The present disclosure pertains generally to gas sensors and more particularly to gas sensors that are configured for detecting a gas in a high temperature environment.
Gas sensors are used in a variety of different environments for detecting and/or quantifying a variety of different gases. For example, internal combustion engines utilize gas sensors to detect and/or quantify gas concentrations in an exhaust stream emanating from the internal combustion engine. In this example, gases of interest may include carbon monoxide (CO), carbon dioxide (CO2), nitric oxide (NO), nitrogen dioxide (NO2) and/or any other suitable gas of interest. Oxides of nitrogen are commonly referred to as NOx (where x is equal to 1 or 2). Continuing with this example, an engine management system of the internal combustion engine may utilize information regarding the gas concentrations to help improve performance of the engine while reducing pollution. It will be appreciated that gas sensors exposed to an exhaust gas stream need to operate at high temperature. A need remains for improved gas sensors, particularly those that are configured to operate at high temperatures.
The disclosure relates generally to gas sensors for sensing gases of interest, such as in an engine exhaust stream. In a particular example of the disclosure, a gas sensor for sensing a gas of interest includes a ceramic carrier and a porous ceramic lid that is secured to the ceramic carrier. The porous ceramic lid and the ceramic carrier together define a sensor cavity. A gas sensor is situated in the sensor cavity and is spaced from the porous ceramic lid. The porous ceramic lid is configured to allow the gas of interest to move through at least part of the porous ceramic lid and into the sensor cavity to be sensed by the gas sensor.
In another example of the disclosure, a gas sensor for sensing a gas of interest includes a sensor die that defines a diaphragm with a gas sensing active region supported by a first side of the diaphragm and a heater for heating the gas sensing active region. The illustrative gas sensor includes a ceramic housing that defines a sensor cavity for housing the sensor die and that is configured to expose the gas sensing active region to the gas of interest, and to vent a second side of the diaphragm, opposite to the first side, to reduce a pressure differential across the diaphragm.
Another particular example of the disclosure may be found in a gas sensor for sensing a gas of interest. The gas sensor may include a sensor die that defines a diaphragm. A gas sensing active region is supported by the diaphragm, and the gas sensor includes a heater for heating the gas sensing active region. A ceramic housing may define a sensor cavity for housing the sensor die. The ceramic housing may include a plurality of ceramic layers, and at least some of the plurality of ceramic layer may include an aperture, trench or other opening that defines at least part of the sensor cavity.
The above summary of some embodiments is not intended to describe each disclosed embodiment or every implementation of the present disclosure. The Figures, and Detailed Description, which follow, more particularly exemplify some of these embodiments.
The disclosure may be more completely understood in consideration of the following description of various illustrative embodiments of the disclosure in connection with the accompanying drawings, in which:
While the disclosure is amenable to various modifications and alternative forms, specifics thereof have been shown by way of example in the drawings and will be described in detail. It should be understood, however, that the intention is not to limit aspects of the disclosure to the particular illustrative embodiments described. On the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the disclosure.
The following description should be read with reference to the drawings wherein like reference numerals indicate like elements. The drawings, which are not necessarily to scale, are not intended to limit the scope of the disclosure. In some of the figures, elements not believed necessary to an understanding of relationships among illustrated components may have been omitted for clarity.
All numbers are herein assumed to be modified by the term “about”, unless the content clearly dictates otherwise. The recitation of numerical ranges by endpoints includes all numbers subsumed within that range (e.g., 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4, and 5).
As used in this specification and the appended claims, the singular forms “a”, “an”, and “the” include the plural referents unless the content clearly dictates otherwise. As used in this specification and the appended claims, the term “or” is generally employed in its sense including “and/or” unless the content clearly dictates otherwise.
It is noted that references in the specification to “an embodiment”, “some embodiments”, “other embodiments”, etc., indicate that the embodiment described may include a particular feature, structure, or characteristic, but every embodiment may not necessarily include the particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is contemplated that the feature, structure, or characteristic may be applied to other embodiments whether or not explicitly described unless clearly stated to the contrary.
Gas sensors are used in a variety of different environments including, for example, industrial, military, marine and automotive environments. In one non-limiting example, gas sensors are often used for detecting various gases that are present within automotive exhaust streams. While theoretical combustion turns hydrocarbons (gasoline) and oxygen into water and carbon dioxide, combustion in reality provides a number of other gaseous components as well. Gas sensors may be used in sensing the presence and/or concentration of various gases such as O2, NO2, NOx, CO2, NH3, or combinations thereof, in vehicle exhausts. For example, a gas sensor may be used to sense NOx, which generically represents a variety of different oxides of nitrogen, including NO and NO2. Improved sensing of NOx can lead to improved engine efficiency and reduced CO2/NOx emissions through improved operation of Selective Catalytic Reduction (SCR) systems. Accordingly, a modern internal combustion engine may include one or more gas sensors that are positioned such that they are exposed to exhaust gases of the engine. It will be appreciated that an engine is referenced merely as a possible environment for the gas sensors discussed herein, as gas sensors may be used in a variety of other environments as well.
