JP2010151542A - Heat sensitive flowrate sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heat sensitive flowrate sensor for suppressing occurrence of turning vortex and degradation of precision in detection of a flowrate due to an outer stress and a thermal stress. <P>SOLUTION: This heat sensitive flowrate sensor includes a sensor chip that is constituted such that a flowrate detecting section for detecting a flowrate of a fluid to be detected is formed on its front face and a cavity portion opened to its rear face is formed at a portion where a heater forming the flowrate detecting section is formed, and a carrying member that carries the sensor chip mounted thereon. In the heat sensitive flowrate sensor, a projection extending in a direction from the carrying member to the sensor chip is formed on the carrying member at a portion facing the cavity portion away from the sensor chip. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a thermal type flow sensor used for measuring an intake air flow rate of an internal combustion engine, for example.

Conventionally, as shown in, for example, Patent Document 1, a heating element (flow rate detection unit) made of a thermosensitive resistance film is formed on the surface of a flat substrate, and the lower part of the flow rate detection unit in the flat substrate is partially A flow rate detecting element (sensor chip) having a diaphragm in which a hollow portion formed by removal is formed, a support having a concave storage portion for mounting the sensor chip, and installed in a conduit through which a fluid to be measured flows. There has been proposed a thermal flow sensor including a body (mounting member). The thermal flow sensor has a protruding surface that protrudes so as to close the cavity on the bottom surface of the storage portion of the mounting member, and the entire surface of the cavity or a part of the cavity is blocked by the protruding surface. It becomes the composition. As described above, in the heat-sensitive flow sensor disclosed in Patent Document 1, the protruding surface suppresses the flow of the fluid to be detected into the cavity and suppresses the occurrence of turbulence (swirl vortex) in the cavity. It is a thermal flow sensor.
JP 2002-139360 A

  By the way, the thermal flow sensor shown in Patent Document 1 has a configuration in which at least a part of the open end of the cavity and the projecting surface are in contact with each other in order to close the cavity with the projecting surface. That is, the sensor chip and at least a part of the protruding surface are in contact with each other. As described above, when the sensor chip and the projecting surface are in contact with each other, the external stress such as vibration acting on the mounting member from the mounting member to the flow rate detection unit of the sensor chip, and the sensor chip and the mounting member via the projecting surface. There is a risk that thermal stress due to the difference in linear expansion coefficient from the above will be transmitted, and the flow rate detection accuracy may be reduced by these stresses.

  In view of the above problems, an object of the present invention is to provide a thermal flow sensor that suppresses the generation of swirling vortices and suppresses a decrease in flow rate detection accuracy due to external stress and thermal stress.

  In order to achieve the above-described object, the invention according to claim 1 is provided at a portion where a flow rate detection unit for detecting a flow rate of a fluid to be detected is formed on a surface, and a heater forming the flow rate detection unit is formed. A heat-sensitive flow sensor comprising a sensor chip having a hollow portion formed in the back surface and a mounting member on which the sensor chip is mounted, wherein the sensor from the mounting member to a portion of the mounting member facing the cavity portion The protrusion extending in the direction of the chip is formed away from the sensor chip.

  As described above, according to the present invention, since the protrusion is formed in the portion of the mounting member facing the cavity, the wall surface forming the cavity is compared with the configuration in which the protrusion is not formed in the facing portion. In the flow path formed by the mounting member (hereinafter simply referred to as a flow path), the area (the opening area of the cavity) where the detected fluid flows into the cavity is reduced. As a result, the flow rate of the fluid to be detected flowing into the cavity is reduced, the flow of the fluid to be detected flowing through the flow path is rectified, and turbulence (swirl vortex) is prevented from being generated in the cavity.

  Further, the protrusion is formed away from the sensor chip. That is, the protrusion is formed in a non-contact manner with the sensor chip. As a result, the external stress such as vibration acting on the mounting member from the mounting member to the sensor chip and the thermal stress due to the difference in linear expansion coefficient between the sensor chip and the mounting member via the protrusion are caused by the flow rate of the sensor chip. Transmission to the detection unit is suppressed. As described above, the thermal flow sensor according to the present invention is a thermal flow sensor in which the generation of swirling vortices is suppressed and a decrease in flow rate detection accuracy due to external stress and thermal stress is suppressed.

