JPH06112657A - Multilayer circuit board - Google Patents

Abstract

PURPOSE:To provide a multilayer circuit board where the dielectric constant temperature characteristic of the board body is stable, and further resistance characteristic is stable even if a thick resistor film is made on the surface of itself. CONSTITUTION:In a multilayer circuit board 10, where a plurality of insulating layers 1a, 1b,... consisting of glass ingredients and inorganic fillers are stacked, and specified wiring patterns 2 consisting of gold, silver, or copper conductor material and capacitance generating patterns 3 are formed inside, and a thick film resistor 6 is formed on the surface, the inorganic filler contains alumina, strontium titanate.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-layer circuit board, and more particularly to a multi-layer circuit board having a capacitance generating pattern therein by utilizing an insulating layer of glass-ceramic as a dielectric layer.

[0002]

2. Description of the Related Art A multilayer circuit board used for a hybrid circuit of an electronic device is mainly made of alumina as a substrate body in which insulating layers are laminated in consideration of electric insulation, mechanical strength and thermal conductivity. It is often used as an ingredient. However, since the insulating layer containing alumina as a main component must be fired at a high temperature of 1400 to 1650 ° C. in the sintering process after lamination, the internal wiring pattern of the multilayer circuit board has a high content of tungsten, molybdenum, or the like. It was limited to melting point metallic materials. Such a high melting point metal material has a high wiring resistance because of its high specific resistance, and is not suitable for an electronic circuit or a high frequency circuit having a high signal propagation speed.

Therefore, a substrate composition obtained by mixing a glass component and an inorganic filler such as alumina is used as an insulating layer constituting the substrate body, and is sintered at a low temperature of about 900 ° C. As a result, a low resistance material such as gold, silver or copper can be used as the internal wiring pattern, and an electronic circuit or high frequency circuit with a high signal propagation speed can be realized.

However, if only the internal wiring pattern is formed, it is possible to form a multilayer circuit board by using a substrate composition material in which a glass component and alumina are mixed, but this insulating layer is used as a dielectric layer. Therefore, when arranging the capacitance generation pattern in parallel with the internal wiring pattern inside, the temperature characteristics of the dielectric constant of the substrate composition material are not taken into consideration.Therefore, when forming the capacitance inside the substrate body, it depends on the ambient temperature. The capacity-temperature characteristic changed greatly, and it was not possible to construct a satisfactory capacity. That is, the glass component is borosilicate glass or alumino acid glass, the inorganic filler is alumina powder, these materials show positive temperature characteristics of the dielectric constant, and naturally the sintered circuit board also has a dielectric constant of The temperature characteristic becomes positive.

If an LC resonance circuit is formed inside the multilayer circuit board, the capacitance value fluctuates due to a change in temperature, and a stable LC resonance circuit cannot be formed.

In order to control the temperature characteristic of the dielectric constant of the substrate material, titania (TiO ₂ ) powder having a negative dielectric constant temperature coefficient is added together with alumina powder as an inorganic filler constituting the insulating layer constituting the substrate body. Then, there has been a proposal to compensate the temperature characteristic of the dielectric constant of the insulating layer (Japanese Patent Laid-Open No. 4-82297).

As a result, the multilayer circuit board has a capacitance characteristic which is relatively stable with respect to the ambient temperature change even if the capacitance component is formed inside the substrate body.

The inorganic filler added with the glass component to achieve a low temperature calcinable substrate composition is
(1) When the insulating layer is fired, it reacts with the glass component,
It does not form a solid solution, and (2) does not affect the characteristics of the conductor material that forms the internal wiring pattern or capacitance generation pattern formed between insulating layers, and is formed on the surface of the fired substrate body. Does not affect the characteristics of the surface wiring pattern and the thick film resistor film, (3) the inorganic filler is uniformly dispersed between the glass components, and the strength of the substrate body can be maintained (4) the substrate after firing It is required that there be no discoloration.

[0009]

However, in the conventional substrate material in which the alumina powder and the titania powder are mixed as the inorganic filler, the color tone of the substrate after firing becomes yellow, and the quality assurance by the appearance inspection is performed. Therefore, the condition (4) above is not satisfied.

