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The present invention relates to a method of connecting all internal electrodes of an
electrostrictive effect element utilizing a longitudinal effect. In general, when an element of a
multilayer chip capacitor structure is formed using a material having a large electrostrictive
effect, an electrostrictive element (hereinafter abbreviated as an element) in which a large strain
is generated at a low voltage can be obtained. The structure of this element is shown in FIGS. 1
(a) and 1 (b). FIG. 1 (a) is a cross-sectional view as viewed from the front, (bl is a plan view as
viewed from above). The numeral 1 in the figure is an electrostrictive material, 2 and 2 'are
internal electrodes embedded inside the electrostrictive material, and one end is exposed on the
surface of the electrostrictive material. 3 and 3 'indicate external electrode gold which electrically
connects the exposed end of the internal electrode. The internal electrodes are electrically
connected every other layer by the external electrodes. In the figure, reference numeral 4
indicates the overlapping portion of the internal electrode, 5 indicates the non-overlapping
portion, and 6 indicates the portion without the internal electrode. In an element of such a
structure, as is apparent from FIG. 1 (as apparent from bj, the overlapping portions of the
internal electrodes exist only in the central portion of the element. When a voltage is applied
between the external electrodes 3 and 3 ', basically, only the overlapping portion 4 of the positive
internal electrode and the negative internal electrode becomes high in electric field strength. The
peripheral portion close to the end face, that is, the non-overlapping portion 5 of the internal
electrode and the portion 6 without the internal electrode do not not only deform the portion but
function to inhibit the deformation of the entire element. Therefore, in an element with such a
structure, the amount of strain inherent in the material can not be obtained, and boundary stress
concentration occurs in the boundary between the part to be deformed and the non-deformed
part. There is a drawback to destroy. As an element which ameliorates the above-mentioned
drawbacks, the present inventors previously proposed an element having a structure in which all
the ends of the internal electrodes are exposed to the surface of the electrostrictive material as
shown in FIG. . FIG. 2 (a) is a front view of the device of this structure, and FIG. 2 (b) is a crosssectional view as seen from the top of FIG. 2 (a). . The numerals 20 and 21 in the figure are
electrostrictive materials, 22 and 22 'are internal electrodes, 23 is a wire (plus side) connected to
every other layer of the internal electrodes, and 24 is also the negative side. Reference numerals
25 and 26 denote positive and negative electrode terminals. The internal electrode occupies the
entire cross-sectional area of the element as is apparent from FIG. 2 (b), and there is no
peripheral portion which can not be caught by the internal electrode as shown in FIG. In the
device of this structure, the internal electrodes are electrically connected by wires every other
layer, and the electrode terminals 25 and 26 are taken out.
When full pressure is applied between both electrode terminals, an electric field is generated
perpendicularly to the internal electrodes 22 to 22 'as shown by the arrows in the figure. The
electrostrictive material generally extends in the direction of the electric field in proportion to the
absolute value of the electric field and contracts in the direction perpendicular to the electric
field. In the device of this structure, the electric field strength distribution between the internal
electrodes is uniform except for the portion of the electrostrictive material 200 formed on the
surface of the device and acting as a protective film. Therefore, the element of this structure
deforms much more uniformly than the element of the structure shown in FIG. 1 and stress
concentration does not occur. Therefore, it has the feature of showing a large strain inherent to
the material and not breaking when deformed. However, in order to apply a high electric field to
the electrostrictive material, the distance between the internal electrodes is about 250 μm, and
it is extremely difficult industrially to connect every other layer using a wire. Therefore, the
present inventors first apply an insulating material to the surface of the device where the end of
the internal electrode is exposed, bake it, and cover every other layer before the exposure of the
internal electrode, and the external electrode from the top We have proposed a method to
electrically connect the internal electrodes by uniformly coating them. However, in the case of
coating by a printing method or the like, it is necessary to use a fluid insulating material, and it is
difficult to form a fine insulating pattern stably. Moreover, control of coating thickness is also
difficult for the same reason. An unnecessarily thick insulating material inhibits all deformation
of the device. In addition, when the thickness is insufficient, there is a disadvantage that the
insulation withstand voltage is completely reduced. The object of the present invention is to
provide a stable and efficient method for electrically connecting the internal electrodes of the
electrostrictive effect element in which the two points of the metal force are resolved and the
internal electrode ends are exposed on the element surface. It is In the method of the present
invention, first, a plurality of electrostrictive materials coated with a conductive material as a
whole are prepared as a part of the internal electrodes. All the layers are integrated to form an
electrostrictive material laminate. Next, an insulating material film having holes in advance is
attached to the end face of the laminate at intervals of twice the distance between the internal
electrodes formed in the laminate, and is fixed by firing. Then, a conductive material to be an
external electrode is applied on the insulating material film. In this way, every other layer of
multiple internal electrodes can be easily connected to the external electrodes throughout the
holes. According to the present invention, known micro-fine processing techniques can be used,
and it is possible to form stably and easily on a fine-pattern all-insulation material film. It is
possible to take out the terminals and easily mass-produce electrostrictive elements of low
electropositive large distortion amount. Further, since the insulating material is formed in a thin
plate in advance, the thickness can be easily controlled as compared with the method of forming
by coating, and a film having uniform film thickness and film quality can be formed.
