WO2016016026A1 - Pressure sensor and method for producing a pressure sensor - Google Patents

Abstract

The invention relates to a pressure sensor (10) comprising a membrane (12) which is exposed to a medium which is to be measured and from the deflection thereof by means of a piezo-resistive sensor element (14a; 14b; 14c), an electric signal (S) which is proportional to the measured pressure (P) can be produced. Said sensor also comprises a flexible conductor plate (16) which electrically and mechanically contacts the piezo-resistive sensor element (14a; 14b; 14c). The invention also relates to a corresponding method for producing a pressure sensor (10).

Description

 Description title

 Pressure sensor and method of manufacturing a pressure sensor

The invention relates to a pressure sensor and a method for producing a pressure sensor.

State of the art

Currently, two types of sensors are used and manufactured to measure pressures. On the one hand, electrical structures are etched on steel membranes. The steel membrane is deflected under pressure. The electrical structures have piezoresistors, which are stretched or compressed together with the steel membrane. These deformations cause a change in the resistance value of the piezoresistors, so that the pressure acting on the membrane pressure can be detected with a suitable interconnection of the piezoresistors, for example in a Wheatstone bridge in the form of a proportional electrical output signal. Become second

Silicon chips used in which by applying a pressure, a thin silicon membrane bends on the back of a in

Semiconductor technology constructed electrical circuit is located. Both

Methods have strongly delimited their fields of application. Steel diaphragms are used for high pressure systems. There is generated by the high pressures sufficient deformation of the membrane, which is measurable with the electrical structure on the surface. Silicon chips as pressure sensors are used in low to medium pressure applications.

DE 10 2009 044 980 AI discloses a sensor component comprising a deformation body and a piezoresistive sensor layer, which on the Deforming body is applied, wherein the piezoresistive sensor layer comprises at least one metal and carbon and / or hydrocarbon.

Disclosure of the invention

The present invention provides a pressure sensor with a membrane which is exposed to a medium to be measured and from the deflection thereof by means of a piezoresistive sensor element to the measured pressure

proportional electric signal can be generated, and with a flexible

Printed circuit board, which contacts the piezoresistive sensor element electrically and mechanically.

The present invention further provides a method of manufacturing a pressure sensor. The method includes providing a membrane exposed to a medium to be measured. The method further comprises providing a piezoresistive sensor element, by which, from a deflection of the membrane a measured pressure

proportional electrical signal can be generated. The method further includes providing a flexible printed circuit board which is piezoresistive

Sensor element electrically and mechanically contacted.

One idea of the present invention is to design the pressure sensor such that it covers a low, medium, and high pressure region, while providing sufficient sensitivity of the pressure sensor. By providing the flexible printed circuit board which contacts the piezoresistive sensor element electrically and mechanically, it is possible to have different ones

Cover pressure ranges with always the same detection, contacting and connection.

Advantageous embodiments and further developments emerge from the dependent claims and from the description with reference to the figures.

Preferably, it is provided that the piezoresistive sensor element by a bending-sensitive semiconductor chip or one of a Semiconductor material formed thin-film measuring structure is formed. Thus, a high measurement accuracy can be achieved. Furthermore, by reducing the joints and the reliability of the pressure sensor can be increased.

Preferably, it is further provided that the piezoresistive sensor element is embedded in the flexible printed circuit board, arranged on the flexible printed circuit board or on the membrane. The piezoresistive sensor element can thus be selected according to individual requirements.

According to a further preferred embodiment, it is provided that the thin-film measuring structure is applied to the flexible printed circuit board by a photolithographic process, or printed on the membrane. The applied structure thus makes it possible to safely and reliably detect resistance changes induced in the mOhm range by the deflection of the membrane.

According to a further preferred embodiment, it is provided that the thin-film measuring structure is printed on the membrane with electrically conductive inks which have gold or silver particles. Thus, an accurate and reliable pressure measurement can be realized.

Preferably, it is further provided that the flexible printed circuit board arranged adjacent to the membrane, flexibly formed first region in which the flexible printed circuit board is materially connected to the membrane, a substantially rigid second region formed in which an evaluation circuit for evaluating the of the piezoresistive Sensor element is arranged to generate electrical signal, and a flexible

formed connecting region, which is arranged between the first and second region. Due to the flexible design of the first region arranged adjacent to the membrane, this region is likewise movable when the membrane is deflected. The rigid design of the second area allows the arrangement of the evaluation circuit in this area. The flexible forming of the connection region between the first and second region allows a space-saving design of the pressure sensor, wherein the flexible printed circuit board is foldable, at least in the connecting region.

According to a further preferred embodiment, it is provided that the evaluation circuit has at least one application-specific integrated circuit embedded in the flexible printed circuit board, and at least one passive or active component arranged on a surface of the flexible printed circuit board or outside the flexible printed circuit board. The

Evaluation circuit can thus be arranged to save space in the pressure sensor.

