cross-sectional view of the microphone of the tenth embodiment taken along a portion corresponding to line X 10 -X 10  in  FIG. 13A ; 
         FIG. 14A  is a bottom view showing the cover of a microphone according to an eleventh embodiment of the present invention, and  FIG. 14B  is a cross-sectional view of the microphone of the eleventh embodiment taken along a portion corresponding to line X 11 -X 11  in  FIG. 14A ; 
         FIG. 15A  is a bottom view showing the cover of a microphone according to a twelfth embodiment of the present invention, and  FIG. 15B  is a cross-sectional view of the microphone of the twelfth embodiment taken along a portion corresponding to line X 12 -X 12  in  FIG. 15A ; 
         FIG. 16A  is a plan view showing the substrate of a microphone according to a thirteenth embodiment of the present invention, and  FIG. 16B  is a cross-sectional view of the microphone of the thirteenth embodiment taken along a portion corresponding to line X 13 -X 13  in  FIG. 16A ; and 
         FIG. 17A  is a plan view showing the substrate of a microphone according to a fourteenth embodiment of the present invention, and  FIG. 17B  is a cross-sectional view of the microphone of the fourteenth embodiment taken along a portion corresponding to line X 14 -X 14  in  FIG. 17A . 
     
    
    
     DETAILED DESCRIPTION 
     Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. It should be noted that the present invention is not limited to the following embodiments, and that various design changes can be made within a scope not deviating from the present invention. In embodiments of the invention, numerous specific details are set forth in order to provide a more thorough understanding of the invention. However, it will be apparent to one with ordinary skill in the art that the invention may be practiced without these specific details. In other instances, well-known features have not been described in detail to avoid obscuring the invention. 
     First Embodiment 
     An upper surface sound hole type microphone  11  according to a first embodiment of the present invention will be described with reference to  FIGS. 1A and 1B , and  FIGS. 2A and 2B .  FIGS. 1A and 1B  are a perspective view from an upper surface side and a perspective view from a lower surface side of the microphone  11  according to the first embodiment.  FIG. 2A  is a plan view of a substrate  15  on which a microphone chip  12  and a circuit element  13  are mounted, and  FIG. 2B  is a cross-sectional view of the microphone  11  taken along an area corresponding to line X 1 -X 1  in  FIG. 2A . Such a microphone  11  is a MEMS microphone manufactured using the MEMS technique, where the microphone chip  12  and the circuit element  13  are accommodated in a package made from a cover  14  (one of a cover or a substrate) and a substrate  15  (other one of the cover or the substrate). The structure of the microphone  11  will be specifically described below. 
     As shown in  FIGS. 2A and 2B , the substrate  15  is formed by a flat plate shaped multi-layer wiring substrate, where a conductive layer  18  for electromagnetic shield is arranged substantially entirely. A substrate side joining portion  20  is formed by the conductive layer  18  at an outer peripheral part of the upper surface of the substrate  15 . A plurality of pad portions  26   a  conducted to an external connection terminal  29  at the back surface through a through hole  30  and a pad portion  26   b  conducted to the substrate side joining portion  20  are arranged on the upper surface of the substrate  15 . 
     The lower surface of the circuit element  13  such as an IC chip is adhered to the upper surface of the substrate  15  by a die attach material  21  made of an insulating or conductive adhesive, or the like. The entire periphery of the lower surface of the microphone chip  12  is adhered to the upper surface of the circuit element  13  by a die attach material  22  made of an insulating or conductive adhesive, or the like. 
