JP2000182435A - Conductive paste and ceramic electronic component - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance conductivity and ensure sufficient adhesive strength to a substrate by specifying a contact angle of glass frit to be a specified value or lower with respect to a metal plate of the same kind as that of a metal powder. SOLUTION: Glass frit whose contact angle to a metal plate of the same kind as metal powder is 30 degrees or less, when viscosity is 104 Pa.s. Liquid phase sintering of the metal powder is accelerated, the sintered body is made dense, and the conductivity and adhesive strength of a conductive film itself after sintering are enhanced. Superior conductivity and sufficient adhesive strength for various substrates are ensured. Since conductive paste is printed on an insulating ceramic substrate and a conductor pattern is formed through sintering, adhesive strength on the interface between a glass component layer and a conductor component layer in the conductor pattern is improved. Adhesive strength of the conductive paste with the insulating ceramic substrate is improved, reliability is improved, wiring resistance is decreased, and high frequency characteristics are improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a conductive paste obtained by mixing a metal powder, a glass frit, and an organic vehicle, and a ceramic electronic component using the conductive paste.

[0002]

2. Description of the Related Art In general, a conductive paste is applied on an insulating substrate made of glass, ceramic, or the like by a screen printing method or a direct drawing method, and then baked to obtain a desired conductive pattern such as an electrode or a wiring pattern. Technology to form the
That is, the thick film technology has been widely put to practical use. Depending on the firing temperature, the conductive paste used here is a high-temperature firing type that fires at around 800 to 950 degrees,
It can be classified as a medium temperature firing type firing at 50 degrees or less and near 600 degrees.

[0003] High-temperature sintering type conductive pastes provide excellent conductive properties, especially high conductivity and high adhesion to substrates, but because they are baked at high temperatures, they can cause thermal damage to printed resistors and dielectrics. There is a disadvantage of giving. On the other hand, the medium temperature firing type has the advantage that a circuit can be formed by using a normal printed resistor or dielectric as it is, but has the disadvantage that the conductor characteristics are inferior to the high temperature firing type. have.

In general, a medium-temperature firing type conductive paste is obtained by dispersing metal powder and glass frit in an organic vehicle. Here, the metal powder forms a conductor layer by sintering at the time of firing, and the glass frit has an effect of bonding the conductor layer made of the metal powder to the substrate. The organic vehicle also acts as an organic medium for converting these powders into a printable paste.

[0005] The adhesion action of the glass frit to the substrate is called a glass bonding action. When the conductive paste is fired, the glass frit melts and moves to the interface with the substrate.
The fired thick film conductor is brought into close contact with the substrate. Therefore, after firing, there are many metal components in the upper layer portion of the thick film, and the glass component increases in the lower layer portion, so that the glass component reaches out between the metal particles from above the substrate surface, The conductor layer and the substrate are mechanically coupled to each other (hereinafter, the upper portion of the thick film having a large amount of metal component is referred to as a conductor component layer, and the lower portion having a large amount of glass component (glass frit) is referred to as a glass component layer. There is no clear boundary between the conductor component layer and the glass component layer).

[0006]

In recent years, in the technical field of thick-film circuit boards, there has been an increasing demand for higher density and multi-functionality of the boards. In order to minimize thermal damage, medium-temperature firing is desired.

However, in the conventional conductive paste using glass frit, since the wettability between the substrate and the conductive paste is regarded as important, the bonding strength at the interface between the glass component layer and the conductive component layer tends to be weak. And also
The glass frit hinders the sintering of the metal particles and causes a reduction in the strength and conductivity of the thick film itself after sintering.

The present invention has been made in view of the above-mentioned circumstances, and has as its object to provide a conductive paste having excellent conductivity and sufficient adhesive strength to a substrate. And a ceramic electronic component using the same.

[0009]

That is, the present invention relates to a conductive paste obtained by mixing a metal powder, a glass frit and an organic vehicle, wherein the contact angle of the glass frit is 10 ⁴ Pa · s. The conductive paste according to claim 1, wherein the angle is 30 degrees or less with respect to a metal plate of the same kind as the metal powder.

The conductive paste according to the present invention is characterized in that the metal powder has an average particle size in a range of 0.5 to 10 μm.

The conductive paste of the present invention is characterized in that the content of the glass frit is in the range of 2 to 15% by weight based on the total amount of the conductive paste.

The conductive paste of the present invention is characterized in that the metal powder is at least one selected from the group consisting of copper, silver, gold, platinum and palladium, or an alloy thereof.

Further, the present invention is characterized in that a desired conductive pattern is formed by firing the conductive paste according to any one of claims 1 to 4 printed on an insulating ceramic substrate. And a ceramic electronic component.

According to the conductive paste of the present invention, the contact angle between the metal powder and the same kind of metal plate has a viscosity of 10 ⁴ Pa ·
In the case of s, the glass powder contains glass frit of 30 degrees or less, so that the liquid phase sintering of the metal powder is promoted and the sintered body becomes more dense, and the conductivity of the conductive film itself after sintering and The adhesion strength is improved. Therefore, a conductive paste having excellent conductivity and securing sufficient adhesive strength to various substrates can be obtained.

Further, according to the ceramic electronic component of the present invention, the conductive paste of the present invention is printed on an insulating ceramic substrate and is formed into a conductor pattern after firing. The bonding strength at the interface with the conductor component layer is improved, and thus the bonding strength between the conductive paste and the insulating ceramic substrate is improved, and a highly reliable ceramic electronic component is obtained. Further, since the conductor pattern is a conductor pattern having excellent conductivity, a ceramic electronic component having excellent high-frequency characteristics can be obtained.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION The conductive paste according to the present invention comprises:
It is produced by dispersing metal powder and glass frit in an organic vehicle, wherein the glass frit has a contact angle with a metal plate at a viscosity of 10 ⁴ Pa · s of 30 degrees or less. . As the metal plate, for example, when the metal powder is a copper powder, a copper plate is used, and when the metal powder is a silver powder, a silver plate is used. . The viscosity of 10 ⁴ Pa · s is a value set so that the difference in the contact angle due to the glass frit occurs most at such a viscosity. For example, when the viscosity of the glass frit is greater than 10 ⁴ Pa · s, it takes time for the difference in the contact angle due to the glass frit to appear, and
If it is less than ⁴ Pa · s, the metal plate will be wet at a stretch and the difference in the contact angle due to the glass frit will hardly appear.

Here, as shown in FIG. 1, when a glass frit having a small contact angle is used, the wiring resistance tends to decrease. On the other hand, when a glass frit having a contact angle of more than 30 degrees is used, a wiring resistance of more than 3.0 mΩ / □ is exhibited. From this, it is understood that when the contact angle is 30 degrees or less, the sinterability of the conductor pattern is improved and excellent conductivity is obtained.

When a glass frit having a contact angle of more than 30 degrees is used, the initial adhesive strength and the adhesive strength after heat aging are reduced. On the other hand, when the contact angle is 3
When a glass frit of 0 ° or less is used, the initial adhesive strength is large, and the decrease in adhesive strength due to heat aging is small. That is, sufficient adhesive strength is secured with time.

FIG. 1 shows the case where copper powder and copper oxide powder are used as the metal powder. The type and content of the metal powder, the content of the glass frit, the type of the organic vehicle,
Even when the content and the like are variously changed, substantially the same effect can be obtained by using a glass frit having the contact angle of 30 degrees or less.

In the conductive paste of the present invention, the average particle size of the metal powder is in the range of 0.5 μm to 10 μm, and the glass frit is 2 to 15% by weight based on the total amount of the conductive paste. Is preferably within the range.

A metal powder having an average particle size of less than 0.5 μm has a low bulk density and may require a large amount of an organic vehicle for pasting, while a metal powder having an average particle size of more than 10 μm is used. Under normal firing conditions, it is difficult to form a conductive pattern with sufficient sinterability, and it may be difficult to form fine wiring from the viewpoint of printability.

When the amount of glass frit is less than 2% by weight of the total amount of the conductive paste, the above-mentioned effects of the glass frit are small. On the other hand, when the amount of glass frit exceeds 15% by weight, the solderability is poor. And the conductivity tends to deteriorate.

Further, as the metal powder, copper, silver,
It is desirable to use at least one selected from the group consisting of gold, platinum and palladium, or an alloy such as a silver-palladium alloy. That is, the metal plate may be a metal plate corresponding to the type of the metal powder.

Next, an example of the ceramic electronic component of the present invention will be described with reference to FIGS.

First, as shown in FIG. 2, the ceramic electronic component of the present invention can be applied to a chip multilayer capacitor.

The multilayer chip capacitor 1 has a plurality of internal electrodes 3 in a dielectric ceramic layer 2, and the internal electrodes 3 are alternately connected to external electrodes 4 facing each other. Also,
The chip multilayer capacitor 1 is formed, for example, by screen-printing the conductive paste of the present invention on a ceramic green sheet to form an internal electrode pattern, laminating and pressing the resulting ceramic green sheet, and firing under predetermined conditions. Thereafter, an external electrode pattern is formed by an immersion method using the conductive paste of the present invention, and is baked.

According to the chip multilayer capacitor 1, since the conductive paste of the present invention is used to form the internal electrode 3 and the external electrode 4, the glass component layer and the conductive component in the internal electrode 3 and the external electrode 4 are used. The bonding strength at the interface with the layer is improved, and therefore, the bonding strength between the internal electrode 3 or the external electrode 4 and the ceramic layer 2 is improved, and the highly reliable chip multilayer capacitor 1 is obtained. In addition, since the liquid phase sintering of the metal powder is promoted, the obtained sintered body becomes dense,
Accordingly, the conductivity of each electrode itself is improved, and the chip multilayer capacitor 1 excellent in high frequency characteristics can be obtained.

Further, the ceramic electronic component of the present invention can be applied to a thick film circuit board as shown in FIG.

The thick film circuit board 5 has a printed resistor 7 on a ceramic substrate 6 having via holes, electrodes and the like inside. Further, the printed resistor 7 is connected to via holes, internal electrodes, other passive components and mounted components by a thick film conductor 8, and a protective glass film 9 is formed on the printed resistor 7 and the thick film conductor 8. Is formed.

According to the thick film circuit board 5, since the conductive paste of the present invention is used to form the thick film conductor 8, the interface between the glass component layer and the conductor component layer in the thick film conductor 8 is formed. The bonding strength is improved, and therefore, the bonding strength between the thick film conductor 8 and the ceramic substrate 6 is improved, and the highly reliable thick film circuit board 5 can be obtained. Further, as described above, since the liquid phase sintering of the metal powder is promoted, the obtained sintered body becomes dense, and therefore, the conductivity of the thick film conductor itself is improved and the thick film circuit excellent in high frequency characteristics is provided. The substrate 5 is formed.

However, the ceramic electronic component of the present invention is not limited to a chip laminated capacitor and a thick film printed board, but may be, for example, a chip LC filter, a chip coil,
The present invention can be applied to electronic components such as a chip antenna and various ceramic electronic components such as a hybrid IC substrate and a package. That is, the conductive paste of the present invention,
For example, the formation of internal electrodes such as a capacitor pattern, a coil pattern, and inner layer wiring in a chip LC filter and the formation of external electrodes for connection terminals, and various conductors such as electrode pads for wire bonding, electrode pads for soldering, and surface wiring. It can be used for forming patterns.

In the conductive paste of the present invention and the ceramic electronic component of the present invention, the contact angle is, as shown in FIG. 4, the glass frit 1 on a metal plate 11 such as a copper plate.
0, and the viscosity of the glass frit 10 is 10 ⁴ Pa
The contact angle α after being left at s for 30 minutes.

[0033]

EXAMPLES Hereinafter, the conductive paste according to the present invention will be described with reference to specific examples.

As shown in Table 1 below, the glass viscosity was 10
Three types of glass frit having different contact angles α with the copper plate at ⁴ Pa · s were prepared. Note that, specifically, the composition of the glass frit according to Example 2 was PbO:
88.5 mol%, Al ₂ O ₃ : 1.5 mol%, SiO ₂ :
1 mol%, B ₂ O ₃ : 6 mol%, ZnO: 3 mol%, and the composition of the glass frit according to Comparative Example 1 was Si
O ₂ : 40 mol%, B ₂ O ₃ : 50 mol%, K ₂ O: 10 mol%, and the composition of the glass frit according to Comparative Example 3 is:
SiO ₂ : 60 mol%, B ₂ O ₃ : 10 mol%, Li ₂ O:
15 mol%, Na ₂ O: from 15 mol%.

