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JP-2026075063-A - Piezoresistive pressure sensor and method for manufacturing such a piezoresistive pressure sensor

JP2026075063AJP 2026075063 AJP2026075063 AJP 2026075063AJP-2026075063-A

Abstract

[Problem] A piezoresistive pressure sensor for measuring the pressure of a medium in the environment. [Solution] The piezoresistive pressure sensor comprises at least one housing, at least one substrate, and at least one measuring unit. The housing comprises an interior and an opening. The substrate and measuring unit are arranged inside, and the substrate has a blind hole and a diaphragm formed therein, the diaphragm enclosing the blind hole on one side, and the substrate is arranged inside such that the blind hole communicates with the opening. The piezoresistive pressure sensor is designed so that, when exposed to a medium, the medium can penetrate through the opening and the blind hole to the diaphragm. The pressure of the medium that has penetrated the diaphragm causes the diaphragm to flex, generating a change in resistance to the diaphragm's flex, and the change in resistance is proportional to the pressure being measured. [Selection Diagram] Figure 1

Inventors

  • マチュー ローナー
  • イェルク グラミッチ

Assignees

  • キストラー ホールディング アクチエンゲゼルシャフト

Dates

Publication Date
20260507
Application Date
20251002
Priority Date
20241021

Claims (20)

