TW202138802A - Gas sensor - Google Patents

Abstract

A gas sensor includes a substrate, a plurality of electrodes, and at least one sensing structure. The electrodes are disposed on the substrate and spaced apart from each other, and each of the electrodes has a first thickness. The sensing structure is disposed between the electrodes, and the sensing structure is in direct contact with the electrodes, wherein the sensing structure has a second thickness, and the second thickness is 0.01-1.1 times of the first thickness.

Description

Gas sensor

The present invention relates to a gas sensing technology, and particularly relates to a gas sensor with good sensitivity.

Due to the advancement of technology and technology in recent years, smart devices have become popular, and technologically advanced products have increasingly tended to three major directions: intelligence, automation, and cloud; as small as a basic smart phone, However, there are already many sensors integrated in it, as large as an electric car, which can maximize the performance of the sensor and bring people the experience of fully automated driving.

Various types of sensors have been used in different fields. Take gas sensors as an example. Generally, the sensing material is formed on the electrode structure by coating the entire surface, so that the electrode is in the sensing area. Completely covered.

However, although the current gas sensor has a significant variation in the transient response, there is also a non-negligible error interference, which affects the sensitivity of the sensor.

The invention provides a gas sensor, which can improve the sensitivity of the gas sensor and can greatly reduce the amount of sensing materials used on the gas sensor.

A gas sensor of the present invention includes a substrate, a plurality of electrodes, and at least one sensing structure. The electrodes are arranged on the substrate and separated from each other by a distance, wherein each electrode has a first thickness. The sensing structure is between the electrodes, and the sensing structure directly contacts the electrodes, wherein the sensing structure has a second thickness, and the second thickness is 0.01 times to 1.1 times the first thickness.

In an embodiment of the present invention, the second thickness of the above-mentioned sensing structure is smaller than the first thickness.

In an embodiment of the present invention, the second thickness of the above-mentioned sensing structure is less than half of the first thickness.

In an embodiment of the present invention, the second thickness of the above-mentioned sensing structure is higher than the first thickness.

In an embodiment of the present invention, the aforementioned sensing structure partially covers the plurality of electrodes.

In an embodiment of the present invention, the above-mentioned first distance is between 1 μm and 1000 μm.

In an embodiment of the present invention, the above-mentioned sensing structure may be a plurality of sensing structures, and the plurality of sensing structures are separated from each other by a second distance, and the second distance is less than or equal to the width of each electrode.

In an embodiment of the present invention, the rate of change of the second distance is ±20%.

In an embodiment of the present invention, the above-mentioned electrodes include interdigitated electrodes.

In an embodiment of the present invention, the above-mentioned substrate includes a printed circuit board (PCB), and the above-mentioned electrode is a circuit of the printed circuit board.

Based on the above, the present invention reduces the thickness of the film layer in the area not affected by the gas in the sensing structure, in other words, the film layer in the area affected by the gas is relatively increased, so that the rate of change of the gas sensor is increased, thereby improving The sensitivity of the gas sensor. Moreover, due to the reduced film thickness, compared with traditional full-surface covering type sensing materials, the amount of sensing materials used can be greatly reduced.

In order to make the above-mentioned features and advantages of the present invention more comprehensible, the following specific embodiments are described in detail in conjunction with the accompanying drawings.

The following content provides more than one experimental example for implementing different features of the present invention. Specific examples of components and configurations are described below to simplify the disclosure of the present invention. Of course, these are only examples and are not used to limit the scope and application of the present invention. In addition, for the sake of clarity, the relative thickness, distance, and position of each region or film layer may be reduced or enlarged. In addition, similar or identical element symbols are used in the drawings to indicate the existence of similar or identical elements or features.

Fig. 1 is a schematic top view of a gas sensor according to an embodiment of the present invention.