     The microphone chip  12  is mainly configured by an Si substrate  41 , through which a chamber  42  (back chamber) passes in the up and down direction, a diaphragm  43  including a polysilicon thin film, and a back plate  44 . The diaphragm  43  is arranged to cover the chamber  42  while slightly floating from the upper surface of the Si substrate  41 , and sympathizes to acoustic vibration to film vibrate. The back plate  44  is configured by a fixed portion including SiN and a fixed electrode including a polysilicon thin film, where a great number of acoustic holes  45  for passing the acoustic vibration are opened in the back plate  44 . In such a microphone chip  12 , the diaphragm  43  and the fixed electrode of the back plate  44  configure a capacitor, where when the diaphragm  43  vibrates by the acoustic vibration, an electrostatic capacity between the diaphragm  43  and the fixed electrode of the back plate  44  changes according to the acoustic vibration. At least a pair of microphone terminals  23  is provided on the front surface of the microphone chip  12 , and a detection signal corresponding to the change in the electrostatic capacity between the diaphragm  43  and the fixed electrode is output from the microphone terminals  23 . 
     At least a pair of MEMS input/output terminals  24 , and a plurality of external connection input/output terminals  25   a  and ground terminals  25   b  are provided on the upper surface of the circuit element  13 . The microphone terminal  23  of the microphone chip  12  and the input/output terminal  24  of the circuit element  13  are connected by a bonding wire  27  (wire wiring). The input/output terminal  25   a  of the circuit element  13  is connected to the pad portion  26   a  of the substrate  15  by a bonding wire  28  (wire wiring), and the ground terminal  25   b  of the circuit element  13  is connected to the pad portion  26   b  of the substrate  15  by the bonding wire  28 . Thus, the detection signal output from the microphone chip  12  is input into the circuit element  13  from the input/output terminal  24 , and output from the input/output terminal  25   a  to the external connection terminal  29  after a predetermined signal processing is performed. The region where the input/output terminals  24 ,  25   a  and the ground terminal  25   b  are arranged in the upper surface of the circuit element  13  may be covered with a protective material  34  made of insulating resin, or the like. 
     Other than the multi-layer wiring substrate, the substrate  15  may be formed by a copper laminated stacked plate, a glass epoxy substrate, a ceramic substrate, a plastic substrate, a metal substrate, a carbon nano tube substrate, or a compound substrate thereof. For example, the substrate  15  manufactured by performing plating on a front surface of a plate of a plastic molded article may be used. A recess for accommodating the circuit element  13  may be formed at the upper surface of the substrate  15 . 
     As shown in  FIG. 2B , the cover  14  is formed to a box shape, and includes a recess  31  at the lower surface. A conductive layer  32  for electromagnetic shield is formed substantially entirely on the top surface and the side wall surfaces of the recess  31  as well as the lower surface of the side wall surrounding the recess  31 . The conductive layer  32  formed on the top surface of the cover  14  extends to the interior of the insulating material. The conductive layer  32  at the lower surface of the side wall becomes a cover side joining portion  33  to be joined with the substrate  15 . The cover  14  is formed by performing plating on the inner surface and the lower surface of the cover main body made from at least one material of a copper laminated stacked plate or a glass epoxy, ceramic, plastic, metal, or carbon nano tube or a complex material thereof. For example, the cover  14  in which plating is performed on the front surface of the plastic molded article integrally molded to a cover shape may be used. 
     The cover  14  is overlapped on the upper surface of the substrate  15  with the recess  31  facing the lower side, and the cover side joining portion  33  and the substrate side joining portion  20  are joined by the conductive material  17 . The package is configured by the cover  14  and the substrate  15  integrated in such a manner, and the microphone chip  12  and the circuit element  13  are accommodated in the package. One of a conductive adhesive or solder, a conductive both-sided adhesive tape, or a wax material for welding may be used or a plurality of materials of the same may be simultaneously used for the conductive material  17 . A non-conductive resin or a non-conductive tape may be simultaneously used to laminate the cover  14  and the substrate  15 . 
     As a result of joining the cover side joining portion  33  and the substrate side joining portion  20  with the conductive material  17 , the conductive layer  32  of the cover  14  and the conductive layer  18  of the substrate  15  are conducted, so that the conductive layers  32  and  18  are held at ground potential by connecting the conductive layer  18  to an earth line such as a circuit substrate, and the microphone  11  is shielded from the external electromagnetic noise. 
