JPH08181448A - Manufacture of multilayer ceramic circuit board - Google Patents

Abstract

PURPOSE: To share the thick film resistor of ruthenium oxide and inner wirings of copper without impairing electric characteristics by printing conductor paste and resistor paste on the surface of a board body, and simultaneously baking them in an oxidative atmosphere at a temperature of the baking temperature or lower of a board body. CONSTITUTION: A plurality of green sheets made of low temperature sintered ceramic materials in which copper conductive paste to become inner wirings 4 is printed are prepared. Then, after they are laminated and compressed, it is baked in neutral to weak reducing atmospheres to form a board body 2. Thereafter, palladium conductor paste and resistor paste of ruthenium oxide to become a thick film resistor 7 are printed in predetermined pattern, and simultaneously baked in the air of the baking temperature or lower of the body 2. Thus, a multilayer ceramic circuit board 1 having the resistor 7 of the surface ruthenium oxide and containing copper inner wirings 4 is formed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a multilayer ceramic wiring board, and more particularly, a ruthenium oxide-based resistor is used as a thick film resistance portion formed on the surface of the board, and a copper-based conductor is used as internal wiring. The present invention relates to a method for manufacturing a multilayer ceramic wiring board used.

[0002]

2. Description of the Related Art In recent years, a multilayer ceramic wiring board made of a low-temperature sintered ceramic material using a copper-based conductor for internal wiring has been widely put to practical use as a filter, a VCO, a power amplifier, a coupler, etc. for a mobile phone. Depending on these applications, it is necessary to form a thick film resistance portion on the substrate surface. As the resistor used for the thick film resistor, a ruthenium oxide type resistor has high reliability and a wide range of application of the resistance value, but it must be fired in an oxidizing atmosphere, and copper type internal wiring is required. There was a risk of oxidation. Therefore, conventionally, a resistor such as lanthanum boride, niobium boride, or a mixture thereof with glass that can be fired in a non-oxidizing atmosphere has been used.

[0003]

However, such a resistor that can be fired in a non-oxidizing atmosphere has a large variation in resistance value and has poor reproducibility in a high resistance region of 1 MΩ or more or a low resistance region of 100 Ω or less. Therefore, there was a problem in practical use.

As a result of various experiments conducted by the present inventor, the copper-based internal wiring of the multilayer ceramic wiring substrate once fired in a neutral to weakly reducing atmosphere has a temperature of about the firing temperature of the ruthenium oxide-based resistor. It was found that even if fired in an oxidizing atmosphere, it is difficult to be oxidized.

The present invention was devised on the basis of such knowledge, and as a thick film resistor portion formed on the surface of a substrate, a ruthenium oxide resistor having high reliability and a wide range of application of resistance value. And to provide a method for manufacturing a multilayer ceramic wiring board using a copper-based conductor that is inexpensive and has excellent conductivity as internal wiring.

[0006]

In order to achieve the above object, the present invention prepares a plurality of green sheets made of a low temperature sintered ceramic material printed with a copper-based conductor paste, and laminates and compresses the green sheets. After that, a step of forming a substrate body by firing in a neutral to weakly reducing atmosphere, and printing a silver-palladium-based conductor paste and a ruthenium oxide-based resistor paste on the surface of the substrate body, And a step of simultaneously firing in an oxidizing atmosphere at a temperature equal to or lower than the firing temperature.

[0007]

According to the above-described manufacturing method, the copper-based conductor embedded in the fired substrate body is fired in an oxidizing atmosphere at about the firing temperature of the ruthenium oxide-based resistor, which is lower than the firing temperature of the board body. Even if it is difficult to be oxidized, a multilayer ceramic wiring board that shares the ruthenium oxide-based thick film resistor portion and the copper-based internal wiring can be prepared without impairing the electrical characteristics.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A method of manufacturing a multilayer ceramic wiring board according to the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view of an essential part showing an example of a multilayer ceramic wiring board obtained by the method for manufacturing a multilayer ceramic wiring board of the present invention. FIG.
In the figure, 1 is a multilayer ceramic wiring board. Reference numeral 2 is a substrate body in which a plurality of insulating layers 3 are laminated, and is composed of copper-based internal wirings 4 arranged between the plurality of insulating layers 3 and via holes 5 for electrically connecting the internal wirings 4. It

On the surface of the substrate body 2, a surface wiring 6 made of silver-palladium type metal and a thick film resistance portion 7 made of a ruthenium oxide type resistor are formed. Here, the surface wiring 6
Is electrically connected to the internal wiring 4 through the via hole 5 and constitutes a predetermined circuit. Note that other electronic components (not shown) are mounted on the surface of the substrate body 2 as needed.

Next, an example of a method for manufacturing the multilayer ceramic wiring board of the present invention will be described.

As the base material forming the insulating layer 3, for example, B
aO-Al ₂ O ₃ to a plurality prepared green sheet comprising -SiO ₂ based low-temperature co-fired ceramic material. Then, a hole to be the via hole 5 is made in the green sheet and filled with a copper-based paste, and a copper-based (copper or copper plus a small amount of ceramic powder or silver) conductive paste to be the internal wiring 4 is formed into a predetermined pattern. To print. Like this, via hole 5
After stacking and compressing the green sheets on which the internal wiring 4 is formed, the green sheets are fired in a nitrogen gas atmosphere at about 980 ° C. to form the substrate body 2. The substrate body 2 has a via hole 5
Alternatively, a through hole may be provided. In the case of a through hole, after firing, a silver-palladium-based conductor paste is printed or nickel plating is performed.

