Pressure sensor assembly and method for producing a pressure sensor assembly
Patent Information
- Application Number
- EP2023704319
- Authority / Receiving Office
- EP · EP
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2022-02-23
- Filing Date
- 2023-02-08
- Publication Date
- 2025-01-01
AI Technical Summary
Conventional pressure sensor arrangements face accuracy and functionality limitations due to mechanical stresses caused by thermal expansion discrepancies between different materials when exposed to high and low temperatures, especially in aggressive media and industrial applications.
A pressure sensor arrangement featuring a MEMS sensor element with a silicon chip and an optically transparent glass substrate, fused together using ultra-short laser pulses for a connection interface, minimizing thermal expansion discrepancies and eliminating the need for additional joining materials, thus ensuring a mechanically stable and hermetically sealed connection.
The solution provides a durable, accurate, and reliable pressure sensor capable of operating across a wide temperature range (-40°C to 150°C) without mechanical stresses, enhancing performance in aggressive media and industrial applications.
Smart Images
Figure 1.1
Abstract
Description
[0001] Description
[0002] Pressure sensor arrangement and method for producing a pressure sensor arrangement
[0003] The present invention relates to a pressure sensor assembly. The invention further relates to a method for manufacturing a pressure sensor assembly.
[0004] Pressure sensors for differential, relative and absolute pressure are usually hybrid structures made of different functional materials with varying thermal expansion coefficients and therefore have an individually specific profile with regard to mechanical stresses between the materials incorporated in the composite when exposed to high temperatures (e.g. up to at least 150°C) and low temperatures (e.g. down to at least -40°C).
[0005] Known pressure sensor assemblies generally consist of a sensor element that is mechanically held and electrically contacted by a combination of different materials, allowing it to be incorporated into a working arrangement for pressure measurement. The mechanical mounting of the sensor element in aggressive media cannot be achieved using organic adhesives, as organic adhesives are not always able to withstand the aggressive fluids. Therefore, in applications under aggressive conditions, the mechanical mounting of the sensor element is achieved using inorganic joining materials on metal or ceramic substrates, for example using hard or soft solder materials or joining glasses. In such assemblies, the thermal expansion coefficients of the sensor element, solder material, and substrate differ significantly, up to 10 ppm / K and more.
[0006] The resulting mechanical stresses can lead to pressure measurement errors due to thermal hysteresis, pressure hysteresis, zero point stability, output stability under pressure and other non-compensable errors.
[0007] Therefore, state-of-the-art pressure sensor assemblies exhibit technical limitations in their accuracy and functionality when exposed to high or low temperatures. The technical limitations of the pressure sensor assemblies can therefore potentially restrict the functionality of complex technical systems in industrial and automotive applications.
[0008] The aim of the present invention is to describe a pressure sensor arrangement and a manufacturing method which solve the problems prevailing in the prior art.
[0009] This object is achieved by a pressure sensor arrangement and a method according to the independent claims.
[0010] According to one aspect, a pressure sensor arrangement is described. The pressure sensor arrangement is designed to determine differential, relative or absolute pressure. The pressure sensor arrangement is designed to measure the pressure of a liquid or a gas reliably and accurately under aggressive conditions. The pressure sensor arrangement is suitable for withstanding aggressive media such as oil, fuel, urea, refrigerant and the like. The pressure sensor arrangement is further designed to operate in a wide temperature range which includes low temperatures down to at least -40°C and high temperatures up to at least 150°C. The pressure sensor arrangement is further designed to measure the pressure of a liquid or a gas in a pressure range which extends from 0.05 bar up to 100 bar or more.The pressure sensor assembly is suitable for use in a motor vehicle, for example, as a vehicle exhaust application and / or in the powertrain. The pressure sensor assembly is also suitable, for example, as a coolant or hydrogen pressure sensor for monitoring industrial processes.
[0011] The pressure sensor arrangement has at least one sensor element. The sensor element can be designed as a MEMS (microelectronic mechanical system) component. The sensor element preferably has a silicon chip.
[0012] The sensor element has a membrane. The membrane is designed and arranged to be exposed to a medium, in particular a liquid or a gas. The sensor element has a top side and a bottom side. The top side and bottom side are arranged opposite one another. For the orientation of the sensor element, the side of the sensor element on which the membrane is located is referred to below as the top side of the sensor element and the opposite side is referred to as the bottom side of the sensor element. On the bottom side in the sensor element there is a media access which makes the membrane accessible from the bottom to a pressurised medium.
