JPH08298382A - Multilayer ceramic board - Google Patents

Abstract

PURPOSE: To prevent diffusion of silver into a thick film resistor easily by interposing the thick film resistor between the layers of a multilayer ceramic board and employing a silver-palladium alloy powder in the composition of inner conductor to be connected electrically with the thick film resistor. CONSTITUTION: A plurality of unfired inductive green sheets 3a are formed by casting and a resistive paste, principally comprising bismuth ruthenate and glass, is screen printed on the green sheet 3a thus forming a thick film resistor 1. The inner composition, i.e., conductive paste of silver-palladium alloy, of a conductor 2 to be connected electrically with the thick film resistor 1 is then applied by screen printing. The green sheets 3b are then stacked and hot pressed to produce a laminate. With such arrangement, diffusion of silver into the thick film resistor 1 can be prevented easily.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laminated substrate, and more particularly to a ceramic multilayer substrate having a built-in high precision resistance element.

[0002]

2. Description of the Related Art In recent years, hybrid ICs have been required to be more compact and highly accurate, so that electrode patterns are formed by printing on a green sheet and these are laminated and sintered, or by repeating screen printing to form a multilayer. A ceramic multilayer substrate having a wiring pattern inside the multilayer substrate obtained by forming and sintering has been used.

However, as a circuit to be formed inside the substrate, technical development is in progress including not only conductor wiring but also passive elements such as resistors which are conventionally mounted on the surface of the substrate. However, when trying to enclose a resistor inside the substrate, the relationship between the length of the resistor and the resistance value deviates greatly from the proportional relationship, and it is extremely difficult and accurate to design the shape of the resistor having an arbitrary resistance value. It was extremely difficult to incorporate a resistor. This is because the silver-based conductor is used in the internal conductor composition that is electrically connected to the resistor, so that silver diffuses into the resistor and the interface portion connected to the internal conductor and the internal conductor This is because the resistance value of the resistor is different in the distant portions.

As a means for solving such a problem, Japanese Patent Laid-Open No. 5-291755 has been proposed. That is, by adjusting the silver concentration in the thick film resistor arranged between the layers of the ceramic multilayer substrate to 0.2 wt% or less, or adjusting it to 1.5 wt% or more, the thick film arranged between the layers of the ceramic multilayer substrate is adjusted. Distance from the interface between the resistor and the internal conductor is 10 μm
The ratio of the silver concentration in the thick film resistor in the portion of (1) to the silver concentration in the thick film resistor in the portion farthest from the internal conductor can be set to within 2 times. This makes the relationship between the length of the resistor and the resistance value proportional and facilitates the shape design of the resistor having an arbitrary resistance value. Construction between layers can be realized.

[0005]

As described above, in order to improve the accuracy of the thick film resistor, the silver concentration in the thick film resistor is set to 0.2.
To make it less than wt% or more than 1.5 wt%,
The following methods have been proposed. That is, in order to set the silver concentration in the thick film resistor to 0.2 wt%, the thick film resistor is inserted into the thick film resistor by interposing a terminal mainly containing a noble metal such as gold between the thick film resistor and the internal conductor. It prevents the spread of silver. Further, it is said that the same effect can be obtained by setting the silver concentration in the inner conductor to 50 wt% or less. Further, in order to increase the silver concentration in the thick film resistor to 1.5 wt% or more, a method has been proposed in which the resistor contains silver in advance. However, in actual manufacturing, it is difficult to control the silver concentration, which may hinder mass production.

Therefore, the present invention provides a ceramic multilayer substrate using an internal conductor composition, which easily prevents the diffusion of silver into the thick film resistor and does not require the control of the silver concentration in the thick film resistor. The purpose is to provide.

[0007]

In order to achieve the above-mentioned object, the present invention provides an inside of an electrode electrically connected to a thick film resistor when the thick film resistor is arranged between layers of a ceramic multilayer substrate. Silver-palladium alloy powder is used for the conductor composition.

Further, the palladium concentration of the internal conductor composition is 10 wt% or more and 30 wt% or less.

[0009]

[Function] When a thick film resistor is arranged between the layers of the ceramic multi-layer substrate, the length and the resistance value of the resistor deviate greatly from the proportional relationship because the silver is introduced from the inner conductor formed of the silver-based conductor into the resistor. Due to diffusion. Therefore, it is possible to achieve the purpose of obtaining a highly accurate thick film resistor by suppressing the diffusion of silver into the resistor. Therefore, by using an inner conductor made of silver-palladium alloy powder for the inner conductor connected to the thick film resistor, it is possible to suppress the diffusion of silver into the inner resistor, and the relationship between the resistor length and the resistance value. Can be made approximately proportional.