Next, on the surface of the substrate main body 2, a silver-palladium-based conductor paste which becomes the surface wiring 6 and which can be fired in an oxidizing atmosphere, and a ruthenium oxide-based resistor paste which becomes the thick film resistor portion 7 are predetermined. The pattern is printed and simultaneously fired in the air at about 800 ° C., which is lower than the firing temperature of the substrate body 2. As a result, the multilayer ceramic wiring substrate 1 having the ruthenium oxide-based thick film resistor portion 7 on the surface and incorporating the copper-based internal wiring 4 is formed.

Although the substrate body 2 was fired in a nitrogen gas atmosphere in the above-mentioned embodiments, it is not particularly limited to a nitrogen gas atmosphere, and it is fired in another neutral or weakly reducing atmosphere. Good. Further, in the above embodiment, the surface wiring 6
The thick film resistance portion 7 and the thick film resistance portion 7 were fired in air, but the thickness is not limited to air and may be fired in another oxidizing atmosphere.

Next, the results of experiments conducted on the degree of oxidation of the copper-based internal wiring built in the multilayer ceramic wiring board formed by the method for manufacturing a multilayer ceramic wiring board of the present invention are shown below.

A plurality of green sheets made of BaO--Al ₂ O ₃ --SiO ₂ system low temperature sintered ceramic material are prepared.
One of them is a copper conductor paste with a width of 150 μm and a thickness of 5 μ
A thin strip-shaped internal wiring having a length of m and a length of 10 cm is printed, stacked with an unprinted green sheet, compressed, and then cut into an appropriate shape so that both ends of the internal wiring are exposed. Then, a silver-palladium-based conductor paste is printed so as to cover both ends of the internal wiring exposed on the end face to form an external electrode, and the external electrode is fired in a nitrogen gas atmosphere at about 980 ° C. to prepare a sample. Next, assuming firing of a ruthenium oxide-based resistor, in air at about 800 ° C. and about 80 ° C.
Heat treatment was performed in a nitrogen gas atmosphere at 0 ° C., the direct current resistance value of the sample was measured to obtain the resistivity, and the degree of oxidation of the copper internal wiring was examined. Table 1 shows the results.

[0016]

[Table 1]

As shown in Table 1, when heat-treated in air, the resistivity was 3.30 × 10 ⁻⁶ Ω · cm, and when heat-treated in a nitrogen gas atmosphere, the resistivity was 3.01 × 10 ^−6.
It was almost the same as Ω · cm.

From the above experiment, the copper-based internal wiring of the multi-layer ceramic wiring board which is fired in the nitrogen gas atmosphere is almost always heated in air at about 800 ° C. which is lower than the firing temperature of the board. It was found that the resistivity did not increase and was hard to be oxidized.

Next, a multilayer ceramic wiring board manufactured by the method for manufacturing a multilayer ceramic wiring board according to the present invention was used as a power amplifier for amplifying an output signal of a mobile phone, and electric characteristics of this power amplifier were measured.

In this case, the power amplifier 10 is composed of an amplification section 11, strip lines S1 to S11, capacitors C1 to C7, and resistors R1 and R2, as shown in the circuit diagram of FIG. And, on the surface of the multilayer ceramic wiring board used for this, land,
An input / output terminal, a silver-palladium-based conductor that serves as a surface wiring, and a ruthenium oxide-based thick film resistor portion that serves as resistors R1 and R2 are formed, and an IC that serves as the amplification section 11 is mounted. Further, inside the multilayer ceramic wiring board, capacitor electrodes to be capacitors C1 to C7,
Strip lines to be the strip lines S1 to S11 and other internal wiring are formed of copper-based conductors. Further, the thick film resistance portion is trimmed and adjusted to a predetermined resistance value. Table 2 shows the measurement results of the electrical characteristics of the power amplifier 10.

[0021]

[Table 2]

As shown in Table 2, the electric characteristics of the power amplifier 10 are good. As a result, it can be seen that the multilayer ceramic wiring board produced by the method for manufacturing a multilayer ceramic wiring board of the present invention can be sufficiently used in practice.

[0023]

As described above, according to the method for manufacturing a multilayer ceramic wiring board according to the present invention, a thick film resistor portion of ruthenium oxide type, which is excellent in reliability and has a wide range of application of resistance value, can be manufactured at low cost. A multilayer ceramic wiring board that shares copper-based internal wiring with excellent conductivity can be easily obtained,
By using this, a composite electronic component having excellent electrical characteristics can be provided.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of essential parts showing a multilayer ceramic wiring board according to an embodiment of the present invention.

FIG. 2 is a circuit diagram showing a power amplifier for a mobile phone.

[Explanation of symbols]

 1 Multilayer Ceramic Wiring Board 2 Board Body 3 Insulating Layer 4 Internal Wiring 5 Via Hole 6 Surface Wiring 7 Thick Film Resistor

Claims (1)

[Claims] 1. A substrate main body prepared by preparing a plurality of green sheets made of a low-temperature sintered ceramic material printed with a copper-based conductor paste, stacking and compressing the green sheets, and then firing them in a neutral to weakly reducing atmosphere. And a step of printing a silver-palladium-based conductor paste and a ruthenium oxide-based resistor paste on the surface of the substrate body, and simultaneously firing in an oxidizing atmosphere at a temperature not higher than the firing temperature of the substrate body, A method of manufacturing a multilayer ceramic wiring board, comprising: