PRESSURE SENSOR DEVICE WITH A PROGRESSIVE STOPPER

A progressive stopper for a pressure sensing element is able to redistribute and reduce the stress of a diaphragm exposed to high pressure via multi-step contacts, such as at least dual contacts, where the diaphragm (designed for detecting pressure within a defined pressure range) is enabled to withstand much higher pressures above of the defined pressure range, such that the progressive stopper prevents catastrophic failure of the diaphragm. The progressive stopper is created to redistribute and reduce stress on the diaphragm significantly and effectively. The progressive stopper does not limit the output of the pressure sensing element such that the pressure sensing element is able to maintain the output voltage above the maximum output voltage of the defined pressure range when the diaphragm is exposed to high pressures with reduced stresses and strains.

FIELD OF THE INVENTION

The invention relates generally to a pressure sensor assembly having a pressure sensing element which includes at least one progressive stopper to reduce the stress of the pressure sensing element as pressure applied to the diaphragm of the pressure sensing element is increased.

BACKGROUND OF THE INVENTION

A typical ceramic pressure sensing element is formed by a ceramic support substrate bonded with a ceramic diaphragm substrate by a sealing glass having a circular aperture inside the sealing glass to form a diaphragm using the thickness of the sealing glass to create a gap between the ceramic support substrate and the diaphragm substrate. The gap allows the diaphragm to deform when the pressure is applied at the bottom surface of the diaphragm. The pressure sensing element includes four piezoresistors connected into what is known as a “Wheatstone Bridge” configuration. The piezoresistors are printed on the diaphragm so as to detect deflection of the diaphragm due to pressure changes. These MEMS pressure sensing elements are manufactured in different sizes and used for various applications.

In some applications, a pressure sensing element designed to detect pressures from 0 to 10 Bar may be exposed to extremely high pressures, such as pressures up to 200 Bar. However, these types of pressure sensing elements are unable to withstand exposure to such high pressures due to the requirement of the diaphragm having a small thickness, which is required for sufficient pressure sensitivity. For example, a crack at the edge of the diaphragm may occur when the pressure sensor is exposed to a pressure of 200 Bar. The crack is the result of the maximum stress exceeding the ceramic flexural strength.

Accordingly, there exists a need for a pressure sensor which is able to withstand exposure to pressures up to 200 Bar, while maintaining accurate voltage output for a desired operating pressure range.

SUMMARY OF THE INVENTION

In an embodiment, the present invention is a progressive stopper for a pressure sensing element, which in an embodiment is formed by a ring-over-ring stopper on top of a diaphragm to redistribute and reduce the stress of the diaphragm, such that the diaphragm (which is designed for detecting pressure up to 10 Bar) is able to withstand exposure to pressures up to 200 Bar, such that the progressive stopper prevents catastrophic failure of the diaphragm. In an embodiment, the ring-over-ring stopper is a dual-contact ring stopper formed by a thinner inner ring and a thicker outer ring. When pressure applied to the diaphragm is increased, the diaphragm is deformed, the inner radius of the outer ring firstly contacts the bottom of the support substrate to limit the diaphragm deformation. When pressure is further increased, the diaphragm further deforms to move the inner ring such that the inner radius or opening of the inner ring secondly contacts the bottom of the support substrate, further limiting the deformation of the diaphragm. The ring-over-ring stopper is created to redistribute and reduce stress on the diaphragm significantly. The stopper does not limit the output of the pressure sensing element such that the pressure sensing element is able to maintain the output voltage above when the diaphragm is exposed to a pressure of a minimum of 10 Bar, without falling below 10 Bar. In a non-limiting example, for a pressure sensing element designed to detect pressures up to 10 Bar having a progressive stopper according to the present invention, the output voltage for when the pressure applied is above 10 Bar may be clipped via an ASIC as detecting pressure above 10 Bar is not necessary (i.e., the output voltage when the pressure is above 10 Bar may remain a constant voltage output).

