JP2008054007A - Condenser microphone and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a condenser microphone which is capable of reducing a thermal influence upon components in a box member during reflow or the like by increasing heat insulation of the box member. <P>SOLUTION: A condenser microphone includes: a condenser portion including a vibration film 30 and a back plate 31 disposed opposed in opposition to each other; a field effect transistor 26 for converting changes in electrostatic capacity of the condenser portion to electric impedances; and a box member 22 wherein the condenser portion and the field effect transistor 26 are stored. The box member 22 comprises a circuit board 23, a box member base frame 24 not only connected to the circuit board 23 but also surrounding the field effect transistor 26, and a top substrate 25 integrally coupled with the box member base frame 24. A through hole 40 being a cavity is formed in a wall of the box member 22, namely, a wall of the box member base frame. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a condenser microphone used in devices such as a mobile phone, a video camera, and a personal computer, and a method for manufacturing the same.

Conventionally, as this type of condenser microphone, for example, one having a configuration as disclosed in Patent Document 1 has been proposed. This conventional condenser microphone has a circuit board on which electrical components are mounted, a spacer on the lower side, a back plate with a back electrode, a spacer on the upper side, and a diaphragm support frame with a diaphragm on the bottom. It is configured by fixing. In this type of condenser microphone including the condenser microphone disclosed in Patent Document 1, each component member is laminated and assembled as described above, and then passed through a reflow furnace to be heated. It is intended to be reflow soldered on the substrate to be attached.
JP 2002-345092 A

  Since the condenser microphone is heated at the time of reflow as described above, conventionally, in the conventional condenser microphone including the above-mentioned Patent Document 1, in order to reduce the thermal damage of the components inside the condenser microphone at the time of reflow. Measures such as selecting materials with high heat resistance are taken. However, a specific structure for suppressing heat conduction into the condenser microphone is not taken. For this reason, conventionally, there has been a problem that heat during reflow is transferred to the inside of the condenser microphone.

  The present invention has been made paying attention to such problems existing in the prior art. An object of the present invention is to provide a condenser microphone that can increase the heat insulation of the casing and reduce the thermal effects of components in the casing during reflow and the like, and a manufacturing method thereof.

  In order to achieve the above object, the invention according to claim 1 is directed to a capacitor portion in which a diaphragm and an electrode plate are arranged to face each other, and an impedance conversion for converting a change in capacitance of the capacitor portion into an electrical impedance. A condenser microphone comprising an element and a casing that houses the capacitor section and the impedance conversion element is characterized in that the condenser microphone includes a cavity in the wall of the casing. According to the invention of claim 1, since the casing is provided with a cavity, the heat insulation of the casing is enhanced, and when heat is applied during reflow or the like, the thermal effect of the components in the casing is reduced. There is an effect that can be done.

  In the invention of claim 2 and claim 1, the cavity is filled with air. According to the invention of claim 2, since the air layer is formed in the casing by filling the cavity with air, the heat insulation of the casing is enhanced, and the adverse effect due to the heat of the components in the casing at the time of reflowing Is effective.

  The invention of claim 3 is characterized in that, in claim 1, the cavity is evacuated. According to the invention of claim 3, since the vacuum layer is formed in the casing by evacuating the cavity, the heat insulation is further improved than when the cavity forms an air layer, and during reflow This has the effect of reducing the adverse effects caused by the heat of the components in the casing.

  According to a fourth aspect of the present invention, in any one of the first to third aspects, the housing includes a mounting substrate on which the impedance conversion element is mounted and a pair of openings, and one opening. The frame comprises a frame that is integrally connected to the mounting substrate and surrounds the impedance conversion element, and a top cover substrate that is integrally connected to the periphery of the other opening of the frame. It is provided on at least one of the substrate, the frame, and the top cover substrate. According to the invention of claim 4, since the cavity is provided in at least one of the mounting substrate, the frame, and the top cover substrate that form the housing, the heat insulation of the housing is enhanced, and the inside of the housing during reflow is increased. This has the effect of reducing the adverse effects of component heat.

