close

Вход

Забыли?

вход по аккаунту

?

DESCRIPTION JP2009118264

код для вставкиСкачать
Patent Translate
Powered by EPO and Google
Notice
This translation is machine-generated. It cannot be guaranteed that it is intelligible, accurate,
complete, reliable or fit for specific purposes. Critical decisions, such as commercially relevant or
financial decisions, should not be based on machine-translation output.
DESCRIPTION JP2009118264
The present invention provides a microphone device that is easy to adjust sensitivity and has less
variation in characteristics. A capacitor electrode terminal connected to a second electrode of a
capacitor unit and a ground terminal are separately derived from the microphone device, and a
sensitivity adjustment voltage is applied between the capacitor electrode terminal and the ground
terminal. This is characterized in that sensitivity adjustment is made possible, and a microphone
device of desired sensitivity can be realized. In addition, it is possible to realize a microphone
device that can measure the film stiffness of the mounted state with the same configuration.
[Selected figure] Figure 1
Microphone device
[0001]
The present invention relates to a microphone device, and more particularly to a microphone
device having a sensitivity adjustment function.
[0002]
An electrostatic electroacoustic transducer is an electroacoustic transducer that converts sound
into an electrical signal and vice versa, using electrostatic energy as a mediator.
Electret condenser microphones (ECMs) and electret condensers are classified as electrostatic
electroacoustic transducers.
18-04-2019
1
[0003]
ECM can be miniaturized and is widely used in mobile phones. In the conventional ECM, as
shown in FIG. 12, in a case 117 having a sound hole 115, a diaphragm 111 such as a metal
conductor, a fixed electrode 112 on which an electret film 113 is formed, and a printed circuit
element are mounted. The substrate 118 is disposed, the distance between the diaphragm 111
and the fixed electrode 112 is held by the spacer 114, and the back air chamber 16 is formed
between the fixed electrode 112 and the printed circuit board 118.
[0004]
Electret films are usually formed using FEP (fluorinated ethylene propylene resin) and continue
to hold a given charge. In this ECM, when the diaphragm 111 vibrates due to sound pressure, the
capacitance of the flat plate capacitor formed of the diaphragm 111 and the fixed electrode 112
changes, and this capacitance change is converted to a voltage change and output from the ECM
Ru. The polymer film FEP has the property of retaining charge semipermanently, but when
exposed to high temperatures, the charge retaining property tends to deteriorate. Therefore, it is
difficult for ECM to perform solder reflow mounting.
[0005]
In recent years, in order to realize reflowable heat-resistant ECM, technology has been developed
to manufacture ultra-small MEMS (Micro Electro Mechanical Systems) microphones by applying
the ultra-precision processing technology used in semiconductor processes to silicon substrates.
There is.
[0006]
FIG. 4 shows an example of the MEMS microphone 20.
On a silicon substrate, a large number of microphone chips are simultaneously manufactured
using semiconductor manufacturing technology and finally divided individually. FIG. 4 shows a
side view of one of the divided microphone chips. The MEMS microphone 20 has a vibrating film
18-04-2019
2
electrode 23 and an electret film 24 on a silicon substrate 21 via a first insulating layer 22, and a
second insulating layer 25 is formed thereon. There is a fixed electrode 26 in which a sound hole
27 is formed. Further, a back air chamber 28 is formed on the back surface of the vibrating film
electrode 23 by etching the silicon substrate 21.
[0007]
The vibrating film electrode 23 is formed of conductive polysilicon, the electret film 24 is formed
of a silicon nitride film or a silicon oxide film, and the fixed electrode 26 is formed of conductive
polysilicon and a silicon oxide film or silicon nitride It is formed by laminating a film.
[0008]
In the MEMS microphone 20, when the diaphragm electrode 23 vibrates due to sound pressure,
the capacitance of the flat plate capacitor formed of the diaphragm electrode 23 and the fixed
electrode 26 changes, and is taken out as a voltage change.
[0009]
By the way, in the manufacturing field of the microphone and the speaker, the sensitivity is a
very important issue, but the sensitivity is easily fluctuated by the environmental change such as
temperature and humidity, especially when passing through a high temperature process such as
solder reflow. Variations in sensitivity are likely to occur.
[0010]
Furthermore, when the metal cap is soldered in the manufacturing and assembly process of the
MEMS microphone, the temperature is high when the solder is melted, and thus the expansion
and contraction of the substrate due to the temperature occur.
