JP2005043166A - Electrostatic capacitance type acceleration sensor and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To acquire an electrostatic capacitance type acceleration sensor capable of absorbing detection output variations due to variations of parasitic capacitance and components. <P>SOLUTION: The electrostatic capacitance type acceleration sensor 1 is provided with a detection part 2 for detecting acceleration on the basis of changes in electrostatic capacitance, a circuit board 40 having a terminal for electrically connecting the detection part 2 to the outside, and a case 75 or housing both the detection part 2 and the circuit board 40. Part of the circuit board 40 has an adjusting part 45 for adjusting the output of the electrostatic capacitance type acceleration sensor. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a capacitance type acceleration sensor that detects a change in capacitance and detects a force or acceleration in a predetermined axial direction. In particular, the present invention relates to output adjustment in a capacitive acceleration sensor.
[0002]
[Prior art]
In a conventional capacitive acceleration sensor, a flexible plate (diaphragm) made of a conductive material is used as a common electrode, and a detection electrode such as a copper foil is disposed on a printed board opposite to the common electrode, and between these electrodes. The change of the electrostatic capacitance which arises is detected (for example, refer patent document 1).
[0003]
[Patent Document 1]
JP 2000-249609 A (summary of front page and selection diagram for summarization)
[0004]
[Problems to be solved by the invention]
However, in the capacitance type acceleration sensor, the zero point output of the sensor deviates from the set value due to the influence of variations due to the mass production of the finished dimensions of each component and the parasitic capacitance on the pattern formed on the substrate. It will vary.
[0005]
Conventionally, efforts have been made to deal with the effects of parasitic capacitance to some extent within the CV conversion circuit. However, there is no countermeasure for the deviation of the set value due to the assembly of each component with different finishes such as dimensions. Measures have been taken to the limit, but these have not been sufficient.
[0006]
Accordingly, an object of the present invention is to provide a capacitive acceleration sensor that can absorb variations in detection output due to variations in parasitic capacitance and components.
[0007]
[Means for Solving the Problems]
In order to solve the above problems, in the present invention, a detection unit that detects acceleration by a change in capacitance,
A circuit board having terminals for electrical connection between the detector and the outside;
A case for housing the detection unit and the circuit board;
In a capacitive acceleration sensor with
A capacitance type acceleration sensor having an adjustment unit for adjusting the output of the capacitance type acceleration sensor on a part of the circuit board. As a result, the sensor output variation due to the influence of the parasitic capacitance on the pattern formed on the substrate and the variation due to the mass production of each component finished dimension can be adjusted by the adjusting unit provided on a part of the circuit board.
[0008]
In addition, if the adjustment unit is a capacitance type acceleration sensor configured by connecting a plurality of resistors in parallel by a resectable wiring, the sensor output can be easily performed by resecting the resectable wiring connecting the resistors. Can be adjusted.
[0009]
Further, if the adjustment unit is a capacitance type acceleration sensor constituted by a circuit pattern that can be deleted, variation in sensor output can be adjusted by a very simple pattern formation.
[0010]
Further, if the housing case is a capacitance type acceleration sensor provided with a window hole corresponding to the adjustment portion of the circuit board sealed in the housing case, the sensor is opened from the window hole of the case after sealing the circuit board. It is possible to adjust the output variation, and it is possible to adjust the overall variation due to almost all elements that affect the variation in sensor output.
[0011]
A detection unit that detects acceleration by a change in capacitance;
A circuit board having terminals for electrical connection between the detector and the outside;
An adjustment unit for adjusting the output of the capacitive acceleration sensor provided on a part of the circuit board;
A case for housing the detection unit and the circuit board;
In a capacitive acceleration sensor with
Manufacturing of a capacitive acceleration sensor in which the detection unit and the circuit board are assembled in the case, and then the circuit board is sealed, and then the output of the capacitive acceleration sensor is adjusted by the adjustment unit. If the method is adopted, the influence on the sensor output by many factors affecting the sensor output can be adjusted.
