JP2020176889A - Inspection method and inspection device for liquid enclosed type pressure sensor - Google Patents

Abstract

To provide an inspection method and an inspection device that can securely determine a liquid enclosed type pressure sensor, which causes a pressure variation phenomenon due to a liquid enclosing structure, as a defective in a short time.SOLUTION: A liquid enclosed type pressure sensor is fitted to an inspection device at a position where a diaphragm hermetically sealing a liquid enclosed chamber of the pressure sensor is below a liquid level in a bath of the inspection device. A method of inspecting the pressure sensor includes the steps of: applying negative pressure to the diaphragm to decompress the pressure sensor almost to desired reference pressure; maintaining an in-liquid temperature in the bath at a boiling point when reference pressure is boiling pressure of the liquid in the liquid enclosed chamber; applying ultrasonic vibrations to the pressure sensor through the liquid in the bath; and determining, on the basis of an output from the pressure sensor for a predetermined period, that the pressure sensor is a defective.SELECTED DRAWING: Figure 5

Description

The present disclosure relates to an inspection method and an inspection apparatus for a liquid-filled pressure sensor.

Conventionally, pressure sensors have been used in various industrial devices. In particular, a liquid-filled pressure sensor is known as one of the pressure sensors for detecting fluid pressure (for example, Patent Document 1).

FIG. 1 shows a schematic view of a liquid-filled pressure sensor 10. The liquid-filled pressure sensor 10 includes a pressure detecting element 11, a liquid-filled chamber 12 filled with a liquid, and a diaphragm 13 that seals the liquid-filled chamber 12. The liquid degassed in the liquid sealing chamber 12 is sealed at atmospheric pressure by the diaphragm 13. The pressure detecting element 11 is installed in the liquid sealing chamber 12 in which the liquid is sealed. Further, the pressure detecting element 11 is connected to an electric signal output terminal and outputs a signal corresponding to the pressure. Hereinafter, the semiconductor pressure sensor chip is an example of the pressure detecting element 11, and the metal diaphragm is an example of the diaphragm 13.

In the liquid-filled pressure sensor 10, silicon oil is usually used to fill the inside of the liquid-filled chamber 12, which is the sensor body container. Then, when the metal diaphragm 13 is pressurized from the outside, the stress is transmitted to the semiconductor pressure sensor chip 11 via silicon oil. More specifically, in the liquid-filled pressure sensor 10, when pressure is applied to the metal diaphragm 13 from the outside, stress is applied to the silicon diaphragm of the semiconductor pressure sensor chip 11 via the silicon oil in the liquid-filled chamber 12 (not shown). ) Is transmitted.

In the pressure detection element, a piezoresist is generally arranged on a silicon diaphragm, and the resistor is used to form a Wheatstone bridge circuit. When a silicon diaphragm receives stress, it is deformed by the stress, and at the same time, the resistance value of the piezo resistor also changes. By applying a voltage to the Wheatston bridge circuit composed of a piezo resistor, it becomes possible to detect the resistance value changed by stress as a change in voltage, that is, an electric signal.

Japanese Unexamined Patent Publication No. 2003-42883

When the liquid-filled pressure sensor 10 is used for vacuum pressure measurement, a negative pressure is applied to the metal diaphragm 13, and the liquid-filled pressure sensor 10 is depressurized. That is, a vacuum space is formed in the liquid sealing chamber 12, and the metal diaphragm 13 is distorted toward the negative pressure side. Under such pressure conditions, the semiconductor pressure sensor chip 11 is known to suddenly output an electric signal indicating a pressure fluctuation from the negative pressure side to the opposite positive pressure side (hereinafter, referred to as a pressure fluctuation phenomenon). Then, when the pressure fluctuation phenomenon occurs, the liquid-filled pressure sensor 10 becomes unusable.

FIG. 2 is a graph showing a pressure fluctuation phenomenon generated by the liquid-filled pressure sensor 10 decompressed to a negative pressure. More specifically, FIG. 2 shows that in the liquid-filled pressure sensor 10, the pressure was reduced from the state in which the silicon oil was sealed at atmospheric pressure to a negative pressure over time (the vacuum space volume of the liquid-filled chamber 12 increased). It shows the change of the pressure value indicated by the liquid-filled pressure sensor 10 in the case. In the graph, the vertical axis shows the sensor pressure which is the output of the liquid-filled pressure sensor 10, and the horizontal axis shows the time. As shown in the figure, it is understood that the pressure of the liquid-filled pressure sensor 10 suddenly rises to the saturated vapor pressure at a specific timing (time t1), and the above-mentioned pressure fluctuation phenomenon occurs.

