JP2008047953A - Case of microphone, and microphone - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a case of a microphone capable of suppressing deterioration in microphone characteristic due to heat applied by reflow soldering during mounting, and a microphone. <P>SOLUTION: The case 22 comprises a case base frame 24 where space is defined therethrough, and a circuit board 23 and a top substrate 25 which close an opening thereof. The circuit board 23 is formed in multilayered structure having a conductive layer 23d buried in a substrate body 23a made of an insulator, and the conductive layer 23d is formed in a mesh shape. The top substrate 25 is formed in the multilayered structure having a conductive layer 25d buried in a substrate body 25a made of an insulator, and the conductive layer 25d is formed in a mesh shape. The conductive layer 23d is electrically connected to conductive patterns 23b and 23c through a through hole 34, and the conductive layer 25d is electrically connected to conductive patterns 25b and 25c through a through hole 35. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a microphone housing such as a condenser microphone used in devices such as a mobile phone, a video camera, and a personal computer, and a microphone.

An example of this type of microphone is disclosed in Patent Document 1. This electret condenser microphone has a circuit board on which electrical components are mounted, a back electrode board in which a back electrode, electret layer and spacer are integrated on an insulating board, and a vibration film in which a vibration film is stretched on a support frame. The unit is configured to be housed in a laminated state in a metal shield case.
JP 2004-222091 A

  By the way, for example, a capacitor microphone is generally mounted on a circuit board of a mobile phone by reflow soldering. However, during reflow soldering, the condenser microphone is exposed to a high temperature of about 260 ° C., for example. In the condenser microphone disclosed in Patent Document 1, since the shield case is made of metal, the case is easily heated, and the heat is easily transmitted to the vibrating membrane through the support frame. To be easily transmitted to the back electrode and the spacer. As a result, the temperature of the electret layer rises to cause charge loss, or the distance between the vibrating membrane and the back electrode substrate changes from the set value due to the difference in thermal expansion coefficient between the back electrode and the spacer. For this reason, there is a problem that various characteristics such as sensitivity and S / N ratio in the microphone are deteriorated.

  An object of the present invention is to provide a microphone casing capable of suppressing deterioration of microphone characteristics caused by heat applied by reflow soldering during mounting, and a microphone including the casing. is there.

  In order to achieve the above object, an invention according to claim 1 is provided with a base frame made of an electrical insulator, through which an accommodation space is formed, and a substrate that closes an opening of the accommodation space. In the microphone housing in which the electroacoustic conversion means is housed, the substrate is formed in multiple layers by the insulating layer and the conductive layer so that the conductive layer is embedded in the insulating layer, and the conductive layer is meshed. It was formed in the shape.

  In this invention, the thermal conductivity of the substrate is lowered by the conductive layer formed in the mesh shape and embedded in the insulating layer. For this reason, when the microphone is mounted by reflow soldering, the heat applied to the housing is less likely to enter the inside of the housing. Accordingly, it is possible to suppress the occurrence of troubles such as charge removal in the electroacoustic conversion means due to heat transmitted to the inside of the housing.

The invention according to claim 2 is characterized in that, in addition to the invention according to claim 1, a resin constituting the insulating layer is filled in the hole of the conductive layer.
According to a third aspect of the present invention, in the first aspect of the present invention, the holes of the conductive layer constitute a space.

The invention according to claim 4 is the invention according to any one of claims 1 to 3, wherein the conductive layer is electrically connected to a through hole of the substrate.
In this invention, since the conductive layer can be electrically connected to the ground through the through hole, electromagnetic shielding by the conductive layer can be performed.

  According to a fifth aspect of the invention, in addition to the invention according to any one of the first to fourth aspects, the substrate includes a circuit pattern for impedance conversion means, and one of the accommodation spaces is provided. A first substrate that closes the opening and a second substrate that includes a sound hole and closes the other opening of the accommodation space, and the conductive layer is provided on at least one of the first substrate and the second substrate. It is characterized by that.