[0012]
A detection unit that detects acceleration by a change in capacitance;
A circuit board having terminals for electrical connection between the detector and the outside;
An adjustment unit for adjusting the output of the capacitive acceleration sensor configured by parallel connection of a plurality of resistors by a resectable wiring provided on a part of the circuit board;
A case for housing the detection unit and the circuit board;
In a capacitive acceleration sensor with
After the detection unit and the circuit board are assembled in the case, the circuit board is sealed, and then a part of the wiring of the plurality of resistors is cut off to thereby remove the capacitance-type acceleration sensor. If the manufacturing method of the capacitance-type acceleration sensor which performs output adjustment is taken, the influence on the sensor output by many elements which influence a sensor output can be adjusted more simply.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
[0014]
FIG. 1 is a cross-sectional view illustrating the principle of a detection unit as an embodiment of a capacitive acceleration sensor according to the present invention. First, the principle of acceleration detection will be described with reference to FIG. The capacitive acceleration sensor in this embodiment can detect accelerations in the X, Y, and Z axis directions shown in the lower part of FIG. 1, but only the detection principle in the X axis direction will be described here. The same applies to the detection of acceleration in the Y-axis direction, and the Z-axis direction is detected with a simpler configuration as described later.
[0015]
In FIG. 1, the detection unit 2 supports a flexible and conductive diaphragm 30 via spacers 61 and 62 described later in a space between the upper printed circuit board 10 and the lower printed circuit board 20. Is done. Detection electrodes E11 and E12 are formed on the upper printed circuit board 10, and detection electrodes E21 and E22 are formed on the lower printed circuit board 20 so as to face the diaphragm 30. A weight 35 is fixedly supported on the diaphragm 30 at the tip end of the center leg 36. Thus, a capacitance C _x− (1) is formed between the diaphragm 30 and the detection electrode E11, and a capacitance C _{x +} (1) is formed between the diaphragm 30 and the detection electrode E12. In addition, a capacitance C _{x +} (2) is formed between the diaphragm 30 and the detection electrode E21, and a capacitance C _x− (2) is formed between the diaphragm 30 and the detection electrode E22.
[0016]
When the capacitive acceleration sensor 1 receives the acceleration GX in the X-axis direction, the weight 35 tilts as shown by the dotted line in FIG. 1 due to the inertia of the weight 35, and the diaphragm 30 is displaced as shown by the dotted line. As a result, the capacitances C _x− (1), C _{x +} (2), C _{x +} (1), and C _x− (2) change. In a tilt displacement such as a dotted line, each capacitance C _x− (1) and C _x− (2) is small, and each capacitance C _{x +} (2) and C _{x +} (1) is large. Become.
[0017]
In order to increase the detection sensitivity, the sum of the capacitance C _{x +} = [C _{x +} (1)] + [C _{x +} (2)], which increases the capacitance, is output to the terminal 51 by wiring as shown in FIG. The sum C _x− = [C _x− (1)] + [C _x− (2)] of both of which the electric capacity is reduced is output to the terminal 52.
[0018]
FIG. 2 is a circuit diagram of a circuit unit including a circuit for further calculating the capacitance detected by the detection unit of FIG. 1 and performing C / V conversion and an adjustment circuit for adjusting the zero point.
[0019]
The outputs of the terminals 51 and 52 are respectively input to the terminals X + and X− of the circuit unit 50 shown in FIG. 2, and the subtraction / C / V conversion circuit 54 in the conversion arithmetic circuit 53 first subtracts C _x = [ C _{x +} ] − [C _x− ] and C / V conversion (capacitance-voltage conversion) is performed. This voltage output is output from the capacitive acceleration sensor through the adjustment circuit 55 as Xout.
[0020]
The adjustment circuit 55 includes an operational amplifier 56, a non-inverting amplifier circuit including resistors R1 and R2, and R5-1, R5-2, and R5-3 connected in parallel with each other in series with the resistor R4. An adjustment unit 45 that adjusts the voltage, an amplifier circuit, the adjustment unit 45, a filter circuit (R3, C1) connected between Xout, and the like are included.
