U.S. patent application number 08/930440 was filed with the patent office on 2002-05-02 for electronic component and method of manufacture therefor.
Invention is credited to JINNO, RIHO, NAKAMURA, KAZUYUKI.
Application Number | 20020050909 08/930440 |
Document ID | / |
Family ID | 11729579 |
Filed Date | 2002-05-02 |
United States Patent
Application |
20020050909 |
Kind Code |
A1 |
JINNO, RIHO ; et
al. |
May 2, 2002 |
ELECTRONIC COMPONENT AND METHOD OF MANUFACTURE THEREFOR
Abstract
The present invention aims to present an electronic component
which is free from the fear of sneaking-in of water etc. from the
edge of electrode, by covering the electrode edge with resin. For
the purpose, external electrodes (3) are formed at both ends of
varistor (1) comprised of ceramic sheet (1a) and internal electrode
(2) laminated alternately, and then, a within-the-surface
insulation layer (30) is formed by covering the porous surface
inside the varistor (1), or filling the porosity, with silicone
resin, and an outside-the-surface insulation layer (31) is formed
covering the surface of varistor (1) and the edge of external
electrode (3).
Inventors: |
JINNO, RIHO; (MORIGUCHI-SHI,
JP) ; NAKAMURA, KAZUYUKI; (ENIWA-SHI, JP) |
Correspondence
Address: |
EDWARD KUBASIEWICZ
LAURA A. DONNELLY, ESQ.
MCDERMOTT, WILL & EMERY
600 13TH STREET, N.W.
WASHINGTON
DC
200053096
|
Family ID: |
11729579 |
Appl. No.: |
08/930440 |
Filed: |
December 19, 1997 |
PCT Filed: |
January 23, 1997 |
PCT NO: |
PCT/JP97/00146 |
Current U.S.
Class: |
338/21 |
Current CPC
Class: |
H01C 7/10 20130101; H01G
2/12 20130101; H01C 17/02 20130101; Y10T 29/49099 20150115; H01C
7/102 20130101; H01C 1/034 20130101; Y10T 29/43 20150115; H01C 7/18
20130101; Y10T 29/49087 20150115; Y10T 29/49082 20150115 |
Class at
Publication: |
338/21 |
International
Class: |
H01C 007/10 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 24, 1996 |
JP |
8-009773 |
Claims
1. An electronic component comprising: a body; at least a pair of
electrodes formed on the surface of said body at a specified
clearance; and an insulation layer formed on the surface of said
body covering an area where the pair of electrodes is not formed
and the edge part of the pair of electrodes, wherein at least a
part of said insulation layer is formed by impregnating
within-the-surface of said body with an insulation material.
2. An electronic component of claim 1, wherein the insulation layer
is formed with at least one of metal alkoxide and resin.
3. An electronic component of claim 1, wherein the insulation layer
is formed with metal alkoxide, the metal alkoxide comprising at
least one selected from the group consisting of silicon alkoxide,
titanium alkoxide, aluminium alkoxide, zirconium alkoxide, yttrium
alkoxide and magnesium alkoxide.
4. An electronic component of claim 1, wherein the insulation layer
is formed with resin, the resin being at least one selected from
the group consisting of silicone resin, epoxy resin, acrylic resin,
polybutadiene resin and phenolic resin.
5. An electronic component of claim 1, wherein the thickness of
insulation layer impregnated into within-the-surface of the body is
not less than 10 .mu.m.
6. An electronic component of claim 1, wherein the thickness of
insulation layer on outside-the-surface of the body is less than
the greatest thickness of the pair of electrodes contacting the
insulation layer.
7. An electronic component of claim 1, wherein the end of the body
has a curved shape.
8. An electronic component comprising: a body; at least a pair of
electrodes formed on the surface of said body at a specified
clearance; and an insulation layer formed on the surface of said
body covering an area where the pair of electrodes is not formed
and the edge part of the pair of electrodes, wherein the surface of
said body is glossy.
9. A method of manufacturing an electronic component comprising the
steps of: forming at least a pair of electrodes on the surface of a
body at a specified clearance; contacting the surface of said body
with an impregnating solution containing at least an organic
substance for covering the surface of said body with said
impregnating solution; removing a part of the impregnating solution
covering the surface of said body; hardening the organic substance
contained in said impregnating solution; and removing the hardened
organic substance on the surface of the pair of electrodes by
grinding.
10. A method of manufacturing an electronic component of claim 9,
wherein the step of contacting the body with an impregnating
solution is repeated for plural times.
11. A method of manufacturing an electronic component of claim 9,
wherein the organic substance contains at least one of metal
alkoxide and resin.
12. A method of manufacturing an electronic component of claim 9,
wherein the organic substance contains metal alkoxide, the metal
alkoxide comprising at least one selected from the group consisting
of silicon alkoxide, titanium alkoxide, aluminium alkoxide,
zirconium alkoxide, yttrium alkoxide and magnesium alkoxide.
13. A method of manufacturing an electronic component of claim 9,
wherein the organic substance contains resin, the resin being at
least one selected from the group consisting of silicone resin,
epoxy resin, acrylic resin, polybutadiene resin and phenolic
resin.
14. A method of manufacturing an electronic component of claim 9,
wherein the body is pressurized while being contacted with an
impregnating solution.
15. A method of manufacturing an electronic component of claim 9,
wherein the organic substance on the surface of the body is removed
by at least one means of centrifugal separation, washing with an
organics-dissolving liquid, and contacting with a powder inert to
impregnating solution.
16. A method of manufacturing an electronic component of claim 15,
wherein the powder contains at least one selected from the group
consisting of SiO.sub.2, ZrO.sub.2, Al.sub.2O.sub.3 and MgO.
17. A method of manufacturing an electronic component of claim 9,
wherein the grinding is conducted at least by moving a container in
which the body and a liquid are contained.
18. A method of manufacturing an electronic component of claim 9,
wherein the pair of electrodes is formed after the edge of the body
is made to have a curved shape.
Description
TECHNICAL FIELD
[0001] The present invention relates to electronic components such
as a multilayer varistor etc., and a method of manufacturing the
same.
[0002] 1. Background Art
[0003] A conventional electronic component having at least a pair
of electrodes on the surface of body is impregnated with resin on
the surface only in an area where the electrodes are not
formed.
[0004] The water-resisting quality may be improved by the resin
impregnated in the body. However, there is a problem in the above
described structure that the water etc. sneaks into through the
edge of electrode causing deteriorated characteristics.
[0005] 2. Disclosure of the Invention
[0006] The present invention aims to present an electronic
component with which the sneaking of water etc. through the
electrode edge is prevented by covering the electrode edge with an
insulating layer.
[0007] An electronic component according to the present invention
comprises a body, at least a pair of electrodes formed on the
surface of the body at a specified gap, and an insulation layer
provided for covering the surface of the body in an area where the
electrodes are not formed and the edge of the electrode, wherein at
least a part of the insulation layer is formed by impregnating an
insulation material into within-the-surface of the body. With the
above described structure in which an insulation layer provided on
the surface covers the edge of electrodes, peeling-off at the edge
of electrode is prevented, at the same time the sneaking of water
through the electrode edge is also avoided.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] FIG. 1 is a cross sectional view showing a multilayer
varistor according to an embodiment of the present invention. FIG.
2 is a chart showing manufacturing process steps of a multilayer
varistor according to an embodiment of the present invention. FIG.
3 is a cross sectional view showing a varistor after silicone
varnish impregnation according to an embodiment of the present
invention. FIG. 4 is a cross sectional view showing a varistor
after centrifugal processing according to an embodiment of the
present invention. FIG. 5 is a cross sectional view showing a
varistor after toluene impregnation according to an embodiment of
the present invention. FIG. 6 is a cross sectional view showing a
varistor after silicone resin curing according to an embodiment of
the present invention. FIG. 7 is a cross sectional view showing a
varistor after grinding according to an embodiment of the present
invention.
BEST MODE FOR CARRYING OUT THE INVENTION
[0009] In the following, an electronic component according to the
present invention and a method of manufacturing the same is
described in detail referring to drawings.
[0010] As shown in FIG. 1, there are plural internal electrodes 2
made mainly of nickel (Ni), inside varistor 1. These internal
electrodes 2 are alternately pulled out to respective ends of
varistor 1 to be electrically connected with external electrodes 3.
The external electrode 3 is comprised of at least two layers; an
inner layer 3a is made mainly of Ni, an outer layer 3b is made
mainly of silver (Ag). A ceramic sheet la existing between and
outside the internal electrodes 2 is made mainly of SrTiO.sup.3,
containing Nb.sub.2O.sub.5, SiO.sub.2 etc. as subordinate
component. A within-the-surface insulation layer 30 is a layer
formed by covering the porous surface inside the varistor 1 or
filling the pore with silicone resin. An outside-the-surface
insulation layer 31 is a layer of silicone resin covering the edge
of external electrode 3. On the surface of external electrode 3 is
a layer of plating 4, comprised of Ni layer 4a and solder layer
4b.
[0011] As shown in FIG. 2, the ceramic sheet la is manufactured
through the process (11); mixing of raw materials, calcination,
crashing, slurrying and forming in a sheet form. The ceramic sheet
la and internal electrodes 2 are laminated (12), cut (13), binder
is removed (14), chamfered (15), and the edge is curved. Inner
layer 3a of external electrode 3 is formed through coating (16) and
sintering (17) at 1200 - 1300.degree. C. in reducing atmosphere.
Then, outer layer 3b is formed through coating (18) and heating
(19) at 800 - 850.degree. C. for reoxidizing. A completely dried
varistor 1 is immersed (20) in silicone varnish containing 75%
toluene as resolvent to have the varistor 1 impregnated with
silicone varnish.
[0012] Varistor 1 is pressurized (21) by 6 - 1500 kg/cm.sup.2 for
e.g. 2 minutes while being immersed in the silicone varnish in
order to have the varistor 1 impregnated further with the silicone
varnish, and then restored to the normal atmospheric pressure, at
which the multilayer varistor is put on service. The varistor 1 at
this stage is covered thick with silicone varnish 5 for the entire
surface, with the vaistor 1 and the external electrodes 3
impregnated with silicone varnish 5, as shown in FIG. 3. The
pressurizing force may be determined according to the density of
varistor 1; namely, varistor 1 of a higher density may be
pressurized with a higher force for the easier impregnation. In the
case of a varistor whose main component is ZnO, the density of
which is high and the pressurizing force may be raised to 500 -
1500 kg/cm.sup.2.
[0013] The varistor 1 is taken out of the silicone varnish, and put
into a metal basket (or metal net etc.) to be set on a centrifugal
separator having inner diameter of e.g. 60 cm running at 500 - 1500
r/min. (22 in FIG. 2) for removing most portion of unnecessary
silicone varnish sticking on the surface of varistor 1, as shown in
FIG. 4. Then, the metal basket containing the varistor is immersed
in toluene (23), vibrated for 5 - 60 sec., taken out, and quickly
heated at e.g. 60.degree. C. for removing the toluene sticking on
the surface of varistor 1, as shown in FIG. 5. Instead of immersing
in toluene, varistor 1 may be taken out of the metal basket to be
put in SiO.sub.2 powder, which is inert to the silicone varnish, to
have unnecessary silicone varnish 5 sticking on the surface of
varistor 1 absorbed, and then separating the varistor 1 using a
sieve or such other devices. Through the above described procedure,
unnecessary portion of silicone varnish 5 sticking on the surface
of varistor 1 is removed.
[0014] And then, varistor 1 is put on a metal net to be heated at a
temperature (approximately 125 - 200.degree. C. ) higher than the
curing temperature of silicone resin contained in the silicone
varnish 5 for curing (24) the silicone resin. When, a part of the
silicone resin impregnated within external electrodes 3 and inside
of varistor 1 is separated out to cover the surface, and a varistor
1 as shown in FIG. 6 is obtained. After this, varistor 1 is put
into a container of e.g. polyethylene together with an abrasive of
SiC and water, the container sealed, and provided with mechanical
movement such as revolution, vibration etc. for grinding (25) the
surface, in order to remove the silicone resin covering the surface
of external electrodes 3 to a degree so as plating and other
succeeding process steps are not ill-affected. During the surface
grinding (25), the silicone resin on the surface of external
electrodes 3 is selectively removed by a mechanical stress given to
varistor 1 due to a fact that the adhesion strength of silicone
resin after curing is stronger with respect to varistor 1 than with
the surface of external electrode 3. Some of the silicone resin may
remain in the inner surface of external electrode 3, the electrical
contact of external electrode 3 is not affected by the silicone
resin.
[0015] The surface of external electrode 3 of varistor 1 is plated
(26) to obtain a multilayer varistor as illustrated in FIG. 1.
