JP3637051B2 - Thermal flow meter - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a thermal flow meter that measures a flow rate using a resistor (heat wire). More specifically, the present invention relates to a thermal flow meter that can accurately measure the flow rate of a fluid to be measured in both directions.
[0002]
[Prior art]
Conventionally, vacuum suction is used for handling during semiconductor chip mounting, and confirmation of the suction has been performed by a pressure sensor. However, in recent years, semiconductor chips have become smaller and smaller. For this reason, for example, in a 0.5 mm square chip, a suction orifice (nozzle) having a diameter of 0.5 mm or 0.3 mm is used. As a result, as shown in FIG. 20, there is almost no difference in the pressure in the orifice between adsorption and non-adsorption, and it has become impossible to confirm adsorption with the pressure sensor. For this reason, proposals have been made to confirm adsorption by detecting the flow rate of air flowing through the orifice. FIG. 20 shows an output example of the pressure sensor when the nozzle diameter is 0.3 mm and the vacuum pressure is −70 kPa.
[0003]
Therefore, the present applicant has proposed a thermal flow meter suitable for use in adsorption confirmation in Japanese Patent Application No. 2000-368801. And the result of having confirmed adsorption | suction on the above-mentioned conditions is shown in FIG. As is apparent from FIG. 21, it can be seen that if this thermal flow meter is used, it is possible to confirm adsorption, which was difficult with a pressure sensor.
[0004]
[Problems to be solved by the invention]
However, in the thermal type flow meter proposed by the present applicant in Japanese Patent Application No. 2000-368801, as shown in FIG. 22, the pressure characteristics deteriorate as the degree of vacuum increases, and it is not possible to confirm the adsorption with high accuracy. was there. Further, the output characteristics of this thermal flow meter are as shown in FIG. 23, and the same value is output regardless of the flow direction of the fluid to be measured, so there is a problem that the flow direction cannot be detected. . If the bidirectional flow rate cannot be detected in this way, the adsorption can be confirmed, but the release cannot be confirmed. This is because the fluid flows in the opposite direction at the time of adsorption and at the time of release. 22 and 23 are outputs when the full-scale flow rate is 1 L / min.
[0005]
Here, in order to confirm adsorption and release using a flow meter, a flow meter capable of detecting a bidirectional flow rate is required. An example of a flow meter capable of bidirectional flow detection is described in Japanese Patent Application Laid-Open No. 2002-5717. However, the flow meter described in Japanese Patent Laid-Open No. 2002-5717 has a problem that the output characteristics are not linear as shown in FIG. Thus, if the output characteristics are not linear, it is not possible to manage nozzle clogging. In order to make the output characteristics linear, for example, as described in JP-A-2001-165734, an arithmetic circuit may be used. However, it is necessary to separately provide an arithmetic circuit for this purpose, and in terms of cost. It will be disadvantageous.
[0006]
Further, the flow meter described in Japanese Patent Application Laid-Open No. 2002-5717 has a problem that the output becomes unstable due to the influence of turbulence as shown in FIG. If the output becomes unstable, the suction confirmation threshold must be set lower. However, since a slight change in the flow rate is detected in the adsorption confirmation, if the threshold is set to a low value, even if it is not adsorbed in the normal state and becomes smaller than the flow rate during normal adsorption, the adsorption is performed normally. It will be judged that it is done. That is, the suction confirmation could not be performed with high accuracy. Further, when a collet type nozzle that sucks a semiconductor chip while always securing a certain amount of leakage is used, the suction confirmation cannot be performed. Such output wobbling can be eliminated by inserting an electrical filter, but the responsiveness is impaired, which is not preferable.
[0007]
Therefore, the present invention has been made to solve the above-described problems, and can perform bidirectional flow rate detection, linearize output characteristics, and provide stable output without impairing responsiveness. It is an object to provide a thermal flow meter that can be obtained.