[0035]

[Table 1]

A conductive paste was prepared by mixing and kneading the glass frit shown in Table 1, copper powder (Cu) as a metal powder, copper oxide powder (CuO) and an organic vehicle at the following ratios and kneading. As the organic vehicle, a solution prepared by dissolving an ethyl cellulose-based resin, an alkyd-based resin, an acrylic resin, or the like with a terpineol-based solvent or an alcohol-based solvent was used.

76 parts by weight of copper powder 7 parts by weight of glass frit 3 parts by weight of copper oxide powder 14 parts by weight of organic vehicle Then, the obtained conductive paste is applied on an insulating alumina substrate by a screen printing method,
Dried for minutes. Then, up to 600 ° C under N ₂ atmosphere
For 1 hour to form a thick film conductor on the insulating alumina substrate.

The wiring resistance, initial adhesive strength, and adhesive strength after heat aging of the thick film conductor thus obtained were measured and evaluated. The results are shown in Table 2 below.

The wiring resistance in Table 2 (mΩ / □)
Was measured at two points on a patterned thick film conductor having a dimensional relationship (L / W = 100/1) in which length (L) and width (W) were 100: 1 by a well-known four-terminal method. It is a sheet resistance value obtained by the above film thickness conversion. The adhesive strength (Kgf) is a numerical value obtained by connecting a lead wire to a thick film conductor formed by baking a conductive paste by soldering, and then pulling the lead wire. Therefore, in this embodiment, 235 ±
A thick film conductor having a size of 2 mm × 2 mm is immersed in eutectic solder containing 2% of silver (Ag) adjusted to 5 ° C. for 5 ± 1 second, and the thick film conductor is After soldering and connecting a tin-plated copper wire having a diameter of 0.8 mm, which was a lead wire, the lead wire was stretched to 20 cm by a tensile tester.
2 shows the bond strength measured by pulling at a rate of / min.

Further, Table 2 shows both the initial adhesive strength and the adhesive strength after heat aging for the above-mentioned adhesive strength. The initial adhesive strength is the adhesive strength immediately after the above-described soldering of the lead wire. On the other hand, the adhesive strength after thermal aging indicates the adhesive strength after an aging treatment at a temperature of 150 ° C. for 1000 hours.

In Table 2, the results of the determination are shown for each of the wiring resistance, the initial adhesive strength, and the strength after thermal aging. The wiring resistance was 3.0 mΩ.
/ □ was used as a criterion value, and when it was less than this value, it was indicated by “」 ”, and when it exceeded this value, it was indicated by“ × ”. As for the initial adhesive strength, 3.0 Kgf was used as a criterion value, and when it was higher than this value, “○” was displayed, and when it was lower than this value, “×” was displayed.
The adhesive strength after heat aging was 1.0 K
The gf was used as a criterion value, and when it was more than this, “「 ”was displayed, and when it was less than this,“ × ”was displayed.

[0042]

[Table 2]

According to Table 2, the wiring resistance becomes lower as the glass frit having a smaller contact angle is used.
It can be seen that when the contact angle is 30 degrees or less as in Examples 1 to 3, the wiring resistance is 3.0 mΩ / □ or less. On the other hand, in Comparative Examples 1 to 3, the wiring resistance was 4.0 mΩ /
□, 6.0mΩ / □, wiring resistance 3.0mΩ / □
Values were exceeded. From this, Examples 1 to 3
Indicates that the sinterability of the thick film conductor is improved and the conductivity is improved as compared with Comparative Examples 1 to 3.

As can be seen from Table 2, the initial adhesive strength tends to increase as the contact angle of the used glass frit decreases, but also in Example 1 and Comparative Example 1. 3.0K
It showed a sufficient adhesive strength of gf or more. On the other hand, although the adhesive strength after heat aging of Comparative Examples 1 and 3 was reduced to 0.7 kgf and 0.2 kgf, respectively, the conductive material containing the glass frit according to Example 1 was used. In thick film conductors formed using conductive paste,
Adhesive strength of 1.0 kgf or more is secured.

