WO2002075824A2

WO2002075824A2 - Method for producing adaptronic microsystems

Info

Publication number: WO2002075824A2
Application number: PCT/DE2002/000942
Authority: WO
Inventors: Thomas Gesang; Uwe Maurieschat; Harald Knäbel; Helmut Schäfer
Original assignee: Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V.
Priority date: 2001-03-16
Filing date: 2002-03-15
Publication date: 2002-09-26
Also published as: DE10291136D2; WO2002075824A3; DE10291136B4

Abstract

The invention relates to a method for producing adaptronic microsystems, whereby at least one transducer element (2) is incorporated into a matrix (1) and at least one control element (3) for controlling and/or transmitting signals of the transducer elements (2) is applied to the matrix (1) or is introduced into the matrix (1). The control elements (3) are applied to or introduced into the matrix (1) by detachably connecting the control elements (3) to a first surface of a transfer carrier (4), and by applying or introducing the transfer carrier (4) with the control elements (3) to or into the matrix (1). The transfer carrier (4) is then removed. The inventive method enables adaptronic microsystems to be produced using incorporated control elements which are especially suitable for producing Prepeg modules.

Description

Process for the production of adaptronic

microsystems

Technical application area

The present invention relates to a method for producing adaptronic microsystems, in which one or more converter elements are embedded in a matrix and one or more control elements for controlling and / or for transmitting signals of the converter elements are applied to the matrix or are introduced into the matrix.

Adaptronic microsystems of the type mentioned, in particular with actuator and / or sensor transducer elements made of piezoelectric material, are used in many areas of technology in which sensors or actuators of reduced volume are required. In the area of use of composite materials, there is an increasing need for microsystems that can be integrated into the material. Especially for the implementation in fiber composite structures, a reduced stiffness of the sensors and / or actuators is required, as they have adaptronic microsystems.

State of the art

A generic method for producing adaptronic microsystems is known, for example, from US Pat. No. 5,869,189. In this method, several elongated piezoelectric fibers are used as transducer elements in parallel and at a defined distance inserted into one another. A liquid polymer material is then poured into the mold to form a polymer matrix. A polyimide film is coated on one side with a thin electrode structure, applied to the not yet hardened polymer matrix and hardened together with the matrix.

In an alternative embodiment of this method, the matrix with the fibers located therein is first cured. Then the

Electrode structure for controlling the transducer elements by means of an electron beam evaporation technique applied to the surface of the matrix.

The object of the present invention is to specify a method for producing adaptronic microsystems which enables the control elements to be completely embedded in the matrix. and is suitable for the production of prepeg modules.

Presentation of the invention

The object is achieved with the method according to claim 1. Advantageous embodiments of the method are the subject of the dependent claims.

In the present method, one or more converter elements are embedded in a matrix, for example a polymer casting compound, in a known manner, and one or more control elements for controlling and / or for transmitting signals of the converter elements to the matrix are introduced onto or into the matrix , The transducer learnings can be embedded in the matrix, for example, in that the initially liquid matrix material is poured into a mold in which the transducer elements are located.

In the present method, the control elements are applied or introduced onto or into the matrix by first connecting the control elements detachably to a first surface of a transfer carrier, for example a sheet, sheet or plate-shaped material. This transfer carrier with the control elements is then introduced onto or into the matrix in such a way that the first

Surface of the transfer carrier, on which the control elements lie, is directed towards the transducer elements in the matrix. The transfer carrier is then removed from the control elements and removed. This can take place, for example, after the matrix has partially hardened, for example by means of the effect of temperature and / or UV radiation.

After this step, a system consisting of transducer elements embedded in a matrix and control elements incorporated on or into the matrix is available, which can either be fully cured at the current time or further processed as a prepeg module by only partially curing.

In particular, the present method can be used to implement an embodiment of an adaptronic microsystem in which the control elements are completely enclosed by the matrix, the electrical insulation of these control elements being achieved from the outside by the matrix material itself. Such a configuration - without additional inner interfaces through an additional insulation layer - offers good protection against moisture and increases the reliability and service life of the microsystem.

