KR930007902Y1 - Pressure sensor - Google Patents

Abstract

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Description

Pressure sensor

1 is a cross-sectional view showing the structure of a pressure sensor according to an embodiment of the present invention.

2 is a cross-sectional view in the orthogonal direction of FIG. 1 of the first embodiment.

3 is an electric circuit diagram of a control unit in the first embodiment.

Fig. 4 is a characteristic diagram showing a relationship between a reduction rate of an error output due to contrast distortion between the adhesive thickness and the diaphragm thickness in the first embodiment.

* Explanation of symbols for main parts of the drawings

1: pressure sensor 2, 3: case

4, 5: semiconductor chip 4a, 5a: diaphragm

9: adhesive 21: first pressure chamber

22: second pressure chamber 23: third pressure chamber

24: 4th pressure chamber 25, 26: Inlet pipe part

101: first bridge circuit 102: second bridge circuit

103: first differential amplifier circuit 104: second differential amplifier circuit

105: third differential amplifier circuit

[Industrial use]

The present invention relates to a pressure sensor which is highly sensitive and is not affected by external light.

[Prior art]

Conventionally, as a semiconductor pressure sensor, it is disclosed by Unexamined-Japanese-Patent No. 60-100026, 61-87338, etc., In particular, in the case of Unexamined-Japanese-Patent No. 60-10026, each is provided in a common semiconductor substrate, respectively. Two pairs of pressure detection units having the same diaphragm portion and four piezoresistive element groups are provided, and each pressure detection unit is formed to apply a pressure to the pressure detection unit, and each piezo resistor element group is formed. It is formed so as to take the difference in output of the bridge circuit so as to eliminate an error due to residual distortion or the like.

In the case of the latter publication No. 61-87338, an opening is provided at the center of the stem, a pressure inlet pipe is provided downward of the opening, and an atmospheric opening is provided at a position away from the opening. The diaphragm for detecting the differential pressure between the pressure in the pressure introduction pipe and the atmospheric pressure is provided, the semiconductor chip is fixed to the atmospheric opening, and the semiconductor chip is covered with a lid.

Bonding of the semiconductor chip to the substrate is made to be firmly bonded with gold, silicon bonding, or a preliminary clock adhesive in order to improve the signal property of the bonding of the wire and to increase the reliability of the bonding between the substrate and the semiconductor chip.

[Problem that plan is trying to solve]

Since the conventional conductor pressure sensor is constructed as described above, the semiconductor chip is firmly bonded to the substrate, and when attempting to detect the micro pressure, the diaphragm is made thin and the sensitivity of the pressure responsiveness and the control circuit is very high. In this case, there is a problem in that an error occurs in the output due to the influence of a distortion applied to a diaphragm other than pressure, for example, a case applied to a case.

The present invention has been made to solve the above problems, and an object of the present invention is to obtain a pressure sensor capable of measuring pressure with high sensitivity and having excellent external force.

[Means for solving the problem]

The pressure sensor according to the present invention is provided with the first and second diaphragms having the same electrical characteristics in the same shape to be the partition walls of the first and second pressure chambers and the partition walls of the third and fourth pressure chambers. Thus, two semiconductor chips are bonded to the substrate with a flexible adhesive.

[Action]

In the present invention, since the semiconductor chip is bonded with a flexible adhesive, the semiconductor chip and the substrate are flexible, and even if an external pressure is applied to the case, the diaphragm does not affect the diaphragm and the diaphragm functions to detect pressure with high sensitivity. .

EXAMPLE

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

1 is a cross-sectional view of an embodiment of the present invention, Figure 2 is a cross-sectional view cut in a direction perpendicular to the first view.

In the first and second drawings, 1 is a pressure sensor, 2 and 3 are cases of the pressure sensor 1, and the first and fourth pressure chambers 21 are provided by the cases 2 and 3. To 24).

The semiconductor chip 4 which has the diaphragm 4a is provided in the fitting surface of the case 2 and the case 3 so that it may become the partition of the 1st, 2nd input chambers 21 and 22. As shown in FIG.

Similarly, the semiconductor chip 5 which has the diaphragm 5a is provided so that it may become the partition of the 3rd, 4th pressure chamber 23, 24. As shown in FIG.

The semiconductor chips 4 and 5 are bonded to the substrate 6 with a flexible adhesive such as a silicone adhesive. In addition, the thickness of the said adhesive is apply | coated more than the thickness of the diaphragms 4a and 5a.

In this manner, the diaphragm 4a faces the first pressure chamber 21 and the second pressure chamber 22, and the diaphragm 5a faces the third and fourth pressure chambers 23 and 24. It is installed to

7 is a terminal connected via the bridge circuit and the wire 8 for distortion detection which are not shown in FIG. 1, FIG. 2 provided on the diaphragm 4a and the diaphragm 5a.

25 and 26 of FIG. 2 are guide tubes. The pressure guiding pipe part 25, the 1st pressure chamber 21, and the 4th pressure chamber 24 communicate, and the introduction pipe part 26, the 2nd pressure chamber 22, and the 3rd pressure chamber 23 are connected. This communicates.

