JPS62265795A - Ceramic board with built-in capacitor - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a circuit board in which an electronic circuit including a capacitor is provided in a laminated ceramic by co-firing.

[Prior Art] Conventionally, circuit boards using ceramics as an insulator have been used as circuit boards for electronic appliances such as consumer products and computers. Typical examples include conductor-co-fired alumina ceramic substrates that use W or MO as wiring conductors, wiring conductors such as Ag, Aq-Pd, Au, CLJ, and glass on fired alumina ceramic substrates. Thick film circuit boards are known in which circuits are formed by baking an insulating material made of . These boards have been developed due to the demand for higher wiring density and smaller electronic components.
Fine patterns and multilayer wiring have been implemented.

For the ceramic materials used, it is better to have a small dielectric constant due to signal propagation delay issues, and the dielectric constant εr of alumina and glass insulating materials used for thick film substrates is set to a value of 10 or less. Materials with increasingly low dielectric constants are being required. Further, for the capacitors necessary for the circuit, a method is generally used in which chipped capacitor parts are mounted on the wiring board.

Problems to be Solved by the Invention The above-mentioned capacitor mounting method is unfavorable from the viewpoints of high density and miniaturization, and if the capacitor is constructed by forming electrodes inside the substrate, it will be much more difficult to mount the capacitor. High density and miniaturization are practical.

However, the dielectric constant of alumina and glass insulating materials is 10 or less for the reasons mentioned above, and even if a capacitor is constructed, the capacitance obtained is small, and it has been difficult to obtain a large capacitance. To solve this problem, a capacitor with a large capacity can be obtained by laminating a material with a high dielectric constant inside a ceramic substrate with a low dielectric constant and forming electrodes.

However, when ceramics with different compositions are laminated and composited by co-firing, cracks occur due to stress caused by different coefficients of thermal expansion and pores generated at the interface due to reactions between materials with different compositions. However, reliability deteriorated significantly and it was not possible to obtain a practical product.

[Means for Solving the Problems] The present invention aims to solve the above problems, and includes a substrate obtained by co-firing a ceramic insulating layer, a capacitor electrode, and other electronic circuit wiring. has a laminated structure of two or more types of ceramics with different compositions that can be fired at 800 to 1100°C, one or more of which has a dielectric constant of 15 or more, and has an electrode inside that takes the capacity as a capacitor. A ceramic substrate with a built-in condenser is characterized in that a soft metal intermediate layer that can be fired at the above-mentioned temperature is provided on the entire surface or most of the interface with other ceramics.

That is, the present invention constitutes a capacitor by laminating a ceramic material having a dielectric constant of 15 or more inside a ceramic substrate having a small dielectric constant, and provides a highly reliable ceramic circuit board free from cracks.

Ceramic materials that can be fired at 800 to 1100°C are used, such as borosilicate glass and several types of oxides (for example, M!; 10.
CaO, Bad, AI 203, PbO, 20. N
Examples include those made from a mixture of glass containing (a2O, zno, Li 20, etc.) and alumina, quartz, etc., but any other materials that can be fired at 800 to 1100'C may be used. Ceramics with a low dielectric constant are those with a dielectric constant of less than 15, preferably 10 or less. Materials with dielectric constant of 15 or more 800-110
A material that can be fired at 0'(:) is used, but since they are fired at the same time, it is necessary to select a material that almost matches the firing temperature of the material with a small dielectric constant.

Among those that can be fired at 800 to 1100°C are Pb
(Fe1/3 * Nb2/3) 03 (Fe
1/2・W1/2) Pb represented by the 03 series
8 with a dielectric constant of 15 or more, such as a composite perovskite composition or a BaTi0J compound with flux
Any material that can be fired at 00 to 1100'C may be used.

ACI, ACI-Pd, Act-Pt, and Ag
ACI-based materials such as -Pd-Pt and soft materials that are easily plastically deformed such as AU and Cu are used.

The metal intermediate layer needs to be fired simultaneously with the ceramic insulating layer, and powders of these metals or, if necessary, a small amount of ceramic raw material powder is used as the raw material. Since the melting point of these metals is below 1100°C, the firing temperature of the raw material and final product is 800 to 1100°C, which means that the firing temperature of the ceramic material to be fired at the same time is 800°C to 1100°C.
This is the reason for using a temperature range of 00 to 1100°C. Since such metals are soft and easily deformed plastically, they can alleviate the stress caused by thermal g adhesion that occurs at the ceramic interface after co-firing, and stress concentration on defects such as pores that tend to occur at the interface, thereby reducing cracks that occur. can be prevented. By forming opposing electrodes inside the ceramic having a high dielectric constant, a capacitor with a large capacity can be constructed.

In order to provide the above structure, it is preferable to use a sheet lamination method using green sheets or a sheet printing lamination method.

The case of the sheet lamination method will be explained with reference to FIG. FIG. 1 shows all the steps in one drawing for convenience of explanation. First, a green sheet 1 having a thickness of approximately 0.1 to 0.5 mm is obtained by forming a raw material mixed powder for a low dielectric constant material by a doctor blade method. The wiring pattern 2 required for this is 800~11 of Act, Ag-Pd, AU, Cu, etc.
Screen printing is performed using a conductive material paste that can be fired at 00°C. Further, connections to other conductive layers are made through through holes 3 of 0.2 to 0.5 mmφ formed in the green sheet 1 using a punching die or punching machine, and filled with a conductive material paste 4.

Electrodes 6 for forming a capacitor, and necessary through holes 3 and wiring patterns are formed on a green sheet 5 made of a high dielectric constant material and having a thickness of about 30 to 400 μm obtained by the same method as described above.

Using the same Green Sea 1 to 1, a metal material paste such as Ag, Ag-Pd, Au, or CU is printed on the entire surface or most of one side to form the metal intermediate layer 7. However, since the conductor in the connection through-hole must not come into contact with the intermediate coupling layer, the width of about 0.2 to 3 mm around the through-hole should not be marked. After laminating green sheets 1 and 1 on which a metal intermediate layer is printed on the top and bottom of a green sheet 5 on which a capacitor electric (~) is printed, and a low dielectric constant green sheet 1 on which a wiring pattern is roughly printed on the bottom thereof, 80~150°C150~250 kg/cm
Heat-compress and integrate under the conditions of 2. And 800-11
A ceramic substrate with a built-in capacitor is obtained by firing at a firing temperature of 00'C.

Note that the thickness of the metal intermediate layer 7 is preferably 5 to 50 μm;
(If it is thicker than this, it will be more likely to warp during simultaneous firing.) If the material used for the gold, intermediate layer, or conductor can be fired in an oxidizing atmosphere such as Ag, Ag-Pd, or Au, the resistor 8, such as RuO2 type or Bi2Ru2O7 type, is coated with a normal thick film on the substrate after firing. If necessary, it can be formed inside or on the surface of the substrate by co-firing with the substrate. , Cu, etc., which require firing in a neutral or reducing atmosphere, use LaB6, Sn○2, BaRuO3,5
Resistors such as those based on rRuO3 can be obtained by a thick film method or co-firing. Further, in the case of such a structure, the metal intermediate layer can be grounded and used as a guard electrode for preventing crosstalk.

[Example] The present invention will be described in detail below with reference to Examples and Comparative Examples. All percentages are expressed as mono%.

Example 1 Ca018 created by melting at 1450'C and quenching in water
．． 2%, A I 20318.2%, 5iO254°5
%, B20] with a composition of 9.1% and an average particle size of 3 to 3.
A solvent (toluene) and a binder (
Add acrylic resin) and plasticizer (DOP>), mix thoroughly to create a slurry with a viscosity of 2000 to 40000 cos, and use the usual doctor blade method to form a slurry with a thickness of 0.411.
A green sheet 9 made of a low dielectric constant material as shown in FIG. The characteristics of the substrate obtained by firing this green sheet 9 at 900'C are as follows: dielectric constant εr = 7.8, high specific gravity = 2
．． 9, thermal expansion coefficient = 5.3x 10-6 / 'C
1 bending strength = 2400 kg/cm2. After cutting this green sheet 9 into 30mm square, 0.3m
After forming the mφ through hole 3, 90% Ag, Pd
Fill through-all 3 with conductive material paste 4 created by adding line-by-line binder (ethyl cellulose) and solvent (terpineol) to the mixed end of lO%, and print wiring pattern 2 using the same conductive paste 1~ did.

After weighing a predetermined amount of PbO1Fe203, Nb2O5, and WO38, combine them (wet) and dry. Dry: 750 yen for 1
After calcining at °C, wet crushing, and drying at 92°C. A green sheet 1o of a high dielectric constant material of 100μ (IIj'i) was created in the same manner as above.
After cutting 0 into 30mm squares, place them at opposing positions on both sides.
A 2h+m square electrode 6 using the above conductive material paste 4
was screen printed.

After cutting the same green sheet into 30mm squares, 0.3
After forming a through hole of mmφ and filling the through hole with the above conductive paste, the area around the through hole is
AC+100% on one side, leaving a width of 12mm
A conductive paste prepared by adding and kneading an organic binder (ethyl cellulose) and a solvent to powder was screen printed as the intermediate metal layer 7. Roughly one green sheet on which the intermediate metal layer 7 was printed was prepared in the same manner.

