JPH05223842A - Acceleration sensor - Google Patents

Abstract

PURPOSE:To lessen the mounting area of a circuit board constituting a gauge part and an electronic circuit part for signal processing by structuring so that the electronic circuit part is overlapped on the gauge part. CONSTITUTION:Pads 31, 33 for stationary electrodes 5A, 5B and a pad 32 for a movable electrode 3 are formed on the oversurface of a gauge part 1, which is electrically connected with an electronic circuit part 11 (IC chip) through these pads and the mating pads 34-36 formed on the oversurface of the circuit part 11 and wire bonding 14. Also the electroconductive pattern 15 formed on a circuit board 12 and the mating circuit part pads 37-40 are connected through wire bonding 14. This make the mounting area small, so that the stress applied to the joint lessens ever though vibration or shock is applied to lead to reduction of the fatigue. The overlapped provision of the gauge part 1 and circuit part 11 eliminates out of equilibrium of the two in the temp. distribution to lead to enhancement of the thermal characteristics of the sensor.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an acceleration sensor.

[0002]

2. Description of the Related Art Conventionally, an acceleration sensor is mounted on an automobile or the like, and motion control of various vehicles is performed based on the sensor signal.

A strain gauge type or capacitance type semiconductor sensor or the like is used as the acceleration sensor. As a mounting structure of the sensor, as disclosed in Japanese Patent Laid-Open No. 61-230383, a gauge portion (detection element) is provided on a circuit board.
An electronic circuit section for processing the sensor signal from the sensor was formed, and the gauge section was mounted in the remaining space of the circuit board.

FIG. 10 is a plan view showing an example of a typical conventional structure of this kind of acceleration sensor, in which a semiconductor type detection element (gauge section) 1 and an electronic circuit section 11 formed into an IC chip are arranged on a circuit board 12. They are arranged in parallel and are electrically connected to each other through wire bonding 14.

[0005]

According to the sensor mounting structure as described above, the circuit pattern cannot be formed at the mounting portion of the gauge portion 1 on the circuit board 12, and the electronic circuit portion 11 and Since the gauge part 1 and the gauge part 1 are arranged side by side on the circuit board, the mounting area becomes large and the miniaturization of the entire sensor cannot be achieved.

Further, although the gauge portion 1 and the electronic circuit portion 11 are connected by a structure in which they are bridged by the wire bonding 14, such a connection causes different movements due to external vibration or shock. The strength is likely to decrease due to fatigue due to stress concentration on both connecting portions.

Further, due to the effect of heat generation of the electronic circuit section 11, an imbalance occurs in the temperature distribution between the gauge section 1 and the electronic circuit section 11, which affects the output.

The present invention has been made in view of the above points, and an object thereof is to reduce the size and cost of an acceleration sensor of this kind, improve the reliability of the connection portion, and suppress the characteristic change of the sensor due to temperature change. An object is to provide an acceleration sensor that can be used.

[0009]

In order to achieve the above object, the present invention basically proposes the following means for solving the problems.

That is, in an acceleration sensor provided with a gauge section which is an acceleration detecting element and an electronic circuit section which processes an electric signal of the gauge section, an IC is provided on the gauge section.
It has a structure in which the electronic circuit portions formed into chips are stacked.

[0011]

[Function] An electronic circuit section (IC for signal processing) is provided on the gauge section.
By adopting a structure in which chips are stacked, the mounting area of the circuit board on which the gauge section and the electronic circuit section are mounted is reduced.

Further, since the electronic circuit portion is overlaid on the gauge portion, they integrally operate in the same manner against external vibration and impact, so that the connecting portion is not subjected to different stress, Reduces fatigue at the connection. Further, since the gauge section is integrated with the electronic circuit section, the heat generated in the electronic circuit section is transmitted to the gauge section, thereby eliminating the imbalance in the temperature distribution between the two and improving the temperature characteristic of the output.

[0013]

Embodiments of the present invention will be described with reference to the drawings.

FIG. 1 (a) is a partial perspective view of an acceleration sensor according to a first embodiment of the present invention, FIG. 1 (b) is a partial sectional view thereof, FIG. 2 is its plan view, and FIG. 3 is its acceleration sensor. FIG. 4 is a time chart showing its operation waveform.
The same reference numerals as those used in the conventional example of FIG. 10 described above indicate the same or common elements.

First, prior to the description of the sensor mounting structure of this embodiment, the overall circuit configuration of the sensor used in this embodiment will be described with reference to FIGS.

In FIG. 3, the gauge section 1 detects the acceleration G and inputs this signal into the electronic circuit section 11 to output an output voltage Vo proportional to the acceleration G.

The gauge section 1 includes upper and lower glass substrates 2A and 2A.
The movable electrode 3 formed by etching the silicon substrate 3 ′ is interposed between the glass substrate B and the movable electrode 3 on each glass substrate 2A, 2B.
The fixed electrodes 5A and 5B are arranged so as to face each other. The movable electrode 3 is elastically supported by the cantilever 4 while maintaining a small gap with the fixed electrodes 5A and 5B.

Capacitances C1 and C2 exist between the movable electrode 3 and the fixed electrode 5A and between the movable electrode 3 and the fixed electrode 5B.
This value is input to the electronic circuit section 11 side.

The electronic circuit section 11 includes a capacitance detection circuit 6,
It has a pulse width modulation circuit 7, a knot circuit 8, and a filter 9, and these elements constitute an electrostatic servo type electrostatic capacitance type acceleration sensor.

That is, when acceleration G is applied to the gauge section 1 in the direction of the arrow, the movable electrode 3 is displaced due to inertial force in response to this. This displacement is detected by the capacitance detection circuit 6 as C1 and C.
Capacitance difference C from 2 and voltage V proportional to C
It is converted into c and inputted to the pulse width modulation circuit 7. The pulse width modulation circuit 7 generates a pulse voltage VE having a pulse width proportional to the value of Vc, and this pulse voltage VE is applied to one fixed electrode 5A. The voltage VE is inverted by the knot circuit 8 to become the voltage VF, which is applied to the other fixed electrode 5B.

By the above circuit operation, the inertial force due to the acceleration G and the electrostatic force due to the pulse voltages VE and VF are balanced,
By extracting the pulse width of the pulse voltage VE with the filter 9, the voltage Vo exemplified below for the acceleration G can be obtained.

FIG. 4 shows the pulse output waveform VE in the circuit operation of FIG. 3. When the acceleration G is 0, the pulse width TW of the pulse voltage VE is 50% of the period T, and G
Is positive (G> 0), the pulse width TW increases from 50%, and when it is negative (G <0), the pulse width TW decreases from 50%. That is, the pulse width TW changes according to the acceleration G, and the output voltage Vo obtained by filtering this waveform has a value proportional to the acceleration G. In this capacitance type acceleration sensor, in this embodiment, as shown in FIGS. 1 and 2, the gauge section 1 is mounted on the circuit board 12, and the electronic circuit section 11 is formed on the gauge section 1 as an IC chip. Are superposed and mounted via the silicone adhesive 13.

On the upper surface of the gauge section 1, fixed electrodes 5A, 5
B electrode pads 31, 33 and movable electrode 3 electrode pad 3
2 are formed, and these pads and the electronic circuit portion 11 (I
The gauge section 1 and the electronic circuit section 11 are electrically connected via the corresponding pads 34 to 36 formed on the upper surface of the C chip) and the wire bonding 14. In addition, the conductive pattern 15 (signal lead wire, drive power supply lead wire) formed on the circuit board 12 and the corresponding pad 37 of the electronic circuit section 11
-40 are also connected via wire bonding 14 '.
The pads 31 to 40 are formed by patterning a conductor.

According to such a mounting structure, the mounting area of the components is about one third or less of that of the conventional mounting structure illustrated in FIG. 10, and the downsizing and cost reduction of the entire sensor can be achieved. .. Further, since the gauge section 1 and the electronic circuit section 11 are electrically connected to each other through the wire bonding 14 in a state where they are superposed and integrated, the gauge section 1 and the electronic circuit section 11 are connected to each other when vibration or impact is applied. Since they operate integrally, it is possible to reduce the stress applied to the connecting portions of both, reduce the fatigue of the connecting portions, and improve the reliability.

By arranging the gauge section 1 and the electronic circuit section 11 so as to overlap with each other, the heat generation of the electronic circuit section 11 is transmitted to the gauge section 1 and the temperature distribution of both sides is eliminated. improves.

FIG. 5 is a partial sectional view showing a second embodiment of the present invention. The difference from the first embodiment is that the electronic circuit section 11 and the pattern 15 on the circuit board 12 are connected via solder 16 and jumper leads 17. Others have the same structure as that of the first embodiment, and therefore have the same effects as the first embodiment.

