JP2015068812A - Flow sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a flow sensor having a structure where a fluid hardly flows into a gap between a sensor support body and a sensor chip.SOLUTION: A flow sensor 10 includes: a sensor support body 20 having one surface 25; and a groove part 26 in which a part of the one surface 25 is recessed. A bottom surface 27 of the groove part 26 is located on the downstream side of a fluid flow and has a parallel surface 27a parallel to the one surface 25. The bottom surface 27 of the groove part 26 is located on the upper stream side of the fluid flow than the parallel surface 27a and connected to the parallel surface 27a, and has an inclined surface 27b inclined so that the upstream side of the fluid flow is located in a depth direction of the groove part 26 deeper than the parallel surface 27a side. A sensor chip 40 is fixed to the inclined surface 27b in a state in which a connection position 27c between the parallel surface 27a and the inclined surface 27b and a part of the downstream side of the fluid flow are aligned.

Description

  The present invention relates to a flow sensor for detecting a flow rate of a fluid.

  Conventionally, a configuration of a flow sensor in which a sensor chip is fixed to a sensor support is described in Patent Document 1, for example. Specifically, Patent Document 1 proposes a structure in which a groove is provided on the sensor support and a sensor chip is fixed to the bottom of the groove via an adhesive.

JP 2001-12986 A

  However, in the above conventional technique, in order to install the sensor chip in the groove portion so that the groove portion of the sensor support and the sensor chip do not come into contact with each other, the groove portion must be formed large in advance. For this reason, a gap is generated between the side surface of the sensor chip and the groove portion or between the back surface of the sensor chip and the bottom surface of the groove portion. When the fluid flows into the gap, a fluid vortex is generated on the back surface of the sensor chip, which causes a problem of characteristic inflection of the sensor chip.

  An object of this invention is to provide the flow sensor provided with the structure where a fluid becomes difficult to flow into the clearance gap between a sensor support body and a sensor chip in view of the said point.

  In order to achieve the above object, the invention according to claim 1 includes a sensor support (20) having one surface (25) and a groove (26) in which a portion of the one surface (25) is recessed. Yes.

  Moreover, it is plate shape which has the surface (41) and the back surface (42) on the opposite side of the said surface (41), and has the sensing part (45) formed in the surface (41) side, and back surface (42) ) Side is fixed to the bottom surface (27) of the groove portion (26), and a sensor chip (40) for detecting the flow rate of the fluid flowing above the sensing portion (45) is provided.

  The sensor support (20) has a groove portion so that a gap (70) between the fluid flow upstream side of the groove portion (26) and the fluid flow upstream side of the sensor chip (40) is within the reference range. (26) It has the reference | standard part (27c, 29a) for aligning a sensor chip (40) with respect to (26), It is characterized by the above-mentioned.

  According to this, since the sensor chip (40) is fixed to the groove part (26) according to the reference parts (27c, 29a), the gap (70) between the sensor support (20) and the sensor chip (40) is accurate. Well managed. For this reason, it is possible to make it difficult for fluid to flow into the gap (70) between the sensor support (20) and the sensor chip (40). Therefore, the occurrence of characteristic inflection of the sensor chip (40) due to the fluid vortex can be prevented.

  In addition, the code | symbol in the bracket | parenthesis of each means described in this column and the claim shows the correspondence with the specific means as described in embodiment mentioned later.

It is a top view of the flow sensor concerning a 1st embodiment of the present invention. It is II-II sectional drawing of FIG. FIG. 3 is a sectional view taken along line III-III in FIG. 1. It is a partial cross section figure of the periphery of a sensor chip concerning a 2nd embodiment of the present invention. It is a partial top view of the periphery of the sensor chip which concerns on 3rd Embodiment of this invention. It is VI-VI sectional drawing of FIG. It is VII-VII sectional drawing of FIG. It is a partial cross section figure of the circumference of a sensor chip concerning a 4th embodiment of the present invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following embodiments, the same or equivalent parts are denoted by the same reference numerals in the drawings.

(First embodiment)
The first embodiment of the present invention will be described below. As shown in FIG. 1, the flow sensor 10 is configured to detect the flow rate of a fluid such as a gas, and includes a sensor support 20, a lead frame 30, a sensor chip 40, and a sealing material 50. Configured.

