JP2620640B2 - Composite circuit board with built-in capacitor and method of manufacturing the same - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a composite circuit board with a built-in capacitor having a capacitor, a resistor and a conductor layer for electric wiring, and more particularly to a capacitor formed by simultaneously firing an insulating base and a dielectric. The present invention relates to a built-in composite circuit board and a method for manufacturing the same.

[Conventional technology]

In recent years, various electronic devices have been reduced in size and density with the use of semiconductor integrated circuit devices such as ICs and LSIs. Has been required. Therefore, the miniaturization of electric wiring and the increase in density by multi-layering and the development of chips for passive components such as capacitors and resistors in electronic circuits have been promoted, and these miniaturized passive components have been provided on both sides of an insulating substrate. A double-sided mounting connected to a conductor layer for electric wiring has been put to practical use.

However, with the remarkable development of semiconductor materials, further miniaturization and high-density mounting of electronic devices are required, and the miniaturization of the passive components cannot satisfy the demand. I was

As a result, a passive element such as a capacitor or a resistor is thick-film printed by a screen printing method or the like, and the capacitor portion is formed simultaneously with the firing of the insulating base, together with the electric wiring conductor layer formed in the same manner. A composite ceramic substrate which has been miniaturized and densified by baking and hybridizing has been proposed (see JP-A-60-103690 and JP-A-60-177696). .

[Problems to be solved by the invention]

However, this conventional composite ceramic substrate includes a dielectric layer made of, for example, a barium titanate-based ceramic.
Since the mechanical strength is high, it is difficult to match the firing temperature between the alumina-based insulating substrate and the dielectric layer because it is built in an alumina-based insulating substrate that is chemically stable and has excellent insulating properties. Above, when the alumina-based ceramic of the insulating substrate and the barium titanate-based or lanthanum titanate-based ceramic of the dielectric layer are simultaneously fired in contact with each other,
There is a problem that the ceramics react with each other and a dielectric layer having initial characteristics cannot be obtained.

[Object of the invention]

The present invention has been devised in view of the above drawbacks, and its object is to simultaneously sinter an alumina-based insulating substrate and a barium titanate-based and / or lanthanum titanate-based dielectric layer to provide a mechanical strength and a capacitor. An object of the present invention is to provide a composite circuit board with a built-in capacitor capable of obtaining electric characteristics, particularly a wide range of capacitor capacity, and a method for manufacturing the same.

[Means for solving the problem]

In the composite circuit board with a built-in capacitor according to the present invention, titania, calcium titanate, magnesium titanate, strontium titanate or partially stabilized is formed on the outer peripheral portion of a dielectric layer composed of barium titanate-based and / or lanthanum titanate-based ceramic. A protective layer made of at least one kind of zirconia is provided, and electrodes are provided on upper and lower surfaces of a dielectric layer having the protective layer to form a capacitor portion, wherein the capacitor portion is 65% by weight <Al ₂ O ₃ <80% by weight. % and is characterized in that 15 incorporated in the weight% ≦ SiO ₂ ≦ 25 wt% 0.5 wt% ≦ CaO ≦ 5 wt% 0.5 wt% ≦ MgO ≦ 5% by weight of the alumina insulating base made of the composition.

Further, in the method for manufacturing a composite circuit board with a built-in capacitor according to the present invention, the composition of the insulating base may be such that 65% by weight <Al ₂ O ₃ <80% by weight 15% by weight SiO ₂ ≦ 25% by weight 0.5% by weight ≦ CaO ≦ 5% by weight 0.5% by weight ≦ MgO ≦ 5% by weight A ceramic material is blended so as to satisfy 5% by weight, and a mixture of the blended material and a binder is formed by a doctor blade method. Printing a dielectric pattern made of barium titanate-based and / or lanthanum titanate-based ceramic on the lower electrode; and titania, calcium titanate, and titanate on the outer periphery of the dielectric pattern. Printing a protective layer pattern made of at least one of magnesium, strontium titanate or partially stabilized zirconia; and a part of the protective layer. Overlapping and printing the upper electrode in a predetermined pattern on the upper surface of the dielectric pattern to form a capacitor portion, and an insulating substrate on which the capacitor portion is formed and another insulating substrate on which an electric wiring conductor pattern is formed. Alternately laminating and thermocompression bonding, debinding at a temperature of 200 ° C to 400 ° C in air, and then firing and integrating at a temperature of 1280 ° C to 1350 ° C It is.

