JP2005114502A - Flow sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a flow sensor enhanced in responsiveness and sensitivity, and suitable, in particular, for measuring a flow rate of a corrosive fluid. <P>SOLUTION: In this flow sensor 1, provided with a metal sensor chip 110 having a recessed part 112 for forming flow passages on a reverse face, and formed on a surface with a sensor device for measuring the flow rate via an insulation layer, and a metal flow passage forming member 30 integrated with the reverse face of the sensor chip 110 to form the flow passages 138, 139, a banklike welding part 115 having a width substantially equal to a fusing-in depth of a welding beam is formed in a periphery of the recessed part 112 of the sensor chip 110, so as to eliminate a dead space DS wherein a volume thereof is zero geometrically but a slight gap is generated practically. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a flow sensor for measuring a flow velocity or a flow rate of a fluid flowing in a flow path, and particularly relates to a thermal flow sensor.

  There are two types of thermal flow sensors that measure the flow rate and flow rate of fluid. In other words, the spatial temperature distribution of the fluid due to the heat generated by the heater, which is a heating element, is biased through the flow of the fluid, and this is detected by a temperature sensor (side heat type), and the heat of the heating element is caused by the fluid. There is known a type (self-heating type) that detects a change in electric power and a change in resistance due to deprivation and detects a flow velocity or a flow rate. In the former conventional flow sensor, there is a type in which a sensor is patterned on the surface of silicon, and a fluid to be measured is directly flowed through the sensor pattern. However, a sensor chip using silicon is excellent in sensitivity and responsiveness, but has a drawback of being easily corroded by corrosive gas. Therefore, when the fluid to be measured is a gas, only a gas that does not chemically attack silicon can flow.

  However, in addition to flow sensors that are used only for non-corrosive gases, recently, indirectly heated flow sensors that have a structure that can be used for liquids and corrosive gases have come to be used. (For example, refer to Patent Document 1).

  As shown in FIG. 9, the flow sensor 7 has a flow path disposed so that one surface (back surface) 711 side faces the substrate 710 facing the flow path 701 of the fluid to be measured with the substrate 710 interposed therebetween. The structure includes a forming member 720 and a plate 730. The substrate 710 is made of a stainless steel plate having a thickness of about 50 μm to 150 μm, and an electric insulating film is formed on the surface 712 opposite to the flow path side, and a fluid flow velocity (flow rate) measurement temperature is formed thereon. A detection means, an ambient temperature sensor, an electrode pad, and a metal thin film for wiring are formed (not shown in FIG. 7). As described above, a thin stainless steel plate is used for the substrate 710, and the flow path is provided on the side opposite to the sensor forming surface, so that the case where the fluid to be measured is a corrosive fluid can be dealt with.

  However, the above-described conventional flow sensor 7 is merely formed by bonding the plate 730 to the surface 711 of the thin substrate 710 by bolting (not shown). The temperature distribution of the flow sensor was unstable because the thermal and thermal contact was not constant. In addition, the diaphragm portion of the substrate 710 is elastically deformed in the surface direction in accordance with the fluid pressure change, and the contact state between the substrate 710 and the plate 730 is changed, so that the temperature distribution of the diaphragm portion is changed. The flow characteristics and the zero point shifted, and the accuracy, reproducibility, reliability and durability were insufficient.

  Accordingly, the applicant has devised a flow sensor 8 having a structure shown in FIG. 10 as a measure not yet known in order to solve the above-described problems.

  The flow sensor 8 includes a sensor chip 810 that forms a flow path of the fluid to be measured together with the flow path forming member 830. The sensor chip 810 is formed by integrally forming a thin portion 811 and a thick fixing portion 812 surrounding the thin portion 811, and the flow rate detecting means 825 is provided on the surface of the thin portion 811 opposite to the flow path side. I have. The sensor chip 810 is made of stainless steel. Since stainless steel is a conductive material, an oxide film 820 is formed on one surface of the sensor chip 810.

  With such a configuration, the change in flow velocity or flow rate characteristic of the sensor chip 810 due to a change in fluid pressure is reduced, so that the measurement accuracy, reproducibility, reliability, and durability of the flow sensor can be improved, and the number of parts can be reduced. Can be produced.

JP 2002-122454 A (page 3-6, FIG. 1)

  When manufacturing such an improved flow sensor 8, a sensor chip 810 made of stainless steel and a flow path forming member 830 made of stainless steel are joined from the outer periphery thereof by YAG laser welding or the like to form an airtight flow path inside. It is necessary to manufacture a squeezed flow sensor. However, inconveniences that occur when such joining is actually performed will be described below together with the configurations of the sensor chip 810 and the flow path forming member 830.

  In order to package the sensor chip 810 made of stainless steel, the same stainless steel flow path forming member 830 is joined by seam welding using a method such as laser welding. Since the outer shape of the sensor chip 810 is cut off by dicing, which is generally performed in a semiconductor manufacturing process, the outer shape of the sensor chip 810 is generally an elongated rectangular shape in plan view as shown in FIG. In addition, a concave portion 812 is formed on the back surface of the sensor chip 810 by etching, machining, electric discharge machining, or the like, so that a diaphragm structure with an extremely thin plate thickness is obtained, and sensitivity and responsiveness are enhanced (FIG. 11 ( b)).

