JPH08330106A - Electronic component and its manufacture - Google Patents

Abstract

PURPOSE: To provide an electronic component which has an excellent moistureproof property by forming a protective layer which is constituted of a metal oxide layer which is made by oxidizing a metal film layer on the entire surface of an element except for parts where electrodes are formed and forming plating layers on the surfaces of the electrodes. CONSTITUTION: A resist film is first formed on the surface of an upper layer 3b and then an electroless Ni plating layer is applied. After that, these are heated and oxidized to form a metal oxide-made protective layer 5 which is constituted of the burned Aq external electrode 3b and electroless Ni plating. Nextly, the resist film which was carbonized at the time of heating is removed and then an Ni plating layer 4a and a solder plating layer 4b are applied onto the upper layer 3b. Now, the protective film of an elaborate structure is formed on the entire surface of an element except for the part where the upper layer 3b is formed and the Ni plating layer 4a and the solder plating layer 4b are formed on the surface of the upper layer 3b. By this method, a protective film which has an elaborate structure and a high resistance can be formed on the surface of the element.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronic component and its manufacturing method.

[0002]

2. Description of the Related Art Conventionally, in order to protect an element from the outside atmosphere, a protective film is provided on the outer peripheral portion of the element.

[0003]

Conventional protective films, such as those formed of glass, are water-resistant from peeling or cracks caused by impact or heat, and those formed of resin are hygroscopic, so that they are all moisture resistant. Had a problem of low reliability.

Therefore, the present invention has been made to solve the above problems, and an object of the present invention is to provide an electronic component having excellent moisture resistance and a method for manufacturing the same.

[0005]

In order to achieve this object, the present invention is to form at least a pair of electrodes on the surface of an element, form a metal coating layer on the surface of the element other than the electrode forming portion, and then form the element. Is heat-treated in an oxidizing atmosphere to form a protective layer made of a metal oxide obtained by oxidizing the metal coating layer, and further a plating layer is formed on the surface of the electrode.

[0006]

According to the present invention, first, at least a pair of electrodes is formed on the surface of the element, then a metal coating layer is formed on the surface other than the electrode forming portion, and then the element is heat-treated in an oxidizing atmosphere, The metal coating layer is oxidized to be a metal oxide and has a high resistance value.

Therefore, it is possible to provide a protective layer having a dense structure having a high resistance on the element surface. With the above configuration,
Even when the device has a porous structure, the protective layer made of a dense metal oxide formed on the surface makes it less susceptible to the surrounding environment such as humidity and gas. Further, since the element surface is covered with the hard protective layer, the mechanical strength of the element surface is improved, and it is possible to prevent the element from being damaged or distorted by the impact applied during the manufacturing process or the impact applied when mounting the electronic component. .

[0008]

【Example】

(Embodiment 1) A first embodiment of the present invention will be described below with reference to FIG.

In FIG. 1, reference numeral 1 is a varistor element,
A plurality of internal electrodes 2 are provided inside, and both ends are
The partial electrode 3 is provided. Varistor element 1 is SrT
iO ₃As the main component and Nb as the sub-component₂O_Five, Ta
₂O_Five, SiO₂, MnO₂Etc. are added. Well
Further, the internal electrode 2 has Ni as a main component and L as a sub-component.
i ₂CO₃It is formed by adding Further outside
In the partial electrode 3, the lower layer 3a has Ni as a main component and a sub-component.
Li₂CO₃Etc. are added to form the upper layer 3b of Ag.
It was formed. In the above configuration, the varistor element
The element surface other than the electrode forming portion of the upper layer 3b of the child 1 is protected.
Layer 5 is deposited. Furthermore, on the surface of the upper layer 3b
Ni plating layer 4a and solder plating layer 4b are formed.
It

FIG. 3 shows a manufacturing process. As shown in (7), a ceramic sheet 1a was produced by mixing raw materials, pulverizing, slurrying, and sheet forming.

A ceramic sheet 1a and an internal electrode 2 are laminated (8), cut (9), de-baked and calcined (1).
0) and chamfered (11).

Next, the lower layer 3a is formed on the end face of the varistor element 1.
Ni external electrode to be applied is applied (12), and 1200 to 13
After reduction baking (13) at 00 ° C., an Ag external electrode to be the upper layer 3b was applied (15).

Further, a resist film made of glue or resin is provided on the surface of the applied upper layer 3b, and then electroless Ni is used.
A plating layer was attached (14) and heated at 700 to 850 ° C. for reoxidation (16) to form a baked Ag external electrode 3b and a metal oxide protective layer 5 made of electroless Ni plating. Next, after removing the carbonized resist film at the time of heating (16), the Ni plating layer 4a and the solder plating layer 4b were attached (17) on the upper layer 3b.

In the varistor element 1 obtained in Example 1,
A protective layer 5 having a dense structure is formed on the entire surface other than the upper layer 3b forming portion of the varistor element 1, and a Ni plating layer 4a and a solder plating layer 4b are further formed on the surface of the upper layer 3b. Therefore, (I) the airtight insulating property of the varistor element 1 is extremely high,
It can be surely protected from water, gas, acid, alkali, etc., and has improved moisture resistance, chemical resistance (for example, prevention of element etching by plating solution), reduction of surface leak, and external electrode 3. The effects such as prevention of migration are exhibited.

(II) Since the surface of the varistor element 1 is covered with a hard protective layer 5, its mechanical strength is improved, and it is also strong against impact, and it is possible to prevent the occurrence of external damage such as cracks and chips and distortion. You can

(III) Since the surface of the external electrode 3 is covered with the plating layer 4, it exhibits excellent mountability as an electronic component.

(IV) Since a part of the metal oxide protective layer 5 is diffused and reacted on the surface of the varistor element 1, the adhesion strength is extremely high, and peeling or cracking due to impact or heat is unlikely to occur.

(V) When the protective layer 5 is formed, the volume increases due to oxidation of the metal, so that a more dense protective film can be formed. Etc.

(Second Embodiment) A second embodiment of the present invention will be described below with reference to FIG.

In the same manner as in Example 1, the varistor element 1 provided with the upper layer 3b was re-oxidized (16) and then Si (O)
R) ₄ (R is an alkyl group), a silicon compound represented by (Chemical formula 4), Ti (OR) ₄ (R is an alkyl group), a titanium compound represented by (Chemical formula 5), Al (OR) ₃ (R is Alkyl group), and a glass forming substance is attached to the surface of the varistor element 1 by immersing it in a liquid containing at least one of the aluminum compounds represented by Chemical formula 6 (18).
Then, it was embedded in the powder of the reaction inhibitor made of at least one of SiO ₂ , TiO ₂ , Al ₂ O ₃ , MgO, and ZrO ₂ , and heat-treated at 300 to 850 ° C. (19).

[0021]

[Chemical 4]

[0022]

Embedded image

[0023]

[Chemical 6]

After that, chamfering (20), Ni plating layer 4
A and the solder plating layer 4b were attached (17) to obtain an electronic component having a glass layer 21 on the surface of the protective layer 5 as shown in FIG.

In Example 2, the deposition (18) of the glass-forming substance and the heat treatment (19) were carried out only once, but a more uniform glass layer 21 should be formed if they are carried out a plurality of times. You can

The glass layer 21 thus formed is
The adhesion strength is extremely high because it is not simply attached to the outer surface of the protective layer 5 but a part thereof is diffused and reacted in the protective layer 5. In addition, Bi ₂ O ₃ , Sb is added to the glass forming substance.
It is more remarkable when at least one of ₂ O ₃ is contained.

As described above, by newly forming the glass layer 21 on the surface of the protective layer 5 made of a metal oxide, the characteristics described in (I) to (V) above can be further exerted. In particular, even if the varistor element 1 is put into a gas or solution having a strong reducing property, the glass layer 21 is formed, so that the metal oxide of the protective layer 5 is not reduced and may be damaged. There wasn't.

The action of the reaction inhibitor not only suppresses the diffusion reaction of the protective layer 5 and the glass layer 21, but also prevents the varistor elements 1 from sticking to each other.