     An acoustic perforation  16  that enters the acoustic vibration into the package is opened in the upper surface of the cover  14 , where the acoustic vibration that entered the package from the acoustic perforation  16  reaches the diaphragm  43  through the acoustic hole  45  and vibrates the diaphragm  43 . 
     In the microphone  11  of the first embodiment of the present invention, that in which the microphone chip  12  is stacked on the circuit element  13  is mounted on the upper surface of the substrate  15 , and hence the vertical space of the package can be used and the microphone  11  can be miniaturized. In particular, the mounting area of the microphone  11  can be reduced compared to the microphone in which the circuit element and the microphone chip are arranged side by side, and thus it is suited for high density mounting. Furthermore, the properties of the microphone chip  12  do not lower because the microphone chip  12  itself does not need to be miniaturized to miniaturize the microphone  11 . 
     In the manufacturing process of the microphone  11 , the microphone chip  12  and the circuit element  13  can be connected with the bonding wire  27  and the circuit element  13  and the substrate  15  can be connected with the bonding wire  28  with the circuit element  13  installed on the upper surface of the substrate  15  and the microphone chip  12  installed thereon. Accordingly, the cover  14  can be joined onto the substrate  15  after all the wiring tasks are completed, and the assembly task can be easily carried out. The cost is also inexpensive because the microphone  11  has a simple structure. 
     Second Embodiment 
       FIGS. 3A and 3B  are a perspective view from an upper surface side and a perspective view from a lower surface side of a microphone  51  according to a second embodiment of the present invention.  FIG. 4A  is a plan view of a substrate  15  on which a microphone chip  12  and a circuit element  13  are mounted, and  FIG. 4B  is a cross-sectional view of the microphone  51  taken along an area corresponding to line X 2 -X 2  in  FIG. 4A . 
     The microphone  51  of the second embodiment differs from the microphone  11  of the first embodiment in that the acoustic perforation  16  is arranged not in the cover  14  but at a position deviated from the circuit element  13  in the substrate  15 . In particular, the acoustic perforation  16  is opened at a position adjacent to the circuit element  13  to miniaturize the microphone  51 . The structure substantially similar to the microphone  11  of the first embodiment is adopted for other aspects, and thus the same reference numerals are denoted for the same configuring portions in the drawings and the description will be omitted. Functions and effects similar to the first embodiment are also obtained in such a microphone  51 . 
     Third Embodiment 
     A microphone  52  according to a third embodiment of the present invention will now be described.  FIG. 5A  is a bottom view of the cover  14  on which the microphone chip  12  and the circuit element  13  are mounted in the microphone  52  of the third embodiment, and  FIG. 5B  is a cross-sectional view of the microphone  52  taken along an area corresponding to line X 3 -X 3  in  FIG. 5A . 
     In the microphone  52  of the third embodiment, the circuit element  13  and the microphone chip  12  are installed on the lower surface of the cover  14  while being turned upside down. In other words, the circuit element  13  is installed on the top surface in the recess  31  of the cover  14  by the die attach material  21  while being turned upside down. The microphone chip  12  is fixed to the lower surface of the circuit element  13  by the die attach material  22  while being turned upside down. A plurality of pad portions  26   c  is arranged on the lower surface of the cover  14  while being electrically insulated with the cover side joining portion  33  (conductive layer  32 ). 
     The microphone terminal  23  arranged on the lower surface of the microphone chip  12  and the input/output terminal  24  arranged on the lower surface of the circuit element  13  are connected by the bonding wire  27 . The input/output terminal  25   a  arranged at the lower surface of the circuit element  13  is connected to the pad portion  26   c  at the lower surface of the cover  14  by the bonding wire  28 , and the ground terminal  25   b  is connected to the cover side joining portion  33  by the bonding wire  28 . 
