RU2564378C1 - Pressure sensor with normalised or digital output - Google Patents

Abstract

FIELD: electricity.

SUBSTANCE: pressure sensor with normalised or digital output comprises a body with a pressure cell installed in it having IC chip of pressure transducer (PT) and contact pads, IC chip of PT signal converter, protective cover for the pressure cell and IC, output contacts, electric connectors for the pressure transducer, IC and output contacts and a channel in the body intended to supply pressure to the medium. The pressure cell is completed with contact pads, and this type of PT design simplifies and allows automation of the connection process of PT, IC and output contacts with electric conductors. The cover is made of silica and in-built as per IC manufacturing technology, i.e. it is placed inside the body cavity at IC chip and its connection with IC chip is also made of low-temperature glass soldering thus allowing, as known, reduction of thermal stress at IC chip during operation.

EFFECT: placement of IC chip at in-built protective cover of IC chip and their connection with sealing glue improves operating conditions and simplifies assembly technology.

7 cl, 3 dwg

Description

A pressure sensor with a normalized or digital output is designed to receive an electrical signal compatible with the requirements of the computer input interface and can be used in any sector of the national economy. Advantageously, a pressure sensor with a normalized or digital output is designed to measure absolute pressure.

From the analysis of the current level of technology for measuring pressure, the following is known.

At present, digital pressure sensors (microsystems) are widely offered on the world market, which provide an output signal of a given value in a temperature and pressure range that a consumer needs.

There are two main types of microsystems for digital sensors:

- hybrid, consisting of a MEMS structure and a separate microcircuit, which are placed on a common silicon, glass or quartz substrate;

- monolithic, representing a standard CMOS chip and MEMS structure, made on the same crystal with it.

Monolithic structures can improve the characteristics of microsystems, reduce production costs, packaging and testing, since the stages of the formation of MEMS structures and microcircuits are combined, but this approach is quite complicated. If you initially produce a MEMS structure, the flatness of the substrate necessary for the formation of CMOS elements is violated, in addition, the manufactured CMOS scheme cannot withstand the high-temperature operations required to create a MEMS structure.

A known pressure sensor with a normalized or digital output, comprising a sealed enclosure with a pressure sensitive element (CHED) installed in it with a pressure transducer integrated circuit chip (ICI), a primary signal transducer integrated circuit chip (IC), a protective cover for a pressure transducer and IC, output contacts , means of electrical connections for EDI, ICs and output contacts, and at least one channel in the housing for supplying medium pressure (see, for example, US Patent No. 8286496, Applicant Nagano Keiki Co., publ., 10.16.12). The main disadvantage of the known design is the complex technology for the production of ICs on a flexible board, the connection with it of strain gauges IPD located on the membrane. This complicates the technology of production, assembly and alignment of the output signal to the pressure rating when the temperature changes.

A known pressure sensor with a normalized output, comprising a sealed housing with a pressure sensitive element (CHED) installed in it with a pressure transducer integrated circuit chip, a protective cover for the CHED, output contacts, means of electrical connections for the CHED, IC and output contacts, and at least at least one channel in the housing for supplying medium pressure (see, RF patent No. 2362133, applicant, State Research and Production Enterprise Technological Center, Moscow Institute of Electronic Technology, publ. July 20, 2009). The high stability of the parameters and the sensitivity of the IPD strain gauges do not guarantee a sufficient identity of the output signal when the temperature changes and requires for each pressure sensor when changing or repairing the main measuring complex to enter the adjustment data of each specific IPD into the ADC complex, including when changing the operating temperature range.

A known pressure sensor with a normalized or digital output, containing a sealed enclosure with a pressure sensor (CHED) installed in it with an integrated pressure transducer crystal (IPD) and contact pads, an integrated circuit chip (IC) of an IPD signal converter, a protective cover, output contacts, electrical connections for the EDR, IC and output contacts, and at least one channel in the housing for supplying medium pressure (see US patent No. 7954384, applicant Silicon Micro Sensors Gmbh, publ. 07.06.2011). Differences in the production technology of IPD and IP, as well as in the location of their installation sites and mounting methods complicate the production technology, assembly of the pressure sensor and increase its cost. This known design of the pressure sensor has the largest number of essential features that match the features of the proposed design, solves a similar technical problem using similar technical means, for this reason, the applicant selects the specified US patent as the closest analogue of the invention (prototype).

The technical objective of the proposal is to simplify the flexible production of a pressure sensor with a normalized or digital output and reduce the cost of its production for a given pressure range and adjustment with high stability of the value and other parameters of the output signal by using a single microelectronic technology in a wide range of nominal values of the measured pressure from 0.02 up to 0.6 MPa, as well as increasing its reliability, performance and stability.