  According to a fifth aspect of the present invention, in the third aspect, the housing includes a mounting substrate on which the impedance conversion element is mounted, and a pair of openings, and one opening peripheral edge is integrally connected to the mounting substrate. And the frame surrounding the impedance conversion element, and a top cover substrate integrally connected to the periphery of the other opening of the frame, the cavity includes a through-hole formed in the frame, A pair of open ends of the through holes are respectively closed by the mounting substrate and the top cover substrate. According to the invention of claim 5, since the through hole (air gap) is evacuated, unlike the case where air is present in the air gap, thermal expansion of the gas in the through hole does not occur due to heating during reflow. There is no possibility that peeling between the frame body and the mounting substrate and between the frame body and the top cover substrate will occur. In addition, since the through hole is in a vacuum state, an adsorption force can be applied to the mounting substrate and the top cover substrate that are bonded to the frame body due to the pressure difference between the vacuum and the atmospheric pressure. Prevents peeling of substrate / top cover substrate.

  According to a sixth aspect of the present invention, in any one of the first to fifth aspects, the cavity is formed of a substrate having two or more metal layers. According to the sixth aspect of the present invention, when the casing is constituted by the substrate having two or more metal layers, the strength of the casing can be increased.

  According to a seventh aspect of the present invention, in any one of the fourth to sixth aspects, the cavity of the frame is formed in a honeycomb structure. According to the seventh aspect of the invention, since the cavity is formed in a honeycomb structure, the strength of the structure of the portion where the cavity is provided can be increased.

  According to an eighth aspect of the present invention, there is provided a circuit board on which a die having a microphone vibration part manufactured by a semiconductor process technology is mounted, a frame that is bonded to the circuit board and surrounds the die, and is integrated with the frame. The subject matter of the present invention is a condenser microphone provided with a casing that houses the microphone vibrating portion by a connected top cover, wherein the condenser microphone includes a cavity in the wall of the casing. According to the invention of claim 8, since the housing is provided with a cavity, the heat insulation of the housing is enhanced, and when heat is applied during reflow or the like, the thermal effect of the components in the housing is reduced. There is an effect that can be done.

  According to a ninth aspect of the present invention, there is provided a capacitor unit in which a diaphragm and an electrode plate are arranged to face each other, an impedance conversion element for converting an impedance of the capacitor unit into an electrical impedance, and the capacitor unit and the impedance conversion element. A housing for housing the housing, the housing having a mounting substrate on which the impedance conversion element is mounted, and a pair of openings, and a peripheral edge of one opening being connected to the mounting substrate. In the method of manufacturing a condenser microphone including a surrounding frame and a top cover substrate connected to the periphery of the other opening of the frame, the assembly process of the casing includes a through hole in the wall in the vacuum chamber. The mounting board assembly sheet in which the mounting boards are arranged vertically and horizontally with respect to the frame assembly sheet in which the frame bodies to be arranged vertically and horizontally, and the top Capacitor microphones characterized in that the through holes are closed and stacked so as to be in a vacuumed state by a top cover substrate assembly sheet in which covers are arranged vertically and horizontally, and then the casing is divided into individual pieces. The manufacturing method is the gist. According to claim 9, the condenser microphone of claim 5 can be obtained easily.

  As described above, according to the present invention, since the cavity is provided in the housing, the heat insulation of the housing is enhanced, and when heat is applied during reflow or the like, the thermal effect of the components in the housing is increased. Can be reduced.

Embodiments of the present invention will be described below 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 as a mounting board, a square frame-like housing base frame 24 as a frame, A top substrate 25 as a flat top cover substrate as a top cover is laminated and fixed integrally with an adhesive. The circuit board 23, the casing base frame 24, and the top board 25 are made of an electrical insulator made of resin such as epoxy resin. In this embodiment, although it is comprised with the glass cloth base material epoxy resin, it is not limited to an epoxy resin. Conductive patterns 23 a and 23 c made of copper foil are formed on the upper surface of the circuit board 23. The conductive pattern 23 c is a grounding conductive pattern, and is provided in a frame shape so as to face the frame shape of the housing 22. The conductive pattern 23a is a conductive pattern for connecting components, and is used for power supply input and value signal extraction.

A plurality of conductive patterns 23b (only one conductive pattern 23b is shown in FIG. 1) made of copper foil is formed on the lower surface of the circuit board 23.
The circuit board 23 is provided with a plurality of through holes (not shown), and a conductive pattern is formed in the through holes. The conductive pattern 23c is connected to a conductive pattern 23b connected to a ground terminal (not shown) on the lower surface of the circuit board 23 through the conductive patterns of some through holes among the plurality of through holes. Is done. In addition, the conductive pattern 23a is connected to a signal output terminal (not shown) or a power input terminal (not shown) provided on the lower surface of the circuit board 23 through the conductive patterns of the remaining through holes among the plurality. Connected to the conductive pattern 23b.

