JP2018096910A - Pressure sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pressure sensor improving reliability of adhering a metal stem with an adhesive material such as a sensor chip and an adhesive glass.SOLUTION: A sensor chip 40 is adhered on one surface 10a of a metal stem 10 via an adhesive glass 30 comprising a first adhesive glass 31 and a second adhesive glass 32. Specifically, the first adhesive glass 31 is surrounded by the second adhesive glass 32 which is different from the first adhesive glass 31 in thermal expansion coefficient, while the sensor chip 40 is adhered to the first adhesive glass 31. In this way, a sheer stress is reduced among the adhesive glass 30, the metal stem 10, and the sensor chip 40 due to a thin thickness of the adhesive glass 30, and the crack and abrasion of the adhesive glass 30 are prevented from being generated. Thus, a pressure sensor high in reliability of the adhesion with the metal stem 10, the sensor chip 30, and the sensor chip 40 is provided.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a pressure sensor formed by joining a sensor chip to a metal stem having a pressure detection diaphragm.

  Conventionally, as a pressure sensor capable of detecting high pressure, a sensor chip having a bottomed cylindrical metal stem formed with a diaphragm and a sensor chip formed with a strain detection element for detecting strain of the diaphragm is provided through a bonding glass. Is known that is bonded on the diaphragm.

  For example, the sensor chip is composed of a semiconductor substrate made of silicon and the metal stem is composed of a metal material such as SUS430. And the sensor chip is arrange | positioned on the metal stem through the paste-like or tablet-like joining glass. Specifically, the sensor chip is disposed on, for example, a paste-like or tablet-like bonded glass, and the bonded glass is fired or melted by heat treatment and then solidified by cooling, whereby the bonded glass is placed on the metal stem. Are joined through.

  In order to stably perform glass bonding between members having different thermal expansion coefficients such as metal stems and semiconductor elements as described above, the thermal expansion coefficient of the bonding glass is determined in consideration of the thermal expansion coefficients of the two members. It is necessary to adjust to the range. As such a bonding glass, for example, a bonding material described in Patent Document 1 can be mentioned.

  The bonding material described in Patent Document 1 is configured by laminating three or more layers of glass, and a thermal expansion coefficient of 30 ° C. to 500 ° C. increases step by step along the direction of the glass lamination. It is configured as follows. In such a configuration, in the bonding material, any glass layer does not contain an alkali component, and the difference in thermal expansion coefficient between adjacent layers at 30 ° C. to 500 ° C. is 1.5 ppm. / K or less.

  By using the bonding material having the gradient of the thermal expansion coefficient in this way, the difference in the thermal expansion coefficient between the members having different thermal expansion coefficients can be alleviated, and the members can be firmly bonded. .

JP 2016-37422 A

  However, the bonding material described in Patent Document 1 has a structure in which three or more layers of glasses having different thermal expansion coefficients are stacked and integrated in the surface direction, and is applied to a pressure sensor that is thick and thin. hard. That is, in recent years, pressure sensors have been reduced in size, weight, and sensitivity, and it has been studied to reduce the thickness of the bonding glass. It is not preferable that the thickness of the bonding glass be increased.

  Therefore, the present inventors examined a pressure sensor in which the bonding glass and the sensor chip are thinned, and if the bonding glass or the sensor chip is simply thinned, peeling or cracking occurs in the bonding glass and the sensor chip. There was found.

  Specifically, when the bonding glass is thinned, its strength decreases, so that the bonding glass can withstand the shear stress generated inside the bonding glass in the cooling process after glass bonding the sensor chip to the metal stem. And can be destroyed. In a reliability test such as a thermal cycle, peeling between the bonding glass and the sensor chip or cracking of the sensor chip may occur starting from a site having a high shear stress.

  The present invention has been made in view of the above points, and provides a pressure sensor that is highly reliable while having a thinned structure while bonding a sensor chip through a thinned bonding glass. For the purpose.

  In order to achieve the above object, a pressure sensor according to claim 1 is a pressure sensor that generates an electrical output in accordance with an applied pressure, and is provided with a surface (10a) on which a pressure detection diaphragm (11) is formed. ) Having a metal stem (10) having a first bonding glass (31) and a second bonding glass (32) disposed on the diaphragm of one surface, and on the diaphragm A sensor chip (40) including a strain detection unit (41) that is bonded via a first bonded glass and generates an electrical output corresponding to the strain of the diaphragm. In such a configuration, the sensor chip is provided so as to be within the outer region of the first bonding glass as viewed from the normal direction to the one surface, and a part or all of the outer edge portion of the sensor chip is the first bonding glass. And the second bonded glass are arranged so as to overlap the bonded interface (33), the first bonded glass has a thermal expansion coefficient larger than that of the second bonded glass, and the thermal expansion coefficient of the metal stem. The second bonded glass is smaller and is disposed outside the outer region of the first bonded glass that overlaps the outer edge of the sensor chip when viewed from the normal direction, and is formed so as to surround the first bonded glass. The thermal expansion coefficient of the second bonding glass is equal to or higher than the thermal expansion coefficient of the sensor chip.