The invention according to claim 6 is the invention according to any one of claims 1 to 5, wherein the substrate includes a sound hole, and the conductive layer is provided across the sound hole. Features.
In the present invention, since the conductive layer is positioned in the sound hole, it is possible to prevent dust and the like from entering the housing through the sound hole and to prevent heat from entering the housing.

The invention described in claim 7 is characterized in that the electroacoustic conversion means is accommodated in the inside of the casing of the microphone according to any one of claims 1 to 6.
The invention according to claim 8 is the invention according to claim 7, wherein the electroacoustic conversion means includes an electret layer.

  In the present invention, charge leakage in the electret layer due to high heat is prevented.

  According to the present invention, it is possible to obtain an excellent effect that it is possible to suppress deterioration of microphone characteristics due to heat applied by reflow soldering during mounting.

(First embodiment)
Next, a first embodiment in which the present invention is embodied in an electret condenser microphone will be described with reference to FIGS.

  As shown in FIGS. 1 and 2, the housing 22 of the condenser microphone 21 of this embodiment includes a flat circuit board 23 and a housing base frame 24 having a rectangular frame shape as a whole through a housing space. And a flat top substrate 25 are stacked and fixed with an adhesive. The circuit board 23, the casing base frame 24, and the top board 25 are made of an electrical insulator such as an epoxy resin, a liquid crystal polymer, or a ceramic.

  Conductive patterns 23b and 23c made of copper are printed on the upper and lower surfaces of the substrate body 23a of the circuit board 23 that closes one of the housing spaces of the housing base frame 24. Insulating films 23e are printed at required positions on the upper and lower surfaces of the circuit board 23. On the circuit board 23, electrical components such as a field effect transistor 26 and a capacitance 27 constituting impedance conversion means provided in the housing 22 are mounted. The electrical components are accommodated in the housing base frame 24. It is arranged in the space. Conductive patterns 24b, 24c, and 24d made of copper are printed on the upper and lower surfaces and the outer surface of the frame main body 24a of the housing base frame 24. Conductive patterns 25b and 25c made of copper are printed on both upper and lower surfaces of the substrate body 25a of the top substrate 25 that closes the other of the housing space of the housing base frame 24. The top substrate 25 is formed with a sound hole 28 for taking in sound from the outside.

  Further, conductive layers 23 d and 25 d made of copper are embedded in the circuit board 23 and the top board 25. As shown in FIGS. 1 and 3, the conductive layer 25 d of the top substrate 25 has a hole 25 e corresponding to the sound hole 28. The conductive layers 23d and 25d are formed in a mesh shape having a large number of fine through holes 23f and 25f. The through holes 23f and 25f are formed by laser processing or etching, for example. The through holes 23f and 25f of the conductive layers 23d and 25d are filled with an electrically insulating resin that forms the substrate bodies 23a and 25f. Note that the conductive layers 23d and 25d may be formed, for example, by forming fine metal wires such as copper wires in a net shape.

  As shown in FIGS. 1 and 2, in the housing base frame 24, the lower surface of the conductive pattern 25 c forming the ring shape of the top substrate 25 has a vibration made of a synthetic resin thin film sheet material of PPS (Polyphenylene Sulfide). The film 29 is adhered in a stretched state, and a conductive layer 29a is formed on the upper surface of the vibration film 29 by gold vapor deposition. Spacers 30 made of synthetic resin such as PPS of the same material (including the same material) as the material of the vibration film 29 and consisting of four small pieces are bonded and fixed at four locations on the lower surface side of the vibration film 29. Yes. In the housing base frame 24, a back plate 31 is disposed opposite to the lower surface of the vibration film 29 with a spacer 30 interposed therebetween. The back plate 31 is configured by attaching a film 31b such as PTFE (polytetrafluoroethylene) on the upper surface of a substrate 31a made of a stainless steel plate. The film 31b is polarized by corona discharge or the like, and the film 31b forms an electret layer by this polarization. And the said back plate 31 comprises a back pole, Therefore, the condenser microphone of this embodiment is a back electret type. Further, a through hole 32 for allowing air movement due to vibration of the vibration film 29 is formed at the center of the back plate 31. In this embodiment, an electroacoustic conversion means is constituted by the impedance conversion means, the vibration film 29, the back plate 31, and the like.