According to a further preferred embodiment, it is provided that a thickness of the flexible printed circuit board is less than or equal to 100 micrometers, preferably between 30 and 100 micrometers, and that a thickness of the

bend-sensitive semiconductor chip is less than or equal to 50 microns, preferably between 10 and 20 microns, with a

 Track width is less than or equal to 20 microns and a conductor track thickness is less than or equal to 5 microns, preferably 1 micrometer. This allows a sufficient flexibility of the flexible printed circuit board, in particular in the region of the piezoresistive sensor element, as well as a substantially thin design of the bending-sensitive semiconductor chip with a high

 Measuring accuracy can be ensured.

According to a further preferred embodiment, it is provided that an electrical contacting of the flexible printed circuit board with a power supply is formed by connectable with the flexible printed circuit board through-pins.

As a result, the flexibility of the flexible printed circuit board can be adapted to a design of the pressure sensor and yet a simple and reliable contacting of the flexible printed circuit board with the power supply can be provided.

According to a further preferred embodiment, it is provided that a measuring range of the piezoresistive sensor element is between 0.1 and 2200 bar. The pressure sensor can thus a low, middle and

Cover high-pressure area accurately and reliably. Preferably, it is further provided that the piezoresistive sensor element is formed by a bending-sensitive semiconductor chip or by a thin-film measuring structure, wherein the piezoresistive sensor element embedded in the flexible circuit board, applied to the flexible circuit board or applied to the membrane. Thus, a high measurement accuracy can be achieved. Furthermore, by reducing the joints and the reliability of the pressure sensor can be increased. Furthermore, the piezoresistive sensor element can thus also be selected according to individual requirements.

According to a further preferred embodiment, it is provided that an evaluation circuit for evaluating the electrical signal which can be generated by the piezoresistive sensor element is embedded in the flexible printed circuit board. The rigid design of the second area allows the arrangement of the

Evaluation circuit in this area. The evaluation circuit can thus be arranged to save space in the pressure sensor.

According to a further preferred embodiment, it is provided that the thin-film measuring structure on the flexible circuit board by a

photolithographic process is applied or printed on the membrane. The applied structure thus makes it possible to safely and reliably detect resistance changes induced in the mOhm range by the deflection of the membrane.

According to a further preferred embodiment, it is provided that the thin-film measurement structure is printed on the membrane by a printing process with electrically conductive inks which have gold or silver particles. Thus, an accurate and reliable pressure measurement can be realized.

The described embodiments and developments can be combined with each other as desired.

Further possible refinements, developments and implementations of the invention also include combinations of previously or not explicitly mentioned in the following with respect to the embodiments described features of the invention.

Brief description of the drawings

The accompanying drawings are intended to provide a further understanding of the

Embodiments of the invention mediate. They illustrate

Embodiments and in conjunction with the description serve to explain principles and concepts of the invention.

Other embodiments and many of the stated advantages will become apparent with reference to the drawings. The illustrated elements of the drawings are not necessarily shown to scale to each other.

Show it:

Fig. 1 is a sectional view of a pressure sensor according to the invention according to a first embodiment of the invention;

Fig. 2 is a sectional view of the pressure sensor according to the invention according to a second embodiment of the invention;

Fig. 3 is a sectional view of the pressure sensor according to a third

 Embodiment of the invention; and

4 is a flowchart of a method for manufacturing a

 Pressure sensor according to the first to third embodiments of the invention.

In the figures of the drawings, like reference characters designate like or functionally identical elements, components or components, as far as nothing is concerned

The contrary is stated.

Fig. 1 shows a sectional view of a pressure sensor according to the invention according to a first embodiment of the invention. The pressure sensor 10 has a membrane 12, which is preferably made of steel. Alternatively, the membrane 12 may be formed of another suitable material. The membrane 12 is formed with a steel base 13 in one piece. In the steel base 13, a channel is formed, through which the membrane 12 with a pressure P of a to be measured

Medium is acted upon.

The pressure sensor 10 furthermore has a piezoresistive sensor element 14a and a flexible printed circuit board 16. The piezoresistive sensor element 14a is formed in the present first embodiment by a bending-sensitive semiconductor chip 14a. The flexion-sensitive semiconductor chip 14a is preferably embedded in the flexible printed circuit board 16, and configured to form from the deflection of the membrane 12 a measured pressure P

to generate proportional electrical signal S. The flexible printed circuit board 16 contacts the bend-sensitive semiconductor chip electrically and mechanically. The flexible circuit board 16 is preferably connected to the membrane 12 by an adhesive layer. Alternatively, the flexible circuit board 16 may also be connected to the membrane 12 by another suitable connection means.

