阅读说明：本技术 物体表面冲击波测量高灵敏薄膜传感器及制作方法 (High-sensitivity thin film sensor for measuring object surface shock wave and manufacturing method thereof ) 是由 范志强 何天明 张冰冰 郑航 胡敬坤 谭晓丽 于 2021-06-17 设计创作，主要内容包括：本发明属于实验力学测试技术领域,具体是一种物体表面冲击波测量高灵敏薄膜传感器及制作方法。包括压电膜元件和绝缘垫平层,绝缘垫平层中心位置设置有嵌入孔,压电膜元件嵌在嵌入孔内并与绝缘垫平层形成传感器芯层,传感器芯层的上下两侧为纤维聚合物电极,纤维聚合物电极与压电膜元件及绝缘垫平层通过纤维聚合物电极的表面粘性进行粘结固定,纤维聚合物电极的外侧设置绝缘保护层,上述结构共同构成薄膜结构,薄膜结构周向对称开设若干个法兰固定孔,薄膜结构通过法兰固定孔与法兰固定连接,法兰中部开设的法兰孔为压力加载区,法兰上设置有连接点封装端,连接点封装端内封装有引线连接点。(The invention belongs to the technical field of experimental mechanics testing, and particularly relates to a high-sensitivity thin film sensor for measuring surface shock waves of an object and a manufacturing method thereof. Including piezoelectric film element and insulating bedding level, insulating bedding level central point puts and is provided with the embedding hole, piezoelectric film element inlays in the embedding hole and forms the sensor sandwich layer with insulating bedding level, the upper and lower both sides of sensor sandwich layer are the fiber polymer electrode, the fiber polymer electrode bonds fixedly through the surface viscidity of fiber polymer electrode with piezoelectric film element and insulating bedding level, the outside of fiber polymer electrode sets up insulating protective layer, above-mentioned structure constitutes the film structure jointly, a plurality of flange fixed orifices is seted up to film structure circumference symmetry, the film structure passes through flange fixed orifices and flange fixed connection, the flange hole that the flange middle part was seted up is pressure loading district, be provided with tie point encapsulation end on the flange, the interior encapsulation of tie point encapsulation end is equipped with the lead wire tie point.)

1. The utility model provides a high sensitive film sensor of object surface shock wave measurement which characterized in that: the piezoelectric sensor comprises a piezoelectric film element (1) and an insulating leveling layer (4), wherein an embedding hole (7) is formed in the center of the insulating leveling layer (4), the piezoelectric film element (1) is embedded in the embedding hole and forms a sensor core layer with the insulating leveling layer (4), fiber polymer electrodes (2) are arranged on the upper side and the lower side of the sensor core layer, the fiber polymer electrodes (2), the piezoelectric film element (1) and the insulating leveling layer (4) are bonded and fixed through the surface viscosity of the fiber polymer electrodes, an insulating protective layer (3) is arranged on the outer side of each fiber polymer electrode (2), the structures jointly form a film structure, a plurality of flange fixing holes (6) are symmetrically formed in the circumferential direction of the film structure, the film structure is fixed with a flange (5) through the flange fixing holes (6), the flange hole formed in the middle of the flange (5) is a pressure loading area (10), and a packaging connection point end (10) is arranged on the flange (5), the connection point encapsulation end (10) is internally encapsulated with a lead connection point (8).

2. The high-sensitivity thin-film sensor for measuring the surface shock wave of the object according to claim 1, wherein: the flange (5) is made of rubber and resin flexible materials through a die casting method, a bottom flange with a certain height is cast during manufacturing, when the materials are semi-cured, the packaged film structure is slightly adhered to the surface of the flange, then the top flange is continuously cast, when the flange (5) is completely cured, and a high-viscosity bonding layer is coated on the bottom surface of the flange (5).

3. The high-sensitivity thin-film sensor for measuring the surface shock wave of the object according to claim 2, wherein: the part of the thin film structure, which is positioned in the flange hole, divides the flange hole into an upper part and a lower part, wherein the height of the flange hole of the lower part is not less than one third of the radius of the flange hole, and the sensor generates a stress field and outputs electric charge quantity by means of the flexural deformation of the thin film structure in the flange hole.

4. The high-sensitivity thin film sensor for measuring the surface shock wave of the object according to claim 3, wherein: the fiber polymer electrode (2) comprises an insulating layer, polyester fibers and a conductive adhesive polymer, wherein the polyester fibers are plated with metal nickel and copper thin layers with good conductivity, and the conductive adhesive polymer has good conductivity and self-adhesiveness and is soaked in the polyester fiber layers to form the conductive adhesive polymerAn assembly with strong adhesion and conductivity, wherein the front surface of the electrode is a composite of polyester fiber and viscous polymer, the back surface is polyimide insulating film, and the surface resistance of the fiber polymer electrode is not more than 0.1 Ω/m²The electromagnetic shielding effectiveness is not lower than 80db in the range of 100MHz to 3 GHz.