The technical problem is solved in that the pressure sensor with a normalized or digital output contains a housing and a pressure sensing element (CHED) installed in it with an integrated pressure transducer crystal (IPD) and contact pads, an integrated circuit chip (IC) of an IPD signal converter, a protective cover, output contacts, means of electrical connections of EDR, IC and output contacts and at least one channel made in the housing for supplying pressure of the medium. The ChED is equipped with pads on the protective cover, such a ChED design simplifies and allows you to automate the process of connecting electrical conductors to IPD, ICs and output contacts. The cover is made of silicon according to the integrated IC manufacturing technology, i.e. It is placed inside the cavity of the housing on the SPD crystal, and its connection with the SPD crystal is also made by low-temperature glass soldering, which, as is known, allows thermal stresses to be reduced in the SPD crystal during operation.

Placing the IC chip on the built-in IPD protective cover and connecting them with glue-sealant simplifies the assembly technology, because The EDR is connected to the housing in the same way and by the same means, and also reduces the occurrence and influence of unbalanced thermal stresses, since the IPD crystal, protective cover, and IC crystal are made of the same material, for example silicon, and have the same thermomechanical characteristics.

All mechanical connections of the EDR and the integrated protective cover of the IPD are made by low-temperature glass soldering in vacuum. Performing protective grooves along the contours of mechanical connections of the EDR prevents the penetration of excess low-melting glass onto the surface of the IPD and contact pads of strain gauges by the simplest means, which allows the joints to be made using microelectronic technologies without additional operations to prepare the surfaces, for example, “weld”, i.e. connect by welding on a robotic complex the electrical connections of the IPD, IC and contact pads of the output contacts on the housing.

The pressure sensor, in which the contact points of the CHED are made on the built-in protective cover outside the connection between the IC and the cover, allows to simplify the “unwrapping” technology, i.e. connections by welding, electric conductors of IC, which has a large number of small contact pads, IPD and output contacts.

The pressure sensor, in which the cavity under the built-in protective cover is evacuated, makes it possible to manufacture the absolute pressure sensor with the most efficient and simple means and allow the sensor to work for a long time, reliably, stably and effectively in the measuring or control complex.

The pressure sensor, in which the cavity under the built-in protective cover is communicated by an additional channel made in the housing with the second medium pressure source, allows expanding the range of standard sizes of sensors and performing sensors for measuring overpressure and differential pressure on the same technological equipment.

The pressure sensor, in which there is a gas protective medium in the cavity of the housing and the cover, is mainly used for anticorrosive protection of the internal surface of the sensor for measuring absolute pressure.

A pressure sensor in which there is anticorrosion protection inside the cavity of the housing and the cover, which prevents aggressive media from entering the sensor elements. Such a sensor embodiment, in addition to the indicated technical results, can improve the reliability and durability of the operation of the EDR in the sensor embodiment and use it to measure excessive pressure or differential pressure (i.e., differential pressure sensor).

A pressure sensor in which the housing cavity is at least partially filled with a protective anticorrosion gel for anticorrosive protection of the inner surface of the sensor can be used to measure overpressure or differential pressure.

A pressure sensor in which the corrosion protection is made in the form of a corrosion-resistant silicone protective coating on the surface of the body cavity and the cover, for example, by applying a coating such as Razacor, can also be used to measure overpressure or pressure drop of an aggressive environment.

The location of the IC on the built-in IPD protective cover allows you to compactly place the IC in the housing without changing its size and configuration, as well as thermally isolate the IC by reducing the heat flux from the IPD and the working medium through the evacuated cavity under the cover and reduce the influence of rapid temperature changes and high-frequency mechanical vibrations transferred from the workflow stream. In this case, the type of the received signal at the output contacts of the sensor is determined only by the type and topology of the integrated circuit of the primary signal converter. The IC is mounted at low temperature with adhesive-sealant or other similar substance on the protective cover made of the same material as the IC itself, which does not cause additional stresses both in the manufacture and assembly of the sensor, and during its operation in a wide temperature range and measured pressure. For this reason, firstly, the cover protects the IC from overheating, and secondly, the same thermal expansion coefficients of the cover and the IC do not create additional thermomechanical stresses between them during operation, and the relatively flexible adhesive sealant can partially compensate for small mechanical inconsistencies in dimensional changes covers and ICs obtained during assembly and operation.

The proposal is illustrated by the following drawings.

In FIG. 1 shows a longitudinal section through a pressure transducer with an EDR and an IC, in which a transducer with contact pads is shown.

In FIG. 2 shows a longitudinal section of the EDR on an enlarged scale.

In FIG. 3 shows a top view of the CHED of FIG. 2 in the pressure sensor.

The proposed design describes, as an example, a sensing element of absolute pressure (CHED) in the form of an integral pressure transducer with three rigid centers, the topology of which can be optimized depending on the nominal value or the range of variation of the measured pressure.

An example of the absolute pressure sensor shown in FIG. 1 with a normalized or digital output, it contains a sealed enclosure 1 with a pressure sensitive element 2 (EDR) installed in it with a crystal 3 of an integrated circuit of a pressure transducer (IPD), a crystal 4 of an integrated circuit (IC) of an IPD signal transducer, an integrated protective cover 5 of an EDC, contact pads 6 located on the IPD outside the connection of the built-in protective cover with the IPD, means 7 for electrical connections of the EDR, IC and output contacts 8 on the housing 1, for example, in the form of conductors made of thin aluminum wire locks, at least one channel 9 in the housing 1 for supplying the measured fluid pressure. CHED 2 can be connected to the pads 10 of the output contacts 8 of the housing 1. The protective cover 5 is built-in, i.e. located inside the housing 1, and made of silicon or other semiconductor material is the same as the crystals of IP 4 and IPD 3 according to the technology for the production of integrated circuits, and is placed on the crystal 3 IPD. Crystal 4 IP is placed on the built-in protective cover 5 IPD ChED. All mechanical connections of the CHED 2 and the built-in protective cover 5 of the IPD are made by low-temperature glass soldering in vacuum. IS, CHED and case 1 are connected by glue-sealant, for example, of the Elasil type, applied to the joints of the base 11 of the case, CHED 2 and IS 4. The cover 12 of the case 1 is hermetically connected to the base 11 of the case 1, for example, by soldering with metal solder in vacuum .

Protective grooves were made along the contours of the mechanical connections of the integral parts of the EDR to prevent fusible glass 13 (not shown) from getting into electrical connections and elements on the IPD chip 3. Other electrical connections for EDR and IC are made using microelectronic technologies, for example, electrochemical methods, sputtering or ultrasonic welding with aluminum wire. An example of using one of the technologies will be shown below.

The pressure sensor, in which the contact points 14 of the EDR are made on the built-in cover 5 outside the connection with the IC 4 (see Fig. 3), are preferably performed in the manufacture of the pressure sensor with a digital output, since the crystal 4 of the analog-to-digital converter has its own contact platforms 15 are very small. Welding, i.e. welding by thin aluminum wire through such intermediate sites greatly simplifies the process of further manufacturing the sensor.

The pressure sensor, in which the cavity 16 under the integrated protective cover 5 is sealed and evacuated (Fig. 1), allows you to measure the absolute pressure of the medium.

The pressure sensor, in which the cavity 16 under the built-in protective cover 5 is communicated with an additional channel (not shown), made in the housing 1 with a second source of pressure of the medium or the environment, allows you to measure the relative pressure of the medium. As you know, if this is a pressure drop compared to the ambient pressure, then this will be called overpressure, and when measuring the difference in comparison with another pressure source - differential.

If the pressure sensor has a second channel in the housing 1 and the cover 5 for supplying the second measured medium, then it is obvious that all surfaces inside the cavity of the housing 1 and the cover 5 must have anti-corrosion protection.

A pressure sensor in which there is a gas protective medium in the cavity of the housing 1 finds primary use as an absolute pressure sensor.

A pressure sensor in which the cavity of the housing 1 is at least partially filled with a protective anti-corrosion gel can be used for differential pressure sensors.

The pressure sensor, in which the corrosion protection is made in the form of a corrosion-resistant silicone protective coating of the surface of the cavity of the housing 1 and cover 5, can also be used for differential pressure sensors.

Consider, as an example of the design and operation of the pressure sensor with a normalized or digital output, an embodiment in the form of an absolute pressure sensor. The housing 1 consists of a base 11 and a cover 12 connected by a vacuum-tight connection, for example, using Elasil glue-sealant or soldering with metal solder in vacuum.

Inside the housing 1, a pressure sensitive element (CHE) 2 is placed (see Fig. 2), consisting of an IPD crystal 3, on the membrane of which three rigid centers and diffusion strain gages are formed by microelectronic techniques, from a protective cap 5 of an IPP with an airtight cavity 16, for example, in the form of a recess in the protective cover 5, in which a vacuum of a given depth is created. A chip 4 of an IC, for example, such as a programmable interface for ZSC31050 sensors, has contact pads 15 connected by flexible terminals of means 7 for electrical connections with contact pads 6 for IPD and contact pads 10 at the output electrical contacts 8 of housing 1, is rigidly fixed to the protective cover 5 of the IPP.

CHED, the construction of which is shown in FIG. 1 and 2, is installed in the recess of the base 11 of the housing 1 of the pressure sensor. A chip 4 of a programmable interface IC for sensors is glued onto the protective cover 5, for example, in the form of a chip chip type ZSC31050.

The contact pads 15 of the crystal 4 microcircuits are connected to the contact pads 6 of the crystal 3 IPD and contact pads 10 of the output contacts 8 of the housing 1.

In the electrical circuit of crystal 3 of the integral pressure transducer included in the pressure sensitive element of the pressure transducer of the absolute pressure sensor, a diffusion strain gages resistor is used in a strain gage on a membrane with three rigid centers. The pads 6 of the strain bridge on the IPD chip are located outside the protective cover 5, are connected to the pads 15 of the chip 4 of the chip in accordance with its electrical circuit, for example, as shown in FIG. 3. The contact pads 15 of the microcircuit 4 in accordance with the electric circuit are welded to the contact pads 10 metal-glass output contacts 8 of the housing 1.

The absolute pressure sensor operates as follows.

The measured pressure of the medium enters through channel 9 in the sealed housing 1 of the sensor, changes the shape of the crystal 3 SPD and the resistance of the strain gauges in the SPD. In the chip 4 of the IC, the analog signal from the chip 3 of the IPD is converted to a normalized or digital signal and fed to the output contacts 8 on the housing 1.

In other configurations described below, the operation of the sensor occurs similarly under the action on the crystal 3 of the IPD differential pressure from two sides of the IPD.

When performing a pressure sensor with two channels in the housing, it will be easiest to make the first channel for supplying the first measured medium as channel 9 in the absolute pressure sensor, and execute the second channel in the protective cover, communicate it with the channel of the housing, for example, through its cavity inside the housing (not shown). It is obvious that all surfaces of the IC, contacts and electrical connections must be protected from corrosion. This can be done by any known method and using known means described above, for example, fill the body cavity with a protective gel or cover all surfaces exposed to the risk of corrosion with a Razacor protective coating.

At the end of the manufacturing process, an output control of the performance of the pressure sensor and the output signal is carried out. The pressure sensor is ready to work in any measuring or control complex without additional steps to check its parameters.

When the pressure sensor is operating, the decompression circuit of FIG. 3 digital sensors using pads on the protective cover 5. From the crystal 3 of the integral pressure transducer included in the absolute value of the absolute value pressure sensor, a digital signal discrete or normalized by voltage is obtained, a transistor voltage divider can be used as a converter. The specified signal is used in devices or control systems using pressure sensors.

Flexible integrated manufacturing technology of the strain-sensitive transducer of the pressure sensor, the stability of its operating characteristics, the miniature design of the sensor, protection of the sensor from external factors ensure the production of sensors on the same equipment at different nominal pressures with different characteristics of a normalized or digital output signal, its low cost and expand the functionality of application in various fields of the national economy.

Claims (7)

1. A pressure sensor with a normalized or digital output, comprising a housing and installed therein: a pressure sensitive element (CHED) with an integrated pressure transducer crystal (IPD) and contact pads, an integrated circuit chip (IC) of an IPD signal converter, a protective cover, output contacts , means for electrical connections of CHED, IS and output contacts and at least one channel made in the housing for supplying pressure of the medium, characterized in that the CHED is equipped with contact pads on the protective cover outside the connection between the IC and the cover, and the cover is made of silicon built-in according to the manufacturing technology of the IC and placed on the IPD, the crystal of the IC is placed on the built-in protective cover, all mechanical connections of the EDR and the built-in protective cover are made by low-temperature soldering with glass, and the IC and CHED are made with glue sealant, protective grooves are made along the contours of the mechanical connections of the integral parts of the EDR, and the electrical connections are made using microelectronic technologies. 2. The pressure sensor according to claim 1, characterized in that the cavity under the built-in protective cover is evacuated. 3. The pressure sensor according to claim 1, characterized in that the cavity under the built-in protective cover is communicated by an additional channel made in the housing with a medium pressure source. 4. The pressure sensor according to claim 1, characterized in that there is anti-corrosion protection inside the body cavity and protective cover. 5. The pressure sensor according to claim 4, characterized in that in the cavity of the housing and the cover there is a gas protective environment. 6. The pressure sensor according to claim 4, characterized in that the housing cavity is at least partially filled with a protective anti-corrosion gel. 7. The pressure sensor according to claim 4, characterized in that the corrosion protection is made in the form of a corrosion-resistant silicone protective coating on the surface of the cavity of the housing and the cover.

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