     The cover  14  on which the microphone chip  12  and the circuit element  13  are mounted is overlapped on the substrate  15 , and the cover side joining portion  33  and the substrate side joining portion  20  are joined by the conductive material  17 . The pad portion  26   a  is arranged at a position facing the pad portion  26   c  when the cover  14  is overlapped at the upper surface of the substrate  15 , and the pad portion  26   a  is conducted with the external connection terminal  29  arranged at the back surface of the substrate  15 . When overlapping the cover  14  on the substrate  15 , the pad portion  26   c  of the cover  14  is connected to the pad portion  26   a  of the substrate  15  by the conductive material  17 . 
     Therefore, the conductive layer  32  of the cover  14  is conducted with the conductive layer  18  of the substrate  15  through the cover side joining portion  33 , the conductive material  17 , and the substrate side joining portion  20 , and maintained at ground potential. The output signal from the input/output terminal  25   a  of the circuit element  13  is output from the external connection terminal  29  through the pad portion  26   c , the conductive material  17 , and the pad portion  26   a.    
     The acoustic perforation  16  for introducing the acoustic vibration into the package is arranged in the cover  14  at the position adjacent to the circuit element  13 . 
     In the microphone  52  of the third embodiment as well, the microphone chip  12  and the circuit element  13  are mounted in the cover  14  so as to be stacked, and hence the microphone  52  can be miniaturized and in particular, the mounting area of the microphone  52  can be reduced. Furthermore, the assembly task is facilitated because the cover  14  is overlapped and joined to the upper surface of the substrate  15  after the wiring of the microphone chip  12  and the circuit element  13  is carried out by the bonding wire  27  and the wiring of the circuit element  13  and the pad portion  26   c  by the bonding wire  28  is completed. 
     Fourth Embodiment 
       FIG. 6A  is a bottom view of the cover  14  on which the microphone chip  12  and the circuit element  13  are mounted in a microphone  53  of a fourth embodiment of the present invention, and  FIG. 6B  is a cross-sectional view of the microphone  53  taken along an area corresponding to line X 4 -X 4  in  FIG. 6A . 
     The microphone  53  of the fourth embodiment differs from the microphone  52  of the third embodiment in that the acoustic perforation  16  is arranged not in the cover  14  but in the substrate  15 . 
     Fifth Embodiment 
       FIG. 7A  is a plan view of the substrate  15  on which the microphone chip  12  and the circuit element  13  are mounted in a microphone  54  according to a fifth embodiment of the present invention, and  FIG. 7B  is a cross-sectional view of the microphone  54  taken along an area corresponding to line X 5 -X 5  in  FIG. 7A . 
     In the microphone  54  of the fifth embodiment, the circuit element  13  mounted with the microphone chip  12  is mounted on the upper surface of the substrate  15 . The acoustic perforations  16 ,  16   a  are opened in the substrate  15  and the circuit element  13  at the lower surface of the chamber  42  of the microphone chip  12 . Therefore, in the microphone  54 , the chamber  42  is a front chamber because the acoustic vibration enters from the lower surface side of the chamber  42 . The back chamber of the microphone chip  12  becomes wider because the space in the package becomes the back chamber, whereby the sensitivity of the microphone chip  12  improves. 
     Sixth Embodiment 
       FIG. 8A  is a bottom view of the cover  14 , on which the microphone chip  12  and the circuit element  13  are mounted, in a microphone  55  according to a sixth embodiment of the present invention, and  FIG. 8B  is a cross-sectional view of the microphone  55  taken along an area corresponding to line X 6 -X 6  in  FIG. 8A . 
     In the microphone  55  of the sixth embodiment, the circuit element  13  mounted with the microphone chip  12  is mounted on the lower surface of the cover  14 . The acoustic perforations  16 ,  16   a  are opened in the cover  14  and the circuit element  13  at the upper surface of the chamber  42  of the microphone chip  12 . Therefore, the space in the package becomes the back chamber and the sensitivity of the microphone chip  12  improves in the microphone  55  as well. 