In some cases, as discussed herein, one of the features of the MEMS sensing element 28 is that the MEMS sensing element 28 may include a diaphragm that is formed as part of the MEMS sensing element 28. The diaphragm (shown for example in
The MEMS sensing element 28 may include a sense die 32 that includes a substrate portion and a thinner diaphragm 34. In one example, the sense die 32 may be a Silicon-On-Insulator (SOI) sense die that includes a silicon substrate layer, an insulating layer grown on the silicon substrate, followed by an epi layer grown on the insulating layer. In some cases, a cavity is etched into the back side of the sense die, using the insulating layer as an etch stop. This leaves a thin diaphragm, formed by the insulating layer and the epi layer, upon which an active region and/or heater may be placed. Supporting circuitry may be fabricated in the epi layer, often away from the diaphragm, if desired. In another example, an aperture may be etched all the way through a first silicon wafer. A second silicon wafer may be secured to the first silicon wafer to form the diaphragm across the aperture in the first silicon wafer. A chemical and/or mechanical polishing processes may be used to thin the second silicon wafer to achieve a desired thickness for the diaphragm. These are just some example sense die. It is contemplated that the sense die 32 may have any suitable configuration. Further features of the MEMS sensing element 28 are discussed with respect to subsequent Figures.
In some cases, the upper ceramic layer 40a may be secured to the intermediate ceramic layer 40b via an adhesive layer 44a. In some cases, the assembly 38 may include a lower ceramic layer 40c that is secured via an adhesive layer 44b as well as a lower ceramic layer 40d that is secured via an adhesive layer 44c. It will be appreciated that the ceramic structure 30 may include additional ceramic layers beyond those illustrated. In some cases, the ceramic structure 30 may include fewer ceramic layers than illustrated. For example, the ceramic structure 30 may be formed from a single ceramic layer. The illustrative ceramic structure 30 also includes a porous ceramic lid 46. In some cases, the porous ceramic lid 46 is configured to have pore sizes and/or other defining characteristics of porosity that allow exhaust gases (or other gases to be sampled) to pass through the porous ceramic lid 46. An adhesive layer 48, divided into an adhesive portion 48a, an adhesive portion 48b and an adhesive portion 48c, may help to secure the porous ceramic lid 46 to the upper ceramic layer 40a. In some cases, the adhesive layer 48 or portions thereof are fluid-impervious, and thus may help permit gases to flow through portions of the porous ceramic lid 46 lacking the adhesive layer 48 while preventing gases from flowing through portions of the porous ceramic lid 46 including the adhesive layer 48.
In some cases, the sensor assembly 26 includes venting in order to help equalize pressures on either side of the diaphragm 34. As illustrated, the sensor assembly 26 includes a vent 50 that extends from a first end 50a that is proximate the porous ceramic lid 46 and between the adhesive portions 48a and 48b, to a second end 50b that is proximate and is exposed to a cavity 52a that exists underneath the sense die 32. Because there is no adhesive layer 48 directly above the sense die 32, a cavity 52b above the diaphragm 34 is exposed to gases that pass through the porous ceramic lid 46. The vent 50 helps ensure that the cavity 52a below the diaphragm 34 and the cavity 52b above the diaphragm 34, which together form a portion of a sensor cavity 52, remain at the same or at least substantially the same pressure, which helps to relieve forces that could otherwise be applied to the diaphragm 34. In some instances, the sensor cavity 52 may also be considered as including a cavity region 52c, on a first side of the sense die 32, as well as a cavity region 52d, on a second side of the sense die 32. It is contemplated that the cavity 52c and cavity 52d may be fluidly connected, and in some cases may be considered a single cavity. It will also be appreciated that this is just one example of possible venting structures that may be employed, depending on which portions of the sensor cavity 52 are exposed to exhaust gases. Of course, if the sensor assembly 26 was a pressure sensor, the vent 50 would not be included.
