JPH0612911A - Conductive composition and multilayer circuit board - Google Patents

Abstract

PURPOSE:To obtain a multilayer circuit board stable in wiring pattern by using a composition which contains conductive metallic powder and glass flit where the degree of acid base is specified. CONSTITUTION:A conductive composition is composed of conductive metallic powder and glass flit 0.504 or over in degree of acid base. A multilayer circuit board is formed by interposing a baked substance layer rich in glass 0.504 or over in degree of acid base between an insulating substrate layer including glass material and a wiring pattern consisting of conductive material. The conductive metallic powder is a material low in melting point and small in resistivity value such as gold, silver, or copper, and it is desirable that this conductive material should be in powder shape. It is to be desired that the quantity of glass flit added should be set to 30-55vol.% of the volume of a conductive material. By this conductive composition, the reaction between the wiring pattern and the board material is suppressed, and a stable board property can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a conductive composition and a multilayer circuit board, and more particularly to a circuit board provided with a conductive composition containing a conductive metal powder and an insulating substrate layer containing a glass material.

[0002]

2. Description of the Related Art As a circuit board used for a hybrid integrated circuit of electronic equipment, for example, Japanese Patent Application Laid-Open No. 61-108192 discloses a circuit board containing a glass frit made of a metal oxide and an inorganic material filler such as alumina. A multilayer circuit board in which an insulating substrate layer made of a composition (hereinafter, simply referred to as a substrate) and a wiring pattern made of a conductive material having a low melting point and a small specific resistance, such as a gold-based, silver-based, or copper-based material are laminated. Has been done.
The multilayer circuit board has a small relative permittivity of the board and a small specific resistance of the circuit pattern, and thus has a high signal propagation speed. Further, since it can be fired at a low temperature, it can be provided at a low cost.

[0003]

In the conventional multilayer circuit board described above, when the board and the wiring pattern are integrally sintered, when the temperature becomes high, the conductive material forming the wiring pattern is used inside the board layer or the board. May diffuse to the interface with. It is considered that this is because the conductive material reacts with oxygen in the metal oxide forming the substrate to form a weak bond between the two, and the conductive material is apparently in an oxidized state. When such a phenomenon occurs, the multilayer circuit board is discolored and the electrical characteristics such as dielectric loss tangent are deteriorated.

An object of the first invention is to provide a stable conductive composition for a substrate containing a glass material.
A second object of the present invention is to provide a multilayer circuit board whose wiring pattern is stable with respect to the board.

[0005]

The conductive composition according to the first invention contains a conductive metal powder and a metal oxide having an acid-basic degree of 0.504 or more. A multilayer circuit board according to a second aspect of the present invention includes a board containing a glass material and a wiring pattern made of a conductive material and arranged on the board. In this multilayer circuit board, a metal oxide fired body layer having an acid-base degree of 0.504 or more is formed between the board and the wiring pattern.

*** Conductive Metal Powder The conductive metal powder used in the present invention refers to a conductive material having a low melting point and a small specific resistance value, such as gold, silver, or copper.
This conductive material is preferably in powder form. In this case, the average particle size of the conductive material is preferably 5 to 25 μm, particularly preferably 10 to 20 μm.

The conductive materials may be used in combination of two or more kinds. Glass Frit The glass frit used in the present invention contains a plurality of metal oxide components. Especially, the acidity is 0.504
Or more, preferably 0.506 or more, more preferably 0.
It is a glass frit of 508 or more. This is because the glass frit having a low acid-base degree is likely to take in other metal atoms because oxygen in the component metal oxide is easily extracted by, for example, ion exchange. In other words, the above-mentioned conductive material may diffuse into the metal oxide that constitutes the substrate, possibly impairing the electrical characteristics of the multilayer circuit board.