6A and 6B show a third embodiment of the present invention. FIG. 6A is a partial perspective view and FIG. 6B is a partial sectional view. The difference from each of the above-described embodiments is that a part of the gauge portion 1 (silicon substrate 3 ', glass substrate 2B) is provided with a through hole 18A communicating with the upper surface and the lower surface thereof (the through hole 18A penetrates the silicon substrate 3'). (The portion is provided with an insulating coating 23), the hole 18 is filled with the conductor 19A, and the conductor 20 is vapor-deposited on the silicon substrate 3'while being insulated, and the electrode pads 37 to 40 of the electronic circuit section 11 and the circuit are formed. The pattern 15 on the substrate 12 is connected to the wire bonding 14 '.
-The conductor portion 20 on the upper surface of the gauge portion 1-The conductor portion 19 of the through hole 18-The gauge portion 1 and the circuit board 12 are electrically connected via the solder 16.

According to this embodiment, in addition to the same effects as the above-mentioned respective embodiments, the wire bonding 14 'used for electrical connection between the electronic circuit portion 11 and the circuit board 12 is also provided on the gauge portion 1 and above it. Since the connection with the overlapped electronic circuit section 11 is sufficient, the stress applied to the connection section is reduced and the reliability of the connection is improved.

FIG. 7 shows a fourth embodiment of the present invention, in which (a) is a partial perspective view and (b) is a partial sectional view.

The present embodiment is different from the above-mentioned embodiments in that the through hole 1 is formed in a part of the gauge portion 1 (silicon substrate 3 ').
8A is provided (the through hole 18A is provided with the insulating coating 23), the hole 18A is filled with the conductor 19A, and the electrode pads 37 to 40 of the electronic circuit section 11 and the pattern 15 on the circuit board 12 are connected to each other. Wire bonding 14a
′ -The conductor portion 20 on the upper surface of the gauge portion 1-the through-hole conductor portion 19A-the conductor portion 21 on the glass substrate-the point where they are connected via the wire bonding 14b '.

FIG. 8 shows a fifth embodiment of the present invention, in which (a) is a partial perspective view and (b) is a partial sectional view.

The present embodiment is different from each of the above embodiments in that the electrical connection between the gauge portion 1 and the electronic circuit portion 11 overlaid on the gauge portion 1 is formed on the overlapping surface without using wire bonding. There is a point that went through.

That is, the IC chip of the electronic circuit section 11 is turned upside down from the above-described embodiments, and the conductive patterns 34 to 36 on the electronic circuit section 11 side are arranged on the upper surface of the gauge section 1 (upper glass substrate). 2A top surface) conductive pattern 31 to
33 (31 to 33 are fixed electrodes 5A and 5B and movable electrode 3
(Which will be the electrode terminal of) is connected via a conductive adhesive 22. When this electrical connection is made, the conductive patterns 31 to 33 are formed on the upper surface of the upper glass substrate 2A. Therefore, the conductive pattern 32 serving as the terminal of the movable electrode 3 is as shown in FIG. 8B. On the upper glass substrate 2A
A through hole 18B is provided in the
B is filled to electrically connect the conductive pattern to the movable electrode 3. Further, the fixed electrode 5A and its terminal (conductive pattern 33) are provided with a through hole (not shown) in the upper glass substrate 2A, and a conductor (not shown) filled in this hole is used as the silicon substrate 3 '. It is electrically insulated and electrically connected through this conductor. On the other hand, fixed electrode 5B
And the terminal (conductive pattern 31) of the upper glass substrate 2
A and a silicon substrate 3 ′ are provided with through holes (not shown, and the silicon substrate 3 ′ side of the through holes is provided with an insulating coating), and conductors (not shown) filled in the holes. Is electrically conducted through.

On the other hand, the electronic circuit portion 11 and the conductive pattern 15 on the circuit board 12 are respectively the conductive patterns 37 to 40 formed on the superposed surfaces-the conductive adhesive 22 corresponding thereto-on the glass substrate 2A. Of the conductive pattern 20 and the wire bonding 14 '.

The gauge section 1 and the electronic circuit section 11 are
In addition to connecting the portions between the patterns with a conductive adhesive 22, the remaining portion (most of the overlapping of the gauge portion 1 and the electronic circuit portion 11) is attached with a silicone adhesive 13.

According to this embodiment, in addition to the effects similar to the above-mentioned respective embodiments, a simple conductive adhesive 22 is used to electrically connect the gauge portion 1 and the electronic circuit portion 11 without using wire bonding. There is an advantage that it can be performed by a conductive pattern.

FIG. 9 shows a sixth embodiment of the present invention, FIG. 9 (a) is a partial perspective view thereof, and FIG. 9 (b) is a partial sectional view thereof.