  1. A piezoresistive pressure sensor (10) for measuring the pressure (P) of a medium (M) in an environment (E), comprising at least one housing (1), at least one base (2), and at least one measuring unit (3), wherein the housing (1) comprises an interior (1.3) and an opening (1.4), the base (2) and the measuring unit (3) are arranged in the interior (1.3), and the base (2) has a blind hole ( 2.4) and a diaphragm (2.5) are formed, and the diaphragm (2.5) encloses the blind hole (2.4) on one side, and the base (2) is positioned inside (1.3) such that the blind hole (2.4) communicates with the opening (1.4), and when the piezoresistive pressure sensor (10) is exposed to the medium (M), the medium (M) passes through the opening (1.4) and the blind hole (2.4) to the die A piezoresistive pressure sensor (10) is designed to allow penetration to a diaphragm (2.5), the diaphragm (2.5) being deflected by the pressure of the medium (M) that has penetrated the diaphragm (2.5), the measuring unit (3) being positioned on the side of the diaphragm (2.5) opposite to the blind hole (2.4), and generating a change in resistance (ΔR) with respect to the deflection of the diaphragm (2.5), the change in resistance (ΔR) being proportional to the pressure (P) being measured, wherein the piezoresistive pressure sensor (10) comprises at least one material bonding connection (4), the material bonding connection (4) directly connecting the substrate (2) to the housing (1) in a mechanically tight manner, and the material bonding connection (4) exhibits a melting temperature (TM) of 250°C or higher.
  2. The piezoresistive pressure sensor (10) according to claim 1, characterized in that the piezoresistive pressure sensor (10) comprises at least one conductor (5), and the conductor (5) taps the resistance change (ΔR) as a voltage (U) and discharges it to the environment (E).
  3. The piezoresistive pressure sensor (10) according to claim 1 or 2, characterized in that the material bonding connection portion (4) is a solder joint of at least two materials (M1, M2), the materials (M1, M2) include a first material (M1) and a second material (M2), the first material (M1) exhibits a higher melting point than the second material (M2), the first material (M1) is one of the following metals: silver, gold, copper, or nickel, and the second material (M2) is one of the following metals: indium or tin.
  4. The piezoresistive pressure sensor (10) according to claim 3, characterized in that the first material (M1) is gold, the second material (M2) is indium, the mass fraction of the gold in the first material (M1) is 46% or more, and the melting temperature (TM) of the material bonding connection portion (4) is 450°C or more.
  5. The piezoresistive pressure sensor (10) according to claim 3, characterized in that the first material (M1) is gold, the second material (M2) is tin, the mass fraction of the gold in the first material (M1) is 80% or more, and the melting temperature (TM) of the material bonding connection portion (4) is 278°C or higher.
  6. The piezoresistive pressure sensor (10) according to claim 3, characterized in that the first material (M1) is gold, the second material (M2) is tin, the mass fraction of the gold in the first material (M1) is 93% or more, and the melting temperature (TM) of the material bonding connection portion (4) is 522°C or higher.
  7. The piezoresistive pressure sensor (10) according to claim 1 or 2, characterized in that the material bonding connection portion (4) is a solder joint made of at least two materials (M1, M2), the materials (M1, M2) include a first material (M1) and a second material (M2), the first material (M1) is a conductor, the second material (M2) is an electrical semiconductor, the first material (M1) is one of the following metals, namely silver or gold, and the second material (M2) is one of the following semiconductors, namely germanium or silicon.
  8. The piezoresistive pressure sensor (10) according to claim 7, characterized in that the first material (M1) is gold, the second material (M2) is germanium, the mass fraction of the gold in the first material (M1) is 88% or more, and the melting temperature (TM) of the material bonding connection portion (4) is 356°C or higher.
  9. The piezoresistive pressure sensor (10) according to claim 7, characterized in that the first material (M1) is gold, the second material (M2) is silicon, the mass fraction of the gold in the first material (M1) is 96% or more, and the melting temperature (TM) of the material bonding connection portion (4) is 363°C or higher.
  10. The piezoresistive pressure sensor (10) according to claim 1 or 2, characterized in that the material bonding connection (4) is a glass solder comprising at least two materials (M1, M2), the materials (M1, M2) comprising a first material (M1) and a second material (M2), the first material (M1) exhibiting a higher melting point than the second material (M2), the first material (M1) being bismuth(III) oxide or lead(II) oxide, the second material (M2) being boron trioxide, and the material bonding connection (4) exhibiting a melting temperature (TM) of 350°C or higher.
  11. The piezoresistive pressure sensor (10) according to any one of claims 1 to 10, characterized in that the housing (1) has an end face (1.6) facing the interior (1.3) within the region of the opening (1.4), the base body (2) comprises a support layer (2.1) with the blind hole (2.5) formed as a through hole (2.13), the support layer (2.1) comprises a first support front surface (2.11) within the region of the through hole (2.13), the first support front surface (2.11) is mechanically tightly connected to the end face (1.6) via the material bonding connection portion (4), and the base body (2) is arranged in the interior (1.3) such that the opening (1.4) communicates with the through hole (2.13) along the vertical axis (Z).
  12. The piezoresistive pressure sensor (10) according to claim 11, characterized in that the substrate (2) comprises a molded layer (2.2), the blind hole (2.5) in the molded layer (2.2) is formed as a trough-shaped recess (2.23), the molded layer (2.2) comprises a first molded front surface (2.21) and a second molded front surface (2.22), and the region of the molded layer (2.2) along the vertical axis (Z) between the trough-shaped recess (2.23) and the second molded front surface (2.22) forms the diaphragm (2.5).