  On the other hand, the partial shape of the flow path forming member 830 to which the sensor chip 810 is joined is shown in FIGS. In order to make the flow path forming member 830 by machining, a projection 831 having an elongated rectangular shape in plan view is processed on the upper surface of the member main body, and flow paths 838 and 839 are formed on the upper surface of the projection 831. Here, the flow paths 838 and 839 through which the process fluid flows are round holes formed by drilling. Further, the recess 812 forming the flow path on the back surface of the sensor chip is rounded in the inflow portion and the outflow portion in accordance with the flow paths 838 and 839 which are round holes in the cross section of the flow path forming member 830 (FIG. 11A). reference). In addition, the area | region where a sensor device detects a flow volume is an area | region pinched | interposed between wall part 812a, 812b facing mutually parallel among the recessed parts 812. Therefore, when these are integrated, the flow path dug into the back surface of the sensor chip becomes an oval shape like the track outer periphery of a so-called athletics when the outermost portion of the recess 812 is viewed from the back surface side of the sensor chip.

  When the sensor chip 810 is welded to the flow path forming member 830, the sensor chip 810 is brought into contact with the protrusion 831 of the flow path forming member 830. Here, the outer edge of the contact portion between the sensor chip 810 and the protrusion 831 of the flow path forming member 830 has a rectangular shape in plan view. Therefore, when the laser beam is irradiated toward the outer edge of the contact part, a penetration part WD as shown by fine hatching in FIG. 13A is formed.

  Here, as can be seen from the same figure, the outer edge portion of the sensor chip 810 has a rectangular shape in plan view when viewed from the back side of the sensor chip, while the peripheral edge of the recess portion 812 has an oval shape in plan view. The edges are separated at the four corners of the sensor chip 810. Therefore, there is a region (hereinafter referred to as “dead space DS”) that is not joined at the four corners on both contact surfaces (see the rough hatched portion in FIG. 13A). Although the dead space DS is geometrically zero in volume, it is difficult to clean this part after welding because there is actually a slight gap. Further, since the process fluid tends to stay in this portion, the purge characteristics are deteriorated. Therefore, the flow sensor 8 having such a dead space DS has a problem that it is difficult to use it as a flow path measurement product requiring high cleanliness such as a mass flow meter for semiconductor industry.

  In order to prevent thermal distortion in the sensor device formed on the insulating film on the surface of the sensor chip, for example, in the case of a sensor chip having a thickness of 0.6 mm, the melting by the laser is about half the thickness of the sensor chip. Experience has shown that it is necessary to keep it to 0.3 mm. Therefore, if the penetration of welding is deepened as shown in FIGS. 14A and 14B in order to reduce the dead space DS, the amount of heat input increases, welding distortion increases, or the sensor pattern is damaged. In addition, it is impossible to completely eliminate such a dead space DS due to the structural difference between the sensor chip 810 and the flow path forming member 830.

  It is an object of the present invention to provide a flow sensor that is further suitable for measuring the flow rate of a corrosive fluid while further improving responsiveness and sensitivity.

  In order to solve the above-described problems, a flow sensor according to the present invention is a metal sensor having a recess for forming a flow path on the back surface and a sensor portion for measuring a flow rate on the surface via an insulating layer. A flow sensor comprising a chip and a metal flow path forming member that forms a flow path of a fluid to be measured integrated with the back surface of the sensor chip, the flow sensor including the flow path forming member and the periphery of the recess of the sensor chip Are in contact with each other with a constant width, and the contact portion forms a weld portion having a width substantially equal to the penetration depth of the welding beam.

  The flow path forming member comes into contact with the periphery of the recessed portion over the entire circumference of the recessed portion on the back surface of the sensor chip with a constant width, and the contact portion is between the sensor chip and the flow path forming member. A weld is formed. The width of the welded portion is substantially equal to the depth of the welding beam. Thereby, the dead space which is the contact part which is not welded can be eliminated. As a result, cleaning becomes easy and it can be used for products that require high cleanliness. Further, at the time of welding, joining with higher cleanliness can be performed by making the reducing gas atmosphere both inside and outside the penetration.

  In addition, since the amount of welding penetration can be minimized, thermal strain can be reduced and damage to the sensor device can be reduced.

  According to a second aspect of the present invention, there is provided a flow sensor according to the present invention, comprising a metal sensor chip having a recess for forming a flow channel on the back surface and a sensor portion for measuring a flow rate on the surface through an insulating layer; A flow sensor having a metal flow path forming member that forms a flow path of the fluid to be measured integrated with the back surface of the sensor chip, and has a welding beam penetration depth around the recess of the sensor chip. A bank-like welded portion having an equivalent width is formed.

  A bank-like welded portion is formed around the recess on the back surface of the sensor chip, and this overlapped portion is welded by bringing it into contact with the flow path forming member. Thereby, since it melt | dissolves over the perimeter of a dent part circumference | surroundings, the dead space which is a contact part which is not welded can be eliminated. As a result, cleaning becomes easy and it can be used for products that require high cleanliness. Further, at the time of welding, joining with higher cleanliness can be performed by making the reducing gas atmosphere both inside and outside the penetration.

  In addition, since the amount of welding penetration can be minimized, thermal strain can be reduced and damage to the sensor device can be reduced.

  According to a third aspect of the present invention, there is provided a flow sensor according to a third aspect of the present invention, comprising a metal sensor chip having a flow path forming recess on the back surface and a flow rate measuring sensor section formed on the surface, and the back surface of the sensor chip. And a metal flow path forming member that forms a flow path of the fluid to be measured, and a welding beam at a position corresponding to the periphery of the recess of the sensor chip of the flow path forming member A bank-like welded portion having a width substantially equal to the depth of is formed.