  On the circuit board 23, electrical components such as a field effect transistor 26 and a capacitance 27 constituting an impedance conversion circuit provided in the housing 22 are mounted. The field effect transistor 26 corresponds to an impedance conversion element.

  The casing base frame 24 has openings at both upper and lower ends, and conductive patterns 24a, 24b, and 24c as continuous metal layers made of copper foil are formed on the upper and lower surfaces and the outer surface. The conductive pattern 24c provided on the outer surface of the housing base frame 24 is formed by applying a conductive paste to the recess 24i provided on the outer surface. The conductive pattern 24b on the lower surface side is connected to the conductive pattern 23b connected to the ground terminal (not shown) on the lower surface of the circuit board 23 through the conductive pattern 23c on the circuit board 23 as shown in FIG. . The peripheral edge of the opening at the bottom of the housing base frame 24 is integrally connected by the circuit board 23. Electrical components such as the field effect transistor 26 and the capacitance 27 on the circuit board 23 are accommodated in the housing base frame 24.

  As shown in FIG. 1, a metal layer 24 d made of copper foil is embedded in the housing base frame 24. That is, in this embodiment, the housing base frame 24 is configured by a resin multilayer substrate having three metal layers. A plurality of through holes 24e are formed in the wall of the housing base frame 24, and conductive patterns 24f continuous with the conductive patterns 24a and 24b are provided on the inner peripheral surfaces of the through holes 24e. The through hole 24e is filled with a conductive material 24g, and a conductive portion is formed by the conductive material 24g and the conductive patterns 24a and 24b.

  The metal layer 24d is electrically connected to the conductive pattern 23c on the circuit board 23 through the conductive pattern 24f including the conductive pattern 24f of the through hole 24e and the conductive material 24g, and the conductive pattern 24b.

  In addition to the through hole 24e, a plurality of through holes 40 having a circular cross section and an oval cross section are formed in the wall of the housing base frame 24 through the conductive pattern 24a as shown in FIG. It is formed with a predetermined interval. Conductive patterns 41 that are continuous with the conductive patterns 24 a and 24 b and the metal layer 24 d are provided on the inner peripheral surface of each through-hole 40. The inside of the through hole 40 is in a vacuum state, and the lower open end is adhered and closed with a conductive adhesive to the conductive pattern 23c of the circuit board 23, and the airtight state is maintained. The degree of vacuum is preferably higher than the medium vacuum of about 100 Pa or less. Thereby, a desirable heat insulation effect is obtained.

  Conductive patterns 25a and 25b made of copper foil or the like are formed on the upper and lower surfaces and the outer surface of the top substrate 25. The top substrate 25 is formed with a sound hole 28 for taking in sound from the outside.

  As shown in FIGS. 1 and 2, an annular spacer 29 made of an insulating film is sandwiched and fixed between the housing base frame 24 and the top substrate 25. The open end of the upper portion of the through hole 40 of the housing base frame 24 is closed and adhered to the spacer 29 with a conductive adhesive, and the airtight state is maintained. In this manner, the opening periphery of the upper portion of the casing base frame 24 is integrally connected to the top substrate 25 via the spacer 29 and the vibration film 30.

  A vibration film 30 made of an insulating synthetic resin thin film such as a PPS (polyphenylene sulfide) film is stretched on the upper surface of the spacer 29 by adhesion, and a conductive film made of gold vapor deposition is formed on the lower surface of the vibration film 30. Layer 30a is formed. A through hole (not shown) is provided in the vibration film 30 and the spacer 29, and the conductive layer 30a includes the conductive paste filled in the through hole, the spacer 29 and the casing base frame 24 (more precisely, the spacer 29 and the conductive pattern 24a). ) Between the conductive pattern 24a through a conductive adhesive.