In an embodiment, the present invention is a pressure sensor assembly which includes a housing having a port, a pressure sensing element having a support substrate located in a cavity in the housing, a sealing glass layer bonded to the support substrate, the sealing glass layer located in the cavity in the housing, and a diaphragm substrate bonded to the sealing glass layer, the diaphragm substrate located in the cavity in the housing. A diaphragm is part of the diaphragm substrate, and the diaphragm is selectively exposed to fluid pressure in the port. The pressure sensing element also includes a plurality of resistors coupled to the diaphragm such that the plurality of resistors are located between the diaphragm substrate and the support substrate, and at least one progressive stopper is integrally formed with one of the diaphragm substrate or the support substrate. A first portion of the at least one progressive stopper is in contact with one of the at least one of the diaphragm substrate or the support substrate when pressure applied to the diaphragm is above a first predetermined value, and a second portion of the of the at least one progressive stopper is in contact with the other of the at least one of the diaphragm substrate or the support substrate when pressure applied to the diaphragm is above a second predetermined value.

In an embodiment, the progressive stopper includes a first stopper ring mounted to the diaphragm substrate, and a second stopper ring mounted to the diaphragm substrate such that the first stopper ring and the second stopper ring are in contact with and adjacent to one another. In an embodiment, the first stopper ring contacts the support substrate when the pressure applied to the diaphragm is above the first predetermined value, and both the first stopper ring and the second stopper ring contact the support substrate when the pressure applied to the diaphragm is above a second predetermined value.

In an embodiment, the first stopper ring is taller than the second stopper ring.

In an embodiment, at least one of the resistors is circumscribed by the at least one progressive stopper.

In an embodiment, the progressive stopper includes a first stopper ring mounted to the diaphragm substrate, a second stopper ring mounted to the diaphragm substrate such that the second stopper ring is circumscribed by the first stopper ring, and a third stopper ring mounted to the diaphragm substrate such that the third stopper ring is circumscribed by the second stopper ring. In an embodiment, the first stopper ring contacts the support substrate when the pressure applied to the diaphragm is above the first predetermined value, both the first stopper ring and the second stopper ring contact the support substrate when the pressure applied to the diaphragm is above the second predetermined value, and the first stopper ring, the second stopper ring, and the third stopper ring all contact the support substrate when the pressure applied to the diaphragm is above a third predetermined value.

In an embodiment, one of the first stopper ring, the second stopper ring, or the third stopper ring is of a square shape.

In an embodiment, the progressive stopper includes a first recess integrally formed as part of the support substrate, a first contact area integrally formed as part of the first recess, a second recess integrally formed as part of the support substrate, and a second contact area integrally formed as part of the second recess. In an embodiment, the first contact area contacts the diaphragm substrate when the pressure applied to the diaphragm is above the first predetermined value, and both the first contact area and the second contact area contact the diaphragm substrate when the pressure applied to the diaphragm is above a second predetermined value.

In an embodiment, the progressive stopper includes a third recess integrally formed as part of the support substrate, and a contact area integrally formed as part of the third recess. The third contact area contacts the diaphragm substrate when the pressure applied to the diaphragm is above a third predetermined value.

In an embodiment, the progressive stopper includes a curved recess integrally formed as part of the support substrate, and at least one contact area integrally formed as part of the curved recess. In an embodiment, the contact area contacts the diaphragm substrate when the pressure applied to the diaphragm is above a predetermined value.

In an embodiment, the progressive stopper includes a stopper ring connected to the diaphragm substrate, a recess integrally formed as part of the support substrate, a contact area integrally formed as part of the recess, and an inner surface is integrally formed as part of the recess. The contact area contacts the diaphragm substrate when the pressure applied to the diaphragm is above the first predetermined value, and when the pressure applied to the diaphragm is above a second predetermined value, the stopper ring contacts the inner surface and the contact area contacts the diaphragm substrate.

In an embodiment, the contact area is an edge of the recess.

