WO2016017290A1 - Pressure sensor - Google Patents
Pressure sensor Download PDFInfo
- Publication number
- WO2016017290A1 WO2016017290A1 PCT/JP2015/066652 JP2015066652W WO2016017290A1 WO 2016017290 A1 WO2016017290 A1 WO 2016017290A1 JP 2015066652 W JP2015066652 W JP 2015066652W WO 2016017290 A1 WO2016017290 A1 WO 2016017290A1
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- WIPO (PCT)
- Prior art keywords
- sensor
- diaphragm
- sensor chip
- joint
- pressure sensor
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- 230000002093 peripheral effect Effects 0.000 claims description 7
- 230000035945 sensitivity Effects 0.000 abstract description 15
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Classifications
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
- G01L9/00—Measuring steady of quasi-steady pressure of fluid or fluent solid material by electric or magnetic pressure-sensitive elements; Transmitting or indicating the displacement of mechanical pressure-sensitive elements, used to measure the steady or quasi-steady pressure of a fluid or fluent solid material, by electric or magnetic means
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L29/00—Semiconductor devices specially adapted for rectifying, amplifying, oscillating or switching and having potential barriers; Capacitors or resistors having potential barriers, e.g. a PN-junction depletion layer or carrier concentration layer; Details of semiconductor bodies or of electrodes thereof ; Multistep manufacturing processes therefor
- H01L29/66—Types of semiconductor device ; Multistep manufacturing processes therefor
- H01L29/84—Types of semiconductor device ; Multistep manufacturing processes therefor controllable by variation of applied mechanical force, e.g. of pressure
Definitions
- the present invention relates to a pressure sensor that detects the deformation of a diaphragm that receives pressure.
- a pressure sensor having a structure in which a strain gauge is formed on a diaphragm is well known.
- This pressure sensor detects the pressure by utilizing the fact that the resistance of the strain gauge changes due to the deformation of the diaphragm due to the pressure.
- a bridge circuit is constituted by four strain gauges, and pressure is detected by obtaining a differential voltage output proportional to the pressure from the bridge circuit.
- the bridge circuit is mainly used for temperature compensation. This is because if the four strain gauges have the same change, the output of the bridge circuit does not change even if the strain gauge has temperature characteristics.
- a stainless steel diaphragm is used, and a semiconductor strain gauge is attached to the diaphragm or a semiconductor strain gauge is formed.
- a pressure sensor with a chip attached is often used.
- the configuration in which the sensor chip is attached has a great advantage compared to the configuration having the signal processing IC separately from the strain gauge. Since the signal processing circuit can be built in the sensor chip, the transmission path from the strain gauge to the processing circuit is short, and noise can be reduced. In addition, since the temperature sensor can be built in the vicinity of the strain gauge, the temperature of the strain gauge can be measured accurately and the accuracy of temperature compensation can be increased.
- Patent Document 1 discloses that a sensor chip made of a single crystal semiconductor having a strain gauge formed thereon is joined on a circular metal diaphragm.
- the sensor chip is larger than the diaphragm, and the sensor chip is joined so that the strain gauge on the sensor chip is disposed on the periphery of the diaphragm.
- two of the four strain gauges are arranged in the circumferential direction and the other two are arranged in the radial direction, so that the stress generated in the strain gauge by applying pressure is respectively
- the sensor sensitivity is obtained by compressive stress and tensile stress. Further, it is disclosed that the adverse effect of thermal stress caused by the difference in linear expansion coefficient between the sensor chip and the diaphragm can be eliminated as much as possible by making the shape of the sensor chip as close to a circle as possible.
- Patent Document 2 also discloses a pressure sensor in which a semiconductor substrate having a strain gauge is attached to the surface of a metal diaphragm.
- the semiconductor substrate has a structure in which a first semiconductor layer and a second semiconductor layer are joined via an insulating layer, a strain gauge is formed in the first semiconductor layer, and a recess reaching the insulating layer is formed in the second semiconductor layer.
- the diaphragm enters the recess and is joined to the insulating layer on the bottom surface of the recess.
- the diaphragm is joined to the sensor chip over the entire area.
- Low-melting glass or metal solder is used for the bonding, but in order to bond the entire diaphragm area to the sensor chip, the bonding layer is sufficient to absorb the waviness of the bonding surface and to suppress the generation of voids. Need to be thick. When the thickness of the bonding layer is reduced with respect to the bonding area, the deformation of the diaphragm with respect to the pressure to be measured is hindered. Further, when the entire diaphragm is joined to the sensor chip, deformation of the entire diaphragm is hindered by the rigidity of the sensor chip.
- the sensor chip is limited in thickness in consideration of prevention of warpage and cracking in the wafer state and handling during bonding. Even if the diaphragm is thinned to increase sensitivity, it is difficult to obtain high sensitivity due to the high rigidity of the sensor chip. By increasing the size of the sensor chip, the size of the diaphragm can also be increased, and the sensitivity can be increased even if the diaphragm is thick. However, increasing the sensor chip unnecessarily increases the cost.
- Patent Document 2 discloses that the sensitivity is improved by partially thinning the sensor chip.
- a bonding layer is disclosed in order to join the sensor chip having a recess and the diaphragm shaped to enter the recess without any gap. There is a concern that deformation of the diaphragm is hindered by the bonding layer.
- the stress due to the difference in thermal expansion of the constituent materials becomes a problem.
- the sensor chip is usually made of silicon, and the diaphragm is made of metal such as stainless steel. Since the low melting point glass or metal solder of the bonding layer and the sensor chip and the diaphragm have different linear expansion coefficients, thermal stress remains after bonding at a high temperature. If the bonding layer is thick, the thermal stress increases, and deformation due to stress relaxation of the bonding layer increases. Therefore, there is a concern that the characteristic drift due to long-term stress relaxation increases and accuracy deteriorates.
- An object of the present invention is to improve the sensitivity by suppressing the deformation of the diaphragm by the rigidity of the bonding layer and the sensor chip in the pressure sensor having the structure in which the sensor chip is bonded to the diaphragm, and the stress generated in the bonded portion. It is to improve the accuracy by reducing the change of.
- a pressure sensor of the present invention is a pressure sensor having a sensor casing having a diaphragm, a sensor chip provided on the sensor casing, and a strain gauge provided on the sensor chip.
- the sensor chip is connected to the sensor housing via a thin joint, the area of the joint is smaller than the areas of the sensor chip and the diaphragm, and the strain gauge is a projection surface of the joint It is arranged inside.
- FIG. 1A the center line along the X axis is the X center line 10
- the center line along the Y axis is the Y center line 11, and FIG. Yes.
- the pressure sensor 1 has a configuration in which a rectangular sensor chip 4 is joined via a joining portion 5 on a metal sensor housing 3 on which a diaphragm 2 is formed.
- the outer shape of the diaphragm 2 is indicated by a dotted line.
- the sensor chip 4 has a gauge region 6 at the center of the surface not joined to the diaphragm 2, and has four strain gauges 7 (first to fourth strain gauges 7 a to 7 d) in the gauge region 6.
- the four strain gauges 7 are connected by a wiring (not shown) and constitute a Wheatstone bridge circuit shown in FIG.
- the diaphragm 2 has a shape having a short side and a long side, and the short side direction is an X axis and the long side direction is a Y axis.
- the gauge region 6 is disposed on the central portion of the diaphragm 2.
- the first strain gauge 7 a and the second strain gauge 7 b are arranged so that the short direction (X-axis direction) of the diaphragm 2 is the current direction, and the third strain gauge 7 c and the fourth strain gauge 7 d are the longitudinal direction of the diaphragm 2. They are arranged so that (Y-axis direction) is the current direction.
- the joint 5 is circular as shown by a dotted line in FIG. 1A and is disposed on the center of the diaphragm 2. In the planar configuration shown in FIG. 1A, the gauge region 6 is included in the joint portion 5, and the joint portion 5 is included in the sensor chip 4.
- the stress of the strain gauge 7 changes due to the deformation of the diaphragm 2 with respect to the pressure applied to the surface opposite to the joint surface of the sensor chip 4 of the diaphragm 2.
- an output proportional to the pressure is obtained as a differential output of the bridge circuit.
- the sensor housing 3 including the diaphragm 2 is made of a metal such as stainless steel.
- the sensor housing 3 has a cylindrical shape, the center portion is processed from one side, and the thin remaining portion is the diaphragm 2.
- As the processing method cutting, electric discharge machining, press working, or the like can be used.
- An R shape is formed at the end of the processed surface of the diaphragm 2 and has a function of relaxing stress concentration generated at the end when pressure is applied.
- the sensor chip 4 is manufactured from a single crystal silicon substrate, and the strain gauge 7 is a p-type silicon piezoresistive gauge manufactured by impurity diffusion.