Another feature shown in
The MEMS sensing element 102 may have an upper surface 112 and may include a thin diaphragm 114. The sensor assembly 100 may also include a porous ceramic lid 120 that is assembled above the MEMS sensing element 102, where the porous ceramic lid 120 may be attached to the ceramic substrate 104 using a high-temperature adhesive and/or ceramic cement 106. The porous ceramic lid 120 may be attached above a cavity 103 in the ceramic substrate 104, wherein the MEMS sensing element 102 is located within the cavity 103. In some cases, as illustrated, the porous ceramic lid 120 may be spaced from the upper surface 112 of the MEMS sensing element 102. In some instances, the sensor assembly 100 may include a vent channel 105 extending within the ceramic substrate 104. The vent channel 105 may balance the pressure above and below the diaphragm 114 of the MEMS sensing element 102 by extending from a position underneath the MEMS sensing element 102 to a position where it is fluidly coupled with the cavity 103.
In some cases, as illustrated, the sensor assembly 100 includes a spacer element 113 that is disposed above the MEMS sensing element 102. In some instances, the spacer element 113 helps to protect the diaphragm 114, especially during assembly of the sensor assembly 100. The spacer 113 may include an aperture 113a that allows gases to engage an active region on the diaphragm 114. In some cases, as illustrated, the spacer element 113 is also spaced from the porous ceramic lid 120.
Wire bonds 108 (or alternatively bump bonds, ball grid array, etc.) may be used to electrically connect the MEMS sensing element 102 to bond-pads and/or electrical traces 110 on the ceramic substrate 104. The electrical traces 110 may run along the length of the ceramic substrate 104 to where a standard electrical connection can be made. In some cases, at least a portion of the area around the MEMS sensing element 102 may be filled with potting material to cover the wire bonds 108 (when wire bonds are used), while exposing an active area of the diaphragm of the MEMS sensing element 102. The sensor assembly 100 may be configured to detect one or more (potentially hazardous) gases, which may include NO2, NOx, O2, CO2, NH4, and/or other gases. In some cases, the sensor assembly 100 may include additional elements that are not explicitly shown in
The sensor assembly 200 may include one or more wire bonds 208 (which may be similar to the wire bonds 108) configured to electrically connect the MEMS sensing element 202 to other elements within the sensor assembly 200 and/or outside the sensor assembly 200. The sensor assembly 200 may also include one or more optional vent channels 205 and/or 207 (which may be similar to vent channel 105 of
In some cases, as illustrated, the sensor assembly 200 includes a spacer element 213 that is disposed above the MEMS sensing element 202. In some instances, the spacer element 213 helps to protect the diaphragm 214, especially during assembly of the sensor assembly 200. The spacer 213 may include an aperture 213a that allows gases to engage an active region on the diaphragm 214. In some cases, as illustrated, the spacer element 213 may be in contact with and/or adhesively secured to the porous ceramic lid 220.
In
The ceramic substrate 204 may include a first vent channel 205 configured to balance the pressure above and below the diaphragm 214. The ceramic substrate 204 may optionally include a second vent channel 207 configured to vent the cavity 252 to the atmosphere. In some cases, the second vent channel 207 may be used during assembly of the sensor assembly 200 to avoid pressure build-up which could lift the porous ceramic lid 220 from its position within the ceramic substrate 204, which may cause damage to the porous ceramic lid 220, the MEMS sensing element 202 and/or the ceramic substrate 204. In some cases, the second vent channel 207 may be sealed after the sensor assembly 200 is assembled.
Those skilled in the art will recognize that the present disclosure may be manifested in a variety of forms other than the specific embodiments described and contemplated herein. Accordingly, departure in form and detail may be made without departing from the scope and spirit of the present disclosure as described in the appended claims.
This application claims the benefit of U.S. Provisional Application Ser. No. 62/589,187, entitled PACKAGING FOR MICROELECTROMECHANICAL SYSTEMS HIGH TEMPERATURE GAS SENSOR, and filed on Nov. 21, 2017, which application is incorporated by reference herein in its entirety.