(Operation)

The composition of the alumina-based insulating substrate is such that 65% by weight <Al ₂ O ₃ <80% by weight 15% by weight ≦ SiO ₂ ≦ 25% by weight 0.5% by weight ≦ CaO ≦ 5% by weight 0.5% by weight ≦ MgO ≦ 5% by weight The alumina-based insulating substrate is sintered together with the dielectric material at a firing temperature of 1280 ° C. to 1350 ° C. at which the dielectric material composed of barium titanate-based and / or lanthanum titanate-based ceramic is sintered. Can be realized. In particular, it is particularly effective when a dielectric made of barium titanate and a dielectric made of lanthanum titanate are simultaneously present on the insulating base.

Further, in order to prevent the alumina-based insulating substrate and the dielectric layer from directly contacting each other, even if another alumina-based insulating substrate is laminated by forming a protective layer on the outer peripheral portion of the dielectric layer, There is no direct reaction between the insulating base and the dielectric layer.

〔Example〕

Next, a composite circuit board with a built-in capacitor and a method of manufacturing the same according to the present invention will be described in detail with reference to the embodiments shown in FIGS.

FIG. 1 is a cross-sectional view showing an embodiment of a composite circuit board with a built-in capacitor of the present invention, and FIG. 2 is a partially enlarged cross-sectional view for explaining the configuration of the capacitor section of FIG.

In the figure, 1 is an alumina-based insulating substrate, 2 is a capacitor portion, 3 is a conductor for electric wiring, and the capacitor portion 2
Comprises a protective layer 4 and a dielectric layer 7 having upper and lower electrodes 5 and 6 respectively on the upper and lower surfaces.

The alumina-based insulating substrate 1 has a composition of 65% by weight <Al ₂ O ₃ <80% by weight 15% by weight ≦ SiO ₂ ≦ 25% by weight 0.5% by weight ≦ CaO ≦ 5% by weight 0.5% by weight ≦ MgO ≦ 5 A suitable organic binder, dispersant, plasticizer and solvent are added to a ceramic raw material powder composed of alumina (Al ₂ O ₃ ), silica (SiO ₂ ), calcia (CaO), magnesia (MgO), etc. Addition and mixing to produce a slurry, which is formed into a sheet by, for example, a conventionally well-known doctor blade method,
It is formed from a laminate of a plurality of the obtained green sheets.

The green sheet has a lower electrode 6 on its upper surface.
The lower electrode 6 is made of a silver-palladium (Ag-Pd) alloy or the like, and a suitable solvent or solvent is added to and mixed with the metal powder of the alloy to form a paste. The alloy paste is formed on the green sheet in a predetermined pattern by a conventionally known screen printing method or the like. The lower electrode 6 functions as one electrode of the capacitor section 2 built in the alumina-based insulating base 1 described later.

In the green sheet having the lower electrode 6 on the upper surface, a dielectric layer 7 is formed on the upper surface of the lower electrode 6 with a thickness designed according to the capacity of a desired capacitor, and the dielectric layer 7 is made of titanium. A barium titanate-based or lanthanum titanate-based ceramic, and a barium titanate-based or lanthanum titanate-based ceramic powder is mixed with an organic binder such as an ethylcellulose-based solvent and a solvent to form a paste. A dielectric layer 7 is formed on the upper surface of the lower electrode 6 by a method or the like so as to have a dimension slightly smaller than the dimension of the lower electrode 6. The dielectric layer 7 functions as a built-in capacitor by laminating an alumina-based insulating base 1b having a conductor pattern for electric wiring described later.