In an embodiment, the progressive stopper includes a second recess integrally formed as part of the support substrate, where the second recess extends further into the support substrate than the first recess, and the second recess and the first recess are approximately concentric. The progressive stopper also includes a second contact area integrally formed as part of the second recess, and an inner surface integrally formed as part of the second recess. When the pressure applied to the diaphragm is above a third predetermined value, the stopper ring contacts the inner surface of the second recess, the first contact area contacts the diaphragm substrate, and the second contact area contacts the diaphragm substrate.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring toFIGS.1and2, a pressure sensor assembly having a pressure sensing element which includes at least one progressive stopper according to the present invention is shown generally at10. The pressure sensor assembly10is an absolute pressure sensor, and includes a connector12which is molded around part of an aluminum housing14. Integrally formed as part of the connector12are several apertures16, and a portion of a corresponding spring18is located in each aperture16. Although two springs18are shown in two corresponding apertures16, it is within the scope of the invention that more or less springs18being disposed in corresponding apertures16may be used. Also formed as part of the connector12is a cavity, shown generally at20. Disposed in the cavity20is circuitry, which is part of a signal conditioning Application Specific Integrated Circuit (ASIC), shown generally at22, mounted to a support substrate24, where the support substrate24is part of a pressure sensing element, shown generally at26. The pressure sensing element26also includes an intermediate layer28, which in this embodiment is made of printed sealing glass, and the intermediate layer28includes a cavity, shown generally at30inFIG.4. With reference toFIGS.3-4, the pressure sensing element26is formed by the support substrate24and a diaphragm substrate32bonded by the intermediate layer28, where the intermediate layer28is disposed between the support substrate24and the diaphragm substrate32. More specifically, the intermediate layer28is mounted to an outer surface32aof the diaphragm substrate32. The area of the diaphragm substrate32which is not in contact with the intermediate layer28is a diaphragm32b, which deflects when exposed to pressurized fluid. The diameter of the diaphragm32bcorresponds to the inner diameter of the intermediate layer28. Mounted to the outer surface32aof the diaphragm substrate32is a plurality of printed resistors34, which in this embodiment are piezoresistors, and together the resistors34function as a sensing bridge, or Wheatstone bridge. The resistors34are in electrical connection with each other and the signal from the resistors34representing the output voltage is transferred to the ASIC22. Referring again toFIGS.1-2, the substrate24is supported by the springs18, and the use of the springs18allows for the location of the pressure sensing element26to accommodate various tolerances, and still maintain proper electrical connections, and for the ASIC22to be properly located in the cavity20.

In contact with the back surface of the diaphragm substrate32is an O-ring38, and the O-ring38is partially disposed in a recess40formed as part of a port42. Integrally formed as part of the port42is a threaded portion, shown generally at44, which is used to connect the pressure sensor assembly10to another component. A second O-ring may be located on an outer surface of the port42such that the threaded portion44extends through the second O-ring, providing sealing between the port42and another component.

Referring toFIGS.3-4, several components of the pressure sensing element26are shown. In addition to the resistors34, also disposed in the cavity30is a progressive stopper, shown generally at46. In the embodiment shown, the progressive stopper46is a dual-contact ring-over-ring progressive stopper46. The progressive stopper46in this embodiment includes an outer or first stopper ring48aand an inner or second stopper ring48b. The first stopper ring48aand the second stopper ring48bare both attached to the outer surface32aof the diaphragm substrate32. The first stopper ring48acircumscribes and is in contact with the second stopper ring48b. More specifically, as shown inFIG.4, the inner surface50aof the first stopper ring48ais in contact with the outer surface50bof the second stopper ring48b. The height52aof the first stopper ring48ais greater than the height52bof the second stopper ring48b. The first stopper ring48aincludes a first contact area48c, which is an inner edge of the first stopper ring48a, and the second stopper ring48bincludes a second contact area48d, which is an inner edge of the second stopper ring48b.

The second stopper ring48balso includes an aperture56, and two of the resistors34are connected to the outer surface32aof the diaphragm substrate32in a manner to be disposed in the aperture56.

In addition to the support substrate24, the springs18are in contact with a leadframe58, and the leadframe58includes several pins60. The pins60may be connected to another connector (not shown) for transmitting the signal to an external device, such as a controller.

During operation, pressure is applied to an exposed surface32cof the diaphragm substrate32, this pressure causes the diaphragm32bto deflect, such that there are strains on the resistors34printed on the diaphragm32b. These strains cause a change in the output voltage of the resistors34, and the signal of this output voltage is transferred to the ASIC22for amplification and calibration.

FIG.7is a chart depicting a curve, shown generally at100, of diaphragm stress versus pressure applied to the diaphragm32bwhen pressure is applied to the diaphragm32bof the pressure sensor assembly10shown inFIGS.4-6. The curve100includes three regions, a first region102, a second region104, and a third region106. The first region102of the curve100represents the required measurable pressure sensing range for this embodiment.

The chart inFIG.7also includes another curve108, which represents the diaphragm stress versus pressure if the gap between the diaphragm32band the support substrate24is large enough, such that there is a non-contact condition between the diaphragm32band the support substrate24(or the progressive stopper46is not used). Following the curve108, an edge of the diaphragm32bmay crack when the pressure is around 33 Bar and the stress of the diaphragm32breaches the ceramic flexural strength at around 400 MPa.

Referring now toFIGS.4and7, the linear elasticity of the diaphragm32bis such that when pressure is initially applied to the diaphragm32b, the progressive stopper46does not contact the support substrate24. As the pressure applied to the diaphragm32bincreases, the further the diaphragm32bdeflects. The rate of increase in stress of the diaphragm32bwhen the pressure is between 0 Bar and less than 10 Bar is shown in the first region102of the curve100inFIG.7. However, as depicted inFIG.5, once the pressure applied to the diaphragm32breaches above 10 Bar, the first contact area48cof the first stopper ring48acontacts the lower surface24aof the support substrate24, which is represented on the curve100by the first contact110inFIG.7. Also, once the pressure applied to the diaphragm32bis above 10 Bar and the first contact area48cis in contact with the lower surface24aas shown inFIG.5, as the pressure increases, the stress of the diaphragm32bcontinues to increase, but increases at a lower rate compared to the rate at which the stress of the diaphragm32bincreases when exposed to pressures between 0 Bar and slightly higher than 10 Bar (i.e., compared to the first region102). This lower rate of increase in stress on the diaphragm32bis represented in the second region104of the curve100inFIG.7.

Referring now toFIG.6, the pressure sensing element26is shown when the diaphragm substrate32is exposed to pressure near 100 Bar. When the pressure is near 100 Bar, both the first contact area48cof the first stopper ring48aand the second contact area48dof the second stopper ring48bare in contact with the lower surface24aof the support substrate24, represented on the curve100by the second contact112inFIG.7. Once the pressure applied to the diaphragm32bis above the second contact112(i.e., the pressure is near 100 Bar), the stress of the diaphragm32bcontinues to increase, but increases at a lower rate compared to the rate at which the stress of the diaphragm32bincreases from the first contact110(where the pressure is slightly above 10 Bar) to the second contact112(where the pressure is near 100 Bar). This is shown in the third region106of the curve100inFIG.7. The third region106of the curve100inFIG.7represents a pressure increase from the second contact112(when the pressure level near 100 Bar) to 200 Bar, and the corresponding increase in stress on the diaphragm32b.

In the embodiment shown, the maximum flexural strength of the diaphragm substrate32is 400 MPa. The stopper rings48a,48bcounteract some of the force applied to the diaphragm substrate32, such that increased pressure up to 200 Bar may be applied to the diaphragm substrate32, and the structural integrity of the diaphragm substrate32may be maintained. Additionally, the resistors34are able to generate an output voltage which is representative of pressures ranging from 0 to 10 Bar, with desired accuracy, even after the diaphragm substrate32is exposed to pressures up to 200 Bar.

The first stopper ring48ahas a width54a, and the second stopper ring48balso has a width54b. Varying the heights52a,52band the widths54a,54bof the stopper rings48a,48bmay also change the shape of the curve100inFIG.7, and the locations of the contacts110,112along the curve100, depending upon the application, and the shape and orientation of the progressive stopper46.