Furthermore, Al is contained in the above various liquids.₂O₃,
TiO₂, ZnO, SiC, Si₃N _Four, SiO₂, Carbon fiber
Needle-like binding containing at least one type of fiber or glass fiber
When the crystal component is dispersed, the formed glass layer 21 is thermally treated.
Strength and mechanical strength are improved, especially when heat shock etc.
To prevent the occurrence and spread of cracks and peeling that occur
did it. In addition, the anchor effect of the needle-shaped crystal component
The adhesion strength with the protective layer 5 became stronger. In this case, the variance
The particle size of the needle-shaped crystal component should be fine and uniform.
It was remarkable. In addition, it is dispersed in the above reaction inhibitor powder.
The same effect was confirmed.

Bi ₂ O ₃ and Sb ₂ are added to the needle-shaped crystal component.
It was more remarkable when at least one of O ₃ was contained. Furthermore, the same effect was obtained by forming a silicone-based or epoxy-based resin on the surface of the protective layer 5.

(Embodiment 3) A third embodiment of the present invention will be described below.

After carrying out the steps (7) to (13) and (15) shown in FIG.
An electroless Ni plating layer in which at least one kind of powder of O ₂ , TiO ₂ , Al ₂ O ₃ , MgO, and ZrO ₂ is dispersed is attached (14), and the following steps (16) and (17) are performed. By going through the above, an electronic component having the protective layer 5 excellent in reduction resistance shown in FIG. 1 was obtained.

The protective layer 5 obtained in Example 3 had Ni, SiO ₂ , TiO ₂ , Al ₂ O ₃ and M during reoxidation (16).
At least one kind of powder of gO and ZrO ₂ reacts with each other to form the protective layer 5 having excellent reduction resistance. In this case, the particle size of the powder to be dispersed is fine and uniform, and
The higher the purity, the more remarkable. In addition to the above-mentioned various powders, glass powder had the same effect.

As described above, in the varistor element 1 obtained in each of the above Examples 1 to 3, since the protective layer 5 having a dense structure is formed on the surface of the varistor element 1 other than the electrode forming portion, It is less likely to be affected by the surrounding environment such as humidity, gas, acid and alkali. Moreover, since the surface is covered with the hard protective layer 5, the mechanical strength is improved.

Importantly in the manufacturing process, (I) When depositing the electroless Ni plating layer or depositing the glass forming substance, it is necessary that impurities do not deposit on the surface of the varistor element 1. First, thoroughly wash with pure water or ion-exchanged water.

(II) Since the liquid containing the glass-forming substance is hydrolyzed, it is desirable that the varistor element 1 be immersed in water after the water is sufficiently removed.

(III) When the powder is dispersed in the electroless Ni plating solution, it is desirable to stir the powder sufficiently to improve the dispersibility.

Further, the protective layer 5 formed on the surface of the varistor element 1 has a part of its surface under the influence of hydrogen gas generated at the step of attaching (17) the Ni plating layer 4a and the solder plating layer 4b. It may be reduced and the resistance value may decrease.
Therefore, in order to prevent this phenomenon, (IV) it is desirable to form the glass layer 21 on the surface of the protective layer 5 to prevent the influence of hydrogen gas, as shown in the second embodiment.

(V) As shown in Example 3 above, it is desirable to form a reduction resistant protective layer 5 to prevent the influence of hydrogen gas.

(VI) After the plating step (17), it is desirable to oxidize the protective layer 5 whose surface is partially reduced by using an ammonia solution of hydrogen peroxide. In this case, an alkaline solution that does not affect the varistor element 1 may be used. Further, since this solution has a cleaning action, it can be used as a cleaning solution after the plating step (17).

