JP6793579B2 - Manufacturing method of thermal flow sensor and thermal flow sensor - Google Patents

Description

The present invention relates to a manufacturing method for manufacturing a thermal flow rate sensor having a heat generating portion and a sensor chip attached to a pipe, and a thermal flow rate sensor.

Conventionally, a thermal flow rate sensor that measures the flow rate of a fluid flowing in a pipe by using a heater has been known (see, for example, Patent Document 1). In this thermal flow sensor, a sensor chip provided with a heater in the diaphragm portion, a sensor chip provided with a temperature sensor, and a substrate having an adhesive portion located between the sensor chips are attached to a pipe by an adhesive. ing. Then, the heater is heated so as to be a constant temperature higher than the temperature measured by the temperature sensor.

International Publication No. 2001/084087

However, the conventional thermal flow rate sensor has a problem that the accuracy of repeated measurement of the flow rate deteriorates even if the basic flow rate characteristics satisfy the performance.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a method for manufacturing a thermal flow rate sensor capable of improving the accuracy of repeated measurement of flow rate.

The method for manufacturing a thermal flow sensor according to the present invention includes a moving step in which the needle for discharging the adhesive and the sensor chip are separated from each other by a predetermined distance, and an adhesive application in which the adhesive is discharged from the needle and the adhesive is applied to the diaphragm portion. It has a step, and a pasting step of adhesive paste in piping coated sensor chip, the thickness of the adhesive layer between the pipe and the sensor chip state, and are less 30 [mu] m, the adhesive has a viscosity It is characterized by being 40 Pa · s or less .

According to the present invention, since it is configured as described above, the accuracy of repeated measurement of the flow rate can be improved.

1A and 1B are views showing a configuration example of a thermal flow rate sensor according to a first embodiment of the present invention, FIG. 1A is a perspective view, and FIG. 1B is a bottom view. It is a figure which shows the structural example of the manufacturing apparatus of the thermal flow rate sensor which concerns on Embodiment 1 of this invention. It is a flowchart which shows an example of the manufacturing method of the thermal flow rate sensor which concerns on Embodiment 1 of this invention. It is a figure which shows an example of the manufacturing method of the thermal flow rate sensor which concerns on Embodiment 1 of this invention. It is a figure explaining the effect of the thermal flow rate sensor which concerns on Embodiment 1 of this invention, and is the figure which shows the repeat measurement accuracy of a flow rate.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
Embodiment 1.
FIG. 1 is a diagram showing a configuration example of a thermal flow sensor according to a first embodiment of the present invention. In FIG. 1, the signal line connecting the sensor chips 2 and 3 and the substrate 4 is not shown.
The thermal flow rate sensor is a sensor that uses a heater 22 to measure the flow rate of a fluid (liquid or gas) flowing through the pipe (capillary) 1. As shown in FIG. 1, this thermal flow sensor is connected to a pipe 1 through which a fluid flows, sensor chips 2 and 3 attached to a counterbore surface 11 of the pipe 1, and sensor chips 2 and 3 to signal. It is provided with a substrate 4 for inputting and outputting.

The sensor chip 2 is provided with a heater 22 that applies heat to the fluid in the pipe 1 in a diaphragm portion 21 that is a thin film attached to the pipe 1. Further, the thickness of the adhesive layer between the pipe 1 and the sensor chip 2 after the attachment is 30 μm or less.
The sensor chip 3 is provided with a temperature sensor 31 that measures the temperature of the fluid in the pipe 1. A gap is provided between the sensor chip 2 and the sensor chip 3.

The substrate 4 shown in FIG. 1 is a printed circuit board configured in a convex shape having a projecting piece 41 projecting from one side. The projecting piece 41 is located with a gap between the sensor chip 2 and the sensor chip 3, and is a portion to be attached to the pipe 1. The substrate 4 is not limited to a printed circuit board, and may be any substrate that can input and output signals, and a flexible printed circuit board or the like may be used. Further, the shape of the substrate 4 is not limited to the shape shown in FIG.

Then, for example, in the case of constant temperature difference drive, the substrate 4 acquires a signal indicating the temperature measured by the temperature sensor 31 and controls the heater 22 so that the temperature is higher than the temperature by a constant temperature. Then, the substrate 4 measures the flow rate of the fluid by acquiring a signal indicating the power in the heater 22. That is, in the thermal flow sensor, when the fluid in the pipe 1 is stationary, the amount of heat when heat is applied by the heater 22 so that the temperature rises to a constant temperature with respect to the surroundings, and the fluid in the pipe 1 is on the upstream side. There is a difference in the amount of heat when heat is applied by the heater 22 so that the temperature rises to a certain level with respect to the surroundings when the fluid flows from the downstream side. This difference in calorific value correlates with the flow rate of the fluid in the pipe 1. Therefore, the thermal flow rate sensor can measure the flow rate of the fluid flowing in the pipe 1 from this difference in the amount of heat.