For this reason, the stress of expansion and contraction is applied to the MEMS chip, and the
characteristics of the MEMS chip are changed although it is minute.
[0011]
Similarly, even when the surface mounting device MEMS microphone is mounted on the user
substrate (circuit substrate), the expansion and contraction stress is applied to the MEMS chip
due to mutual interference of the expansion and contraction of the substrates, and the
18-04-2019
3
characteristics of the MEMS chip are very small. However, it has been recognized that it changes
(Non-patent Document 2).
[0012]
Nikkei micro device 2007 July P94-95 IEEE 1998 P288
[0013]
The stress change at the time of the mounting causes a stress on the vibrating membrane, which
changes the stiffness of the vibrating membrane and causes a change in sensitivity.
In addition, sensitivity may change due to the influence of temperature and humidity, and
sensitivity adjustment is an important issue.
[0014]
Therefore, in the design of the microphone, it is necessary to consider the change in the stiffness
of the vibrating film in the process of fixing the metal cap or the process of mounting on the
circuit board.
Therefore, in order to confirm or control the stiffness quality of the vibrating film during the
manufacturing process and in the manufacturing process of the microphone device, it is also
required to monitor and measure the characteristic change during surface mounting on the user
side, that is, the change in the stiffness of the vibrating film. Be
Under such circumstances, correcting the resulting sensitivity variation after manufacturing is a
serious problem.
[0015]
Then, if sensitivity adjustment can be performed after manufacturing, it is possible to improve
the quality of the microphone device having variations in sensitivity, and to provide a
microphone device having uniform sensitivity and less variation in characteristics.
18-04-2019
4
[0016]
The present invention has been made in view of the above-described circumstances, and an
object thereof is to provide a microphone device in which sensitivity adjustment is easy and
characteristic variation is small.
In particular, it is an object of the present invention to provide a microphone device capable of
adjusting the sensitivity if there is variation, while measuring the stiffness of the vibrating film
after sealing with a sealing body such as a metal cap or in the process of mounting on a circuit
board. Do.
[0017]
Therefore, in the present invention, the capacitor electrode terminal connected to the second
electrode of the capacitor unit and the ground terminal are separately derived from the
microphone device, and the sensitivity adjustment voltage is applied between the capacitor
electrode terminals and the ground terminal. It is characterized in that the sensitivity adjustment
is made possible by making the other ones the same as in actual use. For example, when
performing the sensitivity measurement, connect the measurement terminals between these
electrode terminals, Film stiffness measurement can be performed, and when used as a
microphone, apply sensitivity adjustment voltage between the capacitor electrode terminal and
the ground terminal, or make common connection by connecting to the same electrode pad, etc.
The sensitivity adjustment is performed to make it possible to realize a microphone device having
a desired sensitivity.
[0018]
That is, the microphone device of the present invention includes a vibrating membrane as a first
electrode, a dielectric film fixed to the vibrating membrane, and a second electrode disposed to
face the first electrode. A capacitor unit constituted by a microphone and an amplifier connected
to the first electrode of the capacitor unit for amplifying a signal from the capacitor unit are
mounted in a container, and the second electrode of the capacitor unit is mounted. A capacitor
electrode terminal to be connected, a voltage supply terminal to be connected to the amplifier, a
ground terminal, and an output terminal from the amplifier are provided.
18-04-2019
5
With this configuration, the sensitivity adjustment voltage is applied between the capacitor
electrode terminal conventionally connected in common and the ground terminal, so that the
sensitivity adjustment can be performed only by the sensitivity adjustment voltage without
changing the original configuration of the microphone device. It is possible to reduce the
sensitivity variation in the mounted state on the microphone device and further on the circuit
board after mounting.
[0019]
In the present invention, in the microphone device, the capacitor unit and the amplifier are
housed in a container, and the voltage supply terminal, the output terminal, the capacitor
electrode terminal, and the ground terminal are derived from the container. Including the
With this configuration, it is possible to adjust the sensitivity only by adjusting the voltage
applied between the capacitor electrode terminal and the ground terminal. Therefore, after
mounting, it is possible to perform sensitivity adjustment with high accuracy, such as
compensating for sensitivity variations due to temperature, humidity, and the like.
[0020]
Further, in the present invention, in the above-mentioned microphone device, the capacitor
electrode terminal includes one which is a sensitivity control voltage application input terminal.