  As shown in FIGS. 1 and 2, in the housing base frame 24, a holding member 33 made of a leaf spring material is interposed between the back plate 31 and the circuit board 23 in a compressed state. The back plate 31 is pressed from the opposite side of the vibration film 29 by the elastic force of 33 in a direction in contact with the lower surface of the spacer 30. For this reason, the space | interval for the thickness of the spacer 30 is hold | maintained between the vibration film 29 and the backplate 31, and the capacitor | condenser part which ensured the predetermined capacity | capacitance between them is formed. The holding member 33 is formed by performing gold plating on both the front and back surfaces of a stainless steel plate, and the back plate 31 is electrically connected to the terminal 44 of the impedance conversion circuit on the circuit board 23 through the holding member 33.

  As shown in FIG. 1, a plurality of through holes 34 and 35 are formed in the circuit board 23 and the top board 25, respectively, and the conductive patterns 23b, 23c and 25b are formed on the inner peripheral surfaces of the through holes 34 and 35, respectively. , 25c and conductive patterns 34a, 35a, respectively, are provided. The through holes 34 and 35 are filled with conductive materials 36 and 37, respectively, and conductive portions 57 and 58 are formed by the conductive materials 36 and 37 and the conductive patterns 34a and 35a. And from the conductive part 58 including the conductive patterns 25b and 25c and the through hole 35 of the top substrate 25 to the conductive patterns 23b and 23c on the circuit board 23 through the conductive patterns 24b to 24d on the housing base frame 24, A conductive path to a ground terminal (not shown) is formed through the conductive portion 57 including the through hole 34.

  As shown in FIGS. 1 and 2, the exposed portions 38 and 39 of the frame body 24 a where the conductive patterns 24 c and 24 b do not exist form a ring shape as a whole on the inner peripheral edges of the lower surface and the upper surface of the housing base frame 24. Is formed. On the upper surface of the circuit board 23, a plurality of exposed portions 40 of the board body 23a where the conductive pattern 23b does not exist are formed so as to be arranged along the annular region. On the lower surface of the top substrate 25, a plurality of exposed portions 41 of the substrate body 25a where the conductive pattern 25c does not exist are arranged along the annular region. And between each exposed portion 40 of the circuit board 23 and the exposed portion 38 of the housing base frame 24 and between each exposed portion 41 of the top substrate 25 and the exposed portion 39 of the housing base frame 24. Adhesive members 42 and 43 are interposed, and the casing base frame 24, the circuit board 23, and the top board 25 are bonded and fixed by the adhesive members 42 and 43, respectively. In portions other than the exposed portions 41 and 39, the conductive pattern 23b on the upper surface of the circuit board 23, the conductive pattern 25c on the lower surface of the top substrate 25, the conductive pattern 24c on the lower surface of the housing base frame 24, and the conductive pattern 24b on the upper surface Are joined directly, and the top substrate 25 and the housing base frame 24, and the housing base frame 24 and the circuit board 23 are electrically connected.

  In the condenser microphone 21 of this embodiment configured as described above, when a sound wave from a sound source reaches the vibration film 29 through the sound hole 28 of the top substrate 25, the vibration film 29 has a sound frequency, amplitude and waveform. It is vibrated according to. As the vibration film 29 vibrates, the distance between the vibration film 29 and the back plate 31 changes from the set value, and the impedance of the capacitor changes. This change in impedance is converted into a voltage signal by an impedance conversion circuit and output.