  Instead of forming a bank-shaped weld around the outer periphery of the recess of the sensor chip as in the flow sensor according to claim 2, the flow path forming member is welded to a position corresponding to the periphery of the recess of the sensor chip. A bank-like welded portion having a width substantially equal to the beam depth is formed, and a sensor chip is brought into contact with the welded portion to weld the overlapped portion. Also by this, since it melt | dissolves over the perimeter of a dent part, the dead space which is a contact part which is not welded can be eliminated. As a result, cleaning becomes easy and it can be used for products that require high cleanliness.

  By having the above-described configuration, the sensor chip can be welded to the flow path forming member with a minimum amount of heat without causing a dead space in the sensor chip. Therefore, heat input to the sensor device can be minimized, and the output characteristics of the sensor device can be stabilized.

  In addition, since there is no dead space at the contact portion between the sensor chip and the flow path forming member, residues such as welding residue and purge nitrogen gas do not remain in the dead space as in the past. There is no possibility of being mixed into the fluid to be measured as impurities during use of the flow sensor.

  Hereinafter, a flow sensor according to an embodiment of the present invention will be described.

  As shown in FIGS. 1 to 3, the flow sensor 1 according to the first embodiment of the present invention has a recess 112 for forming a flow path on the back surface and an oxide film (insulating layer) 120 on the surface. The sensor chip 110 made of stainless steel on which the sensor device 125 for flow rate measurement is formed, and the metal channel forming member 130 that forms a channel by integrating with the back surface of the sensor chip 110 are provided.

  The flow sensor 1 is characterized in that a sensor chip 110 having the same structure as the sensor chip 810 shown in FIG. 11 is welded to a flow path forming member 130 having a shape different from that of the flow path forming member 830 shown in FIG. Yes.

  Hereinafter, the structure of the sensor chip 110 and the flow path forming member 130 will be described. The sensor chip 110 is made of stainless steel such as SUS316L, and in the case of this embodiment, as shown in FIGS. 1A and 1B, a thin and long rectangular plate having a thickness of about 0.6 mm. A recess 112 is formed in the center of the back side of the sensor chip 110. The recess 112 has an oval shape (hereinafter simply referred to as a track outer periphery of a so-called athletics) composed of semicircular end portions 112a and 112b and two straight portions 112c and 112d connecting the both end portions in plan view. "Oval shape"). The semicircular end portions have such dimensions that the two flow paths 138 and 139 of the flow path forming member 130 are positioned at both ends of the recess when the sensor chip 110 is positioned on the flow path forming member 130 described later. It is formed on the chip 110. That is, the length of the recess 112 in the longitudinal direction corresponds to the distance between the two flow paths 138 and 139 of the flow path forming member 130. Further, the interval between the parallel straight portions 112c and 112d of the recess 112, that is, the width of the recess 112 is a dimension that is slightly larger than the diameter of the two flow paths 138 and 139 (see FIG. 3A). ).

  A thin portion 113 is formed in the sensor chip 110 by the recess 112. The thin portion 113 has a thickness of about 50 μm to 150 μm and forms a diaphragm structure sensor portion. The length in the direction perpendicular to the flow direction of the thin portion 113 (width) is preferably about 1 mm to 3 mm in terms of strength.

  The recess 112 of the sensor chip 110 and its periphery are formed by photolithography and etching techniques, an end mill, or a composite technique thereof. In the case of photolithography and etching techniques, first, a resist is applied to the entire back surface of a stainless steel wafer by spin coating or the like, or a dry film resist is applied, and ultraviolet (or electron beam) is irradiated to the resist. The mask pattern is transferred and exposed. Next, the exposed resist is developed with a developer, and unnecessary portions of the resist are removed. A negative resist or a positive resist is selected depending on whether to leave or remove the exposed portion. The portion where the resist has been removed exposes the wafer, and the portion thus derived is removed by wet etching or dry etching until the thickness reaches about 50 μm to 150 μm. Then, when the remaining resist is peeled off, removed, and washed, a thin portion 113 (recessed portion 112) is formed. In the case of wet etching, it is immersed or sprayed in an etching solution and gradually dissolved. In the case of dry etching, it can be formed by irradiating the back surface of the wafer with ions or electrons by sputtering, plasma, or the like and scraping it little by little.

  On the other hand, the opposite side surface of the thin portion 113 of the sensor chip 110 that is not in contact with the fluid to be measured is mirror-polished to form an oxide film (electrical insulating film) 120 over the entire surface. On the surface of the oxide film 120, a sensor device (sensor unit) 125 including a flow rate detecting means including a plurality of electrode pads and a metal thin film for wiring and an ambient temperature detecting means is formed by a well-known thin film molding technique. This is formed, for example, by depositing a material such as platinum on the surface of the electric insulating film and etching it into a predetermined pattern. The flow rate detecting means and the ambient temperature detecting means are respectively connected to the electrode pad via the wiring metal thin film. Electrically connected. Further, each electrode pad is connected to an electrode terminal of a printed wiring board provided via a spacer above the sensor chip 110 after welding the sensor chip 110 and the flow path forming member 130 via a bonding wire (not shown). (See spacer 840 and printed circuit board 850 in FIG. 10).

The oxide film 120 is formed of, for example, a thin silicon oxide (SiO ₂ ) film, silicon nitride film, alumina, polyimide film or the like having a thickness of about several thousand angstroms to several μm. The silicon oxide film can be formed by, for example, sputtering, CVD, or SOG (spin on glass). The silicon nitride film can be formed by sputtering, CVD, or the like.