A low dielectric constant green sheet 9 and a high dielectric constant green sheet 1 that have been printed have the structure shown in Figure 2.
After laminating 0, 100℃, 100k(]/Cm2
It was heat-pressed. 900 using a regular electric batch furnace
It was fired in an oxidizing atmosphere at C130 minutes. The thickness of the metal intermediate layer of the obtained capacitor built-in substrate was 10 μm.

In addition, no cracks occurred, and the capacity reduced by 1q was 1
At 10 nF, the dielectric constant of the high dielectric constant material is εr = 3800
At 1 k l-1z came to market.

Comparative Example 1 A product with the same structure as Example 1 was made using the same materials except that there was no intermediate metal layer, but this product was made of high dielectric constant material H.
A large number of cranks occurred.

Example 2 Commercially available alumino porcelain glass (Pb0-A120
3-3iO2-8203M>l>f'? Example 1 A mixture of 50% glass powder with an average particle size of 3 to 3.5 μm and 50% alumina powder with an average particle size of 1.2 μm prepared by
A green sheet of low dielectric material having a thickness of 0.4 mm was prepared in the same manner as described above. The characteristics of the substrate obtained by firing this green sheet at 900'C are as follows: dielectric constant εr = 7.5, high specific gravity = 2.95, coefficient of thermal expansion = 5.5x10-6/'C1
The bending strength was 2200 kg/cm2.

Using the green sheet of the high dielectric constant material prepared in Example 1, a capacitor-embedded board having the same @ structure as in Example 1 was prepared. The intermediate metal layer is Ag90%, pd10
% alloy was used, and the thickness was 40 μm by increasing the number of screen printings compared to Example 1.

The 1q board has no cracks and the capacity is 1
At 20nF, the dielectric constant of the high dielectric constant material is εr=4200a
It was t1 kHz.

Comparative Example 2 A similar structure as in Example 2 was made using the same materials except that the intermediate metal layer was not provided, but in this case, many cracks occurred in the high dielectric constant material.

Example 3 An organic binder (ethyl cellulose) was added to a mixed powder consisting of 100 parts of an alloy powder of 99% A0 and 1% Pt and 5 parts of the ceramic raw material powder used for the green sheet of high dielectric constant material prepared in Example 1. Solvent (terpineol)
was added and sufficiently kneaded to prepare a paste for intermediate metal layer. The green sheet of low dielectric constant material prepared in Example 1 and having a thickness of O, h+m was cut into a size of 35×30 mm. Using the above intermediate metal layer paste on this green sheet,
A 26 mm intermediate metal layer was printed. The high dielectric constant material green sheet prepared in Example 1 was cut into 3 pieces of 3 mm x 30 mm, and then the ΔΩ-PdΩ-Pd conductor prepared in Example 1 was used as a base and an electrode for a condenser was printed. After laminating the high-permittivity green sheet with printed electrodes, the unprinted high-permittivity green sheet, and the low-permittivity green sheet with the intermediate metal layer printed on it, the sheets were heated at 100°C. They were integrated by thermocompression bonding under the conditions of 100 kg/am2. Two opposing sides were cut to expose the ends of the condenser electrodes on the sides. The cut side is A above.
A Q-Pd conductor paste was used to print and connect the exposed conductors.The printed conductor is shown in Figure 3.

The volume 1 of the substrate obtained by firing in an oxidizing atmosphere at 900'C for 130 minutes was heated to 380nF to form the high dielectric constant phase γ.
The dielectric constant of Mi1 was εr =4/+00.

[Effect of Bugomei] The present invention is a highly reliable circuit board that can be obtained by co-firing with a ceramic substrate containing a capacitor and does not cause cranking, and can easily produce a multilayer substrate containing a large capacity capacitor. Obtainable.

[Brief explanation of drawings]

1 to 3 are explanatory diagrams showing the configuration of an embodiment of the present invention. 1...Green sheet, 2...Wiring pattern, 3.
...Through hole, 4...Conductor material paste, 5...
- Green sheet, 6... Electrode, 7... Intermediate metal layer, 8... Resistor. 9... Green sheet of low dielectric material, 10... Green sheet of high dielectric material.

Claims (1)

[Claims] (1) In a substrate obtained by co-firing a ceramic insulating layer, a capacitor electrode, and other electronic circuit wiring, the ceramic insulating layer has a composition of 800 to 1100
It has a structure in which two or more types of ceramics that can be fired at °C are laminated, one or more of which has a dielectric constant of 15 or more, has an electrode inside that has a capacitance as a capacitor, and is different from other ceramics. A ceramic substrate with a built-in capacitor, characterized in that a soft metal intermediate layer that can be fired at the above temperature is provided on the entire surface or most of the interface.