In the above embodiment, a thick film conductor made of a conductive paste is formed on an alumina substrate. However, other insulating substrates, for example, a BaO—Al ₂ O ₃ —SiO ₂ low-temperature sintered glass ceramic Even when formed on a substrate,
Substantially equivalent results were obtained.

As described above, according to the conductive paste of this embodiment, when the viscosity is 10 ⁴ Pa · s, the contact angle with the copper plate is 3
Since it contains a glass frit having a temperature of 0 ° or less, it has excellent conductivity even in firing at a relatively low temperature (that is, firing at a medium temperature), and has a sufficient adhesive strength to a substrate, particularly after heat aging. Sufficient adhesive strength was secured.

[0047]

According to the conductive paste of the present invention, since the glass paste contains a glass frit having a contact angle of 30 ° or less with a metal plate at a viscosity of 10 ⁴ Pa · s, the liquid phase of the metal powder is reduced. Sintering is promoted, the sintered body of the metal powder becomes denser, and the conductivity and adhesion strength of the conductive film itself after sintering are improved. Therefore, a conductive paste having excellent conductivity and securing sufficient adhesive strength to various substrates can be obtained.

According to the ceramic electronic component of the present invention, since the conductive paste of the present invention is used for forming various conductor patterns, the bonding strength at the interface between the glass component layer and the conductor component layer is improved, and In addition, the bonding strength between the conductive paste and the insulating substrate is improved, and a highly reliable ceramic electronic component can be obtained. Further, since the wiring resistance in the electrode pattern is reduced, a ceramic electronic component having excellent high frequency characteristics can be obtained.

[Brief description of the drawings]

FIG. 1 is a graph showing changes in wiring resistance and adhesive strength depending on the contact angle of a glass frit.

FIG. 2 is a schematic sectional view of a chip multilayer capacitor using the ceramic electronic component of the present invention.

FIG. 3 is a partial cross-sectional view of a thick-film circuit board using the ceramic electronic component of the present invention.

FIG. 4 is a cross-sectional view for explaining a contact angle of a glass frit in the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Chip laminated capacitor, 2 ... Ceramic layer, 3 ... Internal electrode, 4 ... External electrode, 5 ... Thick film circuit board, 6 ... Ceramic substrate, 7 ... Printed resistor, 8 ... Thick film conductor, 9 ... Protective glass film

Continued on the front page F term (reference) 4E351 AA07 BB01 BB03 BB05 BB09 BB31 CC11 CC12 CC31 CC33 DD04 DD05 DD06 DD20 DD21 DD33 DD52 EE02 EE03 EE10 EE11 EE12 EE13 GG01 GG06 GG16 4G062 AA08 BB04 CC10 DA01 DB03 DC03 DB01 ED01 EE01 EF01 EG01 FA01 FA10 FB01 FC01 FD01 FE01 FF01 FG01 FH01 FJ01 FK01 FL01 GA01 GA10 GB01 GC01 GD01 GE01 HH01 HH03 HH05 HH07 HH09 HH11 HH13 HH15 HH17 HH20 JJ01 KK01 KK03 KK03 JJ03 KK03 JJ03 KK03 DA06 DA11 DA12 DA34 DD01

Claims (5)

[Claims] 1. A conductive paste obtained by mixing a metal powder, a glass frit, and an organic vehicle, wherein a contact angle of the glass frit is 10 ⁴ Pa · s, and a metal plate of the same kind as the metal powder is formed. On the other hand, the conductive paste has a temperature of 30 degrees or less. 2. The metal powder has an average particle size of 0.5 to 10.
The conductive paste according to claim 1, wherein the conductive paste is in a range of μm. 3. The conductive paste according to claim 1, wherein the content of the glass frit is in a range of 2 to 15% by weight based on the total amount of the conductive paste. 4. The method according to claim 1, wherein the metal powder is at least one selected from the group consisting of copper, silver, gold, platinum, and palladium, or an alloy thereof.
The conductive paste according to any one of the above. 5. A ceramic, wherein a desired conductive pattern is formed by firing the conductive paste according to claim 1 printed on an insulating ceramic substrate. Electronic components.