Here, in the conventional thermal flow rate sensor, although the basic flow rate characteristics satisfy the performance, there is a problem that the repeated measurement accuracy of the flow rate is poor. On the other hand, it has been found that by increasing the thermal coupling property between the pipe 1 and the sensor chip 2, the response sensitivity is improved and the accuracy of repeated measurement of the flow rate is improved. Therefore, in the thermal flow sensor according to the first embodiment, the thickness of the adhesive layer between the pipe 1 and the sensor chip 2 is reduced to reduce the heat capacity, whereby the heat between the pipe 1 and the sensor chip 2 is reduced. Increase connectivity.
On the other hand, in the conventional thermal flow sensor, the sensor chip 2 is usually attached to the pipe 1 by using a highly viscous adhesive (for example, about 60 Pa · s). When such a highly viscous adhesive is used, the thickness of the adhesive layer between the pipe 1 and the sensor chip 2 can be reduced to only about 50 μm. Therefore, in the thermal flow sensor according to the first embodiment, the adhesive layer between the pipe 1 and the sensor chip 2 is thinned by applying the adhesive 5 having a lower viscosity only to the diaphragm portion 21 ( 30 μm or less).

Next, a configuration example of the manufacturing apparatus 6 for manufacturing the thermal flow sensor will be described with reference to FIG. In the following, only the process of attaching the sensor chip 2 to the pipe 1 among the manufacturing processes of the thermal flow sensor will be shown. Further, although the case where the manufacturing apparatus 6 automatically performs each step is shown below, it may be performed manually.
As shown in FIG. 2, the manufacturing apparatus 6 includes a moving portion 61, an adhesive coating portion 62, and a sticking portion 63.

The moving unit 61 moves the needle 64 (see FIG. 4) to a position separated from the sensor chip 2 by a predetermined distance. That is, the needle 64 is held at a position away from the sensor chip 2 so that the diaphragm portion 21 is not torn when the adhesive 5 is applied to the diaphragm portion 21. The needle 64 is a portion for discharging the adhesive 5. Further, the moving portion 61 pulls up the needle 64 after the adhesive 5 is applied by the adhesive applying portion 62.

The adhesive application portion 62 discharges the adhesive 5 from the needle 64 to apply the adhesive 5 to the diaphragm portion (heat generating portion) 21. At this time, the adhesive application portion 62 uses an adhesive 5 having a low viscosity (for example, 40 Pa · s or less), and the adhesive 5 is applied only to the diaphragm portion 21. Specific examples of the adhesive 5 include a silicone-based adhesive (SE4402) manufactured by Toray Dow Corning, which has a viscosity of 34 Pa · s.

The sticking portion 63 sticks the sensor chip 2 coated with the adhesive 5 to the pipe 1. At this time, the sticking portion 63 attaches the sensor chip 2 to the pipe 1 by placing the pipe 1 on the sensor chip 2 coated with the adhesive 5 and pressing the pipe 1 against the sensor chip 2 with a constant load. wear.

Next, an example of a method for manufacturing a thermal flow sensor will be described with reference to FIGS. 3 and 4.
In the method of manufacturing a thermal flow sensor, as shown in FIGS. 3 and 4, first, the moving unit 61 moves the needle 64 to a position separated from the sensor chip 2 by a predetermined distance (step ST1, moving step).
Next, the adhesive application portion 62 discharges the adhesive 5 from the needle 64 to apply the adhesive 5 to the diaphragm portion 21 (step ST2, adhesive application step). After that, the moving portion 61 pulls up the needle 64.
Next, the sticking portion 63 sticks the sensor chip 2 coated with the adhesive 5 to the pipe 1 (step ST3, sticking step).

Next, the effect of the thermal flow rate sensor according to the first embodiment will be described with reference to FIG. In FIG. 5, reference numeral 501 indicates a case where the thickness of the adhesive layer is 50 μm, reference numeral 502 indicates a case where the thickness of the adhesive layer is 30 μm, and reference numeral 503 indicates a case where the thickness of the adhesive layer is 10 μm.
As shown in FIG. 5, when the adhesive layer is thick (in the case of 50 μm), the error becomes large by repeating the measurement. On the other hand, when the adhesive layer is thin (30 μm and 10 μm), the error is small (error 0.3% or less) even if the measurement is repeated. That is, it can be seen that the accuracy of repeated measurement of the flow rate is improved by reducing the thickness of the adhesive layer and reducing the heat capacity.