In order to enable the transfer carrier to be pulled off the control elements, the detachable one

Connection of the control elements to the transfer carrier be designed such that the control elements - possibly after partial hardening of the matrix - have greater adhesion to the matrix and / or the transducer elements than to the transfer carrier. This can be made possible, for example, by using suitable, non-strongly adhesive connections between the control elements and the conductive adhesives producing the transfer carrier. Also a coating or treatment of the surface of the surface which reduces the adhesion

Transfer carrier represents a possibility for producing this boundary condition. Comparable measures with the opposite effect can be carried out to improve the adhesion to the matrix and / or the converter elements.

In the present method, electrode structures are preferably applied as control elements on the transfer carrier. This can already be done as a prefabrication step for the manufacturing process. The electrodes can be implemented, for example, in a known manner as large-area plate electrodes, as line electrodes or in an interdigital arrangement. Linear electrode structures are either congruent on the front and back of the matrix, or are introduced onto or into the matrix with a lateral displacement relative to one another. As material or material form for the Electrode structure comes an electrically conductive film or an electrically conductive film, for example made of metal, carbon or an electrolyte, an electrically conductive network or grid, which can consist of the same materials, as well as intrinsically or extrinsically conductive materials or composite systems, such as paste or adhesive in any hardening state in question.

In addition to electrodes, other control elements, such as light guides, can of course also be used for the production of adaptronic microsystems. The transducer elements can be exposed to an electromagnetic field with light guides. Such light guides can, for. B. in similar structures as conventional electrically conductive electrodes in the microsystem.

The control elements can be applied to the matrix or introduced into the matrix in such a way that they are in direct contact with the converter elements. During production, a matrix material layer of adjustable thickness can also be implemented between the control elements and the converter elements. This can further improve the product properties, for example for long-term resistance, since an intermediate layer made of the matrix material breaks down local peaks in the electrical field, which could otherwise permanently damage, for example, piezoceramic fibers. Point-to-point contacting or a partial or complete encapsulation of the converter elements with the control elements can also be achieved if the control elements are not yet or not yet fully cured adhesive are formed and pressed onto the transducer elements.

The control elements can be connected to the transfer carrier by means of a printing technique, for example screen printing or pad printing, by means of an inkjet technique, by dispensing or by other suitable application techniques. Closed or open-pore materials can be used as transfer carriers. Polymer films are particularly suitable, e.g. B. made of polyester, PP, PE, or FEP, non-woven paper or coated paper.

Piezoelectrics, magnetostrictives, shape memory alloys or nanotubes, for example made of carbon, can be used as active material of the transducer elements in the present method. The geometry of the transducer elements can be freely selected depending on the desired application. The transducer elements can, for example, be round, oval, long or short, flat or else three-dimensionally complex, such as long and wavy. The transducer elements can be isotropically disordered, i. H. be statistically distributed, embedded under a preferred orientation or also highly ordered (anisotropic) in the matrix material. A three-dimensionally complex arrangement, for example as a mesh-like fabric or an arrangement in several layers, can also be realized with the present method.

The material of the matrix or the casting compound can be either inorganic or organic, for example as a polymer, or by a mixture of organic and inorganic materials. Both materials that can be hardened using a single hardening mechanism and materials that can be combined with one another are possible. Combined curing is carried out, for example, by combined UV radiation and thermal curing of a polymer. To produce the microsystem as a prepeg, a multi-stage hardening is preferably carried out.

The present method can be used to implement microsystems in which the actuator and / or sensory transducer elements can be controlled by means of an electrical, magnetic or electromagnetic field via the control elements. Depending on the arrangement of the control elements, the microsystems can be implemented in such a way that the control elements can be controlled individually or in any size / many groups. The control elements or groups of control elements can of course also be controlled in a phase-shifted manner in a known manner. Suitable control techniques depending on the desired adaptronic effect and structure of the microsystem are familiar to the person skilled in the art.

The present microsystem can be constructed, for example, from piezoelectric elements in order to utilize the d31 or the d33 effect.

For the control of the microsystem produced by the method via the control elements, corresponding supply lines are required which contact the control elements. The electrical connections Conclusions can in this case be achieved in part by the provision of collecting electrodes, for example in the case of linear control elements, of connecting pads, for example as soldering points for contacting by the user, and / or of conventional supply lines. In the case of an electrical energy input, as is required in the case of electrical electrodes as control elements, the electrically conductive feed lines can be in the form of wire, stranded wire, multi-core cable, paste, adhesive, flexible film, tissue or as an electrically conductive liquid (e.g. electrolyte) be trained.