Number | Name | Date | Kind |
---|---|---|---|
3886785 | Stadler et al. | Jun 1975 | A |
3911386 | Beaudoin et al. | Oct 1975 | A |
3928161 | McIntyre et al. | Dec 1975 | A |
3936794 | Beaudoin et al. | Feb 1976 | A |
3940327 | Wagner et al. | Feb 1976 | A |
4040930 | Dillon | Aug 1977 | A |
4130797 | Hattori et al. | Dec 1978 | A |
4277323 | Muller et al. | Jul 1981 | A |
4282080 | Muller et al. | Aug 1981 | A |
4283261 | Maurer et al. | Aug 1981 | A |
4300990 | Maurer | Nov 1981 | A |
4305803 | Beyer et al. | Dec 1981 | A |
4305903 | Krause | Dec 1981 | A |
4310401 | Stahl | Jan 1982 | A |
4368431 | Rohr et al. | Jan 1983 | A |
4413502 | Ohta et al. | Nov 1983 | A |
4414531 | Novak | Nov 1983 | A |
4419212 | Dietz et al. | Dec 1983 | A |
4437971 | Csanitz et al. | Mar 1984 | A |
4489596 | Linder et al. | Dec 1984 | A |
4535316 | Wertheimer et al. | Aug 1985 | A |
4556475 | Bayha et al. | Dec 1985 | A |
4560463 | Frey et al. | Dec 1985 | A |
4609454 | Ziegler | Sep 1986 | A |
4636293 | Bayha et al. | Jan 1987 | A |
4736618 | Usami et al. | Apr 1988 | A |
4756885 | Raff et al. | Jul 1988 | A |
5246562 | Weyl et al. | Sep 1993 | A |
5625156 | Serrels et al. | Apr 1997 | A |
5942092 | Weyl et al. | Aug 1999 | A |
5955656 | Graser et al. | Sep 1999 | A |
6018982 | Friese et al. | Feb 2000 | A |
6164120 | Friese et al. | Dec 2000 | A |
6206377 | Weyl | Mar 2001 | B1 |
6223583 | Friese et al. | May 2001 | B1 |
6257573 | Munoz et al. | Jul 2001 | B1 |
6273432 | Weyl et al. | Aug 2001 | B1 |
6311453 | Mechnick | Nov 2001 | B1 |
6319376 | Graser et al. | Nov 2001 | B1 |
6344134 | Yamada et al. | Feb 2002 | B1 |
6347543 | Geier et al. | Feb 2002 | B1 |
6352632 | Inagaki et al. | Mar 2002 | B1 |
6375828 | Ando et al. | Apr 2002 | B2 |
6408680 | Friese et al. | Jun 2002 | B2 |
6432288 | Nielsen et al. | Aug 2002 | B1 |
6474655 | Weyl et al. | Nov 2002 | B1 |
6487890 | Weyl et al. | Dec 2002 | B1 |
6527573 | Stein, Sr. et al. | Mar 2003 | B2 |
6585872 | Donelon et al. | Jul 2003 | B2 |
6613206 | Weyl et al. | Sep 2003 | B1 |
6672132 | Weyl et al. | Jan 2004 | B1 |
6672900 | France et al. | Jan 2004 | B2 |
6766817 | da Silva | Jul 2004 | B2 |
6918404 | Dias da Silva | Jul 2005 | B2 |
7021354 | Kobayashi et al. | Apr 2006 | B2 |
7066586 | da Silva | Jun 2006 | B2 |
7159447 | Nakagawa | Jan 2007 | B2 |
7338202 | Kapat et al. | Mar 2008 | B1 |
8359902 | Thanigachalam et al. | Jan 2013 | B2 |
9494543 | Moon et al. | Nov 2016 | B2 |
9506392 | Fix et al. | Nov 2016 | B2 |
9574947 | Cole et al. | Feb 2017 | B2 |
9910023 | Ui et al. | Mar 2018 | B2 |
10126223 | Kim et al. | Nov 2018 | B2 |
20020048991 | France et al. | Apr 2002 | A1 |
20030160844 | da Silva | Aug 2003 | A1 |
20040077201 | Kobayashi et al. | Apr 2004 | A1 |
20040159547 | Haraguchi et al. | Aug 2004 | A1 |
20040187919 | da Silva | Sep 2004 | A1 |
20040196338 | da Silva | Oct 2004 | A1 |
20040237529 | da Silva | Dec 2004 | A1 |
20050109081 | Zribi | May 2005 | A1 |
20050160840 | Allmendinger | Jul 2005 | A1 |
20080016946 | Thanigachalam et al. | Jan 2008 | A1 |
20080206107 | Thanigachalam et al. | Aug 2008 | A1 |
20110126612 | Shimizu | Jun 2011 | A1 |
20110138882 | Moon et al. | Jun 2011 | A1 |
20120103058 | Maeda et al. | May 2012 | A1 |
20170038273 | Krauss et al. | Feb 2017 | A1 |
20170122898 | Akasaka | May 2017 | A1 |
20180106745 | Shibasaki et al. | Apr 2018 | A1 |
Number | Date | Country |
---|---|---|
0936461 | Aug 1999 | EP |
1467735 | Mar 1977 | GB |
2166866 | May 1986 | GB |
2289944 | Dec 1995 | GB |
05052143 | Mar 1993 | JP |
Number | Date | Country | |
---|---|---|---|
20190154613 A1 | May 2019 | US |
Number | Date | Country | |
---|---|---|---|
62589187 | Nov 2017 | US |