JP2001064081A - Ceramic composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a ceramic composition having low specific dielectric constant and low coefficient of thermal expansion by adding a specific amount (wt.%), expressed in term of CaO, of a compound containing Ca or a specific amount (wt.%), expressed in term of MgO, of a compound containing Mg to a raw ceramic composition for a slurry, and to provide a green sheet good in producibility, which is useful for producing a multilayer ceramic substrate. SOLUTION: To a raw ceramic composition for a slurry, 0.1 to 5 wt.%, expressed in term of CaO, of a compound containing Ca or 0.1 to 5 wt.%, expressed in term of MgO, of a compound containing Mg is added. The preferable ceramic composition contains 40 to 72 wt.% borosilicate glass, 8 to 60 wt.% alumina as a filler and 0 to 37 wt.% cordierite. A green sheet is obtained by mixing the borosilicate glass having a softening point of 750 to 840 deg.C, the ceramic filler, an organic binder and a solvent to prepare a slurry and processing the slurry into the form of a sheet to form a green sheet.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a ceramic composition and a multilayer ceramic substrate.

[0002]

2. Description of the Related Art Conventionally, alumina (Al ₂ O ₃ ) is mainly used as a ceramic material for a multilayer ceramic substrate, and molybdenum (Mo), tungsten (W), which is a refractory metal co-sinterable with alumina as a conductor material, ) Is used. However, since the thermal expansion coefficient of alumina is as large as about 7 × 10 ^-6 / ° C, when silicon semiconductor elements are directly mounted on an alumina substrate, large stress acts on those connecting conductors, and reliability is obtained. I can't. Furthermore, the relative dielectric constant of alumina is relatively large, about 10, and signal propagation as a multilayer circuit board is not yet sufficiently fast. In addition, the resistance of the high melting point metal is relatively large, and it is difficult to miniaturize the wiring.

In order to solve the above problems, glass ceramics sintered at about 1000 ° C. or less are used as the ceramic material instead of alumina, and low-resistance copper or silver is used as the conductor material instead of the high melting point metal. / Multilayer circuit boards using palladium and the like are known. Incidentally, as this kind of technology, Japanese Patent Application Laid-Open Nos. 2-30641 and 10-3
No. 30,168 can be mentioned.

[0004]

The problem to be solved by the present invention is about 1
To provide a ceramic composition having a low relative dielectric constant and a low thermal expansion that can be sintered at a temperature of 000 ° C. or lower, to provide a green sheet with high productivity for producing a multilayer ceramic substrate, and recently to provide a multilayer ceramic. Since the demand for lowering the cost of substrates is increasing, it is necessary to provide them at a lower price.

[0005]

In order to solve the above-mentioned problems, the present inventors have studied a ceramic composition mainly composed of borosilicate glass having a low dielectric constant and a low thermal expansion.
The borosilicate glass has a composition in which a glass network structure component of SiO ₂ and B ₂ O ₃ is a main component and a modifying oxide such as an alkali oxide is added thereto. Glass is usually produced by melting a raw material oxide or carbonate and quenching it. If the melting temperature is high, the cost of the glass melting crucible and melting furnace is increased. In order to make a large amount of glass at low cost, the melting temperature is preferably about 1300 ° C. or less. Glass has a viscosity of 10
^7.6 Poise is characterized by a softening point. As the softening point, 750 to 840 ° C is selected. If the softening point exceeds 840 ° C., the above-mentioned glass melting temperature increases and it becomes difficult to produce a large amount of glass at low cost. Softening point
If the temperature is lower than 750 ° C, warpage or deformation is likely to occur when firing the surface conductors and resistors on the multilayer ceramic substrate.
Out of the scope of the present invention.

