JPH0632384B2 - Method for manufacturing laminated ceramic substrate - Google Patents

Description

Detailed Description of the Invention a. BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a low temperature fired laminated ceramic substrate having a capacitor containing a dielectric material having a high dielectric constant, and more particularly to a dielectric for forming the laminated ceramic substrate. TECHNICAL FIELD The present invention relates to a method for manufacturing a laminated ceramic substrate capable of preventing a decrease in the permittivity of a permittivity material due to mutual diffusion of both layers when a layer and a low-dielectric-constant insulating layer are simultaneously fired and obtaining a large-capacity embedded capacitor. .

2. Description of the Related Art As an electric circuit board, a multilayer circuit ceramic board is used in which ceramics are multi-layered and conductor wiring is provided in each layer, and through holes and via holes for connecting each layer are provided. In this circuit board, the capacitor component is usually used by soldering a capacitor element called a chip capacitor on the surface of the circuit board. However, the surface of the circuit board is limited, and there are also semiconductor elements, resistance elements, and surface wiring conductors on the surface, which makes the board large. If these elements can be built in, the substrate can be downsized and highly integrated. Therefore, a laminated substrate in which a high-capacity capacitor using a dielectric layer having a high dielectric constant is incorporated is reported. In this case, a low dielectric constant material having a dielectric constant of 15 or less is used for the insulating layers other than the dielectric layer.
Otherwise, the problem of crosstalk and the problem of signal propagation delay in the signal distribution part will occur.

Problems to be Solved by the Invention Generally, a material having a perovskite structure containing lead is used as a dielectric material for these substrates, but after firing, the dielectric constant of the built-in dielectric material does not become built-in and the dielectric alone is fired. There was a problem that it would be much smaller than if you did. This is because the component of the insulating material diffuses into the dielectric material at the time of co-firing, and vice versa, the component of the dielectric material diffuses into the insulating material. This is because a liquid phase is generated and its diffusion is accelerated. For example, according to U.S. Pat.No. 4,567,542, the dielectric material embedded in the above-mentioned insulating material is about 3,000 at the maximum, which is 10,000 to 20,000 obtained when firing only the dielectric material without incorporating it. You can see that it is much smaller than

By the way, in recent years, as a method for solving such a problem, the following laminated ceramic substrate (component) or its manufacturing method has been proposed.

A heat resistant metal oxide thin film layer is interposed between a high dielectric layer having a via hole and formed of a high dielectric constant material and a low dielectric layer formed of a low dielectric constant material having an electrode on the surface. (See JP-A-60-89995).

A structure in which a dielectric green sheet, an insulator green sheet, and a metal green sheet are formed, through holes for connecting the sheets are provided, laminated and pressure-bonded, and then baked to manufacture (Japanese Patent Laid-Open No. 62-244631). (See the official gazette).

Two or more kinds of ceramic insulating layers that can be fired at 800 to 1500 ° C. are laminated, one or more kinds of the ceramic insulating layers are formed of a high dielectric constant material, and an electrode that has a capacitance as a capacitor is provided. However, a soft metal intermediate layer that can be fired is provided at the interface with another ceramic insulating layer (see Japanese Patent Laid-Open No. 62-265795).

In these laminated ceramic substrates, a barrier layer such as a heat-resistant metal oxide thin film layer, a metal body raw sheet, or a metal intermediate layer is interposed between layers, and the barrier layer forms a dielectric layer ( The liquid phase is prevented from moving due to mutual diffusion of the material when the insulating layer) is co-fired, and the dielectric constant of the material is prevented from lowering.

However, in the case of this monolithic ceramic substrate (component) or its manufacturing method, since a dissimilar material composed of a barrier layer is inserted inside the substrate, there is a problem that the structure of the substrate itself becomes thick in order to obtain a large-capacity capacitor. .

The present inventor has made the following discoveries as a result of various studies in view of such problems. That is, when the barrier layer is used, it is premised that a liquid phase is generated in the dielectric material at the time of firing, and the movement of the liquid phase is prevented.

When the liquid phase is generated in the temperature rising process, an endothermic peak appears, and in the temperature lowering process, an exothermic peak appears, and this endothermic (exothermic) peak temperature can be confirmed by DTA (differential thermal analysis).

The liquid phase is likely to occur when the dielectric material is not sufficiently synthesized. That is, in general, a dielectric material is synthesized by mixing and pulverizing necessary raw materials of respective components prior to sintering and then calcining, but the present situation is that sufficient synthesis is not possible.

The decrease in the dielectric constant during firing of the dielectric material is accelerated by the diffusion of the components of the dielectric material, and the diffusion is accelerated by the liquid phase generated in the dielectric material during firing.

Therefore, from these points, the present inventor has clarified that preventing the generation of the liquid phase is the best means, researching various methods for preventing the same, and preliminarily firing temperature of the dielectric material. It was clarified that the occurrence of the liquid phase can be prevented by setting the temperature above a predetermined temperature in relation to the above endothermic peak temperature at which the generation of the liquid phase can be confirmed.

The present invention is a method created by paying attention to such a clarification point, and an object of the present invention is to provide a method for simultaneously firing a dielectric layer and a low dielectric constant insulating layer forming a laminated ceramic substrate. (EN) A method for manufacturing a multilayer ceramic substrate, which prevents the generation of a liquid phase due to mutual diffusion of both layers, thereby preventing a decrease in the dielectric constant of a dielectric constant material, and capable of obtaining a large-capacity embedded capacitor. is there.

(B) Means for Solving Problems of the Invention And, as a means for achieving the above-mentioned object, a method for manufacturing a laminated ceramic substrate according to the present invention is a dielectric formed by a high dielectric constant material containing lead oxide as a main component. A body layer, and a low dielectric constant insulating layer formed of a material having a dielectric constant lower than that of the high dielectric constant material,
In a method of manufacturing a laminated ceramic substrate, wherein a laminated body having a capacitor forming electrode and a through hole for connecting a necessary wiring pattern and an interlayer is co-fired at a temperature of 1100 ° C. or less, a high dielectric constant material for forming the dielectric layer. As
The high dielectric constant material is composed of a high dielectric constant material that is calcined at a temperature at least 70 ° C. higher than the endothermic peak temperature in the differential thermal analysis.

Action In the method for manufacturing a laminated ceramic substrate of the present invention, the high dielectric constant material forming the dielectric layer is calcined at a temperature higher than the endothermic peak temperature of the high dielectric constant material by at least 70 ° C. by the differential thermal analysis. As a result, the synthesis can be sufficiently performed, and an action of preventing the generation of a liquid phase due to the mutual diffusion of the dielectric constant materials when the above-mentioned laminated body is simultaneously fired is exerted.

Here, the composition of the dielectric material used is Pb (Fe _1/3. Nb _2/3 )-
A Pb-based perovskite composition represented by (Fe _1/2. W _1/2 ) O ₃ is used. This is because since the firing temperature is as low as 1100 ° C. or lower, a low melting point metal such as Au, Ag, or Ag—Pd can be used as a material for the electrodes to be fired at the same time, and thus firing in an oxidizing atmosphere can be performed. In other words, if the firing temperature is high, only refractory metals such as W and Mo can be used. Since these metals are easily oxidized, they can be fired only in a reducing atmosphere. In this atmosphere, the dielectric material is also reduced and cannot be used. Is. On the other hand, if Pd or a metal with a high Pd content is used for the electrode material, it can be fired at a high temperature even in an oxidizing atmosphere, but since Pd is expensive and the conduction resistance increases,
It cannot be used as a conductor material for circuit boards.

As the insulating material, a material that can be fired at 1100 ° C or lower is used because it is fired simultaneously with the dielectric. Also, because of the above-mentioned problem of signal propagation delay, a dielectric constant of 15 or less is used.

For example, borosilicate glass and several oxides (eg MgO, CaO, BaO, SrO, Al ₂ O ₃ , PbO, K ₂ O, Na ₂ O, ZnO, Li ₂ O, Zr
Examples of the raw material include a mixture of glass containing O ₂ and TiO ₂ ) and a mixture of alumina, quartz, mullite, cordierite, spinel, and the like, but any material that can be fired at 800 to 1100 ° C. may be used.

In order to obtain a laminated substrate, it is preferable to use a sheet laminating method using a green sheet or a sheet printing laminating method. The case of the sheet laminating method will be described with reference to FIG. FIG. 1 shows all the steps in one drawing for convenience of explanation.

First, a raw material mixed powder for a low dielectric constant material is used and molded by a doctor blade method to obtain a low dielectric constant green sheet 1 having a thickness of about 0.1 to 0.5 mm. The wiring pattern 2 necessary for this is screen-printed using a conductor material paste such as Ag, Ag-Pd, Au which can be fired at 800 to 1100 ° C. For connecting to other conductor layers, 0.2-0.5m formed on the low dielectric constant green sheet 1 by a punching die or a punching machine.
Conductor paste 4 is filled through the through holes 3 of mΦ.