[0008]
[Means for Solving the Problems]
In order to solve the above problems, the thermal flow meter according to the present invention includes a thermal flow meter having a bypass flow path for the sensor flow path in addition to the sensor flow path provided with a resistor for measuring the flow rate. In the flow meter, the bypass flow path is formed with a fluid flow path having a side opening on a substrate provided with an electrode for an electric circuit connected to an electric circuit for performing a measurement principle using a resistor. Formed by adhering to the body through a laminated body in which a plurality of etched thin plates are laminated so as to close the side opening, and the sensor flow path is a resistor and a resistor connected to the resistor The measurement chip provided with the electrode for the electrode is formed by a groove provided in at least one of the measurement chip or the substrate by bonding the resistor electrode and the electrode for the electric circuit and mounting the electrode on the substrate. The measurement chip includes an upstream temperature detection resistor provided upstream in the flow direction, a downstream temperature detection resistor provided downstream in the flow direction, and an upstream temperature detection resistor and a downstream temperature detection resistor. A heating resistor that heats the upstream temperature detection resistor and the downstream temperature detection resistor, and a fluid temperature detection resistor that detects the temperature of the fluid to be measured. The temperature sensing resistor is controlled to have a certain temperature difference, and the flow rate of the fluid to be measured is measured based on the temperature difference between the upstream temperature sensing resistor and the downstream temperature sensing resistor. is there. In the present specification, the “side opening” means an opening that is open on the side of the body (in other words, the surface where the input / output port is not open) and the substrate is mounted.
[0009]
In this thermal flow meter, the fluid to be measured that has flowed into the flow meter is divided into a sensor flow channel in which a resistor is installed and a bypass flow channel with respect to the sensor flow channel. Then, based on the measurement principle using the resistor, the flow rate of the fluid to be measured flowing through the sensor flow path, and thus the flow rate of the fluid to be measured flowing inside the thermal flow meter is measured. Specifically, the heating resistor and the fluid temperature detection resistor are controlled by an electric circuit so as to have a certain temperature difference, and the measurement is performed based on the temperature difference between the upstream temperature detection resistor and the downstream temperature detection resistor. The fluid flow rate is measured. For this reason, the output increases in the case of forward flow, and the output decreases in the case of reverse flow. Therefore, the flow direction of the fluid to be measured can be detected.
[0010]
In addition, the bypass channel is a substrate on the surface of which an electrode for an electric circuit connected to an electric circuit for performing a measurement principle using a resistor is provided on a body in which a fluid channel having a side opening is formed. On the other hand, it is formed by closing the side opening through a laminated body in which a plurality of etched thin plates are stacked, so the structure of the laminated body (combination of each thin plate) is changed to bypass The cross-sectional area of the flow path can be changed. And if the cross-sectional area of a bypass flow path changes, the ratio (bypass ratio) of the to-be-measured fluid branched to a sensor flow path and a bypass flow path will change. Therefore, since an optimal measurement range can be set by changing the configuration of the stacked body, linear output characteristics can be obtained without providing a separate arithmetic circuit.
[0011]
When changing the bypass ratio, the laminate may be formed by laminating a mesh plate via a grooved both-end opening plate in which openings are formed at both ends of the thin plate and a groove is formed at the center. . Furthermore, you may include the both-ends opening board in which the opening part was formed in the both ends of a thin plate in a laminated body. As a result, the cross-sectional area of the bypass channel can be reduced, and the bypass ratio can be changed.
[0012]
And in the thermal type flow meter which concerns on this invention, it is preferable that the mesh board with which the mesh was formed in the both ends of a thin plate is contained in the laminated body. Moreover, in the thermal type flow meter according to the present invention, it is desirable that the laminated body is obtained by laminating a mesh plate through a spacer that leaves an edge of a thin plate and opens other portions.
[0013]
This is because by forming a laminate including a mesh plate on which a mesh is formed, a fluid to be measured having a very smooth flow can be poured into the sensor flow path. This is because the turbulence of the fluid to be measured is reduced by passing through the mesh. Therefore, it is preferable to include a plurality of mesh plates in the laminate. In this case, it is better to overlap the mesh plates with a predetermined interval than to directly overlap the mesh plates. This is because a larger rectifying effect can be obtained. For this reason, it is desirable to laminate the mesh plate via a spacer.
[0014]
Thus, in the thermal type meter according to the present invention, since the flow of the fluid to be measured flowing through the sensor flow path can be adjusted, a very stable output can be obtained. In addition, since no electrical filter is used, the responsiveness is not impaired.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a most preferred embodiment that embodies a thermal flow meter of the present invention will be described in detail with reference to the drawings. The thermal flow meter according to this embodiment is used for flow rate measurement that requires high-speed response, high sensitivity, linear output characteristics, and bidirectional detection, for example, confirmation of adsorption and release in handling during semiconductor chip mounting. Suitable for use.
[0016]
FIG. 1 shows a schematic configuration of the thermal type flow meter according to the present embodiment. FIG. 1 is a cross-sectional view showing a thermal flow meter 1. As shown in FIG. 1, the thermal flow meter 1 according to the present embodiment has a body 41, a sensor substrate 21, and a laminated body 50. The sensor substrate 21 is in close contact with the body 41 with screws through the seal packing 48 in a state where the laminated body 50 is mounted in the flow path space 44 of the body 41. Thereby, the main flow path M which is a bypass flow path with respect to the sensor flow path S and the sensor flow path S is formed.