- a silicon substrate having a crystal plane (100) is used so that the X-axis and the Y-axis coincide with ⁇ 110> of the silicon crystal axis. Therefore, the first to fourth strain gauges 7a to 7d are all piezoresistive gauges in the p-type silicon ⁇ 110> direction.
- Metal solder such as Au / Sn is used for the bonding layer 5.
- the Ni / Au film is formed on the bonding surface of the sensor chip 4 by sputtering, and the Au film is formed on the bonding area of the sensor chip 4 of the diaphragm 2 by plating. Positioning is performed with / Sn sandwiched, and heating is performed to melt Au / Sn to join.
- the bonding layer 5 can also be a low melting point glass.
- the pressure sensor according to the present invention is characterized in that the diaphragm 2 and the sensor chip 4 are partially joined by a joint 5 having a small area.
- the joint 5 has a smaller area than the diaphragm 2 and a smaller area than the sensor chip 4.
- the gauge region 6 is arranged at a position included in the projection plane in the z direction of the joint 5 so that the strain due to the deformation of the diaphragm 2 is transmitted to the strain gauge 7. In this configuration, since the area of the joint portion 5 can be reduced, even if the joint portion 5 is thin, the generation of voids and unjoined portions can be suppressed and the joining can be performed with high reliability.
- the joint portion 5 Since the joint portion 5 is thin, the rigidity of the joint portion 5 is difficult to prevent the diaphragm 2 from being deformed, and the sensitivity of the pressure sensor can be increased. In addition, since the diaphragm 2 and the sensor chip 4 are only partially joined, the rigidity of the sensor chip 4 is unlikely to hinder the deformation of the diaphragm 2 and the sensitivity can be increased.
- the joint portion 5 is thin, there is a feature that the change in sensor characteristics is suppressed and the accuracy is increased. Since the joint portion 5 has a linear expansion coefficient different from that of the sensor housing 3 and the sensor chip 4, thermal residual stress due to the joint is generated. If this stress is large, the sensor characteristics are likely to change due to a long-term stress change. . Since the joint 5 is thin, the stress can be reduced, and deformation due to stress relaxation can be reduced, so that long-term fluctuations in sensor characteristics can be reduced.
- the joint 5 is thin, there is an effect of suppressing variations in sensor characteristics. If the joint portion 5 is thick, the warp of the sensor chip 4 tends to remain after joining, and the sensor characteristics also change due to the warp. If the joint portion 5 is thin, the sensor chip 4 is hardly warped, and variations in sensor characteristics can be suppressed.
- the joint portion 5 is thin, the amount of material used for the joint portion 5 can be reduced.
- the pressure sensor of the present invention is characterized in that the sensitivity can be increased by making the diaphragm 2 sufficiently large with respect to the joint 5.
- the size of the diaphragm cannot be increased due to the size of the sensor chip, and it is necessary to make the diaphragm thinner in order to increase sensitivity.
- the size of the diaphragm 2 can be increased regardless of the size of the sensor chip 4, so that the sensitivity can be increased without reducing the thickness of the diaphragm 2.
- the pressure sensor of the present invention is characterized in that the joint portion 5 is arranged at a position where the strain generated in the diaphragm 2 with respect to the pressure is different between the X-axis direction and the Y-axis direction.
- the joint 5 is arranged at the center of the diaphragm 2 having a long side and a short side. The distortion at the center of the diaphragm 2 with respect to the pressure is greater in the short X-axis direction than in the long Y-axis direction.
- the gauge region 6 is arranged at a position where a strain difference between the X axis and the Y axis is generated, and the four strain gauges 7 are concentratedly arranged in the gauge region 6. Even if the area is small, all four strain gauges 7 can be appropriately given a strain change due to pressure.
- the output change due to the temperature change is reduced, and the long-term sensor characteristic change is suppressed to increase the accuracy. effective. Since the diaphragm 2 and the sensor chip 4 have different linear expansion coefficients, thermal distortion occurs due to temperature changes. When the thermal strain generated in the gauge region 6 differs between the X axis and the Y axis, the sensor output changes, that is, it has temperature characteristics. If the joint 5 has an isotropic shape with respect to the X-axis and the Y-axis, the thermal strain generated in the sensor chip 4 is also nearly isotropic, so that the temperature characteristics can be reduced.
- the bonding portion 5 has an isotropic shape, the change in strain of the sensor chip 4 due to the relaxation is close to isotropic. And accuracy can be increased.
- the shape of the joint is not limited to a circle, but may be a square or a shape with R added to the corner of the square.
- peripheral circuits such as an output amplifier, a current source, an A / D conversion, an output correction circuit, a memory for storing correction values, a temperature sensor, and the like can be built in, in addition to a bridge circuit.
- amplification of the output signal, temperature correction, zero point correction, etc. can be performed, and the accuracy of the output signal can be increased.
- the temperature correction since the strain gauge 7 and the temperature sensor can be formed on the same sensor chip 4, the temperature of the strain gauge 7 can be accurately measured, and the temperature correction can be performed with high accuracy.
- the material since the diaphragm 2 and the sensor housing 3 that receive pressure are made of stainless steel, the material has a high yield strength, and it is easy to construct a sensor with a high pressure measurement range. It can also be used when the liquid or gas to be measured is highly corrosive.
- the material of the stainless steel can be selected by selecting a precipitation hardening type stainless steel such as SUS630 when importance is attached to the proof stress and selecting a stainless steel having high corrosion resistance such as SUS316 when importance is attached to the corrosion resistance. Further, the material is not limited to stainless steel, and various steel types can be selected in consideration of proof stress, corrosion resistance, difference in linear expansion coefficient from silicon, and the like.
- the material of the bonding layer 5 and the bonding process are not limited to the materials and processes described above.
- the metal solder for example, Au / Ge solder or Au / Si solder can be used to further reduce the creep deformation of the bonding layer 5.
- the joining process there is a method in which metal solder is directly formed on the rear surface of the diaphragm or sensor chip by plating or the like in addition to the above method using the metal solder pellets.
- a second embodiment of the present invention will be described with reference to FIG. The description of the same configuration as in the first embodiment is omitted.
- 3 (a) and 3 (b) show a plan view and a cross-sectional view of a second embodiment of the pressure sensor 1 of the present invention.
- 3A the center line along the X axis is the X center line 10
- the center line along the Y axis is the Y center line 11
- FIG. 3B shows a cross-sectional view along the X center line 10. Yes.
- the surface of the sensor housing 2 has a convex portion 12 having substantially the same shape as the joint portion 5, and the convex portion 12 is joined to the sensor chip 2 via the joint portion 5.
- the convex part 12 By providing the convex part 12, there exists an effect which becomes easy to control the shape of the junction part 5 to the shape of the convex part 12.
- FIG. The case where metal solder is used for the joint portion 5 will be described.
- the metal solder uses a thin pellet, or is thinly formed in advance on the surface of the sensor chip 4 or the surface of the sensor housing 3, and is heated and melted. Join.
- the gap between the sensor housing 3 and the sensor chip 4 is increased around the convex portion 12, so that the metal solder does not wet and spread.
- the joint portion 5 is formed in accordance with the shape of the convex portion 12.
- the joint portion 5 By making the convex portion 12 isotropic with respect to the X axis and the Y axis, the joint portion 5 can also have the same shape.
- a third embodiment of the present invention will be described with reference to FIG. The description of the same configuration as in the first embodiment is omitted.
- FIG. 4 (a) and 4 (b) show a plan view and a sectional view of a third embodiment of the pressure sensor 1 of the present invention.
- the center line along the X axis is the X center line 10
- the center line along the Y axis is the Y center line 11
- FIG. 4B shows a cross-sectional view along the X center line 10. Yes.
- the thin part 13 is formed on the sensor chip 4 in the region including the gauge region 6.
- a thick portion 14 is formed so as to surround the thin portion 13.
- the thick portion 14 has a shape that can include the convex portion 12, and the thin portion 13 of the sensor chip 2 and the convex portion 12 on the sensor housing 3 are joined via the joint portion 5.
- the sensor chip 4 has a recess or groove formed on the back side of the surface on which the strain gauge 7 is formed in the region including the gauge region 6, and the bottom of the recess or groove of the sensor chip 4 and the protrusion 12. Are joined via the joint 5.
- the thickness of the portion of the sensor chip 4 that is joined to the sensor housing 3 can be reduced, so that the deformation of the diaphragm 2 is less likely to be hindered by the rigidity of the sensor chip 4, thereby further improving sensitivity.
- the sensor chip 4 can also be made sufficiently thin compared to the thickness of the diaphragm 2, so that thermal deformation due to temperature change causes the sensor chip 4 and the joint 5 to follow the deformation of the diaphragm 2. It becomes a shape. As a result, the distortion generated in the sensor chip 4 due to the temperature change becomes nearly isotropic, and the temperature characteristics can be reduced. In addition, the change in sensor characteristics due to the relaxation of the thermal residual stress at the time of joining becomes nearly isotropic, and the accuracy is improved.