A process for manufacturing a multi-layer ceramic substrate in which a green sheet is prepared using borosilicate glass powder, a hole is formed in the green sheet, a conductor is printed, the sheets are laminated and pressed, and then sintered. In some cases, boric acid crystals were precipitated on the green sheet under a high humidity atmosphere, and a conductor printing defect occurred, resulting in poor productivity. The boric acid crystals precipitate on the green sheet because the water resistance of the borosilicate glass is poor. Considering the glass structure, in borosilicate glass containing no alkali, B ions are in oxygen three coordination. The three-coordinate oxygen in the glass structure is easily broken by the attack of water molecules and elutes into water. Boric acid crystals (H ₃ BO ₃ ) precipitate from the eluted B ₂ O ₃ . Alkali (Na, K
) Is added, the B ion becomes oxygen 4-coordinate. B in oxygen coordination in the glass structure is not easily broken by the attack of water molecules. Therefore, a composition in which an alkali oxide is added in substantially the same mole number as B ₂ O ₃ has high water resistance. The addition of an alkali can improve the water resistance, but increases the coefficient of thermal expansion and the relative dielectric constant. In order to give priority to low thermal expansion and low dielectric constant, which are the features of borosilicate glass, it is also important to use a glass to which a small amount of alkali is added, that is, a glass having not very good water resistance.

In the present invention, SiO ₂ : 68 to 82% by weight, B ₂ O ₃ : 12 to 23% by weight, R ₂ O (Na ₂ O and / or
K ₂ O): 1 to 5% by weight, Al ₂ O ₃ : A borosilicate glass consisting of 0 to 5% by weight is selected, and in the step of preparing a slurry, a compound containing Ca is added to the ceramic composition of the slurry raw material as CaO. It has been found that the addition of a compound containing 0.1 to 5% by weight in terms of MgO or / and 0.1 to 5% by weight in terms of MgO can suppress the boric acid crystal precipitation on the green sheet. As a compound containing Ca,
CaCO ₃ , Ca (OH) ₂ etc. are used, and as a compound containing Mg, M
gCO ₃ , Mg (OH) _{2 and the} like are used.

The ceramic substrate has a large bending strength (200).
MPa or more). Therefore, the ceramic composition needs to have a large bending strength after sintering. Since high strength cannot be obtained by using a borosilicate glass alone for a ceramic composition, it is necessary to add a ceramic filler. Alumina is most suitable as a filler for increasing the strength, but cordierite having a small characteristic is also added as a filler because of its large thermal expansion coefficient and relative dielectric constant. Preferred ceramic compositions are borosilicate glass: 40-72% by weight (55-75% by volume), alumina as filler: 8-60% by weight (5-45% by volume), cordierite: 0-37% by weight (0-75%). 35% by volume).

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION 77% SiO ₂ and B ₂
Borosilicate glass powder composed of 20% O _3, 2.7% K ₂ O, and 0.3% Al ₂ O ₃ (softening point: 825 ° C., coefficient of thermal expansion: 2.3)
× 10 ⁻⁶ / ° C.), alumina powder, cordierite powder, calcium carbonate powder, and magnesium carbonate powder were weighed to have the ceramic composition shown in Table 1. These ceramic compositions: 100 parts by weight, a water-soluble organic binder containing a modified acrylic resin as a main component: about 14 parts by weight, water as a solvent: about 75 parts by weight, and an ammonium acrylate-based dispersant: 0.3 Parts by weight were mixed with a ball mill to prepare a slurry. Here, as the binder material, a commercially available water-soluble organic binder excellent in environmental safety and health was used. Next, using the slurry, the thickness is 0.2 m by a doctor blade method.
A green sheet having a m and a width of 450 mm was prepared. The green sheet was cut into 50 mm square or 150 mm square.

First, a 150 mm square green sheet is placed in a thermo-hygrostat kept at a temperature of 25 ° C. and a relative humidity of 85 RH%.
Then, it was examined whether or not boric acid crystals having a diameter of 100 μm or more were deposited on the green sheet. The results are shown in Table 1. The compound containing Ca in the ceramic composition is 0.1 to 5% by weight in terms of CaO, and / or the compound containing Mg is MgO.
It was found that by adding 0.1 to 5% by weight in terms of, the precipitation of boric acid crystals on the green sheet can be suppressed.

[0011]

[Table 1]

Next, 30 sheets of 50 mm square sheets are laminated and 1
Pressing was performed at 30 ° C. and a pressure of 20 MPa for 10 minutes. The crimped body is placed in an electric furnace, and is heated from room temperature to 100 ° C./h in the atmosphere.
The temperature was raised to 500 ° C. at a heating rate of 2 ° C. and maintained at that temperature for 2 hours. Thereafter, the temperature was raised to a temperature shown in Table 1 at a heating rate of 100 ° C./h and maintained at that temperature for 2 hours to perform densification sintering. Was. For the obtained ceramic sintered body, the thermal expansion coefficient,
The relative dielectric constant and flexural strength were measured and are shown in Table 1. As shown in Table 1, the ceramic composition of the present invention has a coefficient of thermal expansion smaller than that of alumina (about 7 × 10 ⁻⁶ / ° C.), that is, 2.5 to 5.5 × 10 ^−6.
/ ° C and the relative dielectric constant of that of alumina (about 10)
Smaller than 4.6 to 7.5. Further, the transverse rupture strength is 200 MPa or more, which satisfies practical strength.

Next, holes (via holes) having a diameter of 0.13 mm are punched in a 150 mm square green sheet with a punch at a pitch of 0.5 mm.
The Ag / Pd paste is embedded in the hole by printing method, and the Ag / Pd paste is also printed on the surface of the green sheet by 0.2 mm.
Five layers each having a wiring pattern having a width formed by an ordinary method were laminated, pressed and fired in the same manner as described above. An Ag / Pd conductor was printed on the fired substrate surface, and fired in a belt-type electric furnace set at a maximum temperature of 850 ° C. The total firing time was 1 hour. After the formation of the surface conductor, there was no abnormality such as warpage or deformation, and it was useful as a thick film circuit board.

[0014]

The ceramic composition of the present invention has a temperature of 850.degree.
Since it can be sintered at a low temperature of 1000 ° C, it can be sintered simultaneously with low-resistance conductors such as Ag / Pd, Cu, and Au, and has a thermal expansion coefficient of 2.
It is close to the thermal expansion coefficient of Si at 2 to 5.5 × 10 ^-6 / ° C., and when a semiconductor element made of Si is mounted on a ceramic substrate using this composition, it occurs in the connecting conductor due to the difference in thermal expansion coefficient between the two. Since the stress is small, high reliability is obtained, and the relative dielectric constant is as low as 4.6 to 6.0, the signal propagation becomes high as a circuit board, and the bending strength is as large as 200 MPa or more, so that a practical board can be made. . Further, borosilicate glass, which is a main raw material of the ceramic composition of the present invention, has a softening point of 75%.
The temperature is 0 ° C. to 840 ° C., and boric acid crystals hardly precipitate from the green sheet produced using the ceramic composition of the present invention, and the effect of high productivity is obtained.

Claims (3)

[Claims] A first step of preparing a slurry by mixing a borosilicate glass, a ceramic filler, an organic binder and a solvent to form a slurry; and forming a green sheet by processing the slurry into a sheet. The compound containing Ca in the composition is converted to CaO to 0.1
Or 5% by weight, or / and 0.1 to 5% by weight of a compound containing Mg in terms of MgO. 2. A slurry preparing step of preparing a slurry by mixing borosilicate glass having a softening point of 750 ° C. to 840 ° C., a ceramic filler, an organic binder and a solvent, and processing the slurry into a sheet to form a green sheet. In the producing step, the compound containing Ca is added to the slurry raw material ceramic composition in an amount of 0.1 to 5% by weight in terms of CaO, and / or the compound containing Mg is added in an amount of 0.1 to 5% by weight converted to MgO. A ceramic composition. 3. The method according to claim 1, wherein the ceramic composition is borosilicate glass: 40 to 72% by weight (55 to 75% by volume), alumina as a filler 8 to 60% by weight (5 to 45% by volume), Cordierite: 0-37% by weight (0-35% by volume)
A ceramic composition comprising: