JPH03285965A - Conductor paste composition for green sheets - Google Patents

Abstract

PURPOSE:To obtain the subject composition, containing a prescribed amount of at least either of hydrogenated castor oil and silicon oxide in a paste composition containing electrically conductive metallic powder, an organic binder and a solvent, excellent in leveling properties and useful as computers, etc. CONSTITUTION:The objective composition containing further at least either of hydrogenated castor oil (preferably having 2.0-5.0 iodine value) and silicon oxide (preferably having 0.01-1mum particle diameter) in an amount of 1-10wt.% based on the solid weight contained in a conductor paste composition for green sheets containing electrically conductive metallic powder (e.g. copper powder), an organic binder (e.g. polymethyl methacrylate resin) and a solvent (e.g. terpineol) therein.

Description

[Detailed Description of the Invention] [Summary] This invention relates to a conductive paste composition for forming a pattern by screen printing on a glass-ceramic green sheet used for high-density mounting substrates such as those for combi coaters. The object of the present invention is to provide a conductive paste composition with improved leveling properties that can be used to produce a multilayer glass-ceramic circuit board by the green sheet method, the green paste composition comprising a conductive metal powder, an organic binder and a solvent. In the conductor paste composition for sheets, at least one of hydrogenated castor oil and silicon oxide is added in an amount of 1 to 10% by weight based on the weight of solids contained in the composition, or liquid polyethylene wax and urethane modified The composition further contains at least one of the polyethers in an amount of 0.1 to 5.0% by weight based on the weight of solids contained in the composition.

[Industrial application field]

The present invention relates to a conductive paste composition for forming a pattern by screen printing on a glass-ceramic green sheet used for high-density mounting boards for computers and the like.

[Conventional technology]

Elements used in convenience stores and the like are becoming more and more densely packed, and as a result, high-density wiring is also required for the substrates on which the elements are mounted. Therefore,
It has become necessary to miniaturize conductor patterns. Since miniaturization of conductor patterns, that is, a decrease in pattern width, leads to an increase in wiring resistance, it is necessary to increase the thickness of the patterns in order to avoid this.

In order to satisfy the need to reduce the conductor pattern width and increase the thickness (high aspect ratio), the viscosity and thixotropy index of the copper paste used must be optimized, or the emulsion used in screen printing may be thickened, and the angle of the mesh should be adjusted. Various measures have been taken in the past, such as making the size smaller.

In addition to the main components of conductive metal powder, organic binder, and solvent, conventional conductive paste contains a small amount (0.5% by weight or less) of thixotropy as an additive to improve the thixotropic properties of the paste during printing. A sexing agent (for example, hydrogenated castor oil, silicon oxide powder, etc.) is added. However, conventional pastes do not take into consideration the leveling of the printed pattern surface, and leveling of the printed pattern surface is done by leaving it at room temperature after printing.

[Problem to be solved by the invention]

In order to achieve high-density packaging, multilayer circuit boards are essential. The conventionally widely used method of manufacturing multilayer circuit boards by alternately printing and firing conductor paste and insulator paste is a method that can be used to manufacture multilayer circuit boards such as those used in combi coaters. Not suitable for manufacturing. Therefore, recently, a method has been adopted in which a required number of green sheets printed with conductive patterns are laminated and fired together (green sheet method) to manufacture circuit boards that can be mounted at high density.

However, a new problem has arisen due to printing the conductive paste on the green sheet. Unlike a pre-fired base material, the green sheet easily absorbs the solvent in the printed conductor paste, leaving traces of the screen mesh on the printed conductor pattern. That is, when printing on a pre-fired base material, absorption of solvent into the base material can be ignored, so it is possible to make the pattern surface smooth by reducing the viscosity of the paste to 1500 poise or less. This is not possible when printing on green sheets. If the surface of the pattern is not smooth, that is, if the leveling is poor, variations in electrical resistance and characteristic impedance occur, making it difficult to manufacture a highly reliable high-density mounting multilayer circuit board.

SUMMARY OF THE INVENTION An object of the present invention is to provide a conductor paste composition with improved leveling properties that can be used to manufacture a multilayer glass-ceramic circuit board capable of high-density mounting using a green sheet method.

[Means to solve the problem]

The conductor paste composition for green sheets of the present invention includes at least one of hydrogenated castor oil and silicon oxide in the conductor paste composition for green sheets comprising a conductive metal powder, an organic binder, and a solvent. , 1 to 1 based on the weight of solids contained in the composition
Another composition is a conductive paste composition for a green sheet comprising a conductive metal powder, an organic binder and a solvent, further comprising a liquid polyethylene wax and a solvent. The composition further comprises at least one of the urethane-modified polyethers in an amount of 0.1 to 5.0% by weight based on the weight of the solid content contained in the composition.