- the sensor chip 4 is thin. However, if the sensor chip 4 is made thin as a whole, warping and cracking in the wafer state and handling at the time of bonding become difficult. There is. By leaving the thick portion 14 around the periphery as in this configuration, the sensor chip having the thickness of the thick portion 14 can be handled to the same extent.
- the depth of the concave portion formed in the thin-walled portion 13, that is, the difference in thickness between the thick-walled portion 14 and the thin-walled portion 13 is the same as the sum of the thicknesses of the convex portion 12 and the joint portion 5, but is desirably small.
- the thickness of the bonding layer 5 can be determined to be constant. it can.
- the bonding layer 5 is thin, the change in the thickness of the bonding portion 5 due to the pressing load of the sensor chip 4 is not large, so even if each thickness is determined so that the thick portion 14 does not contact the sensor housing 3, It can be manufactured without increasing variations in sensor characteristics.
- a fourth embodiment of the present invention will be described with reference to FIG. The description of the same configuration as in the first embodiment is omitted.
- FIG. 5 (a) and 5 (b) show a plan view and a cross-sectional view of a third embodiment of the pressure sensor 1 of the present invention.
- 5A the center line along the X axis is the X center line 10
- the center line along the Y axis is the Y center line 11
- FIG. 5B is a cross-sectional view along the X center line 10. Yes.
- the convex part 12 is configured by forming a groove 15 in the sensor housing 3 so as to surround the convex part 12. Further, the outer peripheral side of the groove 15 is formed in a shape that can contain the sensor chip 4. By forming the outer peripheral side wall of the groove 15 slightly larger along the outer shape of the sensor chip 4, the sensor chip 4 can be used for positioning when the sensor chip 4 is joined. By doing so, it is not necessary to separately prepare a positioning jig when the sensor chip 4 is joined, and the sensor chip 4 can be easily and accurately positioned.
- the outer shape of the groove 15 is not limited to the shape along the entire outer periphery of the sensor chip 4, and only the portion necessary for positioning needs to be close to the sensor chip 4.
- a fifth embodiment of the present invention will be described with reference to FIG. The description of the same configuration as in the first embodiment is omitted.
- FIG. 6 shows a sectional view of a fifth embodiment of the pressure sensor of the present invention.
- the present embodiment shows a configuration example of a pressure sensor assembly 21 in which the pressure sensors described in the first to fourth embodiments are assembled in a product form.
- the sensor housing 3 has a cylindrical portion 22 whose outer peripheral portion extends downward in a cylindrical shape, and a flange portion 23 and a screw portion 24 are installed on the outer surface. It is integrally formed in the shape.
- the threaded portion 24 is a male thread, and a female threaded joint (not shown) is prepared and attached to the pipe to be measured.
- a pressure introduction port 25 is formed inside the cylindrical portion 22, and a liquid or gas to be measured is introduced to the surface of the diaphragm 2 through the pressure introduction port 25.
- a wiring board 26 is disposed on the upper surface of the sensor housing 3 so as to be adjacent to the sensor chip 4.
- the wiring board 26 is bonded and held on the upper surface of the sensor housing 3 by an adhesive 27.
- the sensor chip 4 and the electrode pads of the wiring board 26 are electrically connected by wires 28.
- a cylindrical cover 29 is connected to the flange portion 23 of the sensor housing 3 to protect the surface of the sensor chip 4 and its peripheral portion.
- a plurality of external electrode pins 30 are provided at the upper end of the cover 29 so as to penetrate the cover 29.
- the external electrode pins 30 and the wiring board 26 are electrically connected via a flexible wiring board 31.
- the sensor chip 4 transmits a signal to the outside via the wire 28, the wiring board 26, the flexible wiring board 31, and the external electrode pin 30.
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Abstract
To provide a pressure sensor having high sensitivity, little characteristics variation, and good accuracy and having a configuration whereby a sensor chip is joined to a sensor case having a diaphragm. The pressure sensor has: the sensor case having the diaphragm; the sensor chip provided upon the sensor case; and a strain gauge provided upon the sensor chip. The sensor chip is connected to the sensor case via a thin join section; the area of the join section is smaller than the area of the sensor chip and the diaphragm; and the strain gauge is arranged inside the projection plane of the join section.
Description
本発明は、圧力を受けたダイアフラムの変形を利用して検出する圧力センサに関する。
The present invention relates to a pressure sensor that detects the deformation of a diaphragm that receives pressure.
ダイアフラム上に歪ゲージを形成した構成の圧力センサがよく知られている。この圧力センサは、圧力によるダイアフラムの変形により歪ゲージの抵抗が変化することを利用して圧力を検出する。一般的に、4つの歪ゲージでブリッジ回路を構成し、このブリッジ回路から圧力に比例した差動電圧出力を得ることで圧力を検出している。ここで、ブリッジ回路は主に温度補償を目的に用いられる。これは、4つの歪ゲージの変化が同じであれば、歪ゲージが温度特性を有していてもブリッジ回路の出力が変化しないからである。
A pressure sensor having a structure in which a strain gauge is formed on a diaphragm is well known. This pressure sensor detects the pressure by utilizing the fact that the resistance of the strain gauge changes due to the deformation of the diaphragm due to the pressure. In general, a bridge circuit is constituted by four strain gauges, and pressure is detected by obtaining a differential voltage output proportional to the pressure from the bridge circuit. Here, the bridge circuit is mainly used for temperature compensation. This is because if the four strain gauges have the same change, the output of the bridge circuit does not change even if the strain gauge has temperature characteristics.
1 MPa程度以上の高圧用、あるいは耐食性が必要でシリコンを露出させられない用途などには、ステンレス製のダイアフラムを用い、ダイアフラム上に半導体歪ゲージを貼り付けるか、あるいは半導体歪ゲージを形成したセンサチップを貼り付けた構成の圧力センサがよく用いられる。特に、センサチップを貼り付けた構成は、歪ゲージと別に信号処理ICを有する構成と比較して利点が大きい。センサチップ内に信号処理回路を内蔵できるので、歪ゲージから処理回路までの伝送路が短く、ノイズを小さくできる。また、温度センサも歪ゲージの近くに内蔵できるので、歪ゲージの温度が正確に測定でき、温度補償の精度を高くできる。
For high pressure of about 1 MPa or more, or for applications where corrosion resistance is required and silicon cannot be exposed, a stainless steel diaphragm is used, and a semiconductor strain gauge is attached to the diaphragm or a semiconductor strain gauge is formed. A pressure sensor with a chip attached is often used. In particular, the configuration in which the sensor chip is attached has a great advantage compared to the configuration having the signal processing IC separately from the strain gauge. Since the signal processing circuit can be built in the sensor chip, the transmission path from the strain gauge to the processing circuit is short, and noise can be reduced. In addition, since the temperature sensor can be built in the vicinity of the strain gauge, the temperature of the strain gauge can be measured accurately and the accuracy of temperature compensation can be increased.
特許文献1は、円形の金属製ダイアフラムの上に、歪ゲージを形成した単結晶半導体製のセンサチップを接合することを開示している。なお、センサチップはダイアフラムよりサイズが大きく、センサチップ上の歪ゲージが、ダイアフラム周辺部上に配置されるようにセンサチップが接合されている。特許文献2によると、4つの歪ゲージのうち2つを円周方向に向けて配置し、他の2つを半径方向に向けて配置することで、圧力印加により歪ゲージに発生する応力がそれぞれ圧縮応力と引張応力になり、センサ感度が得られるようにしている。さらに、センサチップの形状を、なるべく円形に近い多角形とすることで、センサチップとダイアフラムの線膨脹係数差に起因した熱応力の悪影響を極力排除できることが開示されている。
Patent Document 1 discloses that a sensor chip made of a single crystal semiconductor having a strain gauge formed thereon is joined on a circular metal diaphragm. The sensor chip is larger than the diaphragm, and the sensor chip is joined so that the strain gauge on the sensor chip is disposed on the periphery of the diaphragm. According to Patent Document 2, two of the four strain gauges are arranged in the circumferential direction and the other two are arranged in the radial direction, so that the stress generated in the strain gauge by applying pressure is respectively The sensor sensitivity is obtained by compressive stress and tensile stress. Further, it is disclosed that the adverse effect of thermal stress caused by the difference in linear expansion coefficient between the sensor chip and the diaphragm can be eliminated as much as possible by making the shape of the sensor chip as close to a circle as possible.
