JP2008136195A - Condenser microphone - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a condenser microphone with a high resonant frequency of an acoustic hole and an electroacoustic transducer comprising the same. <P>SOLUTION: The present invention relates to a condenser microphone comprising a package forming a cavity inside and including a through-hole; a plate being bonded to the package, including an acoustic hole overlapped with the through-hole and being thinner than a length of the through-hole; and an electroacoustic transducer die housed in a part of the cavity. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a condenser microphone and an electroacoustic transducer including the same, and more particularly to a condenser microphone as a MEMS sensor package.

Conventionally, a condenser microphone as a MEMS sensor package is known. In Patent Document 1, an electroacoustic conversion die bonded to a wiring board is covered with a cover, and an acoustic hole for allowing sound waves to reach the electroacoustic conversion die in the package is formed in the cover of the package or the wiring board. A condenser microphone is described. Since an element that adversely affects the operation of the die in the package, such as dust, light, and water droplets, can enter from the acoustic hole, it is desirable that the acoustic hole be as small as possible.
US Patent Application Publication No. 2005/0185812

  However, resonance at the acoustic hole occurs at a lower frequency as the acoustic hole becomes smaller and longer. Therefore, if a small-diameter acoustic hole is formed in the wiring board itself or the cover itself corresponding to the bottom of the package, the length of the acoustic hole becomes equal to these thicknesses, so that resonance can occur in the audible range.

  An object of the present invention is to provide a condenser microphone having a high resonance frequency of an acoustic hole and an electroacoustic transducer having the same.

(1) A condenser microphone for achieving the above object includes a package having a cavity inside and having a through hole, an acoustic hole joined to the package and overlapping the through hole, and the length of the through hole. A thinner plate and an electroacoustic transducer die housed in a portion of the cavity.
According to this condenser microphone, a plate that is thinner than the length of the through hole of the package is joined to the package, and an acoustic hole is formed in the plate. Therefore, the length of the acoustic hole is shorter than when the acoustic hole is formed in the package itself. can do. Therefore, according to this condenser microphone, the resonance frequency of the acoustic hole can be increased.

(2) In the condenser microphone for achieving the above object, the package has a bottom portion having the through hole and joined to an external wiring board, and the cavity is formed on the inside together with the bottom portion and joined to the bottom portion. And a cover. In this case, the plate may be bonded to the bottom and thinner than the bottom. Further, in this case, the electroacoustic conversion die is bonded to the bottom portion or the plate around the acoustic hole and supports the stationary electrode and the vibrating electrode on the inner side, the vibrating electrode with respect to the stationary electrode, and the acoustic hole. And an annular support portion.
In this case, since the acoustic hole and the electroacoustic conversion die overlap, the footprint of the condenser microphone can be reduced. In this case, since the sound wave directly reaches the inside of the electroacoustic transducer die from the bottom of the package, a large volume of the outer space of the electroacoustic transducer die in the package can be used as a back cavity, and as a result, the cut-off The frequency can be lowered. The ring-shaped support portion may have any shape that surrounds the stationary electrode and the vibration electrode, and the inner and outer contours may be circular, rectangular, square, or polygonal. Good.

(3) In the condenser microphone for achieving the above object, it is preferable that the acoustic hole has a length of 100 μm or less, and the acoustic hole has a diameter of 100 μm or less.
The length of the acoustic hole corresponds to the thickness of the plate around the acoustic hole.

  (4) In the condenser microphone for achieving the above object, the plate is preferably made of a metal material.

(5) In the condenser microphone for achieving the above object, the plate may comprise a lead frame.
In the case of a package using a lead frame, the structure can be simplified and the manufacturing cost can be reduced by forming an acoustic hole in the lead frame.

(6) In the condenser microphone for achieving the above object, the bottom portion may be a multilayer wiring board, and the plate may be made of a conductive film bonded to the multilayer wiring board.
In this case, since the plate can be bonded to the multilayer wiring board in the manufacturing process of the multilayer wiring board, the manufacturing cost can be reduced.

