JP2000076931A - Manufacture of ceramic substrate, thick film paste and organic binder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve an unbinding characteristic and a pattern forming characteristic. SOLUTION: This organic binder uses an organic compound, having a weight- average molecular weight of not more than Mc and enabling the presence of the value Mc satisfying the formulae η being proportional to Man (where n>1), if Ma>Mc and 0<Ma<1010, or η∝ Ma if Ma<=Mc and 0<Ma<1010. Here ηis the viscosity of a solution (that is, a vehicle) of the organic compound in a solvent with the shear rate of 0.2 sec-1, and Ma is the weight-average molecular weight of the organic compound.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a thick film paste,
And a method of manufacturing a ceramic substrate using the same.

[0002]

2. Description of the Related Art In the production of ceramic substrates, a thick film obtained by kneading a conductor powder such as copper or silver or an insulating powder such as a glass powder with an organic binder and a solvent (and an additive if necessary) and the like. The paste is used to form a wiring portion or an insulating portion on the green sheet by screen printing or the like. Here, the conductive paste using the conductive powder is used to form a conductor portion such as a wiring, and the insulating paste using the insulating powder is used to form an insulating portion.

A ceramic substrate is manufactured by laminating, bonding, and sintering a green sheet on which a wiring portion and / or an insulating portion formed of this thick film paste is formed, if necessary. This sintering step is generally performed in a nitrogen atmosphere in order to prevent oxidation of the conductor wiring portion, and the binder removal property of the organic binder determines the quality of the product.

[0004] As a binder for a thick film paste, an ethylcellulose-based resin has been generally used until recently due to its relatively good pattern formability. However, it is said that the ethyl cellulose resin has poor thermal decomposability and has a problem in binder removal. If the binder removal property of the organic binder in the thick film paste is poor, carbon remains even after sintering, and due to the influence of the residual carbon, disconnection of the conductor wiring, pinholes in the insulating portion, etc. There was a problem that cracks and the like occurred.

Therefore, in recent years, polystyrene resins and acrylic resins having good binder removal properties have been proposed as organic binders. However, these resins still have a problem in terms of pattern formability. For example, Japanese Patent Application Laid-Open No. Hei 5-234424 discloses a technique for improving pattern formability by using an acrylic resin. In this technique, the problem of thick film paste bleeding has been solved. Is not improved. This is because these conventional polystyrene resins and acrylic resins have strong spinnability and adhesiveness. When using a thick film paste using these conventional resins as a binder, when forming a pattern by a method such as printing,
The shape of the screen mesh is easily transferred to the pattern, and as a result, irregularities occur on the pattern surface. In particular, when a fine wiring having a width of about 20 μm to 80 μm is formed, irregularities on the surface of the pattern cause the pattern to break during sintering, and are fatal defects. Further, when these thick film pastes are used, stringing of the thick film paste or dripping of the pattern may occur during printing due to the strength of the spinnability, and in severe cases, the paste may come into contact with a nearby pattern.

[0006]

SUMMARY OF THE INVENTION Accordingly, the present invention is directed to a method of manufacturing a ceramic substrate free from defects such as disconnection of a wiring pattern, cracking of a substrate, and pinholes, and the like. A thick film paste which is free of defects and has good binder removal properties in a nitrogen atmosphere;
It is an object of the present invention to provide a method for manufacturing a ceramic substrate using the same.

[0007]

Means for Solving the Problems In order to achieve the above object, the present inventors have studied in detail the relationship among the weight average molecular weight, viscosity, binder removal property, paste printability, etc. of the organic binder in the paste. . As a result, they have found that the weight average molecular weight of the organic binder, which has conventionally been considered to be as high as possible because of obtaining a high viscosity, is desirably equal to or less than a certain value Mc. Here, the value Mc is a value determined by the relationship between the weight average molecular weight of the organic compound used as the organic binder and the solvent, and specifically, a vehicle obtained by mixing the organic compound and the solvent. The viscosity at a shear rate of 0.2 sec ^-1 is defined as η (however, the concentration (% by weight) of the organic compound in the vehicle is constant)
When the weight average molecular weight of the organic compound used as an organic binder to the Ma, Ma is 0 <a range of Ma <10 ^10, between η and ^{Ma, ηαMa n (Ma> Mc} , n>
1), η∝Ma (Ma ≦ Mc). Here, the relationship between ItaarufaMa is satisfied, means that the correlation coefficient r by the curve fitting is 0.8 or more by the least squares method, the relationship between ItaarufaMa ⁿ is satisfied, a power equation Means that the correlation coefficient r becomes 0.8 or more in the curve fitting by.

A range of the weight average molecular weight having a linear relationship between the viscosity η of the vehicle and the weight average molecular weight Ma of the organic compound (that is, a range in which the weight average molecular weight Ma is equal to or less than Mc).
In this case, the molecules of the organic binder are less likely to be entangled with each other, and the intermolecular interaction is small. Therefore, it is considered that a smooth pattern can be formed even with a highly adhesive polystyrene resin or acrylic resin. In addition, even with an ethylcellulose-based resin having a poor binder removal property, if it has a weight average molecular weight in this range, since the intermolecular interaction is small, it is considered that thermal decomposition easily proceeds easily and the binder removal property is improved. .

According to the present invention, by using an organic compound having such a value Mc having a weight-average molecular weight M of not more than Mc as an organic binder, good pattern forming properties and good binder removal properties can be obtained. It is based on a new finding by the present inventors that a thick film paste can be obtained. Incidentally, the present invention, polystyrene-based, acrylic,
Not only when using an ethylcellulose-based organic binder but also any of the commonly used thick-film paste binders and solvents, it is applicable by selecting a combination that satisfies the above relationship, and is particularly limited. There is no. For example, when terpineol is used as the solvent, Mc of ethyl cellulose is about 60,000, and Mc of acrylic resin is about 250,000. Therefore, when ethyl cellulose is used as the organic binder, one having a weight average molecular weight of 60,000 or less is used, and if it is an acrylic resin, one having 250,000 or less is used. In addition, as a solvent, besides terpineol, for example, butyl carbitol acetate, methyl-3-hydroxyhexanoate, trimethylpentanediol monoisobutyrate and the like can be used.

According to the present invention, there is provided a paste for a ceramic substrate comprising a powder for a thick film paste, a solvent, and an organic binder comprising an organic compound, wherein the organic compound comprises a solution comprising the organic compound and the solvent. Ie vehicle)
When the viscosity at a shear rate of 0.2 sec ^-1 is η and the weight average molecular weight of the organic compound is Ma, 0 <Ma <
10 ¹⁰ range, if Ma> Mc eta is proportional to Ma ⁿ (provided that n> 1), a compound if Ma ≦ Mc eta exists a value Mc as proportional to Ma, Organic A thick film paste having a binder having a weight average molecular weight M of Mc or less is provided. Usually, the weight average molecular weight M of the organic binder is preferably at least 20,000, at which a viscosity that is practically acceptable is obtained.

The thick-film paste of the present invention may be either a conductive paste containing a conductive powder as a powder for a thick-film paste or an insulating paste containing a ceramic powder as a powder for a thick-film paste. Good. Further, an additive or the like may be further included as necessary. The composition ratio of each component can also be appropriately changed as required, but usually, the powder for the thick film paste is 75 to 97% by weight, the organic binder is 0.5 to 5% by weight, and the solvent is 5 to 20% by weight. And When an additive is contained, the amount of the additive is usually 0.01 to 5% by weight.
And

Further, the present invention provides a method for manufacturing a ceramic substrate, comprising the steps of printing the above-mentioned thick film paste of the present invention to form a pattern made of the thick film paste, and heating and sintering the pattern. Is done. The thick-film paste of the present invention includes various components of a ceramic substrate such as a conductor such as a wiring pattern, an insulator such as an interlayer insulating film, a resistor or a protective film by appropriately selecting a powder for a thick-film paste to be contained. Can be used as a material for forming The ceramic substrate may be a multilayer substrate.

Further, the thick film paste of the present invention has no defects such as unevenness, bleeding or dripping of the pattern at the time of printing, and has good binder removal properties in a nitrogen atmosphere. It is possible to form a fine and uniform wiring pattern which was not present. Therefore, in the present invention, a substrate made of glass ceramic and a wiring pattern formed on the surface of the substrate and having a width of 20 μm to 80 μm and a thickness unevenness of 1/4 or less of the wiring pattern width are used. Provided are a ceramic substrate provided and a method of manufacturing a ceramic substrate for forming the wiring pattern using the conductive paste of the present invention.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to Examples and Comparative Examples. In the following examples, the viscosity was measured by a B-type viscometer, and the molecular weight was measured by GPC.
(Gel filtration chromatography).

<Examples 1 to 3 and Comparative Example 1> In this example, the case where ethyl cellulose was used as the organic binder for the thick film paste and α-terpineol was used as the solvent was examined.