  As shown in FIG. 8, the flow velocity detection means and the ambient temperature detection means formed on the oxide film 120 have a configuration using one heating element HT, and the flow velocity is converted into a voltage signal by using a constant temperature difference circuit. Can be converted. As shown in the figure, this constant temperature difference circuit includes resistors R1, R2, a heating element (resistance heater) HT, a resistor R3, an ambient temperature sensor TS, a bridge circuit, and a resistor R1 and a heating element HT. An operational amplifier OP1 having a point voltage as an inverting input and a midpoint voltage of the resistor R2 and the resistor R3 as a non-inverting input is provided. The output of the operational amplifier OP1 is commonly connected to one end of the resistors R1 and R2 constituting the bridge circuit. Has been. Here, the resistance values of the resistors R1, R2, and R3 are set so that the heating element HT is always higher than the ambient temperature sensor TS by a certain temperature.

  When the fluid is allowed to flow in a predetermined direction in this state, the heat generating element HT is deprived of heat by the fluid, the resistance value of the heat generating element HT is lowered, and the equilibrium state of the bridge circuit is lost. However, since a voltage corresponding to the voltage generated between the inverting input and the non-inverting input is applied to the bridge circuit by the operational amplifier OP1, the amount of heat generated by the heating element HT increases so as to compensate for the heat taken away by the fluid. As a result, the resistance value of the heating element HT increases, so that the bridge circuit returns to an equilibrium state. Therefore, a voltage corresponding to the flow velocity is applied to the bridge circuit in an equilibrium state. The constant temperature difference circuit in FIG. 8 outputs the voltage between the terminals of the heating element HT among the voltages applied to the bridge circuit at this time as a voltage output.

  Thus, the constant temperature difference circuit controls the current or voltage so that the temperature of the heating element HT is higher than the ambient temperature measured by the ambient temperature sensor TS to keep the temperature difference constant. Alternatively, the flow rate or flow rate of the fluid can be measured by detecting a power change.

  On the other hand, the flow path forming member 130 shown in FIG. 2 is made of an elongated metal plate made of stainless steel like the sensor chip 110 and has a rectangular shape in plan view whose outer shape matches the rectangular shape in plan view of the sensor chip 110 at the center of the surface. The first convex portion 131 is provided. Then, the upper surface of the first convex portion has an elliptical second shape whose overall length, width, and radius of curvature of the semicircular end portion are larger than the elliptical shape of the concave portion 112 of the sensor chip 110 in plan view. The convex part 132 is formed. In addition, two flow paths 138 and 139 are formed on the upper surface of the second convex portion 132 at a predetermined interval. Thus, when the sensor chip 110 is placed on the second convex portion 132 of the flow path forming member 130, the periphery of the concave portion of the sensor chip 110 and the second convex portion 132 of the flow path forming member 130 are shown in FIG. It comes to contact | abut in the area | region shown by the hatching of a). Hereinafter, this area is referred to as “contact area A”. The contact area A has a certain width that approximates the track shape of a so-called track and field event (hereinafter referred to as “track shape”) sandwiched between the first ellipse A1 and the second ellipse A2 that is larger than the first ellipse A1. It is an area. The width of the contact area A in which the sensor chip 110 comes into contact with the flow path forming member 130 is substantially the same as the penetration depth by laser beam welding.

  Hereinafter, a method of joining the sensor chip 110 and the flow path forming member 130 will be described. First, the sensor chip 110 is positioned on the second convex portion 132 of the flow path forming member 130 so that the above-described track-shaped contact region A is formed between the two. In this state, the laser beam is irradiated from the direction indicated by the arrow LB1 in FIG. 3 over the entire outer edge of the contact area. As a result, the sensor chip 110 and the flow path forming member 130 are melted in the contact area A and joined together to form a closed flow path between the sensor chip 110 and the flow path forming member 130. In welding, it is preferable to make a reducing gas atmosphere both inside and outside the penetration. As a result, it is possible to obtain a joint with high cleanliness.

  The state of the penetration depth of the welds thus welded is shown as hatching in FIG. 3 (a) and black triangle marks in FIG. 3 (b). As shown in the figure, the width of the contact area A (the width of the thick hatched portion in FIG. 3A) is the penetration depth by laser beam welding (the penetration depth represented by the black triangle in FIG. 3B). It can be seen that the contact area A coincides with the penetration area WD as a result.

  Then, the effect | action of the flow sensor 1 manufactured as mentioned above is demonstrated. As described above, a weld penetration portion WD (substantially) formed in a track shape between the second convex portion 132 of the flow path forming member 130 and the sensor chip 110 and having a width substantially matching the penetration depth by laser beam welding. The fine hatching area in FIG. 3A that is the same as the contact area A is formed over the entire circumference. In the case of the flow sensor 1 according to the present embodiment, the penetration depth is about half (about 0.3 mm) of the sensor chip 110 having a thickness of 0.6 mm. In addition, a so-called dead space DS as shown in FIG. 13 in which impurities enter and remain in the vicinity of this region does not occur (in FIG. 3A, there is no rough hatching region corresponding to FIG. 13A). That is, the flow sensor 1 is geometrically zero in volume, but does not actually have a dead space DS with a slight gap. If the dead space DS can be eliminated, cleaning becomes easy and the product can be used for products that require high cleanliness. That is, the retention of the process fluid is less likely to occur, so the purge characteristics are improved, and the process fluid can be suitably used for products that require high cleanliness such as mass flow meters used in the semiconductor industry.

