JP2009187695A - Conductor paste composition for display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a conductor paste capable of forming a thin Ag film having a baked film thickness of 1-2 μm, small in voids, and capable of securing a low resistance value. <P>SOLUTION: An Ag conductor paste composition is prepared by dispersing Ag powder as a conductive constituent and glass powder as an adhesion constituent in an organic vehicle. The Ag conductor paste composition for a display contains a sintering accelerator formed of at least one out of a Bi organic metal compound and a Si organic metal compound, has 0.1-0.5 μm of the average particle diameter of the Ag powder, contains 25-40 wt.% of the Ag powder, and totally includes 0.2-10 wt.% of a sintering accelerator based on 100 wt.% of the Ag powder in terms of metal. It is preferable that the conductor paste further contains a sintering inhibitor comprising one or more organic metal compounds of which the metal constituents are Zn, Zr, Mn, Ni, Rh and Ru. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a thick film conductor paste formed on a glass substrate or an alumina substrate, and more particularly to a conductor electrode forming paste on a circuit board including a conductor electrode for display, a protective layer, and a dielectric layer.

  Circuit board conductor electrodes, plasma display wiring electrodes, and the like are formed by applying and firing a thick film conductor paste mainly composed of Au or Ag. Thick film conductor paste is composed of Ag powder, Au powder, which are conductive components, and glass frit according to the substrate material, firing temperature, and target adhesion characteristics, dispersed in an organic vehicle, and added as necessary. Add the agent to adjust the film quality.

  The film thickness that appears after firing the thick-film conductor paste is generally determined by the proportion of the conductive component in the paste (metal content), but firing when the conductive particles are 50 parts by weight or less (50% or less) with respect to 100 parts by weight of the paste. The denseness of the film tends to deteriorate. Therefore, conventionally, the conductor thick film paste is generally composed of about 60 to 90 parts by weight of conductive particles with respect to 100 parts by weight of the paste.

  In recent years, there is a high need for reducing the thickness of flat display panels, and improvements have been made to reduce the thickness as much as possible. On the other hand, with respect to the drive electrode, if the film thickness is reduced, the wiring resistance increases. Therefore, a means for increasing the film thickness is taken in order to reduce the resistance. However, when the thickness of the electrode is increased in this way, the level difference between the portion where the electrode is present and the portion where the electrode is not present becomes large, which adversely affects the flatness of the film laminated on the electrode. In addition to this problem, if the electrode film thickness can be reduced, the electrode material can be reduced, and an effect of reducing the panel cost can be expected. Therefore, there is a very high demand for electrode members and materials that can realize low resistance even when the thickness is reduced.

  As a technique for realizing the thin film conductor electrode, the metal content in the paste can be reduced. For example, in the case of an Ag paste, a thin film thickness of about 1 to 2 μm can be realized at an Ag content of 40 wt%. However, when the metal content is simply reduced, the density of Ag particles in the paste is lowered, so that the sintering of the particles is hindered, voids increase, and the denseness deteriorates. Then, as the voids in the fired film increase, the conductive path becomes complicated and the resistance value also increases. In the case of a display electrode, when the resistance value increases, the luminance is greatly affected by a voltage drop, which greatly affects the characteristics.

  As another method for reducing the thickness of the thick-film conductor electrode, it can be considered that the Ag particles are atomized to a size of several tens of nm. In this case, even if the Ag content is reduced to about 40 wt%, a fired film having a relatively high density can be obtained. However, as the Ag particle size becomes finer, the manufacturing cost increases and it becomes impossible to deal with mass production. Further, as the particle size becomes finer, the particles are more likely to be aggregated, more projections are generated on the electrode, and the flatness of the electrode is deteriorated.

Furthermore, application of a metallo-ganic paste is also known as a technique for forming a thin film with excellent denseness. The metallo-ganic paste is obtained by dissolving an organic metal compound such as Au or Ag in an organic solvent without containing conductive particles or glass frit. The metallo-ganic paste has a finer conductive component than the particulate one and has good dispersibility, so that it can be easily formed into a thin film and can be manufactured with an excellent denseness. However, this paste has a problem that the manufacturing cost is high and the film thickness tends to be too thin, about 0.3 to 0.8 μm, and the appearance resistance value is increased.
Japanese Patent Laid-Open No. 10-204297

  The present invention has been made against the background described above, and an object of the present invention is to provide a conductor paste having a fired film thickness of 1 to 2 μm, less voids, and a lower resistance value.