The flexible circuit board 16 has a membrane 12 adjacent

arranged, flexibly formed first region 16 a, in which the flexible printed circuit board 16 is connected to the membrane 12 cohesively.

The flexible printed circuit board 16 furthermore has a substantially rigidly formed second region 16b, in which an evaluation circuit 18 is arranged for evaluating the electrical signal S that can be generated by the bending-sensitive semiconductor chip 14a. The flexible printed circuit board 16 moreover has a flexibly formed connecting region 16c, which is arranged between the first and second regions 16a, 16b.

The evaluation circuit 18 has an application-specific integrated circuit 18 a embedded in the flexible printed circuit board 16 and a passive component 18 b arranged on a surface of the flexible printed circuit board 16. The application-specific integrated circuit 18a can alternatively also be used on a Surface of the flexible circuit board 16 may be arranged. The component 18b may alternatively also be arranged outside the flexible printed circuit board 16 and / or be formed by an active component. An electrical contacting of the flexible printed circuit board 16 with a

 Power supply 20 is preferably formed by connectable with the flexible circuit board 16 through-pins 22. Alternatively, the electrical contacting of the flexible printed circuit board 16 may also be formed by other suitable electrical contacting means.

A thickness of the flexible circuit board 16 is preferably 100 micrometers. Alternatively, the thickness of the flexible circuit board may be less than 100

Micrometers, in particular preferably between 30 and 100 micrometers. A thickness of the flex-sensitive semiconductor chip 14a is preferably 50 micrometers. Alternatively, the thickness of the

bending-sensitive semiconductor chips 14a are also less than 50 micrometers, in particular preferably between 10 and 20 micrometers. A trace width of the flex-sensitive semiconductor chip 14a is preferably 20 micrometers. Alternatively, the track width may be less than 20 microns. A trace thickness of the bend sensitive

Semiconductor chips 14a is preferably 5 micrometers. Alternatively, the conductor track thickness can also be less than 5 micrometers, preferably 1 micrometer. A measuring range of the bending-sensitive semiconductor chip 14a is preferably between 0.1 and 2200 bar.

Fig. 2 shows a sectional view of the pressure sensor according to the invention according to a second embodiment of the invention.

A piezoresistive sensor element 14b is in the present second

Embodiment by a thin film formed of a semiconductor material

Measuring structure 14b formed. The thin-film measuring structure 14b is preferably arranged on the flexible printed circuit board 16. The thin-film measuring structure 14b is further preferably applied to the flexible printed circuit board 16 by a photolithographic process. Alternatively, the thin film sensing structure 14b may also be applied to the flexible printed circuit board 16 by another suitable method be upset. A trace width of the thin-film sensing structure 14b is preferably 20 micrometers. Alternatively, the track width may be less than 20 microns. A trace thickness of the thin-film sensing structure 14b is preferably 5 micrometers. Alternatively, the conductor track thickness can also be less than 5 micrometers, preferably 1 micrometer.

Fig. 3 shows a sectional view of the pressure sensor according to a third

Embodiment of the invention.

A piezoresistive sensor element 14c is formed according to the third embodiment by a formed of a semiconductor material thin-film measuring structure 14c.

The thin film measuring structure 14 c is preferably on the membrane 12

arranged. The thin-film measuring structure 14 c is preferably printed on the membrane 12. Preferably, the thin film sensing structure 14c is printed on the membrane 12 by an aerosol jet of electrically conductive inks comprising gold or silver particles. Alternatively, the thin film sensing structure 14c may also be printed by another suitable printing method, such as inkjet printing.

A trace width of the thin film sensing structure 14c is preferably 20 micrometers. Alternatively, the track width may be less than 20 microns. A trace thickness of the thin-film sensing structure 14c is preferably 5 micrometers. Alternatively, the conductor track thickness can also be less than 5 micrometers, preferably 1 micrometer.

FIG. 4 shows a flowchart of a method for producing a

Pressure sensor according to the first to third embodiments of the invention.

The method for producing a pressure sensor 10 comprises, in step S1, providing a membrane 12 which is exposed to a medium to be measured. The method further comprises, in step S2, providing a piezoresistive sensor element 14a; 14b; 14c, through which a, from a deflection of the diaphragm 12 a measured pressure P proportional electrical signal S can be generated. The method further comprises, in step S3, providing a flexible circuit board 16 which is the piezoresistive

Sensor element 14a; 14b; 14c electrically and mechanically contacted.

The method further comprises that the piezoresistive sensor element 14a; 14b; 14c through a bending-sensitive semiconductor chip 14a or through a thin-film measuring structure 14b formed of a semiconductor material; 14c is formed, wherein the piezoresistive sensor element 14a; 14b; 14c embedded in the flexible printed circuit board 16 in step S4, applied to the flexible printed circuit board 16 or applied to the membrane 12.