An alternate embodiment of the progressive stopper46according to present invention is shown inFIG.8, with like numbers referring to like elements. In the embodiment shown, an outer stopper ring62aand an inner stopper ring62bare printed on the outer surface32aof the diaphragm substrate32. As with the previous embodiment, the height of the outer stopper ring62ais greater than the height of the inner stopper ring62b, such that when the diaphragm32bdeflects, a contact area62cof the outer stopper ring62acontact comes into contact with the lower surface24aof the support substrate24when the pressure is higher than 10 Bar. Additionally, both the contact area62cof the outer stopper ring62aand a contact area62dof the inner stopper ring62bcome into contact with the lower surface24aof the support substrate24when the pressure is near 100 Bar. In this embodiment, the contact area62cis an outer edge of an inner radius formed as part of the outer stopper ring62a, and the contact area62dis an outer edge of an inner radius formed as part of the inner stopper ring62b. In this embodiment, the widths78a,78bof the stopper rings62a,62bare approximately the same, but it is within the scope of the invention that the widths78a,78bof the stopper rings62a,62bmay be varied in other embodiments such that the progressive stopper46shown inFIG.8may be suitable for use in other applications having various pressure ranges. In this embodiment, there is spacing80in between the stopper rings62a,62b, such that the stopper rings62a,62bare not in contact with one another. Varying the widths78a,78band the spacing80would change the shape of the curve100inFIG.7, and the locations of the contacts110,112along the curve100, depending upon the application, and the shape and orientation of the progressive stopper46.

Also, in this embodiment, alternatively, the outer stopper ring62amay be mounted to the lower surface24aof the support substrate24and the inner stopper ring62bis printed on the outer surface32aof the diaphragm substrate32. Furthermore, the inner stopper ring62bmay be mounted to the lower surface24aof the support substrate24and the outer stopper ring62amay be printed on the outer surface32aof the diaphragm substrate32. In yet another embodiment, both the outer stopper ring62aand the inner stopper ring62bmay be mounted to the lower surface24aof the support substrate24.

Another alternate embodiment of the present invention is shown inFIG.9. InFIG.9, the progressive stopper46includes three approximately concentric stoppers. The outer stopper ring64a, the middle stopper ring64b, and the inner stopper ring64care all circular. The middle stopper ring64bhas a smaller diameter than the outermost stopper ring64a, and the inner stopper ring64chas a smaller diameter than the middle stopper ring64b. Furthermore, in this embodiment, the outer stopper ring64ais the tallest of the three rings64a,64b,64cand contacts the lower surface24aof the support substrate24first when the pressure applied to the diaphragm32bis above a first predetermined value. The middle stopper ring64bhas a height which is taller than the inner stopper ring64cbut less than the outer stopper ring64a, such that the middle stopper ring64bcontacts the lower surface24aof the support substrate24second when the pressure applied to the diaphragm32bis above a second predetermined value. The inner stopper ring64cis the shortest of the three rings64a,64b,64c, and contacts the lower surface24aof the support substrate24third when the pressure applied to the diaphragm32bis above a third predetermined value. The spacing82a,82bbetween each of the stopper rings64a,64b,64cis approximately the same, and the widths84a,84b,84cof each of the stopper rings64a,64b,64cis approximately the same, but it is within the scope of the invention that the stopper rings64a,64b,64cmay be various widths84a,84b,84cand have various spacing82a,82bin other embodiments to accommodate other applications. Varying the widths84a,84b,84cand the spacing82a,82bwould change the shape of the curve100inFIG.7, and the locations of the contacts110,112along the curve100, depending upon the application, and the shape and orientation of the progressive stopper46.

Another alternate embodiment of the present invention is shown inFIG.10, with like numbers referring to like elements. In this embodiment, the outer stopper ring64ais square-shaped. It should be noted that it is within the scope of the invention that the various embodiments of the progressive stopper46may include any number of rings with various shapes having a decrease in height from the outermost stopper ring to the innermost stopper ring, such that multiple contacts are formed at various pressure levels to limit the deformation of the diaphragm substrate32, reducing the stress of the diaphragm32bwhen high pressure is applied to the exposed surface32cof the diaphragm substrate32. Limiting the stress of the diaphragm32bis such that the resistors34are able to generate an output voltage which is representative of pressures ranging from 0 to 10 Bar, with desired accuracy, even after the diaphragm substrate32is exposed to pressures up to 200 Bar.

