Pressure sensor assembly

Abstract

The present disclosure relates to a pressure sensor assembly comprising a pressure sensor, a base, and a conductive manifold having a manifold cavity. The pressure sensor comprises: a conductive sensing layer having a sensor diaphragm; a conductive backing layer having a bottom surface bonded to the sensing layer; an electrically insulating layer having a bottom surface bonded to a top surface of the backing layer; and a sensor element having an electrical parameter that changes in response to a pressure differential based on deflection of the sensor diaphragm. The base is bonded to the electrically insulating layer and attached to the manifold within the manifold cavity.

Description

Technical Field

[0001] Embodiments of the present disclosure relate to industrial process transmitters and, more particularly, to pressure sensor assemblies for use in such transmitters. Background Art

[0002] Industrial process field devices, such as process transmitters, are used in industrial process control and monitoring systems to monitor industrial process variables and transmit their measurements back to a control room, for example, in chemical, oil, gas, pharmaceutical, or other fluid processing plants. The term "process variable" refers to the physical or chemical state of a substance or the transformation of energy. Examples of process variables include pressure, temperature, flow, conductivity, pH, and other properties.

[0003] Pressure transmitters and other pressure-sensing field devices or instruments include a pressure sensor that senses pressure, such as the pressure of a process fluid. The pressure sensor provides an electrical output indicative of the sensed pressure. The sensed pressure may be processed by the pressure transmitter's circuitry and / or transmitted to an external control unit.

[0004] Some types of pressure sensors need to be electrically isolated from the body of the transmitter. Additionally, it may be necessary to reliably seal the oil-filled isolation unit that transmits the process pressure to the pressure sensor. Summary of the Invention

[0005] Embodiments of the present disclosure generally relate to pressure sensor assemblies and methods of producing the same. One embodiment of the pressure sensor assembly includes a pressure sensor, a base, and a conductive manifold having a manifold cavity. The pressure sensor includes a conductive sensing layer having a sensor diaphragm extending between a peripheral support area, the sensor diaphragm having a reduced thickness relative to the peripheral support area. The pressure sensor also includes: a conductive backing layer having a bottom surface bonded to the top surface of the sensing layer; an electrically insulating layer having a bottom surface bonded to the top surface of the backing layer; and a sensor element having an electrical parameter that changes based on a deflection of the sensor diaphragm in response to a pressure difference between a first pressure on a first side of the sensor diaphragm and a second pressure on a second side of the sensor diaphragm opposite the first side. The base includes a bottom surface bonded to the top surface of the electrically insulating layer. The base is attached to the manifold within the manifold cavity, and the electrically insulating layer electrically insulates the sensing layer from the base and the manifold.

[0006] In one example of a method for producing a pressure sensor assembly, a pressure sensor is formed by bonding the top surface of a conductive backing layer to the bottom surface of an electrically insulating layer. A conductive sensing layer is provided, the conductive sensing layer including a sensor diaphragm extending between peripheral support areas. The sensor diaphragm has a reduced thickness relative to the peripheral support areas. The top surface of the sensing layer is bonded to the bottom surface of the backing layer. A sensor element is formed, the sensor element having an electrical parameter that changes based on deflection of the sensor diaphragm in response to a pressure difference between a first pressure on a first side of the sensor diaphragm and a second pressure on a second side of the sensor diaphragm opposite the first side. The pressure sensor is attached to a base by bonding the bottom surface of the base to the top surface of the electrically insulating layer. The base is attached to a conductive manifold within a manifold cavity. The electrically insulating layer electrically insulates the pressure sensor from the base and the manifold.

[0007] Another embodiment of the pressure sensor assembly includes a pressure sensor, a base, and a conductive manifold having a manifold cavity. The pressure sensor includes a conductive sensing layer comprising a sensor diaphragm extending between a peripheral support region. The sensor diaphragm has a reduced thickness relative to the peripheral support region. The pressure sensor also includes a backing layer assembly having one or more conductive backing layers, the one or more conductive backing layers including a first backing layer having a bottom surface bonded to a top surface of the sensing layer via a first electrically insulating bond; and a sensor element having an electrical parameter that changes based on deflection of the sensor diaphragm in response to a pressure difference between a first pressure on a first side of the sensor diaphragm and a second pressure on a second side of the sensor diaphragm opposite the first side. A notch is formed in an exposed, uninsulated side of at least one of the sensing layer and the backing layer assembly. The notch defines a gap between conductive side edges of the pressure sensor, the gap providing electrical insulation from voltage arcing between the conductive side edges. The base includes a bottom surface bonded to the top surface of the backing layer assembly. The first electrically insulating layer electrically insulates the sensing layer from the base and the header.