5. The high-sensitivity thin film sensor for measuring the surface shock wave of the object according to claim 4, wherein: the piezoelectric film element (1) is a piezoelectric polymer and composite material film thereof.

6. The high-sensitivity thin film sensor for measuring the surface shock wave of the object according to claim 5, wherein: the insulating leveling layer (4) and the piezoelectric film element (1) are the same in material and thickness, but are not polarized, and do not have piezoelectric property, and an embedding hole (7) which is the same as the piezoelectric film element in geometric shape and slightly larger in size is formed in the insulating leveling layer (4) and used for installing the piezoelectric film element (1).

7. A method for manufacturing a high-sensitivity thin-film sensor for measuring the surface shock wave of an object according to claim 6, wherein the method comprises the following steps: comprises the following steps of (a) carrying out,

s1, providing a polarized PVDF and composite piezoelectric film thereof, cutting a circular piezoelectric film element from the whole piezoelectric film by adopting a laser cutting or punching mode, removing burrs and an oxide layer on the edge, and cleaning by adopting alcohol/acetone soaking to remove impurities and a short circuit area possibly generated by cutting;

s2, providing an unpolarized PVDF film, cutting into a sensor shape, then forming an embedding hole in a laser cutting mode, forming a plurality of flange mounting small holes at the periphery of the embedding hole, and cutting the insulating film subjected to hole forming treatment to be used as an insulating leveling layer for later use;

s3, providing a fiber polymer electrode with good conductivity and electromagnetic shielding effect, manufacturing the shape of the sensor by laser cutting, uniformly forming small holes in the circumferential direction to prepare for later installation in a flange, wherein the diameter of the small holes for installation in the flange is not less than that of the small holes formed in an insulating cushion layer, removing burrs from the edge after cutting, removing impurities and a short-circuit area possibly generated due to cutting, reserving a lead connecting position at the end part of the fiber polymer electrode, wherein the front surface of the fiber polymer electrode is a complex of exposed fiber and viscous polymer, the surface has strong cohesiveness and conductivity, and the back surface of the electrode is a polyimide insulating film;

s4, completely bonding the insulation mat layer obtained in the step S2 and the fiber polymer electrode obtained in the step S3, aligning the centers of the flange fixing holes on the insulation mat layer and the fiber polymer electrode one by one, exposing the electrode area on the fiber polymer electrode through an embedding hole formed in the insulation mat layer of the core layer, then installing the piezoelectric film element obtained in the step S1 in the embedding hole, and directly contacting the lower surface of the piezoelectric film element with the bottom electrode to realize viscosity and electrical connection to obtain a combination of the core layer and the bottom electrode of the film sensor;

s5, providing the electrode obtained in the step S3 as a top electrode layer of the sensor, transferring the electrode, the core layer and the bottom electrode assembly obtained in the step S4 to a vacuum environment, bonding the front surface of the top electrode and the core layer surface of the assembly to obtain a thin film type sensor structure with a symmetrical structure in the thickness direction, prepressing for a period of time through a certain pressing pressure to enable the internal structure of the sensor to be flat, tight and firm in pressing, cutting redundant areas, and connecting external leads to form the shape of the thin film structure;

s6, providing a pouring mold of the flange body, pouring rubber or high polymer flexible packaging material into the mold in a vacuum environment to form a bottom flange with a certain thickness for later use, and slightly adhering the film structure obtained in the step S5 to the upper surface of the semi-solidified flange and adjusting the position when the solidification time of the bottom flange body reaches half of the full solidification time;

s7, installing a pouring mold of the top flange body on the surface of the assembly obtained in the S6, continuously pouring a thick flexible packaging material on the surface of the semi-cured bottom flange to form the top flange, removing the mold after the flexible packaging material is completely cured, and modifying the inner edge and the outer edge of the sensor to obtain the sensor.

8. The method for manufacturing a thin film sensor suitable for measuring the surface shock wave of an object according to claim 7, wherein: in steps S4 and S5, when the electrodes are bonded to the insulating spacer, the positions of the flange mounting holes on the core layer and the electrodes on both sides need to be controlled to correspond one to one, and the aperture of the mounting hole on the electrode is slightly larger than that of the core layer, so as to ensure that the mounted film structure does not have short-circuit connection near the mounting hole.

Technical Field

The invention belongs to the technical field of experimental mechanics testing, and particularly relates to a high-sensitivity thin film sensor for measuring surface shock waves of an object and a manufacturing method thereof.

Background

The film type pressure sensor using PVDF and composite material piezoelectric film (piezoelectric film for short) as sensitive element has the advantages of wide frequency response, large dynamic pressure test range, high force-electricity conversion coefficient, good flexibility and biological interface compatibility, etc., and is widely applied to impact pressure measurement on the structure surface, material internal interface, organism body surface, etc. At present, the piezoelectric film pressure gauge is mainly manufactured by adopting a sandwich structure, namely, a piezoelectric element is positioned between two electrodes, and the electrodes on two sides are bonded by adopting gluing and other modes. The two orthogonal directions in the piezoelectric film surface are set as 1 and 2, the normal line out of the surface is set as 3, the main measurement principle of the current film pressure gauge is to utilize the out-of-surface compressive stress of the sensorf ₃₃ Out-of-plane 3 direction charge outputq ₃ The linear relation between the two is measured and calculated by detecting the output charge quantity in the out-of-plane 3 direction. Current research shows that the piezoelectric film is only 10¹~10³Has good force-electric wire characteristic in the MPa pressure range, and is too high (more than or equal to 10)³MPa) and too low (less than or equal to 10)¹MPa) pressure range, which is not favorable for accurate measurement.

The piezoelectric film type pressure sensor is mainly used for measuring dynamic stress waves and shock waves with high amplitude, and the pressure of the shock waves acted on the surface of a soft organism or on individual equipment by air explosion is generally 10^-1~10¹MPa, action time of only 10^-3~10¹ms, has the characteristics of low amplitude, high loading rate, strong nonlinearity and the like; the pressure of shock waves outside the traditional pressure meter is utilized for measuring, and for low pressure such as air shock waves, the electric charge quantity generated by the compression outside the piezoelectric film is too small, the sensitivity of the sensor is too small, and the signal-to-noise ratio and the measurement accuracy are too low. In addition, when the air shock wave is incident/reflected on the interface, an air compressible equal-strength nonlinear process exists, the reflection rule is complex, and the response of the structural surface can influence the force-electricity of the thin film sensor adhered with the structural surface to a certain extentThe response, and therefore the introduction of a non-measured charge output, increases the signal-to-noise ratio of the output and leads to unstable sensor sensitivity and poor linearity of the force-electric response. Therefore, the current pressure sensor is not suitable for pressure measurement of the surface of a structure which is supported by soft back and is rapidly deformed under pressure. Such as explosive shock wave measurements of a biological surface, the rapid deformation of the back support resulting in a change of stress state and flexible flexing of the piezoelectric element will cause a large deviation of the measurement result from the real situation. Therefore, it is highly desirable to improve the structure and measurement format of the diaphragm gauge, and to improve the force-electric response sensitivity and measurement signal-to-noise ratio of the sensor.

Disclosure of Invention

The invention aims to solve the problem that the traditional piezoelectric film pressure gauge is low in amplitude (10)^-1~10¹MPa) explosion shock wave measurement, and the like, and provides a thin film sensor suitable for measuring the shock wave on the surface of an object and a manufacturing method thereof.

The invention adopts the following technical scheme: the utility model provides a high sensitive film sensor is measured to object surface shock wave, including piezoelectric film element and insulating bedding layer, insulating bedding layer central point puts and is provided with the embedding hole, piezoelectric film element inlays in the embedding hole and forms the sensor sandwich layer with insulating bedding layer, the upper and lower both sides of sensor sandwich layer are the fibre polymer electrode, fibre polymer electrode bonds fixedly through the surface viscidity of fibre polymer electrode with piezoelectric film element and insulating bedding layer, the outside of fibre polymer electrode sets up insulating protective layer, above-mentioned structure constitutes the film structure jointly, a plurality of flange fixed orifices is seted up to film structure circumference symmetry, the film structure passes through flange fixed orifices and flange fixed connection, the flange hole that the flange middle part was seted up is the pressure loading district, be provided with tie point encapsulation end on the flange, the lead wire tie point is equipped with in the tie point encapsulation end.

Furthermore, the flanges are made of rubber and resin flexible materials through a die casting method, the bottom flange with a certain height is cast during manufacturing, when the materials are semi-cured, the packaged film structure is slightly adhered to the surface of the flange, then the top flange is continuously cast, when the flanges are completely cured, and the bottom surfaces of the flanges are coated with high-viscosity bonding layers.

Furthermore, the part of the thin film structure, which is positioned in the flange hole, divides the flange hole into an upper part and a lower part, wherein the height of the flange hole of the lower part is not less than one third of the radius of the flange hole, and the sensor mainly depends on the flexural deformation of the thin film structure in the flange hole to generate a stress field and output electric charge. Different from the traditional pressure gauge, the piezoelectric film generates charge output only through out-of-plane pressure, when the film structure which is overhead through a flange and is fixed and supported in the circumferential direction bears out-of-plane pressure, the film structure without the support on the back generates obvious out-of-plane deflection deformation, two orthogonal directions in the piezoelectric film surface generate larger tensile stress (generally higher than the out-of-plane pressure by one order of magnitude), higher charge output is caused, and the internal stress of the piezoelectric film is promoted to be within the working stress range with higher force-electric linearity of the material. Therefore, the structure can generate more electric charge under the action of lower out-of-plane pressure, and the sensitivity of the sensor and the linearity of the force-electricity relation are greatly improved. In addition, according to the elastic theory, the corresponding characteristics of the film structure can be regulated and controlled by adjusting the parameters of the film material, the thickness, the radius of a deformation area and the like in the elastic small deformation range of the film structure which is circumferentially supported, so that the force-electric response sensitivity of the sensor can be regulated and controlled.

Furthermore, the fiber polymer electrode comprises an insulating layer, polyester fibers and a conductive adhesive polymer, wherein the polyester fibers are plated with a metal nickel and copper thin layer with good conductivity, the conductive adhesive polymer has good conductivity and self-adhesiveness and is soaked in the polyester fiber layer to form a combination with strong adhesiveness and conductivity, the front surface of the electrode is a composite body formed by the polyester fibers and the adhesive polymer, the back surface of the electrode is a polyimide insulating film, and the surface resistance of the fiber polymer electrode is not more than 0.1 ohm/m²The electromagnetic shielding effectiveness is not lower than 80db in the range of 100MHz to 3 GHz.

Furthermore, the piezoelectric film element is a piezoelectric polymer and a composite material film thereof.

Furthermore, the insulating pad layer and the piezoelectric film element are the same in material and thickness, but are not polarized and do not have piezoelectric property, and the insulating pad layer is provided with an embedding hole which is the same as the piezoelectric film element in geometric shape and slightly larger in size and is used for installing the piezoelectric film element.

A method for manufacturing a high-sensitivity film sensor for measuring the shock wave on the surface of an object comprises the following steps.

S1, providing the polarized PVDF and the composite piezoelectric film thereof, cutting a circular piezoelectric film element from the whole piezoelectric film by adopting a laser cutting or punching mode, removing burrs and an oxide layer on the edge, and cleaning by adopting alcohol/acetone soaking to remove impurities and a short circuit area possibly generated by cutting.

S2, providing an unpolarized PVDF film, cutting into a sensor shape, then forming an embedding hole in a laser cutting mode, forming a plurality of flange mounting small holes at the periphery of the embedding hole, and cutting the insulating film subjected to hole forming treatment to be used as an insulating leveling layer for later use.

S3, providing a fiber polymer electrode with good conductivity and electromagnetic shielding effect, manufacturing the shape of the sensor by laser cutting, uniformly forming small holes in the circumferential direction to prepare for later installation in a flange, wherein the diameter of the small holes for installation in the flange is not less than that of the small holes formed in the insulating cushion layer, removing burrs from the edge after cutting, removing impurities and short-circuit regions possibly generated by cutting, reserving lead connection positions at the end parts of the fiber polymer electrode, and the front surface of the fiber polymer electrode is a complex of exposed fibers and viscous polymers, and has strong cohesiveness and conductivity, and the back surface of the electrode is a polyimide insulating film.

S4, completely bonding the insulation mat layer obtained in the step S2 and the fiber polymer electrode obtained in the step S3, aligning the centers of the flange fixing holes on the insulation mat layer and the fiber polymer electrode one by one, exposing the electrode area on the fiber polymer electrode through the embedding hole formed in the insulation mat layer of the core layer, then installing the piezoelectric film element obtained in the step S1 in the embedding hole, and directly contacting the lower surface of the piezoelectric film element with the bottom electrode to realize adhesion and electrical connection to obtain the combination of the core layer and the bottom electrode of the film sensor.

S5, providing the electrode obtained in the step S3 as a top electrode layer of the sensor, transferring the electrode, the core layer and the bottom electrode assembly obtained in the step S4 to a vacuum environment, bonding the front surface of the top electrode and the core layer surface of the assembly to obtain a thin film type sensor structure with a symmetrical structure in the thickness direction, prepressing for a period of time through a certain pressing pressure to enable the internal structure of the sensor to be flat, tight and firm in pressing, cutting redundant areas, and connecting external leads to form the appearance of the thin film structure.

S6, providing a pouring mold of the flange body, pouring rubber or high polymer flexible packaging material into the mold in a vacuum environment to form a bottom flange with a certain thickness for later use, and slightly adhering the film structure obtained in the step S5 to the upper surface of the semi-solidified flange and adjusting the position when the solidification time of the bottom flange body reaches 1/2 of the complete solidification time.