  The present invention that solves the above-mentioned problems is an Ag conductor paste composition in which Ag powder as a conductive component and glass powder as a close-contact component are dispersed in an organic vehicle, wherein at least one of a Bi organometallic compound and a Si organometallic compound Including one or more kinds of sintering accelerators, and the Ag powder is an Ag powder having an average particle size of 0.1 to 0.5 μm, and the Ag powder is contained in an amount of 25 to 40% by weight based on the paste composition. An Ag conductor paste composition for displays, comprising a total of 0.2 to 10 parts by weight of the sintering accelerator in terms of metal with respect to 100 parts by weight of Ag powder.

  The gist of the present invention is that the ratio of the conductive particles made of Ag powder is as low as 25 to 40 parts by weight (25 to 40% by weight) with respect to 100 parts by weight of the paste, thereby promoting the sintering of Ag powder. And Bi are uniformly dispersed in an organic vehicle together with glass powder. By doing so, the melting point of Ag is lowered by the influence of Si or Bi component, the softening of adjacent Ag particles is promoted at a firing temperature of 400 ° C. or higher, the grain grows and the voids are less dense. A conductive path is formed. Hereinafter, the present invention will be described in detail.

  The reason why the average particle diameter of the Ag particles is 0.5 μm or less is to obtain a target fired film thickness of about 1 to 2 μm. When the size of the Ag particles is increased, the surface of the particles is easily accelerated by the influence of Si and Bi, but since the particle central portion is not in contact with Si and Bi, it is difficult to obtain the effect of promoting the sintering. The particle size is 0.5 μm or less. In this regard, in the configuration of the present invention, the surface form of the Ag film when firing pastes containing Ag powders having different particle sizes is shown in FIGS. As shown in these figures, the particle size of the Ag powder affects the sinterability of the film. The smaller the average particle diameter, the more easily the effect of promoting the sintering by Si and Bi can be obtained, and a dense fired film can be formed. Therefore, the average particle diameter is more preferably 0.4 μm or less.

  The reason why the content of Ag powder is 25 to 40% by weight is to make the fired film thickness within an appropriate range, and when it exceeds 40% by weight, the film thickness becomes too thick. On the other hand, if it is less than 25% by weight, the film thickness becomes too thin, and the denseness deteriorates and the appearance resistance value also increases.

  In the present invention, organometallic compounds of Bi and Si are used as the sintering accelerator. In addition to these, there are Pb, B, Cu, and the like as metals having a lower melting point of Ag as described above, and have a sintering promoting action, but Bi and Si have a good fired film in addition to the sintering promoting action. This is because conductivity can be secured. The sintering accelerator contains at least one of a Bi organometallic compound and a Si organometallic compound, and a total of 0.00 in terms of metal (total amount of Bi and Si) with respect to 100 parts by weight of Ag powder. 2 to 10 parts by weight. By setting such a mixing ratio, a highly dense film is formed.

  Bi organic metal compounds that are sintering accelerators may be organic acid compounds of octylic acid, naphthenic acid, ethylhexanoic acid, abietic acid, acetylacetone, and stearic acid. Similarly, for Si organometallic compounds, organic acid compounds of octylic acid, naphthenic acid, ethylhexanoic acid, abietic acid, acetylacetone, and stearic acid can be applied. In the case of Si, silicon varnish can also be applied. As these metal compounds, for example, bismuth octylate, bismuth naphthenate, silicon octylate, zirconium ethylhexanoate and the like are used.

  In the present invention, sintering suppression may be further added. When only the sintering accelerator is added, the island shape deteriorates due to the shrinkage at the end of the pattern as the sintering of the Ag particles is promoted, and the effective area of the pattern may be impaired. Therefore, it may be effective to adjust the sintering property of Ag by adding a sintering inhibitor. This sintering inhibitor is preferably one in which the metal component contains Zn, Zr, Mn, Ni, Rh, Ru. Examples of metals having a sintering suppressing effect include Zn, Zr, Mn, Ni, Rh, Ru, Sn, and In. In the present invention, among these, Zn, Zr, Mn, Ni, Rh, and Ru are preferable. In addition, Zn and Zr are particularly preferable for suppressing sintering without impairing the conductivity of the fired film.

  The sintering inhibitor may be contained in the form of an oxide such as zinc oxide, zirconia, alumina, ruthenium oxide, etc., but by being in the form of an organometallic compound, the sintering inhibitor is easily dispersed uniformly with Ag particles. -It is more preferable because kneading by a rumill or the like is unnecessary. The organometallic compound is preferably an organic compound of octylic acid, naphthenic acid, ethylhexanoic acid, abietic acid, acetylacetone, and stearic acid, and the sintering inhibitor is preferably composed of at least one of the above metal organometallic compounds.

  The addition amount of the sintering inhibitor is a total amount in terms of metal, and is preferably 0.1 to 3 parts by weight with respect to 100 parts by weight of the Ag conductive component. Since a large amount of metal oxide precipitates on the film surface, it is necessary to select an addition amount suitable for the substrate material and firing conditions.

The glass component mixed as an adhesion component with respect to the above Ag particles, sintering accelerator, and sintering inhibitor is a glass frit having a particle size distribution average particle size of 0.1 to 2 μm and a glass softening point of 350 to 600 ° C. It is preferable to use a glass frit having a sufficiently low softening point with respect to the intended firing temperature. Examples of the glass include bismuth-based glass (Bi ₂ O ₃ —SiO ₂ , Bi ₂ O ₃ —B ₂ O ₃ ), zinc-based glass (ZnO—Bi ₂ O ₃ —SiO ₂ , ZnO—B ₂ O ₃ — Bi ₂ O ₃ ), silica-based glass (SiO ₂ —B ₂ O ₃ ), and the like are selected according to the substrate material and the firing temperature.

  Since the conductive paste according to the present invention aims to form a thin film having a fired film thickness of about 1 to 2 μm, the average particle size distribution of the glass frit is preferably 1.5 μm or less. The amount of glass frit added is preferably 0.2 to 5 parts by weight with respect to 100 parts by weight of the paste. If the amount of glass is too small, adhesion to the substrate is insufficient, while the amount of glass is large. If it is too high, there are adverse effects such as deterioration of the denseness, deterioration of the shape of the pattern end, and film quality change during repeated baking, and it is necessary to select an addition amount suitable for the substrate material and baking conditions.

  Moreover, the resin component contained in the organic vehicle in which Ag powder, glass frit, etc. are dispersed has a function of adjusting the applicability and printing characteristics by imparting an appropriate viscosity to the Ag conductor paste, and the type is limited in the present invention. Although it is not a thing, a cellulose type and acrylic resin are mainly used.

  The Ag conductor paste according to the present invention may further contain an organic solvent component. The organic solvent component is determined in relation to the conductive component and the resin component, and is not limited in kind in the present invention. However, the organic solvent component is mainly an alcohol solvent, an ester solvent, an ether solvent, carbonization. A hydrogen-based solvent or the like is used. Moreover, a thickener and surfactant may be contained. The conductive paste according to the present invention can be obtained by kneading the above-described components by a known method such as a three-roll mill.

  The Ag conductor paste of the present invention can form a conductor film having a thinner film thickness than that of the conventional conductor paste, and can be a conductor film having a very low resistance value with less voids. Is. The present invention, for example, can be used to form display panel electrodes, so that a very thin electrode can be formed. Therefore, the step of the layer formed on the top of the electrode is reduced, and the surface smoothness is excellent. This is advantageous for forming the upper layer circuit. In addition, since a low resistance value can be ensured, electrical loss due to a voltage drop is small, and power consumption can be suppressed as a display, and good characteristics can be realized. In addition, the present invention is also suitable as a wiring electrode for a hybrid IC or the like, and an effect of cost reduction can be expected by reducing the thickness.

  Hereinafter, the best embodiment of the present invention will be described.

First Embodiment : In this embodiment, Ag powder, glass powder, sintering accelerator, sintering inhibitor, vehicle, organic solvent, thickener, surfactant and the like are kneaded using a three-roll mill. A conductor paste was prepared.

As the Ag particles, monodispersed spherical Ag powder having an average particle size of 0.3 μm (FIG. 2) was prepared so that the Ag content was 26 to 40 wt%. As glass _component, the Bi ₂ O 3 _-B 2 _{O 3} based glass was added 0.5 to 15% relative to the amount of Ag. The sintering accelerator added 0.3 to 6.5 wt% of Si and Bi organometallic compounds in terms of metal with respect to the Ag amount. The organometallic compounds used here are bismuth octylate, silicon oil, zinc octylate, and zirconium octylate. Then, Ag powder, glass powder, sintering accelerator, sintering inhibitor, organic vehicle, organic solvent, thickener, and surfactant were kneaded using a three-roll mill to obtain a conductor paste.

  Next, the produced Ag conductor paste was applied on a glass substrate by screen printing, dried for 10 to 15 minutes with a 120 ° C. dryer, and then held at 650 ° C. or higher (peak temperature 690 ° C.) for 9 minutes. The Ag film was formed so as to have a fired film thickness of 1.0 to 2.0 μm by firing in a conveyor furnace set at a temperature rising rate of 200 ° C. to 600 ° C. and 66 ° C./min.

  And the appearance film thickness and the sheet resistance value were evaluated with respect to the Ag fired film formed on the glass substrate, and the density of the fired film was confirmed with an electron microscope. Tables 1 and 2 below summarize the results. Table 1 summarizes the results of compositions within the scope of the present invention, and Table 2 summarizes comparative examples outside the scope of the present invention. In each table, the Ag content is expressed as a ratio with respect to 100 parts by weight of the paste, and the addition ratio of the glass addition rate, sintering accelerator, and sintering inhibitor is expressed as a ratio with respect to 100 parts by weight of the Ag particles. The resistance value is not converted into a film thickness, and is indicated by a sheet resistance value at the appearing film thickness.

  Moreover, the SEM external appearance of the fired film of an Example and a comparative example is shown to FIGS. The determination of the density was shown in the table as “X” for the SEM appearance with many voids, “◯” for those with few voids, and “◎” for those with very few voids.

  The fired Ag film formed in each example is as thin as the current film thickness of 2.0 μm or less, the film thickness conversion resistance is as low as 25 mΩ / □ / 1.5 μm or less, and the denseness is also good. I know that there is. In particular, in Examples 1 to 5 and Example 8, the film thickness is as thin as 1.5 μm or less, an extremely low resistance value is maintained, and it can be said that the denseness is excellent.

  Moreover, in Examples 6-14, the addition amount of a sintering accelerator and a sintering inhibitor was further increased. As the added amount increases, more oxide is deposited on the Ag film surface and the film thickness tends to be thicker, but the denseness is good and the resistance value is sufficiently low.

  When examined in detail, in Example 1, Zn which is a sintering inhibitor is added in addition to Si, and the pattern end portion shape deteriorated due to the sintering promotion effect of Si has a sintering suppressing effect of Zn. Adjusted. It can be said that the shape of the pattern end is good (FIG. 6A). Thus, a uniform and dense Ag film could be obtained by using a sintering accelerator and a sintering inhibitor in combination.

  In Example 3, the amount of Si added was increased in order to further improve the denseness of Example 1. In Example 3, the sintering was further promoted and the denseness was improved, but the shrinkage at the pattern end was deteriorated (FIG. 6B). In Example 4, the amount of sintering inhibitor was increased, but the shrinkage at the pattern end was not improved (FIG. 6C).

  In Example 5, the sintering promoting action is adjusted by the combined use of Si and Bi, and the sintering is further adjusted by Zn. Compared with Example 3 in which the amount of Si was increased, the denseness was further improved, and the shape of the pattern end was also kept good (FIG. 6 (d)). By using two types of sintering accelerators together, the timing for promoting the sintering of Ag is shifted during the temperature rising process, so that the Ag flow due to oversintering is less likely to occur than in the case of simply having a large amount of Si. The shrinkage of the pattern end is reduced.

  In this example, the Si component as a sintering accelerator was added in the form of silicon oil, but it has been confirmed that silicon octylate has the same effect.

  In contrast to the above examples, Comparative Example 1 had good denseness, but the appearance thickness was large due to the high Ag content, and it was not the object of the present application. In Comparative Examples 2 to 4, the Ag content is decreased, but it can be seen that when the film thickness appears in the vicinity of 2 μm, voids increase and the resistance value with respect to the film thickness increases (FIG. 7 ( b) to (d)).

  Comparative Examples 3 to 6 show transitions when the Ag content is decreased and the glass content is increased. Bi-based glass has an effect of promoting the sintering of Ag, and it was confirmed that the sintering was promoted as the amount of glass increased, but it was confirmed that voids increased due to the influence of Ag easily flowing (Fig. 7 (c)-(f)).

  In Comparative Example 7, Ag colloid having a particle size of several tens of nm is used as Ag particles. Compared with other comparative examples, although it was excellent in denseness and low in resistance value, it resulted in a lot of aggregation and poor surface smoothness of the electrode. In addition, it can be said that the one to which this colloid is applied is not practical because the particles are more easily aggregated as the particle size becomes smaller and the manufacturing cost becomes higher (FIG. 8G).

  In Comparative Examples 8 and 9, Zn components and Sn components were added as sintering inhibitors. As can be seen from Table 2, even when the sintering inhibitor was added, no improvement in the compactness was observed (FIGS. 8 (h) and (i)).

Second Embodiment : In this embodiment, a conductor paste was produced in which the Ag content was changed from 38 wt% to 22 wt% based on Example 5 in which the denseness of the first embodiment was the best. And the same evaluation test was done. Table 3 shows the results. Moreover, the SEM external appearance of the fired film of an Example and a comparative example is shown to FIG.

  From Table 3 and FIGS. 9 and 10, it is possible to form an Ag film in which the denseness is good and the resistance value is kept low within the range of the Ag content of 26 to 38 wt% (Examples 5 and 15 to 17). confirmed. On the other hand, when the Ag content is 22 wt% (Comparative Example 10), the film thickness becomes too thin, so that the denseness deteriorates and the appearance resistance value also increases.

The photograph which shows the film | membrane surface after baking of the paste containing Ag particle | grains with a particle size of 0.6 micrometer. The photograph which shows the film | membrane surface after baking of the paste containing Ag particle | grains with a particle size of 0.3 micrometer. The photograph which shows the surface form of the baking Ag film | membrane of Examples 1-6. The photograph which shows the surface form of the baking Ag film | membrane of Examples 7-10. The photograph which shows the surface form of the baking Ag film | membrane of Examples 11-14. The photograph which shows the edge part of the baking Ag film | membrane of Examples 1, 3-5. The photograph which shows the surface form of the baking Ag film | membrane of Comparative Examples 1-6. The photograph which shows the surface form of the baking Ag film | membrane of Comparative Examples 7-9. The photograph which shows the surface form (center part) of the baking Ag film | membrane of Examples 5, 15-17, and the comparative example 10. FIG. The photograph which shows the edge part of the baking Ag film | membrane of Examples 5, 15-17, and the comparative example 10. FIG.

Claims (5)

In an Ag conductor paste composition obtained by dispersing an Ag powder as a conductive component and a glass powder as an adhesion component in an organic vehicle,
Including a sintering accelerator composed of at least one of Bi organometallic compound and Si organometallic compound,
The Ag powder is an Ag powder having an average particle size of 0.1 to 0.5 μm,
A display comprising 25 to 40% by weight of the Ag powder with respect to the paste composition, and a total of 0.2 to 10 parts by weight of the sintering accelerator in terms of metal with respect to 100 parts by weight of the Ag powder. Ag conductor paste composition. The Ag conductor paste composition for a display according to claim 1, wherein the Bi organometallic compound which is a sintering accelerator is an organic acid compound of octylic acid, naphthenic acid, ethylhexanoic acid, abietic acid, acetylacetone, and stearic acid. 3. The display according to claim 1, wherein the Si organometallic compound which is a sintering accelerator is an organic acid compound of octylic acid, naphthenic acid, ethylhexanoic acid, abietic acid, acetylacetone, stearic acid, or silicon varnish. Ag conductor paste composition. Furthermore, it contains a sintering inhibitor, and the sintering inhibitor is composed of at least one or more organometallic compounds whose metal components are Zn, Zr, Mn, Ni, Rh, and Ru, and the organometallic compound The Ag conductor paste composition for display according to any one of claims 1 to 3, which is an organic compound of octylic acid, naphthenic acid, ethylhexanoic acid, abietic acid, acetylacetone, and stearic acid. The Ag conductor paste composition for display according to claim 4, comprising 0.1 to 3 parts by weight of a sintering inhibitor with respect to 100 parts by weight of Ag powder.