JPS601886A - Ceramic circuit board with 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 FIELD OF INDUSTRIAL APPLICATION The present invention relates to a ceramic circuit board that can be used in electrical circuits requiring high-density packaging.

Conventional Structures and Problems The remarkable development of semiconductor materials in recent years has had a great impact on the miniaturization of equipment. Along with this, the circuit components and circuit boards that constitute the components of devices are undergoing major changes, especially in terms of miniaturization. As a result, passive elements such as resistors and capacitors have changed to high-density, low-cost mounting formats, such as chips or hybridization by baking thick films onto substrates. In addition, wiring boards used for mutual wiring of electric circuits have been miniaturized through fine-line wiring and high-density wiring through multilayer wiring.

However, when trying to further miniaturize devices, there is a limit to simply miniaturizing individual circuit components and circuit boards as has been done in the past, and it is difficult to miniaturize the entire circuit including circuit parts and circuit boards. There must be.

A typical high-density wiring board is an alumina wiring board. This wiring board uses a high melting point metal such as tungsten (W) or molybdenum (Mo) as a wiring conductor material, so the board material alumina (Mo)
203) can be simultaneously sintered in a reducing atmosphere. Therefore, by simply repeatedly providing an alumina insulating layer and a wiring conductor layer on a raw alumina sheet and firing them simultaneously,
A multilayer wiring board can be easily obtained. In addition, the thermal, mechanical, and electrical properties of the alumina sintered body are the best for use as a circuit board. Taking advantage of these characteristics, alumina wiring boards are widely used as high-density wiring boards for ICs, LSIs, etc., and are especially effective as wiring boards for digital ICs that handle high-speed signals and have a large number of wires. .

However, although the alumina wiring board has such great features, it has one drawback that cannot be overcome. The above-mentioned wiring board is characterized only by high wiring density, and in circuits such as analog circuits that require a large number of resistors and capacitors, a large effect cannot be obtained in terms of high density of the entire board. In other words, unlike digital circuits, in analog circuits it is not sufficient to simply have high wiring density, and it is important to increase the density of the entire circuit board, including many resistors and capacitors. However, since the conductive material used in alumina wiring boards is a base metal that is easily oxidized, for example, when trying to form a resistor or capacitor as a thick film after sintering the board, the atmosphere must be reducing. Recently, silicide-glass based glazed resistors that can be fired in a reducing atmosphere have been put into practical use as resistor materials, but none have been used as capacitor materials. In this case, we had no choice but to use a method that was extremely tedious and could not be called high-density mounting, such as mounting chip-shaped capacitor parts sintered in the air on a sintered wiring board later. Ta. Another possibility is to use the alumina insulation layer between the conductor layers as a capacitor. However, since the dielectric constant of the alumina sintered body is at most about 8 to 1o, if the thickness of the insulating layer is 30 μm, there will be no difference between the opposing electrodes! 1m7
The capacitance per unit is only around 3pF. For this reason,
To obtain a capacitor with a large capacity, it is necessary to increase the electrode area, further reduce the thickness of the insulating layer, or increase the number of laminated layers.

Such a method cannot be said to be a good idea in terms of cost and process.

As explained above, conventional alumina wiring boards with conductor wiring made of tungsten or molybdenum can achieve high wiring density, but cannot form large capacitors, and the board as a whole must be mounted at high density. For this reason, the actual situation is that its scope of use is extremely limited.

OBJECTS OF THE INVENTION An object of the present invention is to provide a ceramic circuit board that enables high-density packaging in which a large capacitor is formed simultaneously with sintering.

Structure of the Invention The ceramic circuit board of the present invention comprises a ceramic insulating substrate, a conductive layer made of tungsten or molybdenum as a wiring material, and an insulating layer mainly composed of lanthanum chromate coated with tungsten particles or molybdenum particles. It is characterized by being composed of a capacitor layer consisting of an aggregate.

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described with reference to the drawings.