A capacitor forming electrode 6 and necessary through holes 3 and wiring patterns are formed on a green sheet 5 made of a high dielectric constant material having a thickness of about 30 to 400 μm obtained by the same method as described above. Furthermore, after laminating the low dielectric constant green sheet 1 on which a wiring pattern is printed underneath, 80-150 ° C, 50-250k
Thermocompression bonded under the condition of g / cm ² to integrate. And 800-1100
The ceramic substrate with a built-in capacitor is obtained by firing at a firing temperature of ℃. As shown in Fig. 1, a resistor ₇ such as RuO ₂ system or Bi ₂ Ru ₂ O ₇ system is formed on the substrate after firing by a normal thick film method, and if necessary, at the same time inside the substrate and on the surface simultaneously with the substrate. It can also be obtained by firing.

EXAMPLES The present invention will be described in detail below with reference to examples and comparative examples. The unit is shown in% by weight.

Example 1 CaO 18.2%, Al ₂ O ₃ 1 prepared by melting at 1450 ° C. and quenching in water
Average particle size _{3 to 3} with composition of 8.2%, SiO ₂ 54.5%, B ₂ O ₃ 9.1%.
Solvent (toluene), binder (acrylic resin) plasticizer (DOP) was added to a mixture of 60% of 5 μm glass powder and 40% of alumina powder with an average particle size of 1.2 μm, and they were sufficiently kneaded to obtain a viscosity of 2,000-40,000 CPS. Of the low dielectric constant material shown in FIG. 2 having a thickness of 0.4 mm was prepared by using an ordinary doctor blade method. The characteristics of the substrate obtained by firing this green sheet 1 at 900 ° C are:
_r = 7.8, specific gravity = 2.9, thermal expansion coefficient = 5.3 × 10 ⁻⁶ / ° C., and anti-deposition strength = 2400 kg / cm ² . This green sheet 1
After cutting into 30mm square, 0.3mm Φ through hole 3 is formed, and then conductive material paste 4 made by adding organic binder (ethyl cellulose) and solvent (terpineol) to mixed powder of Ag90%, Pd10% is through hole. 3 was filled, and the wiring pattern 2 was printed using the simultaneous conductor paste.

A predetermined amount of PbO, Fe ₂ O ₃ , Nb ₂ O ₅ , WO ₃ and ZnO is weighed, then wet pulverized and dried. The dry raw material is calcined at 850 ° C, wet-ground and then dried.

A high-permittivity green sheet 5 having a thickness of 100 μm was prepared in the same manner as above. After this green sheet 5 was cut into 30 mm squares, 20 mm square electrodes 6 were screen-printed at the opposite positions on both sides using the conductor paste 4. After printing, the low dielectric constant green sheet 1 and the high dielectric constant green sheet 5 were laminated so as to have the structure shown in FIG. ² and then thermocompression bonded at 100 ° C. and 100 kg / cm ² . Using an ordinary electric batch furnace, baking was performed at 900 ° C. for 30 minutes in an oxidizing atmosphere.
The obtained capacitance is 110 nF and the permittivity of the high dielectric constant material is ε _r =
It was 4,200 at 1kHZ. Calcination of the used dielectric material
When analyzed by DTA, as shown in Fig. 3, no endothermic peak in the temperature rising process, which indicates the generation of the liquid phase, is observed, indicating that the liquid phase does not occur in the firing process. A similar structure
When a dielectric material prepared by calcination at 800 ° C. was used, the obtained dielectric constant was 4,100, which was almost the same as that in the above-mentioned example. Moreover, the liquid phase did not occur in the analysis result of the dielectric material by DTA.

Comparative Example 1 A dielectric material having the same structure as that of Example 1 and having the same composition as that of Example 1 was prepared by calcination at 750 ° C. The obtained capacitance was 80 nF and the dielectric constant was 3,000, which was low. The dielectric material used was heated at a heating rate of 5 ° C / min and analyzed by DTA.
There was an endothermic peak during the temperature rising process at ℃, indicating that a liquid phase was generated. Thus, it was found that there is a strong relationship between the presence or absence of liquid phase generation indicated by DTA and the permittivity of the built-in dielectric material. At least the calcination temperature must be 70 ° C higher than the endothermic peak temperature of DTA. I understood.

Example 2. Commercially available alumino-lead borosilicate glass (PbO-Al ₂ O ₃ -SiO ₂ -B
0.4mm thick green in ₂ O ₃ system) In a similar manner 50% glass powder pulverized average particle size 3-3.5 created in μm and the average particle diameter 1.2 mixture Example 1 Alumina powder 50% of μm to The characteristics of the substrate obtained by firing the sheet at 900 ° C are: dielectric constant ε _r = 7.
5, Cao specific gravity = 2.95, thermal expansion coefficient = 5.5 × 10 ^{−6 /} ° C., and electrolysis strength = 2,200 kg / cm ² .

As shown in FIG. 5, this low dielectric constant green sheet 1
After cutting into mm squares and forming through holes 3 of 0.3 mm Φ, the Ag-Pd conductor paste 4 prepared in Example 1 is filled into the through holes 3 and the wiring pattern 2 is printed using the same conductor paste. did. After cutting the high dielectric constant material green sheet calcined at 850 ° C. prepared in Example 1 into 30 mm × 30 mm, a 20 mm square capacitor electrode 6 was formed using the Ag-Pd conductor paste prepared in Example 1. Printed. After stacking the high-permittivity green sheet 5 on which electrodes are printed, the high-permittivity green sheet (intermediate layer) 8 not printed, and the low-permittivity green sheet 1 as described above, thermocompression bonding is performed at 100 ° C. and 100 kg / cm ² conditions. And unite. A substrate with a built-in capacitor was prepared by simultaneous firing at 900 ° C. After firing, the high dielectric constant layer (intermediate layer) 8 is provided as an intermediate layer in order to reduce mutual diffusion between the high dielectric constant layer 5 and the low dielectric constant layer 1. The capacitance of the built-in capacitor of the obtained substrate was 140 nF and the dielectric constant of the high dielectric constant layer 5 was 4,800.

Comparative Example 2 A laminated substrate of Example 2 was prepared using the dielectric material used in Comparative Example 1 and calcined at 750 ° C. The obtained dielectric had a dielectric constant of 3,400, which was considerably smaller than that of Example 2.

C. EFFECTS OF THE INVENTION According to the method for manufacturing a laminated ceramic substrate of the present invention, as the high dielectric constant material for forming the dielectric layer, a high temperature of at least 70 ° C. or higher than the endothermic peak temperature of the high dielectric constant material by differential thermal analysis. The high-dielectric constant material calcined in 1. is used, and the high-dielectric-constant material can be sufficiently synthesized by calcination at the temperature, and the high-dielectric-constant material for forming a capacitor in the temperature rising process at the time of simultaneous firing of the substrate laminate is formed. Since the liquid phase is not generated in the dielectric constant material, there is an effect that a built-in capacitor having a higher capacity (dielectric constant) can be obtained as compared with the conventional laminated ceramic substrate.

Further, since a barrier layer such as a heat-resistant metal oxide thin film layer or a metal layer is not required, a large capacity capacitor can be obtained without making the substrate thickness extremely thick.

Therefore, according to the present invention, it is possible to manufacture a ceramic substrate of a small size and a highly integrated circuit.

[Brief description of drawings]

1, 2 and 5 show an embodiment of the laminated ceramic substrate of the present invention. Figures 3 and 4 show differential thermal analysis (DTA)
3 is a diagram showing the relationship between the general temperature and the differential heat in the temperature rising process by. FIG. 3 shows the case of the present invention in which neither heat generation nor heat absorption occurs, and FIG. 4 shows the case of a comparative example in which a liquid phase occurs and an endothermic peak occurs. 1 …… Low-permittivity green sheet, 2 …… Wiring pattern, 3
...... Through hole, 4 ...... Conductor paste, 5 ...... High permittivity green sheet, 6 ...... Capacitor forming electrode, 7 ...... Resistor, 8 ...... High permittivity green sheet (intermediate layer)

 ─────────────────────────────────────────────────── ─── Continuation of front page (56) References JP-A-60-89995 (JP, A) JP-A-61-48996 (JP, A) JP-A-62-196811 (JP, A) JP-A-62- 244631 (JP, A) JP 62-265795 (JP, A)

Claims (1)

[Claims] 1. A dielectric layer formed of a high dielectric constant material containing lead oxide as a main component, a low dielectric constant insulating layer formed of a material having a dielectric constant lower than the high dielectric constant material, and a capacitor forming electrode. In the method for manufacturing a laminated ceramic substrate, in which a laminated body having a required wiring pattern and through holes connecting layers is co-fired at a temperature of 1100 ° C. or less, the high dielectric constant material is used as the high dielectric constant material. A method for producing a laminated ceramic substrate, which comprises using a high dielectric constant material that is calcined at a temperature at least 70 ° C. higher than the endothermic peak temperature of the high index material by differential thermal analysis.