In particular, when a thick film resistor film is formed together with the surface wiring pattern on the surface of the substrate body, the titania component in the substrate is deposited even on the substrate surface, and the thick film resistor film on the surface is printed and printed. At this time, the condition (2) described above that the temperature characteristic of the resistance is negatively shifted by reacting with the titania component is not satisfied.

Other inorganic fillers having negative dielectric constant temperature characteristics include calcium titanate and strontium stannate. However, since their crystal structures are not strong, they react with the glass component during sintering. After sintering, this crystal structure cannot be retained, and the condition (1) above cannot be satisfied.

As the inorganic filler having a negative dielectric constant temperature characteristic, strontium titanate can be cited. However, if only strontium titanate is used as the inorganic filler, the above conditions (1) and (2) are satisfied. Although satisfactory, there was a problem that the strength of the substrate body after sintering was deteriorated.

The present inventor has conducted various experiments using the above-mentioned strontium titanate to prevent the deterioration of the strength of the substrate body. As a result, the alumina powder and the strontium titanate powder are used as the inorganic filler. It was found that the deterioration of the strength of the substrate body can be prevented.

The present invention has been devised on the basis of the above findings, and its object is to stabilize the dielectric constant temperature characteristics of the insulating layer and further form a thick film resistor film on the surface of the substrate. Even so, it is intended to provide a multilayer circuit board which can obtain stable resistance characteristics.

[0015]

The present invention comprises a plurality of insulating layers composed of a glass component and an inorganic filler,
A multilayer circuit board having an internal wiring pattern made of a gold-based, silver-based or copper-based conductor material and a capacitance generating pattern therein, wherein the inorganic filler is made of alumina and strontium titanate.

Particularly, it is suitable for a multilayer circuit board in which a thick film resistor film is formed on the surface of the multilayer circuit board.

[0017]

As described above, according to the present invention, since the material of the insulating layer is composed of the glass component and the inorganic filler, it is possible to sinter at a relatively low temperature (up to 1000 ° C.). A metal material having a small specific resistance such as gold, silver, or copper can be used for the capacitance generation pattern.

As the inorganic filler, strontium titanate having a negative dielectric constant temperature characteristic is contained, and this strontium titanate can sufficiently maintain the perovskite structure even after sintering, and further has a glass component. The temperature characteristic of the substrate body is ±
It is in the range of 60 ppm, and it is possible to form a white substrate by preventing yellowing of the substrate after firing. If the relative dielectric constant is further increased and a capacitance generation pattern is formed inside, a capacitance having a large capacitance value can be obtained with stable temperature characteristics.

Further, since the inorganic filler strontium titanate is less likely to be decomposed into titania,
Even if a thick film resistor film is formed on the surface of the substrate body, its resistance characteristics are not significantly changed.

Further, by using alumina together with strontium titanate, sufficient bending strength can be maintained.

The strontium titanate added as the inorganic filler is preferably in the range of 20% by weight or less of the substrate composition. This is because if it exceeds 20% by weight, the temperature characteristic of the substrate body becomes too large in the negative region.

As described above, the temperature characteristic of the dielectric constant of the substrate body can be compensated for near zero, and even if the thick film resistor film is formed on the surface of the substrate, stable resistance characteristic can be obtained and the substrate strength can be improved. It becomes a sufficient multilayer circuit board.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The multilayer circuit board of the present invention will be described below in detail with reference to the drawings. FIG. 1 shows a cross-sectional structure of a multilayer circuit board of the present invention. In the figure, 10 is a multilayer circuit board, 1 is a board body in which a plurality of insulating layers 1a, 1b ... Are laminated, and 2 is a predetermined internal wiring pattern formed between the insulating layers 1a, 1b. , 3 is a capacitance generating pattern formed between the insulating layers 1a, 1b ..., 4 is a via hole conductor, 5 is a surface wiring pattern, and 6 is a thick film resistor film.

The substrate body 1 comprises a plurality of glass-ceramic insulating layers 1a, 1b ...
1b ... from a predetermined internal wiring pattern 2 and a capacitance generating pattern 3 made of a gold-based, silver-based, or copper-based conductor and a via-hole conductor 4 penetrating the insulating layers 1a, 1b. It is configured. As a result, a part of the predetermined circuit including the capacitive component is formed inside the substrate body 1.