[0021]
Further, according to the present invention, in the microphone device, the capacitor unit and the
amplifier are mounted on a first surface of the same substrate, and the capacitor electrode
terminal, the voltage supply terminal, the ground terminal, and the output terminal are the same.
The second side of the substrate includes one disposed as a surface mount terminal.
According to this configuration, a variable voltage can be easily applied between the capacitor
electrode terminal and the ground terminal, and sensitivity adjustment is easy.
18-04-2019
6
[0022]
In addition, it is possible to adjust between the capacitor electrode terminal and the ground
terminal without changing the original configuration of the microphone device only by
separately and separately deriving the capacitor electrode terminal commonly connected in
common and the ground terminal separately. By applying a voltage, sensitivity adjustment is
possible, and it is possible to realize sensitivity adjustment of the microphone device after
mounting, and further, the microphone device in a state of being surface mounted on a circuit
board. In addition, film stiffness measurement extremely close to the mounting state can be
realized nondestructively for itself as a microphone device. Therefore, if this measurement result
is fed back to the design of the microphone device, it is possible to realize extremely accurate
characteristic control.
[0023]
Further, according to the present invention, in the above-mentioned microphone device, the
capacitor electrode terminal, the voltage supply terminal, the ground terminal, and the output
terminal have the same terminal shape and are arranged in two rows and two columns.
According to this configuration, surface mounting is easily possible at the time of mounting, and
connection is extremely easy even when adjusting the voltage between the capacitor electrode
terminal and the ground terminal.
[0024]
Further, in the present invention, the above-mentioned microphone device includes one in which
the capacitor electrode terminal and the ground terminal are disposed adjacent to each other.
According to this configuration, connection is extremely easy when adjusting the voltage
between the capacitor electrode terminal and the ground terminal.
[0025]
In the present invention, it is possible to adjust the sensitivity of the microphone device only by
adjusting the applied voltage between the capacitor electrode terminal and the ground terminal.
Further, with regard to the sensitivity variation in the mounting process, it is possible to provide
18-04-2019
7
a microphone device having a truly uniform sensitivity only by adjusting the sensitivity control
application voltage according to the state after mounting.
[0026]
Hereinafter, embodiments of the present invention will be described in detail with reference to
the drawings. FIG. 1 is a diagram schematically showing the configuration of a microphone
device according to an embodiment of the present invention. In the present embodiment, the
microphone device is characterized in that the capacitor electrode terminal connected to the
second electrode of the MEMS microphone chip M constituting the capacitor unit and the ground
terminal are separately derived. The sensitivity adjustment is easily realized by applying a
desired voltage between the capacitor electrode terminal and the ground terminal in the
sensitivity adjustment.
[0027]
1 (a), FIG. 2 is a top view, a side view and a bottom view of the microphone device, FIG. 3 is an
internal configuration of the microphone device, and FIG. As shown in the cross-sectional view, a
MEMS microphone (chip) M constituting a common capacitor unit and a CMOS amplifier A
connected thereto and an amplifier are mounted on the circuit board 100 for mounting, and a
metal cap 101 is used. It is sealed. The equivalent circuit diagram of this microphone device is
shown in the broken line portion 11 of FIG. 1A, in which a capacitor portion M and a CMOS
amplifier A are connected, and a capacitor electrode terminal Ei which is a second electrode of
the capacitor portion The ground terminal EG of the amplifier A is independently taken out as a
capacitor electrode pad Pi and a ground pad PG, and constitutes an external terminal. On the
other hand, as shown in FIG. 1 (b), in a normal microphone device, a capacitor electrode terminal
Ei which is a second electrode of the capacitor unit and a ground terminal EG of the CMOS
amplifier A are formed on an internal circuit or a circuit board. Are commonly connected and
taken out as the ground terminal EG. Although details will be described later, as shown in FIG.
1A, the capacitor electrode terminal Ei and the ground terminal EG of the CMOS amplifier A are
separately taken out, and sensitivity adjustment is performed between the capacitor electrode
pad Pi and the ground pad PG. The sensitivity control voltage composed of the variable voltage
VR of each unit is connected and used as a sensitivity variable microphone.