  This makes it possible to suppress peeling and cracking of the sensor chip and the bonding glass by reducing the shear stress generated in the bonding glass while reducing the thickness of the sensor chip and the bonding glass, and a pressure sensor with high bonding reliability. It becomes.

  In addition, the code | symbol in the bracket | parenthesis of each said means shows an example of a corresponding relationship with the specific means as described in embodiment mentioned later.

It is sectional drawing which shows the pressure sensor of 1st Embodiment. It is the elements on larger scale of the area | region II enclosed with the broken line in FIG. FIG. 6 is a top layout diagram illustrating an arrangement example of a first bonding glass and a second bonding glass which are bonded glasses for bonding a sensor chip indicated by a two-dot chain line to a metal stem and have different thermal expansion coefficients. It is a figure which shows the result of having performed the reliability test about the some Example in which joining glass was comprised by two materials from which a thermal expansion coefficient differs, and the some comparative example by which joining glass was comprised by one material. It is an upper surface layout figure showing the example of arrangement of the 1st joined glass, the 2nd joined glass, and the sensor chip in the pressure sensor of a 2nd embodiment. It is sectional drawing which shows the cross-sectional structure between the dashed-dotted lines VI-VI shown in FIG. It is a top surface layout figure showing the example of the 1st joined glass in the pressure sensor of other embodiments, the 2nd joined glass, and a sensor chip. It is a top surface layout figure showing the example of the 1st joined glass in the pressure sensor of other embodiments, the 2nd joined glass, and a sensor chip.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following embodiments, parts that are the same or equivalent to each other will be described with the same reference numerals.

(First embodiment)
The pressure sensor according to the first embodiment will be described. The pressure sensor of the present embodiment is applied to a product that detects a high pressure, for example, about 200 to 300 MPa, for example, for detecting the fuel pressure or the brake fluid pressure of a fuel pipe for fuel injection in an automobile. It is preferable.

  As shown in FIG. 1, the pressure sensor includes a metal stem 10, a housing 20, a bonding glass 30, a sensor chip 40, a circuit board 50, leads 60 and 61, a connector 70, a terminal 71, and the like.

  The metal stem 10 is made of a metal such as stainless steel such as SUS430, SUS630, and SUS304, and is a bottomed cylindrical member. A thin diaphragm 11 is formed on the bottom surface of the metal stem 10, and the other end of the metal stem 10 opposite to the diaphragm 11 is a hollow opening 12. A hollow internal space 13 formed from the opening 12 has a cylindrical shape, and the upper surface of the diaphragm 11 has a circular shape.

  Further, the metal stem 10 is formed with a bottom portion 14 having a flange shape so that the outer diameter of the diaphragm 11 is larger than that of the opening 12. The surface of the bottom 14 opposite to the opening 12 is defined as one surface 10a, and the sensor chip 40 is disposed on the one surface 10a via the bonding glass 30, and a circuit is formed around the bonding glass 30 and the sensor chip 40. A substrate 50 is disposed. More specifically, the sensor chip 40 is bonded to the position corresponding to the diaphragm 11 in the bottom portion 14 via the bonding glass 30, and the circuit board 50 is fixed to a portion around the diaphragm 11. The pressure of the pressure medium introduced through the opening 12 is applied to the pressure receiving surface of the diaphragm 11, and the strain corresponding to the pressure is transmitted to the sensor chip 40 through the bonding glass 30.

  Further, a recess 15 is formed at a position corresponding to the circuit board 50 in the bottom portion 14, and a tip of a lead 60 provided so as to penetrate the circuit board 50 enters the recess 15. The recess 15 is filled with an adhesive or the like (not shown), and the circuit board 50 is attached to the bottom 14 via the adhesive.

  The housing 20 is directly attached to an attachment target such as a fuel pipe (not shown), for example, and an attachment screw 21 is formed on the outer peripheral surface. By screwing the screw 21 into, for example, a fuel pipe, the opening 12 communicates with the inside of the fuel pipe, and the pressure medium can be introduced into the metal stem 10.

  Inside the housing 20, a hollow portion 22 into which a part of the metal stem 10 is fitted and an accommodation space 23 in which the sensor chip 40 and the like are accommodated are formed. The diameter of the accommodation space 23 is made larger than the diameter of the hollow portion 22. The metal stem 10 described above is fixed to the housing 20 by fitting a portion closer to the opening 12 than the bottom 14 into the hollow portion 22. In the accommodation space 23, in addition to the bottom portion 14, a bonding glass 30, a sensor chip 40, a circuit board 50, and the like are accommodated.

  Further, on the opposite side of the housing 20 from the screw 21, a first stepped portion 24 configured by expanding the inner diameter of the housing 20 and a first step configured by further expanding the inner diameter of the housing 20. A two-stepped portion 25 is formed. The seal member 26 is disposed so as to contact the first stepped portion 24, and the connector 70 is disposed so as to contact the seal member 26. The seal member 26 has an O-ring 26a made of rubber and an annular portion 26b made of resin or metal. The connector 70 is fixed to the housing 20 so as to press the O-ring 26a, so that the sealing property between the housing 20 and the connector 70 is secured.

  Further, the distal end portion 27 on the opposite side of the screw 21 in the housing 20 is caulked inward in the radial direction, so that the connector 70 is fixed to the distal end portion 27 by caulking.

  In the present embodiment, the case where the housing 20 is configured separately from the metal stem 10 is shown, but the metal stem 10 and the housing 20 can also be configured as a single member. For example, it is also possible to prepare a metal stem 10 and the housing 20 as an integrated structure by preparing a single metal material and performing a cutting process.

The bonding glass 30 corresponds to a bonding material for bonding the sensor chip 40 to the metal stem 10. The bonding glass 30 is configured using, for example, a glassy material made of an oxide as a base material. Examples of such a material include lead oxide (PbO), boron oxide (B ₂ O ₃ ), alumina (Al ₂ O ₃ ), silica (SiO ₂ ), and the like. Among these, lead oxide, which is glassy containing lead, has fluidity and is suitable for controlling thermal expansion based on the difference in linear expansion coefficient between the metal stem 10 and the sensor chip 40. It is a material suitable for the bonding glass 30.

  Moreover, the bonding glass 30 may contain a filler. The filler is made of a material that does not change in shape even at a glassy glass transition temperature. For example, a metal oxide containing one or more elements of lead, titanium, calcium, zirconium, and silicon is made into particles. Things can be used. The particle size of the filler is arbitrary, but is preferably 20 μm or less. In addition, the thermal expansion coefficient of the joining glass 30 can also be adjusted to arbitrary values by containing the above fillers in inorganic glass.

  The bonding glass 30 includes a first bonding glass 31 and a second bonding glass 32 having different thermal expansion coefficients. Specifically, the first bonding glass 31 is a bonding material that is disposed under the sensor chip 40 as illustrated in FIG. 2, for bonding the sensor chip 40 to the metal stem 10, for example. As shown in FIG. 3, the second bonding glass 32 is in contact with the first bonding glass 31 so as to surround the first bonding glass 31 when viewed from the normal direction to the one surface 10 a of the metal stem 10 (hereinafter referred to as “one surface normal direction”). Are arranged to relieve the stress of the first bonding glass 31. These specific arrangements and thermal expansion coefficients will be described in detail later.

  The first bonding glass 31 and the second bonding glass 32 are made by using, for example, pasty glass obtained by adding a solvent to the glassy material as described above, and solidifying this paste. For example, paste glass made by adding a solvent to the material of the first bonding glass 31 and applying a paste to the surface 10a of the metal stem 10 on which the diaphragm 11 is formed is applied in a substantially square shape with a dispenser. Subsequently, the paste-like glass obtained by adding a solvent to the material of the second bonding glass 32 to form a paste, for example, surrounds the paste-like glass that becomes the first bonding glass 31, and forms a metal stem so as to form one circle as a whole. 10 is applied on one surface 10a by a dispenser.

  Then, for example, the sensor chip 40 having a quadrangular shape is arranged so that the outline of the sensor chip 40 and the outline of the paste-like glass to be the first bonding glass 31 having a substantially quadrangular shape overlap. Thereafter, for example, heating is performed at 440 ° C. for 10 minutes in a heating furnace, the materials of the first bonding glass 31 and the second bonding glass 32 are heated and melted, and then naturally cooled and solidified. In this way, the sensor chip 40 can be bonded as shown in FIG.

  In addition, although the example which apply | coats the material of the joining glass 30 to the metal stem 10 before fixing to the housing 20 was demonstrated above, the metal stem 10 after fixing to the housing 20 and the metal integrated with the housing 20 were demonstrated. The material of the bonding glass 30 may be applied to the stem 10.

  The sensor chip 40 detects distortion generated when the diaphragm 11 is deformed by the pressure of the pressure medium introduced into the metal stem 10 from the opening 12. Specifically, as shown in FIG. 2, the sensor chip 40 is formed with a strain detection unit 41 as a strain detection element that outputs an electrical output corresponding to the strain of the diaphragm 11 as a sensor signal. For example, in this embodiment, the sensor chip 40 is configured by a silicon substrate having a quadrangular shape. The strain detection unit 41 is configured by, for example, a diffused resistor formed in the sensor chip 40, and a Wheatstone bridge circuit is formed by four gauge resistors.

  In the sensor chip 40 having such a configuration, when the diaphragm 11 is deformed as pressure is applied, a compressive stress is applied to one opposing pair of the four gauge resistors constituting the Wheatstone bridge circuit due to distortion based on the deformation. Will be added. Then, a tensile stress is applied to the other opposing pair. As a result, the midpoint voltage of the Wheatstone bridge circuit formed by the gauge resistor changes, so that the strain detection unit 41 can output an electric signal obtained by converting the applied pressure into an electric signal.

  In addition, the desired location of the sensor chip 40 and the desired location of the circuit board 50 are electrically connected via the bonding wire 42, and, for example, the electrical output of the strain detector 41 is transmitted to the circuit board 50. In addition, the sensor chip 40 may be provided with a signal processing circuit that performs signal processing on the electrical output of the strain detector 41. In that case, the electrical output of the strain detector 41 is processed on the circuit board 50 after being processed by the signal processing circuit.