The acid-basicity referred to in the present invention is as described in J. A. Duffy and M.D. D. Ingram's paper (GLASS SCI
ENCE AND TECHNOLGY, 7 , 8). According to this, the acid basicity (pO) of the multi-component glass frit containing the i-type metal oxide is defined by the following formula (1).

[0009]

[Equation 1]

In the formula, Zi is the oxidation number of the metal component contained in each metal oxide, ei is the atomic ratio of the component i when the oxygen atom in the component i is 1 g atom, and Gi is the basicity of the component i. Is. Here, Gi is L. G. Since the electronegativity Xi of Pauling can be used to obtain the following equation (2), the equation (1) can be rewritten as the following equation (3).

[0011]

[Equation 2]

[0012]

[Equation 3]

The acid-base degree used in the present invention is 0.504.
The above glass frit is, for example, CaO or ThO.₂, B
eO, SrO, MgO, Y₂O₃, Rare earth oxides, Sc
₂O ₃, BaO, HfO₂, ZrO₂, Al₂O₃, L
i₂O, TiO, CeO₂, SiO₂, B₂O₃, Ta
₂O_Five, Cr₂O₃And a group consisting of ZnO
It is preferable to use a metal oxide as a main component. like this
Glass frit is a main component of metal oxide at high temperature
Non-reducing Gibbs free energy of formation
Since it is an oxide, it can be returned even when firing in a non-oxidizing atmosphere.
It is not sourced.

As an example of the glass frit containing a non-reducing oxide as a main component, Al ₂ O ₃ is 18.0.
Mol%, SiO ₂ 50.0 mol%, B ₂ O ₃ 5.0
Examples include those containing mol%, 9.0 mol% ZnO and 18.0 mol% MgO. In this glass frit,
Xi, Zi and ei of each component are shown in Table 1 below.

[0015]

[Table 1]

Based on the data in Table 1, the pO value obtained by the above equation (3) is 0.5067. here,
The method of obtaining the ei value will be described by taking the above glass frit as an example. First, the atomic weight of total oxygen in the glass frit is calculated. This is obtained by calculating the oxygen amount for each component and adding them. The amount of oxygen for each component can be obtained by multiplying the ratio of the component in the glass frit by (the number of moles of oxygen atoms / the total number of moles of atoms contained in the component). For example, with Al ₂ O ₃ , the following formula (4) is obtained.

[0017]

[Equation 4]

This is treated with SiO ₂ , B ₂ O ₃ , ZnO and M
When gO is also calculated and the obtained values are added to obtain the atomic weight of total oxygen, it becomes 0.61. The ei of each component is
It is determined from the atomic weight of the non-oxygen component (Al in the case of Al ₂ O ₃ ) when the atomic weight of the total oxygen obtained is 1.
The ei value of Al ₂ O ₃ is derived from the following equation (5).

[0019]

[Equation 5]

The glass frit used in the present invention is a crystallized glass which precipitates at least one crystal of cordierite, mullite, spinel, anorthite, celdian, β-spodumene, dolomite, betalite and its substituted derivative after firing. A frit is more preferable. When a crystallized glass frit that precipitates the above-mentioned crystals is used, the strength after firing becomes higher. In particular, when a crystallized glass frit that precipitates anorthite or Celsian is used, the strength of the sintered body is further increased. Since crystallized glass frit capable of depositing cordierite, mullite or β-spodumene has a small coefficient of thermal expansion after firing, it is effective in constructing a wiring pattern for mounting silicon chip electronic components such as ICs. Is.

Particularly preferred as a crystallized glass for precipitating the above-mentioned crystals is B ₂ O as a network homer.
Contains ₃ and SiO ₂ , A as an intermediate
l ₂ O ₃ , and further includes alkaline earth metal oxides (MgO, CaO, Sr) as a network modifier.
It is a glass frit containing O, BaO) or ZnO.
Such a glass frit has a wide range of vitrification,
Moreover, since the yield point is around 600 to 800 ° C., it is suitable for low temperature firing of the conductive composition according to the present invention at about 800 to 1050 ° C. In this glass frit, CaO and S are used as network modifiers.
If rO or BaO is selected, RO.Al ₂ O ₃ .2SiO ₂ (R is an alkaline earth metal) type crystal such as anorthite or Celsian can be deposited. Also,
If MgO is selected, cordierite crystals can be obtained, and Z
If nO is selected, garnite crystals can be obtained.