  Thus, in addition to eliminating the dead space DS, the amount of welding penetration can be reduced, so that thermal strain can be suppressed and damage to the sensor device can be avoided. Further, since it does not have a conventional structure in which a fixed portion is formed by welding outside the dead space DS, pressure is applied to the diaphragm portion of the sensor chip 110 from the fluid to be measured as in the conventional case, and the sensor is accordingly detected. There is no inconvenience that the gap of the inner dead space DS becomes larger or smaller with the welded joint between the tip 110 and the flow path forming member 130 as a fulcrum. Therefore, there is no inconvenience that heat does not transfer from the sensor chip 110 to the flow path forming member 130 by changing the contact area between the sensor chip and the flow path forming member in accordance with the deformation phenomenon of the sensor chip. As a result, the heat transfer system of the entire flow sensor due to this does not break. As a result, the sensitivity of the sensor device can always be kept good, and the output characteristics of the flow sensor can be maintained at a high level.

  Subsequently, a flow sensor according to a second embodiment of the present invention will be described. In addition, about the structure equivalent to the flow sensor concerning the 1st Embodiment of this invention, corresponding code | symbol is attached | subjected to drawing and detailed description is abbreviate | omitted.

  As shown in FIG. 4, the flow sensor 2 according to the second embodiment of the present invention has a recess 212 for forming a flow channel on the back surface, and measures the flow rate via an oxide film (insulating film) 220 on the front surface. The sensor chip 210 made of stainless steel in which the sensor device 225 for use is formed, and a metal flow path forming member 230 that forms a flow path integrally with the back surface of the sensor chip 210 are provided.

  The flow sensor 2 is characterized in that a sensor chip 210 having a shape different from that of the sensor chip 110 shown in FIG. 1 is welded to a flow path forming member 230 having the same structure as the flow path forming member 830 shown in FIG. Yes.

  Hereinafter, the structure of the sensor chip 210 and the flow path forming member 230 will be described. The sensor chip 210 has the same basic configuration as that of the sensor chip 110 according to the first embodiment. However, as shown in FIG. 4A, the welding beam is melted around the recess 212 of the sensor chip 210. A bank-like welded portion 215 having a width substantially equal to the depth is formed in a so-called track shape. The width of the bank-like welded portion 215 is about half of the thickness of the sensor chip 210, and in the case of the present embodiment, it is about 0.3 mm and is substantially equal to the welding penetration amount as described above.

  On the other hand, the flow path forming member 230 partially shown in FIG. 4B is made of an elongated metal plate made of stainless steel like the sensor chip 210, and has an outer shape with a rectangular shape in plan view of the sensor chip 210 at the center of the surface. The projection 231 has a rectangular shape in plan view and protrudes so as to substantially match, and two channels 238 and 239 are formed in the projection 231.

  Then, the sensor chip 210 is positioned on the convex portion 231 of the flow path forming member 230 so that the welded portion 215 of the sensor chip 210 surrounds the convex portion side openings around the flow paths 238 and 239 of the flow path forming member 230. As a result, the sensor chip 210 contacts the flow path forming member 230 only at the welded portion 215. Then, this contact region becomes a track-shaped contact region A having a width substantially equal to the penetration depth of the welding beam over the entire circumference as in the first embodiment. Next, the entire circumference of the outer peripheral edge of the contact area A is irradiated with a laser beam as indicated by an arrow LB2 in FIG. 4C, so that a track-like welding area having a width substantially equal to the penetration depth of the welding beam. WD is formed and the sensor chip 210 is joined to the flow path forming member 230. As a result, the sensor device is formed on one surface of the sensor chip 210, and the flow sensor 2 can flow the fluid to be measured through the other surface, that is, the flow path formed by the sensor chip 210 and the flow path forming member 230. Can be obtained.

  In the flow sensor 2 welded as described above, a so-called dead space DS in which impurities enter and remain between the flow path forming member 230 and the sensor chip 210 is not generated as in the first embodiment. Thus, in addition to eliminating the dead space DS, the amount of welding penetration can be reduced, so that thermal strain can be suppressed and damage to the sensor device can be avoided. Further, if the dead space DS can be made almost zero, cleaning becomes easy and it can be used for products that require high cleanliness.

  Further, since the deformation phenomenon of the sensor chip 225 received from the fluid to be measured as in the conventional case does not occur, the heat transfer system of the entire flow sensor due to this phenomenon does not occur. As a result, the sensitivity of the sensor device 225 can always be kept good, and the output characteristics of the flow sensor 2 can be maintained at a high level.

  Subsequently, a flow sensor according to a third embodiment of the present invention will be described. In addition, about the structure equivalent to the flow sensor concerning embodiment mentioned above, a corresponding code | symbol is attached | subjected to drawing and detailed description is abbreviate | omitted.

  As shown in FIG. 5, the flow sensor 3 according to the third embodiment of the present invention has a recess portion 312 for forming a flow path on the back surface, and measures the flow rate via an oxide film (insulating film) 320 on the front surface. For example, a sensor chip 310 made of stainless steel on which a sensor device 325 is formed, and a metal channel forming member 330 that forms a channel by being integrated with the back surface of the sensor chip 310.

  The flow sensor 3 welds the sensor chip 310 having the same shape as the sensor chip 210 according to the second embodiment to the flow path forming member 330 having the same structure as the flow path forming member 130 according to the first embodiment. It is characterized by that.

  Hereinafter, the structure of the sensor chip 310 and the flow path forming member 330 will be described. Like the sensor chip 210 according to the second embodiment, the sensor chip 310 has a width substantially equal to the penetration depth of the welding beam as shown in FIG. 5A around the recess 312 of the sensor chip 310. A bank-like welded portion 315 having a track shape is formed. The width of the bank-like welded portion 315 is about half of the thickness of the sensor chip 310, and in the case of the present embodiment, it is about 0.3 mm and is substantially equal to the welding penetration amount as described above. .