  In the housing base frame 24, a back plate 31 as an electrode plate is disposed opposite to the lower surface of the vibration film 30 with a spacer 29 interposed therebetween. The back plate 31 is configured by attaching a film 31b such as PTFE (polytetrafluoroethylene) to the upper surface of a back plate body 31a made of a stainless steel plate. The film 31b is subjected to polarization treatment by corona discharge or the like, and the film 31b constitutes an electret layer by this polarization treatment. In the present embodiment, the back plate 31 constitutes a back electrode, and the condenser microphone of this embodiment is constituted by a back electret type.

  Further, the back plate 31 is formed so as to have a substantially oval shape in a planar shape having an outer peripheral shape smaller than the inner peripheral shape of the housing base frame 24, and a gap P is formed between the inner and outer peripheral surfaces thereof. Is formed. A through-hole 32 for allowing air movement due to vibration of the vibration film 30 is formed at the center of the back plate 31. The back plate 31 is formed by punching a stainless steel plate with a film 31b attached from the film 31b side, that is, from the upper side to the lower side in FIG. 2 with a punching blade (not shown).

  As shown in FIGS. 1 to 3, in the housing base frame 24, a holding member 33 made of a 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 30 in a direction in contact with the lower surface of the spacer 29 by the elastic force. As a result, a predetermined interval is maintained between the vibration film 30 and the back plate 31, and a capacitor portion that secures a predetermined capacity is formed between them.

  The holding member 33 is formed by stamping and forming a plate material obtained by performing gold plating on both the front and back surfaces of a stainless steel plate. The holding member 33 is substantially square-shaped frame portion 33a and obliquely toward the lower side from the four corners of the frame portion 33a. And four leg portions 33b projecting from each other. Accordingly, a space S is formed between the leg portions 33b below the frame portion 33a. In this embodiment, as shown in FIG. 1, the field effect transistor 26 on the circuit board 23 is disposed in the space S, and the capacitance 27 is disposed between each pair of legs 33b. The On the upper surface of the frame portion 33a of the holding member 33, contact portions 34 as four spherical protrusions that contact the lower surface of the back plate 31 are formed so as to project, and a circuit board is formed on the lower surface of the tip of each leg portion 33b. Four contact portions 35 as four spherical protrusions that contact a part of the conductive pattern 23 a on the protrusion 23 are formed to protrude. The back plate 31 is electrically connected to the impedance conversion circuit of the circuit board 23 through the holding member 33.

  As shown in FIG. 1, a plurality of through holes 36 are formed in the top substrate 25, and conductive patterns 25c continuous with the conductive patterns 25a and 25b are provided on the inner peripheral surfaces of the through holes 36. . The through hole 36 is filled with a conductive adhesive 37a, and a conductive portion 37 is formed by the conductive adhesive 37a and the conductive pattern 25c. The conductive portion 37 is electrically connected to the lower surface of the vibrating membrane 30 by folding the conductive layer 30a. Note that the conductive pattern 25c may be formed even if the conductive adhesive 37a in the through hole 36 is not filled, and if the conductive pattern 25c in the through hole 36 is not formed, the conductive adhesive 25a may be formed. It is also possible to only fill the agent 37a. In addition, electroconductivity and shielding property improve by forming both the conductive pattern 25c and the electroconductive adhesive agent 37a.

  The conductive patterns 25a and 25b of the top substrate 25 include a conductive portion 37, a conductive layer 30a, a conductive paste in a through hole (not shown) provided in the vibration film 30, and a conductive adhesive between the spacer 29 and the conductive pattern 24a. In addition, a conductive path to the ground terminal on the circuit board 23 is formed through the conductive patterns 24 a to 24 c on the housing base frame 24.

  In the condenser microphone 21, when the sound wave from the sound source reaches the vibration film 30 through the sound hole 28 of the top substrate 25, the vibration film 30 is vibrated according to the frequency, amplitude, and waveform of the sound. As the vibration film 30 vibrates, the distance between the vibration film 30 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.

(Production method)
Next, a method for manufacturing the condenser microphone 21 configured as described above will be described.

  The condenser microphone 21 is formed by laminating a plurality of assembly members by stacking or the like and then dividing the assembly. In this manufacturing method, as shown in FIG. 3, a plurality of circuit board members 140, a housing base frame forming member 150, a vibration film forming member 200, a top cover forming member 250, a back plate 31, a holding member 33, and the like are used. The condenser microphone 21 is manufactured.