[0008] This summary is provided to introduce some concepts in a simplified form, which are further described in the detailed description below. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter. The claimed subject matter is not limited to implementations that solve any or all of the disadvantages identified in the background. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1is a partial cutaway sectional view of an example of a pressure transmitter in a process control or measurement system according to an embodiment of the present disclosure.

[0010] Figure 2 According to the embodiment of the present disclosure Figure 1 A cross-sectional view of a portion of a pressure transmitter.

[0011] Figure 3 is a simplified cross-sectional view of a portion of a pressure sensor assembly according to an embodiment of the present disclosure.

[0012] Figure 4A -D is a simplified side cross-sectional view illustrating steps of a method of producing a pressure sensor and pressure sensor assembly according to an embodiment of the present disclosure.

[0013] Figure 5 is a simplified cross-sectional view of an example of a pressure sensor and pressure sensor assembly according to an embodiment of the present disclosure.

[0014] Figure 6 yes Figure 5 , which shows an example of an electrically insulating bonding portion according to an embodiment of the present disclosure.

[0015] Figure 7-11 is a simplified cross-sectional view of a pressure sensor assembly and a pressure sensor according to an embodiment of the present disclosure.

[0016] Figure 12 is a cross-sectional view of a sensor assembly according to an embodiment of the present disclosure.

[0017] Figure 13 According to the embodiment of the present disclosure Figure 12 Bottom plan view of the backing layer of the sensor assembly.

[0018] Figure 14 and 15 According to the embodiments of the present disclosure Figure 12 A cross-sectional view of a pressure sensor assembly and a bottom plan view of a backing layer of the pressure sensor assembly.

[0019] Figure 16 is a simplified cross-sectional view of a sensor assembly according to an embodiment of the present disclosure. DETAILED DESCRIPTION

[0020] The embodiments of the present disclosure are described more fully below with reference to the accompanying drawings. Elements identified with the same or similar reference numerals refer to the same or similar elements. In order to simplify the illustration, some elements may not be shown in every figure.

[0021] However, various embodiments of the present disclosure can be embodied in many different forms and should not be construed as limited to the specific embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and these embodiments will fully convey the scope of the present disclosure to those skilled in the art.

[0022] Figure 1 is a partial cutaway sectional view of an example of a process control or measurement system 100 including a pressure transmitter 102 according to an embodiment of the present disclosure. Figure 2 yes Figure 1 1 is a cross-sectional view of a portion of a transmitter 102. System 100 may be used in the processing of materials (e.g., process media) to transform the materials from a less valuable state into a more valuable and useful product, such as petroleum, chemicals, paper, food, etc. For example, system 100 may be used in a refinery that performs an industrial process that processes crude oil into gasoline, fuel oil, and other petrochemical products.

[0023] The pressure transmitter 102 may include a housing 104 that may be coupled to an industrial process 106 via a process coupling 108. The housing 104 and the process coupling 108 may be formed of stainless steel or another suitable material. The transmitter 102 includes a pressure sensor assembly 110 that is attached to and / or housed within the housing 104. The assembly 110 includes a pressure sensor or pressure sensor die 112 (hereinafter referred to as a "pressure sensor") formed according to one or more embodiments described herein for measuring pressure of the process. The pressure sensor assembly 110 may include a manifold 114 and a base 116 that connects the pressure sensor 112 to the manifold 114, such as Figure 2 Best shown.

[0024] Process coupling 108 may be connected to piping 118 that is connected to process 106 and contains process material (e.g., fluid) at a pressure P to be measured by pressure sensor 112. Process coupling 108 may include an isolation diaphragm 120 for transmitting pressure P to pressure sensor 112 without exposing pressure sensor 112 to the process material, such as Figure 1 As shown in FIG. 1 , isolation diaphragm 120 seals one end of a fluid passage 122 that extends through manifold 114 and into cavity 144 containing pressure sensor 112. When pressure P is applied from the process material, isolation diaphragm 120 applies pressure to the fill fluid contained in fluid passage 122, causing pressure P to be transmitted through the fill fluid to pressure sensor 112 for measurement.

[0025] Pressure sensor 112 includes a sensor element having an electrical parameter indicative of the applied pressure P. Measurement circuitry 124 may detect and process the electrical parameter of the sensor element via suitable electrical connections 126 to establish a value for the sensed pressure P. Measurement circuitry 124 may be connected to a junction box 127 of transmitter 102 having communication circuitry 128 for transmitting information related to the sensed pressure P (such as the value of the pressure P) to an external computer control unit 130 via a process control loop 132, as shown. Figure 1 shown.