The occurrence of the pressure fluctuation phenomenon is largely due to individual differences in the liquid-filled pressure sensor 10. That is, the conditions under which the pressure fluctuation phenomenon occurs differ from individual to individual depending on various characteristics such as viscosity, vapor pressure, and degassed state of the silicone oil 10 sealed in the liquid-filled pressure sensor.

The liquid-filled pressure sensor 10 that causes such a pressure fluctuation phenomenon should be removed at the time of inspection as a defective product. At present, it is known that the pressure fluctuation phenomenon may be reproduced when the liquid-filled pressure sensor 10 is placed in a constant temperature bath at about 90 ° C. for 10 hours or more. Is long-term and has poor reproducibility.

Further, it is known that the liquid-filled pressure sensor 10 behaves normally when it does not correspond to a specific condition that may cause a pressure fluctuation phenomenon. In particular, it is known that even if the pressure fluctuation phenomenon occurs once, the normal behavior is restored again when the specific conditions are no longer met. Further, when the pressure fluctuation phenomenon occurs, not only the pressure rise may occur suddenly, but also the pressure may gradually rise. Therefore, it is difficult to reproduce the pressure fluctuation phenomenon itself, and even if the pressure fluctuation phenomenon is reproduced, it is difficult to properly identify the defective product.

The present disclosure has been made in view of the above points. An object of the present disclosure is to provide an inspection method and an apparatus capable of reliably discriminating a liquid-filled pressure sensor 10 that causes a pressure fluctuation phenomenon due to a liquid-filled structure as a defective product in a short time. To do.

According to one embodiment, a method for inspecting a liquid-filled pressure sensor is provided. In such an inspection method, the pressure sensor is attached to the inspection device at a position where the diaphragm sealing the liquid encapsulation chamber of the pressure sensor is below the liquid level in the bathtub provided in the inspection device. In the method, a negative pressure is applied to the diaphragm to reduce the pressure of the pressure sensor to near a desired reference pressure, the submerged temperature of the bathtub is set, and the reference pressure is vapor pressure of the liquid in the liquid encapsulation chamber. Based on the step of maintaining the boiling point of the pressure sensor, the step of applying ultrasonic vibration to the pressure sensor through the liquid in the bathtub, and the output from the pressure sensor over a predetermined period of time, the pressure sensor fails. Includes a step to determine if it is a good product.

The inspection method according to one embodiment includes the step of determining whether the pressure sensor is a defective product to identify the pressure fluctuation in the liquid encapsulation chamber based on the output over the predetermined period.

In the inspection method according to one embodiment, the predetermined period is about 2 to 10 minutes.

In the inspection method according to the embodiment, the pressure sensor is attached to the inspection device at a position where the entire liquid encapsulation chamber is below the liquid level in the bathtub.

Further, according to one embodiment, an inspection device for a liquid-filled pressure sensor is provided. Such an inspection device includes a bathtub, a heater, an ultrasonic vibrator, a vacuum pump, and a recording unit for recording the pressure of the pressure sensor to be measured, and the liquid encapsulation chamber is sealed by the pressure sensor. The pressure sensor is attached to the inspection device at a position where the diaphragm is below the liquid level in the bathtub, and the vacuum pump applies a negative pressure to the diaphragm to apply a negative pressure to the attached pressure sensor. Is depressurized to near a desired reference pressure, the heater heats the bathtub to the boiling point when the reference force is the steam pressure for the liquid in the liquid encapsulation chamber, and the ultrasonic vibrator heats the liquid. Based on the pressure fluctuation of the pressure sensor over a predetermined period recorded in the recording unit, the pressure sensor is configured to generate ultrasonic waves to generate ultrasonic vibrations in the tub. It is possible to determine whether the pressure sensor is a defective product.

In the inspection device according to the embodiment, the diaphragm is attached to the inspection device at a position where the entire liquid encapsulation chamber is below the liquid level in the bathtub.

In the inspection device according to the embodiment, the plurality of pressure sensors are arranged so that the distances of the ultrasonic vibrator from the ultrasonic vibrating element are equal.

The inspection device according to the embodiment further includes a temperature controller, and the submerged temperature of the bathtub heated by the heater is maintained by the temperature controller.