A predetermined surface wiring pattern 5 and a thick film resistor film 6 made of a gold-based, silver-based, or copper-based conductor are formed on the main surface of the substrate body 1, and these are connected via a via-hole conductor 4. , Is electrically connected to the internal wiring pattern 2 and the capacitance generation pattern 3, and a predetermined circuit is achieved as a whole. Although not shown in the drawing, a protective film is formed on the surface, and an IC chip, a chip electronic component, etc. are mounted as needed.

Here, the capacitance formed inside the substrate body 1 is generated, for example, between the capacitance generating patterns 3 having a predetermined facing area and arranged so as to sandwich the insulating layer 1c in the figure, Furthermore, a predetermined capacitance is also generated between the capacitance generation patterns 3 arranged so as to sandwich the insulating layer 1d.

The insulating layers 1a, 1b, ... Are composed of glass components such as crystallized glass and amorphous glass, and an inorganic filler composed of alumina powder and strontium titanate powder having a negative dielectric constant in temperature characteristics. Has been done.
The composition ratio of the glass component is 40 to 90% by weight, and the composition ratio of the plurality of inorganic fillers is 10 to 60% by weight. If the inorganic filler is less than 10% by weight, the strength of the sintered substrate body 1 will be reduced. Meanwhile, 60% by weight
If it exceeds the range, the glass component in the substrate body 1 after sintering becomes insufficient, and a dense circuit board cannot be achieved. The inorganic filler preferably has a composition ratio of 30 to 50% by weight, and the balance is a glass component.

Further, the strontium titanate powder added as an inorganic filler is preferably added within the range of 20% by weight. This is because if it exceeds 20% by weight, the temperature characteristics are excessively shifted to the negative side, which is not practical and the bending strength of the substrate tends to deteriorate.

Examples of the above-mentioned glass component include borosilicate glass, aluminosilicate glass and other low melting point glass. Alumina powder is added to the inorganic filler in consideration of the strength of the substrate body 1. However, both the glass component and the alumina powder described above show temperature characteristics with a positive dielectric constant. Strontium titanate powder is a component that compensates for the temperature characteristic in which the dielectric constant is positive.

As described above, the strontium titanate powder added with the alumina powder has a negative dielectric constant temperature characteristic, and can maintain a very stable crystal structure even when sintered at a temperature up to 1050 ° C. .

Therefore, in the substrate body 1, the effect of compensating for the temperature characteristic having a positive dielectric constant is sufficiently exhibited, and the temperature characteristic can be kept within ± 60 ppm. Thus, by forming the capacitance generation pattern 3, it is possible to easily form a capacitance having stable temperature characteristics.
Furthermore, the relative permittivity can be increased to 8.0 or more,
Even if the facing area of the capacitance generation pattern 3 is reduced, a capacitance having a sufficient capacitance value can be achieved.

Further, since the color tone of the board after firing can be made white, the visual inspection of the appearance of the multilayer circuit board 1 can be easily carried out.

Furthermore, since titania is less likely to be deposited on the surface of the substrate body 1, even if the thick film resistor film 6 is formed on the surface of the substrate body 1, the temperature characteristic of the resistor is shifted to the negative side. Can be prevented.

Further, the characteristics of the conductor material forming the internal wiring pattern 2 and the capacitance generating pattern 3 formed between the insulating layers 1a, 1b ... Are not affected.

Further, by using it together with the alumina powder of the inorganic filler, the strength of the substrate body 1 can be obtained at a sufficient value in a practical range.

Materials having negative dielectric constant temperature characteristics include titania, calcium titanate, strontium stannate, etc. When titania is used,
Titania is also deposited on the sintered substrate body 1, and when a thick film resistor film 6 of ruthenium oxide, lanthanum hexaboride, tin oxide or the like is formed on the substrate body 1,
This resistance imparts semiconducting conductivity, and the temperature characteristics of the resistance are negatively shifted. In addition, calcium titanate has a smaller ionic radius than strontium titanate, so that the reaction with the glass component becomes remarkable, the crystal structure collapses, and the effect of adding an inorganic filler having a negative dielectric constant temperature characteristic Can't get enough. Furthermore, strontium stannate cannot retain the perovskite structure after sintering, and as described above, the effect of adding the inorganic filler having a negative dielectric constant temperature characteristic cannot be sufficiently obtained.

As the insulating layers 1a, 1b, ..., In addition to a glass component, alumina powder, strontium titanate having a negative dielectric constant temperature characteristic, an oxidizing agent may be added if necessary. .