(1) Preparation of Vehicle First, vehicles containing ethyl cellulose having various average molecular weights were prepared. Prepare ethyl cellulose (commercially available) having a weight average molecular weight of about 200,000, and add 10 to α-terpineol.
It dissolved so that it might become weight%. In the present example, the initial molecular weight of ethyl cellulose was 200,000, but it can be appropriately selected as needed. Further, in this embodiment, the concentration of ethyl cellulose is set to 10% by weight, but this concentration can be appropriately adjusted according to the desired composition of the thick film paste. This concentration is the concentration of the vehicle in the thick film paste.

The obtained solution is heated with stirring so that the solution temperature becomes 120 ° C., and the solution having a desired viscosity (ie,
Vehicle containing ethyl cellulose of the desired weight average molecular weight) was obtained. The viscosity (that is, the weight average molecular weight of the contained ethyl cellulose) can be adjusted by the heating temperature and the heating time. However, when the temperature is 140 ° C. or more, the heating temperature is 80 to 12 because ethyl cellulose is denatured.
0 ° C.

(2) Determination of Mc The relationship between the viscosity of the vehicle prepared as described above and the average molecular weight of ethyl cellulose was examined.
As shown ^{in, ηαMa n (Ma> Mc,} n> 1), η
It was confirmed that there was Mc such that ∝Ma (Ma ≦ Mc), and this was about 60,000. In FIG. 1, M
Samples having an average molecular weight of c or less are represented by ■, and samples having an average molecular weight greater than Mc are represented by ◇. As can be seen from this figure, in the case of ethylcellulose, in the region where the weight average molecular weight is equal to or less than Mc, the viscosity and the molecular weight (viscosity y) = 8.6 × 10 ⁻⁵ × (weight average molecular weight x).
A linear relationship of −2.02 is established, and in a region having a weight average molecular weight larger than Mc, (viscosity y) = 6.9 × 10 ⁻¹⁴ ×
(Weight average molecular weight x) ^2.9 is established.

(3) Preparation of Thick Film Paste A thick film paste was prepared based on the value of Mc obtained as described above. That is, a copper powder having an average particle size of 5 μm was used as the powder for the thick film paste, and the vehicle prepared in (1) and an amine-based dispersant as an additive were added thereto and kneaded with three rolls. A paste was prepared. The weight average molecular weight of ethyl cellulose in the vehicle was 10,000 in Example 1, 30,000 in Example 2, 60,000 in Example 3, and Comparative Example 1
Then, it was set to 100,000. The amount of each component is 90% copper powder.
% By weight, 1% by weight of ethyl cellulose, 8.9% by weight of α-terpineol, and 0.1% by weight of an amine-based dispersant.

(4) Preparation of Ceramic Substrate Next, as shown in FIG. 1, a glass ceramic green sheet 1 mainly composed of borosilicate glass (FIG. 1A)
A through-hole is formed by a punch in (FIG. 2 (b)),
After filling the prepared copper paste 5 to form the via hole 3, the wiring 4 was formed by screen printing using a copper paste on a suspended metal screen having a wiring width of 60 μm (FIG. 2C).

Here, the printability of the thick film paste was evaluated as follows. The value shown as smoothness is the difference between the maximum height and the minimum height of the wiring pattern, and the amount of bleeding is 60 μm, which is the width of the screen from the width of the printed pattern.
This is a value obtained by subtracting m. The average height of the pattern was determined as the pattern film thickness. Table 1 shows the results.

Further, the green sheet after printing the wiring pattern was cut into 100 mm × 100 mm, and 40 layers were laminated and bonded, and heated and sintered in a nitrogen atmosphere (FIG. 2D). In addition, the sintering is performed by raising the temperature to 850 ° C. at 100 ° C./hour in steam and maintaining the temperature for 3 hours.
The temperature was raised to 0 ° C. and maintained for 2 hours.

Here, the amount of residual carbon contained in the ceramic after sintering was analyzed, and the debinding property of the organic binder and the reliability of the ceramic substrate were examined. In addition,
The reliability of the ceramic substrate was evaluated based on the presence or absence of disconnection in the wiring pattern after sintering. Table 1 shows the results.

Finally, the obtained sintered body 6 (FIG. 2E)
Then, plating was performed, and pins were attached to obtain a ceramic multilayer wiring board 7 (FIG. 2F). As can be seen from Table 1, in Examples 1 to 3, by using ethyl cellulose having a weight average molecular weight (Mw) of 60,000 or less, it is possible to obtain a thick film paste having good pattern formability and binder removal properties. It was possible to obtain a highly reliable ceramic multilayer wiring substrate without disconnection by using it.

[0025]

[Table 1]

<Examples 4 to 6 and Comparative Example 2> In this example, a copolymer containing ethyl methacrylate and butyl methacrylate, which are one kind of acrylic resin, was used as an organic binder for a thick film paste. The case where α-terpineol was used as a solvent was examined.

First, 40% by weight of ethyl acrylate, 55% by weight of butyl methacrylate, and 5% by weight of methyl acrylate are heated together with a polymerization initiator in isopropyl alcohol to obtain ethyl methacrylate. Having a desired weight average molecular weight. A butyl methacrylate copolymer was synthesized. In addition,
The weight average molecular weight can be changed by adjusting the heating temperature and the overall heating time. Here, the heating temperature was 55 to 80 ° C., and the total heating time was 3 to 9 hours. By the way, after heating at 55 ° C. for 7 hours and then heating at 80 ° C. for 2 hours, a copolymer having a weight average molecular weight of 300,000 was obtained.

Using the obtained acrylic resins of various molecular weights and using α-terpineol as the solvent, the concentration is 10% by weight.
Was prepared and Mc was determined from the relationship between the viscosity of the vehicle and the weight average molecular weight in the same manner as in Examples 1 to 3 above. As a result, Mc was about 250,000.

Next, a thick film paste was prepared in the same manner as in Examples 1 to 3, except that the above-described vehicle containing an acrylic resin was used instead of the vehicle containing ethyl cellulose. Was evaluated. Table 1 shows the results
Shown in The weight average molecular weight of the acrylic resin was 100,000 in Example 4, 150,000 in Example 5, and 2 in Example 6.
50,000, and 300,000 in Comparative Example 2. As can be seen from Table 1 above, by using an acrylic resin having a weight average molecular weight of Mc of about 250,000 or less, it is possible to obtain a ceramic multilayer wiring board having good pattern forming properties and binder removal properties and no disconnection. Was.

[Brief description of the drawings]

FIG. 1 is a graph showing the relationship between the weight average molecular weight and the viscosity of ethyl cellulose.

FIG. 2 is an explanatory view showing a manufacturing process of the ceramic multilayer substrate.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Green sheet, 2 ... Drilling punch, 3 ... Through-hole, 4 ... Conductor wiring, 5 ... Conductive paste, 6 ... Sintered body, 7 ... Ceramic substrate.

Claims (8)

[Claims] 1. A ceramic substrate paste comprising a powder for a thick film paste, a solvent, and an organic binder comprising an organic compound, wherein the organic compound comprises a shear rate of a solution comprising the organic compound and the solvent. and a viscosity eta at 0.2 sec ^-1, when the weight average molecular weight of the organic compound and Ma, 0 <a range of Ma <10 ^10, if Ma> Mc eta is proportional to Ma ⁿ (where n > 1) If Ma ≦ Mc, the thick film paste is a compound having a value Mc in which η is proportional to Ma, wherein the weight average molecular weight of the organic binder is equal to or less than Mc. 2. The thick film paste according to claim 1, comprising 75 to 97% by weight of the powder, 0.5 to 5% by weight of the organic binder, and 5 to 20% by weight of the solvent. 3. A thick film paste comprising 0.5 to 5% by weight of ethyl cellulose having a weight average molecular weight of 20,000 to 60,000. 4. A thick film paste comprising an acrylic resin having a weight average molecular weight of 20,000 to 250,000, in an amount of 0.5 to 5% by weight. 5. A method of manufacturing a ceramic substrate, comprising the steps of: printing the thick film paste according to claim 1 to form a pattern made of the thick film paste; and heating and sintering the pattern. 6. A pattern made of a thick film paste containing a conductor powder, a solvent, and an organic binder made of an organic compound is formed on a surface of a base material made of glass ceramic, and the pattern is formed by heating and sintering to form a pattern. A method of manufacturing a ceramic substrate, comprising a step of forming a wiring pattern having a thickness of 20 μm to 80 μm and a thickness unevenness of 1/4 or less of the wiring pattern width. 7. The organic compound according to claim ^1, wherein the viscosity at a shear rate of 0.2 sec ^-1 is η and the weight-average molecular weight of the organic compound is Ma in a solution comprising the organic compound and the solvent. <in the range of ¹⁰ 10, Ma> Ma if Mc eta is proportional to ma ⁿ (provided that n> 1), a compound if Ma ≦ Mc eta is present the value Mc is proportional to the ma, the The method according to claim 6, wherein the weight average molecular weight of the organic binder is equal to or less than the Mc. 8. A substrate comprising a glass ceramic substrate and a wiring pattern formed on the surface of the substrate, wherein the width of the wiring pattern is 20 μm to 80 μm, and the unevenness of the film thickness of the wiring pattern is A ceramic substrate having a width of 1/4 or less.