When silver-palladium alloy powder is used as the inner conductor, alloying reduces the diffusivity of silver. Therefore, better results can be obtained than when mixed powders having the same ratio are used. That is, in order to obtain the same effect, it is possible to suppress the palladium content as compared with the case of using the mixed powder, it is possible to suppress the resistance value of the internal conductor to a low level, and good results can be obtained in terms of cost as well. To be

Therefore, since it is easy to design the shape of a resistor having an arbitrary resistance value, it is possible to form a highly accurate thick film resistor between the layers of the ceramic multilayer substrate.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, a first embodiment of a ceramic multilayer substrate according to the present invention will be described with reference to the drawings.

FIG. 1 is a sectional view of a ceramic multilayer substrate using the internal conductor composition for a thick film resistor according to the present invention.

An acrylic resin binder was added to borosilicate glass powder and alumina powder as a frit, and the mixture was stirred to form a slurry. A plurality of unfired dielectric green sheets were formed from this slurry by a casting film forming method using a doctor blade.

A resistor 1 containing bismuth ruthenate and glass as main components was screen-printed on the green sheet 3a to form a resistor 1. Next, a conductor paste made of an alloy powder having a metal component ratio of 75 wt% silver and 25 wt% palladium is applied by a screen printing method,
The conductor 2 was formed. Next, the green sheets 3b formed previously are shaped after being shaped by a metal mold made of stainless steel or the like, and then stacked. Then, using a hot press or the like, a temperature of 50
The laminate was heat-compressed from the upper and lower surfaces under conditions of ° C and a pressure of 700 kg / cm2. Further, by firing this laminated body in the air at a temperature of 900 ° C. for about 15 minutes, a ceramic multilayer substrate having a thick film resistor built therein can be obtained.

In this case, further resistors and wiring conductors are formed on the green sheet 3b, and a new green sheet is laminated on the green sheet 3b to form a three-layer ceramic multilayer substrate. It goes without saying that a ceramic green board having a multi-layer structure of four or more layers can be obtained by further laminating a new green sheet thereon.

Here, in the resistor 1 inside the ceramic multilayer substrate, an increase in resistance value due to diffusion of silver (hereinafter, referred to as
The "interface resistance") and the resistance value unique to the resistor 1 (hereinafter referred to as "sheet resistance") are measured, and the ratio thereof is calculated to be 0.1 or less. From this result, it is found that the difference in the resistivity of the resistor between the interface part connected to the internal conductor and the part away from the internal conductor is small, and the diffusion of silver in the conductor is small. I understand. Therefore, since it is easy to design the shape of the resistor having an arbitrary resistance value, the resistance value of the resistor 1 can be suppressed to a value calculated by the length of the resistor 1 with high accuracy.

FIG. 2 shows the ratio of the interfacial resistance and the sheet resistance when a conductor paste made of a silver-palladium alloy with different component ratios is used. As the palladium concentration increases,
Since the ratio of the interface resistance and the sheet resistance is close to 0 and the resistance of the resistor 1 is close to the calculated value, the resistance value of the resistor built in the ceramic multilayer substrate can be set to the target resistance value without error.

FIG. 2 shows the ratio of the interface resistance and the sheet resistance when the silver-palladium mixed powder was used at the same time. By forming an internal conductor composition for a thick film resistor by using silver-palladium alloy powder, the error of the target resistance value can be reduced with a lower palladium concentration than that when using the silver-palladium mixed powder, and a ceramic multilayer substrate can be obtained. It can be seen that the interior can be formed.

As described above, having a highly accurate built-in resistor,
Since a ceramic multilayer substrate can be easily formed, when manufacturing products such as high frequency compatible multi-chip modules equipped with resistor elements and hybrid ICs,
Compared to the conventional product in which resistors are formed on the front and back surfaces, the resistors and conductors placed inside are fired at the same time, which makes it possible to greatly reduce the firing process.

[0021]

As a ceramic multilayer substrate having a thick film resistor built-in, it is possible to obtain a ceramic multilayer substrate in which the resistance value error of the internal resistor is small. Therefore, a circuit substrate using a highly accurate resistor is used. Can be easily miniaturized.

[Brief description of drawings]

FIG. 1 is a sectional view of a ceramic multilayer substrate using an internal conductor composition for a thick film resistor.

[Fig. 2] Graph of relation between palladium concentration and interface resistance

Claims (2)

[Claims] 1. A ceramics characterized by using silver-palladium alloy powder for an internal conductor composition electrically connected to a thick film resistor when the thick film resistor is arranged between layers of the ceramic multilayer substrate. Multilayer board. 2. The palladium concentration of the inner conductor composition is 1
The ceramic multilayer substrate according to claim 1, wherein the content is 0 wt% or more and 30 wt% or less.