Further, as shown in the second embodiment, when the glass layer 21 is formed, the glass layer 2 is also formed on the surface of the upper layer 3b.
1 may be formed, and the plating layer 4 may be difficult to adhere even if the plating step (17) is performed. Therefore,
In order to solve that, (VII) a resist film made of polyvinyl alcohol, vinyl acetate or the like, a paste made of a washing glue or a polysaccharide such as ethyl cellulose, is provided on the surface of the upper layer 3b in advance, and then a glass forming substance is attached ( 18), heat treatment (19), carbonization of the resist film, and removal with an ultrasonic cleaner are desirable. Then, when forming the resist film, it is possible to know whether or not the resist film can be uniformly formed by mixing and coloring a dye or a pigment. In addition, in the above-mentioned examples, the protective layer 5 of the metal oxide formed on the surface of the varistor element 1 is shown only for Ni, but any other oxide having a high resistance and chemical resistance can be used. It doesn't matter. And
The formation method was also shown only for electroless plating,
Similar effects can be obtained by forming by vapor deposition, sputtering, dipping, thermal spraying, printing, or the like.

(Fourth Embodiment) A fourth embodiment of the present invention will be described below with reference to FIG.

In FIG. 6, reference numeral 1 is a varistor element,
A plurality of internal electrodes 2 are provided inside, and both ends are
The partial electrode 3 is provided. Varistor element 1 is SrT
iO ₃As the main component and Nb as the sub-component₂O_Five, Ta
₂O_Five, SiO₂, MnO₂Etc. are added. Well
Further, the internal electrode 2 has Ni as a main component and L as a sub-component.
i ₂CO₃It is formed by adding Further outside
In the partial electrode 3, the lower layer 3a has Ni as a main component and a sub-component.
Li₂CO₃Etc. are added to form the upper layer 3b of Ag.
It was formed. In the above configuration, the varistor element
A protective layer 5 of high resistance is attached to the entire surface of the child 1 excluding the end surface.
Has been established. Further, a Ni plating layer is formed on the surface of the upper layer 3b.
4a and a solder plating layer 4b are formed.

FIG. 8 shows the manufacturing process. As shown in (7), the ceramic sheet 1a was prepared by mixing the raw materials, pulverizing, slurrying, and sheet forming.

The ceramic sheet 1a and the internal electrode 2 are laminated (8), cut (9), de-baked and calcined (1).
0) and chamfered (11).

Next, the lower layer 3a is formed on the end face of the varistor element 1.
Ni external electrode to be applied is applied (12), and 1200 to 13
After reducing and baking (13) at 00 ° C., a resist film formed of glue or resin is provided on the end face of the element, an electroless Ni plating layer is attached (14), and the resist is washed with water or an organic solvent. After removal, an Ag external electrode to be the upper layer 3b is applied (15) and heated at 700 to 850 ° C. for reoxidation (16) to protect the baked Ag external electrode 3b and a metal oxide composed of electroless Ni plating. Layer 5 was formed. next,
The Ni plating layer 4a and the solder plating layer 4b were adhered (17) on the upper layer 3b.

In the varistor element 1 obtained in this example,
A protective layer 5 having a dense structure is formed on the entire surface of the varistor element 1 excluding the end face, and Ni is further formed on the surface of the upper layer 3b.
Because of the structure in which the plating layer 4a and the solder plating layer 4b are formed, (I) the airtight insulating property of the varistor element 1 is extremely high,
It can be surely protected from water, gas, acid, alkali, etc., and has improved durability, chemical resistance (for example, prevention of element etching by plating solution), surface leak reduction, and external electrode Effects such as prevention of migration are exhibited.

(II) Since the surface of the varistor element 1 is covered with the hard protective layer 5, the mechanical strength is improved and it is also strong against impact, and it is possible to prevent the occurrence of external damage such as cracks and chips and distortion. You can

(III) Since the surface of the electrode is covered with the plating layer, excellent mountability as an electronic component is exhibited.

(IV) Since a part of the protective layer 5 of metal oxide diffuses and reacts on the surface of the varistor element 1, the adhesive strength is extremely high, and peeling or cracking due to impact or heat is unlikely to occur.

(V) When the protective layer 5 is formed, the volume increases due to the oxidation of the metal, so that a more dense protective film can be formed. Etc.

(Fifth Embodiment) A fifth embodiment of the present invention will be described below with reference to FIG.

In the same manner as in Example 3, the varistor element 1 provided with the upper layer 3b was reoxidized (16) and then Si (O)
R) ₄ (R is an alkyl group), a silicon compound represented by (Chemical formula 4), Ti (OR) ₄ (R is an alkyl group), a titanium compound represented by (Chemical formula 5), Al (OR) ₃ (R is Alkyl group), and a glass forming substance is attached to the surface of the varistor element 1 by immersing it in a liquid containing at least one of the aluminum compounds represented by Chemical formula 6 (18).
Then, it was embedded inside the powder of the reaction inhibitor consisting of at least one of SiO ₂ , TiO ₂ , Al ₂ O ₃ , MgO, and ZrO ₂ , and heat-treated at 300 to 850 ° C. (19).

After that, chamfering (20), Ni plating layer 4
A and the solder plating layer 4b were attached (17) to obtain an electronic component having the glass layer 21 on the surface of the protective layer 5 as shown in FIG.

In Example 4, the deposition (18) of the glass forming substance and the heat treatment (19) were carried out only once, but a more uniform glass layer 21 can be formed by carrying out a plurality of cycles. You can

Then, the glass layer 21 thus formed is
The adhesion strength is extremely high because it is not simply attached to the outer surface of the protective layer 5 but is partially diffused and reacted. Further, it is more remarkable when the glass forming substance contains at least one of Bi ₂ O ₃ and Sb ₂ O ₃ .

As described above, by newly forming the glass layer 21 on the surface of the protective layer 5 made of a metal oxide, the characteristics described in the above (I) to (V) can be further exerted. In particular, even if the varistor element 1 is put into a gas or solution having a strong reducing property, the glass layer 21 is formed, so that the metal oxide of the protective layer 5 is not reduced and may be damaged. There wasn't.

The action of the reaction inhibitor not only suppresses the diffusion reaction between the protective layer 5 and the glass layer 21, but also prevents the varistor elements 1 from sticking to each other.

Furthermore, in the above various liquids, Al₂O₃,
TiO₂, ZnO, SiC, Si₃N _Four, SiO₂, Carbon fiber
Needle-like binding containing at least one type of fiber or glass fiber
When the crystal component is dispersed, the formed glass layer 21 is thermally treated.
Strength and mechanical strength, especially the cracks generated by heat shock, etc.
The occurrence and spread of racks and peeling could be suppressed.
Further, due to the anchor effect of the needle-shaped crystal component,
The adhesive strength of was stronger. In this case, the needle to disperse
It is more remarkable that the particle size of the crystal component is fine and uniform.
there were. Also, even if dispersed in the powder of the reaction inhibitor
I confirmed the effect.

Bi ₂ O ₃ and Sb ₂ are added to the needle-like crystal component.
It was more remarkable when at least one of O ₃ was contained. Furthermore, the same effect was obtained by forming a silicone-based or epoxy-based resin on the surface of the protective layer 5.

(Sixth Embodiment) The sixth embodiment of the present invention will be described below.

After the steps (7) to (13) shown in FIG. 10 were carried out in the same manner as in Examples 4 and 5, SiO ₂ , Ti were used.
An electroless Ni plating layer in which at least one kind of powder of O ₂ , Al ₂ O ₃ , MgO, and ZrO ₂ is dispersed is attached (14), and the following steps (15) to (17) are performed. Thus, an electronic component having the protective layer 5 having excellent reduction resistance shown in FIG. 6 was obtained.

The protective layer 5 obtained in Example 6 had Ni, SiO ₂ , TiO ₂ , Al ₂ O ₃ and M during reoxidation (16).
At least one kind of powder of gO and ZrO ₂ reacts with each other to form the protective layer 5 having excellent reduction resistance. In this case, the particle size of the powder to be dispersed is fine and uniform, and
The higher the purity, the more remarkable. In addition to the above-mentioned various powders, glass powder had the same effect.

As described above, in the varistor element 1 obtained by the above Examples 3 to 6, since the protective layer 5 having a dense structure is formed on the entire surface except the end face of the varistor element 1, the surrounding environment. For example, it is less likely to be affected by humidity, gas, acid, alkali and the like. Moreover, since the surface is covered with the hard protective layer 5, the mechanical strength is improved.