[0021]
The above is the principle of detecting the acceleration component in the X-axis direction, but the acceleration component in the Y-axis direction is also detected in the same principle by the same detection electrode arrangement and is input to the terminals Y− and Y + in FIG. The detection result is output as Yout.
[0022]
The acceleration component in the Z-axis direction was provided in a ring shape on the lower printed circuit board 20 in the same manner between the detection electrode and the diaphragm provided in the vicinity of the center of the periphery of the hole 11 of the upper printed circuit board 10 and the diaphragm. Capacitances between the detection electrode and the diaphragm are respectively input to terminals Z− and Z + in FIG. 2, and the difference between them is calculated by the circuit unit 50 and output to the terminal Zout as a voltage output. Further, as shown in FIG. 2, an adjustment circuit having an adjustment unit similar to the acceleration component circuit unit in the X-axis direction is also provided in the acceleration component circuit unit in the Y-axis direction and the acceleration component circuit unit in the Z-axis direction. Provided.
[0023]
Next, a specific structure of the capacitive acceleration sensor according to this embodiment will be described with reference to FIGS. FIG. 3 is a cross-sectional view taken along line AA of FIG. 4 showing a specific structure of the capacitive acceleration sensor according to the principle of FIG. FIG. 4 is a bottom view showing a specific structure of the capacitive acceleration sensor according to the principle of FIG. FIG. 5 is a bottom view of the circuit board used in FIGS. 3 and 4.
[0024]
As described above, the detection unit 2 is sandwiched between the upper printed circuit board 10 and the lower printed circuit board 20 by the spacers 61 and 62 and the diaphragm 30 is supported. The end of the weight 35 is fixed to the diaphragm 30 by caulking. A guide 70 for maintaining the mobility of the weight 35 is attached thereto. On the surface opposite to the guide 70, the circuit board 40 on which the chip components 41 and 42 are mounted is attached. These attachments are performed by rivets 63, pins 65, adhesion, and the like. The circuit board 40 holds five pins 64 for transmitting output to the outside, and the pins 64 extend out of the case bottom plate 76. A detection body S2 in which the detection unit 2, the guide 70, and the circuit board 40 are integrated is housed in a case 75 and sealed by a case bottom plate 76. A window hole 90 corresponding to the adjustment unit 45 is installed in the case bottom plate 76. The case bottom plate 76 finally seals the case 75 with the sealings 80, 81, 83, 84, and 82, but necessary adjustment is performed by cutting the adjustment circuit pattern 46 before the sealing 82 is sealed.
[0025]
The assembly process of the capacitive acceleration sensor in this embodiment is as follows. This will be described with reference to FIGS.
Step 1: The detection body S2 is placed in the case 75.
Step 2: An adhesive for forming the sealing 80 is applied to the periphery of the detection body S2.
Step 3: The case bottom plate 76 is set, and the adhesive applied in Step 2 is cured.
Step 4: Adhesive for forming the sealings 81, 83, 84 is applied to the base of the pin 64 and cured.
Step 5: Measure the zero point output without applying acceleration.
Step 6: An appropriate portion of the adjustment circuit pattern 46 is cut out from the window hole 90 of the adjustment unit 45 as necessary based on the measurement value of the step 5.
Step 7: An adhesive is applied and cured to form the sealing 82.
Step 8: The zero point output is measured again with no acceleration applied (Step 8 can be omitted if the adjustment in Step 6 is reliable enough). This completes the assembly.