A possible variable orientation and mutual chaining of anisotropically operating microsystems may require providing several contact points for each of the microsystems. Such contact points can be formed, for example, by plug connections. The long-term reliability of the contact points can be improved by the additional introduction of an adhesive. The adhesive required for this can originate, for example, from the microsystem itself, in which, for. B. UV curing in the area of the connection pads is prevented with a combination curing casting compound, with the possibility of thermal post-curing after the plug connection has been produced. Furthermore, the necessary adhesive from the actual component, for. B. a prepeg, originate itself or be fed separately.

In addition, the gluing allows - at least selectively - metallic contact of the partners of the plug connection and maintains them permanently. The electrical connections can be made of the same material or different materials consist. For example, they can be applied to the transfer carrier together with the control elements and transferred to the matrix with this.

The present method is advantageously suitable for the electroding of microsystems to be produced using prepeg technology. In this production variant, the piezo fibers (piezo fiber laminate) infiltrated with the prepeg polymer matrix are gelled onto transfer carriers as transducer elements between two opposite, congruently positioned electrode structures. This condition can be maintained at room temperature. If required, these prepegs can be laminated in CFRP / GFRP laminate layers. The material composite is then cured as usual (e.g. autoclave) using temperature and pressure.

Another possible application for the microsystems manufactured in prepeg technology is to stack the electrodized piezo fiber laminate congruently on one another in the gelled state, in order thereby to produce stacked microsystems. These stacked microsystems can then only be cured without the application of additional adhesive by applying pressure and temperature, so that the individual microsystems fuse together without the formation of an interface between them. This increases the long-term stability of such systems to a considerable extent, since there are no contact surfaces for moisture or other external influences, such as those formed by a boundary layer. Brief description of the drawings

The present method is briefly explained again below using an exemplary embodiment in conjunction with the figure. The single figure shows various process steps in the production of a microsystem according to the present method.

Ways of Carrying Out the Invention

The following exemplary embodiment shows the production of an adaptronic microsystem in which piezoelectric fibers are used as transducer elements and electrically conductive electrodes made of conductive adhesive are used as control elements.

When manufacturing the microsystem, a polymer film is first provided as a transfer carrier 4. An electrically conductive adhesive for forming an interdigital electrode structure 3 is applied to the surface of this transfer carrier 4 (first surface) by means of screen printing. The electrically conductive adhesive is then z. B. fully cured by means of UV radiation or temperature or only partially cured (Figure la).

Before or after this connection of the electrodes 3 to the transfer carrier 4, the piezoelectric fibers 2 are embedded in a liquid polymer matrix 1, as can be seen from FIG. 1b, and hardened or hardened if necessary. After this infiltration, the transfer support 4 provided with the interdigital electrode structure 3 is covered on both sides immediately pressed onto the polymer matrix 2 or pressed into this matrix so that the electrodes 3 touch the fibers 2. The matrix 1 is then cured by means of radiation or temperature. The hardening takes place under defined mechanical pressure in order to maintain contact between the piezoelectric fibers 2 and the electrodes 3 and thus to ensure the electrical contact. If a corresponding contact pressure is applied, it is also possible to press the fibers 2 into the hardened conductive adhesive of the electrodes 3, so that the electrodes 3 completely or partially envelop the fibers 2.

After the polymer matrix 1 has hardened, the transfer carrier 4 is pulled off. It is of crucial importance here that the adhesion of the electrodes 3 to the transfer carrier 4 is less than to the polymer matrix 1 (FIG. 1d).

After removal of the transfer carrier 4, there is a microsystem 5, as shown in FIG. 1d. The electrodes 3 have direct contact with the fibers 2 and at the same time are completely enclosed by the polymer matrix 1.

Of course, an embodiment can also be implemented in which the electrodes 3 in FIG. 1c are not pressed against the piezo fibers 2, so that a gap with polymer material remains between the piezo fibers 2 and the electrodes 3. If the polymer matrix 1 is not fully cured, a plurality of such microsystems 5 can also be stacked one above the other and only then cured completely using mechanical pressure - and possibly temperature and / or UV radiation - so that a stacked microsystem is created (see FIG. 1). ,

LIST OF REFERENCE NUMBERS

1 polymer matrix

2 converter elements, e.g. B. piezoelectric fibers

3 control elements, e.g. B. electrodes

4 transfer carriers

5 microsystem

Claims

claims

1. Process for the production of adaptronic

Microsystems, in which one or more transducer elements (2) are embedded in a matrix (1) and one or more control elements (3) for

Control and / or for transmitting signals from the converter elements (2) to the matrix (1) or to the matrix (1), characterized in that the application or introduction of the control elements (3) to or into the matrix ( 1) through the following steps:

- Detachable connection of the control elements (3) to a first surface of a transfer carrier (4);

- Applying or introducing the transfer carrier (4) with the control elements (3) onto or into the matrix (1) so that the first surface of the transfer carrier (4) is directed towards the transducer elements (2); and

- Pull off the transfer carrier (4).