S7, installing a pouring mold of the top flange body on the surface of the assembly obtained in the S6, continuously pouring a thick flexible packaging material on the surface of the semi-cured bottom flange to form the top flange, removing the mold after the flexible packaging material is completely cured, and modifying the inner edge and the outer edge of the sensor to obtain the sensor.

In steps S4 and S5, when the electrodes are bonded to the insulating spacer, the positions of the flange mounting holes on the core layer and the electrodes on both sides need to be controlled to correspond one to one, and the aperture of the mounting hole on the electrode is slightly larger than that of the core layer, so as to ensure that the mounted film structure does not have short-circuit connection near the mounting hole.

Compared with the prior art, the invention has the following beneficial effects:

1. the element force-electric coupling relation is different from that of the traditional method, the piezoelectric element generates electric charge by utilizing higher in-plane tension caused by the compression, deflection and deformation of the film, the electric charge output quantity of the piezoelectric element under the action of low pressure is improved, and the signal-to-noise ratio and the sensitivity are improved; the two orthogonal directions in the plane of the piezoelectric film are respectively 1 and 2, the out-of-plane direction is 3, and the charge quantity density in the 3 direction is mainly detected during actual measurementq ₃ The charge generation is related to the stress in three directions, the charge density generated by the acting force in three directions is linear, and the force-electricity conversion coefficients are respectivelyd ₃₁ 、d ₃₂ Andd ₃₃ is provided withf ₁ 、f ₂ Andf ₃ the positive stresses in three directions are applied, the charge output of the piezoelectric film element in the thickness direction can be expressed as:q ₃ =d ₃₁ f ₁ + d ₃₂ f ₂ + d ₃₃ f ₃ in the conventional measurement, only the pressure in 3 directions is considered, so that the output charge amount isq ₃ = d ₃₃ f ₃ . The thin film structure is a thin film which is supported fixedly on the periphery in a flange overhead mode, the thin film is elastically deflected and deformed under the action of pressure in the out-of-plane 3 direction, the stressed and deformed area is considered to be a mean value circular thin film with the radius of r and the thickness of h, and then the radial stress and the tangential stress are respectively as follows:

whereinμIs the equivalent poisson's ratio of the stacked sensor,xis the distance from a point on the film to the center of the circle. It can thus be calculated that at the center of the film, the ratio of the in-plane stress to the out-of-plane stress isThe Poisson's ratio was calculated to be 0.3. The radial-thickness ratio of the general thin film structure is not less than 10, so that the in-plane stress is 10 of the out-of-plane pressure¹~10²And (4) doubling. The output of the sensor at this time isq ₃ =d ₃₁ f ₁ + d ₃₂ f ₂ + d ₃₃ f ₃ Whereinf ₁ ，f ₂ Is at least higher in value thanf ₃ An order of magnitude, and therefore the amount of charge generated is much greater than that conventionally generated using only out-of-plane compression, the sensitivity of the sensor must also be significantly improved.

2. The pressure gauge provided by the invention has a smooth internal structure, the thickness and the material of the core layer are uniform, and the problems of unstable sensitivity caused by local stress concentration and core layer deformation detuning are solved; the pressure gauge is pressed under a vacuum environment, and the influence of air in an internal packaging gap on low-pressure measurement is eliminated.

3. All materials used by the sensor provided by the invention are flexible materials, the size and the mass are small, the sensor can be installed on the surface of a structure in a direct sticking mode, and different from the traditional hard sensor in punching and installation on the surface of the structure, the flexible installation has small inertia, negligible influence on the response of the structure, simple and convenient installation and wide application range.

4. The invention adopts the fiber polymer viscous electrode, which not only can ensure the smooth conduction of charges on two sides of the piezoelectric film element, but also can improve the bonding strength between internal layers; the electrode uses the polyester fiber woven vertically and horizontally as a main body bearing tensile load, has the advantages of good linear elasticity and high strength, and is more suitable for a sensor structure which mainly takes in-plane tensile deformation compared with a metal electrode layer. In addition, the fiber polymer electrode layer can improve the electromagnetic shielding performance of the sensor on the piezoelectric element and improve the signal-to-noise ratio.

5. The invention provides the sensor which has higher consistency of the configurations and the sizes of all parts and is convenient for batch manufacturing, thereby ensuring the unification of the material, the process parameter and the mechanical and electrical properties of the sensor and reducing the individual difference of the sensor.

Drawings

FIG. 1 is a cross-sectional view of a sensor;

FIG. 2 is a schematic view showing the structure of an insulating mat used in example 1;

FIG. 3 is a schematic view of the structure of an electrode used in example 1;

FIG. 4 is a schematic view of the outer shape of the sensor obtained in example 1;

FIG. 5 is a graph comparing a measured shock wave curve of the sensor obtained in example 1 with a standard curve;

FIG. 6 is a calibration chart of the sensitivity coefficient of the sensor obtained in example 1;

wherein figure 1 is a cross-sectional view a-a of figure 4.

In the figure, 1-a piezoelectric film element, 2-a fiber polymer electrode conducting layer, 3-an insulating protective layer, 4-an insulating leveling layer, 5-a flange, 6-a flange fixing hole, 7-an embedding hole, 8-a lead connecting point, 9-a connecting point packaging end and 10-a pressure loading area.

Detailed Description

The present invention will be described in further detail with reference to the accompanying drawings and examples.

As shown in figure 1, a film sensor suitable for measuring the surface shock wave of an object comprises a piezoelectric film element 1 and an insulating leveling layer 4, wherein an embedding hole 7 is arranged at the center of the insulating leveling layer 4, the piezoelectric film element 1 is embedded in the embedding hole and forms a sensor core layer with the insulating leveling layer 4, fiber polymer electrodes 2 are arranged on the upper side and the lower side of the sensor core layer, the fiber polymer electrodes 2, the piezoelectric film element 1 and the insulating leveling layer 4 are bonded and fixed through the surface viscosity of the fiber polymer electrodes, an insulating protective layer 3 is arranged on the outer side of the fiber polymer electrodes 2, the structures jointly form a film structure, a plurality of flange fixing holes 6 are symmetrically arranged in the circumferential direction of the film structure, the film structure is fixed with a flange 5 through the flange fixing holes 6, a flange hole arranged in the middle of the flange 5 is a pressure loading area 10 of the film structure, and a connection point packaging end 10 is arranged on the flange 5, the connection point package end 10 has the lead connection point 8 packaged therein.

In this embodiment, the piezoelectric film element is a piezoelectric polymer having piezoelectric properties and a composite film thereof, such as PVDF, PZT/PVDF, PVDF-TrFE, and the like, after polarization.

Fig. 2 is a schematic diagram of the core layer insulation spacer layer 4, which is made of unpolarized PVDF film and has no piezoelectric property, and includes six flange fixing holes 6 on the periphery and an insertion hole 7 in the center of a piezoelectric film element, wherein the diameter of the insertion hole 7 is slightly larger than that of the piezoelectric film element.

The structure of the fiber polymer electrode is schematically shown in fig. 3, and comprises an electrode conducting layer 2 consisting of polyester fibers and conductive adhesive polymer, an insulating layer 3 coated outside, six flange fixing holes 6 in the circumferential direction and a tail lead connecting point 8. The flange fixing hole on the electrode is slightly larger than the diameter of the flange fixing hole on the insulating leveling layer 4, but the centers of all the round holes are aligned. Wherein the polyester fiber is plated with metal nickel and copper thin film with good conductivityThe conductive adhesive polymer has better conductive performance and self-adhesive performance, and is soaked in the polyester fiber layer to form a combination with stronger adhesive performance and conductive performance, the front surface of the electrode is a composite body formed by the polyester fiber and the adhesive polymer, the back surface of the electrode is a polyimide insulating film, and the surface resistance of the fiber polymer electrode is not more than 0.1 Ω/m²The electromagnetic shielding effectiveness is not lower than 80db in the range of 100MHz to 3 GHz.

The flexible flange body is made of materials such as rubber, resin and polyurethane which can be continuously poured in a split mode, and as shown in figure 4, the flexible flange body comprises a packaging end 9 of a lead connecting point and a central circular pressure loading area 10.

4-6 through holes are symmetrically formed in the circumferential direction of the packaged film structure, so that the upper part material and the lower part material of the flange can form a whole through the through holes, and the circumferential fixing strength of the film structure is improved. In order to improve the structural strength of the sensor, the electrodes and the welding points of the external lead are all packaged in the flexible flange body.

In the packaged sensor, a flange hole below the thin film layer provides an out-of-plane stressed deformation space for the sensor thin film, and the height of the lower flange hole is not less than one third of the radius of the flange hole.

The two orthogonal directions in the piezoelectric film surface are respectively 1 and 2, the out-of-plane direction is 3, the piezoelectric film is enabled to generate charge output only by out-of-plane pressure different from the traditional pressure gauge, when the film structure which is supported by flanges in an overhead and circumferential mode bears out-of-plane pressure, the out-of-plane direction generates compression deformation, the film bends downwards under pressure, the 1 and 2 directions in the piezoelectric film surface generate larger tensile stress (generally higher than the out-of-plane pressure by one order of magnitude), the internal stress of the piezoelectric film is promoted to the working stress range with higher force-electric wire linearity of the material, and therefore the structure can generate more charge under the action of the lower out-of-plane pressure, and the sensitivity of the sensor and the linearity of the force-electric relation are greatly improved. In addition, according to the elastic theory, the corresponding characteristics of the film structure can be regulated and controlled by adjusting the parameters of the film material, the thickness, the radius of a deformation area and the like in the elastic small deformation range of the film structure which is circumferentially supported, so that the force-electric response sensitivity of the sensor can be regulated and controlled.

