WO1997013130A2

WO1997013130A2 - Static and dynamic pressure sensing electronic component

Info

Publication number: WO1997013130A2
Application number: PCT/DE1996/001718
Authority: WO
Inventors: Margit Biehl
Original assignee: Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V.
Priority date: 1995-09-12
Filing date: 1996-09-12
Publication date: 1997-04-10
Also published as: WO1997013130A3; DE19533756A1

Abstract

An electronic component for sensing static and dynamic pressure has a non-conducting base substrate that carries at least two electrodes mutually spaced on the surface of the substrate, as well as a non-conducting, flexible carrier layer arranged above the base substrate and the electrode pairs. A number of elastic, electroconductive deformation elements which correspond to the number of electrode pairs are arranged on the bottom side of the non-conducting carrier layer, substantially in the centre of the individual electrode pairs, and may be pressed against the pairs of conductive tracks. The cross-sectional area of these elastic deformation elements is smaller in diameter near the base substrate than the distance between the electrodes, continuously increases in the direction of the carrier layer and at the level of the carrier layer approximately corresponds to the substrate surface covered by the electrodes. The invention is characterised in that the individual electrodes are mutually insulated conductive tracks which fan out into at least two individual conductive tracks arranged in such a way on the substrate surface that the individual conductive tracks of each electrode alternate in pairs with the conductive tracks of the other electrode.

Description

Electronic component for static and dynamic

Printer acquisition

Description

Technical field

The invention relates to an electronic component for static and dynamic pressure detection with a non-conductive base substrate, on which at least two electrodes are applied, which are arranged on the substrate surface such that the electrodes are spaced apart, and with one, above the base substrate and the Flexible, non-conductive carrier layer arranged on the electrode pairs, on the underside of which, depending on the number of the electrode pairs, elastic, electrically conductive deforming elements which are oriented essentially centrally to the individual electrode pairs and have a cross-sectional area whose diameter is in Near the base substrate is smaller than the electrode spacing and which increases continuously in the direction of the carrier layer and corresponds approximately to the substrate area covered by the electrodes, which can be pressed against the conductor track pairs.

State of the art

Electronic components of the type described above are used in the technical field of tactile sensors. For the purpose of recording area-distributed pressure, pressure sensor arrays are used, which are preferably designed as matrix sensors and for Robotics and telemanipulation, but also for medical applications such as prosthetics. Components of this type are aids for detecting surface topologies or positions of touched or gripped objects and, with suitable tactile feedback, make telemanipulation considerably easier.

Great technical efforts have been made to develop pressure sensor arrays with a sufficiently good resolution. A wide variety of physical principles have been tested, such as piezoelectric sensors, which are robust and inexpensive, but are only suitable for receiving dynamic pressure signals. Even the use of optical sensors has been tested for pressure detection, especially since they provide very sensitive measurement signals, but they are expensive and relatively bulky to use.

In contrast to piezoelectric sensors, the so-called piezoresistive sensors change their electrical resistance under the action of pressure and also permit the detection of static pressures. Conductive elastomers have been used in connection with piezoresistive sensors, which makes the sensors inexpensive, mechanically robust and flexible. However, it has not hitherto been possible to produce such sensors with a resolution of less than one millimeter, so far only a low measuring sensitivity has been achievable and, moreover, such a small dynamic range can be achieved, so that the measuring signal response to one mere binary response characteristics limited. Finally, the measurement result is subject to a high degree of hysteresis if the pressure-dependent change in the specific resistance of the elastomer material is used as the sensor principle. Further problems that arise with the use of elastomer in pressure sensor arrays are mechanical and electrical coupling between two adjacent pressure sensor units. In particular, Raibert MH, Tanner JE, "Design and Implementation of a VLSI Tactile Sensing Computer", in The International Journal of Robotics Research, Vol. 3, (1982), pp. 3-18.

As an alternative to the aforementioned sensor arrangement, pressure sensor arrays are known which have been produced with the aid of micromechanical silicon technology, which capacitively or piezoresistively determine the pressure-induced deflection of a membrane and thus quantitatively the applied pressure. Such silicon pressure sensor arrays can be produced with a high resolution, but are inflexible and fragile due to the silicon carrier material, and are very complex and therefore very expensive to produce. In this context, reference is made to the following publications: Sugiyama S. et al. , "Tactile Image Detection Using an IK-element Silicon Pressure Sensor Array", in Sensors and Actuators, A21-A23 (1990), pp. 397-400; Wolffenfuttel M.R., Regtien P.P.L. "Polysilicon Bridges for the Realization of Tactile Sensors", in Sensors and Actuators A, 25-27 (1991), pp. 257-264.