  The circuit board member 140 is an insulating substrate as a collective member for forming a plurality of the circuit boards 23. The conductive patterns 23a and 23c are formed on the upper surface, and the conductive patterns 23b are formed on the lower surface in the vertical and horizontal directions at a predetermined pitch. A plurality are formed. The circuit board member 140 corresponds to a mounting board assembly sheet.

  The casing base frame forming member 150 is a plate member as a collective member for forming a plurality of casing base frames 24. Between the portions to be the casing base frame 24, holes 152 are formed by drilling with a router or the like. Are formed at a predetermined pitch vertically and horizontally. The hole 152 is filled with a conductive paste or applied to a surface in the hole. The hole 152 becomes a recess 24i of the housing base frame 24 after dicing, which will be described later, and a conductive pattern 24c is formed by a conductive paste filled in or applied to the hole 152. The The casing base frame forming member 150 corresponds to a frame aggregate sheet.

  The vibration film forming member 200 is a sheet material as a collective member in which island members 202 for forming a plurality of vibration films 30 are arranged vertically and horizontally. Further, in the vibration film forming member 200, each island member 202 that becomes the vibration film 30 is connected to the frame member 206 and the adjacent island member 202 via the connecting portion 204. The spacer 29 is bonded to the lower surface of each island member 202.

  The top cover forming member 250 is a substrate as an assembly member for forming a plurality of top substrates 25, and the sound holes 28 and the conductive patterns 25a and 25b are formed at a predetermined pitch in the vertical and horizontal directions. The top cover forming member 250 corresponds to a top cover substrate aggregate sheet.

  In order to manufacture the capacitor microphone 21, the circuit board member 140 is mounted on the circuit board member 140 in a vacuum chamber (not shown) with the field effect transistor 26 and the capacitance 27 mounted in advance. Are bonded to each other by a conductive adhesive to integrate them. Next, the holding member 33 and the back plate 31 are housed in a portion corresponding to the housing base frame 24 with respect to the assembled assembly. Next, the vibration film forming member 200 is bonded to the assembly using a conductive adhesive. At this time, the conductive pattern 24 a corresponding to the housing base frame 24 and the spacer 29 of the island member 202 are bonded by the conductive adhesive. At this time, the through-hole 40 (gap) is kept in a vacuum state. Thereafter, the top cover forming member 250 is bonded to the assembly on which the vibration film forming member 200 is laminated using a conductive adhesive. At this time, each conductive pattern 25b of the top cover forming member 250 and the vibration film 30 are bonded with the adhesive. Thereafter, the assembly is taken out from a vacuum chamber (not shown) and diced (cut) with a diamond blade or the like to form a plurality of condenser microphones 21.

  Note that FIG. 3 shows a state in which 2 × 2 = 4 condenser microphones 21 are formed for convenience of explanation, but in practice, several hundred condenser microphones 21 are formed at a time.

The condenser microphone 21 of this embodiment that operates as described above exhibits the following effects.
(1) In the present embodiment, the through-hole 40 serving as a cavity is formed in the wall of the housing 22, that is, the wall of the housing base frame 24. Since the heat insulation of the housing 22 is enhanced by this cavity, there is an effect that the thermal influence of the components in the housing 22 during reflow can be reduced. Therefore, for example, even when the surface mounting of the condenser microphone 21 on the external substrate is performed by reflow processing, the film 31b of the back plate 31 of the capacitor portion is charged by the heat applied during the reflow processing. It can suppress effectively that a charge lose | disappears or decreases.

  (2) In this embodiment, since the through-hole 40 is evacuated, a vacuum layer is formed in the casing 22 in the cavity, so that the heat insulation is further improved than when the cavity forms an air layer, There is an effect that the adverse effect of the heat of the components in the housing 22 during reflow can be reduced.

  (3) In the present embodiment, the open end of the through hole 40 (cavity) is closed by the circuit board 23 (mounting board) and the top board 25 (top cover board). As a result, since the through-hole 40 (cavity) is evacuated, unlike the case where there is air in the cavity, thermal expansion of the gas in the through-hole 40 does not occur due to heating during reflow, and the housing base There is no possibility that the frame 24 and the circuit board 23, and the casing base frame 24 and the top substrate 25 are peeled off. Further, since the through hole 40 is in a vacuum state, an adsorption force can be exerted on the circuit board 23 and the top board 25 joined to the housing base frame 24 due to a pressure difference between the vacuum and the atmospheric pressure. It is possible to prevent the circuit board 23 and the top board 25 from being detached after assembly.