[0017]
As shown in FIGS. 2 and 3, the body 41 has a rectangular parallelepiped shape and is configured symmetrically. FIG. 2 is a plan view showing the body 41. 3 is a cross-sectional view taken along line AA in FIG. The body 41 is formed with an inlet port 42 and an outlet port 46 on both end faces. An inlet channel 43 is formed from the inlet port 42 toward the center of the body. Similarly, an outlet channel 45 is formed from the outlet port 46 toward the center of the body. The inlet channel 43 and the outlet channel 45 are formed below the main channel M. That is, the inlet channel 43 and the outlet channel 45 are not arranged on the same straight line with respect to the main channel M.
[0018]
In addition, a channel space 44 for forming the main channel M and the sensor channel S is formed in the upper portion of the body 41. The cross section of the flow path space 44 has a shape in which both short sides of the rectangle are arcuate (semicircle), and an arcuate convex part 44C is formed at the center. The convex portion 44C is for positioning the laminated body 50 (each thin plate). A part of the lower surface of the channel space 44 communicates with the inlet channel 43 and the outlet channel 45. That is, the inlet channel 43 and the outlet channel 45 are communicated with the channel space 44 via elbow portions 43A and 45A bent at 90 degrees, respectively. Further, a groove 49 for mounting the seal packing 48 is formed on the upper surface of the body 41 along the outer periphery of the flow path space 44.
[0019]
As shown in FIG. 4, the laminate 50 is obtained by laminating two types of thin plates in total. FIG. 4 is an exploded perspective view showing the structure of the laminated body 50. In this laminated body 50, the mesh plate 51, the spacers 52, 52, 52, the mesh plate 51, the spacers 52, 52, the mesh plate 51, the spacers 52, 52, and the mesh plate 51 are laminated and bonded in order from the bottom. Is. Both the mesh plate 51 and the spacer 52 have a thickness of 0.5 mm or less, and each shape is processed (micromachining) by etching. The projected shape is the same as the cross-sectional shape of the flow path space 44. Thereby, the laminated body 50 is attached to the flow path space 44 without a gap.
[0020]
And by installing the laminated body 50 of such a combination in the flow path space 44, the full-scale flow rate of the thermal type flow meter 1 is 5 L / min. That is, by changing the shape (combination) of the thin plates constituting the laminated body 50, the cross-sectional area of the main flow path M is changed and the bypass ratio of the fluid to be measured is changed, so that an arbitrary flow rate range can be set. is there. An example of changing the full scale flow rate (full scale flow rate 1 L / min) will be described later.
[0021]
Here, individual thin plates will be described. First, the mesh plate 51 will be described with reference to FIGS. 5A is a plan view showing the mesh plate 51, and FIG. 5B is a cross-sectional view taken along line AA in FIG. 5A. FIG. 6 is an enlarged view of the mesh portion 51M of the mesh plate 51. FIG. As shown in FIG. 5, the mesh plate 51 is a thin plate having a thickness of 0.3 mm in which mesh portions 51M are formed at both ends thereof. The mesh part 51M has a circular shape with a diameter of 4 mm, and is formed such that the distance between the centers of the holes (diameter 0.2 mm) constituting the mesh is 0.27 mm as shown in FIG. That is, the holes are formed so that the centers of the holes are the vertices of the equilateral triangle. In addition, the thickness of the mesh part 51M is thinner than other parts as shown in FIG.5 (b), The thickness is 0.05-0.1 mm.
[0022]
Next, the spacer 52 will be described with reference to FIG. 7A is a plan view showing the spacer 52, and FIG. 7B is a cross-sectional view taken along line AA in FIG. 7A. As shown in FIG. 7, the spacer 52 is etched so as to leave the outer peripheral portion 52B. Thereby, an opening 61 is formed in the spacer 52. The spacer 52 has a thickness of 0.5 mm.
[0023]
Here, returning to FIG. 1, the above-described mesh plate 51 and the spacer 52 are combined, and the laminated body 50 laminated and bonded as shown in FIG. Is formed. More specifically, the main flow path M is formed by the opening 61 of the spacer 52. Further, the communication flow paths 5 and 6 are formed by the mesh portion 51M provided in the mesh plate 51 and the opening 61 provided in the spacer 52. The communication channel 5 communicates the inlet channel 43 with the main channel M and the sensor channel S, and the communication channel 6 communicates the outlet channel 45 with the main channel M and the sensor channel S. Is.