(7) In the condenser microphone for achieving the above object, the bottom portion may be a multilayer wiring board, and the plate may be made of a conductive film included in the multilayer wiring board.
Also in this case, since the plate can be bonded to the multilayer wiring board in the manufacturing process of the multilayer wiring board, the manufacturing cost can be reduced.

(8) A condenser microphone for achieving the above object, comprising a plurality of the plates, wherein the bottom is a multilayer wiring board, each of the plurality of plates being bonded to the multilayer wiring board and sandwiching an insulating layer therebetween It may consist of conductive films overlapping with each other.
Also in this case, since the plate can be bonded to the multilayer wiring board in the manufacturing process of the multilayer wiring board, the manufacturing cost can be reduced.

(9) In the condenser microphone for achieving the above object, the acoustic hole formed by the first conductive film and the acoustic hole formed by the second conductive film may not overlap. desirable.
In this case, since the dust, light, and water droplets cannot enter the package unless they pass through the acoustic holes formed in the two conductive films, the use environment adaptability of the condenser microphone is improved.

(10) In the condenser microphone for achieving the above object, a breathable sheet may be further provided between the first conductive film and the second conductive film.
In this case, the use environment adaptability of the condenser microphone is improved.

(11) In the condenser microphone for achieving the above object, a water repellent film may be formed around at least the acoustic hole on the back surface of the plate with the electroacoustic conversion die as a reference.
In this case, the drip-proof performance of the condenser microphone is improved.

(12) In the condenser microphone for achieving the above object, the outer periphery of the plate may include the projection area of the electroacoustic conversion die.
In general, the output impedance of an electroacoustic transducer die of a condenser microphone is high. In this case, since the plate functions as a noise shield of the electroacoustic conversion die, the S / N of the condenser microphone can be improved.

(13) In the condenser microphone for achieving the above object, the plate may be connected to a ground potential wiring.
In this case, since the noise shielding effect of the plate is improved, the S / N of the condenser microphone can be further improved.

(14) An electroacoustic transducer for achieving the above object includes a condenser microphone and an external wiring board to which the condenser microphone is joined. The condenser microphone has a bottom having a through hole and joined to an external wiring board, a cover joined to the bottom and forming a cavity inside with the bottom, and joined to the bottom, from the length of the through hole A thin plate having an acoustic hole that overlaps with the through-hole, and a ring that is housed in a part of the cavity and supports the stationary electrode, the vibrating electrode with respect to the stationary electrode, and the stationary electrode and the vibrating electrode on the inside. And an electroacoustic conversion die provided with a support part. The external wiring board has a second through hole that overlaps the through hole.
According to this electroacoustic transducer, since the acoustic hole is formed in the plate that is thinner than the length of the bottom through hole joined to the external wiring board, the acoustic hole is formed in the bottom part joined to the external wiring board. In comparison, the length of the acoustic hole can be shortened. Therefore, according to this condenser microphone, the resonance frequency of the acoustic hole can be increased.

(15) In the electroacoustic transducer for achieving the above object, the support portion may be joined to the bottom portion or the plate around the acoustic hole.
In this case, since the acoustic hole and the electroacoustic conversion die overlap, the footprint of the condenser microphone can be reduced, and as a result, the entire apparatus can be reduced in size. In this case, since the sound wave directly reaches the inside of the electroacoustic conversion die from the bottom part joined to the external wiring board, a large volume of the outer space of the electroacoustic conversion die in the package can be used as a back cavity. As a result, the cutoff frequency can be lowered.

