JP2652229B2 - Multilayer circuit ceramic substrate - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a low-temperature co-fired multilayer circuit ceramic substrate having a large-capacity capacitor having a dielectric layer with a high dielectric constant.

2. Description of the Related Art In recent years, in electronic equipment or electronic devices, IC, LS
There is an increasing demand for miniaturization of circuit boards on which I is mounted.
2. Description of the Related Art Conventionally, as an electronic circuit board, a multilayer circuit ceramic board having a multilayer ceramic, wiring conductors in each layer, and having through holes and via holes connecting the respective layers has been used. In this circuit board, a capacitor component is generally used by soldering a capacitor element called a chip capacitor to the surface of the circuit board. However, the surface of the circuit board has semiconductor elements and surface wiring conductors, and the mounting of a capacitor element increases the size of the board. Therefore, there is a certain limit in mounting a semiconductor IC or the like with higher integration. If these elements can be built into the substrate, the substrate can be reduced in size and integrated. Therefore, it has been reported that a laminated substrate in which a dielectric layer having a high dielectric constant is built in as a high-capacitance capacitor and a low dielectric constant material having a dielectric constant of 15 or less is used as an insulating layer other than the dielectric layer. .

Problems to be Solved by the Invention The dielectric material of a built-in laminated substrate generally has a composition different from that of an insulating material, and has a perovskite structure containing lead. When two types of dielectric materials having different compositions are laminated by simultaneous firing, warpage occurs due to stress generated due to a difference in thermal expansion coefficient and pores generated at an interface due to reaction between the materials. For this reason, the reliability was remarkably reduced, and a practical laminated substrate could not be obtained.

Also, since the high dielectric constant material to be built in has a specific temperature characteristic depending on the composition, if a material with various types of temperature characteristics is required, the basic composition system must be changed or various additives added. We choose thing and cope. In addition, compatibility with the insulating layer also becomes a problem, and in the end, such a multilayer substrate has been inevitably disadvantageous in terms of process and cost.

The present invention solves the above problems and provides a highly reliable laminated substrate having a built-in capacitor capable of coping with a wide range of temperature characteristics. MEANS FOR SOLVING THE PROBLEMS The laminated circuit ceramic substrate according to claim 1 of the present invention as a means for solving the above-mentioned problem has a dielectric constant of 15 perovskite containing lead oxide on its internal or external surface. On a substrate that is simultaneously fired at a low temperature of 800 to 1100 ° C including a high dielectric layer and a low dielectric constant insulating layer having a dielectric constant of 15 or less,
Providing a buffer electrode between the high dielectric layer and the low dielectric constant insulating layer,
Further, the same dielectric glass component contained in the low dielectric constant insulating layer is added to the high dielectric layer in an amount of 0.1 to 1.0% by weight.

The multilayer circuit ceramic substrate according to claim 2 is the above-described claim 1.
In the invention, the glass _{component, CaO-Al 2 O 3 -SiO} 2
Characterized in that it is a -B ₂ O ₃ system.

Action As a low dielectric constant ceramic material, a material that can be fired at 800 to 1100 ° C. is used. Such materials include borosilicate glass and several more oxides (eg, MgO, CaO, Ba
As a raw material, a mixture of glass containing O, Al ₂ O ₃ , PbO, K ₂ O, Na ₂ O, ZnO, Li ₂ O), alumina, quartz or the like can be used. In addition to the above, any material that can be fired at 800 to 1100 ° C may be used. The dielectric constant is 15 or less, preferably 10 or less.

As the high dielectric constant material, a composition that can be fired at 800 to 1100 ° C. is used, but since it is fired simultaneously, it is necessary to select a material that substantially matches the firing temperature of the low dielectric constant material. 800-110
Materials that can be fired at 0 ° C and have a dielectric constant of more than 15 include Pb
A Pb-based perovskite composition represented by (Fe _1/3 .Nb _2/3 ) O _3- (Fe _1/2 .W _1/2 ) O ₃ is most suitable. As the glass to be added to this, a glass based on a low dielectric constant material having a dielectric constant of 15 or less is used.

