TWI442415B - Conductive paste composition - Google Patents

Description

Conductive paste composition

The present invention relates to a conductive paste composition, and more particularly to a heat-resistant conductive paste composition which can be fired at a high temperature of 950 to 1200 °C.

In the method of forming a conductive circuit or an electrode of various substrates in an electronic circuit or a laminated electronic component, a conductive paste is generally used.

The conductive paste is generally a paste composition in which a metal conductor powder as a conductive component is dispersed in an organic vehicle composed of a resin-based adhesive and a solvent, and is printed or coated on a ceramic substrate or a ceramic green body. After the sheet or the like, the organic vehicle liquid is evaporated and decomposed by firing, and the remaining conductive component is formed into a sintered body to form an electric excellent conductor, and a conductive circuit or an electrode is formed by the sintered body of the conductive component. In actual use, the conductive paste is coated or filled in a hole on the surface or inside of the ceramic substrate or the ceramic green sheet, and heat-treated with the substrate or the sheet to evaporate and decompose to remove the organic medium. The liquid and the metal conductor powder as a conductive component are sintered to each other to form a conductive circuit or electrode that can be energized.

In terms of conductive components, Ag powder is widely used in consideration of factors such as price, conductivity, and firing in the atmosphere. However, when a ceramic substrate or a ceramic green sheet which is printed or coated with a conductive paste is fired at a low temperature of about 900 ° C, it can be made of Ag powder, but the ceramic substrate or ceramic green sheet may be used depending on the application. It is fired at a high temperature of about 950 ° C to 1200 ° C. At this time, when the Ag powder is used as a conductor paste to form wiring or electrodes, Ag It will spread into the substrate or the sheet, which may cause problems such as disconnection or segregation. It is presumed that the melting point of Ag is about 961.9 ° C and the firing temperature is relatively low. Therefore, in the past, a noble metal such as Pt (1770 ° C) and Pd (melting point of 1550 ° C) which is higher in melting point than Ag and which is not oxidized even in the atmosphere is alloyed with Ag. A method or a method of forming a film of a heat resistant metal layer on the surface of an Ag powder to ensure heat resistance of the conductor.

For example, Patent Document 1 discloses a silver powder having a heat resistant metal layer formed on a surface of a silver powder by a film of a heat resistant metal layer such as nickel, a nickel alloy, cobalt or a cobalt alloy.

Patent Document 1: Japanese Patent Laid-Open Publication No. 2003-306701

However, when Pt or Pd which is a noble metal is used in order to improve heat resistance, there is a disadvantage that the manufacturing cost of the conductive paste is increased. A method of improving the heat resistance of a conductor without using a noble metal, as disclosed in Patent Document 1, a method of forming a film of a heat resistant metal layer on the surface of an Ag powder, since the film forming step such as plating is increased, the manufacturing cost is also similar. Will rise.

The present invention has such a problem in view of the prior art, and an object thereof is to provide a conductive paste composition having a low electric resistance value, which does not require the use of alloying Ag or a noble metal such as Pt or Pd or deliberately Ag. The surface of the powder forms a heat-resistant metal layer and the like, and contains a heat-resistant conductor.

The inventors have found that the softening point is caused by the general use of alloying. The atomized powder of the Ag and Ni alloy which is not imparted with heat resistance can obtain a conductor having heat resistance, and the conductive paste composition of the present invention is characterized in that the atomized powder of the AgNi alloy is added with Cu. The substance acts as a conductive component.

That is, when the atomized powder of Ag and the Ni alloy is fired in an atmospheric atmosphere, Ni in the alloy is oxidized during firing, and an oxide of Ni is formed on the surface of the atomized powder of the AgNi alloy. Since the film of the Ni oxide is naturally formed on the surface of the atomized powder of the AgNi alloy in this manner, the surface of the Ag powder is applied in a state where the coating of the oxide is performed, and the heat resistance is improved. Further, since Cu is oxidized at 1000 ° C or lower to become CuO, and Cu ₂ O (melting point is 1230 ° C) at a temperature of 1000 ° C or higher, heat resistance can be further improved.

According to the present invention, it is possible to provide a conductive paste composition having a low electric resistance value, which does not require the use of a method of alloying Ag with a noble metal such as Pt or Pd or deliberately forming a heat resistant metal layer on the surface of the Ag powder, and contains heat resistance. The conductor.

Hereinafter, the best mode for carrying out the invention will be described.

Since the present invention can obtain a conductive component in the same manner as in the production of atomized Ag powder without a special step, it is possible to inexpensively produce a conductive component having heat resistance.

Atomizing refers to the improvement of the material composition or organization to improve the reliability of the heat-resistant metal material to produce a homogeneous and fine structure. The method of applying is a method in which a molten metal is sprayed and rapidly cooled to be refined. The atomization method which can be used in the present invention includes the water atomization method, the gas atomization method, the vacuum atomization method, and the like described below.

(1) The water atomization method is a method of spraying high-pressure water having an injection pressure of about 15 MPa onto a molten metal molten metal to obtain a fine powder having an average particle diameter of about 10 μm. Most of the fine powder shapes produced are not necessarily. The cooling rate is approximately 10 ³ ~ 10 ⁵ K/sec. When a high-pressure spray water exceeding 20 MPa is sprayed, a fine powder having a particle diameter of about several μm can be obtained.

(2) The gas atomization method is a method of spraying N ₂ or Ar gas to replace water atomized high-pressure water. A powder which is less oxidized and spherical in shape can be obtained. The gas spray method has a natural drop type and a restraint type.

(3) The vacuum atomization method is a method in which a molten powder of H ₂ is sufficiently absorbed by a pressure difference in a vacuum to obtain a spherical powder. The purity is the same as that produced by the gas spray.

(4) Other atomization methods may also employ "two-roll atomization method of pulverizing a molten metal stream by caviatation between rolls, and quenching in water", "by rotating body The collision atomization method in which the molten metal is pulverized, and quenched in water, or the "rotating water atomization method in which the molten metal flow is injected into the rotating water to obtain a rapid cooling solidified powder".

Since the alloy powder of Ag has a higher electric resistance than the powder of 100% of Ag, in order to suppress an increase in the electric resistance value, the film thickness of the oxide formed by firing on the surface of the Ag powder is thinner. It is better. On the other hand, when the thickness of the film formed on the surface of the Ag powder is too thin, heat resistance cannot be improved. Therefore, it is necessary to consider the resistance value and resistance The balance of heat is chosen to select the preferred alloy. That is, it is preferable that Ag is from 90.0 to 99.9% by weight and Ni is from 0.1 to 10.0% by weight. When Ni is less than 0.1% by weight, heat resistance similar to that of 100% of Ag powder cannot be obtained. On the other hand, when Ni exceeds 10.0% by weight, the electric resistance value becomes high and it is not suitable for use as a conductive paste.

The average particle diameter of the atomized powder of the AgNi alloy is preferably 1.0 to 10.0 μm. A powder of less than 1.0 μm is difficult to manufacture. On the other hand, when it exceeds 10.0 μm, it is easy to produce a foil at the time of gelatinization, and it is difficult to obtain the paste of the objective of this invention.

Further, when the Ag-based conductor and the low-temperature fired ceramic substrate are simultaneously fired, there is a disadvantage that the shrinkage behavior of the two is greatly different. After the start of the firing, the organic substance (binder resin, etc.) is thermally decomposed at 300 to 400 ° C, and the Ag-based conductive paste starts to shrink due to Ag sintering, but the low-temperature fired ceramic green sheet is made of glass. The main component is therefore generally contracted only around 650 ° C where the glass component begins to melt.

Therefore, in the temperature range of about 400 ° C to 650 ° C, the difference in shrinkage ratio between the Ag-based conductor and the low-temperature fired ceramic substrate increases as the temperature rises. When the difference in the shrinkage ratio between the two becomes large, a large thermal stress is generated in the joint portion between the two, and the sintered substrate may be warped or the joint strength of the joint portion may be lowered to cause the joint portion to peel off. Furthermore, in recent years, with the lead-free electronic components, ceramic materials have gradually become the mainstream of lead-free materials. Therefore, since the shrinkage start temperature of the ceramic moves toward the high temperature side and the ceramic itself crystallizes, the speed of heat shrinkage also becomes quite fast. Therefore, the difference between the shrinkage ratio of the Ag-based conductor and the shrinkage ratio of the low-temperature fired ceramic substrate is further expanded. Large, the cracking or warping of the substrate after firing has become more pronounced.

Therefore, when the atomized powder of the present invention is used, since the film of Ni oxide is naturally formed on the surface of the Ag powder, it is expected to have an effect of increasing the heat shrinkage starting temperature of the conductor. Therefore, the occurrence of cracks or warpage of the substrate can be suppressed.

Preferably, the substance containing Cu is added to the conductive paste in an amount of 0.1 to 15.0% by weight in terms of Cu. When it is less than 0.1% by weight in terms of Cu, heat resistance cannot be improved, and when it exceeds 15.0 by weight in terms of Cu, the electric resistance value becomes high. The substance containing Cu may be one or more selected from the group consisting of inorganic salts of Cu, CuO, Cu ₂ O, Cu, and organic acid salts of Cu. Examples of the inorganic salt of Cu include copper chloride or copper nitrate. Examples of the organic acid salt of Cu include copper oleate, copper citrate, copper gluconate, and copper phthalate.

The ratio of the conductor powder to the organic vehicle in the conductive paste can be a general blending ratio. For example, the weight fraction of the conductor powder is preferably 80 to 20 to 90 to 10 by weight based on the weight of the organic vehicle. When the conductor powder is less than 80 parts by weight (more than 20 parts by weight of the organic vehicle), the electrical resistance of the conductor is increased to lower the electrical characteristics, which is not preferable. When the conductive powder exceeds 90 parts by weight (the organic vehicle is less than 10 parts by weight), the workability for filling the via holes and the formation of the wiring pattern is lowered because the appropriate paste viscosity cannot be obtained.

The organic vehicle liquid includes a binder resin (for example, an ethyl cellulose resin or an acrylic resin), and an organic solvent (for example, rosin alcohol, and Butyl carbitol acetate, etc.) may also be added with a plasticizer, a dispersant, or a glass frit, if necessary.

[Examples]

In the following, the embodiments of the present invention are described, but the present invention is not limited to the following embodiments, and may be appropriately modified and modified without departing from the technical scope of the present invention.

As shown in the following Table 1, an atomized powder (manufactured by N ₂ spray) of an alloy of Ag and Ni having an average particle diameter of 5 μm (Ag of 97% by weight, Ni of 3% by weight) was used in an amount of 75 to 80 by weight. %, an organic medium containing Cu in an amount of 0.1 to 15.0% by weight in terms of Cu, and 10.0 to 19.9% by weight of an organic vehicle solution in which an ethyl cellulose resin is dissolved in rosin alcohol is mixed using a three-roll mill to obtain a conductive paste.

Further, for comparison, as shown in the following Table 2, 80% by weight of the atomized powder of the alloy of Ag and Ni, and 20% by weight of the organic vehicle liquid of the above, were mixed using a three-roll mill, or the same as above. 80% by weight of the atomized powder of the alloy of Ag and Ni, 5.0% by weight of the inorganic material containing no Cu, and 15.0% by weight of the organic vehicle liquid of the same composition were mixed using a three-roll mill to obtain a conductive paste of a comparative example.

Next, using these conductive pastes, a wiring pattern 1 as shown in FIG. 1 was formed by screen printing on an alumina substrate (not shown), and dried at 120 ° C for 10 minutes, and then exposed to an atmospheric atmosphere. The batch type kiln was fired under the conditions of holding at 1200 ° C for 20 minutes for Example 6, and for 20 minutes at 1150 ° C for all other examples and comparative examples. to make.

Next, it was visually confirmed whether or not the surface of the substrate after firing was broken. Further, in the wiring pattern 1 shown in FIG. 1, the sheet resistance value (mΩ/mm ² / of the value per unit area) was measured for the wiring pattern 2 (line width W = 100 μm) shown in FIG. 2 . 10 μm). The presence or absence of the disconnection and sheet resistance values are shown in Tables 1 and 2.

As shown in Table 1, in the examples 1 to 15 of the present invention, the disconnection was not observed in the wiring pattern, and it was found that the conductive paste composition of the present invention has heat resistance to 1200 ° C and has a low electric resistance value. Conductive material.

However, since Comparative Example 1 did not add any atomized powder of AgNi alloy, Comparative Examples 2 to 6 added inorganic substances containing no Cu to the atomized powder of the AgNi alloy, and thus may be in some parts of the pattern 1 shown in FIG. It is confirmed that the wire is broken and the sheet resistance cannot be measured.

Industrial availability

Since the conductive paste composition of the present invention is excellent in heat resistance, it can be widely used in an electronic component related industry exposed to a high-temperature use environment.

1‧‧‧Wiring pattern

2‧‧‧Wiring pattern

Fig. 1 is a plan view showing an example of a wiring pattern.

Fig. 2 is a view showing a part of the wiring pattern of Fig. 1.

Claims (3)

The conductive paste composition is an atomized powder of an AgNi alloy having an alloy composition of Ag of 90.0 to 99.9% by weight and Ni of 0.1 to 10.0% by weight, and a substance containing Cu in an amount of 0.1 to 15.0% by weight in terms of Cu is added. Come as a conductive component. The conductive paste composition according to the first aspect of the invention, wherein the substance containing Cu is one or more selected from the group consisting of Cu, CuO, Cu ₂ O, Cu inorganic salts, and Cu organic acid salts. A ceramic circuit substrate obtained by using the conductive paste composition of claim 1 or 2 to form an electric circuit.