[0028]
That is, the microphone device of the present invention is configured of a microphone provided
18-04-2019
8
with a first electrode which is the diaphragm 23, and a second electrode as the fixed electrode 26
disposed opposite to the first electrode. A capacitor unit (see FIG. 4) and an amplifier A
connected to the first electrode of the capacitor unit and amplifying a signal from the capacitor
unit are mounted in a container made of a metal cap 101, as shown in FIG. ) Through (c) show
external views (top view, side view, bottom view), a capacitor electrode terminal Ei connected to
the second electrode of the capacitor unit, and a voltage connected to the amplifier A. The supply
terminal EV, the ground terminal EG, and the output terminal EO from the amplifier A are led out
from the container, and pads (capacitor electrode pad Pi, voltage supply pad PV) are provided on
the back side of the circuit board 100, respectively. , A ground pad PG, and an output pad PO
from the amplifier (CMOS amplifier) A.
[0029]
Then, as shown in FIGS. 3A and 3B, the inside of the microphone device is mounted on a printed
wiring board (circuit board) 100 on which a capacitor portion M and a CMOS amplifier A have a
circuit pattern formed, and a metal The four pads described above, ie, the capacitor electrode pad
Pi, the voltage supply pad PV, the ground pad PG, and the output pad PO are formed on the back
surface side of the circuit board 100, and sealed with a cap 101. .
[0030]
This silicon microphone chip M, as shown in FIG. 4, comprises a silicon substrate 21 and a
polycrystalline silicon film formed on this surface, and a vibrating film 23 as a first electrode
which functions as one pole of a capacitor. A silicon oxide film as an electret film (film to be
electretized) 24, a spacer portion 25 made of a silicon oxide film, and a fixed electrode 26
functioning as the other electrode of a capacitor and a silicon substrate 21 are formed by
etching. The back air chamber 28 is provided.
The fixed electrode 26 is provided with a plurality of sound holes (openings for introducing
sound waves to the vibrating film 23) 27.
Reference G indicates an air gap, and H indicates a contact hole for electrical connection.
[0031]
The vibrating film 23, the fixed electrode 26, and the inorganic dielectric film 24 constituting the
microphone are manufactured using silicon microfabrication technology and CMOS
18-04-2019
9
(complementary field effect transistor) manufacturing process technology, and so-called MEMS
element Configure.
[0032]
The result of measuring the microphone output voltage when changing the sensitivity control
voltage configured by the variable voltage VR of the sensitivity adjustment unit using this
microphone device is shown in FIG.
As is apparent from this figure, as the voltage adjustment unit consisting of the variable voltage
VR connected between the capacitor electrode pad Pi and the ground pad PG is connected to
change the applied voltage, the sensitivity can be changed. It turns out that you can do it.
[0033]
Therefore, it is extremely easy to adjust the sensitivity variation by this voltage control after
completion. Further, even when it is desired to change the sensitivity at the time of use, the
desired sensitivity can be extremely easily obtained only by the voltage control.
[0034]
Next, the change in sensitivity of the microphone device according to the sensitivity control
voltage will be described mathematically using FIG. Here, an electret type MEMS microphone
device in which a dielectric film fixed to a vibrating film holds a permanent charge is used. As the
sensitivity of the microphone is well known,
[0035]
であらわされる。 Each symbol is as shown below. v [dBV]: Microphone output voltage P [Pa]:
Specified sound pressure Sdis [m <2>]: Vibrating film area S0 [N / m]: Vibrating film stiffness SB
[N / m]: Back air chamber stiffness d0 [ m]: Air gap length EBIAS [v]: Electret voltage Cm [F]:
MEMS chip capacity Cin [F]: CMOS amplifier input capacity G [V / V]: CMOS amplifier
18-04-2019
10
amplification degree
[0036]
In FIG. 5, the sensitivity control voltage is 0 [V] (in a state where the capacitor electrode terminal
and the ground terminal are shorted) and the microphone output voltage is finite (here, about 9
[mV / Pa] =-41 [dBV / Pa] The symbol) indicates that it is equivalent to the voltage of EBIAS [V]
due to permanent charge. Therefore, when a voltage of ± Vc is applied to the capacitor electrode
terminal and the ground terminal through the variable voltage VR of the external sensitivity
adjustment unit as shown in the configuration of FIG. 1 (a), the microphone output voltage
changes as shown in FIG. Do. For example, when +5 [V] is applied, it changes from about 9 [mV /
Pa] to about 4 [mV / Pa], and when -5 [V] is applied, about 9 [mV / Pa] to about 15 Change to
"mV / Pa". Mathematically,
[0037]
The microphone output voltage can be adjusted by the sensitivity control voltage Vc.