Although the present invention has been described above with reference to preferred embodiments, it is not limited thereto but is modifiable in a variety of ways. In particular, the invention can be varied or modified in many ways without deviating from the gist of the invention.

For example, material and thickness of the flexible printed circuit board 16 and the membrane 12 can be adapted to individual requirements.

Claims

claims 1. pressure sensor (10) with a membrane (12) which is exposed to a medium to be measured and from whose deflection by means of a piezoresistive sensor element (14a; 14b; 14c) a measured pressure (P)  proportional electrical signal (S) can be generated, and with a flexible printed circuit board (16) which electrically and mechanically contacts the piezoresistive sensor element (14a; 14b; 14c). 2. Pressure sensor according to claim 1, characterized in that the  Piezoresistive sensor element (14a, 14b, 14c) by a  bend-sensitive semiconductor chip (14a) or one of a  Semiconductor material formed thin-film measuring structure (14b, 14c)  is trained. 3. Pressure sensor according to claim 1 or 2, characterized in that the piezoresistive sensor element (14a, 14b, 14c) embedded in the flexible printed circuit board (16), on the flexible printed circuit board (16) or on the membrane (12) is arranged. 4. Pressure sensor according to claim 2 or 3, characterized in that the thin-film measuring structure (14b, 14c) by a photolithographic process applied to the flexible printed circuit board (16), or printed on the membrane (12). 5. Pressure sensor according to claim 4, characterized in that the thin-film measuring structure (14c) with electrically conductive inks, the gold or  Have silver particles on the membrane (12) is printed. Pressure sensor according to one of the preceding claims, characterized in that the flexible printed circuit board (16) has a connection to the membrane (12). adjacently arranged, flexibly formed first region (16a), in which the flexible printed circuit board (16) is materially connected to the membrane (12), a substantially rigid second region (16b), in which an evaluation circuit (18) for evaluating the of the piezoresistive sensor element (14a; 14b; 14c) producible electrical signal (S) is arranged, and a flexible formed  Connecting portion (16c), which is arranged between the first and second region (16a, 16b). Pressure sensor according to claim 6, characterized in that the  Evaluation circuit (18) at least one application-specific integrated circuit (18a) embedded in the flexible printed circuit board (16), and at least one passive or active component (18b) arranged on a surface of the flexible printed circuit board (16) or outside the flexible printed circuit board (16) having. Pressure sensor according to one of claims 2 to 7, characterized in that a thickness of the flexible printed circuit board (16) is less than or equal to 100 microns, preferably between 30 and 100 microns, and that a thickness of the deflection-sensitive semiconductor chip (14a) is less than or equal to 50 microns , preferably between 10 and 20 microns, wherein a conductor width is less than or equal to 20 microns and a conductor thickness is less than or equal to 5 microns, preferably 1 micrometer. 9. Pressure sensor according to one of the preceding claims, characterized  characterized in that an electrical contacting of the flexible  Printed circuit board (16) with a power supply (20) by means of the flexible circuit board (16) connectable through-pins (22) is formed. 10. Pressure sensor according to one of the preceding claims, characterized in that a measuring range of the piezoresistive sensor element (14a; 14b; 14c) is between 0.1 and 2200 bar. A method of manufacturing a pressure sensor (10), comprising the steps of: providing (Sl) a membrane (12) exposed to a medium to be measured;  Providing (S2) a piezoresistive sensor element (14a, 14b, 14c), by means of which a, from a deflection of the membrane (12) a measured pressure (P) proportional electrical signal (S) can be generated; and  Providing (S3) a flexible printed circuit board (16) which electrically and mechanically contacts the piezoresistive sensor element (14a; 14b; 14c). 12. The method according to claim 11, characterized in that the  Piezoresistive sensor element (14a, 14b, 14c) by a  bending-sensitive semiconductor chip (14a) or by a thin-film measuring structure (14b; 14c) formed of a semiconductor material, the piezoresistive sensor element (14a; 14b; 14c) being embedded in the flexible printed circuit board (16) on the flexible printed circuit board (16). applied or applied to the membrane (12) (S4). 13. Method according to claim 11, characterized in that an evaluation circuit (18) for evaluating the electrical signal (S) which can be generated by the piezoresistive sensor element (14a; 14b; 14c) is embedded in the flexible printed circuit board (16). 14. The method according to claim 12 or 13, characterized in that the thin-film measuring structure (14b, 14c) is applied to the flexible printed circuit board (16) by a photolithographic process, or printed on the membrane (12). 15. The method according to any one of claims 12 to 14, characterized in that the thin-film measuring structure (14c) by a printing method with electrically conductive inks having gold or silver particles, is printed on the membrane (12).