Next, one or more kinds of titania, calcium titanate, magnesium titanate, strontium titanate or partially stabilized zirconia are mainly formed in a frame shape so as to partially overlap the dielectric layer 7 on the outer peripheral portion of the dielectric layer 7. The paste as a component is printed in a film thickness by the same screen printing method or the like as described above to form the protective layer 4.

As the thickness of the protective layer 4 is larger, the effect of preventing the reaction between the dielectric layer 4 and the alumina-based insulating substrate 1b is greater.
In order to form the conductor layer 3 for electric wiring and the resistor 8 on the surface by the screen printing method, the thickness of the protective layer 4 is desirably about 10 μm to 50 μm in order to minimize surface irregularities.

The material of the protective layer 4 needs to be densified in a temperature range of 1280 ° C. to 1350 ° C. which is fired simultaneously with the alumina-based insulating substrate 1 and the dielectric layer 7 and must be firmly adhered to the alumina-based insulating substrate 1b. It is limited to at least one of titania, calcium titanate, magnesium titanate, strontium titanate and partially stabilized zirconia.

Further, a protective layer 4 formed on the outer peripheral portion of the dielectric layer 7 is provided.
The upper electrode 5 is thick-film-printed in a predetermined pattern on the upper surface of the dielectric layer 7 using an alloy paste made of the same alloy as the lower electrode 6 by a similar screen printing method or the like. The upper electrode 5 functions as the other electrode of the capacitor section 2 built in the alumina-based insulating base 1 described later.

It is desirable that the upper electrode 5 and the lower electrode 6 be made dense without pinholes by firing.

Then, screen printing is performed using the same alumina-based insulating substrate 1a as the above-mentioned capacitor portion 2 and the same electrode alloy paste as described above, and the above-mentioned alloy-based paste is applied to the through-hole 9 for conducting the upper and lower surfaces of the alumina-based insulating substrate 1b. And alternately laminated with another alumina-based insulating substrate on which a conductor pattern for electric wiring is formed, and thermocompression-bonded.

The obtained laminate is debindered in the air at a temperature of 200 ° C. to 400 ° C., and then integrally fired at a temperature of 1280 ° C. to 1350 ° C., so that the capacitor portion 2 having a densified electrode layer is incorporated. The obtained alumina based insulating substrate is obtained.

Thus, the conductor layer 3 for electrical wiring is formed on the surface of the alumina-based insulating substrate 1 after the integral firing by using the Ag-Pb-based alloy paste by a screen printing method, and ruthenium oxide (Ru ₂ O ₃ ) or the like as a main component if desired. Each of the resistors 8 is printed using the paste described below, and baked at a temperature of about 850 ° C. in the atmosphere to obtain a composite circuit board with a built-in capacitor.

When a paste mainly containing copper (Cu) is used as the conductor layer 3 for electric wiring, the resistor 8 mainly contains lanthanum boride (LaB ₆ ) or tin oxide (SnO ₂ ). By printing using a paste and firing at a temperature of about 900 ° C. in a nitrogen atmosphere, a composite circuit board with a built-in capacitor similar to the above is obtained.

 Next, the operation and effect of the present invention will be described based on experimental examples.

Alumina, silica, calcia, and magnesia are blended so that the composition of the alumina-based insulating substrate is as shown in Table 1, and an appropriate organic binder and a solvent are added to the blend to form a slurry. A green sheet having a thickness of about 200 μm was formed by a blade method. Thereafter, the green sheet was subjected to a punching process to obtain a 150 mm square sheet.

Next, by a thick film printing method such as screen printing,
Using an Ag-Pb alloy paste, a lower electrode pattern of about 2 to 10 mm square is mixed and kneaded with a barium titanate-based or lanthanum titanate-based dielectric powder on an organic binder and a solvent such as ethyl cellulose based on the lower electrode pattern. 20 μm to 60 μm, 1 to 8 m depending on the dielectric paste obtained
The dielectric pattern of m-square, the protective layer pattern in a frame shape with a paste mainly composed of the protective layer material shown in Table 1 so as to overlap a part of the outer periphery of the dielectric pattern on the outer peripheral portion of the dielectric pattern, An upper electrode is formed on the dielectric pattern so as to overlap with a part of the protective layer and to be formed of the same Ag-Pb alloy paste as the lower electrode. Thereafter, the binder is removed in the air at a temperature of 200 ° C. to 400 ° C., and then fired in the air at the temperature shown in Table 1.