[0013] The sensor element has at least one detection element, preferably a plurality of detection elements. The detection element is designed to measure a pressure of the medium. The detection element is formed on the membrane.
[0014] The pressure sensor arrangement further comprises a substrate. The substrate has a top side and a bottom side. The substrate serves as a carrier for the sensor element. The sensor element is arranged on the substrate, in particular on the top side of the substrate. The substrate is optically transparent. The substrate comprises glass. The substrate is preferably made of glass.
[0015] The sensor element and the substrate are mechanically firmly and permanently connected to one another. The sensor element and the substrate are fused or welded together. A connection interface is formed between the sensor element and the substrate. The connection interface is an area in which the substrate and sensor element are connected to one another. The connection interface is formed between the underside of the sensor element and the top side of the substrate.
[0016] The connection interface is created by laser welding. In other words, the substrate and sensor element are joined, in particular fused, by laser welding. Laser welding is preferably carried out using ultrashort laser pulses (pulse lengths in the picosecond range and shorter). The heat input generated by laser welding is locally limited, i.e., the substrate is not completely heated. Heating and thus fusing of the substrate and sensor element only occurs in a joining region between the substrate and the sensor element, i.e., in an area where the substrate and sensor element are joined to one another.In particular, during laser welding with ultrashort laser pulses, the light is focused through the optically transparent substrate without heat input into it to the joining area, where the heat, via multiphoton absorption in the focal area over a few 10 micrometers, leads extremely locally to a mechanically stable joining of the sensor element and the substrate via fusion and thus to the formation of the connection interface.
[0017] This eliminates the need for an additional connecting element or joining material for connecting the sensor element and substrate. The sensor element and the substrate are mechanically and hermetically sealed together at the connection interface.
[0018] By joining the sensor element and substrate using laser welding, additional joining materials / joining agents, which can lead to mechanical stress due to different expansion coefficients, are eliminated. This provides a particularly durable and reliable pressure sensor assembly. Furthermore, the pressure sensor assembly is more accurate and functional than conventional pressure sensor assemblies when exposed to high temperatures (up to at least 150 °C) and low temperatures (e.g., down to at least -40 °C).
[0019] According to one embodiment, the substrate has a thermal expansion coefficient that differs from the thermal expansion coefficient of the sensor element by less than 1 ppm / K. Thus, the substrate and sensor element have an almost identical thermal expansion coefficient. Due to the minimal or complete absence of thermal expansion discrepancies, only minimal or no mechanical stresses arise in the pressure sensor arrangement that could be transferred from the substrate to the sensor chip at high and low temperatures. This provides a particularly reliable pressure sensor arrangement.
[0020] According to one embodiment, the sensor element has a connecting base. The connecting base is arranged between the sensor element and the substrate. The connecting base is arranged on the underside of the sensor element. The sensor element and the connecting base constitute a sensor system.
[0021] The connection base ensures mechanical decoupling of the sensor element from the joining area with the substrate. The connection base is preferably used for very precise pressure sensors. The laser welding with ultrashort laser pulses described above is possible both with the sensor element and with a connection base located between the sensor element and the substrate.
[0022] The connection base comprises glass. The connection base is preferably made of glass. The connection base preferably comprises a material that is very similar or identical to the substrate material. In particular, a thermal expansion coefficient of the connection base differs by less than 1 ppm / K from the thermal expansion coefficient of the substrate. This allows the pressure sensor arrangement to be kept largely free of mechanical stresses.
[0023] According to one embodiment, the connecting base is attached to the sensor element. For example, the connecting base is connected to the sensor element by anodic bonding. The connection interface is formed between the connecting base and the substrate. In other words, the sensor system comprising the sensor element and the connecting base is connected to the substrate by laser welding with ultrashort laser pulses. Laser energy for connecting the substrate and the sensor system is coupled into a side of the substrate opposite the sensor system, i.e., onto an underside of the substrate.
[0024] According to a further aspect, a method for manufacturing a pressure sensor assembly is described. Preferably, the method produces the pressure sensor assembly described above. All properties disclosed with respect to the pressure sensor assembly or the method are also disclosed correspondingly with respect to the respective other aspect, and vice versa, even if the respective property is not explicitly mentioned in the context of the respective aspect. The method comprises the following steps:
[0025] A) Providing a substrate, preferably the substrate described above. The substrate comprises glass.