     Seventh Embodiment 
       FIG. 9A  is a plan view of the substrate  15 , on which the microphone chip  12  and the circuit element  13  are mounted, in a microphone  56  according to a seventh embodiment of the present invention, and  FIG. 9B  is a cross-sectional view of the microphone  56  taken along an area corresponding to line X 7 -X 7  in  FIG. 9A .  FIG. 10  is a plan view of the circuit element  13  used in the microphone  56  of the seventh embodiment. 
     In the microphone  56  of the seventh embodiment, the acoustic perforations  16 ,  16   a  opened in the substrate  15  and the circuit element  13  at the lower side of the chamber  42  are bent. In  FIG. 10 , the acoustic perforation  16   a  is bent in the circuit element  13 , but the acoustic perforation  16  may be bent in the substrate  15  or both acoustic perforations  16 ,  16   a  may be bent. The acoustic perforation  16  and the acoustic perforation  16   a  are bent such that the opening on the outer surface side of the package of the acoustic perforation  16  and the opening on the inner surface side of the package (chamber  42  side) of the acoustic perforation  16   a  do not overlap when viewed from a direction perpendicular to the bottom surface of the package. The acoustic perforations are bent so that one opening cannot be seen linearly from the other opening. 
     In the microphone  56 , the acoustic perforations  16 ,  16   a  are bent and the opening on the outer surface side of the package of the acoustic perforation  16  and the opening on the inner surface side of the package of the acoustic perforation  16   a  are not overlapped when viewed from the direction perpendicular to the bottom surface of the package, and hence foreign substances such as dust are less likely to enter the chamber  42  from the acoustic perforations  16 ,  16   a , so that the lowering of the performance of the microphone chip  12  when the foreign substance that entered clogs up, for example, the gap between the diaphragm  43  and the Si substrate  41  can be prevented. Furthermore, the acoustic perforations  16 ,  16   a  are bent such that the opening on the inner surface side of the package is not linearly seen from the opening on the outer surface side of the package, and hence light rays, moisture (humidity), and the like are less likely to enter from the acoustic perforations  16 ,  16   a  and the microphone chip  12  is less likely to degrade by such environmental factors. 
     Note that, a case in which the microphone chip  12  and the circuit element  13  are mounted on the substrate  15  has been described, but the acoustic perforations  16 ,  16   a  may be bent for a case in which the microphone chip  12  and the circuit element  13  are mounted on the cover  14 . 
     Eighth Embodiment 
       FIG. 11A  is a plan view of the substrate  15 , on which the microphone chip  12  and the circuit element  13  are mounted, in a microphone  57  according to an eighth embodiment of the present invention, and  FIG. 11B  is a cross-sectional view of the microphone  57  taken along an area corresponding to line X 8 -X 8  in  FIG. 11A . 
     In the microphone  57 , the circuit element  13  is mounted on the upper surface of the substrate  15 , the microphone chip  12  is fixed on the circuit element  13 , the acoustic perforation  16  is opened in the substrate  15  at immediately below the microphone chip  12 , and the acoustic perforation  16   a  is opened in the circuit element  13 . The acoustic perforation  16  and the acoustic perforation  16   a  are communicated to each other, where the opening on the outer surface side of the package of the acoustic perforation  16  and the opening on the inner surface side of the package (chamber  42  side) of the acoustic perforation  16   a  may be substantially overlapped (may be completely overlapped or partially overlapped) when viewed from the direction perpendicular to the bottom surface of the package. The acoustic perforations  16 ,  16   a  are bent such that the opening on the inner surface side of the package is not linearly seen from the opening on the outer surface side of the package. To this end, the acoustic perforations  16 ,  16   a  are refracted twice, as shown in  FIG. 11B . 
     Therefore, in the microphone  57  as well, foreign substances such as dust are less likely to enter the chamber  42  from the acoustic perforations  16 ,  16   a  because the acoustic perforations  16 ,  16   a  are bent such that the opening on the inner surface side of the package cannot be linearly seen from the opening on the outer surface side of the package. Furthermore, light rays, moisture (humidity), and the like are also less likely to enter from the acoustic perforations  16 ,  16   a , so that the microphone chip  12  is not likely to degrade by such environmental factors. 