Furthermore, JP 2-275603, which is considered to be the closest prior art, shows a pressure sensor which consists of an electrically insulating base plate 4, on which two elongate electrodes 10, 11 are formed, which are at a distance from one another are upset. There is an electrically conductive rubber over the electrode gap manufactured contact wedge 13 attached, which can be pressed under pressure on the electrode gap. If the contact wedge is pressed completely onto the electrode gap, the latter short-circuits the opposite electrodes, as a result of which a current flows between the electrodes.

This pressure sensor can only differentiate between two states, namely the state without exerting pressure, in which there is no current flow between the electrodes and the state in which the contact wedge shorts the two electrodes, so that a current flow is generated between the two electrodes, a statement over which the force or pressure holding down the contact wedge is not possible.

Presentation of the invention

The invention is based on the object of developing an electronic component for static and dynamic pressure detection of the type described above in such a way that, with the aid of known micromechanical production methods and the use of conductive elastomers, a pressure sensor array can be produced which can be both a has high sensitivity as well as a large dynamic range and a high resolution. In addition, the poor overcoupling properties should be eliminated when using elastomers, so that mechanical overcoupling is reduced to a minimum. Finally, it should be possible to produce a two-dimensionally bendable sensor which is to be attached, for example, to the tip of a touch finger. Finally, the manufacturing process should be less complex and therefore less expensive. The solution to the problem underlying the invention is specified in claim 1. Advantageous embodiments can be found in claims 2 ff.

According to the invention is an electronic component for static and dynamic pressure detection with a non-conductive base substrate, on which at least two electrodes are applied, which are arranged on the substrate surface in such a way that the electrodes are spaced apart, and with one, above the base substrate and the electrode pairs arranged flexible, non-conductive carrier layer, on the underside of which, depending on the number of electrode pairs, elastic, essentially centrally aligned to the individual electrode pairs, electrically conductive deformation elements with a cross-sectional area, the diameter of which in the vicinity of the base substrate is less than the electrode spacing is and which increases continuously in the direction of the carrier layer and is attached to the carrier layer and corresponds approximately to the substrate area covered by the electrodes, which can be pressed against the conductor track pairs, in such a way that the individual electrodes are in each case in at least two individual conductor tracks fanning out, mutually insulated conductor tracks which are applied to the substrate surface in such a way that one conductor track of the one alternates with the conductor track of the other electrode.

The electronic component consists essentially of two parts, the base substrate, which can be rigid or flexible, on the upper side of which thin-film technology, conductor track structures and spacer structures are applied, and a carrier layer is arranged exactly over the top of the base substrate and has a three-dimensional structured elastomer matrix with conductive and non-conductive elastomer areas.

According to the invention, the conductor track structures applied to the upper side of the base substrate form individual array elements which have the shape of two interdigital electrodes, each with at least two fingers. The simplest form of interdigital electrodes each consist of two electrodes, the electrode structure of which corresponds to the shape of an "F" and are arranged with respect to one another such that the transverse electrode sections of the "F" arrangement come to lie parallel next to one another in an alternating order. The manufacture of such interdigital electrodes is accomplished in thin-film technology with the aid of standard photolytographic methods from a non-corrosive metal, for example gold or platinum. The substrate areas between the metal electrodes are also coated with a non-conductive spacer material with the aid of microsystem technology production methods so that the spacer structures protrude slightly beyond the conductor track structures. The typical peaks are in the micrometer range.

The carrier layer opposite the conductor track structures, on the underside of which electrically conductive deforming elements are attached, consists of a non-conductive elastomer layer and a conductive elastomer matrix applied thereon, which has a large number of adjoining elastomer pyramids. The pyramid shapes are produced by molding a silicon wafer structured with the aid of anisotropic standard etching technology. To produce such structures, uncrosslinked conductive elastomer is first knife-coated into the pyramid-shaped etching pits, then a layer of insulating elastomer that is as thin as possible is applied to the entire wafer surface. In principle, both types of elastomer must have the highest possible resistance to tearing and tear. The softness of the conductive elastomer in the crosslinked state determines the dynamic range of the sensor. Furthermore, the extensibility and thickness of the non-conductive elastomer influence the mechanical coupling between the sensor elements, so that the greatest possible extensibility with the smallest possible thickness should be sought. After the elastomers have been crosslinked, the structured elastomer matrix can be removed from the silicon mold.

