JP2000058306A - Chip-shaped electronic component - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a base layer which contains metallic powder but not glass frit, and to prevent plating currents from easily flowing on the outer surface of an electronic component main body at the time of a plating operation for forming an outer layer due to the segregation of the glass frit or the like. SOLUTION: At plating operation for forming an outer layer 5 on an electronic component main body 2, a base layer 4 is formed as a material composition which does not contain glass frit which is insulator preventing a plated growing film 6 from being formed. Thus, the flow of plating currents on the base layer 4 can be guaranteed, and the outer layer 5 can be positively formed on the base layer 4, while the formation of the plated growing layer 6 can be suppressed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a chip-shaped electronic component, and more particularly to an improvement in a material for forming a terminal electrode formed on an outer surface of a chip-shaped electronic component body.

[0002]

2. Description of the Related Art Chip-shaped electronic components which are of interest to the present invention include, for example, chip-shaped negative characteristic thermistor elements. FIG. 1 is a front view of the chip-shaped negative temperature coefficient thermistor element 1 in a partially broken view.

The negative characteristic thermistor element 1 includes a chip-shaped electronic component main body 2 and terminal electrodes 3 formed on the outer surface of the electronic component main body 2 and on each end.

The electronic component body 2 is made of a ceramic material that gives a negative thermistor characteristic. Inside the electronic component main body 2, a plurality of internal electrodes (not shown) are laminated. These internal electrodes are electrically connected to any of the terminal electrodes 3.

[0005] The terminal electrode 3 is usually formed by applying a paste containing a metal powder on the outer surface of the electronic component body 2 and baking it, and is formed by plating on the underlayer 4. And a skin layer 5 made of a metal film.

The paste used for forming the above-described underlayer 4 usually contains glass frit in addition to metal powder.

For the plating for forming the outer skin layer 5, for example, a rotary barrel method is applied. That is,
The plurality of electronic component bodies 2 each having the underlayer 4 formed thereon are
Put it in a rotating barrel with conductive media,
The plating operation is performed by being immersed in the plating solution. At this time, when the medium contacts the underlayer 4 in the barrel, the plating current flows through the medium to the underlayer 4, whereby the underlayer 4
An outer skin layer 5 is formed thereon by plating.

[0008]

However, in the above-described plating for forming the outer skin layer 5, as shown by a broken line in FIG.
The plating growth film 6 may be undesirably formed directly on the outer surface of the electronic component body 2. The cause is as follows.

As described above, the material constituting at least the outer surface of the electronic component body 2 is a negative thermistor material, for example, a low resistivity ceramic material having a resistivity of 2000 Ω · cm or less, ie, a semiconductor. Therefore, at the time of the plating process, a current also flows to a region other than the base layer 4 in the electronic component body 2.

On the other hand, the paste for forming the underlayer 4 contains glass frit as an insulator as described above. However, this glass frit
The firing of the paste may cause segregation on the ceramic surface, that is, on the electrode interface. Of the glass frit segregated on the ceramic surface, that is, on the electrode interface, the easily reduced (eg, Bi ₂ O ₃ ) glass frit has high conductivity during plating, and as a result, current easily flows on the ceramic surface. Further, the glass frit may segregate in a state of being more distributed on the surface side of the underlayer 4. In this case, the current supplied from the medium during the plating process hardly flows on the underlayer 4 due to the influence of the glass frit.

From the above, as compared with the case where no glass frit exists near the interface between the electrode and the ceramic and the case where the glass frit is not segregated on the surface of the underlayer 4, the outer surface of the electronic component body 2 is more likely to be formed. A large amount of current flows, and as a result, plating growth tends to occur on the outer surface of the electronic component body 2,
The plating growth film 6 is formed.

As described above, if the plating growth film 6 is formed undesirably, the insulation resistance between the two terminal electrodes 3 decreases, and in extreme cases, these terminal electrodes 3 May cause a short circuit. As a result, in the case of the negative temperature coefficient thermistor element 1, the difference in resistance value before and after the plating process for forming the skin layer 5 becomes large,
The problem of lack of stability results.

In particular, such a problem arises as shown in FIG. 1 in that two terminal electrodes 3 are formed on the outer surface of the electronic component body 2 with their edges facing each other. When you are, it becomes more serious.

Conventionally, in order to prevent such a problem from occurring as much as possible, for example, the specific resistance of the material constituting the electronic component body 2 is increased, or the current density during the plating operation is reduced. Suppressing leakage of current to the outer surface of the electronic component body 2, thereby suppressing deposition of the plating growth film 6 on the outer surface of the electronic component body 2;
Such measures are taken.

However, in order to reduce the resistance of the electronic component main body 2 as a whole in order to compensate for this while increasing the specific resistance of the material constituting the electronic component main body 2, the internal electrodes of the electronic component main body 2 are required to have a higher resistance. It is necessary to increase the number of layers, which leads to an increase in cost and an increase in capacitance.
Cause the problem.

On the other hand, when an attempt is made to reduce the current density during the plating operation, the time required for the plating is lengthened, which leads to an increase in cost and to the electronic component body 2.
This causes a problem that the amount of elution of the ceramic material constituting the material increases.

An object of the present invention is to provide a chip-shaped electronic component capable of solving the above-mentioned problems.

[0018]

SUMMARY OF THE INVENTION The present invention comprises a chip-shaped electronic component body and terminal electrodes formed on the outer surface of the electronic component body, and at least the outer surface of the electronic component body has, for example, 2000 Ω. Cm or less such that the terminal electrodes are made of a low-resistivity ceramic material, and the terminal electrodes are formed by applying a paste containing a metal onto the outer surface of the electronic component body and firing the same. Comprising a skin layer made of a metal film formed by plating,
The present invention is directed to such a chip-shaped electronic component, and is characterized in that the underlayer contains a metal powder but does not contain a glass frit in order to solve the above-described technical problem.

In the present invention, the underlayer is preferably formed by applying a paste containing a metal powder but not containing a glass frit and firing the paste.

Further, the present invention is advantageously applied to a negative characteristic thermistor element. In this case, the low resistivity ceramic material is a negative characteristic thermistor material.

Further, the present invention is advantageously applied to a chip-shaped electronic component in which a plurality of terminal electrodes are formed on the outer surface of the electronic component body with their respective edges facing each other. .

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS For describing one embodiment of the present invention, reference is made to FIG.

The negative temperature coefficient thermistor element 1 according to this embodiment is characterized by the material for forming the underlayer 4, and the other structure is substantially the same as the conventional one.

That is, the negative characteristic thermistor element 1 includes a chip-shaped electronic component main body 2 and terminal electrodes 3 formed on the outer surface of the electronic component main body 2. Terminal electrode 3
Are formed on each end of the electronic component main body 2, and the two terminal electrodes 3 are in a state where their respective edges face each other on the outer surface of the electronic component main body 2.

The electronic component body 2 is, for example, 2000 Ω ·
A low specific resistance ceramic material having a specific resistance of not more than 1 cm, more specifically, a negative temperature coefficient thermistor material is formed therein, and a plurality of internal electrodes (not shown) are formed in a laminated shape therein. These internal electrodes are terminal electrodes 3
Is electrically connected to any one of

The terminal electrode 3 includes a base layer 4 formed by applying a paste containing a metal powder on the outer surface of the electronic component body 2 and firing the same, and a metal film formed on the base layer 4 by plating. And an outer skin layer 5 comprising:

In this embodiment, the underlayer 4 contains metal powder but does not contain glass frit. As described above, the electronic component main body 2 is formed to form the base layer 4 so as not to include the glass frit.
A paste containing metal powder but not containing glass frit is used as a paste applied on the outer surface of the substrate and fired.

That is, the paste for forming the underlayer 4 can be provided, for example, by a mixture of a specific metal powder and a varnish, and by appropriately selecting conditions such as a firing temperature and a firing time. Thus, a thick film to be the base layer 4 can be formed using the paste containing no glass frit.