FIG. 1 is a schematic view of a liquid-filled pressure sensor 10. FIG. 2 is a graph showing an exemplary pressure fluctuation phenomenon. FIG. 3 is a schematic view of the liquid-filled pressure sensor 10 decompressed to a negative pressure. FIG. 4 is an exemplary vapor pressure curve of silicone oil. FIG. 5 is an exemplary inspection device for the liquid-filled pressure sensor according to the embodiment. FIG. 6 is a schematic view showing the liquid-filled pressure sensor 10 in the inspection state. FIG. 7 is an exemplary inspection method of the liquid-filled pressure sensor according to the embodiment. FIG. 8 is a graph showing the reproduction of the illustrated pressure fluctuation phenomenon through the inspection.

Hereinafter, embodiments of an inspection device and an inspection method for a liquid-filled pressure sensor according to the present disclosure will be described together with the accompanying drawings. In the accompanying drawings, the same or similar elements are designated by the same or similar reference numerals, and duplicate description of the same or similar elements may be omitted in the description of each embodiment. In addition, the features shown in each embodiment can be applied to other embodiments as long as they do not contradict each other. Furthermore, the drawings are schematic and do not necessarily match the actual dimensions, ratios, etc. Even between drawings, there may be parts where the relationship and ratio of dimensions differ from each other.

First, the cause of the above-mentioned pressure fluctuation phenomenon in the liquid-filled pressure sensor 10 is considered as follows, and on the premise of this, the pressure fluctuation phenomenon can be reproduced. The inspection device and the inspection method of the liquid-filled pressure sensor 10 of the embodiment will be described.

FIG. 3 shows a schematic view of a state in which the liquid-filled pressure sensor 10 is depressurized to a negative pressure. As a result of the reduced pressure, it is understood that the metal diaphragm 13 is pulled toward the negative pressure side and is distorted, and a slight vacuum space is formed in the liquid sealing chamber 12 in which the silicone oil is sealed. It is understood that the vacuum space has a strong negative pressure, and the lower the pressure in the liquid encapsulation chamber 12, the higher the degree of vacuum and the larger the space volume.

FIG. 4 shows an exemplary steam pressure curve for silicon oil. The vapor pressure curve is determined for each type of silicone oil. As shown in the figure, the vapor pressure of silicone oil increases with increasing temperature, while the vapor pressure of silicone oil decreases as the temperature decreases. In the illustrated example vapor pressure curve (dotted line), the temperature corresponding to the vapor pressure is the boiling point at which the silicone oil boils. In the illustrated example, the boiling point of the silicone oil when the vapor pressure is 10 Torr is 100 ° C. (boiling point 1). On the other hand, when the steam pressure is 1 Torr, the boiling point is 60 ° C. (boiling point 2).

When the pressure in the liquid sealing chamber 12 is equal to the vapor pressure of the silicone oil and the temperature reaches the boiling point of the silicone oil, the silicone oil will boil. Then, when the silicon oil boils, in the liquid encapsulation chamber 12, gas such as air dissolved in the silicon oil becomes vaporized molecules (microbubbles) and jumps out from the oil surface, and air bubbles are generated inside the liquid encapsulation chamber 12. It will occur.

Considering the vapor pressure curve of silicon oil in FIG. 4, when a vacuum space is formed in the liquid encapsulation chamber 12 and the internal pressure decreases, the boiling point when the pressure is taken as the vapor pressure of silicon oil also decreases. It is considered that the silicon oil in the liquid encapsulation chamber 12 boils even at a low temperature.

Then, the silicone oil reaches the boiling point and boils, and the microbubbles of the silicone oil pop out from the surface of the silicone oil and fill the liquid sealing chamber 12, so that the pressure in the liquid sealing chamber 12 rises. More specifically, the pressure in the liquid-filled chamber 12 rises until the pressure is in equilibrium with the atmospheric pressure in which the liquid-filled pressure sensor 10 is arranged. Then, in the pressure equilibrium state, when the equilibrium is lost due to some external stimulus, the above-mentioned pressure fluctuation phenomenon occurs, and it is considered that the electric signal output from the semiconductor pressure sensor chip 11 indicates the pressure fluctuation phenomenon. Will be done.