The embodiments of the progressive stopper46shown inFIGS.8-10are shown with spacing between the stopper rings64a,64b,64c. However, it is within the scope of the invention that in addition to being approximately concentric, the stopper rings64a,64b,64cmay also be adjacent and in contact with one another.

Another embodiment of the present invention is shown inFIG.11, with like numbers referring to like elements. In this embodiment, the progressive stopper46is a plurality of recesses formed as part of the support substrate24. More specifically, the progressive stopper46is two recesses, such that the progressive stopper46in this embodiment is a dual-stepped progressive stopper46. In the embodiment shown inFIG.11, a first recess66a, and a second recess66bare formed as part of the support substrate24, and each of the recesses66a,66bare cylindrical in shape. The first recess66ahas a contact area68a, which is an edge of the first recess66a, and the second recess66balso has a contact area68b, which is an edge of the second recess66b. The contact area68aof the first recess66acontacts the outer surface32aof the diaphragm substrate32once the pressure applied to the diaphragm32breaches a first predetermined value, which is above 10 Bar. As the pressure applied to the diaphragm32bcontinues to increase, the stress applied to the contact area68aalso continues to increase.

The contact area68bof the second recess66bis does not contact the outer surface32aof the diaphragm substrate32until the pressure applied to the diaphragm32breaches at or above a second predetermined value, which in this embodiment is near 100 Bar. Once the pressure applied to the diaphragm32bis above the second predetermined value, the contact area68bof the second recess66bcomes in contact with the outer surface32aof the diaphragm substrate32. Both contacts areas68a,68bare in contact with the outer surface32aof the diaphragm substrate32when the pressure applied to the diaphragm32bis between the second predetermined value and 200 Bar.

Another embodiment of the present invention is shown inFIG.12, with like numbers referring to like elements. In this embodiment, the progressive stopper46is three recesses formed as part of the support substrate24, such that the progressive stopper46in this embodiment is a triple-recessed progressive stopper46. More specifically, there is a first recess70a, a second recess70b, and a third recess70c. Each of the recesses70a,70b,70cis generally cylindrical in shape, and has a corresponding contact area72a,72b,72c. The first contact area72ais an edge of the first recess70a, the second contact area72bis an edge of the second recess70b, and the third contact area72cis an edge of the third recess70c. Following is an example to illustrate how the contact areas72a,72b,72ccome into contact with the outer surface32aof the diaphragm substrate32in different pressure ranges. In an embodiment, none of the contact areas72a,72b,72care in contact with the outer surface32aof the diaphragm substrate32when the pressure applied to the diaphragm32bis below a first predetermined value above 10 Bar, such as 12 Bar. The first contact area72acomes into contact with the outer surface32aof the diaphragm substrate32when the pressure is at or above 12 Bar. The first contact area72aand the second contact area72bcome into contact with the outer surface32aof the diaphragm substrate32when the pressure is at a second predetermined value near 70 Bar, and all three contact areas72a,72b,72care in contact with the outer surface32aof the diaphragm substrate32when the pressure applied to the diaphragm32bis at a third predetermined value near 120 Bar. In this embodiment, the maximum diaphragm stress is 300 MPa. It should be noted that the size and shape of the recesses70a,70b,70cmay be varied such that the contact areas72a,72b,72ccome into contact with the outer surface32aof the diaphragm substrate32at different pressure levels to suit any particular application.

Another embodiment of the present invention is shown inFIG.13, with like numbers referring to like elements. In this embodiment, the progressive stopper46is a curved recess74. The profile of the curved recess74is formed by two symmetrical S-shaped curves. The curved recess74has contact areas76a,76bnext to the edges74a,74bof the curved recess74. Each S-shaped curve of the curved recess74also includes an inflection point74c,74d, respectively, where the inflection point74cis adjacent the first contact area76a, and the other inflection point74dis adjacent the second contact area76b. The shape of the curved recess74may be varied such that the outer surface32aof the diaphragm substrate32contacts the contact areas76a,76bwhen pressure is applied to the diaphragm32b.