For example, when the above-mentioned paste contains silver powder, varnish is added to 50 to 80% by weight of silver powder.
By adding 0 to 50% by weight, a paste can be obtained, and by firing at a temperature of 600 to 900 ° C. for 1 to 5 hours, a thick film to be the base layer 4 can be formed.

When the paste contains palladium powder, the paste can be obtained by adding 20 to 50% by weight of a varnish to 50 to 80% by weight of the palladium powder. 1-5 at temperature
By baking for a time, a thick film to be the base layer 4 can be formed.

When the paste contains both silver powder and palladium powder, the varnish is added by 10 to 40% by weight to 40 to 60% by weight of silver powder and 20 to 30% by weight of palladium powder. By baking at a temperature of 600 to 1000 ° C. for 1 to 5 hours, a thick film to be the base layer 4 can be formed.

When the paste contains copper powder,
20 to 50 varnish is added to 50 to 80% by weight of copper powder.
By adding wt%, a paste can be obtained, and by baking at a temperature of 400 to 700 ° C. for 1 to 5 hours, a thick film to be the base layer 4 can be formed.

When the paste contains nickel powder, the paste can be obtained by adding 20 to 50% by weight of a varnish to 50 to 80% by weight of the nickel powder. By baking at a temperature for 1 to 5 hours, a thick film to be the base layer 4 can be formed.

As described above, when the glass frit is not included in the underlayer 4, the phenomenon that the plating current easily flows on the outer surface of the electronic component body 2 due to the segregation of the glass frit cannot occur. Therefore, a favorable flow of the plating current on the underlayer 4 is guaranteed, and the current can be made hard to flow on the outer surface of the electronic component body 2 during the plating operation. Therefore, it is possible to prevent the plating growth film 6 as indicated by the broken line in FIG. 1 from being undesirably formed.

In order to confirm the effect of the present invention, the following experiment was conducted.

Referring to FIG. 1, negative thermistor element 1
The electronic component body 2 has a specific resistance of about 2000Ω
· A material composed of a negative characteristic thermistor material having a size of 1.6 mm × 0.8 mm × 0.8 mm was prepared.

In order to form the terminal electrodes 3 at both ends of the electronic component body 2, first, a paste containing a specific metal powder, which will be described later, is applied to the outer surface of the electronic component body 2 and fired to form a base layer. Then, a skin layer 5 made of a specific metal film described later was formed on the underlayer 4 by plating.

More specifically, pastes having the compositions shown in Table 1 below were prepared as pastes for forming the underlayer 4.

[0039]

[Table 1] As can be seen from Table 1, each paste according to Examples 1 to 5 contains only a specific metal powder and a varnish, and does not contain a glass frit. On the other hand, the paste according to each of Comparative Examples 1 to 5 further includes a glass frit in addition to the composition corresponding to the paste according to each of Examples 1 to 5, respectively.

Examples 1 to 5 and Comparative Example 1 as described above
To 5 are applied to each end of the electronic component body 2 and baked to form an underlayer 4. Then, on these underlayers 4, nickel plating, tin plating, and solder plating are applied. With a current density of 0.2 A / dm ² ,
The coating was performed in a plating time of 60 minutes to form the outer skin layer 5.

After performing the above-described plating treatment, it is evaluated whether or not the plating growth film 6 is formed on the outer surface of the electronic component body 2. The maximum growth width W was measured as shown in FIG. The measurement results (unit: μm) of the growth width W are shown in Table 2 below.

[0042]

[Table 2] In Table 2, as can be seen by comparing each of Examples 1 to 5 and each of Comparative Examples 1 to 5, plating was performed on the underlayer 4 containing glass frit as in Comparative Examples 1 to 5. In this case, while the plating growth film 6 having a relatively large growth width W is formed, as in Examples 1 to 5,
When plating is performed on the underlayer 4 containing no glass frit, the plating growth film 6 is not formed or hardly formed.

Although the above-described embodiment is directed to the negative temperature coefficient thermistor element 1 as shown in FIG. 1, the present invention provides at least the outer surface of the electronic component body made of a low resistivity ceramic material, On this outer surface, a terminal electrode is formed with a base layer formed by sintering a paste and a skin layer formed by plating. Such a chip-shaped electronic component is also advantageous for other chip-shaped electronic components. Applied.