The fiber polymer electrode can directly output charges on two sides of the piezoelectric film 3 due to the conductive property of the fiber polymer electrode, and the outer surface of the electrode is a Polyimide (PI) film insulating layer. And based on a continuous casting method, the encapsulated sandwich type film structure is circumferentially fixed by using rubber or high polymer flexible materials to form the film type pressure sensor with a certain stressed and deformed circular area and circumferential support.

The embodiment of the invention provides a manufacturing method of a film sensor suitable for measuring the surface shock wave of an object, which comprises the following specific steps:

s1: and providing a polarized PVDF piezoelectric film, wherein the PVDF is polyvinylidene fluoride and has piezoelectric performance after polarization. A circular piezoelectric film element is cut from the whole piezoelectric film by laser cutting, the edge of the circular piezoelectric film element is round with the thickness of 52 mu m and the diameter of 6mm, burrs and an oxide layer are removed, and the circular piezoelectric film element is soaked and cleaned by alcohol/acetone to remove impurities and a short-circuit area possibly generated by cutting. The piezoelectric film has a force-electric sensitivity coefficient of d₃₁=12pC/N，d₃₂=7pC/N，d₃₃=21pC/N。

S2: an unpolarized PVDF film is provided which does not have piezoelectric properties and is an insulating material. The thickness of the film is 52 mu m, the film is perforated by adopting a laser cutting mode to form an embedding hole 7 with the diameter of 6.1mm, flange fixing holes 6 with the diameter of 1.5mm are symmetrically formed in the periphery of the film, the cushion layer 4 is cut into the shape of a sensor, and the circular outline has the outer diameter of 26 mm.

S3: the fiber polymer electrode has excellent conductivity and good electromagnetic shielding effect, the fiber polymer electrode adopts a polyimide film with the thickness of 28 microns as an insulating layer 3, a viscous conducting layer 2 consisting of polyester fibers and conductive viscous polymers, the thickness of the viscous conducting layer is 120 microns, the tail end of the viscous conducting layer is provided with an external lead connecting point 8 with the thickness of about 3 x 5mm, six flange fixing holes 6 are arranged on the periphery of the viscous conducting layer, the diameter of the flange fixing holes is 2mm, the outer diameter of a circular outline is 24mm, and the centers of all the holes of the flange fixing holes are consistent with those of the flange fixing holes in S2.

S4: completely bonding the leveling layer 4 obtained in the step S2 with the conducting layer 2 of the bottom fiber polymer electrode obtained in the step S3, installing the piezoelectric film element 1 obtained in the step S1 in the embedding hole 7 in the insulating leveling layer 4, and pressing the lower surface of the piezoelectric film element 1 and the conducting layer 2 of the bottom fiber polymer electrode to realize electrical and adhesive connection;

s5: and (4) providing the electrode obtained in the step (S3) as a top electrode layer of the sensor, transferring the electrode, the core layer and bottom electrode assembly obtained in the step (S4) into a vacuum environment, bonding the front surface of the top electrode and the core layer surface of the assembly to obtain a thin film type sensor structure with a symmetrical structure in the thickness direction, and prepressing for a period of time through certain pressing pressure to promote the internal structure of the sensor to be flat, tight and firm in pressing. Cutting the redundant area and connecting the external lead to form the shape of the film structure. Wherein, the fiber high polymer electrode can not be soldered directly, and copper sheets with thickness of 50 μm and length and width of 3mm x 3mm can be pasted on the surface of the fiber high polymer electrode as soldering points. When the electrode is bonded with the insulating cushion layer, the positions of the flange mounting holes on the electrodes on two sides and the core layer are required to be controlled to be in one-to-one correspondence, the inner edge of the flange fixing hole and the outer edge of the electrode are insulated, and the upper layer of electrode and the lower layer of electrode are insulated through the edge of the protruded insulating core layer.

S6, providing a pouring mold of the flange body, pouring silicon rubber with the hardness of 20 degrees and the complete curing time of 24 hours into the mold under the vacuum environment to form a bottom flange with the thickness of 3mm, wherein the diameter of a circular area of the flange is 30mm, and the diameter r =10mm of a flange hole for later use. And (3) slightly adhering the film structure obtained in the step (S5) to the upper surface of the semi-solidified flange and adjusting the film structure to be positioned at the center of the sensor when the flange body at the bottom is solidified for 12h and the surface still has slight viscosity and fluidity, and positioning the wire connecting point at the tail part of the sandwich type film structure at the protruding tail part of the flange body.