Further, what is important in the manufacturing process is (I) when depositing the electroless Ni plating layer or depositing the glass forming substance, make sure that no impurities are deposited on the surface of the varistor element 1. First, thoroughly wash with pure water or ion-exchanged water.

(II) Since the liquid containing the glass-forming substance is hydrolyzed, it is desirable that the water content of the varistor element 1 be sufficiently removed before the varistor element 1 is dipped.

(III) When the powder is dispersed in the electroless Ni plating solution, it is desirable to stir the powder sufficiently to improve the dispersibility.

Further, the protective layer 5 formed on the surface of the varistor element 1 has a part of its surface under the influence of hydrogen gas generated during the step of attaching (17) the Ni plating layer 4a and the solder plating layer 4b. It may be reduced and the resistance value may decrease.
Therefore, in order to prevent this phenomenon, (IV) it is desirable to form the glass layer 21 on the surface of the protective layer 5 to prevent the influence of hydrogen gas, as shown in the fifth embodiment.

(V) As shown in Example 6 above, it is desirable to form the reduction resistant protective layer 5 to prevent the influence of hydrogen gas.

(VI) After the plating step (17), it is desirable to oxidize the protective layer 5 whose surface is partially reduced by using an ammonia solution of hydrogen peroxide. In this case, an alkaline solution that does not affect the varistor element 1 may be used. Further, since this solution has a cleaning action, it can be used as a cleaning solution after the plating step (17).

In addition, as shown in the fifth embodiment, when the glass layer 21 is formed, the glass layer 2 is also formed on the surface of the upper layer 3b.
1 may be formed, and the plating layer may be difficult to adhere even if the plating step (17) is performed. Therefore, in order to solve this, (VII) a surface of the upper layer 3b is previously provided with a paste composed of laundry paste, a polysaccharide such as ethyl cellulose, a resist film made of polyvinyl alcohol, vinyl acetate, etc., and then a glass forming substance is added. It is desirable to have a step of adhering (18), heat treating (19), carbonizing the resist film, and removing it with an ultrasonic cleaner or the like. Then, when forming the resist film, it is possible to know whether or not the resist film can be uniformly formed by mixing a dye or a pigment. In addition,
In Examples 4 to 6 above, the protective layer 5 of metal oxide formed on the surface of the element is shown only for Ni, but what kind of oxide other than this is a metal having high resistance and chemical resistance? Anything is fine. Also, the forming method is shown only for electroless plating, but the same effect can be obtained by forming by vapor deposition, sputtering, dipping, thermal spraying, printing or the like.

In the laminated varistor of Examples 1 to 3, the protective layer 5 is formed on the surface of the varistor element 1 other than the portion where the external electrode 3 is formed. In the laminated varistor of Examples 4 to 6, the end face of the varistor element 1 is formed. A protective layer 5 was formed on the entire surface except the surface.

Therefore, the laminated varistors of Examples 4 to 6 are different from the laminated varistors of Examples 1 to 3 in the upper layer 3b.
Migration is unlikely to occur between the Ag external electrode and the internal electrode 2.

Moreover, in Examples 1 to 6, the thickness of the Ni plating to be the protective layer 5 is preferably 6 μm or less. The reason is that when the thickness of the Ni plating exceeds 6 μm, Ni may shrink and cracks or cracks may occur in the varistor element.

In the first to sixth embodiments, the laminated varistor is taken as an example. However, the present invention uses a ceramic porcelain such as a capacitor, thermistor, ceramistor, varistor, piezoelectric element, ferrite, ceramic substrate, or not. Also, the shape can be adapted to any shape such as a disk type, a cylindrical type, and a laminated type.

[0076]

As described above, according to the present invention, first, at least a pair of electrodes is formed on an element, and then a metal coating layer is deposited on the entire surface of the element except an electrode forming portion, and then heat treatment is performed in an oxidizing atmosphere. To form a protective layer made of metal oxide,
Further, a plating layer is formed on the electrode surface.

With this structure, a protective layer having a high resistance and a dense structure can be provided on the surface of the device.