Embodiments of the present invention will be described below with reference to the accompanying drawings.
(First Example)
Configuration of electroacoustic transducer FIG. 1A is a cross-sectional view showing the main part of a first embodiment of the electroacoustic transducer according to the present invention. This electroacoustic conversion device is a device having a function of converting sound into an electric signal, such as a mobile phone terminal, a voice recorder, and a notebook personal computer. An external wiring board 17 on which various electronic components are mounted is housed in a housing (not shown) that constitutes the outer shell of the electroacoustic transducer. The condenser microphone 1 is joined to the external wiring board 17 via a BGA (Ball Grid Array) not shown. A second through-hole 171 is formed in the external wiring board 17 immediately below the condenser microphone 1. The second through-hole 171 is a hole for allowing sound waves to pass to the condenser microphone 1. A through hole for allowing sound waves to pass through to the second through hole 171 is formed in the casing constituting the outer shell of the electroacoustic transducer.

Configuration of Condenser Microphone The condenser microphone 1 includes an electroacoustic conversion die 12, an impedance conversion die 18, a package 16 that accommodates these, and a plate 19 joined to the package 16. The electroacoustic conversion die 12 and the impedance conversion die 18 are electrically connected by wire bonding using a gold wire 13 or the like. The impedance conversion die 18 is electrically connected to the wiring of the package 16 by wire bonding, flip chip bonding, or the like.

.. Electroacoustic Conversion Die The electroacoustic conversion die 12 has a function of converting sound waves into electrical signals. The electroacoustic conversion die 12 has a structure in which a conductive film such as a doped silicon thin film and an insulating film such as a silicon oxide film are stacked on a silicon wafer. The electroacoustic conversion die 12 is provided with a vibrating electrode 123 that constitutes a counter electrode of a capacitor, a stationary electrode 122 corresponding thereto, and an annular support portion 124 that supports these electrode films. The support portion 124 is joined around the acoustic hole 191 of the plate 19.

  The vibrating electrode 123 is configured as a diaphragm that partitions two spaces. Of the two spaces partitioned by the vibrating electrode 123, a space where a sound wave that is a conversion target of the electroacoustic conversion die 12 arrives is referred to as an acoustic space, and the other space is referred to as a back cavity. Since the plurality of rear through holes 121 are formed in the stationary electrode 122 positioned in the back cavity, the back cavity partitioned by the vibration electrode 123 includes the external space of the electroacoustic conversion die 12 inside the package 16. Although FIG. 1A shows an example in which the stationary electrode 122 is positioned in the back cavity, the stationary electrode 122 may be positioned in the acoustic space. In this case, the sound wave that has passed through the through hole formed in the stationary electrode 122 reaches the vibrating electrode 123.

  FIG. 6A is a schematic cross-sectional view showing an example of a laminated structure of the electroacoustic conversion die 12. The electroacoustic conversion die 12 is a laminated structure of a substrate and a thin film made of a die substrate 12a, a lower insulating film 12b, a lower conductive film 12c, a spacer insulating film 12d, an upper conductive film 12e, a surface insulating film 12f, and the like. The substrate and the thin film constituting the electroacoustic conversion die 12 are bonded to each other. Such an electroacoustic conversion die 12 has, for example, a lower conductive film 12c, an upper conductive film 12e, a lower conductive film 12c, a spacer insulating film 12d, an upper conductive film 12e, and a surface insulating layer on a silicon wafer to be a die substrate 12a. The film 12f and the like are formed by deposition, or these thin films are patterned and then diced.

