DD287357B5 - Method for producing a stack of piezoceramic discs - Google Patents

Abstract

A process for producing a stack of laminar piezoceramic elements, wherein the piezoceramic elements have a surface roughness of Rm < 5 mu m. and Ra 0.15 to 0.5 mu m., electrode layers, formed from a relatively hard conducting material, are deposited on a face of each element, each layer extending to an edge of the element, the elements are formed into a stack by repeating a process of applying an interrupted layer of adhesive, having a viscosity of 100-500 mPa.S, to a face of a first element, pressing a second element onto the adhesive coated face of the first element, with an electrode layer sandwiched between said elements, and holding the elements pressed together under a pressure of 0.5-1 mPa until the adhesive hardens and, thereafter, forming electrical contacts connected to the electrode layers on a side of the stack.

Description

Characteristic of bekannton state of the art

It is known to combine piezoceramic discs into a stack. In this case, the individual panes are provided on both sides in a planar manner by a thick-film or thin-film process with contacting layers (electrodes). Adjacent disks are bonded to an adhesive which is either itself electrically conductive (DE 2900609) or embedded in a non-conductive adhesive are profiled metal interlayers such as metal nets (DE 3223801) or world bending metal electrodes (US 4,530,138) which contact the contacting layers. The assembly (s) is effected under pressure which is often maintained during operation of the component by suitable arrangements The known methods for stacking piezoceramic wafers and their bonding by adhesive have the following disadvantages:

1. By using metal liners:

- The large non-active mass of the intermediate layers leads to deterioration (reduction) of the rigidity and the resonance frequency (positioning speed in the axial direction of the stack).

- overhead in stacking;

- obstruction of the transverse contraction of the discs.

2. By using adhesive layers:

- The high temperature coefficient affects length measurement applications.

- There is also a reduction in stiffness.

Object of the invention

The aim of the invention is to provide 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 an ancestor according to the title of the invention, which makes it possible to match the elastic behavior of the stack (stiffness, Ε-module) as close as possible to the ideal state of the solid ceramic material, wherein the aim of the invention is observed. To produce the stack, the individual disks are connected to one another via their laminar thin-film contacts and via additional connecting means, in particular adhesives, under pressure.

Piezoceramic discs having a surface roughness R _n , <5 μm (maximum difference) and R, = 0.15 to 0.5 μm (mean value) are used according to the invention. By means of a sputtering method known per se, electrode layers made of relatively hard material, in particular of CuNi, are deposited on the disks on both sides up 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 with a pressure in the range of 0.5 to 1 MPa congruent laid, the pressure until the curing of the 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.

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; pie disks have the following roughness values:

maximum difference R _m = 3.7pm

Middle word R ₁ = 0.41 pm.

The discs have a diameter of 10 mm and a thickness of 0.5 mm.

Thereafter, a correspondingly shaped substantially consisting of CuNi electrode with a layer thickness of 0.8 μιη is sputtered onto each side of a disc. The electrode is partially pulled up to the edge to allow later contacting 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 400 mPa · s. Immediately thereafter, the next disc is placed congruent, with a pressure of 0.5 MPa is applied to the entire surface. This pressure is maintained until the adhesive has cured.

After a stack of piezoceramic disks has been erected according to said process steps, the edge contact surfaces are also reinforced by sputtering to a thickness of about 1.8 pm.

The properties of the translator (with armature) produced according to the invention are to be compared with a comparable, prior art translator:

invention Stand d. technology applied voltage 100OV 1000V achieved change in length 1 22 pm 15μπΊ Diameter d. slices 10mm 10mm Stiffness d. Stack C 150 W / μηι 70N / pm (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:

massive material 290Η / μιη

inventive stack 200-290 Ν / μπΊ

(Stack with thick film electrodes

and metal liners 100 Ν / μιη).

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 _m <5 MmundRa = 0.15 to Warts 0.5 μηι be used that are deposited by a per se known sputtering on the discs on both sides to the side edge reaching electrode layers of relatively hartom material, especially CuNi, that then each on a slice of the adhesive in a dot matrix with a viscosity is applied in the range of 100 to 50OmPa · s and immediately thereafter, the next disc is applied congruently with a pressure in the range of 0.5 to 1 MPa, wherein the pressure is maintained until the adhesive is cured, that finally after sticking 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 areal thin-film contacts and via additional connecting means, namely adhesives, under pressure. The stack finds application as Mikrotranslator.z.B. in precision equipment construction.