[0016] As described in the above, a multilayer varistor having
enhanced water-resisting property is implemented by the formation
of a silicone resin-impregnated within-the-surface insulation layer
30 inside the varistor 1, with which multilayer varistor the
peeling-off at the edge of external electrode 3 is also prevented
by the formation of an outside-the-surface insulation layer 31, and
the external electrode 3 does not ill-affect plating (26) and other
post processes.
[0017] Now in the following, description will be made on some of
the noticeable items regarding a multilayer varistor according to
the present embodiment and its manufacturing method.
[0018] Referring to FIG. 1, by forming an outside-the-surface
insulation layer 31 so as it covers the edge of external electrodes
3 formed at the ends of varistor 1 covering a part of the side
surface, the sneaking of plating liquid, water etc. into inside of
varistor 1 through the boundary between external electrode 3 and
varistor 1 is prevented.
[0019] As an outside-the-surface insulation layer 31 and a
within-the-surface insulation layer 30 have glossy surface, whether
or not the within-the-surface insulation layer 30 and the
outside-the-surface insulation layer 31 are formed can be visually
identified by inspecting the surface of a multilayer varistor. This
makes the selection work easier.
[0020] Although silicone resin has been exemplified as the
insulation material for forming the outside-the-surface insulation
layer 31 and the within-the-surface insulation layer 30, other
resins may of course be used provided that they satisfy a certain
heat resistivity, insulating property, water-repellent property,
and low water-absorbing property; either one, or more than one, of
epoxy resin, acrylic resin, polybutadiene resin, phenolic resin,
etc. may be used for the purpose, besides the silicone resin.
[0021] Instead of the resin, or in mixture with the resin, at least
one kind of metal alkoxide selected from the group of silicon,
titanium, aluminium, zirconium, yttrium and magnesium may be used
to obtain a same effect.
[0022] When the metal alkoxide is used, the impregnating solution
is made with alcohol or other such solvents that dissolve metal
alkoxide.
[0023] The within-the-surface insulation layer 30 has preferably a
greatest possible thickness in so far as the characteristics of a
multilayer varistor is not affected, at the same time the thinnest
part of the within-the-surface insulation layer 30 of silicone
resin after curing is preferably equal to or thicker than 10 .mu.m.
This is adjustable through the selection of the viscosity of
silicone varnish 5, the rate of solvent and the pressurizing
force.
[0024] The effect of pressurizing is enhanced by providing a state
where the pressure is lower than the normal atmospheric pressure
prior to the step of pressurizing for impregnation of silicone
varnish 5 into varistor 1.
[0025] Besides SiO.sub.2 exemplified as the powder inert to
silicone varnish 5, other powders may also be used provided that
they do not react with the impregnation solution to be impregnated
into varistor 1; either one, or a mixture, of ZrO.sub.2,
Al.sub.2O.sub.3, MgO may serve a same purpose.
[0026] A harder outside-the-surface insulation layer 31 is formed
by thoroughly removing a solvent contained in silicone varnish 5
impregnated into varistor 1 by heating, prior to curing, at a
temperature lower than boiling point.
[0027] The moisture-resisting property may be improved further by
repeating the process steps from the immersion in silicone varnish
5 through the surface grinding for plural times, preferably twice.
By so doing, the silicone resin is impregnated further into inside
of varistor 1.
[0028] It is preferred that the edge of body has a curved shape.
This shape alleviates the concentration of stress to one part of
external electrode 3 when removing organic substance on external
electrode 3 by grinding.
[0029] Although in the present embodiment a multilayer varistor
using strontium titanium oxide as the main component is
exemplified, the same effects are implementable also with a
multilayer varistor using zinc oxide as the main component, as well
as ceramic thermistors, capacitors, resistors and other electronic
components in general. Not only in the multilayer type electronic
components, the present invention implements the same effects in
electronic components of any shapes, for example a disk shape
electronic component.
[0030] Industrial Applicability
[0031] The insulation layer formed by impregnation into inside of
the surface prevents deterioration of the moisture-resisting
property, and the insulation layer formed on the surface enhances
the strength of electrode preventing the peeling-off at the edge of
electrode. Furthermore, this contributes to prevent the sneaking of
moisture etc. into the inside through the edge of electrode. The
moisture-resisting property is enhanced a step further.
* * * * *