  When the condenser microphone 21 configured as described above is mounted on a circuit board of a mobile phone by reflow soldering, for example, high heat tends to enter the housing 22 through the circuit board 23 and the top board 25. At this time, the heat transmitted to the circuit board 23 and the top board 25 is transferred from the boards 23 and 25 to the inside of the housing base frame 24 by the mesh-like conductive layers 23d and 25d embedded in the board bodies 23a and 25a. Transmission is suppressed. This is because the conductive layers 23d and 25d having a large number of through holes 23f and 25f are formed in a mesh shape, and the electrically insulating resin of the substrate bodies 23a and 25a is filled in the through holes 23f and 25f. On the other hand, this is because the thermal conductivity is not better than the conductive layer having no through holes 23f and 25f.

  For this reason, the temperature rise of the film 31b of the back plate 31 is suppressed, and the charge omission from the electret layer is prevented. Moreover, the temperature rise of the spacer 30 or the back plate 31 is suppressed, and the deformation of the spacer 30 or the back plate 31 due to the difference in their thermal expansion coefficients is suppressed. In addition, the deviation of the tension of the vibration film 29 caused by the deformation of the spacer 30 and the back plate 31 and the deviation of the distance between the vibration film 29 and the back plate 31 are suppressed. Therefore, deterioration of various characteristics such as sensitivity and S / N ratio due to missing charge from the electret layer, change in tension of the vibration film 29, gap in spacing, and the like are suppressed.

The condenser microphone 21 of this embodiment configured as described above has the following effects.
(1) Mesh-like conductive layers 23d and 25d were embedded in the substrates 23 and 25, and electrically insulating resin was filled in the through holes 23f and 25f. For this reason, the thermal conductivity of each of the conductive layers 23d and 25d is lower than the thermal conductivity of the conductive layer that is not mesh-shaped. Accordingly, the high heat applied to the housing 22 during reflow soldering does not easily enter the housing 22. Therefore, deterioration of various characteristics such as sensitivity and S / N ratio due to heat applied to the film 31b, the spacer 30, the back plate 31, and the like can be suppressed.

  (2) The conductive layers 23d and 25d of the substrates 23 and 25 are electrically connected to the conductive patterns 23b, 23c, 25b and 25c of the substrates 23 and 25 through the through holes 34 and 35, respectively. Therefore, in addition to the conductive patterns 23b, 23c, 25b, and 25c, the conductive layers 23d and 25d can also electromagnetically shield the capacitor portion and the impedance conversion circuit in the housing 22.

(Second Embodiment)
Next, a second embodiment in which the present invention is embodied in an electret condenser microphone will be described with reference to FIGS. This embodiment is different from the condenser microphone 21 of the first embodiment only in that the form of the conductive layer 25d of the top substrate 25 is changed.

  As shown in FIGS. 4 and 5, the conductive layer 25 d of this embodiment does not include the hole 25 e corresponding to the sound hole 28 and is provided across the sound hole 28. Therefore, the conductive layer 25d is exposed to the outside at the sound hole 28 portion.

The condenser microphone 21 of this embodiment configured as described above operates in the same manner as the condenser microphone 21 of the first embodiment.
In particular, this embodiment has the following effects in addition to the effects described in (1) and (2) of the first embodiment.

  (3) Since the conductive layer 25d is positioned in the sound hole 28, dust or the like is prevented from entering the vibration film 29 through the sound hole 28, and the operating state of the vibration film 29 is hindered by dust. Is prevented. Note that the sound from the outside reaches the vibration film 29 through the through hole 25f of the sound hole 28 portion.

(4) Since the conductive layer 25d is also provided in the sound hole 28, the electromagnetic shielding property can be improved and the heat intrusion from the sound hole 28 into the housing 22 can be suppressed.
In addition, this embodiment can also be changed and embodied as follows.