[0026]
Next, the arrangement state of the wiring pattern 44 and the chip component 42 formed on the bottom surface side of the circuit board 40 will be described with reference to FIGS. FIG. 2 is a circuit diagram of a circuit unit that further calculates the capacitance detected by the detection unit of FIG. 1 and performs C / V conversion and adjustment as described above. FIG. 4 is a bottom view showing the specific structure of the capacitive acceleration sensor according to the principle of FIG. 1 as described above. FIG. 5 is a bottom view of the circuit board used in FIGS. 3 and 4. In FIG. 5, a conductive pattern 47 and a wiring pattern 44 are formed on the bottom surface of the circuit board 40 by printing or printing and etching. Chip components 42 such as resistors and capacitors are mounted by soldering or the like in connection with these wiring patterns. Resistors R5-1, R5-2, R5-3, R4, R10-1, R10-2, R10-3, R15-1, R15-2, R15-3, R4, R9, R14, etc. shown in FIG. Is also shown on FIG. The positions of the window holes 90 provided in the case bottom plate 76 of FIG. 4 are indicated by dotted lines in FIG. FIG. 2 is also shown by three broken lines for convenience.
[0027]
Next, the operation of the adjustment circuit 55 and the zero point adjustment will be described with reference to FIG. Similar to the description of the circuit configuration based on FIG. 2 described above, the circuit portion for the X-axis direction acceleration will be described first.
[0028]
When the acceleration in the X-axis direction applied by the capacitance type acceleration sensor is zero, that is, 0G, the output of the terminal Xout (zero point output) is ½ the power supply voltage Vcc (that is, Xout = Vcc / 2). And want to set. Here, for example, the standard value of the zero point output is Vcc / 2 ± 20%. Ideally, resistance R4≈resistor R5 and Xout≈Vcc / 2. However, the variation in Xout tends to be very large as described above due to the influence of parasitic capacitance and the like.
[0029]
When R4> R5, Xout> Vcc / 2 theoretically. Therefore, the resistor R5 is configured as a parallel connection of R5-1, R5-2, and R5-3. The resistor R5 having this configuration is intentionally set lower than the resistor R4. As a result, Xout as the zero point output is intentionally set high. Xout as the zero point output falls within the standard or is highly deviated from the standard.
[0030]
Therefore, R5-3 is cut with respect to those that deviate from this standard, and the combined resistance value of R5 is increased. As a result, the zero point output at the terminal Xout is shifted downward. If it falls within the standard, the cut is complete. If the zero point output is not high enough to fall, R5-2 is further cut and adjusted. In this embodiment, the above three adjustments are possible.
[0031]
Thus, the signals input from the detection unit to the terminals X + and X− are X + = X− and Xout = ½ Vcc when no acceleration is applied. However, Xout deviates from 1/2 Vcc due to the influence of parasitic capacitance and the like due to manufacturing variations. The zero point adjustment is performed by finely adjusting the reference voltage (1/2 Vcc) set by the resistors R4 and R5 for the Xout at the time of no acceleration.
[0032]
In particular, when the adjustment is performed by the adjustment unit 45 after the sealing 81, 83, 84 is performed on the root of the pin 64, the adjustment can be performed after the sealing is performed on a portion that is susceptible to a capacitance change due to the sealing. Therefore, the capacitive acceleration sensor 1 that has been accurately adjusted is obtained.
[0033]
Next, based on FIG. 6, an adjustment unit used in another embodiment of the capacitive acceleration sensor according to the present invention will be described. FIG. 6 is a bottom view of a circuit board showing an adjustment unit used in another embodiment of the capacitive acceleration sensor. The input terminals 144a and 144c, which are part of the circuit pattern, are lands to which the X− and X + terminals of the circuit portion in FIG. 2 are respectively connected. Wiring is performed on the opposite surface (not shown) to the IC that is the conversion operation circuit, but the portion until these wiring lines enter the IC greatly affects the capacitance output of the detection unit. Therefore, adjustment is performed by extending (cutting) the circuit patterns to these input terminals 144a and 144c and providing cut portions 144b and 144d as adjustment portions, respectively. This embodiment has a simple structure in which the shape of the circuit pattern is changed and built, and can be easily adjusted in the production process.