Next, a method for manufacturing the multilayer circuit board of the present invention will be described.

First, the substrate composition (insulating layers 1a, 1b.
・ ・) Crystallized or amorphous low melting point glass frit, alumina powder, strontium titanate powder, organic binder (eg polymethacrylate resin), plasticizer (eg dibutyl phthalate) and solvent (eg methyl ethyl ketone) , Other additives (for example, defoaming agent) are mixed in a predetermined ratio, and this is mixed with a ball mill for 24 to
Knead for about 72 hours to prepare a homogeneous slurry. After defoaming the slurry, a green sheet having a thickness of about 50 to 300 μm is formed by a known method such as a doctor blade method.

Next, a hole to be the via-hole conductor 4 is punched on the surface of the obtained green sheet to fill the via-hole conductor 4 and print the internal wiring pattern 2 and the capacitance generating pattern 3. The filling of the via-hole conductor 4 may be performed after printing the internal wiring pattern 2 and the capacitance generating pattern 3.

Internal wiring pattern 2, capacitance generation pattern 3
As the conductor paste for use, a conductor paste containing as a main component at least one metal selected from gold, silver, copper and alloys thereof is used. The green sheets on which the internal wiring pattern 2, the capacitance generating pattern 3 and the via-hole conductor 4 are formed are sequentially laminated in consideration of the layer structure of the insulating layers 1a, 1b, ... A laminated body to be the main body 1 is formed.

The laminate thus obtained is fired. First, in the first step, the organic substances contained in the laminate are removed at a temperature equal to or lower than the softening point of the glass component, for example, around 500 ° C. In the next step, the insulating layers 1a, 1b, ... Made of glass component, alumina powder, strontium titanate, the internal wiring pattern 2, the capacitance generating pattern 3, and the via-hole conductor 4 are integrally sintered. This firing temperature is the same as the insulating layer
is determined by the melting point of the glass component of a, 1b, ...
It is carried out at a temperature of 50 ° C. The firing atmosphere is determined by the conductor material of the internal wiring pattern 2. Thereby, the sintered substrate body 1 is achieved.

A surface wiring pattern 5 and a thick film resistor film 6 are formed on the obtained substrate body 1.

The thick-film resistor film 6 is determined by the baking atmosphere of the surface wiring pattern 5 and the like. When baking in a non-oxidizing atmosphere, the resistance mainly containing lanthanum hexaboride, tin oxide, etc. It is formed using body paste.
When firing in an oxidizing atmosphere, a resistor paste containing ruthenium oxide as a main component is used.

The surface wiring pattern 5 may be made of a silver-based conductor (silver or silver alloy) or a copper-based material (copper or copper alloy), but a copper-based material is preferable in consideration of migration resistance and the like. .

Experimental Example As a glass frit, 51 mol% of silicon oxide, 19 mol% of aluminum oxide, 19 mol% of magnesium oxide, 8 mol% of zinc oxide, and 3 mol% of boron oxide (boric acid corresponding thereto) were mixed, After melting at about 1600 ° C., it was poured into water and rapidly cooled to obtain glass. The obtained glass was put into an alumina pot together with alumina balls, wet-ground and dried. As a result, a crystallized glass frit having an average particle size of 2 to 3 μm was obtained.

Next, the crystallized glass frit, alumina powder, and strontium titanate powder were mixed in the proportions shown in Table 1. The mixture was placed in an alumina pot together with alumina balls, mixed by a ball mill and then dried to obtain a composition for a multilayer circuit board.

1000 g of the obtained product for a multilayer circuit board
On the other hand, 100 g of an acrylic resin, 70 g of a plasticizer and 400 g of toluene were added to prepare a slurry, and this slurry was subjected to vacuum defoaming treatment.

Next, using the slurry, a green sheet having a thickness of 200 μm was prepared by the doctor blade method. Then, 10 green sheets were laminated and hot pressed, and the obtained lamination resistance was fired at 870 ° C. for 1 hour to prepare a multilayer substrate body.

Indium-gallium conductor films were formed on both surfaces of the obtained substrate body, and in conformity with JIS 2141,
The dielectric constant was measured at 1 MHz with a Q meter.

As a comparative example, a composition for a multilayer circuit board to which strontium titanate was not added was prepared at a ratio shown in Table 1.