また、特許文献2にも金属製のダイアフラムの表面に歪ゲージを有する半導体基板を取り付けた圧力センサが開示されている。半導体基板は第1の半導体層と第2の半導体層を絶縁層を介して接合した構成とし、第1の半導体層に歪ゲージを形成し、第2の半導体層に絶縁層まで達する凹部を形成し、ダイアフラムが凹部に入り込んで凹部の底面の絶縁層に接合されている。
Patent Document 2 also discloses a pressure sensor in which a semiconductor substrate having a strain gauge is attached to the surface of a metal diaphragm. The semiconductor substrate has a structure in which a first semiconductor layer and a second semiconductor layer are joined via an insulating layer, a strain gauge is formed in the first semiconductor layer, and a recess reaching the insulating layer is formed in the second semiconductor layer. The diaphragm enters the recess and is joined to the insulating layer on the bottom surface of the recess.
上記のような従来の圧力センサにおいては、ダイアフラムが全域にわたってセンサチップと接合されている。その接合には、低融点ガラスや金属はんだなどが用いられるが、ダイアフラムの全域をセンサチップと接合するためには、接合面のうねりの吸収や、ボイドの発生の抑制のため、接合層が十分に厚い必要がある。接合面積に対して接合層厚さが薄くなると、測定対象の圧力に対するダイアフラムの変形を妨げるので、感度が低くなりやすい。また、ダイアフラム全域がセンサチップに接合されていると、ダイアフラム全域の変形がセンサチップの剛性により妨げられる。センサチップはウエハ状態での反りや割れの防止や、接合時のハンドリングなどを考慮すると薄くするのに限界がある。感度を高くするためにダイアフラムを薄くしても、センサチップの剛性が高いために高い感度を得にくい。センサチップのサイズを大きくすることで、ダイアフラムのサイズも大きくでき、ダイアフラムが厚くても感度を高くできるが、センサチップを不要に大きくすることはコストの増加を招く。
In the conventional pressure sensor as described above, the diaphragm is joined to the sensor chip over the entire area. Low-melting glass or metal solder is used for the bonding, but in order to bond the entire diaphragm area to the sensor chip, the bonding layer is sufficient to absorb the waviness of the bonding surface and to suppress the generation of voids. Need to be thick. When the thickness of the bonding layer is reduced with respect to the bonding area, the deformation of the diaphragm with respect to the pressure to be measured is hindered. Further, when the entire diaphragm is joined to the sensor chip, deformation of the entire diaphragm is hindered by the rigidity of the sensor chip. The sensor chip is limited in thickness in consideration of prevention of warpage and cracking in the wafer state and handling during bonding. Even if the diaphragm is thinned to increase sensitivity, it is difficult to obtain high sensitivity due to the high rigidity of the sensor chip. By increasing the size of the sensor chip, the size of the diaphragm can also be increased, and the sensitivity can be increased even if the diaphragm is thick. However, increasing the sensor chip unnecessarily increases the cost.
特許文献2には、センサチップを部分的に薄くして感度を向上させることが開示されているが、凹部を有するセンサチップと凹部に入り込む形状のダイアフラムを隙間なく接合するためには、接合層を十分に厚くする必要があり、接合層によりダイアフラムの変形が妨げられる懸念がある。
Patent Document 2 discloses that the sensitivity is improved by partially thinning the sensor chip. However, in order to join the sensor chip having a recess and the diaphragm shaped to enter the recess without any gap, a bonding layer is disclosed. There is a concern that deformation of the diaphragm is hindered by the bonding layer.
また、センサチップをダイアフラムに接合した構造の圧力センサでは、構成材料の熱膨張差による応力が課題となる。センサチップは通常シリコン製で、ダイアフラムはステンレスなどの金属で製作される。接合層の低融点ガラスや金属はんだと、センサチップおよびダイアフラムはそれぞれ線膨張係数が異なるので、高温で接合した後に熱応力が残留する。接合層が厚いと、上記熱応力が大きくなると共に、接合層の応力緩和による変形が大きくなるので、長期的な応力緩和による特性のドリフトが大きくなって精度が悪化する懸念がある。
Also, in a pressure sensor having a structure in which a sensor chip is joined to a diaphragm, the stress due to the difference in thermal expansion of the constituent materials becomes a problem. The sensor chip is usually made of silicon, and the diaphragm is made of metal such as stainless steel. Since the low melting point glass or metal solder of the bonding layer and the sensor chip and the diaphragm have different linear expansion coefficients, thermal stress remains after bonding at a high temperature. If the bonding layer is thick, the thermal stress increases, and deformation due to stress relaxation of the bonding layer increases. Therefore, there is a concern that the characteristic drift due to long-term stress relaxation increases and accuracy deteriorates.
本発明の目的は、センサチップをダイアフラムに接合した構造の圧力センサにおいて、接合層およびセンサチップの剛性によりダイアフラムの変形が妨げられることを抑制して感度を向上するとともに、接合部に発生する応力の変化を低減して精度を向上することである。
An object of the present invention is to improve the sensitivity by suppressing the deformation of the diaphragm by the rigidity of the bonding layer and the sensor chip in the pressure sensor having the structure in which the sensor chip is bonded to the diaphragm, and the stress generated in the bonded portion. It is to improve the accuracy by reducing the change of.
上記課題を解決するために本発明の圧力センサは、ダイアフラムを有するセンサ筐体と、前記センサ筐体上に設けられるセンサチップと、センサチップ上に設けられる歪ゲージと、を有する圧力センサであって、前記センサチップは薄い接合部を介して前記センサ筐体に接続されており、前記接合部の面積は前記センサチップおよび前記ダイアフラムの面積よりも小さく、前記歪ゲージは前記接合部の投影面内に配置されていることを特徴とする。
In order to solve the above problems, a pressure sensor of the present invention is a pressure sensor having a sensor casing having a diaphragm, a sensor chip provided on the sensor casing, and a strain gauge provided on the sensor chip. The sensor chip is connected to the sensor housing via a thin joint, the area of the joint is smaller than the areas of the sensor chip and the diaphragm, and the strain gauge is a projection surface of the joint It is arranged inside.
本発明によれば、感度が高く、特性変化が小さく精度のよい圧力センサを実現することができる。
According to the present invention, it is possible to realize a pressure sensor with high sensitivity, small characteristic change, and high accuracy.
図1(a)および(b)は、本発明の圧力センサの第一実施例の平面図および断面図を示している。図1(a)において、X軸に沿った中心線をX中心線10、Y軸に沿った中心線をY中心線11とし、図1(b)はX中心線10における断面図を示している。圧力センサ1は、ダイアフラム2が形成された金属製のセンサ筐体3上に、方形状のセンサチップ4を接合部5を介して接合した構成となっている。図1(a)には、ダイアフラム2の外形を点線で示している。センサチップ4には、ダイアフラム2と接合しない側の表面の中央部にゲージ領域6を有し、ゲージ領域6内に4つの歪ゲージ7(第1~第4歪ゲージ7a~7d)を有する。4つの歪ゲージ7は、図示されていない配線で接続され、図2に示すホイートストンブリッジ回路を構成している。ダイアフラム2は短手と長手を有する形状であり、短手方向をX軸、長手方向をY軸としている。ゲージ領域6はダイアフラム2の中央部上に配置されている。第1歪ゲージ7aおよび第2歪ゲージ7bはダイアフラム2の短手方向(X軸方向)が電流方向となるように配置され、第3歪ゲージ7cおよび第4歪ゲージ7dはダイアフラム2の長手方向(Y軸方向)が電流方向となるように配置されている。接合部5は、図1(a)に点線で示すように円形状で、ダイアフラム2の中央部上に配置されている。図1(a)に示す平面構成において、ゲージ領域6は接合部5に内包され、接合部5はセンサチップ4に内包されている。
1 (a) and 1 (b) show a plan view and a sectional view of a first embodiment of the pressure sensor of the present invention. In FIG. 1A, the center line along the X axis is the X center line 10, the center line along the Y axis is the Y center line 11, and FIG. Yes. The pressure sensor 1 has a configuration in which a rectangular sensor chip 4 is joined via a joining portion 5 on a metal sensor housing 3 on which a diaphragm 2 is formed. In FIG. 1A, the outer shape of the diaphragm 2 is indicated by a dotted line. The sensor chip 4 has a gauge region 6 at the center of the surface not joined to the diaphragm 2, and has four strain gauges 7 (first to fourth strain gauges 7 a to 7 d) in the gauge region 6. The four strain gauges 7 are connected by a wiring (not shown) and constitute a Wheatstone bridge circuit shown in FIG. The diaphragm 2 has a shape having a short side and a long side, and the short side direction is an X axis and the long side direction is a Y axis. The gauge region 6 is disposed on the central portion of the diaphragm 2. The first strain gauge 7 a and the second strain gauge 7 b are arranged so that the short direction (X-axis direction) of the diaphragm 2 is the current direction, and the third strain gauge 7 c and the fourth strain gauge 7 d are the longitudinal direction of the diaphragm 2. They are arranged so that (Y-axis direction) is the current direction. The joint 5 is circular as shown by a dotted line in FIG. 1A and is disposed on the center of the diaphragm 2. In the planar configuration shown in FIG. 1A, the gauge region 6 is included in the joint portion 5, and the joint portion 5 is included in the sensor chip 4.