3 is an electrical circuit diagram of the control unit of the pressure sensor 1. In FIG. 3, 101 and 102 are bridge circuits for distortion detection including four piezoresistors provided in each of the diaphragms 4a and 5a of FIG. 1, and 103 and 104 are first bridge circuits 101. In FIG. ) And the first and second differential amplifier circuits that operate by receiving the outputs of the second bridge circuit 102 and 105 are the outputs of the first differential amplifier circuit 103 and the second differential amplifier circuit 105. Is a third differential amplifier circuit for receiving and operating, 106 is a waveform shaping circuit for receiving the output of the third differential amplifier circuit 104, and 107 is a first bridge circuit 10 and a second bridge circuit. 102 is a power supply circuit.

Next, the operation will be described. Now, if a differential pressure is generated between the pressure guiding pipe 25 and the pressure guiding pipe 26, and the pressure of the pressure guiding pipe 25 becomes larger than the pressure guiding pipe 26, the second pressure chamber of the diaphragm 4a ( It is bent to 22) side and the diaphragm 5a is bent to the third pressure chamber 23 side.

Here, the signal output of the bridge circuit 101 when the diaphragm 4a is bent to the second pressure chamber 22 side is + V _B , and the diaphragm 5a is the third pressure chamber 23. When the signal output of the bridge circuit 102 when bent toward the side is -V _B , the respective signals passing through the first differential amplifier circuit 103 and the second differential amplifier circuit 104 having the same amplification rate are Output becomes + V _B , -V _B. Provided that V _B = β. _vb .

In this case, when the pressure in the pressure guiding tube 26 is greater than the pressure guiding tube 25, the output of the first and second bridge circuits 101 and 102 which are completely in reverse mode as described above is obtained. The output of the amplifying circuit 105 is unchanged and is 2V _B.

Therefore, the output of the pressure sensor 1 due to the differential pressure generation between the pressure guiding tube 25 and the pressure guiding tube 26 is always twice as large as one diaphragm.

Next, when an external force other than pressure is applied. Now, when the vibration force is applied to the pressure sensor 1, when the vibration force is applied in the non-moving direction of the diaphragms 4a and 5a, the diaphragms 4a and 5a do not move correspondingly. No output

However, when a vibration force is applied in the movable directions of the diaphragms 4a and 5a of the pressure sensor 1, the diaphragm 4a and the diaphragm 5a are distorted in the same amount and in the same direction at the same time. Therefore, if the output V _B generated in the first bridge circuit 101 occurs, the output V _B to the bridge circuit 102 of the second.

As described above, the outputs of the first and second bridge circuits 101 and 102 are amplified to V _B at a predetermined amplification rate by the first and second differential amplifier circuits 103 and 104, and then the third It is input to the differential amplifier circuit 105.

By the way, since V _B of the same value is simultaneously applied to both the (+) terminal and the (-) terminal of the third differential amplifier circuit 105, the output of the third differential amplifier circuit 105 is not output. Therefore, there is no output of the pressure sensor 1. Here, if the output of the first bridge circuit 101 and the output of the second bridge circuit 102 are completely equal, it is as described above. If the equivalence is lost a little, the third differential amplifier circuit 105 ) Is output in accordance with the vibration, and also outputs the pressure sensor (1).

Therefore, perfection of the output equivalence of the 1st bridge circuit 101 and the 2nd bridge circuit 102 becomes essential.

For this reason, the diaphragm 4a and the diaphragm 5a should have the same shape and electrical characteristics.

In addition, since the semiconductor chips 4 and 5 are bonded to the board | substrate 6 by the flexible adhesive agent, Moreover, since the thickness of this adhesive agent is thicker than the thickness of the diaphragms 4a and 5a, the case 2 and 3 is carried out. Even if external force or heat distortion is applied to the adhesive, the adhesive is absorbed by the adhesive, which does not affect the diaphragms 4a and 5a, and chip distortion of the diaphragms 4a and 5a does not occur.

Therefore, the diaphragms 4a and 5a are high sensitivity and can detect a pressure accurately.

4 is a characteristic diagram showing the relationship between the ratio of the thickness d of the adhesive and the diaphragm thickness D, that is, the error reduction ratio due to the d / D vs. distortion, and the distortion force is constant.

As is apparent from the fourth road, it can be seen that as the thickness d of the adhesive becomes larger than the thickness D of the diaphragm, the false output by the distortion becomes smaller.

[Effect of design]

As described above, according to the present invention, the two diaphragms for detecting the differential pressure of the first and second pressure chambers and the third and fourth pressure chambers formed in the case have the same shape and the same electrical characteristics. Since it is configured to bond to the substrate with an adhesive having a pram, the detection ability of the differential pressure is improved, and even if an external force or heat distortion is applied to the case, there is no effect of affecting the diaphragm, and the effect is very strong against the external force. .

Claims (1)

First and fourth pressure chambers 21 and 24 in communication with the first pressure pipe section 25 formed in the case; Second and third pressure chambers 22 and 23 communicating with the second pressure guiding tube part 26 formed in the case; First and second diaphragms having the same shape and the same electrical characteristics and are installed in the semiconductor chip so as to be partition walls of the first pressure chamber and the second pressure chamber and partition walls of the third and fourth pressure chambers, respectively. (4a, 5a); An adhesive (9) having flexibility to bond the semiconductor chip to a substrate; When the first and second diaphragms are formed on the first and second diaphragms and are reacted by the differential pressure generated in the first and second pressure guiding pipe portions, signals having the same value and antiphase are mutually equal. Outputting first and second bridge circuits (101, 102); And a first and second differential amplifiers (103, 104) for differentially amplifying the signal outputs of said first and second bridge circuits, respectively.