DD287357A5 - Method for producing a stack of piezoceramic discs - Google Patents

Abstract

The invention relates to a method for producing a stack of piezoceramic discs and finds application in the construction of microtranslators. According to the invention, disks with defined surface roughness are used. By means of a sputtering method, electrode layers of relatively hard material, in particular of CuNi, are deposited on the disks on both sides to the edge. Anschlieszend is applied in each case on a layer in a dot matrix adhesive with a defined Viskositaet and immediately thereafter, the next disc with a defined pressure applied, the pressure is maintained until the hardening of the adhesive {stack; Discs, piezoceramic; Micro translators; surface roughness; sputtering; Electrode layers, hard; Glue; Dot matrix; Viscosity; Print; Harden}

Description

Characteristic of the known state of the art It is known to combine piezoceramic discs into a stack (DE 3218 576). Here are the individual discs

areally provided on both sides by a thick-film or thin-film process with contacting layers (electrodes).

Adjacent disks are oppositely polarized. The individual slices are connected with an adhesive,

wherein in the adhesive metal liners are still embedded, leading to the outside (DE 3 218 576). The joining of the discs is done by means of pressure, often by suitable arrangements even during operation of the device

is maintained. .

The electrodes can also be applied for external contact down to the edge of the pane. By the methods and arrangements used so far for stacking piezoceramic discs, the following results

Disadvantage:

1. By using metal liners:

- Large non-active mass of the intermediate layers leads to the deterioration (reduction) of the rigidity and the resonance frequency (Stellgesrt.geschwindigkeit) in the axial direction of the stack

- Extra work on the staple days

- obstruction of the transverse contraction of the discs

2. By using thick film contacts:

still relatively large non-active mass, especially with very thin discs (d <0.2 mm)

- Low hardness of the thick film (Ag / Pd) also leads to the reduction of the rigidity in the axial direction of the stack

- obstruction of the transverse contraction of the discs through the thick film contacts

3. By using adhesive layers:

- High temperature coefficient of the adhesive enters the length measuring technique (in this use of the stack)

- The reduction in stiffness is also noticeable

4. By using thin-film contacts:

- In addition to the advantages of extremely low non-active mass and the non-interference of the transverse contraction of the discs, there are also disadvantages:

- The existing surface roughness of the ceramic, which is also reflected in the thin layer, in turn, a compensation by the insertion of metal liners and / or adhesive to prevent destruction in Mikroboreich (grain breakouts) necessary.

- The above advantages of each disc are therefore not available in the stack.

Object of the invention

The aim of the invention is to realize a method for producing a stack of piezoceramic discs, which is less expensive in the assembly of the stack.

Explanation of the essence of the invention

The object of the invention is to provide a method according to the title of the invention, which makes it possible to match the elastic behavior of the stack (stiffness, Ε modulus) as closely as possible to the ideal state of the solid ceramic material, while respecting the aim of the invention is. To produce the stack, the individual panes are connected to one another via their laminar thin-film contacts and via additional connecting means, in particular adhesives, under pressure.

According to the invention, piezoceramic disks having a surface roughness R _n , <5 pm (maximum difference) and R, = 0.15 to 0.5 μm (average) are used. By means of a known sputtering method, electrode layers made of relatively hard material, in particular of CuNi, are deposited on the disks on both sides, down to the edge. Adhesive with a viscosity in the range of 100 to 50OmPa · s is then applied in each case to a disk in a dot matrix, and immediately thereafter the next disk is placed congruently with a pressure in the range from 0.5 to 1 MPa, the pressure until hardening of the ink Adhesive is maintained. Finally, after the last pane of the stack has been glued on, the edge contact surfaces are likewise covered again with electrode material by a sputtering process. By applying the adhesive in a dot matrix to be achieved according to the invention that forms no continuous adhesive film when placing two discs. It should only be filled with adhesive by the existing roughness when joining the discs cavities. This achieves an "intimate" ceramic / ceramic contact without causing the negative properties of an adhesive interlayer.The pressure is needed not only for the action of the adhesive, but also for this intimate contact between the ceramic surfaces during the curing of the adhesive and after completion to ensure the stack.

embodiment The invention will be described below with reference to an embodiment. To produce a microtranslator, first piezoceramic disks of a PZT ceramic are provided. The Slices have the following roughness values:

maximum difference R _n , = average R, = 0.41 μπι.

The discs have a diameter of 10mm and a thickness of 0.5mm. Thereafter, on each side of a disc a correspondingly designed substantially consisting of Cu Ni electrode with a Layer thickness of 0.8 mm splintered. The electrode is partially pulled to the edge, to later contact

to allow the stack. For the production of the stack is now punctiform a suitable adhesive, for. B.

Epoxy resin of cyanoacrylate, applied. The adhesive has a viscosity of 40OmPa · s. Immediately thereafter, the next Slice placed congruent, with a pressure of 0.5 MPa is applied to the entire surface. This pressure will be like this

long maintained until the adhesive has cured.

After a stack of piezoceramic discs was built according to these steps, the Edge contact surfaces also reinforced by sputtering to a thickness of about 1.8mm. The properties of the translator produced according to the invention (with armature) should be concluded with a comparable,

The prior art translator will be contrasted with:

invention Stand d. technology applied voltage 1000V 1000V achieved change in length 1 22 pm 15mm Diameter d. slices 10mm 10mm Stiffness d. Stack C 150 N / mm 70 N / mm (in axial direction)

Also, the stiffness rating of the inventive stack (without armature) indicates that the desired value for the bulk ceramic material is approaching. They amount to:

solid material 290 N / mm

stack according to the invention 200-290 N / mm (stack with thick-film electrodes

and metal liners 100Ν / μτι).

Claims (1)

Method for producing a stack of piezoceramic disks, in which the individual disks are connected to one another via their laminar thin-film contacts and via additional connecting means, in particular adhesives, under pressure, characterized in that piezoceramic disks with a surface roughness R _n , <5 μm and Ra = 0.15 to 0.5 pm are used, that are deposited by a per se known sputtering on both sides of the disks to the side edge reaching electrode layers of relatively hard material, in particular of CuNi, that subsequently each on a disc of Adhesive is applied in a dot matrix with a viscosity in the range of 100 to 500 mPa · s and immediately after the next disc is placed congruent with a pressure in the range of 0.5 to 1 MPa, wherein the pressure is maintained until the adhesive has cured in that finally after pasting the last Disc of the stack, the edge contact surfaces are also covered by a sputtering process again with electrode material. Field of application of the invention The invention relates to the field of piezoelectric components. It relates to a method for producing a stack of piezoceramic disks, in which the individual disks are connected to one another via their laminar thin-film contacts and via additional connecting means, in particular adhesives, under pressure. The stack is used as a microtranslator, e.g. B. in precision equipment.