  The circuit board 50 is fixed to the bottom 14 of the metal stem 10 via an adhesive or the like. For example, the circuit board 50 is configured by an annular plate shape or a C-shaped plate shape in which a portion corresponding to the diaphragm 11 is opened. A plurality of pads (not shown) that are electrically connected to the bonding wires 42 are formed on the circuit board 50. In addition, a plurality of leads 60 are mounted on the circuit board 50, and each lead 60 is electrically connected to each of the plurality of pads.

  Note that an IC chip or the like on which a signal processing circuit or the like that performs signal processing on the electrical output of the strain detection unit 41 may be disposed on the circuit board 50. In this case, the electrical output of the distortion detector 41 is signal-processed by a signal processing circuit in the IC chip and then output to the outside through the lead 60 and the like.

  The lead 60 is a conductor member for electrical connection with the sensor chip 40 through the circuit board 50, and is made of a metal such as copper, for example. A plurality of leads 60 are provided, each of which is erected with respect to the circuit board 50, one end of which is electrically connected to each pad of the circuit board 50 and the other end is electrically connected to the lead 61. Has been.

  The lead 61 is a conductor member that physically and electrically connects the lead 60 and the terminal 71 and is made of a metal such as copper. A plurality of leads 61 are provided corresponding to the leads 60, and each of them is connected to each lead 60 by welding or the like.

  The connector 70 is a member in which a terminal 71 is insert-molded in a connector case 72. The terminal 71 is electrically connected to the circuit board 50 and the sensor chip 40 via leads 60 and 61. As a result, the electrical output from the sensor chip 40 is signal-processed by the signal processing circuit as necessary, and then transmitted from the bonding wire 42 to the circuit board 50 and then to the leads 60 and 61 and the terminal 71. ing.

  Further, the connector 70 has the front end portion 27 of the housing 20 caulked in a state where the surface of the connector case 72 on which the other end of the terminal 71 protrudes is the lower surface and the lower surface is pressed toward the seal member 26 side. The housing 20 is fixedly held. Although two terminals 71 are shown in FIG. 1, the number of terminals 71 necessary for power application, GND connection, output, inspection, etc. is actually provided. And the detection signal of a pressure sensor is transmitted to ECU etc. by connecting to the connector 70 the external connector which is not shown in figure connected to the wiring connected with ECU etc. of a motor vehicle.

  The connector case 72 constitutes the outer shape of the connector 70 and is made of, for example, PBT (abbreviation of polybutylene terephthalate resin). The connector case 72 has a flange-shaped lower surface, and the flange-shaped portion is inserted into the inside of the distal end portion 27 of the housing 20 so that the flange-shaped portion is in contact with the seal member 26 and is crimped. Thus, the housing 20 is fixedly held. That is, the connector case 72 constitutes a package that is assembled to the housing 20, and fulfills a function of protecting the sensor chip 40, electrical connection locations, and the like housed in the housing 20 from moisture and mechanical external force.

  The above is the basic configuration of the pressure sensor in the present embodiment. Next, the thermal expansion coefficients of the metal stem 10, the first bonding glass 31, the second bonding glass 32, and the sensor chip 40 in the pressure sensor will be specifically described.

For example, the thermal expansion coefficient of the metal stem 10 made of SUS430 is about 110 × 10 ⁻⁷ / ° C. within a range of 20 ° C. to 300 ° C. Further, for example, the thermal expansion coefficient of the sensor chip 40 mainly made of silicon is about 30 × 10 ⁻⁷ / ° C. within a range of 20 ° C. to 300 ° C.

Further, in the present embodiment, the thermal expansion coefficients of the first bonding glass 31 and the second bonding glass 32 are not less than the thermal expansion coefficient of the sensor chip 40 and not more than the thermal expansion coefficient of the metal stem 10. More specifically, the thermal expansion coefficient of the first bonding glass 31 is larger than the thermal expansion coefficient of the second bonding glass 32 and is closer to the thermal expansion coefficient of the metal stem 10 than the second bonding glass 32. It is preferable that Examples of the thermal expansion coefficient of the first bonding glass 31 include about 55 × 10 ^{−7 to} 65 × 10 ⁻⁷ / ° C. within a range of 20 ° C. to 300 ° C., for example. Moreover, about the thermal expansion coefficient of the 2nd joining glass 32, it is a numerical value close | similar to the thermal expansion coefficient of the sensor chip 40 compared with the 1st joining glass 31, for example, 30 * 10 < ^-7 > -40 in the range of 20 to 300 degreeC. It is preferable to be set to about × 10 ⁻⁷ / ° C.

  In addition, about the thermal expansion coefficient of the 1st joining glass 31 and the 2nd joining glass 32, what is necessary is just to be made into the above magnitude relationships, and is not limited to said specific numerical range. Further, even when the thicknesses of the first bonding glass 31 and the second bonding glass 32 are changed in accordance with the thickness of the sensor chip 40, the thermal expansion coefficients of the two bonding glasses are set to have the above-described magnitude relationship. What is necessary is just to adjust suitably. The reason for adjusting the first bonding glass 31 and the second bonding glass 32 as described above will be described in the arrangement relationship of the first bonding glass 31, the second bonding glass 32, and the sensor chip 40 described below.