圧力センサ1は、ダイアフラム2のセンサチップ4接合面と反対側の面に印加された圧力に対して、ダイアフラム2が変形することで歪ゲージ7の応力が変化し、それに伴って歪ゲージ7の抵抗が変化することで、ブリッジ回路の差動出力として圧力に比例した出力が得られる仕組みとなっている。
In the pressure sensor 1, the stress of the strain gauge 7 changes due to the deformation of the diaphragm 2 with respect to the pressure applied to the surface opposite to the joint surface of the sensor chip 4 of the diaphragm 2. By changing the resistance, an output proportional to the pressure is obtained as a differential output of the bridge circuit.
ダイアフラム2を含むセンサ筐体3はステンレスなどの金属を材質とする。センサ筐体3は円筒形をしており、中央部を片面から加工し、薄く残った部分がダイアフラム2となっている。加工方法には、切削や放電加工、あるいはプレス加工などを用いることができる。ダイアフラム2の加工された側の面の端部には、R形状が形成されており、圧力印加時に端部に発生する応力集中を緩和する働きがある。
The sensor housing 3 including the diaphragm 2 is made of a metal such as stainless steel. The sensor housing 3 has a cylindrical shape, the center portion is processed from one side, and the thin remaining portion is the diaphragm 2. As the processing method, cutting, electric discharge machining, press working, or the like can be used. An R shape is formed at the end of the processed surface of the diaphragm 2 and has a function of relaxing stress concentration generated at the end when pressure is applied.
センサチップ4は単結晶シリコン基板を材料として製作され、歪ゲージ7は、不純物拡散により製作された、p型シリコンのピエゾ抵抗ゲージである。シリコン基板は結晶面(100)のものを用い、X軸およびY軸が、シリコン結晶軸の<110>と一致するようにしている。よって第1~第4歪ゲージ7a~7dは、全てp型シリコン<110>方向のピエゾ抵抗ゲージである。
The sensor chip 4 is manufactured from a single crystal silicon substrate, and the strain gauge 7 is a p-type silicon piezoresistive gauge manufactured by impurity diffusion. A silicon substrate having a crystal plane (100) is used so that the X-axis and the Y-axis coincide with <110> of the silicon crystal axis. Therefore, the first to fourth strain gauges 7a to 7d are all piezoresistive gauges in the p-type silicon <110> direction.
接合層5にはAu/Snなどの金属はんだが用いられている。接合のプロセスは、例えば、センサチップ4の接合面にNi/Au膜をスパッタで形成しておき、ダイアフラム2のセンサチップ4接合領域にはAu膜をめっきで形成しておき、ペレット状のAu/Snを挟んで位置合わせし、加熱してAu/Snを溶融することで接合する。また、接合層5には、低融点ガラスを用いることもできる。
Metal solder such as Au / Sn is used for the bonding layer 5. For example, the Ni / Au film is formed on the bonding surface of the sensor chip 4 by sputtering, and the Au film is formed on the bonding area of the sensor chip 4 of the diaphragm 2 by plating. Positioning is performed with / Sn sandwiched, and heating is performed to melt Au / Sn to join. The bonding layer 5 can also be a low melting point glass.
本発明の圧力センサにおいては、ダイアフラム2とセンサチップ4が、面積の小さい接合部5により部分的に接合されることに特徴がある。接合部5はダイアフラム2よりも面積が小さく、またセンサチップ4よりも面積が小さい。ダイアフラム2の変形によるひずみが歪ゲージ7に伝わるように、ゲージ領域6は、接合部5のz方向の投影面内に内包される位置に配置されている。本構成では、接合部5の面積を小さくできるため、接合部5が薄くても、ボイドや未接合部の発生を抑えて信頼性よく接合が可能である。接合部5が薄いため、接合部5の剛性によりダイアフラム2の変形が妨げられにくく、圧力センサの感度を高くすることができる。また、ダイアフラム2とセンサチップ4が部分的にしか接合されないので、センサチップ4の剛性によりダイアフラム2の変形が妨げられにくく、感度を高くすることができる。
The pressure sensor according to the present invention is characterized in that the diaphragm 2 and the sensor chip 4 are partially joined by a joint 5 having a small area. The joint 5 has a smaller area than the diaphragm 2 and a smaller area than the sensor chip 4. The gauge region 6 is arranged at a position included in the projection plane in the z direction of the joint 5 so that the strain due to the deformation of the diaphragm 2 is transmitted to the strain gauge 7. In this configuration, since the area of the joint portion 5 can be reduced, even if the joint portion 5 is thin, the generation of voids and unjoined portions can be suppressed and the joining can be performed with high reliability. Since the joint portion 5 is thin, the rigidity of the joint portion 5 is difficult to prevent the diaphragm 2 from being deformed, and the sensitivity of the pressure sensor can be increased. In addition, since the diaphragm 2 and the sensor chip 4 are only partially joined, the rigidity of the sensor chip 4 is unlikely to hinder the deformation of the diaphragm 2 and the sensitivity can be increased.
また、接合部5が薄いことにより、センサ特性の変化を抑制して精度が高くなる特徴がある。接合部5はセンサ筐体3やセンサチップ4と線膨張係数が異なるため、接合による熱残留応力が発生するが、この応力が大きいと、長期的な応力の変化によりセンサ特性が変化しやすくなる。接合部5が薄いことにより、上記応力が低減でき、また応力緩和による変形も小さくできるので、長期的なセンサ特性の変動を小さくできる。
Also, since the joint portion 5 is thin, there is a feature that the change in sensor characteristics is suppressed and the accuracy is increased. Since the joint portion 5 has a linear expansion coefficient different from that of the sensor housing 3 and the sensor chip 4, thermal residual stress due to the joint is generated. If this stress is large, the sensor characteristics are likely to change due to a long-term stress change. . Since the joint 5 is thin, the stress can be reduced, and deformation due to stress relaxation can be reduced, so that long-term fluctuations in sensor characteristics can be reduced.
また、接合部5が薄いことにより、センサ特性のばらつき抑制の効果がある。接合部5が厚いと、接合後にセンサチップ4の反りが残留しやすく、反りによりセンサ特性も変化する。接合部5が薄くなれば、センサチップ4が反りにくくセンサ特性のばらつきを抑えられる。
Also, since the joint 5 is thin, there is an effect of suppressing variations in sensor characteristics. If the joint portion 5 is thick, the warp of the sensor chip 4 tends to remain after joining, and the sensor characteristics also change due to the warp. If the joint portion 5 is thin, the sensor chip 4 is hardly warped, and variations in sensor characteristics can be suppressed.
また、接合部5が薄いことにより、接合部5の材料の使用量を少なくすることができる。
Also, since the joint portion 5 is thin, the amount of material used for the joint portion 5 can be reduced.
また本発明の圧力センサは、ダイアフラム2を接合部5に対して十分大きくできることで感度を高くできる特徴がある。ダイアフラム全体をセンサチップに接合する従来の圧力センサでは、ダイアフラムの寸法がセンサチップの寸法に制約されて大きくできず、感度を大きくするにはダイアフラムを薄くする必要があった。本発明では、センサチップ4の寸法に拠らず、ダイアフラム2の寸法を大きくできるので、ダイアフラム2を薄くしなくても感度を高くできる。ダイアフラム2を薄くしなくて済むことで、ダイアフラム2の加工がしやすく、厚さばらつきによるセンサ特性のばらつきを低減できる、温度変化によるセンサ出力変化を低減できるなどの効果がある。
Also, the pressure sensor of the present invention is characterized in that the sensitivity can be increased by making the diaphragm 2 sufficiently large with respect to the joint 5. In the conventional pressure sensor in which the entire diaphragm is joined to the sensor chip, the size of the diaphragm cannot be increased due to the size of the sensor chip, and it is necessary to make the diaphragm thinner in order to increase sensitivity. In the present invention, the size of the diaphragm 2 can be increased regardless of the size of the sensor chip 4, so that the sensitivity can be increased without reducing the thickness of the diaphragm 2. By eliminating the need for making the diaphragm 2 thinner, it is easy to process the diaphragm 2, and it is possible to reduce variations in sensor characteristics due to variations in thickness, and to reduce changes in sensor output due to temperature changes.