[0026] Pressure transmitter 102 may include a passage 134 for connecting sensor 112 to ambient pressure or air, such as through a vent 135 in housing 104. Figure 2 The passageway may extend through the base 116 .

[0027] In some embodiments, the process control loop 132 includes a physical communication link (such as a two-wire control loop, such as Figure 1 (as shown) and / or wireless communication links. Communications between the control unit 130 or another external computing device and the pressure transmitter 102 may be performed over the control loop 132 according to conventional analog and / or digital communication protocols. In some embodiments, the two-wire control loop 132 comprises a 4-20 mA control loop, wherein the measured pressure value may be represented by the level of loop current flowing through the two-wire control loop 132. Exemplary digital communication protocols include, for example, those according to The communication standard modulates the digital signal onto analog current levels for the two-wire control loop 132. Other purely digital technologies may also be used, including FieldBus and Profibus communication protocols.

[0028] Exemplary wireless versions of the process control loop 132 include, for example, wireless mesh network protocols such as (IEC 62591) or ISA 100.11a (IEC 62734), or another wireless communication protocol such as WiFi, LoRa, Sigfox, BLE or any other suitable protocol.

[0029] Power can be supplied to pressure transmitter 102 from any suitable power source. For example, pressure transmitter 102 can be powered entirely by the current flowing through control loop 132. Pressure transmitter 102 can also be powered by one or more power sources, such as internal or external batteries. A generator (e.g., a solar panel, a wind turbine, etc.) can also be used to power the pressure transmitter or to recharge a power source used by pressure transmitter 102.

[0030] Figure 31 is a simplified cross-sectional view of a portion of a pressure sensor assembly 110, such as a gauge pressure assembly, according to an embodiment of the present disclosure. The pressure sensor assembly 110 includes a pressure sensor 112 formed according to an embodiment of the present disclosure, which is attached to an electrically conductive manifold 114 (e.g., stainless steel) via a base 116. A top surface 136 of the pressure sensor 112 is attached to a bottom surface 138 of the base 116, such as within a cavity 144 of the manifold 114, and a top surface 140 of the base 116 is attached to a surface 142 of the manifold 114.

[0031] To protect and ensure proper operation of pressure sensor 112, pressure sensor 112 must be electrically isolated from electrically conductive manifold 114, housing 140, and process coupling 108. Conventional techniques for providing such electrical isolation of pressure sensor 112 typically require the use of an electrically insulating base 116 that prevents electrical charge and current from manifold 114 from reaching pressure sensor 112. For example, base 116 may include at least a portion formed of ceramic or another electrically insulating material that electrically isolates pressure sensor 112 from manifold 114. However, due to the substantial mismatch in the materials' coefficients of thermal expansion, such a configuration can result in high stresses at the interface between electrically insulating base 116 and pressure sensor 112.

[0032] Some embodiments of the present disclosure relate to an improved pressure sensor design with integrated electrical isolation features. Some of these electrical isolation features can be implemented during wafer stack assembly, significantly reducing cost and complexity while providing improved quality. Additional advantages of some embodiments include pressure sensor geometry that can provide enhanced stress isolation, among other advantages.

[0033] One embodiment of the pressure sensor 112 includes a conductive sensing layer 150, a conductive backing layer 152, and an electrically insulating layer 154, such as Figure 3 As shown. In some embodiments, the conductive sensing layer 150 and the conductive backing layer 152 each include crystalline silicon and can be formed in separate wafers. An electrically insulating layer 154 electrically insulates the sensing layer 150 from the base 116 and the manifold 114. The electrically insulating layer 154 can be formed of or include, for example, glass, ceramic, borosilicate glass, silicon nitride, silicon dioxide, or aluminum nitride ceramic, and can also be formed in a wafer. In some embodiments, each of the layers 150, 152, and 154 has a thickness measured along the axis 156 of the pressure sensor that can be less than 20 mils, such as 12.5 mils.

[0034] Because of the electrical isolation built into the pressure sensor 112, the base 116 does not have to provide electrical isolation functionality as with conventional bases 116. Some embodiments take advantage of this to reduce stress at the joints between the base 116 and the manifold 114 and at the joints between the base 116 and the pressure sensor 112. In some embodiments, the base 116 is made of a conductive material such as or another suitable conductive material) and includes a generally planar surface 138 that is bonded to a generally planar surface 136 of an electrically insulating layer 154, such as Figure 3 As shown. Preferably, the electrically insulating layer 154 is formed of a material having a coefficient of thermal expansion similar to that of the material forming the base 116, such as those described above, to further reduce the likelihood of significant stresses being generated at their junction. In some embodiments, the bond 157 between the surface 136 of the electrically insulating layer 154 and the surface 138 of the base 116 can be formed by a solder joint or another suitable bond. The bond 158 between the base 116 and the manifold 114 can include a brazed joint or another suitable bond.