For this reason, it is possible to produce an element without deterioration of the withstand
voltage without inhibiting deformation of the element. Hereinafter, the present invention will be
described in detail according to examples. EXAMPLE First, an electrostrictive material green ′
′ sheet 31 having an internal electrode 32 as shown in FIG. 3A is produced by the following
method. Pre-fired powder of electrostrictive material containing lead niobate magnesium (Pb
(Mgt / 3Nb2 / 3) Os) and lead titanate (pbTto) as a main component k Add a trace amount of
organic binder and disperse it in organic solvent I was prepared for all the mud. The casting filmforming apparatus used to manufacture conventional laminated ceramic capacitors was coated
and dried to a thickness of several hundred microns on the whole mylar film. The whole film was
peeled off to obtain an electrostrictive green sheet 31. Some sheets are more internal! Platinum
Pace 14 screen printed as 32, 32 '. Several tens of these green sheets were stacked, pressurebonded and integrated by hot pressing, and then sintered at 1250 ° C. to obtain an
electrostrictive material laminate having internal electrodes as shown in FIG. 3 (b). The interelectrode distance was 250 microns. Next, a method of manufacturing the insulating material
film 33 shown in FIG. 3C will be described. The whole of the slurry is prepared by dispersing
powder glass and alumina as insulating material warm powder 6 K, g and organic binder 300 f ′
′ k high-speed mixer and dispersed in organic solvent 61. The slurry was applied to a thickness
of 60 microns on a mylar film by a casting film forming apparatus using a doctor blade method
and dried. It peeled from mylar film and obtained the insulation material green sheet. Several
dozen holes 34 having a diameter of 250 microns were punched in a row in this green sheet
(number 34 in the figure). The pitch of the array of holes was 500 microns. The insulating
material green sheet 33 prepared in this manner was thermocompression-bonded to the
electrostrictive material sintered body at 110 ° C. (FIG. 3 (d)). However, as shown in FIG. 3 (d),
the above-mentioned holes were crimped to such a position that a part of the internal electrode
was exposed alternately. It was sintered at Th 900 ° C. to be integrated. An insulating pattern
was similarly formed on the back of the sintered body. (No. 33 'in the figure) However, it was
formed in such a position that the hole of the insulating pattern would come on the internal
electrode shown by No. 32' in the figure. Further, as shown in FIG. 3E, the silver paste was
applied on the entire surface of the insulating material film 33 by covering the holes 34 and
firing to form external electrodes 35. 35 '. The inner electrode and the outer electrode are
electrically connected through the hole of the insulating pattern.
By applying a total DC voltage of 250 V between the two external electrodes, an electric field was
generated in the entire electrostrictive material except for the portion shown by the p protective
film portion 30, and an elongation of about 6 μm was obtained. As apparent from the above
embodiments, according to the method of the present invention, as compared with the case of
connecting one by one using a wire, the yield is simplified and the yield is greatly improved. In
addition, since the insulating material film which satisfies all conditions of pattern accuracy and
thickness is used in advance, reliability of withstand voltage can be greatly improved as
compared with the printing method which is formed by coating the entire insulating material
film. As a result, it is possible to industrially easily produce a high-reliability laminated
electrostrictive effect element driven by low voltage and large strain.
Brief description of the drawings
FIG. 1 shows a laminated chip capacitor type electrostrictive effect element. (,) Is a cross-sectional
view as viewed from the front, and (b) is a one-sided view as viewed from above.
In the figure, reference numeral 1 denotes an electrostrictive material, -2 and 2 'are internal
electrodes, 3 and 3' are external electrodes, 4 is a heavy 9 portion of the internal electrode, 5 is a
non-overlapping portion of the internal electrode, and 6 is an internal electrode The non-parts
are shown respectively. FIG. 2 shows a laminated electrostrictive effect element in which the end
of the internal electrode is exposed to the element surface. (Al is a front view, (b) is a crosssectional view when (-) is viewed from above and cut at the position of the internal electrode. In
the figure, reference numerals 20 and 21 denote electrostrictive materials, 22 and 22 'denote
internal electrodes, 23 and 24 denote wires connecting the internal electrodes, and 25 and 26
denote electrode terminals. 3 (a) (b) (c) (dl (e) are diagrams showing each step in the
manufacturing method including the method of the present invention. In the figure, numerals 30
and 31 denote electrostrictive materials, 32 and 32 'denote internal electrodes, 33 and 33'
denote insulating material films, 34 denotes holes in the insulating material film, and 35 and 35
'denote external electrodes.
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description, jps59122200
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