2. The method according to claim 1, characterized in that a film, sheet or plate-shaped transfer carrier (4) is used, with the first surface of the control elements (3) are adhesively connected.

3. The method according to claim 1 or 2, characterized in that the connection of the control elements (3) with the transfer carrier (4) is such that the liability of the control elements (3) on the transfer carrier (4) is less than the liability of the control elements ( 3) on the matrix (1).

4. The method according to claim 1 or 2, characterized in that the adhesion of the control elements (3) to the transfer carrier (4) and / or the matrix (1) is modified such that the adhesion of the control elements (3) to the transfer carrier (4) is less than the adhesion of the control elements (3) to the matrix (1).

5. The method according to any one of claims 1 to 4, characterized in that after the introduction or application of the

Control elements (3) in or on the matrix (1) an intermediate hardening of the matrix (1) and / or the control elements (3) is carried out.

6. The method according to any one of claims 1 to 5, characterized in that the control elements (3) are applied to the transfer carrier (4) by means of a printing technique.

Method according to one of claims 1 to 5, characterized in that the control elements (3) by means of a Inkjet technology can be applied to the transfer carrier (4).

8. The method according to any one of claims 1 to 5, characterized in that the control elements (3) are applied to the transfer carrier (4) by dispensing.

9. The method according to any one of claims 1 to 8, characterized in that electrodes are applied in an interdigital arrangement to the transfer carrier (4) as control elements (3).

10. The method according to any one of claims 1 to 9, characterized in that electrodes made of electrically conductive adhesive are applied to the transfer carrier (4) as control elements (3).

11. The method according to claim 10, characterized in that the electrically conductive adhesive is partially hardened or fully hardened after application, in particular by exposure to radiation or by the action of temperature.

12. The method according to any one of claims 10 or 11, characterized in that the transfer carrier (4) with the control elements (3) is pressed onto the matrix (1) using mechanical pressure or into the The matrix (1) is pressed in and the matrix is partially hardened or completely hardened, in particular by exposure to radiation or by the action of temperature.

13. The method according to any one of claims 1 to 5, characterized in that electrically conductive films or foils are used as control elements (3).

14. The method according to any one of claims 1 to 8, characterized in that the control elements (3) are applied to the transfer carrier (4) as electrically conductive line, network or grid structures.

15. The method according to claim 13 or 14, characterized in that the control elements (3) are formed from an intrinsically or extrinsically electrically conductive material.

16. The method according to any one of claims 1 to 8, characterized in that optical fibers are used as control elements (3).

17. The method according to any one of claims 1 to 15, characterized in that as transducer elements (2) piezoelectric,

Magnetostrictives, shape memory alloys or nanotubes can be used.

18. The method according to any one of claims 1 to 17, characterized in that the control elements (3) are applied to the transducer elements (2) while making direct contact.

19. The method according to any one of claims 1 to 18, characterized in that connection elements connected or connectable to the control elements (3) are connected to the at least one transfer carrier (4) or one or more further transfer carriers and in the same way as the control elements (3) be transferred to or into the matrix (1).

20. The method according to any one of claims 1 to 19, characterized in that a polymer film is used as the transfer carrier (4).

21. The method according to any one of claims 1 to 19, characterized in that a sheet of non-woven paper is used as the transfer carrier (4).

22. The method according to any one of claims 1 to 19, characterized in that a sheet of coated paper is used as the transfer carrier (4).

23. The method according to any one of claims 1 to 22, characterized in that the control elements (3) in the matrix (1) that they are completely surrounded by the matrix (1).

24. The method according to claim 23, characterized in that a plurality of the microsystems produced are stacked one above the other before the matrix (1) has completely hardened and are then fully hardened using mechanical pressure and temperature.