[0035] Conductive backing layer 152 has a bottom surface 160 bonded to top surface 162 of sensing layer 150 by bonding 164, and electrically insulating layer 154 has a bottom surface 166 bonded to top surface 168 of backing layer 152 by bonding 170. Bonds 164 and 170 may comprise frit bonds, which may include an electrically insulating material (e.g., thermally grown silicon dioxide) on the surfaces to be bonded and may increase the electrical isolation of sensing layer 150 from submount 116 and manifold 114. Alternatively, bonds 164 and 170 may comprise thermocompression bonds, fusion bonds, anodic bonds, or another suitable bond.

[0036] In some embodiments, a bond 170 between the backing layer 152 and the electrically insulating layer 154 seals (e.g., hermetically seals) the junction of the channel 172 through the electrically insulating layer 154 and the channel 174 through the backing layer 152. Additionally, a bond 157 (e.g., a solder joint) between the electrically insulating layer 154 and the base 116 also seals (e.g., hermetically seals) the junction of the fluid channel 134 through the base 116 and the fluid channel 172 through the electrically insulating layer 154.

[0037] The sensing layer 150 is configured to sense pressure P using a sensor diaphragm 176 extending between peripheral support areas 178. The sensor diaphragm 176 has a reduced thickness relative to the peripheral support areas 178 as measured along the axis 156 of the sensor 112. A cavity 180 is formed in the sensing layer 150 between the peripheral support areas 178 and the sensor diaphragm 176. The bond 164 between the backing layer 152 and the sensing layer 150 seals (e.g., hermetically seals) the channel 174 to the cavity 180. Thus, the cavity 180 can be exposed to ambient pressure through the channel 134, while the cavity 144 on the opposite side of the sensor diaphragm 176 is exposed to the process pressure P ( Figure 1 ).

[0038] Sensor diaphragm 176 flexes or deflects in response to the pressure differential between pressure P within cavity 144 and pressure within cavity 180. The known relationship between the deflection of diaphragm 176 and pressure P is used to measure pressure P.

[0039] In one embodiment, the sensor element 182 is used to detect the deflection of the sensor diaphragm 176 and thereby detect the pressure P. The sensor element 182 can be mounted within or on the sensor diaphragm 176, such as on the surface 184 of the sensing layer 150, as shown in FIG. Figure 3 1 and has an electrical parameter that varies based on the deflection of the sensor diaphragm 176. The measurement circuit 124 may detect or receive a measurement of the electrical parameter of the sensor element 182 via the electrical connection 126.

[0040] In some embodiments, the sensor element 182 may include one or more strain gauges. When the sensor diaphragm 176 deflects in response to the process pressure P within the cavity 180, an electrical parameter (eg, resistance) of the strain gauge changes and represents the process pressure P.

[0041] Figure 4A -D is a simplified side cross-sectional view illustrating an example of a method of producing pressure sensor 112 and pressure sensor assembly 110 according to an embodiment of the present disclosure. In some embodiments, sensing layer 150, backing layer 152, and electrically insulating layer 154 can each be formed in their own wafer, as shown by the dashed lines. In addition, multiple formations of sensing layer 150, backing layer 152, and electrically insulating layer 154 can be formed in each wafer to allow for mass production of sensors. Features of layers 150, 152, and 154 can be formed in the wafer using conventional etching or other suitable techniques.

[0042] like Figure 4AAs shown, a backing layer 152 and an electrically insulating layer 154 may be provided wherein the channels 174 of the backing layer 152 are aligned with the channels 172 of the electrically insulating layer 154. The surface 168 of the backing layer 152 is then bonded to the surface 166 of the electrically insulating layer 154 by the bonding portion 170, as shown. Figure 4B As described above, the bonding portion 170 seals the junction between the channel 174 of the backing layer 152 and the channel 172 of the electrically insulating layer 154 .

[0043] The sensing layer 150 may be positioned so that the cavity 180 is aligned with the channel 174 of the backing layer 152, as shown in FIG. Figure 4C Then, the surface 162 of the sensing layer 150 is bonded to the surface 160 of the backing layer 152 using the bonding portion 164 to form Figure 4D Pressure sensor 112 is shown. In some embodiments, bonding portion 164 seals the junction between channel 174 and cavity 180 of backing layer 152.