Therefore, even if the element structure is porous, the dense protective layer can make it difficult to be affected by the surrounding environment, for example, moisture, gas, acid or alkali.

Further, even when the surface resistance of the element is low, the protective layer made of a metal oxide having a high resistance on the surface can suppress, for example, leakage current, flow of plating, and etching by the plating solution. .

Furthermore, since this protective layer is resistant to cracks and strains, and is dense, homogeneous, and solid, it enhances the mechanical strength of the device surface and prevents the occurrence of external damage or strain due to the impact received during the manufacturing process or mounting. it can.

As described above, the electronic component of the present invention has excellent reliability and has a very great practical effect.

[Brief description of drawings]

FIG. 1 is a sectional view of a varistor according to first and third embodiments of the present invention.

FIG. 2 is a sectional view of a varistor according to a second embodiment of the present invention.

FIG. 3 is a manufacturing process diagram of the varistor according to the first embodiment of the present invention.

FIG. 4 is a manufacturing process diagram of a varistor in the second embodiment of the present invention.

FIG. 5 is a manufacturing process diagram of a varistor in a third embodiment of the present invention.

FIG. 6 is a sectional view of a varistor according to the fourth and sixth embodiments of the present invention.

FIG. 7 is a sectional view of a varistor according to a fifth embodiment of the present invention.

FIG. 8 is a manufacturing process diagram of a varistor in a fourth embodiment of the present invention.

FIG. 9 is a manufacturing process diagram of a varistor in a fifth embodiment of the present invention.

FIG. 10 is a manufacturing process diagram of a varistor in a sixth embodiment of the present invention.

[Explanation of symbols]

 1 Varistor element 2 Internal electrode 3 External electrode 4 Plating layer 5 Protective layer 21 Glass layer

Claims (35)