[0026] B) Providing a sensor element, preferably the sensor element described above. The sensor element preferably has a silicon chip. The sensor element has a top side and a bottom side. A membrane is formed on the top side of the sensor element. The substrate preferably has a thermal expansion coefficient that differs from a thermal expansion coefficient of the sensor element by less than 1 ppm / K. C) Mechanically strong and hermetically sealed joining of substrate and sensor element by laser welding. The laser welding is carried out using ultrashort laser pulses. The pulse lengths are in the picosecond and / or femtosecond range. The material of the substrate is completely transparent to the laser wavelength. In this method, the light is focused through the optically transparent substrate without heat input into it to a joining area between the substrate and sensor element.At the joining area, the heat, via nonlinear absorption (multiphoton absorption) in the focal range over a few tens of micrometers, leads to a mechanically stable joining of the sensor element and substrate extremely locally through fusion. The laser energy for connecting the substrate and sensor element is coupled into a side of the substrate opposite the sensor element (i.e., onto the underside of the substrate). The energy is supplied without physical contact with the substrate / sensor element and can be selectively coupled into the desired joining area.
[0027] Furthermore, laser welding eliminates the need for additional joining agents to connect the substrate and sensor element. Due to the minimal or complete absence of thermal expansion discrepancies, minimal or no mechanical stresses are generated in the pressure sensor assembly, which are transferred from the substrate to the sensor chip at both high and low temperatures. This provides a highly flexible and efficient process for producing an extremely reliable, highly efficient, and durable pressure sensor assembly.
[0028] According to one embodiment, an optional
[0029] In step 1, a connection base is provided before the sensor element is connected to the substrate. The connection base comprises glass. Preferably, the substrate has a thermal expansion coefficient that differs from a thermal expansion coefficient of the sensor element and the connection base by less than 1 ppm / K. Preferably, the connection base and the substrate comprise the same material.
[0030] The connecting base, in particular a top side of the connecting base, is connected to the bottom side of the sensor element to form a sensor system comprising the connecting base and the sensor element. Preferably, the connecting base is connected to the sensor element by anodic bonding.
[0031] The sensor system is then connected, in particular fused, to the substrate using the laser welding process described above (laser welding with ultrashort laser pulses). In particular, laser welding creates a mechanically strong and hermetically sealed bond between the underside of the sensor system and the top side of the substrate. The laser energy for connecting the substrate and the sensor system is coupled into a side of the substrate opposite the sensor system.
[0032] The following drawing is not to be considered to scale. Rather, individual dimensions may be enlarged, reduced, or distorted for clarity.
[0033] It shows: Figure 1 a sectional view of a pressure sensor arrangement according to an embodiment.
[0034] Figure 1 shows a pressure sensor assembly 100 for measuring absolute, relative, or differential pressure. The pressure sensor assembly 100 is suitable for use in a motor vehicle, for example, as a vehicle exhaust application and / or in the powertrain. The pressure sensor assembly 100 is also suitable, for example, as a coolant or hydrogen pressure sensor for monitoring industrial processes. The pressure sensor assembly 100 can be used over a very wide temperature range (e.g., -40°C to 150°C).
[0035] The pressure sensor arrangement 100 has a sensor element 202 with a top side 118 and a bottom side 204. The sensor element 202 is preferably a silicon chip. The sensor element 202 has a membrane 106 on the top side 118, which outwardly delimits a cavity 107 in an interior region of the pressure sensor arrangement 100. The membrane 106 is designed and arranged to be exposed to a medium (e.g., a fluid or a gas). Furthermore, a sensing element 109 is arranged on the membrane 106 for measuring a pressure of the medium. Of course, the pressure sensor arrangement 100 can also have more than one sensing element 109.
[0036] The pressure sensor assembly 100 further includes a substrate 104 supporting the sensor element 202. The substrate 104 has a top side 115 and a bottom side 114. The sensor element 202 is arranged on the top side 115 of the substrate 202 or is attached to the substrate 202. The sensor element 202 is welded or fused to the top side 115 of the substrate 202, as described in detail later.
[0037] The substrate 104 comprises glass. The substrate 104 has a thermal expansion coefficient that differs from the thermal expansion coefficient of the sensor element 202 by less than 1 ppm / K. Consequently, the substrate 104 and the sensor element 202 have approximately the same thermal expansion coefficients, which leads to a reduction or avoidance of mechanical stresses, particularly at very high and very low temperatures.
[0038] A connection interface 201 is formed between the sensor element 202 and the substrate 104. The connection interface 201 is a region in which the sensor element 202 and the substrate 104 are mechanically firmly and hermetically connected to one another, in particular fused.