[0044] Embodiments of the method are not limited to the specific order described above. For example, the sensing layer 150 can be bonded to the backing layer 152 before the backing layer 152 is bonded to the electrically insulating layer 154. Other adjustments can also be made.

[0045] In some embodiments of the method, a metal layer 186 is formed on the surface 136 of the electrically insulating layer 154, such as Figure 4D The metal layer 186 may include solder for attaching the surface 136 of the electrically insulating layer 154 to the surface 138 of the base 116, as shown. Figure 3 The pressure sensor assembly 110 may then be completed by connecting the base 116 to the manifold 114, such as by forming a bond (e.g., a brazed joint) 158 between the surface 140 of the base 116 and the surface 142 of the manifold 114. Figure 3 ).

[0046] when Figure 4D When the illustrated pressure sensor 112 is one of a plurality of pressure sensors formed in a wafer stack, each of the pressure sensors 112 may be cut from the wafer stack using a suitable die-cutting process that cuts along line 188 to separate the individual pressure sensors 112 from the wafer stack.

[0047] Figure 5FIG2 is a simplified cross-sectional view of another example of a pressure sensor 112 and pressure sensor assembly 110 according to an embodiment of the present disclosure. Pressure sensor 112 includes a conductive sensing layer 150, which may include one or more of the features described above, and a backing layer assembly 190, which includes one or more conductive backing layers 152, such as backing layers 152A and 152B. As described above, these layers may include crystalline silicon and may be formed in separate wafers. In addition, multiple pressure sensors 112 may be formed simultaneously by stacking and bonding wafers, as described above.

[0048] A channel 192 extends through the backing layer assembly 190 and connects to the cavity 180. Figure 5 In the example shown, channels 192 through the backing layer assembly include channels 192A through conductive backing layer 152A and channels 192B through conductive backing layer 152B. The junctions along channels 192 can be sealed by bonds 194 and 196 connecting the layers together.

[0049] The surface 198 of the backing layer assembly 190 (such as the top surface of the conductive backing layer 152A) can be configured to be connected to the base 116 using any suitable technique. In one embodiment, a metal layer 186, such as a solder layer, is formed on the surface 198 of the backing layer assembly 190 and is used to attach the pressure sensor 112 to the base 116, such as Figure 5 The base 116 can then be attached to the header 114 ( Figure 3 ), as discussed above with respect to pressure sensor 112.

[0050] In some embodiments, the pressure sensor 112 does not rely on an electrically insulating layer, such as layer 154 ( Figure 3 )) provides electrical isolation of the sensing layer 150 and / or sensor element 182. Instead, electrical isolation of the sensing layer 150 or sensor element 182 is provided by a bond 194 formed between the sensing layer 150 and the backing layer assembly 190 and / or bonds between layers of the backing layer assembly 190, such as a bond 196 between the backing layer 152A and the backing layer 152B.

[0051] Figure 6 yes Figure 5192B and 180. The embodiment of the present disclosure further illustrates an enlarged view of a portion 200 of the sensing layer 150 and an example of an electrically insulating bond 194 according to an embodiment of the present disclosure. In one embodiment, the electrically insulating bond 194 includes a layer or coating 202 of electrically insulating material (such as thermally grown silica) on the surface 162 of the sensing layer 150 and the surface 206 of the backing layer 152B, and a glass layer 208 between the coatings 202 for forming a bond (e.g., a frit bond) with the coatings 202 and the surfaces 162 and 206. The frit bond 194 can be used to fuse the glass layer 208 to the coatings 202 and seal the junction of the channel 192B and the cavity 180. Similar techniques can be used to form the bond 196 between the backing layers 152A and 152B.

[0052] In some embodiments, coatings 202 may each have a thickness 210 of approximately 0.1 mils, measured along axis 156 of pressure sensor 112, and glass layer 208 may have a thickness 212 of approximately 0.6 mils. Thus, the thickness of electrically insulating bond 194 or 196 may be approximately 0.8 mils.

[0053] While the one or more electrically insulating bonds may prevent charge from being conducted from the base 116 to the sensing layer 150 or the sensor element 182, the thickness of each electrically insulating bond 194, 196 may not provide sufficient clearance between the uninsulated and exposed side surfaces 214 of the pressure sensor 112 to prevent arcing (high potential faults) around the bond, such as after the sensor 112 is die-cut from a wafer stack. Figure 5 14. For typical voltages that may be applied to pressure sensor 112 from header 114 and base 116, a gap of approximately 5 mils is required between conductive surfaces 214 to prevent such arcing. Therefore, electrically insulating bonds 194 and 196 may not provide adequate protection for sensing layer 150 or sensor element 182 from high potential faults.