  According to a second aspect of the present invention, a configuration in which a part of the protrusion is disposed inside the cavity is preferable. According to this, the space in which the swirl vortex can be generated in the hollow portion can be eliminated, and the flow of the detected fluid flowing through the flow path can be rectified. Thereby, generation | occurrence | production of the swirl | vortex vortex in a cavity part is suppressed effectively, and it is a thermal type flow sensor in which the fall of the flow volume detection precision by swirl | vortex vortex was suppressed effectively.

  As described in claim 3, it is preferable that the shape of the protrusion is similar to the shape of the cavity. According to this, compared with the structure in which the shape of the protrusion is different from the shape of the cavity, it is possible to efficiently eliminate the space where the swirl vortex can be generated in the cavity.

  According to a fourth aspect of the present invention, it is preferable that the protrusion is formed with a groove that penetrates from the upstream end surface to the downstream end surface with respect to the normal flow direction of the fluid to be detected. According to this, the flow of the fluid to be detected flowing through the flow path can be rectified by the groove portion.

  As described in claim 5, the mounting member and the protrusion are preferably made of the same material and integrally formed. According to this, compared with the structure which a mounting member and a projection part are separate members, a number of parts can be reduced and the manufacturing process of a thermal type flow sensor can be simplified.

  As described in claim 6, a through-hole penetrating the front surface and the back surface of the mounting member is formed in a portion of the mounting member facing the cavity, and the protrusion is inserted into the through-hole, A configuration that is press-fitted and fixed to the mounting member is preferable. According to this, since the position of the cavity portion can be confirmed through the through hole after the sensor chip is mounted on the mounting member, the position of the through hole is adjusted so that the position of the cavity portion and the protrusion portion is within a desired position. After finely adjusting the shape, the positions of the protrusion and the cavity can be determined. Therefore, after forming the protrusion on the mounting member, compared to the heat-sensitive flow sensor formed through the manufacturing process of mounting the sensor chip on the mounting member, the thermal type with improved positional accuracy between the cavity and the protrusion It is a flow sensor.

  According to a seventh aspect of the present invention, the protrusion is preferably formed of a black material. When the heater generates heat, heat radiation is emitted from the heater, and a part of the emitted heat radiation is irregularly reflected by the mounting member. Then, this irregular reflection may cause fluctuations in the temperature distribution formed around the heater, and the flow rate detection accuracy may be reduced. In particular, in the case of the thermal type flow sensor according to the present invention, as shown in claim 1, since the protrusion is formed at the portion facing the cavity in the mounting member, the heater on the wall surface forming the cavity is formed. The distance between the bottom portion and the mounting member is shorter than that of a thermal flow sensor without a protrusion. Therefore, in the thermal flow sensor according to the present invention, the amount of heat radiation reflected to the bottom portion where the heater is formed by the mounting member is larger than that of the thermal flow sensor without the protrusions, and is due to thermal radiation. The configuration is easily affected.

  On the other hand, in the invention described in claim 7, the protrusion is formed of a black material. Since black has a property of absorbing heat radiation, this can reduce the amount of heat radiation reflected to the bottom part where the heater is formed by the protrusion. Thus, the thermal type flow sensor according to claim 7 is a thermal type flow sensor in which a decrease in flow rate detection accuracy due to thermal radiation is suppressed. In addition, as a structure which suppresses reflection of a heat radiation, the structure by which the black coating material was apply | coated to the surface of a projection part can also be employ | adopted, for example, as described in Claim 8.

  According to a ninth aspect of the present invention, the facing surface of the protruding portion facing the bottom portion (hereinafter simply referred to as the bottom portion) where the heater is formed on the wall surface forming the hollow portion is parallel to the facing surface of the bottom portion facing the protruding portion. The structure which is is good. According to this, even if the protruding portion is displaced in the direction along the opposing surface of the bottom portion, the distance between the opposing surface of the protruding portion and the opposing surface of the bottom portion can be made constant. Thereby, even if a projection part shifts | deviates to the direction in alignment with the opposing surface of a bottom part, the area which absorbs heat radiation with the opposing surface of a projection part is securable. The bottom portion described above corresponds to the portion where the heater is formed.

  According to a tenth aspect of the present invention, it is preferable that the facing surface of the protruding portion facing the bottom portion of the wall surface forming the hollow portion is a curved surface that is recessed from the sensor chip toward the mounting member. According to this, the amount of heat radiation radiated to the opposing surface of the protrusion can be made substantially uniform. Therefore, the temperature distribution formed on the opposing surface of the protrusion is made constant by heat radiation, and the heat radiation radiated by the protrusion does not easily affect the temperature distribution formed around the heater. .