  The sensor support 20 is a base of the flow sensor 10 and includes a circuit unit 21, a relay unit 22, and a sensor unit 23. The sensor support 20 is formed by molding, for example, PPS (polyphenylene sulfide) or epoxy resin.

  The circuit portion 21 is a portion where a part of the lead frame 30 and a circuit board (not shown) are sealed. The circuit board is mounted on an island portion (not shown) of the lead frame 30. The circuit board is formed with a control circuit having a function of outputting a drive signal to the sensor chip 40, a function of inputting a flow rate signal from the sensor chip 40, calculating and amplifying it, and outputting the signal to the outside. Is. Such a circuit board is, for example, a semiconductor chip in which a CMOS transistor or the like is formed by a semiconductor process on a silicon substrate or the like. The circuit unit 21 is connected to the relay unit 22.

  The relay part 22 is a part in which a part of the lead frame 30 is sealed and a part of the sensor chip 40 is disposed. In addition, the relay unit 22 includes a wall 24 that extends in the connection direction in a direction perpendicular to the connection direction between the circuit unit 21 and the relay unit 22. That is, the relay part 22 has two wall parts 24. The two wall portions 24 are portions for preventing the sealing material 50 from flowing out from the relay portion 22.

  The sensor part 23 is a part where the sensor chip 40 is disposed, and is a part protruding from the relay part 22. As shown in FIG. 2, the sensor portion 23 has a surface 25 and a groove portion 26 in which a portion of the surface 25 is recessed. In FIG. 2, the sensor chip 40 is omitted.

  The lead frame 30 is a metal terminal component for electrically connecting the flow sensor 10 and the outside. The lead frame 30 is partially exposed from the circuit portion 21 and electrically connected to the outside, an island portion on which the circuit board is mounted and sealed by the circuit portion 21, and the relay portion 22. And a relay portion sealed in the middle.

  The lead part of the lead frame 30 and the circuit board, the circuit board and the relay part of the lead frame 30, and the relay part of the lead frame 30 and the sensor chip 40 are connected by bonding wires (not shown), respectively. ing.

  As shown in FIG. 3, the sensor chip 40 is a plate-like semiconductor chip having a front surface 41 and a back surface 42 opposite to the front surface 41, and a side surface 43 adjacent to the front surface 41 and the back surface 42. In addition, the sensor chip 40 has a membrane 44 that is thinned because a part of the back surface 42 is recessed toward the front surface 41 side.

  On the membrane 44, a heater resistor (not shown) or a resistor (temperature measuring resistor) different from the heater resistor is formed. The resistance temperature detector includes a resistance for monitoring the heat generation temperature of the heater and a resistance for detecting the temperature upstream and downstream of the heater resistance. The heat generation temperature of the heater resistor is controlled to be a constant heat generation temperature by the monitor resistance. Further, a bridge circuit is configured by temperature measuring resistors respectively arranged upstream and downstream of the heater resistance, and the output of the bridge circuit changes due to the temperature difference between the upstream and downstream of the heater resistance, and the flow rate of the fluid flowing above the membrane 44 Is to be detected. In the sensor chip 40, the part where the bridge circuit is formed corresponds to the sensing unit 45 that detects the flow rate of the fluid. The sensor chip 40 detects the flow rate of the fluid flowing above the sensing unit 45 by the sensing unit 45 and outputs a flow rate signal corresponding to the detected flow rate.

  The sensor chip 40 is disposed on the bottom surface 27 of the groove portion 26 so that the back surface 42 is directed to the groove portion 26 side of the sensor portion 23 and the sensing portion 45 is exposed to the opening side of the groove portion 26. The sensor chip 40 is fixed to the bottom surface 27 of the groove 26 by an adhesive 60.

  The sealing material 50 is a bonding wire that connects the relay portion of the lead frame 30 and the sensor chip 40 and a resin member that protects the bonding portion. The sealing material 50 seals a part of the sensor chip 40, a relay portion of the lead frame 30, a bonding wire, and the like so that the membrane 44 of the sensor chip 40 is exposed.

  As shown in FIG. 1, the sealing material 50 is blocked by a dam portion 51 provided on the surface 41 of the sensor chip 40 so as not to flow out from the relay portion 22 to the sensing portion 45 side. As the sealing material 50, for example, an epoxy resin is employed. The above is the overall configuration of the flow sensor 10.