[0052]

[Table 1]

In the comparative example, the relative dielectric constant is as small as 6.5,
In addition, the dielectric constant-temperature characteristic is also practically used (25 to 80
(° C) is 130 ppm / ° C, which is large on the plus side, whereas in any of the experimental examples, the relative dielectric constant is 8.0.
And the dielectric constant-temperature characteristic is within a practical range of ± 60 pp when forming a capacitance inside the substrate body 1.
It can be seen that m / ° C or lower.

In particular, since the temperature characteristics of the dielectric constants of the insulating layers 1a, 1b, ... Are ± 60 ppm / ° C., the capacitance generating pattern 3 is formed inside the multilayer circuit board to obtain a predetermined capacitance. However, the capacity can maintain a stable capacity even when the ambient temperature changes.

Further, since the relative permittivity can be increased more than ever before, a sufficient value of capacitance can be obtained even if the area of the capacitance generating pattern 3 is reduced, for example.
Furthermore, the microstrip line pattern 7 shown in FIG.
Even when the substrate is formed inside the substrate body 1, the miniaturized line pattern 7 is achieved, and the microstrip line is further minimized by controlling the compounding amount of strontium titanate according to the wavelength shortening rate. Can be made.

Further, strontium titanate is used as the internal wiring pattern 2, the capacitance generating pattern 3, the via hole conductor 4 and the surface wiring pattern 5, the thick film resistance film 6 of the substrate body 1.
Etc. is not adversely affected, and, for example, the resistance temperature characteristic of the thick film resistor film 6 on the surface of the substrate body 1 is never changed.

Further, when the bending strength of the substrate body 1 was measured, it was confirmed that the strength was 2.0 kgf / cm ³ which was practically endurable in any of the experimental examples.

In the above embodiment, the multilayer circuit board 1 in which the capacitance generating pattern 3 and the microstrip line pattern 7 are formed is illustrated, but other coil patterns may be provided inside the board body 1 or in the board body 1. It can be widely used for various circuit networks, such as forming on the surface and forming an LC resonance circuit together with the capacitance component formed inside.

[0059]

As described above, according to the present invention, gold, silver, which has a low specific resistance, is used as an internal wiring conductor which is fired at a low temperature.
A multilayer circuit board comprising a metal material such as copper, wherein an insulating layer constituting the multilayer board body includes a glass component, an alumina component, and a strontium titanate component having a negative dielectric constant temperature characteristic. Since the temperature characteristics of the substrate body can be kept within ± 60 ppm,
By forming a capacitance generation pattern in the substrate body, a stable capacitance can be installed.

Further, the color tone of the board after baking the board does not turn yellow, and the board can be a white board, and the multilayer circuit board is very easy for visual inspection.

Further, since strontium titanate having a negative dielectric constant temperature characteristic can maintain a stable crystal structure even after being sintered, it affects the resistance temperature characteristic of the thick film resistor film on the substrate surface. Never give.

Therefore, the capacitance component can be incorporated inside the substrate, the restriction of the arrangement of the internal wiring pattern is reduced, and the thick film resistor film having stable characteristics can be formed on the surface. The mounting density of the surface wiring pattern is improved, and a miniaturized multilayer circuit board can be achieved as a whole.

[Brief description of drawings]

FIG. 1 is a diagram showing a cross-sectional structure of a multilayer circuit board of the present invention.

[Explanation of symbols]

 10 ... Multi-layer circuit board 1 ... Board body 1a, 1b ... Insulating layer 2 ... Internal wiring pattern 3 ... Capacitance generation pattern 4 ...・ ・ ・ Via hole conductor 5 ・ ・ ・ ・ ・ Surface wiring pattern 6 ・ ・ ・ Thick film resistor film 7 ・ ・ ・ ・ ・ Microstrip line pattern

Claims (2)

[Claims] 1. A multilayer circuit board comprising a plurality of insulating layers composed of a glass component and an inorganic filler, and having an internal wiring pattern and a capacitance generating pattern made of a gold-based, silver-based or copper-based conductive material inside. A multilayer circuit board, wherein the inorganic filler is composed of alumina and strontium titanate. 2. The multilayer circuit board according to claim 1, wherein a thick film resistor film is formed on the surface of the multilayer circuit board.