  According to the eleventh aspect, the mounting member includes an upstream rectification unit disposed adjacent to the upstream end surface with a predetermined gap with respect to a normal flow direction of the fluid to be detected in the sensor chip, and a sensor chip. It is preferable that the downstream rectifier is disposed adjacent to the downstream end face with a predetermined gap, and the upper surfaces of the upstream rectifier and the downstream rectifier are substantially flush with the surface of the sensor chip.

  According to this, by obtaining a flat distance from the upstream rectification unit (or downstream rectification unit) to the flow rate detection unit, turbulence (turbulent flow) of the fluid to be detected on the flow rate detection unit is reduced (in other words, Can be rectified). In addition, since the sensor chip and the rectifying unit do not contact each other, it is possible to suppress external stress such as vibration acting on the mounting member from being transmitted to the flow rate detecting unit of the sensor chip via the rectifying unit. In addition, the fluid to be detected around the thermal flow sensor is communicated with the cavity through the air gap, and the temperature of the fluid in the cavity follows the temperature of the fluid to be detected around the thermal flow sensor. Can be changed.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a plan view showing a schematic configuration of a thermal flow sensor according to the first embodiment. 2 is a cross-sectional view taken along line II-II in FIG. FIG. 3 is a plan view showing a schematic configuration of the sensor chip. 4A is a cross-sectional view when there is no protrusion as a comparative example, and FIG. 4B is a cross-sectional view taken along line IVb-IVb in FIG. 1 and 3, the normal flow direction of the fluid to be detected is indicated by a white arrow, and in FIG. 4, the flow of the fluid to be detected is indicated by a dashed arrow. In the following, the flow direction of the fluid to be detected is simply referred to as the flow direction.

  As shown in FIGS. 1 and 2, the thermal flow sensor 100 includes a sensor chip 10 and a mounting member 90 on which the sensor chip 10 is mounted as a main part. Furthermore, in the present embodiment, the circuit chip 30 that controls the input / output of the flow rate detection unit 13 in the sensor chip 10, the lead 50 as an external connection terminal that is electrically connected to the circuit chip 30, and the lead 50 It has the connection part with the circuit chip 30, the circuit chip 30, and the sealing resin 70 which covers and protects the connection part between the circuit chip 30 and the sensor chip 10.

  The sensor chip 10 has a flow rate detection unit 13 that detects the flow rate of a fluid to be detected on a surface 11a of a substrate 11 made of single crystal silicon. As shown in FIGS. 2 and 3, the insulating film 12 is formed on the surface 11 a of the substrate 11, and the flow rate detection unit 13 is formed on the insulating film 12. The flow rate detection unit 13 includes a heating element 14 and a temperature sensing element 15, and these elements 14, 15 are a metal thin film such as platinum (Pt), polycrystalline silicon (Si), or polycrystalline silicon carbide ( After the semiconductor thin film such as SiC) is formed on the insulating film 12, the thin film is patterned and formed together with the wiring 16 that electrically connects the flow rate detection unit 13 and the first pad 17. Note that when the elements 14 and 15 and the wiring 16 are formed of a semiconductor thin film, the elements 14 and 15 and the wiring 16 can be formed by patterning the silicon layer of the SOI substrate. An insulating protective film (not shown) for protecting the flow rate detection unit 13 is formed on the surfaces of the flow rate detection unit 13 and the wiring 16, so that the flow rate detection unit 13 and the wiring 16 are connected to each other. It is configured to be prevented from being damaged by foreign matter contained in the fluid to be detected. The heating element 14 corresponds to the heater described in the claims.

  As shown in FIGS. 1 and 2, the substrate 11 includes a rectangular pyramid-shaped cavity 18 having a flat tip and an insulating film 12 by anisotropic etching from the back surface of the substrate 11. A membrane 19 is formed. The heating element 14 is formed on the membrane 19, and the temperature sensing element 15 is formed in a region of the substrate 11 excluding the membrane 19, whereby the heating element 14 and the temperature sensing element 15 are thermally separated. . The membrane 19 corresponds to a bottom portion on which a heater is formed on the wall surface forming the cavity described in the claims.