In addition, even when the pressure in the liquid sealing chamber 12 is equal to the vapor pressure of the silicone oil and the temperature reaches the boiling point of the silicone oil, the silicone oil may not boil. Such a state is generally referred to as vapor-liquid equilibrium. Then, even in the state of vapor-liquid equilibrium, when the equilibrium is lost due to some external stimulus, the above-mentioned pressure fluctuation phenomenon occurs, and the electric signal output from the semiconductor pressure sensor chip 11 shows the pressure fluctuation phenomenon. It is considered to indicate a fluctuating signal.

In order to give the liquid encapsulation chamber 12 an external stimulus such as pressure equilibrium and vapor-liquid equilibrium that causes the equilibrium state to collapse and become unstable, silicon oil is added by increasing the pressure in the liquid encapsulation chamber 12. It is better to bring it to a boil and make the remaining gas into microbubbles. The microbubble formation of gas is generally referred to as cavitation.

Therefore, in one embodiment, as an aspect of such an external stimulus, a method of stimulating the silicone oil from the outside such as ultrasonic vibration is adopted. Cavitation is generated in the silicone oil by applying ultrasonic vibration to the liquid sealing chamber 12. More specifically, the liquid-filled pressure sensor 10 (particularly, the liquid-filled chamber 12) is subjected to ultrasonic vibration in a predetermined frequency band from the outside to generate cavitation in silicon oil, and the remaining microbubbles are siliconized. Evaporate from the oil surface. In this way, the phenomenon of pressure equilibrium and vapor-liquid equilibrium being disrupted inside the liquid encapsulation chamber 12 is caused.

Inspection device of the liquid-filled pressure sensor according to one embodiment FIG. 5 shows a schematic view of the inspection device 20 of the liquid-filled pressure sensor 10 according to one embodiment. By using the inspection device 20, it is possible to cause a phenomenon in which the pressure equilibrium and the gas-liquid equilibrium are disrupted inside the liquid sealing chamber 12.

The inspection device 20 includes a power supply 21, a recording unit 22, a temperature controller 23, a vacuum pump 24, a reference sensor 25, a metal bathtub (hereinafter referred to as a bathtub) 26, an ultrasonic vibrator 27, a thermometer 28, and a heater 29.

The liquid-filled pressure sensor 10 (10a, 10b) to be inspected is arranged at a position where the metal diaphragm 13 portion that seals the liquid-filled chamber 12 is below the liquid level in the bathtub 26. More specifically, the inspection device 20 includes a concave mounting jig (not shown) that can be mounted by fitting the liquid-filled pressure sensors 10a and 10b. A part of the outer circumference of the mounting jig is immersed in the liquid in the bathtub 26.

By fitting the liquid-filled pressure sensors 10a and 10b into the mounting jig with the metal diaphragm 13 of the liquid-filled pressure sensor facing down, the metal diaphragm 13 portion is positioned below the liquid level in the bathtub 26. become. At that time, the liquid-filled pressure sensors 10a and 10b themselves are not immersed in the liquid surface. Further, the mounting jig is provided with a pressure introduction hole and communicates with the vacuum pump 24 and the reference sensor 25. When carrying out the inspection, the liquid-filled pressure sensors 10a and 10b are attached to the mounting jig, and a negative pressure is applied to the metal diaphragm 13 by the vacuum pump 24 to cause the liquid-filled pressure sensors 10a and 10b. The pressure is reduced to near the desired reference pressure. The reference pressure is preferably 10 Torr or less, more preferably about 1 Torr. As will be described later, the liquid-filled pressure sensors 10a and 10b are not limited to two.

The power supply 21 supplies electric power to various devices such as the recording unit 22 and the reference sensor 25, and the liquid-filled pressure sensors 10a and 10b, respectively. The recording unit 22 records various inspection data including the pressure data which is the output signal of the liquid-filled pressure sensors 10a and 10b to be measured and the temperature data in the bathtub 26 over the inspection period. The control unit (not shown) observes the output state of the electric signal output of the liquid-filled pressure sensors 10a and 10b by using this inspection data. As a result, it is possible to determine whether or not the product is defective based on the pressure fluctuations of the liquid-filled pressure sensors 10a and 10b recorded in the recording unit 22 over a predetermined period.