The additive substance that can be used to improve leveling properties in the present invention is hydrogenated castor oil (iodine value 2.0 to 5.0 ), silicon oxide powder (particle size 0.01-1i1 m), or liquid polyethylene wax (viscosity 1.000-1 m at 20°C).
0.0OOcP), a liquid urethane-modified polyether (viscosity 100-1.000cP at 20°C). Silicon oxide, which is an inorganic substance, can be used to the extent that it remains in the conductor pattern after firing. Organic substances other than this are decomposed by firing in a nitrogen atmosphere and do not remain in the conductor pattern.

Conventional materials such as hydrogenated castor oil and silicon oxide powder are added to the conductor paste to increase thixotropy.
When using substances that are added in amounts of up to 5% by weight, these amounts should be between 1 and 10% by weight, based on the weight of solids in the composition to which they are added. %, preferably 2 to 8% by weight. These substances may be used alone or in combination so that the total amount of both falls within the above-mentioned range. Or again,
When using polyethylene wax or modified polyether, the amount used is 0.1 to 5.0% by weight, preferably 0.4 to 2.0% by weight, based on the weight of solids in the mixture to which they are added. It is 0% by weight. These substances may be used alone or in combination so that the total amount of both falls within the above-mentioned range. The leveling property of the conductive paste composition printed on the green sheet is good when the amount of the above-mentioned additive substance used is within the above-mentioned range, and becomes poor as it deviates from these ranges.

The conductive metal powder, organic binder and solvent, which are the main components constituting the conductor paste composition of the present invention, may be any substance used in ordinary conductor pastes. A typical example of metal powder is copper powder, and in addition, Ag and Ag
Powder such as /Pd can be used. As the organic binder, polymethyl methacrylate (PMMA) resin, ethyl cellulose, etc. can be used. Further, as the solvent, high boiling point organic solvents such as terpineol and butyl carpitol acetate, and low boiling point organic solvents such as methyl ethyl ketone and acetone can be used.

The conductor paste composition of the present invention can also contain arbitrary components other than those mentioned above. For example, in order to prevent the copper powder in the conductor paste printed on the green sheet from sintering much earlier than the glass-ceramic component of the green sheet during firing, the sintering of the copper powder is delayed. It may contain added cupric oxide powder.

When the additive substance for improving the leveling property is polyethylene wax or modified polyether, etc., which is not useful for improving the thixotropic property of the paste composition during printing, the conductive paste composition of the present invention It may contain substances such as hydrogenated castor oil to increase thixotropy. In this case, the amount of the thixotropic agent is sufficient to be about 0.5% by weight based on the weight of solids in the mixture to which it is added.

The conductor paste composition of the present invention can be prepared as follows. That is, a conductive metal powder, an organic binder, a solvent (consisting of a high boiling point solvent and a low boiling point solvent),
The leveling property improving additive and other optional additives are combined and milled in a ball mill. Next, the low boiling point solvent is removed using a miller, and the mixture is further kneaded using a three-roll mill.

Formation of a conductor pattern on a green sheet using the conductor paste composition of the present invention can be performed as follows. That is, a conductive paste composition is screen printed on a formed green sheet through a screen mesh, and after being left at room temperature, it is dried at an elevated temperature. The surface roughness of the conductor pattern thus formed is 13p (
The maximum height (R,,,') value measured by a stylus method surface roughness meter) or less is sufficient leveling.

[For production]

The additive substance for improving the leveling property present in the conductor paste composition of the present invention is effective when the conductor paste composition is printed on a green sheet on which leveling of the printed conductor pattern surface is essentially not easy. It facilitates subsequent leveling to make the pattern surface more flat, and as a result serves to suppress variations in electrical resistance and characteristic impedance of the printed conductor wiring.

〔Example〕

Next, examples of the most common copper paste composition will be described.

First, a green sheet was produced as follows. That is, 230 g of borosilicate glass with a particle size of 4iHA
, 230 g of alumina with a particle size of 4-, 230 g of quartz glass with a particle size of 4β, 80 g of PMMA resin, 30 g of dibutyl phthalate), 120 g of acetone, and 530 g of methyl ethyl ketone were placed in a ball mill and milled for 16 hours. Next, a green sheet with a thickness of 0.3 mm was formed using the doctor blade method, and after drying,
It was punched out to a size of 50 mm.

