The present disclosure relates generally to pressure sensors, and more particularly, to pressure sensors for sensing pressure of a media.
Sensors, such as pressure and flow sensors, are often used to sense the pressure and/or flow of a media (e.g. gas or liquid) in a fluid channel. Such sensors are commonly used in a wide variety of applications including, for example, medical applications, flight control applications, industrial process applications, combustion control applications, weather monitoring applications, water metering applications, as well as many other applications.
The present disclosure relates generally to pressure sensors, and more particularly, to pressure sensors for sensing a pressure of a media such as a gas or a liquid. In some embodiments, certain sensor features can help isolate the sensor and/or sensor components from media in harsh environments, such as environments in which the media can freeze. In one illustrative embodiment, a pressure sensor may include a substrate having a first side and a second side. A pressure sensing die may be mounted on the first side of the substrate with, for example, an adhesive, solder or other attachment mechanism. In some cases, a first housing member is positioned on the first side of the substrate, and may define a first cavity around the pressure sensing die. In some cases, a second housing member may be positioned on the second side of the substrate, and may define a second cavity. A passivating agent, such as a gel, can be positioned in one or both of the first cavity and the second cavity. The passivating agent may be configured to transmit pressure from a media to a pressure sensing element (e.g. diaphragm) of the pressure sensing die, while isolating the pressure sensing element (e.g. diaphragm) and/or other electronics or components of the pressure sensor from the media. In some cases, the passivating agent in the second cavity, when present, may have a non-uniform thickness and/or may be thinner than the passivating agent in the first cavity, but this is not required.
In some cases, an opening in the first housing member and/or the second housing member may be defined by one or more tapered and/or chamfered edges that are angled away from an axis extending perpendicular to the substrate. The one or more tapered and/or chamfered edges may help provide freeze damage protection to the pressure sensor by, for example, providing a relief so that when a freezing media expands, the freezing media is directed away from the pressure sensor.
In another illustrative embodiment, a method of manufacturing a pressure sensor is disclosed. The method may include, for example, mounting a pressure sensing die on a first side of a substrate, mounting a first housing member on the first side of the substrate to form a first cavity around the pressure sensing die, and mounting a second housing member on the second side of the substrate to form a second cavity. The first housing member and the second housing member may each include a pressure opening defined by one or more edges of the respective housing member. The method may further include filling at least a portion of the first cavity with a first gel and filling at least a portion of the second cavity with a second gel. In some cases, the first and second gel may be configured to transmit pressure from a media to be sensed to a pressure sensing element of the pressure sensing die.
The preceding summary is provided to facilitate a general understanding of some of the innovative features of the present disclosure, and is not intended to be a full description. A full appreciation of the disclosure can be gained by taking the entire specification, claims, drawings, and abstract as a whole.
The disclosure may be more completely understood in consideration of the following detailed description of various illustrative embodiments of the disclosure in connection with the accompanying drawings, in which:
The following description should be read with reference to the drawings wherein like reference numerals indicate like elements throughout the several views. The description and drawings show several embodiments which are meant to be illustrative in nature.
As shown in
When provided, the piezoresistive components may be configured to have an electrical resistance that varies according to an applied mechanical stress (e.g. pressure sensing diaphragm 26 deflection). In some cases, the piezoresistive components may include a silicon piezoresistive material, however, other non-silicon materials may be used. In some cases, the piezoresistive components may be connected in a Wheatstone bridge configuration (full or half bridge). It is to be understood that the piezoresistive components are only one example of a pressure sensing element that can be used, and it is contemplated that any other suitable sensing elements may be used, as desired.
In some embodiments, such as the illustrative embodiment shown in
In some cases, signal conditioning circuitry 36 may be mounted to the package substrate 12 using an adhesive 40 or any other suitable bonding mechanism (e.g. solder, eutectic, etc.). As shown, signal conditioning circuitry 36 may be secured to the package substrate 12 adjacent to the pressure sense die 18, and may be electrically connected to pressure sensing die 18 via direct die-to-die wire bonds, but this is not required. As shown in
In the illustrative embodiment, the package substrate 12 may include a ceramic material, however, it is contemplated that other suitable materials may be used as desired. In some cases, the pressure sensing die 18 may be mounted to the substrate 12 using an adhesive 32 such as a silicone, RTV, a silicone-epoxy, a soft epoxy, or a regular or hard epoxy. In some cases, the adhesive 32 may have a thickness providing mechanical stress isolation between the pressure sensing die 18 and the package substrate 12 such that the pressure sensing die 18 is effectively unconstrained relative to the package substrate 12. In some cases, the thickness of adhesive 32 may be thick enough for adequate adherence of pressure sense die 18 to substrate 12, but not so thick so as to interfere with the bonding or diaphragm of pressure sense die 18. In other cases, the pressure sensing die 18 may be mounted to the substrate 12 using any other suitable bonding mechanism (e.g. solder, eutectic, etc.).
In some instances, an alumina based ceramic package substrate 12 may be used, and a pressure sensing die 18 may be directly attached or glued to the package substrate 12, sometimes using an RTV, silicone, epoxy, or other suitable adhesive. In some instances, no intervening isolation layers or substrates are provided between the pressure sensing die 18 and the package substrate 12, but this is not required. Thermal and mechanical stresses may be minimized by careful design of the entire package. The ceramic substrate 12 itself may be thick relative to its surface area to help improve stability. In some embodiments, the pressure sensing die 18 may include a silicon material, and the package substrate 12 may include an alumina ceramic, which may have similar temperature expansion coefficients. The pressure sensing die 18 and package substrate 12, however, may be made of materials other than those stated herein. Additionally, it is contemplated that an isolation layer or glass substrate may be provided in pressure sensor 10, if desired.
In some cases, the pressure sensing die 18 may be mounted over an opening 24 in the package substrate 12 that is sized to expose the back side of the pressure sensing diaphragm 26 to the bottom side of the package substrate 12. In this instance, a pressure applied to the back side of pressure sensor 10 may be transmitted to the back side of pressure sensing diaphragm 26 via passivating agent 13 and opening 24.
In the illustrative embodiment, a protective housing of the pressure sensor 10 may be provided. The protective housing may include a top protective cover 14 defining a cavity 28 for the pressure sensing die 18 and a bottom protective cover 16 defining cavity 29. As illustrated, the top protective cover 14 is disposed on a top side of the substrate 12. The bottom protective cover 16 is disposed on a bottom side of the substrate 12. With such a configuration, the top and bottom protective covers 14 and 16 may help protect the pressure sensing element of pressure die 18. In some cases, the top protective cover 14 and the bottom protective cover 16 may be formed from, for example, plastic, polyamide, ceramic, or any other suitable material. In some cases, these covers may be attached to the substrate with the same or substantially the same “footprint” on each side, but this is not required.
In the illustrative embodiment shown in
In the illustrative embodiment of
In
In some embodiments, the inner housing member 17 may include one or more tapered and/or chamfered edges 21 that define pressure opening 20. The one or more tapered and/or chamfered edges 21 may be angled away from an axis extending perpendicular to the substrate 12, as shown. In this configuration, the one or more tapered and/or chamfered edges 21 may help provide freeze damage protection to the pressure sensor 10 by, for example, providing a relief so that when a freezing media expands, the freezing media is directed away from the pressure sensor. Said another way, tapered and/or chamfered edges 21 may cause a freezing media to expand out of the pressure sensor 10. As shown in
In the illustrative embodiment, cavity 28 and/or cavity 29 may be at least partially filled with a passivating agent 13 or coating, which may include a gel or other passivating agent. In some cases, the passivating agent 13 may include an incompressible material to transmit pressures from openings 20 and 22 to the pressure sensing diaphragm 26. As shown in
In some cases, the passivating agent 13 may help isolate the pressure sensing die 18, signal conditioning circuitry 36, and/or other electronics from a sensed media. Example passivating agents may include gels, such as a flourosilicone gel. Some example gels include Sylgard® 527 and TSE 118, which are available from Dow Corning Corporation. In some cases, the top side and bottom side of pressure sensor 10 may be filled with different passivating agents 13 or gels. For example, cavity 28 may be filled with a first gel, such as Sylgard® 527, and cavity 29 may be filled with a second gel, such as TSE 118. In some cases, filling both cavities 28 and 29 of pressure sensor 10 with the same passivating agent 13 with the same thickness may help stabilize the pressure sensor 10 for age (e.g. drift), help equalize and cancel out the stress caused by the passivating agent 13 at the sensing element, and/or help reduce temperature (e.g. thermal expansion) induced variations in the sensor.
In some cases, the passivating agent 13 may be filled in cavities 28 and 29 with a thickness in the range of 0.1 to 5 millimeters. The cavities 28 and 29 may be filled with the same or different thicknesses of a passivating agent 13. For example, cavity 28 of the top protective cover 14 may be filled with a passivating agent 13 having a thickness in the range of about 1 to about 2 millimeters, and cavity 29 may be filled with a passivating agent 13 having a thickness in the range of about 0.1 to about 1 millimeter. Further, it is contemplated that cavities 28 and/or 29 may have varying thicknesses of passivating agents 13. For example, as shown in
In the illustrative embodiment, the passivating agent 13 may be filled and/or processed to reduce air and/or bubbles from being trapped in passivating agent 13 within the cavities 28 and 29. Example procedures to reduce air and/or bubbles may include filling the cavities 28 and 29 with the passivating agent 13 under a vacuum, pulling a vacuum on the passivating agent 13 prior to curing, curing the passivating agent 13 under a vacuum (e.g. outgas during curing), and/or using any other suitable procedure, as desired.
In operation, a first pressure may be applied to passivating agent 13 in opening 20 defined by top cover 14, which is transmitted to a first side of the pressure sensing diaphragm 26 via cavity 28. A second pressure may be applied to passivating agent 13 in opening 22 defined by bottom cover 16, which is transmitted through cavity 29 to a second side of the pressure sensing diaphragm 26. A pressure difference between the first pressure and second pressure can cause a deflection of pressure sensing diaphragm 26, which may then stress one or more piezoresistive elements on the pressure sensing diaphragm 26. Applying a current through the piezoresistive elements may provide a signal that corresponds to the pressure difference between the first pressure and the second pressure. In some cases, the resulting signal may be conditioned by conditioning circuitry 36 and output via electrical leads 30 (shown in
As shown in
In the illustrative embodiment of
In the illustrative embodiment of
In the illustrative embodiment of
In the illustrative embodiment, the one or more side walls may include an inner surface defining cavity 28 for housing the pressure sensing die 18, optional signal conditioning circuitry 36, and any other suitable electronics, as desired. As discussed above, cavity 28 may be at least partially filled with a passivating agent 13 or gel when assembled on substrate 12. In some embodiments, to reduce air or other bubbles from being trapped within the passivating agent or gel, the side walls may be chamfered or rounded to aid in releasing air from the cavity.
As shown in
Further, while openings 54, 64, 74, 76, 84 and 94 are shown as being formed in the top protective cover 14, it is contemplated that the bottom protective cover 16 may include similar openings, as desired.
Having thus described the preferred embodiments of the present disclosure, those of skill in the art will readily appreciate that yet other embodiments may be made and used within the scope of the claims hereto attached. Numerous advantages of the disclosure covered by this document have been set forth in the foregoing description. It will be understood, however, that this disclosure is, in many respect, only illustrative. Changes may be made in details, particularly in matters of shape, size, and arrangement of parts without exceeding the scope of the disclosure. The disclosure's scope is, of course, defined in the language in which the appended claims are expressed.