  13. The piezoresistive pressure sensor (10) according to claim 12, characterized in that the second support surface (2.12) and the first molded surface (2.21) are in direct contact to form a contact surface, and at the contact surface, the support layer (2.1) and the molded layer (2.2) are connected to each other via a connecting portion (2.6) in a mechanically tight manner.
  14. A piezoresistive pressure sensor (10) according to any one of claims 11 or 12, characterized in that the substrate (2) comprises an oxide layer (2.3), the oxide layer (2.3) is disposed on the second molded surface (2.22), and the measuring unit (3) is disposed on the oxide layer (2.3), and the measuring unit (3) comprises a plurality of resistive elements made of a piezoresistive material.
  15. The piezoresistive pressure sensor (10) comprises at least one cover (6), the cover (6) being pot-shaped and having a cavity (6.2) surrounded by an edge region (6.1), and the cover (6), which is placed on the oxide layer (2.3) having the edge region (6.1), is designed to completely house the measuring unit (3) within the cavity (6.2) and to maintain a constant reference pressure (P') within the cavity (6.2) over time, thereby enabling the piezoresistive pressure sensor (10) to measure the pressure (P) absolutely with respect to the reference pressure (P'). The piezoresistive pressure sensor (10) according to claim 14, characterized in that, or, when the passivation layer (2.3') is applied to the oxide layer (2.3), the cover (6) installed on the passivation layer (2.3') having the edge region (6.1) is designed to completely house the measuring unit (3) within the cavity (6.2) and to maintain a constant reference pressure (P') within the cavity (6.2) over time, thereby enabling the piezoresistive pressure sensor (10) to absolutely measure the pressure (P) with respect to the reference pressure (P').
  16. The housing (1) is a single component having a housing body (1.0), or the housing (1) is a plurality of components having a first housing body (1.0') and at least one second housing body (1.0''), the support layer (2.1) is mechanically tightly connected to the housing body (1.0) or the second housing body (1.0'') via the material bonding connection portion (4), the housing body (1.0) or the second housing body (1.0'') is made of a mechanically resistant material exhibiting a thermal expansion coefficient of 7.0 10⁻⁶ K⁻¹ or less in the range of 20°C to 450°C, and the support layer (2.1) has a thermal expansion coefficient of 4.5 10⁻⁶ K⁻¹ in the range of 20°C to 450°C. The piezoresistive pressure sensor (10) according to any one of claims 11 to 15, characterized in that it is made of an electrical insulating material exhibiting a thermal expansion coefficient of -1 or less, and in the material bonding connection portion (4), the difference in thermal expansion coefficients between the housing body (1.0) or the second housing body (1.0'') and the support layer (2.1) is 3.0 10⁻⁶ K⁻¹ or less, preferably 2.0 10⁻⁶ K⁻¹ or less, in the range of 20°C to 450°C.
  17. A method for manufacturing a piezoresistive pressure sensor (10) for measuring the pressure (P) of a medium (M) in an environment (E), wherein the piezoresistive pressure sensor (10) comprises at least one housing (1), at least one substrate (2), and at least one measuring unit (3), wherein the housing (1) comprises an interior (1.3) and an opening (1.4), and the substrate (2) and the measuring unit (3) are arranged in the interior (1.3). The base (2) is positioned such that a blind hole (2.4) and a diaphragm (2.5) are formed therein, the diaphragm (2.5) encloses the blind hole (2.4) to one side, and the base (2) is positioned inside (1.3) such that the blind hole (2.4) communicates with the opening (1.4), and when the piezoresistive pressure sensor (10) is exposed to the medium (M), the medium (M) communicates with the opening (1.4) and the blind hole (2.4) A method comprising: a device designed to allow penetration through a hole (2.4) to the diaphragm (2.5), the pressure of the medium (M) penetrating the diaphragm (2.5) causing the diaphragm (2.5) to flex, the measuring unit (3) positioned on the side of the diaphragm (2.5) opposite to the blind hole (2.4), generating a resistance change (ΔR) to the flexure of the diaphragm (2.5), the resistance change (ΔR) being proportional to the pressure (P) being measured, characterized in that, in a first step (MI) of the method, the housing (1) and the substrate (2) are provided, and in further steps (MIa to MIV) of the method, the substrate (2) is directly connected to the housing (1) in a mechanically tight manner via at least one material bonding connection (4), the material bonding connection (4) exhibiting a melting temperature (TM) of 250°C or higher.
  18. The method according to claim 17, characterized in that, in a further fifth step (MV) of the method, at least one conductor (5) is provided, and in a further sixth step (MVI) of the method, the conductor (5) is electrically connected to the measuring unit (3), and the conductor (5) taps the resistance change (ΔR) as a voltage (U) and discharges it to the environment (E).
  19. The method according to any one of claims 17 or 18, characterized in that, in a further first step (MIa) of the method, a substrate (S1) containing a first material (M1) is provided; the housing (1) forms an end face (1.6) toward the interior (1.3) within the region of the opening (1.4); and in yet another first step (MIb) of the method, the first material (M1) is deposited from the substrate (S1) onto the end face (1.6) to form a first connecting layer (L1), wherein the thickness of the first connecting layer (L1) is 20 μm or less, preferably 10 μm or less.
  20. The method according to claim 19, characterized in that the substrate (2) comprises a support layer (2.1), the blind hole (2.5) is formed in the support layer (2.1) as a through hole (2.13), the support layer (2.1) comprises a first support front surface (2.11) within the region of the through hole (2.13), and in an additional further first step (Mic) of the method, the first material (M1) is deposited from the substrate (S1) onto the first support front surface (2.11) to form a second connecting layer (L2), the thickness of the second connecting layer (L2) being 20 μm or less, preferably 10 μm or less.