The presence or absence of a short circuit between the upper and lower electrode layers was measured using the above-mentioned evaluation sample using an LCR meter, and the presence or absence of a reaction between the dielectric layer and the alumina-based insulating substrate was confirmed.

 Table 1 shows the results.

Incidentally, the evaluation sample was confirmed that the reaction between the dielectric layer and the alumina-based insulating substrate was effectively prevented by the protective layer, using the LCR meter, frequency 1MHz, input signal level 1.0Vrns under the measurement conditions Measure the capacitance and dielectric loss tangent as a capacitor, calculate the relative dielectric constant from the capacitance, measure the capacitance at −25 ° C. to 125 ° C., and measure the amount of change in the capacitance as a temperature characteristic. (TCC).

As a result, each of the barium titanate-based capacitors has a relative dielectric constant (εr) of 1600 to 2000 and a dielectric loss tangent (ta
nθ) shows 0.8% to 1.8%, and the capacitor part of lanthanum titanate has a relative dielectric constant (εr) of 52 to 56 and a temperature characteristic within a range of −55 PPM / ° C. to −81 PPM / ° C. confirmed.

Further, simultaneously with the firing, a bending test piece having the same composition as the alumina-based insulating substrate was fired, and a three-point bending test was performed using the bending test piece according to the JISR1601 standard, and the bending strength was 24 kg / mm ^2. It was confirmed that the value was within the range of 35 to 35 kg / mm ² .

As is clear from Table 1, in the composition of the alumina-based insulating substrate, the content of Al ₂ O ₃ was 65% by weight or less (sample Nos. 78 and 79) or the content of SiO ₂ , CaO and MgO was either When the value exceeds the upper limit of the claims (sample numbers 25, 39, 47, 48, 49, 54, 5
7,58,59,60,61,67,68,72,73) or the firing temperature is 1350
If the temperature exceeds ℃ (Sample No. 1, 15, 28, 42, 62), the dielectric layer will be over-sintered or the protective layer will effectively prevent the reaction between the dielectric layer and the alumina-based insulating substrate. As a result, a reaction between the dielectric layer and the alumina-based insulating substrate occurs.

Further, the content of Al ₂ O ₃ is 80% by weight or more (sample number
1,2) or when the content of any of SiO ₂ , CaO, and MgO does not reach the lower limit of the claims (sample numbers 3, 10, 11,
12, 22, 23, 24, 37, 38) or when the firing temperature is lower than 1280 ° C (sample numbers 8, 19, 31, 46, 66, 76), the alumina-based insulating substrate becomes insufficiently sintered, and The mechanical strength as a substrate cannot be obtained and cannot be used.

On the other hand, in the experimental examples according to the present invention, in each case, the reaction between the dielectric layer and the alumina-based insulating substrate was effectively prevented, the mechanical strength as the insulating substrate was sufficiently high, and the capacitor as the capacitor was used. It was confirmed that the electrical characteristics were sufficiently satisfied.

Incidentally, on the alumina-based insulating substrate according to the present invention, Ag-Pd-based and Cu-based electrical wiring and a resistor such as Ru ₂ O ₃ -based, LaB ₆ -based, or SnO ₂ -based were screen-printed on a conventional alumina-based insulating substrate. It can be formed similarly to the insulating substrate.

