JPH09126925A - Semiconductor pressure sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce noise to be caused due to an external influence such as temperature change and accurately use a semiconductor pressure sensor for measuring pressure of an organic solvent gas. SOLUTION: A pressure sensor element 20 of a semiconductor and a pressure introduction part 25 where the pressure sensor element 20 is placed and pressure to be measured is introduced are airtightly joined. A plurality of protrusions 52 are provided on the surface of the pressure introduction part 25 where the bottom surface of the pressure sensor element 20 is placed or the bottom surface of the pressure sensor element 20 and an adhesive 32 is filled into a formed gap while the pressure sensor element 20 is placed at the pressure introduction part 25.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor pressure sensor which receives a fluid pressure by a semiconductor diaphragm, converts the pressure into an electric signal and outputs the electric signal.

[0002]

2. Description of the Related Art Conventionally, a semiconductor pressure sensor has been provided as a small pressure sensor capable of accurately measuring the pressure of a fluid. In particular, Japanese Patent Laid-Open No. 59-102131 discloses a semiconductor pressure sensor that eliminates noise caused by a difference in thermal expansion coefficient between a sensor element and a base to which it is attached. In this semiconductor pressure sensor, a gel silicon resin is interposed as an adhesive between the sensor element and the base to absorb a difference in expansion and contraction caused by a difference in thermal expansion coefficient between the sensor element and the base. As a result, noise associated with temperature change is eliminated.

[0003]

When the above conventional semiconductor pressure sensor is used to measure the pressure of an organic solvent gas such as xylene gas, LPG, or gasoline, the organic solvent gas permeates the silicon resin and swells the silicon resin. There was a problem. As shown in FIGS. 8 to 10, this mechanism is such that when the introduction of the organic solvent gas is started, the diaphragm of the sensor element 20 is first distorted by the pressure, and the bonding layer 28 gradually comes in contact with the organic solvent gas with the passage of time. Swells, causing distortion in the direction opposite to the direction in which pressure is applied to the diaphragm of the sensor element 20, and noise is generated in the output signal when pressure is initially introduced, as shown in FIG. 7B. As shown in FIG. 9, this distortion occurs at the corner of the sensor element 20 as the fulcrum D. Then, as the swelling spreads throughout the bonding layer 28 as shown in FIG.
As shown in the graph of (B), the distortion of the sensor element 20 is eliminated and the output signal becomes stable. As described above, it takes a considerable amount of time for the output signal to stabilize, and when the organic solvent gas is switched to air, the output signal goes through the reverse process of the above and becomes unstable. . Therefore, the silicone resin has many problems when used for measuring organic solvent gas.

On the other hand, as an adhesive between the sensor element of the semiconductor pressure sensor and the base, which can be used for measuring the organic solvent gas, an inorganic bonding agent such as metal wax or a part of solvent resistant synthetic rubber is used. It was limited to organic binders. However, such an adhesive does not always match the required joining conditions of the semiconductor pressure sensor, but sacrifices sensor element characteristics such as accuracy, linearity, and temperature characteristics.

The present invention has been made in view of the above-mentioned problems of the prior art, and has little noise due to external influences such as temperature change, and can be used with high accuracy for measuring the pressure of an organic solvent gas. An object is to provide a semiconductor pressure sensor.

[0006]

SUMMARY OF THE INVENTION The present invention is a semiconductor pressure sensor in which a semiconductor pressure sensor element and a pressure introducing portion on which the pressure sensor element is mounted and which introduces a measured pressure are joined in an airtight state. A state in which a plurality of protrusions are provided on the surface of the pressure introducing portion on which the bottom surface of the pressure sensor element is placed, or on the bottom surface of the sensor element, and the pressure sensor element is placed on the pressure introducing portion. It is a semiconductor pressure sensor in which an adhesive is filled in the gap formed in (1) and joined. The adhesive is a silicone resin adhesive, and a fluorosilicone resin is more preferable.

In the semiconductor pressure sensor of the present invention, the organic solvent gas or the like, which is the pressure medium to be measured, directly penetrates into the pressure sensor element side of the semiconductor through the pressure introducing portion, and the gap between the pressure sensor element and the pressure introducing portion is bonded. Organic solvent gas comes into contact with the agent and begins to swell. As a result, the diaphragm of the pressure sensor element tends to be displaced, but the protrusion of the pressure sensor element or the protrusion of the pressure introducing portion serves as a fulcrum of displacement of the diaphragm.
It does not act to cancel the applied pressure as shown in FIG. 9 of the related art.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. 1 to 3 show a pressure sensor of the present invention, in which a rectangular Si semiconductor pressure sensor element 20 is provided in a sensor case 21,
The pressure sensor element 20 and the base end portion 22 a of the lead frame terminal 22 are wire-bonded with a gold wire 23. The sensor case 21 has a lead frame terminal 22.
The pressure introducing cylinder 25, which is a pressure introducing portion, is insert-molded. The pressure introducing cylinder 25 has a flange portion 26 for sensor attachment formed at the base end portion thereof, and the pressure sensor element 20 is attached to the upper surface of the flange portion 26.