[0038]
Second Embodiment When it is desired to perform film stiffness measurement using the
microphone device of the first embodiment, the measurement terminals are connected between
these electrode terminals, and the film stiffness measurement is performed in the mounted state.
To achieve.
This device is also applicable as a film stiffness measuring device.
[0039]
When the measurement target is, for example, a diaphragm of a MEMS microphone, as shown in
FIG. 6 and FIG. 7A, the film stiffness measurement device changes the measurement frequency
and the vacuum container 30 housing the MEMS microphone device 20. The response
measurement unit 40 for measuring the input / output response characteristics of the MEMS
microphone 20 placed in vacuum, and the stiffness calculation for calculating the film stiffness of
18-04-2019
11
the MEMS microphone 20 by obtaining the resonance frequency of the diaphragm from the
frequency-input / output response characteristic curve And a display unit 52 for displaying a
frequency-input / output response characteristic curve and the like. FIG. 7A is an equivalent
circuit diagram showing this film stiffness measuring device.
[0040]
The vacuum vessel 30 includes a mounting table on which the MEMS microphone device 20 is
set, and also includes a terminal mechanism that enables the MEMS microphone device 20 to be
energized from the outside of the vacuum vessel. In the MEMS microphone device 20, the MEMS
device (M) is connected to the CMOS amplifier (A), and further, a microphone device 20
configured by a circuit board with predetermined wiring connection to the external terminal of
the microphone device and a cap covering them. The terminal mechanism is set so as to be able
to energize each conductive portion in the state of (1).
[0041]
The stiffness calculation unit 51 obtains the resonance frequency of the diaphragm from the
frequency-input / output response characteristic curve measured by the input / output response
characteristic measurement unit 40, and substitutes this resonance frequency into (Equation 3)
to vibrate the MEMS microphone device 20 Calculate the board stiffness. Where f0: resonant
frequency of the vibrating membrane [Hz] s0: membrane strength (stiffness) [N / m] m0: mass of
the vibrating membrane [kg]
[0042]
As described above, in this measurement device, the resonance frequency to be substituted into
(Equation 3) is obtained from the measurement result of the input / output response
characteristic of the MEMS microphone device 20.
[0043]
As shown in FIG. 7A, the input / output response characteristic measurement unit 40 that
performs input / output response characteristic measurement is connected to an AC voltage
source 61 and a DC voltage source 62 that are excitation sources of the MEMS microphone
18-04-2019
12
device 20, And a voltmeter for measuring each voltage of the output and a phase measurement
meter for measuring the phase difference between the input and the voltage.
The DC voltage source 62 is installed as needed. As shown in FIG. 7A, the equivalent circuit
diagram of the microphone device at the time of film stiffness measurement is a capacitor
electrode terminal Ei, which is a second electrode of the capacitor unit, in which the capacitor
unit M and the CMOS amplifier A are connected. The ground terminal EG of the amplifier A is
independently taken out as a capacitor electrode pad Pi and a ground pad PG, and constitutes an
external terminal.
[0044]
When an excitation voltage is applied to one input end of the MEMS chip, a voltage divided by
the capacitance of the MEMS chip and the input capacitance of the CMOS amplifier is generated
at the input end of the CMOS amplifier. This voltage is multiplied by the gain of the CMOS
amplifier (G The output voltage amplified by the) is generated at the output end of the CMOS
amplifier.
[0045]
The characteristics of this input / output voltage are represented by impedance division ratio and
gain.
[0046]
Next, it will be described that this Vo or Vo / Vin is represented by the characteristics of the
capacitance and mechanical impedance of the MEMS chip.
The mechanical impedance of the acoustic system of the MEMS microphone 20 can be
represented by an electrical equivalent circuit shown in FIG. 7B.
[0047]
Here, A is the mechanical impedance composed of the cap 101 and the substrate 100 of the
MEMS microphone shown in FIG. 3, r1 and m1 are the mechanical impedances of the holes of
18-04-2019
13
the cap and C1 is the compliance of the air chamber composed of the cap and the substrate (Ie,
the reciprocal of the stiffness).
B is the mechanical impedance of the diaphragm (diaphragm electrode 23 + electret film 24)
shown in FIG. 4, m0 is the mass of the diaphragm, c0 (= 1 / so) is the compliance of the
diaphragm, r0 is the diaphragm It is its own mechanical resistance. rs is the mechanical
resistance of a thin fluid layer composed of a diaphragm and a fixed electrode. Also, r2 and m2
are the radiation impedance of the diaphragm, C2 is the compliance of the thin fluid layer, and
C3 is the air compliance of the air chamber composed of the back air chamber 28 and the
substrate of FIG.