As described above, according to the first embodiment, the needle 64 for discharging the adhesive 5 is moved to a position separated from the sensor chip 2 by a predetermined distance, and the adhesive 5 is discharged from the needle 64 to discharge the adhesive 5 to the diaphragm portion 21. The adhesive 5 is applied to the surface, and the sensor chip 2 coated with the adhesive 5 is attached to the pipe 1, so that the thickness of the adhesive layer between the pipe 1 and the sensor chip 2 is 30 μm or less. , The accuracy of repeated measurement of flow rate can be improved.

That is, in the thermal flow sensor according to the first embodiment, the adhesive 5 is applied only to the diaphragm portion 21 using the adhesive 5 having a low viscosity, and the sensor chip 2 is attached to the pipe 1. As a result, the thickness of the adhesive layer between the pipe 1 and the sensor chip 2 can be reduced to 30 μm or less, and the heat capacity can be reduced. As a result, the thermal coupling property between the pipe 1 and the sensor chip 2 is improved, and the response sensitivity is improved, so that the accuracy of repeated measurement of the flow rate is improved.

Further, since the conventional thermal flow sensor uses an adhesive having a high viscosity, the adhesive cannot be applied only to the diaphragm portion 21 of the sensor chip 2. That is, if a highly viscous adhesive is applied only to the diaphragm portion 21 and pressed from above, the diaphragm portion 21 may be over-pressurized and the diaphragm portion 21 may be torn. Therefore, conventionally, an adhesive is applied to the pipe 1 and the sensor chip 2 is placed on the adhesive. Alternatively, an adhesive is applied to the entire surface of the sensor chip 2 to disperse the pressure applied to the diaphragm portion 21. However, in these cases, the adhesive is applied to the region other than the diaphragm portion 21 on the sensor chip 2, so that the heat capacity becomes large.
On the other hand, in the thermal flow rate sensor according to the first embodiment, since the adhesive 5 having a low viscosity is used, even if the adhesive 5 is applied only to the diaphragm portion 21 of the sensor chip 2, the adhesive 5 is applied to the diaphragm portion 21. The pressure is low and the diaphragm portion 21 is not torn. Therefore, the heat capacity can be reduced. Further, by placing the pipe 1 on the sensor chip 2 coated with the adhesive 5 and attaching the sensor chip 2 to the pipe 1, the position accuracy of the sensor chip 2 on the pipe 1 is improved.

In the above, the case where the sensor chip 2 has a diaphragm portion 21 and the heater 22 is provided in the diaphragm portion 21 is shown. However, not limited to this, the sensor chip 2 does not have to have the diaphragm portion 21. For example, a sensor chip 2 in which the heater 22 is directly patterned on ceramic may be used. In this case, the adhesive application portion 62 discharges the adhesive 5 from the needle 64, and applies the adhesive 5 to the ceramic portion (heat generating portion) in which the heater 22 is patterned.

Further, in the above, the case where the moving portion 61 moves the needle 64 is shown. However, the present invention is not limited to this, and the moving unit 61 may move the sensor chip 2.

In the present invention, within the scope of the invention, it is possible to modify any component of the embodiment or omit any component of the embodiment.

1 Piping 2 Sensor chip 3 Sensor chip 4 Board 5 Adhesive 6 Manufacturing equipment 11 Counterbore surface 21 Diaphragm part 22 Heater 31 Temperature sensor 41 Protruding piece 61 Moving part 62 Adhesive application part 63 Sticking part 64 Needle

Claims (3)

In a method for manufacturing a thermal flow sensor having a diaphragm portion that is a thin film and a sensor chip attached to a pipe.
A moving step that separates the needle that discharges the adhesive from the sensor chip by a predetermined distance,
An adhesive application step of ejecting an adhesive from the needle and applying the adhesive to the diaphragm portion ,
It has a sticking step of sticking the sensor chip coated with the adhesive to the pipe.
The thickness of the adhesive layer between the sensor chip and the pipe state, and are less 30 [mu] m,
The adhesive is a method for manufacturing a thermal flow sensor, characterized in that the viscosity is 40 Pa · s or less . The method for manufacturing a thermal flow sensor according to claim 1, wherein in the sticking step, the pipe is placed on the sensor chip coated with an adhesive, and the sensor chip is stuck to the pipe. It has a diaphragm part that is a thin film, and is equipped with a sensor chip in which the diaphragm part is attached to a pipe by an adhesive.
The thickness of the adhesive layer between the sensor chip and the pipe state, and are less 30 [mu] m,
The adhesive is a thermal flow sensor having a viscosity of 40 Pa · s or less .

Images