  Next, the positional relationship of the first bonding glass 31, the second bonding glass 32, and the sensor chip 40 in the pressure sensor and the effects thereof will be specifically described with reference to FIGS.

  In the present embodiment, as shown in FIG. 2 or FIG. 3, the sensor chip as viewed from the normal direction of the one surface is formed in the lower region of the sensor chip 40 indicated by a two-dot chain line in FIG. A first bonded glass 31 having the same area as that of 40 is disposed. The second bonding glass 32 is disposed in contact with the four sides of the first bonding glass 31 that has a quadrangular shape as viewed from the normal direction of the first surface. Specifically, as shown in FIG. 3, the second bonded glasses 32 having four arc shapes are arranged one by one in contact with the four sides of the first bonded glass 31 having a rectangular shape. In other words, the second bonded glass 32 is arranged so as to form a circumscribed circle that passes through all corners of the sensor chip 40 that is formed in a square shape when the arc portions of the four second bonded glasses 32 are connected.

  In other words, in the present embodiment, the sensor chip 40 is a bonded interface in which the outer edge portion of the sensor chip 40 is an interface where the first bonded glass 31 and the second bonded glass 32 are bonded as viewed from the normal direction of one surface. 33 are arranged so as to all overlap.

  Here, “the outer edge portion of the sensor chip 40 overlaps with the bonding interface 33” does not mean only a state in which they are completely overlapped when viewed from the normal direction of one surface. In other words, this also includes a state in which a positional deviation occurs between the outer edge portion of the sensor chip 40 and the bonding interface 33 due to an inevitable error factor such as a dimensional error due to member processing or an error due to a process.

  Next, the reason why the first bonding glass 31, the second bonding glass 32, and the sensor chip 40 having the above-described thermal expansion coefficient are arranged in this manner will be described.

  Conventionally, a pressure sensor in which one sensor chip is bonded to a metal stem via one bonding glass is known, and bonding is performed by controlling the thermal expansion coefficient of the one bonding glass within a predetermined range. The reliability of was improved. Specifically, for example, a metal stem made of SUS430 and a sensor chip mainly made of silicon are bonded with bonding glass, and the thermal expansion coefficient of the bonding glass is adjusted to be between the two. . As a result, for example, stress in the thermal expansion / contraction between the metal stem and the sensor chip in the thermal cycle can be relaxed by the bonding glass, and the occurrence of cracks and cracks in the bonding glass and the sensor chip can be suppressed. It becomes a high pressure sensor.

  Here, in recent years, demands for higher sensitivity, lighter weight, and smaller size of pressure sensors are increasing, and thinning of bonded glass and sensor chips is being studied. However, the present inventors tried to join the sensor chip thinned to near the processing limit through the thinned joining glass on the metal stem, and the sensor chip could not withstand the thermal stress generated during glass joining. It was found that cracks occurred in the sensor chip. Further, when the bonding glass of Patent Document 1 is used, it is necessary to integrate at least three glasses having different thermal expansion coefficients in the laminating direction. For this reason, the thickness of the bonding glass is increased, and the transmission efficiency of the distortion of the diaphragm formed on the metal stem is lowered, so that it is difficult to increase the sensitivity.

  Therefore, as a result of intensive studies, the inventors of the present invention have used one bonding glass to bond the sensor chip to the metal stem and surround another bonding glass having a different thermal expansion coefficient around the one bonding glass. It has been found that the arrangement can achieve both thinning and bonding reliability.

  Specifically, when the sensor chip is bonded to the metal stem with one bonded glass, thermal stress is generated in the bonded glass in the bonding process of the sensor chip with the bonded glass. At this time, the thermal stress of the bonding glass is larger in the outer region where there is more movement than in the central portion where there is less movement. Therefore, the second bonding glass 32 having a smaller thermal expansion coefficient than the first bonding glass 31 for bonding the sensor chip 40 onto the metal stem 10 is disposed so as to surround the first bonding glass 31 while being in contact with the first bonding glass 31. Thereby, since the movement of the outer region of the first bonding glass 31 is limited by the second bonding glass 32, the thermal stress in the outer region of the first bonding glass 31 can be relieved, and the shear stress applied to the sensor chip 40 It is thought that can be relaxed. Moreover, peeling between the 1st joining glass 31 and the metal stem 10 can be suppressed by adjusting the thermal expansion coefficient of the 1st joining glass 31 to the value nearer to the metal stem 10 than the 2nd joining glass 32. Therefore, cracking of the sensor chip 40 due to the stress caused by the first bonding glass 31 can be suppressed while reducing the thickness of the sensor chip 40 to near the processing limit, and a pressure sensor with high bonding reliability can be obtained.