Number | Name | Date | Kind |
---|---|---|---|
4658651 | Le | Apr 1987 | A |
4823605 | Stein | Apr 1989 | A |
4942383 | Lam et al. | Jul 1990 | A |
4990462 | Silwa, Jr. | Feb 1991 | A |
5086777 | Hishii | Feb 1992 | A |
5225373 | Takahashi et al. | Jul 1993 | A |
5257547 | Boyer | Nov 1993 | A |
5327785 | Maurer | Jul 1994 | A |
5410916 | Cook | May 1995 | A |
5438877 | Vowles et al. | Aug 1995 | A |
5465626 | Brown et al. | Nov 1995 | A |
5644285 | Maurer | Jul 1997 | A |
5691480 | Cook, Sr. et al. | Nov 1997 | A |
6025252 | Shindo et al. | Feb 2000 | A |
6058782 | Kurtz et al. | May 2000 | A |
6143673 | Jang et al. | Nov 2000 | A |
6148673 | Brown | Nov 2000 | A |
6209398 | Fowler, Jr. et al. | Apr 2001 | B1 |
6350630 | Wildgen | Feb 2002 | B1 |
6401545 | Monk et al. | Jun 2002 | B1 |
6577224 | Kurtz | Jun 2003 | B2 |
6612178 | Kurtz et al. | Sep 2003 | B1 |
6691581 | Kurtz et al. | Feb 2004 | B2 |
6732588 | Mullenborn et al. | May 2004 | B1 |
6756248 | Ikeda et al. | Jun 2004 | B2 |
6756316 | Bothra et al. | Jun 2004 | B1 |
6979872 | Borwick, III et al. | Dec 2005 | B2 |
7162927 | Selvan et al. | Jan 2007 | B1 |
7231827 | Kumpfmuller | Jun 2007 | B2 |
7243552 | Vas et al. | Jul 2007 | B2 |
7252007 | Ruohio et al. | Aug 2007 | B2 |
7290453 | Brosh | Nov 2007 | B2 |
7343080 | Gally et al. | Mar 2008 | B2 |
7400042 | Eriksen et al. | Jul 2008 | B2 |
7430918 | Selvan et al. | Oct 2008 | B2 |
7434474 | DuPuis | Oct 2008 | B1 |
7462831 | Gooch et al. | Dec 2008 | B2 |
7478562 | Kurtz et al. | Jan 2009 | B2 |
7538401 | Eriksen et al. | May 2009 | B2 |
7571651 | Kim et al. | Aug 2009 | B2 |
7622782 | Chu et al. | Nov 2009 | B2 |
7624632 | Hoyle et al. | Dec 2009 | B1 |
7644625 | Ricks | Jan 2010 | B2 |
7654155 | Johansen et al. | Feb 2010 | B2 |
7659610 | Chen et al. | Feb 2010 | B2 |
7677109 | Bentley et al. | Mar 2010 | B2 |
7740273 | Breed | Jun 2010 | B2 |
7810394 | Yazdi | Oct 2010 | B2 |
7826267 | Frayer et al. | Nov 2010 | B2 |
20050120798 | James | Jun 2005 | A1 |
20070238215 | Stewart et al. | Oct 2007 | A1 |
20070279845 | Kuhnt et al. | Dec 2007 | A1 |
20080290494 | Lutz et al. | Nov 2008 | A1 |
20090288484 | Selvan et al. | Nov 2009 | A1 |
20090288492 | Stewart et al. | Nov 2009 | A1 |
20100013165 | Speldrich et al. | Jan 2010 | A1 |
20100122583 | Rozgo et al. | May 2010 | A1 |
20100199777 | Hooper et al. | Aug 2010 | A1 |
20100242628 | Knobloch et al. | Sep 2010 | A1 |
20100271735 | Schreiber | Oct 2010 | A1 |
20100281993 | Lo et al. | Nov 2010 | A1 |
20100281994 | Brown et al. | Nov 2010 | A1 |
20110005326 | Bentley et al. | Jan 2011 | A1 |
20110036174 | Hooper et al. | Feb 2011 | A1 |
Number | Date | Country |
---|---|---|
0659910 | Jun 1995 | EP |
0312532 | Sep 1995 | EP |
2184594 | May 2010 | EP |
09092670 | Apr 1997 | JP |
20030130743 | May 2003 | JP |
8602446 | Apr 1986 | WO |
2008036701 | Mar 2008 | WO |
2008036705 | Mar 2008 | WO |
Number | Date | Country | |
---|---|---|---|
20120042734 A1 | Feb 2012 | US |