  On the other hand, the flow path forming member 330 partially shown in FIG. 5B is made of a long and narrow stainless steel plate, like the flow path forming member 130 according to the first embodiment, and has an outer shape at the center of the surface. The chip 310 has a first convex portion 331 having a rectangular shape in plan view that matches the outer shape of the rectangular shape in plan view. Then, on the upper surface of the first convex portion, an oval second convex portion 332 having a length, a width, and a radius of curvature larger than the ellipse of the concave portion 312 of the sensor chip 310 in a plan view is formed. Has been. Further, the above-described two flow paths 338 and 339 are formed at predetermined intervals on the upper surface of the second convex portion 332. Thus, when the sensor chip 310 is placed on the second convex portion 332 of the flow path forming member 330, the welded portion 315 of the sensor chip 310 and the second convex portion 332 of the flow path forming member 330 are shown in FIG. The contact is made in the contact area A having the track shape of a). The width of the track-like region is substantially the same as the penetration depth by laser beam welding as in the above-described embodiment.

  When the flow sensor 310 and the flow path forming member 330 are joined, first, the sensor chip 310 is attached to the flow path forming member 330 such that the welded portion 315 of the sensor chip 310 matches the second convex portion 332 of the flow path forming member 330. Position to. As a result, both contact with each other in the track-like contact area A having a width substantially equal to the penetration depth of the welding beam over the entire circumference as in the first embodiment. Next, the entire circumference of the outer peripheral edge of the contact area A is irradiated with a laser beam as shown by an arrow LB3 in FIG. 5C, so that a track-shaped welding area having a width substantially equal to the penetration depth of the welding beam. WD is formed and the sensor chip 310 is joined to the flow path forming member 330. As a result, the sensor device 325 is formed on one surface of the sensor chip 310, and the flow sensor capable of flowing the fluid to be measured through the other surface, that is, the flow path formed by the sensor chip 310 and the flow path forming member 330. 3 can be obtained.

  In the flow sensor 3 welded as described above, a so-called dead space DS in which impurities enter and remain between the flow path forming member 330 and the sensor chip 310 does not occur as in the first embodiment. Thus, in addition to eliminating the dead space DS, the amount of welding penetration can be reduced, so that thermal strain can be suppressed and damage to the sensor device 325 can be avoided. Further, if the dead space DS can be made almost zero, cleaning becomes easy and it can be used for products that require high cleanliness.

  Further, since the deformation phenomenon of the sensor chip 325 received from the fluid to be measured as in the conventional case does not occur, the heat transfer system of the entire flow sensor due to this phenomenon does not occur. As a result, the sensitivity of the sensor device 325 can always be kept good, and the output characteristics of the flow sensor 3 can be maintained at a high level.

  In addition to this, the peripheral surface to be laser-welded is a width (height H1 in FIG. 5C) obtained by combining the height of the second convex portion 332 in the flow path forming member 330 and the height of the welded portion 315 in the sensor chip 310. Therefore, the peripheral surface area to be laser-welded is wider than the flow sensors 1 and 2 according to the above-described embodiment, and the additional merit that the laser welding work is facilitated is generated.

  Subsequently, a flow sensor according to a fourth embodiment of the present invention will be described. In addition, about the structure equivalent to the flow sensor concerning embodiment mentioned above, a corresponding code | symbol is attached | subjected to drawing and detailed description is abbreviate | omitted.

  As shown in FIG. 6, the flow sensor according to the fourth embodiment of the present invention has a recess 412 for forming a flow channel on the back surface, and is used for flow measurement via an oxide film (insulating film) 420 on the front surface. The sensor chip 410 made of stainless steel on which the sensor device 425 is formed, and a metal flow path forming member 430 that forms a flow path integrally with the back surface of the sensor chip 410 are provided.

  The flow sensor 4 welds the sensor chip 410 having the same structure as the sensor chip 110 according to the first embodiment to the flow path forming member 430 having a structure different from that of the flow path forming member 330 according to the third embodiment. It is characterized by that.

  The sensor chip 410 is formed in a thin and elongated rectangular plate shape with a plate thickness of about 0.6 mm, and a recess 412 is formed at the center of the back side of the sensor chip 410. The shape of the recess 412 in plan view has an oval shape.

  On the other hand, the flow path forming member 430 partially shown in FIG. 6B is made of a long and narrow stainless steel plate, like the flow path forming member according to the above-described embodiment, and has an outer shape at the center of the surface. A convex portion 431 having a rectangular shape in plan view that matches the outer shape of the rectangular shape in plan view is formed. In addition, the above-described embodiment is such that a bank-like welded convex portion 435 having a length, a width, and a radius of curvature larger than the concave portion 412 of the sensor chip 410 in a plan view is formed on the upper surface of the convex portion. The configuration differs from that of the flow path forming member. In addition, two flow paths 438 and 439 are formed at predetermined intervals inside the welding projection 435. Accordingly, when the sensor chip 410 is placed on the welding convex portion 435 of the flow path forming member 430, the periphery of the concave portion of the sensor chip 410 and the welding convex portion 435 of the flow path forming member 430 are tracked as shown in FIG. It comes to contact in the contact area A. The welding width of the contact area A is a width that substantially matches the penetration depth by laser beam welding, as in the above-described embodiment.

