JP2003217934A - Layered impedance element and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for avoiding degradation due to internal strains and variations in characteristics, in an impedance element which is obtained by printing magnetic paste and conductive paste alternately to build a laminate, sintering it and attaching leads through heating. <P>SOLUTION: A sintered laminate is immersed for 10 minutes to 12 hours in one acid solution among hydrochloric acid, nitric acid, or sulfuric acid, making its concentration 0.001 mole/L to 1.2 moles/L and keeping it at 20 to 60°C and subsequently, leads are attached through heating. By immersing in a acid liquid, a gap is formed at the boundary of the magnetic material and the conductive material. By the above gap, warpages or strains can be avoided, in spite of the difference between the thermal expansions of the magnetic material and the conductive material. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a surface mount multilayer impedance element comprising magnetic ceramics and a coil-shaped inner conductor.

[0002]

2. Description of the Related Art Due to downsizing and higher frequency of electronic equipment, E
MI (Electro Magnetic Interference) countermeasures are becoming more important. In general, an impedance element cuts off noise of a target frequency by impedance characteristics to prevent EMI. That is, it is common practice to mount an impedance element in series with a signal system to block noise.

Further, also for power supply line systems of active elements such as power amplifiers, impedance elements are mounted in series to prevent noise of the signal frequency from leaking from the active elements to the power supply line. Is being done.

Due to the recent demand for miniaturization of electronic components, the mainstream of electronic components typified by impedance elements is shifting to the laminated type. A laminated impedance element used by being mounted on a printed wiring board or the like usually has a magnetic layer made of soft magnetic ferrite powder and a binder, and a conductor pattern made of conductive powder and a binder. After alternately laminating by a printing method to form a coil made of a conductor with a uniform pitch in the magnetic body,
It is obtained by integrally firing and providing an electrode.

FIG. 1 is a diagram showing an outline of an example of such a laminated impedance element. FIG. 1 (a) is a perspective view of the appearance, and FIG. 1 (b) shows the internal coil formation state. In FIG. 1, reference numeral 100 is a laminated impedance element, 101 is a magnetic material made of ferrite or the like, 102 is an external electrode containing silver as a main component, and 103 is a coil made of a conductor also containing silver as a main component. It is connected to the external electrode 102.

FIG. 2 is a flowchart showing the above-mentioned manufacturing process of the laminated impedance element.
In FIG. 2, 201 is a magnetic layer, 202 is a conductor pattern, 203 is a laminated body after cutting, 204 is a fired body, 20
Reference numeral 5 is an external electrode.

Impedance (Z) at a specific frequency is one of the characteristics required of the impedance element.
There is a value and its variation (σ). For example, at frequency (f) = 100 MHz, Z = 1000Ω, σ ≦
It may be required to be 40.

[0008]

However, in an impedance element obtained by integrally firing a magnetic body and a conductor coil formed therein, the magnetic body and the conductor are integrated, so that both The stress caused by the difference in the coefficient of thermal expansion deteriorates the magnetic characteristics of the magnetic substance, and causes a decrease or variation in the Z value of the element.

Therefore, the technical problem of the present invention is to solve the above-mentioned drawbacks and to suppress the deterioration of the magnetic characteristics and the variation of the Z value of the impedance element due to the stress generated in the magnetic material, and its method. It is to provide a laminated impedance element having high characteristics obtained by the method.

[0010]

[Means for Solving the Problems] The stress generated in a magnetic material is
As described above, it is caused by the difference in thermal expansion coefficient between the magnetic substance and the conductor. In other words, if materials with different coefficients of thermal expansion are integrated, distortion and stress will occur due to changes in temperature.
It is logical. From this point of view, the present invention has been made as a result of studying how to avoid the influence of the stress from the internal conductor by providing a gap between the magnetic body and the conductor.

That is, the present invention provides an impedance element having a spiral conductor coil inside, which is formed by laminating a magnetic ceramic layer and a conductor pattern, and integrally firing the magnetic ceramic and the conductor coil. The laminated impedance element is characterized in that a discontinuous void is formed between the two.

Further, according to the present invention, a laminated impedance is formed by laminating a magnetic ceramic layer and a conductor pattern so that the conductor forms a coil, and then firing the laminated body. In the method for manufacturing an element, there is provided the method for manufacturing the multilayer impedance element described above, which comprises forming a discontinuous gap between the magnetic ceramics and the conductor coil after firing the laminated body.