  FIG. 6B is a schematic diagram for explaining a correspondence relationship between a substrate, a thin film, and mechanical components of the electroacoustic transducer die 12 that constitute the electroacoustic transducer die 12. In FIG. 6B, the substrate constituting the electroacoustic conversion die 12, the thin film interface, and the thin film interface are indicated by broken lines. The stationary electrode 122 is made of an upper conductive film 12e such as a doped silicon thin film. The outer periphery of the stationary electrode 124 may be circular, rectangular, or polygonal. The vibrating electrode 123 is made of a lower conductive film 12c such as a doped silicon thin film. The outer periphery of the vibrating electrode 123 may be circular, rectangular, or polygonal. The vibrating electrode 123 is at least partially opposed to the stationary electrode 122 with a gap in between. That is, the vibrating electrode 123 and the stationary electrode 122 constitute a counter electrode of the capacitor. The support portion 124 is a multilayer structure including a die substrate 12a, a lower insulating film 12b, a lower conductive film 12c, a spacer insulating film 12d, an upper conductive film 12e, a surface insulating film 12f, and the like. The support portion 124 has a shape surrounding the stationary electrode 122 and the vibrating electrode 123. The vibration electrode 123, the stationary electrode 122, and the die substrate 12a are electrically connected to the impedance conversion die 18 through a through electrode or a bonding pad formed of a conductive film (not shown).

  As described above, a part of the upper conductive film 12e constitutes the stationary electrode 122, and the remaining part of the upper conductive film 12e constitutes a part of the support part 124. Therefore, as a mechanical structure, all or a part of the outer periphery of the stationary electrode 122 is coupled to the support portion 124, and the stationary electrode 122 is supported inside the support portion 124. Further, as described above, a part of the lower conductive film 12 c is included in the vibrating electrode 123, and the remaining part of the lower conductive film 12 c is included in the support part 124. For this reason, as a mechanical structure, all or part of the outer periphery of the vibration electrode 123 is coupled to the support portion 124, and the vibration electrode 123 is supported inside the support portion 124.

  When the electroacoustic conversion die 12 having the structure shown in FIGS. 6A and 6B is bonded to the plate 19 so that the stationary electrode 122 is located in the back cavity, the die substrate 12a is airtightly bonded to the plate 19 by an adhesive, for example. The When the electroacoustic conversion die 12 having the structure shown in FIGS. 6A and 6B is bonded to the plate 19 so that the stationary electrode 122 is located in the acoustic space, the surface insulating film 12f is bonded to the plate 19 in an airtight manner, for example, by an adhesive. Is done.

  Conventionally, the back cavity is formed in the substrate of the electroacoustic conversion die 12 and is formed by a through hole whose one end is closed by a package. The cutoff frequency of the condenser microphone 1 can be lowered as the volume of the back cavity increases. Although it is not easy to form through holes in a substrate made of a silicon wafer or the like by etching, if it is necessary to secure the volume of the back cavity with the through holes formed in the silicon wafer, it is necessary to form deep through holes in the thick silicon wafer. is there. In this embodiment, since the surplus space inside the package 16 can be used as a back cavity, the cut-off frequency can be increased as compared with the case where the back cavity is formed by etching. In addition, since it is not necessary to secure the volume of the back cavity only in the inner space of the electroacoustic conversion die 12, the condenser microphone 1 can be thinned by thinning the electroacoustic conversion die 12. Note that the smaller the volume of the space between the plate 19 and the vibrating electrode 123 and the larger the area of the vibrating electrode 123, the more the sensitivity of the condenser microphone 1 is improved. Therefore, the distance between the plate 19 and the vibrating electrode 123 is reduced to reduce vibration. It is desirable to increase the area of the electrode 123.

  Since the stationary electrode 122 in which the rear through-hole 121 is formed does not vibrate due to the sound wave transmitted through the acoustic space, the vibrating electrode 123 vibrates with respect to the stationary electrode 122. When the vibrating electrode 123 receiving the sound wave vibrates with respect to the stationary electrode 122, the capacitance of the capacitor formed by these counter electrodes changes, so that the sound is converted into an electric signal by the electroacoustic conversion die 12.

.. Impedance conversion die The impedance conversion die 18 is a charge pump (not shown) for applying a bias voltage to one of the stationary electrode 122 and the vibrating electrode 123, and the impedance connected to the other of the stationary electrode 122 and the vibrating electrode 123. A converter (not shown) is provided. The impedance converter reduces the high impedance output of the electroacoustic conversion die 12 to low impedance and improves the noise resistance of the condenser microphone 1.