The carrier layer consisting of a non-conductive elastomer and the elastomer pyramid matrix structure applied thereon are now positioned on the surface of the base substrate in such a way that the individual pyramid tips each rest on the space between two conductor tracks, so that no current flow between the conductor track Electrodes are made over the conductive elastomer pyramid tip. If pressure is now exerted on the back of the support structure, which is also the sensor surface, the pyramid tips are pressed against the substrate and flattened accordingly. As a result of the flattening, individual electrode contact fingers of the interdigital electrodes are contacted with one another via the conductive elastomer, so that the resistance between the two electrodes decreases. With increasing pressure, the flattening surface increases as a result of the pyramidal shape of the conductive elastomer, as a result of which, on the one hand, an increasing number of interdigital fingers and, on the other hand, two fingers contact each other over a greater length become. The resistance between the electrons consequently decreases with increasing contact pressure. The insulating spacer structures between the electrodes only serve to rule out electrode contact in a completely unloaded state.

Since the individual contact pyramids are only connected to one another via a very thin elastomer membrane, the mechanical coupling of individual sensor elements onto one another is reduced to a minimum, so that a high spatial resolution is achieved.

Brief description of the drawing

The invention is described below using an exemplary embodiment with reference to the drawings. Show it:

Fig. 1 interdigital electrodes

2 embodiment of a sensor array according to the invention in the unloaded state and

Fig. 3 embodiment of a sensor array according to the invention under the action of pressure.

Representation of exemplary embodiments

FIG. 1 shows a pair of interdigital electrodes, each consisting of two electrode arrangements E1 and E2. The individual electrodes have the shape of an "F". The transverse electrode sections of both electrode tracks project into one another in such a way that they are spaced apart from one another by an insulation layer I. Figure 2 shows an embodiment of a pressure sensor array according to the invention, which is shown in cross section. The example shown consists of 4 x 4 pressure sensor array elements, four of which can be seen in the cross-sectional representation. A sensor array element consists of the base substrate 1, on which the interdigital electrode pair 2 shown in FIG. 1 is applied. Electrically isolating spacer structures I are incorporated between the electrode conductor structures, which are shown as black areas in FIG. 2, which slightly protrude above the electrode conductor structures. The carrier layer 3 made of a non-conductive elastomer is arranged above this electrode arrangement, and elastomer pyramids 4 made of conductive elastomer are attached to the underside thereof. The tips of the pyramids are positioned in such a way that they lie exactly on the insulating layer I. If pressure is now exerted on the sensor surface 5, as can be seen in FIG. 3, the contact surface of the elastomer pyramids on the conductor track structures expands, so that the individual interdigital electrodes are contacted with one another, as a result of which the resistance between the two electrodes decreases . In the case shown in FIG. 3, a uniform pressure is exerted on the entire sensor surface 5, so that all four individual sensor elements shown are flattened in the same way. Due to the high elasticity of the carrier layer 3, however, the individual pressure sensor elements are largely mechanically decoupled from one another, so that pressure differences can also be measured locally resolved.

Functional samples have been produced which consist of 4 x 4 pressure sensor array elements, each with a grid dimension of 0.76 mm x 0.51 mm. The circumference of the whole The pressure sensor is approximately 2 mm x 3 mm. A glass substrate with gold electrodes of 50 μm conductor width and a gold layer thickness of 400 nm as well as an insulating polyimide spacer structure of approx. 1 μm have been used as materials for the pressure sensor. Each individual interdigital electrode consists of two fingers with a conductor width of 50 μm and an interdigital distance of 50 μm. For each individual pressure sensor element, one of the two electrodes is individually contacted to the outside, while the respective counter electrode of all sensor elements are connected to one another and are at a common potential.