また本発明の圧力センサは、圧力に対してダイアフラム2に発生する歪が、X軸方向とY軸方向で差が出る位置に、接合部5が配置されていることに特徴がある。本実施例においては、長手と短手を有するダイアフラム2の中心に接合部5が配置されている。圧力に対するダイアフラム2中央の歪は、短手であるX軸方向が、長手であるY軸方向よりも大きくなる。よって、電流方向をX軸方向に合わせた第1歪ゲージ7aおよび第2歪ゲージ7bと、電流方向をY軸方向に合わせた第3歪ゲージ7cおよび第4歪ゲージ7dとの間で、発生する応力が異なり、応力変化に応じた抵抗変化量が異なるため、センサ感度を得ることができる。本実施例のように、X軸とY軸の歪差が発生する位置にゲージ領域6を配置し、4つの歪ゲージ7をゲージ領域6に集中配置した構成とすることで、接合部5の面積が小さくても、4つの歪ゲージ7全てに圧力による歪変化を適切に与えることができる。
Further, the pressure sensor of the present invention is characterized in that the joint portion 5 is arranged at a position where the strain generated in the diaphragm 2 with respect to the pressure is different between the X-axis direction and the Y-axis direction. In the present embodiment, the joint 5 is arranged at the center of the diaphragm 2 having a long side and a short side. The distortion at the center of the diaphragm 2 with respect to the pressure is greater in the short X-axis direction than in the long Y-axis direction. Therefore, it is generated between the first strain gauge 7a and the second strain gauge 7b whose current direction is aligned with the X-axis direction, and the third strain gauge 7c and the fourth strain gauge 7d whose current direction is aligned with the Y-axis direction. Since the stress to be applied is different and the resistance change amount corresponding to the stress change is different, the sensor sensitivity can be obtained. As in this embodiment, the gauge region 6 is arranged at a position where a strain difference between the X axis and the Y axis is generated, and the four strain gauges 7 are concentratedly arranged in the gauge region 6. Even if the area is small, all four strain gauges 7 can be appropriately given a strain change due to pressure.
また、接合部5の形状をX軸およびY軸に対して等方的な円形状とすることで、温度変化による出力変化を小さくし、長期的なセンサ特性の変化を抑えて精度を高くする効果がある。ダイアフラム2とセンサチップ4は線膨張係数が異なるため、温度変化により熱歪が発生する。ゲージ領域6に発生する熱歪がX軸とY軸で差が出ると、センサ出力が変化し、すなわち温度特性を持つことになる。接合部5がX軸およびY軸に対して等方的な形状であると、センサチップ4に発生する上記熱歪も等方に近くなるので、温度特性を小さくすることができる。また、上述した接合時の熱残留応力の緩和についても、接合部5が等方形状であると、緩和の影響によるセンサチップ4の歪変化も等方に近くなるので、センサ特性の変化を小さくでき、精度を高くできる。接合部の形状は円形に限らず、正方形や、正方形の角にRをつけた形状などとしてもよい。
In addition, by making the shape of the joint portion 5 isotropic with respect to the X axis and the Y axis, the output change due to the temperature change is reduced, and the long-term sensor characteristic change is suppressed to increase the accuracy. effective. Since the diaphragm 2 and the sensor chip 4 have different linear expansion coefficients, thermal distortion occurs due to temperature changes. When the thermal strain generated in the gauge region 6 differs between the X axis and the Y axis, the sensor output changes, that is, it has temperature characteristics. If the joint 5 has an isotropic shape with respect to the X-axis and the Y-axis, the thermal strain generated in the sensor chip 4 is also nearly isotropic, so that the temperature characteristics can be reduced. Further, regarding the relaxation of the thermal residual stress at the time of bonding described above, if the bonding portion 5 has an isotropic shape, the change in strain of the sensor chip 4 due to the relaxation is close to isotropic. And accuracy can be increased. The shape of the joint is not limited to a circle, but may be a square or a shape with R added to the corner of the square.
センサチップ4には、ブリッジ回路だけでなく、出力アンプ、電流源、A/D変換、出力補正回路、補正値を格納するメモリ、温度センサなど、周辺回路を作り込むことができる。上記のような信号処理回路をセンサチップ4内に有することにより、出力信号の増幅や温度補正、ゼロ点補正などが行え、出力信号の精度を高くすることができる。温度補正においては、歪ゲージ7と温度センサを同じセンサチップ4上に形成できるので、歪ゲージ7の温度を正確に測定でき、温度補正を高い精度で行うことができる。
In the sensor chip 4, peripheral circuits such as an output amplifier, a current source, an A / D conversion, an output correction circuit, a memory for storing correction values, a temperature sensor, and the like can be built in, in addition to a bridge circuit. By having the signal processing circuit as described above in the sensor chip 4, amplification of the output signal, temperature correction, zero point correction, etc. can be performed, and the accuracy of the output signal can be increased. In the temperature correction, since the strain gauge 7 and the temperature sensor can be formed on the same sensor chip 4, the temperature of the strain gauge 7 can be accurately measured, and the temperature correction can be performed with high accuracy.
本実施例では、圧力を受けるダイアフラム2およびセンサ筐体3がステンレス製であるため、材料の耐力が高く、高い圧力測定範囲のセンサを構成しやすい。また、測定対象の液体や気体の腐食性が高い場合にも使用できる。ステンレスの種類は、耐力を重視する場合はSUS630など析出硬化型のステンレスを選び、耐腐食性を重視する場合はSUS316など、耐腐食性の高いステンレスを選ぶなど、材質を選択できる。また、材質はステンレスに限ったものではなく、耐力や耐腐食性、シリコンとの線膨脹係数差などを考慮して、様々な鋼種を選択できる。
In this embodiment, since the diaphragm 2 and the sensor housing 3 that receive pressure are made of stainless steel, the material has a high yield strength, and it is easy to construct a sensor with a high pressure measurement range. It can also be used when the liquid or gas to be measured is highly corrosive. The material of the stainless steel can be selected by selecting a precipitation hardening type stainless steel such as SUS630 when importance is attached to the proof stress and selecting a stainless steel having high corrosion resistance such as SUS316 when importance is attached to the corrosion resistance. Further, the material is not limited to stainless steel, and various steel types can be selected in consideration of proof stress, corrosion resistance, difference in linear expansion coefficient from silicon, and the like.
また、接合層5の材質および接合プロセスについても、上述した材質、プロセスに限るものではない。金属はんだでは、例えばAu/Geはんだや、Au/Siはんだを用いることで、接合層5のクリープ変形をより小さくすることができる。接合プロセスについては、上述の金属はんだのペレットを用いる方法以外にも、金属はんだを直接ダイアフラムまたはセンサチップ裏面にめっきなどで形成する方法などがある。
Also, the material of the bonding layer 5 and the bonding process are not limited to the materials and processes described above. In the metal solder, for example, Au / Ge solder or Au / Si solder can be used to further reduce the creep deformation of the bonding layer 5. As for the joining process, there is a method in which metal solder is directly formed on the rear surface of the diaphragm or sensor chip by plating or the like in addition to the above method using the metal solder pellets.
本発明の第二実施例を、図3を用いて説明する。なお、第一実施例と同様の構成は説明を省略する。
A second embodiment of the present invention will be described with reference to FIG. The description of the same configuration as in the first embodiment is omitted.
図3(a)および(b)は、本発明の圧力センサ1の第二実施例の平面図および断面図を示している。図3(a)において、X軸に沿った中心線をX中心線10、Y軸に沿った中心線をY中心線11とし、図3(b)はX中心線10における断面図を示している。
3 (a) and 3 (b) show a plan view and a cross-sectional view of a second embodiment of the pressure sensor 1 of the present invention. 3A, the center line along the X axis is the X center line 10, the center line along the Y axis is the Y center line 11, and FIG. 3B shows a cross-sectional view along the X center line 10. Yes.
センサ筐体2の表面に接合部5とほぼ同形状の凸部12を有し、凸部12において、センサチップ2と接合部5を介して接合する。凸部12を設けることで、接合部5の形状を凸部12の形状に制御しやすくなる効果がある。接合部5に金属はんだを用いた場合で説明すると、金属はんだは、薄いペレットを用いるか、あるいはあらかじめセンサチップ4の表面か、センサ筐体3の表面に薄く形成しておき、加熱溶融して接合する。その際、凸部12を形成しておくことで、凸部12の周囲ではセンサ筐体3とセンサチップ4の間の隙間が大きくなるので、金属はんだがぬれ広がらない。その結果、凸部12の形状に合わせて接合部5が形成される。凸部12をX軸とY軸に対して等方な形状としておくことで、接合部5も同じ形状にすることができる。
The surface of the sensor housing 2 has a convex portion 12 having substantially the same shape as the joint portion 5, and the convex portion 12 is joined to the sensor chip 2 via the joint portion 5. By providing the convex part 12, there exists an effect which becomes easy to control the shape of the junction part 5 to the shape of the convex part 12. FIG. The case where metal solder is used for the joint portion 5 will be described. The metal solder uses a thin pellet, or is thinly formed in advance on the surface of the sensor chip 4 or the surface of the sensor housing 3, and is heated and melted. Join. At this time, by forming the convex portion 12, the gap between the sensor housing 3 and the sensor chip 4 is increased around the convex portion 12, so that the metal solder does not wet and spread. As a result, the joint portion 5 is formed in accordance with the shape of the convex portion 12. By making the convex portion 12 isotropic with respect to the X axis and the Y axis, the joint portion 5 can also have the same shape.
本発明の第三実施例を、図4を用いて説明する。なお、第一実施例と同様の構成は説明を省略する。
A third embodiment of the present invention will be described with reference to FIG. The description of the same configuration as in the first embodiment is omitted.
図4(a)および(b)は、本発明の圧力センサ1の第三実施例の平面図および断面図を示している。図4(a)において、X軸に沿った中心線をX中心線10、Y軸に沿った中心線をY中心線11とし、図4(b)はX中心線10における断面図を示している。
4 (a) and 4 (b) show a plan view and a sectional view of a third embodiment of the pressure sensor 1 of the present invention. 4A, the center line along the X axis is the X center line 10, the center line along the Y axis is the Y center line 11, and FIG. 4B shows a cross-sectional view along the X center line 10. Yes.
センサチップ4に、ゲージ領域6を含む領域に薄肉部13を形成する。薄肉部13の周囲を囲むように厚肉部14が形成される。厚肉部14は、凸部12を内包できる形状であり、センサチップ2の薄肉部13と、センサ筐体3上の凸部12が、接合部5を介して接合される。言い換えると、センサチップ4は、ゲージ領域6を含む領域における歪ゲージ7が形成される面の裏面側に凹部或いは溝を形成しており、センサチップ4の凹部或いは溝の底面と凸部12とが接合部5を介して接合されている。本構成により、センサチップ4のセンサ筐体3に接合される部分の厚みを薄くできるので、ダイアフラム2の変形がセンサチップ4の剛性により妨げられにくくなるので、より感度が向上する。また、接合部5に加えて、センサチップ4も、ダイアフラム2の厚さと比較して十分に薄くできるので、温度変化による熱変形が、センサチップ4と接合部5がダイアフラム2の変形に追従する形となる。その結果、温度変化によりセンサチップ4に発生する歪は等方に近くなり、温度特性を小さくできる。また、接合時の熱残留応力の緩和によるセンサ特性の変化も等方に近くなり、精度が向上する。
The thin part 13 is formed on the sensor chip 4 in the region including the gauge region 6. A thick portion 14 is formed so as to surround the thin portion 13. The thick portion 14 has a shape that can include the convex portion 12, and the thin portion 13 of the sensor chip 2 and the convex portion 12 on the sensor housing 3 are joined via the joint portion 5. In other words, the sensor chip 4 has a recess or groove formed on the back side of the surface on which the strain gauge 7 is formed in the region including the gauge region 6, and the bottom of the recess or groove of the sensor chip 4 and the protrusion 12. Are joined via the joint 5. With this configuration, the thickness of the portion of the sensor chip 4 that is joined to the sensor housing 3 can be reduced, so that the deformation of the diaphragm 2 is less likely to be hindered by the rigidity of the sensor chip 4, thereby further improving sensitivity. In addition to the joint 5, the sensor chip 4 can also be made sufficiently thin compared to the thickness of the diaphragm 2, so that thermal deformation due to temperature change causes the sensor chip 4 and the joint 5 to follow the deformation of the diaphragm 2. It becomes a shape. As a result, the distortion generated in the sensor chip 4 due to the temperature change becomes nearly isotropic, and the temperature characteristics can be reduced. In addition, the change in sensor characteristics due to the relaxation of the thermal residual stress at the time of joining becomes nearly isotropic, and the accuracy is improved.
上記のようにセンサチップ4は薄いことが望ましいが、センサチップ4を全体的に薄くすると、ウエハ状態での反りや割れの発生、接合時のハンドリングが難しくなることなどから、薄くするのに限界がある。本構成のように、周辺に厚肉部14を残すことで、厚肉部14の厚みのセンサチップと同じ程度に扱うことができる。
As described above, it is desirable that the sensor chip 4 is thin. However, if the sensor chip 4 is made thin as a whole, warping and cracking in the wafer state and handling at the time of bonding become difficult. There is. By leaving the thick portion 14 around the periphery as in this configuration, the sensor chip having the thickness of the thick portion 14 can be handled to the same extent.
薄肉部13の部分にできる凹部の深さ、すなわち厚肉部14と薄肉部13の厚みの差は、凸部12と接合部5の厚みの和と同じとするが、小さくすることが望ましい。上記を同じとした場合、すなわち接合時にセンサチップ4の厚肉部14の底面が、センサ筐体3表面に接地するまでセンサチップ4を押し付けることで、接合層5の厚みが一定に決めることができる。ただし、接合層5は薄いため、センサチップ4の押し付け荷重による接合部5の厚みの変化は大きくないので、厚肉部14がセンサ筐体3に接地しないようにそれぞれの厚みを決めても、センサ特性のばらつきを大きくせずに製作することができる。
The depth of the concave portion formed in the thin-walled portion 13, that is, the difference in thickness between the thick-walled portion 14 and the thin-walled portion 13 is the same as the sum of the thicknesses of the convex portion 12 and the joint portion 5, but is desirably small. When the above is the same, that is, when the sensor chip 4 is pressed until the bottom surface of the thick portion 14 of the sensor chip 4 contacts the surface of the sensor housing 3 at the time of bonding, the thickness of the bonding layer 5 can be determined to be constant. it can. However, since the bonding layer 5 is thin, the change in the thickness of the bonding portion 5 due to the pressing load of the sensor chip 4 is not large, so even if each thickness is determined so that the thick portion 14 does not contact the sensor housing 3, It can be manufactured without increasing variations in sensor characteristics.
本発明の第四実施例を、図5を用いて説明する。なお、第一実施例と同様の構成は説明を省略する。
A fourth embodiment of the present invention will be described with reference to FIG. The description of the same configuration as in the first embodiment is omitted.
図5(a)および(b)は、本発明の圧力センサ1の第三実施例の平面図および断面図を示している。図5(a)において、X軸に沿った中心線をX中心線10、Y軸に沿った中心線をY中心線11とし、図5(b)はX中心線10における断面図を示している。
5 (a) and 5 (b) show a plan view and a cross-sectional view of a third embodiment of the pressure sensor 1 of the present invention. 5A, the center line along the X axis is the X center line 10, the center line along the Y axis is the Y center line 11, and FIG. 5B is a cross-sectional view along the X center line 10. Yes.
凸部12を、センサ筐体3に凸部12を取り囲むように溝15を形成することで構成している。また、溝15の外周側は、センサチップ4を内包できる形状に形成されている。溝15の外周側壁を、センサチップ4の外形に沿って少し大きく形成することで、センサチップ4を接合する際に、センサチップ4の位置決めに用いることができる。こうすることで、センサチップ4の接合の際に、位置決めのための治具を別途用意する必要がなく、容易に精度よくセンサチップ4を位置決めできる。溝15の外形は、センサチップ4の外形全周に沿った形状に限られたものではなく、位置決めに必要な部分のみセンサチップ4に近接していればよい。
The convex part 12 is configured by forming a groove 15 in the sensor housing 3 so as to surround the convex part 12. Further, the outer peripheral side of the groove 15 is formed in a shape that can contain the sensor chip 4. By forming the outer peripheral side wall of the groove 15 slightly larger along the outer shape of the sensor chip 4, the sensor chip 4 can be used for positioning when the sensor chip 4 is joined. By doing so, it is not necessary to separately prepare a positioning jig when the sensor chip 4 is joined, and the sensor chip 4 can be easily and accurately positioned. The outer shape of the groove 15 is not limited to the shape along the entire outer periphery of the sensor chip 4, and only the portion necessary for positioning needs to be close to the sensor chip 4.
本発明の第五実施例を、図6を用いて説明する。なお、第一実施例と同様の構成は説明を省略する。
A fifth embodiment of the present invention will be described with reference to FIG. The description of the same configuration as in the first embodiment is omitted.
図6は、本発明の圧力センサの第五実施例の断面図を示している。本実施例は、第一から第四実施例に記載の圧力センサを、製品形態に組み上げた圧力センサアセンブリ21の構成例を示している。
FIG. 6 shows a sectional view of a fifth embodiment of the pressure sensor of the present invention. The present embodiment shows a configuration example of a pressure sensor assembly 21 in which the pressure sensors described in the first to fourth embodiments are assembled in a product form.