Package The package 16 includes a bottom portion 162 formed of a multilayer wiring board, and a cover 161 that forms a cavity inside the package 16 together with the bottom portion 162.

  The bottom portion 162 has an open box shape having a laminated structure of a conductive film (not shown) for forming wiring for connecting the impedance conversion die 18 and the external wiring board 17 and a ceramic sheet (not shown). A through hole 163 that overlaps and communicates with the second through hole 171 formed in the external wiring substrate 17 is formed in the bottom portion 162. As shown in FIG. 1B, the through-hole 163 is located immediately below the electroacoustic conversion die 12, and overlaps the vibration electrode 123 with the plate 19 interposed therebetween.

  The cover 161 joined to the bottom portion 162 covers the bottom portion 162 so that sound waves do not enter the inside of the package 16 from other than the through holes 163 of the bottom portion 162. The cover 161 is preferably made of a conductor that provides a shielding effect against noise, and more preferably connected to a ground potential.

.. Plate The plate 19 is thinner than the minimum thickness of any of the cover 161 and the bottom portion 162 constituting the package 16. When the thickness of the plate 19 is compared with the through hole 163 formed in the package 16, the plate 19 is thinner than the length of the through hole 163. The plate 19 has an outer periphery that includes the projection region F1 of the electroacoustic transducer die 12, as shown in FIG. 1B. The plate 19 is made of a conductive film made of a metal material or the like, and is joined to the bottom 162 of the package 16. As the material of the plate 19, for example, stainless steel, beryllium copper, Fe—Ni alloy (64 alloy), or the like can be selected. Since the plate 19 is bonded to the electroacoustic transducer die 12, it is desirable to select a material having a thermal expansion coefficient close to that of the silicon wafer. Further, it is desirable to connect the plate 19 to the ground potential in order to enhance the shielding effect against noise.

An acoustic hole 191 is formed in the plate 19. As shown in FIG. 1B, the acoustic hole 191 overlaps and communicates with the through hole 163 of the bottom portion 162. Since dust, water droplets, light, and the like other than sound can enter from the acoustic hole 191, the smaller the cross-sectional area of the acoustic hole 191 is better from the viewpoint of preventing the entry of dust, water droplets, light, and the like. On the other hand, the smaller the cross-sectional area of the acoustic hole 191 is, the lower the resonance frequency of the acoustic hole 191 is. Therefore, the larger the cross-sectional area of the acoustic hole 191 is better from the viewpoint of raising the resonance frequency beyond the audible range. Moreover, in order to make the resonant frequency of the acoustic hole 191 higher than the audible range, the shorter the acoustic hole 191 is, the better. Since the length of the acoustic hole 191 is equal to the thickness of the plate 19, the thinner the plate 19, the better. In this embodiment, the resonance frequency is increased by shortening the length of the acoustic hole 191, and the entry of dust, water droplets, light, etc. is prevented by reducing the cross-sectional area of the acoustic hole 191. Specifically, when the cross section of the acoustic hole 191 is circular, the diameter is desirably 100 μm or less, and the thickness of the plate 19 is desirably 100 μm or less. Thus, the plate 19 for forming the short acoustic hole 191 can be formed of a film formed of a metal material on the surface of the bottom portion 162 by printing or coating. If the plate 19 is thin, it is easy to form a through-hole having a small cross-sectional area, and the acoustic hole 191 having a small cross-sectional area can be formed in the plate 19 by etching using photolithography, laser processing, pressing, or the like. it can.
..Effect In the structure of the first embodiment described above, the diameter of the acoustic hole 191 is 100 μm, the length of the acoustic hole 191 is 100 μm, the distance between the vibration electrode 123 and the plate 19 is 512 μm, and the vibration electrode 123 is a circle having a diameter of 700 μm. When the resonance frequency of the condenser microphone 1 is simulated, it becomes about 25 kHz, and the resonance frequency of the condenser microphone 1 becomes higher than the audible range.