[0034]
【The invention's effect】
As described above, according to the present invention, the adjustment unit for adjusting the output of the capacitive acceleration sensor is provided on a part of the circuit board of the capacitive acceleration sensor. The sensor output variation due to the influence of the parasitic capacitance on the pattern and the variation due to the mass production of the finished dimensions of each component can be adjusted by the adjusting unit provided on a part of the circuit board. In particular, it is suitable for adjusting the zero point output.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view illustrating the principle of a detection unit as an embodiment of a capacitive acceleration sensor according to the present invention.
FIG. 2 is a circuit diagram of a circuit unit that further calculates the capacitance detected by the detection unit of FIG. 1 and performs C / V conversion and adjustment.
3 is a cross-sectional view taken along the line AA of FIG. 4 showing a specific structure of the capacitive acceleration sensor according to the principle of FIG. 1;
4 is a bottom view showing a specific structure of a capacitive acceleration sensor according to the principle of FIG. 1; FIG.
5 is a bottom view of the circuit board used in FIGS. 3 and 4. FIG.
FIG. 6 is a bottom view of a circuit board showing an adjustment unit used in another embodiment of the capacitive acceleration sensor according to the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Capacitance type acceleration sensor, 2 detection part, 10 Upper printed circuit board, 11 holes, 18, 19 wiring, 20 Lower printed circuit board, 30 Diaphragm, 35 Weight, 36 Center leg part, 40 Circuit board, 41, 42 Chip components 45 adjustment unit 46 adjustment unit 44 wiring pattern 47 conductive pattern 50 circuit unit 51 terminal 52 terminal 53 conversion operation circuit 54 subtraction / C / V conversion circuit 55 adjustment circuit 56 operational amplifier 61 62 spacer, 63 rivet, 64, 65 pin, 70 guide, 75 case, 76 case bottom plate, 80, 81, 82, 83, 84 sealing, 90 window hole, 144b, 144d cut part, 144a, 144c input terminal, E11, E12, E21, E22 detection electrodes, R1, R2, R5, R5-1, R5-2, R5-3, R10- , R10-2, R10-3, R15-1, R15-2, R15-3, R4, R9, R14 resistors, Z-, Z + terminal, Zout terminal, S2 detector.

Claims (6)

A detection unit for detecting acceleration by a change in capacitance;
A circuit board having terminals for electrical connection between the detector and the outside;
A case for housing the detection unit and the circuit board;
In a capacitive acceleration sensor with
A capacitance-type acceleration sensor comprising an adjustment unit for adjusting an output of the capacitance-type acceleration sensor on a part of the circuit board. The capacitive acceleration sensor according to claim 1, wherein the adjustment unit is configured by connecting a plurality of resistors in parallel by a resectable wiring. The capacitive acceleration sensor according to claim 1, wherein the adjustment unit includes a circuit pattern that can be deleted. 4. The capacitive acceleration sensor according to claim 2, wherein the housing case has a window hole corresponding to an adjustment portion of a circuit board sealed in the housing case. A detection unit for detecting acceleration by a change in capacitance;
A circuit board having terminals for electrical connection between the detector and the outside;
An adjustment unit for adjusting the output of the capacitive acceleration sensor provided on a part of the circuit board;
A case for housing the detection unit and the circuit board;
In a capacitive acceleration sensor with
Capacitance characterized in that after the detection unit and the circuit board are assembled in the case, the circuit board is sealed, and then the output of the capacitive acceleration sensor is adjusted by the adjustment unit. Type acceleration sensor manufacturing method. A detection unit for detecting acceleration by a change in capacitance;
A circuit board having terminals for electrical connection between the detector and the outside;
An adjusting unit for adjusting the output of the capacitive acceleration sensor configured by parallel connection of a plurality of resistors by a resectable wiring provided on a part of the circuit board;
A case for housing the detection unit and the circuit board;
In a capacitive acceleration sensor with
After the detection unit and the circuit board are assembled in the case, the circuit board is sealed, and then a part of the wiring of the plurality of resistors is cut off to thereby remove the capacitance-type acceleration sensor. A method for manufacturing a capacitance type acceleration sensor, characterized by performing output adjustment.

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