FIG. 1 shows the relationship between the dielectric constant of a high dielectric layer in a low-temperature co-fired substrate and the amount of glass added to temperature. Although the ε _r (dielectric constant) of the inner layer capacitor is about 3000, the ε _{r at} the Curie point near room temperature (about 25 ° C.) as the glass addition amount increases to 0.2, 0.4, and 0.6% by weight.
Is gradually decreasing. As a result, the temperature characteristic of ε _r is gradually flattened, and it can be seen that the glass acts as a shifter.

FIG. 2 shows the relationship between the dielectric loss (tan δ) and the amount of glass added to the temperature. It can be seen that when the glass addition amount is increased, tan δ deteriorates at room temperature or higher. The preferable dielectric loss is 2% or less at room temperature, but the material added with 1.0% by weight of glass has a tan δ of about 1.7% at 25 ° C., which is about 1.5% deteriorated compared to the material without glass added. Based on this result, the upper limit of the glass addition amount was 1% by weight. Table 1 shows the relationship between the amount of glass added to the high dielectric layer having a substrate area of 40 × 40 mm and the amount of warpage of the substrate. It can be seen that the amount of warpage is reduced as the glass addition increases. In particular, when glass is added in an amount of 0.1% by weight or more, the amount of warpage is suppressed to 1/5 or less as compared with the case where no glass is added, so that a remarkable effect is exhibited.

Since the high dielectric constant material and the low dielectric constant material described above have the same component system of glass, they have good compatibility and are advantageous in terms of process and cost. That is, during firing, the liquid phase generated in the dielectric material performs an interaction more smoothly, and accordingly, the diffused glass wets the dielectric substrate more uniformly, thereby relaxing the stress generated due to the difference in the coefficient of thermal expansion. .

As shown in Table 1, the same component glass component contained in the low dielectric constant insulating layer was added to the high dielectric layer in an amount of 0.1%.
Even in the case of adding about 1.0% by weight, complete warpage cannot be prevented. Further, since the addition rate of the glass component is different between the high dielectric layer and the low dielectric constant insulating layer, the glass component is changed from the low dielectric constant insulating layer having a large amount of the glass component to the high dielectric layer having a small glass component. The transition occurs and the dielectric constant decreases. However, in the present invention, by providing a buffer electrode between the high dielectric layer and the low dielectric constant insulating layer, the occurrence of warpage can be further reduced. Migration can be reduced, and a decrease in dielectric constant can be prevented.

Therefore, the warpage of the substrate and the decrease in the dielectric constant caused by the difference in the thermal expansion coefficient between the high dielectric layer and the low dielectric constant insulating layer are suppressed, and a highly reliable substrate can be obtained.

Example As a low dielectric constant material, CaO 18.2% Al ₂ O ₃ 18.2%, SiO ₂ 54.5%, B ₂ O ₃ 9.1 produced by melting at 1450 ° C. and quenching in water
60% glass powder with an average particle size of 3 to 3.5 μm
And a mixture of 40% alumina powder with an average particle size of 1.2 μm,
A toluene solvent, an acrylic resin binder, and a DOP plasticizer were added and sufficiently kneaded to prepare a slurry having a viscosity of 2,000 to 40,000 CPS. Further, a low dielectric constant green sheet 1 having a thickness of 0.4 mm as shown in FIG. 3 was prepared by using a usual doctor blade method.

The characteristics of the substrate obtained by firing this green sheet at 900 ° C. are as follows: dielectric constant ε _r = 7.8, bulk specific gravity = 2.9, thermal expansion coefficient 5.3 × 10 ⁻⁶ /
° C., precipitation strength = 2400 kg / cm ² .

Furthermore, after cutting this green sheet into 60 mm square,
A through hole 3 is formed by forming a through hole 3 having a diameter of 0.3 mm, and a conductive material paste 4 prepared by adding an organic binder of ethyl cellulose and a terpineol solvent to a mixed powder of Ag 90% and Pd 10% is used. The wiring pattern 6 was printed.