Further, according to the present invention, in the method for manufacturing a laminated impedance element as described above, the formation of discontinuous voids between the magnetic ceramics and the conductive coil can be prevented by adding 5 It is a method of manufacturing a laminated impedance element, characterized in that the dipping treatment is carried out for from minutes to 12 hours.

Further, in the invention, in the method for manufacturing the laminated impedance element, the temperature of the acidic liquid is 20.
It is the manufacturing method of the laminated impedance element characterized by being 60 to 60 degreeC.

Further, according to the present invention, in the method for manufacturing a multilayer impedance element, the acidic liquid is a solution containing at least one of hydrochloric acid, nitric acid and sulfuric acid. Is.

The present invention also provides the method for manufacturing a laminated impedance element as described above, wherein the acid concentration is 0.0
The method for producing a laminated impedance element is characterized in that it is from 01 mol / L to 1.2 mol / L.

[0017]

In the laminated impedance element of the present invention, by providing an air gap between the magnetic body and the conductor, the occurrence of stress due to the difference in the coefficient of thermal expansion is extremely reduced, and the magnetic characteristics of the material are improved. It is possible to suppress a decrease in impedance due to deterioration and variation.

In the present invention, various acid solutions can be used as the acidic liquid, but hydrochloric acid, nitric acid or sulfuric acid is used because the effect cannot be obtained unless a strong acid having a certain amount or more is used. desirable. It is needless to say that these can be appropriately mixed and used.

Further, in the present invention, the soaking time, the liquid temperature and the acid concentration at the time of soaking the fired body are limited respectively, but the reason is that below these ranges, a sufficient effect cannot be obtained. Above these ranges, the effect of immersion is excessive,
This is because the magnetic substance or the conductor is damaged, and in a remarkable case, the conductor pattern is broken.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described below with reference to specific examples.

First, Ni- having a specific surface area of 5.2 m ² / g.
A required amount of Cu-Zn ferrite powder, polyvinyl butyral as a binder, and ethyl cellosolve as a solvent were weighed and mixed and dispersed using a spiral mixer and a bead mill to obtain a paste for magnetic material. Table 1 shows
The composition of these is shown.

[0022]

[Table 1]

Next, required amounts of silver powder having an average particle size of 0.5 μm, ethyl cellulose as a binder, α-terpineol as a solvent, and butyl carbitol acetate were weighed and mixed and dispersed with a three-roll to obtain a conductor. I got a paste for. Table 2 shows these compositions.

[0024]

[Table 2]

Next, a green sheet having a thickness of 200 μm was produced by the doctor blade method using the magnetic paste. On top of that, a conductor paste and a magnetic paste are used, and a conductor coil is placed in the magnetic body.
Lamination printing was performed so that 5 turns were formed. Furthermore, a 200 μm-thick green sheet produced by the doctor blade method using a magnetic paste was laminated on top of this, and integrated by hot pressing, and then 2.4 mm × 1.4 m
Cut into m size, de-binder this, 900 ℃
It was fired together.

Thereafter, the fired body was immersed in an aqueous hydrochloric acid solution having a concentration of 0.0001 mol / L to 1.3 mol / L, which was kept at 23 ° C., for 8 minutes to 13 hours. .
A conductive paste containing silver as a main component is applied to the exposed surface of the conductor coil formed inside the fired body subjected to the immersion treatment, and the paste is baked at about 600 ° C. to form an external electrode. Then, a laminated impedance element was formed.

With respect to these laminated type impedance elements, impedance frequency characteristics were evaluated using an impedance analyzer: HP4291A manufactured by Agilent Technologies. The DC resistance was also measured. Table 3 shows the evaluation results of these impedance elements. Here, the target characteristics are set such that the impedance (Z) is 950 to 1050Ω, the impedance variation (σ) is 40 or less, and the direct current resistance (RDC) is 0.1Ω or less. The impedance shown in Table 3 is
It is a numerical value at 100 MHz, and the result shown by "-" is that measurement was impossible.

[0028]

[Table 3]

From the results shown in Table 3, the following matters are clear. That is, (1) no effect is observed when the immersion time is 8 minutes. (2) It is considered that when the immersion time was 13 hours, the characteristics could not be measured, and the conductor pattern was excessively corroded by the acid and fracture occurred. (3) Acid concentration is 0.0
At 001 mol / L, no effect is observed. (4) When the acid concentration is 1.3 mol / L, it is still impossible to measure the characteristics.
Also in this case, it is considered that the conductor pattern was excessively corroded by the acid and was broken. That is, the acid concentration is 0.00
1 mol / L to 1.2 mol / L, immersion time 10 minutes to 12
As a result, it was possible to obtain the impedance element having the required characteristics within the time range.