  As shown in FIG. 3, the heat generating element 14 includes a heat generating element 14a disposed on the upstream side with respect to the flow direction in a normal state and a heat generating element 14b disposed on the downstream side. It has a function of generating heat according to the supply amount and a function of sensing its own temperature based on a change in its own resistance value. Therefore, the flow rate of the fluid is detected based on the heat taken by the fluid among the heat generated in the heating elements 14a and 14b on the upstream side and the downstream side. Further, the flow direction is detected based on the difference in the amount of heat taken away by the fluid among the heat generated in each of the upstream heating element 14a and the downstream heating element 14b.

  The temperature sensing element 15 has a temperature sensing element 15a disposed on the upstream side in the flow direction and a temperature sensing element 15b disposed on the downstream side, and is based on a change in its own resistance value. , Has the function of sensing its own temperature. Therefore, based on the temperature difference between the upstream heating element 14a and the upstream temperature sensing element 15a, and the temperature difference between the downstream heating element 14b and the downstream temperature sensing element 15b, each heating element 14a, 14b. The amount of current supplied to is controlled.

  The circuit chip 30 is formed by forming a control circuit (not shown) for controlling input / output of the flow rate detector 13 on a substrate 31 made of single crystal silicon. On the surface 31a of the substrate 31, the above-described control circuit, the second pad 32 connected to the wiring end of the control circuit, and the third pad electrically connected to the second pad 32 via the control circuit. Pad 33 is formed. The second pad 32 is electrically connected to the first pad 17 of the sensor chip 10 via the first bonding wire 71 made of Al, Au or the like, and the third pad 33 is the second bonding made of Al, Au or the like. The lead 50 is electrically connected via the wire 72. Thus, the sensor chip 10 and the lead 50 are electrically connected via the circuit chip 30, and the sensor chip 10 is configured to be able to exchange signals with the outside (for example, an external ECU).

  The lead 50 is electrically connected to the circuit chip 30 and exchanges signals with the outside. In the present embodiment, the lead 50 and the support member 51 are constituted by a single lead frame, and after a mounting member 90 described later is molded (after the lead 50 and the support member 51 are connected by the mounting member 90). The lead 50 and the support member 51 are made independent from each other by separating unnecessary portions that connect the lead 50 and the support member 51. The unnecessary portion corresponds to the outer peripheral frame of the lead frame and fulfills the function of temporarily connecting the lead 50 and the support member 51. The support member 51 corresponds to an island of the lead frame, and the circuit chip 30 and the sensor chip 10 are arranged on the surface thereof.

  The sealing resin 70 covers and protects the connection portion between the lead 50 and the circuit chip 30, the circuit chip 30, and the connection portion between the circuit chip 30 and the sensor chip 10. The sealing resin 70 bonds and fixes the circuit chip 30 and the sensor chip 10 to the support member 51 connected to the mounting member 90, and electrically connects the leads 50 and the circuit chip 30 via the second bonding wires 72. After connecting and electrically connecting the circuit chip 30 and the sensor chip 10 via the first bonding wires 71, a molten resin is applied in a region surrounded by a base side wall portion 96 described later, It is formed by cooling and solidifying the resin. Although not shown, a dam that prevents the molten resin from flowing into the flow rate detection unit 13 between the first pad 17 and the flow rate detection unit 13 on the surface 11a of the sensor chip 10 (substrate 11). A material is provided, and the flow rate detection unit 13 is not covered with resin by the dam material.

  The mounting member 90 mounts the sensor chip 10. The mounting member 90 according to the present embodiment is configured to connect the lead 50 and the support member 51 and mount the sensor chip 10 and the circuit chip 30 via the support member 51. As shown in FIGS. 1 and 2, the mounting member 90 is provided at the peripheral portion of the bottom portion 91 so as to surround the bottom portion 91 connecting the lead 50 and the support member 51 and the periphery of the sensor chip 10 and the circuit chip 30. And a protruding portion 93 formed at a portion of the bottom portion 91 facing the cavity portion 18. The bottom 91, the wall 92, and the protrusion 93 are made of the same material and are integrally formed by molding.