  For this reason, in the present embodiment, the arrangement relationship of the first bonding glass 31, the second bonding glass 32, and the sensor chip 40 is as described above. Further, the area (hereinafter simply referred to as “area”) viewed from the normal direction of the first surface of the first bonding glass 31 is arranged so that the outer region of the first bonding glass 31 is entirely overlapped with the outer edge portion of the sensor chip 40. Therefore, in this embodiment, the area of the sensor chip 40 is the same. Moreover, about the area of the 2nd joining glass 32, since the thermal stress of the 1st joining glass 31 should just be relieve | moderated, it is arbitrary.

  Next, the result of the joint reliability evaluation in the pressure sensor of the present embodiment will be described with reference to each example and each comparative example shown in FIG.

  In FIG. 4, the bonded glass 30 is configured by a plurality of examples in which the bonded glass 30 is configured by the first bonded glass 31 and the second bonded glass 32 having different thermal expansion coefficients and a material having one thermal expansion coefficient. The result of having performed the reliability test about the some comparative example is shown. As a reliability test, after performing a thermal cycle test, it was visually confirmed whether peeling or cracking occurred in the first bonding glass 31 or the sensor chip 40. For the cooling / heating cycle test, a heating / cooling step of heating to 160 ° C. and holding for 5 minutes, then cooling to −40 ° C. and holding for 5 minutes is repeated 200 cycles.

  In FIG. 4, the presence or absence of peeling / cracking cracks of the bonding glass 30 or the sensor chip 40 is shown. Here, “no crack” means that no cracks or cracks can be confirmed by visual confirmation, and that there are no cracks that do not affect reliability. It is not. “The thickness of the member” refers to the thickness of the sensor chip 40, the first bonded glass 31, or the second bonded glass 32 in the normal direction of one surface. "-" In the column of the thermal expansion coefficient of the second bonded glass in Comparative Examples 1 to 6 means that the bonded glass 30 is composed of one glass having the same thermal expansion coefficient as a whole in each comparative example, and the thermal expansion coefficient thereof. Is described in the column of the first bonded glass, and the numerical values are omitted. Moreover, the thermal expansion coefficient of the 1st joining glass 31 and the 2nd joining glass 32 has shown the numerical value in the range of 20 to 300 degreeC.

  In each example and each comparative example shown in FIG. 4, a sensor chip 40 having a 4.2 mm square size was used. In each Example shown in FIG. 4, the metal stem 10, the 1st joining glass 31, the 2nd joining glass 32, and the sensor chip 40 were set as the arrangement | positioning shown in FIG. 2 or FIG. That is, in each Example, the 1st joining glass 31 is made into 4.2 mm square size similarly to the sensor chip 40, and the outline of the 1st joining glass 31 is the outer edge part of the sensor chip 40 seeing from one surface normal line direction. And all are arranged to overlap. Further, in each embodiment, the second bonding glass 32 surrounds the first bonding glass 31 when viewed from the normal direction of the one surface, and the first bonding glass 31 and the second bonding glass 32 form four sensor chips 40. They are arranged to form one circumscribed circle that passes through all corners. On the other hand, in each comparative example, the sensor chip 40 is only bonded by the first bonding glass 31 having the same area, and the second bonding glass 32 is not formed as in each embodiment.

  As shown in FIG. 4, in Examples 1 to 21 in which the bonded glass 30 is configured by the first bonded glass 31 and the second bonded glass 32 having different thermal expansion coefficients, cracks in the bonded glass 30 and the bonded glass 30. And peeling between the metal stem 10 and the sensor chip 40 did not occur.

Specifically, in Examples 1 to 9, the thickness of the sensor chip 40 is 90 μm. In Examples 1 to 9, the thermal expansion coefficient of the first bonding glass 31 is 55 × 10 ^{−7 to} 65 × 10 ⁻⁷ / ° C. close to the metal stem 10, and the thermal expansion coefficient of the second bonding glass 32. About 30 × 10 ⁻⁷ to 40 × 10 ⁻⁷ / ° C. closer to the sensor chip 40. Moreover, in Examples 1-9, the thickness of the 1st joining glass 31 and the 2nd joining glass 32 is made thin in steps from 300 micrometers to 200 micrometers. About such Examples 1-9, peeling and cracking between the metal stem 10 and the sensor chip 40 did not occur even after the thermal cycle test.

In Examples 10 to 21, the thickness of the sensor chip 40 is further reduced to 50 μm. In Examples 10 to 21, the thermal expansion coefficient of the first bonding glass 31 is 55 × 10 ^{−7 to} 65 × 10 ⁻⁷ / ° C. close to the metal stem 10, and the thermal expansion coefficient of the second bonding glass 32. Is about 30 × 10 ⁻⁷ to 40 × 10 ⁻⁷ / ° C. near the sensor chip 40. Moreover, in Examples 10-21, the thickness of the 1st joining glass 31 and the 2nd joining glass 32 is made thin in steps from 150 micrometers to 50 micrometers. Also in Examples 10 to 21 as described above, peeling and cracking between the metal stem 10 and the sensor chip 40 did not occur even after the thermal cycle test.

  These results indicate that the first bonding glass 31 has a thermal expansion coefficient close to the sensor chip 40 while the sensor chip 40 is bonded by the first bonding glass 31 having a thermal expansion coefficient close to the metal stem 10. It is shown that the reliability of the bonding is increased by enclosing with.

  On the other hand, as for Comparative Examples 1 to 6 in which the bonding glass 30 is formed of a material having one thermal expansion coefficient, the cracks in the bonding glass 30 or the bonding glass 30 and the metal stem 10 or the sensor chip 40 are all included. Peeling occurred between the two.

Specifically, when the coefficient of thermal expansion of the bonding glass 30 is adjusted to 30 × 10 ⁻⁷ / ° C. close to the sensor chip 40 as in Comparative Examples 1 and 2, peeling between the metal stem 10 and the bonding glass 30 occurs. There has occurred. This is considered to be because the difference in thermal expansion coefficient between the metal stem 10 and the bonding glass 30 bonded to the sensor chip 40 is large, and the bonding glass 30 cannot follow the thermal stress generated at the interface.

When the thermal expansion coefficient of the bonding glass 30 was adjusted to 50 × 10 ⁻⁷ / ° C. slightly closer to the metal stem 10 from the sensor chip 40 as in Comparative Examples 3 and 4, cracks occurred in the bonding glass 30. This is because the thermal expansion coefficient difference between the bonding glass 30 and the metal stem 10 or the sensor chip 40 is alleviated and peeling at these interfaces is suppressed, but the bonding glass 30 is caused by shear stress generated by itself due to thermal stress. It is thought that it was because I could not stand it.

When the thermal expansion coefficient of the bonding glass 30 was adjusted to 65 × 10 ⁻⁷ / ° C. close to the metal stem 10 as in Comparative Examples 5 and 6, peeling occurred between the bonding glass 30 and the sensor chip 40. This is considered to be because the difference in thermal expansion coefficient between the sensor chip 40 and the bonding glass 30 bonded to the metal stem 10 is large and the bonding glass cannot follow the thermal stress generated at the interface.

  That is, the result of each comparative example shown in FIG. 4 occurs at the interface between the bonding glass and the metal stem or the sensor chip or in the layer of the bonding glass when the thinned sensor chip is only bonded with one bonding glass. This indicates that it is difficult to ensure reliability by controlling thermal stress.

  In this manner, the first bonding glass 31 is surrounded by the second bonding glass 32 having the thermal expansion coefficient close to the sensor chip 40 while the sensor chip 40 is bonded by the first bonding glass 31 having the thermal expansion coefficient close to the metal stem 10. The pressure sensor has a structure. Thereby, even when the thinned bonding glass 30 and the sensor chip 40 are used, a pressure sensor with high reliability of bonding between the metal stem 10 and the sensor chip 40 is obtained.

  Further, since the bonding glass 30 is thinned, it is possible to detect the distortion of the diaphragm 11 formed on the metal stem 10 with high accuracy, so that a highly sensitive pressure sensor is obtained. In addition, by reducing the thickness of the bonding glass 30 and the sensor chip 40, a pressure sensor with high sensitivity can be obtained, so that the required size of the sensor chip 40 and the size of the bonding glass 30 associated therewith can be further reduced. The pressure sensor is reduced in weight. And it becomes a pressure sensor with low manufacturing cost by high sensitivity, size reduction, and weight reduction.

(Second Embodiment)
A pressure sensor according to a second embodiment will be described with reference to FIGS. As shown in FIG. 5, the pressure sensor of the present embodiment is different from the first embodiment in that the arrangement of the first bonded glass 31, the second bonded glass 32, and the sensor chip 40 is changed. In the present embodiment, this difference will be mainly described.

  In the present embodiment, the first bonding glass 31 has a circumscribed circle shape that passes through all of the corners of the outer edge of the sensor chip 40 as shown in FIG. 5 when viewed from the normal direction of one surface. Has been. And in this embodiment, the 2nd joining glass 32 is made into the frame circle shape which surrounds this, touching all the outer regions of the 1st joining glass 31, as shown in FIG. ing.

  That is, as shown in FIG. 5, the sensor chip 40 is arranged so that all of the corners of the outer edge portion of the sensor chip 40 indicated by the two-dot chain line overlap with the bonding interface 33 when viewed from the normal direction of one surface. ing. Therefore, the cross-sectional configuration on the diagonal line of the sensor chip 40 is the same as that in FIG. 2 of the first embodiment, but the cross-sectional configuration between the alternate long and short dashed lines VI-VI in FIG. One bonded glass 31 protrudes outward from the outer edge of the sensor chip 40.

  Note that the sensor chip 40 is preferably arranged so that all of the corners thereof overlap with the bonding interface 33 when viewed from the normal direction of the one surface, and all the outer edge portions are bonded as in the first embodiment. More preferably, it is arranged so as to overlap the interface 33. This is because the shear stress applied to the sensor chip 40 in the outer region of the first bonding glass 31 can be relieved as described in the first embodiment.