The flange portion 26 is provided with four projections 52 each having a diameter of about 50 μm so that the projections 52 come into contact with the inner portions of the outer wall of the pressure sensor element 20 at the four corners of the pressure sensor element 20, respectively. ing. The pressure sensor element 20 abuts on the protrusion 52, and the adhesive 32 made of fluorosilicone resin is applied to the gap between the pressure sensor element 20 and the flange portion 26 so as to wrap the protrusion 52.
Is formed, and the periphery of the pressure sensor element 20 is joined in an airtight state. The method for joining is to apply a fluorosilicone resin adhesive 32 on the joining surface, place the pressure sensor element 20 on it, and press the pressure sensor element 20 while slightly vibrating it horizontally so as to sufficiently join, Adhesive 3
Adapt 2 to the joint surface and cure. At this time, the protrusion 52
Plays a role of a spacer, and the bonding layer 28 can maintain a constant thickness.

The lead frame terminal 22 is soldered to the substrate 40 as shown in FIG.
Is connected to the external connection terminal 42 attached to. Here, in FIG. 4, the right side of the center line is the lead frame terminal 22.
Is a vertical cross-sectional view in the longitudinal direction of FIG. 4, and the left side of the center line is a vertical cross-sectional view in a direction orthogonal to the longitudinal direction of the lead frame terminal 22. Sensor case 21 to which the substrate 40 is fixed
Is attached to the outer case body 41, and the pressure introducing tube 2
An O-ring 46 made of organic solvent resistant rubber or the like is tightly fitted between 5 and the inner wall surface of the outer case body 41.
A lid member 48 is attached to the outer case body 41, and an atmospheric pressure inlet port 49 connected to the atmospheric pressure side is formed in the lid member 48.

The method of using the pressure sensor of this embodiment is as follows.
First, the pressure introducing unit 45 is connected to the measured pressure side, and the atmospheric pressure introducing port 49 is opened to the atmospheric pressure side. The organic solvent gas or the like for pressure measurement passes through the pressure introducing section 45 and passes through the pressure introducing cylinder 25.
After that, the pressure sensor element 20 comes into direct contact with the back surface side of the pressure sensor element 20, and the pressure sensor element 20 is distorted by this pressure, and the resistance value of the pressure sensor element 20 which changes with it is detected to measure the pressure of the organic solvent gas or the like. .

When the pressure sensor of this embodiment is used for measuring the organic solvent gas, the adhesive 32 used in the bonding layer 28 is slightly changed to the organic solvent gas as shown in FIGS. Upon contact, swelling occurs from the inner wall side of the pressure sensor element 20. When the stress is applied, the displacement of the pressure sensor element 20 uses the apex of the protrusion 52 as a fulcrum. Since these portions are the four corners of the pressure sensor element 20 and have the highest strength and the smallest change due to stress, the displacement of the pressure sensor element 20 is small and the strain of the pressure sensor element 20 can be minimized. Further, the fluorosilicone resin 32 having a constant thickness absorbs the swelling from each other, and the strain of the pressure sensor element 20 can be suppressed. Further, when the pressure sensor element 20 is attached to the flange portion 26, as shown by the chain double-dashed line in FIG. 2, the protruding adhesive 32 generated in the conventional pressure sensor crawls up to the side surface of the pressure sensor element 20. Therefore, no stress is generated on the side surface of the pressure sensor element 20, and no extra strain is generated on the pressure sensor element 20.

Further, the pressure sensor element 2 is affected by changes in temperature.
Even when a stress is generated between 0 and the flange portion 26 due to a difference in thermal expansion, the pressure sensor element 20 and the protrusion 52 are in contact with each other at a point, and therefore the stress is less likely to be transmitted than in the case of being in contact with the surface.
Further, the fluorosilicone resin adhesive 32 having a constant thickness also absorbs the stress caused by the difference in thermal expansion.