  The bottom portion 91 includes a planar substantially rectangular base portion 94 on which a part of the lead 50 and the circuit chip 30 are disposed, and a planar substantially rectangular tongue portion 95 on which the sensor chip 10 is disposed. . The base portion 94 functions to connect the lead 50 and the support member 51, and the tongue portion 95 has a function of suppressing the fluid to be detected flowing on the back side of the thermal flow sensor 100 from flowing into the cavity portion 18. Fulfill. As shown in FIG. 2, the sensor chip 10 is fixed to the tongue portion 95 via an adhesive provided on the back surface of the formation area of the first pad 17 in the sensor chip 10. Accordingly, a gap is formed between the sensor chip 10 and the tongue portion 95.

  The wall portion 92 includes a substantially C-shaped base side wall portion 96 provided on the peripheral portion of the base portion 94 on the upper surface 91a of the bottom portion 91, and a substantially flat surface provided on the peripheral portion of the tongue portion 95 on the upper surface 91a. A tongue-shaped side wall portion 97, and an end outer surface of the base side wall portion 96 and an end portion of the tongue side wall portion 97 are connected to each other. The upper surface of the tongue side wall 97 on the upper surface 92a of the wall 92 is designed to be substantially flush with the surface 11a of the sensor chip 10, and the end of the tongue side wall 97 facing the sensor chip 10 in the flow direction. The turbulent flow on the flow rate detection unit 13 is reduced (in other words, rectified) by increasing the distance of the flat portion from the opposite end to the flow rate detection unit 13. Yes. In addition, a predetermined gap (clearance) is formed between the side surface of the sensor chip 10 and the inner wall surface of the tongue side wall 97, and the clearance and the gap between the sensor chip 10 and the tongue 95 are communicated with each other. It has become so. As a result, the fluid to be detected around the thermal flow sensor 100 communicates with the cavity 18, and the temperature of the fluid to be detected in the cavity 18 follows the temperature of the fluid to be detected around the thermal flow sensor 100. To be able to change. Further, the base side wall portion 96 is set such that the height from the upper surface 91 a of the bottom portion 91 is set higher than that of the circuit chip 30, thereby connecting the lead 50 and the circuit chip 30, the circuit chip 30, and the circuit chip 30. The height for filling the sealing resin 70 that covers the connection portion with the sensor chip 10 is secured. In addition, the site | part arrange | positioned upstream with respect to the sensor chip 10 in the above-mentioned tongue side wall part 97 is corresponded to the upstream rectification | straightening part as described in a claim, and is arrange | positioned downstream with respect to the sensor chip 10. The part made corresponds to the downstream rectification unit described in the claims.

  Next, the protrusion 93 that is a characteristic point of the present embodiment and its operation and effect will be described. As shown in FIG. 2, a protrusion 93 extending from the bottom 91 toward the sensor chip 10 is formed at a position facing the cavity 18 in the bottom 91 of the mounting member 90 so as to be separated from the sensor chip 10. The protrusion 93 according to this embodiment has a shape similar to the shape of the cavity 18 and has a quadrangular pyramid shape with a flat tip. In addition, a part of the protrusion 93 is disposed inside the cavity 18. Thereby, the fluid to be detected flows into the cavity portion 18 in the channel formed by the wall surface forming the cavity portion 18 and the mounting member 90 (bottom portion 91) by the protrusion 93 (hereinafter simply referred to as a channel). It is possible to reduce the area (the opening area of the cavity 18, hereinafter simply referred to as the inflow area), and to eliminate the space in which the fluid to be detected swirls in the cavity 18.

  As shown in FIG. 4, the fluid to be detected is a gap between the sensor chip 10 and the bottom 91 (tongue 95) via the clearance between the sensor chip 10 and the wall 92 (tongue side wall 97). Flow into. As shown in FIG. 4A, when the protrusion 93 is not provided at the portion of the bottom 91 facing the cavity 18, the inflow area of the flow path is sufficiently secured, and the space of the cavity 18 is increased. Since it is sufficiently secured, there is a possibility that the fluid to be detected flows into the cavity 18 and a swirl vortex is generated in the cavity 18. When a swirl vortex is generated in the cavity 18, the temperature distribution on the membrane 19 varies, which causes variations in the resistance value of the heating element 14 formed on the membrane 19, which may reduce the flow rate detection accuracy. .