[Effects of the Invention] According to the composite circuit board with a built-in capacitor and the method of manufacturing the same of the present invention, the alumina-based insulating substrate having the composition within the scope of the present invention is made of barium titanate-based and / or lanthanum titanate-based dielectric material. At the same time, it can be fired and integrated at a firing temperature of 1280 ° C. to 1350 ° C., and titania, calcium titanate, titanium titanate may be added to the outer peripheral portion of the dielectric layer to prevent direct contact between the alumina-based insulating substrate and the dielectric material. By forming a protective layer made of one of magnesium oxide, strontium titanate or partially stabilized zirconia, the alumina-based insulating substrate and the dielectric material can be fired and integrated simultaneously without any reaction, It has the electrical characteristics required for capacitors, in particular, it has a wide range of capacitor capacity and extremely excellent mechanical strength of the substrate. None shall have, moreover, it can obtain a capacitor built-composite circuit board capable of forming an electrical wiring conductor layer and the resistor to the substrate surface.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing an embodiment of a composite circuit board with a built-in capacitor of the present invention, and FIG. 2 is a partially enlarged cross-sectional view for explaining the configuration of the capacitor section of FIG. 1, 1a, 1b ... alumina-based insulating substrate 2 ... capacitor part 3 ... conductor layer for electric wiring 4 ... protective layer 5 ... upper electrode 6 ... lower electrode 7 ... dielectric layer

 ──────────────────────────────────────────────────の Continued on the front page (72) Inventor Masakazu Yasui 1-1, Yamashita-cho, Kokubu-shi, Kagoshima Kyocera Inspector Minoru Kina, Kagoshima Kokubu Plant

Claims (4)

(57) [Claims] 1. A dielectric layer comprising barium titanate (BaTiO ₃ ) -based and / or lanthanum titanate (LaTi ₂ O ₅ ) -based ceramics, and a protective layer provided on an outer peripheral portion of the dielectric layer. Electrodes are provided on the upper and lower surfaces of the dielectric layer to form a capacitor portion, and the capacitor portion has a content of 65% by weight <Al ₂ O ₃ <80% by weight 15% by weight ≦ SiO ₂ ≦ 25% by weight 0.5% by weight CaO A composite circuit board with a built-in capacitor characterized by being incorporated in an alumina (Al ₂ O ₃ ) -based insulating substrate having a composition of ≦ 5% by weight 0.5% by weight ≦ MgO ≦ 5% by weight. 2. The method according to claim 1, wherein the protective layer is made of titania (TiO ₂ ), calcium titanate (CaTiO ₃ ), magnesium titanate (MgTi
2. The composite circuit board with a built-in capacitor according to claim 1, comprising at least one of O ₃ ), strontium titanate (SrTiO ₃ ) and partially stabilized zirconia (ZrO ₂ ). 3. The composition of the insulating base is 65% by weight <Al ₂ O ₃ <80% by weight ≦ 15% by weight ≦ SiO ₂ ≦ 25% by weight 0.5% by weight ≦ CaO ≦ 5% by weight 0.5% by weight ≦ MgO ≦ 5% by weight %, And a step of printing a lower electrode in a predetermined pattern on a green sheet formed from a mixture of the mixture and the binder with a ceramic raw material, and forming barium titanate (BaTiO ₃₎ on the lower electrode. ) System and / or
A step of printing a dielectric pattern made of a lanthanum titanate (LaTi ₂ O ₅ ) -based ceramic; a step of printing a protection pattern on an outer peripheral portion of the dielectric pattern; On the upper surface of the body pattern, a step of printing an upper electrode in a predetermined pattern to form a capacitor portion, and alternately laminating an insulating substrate on which the capacitor portion is formed and another insulating substrate on which an electric wiring conductor pattern is formed. ,
Thermocompression bonding and debinding in air, then 12
And baking at a temperature of 80 ° C. to 1350 ° C. to obtain a composite circuit board with a built-in capacitor. 4. The method according to claim 1, wherein the protective layer is made of titania (TiO ₂ ), calcium titanate (CaTiO ₃ ), magnesium titanate (MgTi
4. The method for manufacturing a composite circuit board with a built-in capacitor according to claim 3, wherein the composite circuit board comprises at least one of O ₃ ) strontium titanate (SrTiO ₃ ) and partially stabilized zirconia (ZrO ₂ ).