JPH08162304A - Electronic part and its manufacture - Google Patents

Abstract

PURPOSE: To obtain protective films having high adhesion strength, and strong to heat and impulses by forming protective films with scattered needlelike crystal components on the periphery of an element, diffusing the components of these protective films between the element surface and the protective films, and providing diffusion layers. CONSTITUTION: A plurality of internal electrodes 2 are provided in a varistor element 1, and external electrodes 3 are provided on both ends of the element. Protective films 4 being scattered needlelike crystal components are formed by adhesion, on both upper and lower surfaces of the varistor element 1 and on a part of the surface of the upper layer 3b touching those surfaces. Besides, layers 5 in which components of the protective films 4 have diffused are formed on the surface of the varistor element 1. These layers 5 contain at least one kind of Si, Ti, and Al. Here, the needlelike crystal components contain at least one kind of Al2 O3 , TiO2 , ZnO, SiC, Si3 N4 , SiO2 , carbon fiber, and glass fiber.

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]

The conventional protective film has been formed by coating glass on the outer peripheral portion of the element, for example, but it has a problem of low adhesive strength. That is, since the glass was simply attached to the outer surface of the element, it was peeled off or cracked due to expansion and contraction due to impact or heat. Therefore, it is an object of the present invention to provide an electronic component having a protective film that has high adhesion strength and is resistant to heat and impact.

[0004]

In order to achieve this object, the present invention forms a protective film in which needle-like crystal components are dispersed on the outer periphery of the device, and at the same time, the device surface and the protective film are formed. In between, a component of the protective film is diffused to provide a diffusion layer.

[0005]

With the above structure, (1) since a part of the protective film is diffused on the surface of the device, the conclusion is that the adhesion strength of the protective film to the device is extremely strong. Moreover, it is possible to prevent moisture and the like from entering the inside of the element. (2) The acicular crystal component is dispersed in the protective film, and even if a crack occurs, the crack is prevented from spreading, and as a result, a protective film resistant to heat and impact can be formed.

As described above, it is possible to provide an electronic component having excellent moisture resistance and thermal shock resistance.

[0007]

【Example】

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

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, MnO₂It is formed by adding
is there. The internal electrode 2 has Ni as a main component and a sub-component as
Li₂CO₃It is formed by adding Further
In the external electrode 3, the lower layer 3a is mainly composed of Ni
As Li₂CO₃To form the upper layer 3b.
It is formed by g. With the above configuration,
Upper and lower surfaces of the switching element 1 and the surface of the upper layer 3b in contact therewith
A protective film 4 in which needle-shaped crystal components are dispersed is attached to a part of the
Is formed.

Further, here, a layer 5 in which the components of the protective film 4 are diffused is formed on the surface of the varistor element 1, and the layer 5 has a structure containing at least one kind of Si, Ti and Al. ing. Therefore, the varistor element 1 has its outer surface covered with the protective film 4 and the external electrode 3 in which needle-like crystal components are dispersed, and the layer 5 in which the components of the protective film 4 are diffused on the surface of the varistor element 1. Since it is interposed, its airtightness is extremely high, so that it can be surely protected from moisture and the like, and at the same time, the acicular crystal component prevents cracking of the protective film 4, and the varistor element 1 and Since it has a function of an anchor effect that strengthens the adhesion of the above, the protective film 4 that is resistant to thermal shock can be formed.

FIG. 2 shows a manufacturing process. As shown in (5), a ceramic sheet 1a was produced by mixing raw materials, pulverizing, slurrying, and sheet forming.

A ceramic sheet 1a and an internal electrode 2 were laminated (6), which was cut (7), de-baked / calcined (8) and chamfered (9).

Next, the lower layer 3a is formed on the end face of the varistor element 1.
Ni external electrode to be applied is applied (10), and 1200 to 13
Reduction baking is performed at 00 ° C. (11), and then an Ag external electrode to be the upper layer 3b is applied (12) on the lower layer 3a, and 7
Heat (13) to reoxidize at 00-850 ° C. Next, the reoxidized varistor element 1 was immersed in a liquid containing a protective film forming substance, and the protective film forming substance was attached (14) to the surface of the varistor element 1.

Thereafter, a ceramic plate 19 is provided on the pan 18 shown in FIG. 3, and the varistor element 1 is embedded in the powder 20 on the plate 19 and heat-treated at 200 to 600 ° C. (15).
did.

Here, the powder 20 is made of Al ₂ O ₃ , TiO ₂ ,
It is a powder composed of needle-like crystal components containing at least one kind of ZnO, SiC, Si ₃ N ₄ , SiO ₂ , carbon fiber and glass fiber.

The powder 20 is mixed with Bi ₂ O ₃ and Sb ₂ O ₃
By mixing at least one of the above, the diffusivity is improved.

As the liquid containing the substance for forming a protective film, Si (OR) ₄ (R is an alkyl group), a silicon compound represented by Chemical formula ₄ , Ti (OR) ₄ (R is an alkyl group), Titanium compound represented by Chemical formula 5, Al (OR)
₃ (R is an alkyl group), at least one or more of the aluminum compounds represented by (Chemical Formula 6), and a substance composed of Na, Si, B, Bi, Sb, Pb, etc. as a glass forming substance, As the organic binder, a mixture of polyvinyl alcohol, ethyl cellulose, butyral resin and the like and an organic solvent such as alcohol, ketone and ether was used.

[0017]

[Chemical 4]

[0018]

Embedded image

[0019]

[Chemical 6]

If a liquid in which needle-like crystal components are dispersed in advance is used for this liquid, the protective film 4 is easily formed and the varistor elements 1 are less likely to stick to each other.

After that, chamfering (16) and plating (17)
By performing the above, as shown in FIG. 1, an electronic component having a protective film 4 in which needle-shaped crystal components were dispersed and a layer 5 in which the components of the protective film 4 were diffused was obtained.

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

In the same manner as in Example 1, the varistor element 1 heated (13) for reoxidation contains the protective film forming substance in which the powder of the needle-shaped crystal component described in Example 1 is dispersed. By immersing in a liquid, a substance for forming a protective film and a needle-shaped crystal component were attached (14) to the surface of the varistor element 1.

Then, as shown in FIG. 4, it was placed on a nickel net 21 and heat-treated (15) at 200 to 600.degree. After that, chamfering (16) and plating (17) are performed,
An electronic component was obtained as shown in FIG.

At this time, in the heat treatment (15), the varistor element 1 may be embedded in the powder 20 as shown in FIG.

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

In the same manner as in Example 1, the varistor element 1 heated (13) for reoxidation is embedded in the powder 20 as shown in FIG. 3, and the liquid containing the protective film forming substance is powdered. Permeate from above the body and heat-treat at 200-600 ℃ (15)
Then, the protective film 4 was formed, and then chamfering (16) and plating (17) were performed to obtain the electronic component shown in FIG.

As described above, by carrying out Examples 1 to 3, it was possible to obtain an electronic component having a protective film 4 having high adhesive strength and being resistant to heat and impact.

Here, the protective film 4 obtained in Examples 1 to 3
(1) The surface of the varistor element 1 should be 1-2 from the surface.
The protective film 4 has a uniform film thickness of about μm, and the diffused layer 5 of about 1 μm is formed on the surface of the varistor element 1. Here, when the thickness of the protective film 4 exceeds 3 μm, peeling is likely to occur and the adhesion strength is lowered, and conversely, when it is less than 1 μm, the film thickness becomes non-uniform, which is a factor of deterioration of moisture resistance. The film pressure can be adjusted by the amount of organic solvent.

(2) The acicular crystal component was uniformly dispersed in the protective film 4. When the protective film 4 in which the needle-shaped crystal components are dispersed and the protective film in which the crystalline components are not dispersed are compared with each other, there is a large difference in thermal shock resistance. For example, when a temperature cycle test of −55 to 125 ° C. was performed, cracks and peeling were not found in the former protective film 4, but in the latter protective film, a large number of cracks were generated in the vicinity of the external electricity 3b, and the moisture resistance was high. It became a factor of sexual deterioration. The reason for this is considered to be that the needle-shaped crystal component suppresses crack propagation and further strengthens the adhesion strength with the varistor element 1 by the anchor effect.

(3) Since the protective film 4 and the layer 5 formed by partially diffusing the components of the protective film 4 have high resistance, migration does not occur.

(4) The protective film 4 is formed by plating (17).
It has an excellent acid resistance that does not cause plating flow and is not affected by the plating flow.

In Examples 1 to 3, the protective film-forming substance was deposited and heat-treated only once, but it was more uniform if it was deposited a plurality of times (2 or 3 times), especially 2 or 3 times. The protective film 4 having a film thickness was formed. Further, when the protective film forming substance or at least one of Bi ₂ O ₃ and Sb ₂ O ₃ was added to the powder 20, the diffused layer 5 was formed more easily. Furthermore, in Examples 1 to 3, since the protective film 4 is also formed on the outer surface of the external electrode 3, chamfering (1
6) is performed to remove the protective film 4 on the external electrode 3b. After that, Ni plating and solder plating (1
7) should be performed.

