Respective first end portions of first and second internal electrodes are exposed at respective end surfaces of a varistor body, which is in the form of a rectangular parallelepiped. These end surfaces of the varistor body are covered with low resistance parts which include ceramic material in order to prevent the internal electrodes from decomposition. External electrodes are formed on the low resistance parts, so as, to be electrically connected with corresponding ones of the internal electrodes through the low resistance parts.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a laminated varistor, and more 
particularly, it relates to structure in a laminated varistor for 
preventing decomposition of internal electrodes. 
2. Description of the Background Art 
A varistor is a resistor element whose resistance value nonlinearly changes 
in response to applied voltage. 
FIG. 17 shows a conventional varistor 1 of a laminated type provided in the 
form of a rectangular parallelepiped. The laminated varistor 1 shown in 
FIG. 17 is substantially identical in structure to a laminated varistor 
which is disclosed in U.S. Pat. No. 4,290,041. 
Referring to FIG. 17, the laminated varistor 1 comprises a sintered body 5, 
which is obtained by alternately stacking ceramic layers 2 and internal 
electrodes 3 or 4 and integrally sintering the same. First and second 
external electrodes 8 and 9 of metal are provided on first and second 
opposite end surfaces 6 and 7 of the sintered body 5. The internal 
electrodes 3 of a first group have end portions 10 reaching the first end 
surface 6, to be electrically connected to the first external electrode 8. 
The internal electrodes 4 of a second group, which are arranged 
alternately with the internal electrodes 3 of the first group, have end 
portions 11 reaching the second end surface 7, to be connected to the 
second external electrode 9. 
This laminated varistor 1, and more specifically the sintered body 5, has 
such structure that the respective end portions 10 and 11 of the internal 
electrodes 3 and 4 are exposed toward the exterior of the sintered body 5. 
Therefore, when the sintered body 5 is placed in a humid atmosphere, the 
exposed portions of the internal electrodes 3 and 4 are easily decomposed. 
Further, when the external electrodes 8 and 9 are formed by plating, the 
plating solution easily permeates the sintered body 5 from the exposed 
portions of the internal electrodes 3 and 4. Consequently, characteristics 
of the laminated varistor 1 are deteriorated. 
SUMMARY OF THE INVENTION 
Accordingly, an object of the present invention is to provide a laminated 
varistor with structure which can circumvent deterioration of varistor 
characteristics by preventing decomposition of internal electrodes. 
Another object of the present invention is to provide a laminated varistor 
which can improve reliability and maintain quality. 
A laminated varistor according to the present invention comprises a 
varistor part which is formed of a ceramic material which has a varistor 
function. A plurality of internal electrodes, which are arranged in 
parallel with each other, are embedded in the varistor part except for 
portions extended toward the exterior of the varistor part for providing 
electrical connections. Portions of the varistor part deriving the 
internal electrodes extend toward the exterior are covered with low 
resistance parts (layers) which comprise a ceramic material. External 
terminal means are electrically connected with the internal electrodes 
through the low resistance parts respectively. 
According to one aspect of the present invention, the portions, of the 
internal electrodes which would otherwise have been exposed from the 
varistor part can be completely covered with the low resistance parts. 
Therefore, the internal electrodes can be prevented from decomposition in 
a humid atmosphere as well as from permeation of a plating solution 
employed for forming external electrodes. Consequently, deterioration of 
characteristics in the laminated varistor can be circumvented while 
reliability and quality of the varistor can be improved. 
According to another aspect of the present invention, the internal 
electrodes are so electrically connected with the low resistance parts 
that the internal electrodes embedded in the varistor part can be 
electrically connected to the exterior by providing the external terminal 
means on outer surfaces of the low resistance parts. 
Preferably the varistor part is in the form of a rectangular parallelepiped 
which has first and second opposite major surfaces, extending in parallel 
with the internal electrodes, and first and second opposite end surfaces. 
The plurality of internal electrodes include first and second internal 
electrodes, which are extended to the first and second end surfaces of the 
varistor part respectively. The low resistance parts include first and 
second low resistance parts which cover the first and second end surfaces 
of the varistor part respectively. Further, the external terminal means 
are provided by first and second external electrodes which are formed on 
the first and second low resistance parts respectively. 
The internal electrodes may include those of a first group which are 
extended to the first end surface and those a second group which are 
extended to the second end surface. The internal electrodes of the first 
group are alternately arranged with those of the second group. Those of 
the internal electrodes which are closest to the first and second major 
surfaces of the varistor part are preferably spaced away from the end 
surfaces to which they are not intended to extend by a greater distance 
than are the remaining internal electrodes of the same groups, in order to 
prevent the low resistance parts from approaching or coming into contact 
with the internal electrodes at undesired locations thereby to prevent the 
varistor from the flowing of any undesired leakage current. 
The low resistance parts may be arranged so as to partially form at least 
one of the major surfaces of the varistor part. In this case, a plurality 
of internal electrodes may be connected with the same low resistance part 
and with each other through viahole connecting parts which are defined in 
the varistor part. 
The varistor part is preferably formed by the firing of a ceramic material 
which has a varistor function, and the low resistance parts are formed of 
a ceramic material which is semiconductorized (made semiconductive) by 
firing. In this case, the varistor part and the low resistance parts may 
be cofired to be integrated with each other, or a raw ceramic material for 
forming the low resistance parts may be applied to a fired varistor part, 
and then fired. In either case, the raw ceramic material for forming the 
low resistance parts is prepared in the form of paste or sheets containing 
the ceramic material, and applied to prescribed regions of the varistor 
part. In the low resistance parts thus formed the, composition of the 
ceramic material contained therein and the thickness thereof can be so 
correctly controlled so as to prevent the varistor from undergoing any 
variation of its characteristics caused by any change in the state of 
connection between the low resistance parts and the internal electrodes. 
The raw ceramic material for forming the low resistance parts preferably 
contains a ceramic material which is identical in composition to that 
forming the varistor part and at least one element selected from the group 
consisting of Al, Ga, Gd, Zn and Y. 
As just mentioned, the varistor part and the low resistance parts may be 
comprised by an integrally fired common ceramic body; thus, the low 
resistance parts are obtained by partially lowering the resistance of this 
ceramic body. In this case, the low resistance parts are formed on the 
ceramic body by applying paste containing at least one element selected 
from the group of Al, Ga, Gd, Zn and Y to parts of the ceramic body and 
performing heat treatment. Alternatively, the low resistance parts can be 
also formed on the ceramic body by applying a reducing solution to parts 
of the ceramic body. The reducing solution is preferably prepared from an 
organic borane compound solution. 
These and other objects, features, aspects and advantages of the present 
invention will become more apparent from the following detailed 
description of the present invention when taken in conjunction with the 
accompanying drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
FIGS. 1-6 
Referring to a first embodiment of the invention shown in FIGS. 1 to 4, a 
laminated varistor 12 provided in the overall form of a rectangular 
parallelepiped. It comprises a sintered body (varistor part) 16, which is 
obtained by alternately stacking ceramic layers 13 which have a varistor 
function and internal electrodes 14 or 15 made of platinum, for example, 
and integrally firing the same. The sintered body 16 has first and second 
opposite end surfaces 17 and 18. Film-type first and second low resistance 
parts 19 and 20 are provided on the first and second end surfaces 17 and 
18 respectively. First and second external electrodes 21 and 22, which are 
formed of silver, palladium or an alloy thereof, are provided on the first 
and second low resistance parts 19 and 20 respectively. 
The internal electrodes 14 of a first group are exposed only at first end 
portions 23 thereof from the sintered body, i.e., varistor part 16, and 
such exposed portions are positioned at the first end surface 17 of the 
varistor part 16. The first end surface 17 is covered with the first low 
resistance part 19 as hereinabove described, thereby to prevent the 
internal electrodes 14 from permeation of moisture or a plating solution. 
Further, since the low resistance part 19 is in contact with the internal 
electrodes 14, the first external electrode 21 is electrically connected 
with the internal electrodes 14 through the low resistance part 19. 
Similarly, the internal electrodes 15 of a second group are exposed to the 
exterior of the second end surface 18 of the varistor part 16 only at 
first end portions 24 thereof. The second end surface 18 is covered with 
the second low resistance part 20, thereby to prevent the internal 
electrodes 15 from permeation of moisture or the plating solution and to 
electrically connect the second external electrodes 22 with the internal 
electrodes 15 through the low resistance part 20. 
The low resistance parts 19 and 20 are formed by applying paste mainly 
composed of ceramic powder having the same composition as the ceramic 
layers 13, plus aluminum, for example, to the end surfaces 17 and 18 of 
the sintered body, i.e., varistor part 16, and firing the same. 
A method of fabricating the laminated varistor 12 is now described in more 
concrete terms. 
(1) 10 percent by weight of glass powder formed of B.sub.2 O.sub.3, 
SiO.sub.2, PbO and ZnO is added to a ceramic material prepared by mixing 
95.0 mole percent of ZnO, 1.0 mole percent of CoO, 1.0 mole percent of 
MnO, 2.0 mole percent of Sb.sub.2 O.sub.3 and 1.0 mole percent of Cr.sub.2 
O.sub.3 and mixed with each other with addition of an organic binder. A 
ceramic green sheet is obtained by applying the doctor blade coater to the 
mixture thus obtained. Then, this green sheet is cut into rectangles of 
prescribed dimensions, thereby to obtain the plurality of ceramic layers 
13. 
(2) Then, paste prepared by mixing platinum with a vehicle is applied to 
upper surfaces of the ceramic layers 13, to form the internal electrodes 
14 and 15. At this time, the first end portions 23 and 24 of the internal 
electrodes 14 and 15 are made to reach respective edges of the ceramic 
layers 13 while second end portions of the internal electrodes 14 and 15 
are made not to reach corresponding edges of the ceramic layers 13. 
(3) Then, the ceramic layers 13 are successively stacked so that the 
ceramic layers 13 and the internal electrodes 14 or 15 alternately overlap 
with each other and the internal electrodes 14 and 15 of the first and 
second groups are alternately arranged, as shown in FIG. 3. Further, 
ceramic sheets 25 and 26, which are provided with no internal electrodes, 
are placed on upper and lower surfaces of the laminate and pressurized in 
the direction of lamination. 
(4) Then, the laminate obtained at the step (3) is fired in the air at a 
temperature of 1200.degree. C. for three hours, thereby to obtain the 
sintered body 16. 
(5) Then, first and second low resistance parts 19 and 20 are formed to 
cover the first and second end surfaces 17 and 18 of the sintered body 16 
respectively, as shown in FIG. 4. The low resistance parts 19 and 20 are 
formed by applying paste obtained by adding 5 percent by weight of 
aluminum powder to ceramic powder having the same composition as the 
ceramic layers 13 prepared at the above step (1) and mixing the same with 
a vehicle to be 50 .mu.m in thickness and firing the same in the air at a 
temperature of 1100.degree. C. In this firing step, Al.sub.2 O.sub.3 is 
dissolved in ZnO by reaction between ZnO and aluminum, whereby a 
semiconductor material whose resistance value is lowered is obtained. 
Consequently, the low resistance parts 19 and 20 are supplied with 
prescribed conductivity. 
The raw ceramic material for forming the low resistance parts 19 and 20 may 
contain metal such as Ga, Gd or Y, in place of the aforementioned 
aluminum. Further, the low resistance parts 19 and 20 may be formed of a 
low resistance ceramic material such as RuO.sub.2, in place of ZnO. If the 
sintered body 16 is of a ceramic material containing ZnO, the raw ceramic 
material for forming the low resistance parts 19 and 20 may contain metal 
zinc and zinc oxide. 
As an alternative to the above method of applying paste to form the low 
resistance parts 19 and 20, or in addition thereto, the low resistance 
parts 19 and 20 can also be formed by of adhering green sheets, which are 
substantially identical in composition to the aforementioned paste, onto 
the first and second end surfaces 17 and 18. 
(6) Then, masks are applied, to portions of the sintered body 16 obtained 
in the above step (5) except for both end portions and the low resistance 
parts 19 and 20, and then electrolytic plating with nickel or copper, for 
example, is performed to form the external electrodes 21 and 22 on the 
outer surfaces of the low resistance parts 19 and 20 as shown in FIG. 1. 
The external electrodes 21 and 22 may alternatively be formed by applying 
paste obtained by adding palladium to silver onto the outer surfaces of 
the low resistance parts 19 and 20 respectively and baking the same. 
Further, each of the external electrodes 21 and 22 may have a multilayer 
structure comprising a plurality of metal layers. 
Thus, the laminated varistor 12 is obtained. 
The raw ceramic material, employed at the above step (5), for forming the 
low resistance parts 19 and 20, may be applied to the unfired laminate 
obtained at the step (3), and then to the varistor part 16, and the low 
resistance parts 19 and 20 may be cofired. In this case, the same firing 
conditions as those of the above step (4) may be employed. 
In the laminated varistor 12, the low resistance parts 19 and 20 are formed 
to cover the end portions 23 and 24 of the internal electrodes 14 and 15 
exposed on the end surfaces 17 and 18 of the sintered body, i.e., varistor 
part 16. Therefore, the internal electrodes 14 and 15 will not be 
decomposed even if the varistor 12 is used in a humid atmosphere, and also 
no plating solution will permeate through the internal electrodes 14 and 
15 even if the sintered body, i.e., varistor part 16 is dipped in a 
plating solution. Therefore, the varistor 12 can be prevented from 
deterioration of characteristics originally provided therein. 
In this varistor 12, further, the internal electrodes 14 and 15 are 
respectively connected with the external electrodes 21 and 22 through the 
low resistance parts 19 and 20 which are formed to cover the respective 
end portions 23 and 24 exposed from the varistor part 16. Thus, the 
internal electrodes 14 and 15, which are completely contained within the 
varistor part 16 and the low resistance parts 19 and 20 formed of ceramic 
materials respectively, can be electrically connected with the exterior. 
The low resistance parts 19 and 20 can be easily formed by carrying out the 
above step (5). As for the low resistance parts 19 and 20, further the, 
composition of the, ceramic material contained therein, the amount of 
added metal such as aluminum, and the thickness thereof, can be correctly 
controlled, thereby reducing variations in electrical properties among the 
varistors 12 thus obtained. 
FIGS. 5 and 6 illustrate the results of a humidity test made for confirming 
the effect of this embodiment. In this test, the laminated varistor 12 
shown in FIG. 1 was left in an atmosphere having a temperature of 
60.degree. C. and relative humidity of 90 % for 1000 hours and thereafter 
placed back into an ordinary atmosphere, to examine the rates of change 
over time of V.sub.lmA and V.sub.0.1mA. V.sub.lmA and V.sub.0.1mA, called 
threshold voltages, represent the voltage values observed when currents 
flowing in the varistor were 1 mA and 0.1 mA respectively. A similar test 
was made on a varistor which was identical in structure to the varistor 12 
except that no low resistance parts 19 and 20 as shown in FIG. 1 were 
provided, for the purpose of reference. 
FIG. 5 shows the relation between the percentage of change in V.sub.lmA and 
the elapsed time, and FIG. 6 shows the relation between the percentage 
change in V.sub.0.1mA and the elapsed times time. In these figures, curves 
A (solid lines) show the relation for the embodiment and curves B (broken 
lines) show the relation for the reference example. 
Although no significant difference was observed between the samples A and B 
as to the rates of change in V.sub.lmA, as significant improvement was 
seen for V.sub.0.1mA. The sample B exhibited the a change of -25 % while 
the sample A exhibited the a change of only -9 % after lapse of 1000 
hours, as understood from FIGS. 5 and 6. Thus, it is understood that 
moisture resistance was improved in the sample A. 
While the external electrodes were formed by baking metal paste in both of 
the samples subjected to the aforementioned tests, no deterioration of 
characteristics was seen in another sample of the present invention in 
which the external electrodes were formed by plating. 
FIG. 7-9 
With reference to FIGS. 7 and 8, a second embodiment of the present 
invention is now described. 
A laminated varistor 12a and a sintered body 16a shown in FIG. 7 and/or 
FIG. 8 comprise elements which are substantially identical to those 
included in the laminated varistor 12 and the sintered body 16 shown in 
FIG. 1. Referring to FIGS. 7 and 8, therefore, elements or parts 
corresponding to those shown in FIG. 1 are indicated by the same reference 
numerals as those in FIG. 1 with subscripts "a", to omit redundant 
description. 
In order to obtain the laminated varistor 12a, the sintered body 16a shown 
in FIG. 8 is first prepared. This sintered body 16a is formed by 
alternately stacking ceramic layers 13a of a ceramic material having a 
varistor function and internal electrodes 14a or 15a. The internal 
electrodes 14a and 15a are completely embedded within the sintered body 
16a. The internal electrodes 14a of a first group have end portions 24a 
which are relatively closer to a first end surface 17a, than are the 
corresponding end portions 27 of the internal electrodes 15a of a second 
group. Similarly, the internal electrodes 15a of the second group have end 
portions 24a which are closer to a second end surface 18a than the 
corresponding end portions 28 of the internal electrodes 14a of the first 
group. 
As shown in FIG. 7, first and second low resistance parts 19a and 20a are 
provided on respective end portions of the sintered body 16a. The low 
resistance parts 19a and 20a are formed by semiconductorizing the end 
portions of the sintered body 16a shown in FIG. 8. Thus, the first and 
second low resistance parts 19a and 20a and the varistor part 29 are all 
comprised in the sintered body 16a, which is a common ceramic body, while 
first and second end surfaces 30 and 31 of the varistor part 29 are 
defined by interfaces between the respective ones of the first and second 
low resistance parts 19a and 20a and the varistor part 29. The internal 
electrodes 14a of the first group are electrically connected to the first 
end surface 30, since the respective end portions 23a are positioned in 
the first low resistance part 19a. On the other hand, the internal 
electrodes 15a of the second group are electrically connected to the 
second end surface 31, since the respective end portions 24a are 
positioned in the second low resistance part 20a. Therefore, the internal 
electrodes 14a of the first group are electrically connected to a first 
external electrode 21a through the first low resistance part 19a, while 
the internal electrodes 15a of the second group are electrically connected 
to a second external electrode 22a through the second low resistance part 
20a. 
A method of fabricating the laminated varistor 12a shown in FIG. 7 is now 
described. 
(1) The step (1) in the aforementioned first embodiment is carried out to 
prepare the ceramic layers 13a. 
(2) The step (2) in the aforementioned first embodiment is carried out to 
form the internal electrodes 14a or 15a on the ceramic layers 13a. 
(3) The step (3) in the aforementioned first embodiment is carried out to 
obtain a laminate for forming the sintered body 16a. 
(4) The step (4) in the aforementioned first embodiment is carried out to 
obtain the sintered body 16a shown in FIG. 8. 
(5) Paste mainly composed of Al is applied onto the first and second end 
surfaces 17a and 18a of the sintered body 16a and heated at 1000.degree. 
C. for one hour. Thus, Al.sub.2 O.sub.3 is dissolved in ZnO on both end 
portions of the sintered body 16a, whereby the first and second low 
resistance parts 19a and 20a are formed through semiconductorization by 
lowering the resistance values of the end portions. 
The aforementioned paste may contain metal such as Ga, Gd, Zn or Y in place 
of Al. 
(6) The step (6) in the aforementioned first embodiment is carried out to 
form the external electrodes 21a and 22a, thereby to obtain the laminated 
varistor 12a. 
Characteristics similar to those shown in FIGS. 5 and 6 can be attained 
also by the laminated varistor 12a. 
The above described paste containing aluminum may be applied onto 
respective end surfaces of the unfired laminate obtained in the above step 
(3), and then step (4) may be carried out. The first and second low 
resistance parts 19a and 20a can similarly be formed on the respective end 
portions of the sintered body 16a also by this method. 
Further, it is also possible to form the low resistance parts 19a and 20a 
as shown in FIG. 7, by reducing both end portions of the sintered body 16a 
shown in FIG. 8 by means of reducing solution. For example, the low 
resistance parts 19a and 20a can be formed on the sintered body 16a by 
dipping the end portions of the sintered body 16a in the reducing solution 
or bringing the former into contact wit the latter by some other method. 
The reducing solution is prepared from an organic borane compound solution 
such as a saturated solution of dimethylamine borane, for example. 
In more concrete terms, the first and second end surfaces 17a and 18a of 
the sintered body 16a are brought into contact with paper infiltrated with 
a saturated solution of dimethylamine borane, and retained in this state 
at a temperature of 60.degree. C. for five hours. Thus, the end portions 
of the sintered body 16a are reduced so as to have low resistance values, 
whereby to define the first and second low resistance parts 19a and 20a, 
as shown in FIG. 7. After such reduction processing, the sintered body 16a 
is washed with water to remove the reducing solution remaining on the 
surface of the sintered body 16a, thereby to circumvent any inconvenience 
that may be caused by the reducing solution in the succeeding steps of 
fabricating the varistor 12a. 
One problem with the laminated varistor 12a shown in FIG. 7, for example, 
is that it may easily have leakage or shorting caused by problems in 
fabrication, and shorting may be. This is now described with reference to 
FIG. 9. 
Referring to FIB. 9, when the first and second low resistance parts 19a and 
20a are to be formed by partially lowering the resistance of a sintered 
body 16a, such resistance lowering process can have an excessive effect in 
the vicinity of first and second major surfaces 32 and 33 of the sintered 
body 16a which extend in parallel with the internal electrodes 14a and 
15a. Therefore, the first and second low resistance parts 19a and 20a can 
inwardly project in the vicinity of the major surfaces 32 and 33, as shown 
in a somewhat exaggerated manner in FIG. 9. Consequently, internal 
electrodes 14a-1 and 15a-1, which are closest to the first and second 
major surfaces 32 and 33, may undesirably approach or come into contact 
with the second and first low resistance parts 20a and 19a respectively. 
In other words, an end portion 28 of the internal electrodes 14a-1, which 
must not be electrically connected with the second low resistance part 
20a, inevitably approaches or comes into contact with the second low 
resistance part 20a. Similarly an end portion 27 of the internal electrode 
15a-1, which must not be electrically connected with the first low 
resistance part 19a, of the internal electrode 15a-1 inevitably approaches 
or comes into contact with the first low resistance part 19a. This is 
considered to lead to the risk of the leakage current or shorting. 
FIG. 10 
FIG. 10 shows a third embodiment of a laminated varistor 12b, which can 
solve the aforementioned problems. Referring to FIG. 10, elements or parts 
corresponding to those shown in FIG. 1, 7 or 9 are indicated by the same 
reference numerals with subscripts "b", to omit redundant description. 
Referring to FIG. 10, the laminated varistor 12b comprises a sintered body 
16b obtained by alternately stacking ceramic layers 13b of a ceramic 
material which has a varistor function and internal electrodes 14b or 15b 
and firing the same. First and second external electrodes 21b and 22b are 
formed on first and second end surfaces 17b and 18b of the sintered body 
16b respectively. Further, first and second low resistance parts 19b and 
20b are formed on respective end portions of the sintered body 16b. Thus, 
the remaining portion of the sintered body 16b defines a varistor part 
29b. The varistor part 29b is provided with first and second end surfaces 
30b and 31b in respective interfaces with the first and second low 
resistance parts 19b and 20b. 
The internal electrodes 14b of a first group are electrically connected 
with the first low resistance part 19b in respective end portions 23b 
thereof. On the other hand, the internal electrodes 15b of a second group 
are electrically connected with the second low resistance part 20b at 
respective end portions 24b thereof. 
With one specific exception, a second end portion 28b of each internal 
electrode 14b of the first group is separated from the second end surface 
18b by a distance tl. Similarly, a second end portion 27b of each internal 
electrode 15b of the second group is separated from the first and surface 
17b by a distance tl, with one specific exception. These specific 
exceptions will now be described. 
A second end portion 28b-1 of a specific one of the internal electrodes 14b 
of the first group, namely the internal electrode 14b-1 which is closest 
to the first major surface 32b is separated from the first end surface 18b 
by a distance t2. Similarly, a second end portion 27b-1 of a specific one 
of the internal electrodes 15b of the second group, i.e., internal 
electrode 15b-1 which is closest to the second major surface 33b, is 
separated from the first end surface 17b by a space t2. The space t2 is 
larger than the distance t1. Preferably the internal electrodes 14b-1 and 
15b-1, which are closest to the major surfaces 32b and 33b, are shorter 
than half the length L of the sintered body 16b. 
FIG. 11 
FIG. 11 shows a further embodiment of a laminated varistor 12c, which is 
obtained by slightly modifying the laminated varistor 12b shown in FIG. 
10. The laminated varistor 12b shown in FIG. 11 includes a large number of 
elements which are common with those of the laminated varistor 12b shown 
in FIG. 10. Referring to FIG. 11, therefore, elements or parts 
corresponding to those shown in FIG. 10 are indicated by the same 
reference numerals, to omit redundant description. 
The laminated varistor 12c shown in FIG. 11 is characterized in that a 
dummy electrode 14c is formed to align with the internal electrode 14b-1 
and a dummy electrode 15c is formed to align with the internal electrode 
15b-1. These dummy electrodes 14c and 15c define gaps between themselves 
and the internal electrodes 14b-1 and 15b-1 respectively. 
The dummy electrodes 14c and 15c, which have no particularly remarkable 
electrical functions in the laminated varistor 12c, are printed and formed 
on the same ceramic layers 13b as the respective ones of the internal 
electrodes 14b-1 and 15b-1, to facilitate the operation wherein the 
internal electrodes 14b-1 and 15b-1 are printed and to avoid any inbalance 
in the thickness of the ceramic layers caused by the internal electrodes 
14b-1 and 15b-1, thereby to further facilitate the operation of stacking 
the ceramic layers 13b. 
FIGS. 12-15 
With reference to FIGS. 12 to 15, a fifth embodiment of the present 
invention is now described. 
A laminated varistor 34 shown in FIGS. 12 to 14 comprises a sintered body 
38, which is obtained by alternately stacking ceramic layers 35 of a 
ceramic material which functions as a varistor and internal electrodes 36 
or 37 and firing the same. First and second external electrodes 39 and 40 
are formed on outer surfaces of the sintered body 38. The first external 
electrode 39 is mainly formed over a first end surface 41 and a first 
major surface 43 of the sintered body 38, while the second external 
electrode 40 is mainly formed over a second end surface 42 and a second 
major surface 44 of the sintered body 38. 
The internal electrodes 36 and 37 are completely embedded within the 
sintered body 38. First end portions 45 of the internal electrodes 36 of a 
first group are closer to the first end surface 41, then the first end 
portions 46 of the internal electrodes 37 of a second group. On the other 
hand, second end portions 47 of the internal electrodes 37 of the second 
group are closer to the second end surface 42, than are the second end 
portions 48 of the internal electrodes 36 of the first group. The 
respective first end portions 45 of the internal electrodes 36 of the 
first group are electrically connected with each other through a viahole 
connecting part 49 extending within the sintered body 38 along the 
direction of lamination. On the other hand, the respective first end 
portions 47 of the internal electrodes 37 of the second group are 
electrically connected with each other by a second viahole connecting part 
50 extending within the sintered body 38 along the direction of 
lamination. 
A first low resistance part 51 is formed in a region along the first major 
surface 43 of the sintered body 38 and between the first external 
electrode 39 and an internal electrode 36 which is closest to the same. A 
second low resistance part 52 is formed in a region along the second major 
surface 44 of the sintered body 38 and between the second external 
electrode 40 and an internal electrode 37 which is closest to the same. 
Thus, a major portion of the sintered body 38, with the exception of first 
and second low resistance parts 51 and 52, defines a varistor part 53. In 
this embodiment, the first low resistance part 51 is provided to partially 
form the first major surface 43 of the varistor part 53, while the second 
low resistance part 52 is provided to partially form the second major 
surface 44 of the varistor part 53. 
In the laminated varistor 34 thus obtained, the internal electrodes 36 of 
the first group are electrically connected with the first external 
electrode 39 through the first viahole connecting part 49 and the first 
low resistance part 51. On the other hand, the internal electrodes 37 of 
the second group are electrically connected with the second external 
electrode 40 through the second viahole connecting part 50 and the second 
low resistance part 52. 
The laminated varistor 34 can be fabricated by application of a method 
which is substantially similar to that for the laminated varistor 12a 
shown in FIG. 7, for example. However the fabricating method for the 
laminated varistor 34 is different from that for the laminated varistor 
12a shown in FIG. 7 in that the viahole connecting parts 49 and 50 are to 
be formed, and in the positions where the low resistance parts 51 and 52 
are to be formed. 
To provide the viahole connecting parts 49 and 50, through holes 54 may be 
formed in prescribed positions of the ceramic layers 35 as shown in FIG. 
15, and then filled with metal parts which is identical to that for 
forming the internal electrodes 36 and 37. The through holes 54 may all be 
formed at the same time, by stacking only the ceramic layers 35 to be 
provided with the through holes 54. 
As to the locations of the low resistance parts 51 and 52, the laminated 
varistor 34 is merely different from the laminated varistor 12a shown in 
FIG. 7 in that the process for lowering the resistance of the ceramic 
material is performed toward the first and second major surfaces 43 and 
44. The process itself may be performed through various methods, similarly 
to the case of the laminated varistor 12a. 
According to the embodiment shown in FIGS. 12 to 15, the degree of progress 
of the resistance lowering process for forming the low resistance parts 51 
and 52 is regulated by the internal electrodes 36 or 37. Therefore, the 
inconvenience described above with reference to FIG. 9 not caused and 
there is no need to strictly control the processing conditions in the 
resistance lowering process in order to circumvent such inconvenience. 
FIG. 16 
FIG. 16 shows a sixth embodiment of the present invention. 
A laminated varistor 55 shown in FIG. 16 is basically formed by the same 
technique as that for the aforementioned laminated varistor 34. In this 
laminated varistor 55, first and second external electrodes 58 and 59 are 
formed on respective end portions of a first major surface 57 of a 
sintered body 56, thereby to enable application of wire bonding. 
The sintered body 56 is provided, in a its relatively upper portion as 
shown in FIG. 16, with internal electrodes 60 and 61, which are flush with 
each other. The internal electrode 60 is connected with an internal 
electrode 62, which is located under the same, through a viahole 
connecting part 63. On the other hand, the internal electrode 61 is 
connected with internal electrodes 64 and 65, which are located under the 
same, through a viahole connecting part 66. The internal electrode 62 is 
located between the internal electrodes 64 and 65. 
A first low resistance part 67 is formed between the first external 
electrode 58 and the internal electrode 60. On the other hand, a second 
low resistance part 68 is formed between the second external electrode 59 
and the internal electrode 61. Thus, the sintered body 56 defines a 
varistor part 69, except for portions occupied by the low resistance parts 
67 and 68. 
Although a plurality of pairs of internal electrodes are provided in one 
laminated varistor in each of the above described embodiments, the present 
invention is also applicable to a laminated varistor which is provided 
with only one pair of internal electrodes. As to the laminated varistor 
shown in FIG. 12, for example, the central pair of internal electrodes 36 
and 37 and the viahole connecting parts 49 and 50 may be removed so that 
the laminated varistor comprises only one pair of internal electrodes. 
Although several embodiments of the present invention have been described 
and illustrated in detail, it is clearly understood that the same is by 
way of illustration and example only and is not to be taken by way of 
limitation, the scope of the present invention being limited only by the 
terms of the appended claims.