[0039] The connection interface 201 is created by laser welding with ultrashort laser pulses. In other words, the substrate 104 and the sensor element 202 are joined together by laser welding, thus eliminating the need for additional joining materials. This eliminates the need to introduce additional components to connect the sensor element 202 and the substrate 104. Mechanical stresses that arise from the introduction of components with a thermal expansion coefficient that differs significantly from that of the substrate 104 / the sensor element 202 are thus eliminated.
[0040] In the exemplary embodiment shown, the pressure sensor arrangement 100 additionally has a connecting base 220. The connecting base 220 is arranged between the sensor element 202 and the substrate 104 and comprises glass. A thermal expansion coefficient of the connecting base 220 differs by less than 1 ppm / K from the thermal expansion coefficient of the substrate 104 and the sensor element 202. The occurrence of mechanical stresses due to the introduction of an element with a significantly different thermal expansion coefficient compared to the thermal expansion coefficient of the substrate 104 / the sensor element 202 can thus be avoided.
[0041] The connecting base 220 is attached to the sensor element 202. In particular, the connecting base 220 and the sensor element 202 are firmly connected to one another, for example, by anodic bonding. The sensor element 202 and the connecting base 220 together form a sensor system 102.
[0042] The above-described connection interface 201 is formed between the sensor system 102, in particular an underside of the sensor system 102, and the substrate 104, in particular the top side 115 of the substrate 104. Thus, the sensor system 102 and the substrate 104 are mechanically firmly and hermetically connected to one another at the connection interface 201, in particular fused. The laser energy for generating the connection interface 201 is coupled into a side of the substrate 104 opposite the sensor system 102, i.e., at the underside 114 of the substrate 104.
[0043] In an alternative embodiment (not explicitly shown), the connection base 220 can also be omitted. This means that the sensor element 202 is connected directly (without an intermediate element) to the substrate 104. In this case, the connection interface 201 is formed between the underside 204 of the sensor element 202 and the top side 115 of the substrate 104. A method for producing a pressure sensor arrangement, preferably the pressure sensor arrangement 100 described above, is described below. All properties disclosed with respect to the pressure sensor arrangement 100 or the method are also disclosed correspondingly with respect to the respective other aspect and vice versa, even if the respective property is not explicitly mentioned in the context of the respective aspect. The method comprises the following steps:
[0044] In a first step A), the substrate 104 is provided. The substrate 104 comprises glass as described above.
[0045] In a second step B), at least one sensor element 202, preferably a plurality of sensor elements 202, is provided. The sensor element 202 preferably comprises a silicon chip. The sensor element 202 has a top side 118 and a bottom side 204, with a membrane 106 formed on the top side 118. As described above, the substrate 104 has a thermal expansion coefficient that differs from a thermal expansion coefficient of the sensor element 202 by less than 1 ppm / K.
[0046] In a next step C ), the mechanically strong and hermetically sealed connection of substrate 104 and sensor element 202 is carried out by laser welding . The laser energy for connecting substrate 104 and sensor element 202 is coupled into a side of the substrate 104 opposite the sensor element 202 (i.e., at the underside 114 of the substrate 104). The laser welding creates the connection interface 201 , i.e., the area in which substrate 104 and sensor element
[0047] 202 are firmly connected to each other .
[0048] Laser welding is performed using ultrashort laser pulses. The pulse lengths are in the picosecond and / or femtosecond range. The material of substrate 104 is completely transparent to the laser wavelength. The light is focused through substrate 104 without heat input into it to a joining region between substrate 104 and sensor element 202. At this joining region, the heat, via nonlinear absorption (multiphoton absorption) in the focal range over a few tens of micrometers, leads to a mechanically stable joining of sensor element 202 and substrate 104 extremely locally via fusion, i.e., to the formation of the connecting interface 201.
[0049] In an optional step, the connection base 220 is provided prior to step C). The connection base 220 comprises glass. A thermal expansion coefficient of the connection base 220 differs from a thermal expansion coefficient of the substrate 104 by less than 1 ppm / K. The connection base 220 is connected to the underside 204 of the sensor element, e.g., by anodic bonding, to form the sensor system 102.
[0050] Subsequently, in this exemplary embodiment, the sensor system 102 is connected to the substrate 104 by the laser welding described above using ultrashort laser pulses. This means that the connection interface 201 is formed here between the sensor system 102 and the substrate 104. As described above, the welding can only be carried out due to the special feature of the locally limited heat supply via multiphoton absorption. The laser energy for connecting the substrate 104 and the sensor system 102 is coupled in at a side of the substrate 104 opposite the sensor system 102. In a final step, separation takes place to provide individual pressure sensor assemblies 100.