[0024]
Between the main flow path M and the sensor flow path S, three layers of mesh portions 51M are arranged. The interval between the mesh portions 51M is equal to the thickness of the two spacers 52 (1.0 mm). As a result, the fluid to be measured whose flow has been adjusted can be poured into the sensor flow path S. This is because each time the fluid to be measured passes through each mesh part 51M, the turbulence of the flow can be reduced. Furthermore, the mesh part 51M is also arranged at the communication part between the elbow parts 43A, 45A and the flow path space 44 (main flow path M).
[0025]
On the other hand, the sensor substrate 21 outputs the measured flow rate as an electrical signal. For this reason, as shown in FIG. 8, the sensor substrate 21 has a groove 23 formed in the center thereof on the surface side (the mounting surface side to the body 41) of the printed circuit board 22 as a base. Electric circuit electrodes 24, 25, 26, 27, 28, and 29 are provided on both sides of the groove 23. On the other hand, an electrical circuit composed of electrical elements 31, 32, 33, 34, and the like is provided on the back side of the printed circuit board 22 (see FIG. 1). In the printed circuit board 22, the electric circuit electrodes 24 to 29 are connected to an electric circuit including the electric elements 31 to 34. Further, the measurement chip 11 is mounted on the surface side of the printed circuit board 22 as described later.
[0026]
Here, the measurement chip 11 will be described with reference to FIG. FIG. 9 is a plan view showing the measurement chip 11. As shown in FIG. 9, the measurement chip 11 is obtained by performing a semiconductor micromachining processing technique on the silicon chip 12. At this time, a groove 13 is processed at the center of the chip and a resistor (heat wire) is used. ) Electrodes 14, 15, 16, 17, 18, 19 are provided at both ends of the chip.
[0027]
At this time, the upstream temperature detection resistor R <b> 1 extends from the resistor electrodes 15 and 17 and is laid over the groove 13. Further, a downstream temperature detection resistor R2 extends from the resistor electrodes 17 and 19 and is laid over the groove 13. Furthermore, the heating resistor Rh extends from the resistor electrodes 16 and 18 and is laid over the groove 13 between the upstream temperature detection resistor R1 and the downstream temperature detection resistor R2. In the measurement chip 11, a fluid temperature detection resistor Rt extends from the resistor electrodes 14 and 16 on the upstream side in the forward direction of the sensor flow path S.
[0028]
Then, the electrodes 14, 15, 16, 17, 18, 19 for the hot wire of the measuring chip 11 are respectively connected to the electrodes 24, 25, 26, 27, 28, 29 (see FIG. 8) The measurement chip 11 is mounted on the sensor substrate 21 by bonding with solder reflow or a conductive adhesive. Therefore, when the measurement chip 11 is mounted on the sensor substrate 21, the fluid temperature detection resistor Rt, the upstream temperature detection resistor R1, the downstream temperature detection resistor R2, and the heating resistor Rh provided on the measurement chip 11 are: It is connected to an electric circuit provided on the back side of the sensor substrate 21 via the resistor electrodes 14 to 19 of the measurement chip 11 and the electric circuit electrodes 24 to 29 (see FIG. 8) of the sensor substrate 21. It will be. Thus, the constant temperature difference circuit shown in FIG. 10 and the output circuit shown in FIG. 11 are configured.
[0029]
Here, the constant temperature difference circuit shown in FIG. 10 is a circuit for controlling the heating resistor Rh so as to have a certain temperature difference from the fluid temperature detected by the fluid temperature detection resistor Rt. The output circuit shown in FIG. 10 is a circuit for outputting a voltage value corresponding to the temperature difference between the upstream temperature detection resistor R1 and the downstream temperature detection resistor R2. In this output circuit, the upstream temperature detection resistor R1 and the downstream temperature detection resistor R2 are connected in series, and a constant voltage Vc is applied. The midpoint potential Vout between the upstream temperature detection resistor R1 and the downstream temperature detection resistor R2 is output as a measurement signal.
[0030]
When the measurement chip 11 is mounted on the sensor substrate 21, the groove 13 of the measurement chip 11 overlaps with the groove 23 of the sensor substrate 21. Therefore, as shown in FIG. 1, when the sensor substrate 21 on which the measurement chip 11 is mounted is brought into close contact with the body 41 via the laminate 50 and the seal packing 48, the sensor 41 is detected in the flow path space 44 of the body 41. Between the substrate 21 and the measurement chip 11, an elongated sensor flow path S including the groove 13 of the measurement chip 11 and the groove 23 of the sensor substrate 21 is formed. Therefore, in the sensor flow path S, the fluid temperature detection resistor Rt, the upstream temperature detection resistor R1, the downstream temperature detection resistor R2, and the heating resistor Rh are provided so as to cross the bridge.