[Claims] 1. An element, at least a pair of electrodes provided on the element surface, a metal oxide protective layer provided at least on the element surface other than the electrode forming portion, and a plating layer provided on the electrode surface. With electronic components. 2. The electronic component according to claim 1, wherein the element is made of ceramic porcelain. 3. The electronic component according to claim 1, wherein the resistance of the protective layer is higher than the resistance of the element. 4. The electronic component according to claim 1, wherein a glass layer is provided on the surface of the protective layer. 5. The electronic component according to claim 1, wherein the protective layer is made of a metal oxide having reduction resistance. 6. The electronic component according to claim 1, wherein the protective layer contains glass. 7. An element surface is formed with at least a pair of electrodes, and then a metal coating layer is formed on a portion other than an electrode forming portion of the element, and then the element is heat-treated in an oxidizing atmosphere to remove the element surface. A method of manufacturing an electronic component, comprising forming a protective layer made of a metal oxide obtained by oxidizing the metal coating layer, and further forming a plating layer on the surface of the electrode. 8. The method of manufacturing an electronic component according to claim 7, wherein the formation of the electrode and the formation of the protective layer made of a metal oxide are performed simultaneously. 9. The method of manufacturing an electronic component according to claim 7, wherein the metal coating layer is formed by an electroless plating method. 10. Ni, C as a material for electroless plating
10. Use of a material having one of u as a main component.
A method for manufacturing the described electronic component. 11. An electroless plating solution containing SiO ₂ , Ti
11. A powder containing at least one of O ₂ , Al ₂ O ₃ , MgO, and ZrO ₂ is dispersed.
A method for manufacturing the described electronic component. 12. The method of manufacturing an electronic component according to claim 9, wherein glass powder is dispersed in the electroless plating solution. 13. A metal coating layer is deposited, sputtered,
The method of manufacturing an electronic component according to claim 7, wherein the electronic component is formed by any one of dipping, thermal spraying, and printing. 14. After forming a plating layer on the electrode surface,
The method of manufacturing an electronic component according to claim 7, wherein the protective layer is oxidized by immersing it in an alkaline solution of hydrogen peroxide. 15. The method of manufacturing an electronic component according to claim 14, wherein aqueous ammonia is used as the alkaline solution. 16. A metal coating layer is formed on the entire surface of the device excluding a portion where an electrode is to be formed, an electrode is formed on a portion of the device where the electrode is to be formed, and then the device is oxidized. A method of manufacturing an electronic component, comprising performing a heat treatment in an atmosphere to form a protective layer made of a metal oxide obtained by oxidizing the metal coating layer on the surface of the element, and further forming a plating layer on the surface of the electrode. 17. The method of manufacturing an electronic component according to claim 16, wherein the formation of the electrode and the formation of the protective layer made of a metal oxide are performed simultaneously. 18. The method of manufacturing an electronic component according to claim 16, wherein the metal coating layer is formed by an electroless plating method. 19. Ni, C as a material for electroless plating
A method using one of u as a main component is used.
8. A method of manufacturing an electronic component according to item 8. 20. The electroless plating solution contains SiO ₂ , Ti
The powder containing at least one of O ₂ , Al ₂ O ₃ , MgO, and ZrO ₂ is dispersed.
9. The method for manufacturing an electronic component according to 9. 21. The method of manufacturing an electronic component according to claim 18, wherein glass powder is dispersed in the electroless plating solution. 22. A metal coating layer is deposited, sputtered,
The method of manufacturing an electronic component according to claim 16, wherein the electronic component is formed by any one of dipping, thermal spraying, and printing. 23. After forming a plating layer on the electrode surface,
The method of manufacturing an electronic component according to claim 16, wherein the protective layer is oxidized by immersing it in an alkaline solution of hydrogen peroxide. 24. The method of manufacturing an electronic component according to claim 23, wherein aqueous ammonia is used as the alkaline solution. 25. An element having a protective layer formed thereon is dipped in a liquid containing a glass-forming substance, and then the element is taken out of the liquid and heated, and a plating layer is further formed on the electrode surface of the element. A method of manufacturing an electronic component to be formed. 26. The liquid is Si (OR) ₄ (R is an alkyl group), a silicon compound represented by (Chemical Formula 1), and Ti (O).
R) ₄ (R is an alkyl group), a titanium compound represented by (Chemical Formula 2), Al (OR) ₃ (R is an alkyl group), an aluminum compound represented by (Chemical Formula 3) 26. The method of manufacturing an electronic component according to claim 25, comprising an additive including a glass forming substance and an organic binder, and an organic solvent. Embedded image Embedded image Embedded image 27. Al ₂ O ₃ , TiO ₂ , ZnO, Si
26. The method of manufacturing an electronic component according to claim 25, wherein a needle-shaped crystal component containing at least one kind of C, Si ₃ N ₄ , SiO ₂ , carbon fiber and glass fiber is dispersed in a liquid. 28. At least one kind of acicular crystal component of Bi ₂ O ₃ and Sb ₂ O ₃ is further dispersed.
A method for manufacturing the described electronic component. 29. A device having a protective layer formed thereon is dipped in a liquid containing a glass-forming substance, and then the device is taken out of the liquid. Then, a reaction inhibitor is brought into contact with the outer surface of the device. A method of manufacturing an electronic component, comprising heating and further forming a plating layer on the electrode surface of the element. 30. The reaction inhibitor is SiO ₂ , TiO ₂ , or A.
30. The method of manufacturing an electronic component according to claim 29, comprising at least one kind of l ₂ O ₃ , MgO, and ZrO ₂ . 31. An element having an electrode formed thereon is preliminarily provided with a resist film on the surface of the electrode, and then immersed in a liquid containing a glass-forming substance, and then the element is taken out of the liquid and then heated. Then, the resist film is carbonized at the same time when the glass layer is formed, then the carbonized resist film is washed and removed, and then a plating layer is formed on the electrode surface. 32. The resist film is formed of glue.
1. A method for manufacturing an electronic component according to 1. 33. The paste has a polysaccharide as a main component.
2. The method for manufacturing an electronic component according to 2. 34. An element on which a protective layer is formed is dipped in a liquid containing a resin component, and then the element is taken out of the liquid and then heat-cured, and a plating layer is formed on the electrode surface of the element. Electronic component manufacturing method. 35. The method of manufacturing an electronic component according to claim 34, wherein the resin is a silicone type or an epoxy type.