High dielectric constant _{material, PbO, Fe 2 O 3,} Nb 2 O 5, WO 3, is ZnO was wet pulverized by a predetermined amount weighed dry. 850 ° C for dry ingredients
Then, a predetermined amount of the glass powder used for the low dielectric material is weighed and added thereto. After wet pulverization, it was dried. High-dielectric-constant green sheets 5 and 9 having a thickness of 100 μm were prepared by the doctor blade method in the same manner as the low-dielectric green sheets. After this green sheet was cut into a 40 mm square, an 8 mm square electrode 6 was screen-printed using the conductive paste 4 at opposite positions on both sides so as to have the structure shown in FIG. After laminating low dielectric constant green sheet 1 and high dielectric constant green sheets 5 and 9, 100 ℃, 100kg / c
and thermo-compression bonding in m ^2. Further, as shown in FIG. 3, a buffer electrode 8 is provided between the high dielectric layer 9 and the low dielectric constant insulating layer 1. The buffer electrode 8 is formed of the low dielectric constant insulating layer 1 of the high dielectric layer 9.
It is formed so as to cover the side surface. Firing in an oxidizing atmosphere was performed at 900 ° C. for 30 minutes using a normal electric batch furnace. The dielectric constant of the obtained high dielectric constant material is ε _r = 5000 at 1 KHz (25
° C).

In this embodiment, the high dielectric constant layer is formed by the green sheet method, but the high dielectric constant layer can be formed by a method of printing a dielectric paste such as screen printing.

Comparative Example A multilayer ceramic substrate having the same structure as in Example 1 and using a glass-free high dielectric constant material was produced. The resulting substrates were warped due to stress generated due to different thermal expansion coefficients.

C. As is clear from the above description, according to the multilayer circuit ceramic substrate of the present invention, the same component glass component contained in the low dielectric constant insulating layer is contained in the high dielectric layer in an amount of 0.1 to 1.0% by weight. % To improve the consistency between the two layers, and since the buffer electrode is provided between the two layers, the warpage of the substrate due to the difference in the thermal expansion coefficient between the two layers can be suppressed. Since the migration of the glass component from the low dielectric constant insulating layer to the high dielectric layer can be prevented, a reduction in the dielectric constant of the substrate can be prevented.

As described above, the multilayer circuit ceramic substrate of the present invention can control the temperature characteristics in a wide range and can reduce the warpage of the substrate.
Moreover, since a decrease in the dielectric constant can be prevented, a substrate having much higher reliability than that of the conventional substrate can be obtained, and the effect is extremely large.

[Brief description of the drawings]

FIG. 1 shows the relationship between the dielectric constant and the amount of glass added to the high dielectric layer with respect to temperature. FIG. 2 shows the relationship between the dielectric loss and the amount of glass added to the high dielectric layer with respect to temperature. FIG. 3 is a cross-sectional view of a multilayer ceramic substrate before firing according to the present invention. 1 ... low dielectric constant green sheet, 2 ... wiring pattern,
3 ... through-hole, 4 ... conductor paste, 5 and 9 ...
… High dielectric constant green sheet, 6… internal electrode, 7… resistor, 8… buffer electrode

Claims (2)

(57) [Claims] 1. A high-permittivity layer having a dielectric constant of more than 15 of a perovskite-based material containing lead oxide on a built-in or outer surface thereof and having a dielectric constant of 15 or more.
In a substrate including the following low dielectric constant insulating layer and co-fired at a low temperature at 800 to 1100 ° C. integrally, a buffer electrode is provided between the high dielectric layer and the low dielectric constant insulating layer, and the high dielectric layer A multilayer circuit ceramic substrate, wherein a glass component of the same component type contained in the low dielectric constant insulating layer is added in an amount of 0.1 to 1.0% by weight. 2. The method according to claim 1, wherein said glass component is CaO--Al ₂ O ₃ --SiO ₂ --B ₂
The multilayer circuit ceramic substrate according to claim 1, which is an O ₃ -based.