Example 1 150 g of copper powder with a particle size of 4μ, 50 g of cupric oxide powder
1 to 30 g (0.5 to 15% by weight based on the solid content in the mixture, that is, the total weight of copper powder and cupric oxide powder) to a mixture consisting of g1 polymethyl methacrylate resin 2g1 35 g of terpineol and 150 g of methyl ethyl ketone. Hydrogenated castor oil within range (iodine value 2.5)
The composition to which was added was milled using a ball mill for 72 hours. Next, the composition was treated with a milling machine to scatter methyl ethyl ketone from the composition, and further kneaded 30 times with a three-roll mill to prepare copper paste compositions having different contents of hydrogenated castor oil.

These copper paste compositions were screen printed onto previously formed and punched green sheets through a 325 mesh stainless steel screen mesh. Afterwards, each green sheet was left at room temperature for 10 minutes, and then at 80°C.
and dried for 20 minutes. The surface roughness of the printed pattern on the green sheet thus obtained was measured using a surface roughness meter using a stylus method. The results are shown in Table 1.

Example 2 As a leveling property improving additive, 1 to 30 g of silicon oxide powder with a particle size of 1 m was used instead of hydrogenated castor oil (0.5 to 15 g based on the total weight of copper powder and cupric oxide powder).
A copper paste composition was prepared and printed on a green sheet in the same manner as in Example 1, except that % by weight) was added, and the surface roughness was measured after drying. The results are also shown in Table 1.

Example 3 Hydrogenated castor oil was added not as a leveling property improving additive but as a thixotropic agent during printing (0.5% of the total weight of the solid content), and then as a leveling property improving additive in the liquid. Polyethylene wax (20℃
The procedure of Example 1 was repeated, except that 0.1 to 14 g (0.05 to 7% of the total weight of solids) was added (viscosity of 10.0 OOcP). Table 1 shows the measured surface roughness of the conductor pattern.

Example 4 The leveling property improving additive was 0.1 to 14 g of liquid urethane-modified polyether (viscosity at 20°C: 1.0OOcP)
(0.05 to 7% of the total weight of solids) was the same as in Example 3. Table 1 shows the measurement results of the surface roughness of the conductor pattern.

Among the results in Table 1, the composition in which hydrogenated castor oil and silicon oxide were added in an amount of 0.5% by weight corresponds to a conventionally known copper paste composition in which these substances were used to improve thixotropy during printing. However, it can be seen that the roughness of the surface of the printed pattern in this case is 20mm. In contrast, the amount of hydrogenated castor oil or silicon oxide added was 0.5% by weight.
When it was increased to 1.0% by weight, the leveling property of the conductor pattern surface was unexpectedly improved and the surface roughness was reduced to about half.
In the range of addition amount of ~8.0% by weight, the surface roughness is 10~4
The surface roughness decreases to 0%, and when the amount added is further increased, the surface roughness gradually increases without further decreasing. This tendency also applies when polyethylene wax or modified polyether is used, and in the case of these substances, good leveling properties can be obtained with a smaller amount added than in the case of hydrogenated castor oil or silicon oxide. . In other words, in the case of these substances, the surface roughness of the conductor pattern is reduced to nearly half of the conventional level with an addition amount of 0.1% by weight.
Furthermore, the surface roughness becomes minimum in the range of 0.4 to 2.0 weight %, and when it exceeds 2.0 weight %, the surface roughness gradually increases.

A multilayer circuit board capable of fully meeting the demands for high-density packaging could be manufactured from a green sheet having a conductor pattern with good surface leveling formed using the copper paste composition of the present invention.

〔Effect of the invention〕

As explained above, by using the conductor paste composition of the present invention, it is possible to achieve good leveling of the surface of the conductor pattern printed on the green sheet, and to effectively reduce variations in the electrical resistance and characteristic impedance of the conductor pattern. It will be possible to reduce the In this way, from green sheets with conductor patterns with good surface leveling, it is possible to manufacture highly reliable circuit boards that can be multi-layered and high-density mounted for convenience stores, etc. become.

Claims (2)

[Claims] 1. In a conductive paste composition for a green sheet comprising a conductive metal powder, an organic binder, and a solvent, at least one of hydrogenated castor oil and silicon oxide is added in an amount of 1 to 1, based on the weight of solid content contained in the composition. 1
A conductive paste composition for a green sheet, further comprising 0% by weight of a conductive paste composition. 2. In a conductive paste composition for a green sheet comprising a conductive metal powder, an organic binder, and a solvent, at least one of liquid polyethylene wax and urethane-modified polyether is added based on the weight of the surface area contained in the composition. A conductive paste composition for a green sheet, further comprising 0.1 to 5.0% by weight of .