(Second embodiment)
FIG. 2A is a cross-sectional view showing a main part of a second embodiment of the electroacoustic transducer according to the present invention. Constituent elements common to the first embodiment are denoted by common reference numerals, and redundant description is omitted. The second embodiment differs from the first embodiment in that the bottom 162 of the package 16 of the condenser microphone 2 is made of resin mold and the plate is made of a lead frame 14 sealed with resin.

  The condenser microphone 2 of the second embodiment includes a lead frame 14 constituting a SOP (Small Outline Package), a QFP (Quad Flat Package), a PGA (Pin Grid Array), and the like. An electroacoustic conversion die 12 and an impedance conversion die 18 are joined to the lead frame 14. The lead frame 14 has a lead (not shown) that is wire-bonded to the impedance conversion die 18, and this lead protrudes outside a bottom portion 162 made of a resin mold. By configuring the plate for forming the acoustic hole 142 having a narrow and short cross-sectional area with the lead frame 14, the structure of the package can be simplified and the manufacturing cost can be reduced.

  A part of the lead frame 14 that is not sealed by the resin mold is formed thinner than the remaining part, and a short acoustic hole 142 having a small cross-sectional area is formed in the thin part. The portion of the lead frame 14 where the acoustic hole 142 is formed is thinner than the minimum thickness of any of the cover 161 and the bottom portion 162 constituting the package 16. It is desirable to form a water repellent film 141 in the vicinity of the acoustic hole 142 on the surface exposed to the outside of the package 16 of the lead frame 14 as shown in FIG. 2B. The water repellent film 141 is formed by coating the lead frame 141 with a water repellent thin film such as silicon rubber or fluororesin. By forming the water repellent film 141 in the vicinity of the acoustic hole 142 exposed to the outside of the package 16, it is possible to prevent water droplets from entering the package 16. The water repellent film 141 is preferably formed on a portion including at least the periphery of the acoustic hole 142 of the lead frame 141, and is preferably formed on both the front and back surfaces of the lead frame 141 around the acoustic hole 142. It is desirable to form.

(Third embodiment)
FIG. 3A is a sectional view showing an essential part of a third embodiment of the electroacoustic transducer according to the present invention. Constituent elements common to the first embodiment are denoted by common reference numerals, and redundant description is omitted. The third embodiment is different from the first embodiment in that the plate 15 is composed of a conductive film included in a bottom portion 162 made of a multilayer wiring board.

  The plate 15 is configured as a conductive film which is a part of the multilayer structure of the multilayer wiring board. The conductive film constituting the plate 15 is thinner than the minimum thickness of any of the cover 161 and the bottom portion 162 constituting the package 16. A short acoustic hole 151 having a small cross-sectional area is formed in the plate 15. The plate 15 has an outer periphery including the projection area F1 of the electroacoustic conversion die 12 and the projection area F2 of the impedance conversion die 18. The plate 15 is connected to the ground potential, and the footprint of the package 16 and the footprint of the plate 15 are substantially equal. Therefore, in the condenser microphone 3 of the third embodiment, the shielding effect against noise of the plate 15 is higher than the shielding effect exhibited by the plates of the first and second embodiments.

  In the structure of the third embodiment described above, the diameter of the acoustic hole 151 is 100 μm, the length of the acoustic hole 151 is 100 μm, the distance between the vibration electrode 123 and the plate 15 is 512 μm, and the surface from the bottom 162 to the surface of the plate 15 When the resonance frequency of the condenser microphone 3 is simulated with a depth of 150 μm and the vibrating electrode 123 having a diameter of 700 μm, the resonance frequency of the condenser microphone 3 is about 22 kHz, and the resonance frequency of the condenser microphone 3 is higher than the audible range.

(Fourth embodiment)
FIG. 4A is a sectional view showing an essential part of a fourth embodiment of the electroacoustic transducer according to the present invention. Constituent elements common to the first embodiment and the third embodiment are denoted by common reference numerals, and redundant description is omitted. The fourth embodiment constitutes a part of a laminated structure of a first plate 19 in which a plate having acoustic holes is bonded to the surface of a bottom portion 162 made of a multilayer wiring substrate and a multilayer wiring substrate constituting the bottom portion 162. In the point comprised by the 2nd plate 15 which consists of the electrically conductive film which is comprised, it is the structure which combined the 1st Example and the 3rd Example.

  The first plate 19 and the second plate 15 of the condenser microphone 4 of the fourth embodiment are joined to the insulating layer of the multilayer wiring board located between them. As shown in FIGS. 4A and 4B, the acoustic hole 191 formed in the first plate 19 and the acoustic hole 151 formed in the second plate 15 do not overlap but communicate with each other. The sound wave that has passed through the two acoustic holes 151 and 191 reaches the vibration electrode 123. Since the acoustic hole 151 and the acoustic hole 191 do not overlap with each other, light, dust, water droplets, or the like hardly enter the package 16 from the two acoustic holes 151 and 191.

  In the structure of the fourth embodiment described above, the diameter of the acoustic holes 191 and 151 is 100 μm, the length of the acoustic holes 191 and 151 is 100 μm, the distance between the vibrating electrode 123 and the first plate 19 is 512 μm, When the resonance frequency of the condenser microphone 1 is simulated with the distance between the plate 19 and the second plate 15 being 150 μm and the vibration electrode 123 being a circle having a diameter of 700 μm, the resonance frequency of the gap between the first plate 19 and the second plate 15 is The resonance frequency of the gap between the vibrating electrode 123 and the first plate 19 is about 25 kHz, and the resonance frequency of the condenser microphone 1 is higher than the audible range.

(Fifth embodiment)
FIG. 5 is a sectional view showing an essential part of a fifth embodiment of the electroacoustic transducer according to the present invention. Constituent elements common to the fourth embodiment are denoted by common reference numerals, and redundant description is omitted. The condenser microphone 5 of the fifth embodiment is different from the fourth embodiment in that a breathable sheet 11 is provided between the first plate 19 and the second plate 15.

  The breathable sheet 11 is sandwiched between the first plate 19 and the second plate 15 inside a through-hole 163 formed in the bottom 162 made of a multilayer wiring board. The breathable sheet 11 is made of a nonwoven fabric or a fiber material having both breathability and drip-proof properties. Since the condenser microphone 5 includes the breathable sheet 11, light, dust, water droplets, and the like are less likely to enter the package 16 from the two acoustic holes 151 and 191.

(Other examples)
Although the embodiments of the present invention have been described in detail according to the examples, the present invention is not limited to the above-described examples, and various modifications can be made without departing from the scope of the present invention. Of course. For example, the smaller the number of acoustic holes formed in the plate, the higher the resonance frequency, but the number of acoustic holes formed in one plate is not limited to one, and three or more plates are formed by three or more plates. A hole may be formed. The acoustic hole may be formed in a plate that is bonded to the cover of the package, or may be formed in a plate that is bonded to the side wall of the package. Further, a plate for forming a short acoustic hole having a small cross-sectional area may be formed of an inorganic material such as a resin other than a metal material or a ceramic. In addition, the configuration in which two dies are accommodated inside the packaged condenser microphone is illustrated, but one die has an electroacoustic conversion function and an impedance conversion function, and one die having these two functions is packaged. Is also possible.

FIG. 1A is a cross-sectional view according to the first embodiment. FIG. 1B is a plan view showing a bottom portion and a plate of the package of the first embodiment. FIG. 2A is a cross-sectional view according to the second embodiment. FIG. 2B is an enlarged view of a portion B in FIG. 2A. FIG. 3A is a cross-sectional view according to the third embodiment. FIG. 3B is a plan view showing a bottom portion and a plate of the package of the third embodiment. FIG. 4A is a cross-sectional view according to the fourth embodiment. FIG. 4B is a plan view showing a bottom portion and a plate of the package of the fourth embodiment. It is sectional drawing concerning a 5th Example. FIG. 6A is a sectional view according to the first to fifth embodiments. FIG. 6B is a schematic diagram according to the first to fourth embodiments.