S7, mounting a pouring mold of the top flange body on the surface of the combined body obtained in the step S6, and continuously pouring a 1 mm-thick silicone rubber material on the surface of the semi-solidified bottom flange to form the top packaging flange. And after the tape packaging material is completely cured for 24 hours, removing the die, and modifying the inner edge and the outer edge to obtain the peripherally-supported and overhead film type pressure sensor with the central loading area of 10mm in diameter.

When the sensor is used, the flange is directly arranged on the surface of a measured object in a sticking mode, an ∅ 10mm flange inner hole provides enough out-of-plane deformation space for the sensor at one side of the sensor close to the measured object, and experimental results show that a 3mm gap is enough to adapt to the out-of-plane deformation of the sensor within the range of 0.7 MPa. The top flange thickness of 1mm is sufficient to provide a clamped boundary condition for the sandwich membrane structure, and the thinner top anchoring layer interferes less with pressure transmission over the loading area.

The sandwich type film structure is poured in the flange, the integrated connection of the upper flange material and the lower flange material is realized through the flange fixing small holes which are communicated with the periphery and the outer edge, and the peripheral fixing and supporting strength is improved; the external lead welding point of the fiber polymer electrode is also encapsulated inside the flange body through pouring, so that the structural strength of the sensor is improved.

In the embodiment, the pressure gauge is of a sandwich structure, and the thickness of the insulating leveling layer of the core layer is the same as that of the piezoelectric film, so that the thickness uniformity of the initial configuration of the pressure gauge is ensured, the uniformity of the whole compression deformation of the core layer material in the compression process is also ensured, the deformation detuning and the local stress concentration of the core layer caused by the problems of the material and the thickness are eliminated, and the stability of the sensitivity coefficient is improved; in addition, the fiber polymer electrode with uniform thickness and high tensile strength is adopted, the in-plane tensile strength of the sensor is improved, the internal structure of the sensor is tighter due to the viscous connection of the electrode, and the integrity and consistency are higher when the sandwich type film structure deforms.

In this embodiment, the final packaging stage of the internal structure of the pressure gauge is performed in a vacuum environment, so that the pressure gauge is ensured to have good adhesive connection on two sides of the piezoelectric film in the testing process of atmospheric pressure and higher pressure environment, and the measuring accuracy and the high resolution ratio of pressure are ensured during the pressure test with the same magnitude as the atmospheric pressure.

In this embodiment, the insulating leveling layer and the fiber polymer electrode can be manufactured in batch by using the array template, so that the pressure gauges made of the same material, the same packaging process and the same pressing pressure can be manufactured in batch, and the individual difference of the pressure gauges can be reduced conveniently.

The shock wave measurement and sensitivity coefficient calibration experiment is carried out on the sensor, based on the shock wave tube experiment device, the loading shock wave is generated, the loading shock wave is measured through the standard PCB 113B24 standard pressure sensor, and the self-made sensor is installed toThe blind plate is faced to the wave surface, and the measurement result of the self-made sensor is compared with the standard PCB sensor, as shown in FIG. 5. It can be seen that the self-made pressure sensor provided by the invention can accurately measure the characteristics of steep rising edge and slow falling edge of shock wave, and the pulse width of the self-made pressure sensor is reduced with the measurement result of a standard pressure sensor, but the pulse width is well matched with the peak value. In addition, by carrying out shock wave loading with different intensities on a group of pressure sensors provided by the invention, the relation between the charge quantity density generated by the sensors and the out-of-plane pressure is compared, and fitting can be carried out to obtainq=Q/A=kpWhereinq(pC/mm²) Is the amount of charge generated by the piezoelectric element per unit area,Q(pC) is the amount of charge produced by the sensor,A(mm²) Is the sensitive area of the piezoelectric element in the sensor,k (pC/N) is the nominal sensitivity coefficient of the sensor,p (MPa) is the stress to which the sensor is subjected. The results of the shock wave pressure calibration of 7 sensors fabricated in the same batch by the method provided by the present invention are shown in FIG. 6, and the fitted nominal sensitivity coefficient is about 334.1pC/N, which is the nominal sensitivity of the piezoelectric film out-of-plane compression used in the present inventiond ₃₃ By contrast, the sensor packaging technology provided by the invention has the remarkable characteristic of high sensitivity in a certain pressure range. As can be seen from fig. 6, the charge output of any sensor increases linearly with the pressure, and the measurement results of different sensors are relatively close, which indicates that the individual differences of the sensors manufactured in batch are small, and the sensitivity of the sensors is relatively stable.

The present invention is not limited to the above preferred embodiments, and any modifications, equivalent substitutions and improvements made within the spirit and principle of the present invention should be included in the protection scope of the present invention.