  (4) In the present embodiment, the circuit board 23 is arranged vertically and horizontally with respect to the case base frame forming member 150 in which the case base frame 24 having the through holes 40 in the wall is arranged vertically and horizontally in the vacuum chamber. The circuit board member 140 and the top cover forming member 250 in which the top cover is arranged vertically and horizontally are closed and laminated so that the through hole is evacuated. And after that, the housing | casing 22 was divided | segmented separately by cut | disconnecting with respect to the assembled assembly. As a result, the condenser microphone having the effect (3) can be easily obtained.

  (5) In the housing base frame 24 of the present embodiment, the through hole 40 (cavity) is configured by a three-layer multilayer substrate having conductive patterns 24a and 24b and a metal layer 24d as metal layers. As a result, there is an effect that the strength of the housing 22 can be increased.

(6) In the present embodiment, the casing base frame 24 (frame body) is constituted by a resin multilayer substrate having a metal layer 24d made of three layers of copper foil.
Therefore, after assembling each component of the condenser microphone 21, the assembly is passed through a reflow furnace, and when the condenser microphone 21 is mounted on an external board (not shown) by reflow soldering, the housing base frame 24 ( The heat capacity of the casing is increasing. For this reason, it can be made difficult to be transmitted to each member inside the housing 22, and even if heat at the time of reflow is applied, a temperature rise in the housing base frame 24 is suppressed. Thereby, the temperature rise of a capacitor | condenser part can be suppressed. As a result, even when high heat is applied to the housing 22 as during reflow, thermal damage to the members housed in the housing 22 can be reduced.

  Therefore, for example, even when the surface mounting to the external substrate is performed by the reflow process, the charge that has been applied to the film 31b of the back plate 31 of the capacitor unit due to the heat applied during the reflow process is lost or lost. It is possible to effectively suppress the decrease.

Incidentally, the heat capacity of an object is the amount of heat required to raise the temperature of the object by 1 ° C., and is expressed by multiplying the mass of the object by the specific heat of the object.
In the example of this embodiment, the metal layer is a copper foil, the specific heat is 0.092 cal / g / k, and the density is 8.96 grams / cubic centimeter.

On the other hand, a general glass cloth base epoxy resin has a specific heat of 0.19 cal / g / k and a density of 1.7 to 2 grams / cubic centimeter.
Here, assuming that the density of the glass cloth base epoxy resin is 2 g / cubic centimeter and the same volume is assumed, the density of the glass cloth base epoxy resin and the copper foil × the specific heat is compared. Then, “density × specific heat” of the copper foil is 8.96 × 0.092 = 0.82432, and “density × specific heat” of the glass cloth base epoxy resin is 2 × 0.19 = 0.38. Therefore, when the volume of the glass cloth base epoxy resin and the copper foil is the same, it is understood that the heat capacity of the copper foil is twice or more larger.

  (7) In the present embodiment, the housing base frame 24 has conductive patterns 24a and 24b and a metal layer 24d formed on both sides and inside, respectively, and the metal layer 24d arranged inside is grounded. . As a result, an electromagnetic shield is provided by the metal layer 24d disposed inside the housing base frame 24, and noise can be reduced.

(Second Embodiment)
Next, a second embodiment will be described with reference to FIG. In addition, about the structure which is the same as that of 1st Embodiment, or equivalent, attaches | subjects the same code | symbol and abbreviate | omits description and demonstrates a different structure.

  In the condenser microphone 21 of the second embodiment, the field effect transistor 26, the capacitance 27, the spacer 29, the vibration film 30, the back plate 31, and the holding member 33 are omitted in the configuration of the first embodiment.

