Method for manufacturing piezoelectric actuators and a piezoelectric actuator

Abstract

The present invention relates to a method for the parallel manufacturing of a plurality of piezoelectric actuators as well as a corresponding piezoelectric actuator. According to the present invention, a plurality of thin foils ( 1 - 3 ) made of an unfired piezoelectric ceramic material are stacked one over another. On surface ( 4 ) of foils ( 1 - 3 ), an electrode ( 5 - 10 ) is provided for each actuator. For contacting electrodes ( 5 - 10 ), first ( 11 - 16 ) and second ( 17 - 22 ) connecting openings are provided. Electrodes ( 5 - 10 ) have cut-outs ( 23 - 28 ) which surround either first ( 11 - 16 ) or second ( 17 - 22 ) connecting openings. An electrically conductive paste ( 53 ) is introduced into connecting openings ( 11 - 22 ). The stacked arrangement is fired and split up into the individual actuators. As internal electrodes, the electrodes are insulated from the surroundings.

1 . A method for the parallel manufacturing of a plurality of piezoelectric actuators, in the following process steps: 
 manufacturing thin foils ( 1 - 3 ) made of an unfired, piezoelectric ceramic material,    forming first and second connecting openings ( 11 - 16 ,  17 - 22 ) penetrating the foils ( 1 - 3 ), first ( 11 - 16 ) and a second ( 17 - 22 ) connecting opening being assigned to each actuator,    coating one surface ( 4 ) of each of the foils ( 1 - 3 ) with a plurality of electrodes ( 5 - 10 ), at least one electrode ( 5 - 10 ) being assigned to each actuator in each foil ( 1 - 3 ), and    the connecting openings ( 11 - 16 ,  17 - 22 ) penetrating the foils ( 1 - 3 ) in the area of the electrodes ( 5 - 10 ), and the electrodes ( 5 - 10 ) in each case having a cut-out ( 23 - 28 ) which surrounds either the first ( 11 - 16 ) or the second ( 17 - 22 ) connecting opening,    stacking a plurality of foils ( 1 - 3 ) one over another so that, in a resulting stacked arrangement, the first and second connecting openings ( 11 - 16 ,  17 - 22 ) are arranged one over another,    the layer sequence of the foils ( 1 - 3 ) being selected in such a manner that the connecting openings ( 11 - 16 , 17 - 22 ), which are arranged one over another, are alternately surrounded by a cut-out ( 23 - 28 ) of the electrodes ( 5 - 10 ) only in every other foil layer ( 1 - 3 ) so that the electrodes ( 5 - 10 ) are alternately connected to either the first connecting openings ( 11 - 16 ) or the second connecting openings ( 17 - 22 ),    introducing an electrically conductive paste ( 53 ) into the connecting openings ( 11 - 16 ,  17 - 22 ),    firing the stacked arrangement, and    separating the stacked arrangement into individual actuators:    
     
     
         2 . The method as recited in    claim 1   , 
 characterized in that, on the surfaces ( 4 ) of the foils ( 1 - 3 ), intermediate areas ( 31 ) which are left free of the electrodes ( 5 - 10 ) are provided in the edge area between the individual actuators.    
     
     
         3 . The method as recited in    claim 1    or    2   , 
 characterized in that perforation holes ( 30 ) are formed in the intermediate areas ( 31 ).  
 
     
     
         4 . The method as recited in    claim 3   , 
 characterized in that the perforation holes ( 30 ) are arranged in lines extending in the intermediate areas ( 31 ) along the edges of the individual actuators.    
     
     
         5 . The method as recited in    claim 3    or    4   , 
 characterized in that, to separate the stacked arrangement into the individual actuators, an oppositely poled electrical field is applied to the electrodes ( 5 - 10 ) of adjacent actuators.  
 
     
     
         6 . The method as recited in one of the claims  1  through  5 , 
 characterized in that the separation of the stacked arrangement into the individual actuators is carried out by sawing or water-jet cutting.  
 
     
     
         7 . The method as recited in one of the claims  1  through  6 , 
 characterized in that the stacked arrangement is dried under pressure at an increased temperature prior to the firing.  
 
     
     
         8 . The method as recited in one of the claims  1  through  7 , 
 characterized in that the electrodes ( 5 - 10 ) are applied using a screen-printing technique, vapor depositing, sputtering, or the like.  
 
     
     
         9 . The method as recited in one of the claims  1  through  8 , 
 characterized in that the stacked arrangement is sintered during the firing under uniaxial pressure at a temperature of at least 1,000° C.  
 
     
     
         10 . A piezoelectric actuator comprising a plurality of layers ( 50 ) made of a piezoelectric ceramic material which are arranged one over another, and which are each coated with at least one electrode ( 5 ) on a surface ( 4 ), the electrodes ( 5 ) being alternately connected to each other, 
 characterized in that, in each layer ( 50 ), a first and second connecting opening ( 11 ,  17 ) is provided which penetrates the layer ( 50 ) in the area of the electrode ( 5 ), that each electrode ( 5 ) has a cut-out ( 23 ) which surrounds either the first ( 11 ) or the second ( 17 ) connecting opening,    that the layers ( 50 ) are stacked in such a manner that the first and second connecting openings ( 11 ,  17 ) of all layers ( 50 ) are arranged one over another, and the connecting openings ( 11 ,  17 ), which are arranged one over another, are alternately surrounded by a cut-out ( 23 ) of the electrodes ( 5 ) only in every other layer so that the electrodes ( 5 ) are alternately connected to the first connecting openings ( 11 ) and the second connecting openings ( 17 ), and    that the connecting openings ( 11 ,  17 ) are filled with an electrically conductive paste ( 53 ).    
     
     
         11 . The piezoelectric actuator as recited in    claim 10   , 
 characterized in that the electrodes ( 5 ) are composed of a netlike metal layer.    
     
     
         12 . The piezoelectric actuator as recited in    claim 10    or    11   , 
 characterized in that the layers ( 50 ) have a peripheral edge area ( 31 ) which is not coated with the electrode ( 5 ).  
 
     
     
         13 . The piezoelectric actuator as recited in one of the claims  10  through  12 , characterized in that the outer surface of the topmost and/or bottommost layer and/or the edge area of the actuator is embedded in an electrically insulating encapsulating material.