[0031]
Next, a case where the full scale flow rate is 1 L / min will be described. Accordingly, FIG. 12 shows a schematic configuration of a thermal flow meter having a full scale flow rate of 1 L / min. FIG. 12 is a cross-sectional view showing the thermal flow meter 1A. As shown in FIG. 12, the thermal flow meter 1 </ b> A has substantially the same configuration as the thermal flow meter 1, but a laminated body 50 </ b> A is attached to the flow path space 44 instead of the laminated body 50. The point is different. That is, in the thermal flow meter 1A, a laminated body 50A for reducing the cross-sectional area of the main flow path M is mounted in the flow path space 44. For this reason, it demonstrates centering on a different point from the thermal type flow meter 1, and about the thing of the structure similar to the thermal type flow meter 1, the same code | symbol is attached | subjected and the description is abbreviate | omitted.
[0032]
Therefore, the stacked body 50A will be described with reference to FIG. FIG. 13 is an exploded perspective view showing the structure of the laminated body 50A. As shown in FIG. 13, the laminated body 50 </ b> A is obtained by laminating a total of 11 types of thin plates. That is, in order from the bottom, mesh plate 51, both-end opening plate 53, grooved both-end opening plate 56, mesh plate 51, grooved both-end opening plates 56, 56, mesh plate 51, grooved both-end opening plates 56, 56, 56, And the mesh board 51 is laminated | stacked and adhere | attached. That is, the laminated body 50 </ b> A uses a both-end opening plate 53 and a grooved both-end opening plate 56 instead of the spacer 52 in the laminated body 50.
[0033]
Here, the both-end opening plate 53 will be described with reference to FIG. 14A is a plan view showing the both-end opening plate 53, and FIG. 14B is a cross-sectional view taken along line AA in FIG. 14A. As shown in FIG. 14, the both-end opening plate 53 is etched so as to leave the outer peripheral portion 53B and the central portion 53D. Thereby, the opening part 63 is formed in the both ends in the opening plate 53 at both ends. In addition, the thickness of the both-end opening plate 53 is 0.5 mm.
[0034]
The grooved both-end opening plate 56 will be described with reference to FIG. 15A is a plan view showing the grooved both-end opening plate 56, FIG. 15B is a cross-sectional view taken along line AA in FIG. 15A, and FIG. 15C is FIG. It is BB sectional drawing in a). As shown in FIG. 15, the grooved both-end opening plate 56 is etched so as to leave the outer peripheral portion 56B and the central portion 56D and to form the groove 56E in the central portion 56D. That is, the grooved both-end opening plate 56 is obtained by providing the groove 56E in the central portion 53D (see FIG. 14) of the both-end opening plate 53. The central portion 56D has three grooves 56E formed on one side. The depth of the groove 56E is 0.35 mm, and the width of the groove 55E is 1.1 mm. The interval between adjacent grooves is 0.2 mm. In addition, the thickness of the grooved both-end opening plate 56 is 0.5 mm.
[0035]
By attaching the laminated body 50A in which the mesh plate 51, the both-end opening plate 53, and the grooved both-end opening plate 56 are laminated and bonded as shown in FIG. 13 to the flow path space 44 formed in the body 41, As shown in FIG. 12, the cross-sectional area of the main flow path M is reduced by the central portion 53D of the both-end opening plate 53 and the central portion 56D of the grooved both-end opening plate 56. Thereby, the bypass ratio of the fluid to be measured is changed so that the full-scale flow rate is 1 L / min. Thus, an arbitrary flow rate range can be set by changing the configuration of the laminate.
[0036]
Next, the operation of the thermal flow meter 1, 1A having the above-described configuration will be described. In the thermal flow meter 1, 1 </ b> A, in the case of a forward flow, the fluid to be measured that flows into the inlet channel 43 via the inlet port 42 flows into the main channel M in the channel space 44. And the flow into the sensor flow path S. Then, the fluids to be measured that have flowed out of the main flow path M and the sensor flow path S merge and flow out of the body 41 from the outlet port 46 via the outlet flow path 45.
[0037]
On the other hand, in the case of a reverse flow, the fluid to be measured that has flowed into the outlet channel 45 via the outlet port 46 flows into the main channel M and the sensor channel S in the channel space 44. Divided into things. Then, the fluids to be measured that have flowed out of the main flow path M and the sensor flow path S merge and flow out of the body 41 from the inlet port 42 via the inlet flow path 43.