The temperature controller 23 is connected to the heater 29 in the bathtub 26. The temperature controller 23 heats and controls the heater 29 with reference to the thermometer 28 so as to keep the submerged temperature of the bathtub 26 constant. At the time of inspection, the vacuum pump 24 communicates with the liquid-filled pressure sensors 10a and 10b via a mounting jig (not shown). More specifically, the vacuum pump 24 is piped through a pipe joint to a pressure introduction hole (not shown) of a mounting jig. Then, when the liquid-filled pressure sensors 10a and 10b are attached to the mounting jig, the liquid-filled pressure sensors 10a and 10b can be applied to a negative pressure by the vacuum pump 24. As a result, a vacuum space can be formed in the liquid sealing chamber 12, and the liquid filling type pressure sensors 10a and 10b can be adjusted to a desired vacuum pressure (for example, 1 Torr). The reference sensor 25 can confirm that the liquid-filled pressure sensors 10a and 10b (particularly the liquid-filled chamber 12) have reached a desired pressure (reference pressure) when the pressure is reduced by the vacuum pump 24.

The bath 26 is covered with a liquid level, and a thermometer 28 and a heater 29 are arranged inside the bath 26. Further, an ultrasonic vibrator 27 is arranged on the bottom surface of the bathtub 26. The liquid in the bathtub 26 is not limited to water, and may be any medium as long as it is a medium through which ultrasonic waves propagate. The oscillating output of the ultrasonic vibrator 27 is sealed in the liquid sealing chamber 12 under a predetermined temperature condition when ultrasonic vibration is applied to the liquid-filled pressure sensors 10a and 10b through the liquid in the bath 26. It is adjusted to the extent that cavitation is excited by the silicon oil.

The intensity of the signal output from the ultrasonic vibrating element (not shown) of the ultrasonic vibrating device 27 is inversely proportional to the square of the distance from the ultrasonic vibrating element. Therefore, the ultrasonic vibration element is preferably arranged at a position where the distances between the plurality of liquid-filled pressure sensors 10a and 10b are equal. If the distances from the ultrasonic vibration elements are the same, it is preferable to arrange two or more, preferably about 8 to 10 liquid-filled pressure sensors 10, and the inspection efficiency can be improved. More specifically, about 8 to 10 bathtubs 26 arranged on a horizontal plane are viewed from above so that the plan view is on the circumference of a predetermined radius centered on the ultrasonic vibration element. A liquid-filled pressure sensor should be placed. The number of liquid-filled pressure sensors 10 to be arranged may be determined according to the diameter of the metal diaphragm 13 and the distance of the ultrasonic vibrator 27 from the ultrasonic vibrating element.

FIG. 6 is a schematic view showing a state of the liquid-filled pressure sensor 10 when the liquid-filled pressure sensor 10 is inspected using the inspection device 20. As shown in the figure, the metal diaphragm 13 of the liquid-filled pressure sensor 10 is arranged at a position below the liquid level in the bathtub 26. Preferably, as shown in the drawing, the entire liquid encapsulation chamber 12 is arranged so as to be below the water surface in the bathtub 26.

In FIG. 6, the liquid-filled pressure sensor 10 (by the vacuum pump 24) is depressurized by applying a negative pressure, and as a result of the metal diaphragm 13 being distorted to the negative pressure side, a vacuum space is formed in the liquid-filled chamber 12. ing. Then, in a state where the water temperature is raised to the boiling point of the silicone oil, ultrasonic vibration is applied to the liquid-filled pressure sensor 10 (particularly, the silicone oil in the liquid-filled chamber 12).

As a result, cavitation is generated in the silicone oil. That is, the microbubbles remaining in the silicon oil are excited to generate silicon vapor, and the vaporized molecular layer shown in the figure is generated. Further, by filling the vacuum space in the silicone oil with microbubbles and silicone vapor, the pressure in the liquid sealing chamber 12 rises, causing pressure fluctuations.

As described above, by using the inspection device 20 of the liquid-filled pressure sensor 10 according to the embodiment, the above-mentioned pressure fluctuation phenomenon that occurs in the liquid-filled pressure sensor 10 due to the structure of the liquid-filled chamber 12 is effective. Can be reproduced in.

Inspection method of liquid-filled pressure sensor according to one embodiment FIG. 7 is an exemplary flowchart showing an inspection method of the liquid-filled pressure sensor 10 according to one embodiment. This inspection method is performed by the following procedure using the inspection device 20 of the liquid-filled pressure sensor 10 according to the embodiment shown in FIG.