FIG. 1 shows a sectional view of a ceramic circuit board including a capacitor in one embodiment of the present invention. ζ FIG. 2 shows a model diagram of the capacitor layer portion in FIG. 1. In both figures, 1 is a ceramic substrate, 2 and 4
is a conductor layer made of tungsten or molybdenum, 3
5 is a capacitor, 5 is a tungsten or molybdenum particle, and 6 is an insulating layer mainly composed of lanthanum chromate.

Turpentine oil prepared by premixing tungsten or molybdenum particles with an average particle size of 0.5 to 6 μm and an insulating layer composition containing lanthanum chromate as a main component, and further adding 1.01% ethyl cellulose (flW). A ceramic insulating substrate was prepared by adding polyvinyl butyral resin as a binder to an inorganic composition mainly composed of aluminum oxide (A1203) and kneading it thoroughly to form a capacitor paste. One small piece of the sheet was soaked.

A conductor layer 2 was provided by printing a conductor paste made of tungsten or molybdenum with a particle size of approximately 1 μm on one side of a small piece of this raw sheet. The capacitor paste is printed on this conductor layer 2 to form a capacitor layer 3, and the conductor paste is further printed to form a conductor layer 4.
Legs. This printed raw sheet small piece was heated for 1,400 hours in a reducing atmosphere containing a small amount of water vapor in a mixed gas of hydrogen and nitrogen.
It was sintered at a high temperature of ~1600'C. The thickness of the capacitor layer after sintering was 30 μm, and the opposing area of conductor layers 2 and 4 was 25 mm. The table below shows typical characteristics of the capacitor section of the circuit board obtained in this example. show. From this table, it can be seen that the circuit board of this example is a circuit board equipped with a large capacitor having excellent capacitor characteristics. Furthermore, no influence on capacitor characteristics due to differences in conductor layer thickness or conductor particles was observed.

As shown in FIG. 2, the capacitor layer of the circuit board of this embodiment has tungsten or molybdenum particles 5 surrounded by an insulating thin layer 6 mainly composed of lanthanum chromate. The structure is such that they are placed side by side.

A large capacitance can be obtained because the capacitor made of this thin insulating layer is arranged in a tilted configuration as if it were three-dimensionally connected in series and parallel by conductive particles.

In the examples, a so-called alumina substrate containing aluminum oxide as a main component was used as the ceramic substrate, but the present invention is not limited to this, and any material may be used as long as it functions as an insulating substrate after sintering. Furthermore, considering the mechanism of the capacitor layer, the thin insulating layer covering the conductor particles only needs to be composed mainly of lanthanum chromate, and may contain additives to improve capacitor characteristics. . Furthermore, in the embodiment, only one capacitor layer is provided on one side of the substrate, but conductor layers and capacitor layers may be laminated alternately to increase the capacitance, or these conductor layers may be provided within the substrate. It is also possible to increase the mounting density of the board by forming a capacitor layer.

Effects of the Invention As is clear from the above explanation, the present invention has a capacitor layer composed of an aggregate of particles coated with tungsten particles or molybdenum particles in an insulating layer mainly composed of lanthanum chromate. A circuit board containing a capacitor with a capacitance can be obtained simultaneously with the sintering of the board. This has the advantage that it is possible to provide a wiring board that includes a capacitor function and is extremely advantageous in terms of circuit configuration, compared to a conventional board where only the wiring function has been emphasized, and has extremely great practical value.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an embodiment of the ceramic circuit board of the present invention, and FIG. 2 is a sectional view of a capacitor portion in FIG. 1. 1... Ceramic substrate, 2, 4... Conductor layer, 3... Capacitor layer, 6... Conductor particles, 6... Insulation Thin layer.

Claims (1)

[Claims] A ceramic insulating substrate, a conductor layer made of tungsten or molybdenum as a wiring material, and a capacitor layer made of an aggregate of particles covered with tungsten particles or molybdenum particles with an insulating layer mainly composed of lanthanum chromate. Ceramic circuit board containing featured capacitors.