  In joining the sensor chip 410 to the flow path forming member 430, the sensor chip 410 is positioned on the flow path forming member 440 such that the periphery of the recess of the sensor chip 410 abuts on the welding convex portion 435 of the flow path forming member 430. As a result, both contact with each other in the track-like contact area A having a width substantially equal to the penetration depth of the welding beam over the entire circumference as in the first embodiment. Next, the entire circumference of the outer peripheral edge of the contact area A is irradiated with a laser beam as shown by an arrow LB4 in FIG. 6C, so that a track-like welding area having a width substantially equal to the penetration depth of the welding beam. WD is formed and the sensor chip 410 is joined to the flow path forming member 430. As a result, the sensor device 425 is formed on one surface of the sensor chip 410, and the flow sensor capable of flowing the fluid to be measured through the other surface, that is, the flow path formed by the sensor chip 410 and the flow path forming member 430. 4 can be obtained.

  In the flow sensor 4 welded as described above, a so-called dead space DS in which impurities enter and remain between the flow path forming member 430 and the sensor chip 410 does not occur as in the first embodiment. Thus, in addition to eliminating the dead space DS, the amount of welding penetration can be reduced, so that thermal strain can be suppressed and damage to the sensor device 425 can be avoided. Further, if the dead space DS can be made almost zero, cleaning becomes easy and it can be used for products that require high cleanliness.

  Further, since the deformation phenomenon of the sensor chip 410 received from the fluid to be measured as in the conventional case does not occur, the heat transfer system of the entire flow sensor due to this phenomenon does not occur. As a result, the sensitivity of the sensor device 425 can always be kept good, and the output characteristics of the flow sensor 4 can be maintained at a high level.

  Subsequently, a flow sensor according to a fifth embodiment of the present invention will be described. In addition, about the structure equivalent to the flow sensor concerning the 5th Embodiment of this invention, corresponding code | symbol is attached | subjected to drawing and detailed description is abbreviate | omitted.

  As shown in FIG. 7, the flow sensor 5 according to the fifth embodiment of the present invention has a recess 512 for forming a flow channel on the back surface, and measures the flow rate through an oxide film (insulating layer) 520 on the front surface. The sensor chip 510 made of stainless steel on which the detection unit 525 is formed and the metal flow path forming member 530 that forms a flow path integrally with the back surface of the sensor chip 510 are provided.

  The flow sensor 5 welds the sensor chip 510 having the same structure as the sensor chip 210 according to the second embodiment to the flow path forming member 530 having the same structure as the flow path forming member 430 according to the fourth embodiment. It is characterized by that.

  As with the sensor chip according to the second embodiment, the sensor chip 510 has a bank-like weld having a width substantially equal to the penetration depth of the welding beam as shown in FIG. A portion 515 is formed in a track shape. The width of the bank-like welded portion 515 is about half of the thickness of the sensor chip 510, and in the case of the present embodiment, it is about 0.3 mm and is substantially equal to the welding penetration amount as described above.

  On the other hand, the flow path forming member 530 partially shown in FIG. 7B is made of a long and narrow stainless steel plate, like the flow path forming member 430 according to the fourth embodiment, and has an outer shape at the center of the surface. A convex portion 531 having a rectangular shape in plan view that matches the outer shape of the chip 510 having a rectangular shape in plan view is provided. A bank-like welded portion 535 having a length, a width, and a curvature radius that matches the bank-like welded portion 515 of the sensor chip 510 in a plan view is formed in a track shape on the upper surface of the convex portion. In addition, two flow paths 538 and 539 are formed at predetermined intervals in a region surrounded by the welded portion 535. As a result, when the sensor chip 510 is positioned at an appropriate position on the flow path forming member 530, the contact portion where the welded portion 515 of the sensor chip 510 and the welded portion 535 of the flow path forming member 530 form the track shape of FIG. A comes in contact. And this width | variety is a width | variety which corresponds substantially with the penetration depth by laser beam welding similarly to the above-mentioned embodiment.

  In joining the sensor chip 510 to the flow path forming member 530, first, the sensor chip 510 is positioned on the flow path forming member 530 so that the welded portion 515 of the sensor chip 510 matches the welded portion 535 of the flow path forming member 530. As a result, both contact with each other in the track-like contact area A having a width substantially equal to the penetration depth of the welding beam over the entire circumference as in the first embodiment. Next, the entire circumference of the outer peripheral edge of the contact area A is irradiated with a laser beam as shown by an arrow LB5 in FIG. 7C, so that a track-like welding area having a width substantially equal to the penetration depth of the welding beam. WD is formed and the sensor chip 510 is joined to the flow path forming member 530. Accordingly, the sensor device 525 is formed on one surface of the sensor chip 510, and the flow sensor capable of flowing the fluid to be measured through the other surface, that is, the flow path formed by the sensor chip 510 and the flow path forming member 530. 5 can be obtained.

  As in the first to fourth embodiments, the flow sensor 5 welded as described above has no so-called dead space DS in which impurities enter and remain between the flow path forming member 530 and the sensor chip 510. Thus, in addition to eliminating the dead space DS, the amount of welding penetration can be reduced, so that thermal strain can be suppressed and damage to the sensor device 525 can be avoided. Further, if the dead space DS can be made almost zero, cleaning becomes easy and it can be used for products that require high cleanliness.

  Further, since the deformation phenomenon of the sensor chip 510 received from the fluid to be measured as in the conventional case does not occur, the heat transfer system of the entire flow sensor due to this phenomenon does not occur. As a result, the sensitivity of the sensor device 525 can always be kept good, and the output characteristics of the flow sensor 5 can be maintained at a high level.

  In addition to this, the peripheral surface to be laser-welded has a width (see height H2 in FIG. 7C) obtained by combining the height of the welded portion 535 in the flow path forming member 530 and the height of the welded portion 515 in the sensor chip 510. Since it is formed as a region having a peripheral surface region to be laser-welded becomes wider than the flow sensors 1, 2, and 4 according to the first, second, and fourth embodiments described above, it is easy to perform laser welding work. An additional merit is generated.