In this embodiment as well, the gauge portion 1 and the electronic circuit portion 11 are electrically connected via the same conductive pattern as in the fifth embodiment of FIG. 8, but the electronic circuit portion 11 and the conductive pattern on the circuit board 12 are connected. The connection with 15 was also made without using wire bonding.

That is, instead of wire bonding, the upper glass substrate 2A of the gauge portion 1 and the silicon substrate 3 '.
Through holes 18 are provided in the lower glass substrate 2B (the silicon substrate 3'of the through holes 18 is provided with an insulating coating 23), and the conductor 1 is provided in the through holes.
9 is filled. The electronic circuit portion 11 and the conductive pattern 15 of the circuit board 12 are respectively the conductive patterns 37 to 40 on the electronic circuit portion 11 side-the conductive adhesive 22 between the electronic circuit portion 11 and the upper glass substrate 2A (this portion). May be solder reflow connection with solder) -electric conductor 20-electric conductor 19-conductive adhesive between lower glass substrate 2B and circuit board 12 (this portion may be solder reflow connection with solder)
It was electrically connected via 22.

In addition to the same effects as the above-described respective embodiments, the present embodiment has an advantage that the wire bonding can be eliminated from the circuit board 12 to further simplify the structure.

Although the above embodiments have been described with respect to the capacitance type acceleration sensor, the mounting structure of the gauge section and the electronic circuit section of the present invention can be applied to other types of acceleration sensors.

[0042]

As described above, according to the present invention, by mounting the electronic circuit portion on the gauge portion in a stacked manner, it is possible to reduce the size of the entire sensor and to improve the reliability of the electrical connection portion between the components. Also, the temperature characteristics can be improved.

[Brief description of drawings]

FIG. 1 is a partial perspective view and a partial sectional view according to a first embodiment of the present invention.

FIG. 2 is a plan view of the first embodiment.

FIG. 3 is a circuit configuration diagram of the first embodiment.

FIG. 4 is a time chart showing an operation example of the first embodiment.

FIG. 5 is a partial sectional view showing a second embodiment of the present invention.

FIG. 6 is a partial perspective view and a partial sectional view showing a third embodiment of the present invention.

FIG. 7 is a partial perspective view and a partial sectional view showing a fourth embodiment of the present invention.

FIG. 8 is a partial perspective view and a partial sectional view showing a fifth embodiment of the present invention.

FIG. 9 is a partial perspective view and a partial sectional view showing a sixth embodiment of the present invention.

FIG. 10 is a plan view showing an example of a mounting structure of a conventional acceleration sensor.

[Explanation of symbols]

1 ... Gauge part, 2A, 2B ... Glass substrate, 3 '... Silicon substrate, 3 ... Movable electrode, 5A, 5B ... Fixed electrode, 11 ...
Electronic circuit part (IC chip), 13 ... Silicone adhesive, 1
4 ... Wire bonding, 31-36 ... Conductive pattern,
22 ... Conductive adhesive (or solder).

Front page continued (72) Inventor Masayoshi Suzuki, 2520 Takaba, Katsuta-shi, Ibaraki Takaba, Hitachi, Ltd. Automotive Equipment Division (72) Inventor Hirokazu Fujita 2520, Takata, Katsuta, Ibaraki Hitachi, Ltd. Automotive Equipment (72) Inventor Keiji Hanzawa 2477 Kashima Yatsu Kashima Yatsu Katsuta City, Ibaraki Prefecture 3 Hitachi Automotive Engineering Co., Ltd.

Claims (6)

[Claims] 1. An acceleration sensor comprising a gauge section which is an acceleration detecting element and an electronic circuit section which processes an electric signal of the gauge section, wherein an IC (integrated circuit) chip is formed on the gauge section. An acceleration sensor having a structure in which electronic circuit parts are stacked. 2. The acceleration sensor according to claim 1, wherein the gauge portion and the electronic circuit portion overlaid on the gauge portion are electrically connected by wire bonding. 3. A conductive pattern according to claim 1, wherein the gauge portion and the electronic circuit portion superposed on the gauge portion are formed with a conductive pattern on the overlapping surface and are electrically connected via the conductive pattern. Acceleration sensor characterized by. 4. The acceleration sensor according to claim 1, wherein the gauge section and the electronic circuit section are electrically connected and fixed at the same time using a conductive adhesive. .. 5. The acceleration sensor according to claim 3, wherein the electrical connection between the gauge section and the electronic circuit section is pattern connection using solder. 6. The gauge portion according to claim 1, wherein the gauge portion includes a movable electrode that is displaced according to acceleration, and a fixed electrode that faces the movable electrode through a minute gap. Capacitance type acceleration sensor.