The above glass frit has a yield point of 700.
It is especially preferable if it is ˜850 ° C. When the yield point is lower than 700 ° C., the softening flow excessively occurs during firing, and it becomes difficult for the conductive material to be uniformly distributed on the particle surface. As a result,
When a wiring pattern made of the conductive composition of the present invention is formed on a multilayer circuit board, the conductive material and the multilayer circuit board are likely to come into direct contact with each other. Therefore, when the multilayer circuit board contains a glass material, the conductive material may diffuse into the circuit board, and the electrical characteristics of the circuit board may be impaired. On the other hand, when the yield point is 850 ° C. or higher, the sintering behavior is similar to that of a green sheet for a multilayer circuit board, so that the softening and flowing may not be completed completely. In this case, the conductive material comes into direct contact with the circuit board.

The above-mentioned glass frit is manufactured by a known method. That is, it can be manufactured by mixing predetermined components in a predetermined ratio, heating and melting the mixture, gradually cooling it, and then pulverizing it. The average particle size of the glass frit is not particularly limited, but is preferably 10 μm or less, particularly 6 to 8 μm. If the average particle size exceeds 10 μm, it becomes difficult to screen print the composition of the present invention in a precise pattern,
Further, the softening flow during firing may be insufficient. Conductive Composition In the conductive composition of the present invention, the addition amount of glass frit is preferably set to 30 to 55% by volume, particularly 40 to 50% by volume of the volume of the conductive material. If the content is 30% by volume or less, the conductive material may come into direct contact with the substrate, which may impair the electrical characteristics of the circuit board. On the contrary, 55% by volume
When it exceeds, the resistance value of the wiring pattern formed by this composition becomes high. Therefore, it is difficult to speed up the signal. Multilayer Circuit Board FIG. 1 is a vertical sectional view of a multilayer circuit board according to an example of the second invention. This multilayer circuit board has a wiring pattern using the conductive composition according to the first invention. In the figure, a multilayer circuit board 1 is mainly composed of a laminated board 2, internal wiring 3 and surface wiring 5.

The laminated substrate 2 is composed of integrated sheets 2a, 2b and 2c obtained by laminating three green sheets to be substrates and integrally firing them. Each green sheet is composed of a composition for circuit boards containing an inorganic material filler and a glass frit. The inorganic material filler is a component for improving the strength of the laminated substrate 2, and includes cristobalite, quartz, corundum (α alumina), mullite, stabilized zirconia, steatite,
Forsterite, cordierite, spinel and zircon can be exemplified. These inorganic material fillers are 2
A mixture of two or more species may be used. Quartz, corundum, and cordierite are particularly preferable as the inorganic material filler. In this case, a high-strength multilayer circuit board can be realized.
In addition, since the thermal expansion coefficient of the substrate decreases and approaches the thermal expansion coefficient of silicon (around 40 × 10 ⁻⁷ / ° C.), silicon chip electronic components such as ICs arranged on the multilayer circuit board 1 are subject to thermal shock. Even if it receives, it becomes difficult to easily separate from the multilayer circuit board 1. When corundum is used as the inorganic material filler, the multilayer circuit board 1 having high cost performance can be realized in addition to the above effects.

On the other hand, the glass frit contains a plurality of metal oxide components. As a glass frit, B
₂ O ₃ , SiO ₂ and PbO as main components, B ₂
Mainly composed of O ₃ , SiO ₂ and BaO, Ca
Those containing O, B ₂ O ₃ and SiO ₂ as main components, SiO
Examples thereof include those containing ₂ , B ₂ O ₃ , CaO and Al ₂ O ₃ as main components or those containing SiO ₂ , B ₂ O ₃ , CaO and ZrO ₂ as main components.