Also, in Examples 1 to 3, only the method of immersing the protective film forming substance in the liquid was shown, but printing, thermal spraying, or the use of a centrifuge can also produce the same effect. can get. Further, in each embodiment, a laminated varistor is taken as an example, but the present invention uses a ceramic porcelain such as a capacitor, a thermistor, a ceramistor, a varistor, a piezoelectric element, a ferrite, and a ceramic substrate. It can be applied to any type such as a mold, a cylinder type, and a laminated type.

[0035]

As described above, according to the present invention, the surface of the device is
In addition to forming a layer in which the components of the protective film are diffused, a protective film in which needle-like crystal components are dispersed is provided on the layer, and with the above configuration, the protective film components diffuse to the element surface. In addition, since the needle-shaped crystal component suppresses the propagation of cracks in the protective film and exerts an anchor effect, the conclusion is that the adhesion strength of the protective film to the element is extremely high, and at the same time, it is very strong against thermal shock. It is possible to manufacture an element having high resistance to humidity and thermal shock resistance.

Further, since the layer formed by partially diffusing the components of the protective film on the surface of the element and the protective film have a high resistance, it is possible to prevent the migration of the external electrodes and the occurrence of plating flow.

Furthermore, since the protective film of the present invention is composed of an inorganic component, it does not undergo strong modification even with chemical resistance or heat.

As described above, the electronic component of the present invention has excellent moisture resistance, thermal shock resistance, and chemical resistance.

[Brief description of drawings]

FIG. 1 is a sectional view of a varistor according to an embodiment of the present invention.

FIG. 2 is a manufacturing process diagram of a varistor according to an embodiment of the present invention.

FIG. 3 is a sectional view showing a manufacturing process of a varistor according to an embodiment of the present invention.

FIG. 4 is a sectional view showing a manufacturing process of a varistor according to another embodiment of the present invention.

[Explanation of symbols]

 1 Varistor element 2 Internal electrode 3 External electrode 4 Protective film 5 layers

Claims (10)

[Claims] 1. An element, an electrode provided on the surface of the element, a diffusion layer provided on at least a portion of the element surface not covered by the electrode, and a protective film provided on at least the diffusion layer. The electronic component includes a component forming the protective film and a component of the device, and the protective film includes needle-like crystals. 2. The electronic component according to claim 1, wherein the protective film contains at least one kind of Si, Ti and Al. 3. The needle-shaped crystal is Al₂O₃, TiO₂, Z
nO, SiC, Si₃N _Four, SiO₂, Carbon fiber, glass
The electronic according to claim 1, comprising at least one kind of fiber.
parts. 4. A method of manufacturing an electronic component, wherein a needle-like crystal component is brought into contact with an outer surface of an element having a protective film forming substance adhered to the surface to heat the element. 5. A method of manufacturing an electronic component, which comprises heating a substance obtained by contacting a material obtained by mixing a substance for forming a protective film and a needle-shaped crystal component with the outer surface of the device, and heating. 6. An electronic component for heating an element by immersing the element in a liquid containing a substance for forming a protective film, then taking out the element, and then bringing a needle-shaped crystal component into contact with the outer surface of the element to heat the element. Production method. 7. The method of manufacturing an electronic component according to claim 6, wherein a needle-shaped crystal component is previously dispersed in a liquid containing a protective film forming substance. 8. A liquid containing a substance for forming a protective film, containing Bi.
7. At least one of ₂ O ₃ and Sb ₂ O ₃ is dispersed.
A method for manufacturing the described electronic component. 9. The liquid is Si (OR) ₄ (R is an alkyl group), a silicon compound represented by Chemical formula 1, Ti (OR)
₄ (R is an alkyl group), a titanium compound represented by (Chemical Formula 2), Al (OR) ₃ (R is an alkyl group), at least one or more of an aluminum compound represented by (Chemical Formula 3), and at least 7. The method of manufacturing an electronic component according to claim 6, which is composed of an organic solvent and an additive containing a glass-forming substance and an organic binder. Embedded image Embedded image Embedded image 10. An acicular crystal component further comprising Bi ₂ O ₃ and S.
The method of manufacturing an electronic component according to claim 6, wherein at least one of b ₂ O ₃ is dispersed.