     The shape or structure of the acoustic perforations in the seventh embodiment and the eighth embodiment can be applied to the acoustic perforations formed in the cover or the acoustic perforations formed in a member different from the member on which the circuit element and the microphone chip are mounted. 
     One opening may be seen from the other opening when the opening on the outer surface side of the package of the acoustic perforation  16  and the opening on the inner surface side of the package of the acoustic perforation  16   a  are overlapped at least partially or not overlapped when viewed from the direction perpendicular to the bottom surface of the package. In this case, the effect of preventing foreign substances, light rays, moisture, and the like from entering lowers but the acoustic vibration can be easily transmitted to the microphone chip  12 . 
     Ninth Embodiment 
       FIG. 12A  is a plan view of the substrate  15 , on which the microphone chip  12  and the circuit element  13  are mounted, in a microphone  58  according to a ninth embodiment of the present invention, and  FIG. 12B  is a cross-sectional view of the microphone  58  taken along an area corresponding to line X 9 -X 9  in  FIG. 12A . 
     In the microphone  58 , the microphone chip  12  is fixed to the upper surface of the substrate  15  by the die attach material  22 , and the circuit element  13  is fixed to the upper surface of the microphone chip  12  by the die attach material  21 . The microphone chip  12  has a larger area than the diaphragm  43  and the back plate  44  in plan view, and the circuit element  13  is arranged in a region where the diaphragm  43 , the back plate  44 , and the microphone terminal  23  are not arranged in the upper surface of the microphone chip  12 . 
     In this case as well, the microphone terminal  23  of the microphone chip  12  and the input/output terminal  24  of the circuit element  13  are connected with the bonding wire  27 , the input/output terminal  25   a  of the circuit element  13  and the pad portion  26   a  of the substrate  15  are connected with the bonding wire  28 , and the ground terminal  25   b  of the circuit element  13  and the pad portion  26   b  of the substrate  15  are connected with the bonding wire  28 . 
     Therefore, the circuit element  13  can be stacked on the microphone chip  12 , so that the microphone  58  can be miniaturized and in particular, the mounting area can be reduced in this mode as well. In the microphone  58 , the chamber  42  becomes the back chamber of the microphone chip  12  and the capacity of the back chamber can be increased, so that the sensitivity of the microphone chip  12  can be enhanced. 
     Tenth Embodiment 
       FIG. 13A  is a plan view of the substrate  15 , on which the microphone chip  12  and the circuit element  13  are mounted, in a microphone  59  according to a tenth embodiment of the present invention, and  FIG. 13B  is a cross-sectional view of the microphone  59  taken along an area corresponding to line X 10 -X 10  in  FIG. 13A . 
     The microphone  59  has a structure substantially similar to the microphone  58  of the ninth embodiment, but differs in that the acoustic perforation  16  is opened in the substrate  15  so as to communicate to the chamber  42  of the microphone chip  12  at the position facing the diaphragm  43 . 
     Eleventh Embodiment 
       FIG. 14A  is a bottom view of the cover  14 , on which the microphone chip  12  and the circuit element  13  are mounted, in a microphone  60  according to an eleventh embodiment of the present invention, and  FIG. 14B  is a cross-sectional view of the microphone  60  taken along an area corresponding to line X 11 -X 11  in  FIG. 14A . 
     The microphone  60  has the microphone chip  12 , on the upper surface of which the circuit element  13  is arranged, turned upside down and installed at the lower surface of the cover  14 , and the acoustic perforation  16  opened in the substrate  15 . 
     Twelfth Embodiment 
       FIG. 15A  is a bottom view of the cover  14 , on which the microphone chip  12  and the circuit element  13  are mounted, in a microphone  61  according to a twelfth embodiment of the present invention, and  FIG. 15B  is a cross-sectional view of the microphone  61  taken along an area corresponding to line X 12 -X 12  in  FIG. 15A . 