Instead, a silicon microphone element 120 manufactured from a silicon substrate by a semiconductor process technique is provided on the circuit board 23.
In the silicon microphone element 120, a vibrating electrode plate 100 as a vibrating membrane and a fixed electrode plate 110 arranged to face the vibrating electrode plate 100 through a gap are formed on a die 130. An insulating film 115 is formed between the fixed electrode plate 110 and the vibrating electrode plate 100 for electrical insulation. The vibration electrode plate 100 is electrically connected to a connection electrode (not shown), and is connected to the conductive pattern 23a on the circuit board 23 through the connection electrode and the wire W1. Further, the fixed electrode plate 110 is electrically connected to a connection electrode (not shown), and is connected to the conductive pattern 23a on the circuit board 23 through the connection electrode and the wire W2. A plurality of through holes 111 are formed in the fixed electrode plate 110. Note that the detailed configurations of the vibrating electrode plate 100 and the fixed electrode plate 110 are known, and thus detailed description thereof is omitted.

  The vibrating electrode plate 100 and the fixed electrode plate 110 constitute a microphone vibrating portion. The silicon microphone element 120 configured as described above is configured so that the capacitance between the fixed electrode plate 110 and the vibrating electrode plate 100 changes due to the vibration electrode plate 100 vibrating according to the sound wave. A change in capacitance is measured by an impedance conversion element (not shown) on the substrate 23, and a sound wave can be converted into an electric signal.

  In the second embodiment, the vibration film 30 is omitted as described above, and the conductive pattern 25b on the lower surface of the top substrate 25 is connected to the conductive pattern 24a on the housing base frame 24 by a conductive adhesive. Has been. In the through hole 40, the upper opening end is closed by the conductive pattern 25b and the lower opening end is closed by the conductive pattern 23c, and is kept in a vacuum state.

  With the above configuration, also in the second embodiment, the through-hole 40 that is evacuated is provided in the wall of the housing base frame 24 to increase heat insulation, and due to the heat of components in the housing 22 during reflow or the like. This has the effect of reducing adverse effects.

In addition, this embodiment can also be changed and embodied as follows.
In each of the embodiments described above, the through hole 40 is evacuated, but may be filled with air. In addition, although air is good about atmospheric pressure, it may be a little lower than atmospheric pressure. Even in this case, since the heat insulating property of the housing 22 is enhanced, the heat influence of the components in the housing can be reduced when heat is applied during reflow or the like.

  In the above embodiment, the through hole 40 (gap) is provided in the wall of the housing base frame 24. However, in the top substrate 25 and the circuit board 23, a concave portion is provided at a position facing the through hole 40. The void volume may be increased. Further, in the top substrate 25 or the circuit substrate 23, a concave portion may be provided at a position facing the through hole 40 to increase the volume of the gap. In this case as compared with the first embodiment, the volume of the gap is increased, so that the heat insulation effect can be further enhanced.

  In addition, the cavity may close the open end side of the recess with respect to the circuit board 23, or may form a through hole and close the both ends to form a void. This air gap may be provided only in the circuit board 23 or may be added to the configuration of the first embodiment. Furthermore, a space may be provided inside the circuit board 23, as in an internal space 43 indicated by a two-dot chain line in FIG. In addition, an opening 44 that is an external opening is provided in the internal space 43 so as to be opposed to the housing base frame 24, and evacuation is performed in the same manner as the housing base frame 24. May be raised. In addition, when forming the circuit board 23 which is a multilayer board without providing the opening 44, the internal space 43 may be evacuated by evacuation by the same method. Further, the strength of the circuit board 23 can be increased by making the internal space 43 into a honeycomb structure. By these, the heat insulation at the time of reflow increases further. Similar to the circuit board 23, the same effect can be obtained by providing the top board 25 with an internal space.

  In addition, the cavity may close the opening end side of the recess with respect to the top substrate 25, or may form a through hole and close the both ends to form a void. This gap may be provided only in the top substrate 25, or may be added to the configuration of the first embodiment. Moreover, you may combine with the structure provided in the above-mentioned circuit board 23. FIG.

  In the above embodiment, the through hole 40 as a cavity is formed to have a circular cross section, but the shape of the through hole is not limited to a circular cross section. For example, the through hole 40 may have a shape such as a regular hexagonal cross section. Further, when a plurality of through holes 40 are arranged, the honeycomb structure may have a regular hexagonal cross section and be arranged close to each other. By adopting the honeycomb structure, the strength of the structure of the portion where the through hole 40 is provided can be increased.

In the above-described embodiment, the housing base frame 24 is configured by a three-layer resin multilayer substrate, but may be four layers or five layers or more. Even in this case, the heat capacity can be increased.
In the above embodiment, the metal layer is formed of copper foil, but it is needless to say that the metal layer may be composed of other metals.