[0048]
As described above, since the MEMS chip 20 in the air has mechanical impedance by air in
addition to the mechanical impedance of the diaphragm, when measuring the input / output
response characteristic of the MEMS microphone device 20 in air, , It is extremely difficult to
measure the mechanical impedance effect of the diaphragm itself.
[0049]
The compliances c1, c2 and c3 caused by the air in the front air chamber and the back air
chamber 28 of this diaphragm are expressed by the following equation (5).
C: acoustic compliance [m <5> / N] γ: volume specific heat of air [J / m <3> K] V: air chamber
volume [m <3>] P0: atmospheric pressure [N / m <2>] It is.
[0050]
In this measurement apparatus, since the MEMS microphone device 20 is disposed in a vacuum,
the value of C (= c1, c2, c3) becomes an extremely large value, which causes a short circuit state.
Therefore, the equivalent circuit of the capacitor section in the vacuum vessel is represented only
by the mechanical impedance of the diaphragm itself. The reversible equation of this capacitor
part is expressed by the following equation (Equation 6) (Equation 7) (see “Introduction to
Electroacoustic Engineering” published by Shokodo Co., Ltd., published by Masatoshi
Kawamura).
18-04-2019
14
[0051]
V1: AC voltage of excitation source [V] Zm: Mechanical impedance of the vibration plate to be
measured EB: DC voltage of excitation source [V] A: Force coefficient ε0: Permittivity of vacuum
8.85E-12 [F / m] S: Area of capacitor section [m <2>] Cm: Electric capacitance of capacitor
section [F] d0: Air gap distance [m] V: Speed of diaphragm [m / sec] sn: Negative stiffness [N / m]
[0052]
Here, the mechanical impedance of the diaphragm to be measured is
[0053]
Also, the force factor is
[0054]
Also, the capacitance of the capacitor unit is represented by
[0055]
Also, negative stiffness is represented by
[0056]
The equation (6) is an equation focusing on the mechanical force relationship of the diaphragm,
and the equation (7) is an equation focusing on the electrical relationship of the diaphragm.
In this measurement apparatus, since the diaphragm of the MEMS microphone 20 is driven by
the excitation source, the external force F is 0, and the equation 6 is expressed as the equation
12.
[0057]
Therefore, the equation (7) can be transformed into the following equation (equation 13) using
the equation (12).
18-04-2019
15
[0058]
Therefore, the impedance of the MEMS chip is given by the following equation (Equation 14).
[0059]
This impedance corresponds to the impedance of an equivalent circuit in which the electric
capacity Cm and the diaphragm mechanical impedance are arranged in parallel as shown in FIG.
From this, Vo / Vin is expressed as follows. The input impedance of the CMOS amplifier is
expressed as follows, and it is expressed as a function of the resonance frequency f0 of the
vibrating film and the processing Q of resonance and has phase information and gain resonance
information. An input / output response curve is obtained.
[0060]
Further, in the measurement circuit of FIG. 7A, the frequency of the AC voltage Ei is measured
while sequentially switching to each frequency of the predetermined frequency band, whereby
the frequency-input / output response curve a and the frequency shown in FIGS. A phase curve b
is obtained.
FIG. 10 is a diagram in which the frequency-phase curve is added to the enlarged view of the
main part of the frequency-input / output response curve of FIG.
[0061]
For example, the frequency-input / output response curve shown in FIG. 9 is displayed on the
display unit 52.
From this curve, the stiffness calculation unit 51 searches for the frequency of the antiresonance
point and the frequency of the resonance point, obtains the resonance frequency f0 by averaging
two frequencies, and substitutes this value into (Equation 1) The stiffness of the diaphragm of the
18-04-2019
16
MEMS microphone 20 is calculated.
[0062]
Alternatively, the stiffness calculation unit 51 obtains an intersection point of the curve portion
of the resonance-antiresonance portion of the frequency-input / output response curve and the
constant gain curve, and substitutes the value into (Equation 1) to set the stiffness of the
diaphragm calculate.
[0063]
Also, for example, the frequency-phase curve shown in FIG.