  The substrate bodies 23a and 25a of the substrates 23 and 25 are formed in multiple layers by laminating a plurality of insulating layers and conductive layers 23d and 25d, and resin is put in the through holes 23f and 25f of the conductive layers 23d and 25d. Make space without filling. If comprised in this way, heat transfer can further be suppressed.

Only one of the conductive layers 23d and 25d of the substrates 23 and 25 is made into a mesh.
The present invention is embodied in a configuration in which two or more conductive layers 23d and 25d of the substrates 23 and 25 are provided.

  The present invention is embodied in a case of a foil electret type condenser microphone in which the vibration film 29 is an electret layer instead of providing an electret layer on the back plate 31.

  The present invention is embodied in a case of a front electret condenser microphone in which an electret layer is formed on the lower surface of the top substrate 25 instead of providing the back plate 31 on which the electret layer is formed.

  The present invention is a MEMS (Micro Electro Mechanical System) type in which a capacitor unit including a vibrating electrode plate and a fixed electrode plate disposed opposite to the vibrating electrode plate is formed on a silicon substrate by a semiconductor process technology. It is embodied in the case of a condenser microphone.

  The present invention is embodied in a case of a charge pump type condenser microphone that does not include an electret layer and in which a voltage is applied between the back plate 31 and the vibration film 29 by an external charge pump circuit.

The present invention is embodied in a case of a condenser microphone in which a capacitor portion is formed in a case in which, for example, a synthetic resin is injection-molded.
The present invention is embodied in various microphone housings such as a crystal type, a piezoelectric type, a magnetic type, and a carbon type.

The longitudinal cross-sectional view which shows the condenser microphone of 1st Embodiment. Similarly disassembled perspective view. The cross-sectional view in the conductive layer of a top board | substrate. The cross-sectional view in the conductive layer of the top board | substrate in 2nd Embodiment. The longitudinal cross-sectional view which shows a condenser microphone.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 21 ... Condenser microphone as a microphone, 22 ... Housing | casing, 23 ... Circuit board as 1st board | substrate, 23a ... Substrate main body which comprises an insulating layer, 23d ... Conductive layer, 24 ... Housing base frame, 25 ... 2nd board | substrate As a top substrate, 25a ... substrate body constituting an insulating layer, 25d ... conductive layer, 26 ... transistor constituting electroacoustic conversion means and impedance conversion means, 27 ... capacitance, 28 ... sound hole, 29 ... electroacoustic conversion Vibrating membrane constituting the means, 31 ... same back plate, 31a ... same substrate, 31b ... film as electret layer, 34, 35 ... through hole.

Claims (8)

In a microphone housing that is made of an electrical insulator, includes a base frame that has a transparent accommodation space, and a substrate that closes an opening of the accommodation space, and that accommodates electroacoustic conversion means in the accommodation space.
A microphone housing characterized in that the substrate is formed in multiple layers by an insulating layer and a conductive layer so that the conductive layer is embedded in the insulating layer, and the conductive layer is formed in a mesh shape.   2. The microphone casing according to claim 1, wherein a resin constituting the insulating layer is filled in the hole of the conductive layer.   The microphone housing according to claim 1, wherein the hole of the conductive layer constitutes a space.   The microphone housing according to any one of claims 1 to 3, wherein the conductive layer is electrically connected to a through hole of the substrate. The substrate includes a circuit pattern for impedance conversion means, and includes a first substrate that closes one opening of the accommodation space, and a second substrate that includes a sound hole and closes the other opening of the accommodation space. ,
The microphone housing according to any one of claims 1 to 4, wherein the conductive layer is provided on at least one of the first substrate and the second substrate.   The microphone housing according to any one of claims 1 to 5, wherein the substrate includes a sound hole, and the conductive layer is provided across the sound hole.   A microphone characterized in that electroacoustic conversion means is housed inside the microphone casing according to any one of claims 1 to 6.   The microphone according to claim 5, wherein the electroacoustic conversion means includes an electret layer.

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