In the above embodiment, the back plate main body 31a is made of a stainless steel plate, but may be made of a brass plate or a titanium plate.
In the above embodiment, the present invention is embodied in a back electret type condenser microphone. However, a front surface in which an electret layer is formed on the inner side surface of the housing 22 (for example, the side surface located above the vibrating membrane 30 in FIG. 1). To embody this invention in the electret type.

O To embody the present invention in a foil electret type condenser microphone in which the vibration film 30 is made of a polymer film for electrets.
○ The present invention is embodied in a charge pump type capacitor microphone having a booster circuit. In the case of such a configuration, electrodes facing each other are provided on the vibration film 30 and the back plate 31 in place of the electret layer.

  The metal layer of each said embodiment should just have electroconductivity like aluminum, silver, etc. besides copper.

Sectional drawing which shows the condenser microphone of 1st Embodiment. The disassembled perspective view of the condenser microphone of FIG. The perspective view which shows each member used for manufacture of a condenser microphone. Sectional drawing which shows the condenser microphone of 2nd Embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 21 ... Condenser microphone, 22 ... Case, 23 ... Circuit board, 24 ... Case base frame (frame body), 25 ... Top substrate (top cover), 26 ... Field effect transistor (impedance conversion element), 30 ... Vibration film , 31... Back plate (electrode plate: the capacitor part is constituted by the back plate and the vibration film 30), 40. Through hole (cavity).

Claims (9)

A capacitor unit in which the diaphragm and the electrode plate are arranged to face each other, an impedance conversion element that converts the change in capacitance of the capacitor unit into an electrical impedance, and a housing that houses the capacitor unit and the impedance conversion element. In the condenser microphone
A condenser microphone comprising a cavity in the wall of the housing.   The condenser microphone according to claim 1, wherein the cavity is filled with air.   The condenser microphone according to claim 1, wherein the cavity is evacuated. The housing includes a mounting substrate on which the impedance conversion element is mounted, a pair of openings, and a frame that surrounds the impedance conversion element while a peripheral edge of one opening is integrally connected to the mounting substrate, A top cover substrate integrally connected to the periphery of the other opening of the frame,
4. The condenser microphone according to claim 1, wherein the cavity is provided in at least one of the mounting substrate, the frame body, and the top cover substrate. 5. The housing includes a mounting substrate on which the impedance conversion element is mounted, a pair of openings, and a frame that surrounds the impedance conversion element while a peripheral edge of one opening is integrally connected to the mounting substrate, A top cover substrate integrally connected to the periphery of the other opening of the frame,
The said cavity contains the through-hole formed in the said frame, The pair of opening end of this through-hole is each obstruct | occluded by the said mounting board | substrate and the said top cover board | substrate. Condenser microphone.   The condenser microphone according to any one of claims 1 to 5, wherein the cavity is configured by a substrate having two or more metal layers.   The condenser microphone according to any one of claims 4 to 6, wherein the cavity of the frame is formed in a honeycomb structure. A circuit board on which a die having a microphone vibration part manufactured by a semiconductor process technology is mounted, a frame that is bonded to the circuit board and surrounds the die, and a top cover that is integrally connected to the frame In the condenser microphone provided with a housing containing the microphone vibration part,
A condenser microphone comprising a cavity in the wall of the housing. A capacitor unit in which a diaphragm and a back plate are arranged to face each other, an impedance conversion element that converts the change in capacitance of the capacitor unit into an electrical impedance, and a housing that houses the capacitor unit and the impedance conversion element. The housing includes a mounting substrate on which the impedance conversion element is mounted, a pair of openings, and a peripheral body of one opening connected to the mounting substrate to surround the impedance conversion element; and the frame In the method of manufacturing a condenser microphone comprising a top cover substrate connected to the periphery of the other opening of the body, the assembling step of the housing comprises:
In a vacuum chamber, the mounting substrate assembly sheet in which the mounting substrate is arranged vertically and horizontally and the top cover are arranged in length and breadth with respect to the frame assembly sheet in which the frame body having through holes in the wall is arranged vertically and horizontally. With the top cover substrate assembly sheet, the through holes are closed and laminated so as to be evacuated,
Thereafter, the method of manufacturing a condenser microphone is characterized in that the casings are individually divided.

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