The internal wiring 3 is formed in a predetermined pattern between the sheets 2a and 2b and between the sheets 2b and 2c.
The internal wirings 3 are connected to each other through the through holes 4 and extend to the surface of the laminated substrate 2 through the through holes 4. Internal wiring 3 extending on the surface of the laminated substrate 2
Of the electrode 3 on the upper surface and the lower surface of the laminated substrate 2
a is formed. The internal wiring 3 is formed by using the conductive composition according to the first invention described above.

The surface wirings 5 are arranged on the upper surface and the lower surface of the laminated substrate 2 in the figure. The surface wiring 5 is formed in a predetermined circuit pattern by using the conductive composition according to the first invention described above. Next, a method of manufacturing the multilayer circuit board 1 will be described. First, the above-mentioned circuit board composition, an organic binder (for example, polymethacrylate resin), a plasticizer (for example, dibutyl phthalate), a solvent (for example, methyl ethyl ketone), and other additives (for example, a defoaming agent) are predetermined. At a ratio of 24 to 40 by using a ball mill.
Knead for about 72 hours to prepare a homogeneous slurry. After defoaming the slurry, it is molded into a green sheet having a thickness of about 100 to 300 μm by a known method such as a doctor blade method. This green sheet is provided with through holes at predetermined locations.

Next, a predetermined internal wiring pattern or surface wiring pattern is formed on the surface of the obtained green sheet. Both wiring patterns are formed by filling the through holes with the paste of the conductive composition according to the first invention (hereinafter referred to as conductive paste), and then printing the conductive paste in a predetermined pattern on the surface of the green sheet. it can. The conductive paste is obtained by adding an organic binder and a solvent to the conductive composition according to the first invention and kneading the mixture. As the organic binder, for example, ethyl cellulose is used. As the solvent, for example, MIBE,
2,2,4-trimethyl-1,3-pentanediol monoisobutyrate or the like is used. In addition, after printing the wiring pattern, the through holes may be filled with a conductive paste.

Next, the green sheets on which the wiring patterns are printed are laminated in a predetermined order and subjected to thermocompression bonding to obtain a laminated body. Then, the obtained laminated body is cut into a predetermined size and fired. The firing of the laminate is preferably performed in two steps. The first-stage firing aims at removing organic substances (organic binders) contained in the green sheet or the like.
The firing temperature is usually around 500 ° C. The firing in the second stage aims at firing the composition for circuit boards and the conductive composition. The firing temperature at this time is determined based on the melting points of the materials contained in each composition, and is usually 800 to 105.
It is about 0 ° C. The firing atmosphere is appropriately adjusted according to the conductive material contained in the conductive composition. For example, when a copper-based conductive paste is used, firing is performed in a non-oxidizing atmosphere. When firing is completed, the multilayer circuit board 1 is obtained.

In the obtained multilayer circuit board 1, as shown in FIG. 2, the glass-rich layer 6 is formed between the sheets 2a and 2b of the laminated board 2 and the internal wiring 3. Note that FIG.
[Fig. 2] is an enlarged schematic view of part A of Fig. 1. The glass-rich layer 6 is formed by the glass frit contained in the conductive paste and prevents the internal wiring 3 from directly contacting the sheets 2a and 2b. In addition, the glass-rich layer 6
Is a glass-rich layer having an acid-base degree of 0.504 or more, and therefore, even when the multilayer circuit board 1 is fired or when the multilayer circuit board 1 is used at a high temperature, a gold-based material that constitutes the internal wiring 3,
A conductive material such as silver or copper is less likely to diffuse. Therefore, the conductive material forming the internal wiring 3 is unlikely to diffuse into the laminated substrate 2. As a result, the multilayer circuit board 1 is less likely to undergo discoloration and is less likely to deteriorate in electrical characteristics such as dielectric loss tangent.