  On the other hand, as shown in FIG. 4B, when the protrusion 93 is provided at a portion of the bottom 91 facing the cavity 18, the inflow area of the flow path is reduced. The flow rate of the fluid to be detected flowing into the flow path can be reduced and the flow of the fluid to be detected flowing through the flow path can be rectified. Thereby, it is possible to suppress the generation of a swirling vortex in the cavity 18. In the present embodiment, a part of the projection 93 is disposed in the cavity 18, and the space of the cavity 18 is reduced. Therefore, the flow of the detected fluid can be rectified by flowing the detected fluid along the flow path. Thereby, it can suppress more effectively that a turning vortex arises in the cavity part 18. FIG. As described above, the thermal flow sensor 100 is a thermal flow sensor in which a decrease in flow detection accuracy due to the swirling vortex is suppressed.

  Further, the protruding portion 93 is configured to be formed on the bottom portion 91 of the mounting member 90 apart from the sensor chip 10. That is, the protrusion 93 and the sensor chip 10 have a non-contact configuration. As a result, external stress such as vibration acting on the mounting member 90 from the mounting member 90 to the sensor chip 10 via the protrusions 93 and thermal stress due to the difference in linear expansion coefficient between the sensor chip 10 and the mounting member 90. Is suppressed from being transmitted to the flow rate detection unit 13 of the sensor chip 10, and the heat-sensitive flow rate sensor 100 is suppressed in which a decrease in flow rate detection accuracy due to these stresses is suppressed. As described above, the thermal flow sensor 100 of the present embodiment is a thermal flow sensor in which the generation of swirling vortices is suppressed and the decrease in flow rate detection accuracy due to external stress and thermal stress is suppressed.

  In the present embodiment, the shape of the protrusion 93 is the same as the shape of the cavity 18. According to this, the space of the cavity 18 can be efficiently eliminated as compared with the configuration in which the shape of the protrusion 93 is different from the shape of the cavity 18.

  In this embodiment, the bottom part 91, the wall part 92, and the projection part 93 which comprise the mounting member 90 are integrally molded by molding. Thereby, compared with the structure which the mounting member 90 and the projection part 93 are separate members, a number of parts can be reduced and the manufacturing process of a thermal type flow sensor can be simplified.

  The preferred embodiments of the present invention have been described above. However, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention.

  In the present embodiment, an example in which a part of the protrusion 93 is disposed in the cavity 18 has been described. However, for example, as shown in FIG. 5, a configuration in which the protrusion 93 is not disposed in the cavity 18 and the protrusion 93 is separated from the sensor chip 10 may be employed. Also in this configuration, since the inflow area of the flow path is reduced, the flow rate of the detected fluid flowing into the cavity 18 can be reduced and the flow of the detected fluid flowing in the flow path can be rectified. it can. Thereby, it can suppress that a swirl | vortex produces | generates in the cavity part 18, and can suppress the fall of flow volume detection accuracy. Further, since the protrusion 93 and the sensor chip 10 are separated from each other, external stress such as vibration acting on the mounting member 90 from the mounting member 90 to the sensor chip 10 via the protrusion 93 and the sensor. It is possible to suppress the thermal stress caused by the difference in linear expansion coefficient between the chip 10 and the mounting member 90 from being transmitted to the flow rate detection unit 13 of the sensor chip 10. FIG. 5 is a cross-sectional view for explaining a modified example of the protrusion, and a broken-line arrow indicates the flow of the fluid to be detected.

  In the present embodiment, an example is shown in which the bottom 91, the wall 92, and the protrusion 93 constituting the mounting member 90 are integrally formed by molding. However, the method for forming the protrusion 93 is not limited to the above example. For example, the protrusion 93 may be formed by bonding and fixing a protrusion member to a portion of the upper surface 91a of the bottom 91 that faces the cavity 18. good. Alternatively, for example, as illustrated in FIG. 6, a through hole 98 is provided in a portion of the bottom 91 facing the cavity 18, and the sensor chip 10 is bonded and fixed to the mounting member 90, and then the bottom is formed in the through hole 98. The protruding portion 93 may be formed by inserting a protruding member from the back surface side of the upper surface 91a of 91 and press-fitting and fixing. As described above, when the mounting member 90 and the protrusion 93 are formed of different members, the material for forming the protrusion 93 can be selected as appropriate. Further, as described above, when the protruding portion 93 is formed by inserting the protruding member into the through hole 98 of the mounting member 90 and press-fitting and fixing, the through hole 98 is bonded and fixed to the mounting member 90. The position of the cavity 18 can be confirmed via Therefore, the position of the protrusion 93 and the cavity 18 can be determined after finely adjusting the shape of the through hole 98 so that the positions of the cavity 18 and the protrusion 93 are within desired positions. Thereby, after forming the protrusion on the mounting member, the positional accuracy of the cavity 18 and the protrusion 93 is improved as compared with the thermal flow sensor formed through the manufacturing process of mounting the sensor chip on the mounting member. be able to. FIG. 6 is a cross-sectional view for explaining the deformability of the mounting member.

  In the present embodiment, an example in which the protrusion 93 has a shape similar to the shape of the cavity 18 is shown. However, the shape of the protrusion 93 may be different from the shape of the cavity 18. However, if the space of the cavity 18 is efficiently eliminated, the shape of the protrusion 93 is preferably similar to the shape of the cavity 18.

  In this embodiment, the protrusion part 93 showed the example which has a quadrangular pyramid shape by which the front-end | tip part was made flat. However, for example, as shown in FIGS. 7 to 9, the protrusion 93 has a conical shape with a flat tip, a rectangular parallelepiped, or a plurality of rectangular parallelepipeds, and the mounting area of the rectangular parallelepiped is from the bottom 91. It is good also as a shape which becomes small as it goes to the sensor chip 10. In addition, when forming the projection part 93 by a rectangular parallelepiped, ceramic is suitable as a forming material of the projection part 93, since ceramic is easy to shape in a rectangular shape compared with a metal. 7-9 is a figure which shows the modification of a projection part, (a) is a top view, (b) has shown sectional drawing.

  As a configuration for rectifying the flow of the fluid to be detected flowing through the flow path, for example, as shown in FIG. 10, a groove 93 a that penetrates from the upstream end surface to the downstream end surface of the protrusion 93 is formed in the protrusion 93. It is good to form. According to this, the flow of the fluid to be detected flowing through the flow path can be rectified by the groove portion 93a. FIG. 10 is a cross-sectional view showing a modification of the protrusion.

  In the present embodiment, the formation material of the protrusion 93 is not particularly mentioned, but the protrusion 93 may be formed of a black material. When the heat generating element 14 formed on the membrane 19 facing the protrusion 93 generates heat, heat radiation is emitted from the heat generating element 14, and a part of the emitted heat radiation is irregularly reflected by the tongue 95 and the protrusion 93. The Then, the irregular reflection causes fluctuations in the temperature distribution formed around the heat generating element 14, and the flow rate detection accuracy may be lowered. In particular, in the case of the thermal type flow sensor 100 of the present embodiment, since the protrusion 18 is formed at a portion of the mounting member 90 that faces the membrane 19, the distance between the membrane 19 (heating element 14) and the mounting member 90 is small. This is shorter than a thermal flow sensor without a protrusion. Therefore, in the thermal flow sensor 100 according to the present invention, the amount of thermal radiation reflected by the mounting member 90 on the membrane 19 is larger than that of a thermal flow sensor without a protrusion, and the influence of thermal radiation is reduced. It is easy to receive.

  As a configuration for reducing the influence of this thermal radiation, a configuration in which the protrusions 93 are formed of a black material as described above can be employed. Since black has the property of absorbing heat radiation, the amount of heat radiation reflected by the protrusions 93 can be reduced. In addition, as a structure which suppresses reflection of a thermal radiation, it is not limited to the said example, For example, the structure by which the black coating material was apply | coated to the surface of the projection part 93 is also employable. As such a black paint, for example, a paint containing graphite can be used. Moreover, since the heat radiation radiated | emitted from the heat generating element 14 is also radiated | emitted also to the tongue part 95 of the mounting member 90, it is good to form the tongue part 95 with a black material. Alternatively, the surface of the tongue portion 95 may be coated with a black paint.

  As described above, when the protrusion 93 is formed of a black material, or when the surface of the protrusion 93 is coated with a black paint, as shown in FIG. A configuration in which the facing surface 93b is parallel to the facing surface 19a of the membrane 19 with the protrusion 93 is preferable. According to this, even if the protruding portion 93 is displaced in the direction along the facing surface 19 a of the membrane 19, the distance between the facing surface 93 b of the protruding portion 93 and the facing surface 19 a of the membrane 19 can be made constant. Thereby, even if the projection part 93 shift | deviates to the direction along the opposing surface 19a, the area which absorbs heat radiation with the opposing surface 93b of the projection part 93 is securable. FIG. 11 is a cross-sectional view for explaining the configuration of the protrusion and the membrane. The facing surface 19a of the membrane 19 corresponds to the facing surface of the bottom portion described in the claims and the protruding portion.