In FIG. 1, the terminal electrode 3 is formed on each end of the electronic component main body 2. However, a chip-like electronic device in which the terminal electrode is formed in another area on the outer surface of the electronic component main body. The present invention can be advantageously applied to parts.

[0045]

As described above, according to the present invention, at least the outer surface of the electronic component body is made of a low resistivity ceramic material, and the terminal electrode formed on the outer surface of the electronic component body is An underlayer formed by applying and firing a paste containing a metal powder on the outer surface of the electronic component body, and an outer layer made of a metal film formed by plating on the underlayer, such In the chip-shaped electronic component, the base layer contains the metal powder but does not contain the glass frit.Therefore, during the plating operation for forming the outer skin layer due to segregation of the glass frit, the plating current is reduced. It is possible to prevent the electronic component from easily flowing on the outer surface.

Therefore, it is possible to suppress an undesired formation of a plating growth film on the outer surface of the electronic component body due to a relatively large plating current flowing on the outer surface of the electronic component body having a low specific resistance. .

Therefore, not only the appearance failure of the chip-shaped electronic component due to such a plated growth film can be prevented, but also the reduction in insulation resistance or short circuit caused by the plated growth film can be suppressed.

In the present invention, if the paste used to form the underlayer does not contain glass frit, the underlayer without glass frit can be easily formed as described above. . Also, since no glass frit is contained at the stage of the paste, it is not necessary to pay attention to prevent segregation of the glass frit in firing for forming the underlayer, and therefore,
The baking process for forming the underlayer can easily proceed.

Further, a negative characteristic thermistor material is used as the low specific resistance ceramic material constituting the electronic component body, and when the present invention is applied to a negative characteristic thermistor element, resistance variation due to formation of an undesired plating growth film is prevented. Therefore, a negative temperature coefficient thermistor element can be manufactured with stable quality.

Further, when a plurality of terminal electrodes are formed on the outer surface of the electronic component body with their edges facing each other, undesired formation of the plated growth film causes the insulation resistance to decrease. The above-described effects of the present invention are more meaningfully exhibited because the situation is more likely to cause a drop or a short circuit.

[Brief description of the drawings]

FIG. 1 is a partially cutaway front view showing the appearance of a negative characteristic thermistor element 1 as an example of a chip-shaped electronic component of interest to the present invention. One embodiment of the present invention and the present invention are to be solved It is for explaining each problem.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Negative thermistor element (chip-shaped electronic component) 2 Electronic component main body 3 Terminal electrode 4 Underlayer 5 Outer layer

 ──────────────────────────────────────────────────の Continued on the front page F term (reference) 5E028 BA23 BB10 CA02 JC01 JC02 JC03 JC06 JC12 5E032 BA23 BB01 BB10 CA02 CC06 CC14 5E033 AA42 BC01 BD01 BG03 BG08 BH02 5E034 BB01 DC01 DC03 DC05 DC09 DE16

Claims (4)

[Claims] 1. An electronic component body comprising: a chip-shaped electronic component main body; and a terminal electrode formed on an outer surface of the electronic component main body, wherein at least an outer surface of the electronic component main body is made of a low resistivity ceramic material. The terminal electrode includes a base layer formed by applying and firing a paste containing a metal powder on the outer surface of the electronic component body, and a skin layer made of a metal film formed by plating on the base layer. The chip-like electronic component, wherein the underlayer contains the metal powder but does not contain glass frit. 2. The underlayer containing the metal powder,
The chip-shaped electronic component according to claim 1, wherein the chip-shaped electronic component is formed by applying and firing a paste that does not include a glass frit. 3. The chip-shaped electronic component according to claim 1, wherein the low resistivity ceramic material is a negative temperature coefficient thermistor material. 4. The chip according to claim 1, wherein the plurality of terminal electrodes are formed on the outer surface of the electronic component main body with their respective edges facing each other. Electronic components.