[0054] Figure 7-11 is a simplified cross-sectional view of a pressure sensor assembly 110 and a pressure sensor 112 according to an embodiment of the present disclosure that includes features for preventing arcing between uninsulated sides 214 of the pressure sensor 112. In some embodiments, a groove or notch 220 is formed in the exposed and uninsulated side surfaces 214 of the sensing layer 150 and / or the backing layer assembly 190. The notch 220 extends around the perimeter of the pressure sensor 112 and defines a gap 222 extending along the axis 156 that is sufficient to prevent arcing between the conductive side surfaces 214. For example, the gap 222 may extend along the axis a distance greater than 5 mils, such as 8 mils or 10 mils, as shown. Figure 8-12 shown.

[0055] The recess 220 may be formed in the sensing layer 150 and / or one or more backing layers 152 of the backing layer assembly 190 using any suitable technique, such as utilizing a potassium hydroxide (KOH) wet etching process. For example, the recess 220 may be formed in adjacent backing layers 152A and 152B of the backing layer assembly, such as Figure 7 This may be a preferred location for the notch when the backing layer 152 is formed from a relatively thin wafer, such as a wafer having a thickness of less than 20 mils, such as 12.5 mils.

[0056] Figure 8-10 An example of a pressure sensor 112 is shown in which a recess 220 is formed in a single backing layer 152A or 152B of the backing layer assembly 190. In some embodiments, the backing layer 150 including the recess 220 has a thickness greater than 12.5 mils, such as 20 mils or 35 mils, for example. Figure 9 and 10 In FIG. 1 , a recess is formed in the lower backing layer 152A attached to the base 116 and in FIG. Figure 11 In FIG. 1 , the recess 220 is formed in the upper backing layer 152B attached to the sensing layer 150 .

[0057] In some embodiments, the insulating bond 196 between the backing layers 152A and 152B may extend over a larger adjoining surface, such as the bottom surface 224 of the backing layer 152B. Figure 8 Alternatively, the bonding portion 196 may extend over a shorter adjacent surface and not over a larger adjacent surface. For example, the bonding portion 196 may extend over a shorter adjacent surface and not over a larger adjacent surface. Figure 9 ) or the surface 224 of the backing layer 152B (as shown Figure 10 shown).

[0058] Figure 11 1 is a simplified cross-sectional view of a pressure sensor assembly 110 including a pressure sensor 112 having a recess 220 extending between a sensing layer 150 and a backing layer assembly 190. Here, the backing layer assembly 190 includes a single conductive backing layer 152. An electrically insulating bond 194 bonds the bottom surface 162 of the sensing layer 150 to a surface 206 of the backing layer 152. The thickness of the sensing layer 150 and the thickness of the backing layer 152 measured along the axis 156 can be, for example, approximately 10-15 mils, such as 12.5 mils.

[0059] Additional embodiments of the present disclosure relate to one or more layers of the pressure sensor 112, such as an electrically insulating layer (e.g., Figure 3The pedestal structures may be formed in a layer 154 of the pressure sensor or in a conductive backing layer (e.g., layer 152A or 152B). The pedestal structures provide stress isolation to the sensing layer 150 by reducing the contact area between adjacent layers of the pressure sensor 112. This reduces the likelihood of harmful stresses reaching the sensing layer 150, which could adversely affect its operation. Each of the pedestal structures may be formed by wet etching or another suitable technique.

[0060] In some embodiments, the base structure within the layer includes a wall that surrounds the axis 156 of the pressure sensor 112 and the opening of the channel extending through the layer and defines the cavity of the channel. The wall reduces the contact area between adjacent layers of the pressure sensor 112 and helps provide stress isolation to the sensing layer 150.

[0061] An example of such a wall feature is Figure 8 and 9 1 is shown in FIG. 1 , in which the backing layer 152A includes a wall 230 that extends vertically from the top surface 198 of the backing layer 152A to the bottom surface 226 along the axis 156. The wall 230 surrounds the axis 156 and includes an inner surface 232 that defines a cavity 234 of the passage 192A through the backing layer 152A. The outer surface 236 of the wall 230 can define the inner surface of the recess 220.

[0062] In some embodiments, surface 238 extends from wall 230 to opening 240 of channel 192A. Contact area 242 is formed on wall 230 and is joined or bonded to an adjacent layer of pressure sensor 112 (in this example, backing layer 152B) via corresponding bonding portion 196. The smaller contact area 242 between backing layer 152A and backing layer 152B via bonding portion 196 isolates stresses that may be generated in backing layer 152A due to attachment of backing layer 152A to base 116 and reduces the transfer of those stresses to sensing layer 150.