Please refer to FIG. 1, the gas sensor 100 includes a substrate 102, a plurality of electrodes 104 and at least one sensing structure 106. The electrode 104 is disposed on the substrate 102 and separated from each other by a first distance d1, and the sensing structure 106 directly contacts the electrode 104. The gas sensor 100 is, for example, a resistive sensor or a capacitive sensor. The sensing principle of the resistive sensor is mainly to use the conductive sensing structure 106 connected with the electrode 104 to absorb gas, the resistance of the sensing structure 106 will correspondingly change, so as to carry out the measurement; The sensing principle is that when the sensing structure 106 is adsorbed to gas molecules, the dielectric coefficient will change and the capacitance value of the sensing structure 106 will be changed for measurement. The electrode 104 is, for example, a finger-shaped electrode, so the first distance d1 represents the distance between the finger-shaped parts of different finger-shaped electrodes. In this embodiment, the first distance d1 is, for example, between 1 μm and 1000 μm. If the electrode 104 is a general block electrode, the distance between the two block electrodes is the first distance d1, and so on. In an embodiment, the aforementioned substrate 102 may be a printed circuit board (PCB), and the electrode 104 is a circuit of the printed circuit board.

Fig. 2A is a schematic cross-sectional view of a gas sensor along the line A-A' of Fig. 1.

In FIG. 2A, each electrode 104 has a first thickness t1, the sensing structure 106 is between the electrodes 104, and the sensing structure 106 has a second thickness t2, wherein the second thickness t2 is smaller than the first thickness t1, and the second thickness t2 is, for example, 0.01 times or more of the first thickness t1. In an embodiment, the first thickness t1 is, for example, about 100 μm; the second thickness t2 is, for example, more than 1 μm. Since the material of the sensing structure 106 is affected by gas, the electrical area 106a is roughly fixed on its surface, while the area 106b that is not affected by the gas is below it. Therefore, if a resistive sensor is used as an example, the two electrodes The sensing structure 106 between 104 is like an equivalent resistance composed of Ra and Rb, where Ra represents the resistance of the region 106a, and Rb represents the resistance of the region 106b, so the total resistance R _total = Ra×Rb/(Ra+Rb) . And Rb=Ra/t, t represents the thickness parameter, that is, t=tb/ta, where ta represents the thickness of the region 106a, and tb represents the thickness of the region 106b. Because ta is almost a fixed value, t is proportional to tb.

Assuming that the thickness of the region 106b is 10 times the thickness of the region 106a (t=10), the trend of the total variation rate (total variation) obtained by the simulation versus the variation rate of the region 106a is shown in Figure 3A, where the Y axis (total variation) The value of the rate of change) is equal to ∆R _total /R _total × 100; the value of the X axis (the rate of change of area 106a) is equal to ∆Ra/Ra × 100. It can be obtained from FIG. 3A that when the rate of change of the region 106a is 10%, the total rate of change is less than 1. Once t becomes smaller (that is, the thickness of the region 106b becomes smaller), the total change rate will be as shown in Figure 3B. The change rate of the region 106a is also 10%, but the total change rate can be increased from less than 1 (t=10) to 3 Above (t=2), a full increase of 400%. In other words, the thinner the thickness of the region 106b, the higher the total change rate. The increase in the total change rate can reduce the influence of error interference on the sensing result, thereby improving the sensitivity of the gas sensor 100. In one embodiment, the sensing structure 106 can be formed between the electrodes 104 by using aerosol jet printing (Aerosol Jet Printing) or the like. Since the thickness of the sensing structure 106 (the second thickness t2) is obviously thinner than traditional requirements, the amount of material will be reduced accordingly, and the effect of cost reduction can be achieved. In addition, this embodiment does not require an additional heater under the substrate 102 to achieve the effect of enhancing the sensitivity.

2B is a schematic cross-sectional view of another gas sensor along the line AA' of FIG. 1, where the difference from FIG. 2A is that the second thickness t2 of the sensing structure 106 is less than half of the first thickness t1, for example When the second thickness t2 of the structure 106 is equivalent to the thickness of the region 106a, the second thickness t2 may be 0.01 times or more of the first thickness t1.

Fig. 4 is a schematic top view of a gas sensor according to another embodiment of the present invention, in which the component symbols of Fig. 1 are used to denote the same or similar components, and the description of the same components can refer to the above-mentioned related content. I will not repeat them here.

In FIG. 4, the sensing structure 402 of the gas sensor 400 partially covers the electrode 104. It can be obtained from the cross-sectional view (FIG. 5) that the second thickness t2 of the sensing structure 402 is slightly higher than the first thickness t1, and the second thickness t2 is, for example, 1.1 times or less of the first thickness t1. In an embodiment, the first thickness t1 is, for example, more than 1 μm, and the second thickness t2 is, for example, about 1.1 μm. In addition, from the cross-section of the line segment A-A', because the sensing structure 402 partially covers the electrode 104, the second distance d2 between the sensing structures 402 is smaller than the width w of each electrode 104. In another embodiment, when the second thickness t2 of the sensing structure 402 is the same height as the first thickness t1 of the electrode 104 (t2/t1=1), the second distance d2 is equal to the width w of the electrode 104.

Fig. 6 is a schematic top view of a gas sensor according to still another embodiment of the present invention, in which the component symbols of Fig. 1 are used to denote the same or similar components, and the description of the same components can refer to the above-mentioned related content. I will not repeat them here.

In FIG. 6, the gas sensor 600 has several sensing structures 602 partially covering the electrode 104. Therefore, the second distance d2 between the sensing structures 602 is smaller than (or equal to) the width w of the electrode 104, and the change rate of the second distance d2 is, for example, ±20%.

In summary, the present invention reduces the thickness of the film in the area not affected by the gas in the sensing structure, and maintains the thickness of the area affected by the gas, which can increase the total change rate of the gas sensor, thereby improving the gas sensing The sensitivity of the device. Moreover, since the thickness of the sensing structure is reduced, compared with the traditional full-surface covering type sensing structure, the amount of material used can be greatly reduced, and the cost can be reduced.

Although the present invention has been disclosed in the above embodiments, it is not intended to limit the present invention. Anyone with ordinary knowledge in the relevant technical field can make some changes and modifications without departing from the spirit and scope of the present invention. The protection scope of the present invention shall be subject to those defined by the attached patent application scope.

100, 400, 600: gas sensor 102: substrate 104: Electrode 106, 402, 602: sensing structure 106a, 106b: area d1: first distance d2: second distance t1: first thickness t2: second thickness ta, tb: thickness w: width

Fig. 1 is a schematic top view of a gas sensor according to an embodiment of the present invention. Fig. 2A is a schematic cross-sectional view of a gas sensor along the line A-A' of Fig. 1. Fig. 2B is a schematic cross-sectional view of another gas sensor along the line A-A' of Fig. 1. Figure 3A is a trend diagram of the total variation versus the variation rate of the area affected by the gas on the electrical properties. Fig. 3B is a trend diagram of the change rate of the total change rate to the area affected by the gas and the change of the thickness parameter. Fig. 4 is a schematic top view of a gas sensor according to another embodiment of the present invention. Fig. 5 is a schematic cross-sectional view of a gas sensor along the line A-A' of Fig. 4. Fig. 6 is a schematic top view of a gas sensor according to still another embodiment of the present invention.

100: Gas sensor

102: substrate

104: Electrode

106: sensing structure

106a, 106b: area

d1: first distance

t1: first thickness

t2: second thickness

ta, tb: thickness

Claims (10)

A gas sensor, including: Substrate A plurality of electrodes are arranged on the substrate, the plurality of electrodes are separated from each other by a first distance, and each of the electrodes has a first thickness; and At least one sensing structure is between the plurality of electrodes, and the sensing structure directly contacts the plurality of electrodes, wherein the sensing structure has a second thickness, and the second thickness is 0.01 ~1.1 times the first thickness. The gas sensor according to claim 1, wherein the second thickness of the sensing structure is smaller than the first thickness. The gas sensor according to claim 2, wherein the second thickness of the sensing structure is less than half of the first thickness. The gas sensor according to claim 1, wherein the second thickness of the sensing structure is higher than the first thickness. The gas sensor according to claim 4, wherein the sensing structure partially covers the plurality of electrodes. The gas sensor according to claim 1, wherein the first distance is between 1 µm and 1000 µm. The gas sensor according to claim 1, wherein the at least one sensing structure is a plurality of sensing structures, and the plurality of sensing structures are separated from each other by a second distance, and the second distance is less than or equal to The width of each electrode. The gas sensor according to claim 7, wherein the rate of change of the second distance is ±20%. The gas sensor according to claim 1, wherein the plurality of electrodes include interdigitated electrodes. The gas sensor according to claim 1, wherein the substrate includes a printed circuit board (PCB), and the plurality of electrodes are circuits of the printed circuit board.

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