On the multilayer circuit board 1, electronic parts such as ICs, thick film resistors, etc. are arranged at a predetermined portion of the surface wiring 5 (for example, between the surface wiring 5 and the electrode 3a).

[0032]

Examples 1 to 18 5.0 parts by weight of ethyl cellulose (organic binder), 2,2,4, based on 100 parts by weight of a mixture of silver powder and the glass frits shown in Tables 3, 4 and 5. -Trimethyl-
1,3-Pentanediol monoisobutyrate (solvent)
95.0% by weight was mixed and further kneaded with a three-roll mill to prepare a conductive paste. The electronegativity Xi and the oxidation number Zi of each metal oxide forming the glass frit are shown in Table 2.

[0033]

[Table 2]

On the other hand, 44.0% by weight of a glass frit containing MgO, Al ₂ O ₃ and SiO ₂ as main components, 19.0% by weight of alumina and 6.5% by weight of an acrylic resin,
2.5 wt% of dibutyl phthalate (plasticizer) and 28.0 wt% of toluene were mixed using a ball mill to produce a composition for circuit boards. Several green sheets were formed from this composition for circuit boards by the doctor blade method. Then, the above-mentioned conductive paste was screen-printed on the green sheet to form a predetermined wiring pattern.

Next, four green sheets were laminated and thermocompression bonded, and this was subjected to an oxidizing atmosphere at 900 ° C. for a peak time of 3 times.
It was set at 0 minutes and baked. The presence or absence of discoloration and the electrical characteristics of the obtained multilayer circuit board were examined. Discoloration is EPM
It was judged by A (X-ray microanalyzer) and colorimetric analysis. For the electrical characteristics, the dielectric loss tangent was examined. The dielectric loss tangent was measured by the bridge method using a capacitance meter (YHP model 4297). The dielectric loss tangent is preferably 7 or less. The results are shown in Tables 3, 4, and 5.

[0036]

[Table 3]

[0037]

[Table 4]

[0038]

[Table 5]

As is clear from Table 3, Table 4 and Table 5,
When the acid-basicity of the glass frit is 0.506 or more, more preferably 0.508 or more, the dielectric loss tangent of the multilayer circuit board becomes better.

[0040]

The conductive composition according to the first invention is stable against a substrate containing a glass material because it contains a glass frit having an acid-base ratio of 0.504 or more. In the multilayer circuit board according to the second aspect of the present invention, since the above-mentioned glass-rich layer is formed between the board and the wiring pattern, the reaction between the wiring pattern and the board material is suppressed, and stable board characteristics are obtained.

[Brief description of drawings]

FIG. 1 is a partial vertical cross-sectional view of an example of a circuit board according to a second invention.

FIG. 2 is an enlarged schematic view of part A of FIG.

[Explanation of symbols]

 1 multilayer circuit board 2 laminated board 3 internal wiring 5 surface wiring

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yutaka Irumagawa 1-1 Yamashita-cho, Kokubun-shi, Kagoshima Prefecture Kyocera stock company Kagoshima Kokubun factory (72) Akira Imoto 1-1 Yamashita-cho, Kokubun-shi, Kagoshima Kagoshima stock company Kokubun Plant (72) Inventor Takuya Yokoyama 1-215, Inagekaigan, Mihama-ku, Chiba, Chiba Prefecture Building No. 402

Claims (2)

[Claims] 1. A conductive composition comprising a conductive metal powder and a glass frit having an acid-base degree of 0.504 or more. 2. A multi-layer circuit board comprising an insulating substrate layer containing a glass material and a wiring pattern made of a conductive material, wherein the insulating substrate layer and the wiring pattern have an acid-base group. A multi-layer circuit board, wherein a glass-rich fired body layer having a degree of 0.504 or more is interposed.