  In addition, as shown in FIG. 12, the opposing surface 93b of the projection part 93 is good at the structure which becomes a curved surface dented from the sensor chip 10 toward the mounting member 90. According to this, the amount of heat radiation radiated to the facing surface 93b of the protrusion 93 can be made substantially uniform on the facing surface 93b. Accordingly, the temperature distribution formed on the opposing surface 93b of the protrusion 93 is made constant by heat radiation, and the heat radiation radiated by the protrusion 93 hardly affects the temperature distribution formed around the heating element 14. It can be configured. FIG. 12 is a cross-sectional view showing a modification of the protrusion.

It is a top view which shows schematic structure of the thermal type flow sensor which concerns on 1st Embodiment. It is sectional drawing which follows the II-II line | wire of FIG. It is a top view which shows schematic structure of a sensor chip. (A) is sectional drawing in case there is no projection part as a comparative example, (b) shows sectional drawing in alignment with the IVb-IVb line | wire of FIG. It is sectional drawing for demonstrating the modification of a projection part. It is sectional drawing for demonstrating the modification of a mounting member. It is a figure which shows the modification of a projection part, (a) is a top view, (b) has shown sectional drawing which follows the VIIb-VIIb line | wire. It is a figure which shows the modification of a projection part, (a) is a top view, (b) has shown sectional drawing which follows a VIIIb-VIIIb line. It is a figure which shows the modification of a projection part, (a) is a top view, (b) has shown sectional drawing which follows the IXb-IXb line | wire. It is sectional drawing which shows the modification of a projection part. It is sectional drawing for demonstrating the structure of a projection part and a membrane. It is sectional drawing which shows the modification of a projection part.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Sensor chip 18 ... Cavity 19 ... Membrane 30 ... Circuit chip 50 ... Lead 70 ... Sealing resin 90 ... Mounting member 93 ... Projection part 100 ...・ Thermal flow sensor

Claims (11)

A sensor chip in which a flow rate detection unit for detecting the flow rate of the fluid to be detected is formed on the front surface, and a hollow portion that is open on the back surface is formed in a portion where the heater constituting the flow rate detection unit is formed;
A thermal flow sensor comprising a mounting member on which the sensor chip is mounted,
A thermal flow sensor characterized in that a protrusion extending from the mounting member in the direction of the sensor chip is formed away from the sensor chip at a portion of the mounting member facing the cavity.   The thermal flow sensor according to claim 1, wherein a part of the protrusion is disposed inside the cavity.   The heat-sensitive flow sensor according to claim 2, wherein the shape of the protrusion is similar to the shape of the cavity.   The groove portion penetrating from the upstream end surface to the downstream end surface with respect to the normal flow direction of the fluid to be detected is formed in the projecting portion. The thermal flow sensor according to the item.   The heat-sensitive flow sensor according to claim 1, wherein the mounting member and the protrusion are made of the same material and are integrally molded. A through-hole penetrating the front surface and the back surface of the mounting member is formed in a portion of the mounting member facing the cavity.
5. The thermal flow sensor according to claim 1, wherein the protrusion is inserted into the through hole and press-fitted and fixed to the mounting member.   The heat-sensitive flow sensor according to claim 5 or 6, wherein the protrusion is made of a black material.   The thermal flow sensor according to claim 5 or 6, wherein a black paint is applied to a surface of the protrusion.   8. The facing surface of the projecting portion facing the bottom portion where the heater is formed on the wall surface forming the hollow portion is parallel to the facing surface of the bottom portion facing the projecting portion. Item 9. The thermal flow sensor according to Item 8.   8. The facing surface of the projecting portion facing the bottom portion where the heater is formed on the wall surface forming the hollow portion is a curved surface that is recessed from the sensor chip toward the mounting member. Or the thermal type flow sensor of Claim 8. The mounting member includes an upstream rectification unit disposed adjacent to the upstream end surface with a predetermined gap with respect to the normal flow direction of the fluid to be detected in the sensor chip, and a predetermined downstream end surface of the sensor chip. And a downstream rectification unit arranged adjacently with a gap of
11. The thermal flow sensor according to claim 1, wherein upper surfaces of the upstream rectification unit and the downstream rectification unit are substantially flush with a surface of the sensor chip.

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