  In addition, the sensor chip 40 is preferably arranged so as to be within the outer region of the first bonded glass 31 when viewed from the normal direction of the first surface. When the sensor chip 40 is arranged so as to protrude on the second bonding glass 32, the sensor chip 40 is caused by a difference in thermal expansion coefficient between the first bonding glass 31 and the second bonding glass 32 in a region on the bonding interface 33 in the sensor chip 40. This is because a thermal stress difference occurs, and defects such as cracks can occur.

  In this way, when the sensor chip 40 has a rectangular shape, for example, all of the corners are arranged on the bonding interface 33 between the first bonding glass 31 and the second bonding glass 32. Thereby, the corners that are likely to cause cracks in the sensor chip 40 are arranged in the outer region where the thermal stress of the first bonding glass 31 is relaxed by the second bonding glass 32. As a result, thermal stress and shear stress due to the first bonding glass 31 applied to the sensor chip 40 are alleviated, and a pressure sensor with high bonding reliability between the metal stem 10 and the sensor chip 40 is obtained. Moreover, since the 1st joining glass 31, the 2nd joining glass 32, and the sensor chip 40 can be thinned for the reason similar to the said 1st Embodiment, it becomes a pressure sensor made high sensitivity, size reduction, and weight reduction.

(Other embodiments)
The pressure sensor shown in the first embodiment described above is an example of the pressure sensor of the present invention, and is not limited to the first embodiment described above, but is described in the claims. Changes can be appropriately made within the range.

  For example, in each of the above embodiments, the example in which the sensor chip 40 has a quadrangular shape has been described. However, the sensor chip 40 is not limited to a quadrangular shape, and may be a polygonal shape, a circular shape, or an elliptical shape. It may be a shape.

  In this case, the first bonded glass 31 may have the same shape as the sensor chip 40 as viewed from the normal direction of the one surface, or may have a shape such as a circumscribed circle shape or a circumscribed ellipse shape of the sensor chip 40. Good. The second bonding glass 32 has an arbitrary shape according to the shapes of the first bonding glass 31 and the sensor chip 40. For example, when the sensor chip 40 has a square shape and the first bonding glass 31 has a square shape with the same area as this, the frame has a square shape surrounding the first bonding glass 31 as shown in FIG. May be. Further, when the sensor chip 40 is rectangular and the first bonded glass 31 is rectangular with the same area, the frame rectangular shape surrounding the first bonded glass 31 as shown in FIG. May be.

  Moreover, since the 2nd joining glass 32 should just be arrange | positioned so that the outline area | region of the 1st joining glass 31 may be enclosed, about the outline of the other side of the 1st joining glass 31 among the outline areas of the 2nd joining glass 32 May be of any shape. In other words, the second bonded glass 32 is not limited to a frame rectangular shape, a frame circular shape, a frame elliptical shape, or the like, and may have other shapes.

DESCRIPTION OF SYMBOLS 10 Metal stem 11 Diaphragm 20 Housing 30 Bonding glass 31 1st bonding glass 32 2nd bonding glass 33 Bonding interface 40 Sensor chip 41 Strain detection part 70 Connector

Claims (8)

A pressure sensor that generates an electrical output in response to an applied pressure,
A metal stem (10) having one surface (10a) on which a pressure detection diaphragm (11) is formed;
A bonded glass (30) comprising a first bonded glass (31) and a second bonded glass (32) disposed on the diaphragm of the one surface;
A sensor chip (40) including a strain detection unit (41) that is bonded onto the diaphragm via the first bonding glass and generates an electrical output corresponding to the distortion of the diaphragm;
The sensor chip is provided so as to be within the outer region of the first bonding glass when viewed from the normal direction to the one surface, and a part or all of the outer edge portion of the sensor chip is the first bonding glass. Arranged so as to overlap the bonded interface (33) bonded to the second bonded glass,
The thermal expansion coefficient of the first bonding glass is larger than the thermal expansion coefficient of the second bonding glass and smaller than the thermal expansion coefficient of the metal stem,
The second bonded glass is arranged outside the region overlapping the outer edge of the sensor chip in the outer region of the first bonded glass as viewed from the normal direction, and is formed so as to surround the first bonded glass. Has been
The pressure sensor, wherein a thermal expansion coefficient of the second bonding glass is equal to or higher than a thermal expansion coefficient of the sensor chip.   The sensor chip is formed in a polygonal plate shape, and when viewed from the normal direction, all corners that are intersections between one side and the other side of the outer edge of the sensor chip overlap the joint interface. The pressure sensor according to claim 1, which is arranged as described above.   3. The sensor chip according to claim 1, wherein a plurality of the sensor chips are arranged on the diaphragm, and a plurality of the first bonding glass and the second bonding glass are formed corresponding to each of the sensor chips. Pressure sensor.   The pressure sensor according to any one of claims 1 to 3, wherein the metal stem is made of stainless steel.   The pressure sensor according to claim 4, wherein the stainless steel is configured by any one of SUS430, SUS630, and SUS304.   The pressure sensor according to any one of claims 1 to 5, wherein the bonding glass includes an oxide.   The pressure sensor according to claim 1, wherein the bonding glass is made of glass.   The pressure sensor according to claim 1, wherein the bonding glass includes a material containing lead.

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