[0038]
Here, even if the fluid to be measured flows in either the forward direction or the reverse direction, the fluid to be measured flowing into the sensor flow path S passes through the three layers of mesh portions 51M in the stacked body 50 or 50A. It flows into the sensor flow path S. Therefore, the fluid to be measured in a state where the flow is very arranged flows through the sensor flow path S.
[0039]
Then, the fluid to be measured flowing through the sensor flow path S removes heat from the heating resistor Rh bridged in the sensor flow path S. Then, the fluid temperature detection resistor Rt and the heating resistor Rh are controlled to have a constant temperature difference by an electric circuit (constant temperature difference circuit shown in FIG. 10) provided on the back side of the sensor substrate 21. .
[0040]
In addition, an upstream temperature detection resistor R1 and a downstream temperature detection resistor R2 connected in series and applied with a constant voltage Vc by an electric circuit (an output circuit shown in FIG. 11) provided on the back side of the sensor substrate 21. The midpoint potential Vout is output as a measurement signal. At this time, when the fluid to be measured is a forward flow, the temperature (resistance value) of the upstream temperature detection resistor R1 decreases and the temperature (resistance value) of the downstream temperature detection resistor R2 increases. The point potential Vout increases. On the other hand, when the fluid to be measured flows in the reverse direction, the temperature (resistance value) of the upstream temperature detection resistor R1 increases and the temperature (resistance value) of the downstream temperature detection resistor R2 decreases. The potential Vout decreases. For this reason, the flow direction of the fluid to be measured can be detected.
[0041]
An example of the output at this time is shown in FIGS. 16 and 17 show the relationship between the flow rate and the output voltage. The graph of FIG. 16 shows the output from the thermal flow meter 1. The graph in FIG. 17 shows the output from the thermal flow meter 1A.
[0042]
As is apparent from FIGS. 16 and 17, when the fluid to be measured flows in the forward direction, the output increases as the flow rate increases. Conversely, when the fluid to be measured flows in the opposite direction, the output decreases as the flow rate increases. Thereby, according to the thermal flowmeters 1 and 1A, the flow direction of the fluid to be measured can be detected.
[0043]
In addition, both the output characteristics of the thermal flowmeters 1 and 1A are greatly improved in linearity as compared with the output characteristics (FIG. 24) of the conventional thermal flowmeter (described in JP-A-2002-5717). You can see that That is, according to the thermal flow meters 1 and 1A, linear output characteristics can be obtained. This is because the main flow path M is constituted by the laminated bodies 50 and 50A, and the optimum bypass ratio is set for each measurement range. Thus, according to the thermal flowmeters 1 and 1A, the flow rate of the fluid to be measured can be accurately measured in both directions. Thereby, clogging management of the nozzle can be performed with high accuracy.
[0044]
Further, another output example of the thermal flow meter 1 is shown in FIG. FIG. 18 shows the relationship between time and output voltage. As is clear from FIG. 18, the output of the thermal flow meter 1 is less stable and less stable than the output (FIG. 25) of a conventional thermal flow meter (described in JP-A-2002-5717). I understand that. That is, according to the thermal flow meter 1, a very stable output with a small output amplitude width can be obtained. And since the electrical filter is not used, responsiveness is not impaired.
[0045]
Here, if the ratio of the vibration width to the output value is defined as noise, the noise in the conventional thermal type flow meter is “± 39.5 (% FS)”, whereas the noise is related to the first embodiment. The noise in the thermal flow meter 1 is “± 0.7 (% FS)”. That is, according to the thermal flow meter 1A, the noise can be reduced to about 1/50. This is because the flow of the fluid to be measured flowing through the sensor flow path S is very well-prepared as described above.
[0046]
Thus, according to the thermal flow meter 1, since a stable output can be obtained, the adsorption confirmation threshold can be set high. Thereby, adsorption confirmation can be performed with high accuracy. Further, even when a collet type nozzle is used, suction confirmation can be performed.
[0047]
Although the thermal flow meter 1 has been described here, it is needless to say that the same result was obtained with the thermal flow meter 1A having a smaller full-scale flow rate than the thermal flow meter 1. This is because the output fluctuation becomes smaller as the measured flow rate becomes smaller.
[0048]
Another output example of the thermal flow meter 1A is shown in FIG. FIG. 19 shows the output when the pressure is changed. As is apparent from FIG. 19, the thermal flow meter 1A has better pressure characteristics than the conventional thermal flow meter (described in Japanese Patent Application No. 2000-368801). That is, according to the thermal flow meter 1A, even if the pressure changes, the output does not drift, and an accurate flow rate can always be measured. Similar results were obtained with the thermal flow meter 1.