センサ筐体3は、第一から第四実施例に記載した構成に加えて、外周部を円筒状に下方に伸ばした円筒部22を有し、外側面にフランジ部23とねじ部24を設置した形状に一体形成されている。ねじ部24はのおねじになっており、測定対象の配管側にめねじの継手(図示せず)を用意して取り付けるようになっている。上記円筒部22の内部は圧力導入口25を形成していて、この圧力導入口25を介して測定対象である液体や気体をダイアフラム2の表面まで導入する。センサ筐体3の上面には、センサチップ4と隣接するよう配線基板26が配置されている。配線基板26は、接着剤27によりセンサ筐体3の上面に接着保持されている。センサチップ4と配線基板26の電極パッド間は、ワイヤ28により電気的に接続されている。センサチップ4の表面やその周辺部を保護するため、円筒形のカバー29が、センサ筐体3のフランジ部23に接続して設置されている。カバー29の上端には、複数の外部電極ピン30が、カバー29を貫通するように設けられている。外部電極ピン30と配線基板26は、フレキシブル配線基板31を介して電気的に接続されている。センサチップ4は、ワイヤ28、配線基板26、フレキシブル配線基板31、外部電極ピン30を介して外部に信号を送信する。本実施例の構成により、測定対象の装置の配管に容易に取り付け可能で、センサへの給電および信号取り出しのための配線も容易な、圧力センサアセンブリ21を得ることができる。
In addition to the configurations described in the first to fourth embodiments, the sensor housing 3 has a cylindrical portion 22 whose outer peripheral portion extends downward in a cylindrical shape, and a flange portion 23 and a screw portion 24 are installed on the outer surface. It is integrally formed in the shape. The threaded portion 24 is a male thread, and a female threaded joint (not shown) is prepared and attached to the pipe to be measured. A pressure introduction port 25 is formed inside the cylindrical portion 22, and a liquid or gas to be measured is introduced to the surface of the diaphragm 2 through the pressure introduction port 25. A wiring board 26 is disposed on the upper surface of the sensor housing 3 so as to be adjacent to the sensor chip 4. The wiring board 26 is bonded and held on the upper surface of the sensor housing 3 by an adhesive 27. The sensor chip 4 and the electrode pads of the wiring board 26 are electrically connected by wires 28. A cylindrical cover 29 is connected to the flange portion 23 of the sensor housing 3 to protect the surface of the sensor chip 4 and its peripheral portion. A plurality of external electrode pins 30 are provided at the upper end of the cover 29 so as to penetrate the cover 29. The external electrode pins 30 and the wiring board 26 are electrically connected via a flexible wiring board 31. The sensor chip 4 transmits a signal to the outside via the wire 28, the wiring board 26, the flexible wiring board 31, and the external electrode pin 30. With the configuration of the present embodiment, it is possible to obtain the pressure sensor assembly 21 that can be easily attached to the piping of the device to be measured and that can easily supply power to the sensor and extract signals.
1 圧力センサ
2 ダイアフラム
3 センサ筐体
4 センサチップ
5 接合層
6 ゲージ領域
7 歪ゲージ
10 X中心線
11 Y中心線
12 凸部
13 薄肉部
14 厚肉部
15 溝
21 圧力センサアセンブリ
22 円筒部
23 フランジ部
24 ねじ部
25 圧力導入口
26 配線基板
27 接着剤
28 ワイヤ
29 カバー
30 外部電極ピン
31 フレキシブル配線板 DESCRIPTION OFSYMBOLS 1 Pressure sensor 2 Diaphragm 3 Sensor housing | casing 4 Sensor chip 5 Bonding layer 6 Gauge area | region 7 Strain gauge 10 X center line 11 Y center line 12 Convex part 13 Thin part 14 Thick part 15 Groove 21 Pressure sensor assembly 22 Cylindrical part 23 Flange Portion 24 Threaded portion 25 Pressure inlet 26 Wiring board 27 Adhesive 28 Wire 29 Cover 30 External electrode pin 31 Flexible wiring board
2 ダイアフラム
3 センサ筐体
4 センサチップ
5 接合層
6 ゲージ領域
7 歪ゲージ
10 X中心線
11 Y中心線
12 凸部
13 薄肉部
14 厚肉部
15 溝
21 圧力センサアセンブリ
22 円筒部
23 フランジ部
24 ねじ部
25 圧力導入口
26 配線基板
27 接着剤
28 ワイヤ
29 カバー
30 外部電極ピン
31 フレキシブル配線板 DESCRIPTION OF
Claims (8)
- ダイアフラムを有するセンサ筐体と、前記センサ筐体上に設けられるセンサチップと、センサチップ上に設けられる歪ゲージと、を有する圧力センサにおいて、
前記センサチップは薄い接合部を介して前記センサ筐体に接続されており、前記接合部の面積は前記センサチップおよび前記ダイアフラムの面積よりも小さく、前記歪ゲージは前記接合部の投影面内に配置されていることを特徴とする圧力センサ。 In a pressure sensor having a sensor housing having a diaphragm, a sensor chip provided on the sensor housing, and a strain gauge provided on the sensor chip,
The sensor chip is connected to the sensor housing through a thin joint, and the area of the joint is smaller than the areas of the sensor chip and the diaphragm, and the strain gauge is within the projection plane of the joint. A pressure sensor which is arranged. - 前記センサチップの平面内に第1の方向とそれに垂直な第2の方向を有し、
前記歪ゲージはブリッジ回路を構成する複数の歪ゲージを有し、
前記複数の歪ゲージは第1の方向に沿うように配置された第一の歪ゲージと第2の方向に沿うように配置された第二の歪ゲージを有し、
前記接合部は、前記ダイアフラム上であって前記圧力センサに圧力が印加された際のダイアフラム表面に発生するひずみが前記第1の方向と前記第2の方向とで差が出る位置に配置されていることを特徴とする請求項1に記載の圧力センサ。 A first direction in the plane of the sensor chip and a second direction perpendicular thereto,
The strain gauge has a plurality of strain gauges constituting a bridge circuit,
The plurality of strain gauges have a first strain gauge arranged along the first direction and a second strain gauge arranged along the second direction,
The joint is disposed on the diaphragm at a position where the strain generated on the surface of the diaphragm when pressure is applied to the pressure sensor makes a difference between the first direction and the second direction. The pressure sensor according to claim 1. - 前記ダイアフラムは前記第1の方向を長手とし、前記第2の方向を短手とする形状であり、前記接合部が前記ダイアフラムの略中央に配置されていることを特徴とする請求項2に記載の圧力センサ。 3. The diaphragm according to claim 2, wherein the diaphragm has a shape in which the first direction is a long side and the second direction is a short side, and the joint portion is disposed at a substantially center of the diaphragm. Pressure sensor.
- 前記ダイアフラムは円形または正方形などの前記第1の方向と前記第2の方向に対して等方的な形状であり、前記接合部の中心が前記ダイアフラムの外周部に合うように配置されていることを特徴とする請求項2に記載の圧力センサ。 The diaphragm has a shape that is isotropic with respect to the first direction and the second direction, such as a circle or a square, and is arranged so that the center of the joint portion matches the outer peripheral portion of the diaphragm. The pressure sensor according to claim 2.
- 前記接合部は円形または正方形など、前記第1の方向および前記第2の方向に対して等方的な形状であることを特徴とする請求項2乃至4の何れかに記載の圧力センサ。 The pressure sensor according to any one of claims 2 to 4, wherein the joint portion has a shape that is isotropic with respect to the first direction and the second direction, such as a circle or a square.
- 前記センサ筐体の表面に前記接合部とほぼ同形状の凸部を有し、前記凸部において、前記センサチップと前記接合部を介して接合されていることを特徴とする請求項1乃至5の何れかに記載の圧力センサ。 6. The sensor housing has a convex portion having substantially the same shape as the joint portion, and the convex portion is joined to the sensor chip via the joint portion. The pressure sensor according to any one of the above.
- 前記センサチップは、前記歪ゲージを含む領域に形成される薄肉部と、前記薄肉部を囲うように形成された厚肉部とを有し、
前記センサチップの厚肉部は、前記凸部を内包できる形状であり、
前記センサチップの前記薄肉部は、前記接合部を介して前記センサ筐体上の前記凸部と接合されることを特徴とする請求項6に記載の圧力センサ。 The sensor chip has a thin portion formed in a region including the strain gauge, and a thick portion formed so as to surround the thin portion,
The thick part of the sensor chip is a shape that can include the convex part,
The pressure sensor according to claim 6, wherein the thin portion of the sensor chip is joined to the convex portion on the sensor housing via the joint portion. - 前記凸部は、前記センサ筐体に溝を形成することで構成され、前記溝の外周側壁を、前記センサチップの接合の際の前記センサチップの位置決めに用いることができることを特徴とする請求項7に記載の圧力センサ。 The convex portion is formed by forming a groove in the sensor housing, and an outer peripheral side wall of the groove can be used for positioning the sensor chip when the sensor chip is joined. 8. The pressure sensor according to 7.
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WO2018038068A1 (en) * | 2016-08-23 | 2018-03-01 | 日本特殊陶業株式会社 | Strain sensor |
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