[0051] The description of the objects specified here is not limited to the individual specific embodiments. Rather, the features of the individual embodiments can be combined with one another as desired—provided technically feasible.
[0052] Reference symbol list
[0053] 100 pressure sensor arrangement
[0054] 102 Sensor system 104 Substrate
[0055] 106 membrane
[0056] 107 Cavity
[0057] 109 Capture element
[0058] 114 Bottom of the substrate 115 Top of the substrate
[0059] 118 Top of the sensor element
[0060] 201 Connection interface
[0061] 202 Sensor element
[0062] 204 Bottom of the sensor element 220 Connection base
Claims
Patent claims 1. pressure sensor arrangement comprising (100) - a sensor element (202) with a top (118) and a bottom (204) , wherein the sensor element (202) has a membrane (106) which is designed and arranged to to be exposed to the medium, and wherein the sensor element (202) has at least one detection element (109) for measuring a pressure of the medium, - a substrate (104) which serves as a support for the sensor element (202), wherein the substrate (104) comprises glass, wherein a connection interface (201) produced by laser welding is formed between the sensor element (202) and the substrate (104), and wherein the sensor element (202) and the substrate (104) are mechanically firmly and hermetically connected to each other at the connection interface (201).
2. Pressure sensor arrangement (100) according to claim 1, wherein the pressure sensor arrangement (100) is free of a connecting means for connecting sensor element (202) and substrate (204).
3. Pressure sensor arrangement (100) according to claim 1 or 2, wherein the substrate (104) has a coefficient of thermal expansion which differs from a coefficient of thermal expansion of the sensor element (202) by less than 1 ppm / K .
4. Pressure sensor arrangement (100) according to one of the preceding claims, wherein the sensor element (202) comprises a silicon chip.
5. Pressure sensor arrangement (100) according to one of the preceding claims, wherein the at least one sensing element (109) is arranged on the membrane (106).
6. Pressure sensor arrangement (100) according to one of the preceding claims, wherein the medium is a liquid or a gas.
7. Pressure sensor arrangement (100) according to one of the preceding claims, wherein a laser energy is coupled to generate the connection interface (201) on a bottom side (114) of the substrate (104) and / or wherein the laser welding is carried out with ultrashort laser pulses.
8. Pressure sensor arrangement (100) according to one of the preceding claims, further comprising a connecting base (220) which is arranged between the sensor element (202) and the substrate (104), wherein the connecting base (220) comprises glass.
9. Pressure sensor arrangement (100) according to claim 8, wherein the connection base (220) is attached to the sensor element (202) and wherein the connection interface (201) is formed between the connection base (220) and the substrate (104).
10. Pressure sensor arrangement (100) according to claim 8 or 9, wherein the connection base (220) is connected to the sensor element (202) by means of anodic bonding.
11. Pressure sensor arrangement (100) according to one of claims 8 to 10, wherein the substrate (104) has a coefficient of thermal expansion which differs from a coefficient of thermal expansion of the compound base (220) by less than 1 ppm / K .
12. Method for manufacturing a pressure sensor arrangement (100) comprising the following steps: A) Providing a substrate (104) wherein the substrate (104) comprises glass; B) Providing at least one sensor element (202) wherein the sensor element has a top (118) and a bottom (204), and wherein a membrane (106) is formed on the top (118); C) Mechanically strong and hermetically sealed joining of substrate (104) and sensor element (202) by laser welding, wherein a connection interface (201) between substrate (104) and sensor element (202) is formed during laser welding.
13. Method according to claim 12, wherein a laser energy is coupled to connect substrate (104) and sensor element (202) on a side of the substrate (104) opposite the sensor element (202).
14. Method according to claim 12 or 13, wherein the laser welding is carried out with ultrashort laser pulses.
15. Method according to any one of claims 12 to 14, wherein a connection base (220) is provided prior to step C), wherein the connection base (220) comprises glass, and wherein the connection base (220) is connected to the underside (204) the sensor element (202) is connected to form a sensor system (102).
16. Method according to claim 15, wherein the connection base (220) is connected to the sensor element (202) by anodic bonding.
17. Method according to claim 15 or 16, wherein the sensor system (102) is connected to the substrate (104) by laser welding with ultrashort laser pulses.
18. Method according to claim 17, wherein a laser energy is coupled to connect substrate (104) and sensor system (102) on a side of the substrate (104) opposite the sensor system (102).
19. Method according to claim 12 or claim 15, wherein the substrate (104) has a coefficient of thermal expansion which differs from a coefficient of thermal expansion of the sensor element (202) and / or the connection base (220) by less than 1 ppm / K.