  Next, a specific installation structure of the sensor chip 40 with respect to the sensor unit 23 of the sensor support 20 will be described. As shown in FIG. 3, the bottom surface 27 of the groove 26 has a parallel surface 27a and an inclined surface 27b.

  The parallel surface 27 a is a surface that is located on the downstream side of the fluid flow and is parallel to the one surface 25 of the sensor unit 23. On the other hand, the inclined surface 27b is located on the upstream side of the fluid flow with respect to the parallel surface 27a and is connected to the parallel surface 27a. Further, the inclined surface 27b is inclined so that the upstream side of the fluid flow is located in the depth direction of the groove portion 26 relative to the parallel surface 27a side. An acute angle portion that is a joint between the parallel surface 27a and the inclined surface 27b is a connection position 27c between the parallel surface 27a and the inclined surface 27b. That is, the connection position 27c is a straight mount reference acute angle portion.

  The sensor chip 40 is fixed to the inclined surface 27b in a state where a part of the fluid flow downstream side and the connection position 27c are aligned. In the present embodiment, a corner 46 constituted by the back surface 42 of the sensor chip 40 and the side surface 43 on the downstream side of the fluid flow is fixed to the inclined surface 27b so as to follow the connection position 27c. That is, the connection position 27c is the position of the sensor chip 40 with respect to the groove 26 so that the gap 70 between the fluid flow upstream of the groove 26 and the fluid flow upstream of the sensor chip 40 is within the reference range. It functions as a reference part for matching.

  The sensor chip 40 is fixed to the inclined surface 27b so that the entire sensor chip 40 is located within the range from the inclined surface 27b to the one surface 25 in the direction perpendicular to the one surface 25 of the sensor support 20. Therefore, the depth of the groove 26 is set in advance so that the sensor chip 40 does not protrude from the one surface 25 even if the sensor chip 40 is inclined at the inclination angle of the inclined surface 27b.

  In the present embodiment, the sensor chip 40 is placed on the inclined surface 27b of the groove portion 26 so that the connection corner between the surface 41 of the sensor chip 40 and the side surface 43 on the downstream side of the fluid flow is located at the same position as the one surface 25 of the sensor portion 23. Has been placed. Thereby, it is possible to prevent foreign substances included in the fluid flowing along the one surface 25 of the sensor unit 23 from adhering to the sensing unit 45 of the sensor chip 40 and accumulating.

  In addition, what is necessary is just to perform the mounting of the sensor chip 40 with respect to the groove part 26 of the sensor part 23 as follows. First, the sensor support 20 and the sensor chip 40 in which the lead frame 30 and the like are sealed are prepared. And the connection position 27c of the groove part 26 of the sensor part 23 and the corner | angular part 46 of the sensor chip 40 are recognized by camera imaging | photography, for example. Subsequently, the sensor chip 40 is attached to the inclined surface 27b with the adhesive 60 so that the corner portion 46 follows the connection position 27c and the gap 70 on the upstream side of the fluid flow between the groove portion 26 and the sensor chip 40 is within the reference range. Secure with.

  For example, alignment can be easily performed by causing the connection position 27 c and the corner 46 of the sensor chip 40 to coincide with each other in a direction perpendicular to the one surface 25 of the sensor unit 23. On the other hand, the corner portion 46 of the sensor chip 40 is aligned with the connection position 27c, and the corner portion 46 of the sensor chip 40 is positioned on the upstream side of the fluid flow, so that the thickness of the adhesive 60 can be recognized and the thickness check can be performed. It can be performed. In this way, the sensor chip 40 can be fixed to the groove portion 26.

  Next, a method for detecting the fluid flow rate will be described. The flow sensor 10 is fixed to a housing (not shown) configured to allow fluid to pass above the membrane 44. The flow sensor 10 heats the circuit board by energizing the heater resistor of the sensor chip 40 in accordance with an external command. Then, since the midpoint potential difference of the bridge circuit changes according to the flow rate, the midpoint potential difference (flow rate signal) is signal-processed by the circuit board and output to the outside. The external device that has acquired the flow signal can acquire fluid flow data based on the flow signal.

  Next, the effect of the structure of the flow sensor 10 will be described. The present embodiment is characterized in that, when the sensor chip 40 is installed in the groove portion 26 of the sensor unit 23, a connection position 27c is provided as a mark for installation. That is, since the sensor chip 40 is aligned with the connection position 27c and fixed to the groove 26, the gap 70 on the upstream side of the fluid flow between the groove 26 and the sensor chip 40 is managed with high accuracy.