Another embodiment of the present invention is shown inFIG.14, with like numbers referring to like elements. In this embodiment, the progressive stopper46is a combination stopper, where a recess86is formed as part of the support substrate24, and a stopper ring88is mounted to the outer surface32aof the diaphragm substrate32. The recess86in one embodiment is circular, and has a contact area86a, which is an edge of the recess86. The stopper ring88includes a contact area88a, which is an outer edge of an inner radius formed as part of the stopper ring88. The recess86has an inner surface86bwhich may come into contact with the contact area88awhen pressure is applied to the diaphragm32b.

During operation, once the pressure applied to the diaphragm32breaches above a first predetermined value, the contact area86aof the recess86contacts the outer surface32aof the diaphragm substrate32. Once the pressure applied to the diaphragm32breaches above a second predetermined value, the contact area86aof the recess86is in contact with the outer surface32aof the diaphragm substrate32, and the inner surface86bof the recess86is in contact with the contact area88aof the stopper ring88, limiting the diaphragm stress.

Another embodiment of the present invention is shown inFIG.15, with like numbers referring to like elements. This embodiment is similar to the embodiment shown inFIG.14, the progressive stopper46and is also a combination stopper, but in this embodiment, there are two circular recesses formed as part of the support substrate24. There is a first recess90ahaving a contact area92a, which is an edge of the first recess90a, and the second recess90bhaving a contact area92b, which is an edge of the second recess90b. The first recess90aincludes an inner surface92c, and the second recess90balso includes an inner surface92d.

During operation, once the pressure applied to the diaphragm32breaches above a first predetermined value, the contact area92aof the recess90acontacts the outer surface32aof the diaphragm substrate32as a first contact. Once the pressure applied to the diaphragm32breaches above a second predetermined value, the contact area92aof the recess90ais in contact with the outer surface32aof the diaphragm substrate32, and the contact area92bof the recess90bcontacts the outer surface32aof the diaphragm substrate32as a second contact. Once the pressure applied to the diaphragm32breaches above a third predetermined value, both contact areas92a,92bare in contact with the outer surface32aof the diaphragm substrate32, and the inner surface92dof the recess90bis in contact with the contact area88aas a third contact, limiting the diaphragm stress.

It should be noted that the present invention is not limited to use with a pressure sensing applications, the various embodiments of the progressive stopper46described above may be used for any type of device having a flexible membrane where balancing stress distribution and reduction of peak stress are needed. Any of the embodiments of the progressive stopper46described may be used with a flexible membrane which is designed to detect pressures over a defined range, even after exposure to high pressures outside of the defined pressure range with a higher safety factor.

Additionally, in any of the embodiments above, the stopper rings are not limited to the shapes shown. The stopper rings shown in the Figures may of any suitable shape, such as, but not limited to, square, rectangular, hexagonal, polygon, or any other shape suitable for limiting the deformation of the diaphragm32b. The stopper rings may be printed on the diaphragm substrate32, or the stopper rings may be coated, plated, or otherwise deposited on the diaphragm substrate32using any suitable method. The stopper rings shown inFIGS.3-6,8-10, and14-15may be made of any suitable material, such as, but not limited to, glass, ceramics, metal, or a polymer. Furthermore, the recesses shown inFIGS.11-15may be formed as part of the support substrate24by any suitable process, such as, but not limited to, etching or layer by layer sintering.

In other embodiments, with the progressive stopper46having sufficient shape, and sufficient spacing between the diaphragm32band the support substrate24, the pressure sensor assembly10may be able to withstand exposure to higher pressures over 200 Bar, such as 300 Bar. Three or more contacts between the diaphragm32band the support substrate24may be used to change the diaphragm stress versus pressure, which would be represented by flatter regions on the curve100(and would be in addition to the regions102,104, and106). Each ofFIGS.9-10,12, and15show example embodiments where the progressive stopper46includes three contacts, but other embodiments having three contacts may be contemplated.FIG.13demonstrates an embodiment of the progressive stopper46with continuous contacts as a result of an increase in pressure.