Explanation of symbols

1: condenser microphone, 2: condenser microphone, 3: condenser microphone, 4: condenser microphone, 5: condenser microphone, 11: breathable sheet, 12: electroacoustic conversion die, 12: support part, 12: electroacoustic conversion die, 13: Gold wire, 14: Lead frame, 15: Plate, 16: Package, 17: External wiring board, 18: Impedance conversion die, 19: Plate, 121: Rear through hole, 122: Stationary electrode, 123: Vibration electrode, 141: lead frame, 141: water repellent film, 151: acoustic hole, 161: cover, 162: bottom, 163: through hole, 171: through hole, 191: acoustic hole, 192: acoustic hole

Claims (15)

A package forming a cavity inside and having a through hole;
A plate that is bonded to the package and has an acoustic hole that overlaps the through hole, and is thinner than the length of the through hole;
An electroacoustic transducer die housed in a portion of the cavity;
Condenser microphone with The package is
A bottom portion having the through hole and bonded to an external wiring board;
A cover joined to the bottom and forming the cavity inside with the bottom;
The plate is joined to the bottom, thinner than the bottom,
The electroacoustic conversion die includes a stationary electrode, a vibrating electrode for the stationary electrode, and an annular support portion that is joined to the bottom or the plate around the acoustic hole and supports the stationary electrode and the vibrating electrode on the inside. And comprising
The condenser microphone according to claim 1. The acoustic hole has a length of 100 μm or less,
The diameter of the acoustic hole is 100 μm or less,
The condenser microphone according to claim 1 or 2. The plate is made of a metal material,
The condenser microphone according to claim 1, 2 or 3. The plate comprises a lead frame;
The condenser microphone according to claim 4. The bottom is a multilayer wiring board,
The plate is made of a conductive film bonded to the surface of the multilayer wiring board.
The condenser microphone according to claim 4. The bottom is a multilayer wiring board,
The plate is made of a conductive film included in the multilayer wiring board.
The condenser microphone according to claim 4. A plurality of the plates;
The bottom is a multilayer wiring board,
Each of the plurality of plates is made of a conductive film bonded to the multilayer wiring board and overlapping with an insulating layer interposed therebetween,
The condenser microphone according to claim 4. The acoustic hole formed by the first conductive film and the acoustic hole formed by the second conductive film do not overlap,
The condenser microphone according to claim 8. Further comprising a breathable sheet between the first conductive film and the second conductive film,
The condenser microphone according to claim 8 or 9. A water repellent film is formed around at least the acoustic hole on the back surface of the plate with respect to the electroacoustic conversion die;
The condenser microphone according to claim 1. The plate includes a projection area of the electroacoustic conversion die on the outer periphery,
The condenser microphone according to any one of claims 1 to 11. The plate is connected to a ground potential wiring,
The condenser microphone according to claim 1. A condenser microphone,
An external wiring board to which the condenser microphone is joined, and
The condenser microphone is:
A bottom portion having a through hole and bonded to an external wiring board;
A cover joined to the bottom and forming a cavity inside with the bottom;
A plate joined to the bottom and having an acoustic hole thinner than the length of the through hole and overlapping the through hole;
Housed in a part of the cavity, a stationary electrode, a vibrating electrode for the stationary electrode, and an annular support portion that supports the stationary electrode and the vibrating electrode on the inside,
An electroacoustic conversion die comprising:
With
The external wiring board has a second through hole that overlaps the through hole.
Electroacoustic transducer. The support is joined to the bottom or the plate around the acoustic hole,
The electroacoustic transducer according to claim 14.

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