  Thereby, since the tolerance factor at the time of mounting of the sensor chip 40 with respect to the groove part 26 becomes small, the sensor chip 40 can be arrange | positioned with respect to the groove part 26 in the predetermined position in the fluid flow upstream. Therefore, the gap 70 between the fluid flow upstream side of the groove 26 and the fluid flow upstream side of the sensor chip 40 can be reduced. In addition, since it is difficult for the fluid to flow into the gap 70 between the groove portion 26 and the sensor chip 40, it is possible to prevent the occurrence of characteristic inflection of the sensing portion 45 of the sensor chip 40 due to the fluid vortex.

  As for the correspondence between the description of the present embodiment and the description of the claims, the connection position 27c corresponds to the “reference portion” of the claims.

(Second Embodiment)
In the present embodiment, parts different from the first embodiment will be described. As shown in FIG. 4, in the present embodiment, the sensor chip 40 is inclined so that a part on the surface 41 side of the sensor chip 40 protrudes from the one surface 25 in a direction perpendicular to the one surface 25 of the sensor unit 23. 27b is fixed. That is, the fluid flow downstream side of the sensor chip 40 protrudes from the groove 26. FIG. 4 is a view corresponding to the III-III cross section of FIG.

  According to this, since the portion of the sensor chip 40 that protrudes from the one surface 25 of the sensor support 20 functions as a wall, it is possible to prevent foreign matter from adhering to and accumulating on the sensing unit 45 when the fluid flows backward. it can. In particular, when the flow sensor 10 is applied to an EGR system that returns the exhaust gas again into the intake manifold in order to purify the exhaust gas, foreign matter contained in the exhaust gas can be prevented from adhering to the sensing unit 45.

(Third embodiment)
In the present embodiment, parts different from the first and second embodiments will be described. As shown in FIG. 5, the groove portion 26 has two stages in the width in the connecting direction between the sensor portion 23 and the relay portion 22, that is, in the extending direction of the sensor portion 23. Specifically, the groove portion 26 has a protruding portion 29 that protrudes from a wall surface 28 that connects the bottom surface 27 and the one surface 25 of the sensor portion 23. As for the protrusion part 29, a part of surface of the fluid flow upstream among the wall surfaces 28 of the groove part 26 protrudes to the fluid flow downstream.

  Further, as shown in FIG. 6, the bottom surface 27 of the groove portion 26 is a surface parallel to the one surface 25 of the sensor portion 23. The sensor chip 40 is fixed to the groove portion 26 so that the side surface 43 of the sensor chip 40 on the upstream side of the fluid flow contacts the tip end portion 29 a of the protrusion portion 29 on the most downstream side of the fluid flow. Accordingly, as shown in FIG. 7, on the membrane 44 side of the sensor chip 40, the gap 70 between the fluid flow upstream side of the groove 26 and the fluid flow upstream side of the sensor chip 40 is within the reference range. Thus, the sensor chip 40 is fixed to the groove portion 26. That is, the tip end portion 29 a of the protruding portion 29 functions as a reference portion for aligning the sensor chip 40 with respect to the groove portion 26.

  As described above, the means for aligning the sensor chip 40 in the groove 26 can be the protrusion 29 provided on the wall surface 28 of the groove 26. The protrusion 29 can be formed by a mold for molding the sensor support 20. That is, the gap 70 between the groove 26 and the sensor chip 40 can be controlled only by the protruding width of the protruding portion 29.

  Further, in the present embodiment, it is only necessary to bring a part of the sensor chip 40 into contact with the tip end portion 29a of the protruding portion 29. Therefore, it is not necessary to recognize the position of the groove portion 26 and the like by camera photographing as in the first embodiment. The sensor chip 40 can be easily mounted on the groove 26.

  As for the correspondence between the description of the present embodiment and the description of the claims, the tip end portion 29a of the protrusion 29 corresponds to the “reference portion” of the claims.

(Fourth embodiment)
In the present embodiment, parts different from the third embodiment will be described. As shown in FIG. 8, corner portions 46 and 47 formed by the back surface 42 and the side surface 43 of the sensor chip 40 are chamfered. In the present embodiment, both the corner 47 on the upstream side of the fluid flow and the corner 46 on the downstream side of the fluid flow are chamfered. 8 is a view corresponding to the VI-VI cross section of FIG.

  On the other hand, in molding by a mold, the corner portion 27d formed by the wall surface 28 and the bottom surface 27 of the groove portion 26 may be formed in an R shape. Even in such a case, the sensor chip 40 can be fixed to the groove part 26 while making the gap 70 small so that the sensor chip 40 does not contact the R shape, that is, without being affected by the corner part 27 d of the groove part 26. . Therefore, the gap 70 between the groove portion 26 and the sensor chip 40 and the gap between the bottom surface 27 of the groove portion 26 and the back surface 42 of the sensor chip 40 can be narrowed over a wide range.

  Further, since the corner portions 46 and 47 of the sensor chip 40 do not contact the corner portion 27d of the groove portion 26, the adhesive 60 can be further thinned. For this reason, the gap between the back surface 42 of the sensor chip 40 and the bottom surface 27 of the groove 26 is reduced, so that it is difficult for fluid to flow into the gap.

(Other embodiments)
The configuration of the flow sensor 10 shown in each of the above embodiments is an example, and is not limited to the configuration shown above, and may be another configuration that can realize the present invention. For example, although the sensor support body 20 was comprised with the circuit part 21, the relay part 22, and the sensor part 23, this is an example of a structure. The sensor support 20 should just have the one surface 25 and the groove part 26. FIG.

  In the fourth embodiment, both the corners 46 and 47 formed by the back surface 42 and the side surface 43 of the sensor chip 40 are chamfered. However, it is sufficient that at least the corner 47 on the upstream side of the fluid flow is chamfered. .

20 sensor support 25 one side 26 groove 27 bottom 27c connection position (reference part)
40 sensor chip 41 front surface 42 back surface 45 sensing part 70 gap

Claims (6)

A sensor support (20) having one surface (25) and a groove (26) in which a portion of the one surface (25) is recessed;
It has a plate shape having a front surface (41) and a back surface (42) opposite to the front surface (41), and has a sensing part (45) formed on the front surface (41) side. ) Side is fixed to the bottom surface (27) of the groove portion (26), and a sensor chip (40) for detecting the flow rate of the fluid flowing above the sensing portion (45);
With
The sensor support (20) has a gap (70) between the fluid flow upstream side of the groove (26) and the fluid flow upstream side of the sensor chip (40) within a reference range. The flow rate sensor has a reference part (27c, 29a) for aligning the sensor chip (40) with respect to the groove part (26). The bottom surface (27) of the groove (26)
A parallel surface (27a) located downstream of the fluid flow and parallel to the one surface (25);
The fluid flow upstream side of the parallel surface (27a) is connected to the parallel surface (27a), and the fluid flow upstream side of the groove (26) is more than the parallel surface (27a) side. An inclined surface (27b) inclined so as to be located in the depth direction;
Comprising
The reference portion is a connection position (27c) between the parallel surface (27a) and the inclined surface (27b),
The sensor chip (40) is fixed to the inclined surface (27b) in a state where a part of the fluid flow downstream side and the connection position (27c) are aligned. The flow sensor described in 1.   The sensor chip (40) is within the range from the inclined surface (27b) to the one surface (25) in the direction perpendicular to the one surface (25) of the sensor support (20). The flow rate sensor according to claim 2, wherein the flow rate sensor is fixed to the inclined surface (27 b) so as to be located at a position.   The sensor chip (40) has a part on the surface (41) side of the sensor chip (40) protruding from the one surface (25) in a direction perpendicular to the one surface (25) of the sensor support (20). The flow sensor according to claim 2, wherein the flow sensor is fixed to the inclined surface (27b). The groove (26) has a wall surface (28) connecting the bottom surface (27) and one surface (25) of the sensor support (20), and the surface of the wall surface (28) on the upstream side of the fluid flow. Has a protrusion (29) protruding partly downstream of the fluid flow,
The reference part is a tip part (29a) on the most downstream side of the fluid flow among the protrusions (29),
The sensor chip (40) is fixed to the groove part (26) so that a part of the sensor chip (40) on the upstream side of the fluid flow comes into contact with the tip part (29a). The flow sensor according to claim 1. The sensor chip (40) has a side surface (43) connecting the front surface (41) and the back surface (42),
6. The corner (47) upstream of the fluid flow among the corners (46, 47) formed by the back surface (42) and the side surface (43) is chamfered. The described flow sensor.

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