[0063] Another example of a wall feature is Figure 10 , where wall 230 is formed in backing layer 152B and smaller contact surface 242 is formed at surface 224 .

[0064] Figure 12 and 13 According to the embodiments of the present disclosure Figure 12 A cross-sectional view of the pressure sensor assembly 110 and a bottom plan view of the backing layer 152A of the assembly 110. Here, the recess 230 is larger than Figure 7The example shown penetrates the side surface 214 of the backing layer 152A a greater distance toward the axis 156. This results in the formation of a wall 230 that operates similarly to the wall described above. For example, the wall 230 extends from the surface 198 of the backing layer 152A to the surface 196, and the surface 196 has a reduced contact area 242 with the surface 224 of the adjacent backing layer 152B through the bonding portion 196, which may be relative to the Figure 8 An electrically insulating bond of the example shown.

[0065] Figure 14 and 15 According to the embodiments of the present disclosure Figure 14 1 and a bottom plan view of the backing layer 152A of the assembly 110. In this example, the backing layer 152A includes a plurality of walls 230, such as walls 230A and 230B. Each of the walls 230 surrounds the axis 156 and the fluid cavity 192A passing through the backing layer 152A, and the wall 230A surrounds the wall 230B. The walls 230A and 230B are arranged relative to each other. Figure 7 The illustrated embodiment reduces the contact area with the adjacent backing layer 152B and isolates the sensing layer 150 from stresses in the backing layer 152A. Wall 230A has a contact area 242A at its surface 226 that contacts or is attached to the surface 224 of the backing layer 152B via the bonding portion 196, and wall 230B has a contact area 242B at its top surface 226 that contacts or is attached to the surface 224 of the backing layer 152B via the bonding portion 196. As described above, the bonding portion 196 can be an electrically insulating bonding portion. The outer surface 236A of the wall 230A can form the inner surface of the recess 220, and the inner surface 232A of the wall 230A can define the boundary of an inner cavity 244. The inner cavity 244 can be sealed from the channel 192 and the sensor exterior, which can reduce or minimize stress caused by the sensor being mounted on the diaphragm 176 by reducing the rigidity of the backing layer 152A. The outer surface 236B of the wall 230B may define the boundaries of the cavity 244, and the inner surface 232B of the wall 230B may define the boundaries of the cavity 234 through the channel 192A of the backing layer 152A.

[0066] Figure 16 is a simplified cross-sectional view of a pressure sensor assembly 110 according to an embodiment of the present disclosure. Figure 16 In the example of the pressure sensor assembly 110 provided in FIG, the layer 256 of the pressure sensor 112 allows the base 116 to be positioned relative to, for example, Figure 3 Here, the layer 256 of the pressure sensor 112 may take the form of an electrically insulating layer (such as Figure 3 layer 154 of the pressure sensor 112) or a conductive backing layer such as Figure 5 in the form of layer 152).

[0067] like Figure 16 As shown, layer 256 is shaped relative to its wafer form (dashed lines) to maintain a gap 258 between layer 256 and manifold 114 while allowing surface 260 of layer 256 to be positioned above shoulder 262 of manifold 114 along axis 156, rather than below shoulder 262 of manifold 114, as shown in FIG. Figure 3 This allows the height 264 of the pressure sensor 112, measured from the shoulder 262 of the manifold 114 along the axis 156, to be compared to other configurations such as Figure 3 Additionally, the base 116 can be formed shorter, thereby allowing the surface 138 of the base to be positioned above the shoulder 262 of the manifold 114. Thus, the pressure sensor assembly 110 can be more compact than other pressure sensor assembly designs (such as Figure 3 In addition, the base 142 ( Figure 3 ) The shorter fluid passage 122 to cavity 180 allows the pressure sensor assembly 110 to use a reduced volume of fill fluid.

[0068] As described above, in some embodiments, the metal layer 186 ( Figure 4D and 5 ) such as solder is applied to the top of the pressure sensor 112 to facilitate attachment of the pressure sensor 112 to the base 116. Some embodiments of the present disclosure include features that reduce the likelihood of contamination of the passage through the pressure sensor 112 and cavity 180 by the applied metal when the metal layer 186 is applied.

[0069] In one example, one or more restrictions 270 are formed in a passageway of the pressure sensor 112, such as Figure 4D and 5 In one embodiment, each restriction 270 is formed by a tapered section of a channel (such as a Figure 4D The pressure sensor 112 is shown in layer 152 or Figure 5 Each restriction 270 provides a partial barrier to potential contamination of the passage through the pressure sensor 112 and cavity 180 during application of the metal layer 186 to the surface 198 of the backing layer 152A. Such restrictions 270 may also be formed in the Figure 4D The electrically insulating layer 154 of the pressure sensor 112 is formed.