  The flow sensor according to the present embodiment is particularly suitable for measuring the flow velocity or flow rate of the corrosive fluid flowing in the flow path, but is not limited to this, for example, measurement of gas containing a lot of dust and the like. Thus, the present invention can also be applied to flow rate measurement in the case where the sensor device unit cannot be brought into direct contact with the fluid to be measured.

It is the top view (Drawing 1 (a)) which looked at the sensor chip of the flow sensor concerning a 1st embodiment of the present invention from the dent part side, and the sectional view (Drawing 1 (b)) along the longitudinal direction center line. . The top view (Drawing 2 (a)) which showed the channel formation member of the flow sensor concerning a 1st embodiment of the present invention partially, and a partial section along the longitudinal direction center line of Drawing 2 (a) It is a figure (FIG.2 (b)). FIG. 3A is a view transparently showing the penetration depth from above the sensor chip when the sensor chip shown in FIG. 1 is welded to the flow path forming member shown in FIG. ) Is a cross-sectional view taken along the longitudinal center line (FIG. 3B). It is the figure which showed the flow sensor concerning the 2nd Embodiment of this invention, the top view (FIG.4 (a)) which looked at the sensor chip from the dent part side, and the top view which showed the flow-path formation member partially (FIG. 4B), and a sectional view (FIG. 4C) showing a state in which the sensor chip is welded to the flow path forming member along the longitudinal center line. It is the figure which showed the flow sensor concerning the 3rd Embodiment of this invention, and is the top view (FIG.5 (a)) which looked at the sensor chip from the dent part side, The top view which showed the flow-path formation member partially (FIG. 5B), and a cross-sectional view (FIG. 5C) showing a state in which the sensor chip is welded to the flow path forming member along the longitudinal center line. It is the figure which showed the flow sensor concerning the 4th Embodiment of this invention, the top view (FIG. 6 (a)) which looked at the sensor chip from the dent part side, and the top view which showed the flow-path formation member partially (FIG. 6B), and a cross-sectional view (FIG. 6C) showing a state in which the sensor chip is welded to the flow path forming member along the longitudinal center line. It is the figure which showed the flow sensor concerning the 5th Embodiment of this invention, and the top view (FIG.7 (a)) which looked at the sensor chip from the dent part side, The top view which showed the flow-path formation member partially It is sectional drawing (FIG.7 (c)) which showed the state which welded the sensor chip to the flow-path formation member (FIG.7 (b)) and the longitudinal direction centerline. It is the circuit diagram which showed the sensor device of the flow sensor concerning the 1st thru | or 5th embodiment of this invention. It is sectional drawing which showed the structure of the conventional flow sensor. It is sectional drawing which showed the improved flow sensor of the flow sensor shown in FIG. It is the top view (Drawing 11 (a)) which looked at the sensor chip of the flow sensor shown in Drawing 10 from the dent side, and the sectional view (Drawing 11 (b)) along the longitudinal direction center line. FIG. 12 is a partial plan view (FIG. 12A) and a partial cross-sectional view (FIG. 12B) of the flow path forming member of the flow sensor shown in FIG. 10. FIG. 13A is a plan view transparently showing the penetration depth from above the sensor chip when the sensor chip shown in FIG. 11 is welded to the flow path forming member shown in FIG. It is sectional drawing (FIG.13 (b)) shown along the line. It is the top view (Drawing 14 (a)) which showed the state which melted deeper than the penetration depth of Drawing 13 from the upper part of a sensor chip, and the sectional view (Drawing 14 (b)) shown along the longitudinal direction center line. .

Explanation of symbols

1-5 Flow sensor 110, 210, 310, 410, 510 Sensor chip 112, 212, 312, 412, 512 Recessed part 120, 220, 320, 420, 520 Oxide film 125, 225, 325, 425, 525 Sensor device 130 , 230, 330, 430, 530 Channel forming member 131, 231, 331, 431, 531 Convex part 132, 332 Convex part 138, 139, 238, 239, 338, 339, 438, 439, 538, 539 Channel 215 , 315,515 Welded part 435,535 Welded part

Claims (3)

A metal sensor chip having a recess for forming a flow path on the back surface and a sensor unit for flow rate measurement formed on the front surface via an insulating layer, and the flow of the fluid to be measured integrated with the back surface of the sensor chip A flow sensor comprising a metal flow path forming member that forms a path,
The flow path forming member and the periphery of the recess of the sensor chip are in contact with each other with a constant width, and the contact portion forms a weld portion having a width substantially equal to the penetration depth of the welding beam. A flow sensor characterized by A metal sensor chip having a recess for forming a flow path on the back surface and a sensor unit for flow rate measurement formed on the front surface via an insulating layer, and the flow of the fluid to be measured integrated with the back surface of the sensor chip A flow sensor comprising a metal flow path forming member that forms a path,
A flow sensor characterized in that a bank-like welded portion having a width substantially equal to the penetration depth of the welding beam is formed around the recess of the sensor chip. A metal sensor chip having a recess for forming a flow path on the back surface and a sensor unit for flow rate measurement formed on the front surface via an insulating layer, and the flow of the fluid to be measured integrated with the back surface of the sensor chip A flow sensor comprising a metal flow path forming member that forms a path,
A flow sensor characterized in that a bank-like welded portion having a width substantially equal to the depth of the welding beam is formed at a position corresponding to the periphery of the recessed portion of the sensor chip of the flow path forming member.

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