     The microphone  61  has the microphone chip  12 , on the upper surface of which the circuit element  13  is arranged, turned upside down and installed at the lower surface of the cover  14 , and the acoustic perforation  16  opened in the cover  14  so as to communicate to the chamber  42  of the microphone chip  12  at the position facing the diaphragm  43 . 
     Thirteenth Embodiment 
       FIG. 16A  is a plan view of the substrate  15 , on which the microphone chip  12  and the circuit element  13  are mounted, in a microphone  62  according to a thirteenth embodiment of the present invention, and  FIG. 16B  is a cross-sectional view of the microphone  62  taken along an area corresponding to line X 13 -X 13  in  FIG. 16A . 
     In the microphone  62 , a connection terminal  36  is provided at the lower surface of the microphone chip  12  in correspondence with the microphone terminal  23  provided at the upper surface of the microphone chip  12 , and the microphone terminal  23  at the upper surface and the connection terminal  36  at the lower surface are conducted by a through-electrode  35  passing through the microphone chip  12  in the up and down direction. Furthermore, a connection terminal  39  is provided at the lower surface of the circuit element  13  in correspondence with the input/output terminal  25   a  provided at the upper surface of the circuit element  13 , and the input/output terminal  25   a  at the upper surface and the connection terminal  39  at the lower surface are conducted by a through-electrode  38  passing through the circuit element  13  in the up and down direction. 
     The microphone chip  12  connects the microphone terminal  23  at the upper surface to the input/output terminal  24  of the circuit element  13  by connecting the connection terminal  36  at the lower surface to the input/output terminal  24  at the upper surface of the circuit element  13  by a solder  37 . Furthermore, the circuit element  13  connects the input/output terminal  25   a  at the upper surface to the pad portion  26   a  of the substrate by connecting the connection terminal  39  at the lower surface to the pad portion  26   a  of the substrate  15  by a solder  40 . 
     Similar to the input/output terminal  25   a , the ground terminal  25   b  at the upper surface of the circuit element  13  is also connected to the pad portion  26   b  of the substrate  15  using a through-electrode, but this is not shown in the drawing. 
     If the microphone chip  12  and the circuit element  13 , and the circuit element  13  and the substrate  15  are connected using the through-electrode in the above manner, the possibility of bending like the bonding wire and making contact with other circuit elements is eliminated, and the short circuit accidents of the microphone  62  can be prevented. 
     Fourteenth Embodiment 
       FIG. 17A  is a plan view of the substrate  15 , on which the microphone chip  12  and the circuit element  13  are mounted, in a microphone  63  according to a fourteenth embodiment of the present invention, and  FIG. 17B  is a cross-sectional view of the microphone  63  taken along an area corresponding to line X 14 -X 14  in  FIG. 17A . 
     In the microphone  63 , the connection terminal  36  provided at the lower surface of the microphone chip  12  is connected to the input/output terminal  24  at the upper surface of the circuit element  13  by the solder, so that the microphone terminal  23  at the upper surface of the microphone chip  12  is connected to the input/output terminal  24  of the circuit element  13 . Furthermore, the input/output terminal  25   a  and the ground terminal  25   b  provided at the upper surface of the circuit element  13  are connected to the pad portions  26   a ,  26   b  of the substrate  15  by the bonding wire  28 . 
     In each embodiment described above, the bonding wire can be appropriately replaced with the through-electrode. For example, in the microphone  11  of  FIGS. 2A and 2B , only the bonding wire  28  connecting the circuit element  13  and the substrate  15  may be replaced with the through-electrode. Furthermore, even in the case in which the microphone chip  12  and the circuit element  13  are mounted on the cover  14  as in the microphone  52  of  FIGS. 5A and 5B , the bonding wire  27  connecting the microphone chip  12  and the circuit element  13  can be replaced with the through-electrode. 
     While the invention has been described with respect to a limited number of embodiments, those skilled in the art, having the benefit of this disclosure, will appreciate that other embodiments can be devised which do not depart from the scope of the invention as disclosed herein. Accordingly, the scope of the invention should be limited only by the attached claims.