[0049]
The reason why the pressure characteristics are improved is as follows. That is, in the conventional method (Japanese Patent Application No. 2000-368801), since the heat transfer itself between the heating resistor Rh and the fluid is output, the output changes when the pressure change, that is, the gas density changes. However, in the thermal flow meter 1A, when the pressure changes, the heat transfer between the heating resistor Rh and the fluid changes, but the upstream temperature detection resistor R1 and the downstream temperature detection resistor R2 have the same resistance value. Therefore, the intermediate potential Vout between the upstream temperature detection resistor R1 and the downstream temperature detection resistor R2 does not change. Therefore, even if the pressure changes, the output is not affected.
[0050]
As described above, the thermal flow meters 1 and 1A can measure the flow rate in both directions, and the measurement output is very stable without impairing the response (about 20 msec). For this reason, when the thermal flow meter 1, 1A is used for confirmation of vacuum adsorption and release in handling during semiconductor chip mounting, the adsorption and release can be accurately determined. This is because the flow rate in the orifice during adsorption and non-adsorption can be measured accurately and stably instantaneously. Therefore, by using the thermal flow meter 1, 1A for confirmation of adsorption and release, it is possible to accurately confirm the adsorption without erroneously determining that it is not adsorbed even though it is actually adsorbed. You can also check the release. Thereby, in recent years, a handling operation at the time of mounting of a semiconductor chip (for example, 0.5 mm square) whose size has been reduced can be performed very efficiently.
[0051]
As described above in detail, according to the thermal flow meter 1, 1 </ b> A according to the present embodiment, the laminated body 50, 50 </ b> A is attached to the flow path space 44 formed in the body 41, and the main flow path M is changed. By configuring, an optimum bypass ratio of the fluid to be measured can be set, and thus linear output characteristics can be obtained. Further, the stacked bodies 50 and 50 </ b> A are provided with a three-layer mesh portion 51 </ b> M disposed between the main channel M and the sensor channel S. Thereby, the flow of the fluid to be measured flowing into the sensor flow path S is adjusted. Therefore, a very stable output can be obtained. Further, the measurement chip 11 is provided with an upstream temperature detection resistor R1, a downstream temperature detection resistor R2, a heating resistor Rt, and a fluid temperature detection resistor Rt, and the heating circuit Rh and the fluid temperature detection resistor Rt are provided by an electric circuit. And a constant temperature difference, and the flow rate of the fluid to be measured is measured based on the temperature difference between the upstream temperature detection resistor R1 and the downstream temperature detection resistor R2. Thereby, bidirectional flow rate detection can be performed.
[0052]
It should be noted that the above-described embodiment is merely an example and does not limit the present invention in any way, and various improvements and modifications can be made without departing from the scope of the invention. For example, in the above-described embodiment, two types of laminates are illustrated, but the present invention is not limited to this, and the laminates can be configured by arbitrarily combining the thin plates 51, 52, 53, and 56.
[0053]
【The invention's effect】
As described above, according to the thermal type flow meter of the present invention, in the thermal type flow meter provided with a bypass channel for the sensor channel in addition to the sensor channel in which a resistor for measuring the flow rate is installed. The substrate on which the electrode for the electric circuit for connecting the bypass channel to the electric circuit for performing the measurement principle using the resistor is provided on the surface is attached to the body in which the fluid channel having the side opening is formed. And forming a sensor flow path through a laminated body in which a plurality of etched thin plates are laminated so as to close the side opening, and a sensor flow path, and a resistor electrode connected to the resistor. Is formed by a groove provided on at least one of the measurement chip or the substrate by bonding the resistor electrode and the electric circuit electrode and mounting the electrode on the measurement chip. Upstream temperature detection resistor provided upstream in the direction of the flow, downstream temperature detection resistor provided downstream in the flow direction, and between the upstream temperature detection resistor and the downstream temperature detection resistor, the upstream temperature A heating resistor that heats the detection resistor and the downstream temperature detection resistor, and a fluid temperature detection resistor that detects the temperature of the fluid to be measured are provided. Is controlled to have a constant temperature difference, and the fluid flow rate is measured based on the temperature difference between the upstream temperature detection resistor and the downstream temperature detection resistor. Can be made linear, and a stable output can be obtained without impairing responsiveness.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of a thermal flow meter (full scale flow rate 5 L / min) according to an embodiment.
FIG. 2 is a plan view of the body.
3 is a cross-sectional view taken along the line AA in FIG.
4 is an exploded perspective view of the laminated body shown in FIG. 1. FIG.