Description

This invention relates to a piezoresistive pressure sensor according to the preamble of an independent claim and to a method for manufacturing such a piezoresistive pressure sensor. Pressure sensors are used to measure the pressure of liquid or gaseous media. Pressure measurements can be performed as absolute pressure measurements referencing a reference pressure, or as relative pressure measurements without such a reference. Pressure measurements can be performed statically over long periods, such as months, when measuring the pressure inside a car tire, or dynamically over fractions of a second, such as during an explosion in a car's combustion engine. In recent years, a wide variety of pressure measurement principles have been developed, which is why piezoelectric, piezoresistive, optical, and capacitive pressure sensors are distinguished. Furthermore, the present invention also relates to a piezoresistive pressure sensor, as known from German Patent Application Publication No. 202009013919U1. The piezoresistive pressure sensor comprises a silicon or glass substrate with a blind hole introduced on one side. In the region of the blind hole, the substrate forms a diaphragm. A medium guided through the blind hole to the diaphragm applies pressure to the diaphragm, causing it to flex. A measuring unit is positioned on the side of the diaphragm opposite the blind hole, comprising a resistive element made of a piezoresistive material. The measuring unit detects the diaphragm's flexure as a change in resistance. A circuit unit, also located on the substrate, converts the resistance change into a measurement signal. By positioning the measuring unit and circuit unit on the diaphragm side opposite the blind hole, the measuring unit and circuit unit are not directly exposed to the medium. As a result, the piezoresistive pressure sensor is also suitable for measuring the pressure of chemically aggressive mediums such as fuel for combustion engines, where the fuel cannot corrode the measuring unit and circuit unit, thus not undesirably impairing the usability of the piezoresistive pressure sensor. To protect the measuring unit and circuit unit from harmful environmental influences such as moisture, dust, and contact, and to mount the piezoresistive pressure sensor at the measurement point, the piezoresistive pressure sensor is provided with a housing. The housing of German Patent Application Publication No. 202009013919U1 has a hollow cylindrical shape and is made of metal. The base on which the measuring unit and circuit unit are arranged is fixed inside the housing via a carrier, also made of metal. Thus, the base is fixed to the carrier via glass solder or adhesive connections, and the carrier is then hermetically welded to the internal housing. The base is positioned internally so that the medium can reach the blind holes in the base only through the front opening of the housing and the through-holes in the carrier. The piezoresistive pressure sensor can be mounted to the measurement point via male threads on the housing side. The object of this invention is to improve upon the piezoresistive pressure sensor described in German Patent Application Publication No. 202009013919U1. The invention also aims to disclose a method for manufacturing a piezoresistive pressure sensor that is improved compared to the method described in German Patent Application Publication No. 202009013919U1. However, there is still room for improvement. The circuit unit described in German Patent Application Publication No. 202009013919U1 comprises integrated circuits and electronic components that are often designed only for continuous operating temperatures within the range of -55°C to 125°C. Therefore, for continuous operating temperatures of piezoresistive pressure sensors exceeding 200°C, special designs of integrated circuits and electronic components are required. Such special designs of integrated circuits and electronic components are manufactured in small quantities, making their acquisition complex and expensive. Furthermore, the integrated circuit and measuring unit described in German Patent Application Publication No. 202009013919U1 are manufactured on a silicon carrier. Silicon is a semiconductor and exhibits high leakage current at continuous operating temperatures exceeding 200°C for piezoresistive pressure sensors. This can distort the measurement signal and thus significantly impair the accuracy of pressure measurement. The circuit unit and measuring unit are also cast with a casting compound on the side of the diaphragm opposite the blind hole described in German Patent Application Publication No. 202009013919U1, protecting the integrated circuit, electronic components, and electrical connections to the measuring unit from mechanical shock and vibration. The casting compound is typically made of plastic materials such as polyurethane, epoxy resin, or silicone, and begins to decompose at the continuous operating temperat