This pressure sensor eliminates distortion of the pressure sensor element 20 due to organic solvent gas, temperature change, etc., stabilizes the output signal, and accurately measures the fluid pressure. Moreover, since the bonding layer 28 having a uniform thickness can be formed without sacrificing workability, a uniform product can be stably manufactured.

Next, a second embodiment of the present invention will be described with reference to FIGS. Here, the same members as those in the above-described embodiment are designated by the same reference numerals, and the description thereof will be omitted. In the pressure sensor of this embodiment, hemispherical protrusions 54 each having an appropriate size are provided at four corners of the bottom surface of the pressure sensor element 20 at positions slightly inside the outer wall. The protrusion 54 is in contact with the flange portion 26, and a gap between the pressure sensor element 20 and the flange portion 26 is filled with a fluorosilicone resin adhesive 32 so as to wrap the protrusion 54 to form a bonding layer 28. Also in this embodiment, the same effect as the above embodiment can be obtained.

The pressure sensor of the present invention is not limited to the above-described embodiments, but the shape and position of each member and the material can be changed. The shape and position of the protrusion can be changed as appropriate, and can be formed integrally with the pressure sensor element or the pressure introducing portion or separately.

[0017]

EXAMPLE FIG. 7 is a chart comparing the change of the output signal when the pressure sensor of one example of the present invention is used for LPG gas with the measurement result of the conventional product. The vertical axis represents the voltage of the output signal, and the horizontal axis represents time. According to this chart, in the case of the conventional product, a large amplitude is generated in the output signal immediately after the introduction of the LPG, and the output is attenuated with the passage of time,
The output will be stable over a considerable period of time. In comparison,
In this embodiment, the waveform changes due to the pressure applied when the LPG is introduced, but the output waveform becomes stable immediately after.

[0018]

EFFECTS OF THE INVENTION The pressure sensor of the present invention does not cause an initial drift in the output and can obtain a stable output signal even when used for a gas having a large ability to dissolve organic substances, such as xylene gas or LPG gas. Accurate measurement is possible from the beginning of use. .

[Brief description of the drawings]

FIG. 1 is a vertical sectional view of a pressure sensor device according to a first embodiment of the present invention.

FIG. 2 is an enlarged vertical cross-sectional view of a bonding layer between a pressure sensor element and a flange portion of the semiconductor pressure sensor of the first embodiment.

FIG. 3 is a front view of a flange portion and a sensor case of the semiconductor pressure sensor of the first embodiment.

FIG. 4 is a vertical cross-sectional view of the semiconductor pressure sensor of the first embodiment attached to an outer case.

FIG. 5 is a partially enlarged vertical sectional view of a semiconductor pressure sensor according to a second embodiment of the present invention.

FIG. 6 is a front view of a pressure sensor element of the semiconductor pressure sensor of the second embodiment.

FIG. 7 is a chart comparing an output signal (A) when an organic solvent gas is introduced into the semiconductor pressure sensor of one embodiment of the present invention and an output signal (B) of a conventional product.

FIG. 8 is a schematic view showing a silicon resin adhesive of a semiconductor pressure sensor before introducing an organic solvent gas.

FIG. 9 is a schematic diagram showing the behavior of the silicone resin adhesive of the semiconductor pressure sensor when an organic solvent gas is introduced.

FIG. 10 is a schematic view showing a silicon resin adhesive of a semiconductor pressure sensor after introducing an organic solvent gas.

[Explanation of symbols]

 20 Pressure Sensor Element 25 Pressure Introducing Tube 28 Bonding Layer 32 Adhesive 52, 54 Protrusion

Claims (3)

[Claims] 1. In a semiconductor pressure sensor in which a semiconductor pressure sensor element and a pressure introducing portion for mounting the pressure sensor element and introducing a pressure to be measured are joined in an airtight state, a bottom surface of the pressure sensor element is mounted. A plurality of protrusions are provided on the surface of the pressure introducing portion to be placed, and an adhesive is filled in and bonded to a gap formed in a state where the pressure sensor element is placed on the pressure introducing portion. And semiconductor pressure sensor. 2. A semiconductor pressure sensor in which a semiconductor pressure sensor element and a pressure introducing portion for mounting the pressure sensor element and introducing a pressure to be measured are joined in an airtight state, and a plurality of pressure sensor elements are provided on a bottom surface of the pressure sensor element. A semiconductor pressure sensor, comprising a plurality of protrusions, wherein an adhesive is filled in and bonded to a gap formed in a state where the pressure sensor element is placed on the pressure introducing portion. 3. The semiconductor pressure sensor according to claim 1, wherein the adhesive is made of fluorosilicone resin.