The stiffness calculation unit 51 obtains the peak of this curve as the resonance frequency f0,
and substitutes this value into (Equation 1) to calculate the stiffness of the diaphragm of the
MEMS microphone 20.
[0064]
As described above, in this film stiffness measurement method, since the resonance frequency is
obtained from the frequency-input / output response curve a-phase curve b shown in FIG. 9 of
the microphone device, measurement can be performed inexpensively.
In addition, even in the case where a diaphragm having high stiffness is a target, such as a MEMS
microphone, it is possible to obtain reproducible measurement results in a short time.
[0065]
In addition, since the measurement object is placed in vacuum and the stress measurement of the
input and output is performed, the influence of air around the diaphragm can be eliminated, and
the input and output response of only the diaphragm can be accurately measured. be able to.
[0066]
18-04-2019
17
The vacuum level at this time may be about 10 <-1> to 10 <-2> Torr, and can be set in a short
time by a vacuum pump.
Further, in this measurement apparatus, since the input / output response measurement unit
measures the absolute value | G | of the gain and the phase angle, accurate measurement results
equivalent to the impedance measurement in the equivalent circuit of FIG. You can get it.
[0067]
Further, in this measuring apparatus, by adjusting the DC voltage Eb supplied from the DC
voltage source 62, the force coefficient A of Equation 14 is changed to set the value of the input /
output response to an appropriate value. Can.
[0068]
Further, measurement of input / output response may be performed using a commercially
available frequency response measuring device.
[0069]
The display unit 52 and the stiffness calculation unit 51 can be realized using the function of a
personal computer (PC).
In this case, when the PC specifies the measurement frequency band to the input / output
response measurement unit 40, and the input / output response measurement unit 40 scans the
specified frequency band and outputs the input / output measurement result to the PC, the PC
screen is displayed. The absolute value of gain | G | and the phase angle can be displayed.
[0070]
Then, in this way, the film stiffness is measured, and as shown in FIG. 11, by connecting the
capacitor electrode pad Pi and the ground pad PG via an external voltage adjustment unit by
solder or the like, the desired sensitivity can be obtained. It can be used as a microphone device.
[0071]
18-04-2019
18
Although the case of using the MEMS microphone device has been described in the above
embodiment, the present invention can also be applied to other electrostatic electroacoustic
transducers.
[0072]
According to the microphone device of the present invention, since sensitivity adjustment can be
realized after mounting, sensitivity control with high accuracy is possible, and can be widely used
for a MEMS microphone and an electret condenser microphone.
[0073]
The figure which shows the microphone apparatus used in Embodiment 1 of this invention, (a) is
an equivalent circuit diagram of the microphone apparatus of Embodiment 1 of this invention, (b)
is an equivalent circuit diagram of a normal microphone apparatus, this invention (A) is a top
view, (b) is a side view, and (c) is a bottom view showing the internal configuration of the
microphone device used in the embodiment of the present invention. Cross-sectional view of
MEMS chip. Diagram showing relationship between sensitivity control voltage and output voltage
of microphone device in the first embodiment of the present invention. Diagram showing the
same film thickness measurement apparatus in the second embodiment of the present invention.
4A shows an equivalent circuit of a film stiffness measuring apparatus, and FIG. 4B shows an
equivalent circuit of mechanical impedance of a MEMS microphone. Film stiffness measurement
according to an embodiment of the present invention The figure which shows the equivalent
circuit of a circuit. The figure which shows the frequency-impedance curve measured by the film
stiffness measurement method in the embodiment of the present invention. The frequency-phase
curve measured by the film stiffness measurement method in the embodiment of the present
invention. The figure which shows the microphone apparatus in embodiment of this invention
The figure which shows the structure of the electret condenser microphone of a prior art
example
Explanation of sign
[0074]
111 diaphragm 112 fixed electrode 113 electret film 114 spacer 115 sound hole 116 back air
chamber 117 case 118 printed board 20 MEMS microphone 21 silicon substrate 22 insulating
layer 23 vibrating film electrode 24 electret film 25 second insulating layer 26 fixed electrode 27
sound Hole 28 back air chamber 30 vacuum vessel 40 input / output response measurement
unit 51 stiffness calculation unit 52 display unit 61 AC voltage source 62 DC voltage source
18-04-2019
19
18-04-2019
20
Документ
Категория
Без категории
Просмотров
0
Размер файла
32 Кб
Теги
jp2009118264, description
1/--страниц
Пожаловаться на содержимое документа