Two component silicone rubbers have been used as elastomer materials. Elastosil LR 3162 from Wacker was used for the conductive elastomer material and likewise from Wacker for the non-conductive component Elastosil LR 3003. The size of the conductive pyramids at the base is 0.56 mm x 0.41 mm, the height is 0.29 mra. The thickness of the non-conductive silicone rubber layer is approximately 0.2 mm.

The two layers of the sensor are positioned exactly one above the other under a microscope and bonded to one another at the sensor edge without tension. A further increase in the number of array elements could be simplified with the aid of so-called row-column coding, since this would allow a reduction in the number of conductor tracks.

With the aid of the mechanical component for pressure detection according to the invention, a measuring sensitivity of at least 14 mN / mm ² can be achieved. Furthermore, there is a high tolerance to large forces of at least 10 N / mm ² reachable. Shock loads, large dynamic ranges and high resolving power with the element size described above can be achieved with the component according to the invention. With the aid of somewhat more complex standard masking techniques, the production method allows the spatial and / or dynamic resolution achieved to be increased by at least a factor of 5. An additional advantage of the sensor principle is that when using a polyimide film substrate, a 2- Dimensionally bendable sensor can be produced, which can be provided, for example, on an artificial finger with a corresponding sense of touch.

Claims

Patent claims

1. Electronic component for static and dynamic pressure detection with a non-conductive base substrate on which at least two electrodes are applied, which are arranged on the substrate surface in such a way that the electrodes are spaced apart, and with one above the base substrate and the flexible, non-conductive carrier layer arranged on the electrode pairs, on the underside of which, in accordance with the number of the electrode pairs, elastic, electrically conductive deforming elements aligned essentially centrally to the individual electrode pairs with a cross-sectional area whose diameter near the base substrate is smaller than that Electrode spacing and which increases continuously in the direction of the carrier layer and is approximately attached to the carrier layer and corresponds to the substrate area covered by the electrodes, which can be pressed against the conductor track pairs, characterized in that the individual electrodes each have at least one are two individual conductor tracks fanning out, mutually insulated conductor tracks which are applied to the substrate surface in such a way that in each case one conductor track of the one alternates with the conductor track of the other electrode.

2. Electronic component according to claim 1, characterized in that the structure of the individual conductor tracks are each modeled in the shape of an "F", a so-called interdigital electrode arrangement, so that a pair arrangement of the leads The tracks are made in such a way that the transverse conductor track sections lie next to one another.

3. Electronic component according to claim 1 or 2 characterized in that a plurality of pairs of electrodes and a corresponding number of deforming elements are arranged in a matrix on the base substrate or on the carrier layer.

4. Electronic component according to one of claims 1 to 3, characterized in that the carrier layer consists of an insulating and the deforming elements consist of an electrically conductive elastomer.

5. Electronic component according to one of claims 1 to 4, characterized in that the Verformele¬ elements have a pyramidal shape, the Basis¬ surface are firmly connected to the support layer and the pramide tips are without pressure at a point of the insulating layer, which lie between the Conductors of the individual pairs of conductor tracks is provided.

6. Electronic component according to one of claims 1 to 5, characterized in that the carrier layer has such an elastic material and a thickness that no mechanical coupling takes place between two adjacent deformation elements when pressure is applied.

7. Electronic component according to one of claims 1 to 6, characterized in that the top of the carrier layer is the sensor surface of the electronic component and is smaller and the individual matrix element is smaller than 500 μm x 500 μm, preferably smaller than 100 μm x 100 μm.

8. Electronic component according to one of claims 1 to 7, characterized g e k e n n z e i c h n e t that the base substrate is rigid or flexible.

9. Electronic component according to one of claims 1 to 8, characterized g e k e n n z e i c h n e t that the base substrate is made of glass.

10. Electronic component according to one of claims 1 to 9, characterized in that an insulating layer is provided between the conductor tracks, which protrudes somewhat beyond the height of the individual conductor tracks.

11. Electronic component according to one of claims 1 to 10, characterized in that the conductor track width is 50 μm and the conductor track height is approximately 400 nm.

12. Electronic component according to one of claims 1 to 11, characterized in that the insulating layer located between the conductor tracks has a height of about 1 micron and a width of 50 microns.

13. Device according to one of claims 1 to 11, characterized in that a sensor array is formed from a plurality of juxtaposed electronic components, the part of a tactile sensor system for a robot gripper, a telemanipulator, an artificial hand, an endoscopic forceps or is an endoscopic probe.