Next, an impedance element was prepared and characteristics were measured in the same manner as above except that the acidic solution used was an aqueous nitric acid solution or an aqueous sulfuric acid solution. Table 4 shows the result of the nitric acid aqueous solution, and Table 5 shows the result of the sulfuric acid aqueous solution.

[0031]

[Table 4]

[0032]

[Table 5]

From the results shown in Tables 4 and 5, the acid concentration was 0.001 mol / L as in the case of the immersion treatment in the hydrochloric acid aqueous solution.
It was found that an impedance element having the required characteristics can be obtained within a range of up to 1.2 mol / L and a dipping time of 10 minutes to 12 hours.

Next, the hydrochloric acid concentration of the acidic liquid was adjusted to 0.1 mol / min.
L, the immersion time is 2 hours, and the temperature of the acidic liquid is 20 ° C to
An impedance element was prepared and the characteristics were measured in the same manner as above except that the temperature was set to 60 ° C. Table 6 shows the results.

[0035]

[Table 6]

As is clear from the results shown in Table 6, the temperature between 20 ° C and
The impedance element processed in the temperature range of 60 ° C. exhibits the target characteristics, but at 20 ° C. and 60 ° C., an increasing tendency of variation is recognized. Therefore, it is presumed that the effect of the immersion treatment is insufficient at a temperature of 20 ° C. or lower, and the effect becomes excessive at a temperature of 60 ° C. or higher. Incidentally, as the liquid temperature rises, the concentration of hydrochloric acid in the atmosphere rises and the working environment is significantly lowered, which is not preferable. Also nitric acid,
Similar results were obtained when sulfuric acid was used.

[0037]

As described above, the acid concentration is 0.0
01 mol / L to 1.2 mol / L, the temperature is 20 ° C to 60 ° C
After immersing the fired body in the acidic liquid held at 10 minutes to 12 hours and then baking the external electrode, an appropriate space is provided between the coil of the conductor formed inside and the magnetic body. You can This makes it possible to prevent stress from being generated inside, and by exhibiting the original magnetic characteristics of the material, it is possible to obtain a laminated impedance element having excellent characteristics.

[Brief description of drawings]

FIG. 1 is a diagram showing an outline of an example of a laminated impedance element, FIG. 1 (a) is a perspective view of an external appearance, and FIG. 1 (b) is a diagram showing a state of forming an internal coil.

FIG. 2 is a flowchart of a manufacturing process of a laminated impedance element.

[Explanation of symbols]

100 Multilayer impedance element 101 magnetic material 102,205 External electrode 103 coil 201 magnetic layer 202 conductor pattern 203 Laminate after cutting 204 fired body

Claims (6)

[Claims] 1. An impedance element having a spiral conductor coil inside, which is obtained by laminating a magnetic ceramic layer and a conductor pattern and firing them integrally, wherein there is no gap between the magnetic ceramic and the conductor coil. A laminated impedance element, characterized in that continuous voids are formed. 2. A method for manufacturing a multilayer impedance element, comprising stacking a magnetic ceramic layer and a conductor pattern so that the conductor forms a coil to form a laminated body, and then firing the laminated body. 2. The method for manufacturing a laminated impedance element according to claim 1, wherein after the laminated body is fired, a discontinuous gap between the magnetic ceramics and the conductor coil is formed. 3. The method for manufacturing a laminated impedance element according to claim 2, wherein the formation of the discontinuous void between the magnetic ceramics and the conductive coil is performed in the acidic liquid of the fired body. A method for manufacturing a laminated impedance element, characterized in that the dipping treatment is carried out for from minutes to 12 hours. 4. The method for manufacturing a laminated impedance element according to claim 3, wherein the temperature of the acidic liquid is 20 ° C.
-60 degreeC, The manufacturing method of the laminated impedance element characterized by the above-mentioned. 5. The method for manufacturing a laminated impedance element according to claim 3,
The method for manufacturing a laminated impedance element, wherein the acidic liquid is a solution containing at least one of hydrochloric acid, nitric acid, and sulfuric acid. 6. The method for manufacturing a laminated impedance element according to claim 5, wherein the acid concentration is 0.001.
Mol / L to 1.2 mol / L.