In this inspection method, first, in step S11, the metal diaphragm 13 that seals the liquid sealing chamber 12 of the liquid filling type pressure sensor 10 is arranged at a position below the liquid level in the bathtub 26. As shown in FIG. 6, the metal diaphragm 13 faces downward. At this position, the liquid-filled pressure sensor 10 is attached to the attachment jig of the inspection device. Next, in step S12, a negative pressure is applied to the metal diaphragm 13 by the vacuum pump 24, and it is confirmed by the reference sensor 25 that the liquid-filled pressure sensor 10 has reached a desired reference pressure. As a result, a vacuum space is formed in the liquid sealing chamber 12 filled with silicone oil.

When a desired reference pressure (for example, 1 Torr) is used as the vapor pressure, the boiling point corresponding to the vapor pressure is specified from the vapor pressure curve of the silicone oil shown in FIG. 4 (in the example of FIG. 4, 60 ° C.). ). At the same time as step S12, in step S13, the inside of the bathtub 26 is heated by using the heater 29 so that the temperature in the bathtub 26 reaches the boiling point (60 ° C.). Further, with reference to the thermometer 28, the temperature controller 23 is used to control the heating of the heater 29 so as to maintain a boiling point of 60 ° C. for a predetermined inspection period.

As a result of step S12 and step S13, the inside of the liquid sealing chamber 12 reproduces a state in which the pressure is the vapor pressure of the silicon oil and the temperature is the boiling point corresponding to the vapor pressure according to the vapor pressure curve of the silicon oil. be able to.

Next, in step S14, an ultrasonic oscillator 27 is used to generate ultrasonic waves in the liquid in the bathtub 26, and ultrasonic vibrations are continuously applied to the liquid-filled pressure sensor 10 over a predetermined inspection period. As a result, it is possible to generate cavitation in the silicone oil in the liquid sealing chamber 12 and promote the vaporization of microbubbles from the surface of the silicone oil. As a result, the pressure in the liquid encapsulation chamber 12 rises, and pressure fluctuation can be caused.

While the liquid-filled pressure sensor 10 is subjected to ultrasonic vibration in step S14, the electric signal output from the liquid-filled pressure sensor 10 is measured and recorded by the recording unit 22. By using the pressure data recorded in the recording unit 22, it can be determined whether the liquid-filled pressure sensor 10 outputs an electric signal indicating a pressure fluctuation.

Specifically, in step S15, it is determined whether the liquid-filled pressure sensor 10 is a defective product. The determination is to identify the pressure fluctuation in the liquid sealing chamber 12 based on the output from the liquid filling type pressure sensor 10 over a predetermined inspection period (for example, about 2 to 10 minutes). That is, the presence or absence of the above-mentioned pressure fluctuation phenomenon is determined. In one example, the determination may be performed by the control unit (not shown) of the inspection device 20 determining whether or not the output pressure fluctuation value exceeds a predetermined threshold value.

FIG. 8 is a graph showing an exemplary pressure fluctuation phenomenon reproduced by applying ultrasonic vibration to the liquid-filled pressure sensor 10. More specifically, assuming that the boiling point of silicon oil with respect to a predetermined reference pressure (vapor pressure) is 90 ° C., the submerged temperature of the bathtub 26 is heated and maintained at 90 ° C., and ultrasonic vibration is applied to the liquid-filled pressure sensor 10. It shows the pressure fluctuation phenomenon when is continuously given. In the graph, the left vertical axis shows the output (% F.S.), the right vertical axis shows the temperature (° C.), and the horizontal axis shows the time.

Here, after the inspection is started, ultrasonic vibration is continuously applied to the liquid-filled pressure sensor 10 in a vacuum state for the first 60 minutes, and ultrasonic vibration is not applied in a vacuum state for the next 10 minutes. Then, the liquid-filled pressure sensor 10 is released to the atmosphere for the next 15 minutes, and then evacuated again for the next 5 minutes.

As shown in FIG. 8, fluctuations in output are observed in the first 10 minutes (2 to 12 minutes), and in particular, rapid fluctuations (rise) are observed in the first 2 minutes (2 to 4 minutes). Therefore, the inspection device 20 determines that the above-mentioned pressure fluctuation phenomenon has occurred by continuously applying ultrasonic vibration with an inspection period of about 2 to 10 minutes and identifying an abnormality due to output fluctuation. Can be done. It should be noted that in FIG. 8, the inspection period is not limited to about 2 to 10 minutes in view of the fact that the output continues to increase even after 12 minutes and the abnormal state continues.

Further, as shown in FIG. 8, the output of the liquid-filled pressure sensor 10 shows a normal value and rises in 5 minutes (about 88 to 93 minutes) when the pressure is evacuated again after the pressure fluctuation phenomenon occurs. Not observed. That is, it is considered that the liquid-filled pressure sensor 10 returns to the normal behavior when the original environment is restored even after the pressure fluctuation phenomenon is once reproduced.

As described above, by executing the inspection method of the liquid-filled pressure sensor 10 according to the embodiment, the above-mentioned pressure fluctuation phenomenon generated in the liquid-filled pressure sensor 10 due to the structure of the liquid-filled chamber 12 can be effectively eliminated. It can be reproduced. In particular, in the past, by placing the liquid-filled pressure sensor 10 in a constant temperature bath at about 90 ° C. for 10 hours or more, the reproduction of the pressure fluctuation phenomenon was confirmed to be significantly shortened, and it took about 2 to 10 minutes. It is possible to determine defective products in a short period of time. That is, the pressure fluctuation phenomenon can be easily reproduced, and it can be efficiently determined whether or not the liquid-filled pressure sensor 10 is a defective product.

Although the inspection device and the inspection method embodiment of the liquid-filled pressure sensor according to the present invention have been described above, the technical scope of the present invention is not limited to the above-mentioned range. It will be apparent to those skilled in the art that various changes or improvements can be made to the above description. It is clear from the description of the scope of claims that such an improved form may also be included in the technical scope of the present invention.

10, 10a, 10b ... Liquid-filled pressure sensor 11 ... Pressure detection element (semiconductor pressure sensor chip)
12 ... Liquid encapsulation chamber 13 ... Diaphragm (metal diaphragm)
20 ... Inspection device 21 ... Power supply 22 ... Recording unit 23 ... Temperature controller 24 ... Vacuum pump 25 ... Reference sensor 26 ... Metal bathtub (bathtub)
27 ... Ultrasonic vibrator 28 ... Thermometer 29 ... Heater

Claims (8)

In the inspection method of the liquid-filled pressure sensor, the pressure sensor inspects the pressure sensor at a position where the diaphragm sealing the liquid-filled chamber of the pressure sensor is below the liquid level in the bathtub provided in the inspection device. Attached to the device
A step of applying a negative pressure to the diaphragm to reduce the pressure of the pressure sensor to near a desired reference pressure.
A step of maintaining the temperature in the bathtub at the boiling point when the reference pressure is the vapor pressure for the liquid in the liquid encapsulation chamber.
The step of applying ultrasonic vibration to the pressure sensor through the liquid in the bathtub,
A method comprising the step of determining whether the pressure sensor is defective based on the output from the pressure sensor over a predetermined period of time. The method of claim 1, wherein the step of determining whether the pressure sensor is defective comprises identifying pressure fluctuations in the liquid encapsulation chamber based on the output over the predetermined period. The method according to claim 1 or 2, wherein the predetermined period is about 2 to 10 minutes. The method according to any one of claims 1 to 3, wherein the pressure sensor is attached to the inspection device at a position where the entire liquid encapsulation chamber is below the liquid level in the bathtub. A liquid-filled pressure sensor inspection device
It includes a bathtub, a heater, an ultrasonic vibrator, a vacuum pump, and a recording unit that records the pressure of the pressure sensor to be measured.
The pressure sensor is attached to the inspection device at a position where the diaphragm sealing the liquid encapsulation chamber is below the liquid level in the bathtub in the pressure sensor.
The vacuum pump applies a negative pressure to the diaphragm to depressurize the attached pressure sensor to near a desired reference pressure.
The heater heats the bathtub to the boiling point when the reference force is the vapor pressure for the liquid in the liquid encapsulation chamber.
The ultrasonic vibrator generates ultrasonic waves in the heated bathtub to give ultrasonic vibration to the pressure sensor.
A device capable of determining whether or not the pressure sensor is a defective product based on the pressure fluctuation of the pressure sensor over a predetermined period recorded in the recording unit. The method according to claim 5, wherein the diaphragm is attached to the inspection device at a position where the entire liquid encapsulation chamber is below the liquid level in the bathtub. The device according to claim 5 or 6, wherein the plurality of pressure sensors are arranged so that the distances of the ultrasonic vibrator from the ultrasonic vibrating element are equal. The device according to any one of claims 5 to 7, further comprising a temperature controller.
A device in which the submerged temperature of the bathtub heated by the heater is maintained by the temperature controller.

Images