5A and 5B are diagrams showing a mesh plate, where FIG. 5A is a plan view and FIG. 5B is a cross-sectional view taken along line AA.
6 is an enlarged view of the mesh portion of FIG. 5. FIG.
7A and 7B are views showing a spacer, in which FIG. 7A is a plan view and FIG. 7B is a cross-sectional view taken along line AA.
FIG. 8 is a perspective view of a sensor substrate.
FIG. 9 is a plan view of a measurement chip.
FIG. 10 is a circuit diagram of a constant temperature difference circuit.
FIG. 11 is a circuit diagram of an output circuit.
FIG. 12 is a schematic configuration diagram of a thermal flow meter (full scale flow rate 1 L / min) according to another embodiment.
13 is an exploded perspective view of the laminate shown in FIG. 12. FIG.
14A and 14B are diagrams showing both-end opening plates, in which FIG. 14A is a plan view and FIG.
15A and 15B are views showing a grooved both-end opening plate, in which FIG. 15A is a plan view, FIG. 15B is a cross-sectional view along AA, and FIG. 15C is a cross-sectional view along BB.
FIG. 16 is a diagram showing output characteristics of the thermal type flow meter according to the embodiment.
FIG. 17 is a diagram showing output characteristics of a thermal flow meter according to another embodiment.
FIG. 18 is a diagram showing output characteristics with respect to time of the thermal type flow meter according to the embodiment.
FIG. 19 is a diagram for explaining pressure characteristics of a thermal flow meter according to another embodiment.
FIG. 20 is a diagram illustrating a pressure change between non-adsorption and adsorption when a small-diameter nozzle is used.
FIG. 21 is a diagram showing a flow rate change between non-adsorption and adsorption when a small-diameter nozzle is used.
FIG. 22 is a diagram for explaining pressure characteristics of a conventional thermal type flow meter that cannot perform bidirectional detection.
FIG. 23 is a diagram showing output characteristics of a conventional thermal flow meter that cannot perform bidirectional detection.
FIG. 24 is a diagram showing output characteristics of a conventional thermal type flow meter capable of bidirectional detection.
FIG. 25 is a diagram showing output characteristics with respect to time of a conventional thermal flow meter capable of bidirectional detection.
[Explanation of symbols]
1,1A thermal flow meter
11 Measuring chip
13 Measuring tip groove
14, 15, 16, 17, 18, 19 Resistor electrodes
21 Sensor board
23 Groove of sensor board
24, 25, 26, 27, 28, 29 Electric circuit electrodes
31, 32, 33, 34 Electrical elements
41 body
44 Channel space
50, 50A laminate
51 mesh board
51M mesh section
52 Spacer
53 Opening plate on both ends
56 Opening plate with grooves on both ends
56E Groove
M Main channel (Bypass channel)
R1 upstream temperature sensing resistor
R2 downstream temperature sensing resistor
Rh heating resistor
Rt Fluid temperature sensing resistor
S Sensor flow path

Claims (5)

In addition to the sensor flow path in which a resistor for measuring the flow rate is installed, a thermal flow meter including a bypass flow path for the sensor flow path,
A symmetrical body,
A bilaterally symmetric laminate that rectifies and rectifies the fluid into the sensor flow path and the bypass flow path by attaching to the body,
An upstream temperature detection resistor provided upstream in the flow direction of the sensor flow path;
A downstream temperature detection resistor provided on the downstream side in the flow direction of the sensor flow path;
A heating resistor provided between the upstream temperature detection resistor and the downstream temperature detection resistor, for heating the upstream temperature detection resistor and the downstream temperature detection resistor;
A fluid temperature detection resistor for detecting the temperature of the fluid to be measured;
The flow rate of the fluid to be measured is measured based on the temperature difference between the upstream temperature detection resistor and the downstream temperature detection resistor by controlling the heating resistor and the fluid temperature detection resistor to have a constant temperature difference. An electrical circuit for
A thermal flow meter characterized by comprising: In the thermal type flow meter according to claim 1,
The thermal flow meter, wherein the laminate includes a mesh plate in which meshes are formed at both ends of a thin plate. In the thermal type flow meter according to claim 2,
The laminated body is a thermal flow meter in which the mesh plate is laminated through a spacer that opens the other part while leaving the edge of the thin plate. In the thermal type flow meter according to claim 2,
The laminated body is obtained by laminating the mesh plate through a grooved both-end opening plate in which openings are formed at both ends of the thin plate and a groove is formed in the center. Total. In the thermal type flow meter according to claim 4,
The laminated body includes a both-end opening plate in which openings are formed at both ends of the thin plate.

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