[0070] Although the embodiments of the present disclosure have been described with reference to preferred embodiments, those skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the present disclosure. Embodiments of the present disclosure include combinations of one or more embodiments described herein. For example, the sensor element may include a capacitive electrode having a capacitance that is measured between the capacitive electrode and a reference electrode and indicates the process pressure P.

Claims

1. A pressure sensor assembly, comprising: A pressure sensor, comprising: a conductive sensing layer comprising a sensor membrane extending between peripheral support regions, the sensor membrane having a reduced thickness relative to the peripheral support regions; a backing layer assembly comprising one or more electrically conductive backing layers, the one or more electrically conductive backing layers including a first backing layer having a bottom surface bonded to a top surface of the electrically conductive sensing layer by a first electrically insulating bond; a sensor element having an electrical parameter that varies based on a deflection of the sensor diaphragm in response to a pressure differential between a first pressure on a first side of the sensor diaphragm and a second pressure on a second side of the sensor diaphragm opposite the first side; and a notch formed in an exposed and uninsulated side of at least one of the conductive sensing layer and the backing layer assembly, wherein the notch defines a gap between conductive side edges of the pressure sensor, the gap providing electrical insulation to prevent voltage arcing between the conductive side edges; a base comprising a bottom surface bonded to the top surface of the backing layer assembly; and A conductive header having a header cavity; The first electrically insulating bonding portion electrically insulates the conductive sensing layer from the base and the conductive header. 2 . The pressure sensor assembly of claim 1 , wherein the first electrically insulating bond comprises a coating of electrically insulating material between a bottom surface of the first backing layer and a top surface of the conductive sensing layer.

3. The pressure sensor assembly of claim 2, wherein: The pressure sensor includes a first channel extending through the electrically insulating layer and the conductive backing layer and into a sensor cavity in the conductive sensing layer, the first channel being exposed at the first side of the sensor diaphragm; The base includes a second channel connected to the first channel; and The conductive header includes a third channel connected to the second channel and to a vent to ambient air. The pressure sensor assembly of claim 3 , wherein the recess is formed in the first backing layer. 5 . The pressure sensor assembly of claim 3 , wherein the recess is formed in the conductive sensing layer and the first backing layer and spans the first electrically insulating bond. 6 . The pressure sensor assembly of claim 3 , wherein the conductive sensing layer and the one or more backing layers each comprise crystalline silicon.

7. The pressure sensor assembly of claim 3, wherein the one or more electrically conductive backing layers of the backing layer assembly comprises a second backing layer having a bottom surface bonded to a top surface of the first backing layer by a second electrically insulating bond. 8 . The pressure sensor assembly of claim 7 , wherein each of the first and second electrically insulating bonds comprises a coating of electrically insulating material between a top surface of the first backing layer and a bottom surface of the conductive sensing layer.

9. The pressure sensor assembly of claim 8, wherein each of the first electrically insulating bond and the second electrically insulating bond is hermetic and selected from the group consisting of a frit bond, a thermocompression bond, a fusion bond, or an anodic bond.

10. The pressure sensor assembly of claim 7, wherein the recess is formed in the first backing layer. 11 . The pressure sensor assembly of claim 7 , wherein the recess is formed in the conductive sensing layer and the first backing layer and spans the first electrically insulating bond.

12. The pressure sensor assembly of claim 7, wherein: The pressure sensor includes one or more pedestal structures formed in the first backing layer or the second backing layer, the one or more pedestal structures providing stress isolation to the conductive sensing layer; When the one or more base structures are formed in the first backing layer, each base structure comprises a top surface of the first backing layer; and When the one or more base structures are formed in the second backing layer, each base structure comprises a bottom surface of the second backing layer. 13 . The pressure sensor assembly of claim 12 , wherein the one or more base structures comprise walls formed in the first backing layer or the second backing layer, the walls defining a boundary of an interior cavity of the first channel.

14. The pressure sensor assembly of claim 12, wherein the one or more base structures include a first wall surrounding an opening of the first channel.

15. The pressure sensor assembly of claim 14, wherein the one or more base structures include a second wall surrounding the first wall.

16. The pressure sensor assembly of claim 1, wherein the sensor element comprises a strain gauge. 17 . The pressure sensor assembly of claim 1 , further comprising measurement circuitry coupled to the sensor element and configured to determine a pressure value based on the electrical parameter.

18. The pressure sensor assembly of claim 1, wherein the base is electrically conductive.

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