JPH1050525A - Impedance element and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To facilitate the impedance value control at a specified high-frequency region by parallel connection of a conductive film on the bobbin surface to both ends of a winding. SOLUTION: A polyvinyl alcohol binder is compounded with a titania-based ceramic powder and granulated by a spray dryer to produce a press-molding powder. This powder is mechanically pressed to form an I-shaped ceramic bobbin 1, and it is baked in air. A Ta film is formed on the surface of the bobbin by the sputtering to make it conductive, an Ag paste is applied to both ends of the bobbin and baked in the air to form Ag-baked terminals 2. The bobbin 1 is heat treated in a mixed gas of N and H in an annular furnace, to reduce the bobbin surface. A covered conductor 3 is wound round the bobbin 1 and both ends thereof are soldered 4 to the terminals 2. Thus it is possible to easily control the impedance value at a specified high-frequency region.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multilayer impedance element for reducing noise in a signal circuit and reducing signal wave distortion and delay, and a method for manufacturing the same.

[0002]

2. Description of the Related Art In recent years, as a measure against EMI of electronic equipment, it has been generally practiced to insert an impedance element in series in a signal system to cut off noise.

[0003] In a power supply line system such as a power amplifier, an impedance element is inserted in series to suppress the leakage of signal system noise from the active element to the power supply line.

However, the countermeasure against EMI by the impedance element has a negative effect that a reactance component causes distortion of a signal waveform or causes a phase delay.

The impedance Za of the impedance element
Is a combination of the real-valued resistance component Ra and the imaginary-part reactance component Xa, and is expressed by the equation Ra + jXa. An ideal impedance element that is effective for noise absorption and does not cause distortion or phase lag has a small value in the real part resistance component Ra and the imaginary part reactance component Xa in a specific high-frequency region having a noise component. It has.

[0006]

The resistance value in the high-frequency region that acts on noise absorption requires a specific value depending on the circuit used. The elements used for this purpose today are a means to achieve the desired frequency response,
It is realized by adjusting the frequency characteristic of the inherent loss of the magnetic material and the number of turns of the formed spiral coil, etc. Today, most are SMD parts, and there are many restrictions on the shape and size. Therefore, there is a problem that a desired frequency characteristic cannot always be obtained.

An object of the present invention is to provide an impedance element capable of easily controlling an impedance value to a target value in a specific high-frequency region and a method of manufacturing the same.

[0008]

SUMMARY OF THE INVENTION The present invention relates to an inductance element formed by winding and winding a non-magnetic ceramic on a bobbin formed by molding and sintering, wherein a film made of a conductive substance formed on the surface of the bobbin is provided. , An impedance element connected in parallel with both ends of the winding.

Further, the present invention is a method for producing an impedance element, characterized in that the surface of a bobbin is partially reduced to form a layer having a predetermined conductivity as a means for forming the film.

[0010]

Embodiments of the present invention will be described with reference to the drawings.

FIG. 1 shows a parallel circuit of an inductance L and a resistance R. The impedance between the terminals of this circuit is given by the equation:

Z = (ω ² L ² R + jωLR) / (R ² + ω ² L ² )

In the impedance element according to the present invention, an inductance element is formed by winding a non-magnetic ceramic on a bobbin, and a resistance element is formed on a surface of the bobbin. By connecting the elements in parallel to form a composite element, a desired frequency characteristic can be obtained.

The value of the inductance L of the circuit is 1 μm.
H or 2 μH and the resistance R of the circuit is set to 500Ω, the frequency characteristics of the impedance Z1 between both terminals, the resistance component R1 of the real part thereof, and the reactance component X1 of the imaginary part are A1, B1, C1, and C1, respectively. FIG. 2 shows the curves of D1, E1, and F1.

A1 is an impedance Z1 when the resistance R of the circuit is 500Ω and the inductance L of the circuit is 1 μH.
FIG. B1 is the resistance R of the circuit is 500Ω
Shows the frequency characteristic of the resistance component R1 of the real part when the inductance L of the circuit is 1 μH. C1 indicates the frequency characteristic of the imaginary part reactance component X1 when the circuit resistance R is 500Ω and the circuit inductance L is 1 μH. D1
Shows the frequency characteristic of the impedance Z1 when the resistance R of the circuit is 500Ω and the inductance L of the circuit is 2 μH. E1 shows the frequency characteristic of the resistance component R1 of the real part when the resistance R of the circuit is 500Ω and the inductance L of the circuit is 2 μH. F1 represents the frequency characteristic of the imaginary part reactance component X1 when the circuit resistance R is 500Ω and the circuit inductance L is 2 μH.

The value of the inductance L of the circuit is 1 μm.
H or 2 μH, and the value of the resistance R of the circuit is 300
When Ω is set, the frequency characteristics of the impedance Z2 between the two terminals, the resistance component R2 of the real part, and the reactance component X2 of the imaginary part are similarly A2, B2, C2, D2, E2,
FIG. 3 shows the curve of F2.

A2 is an impedance Z2 when the circuit resistance R is 300Ω and the circuit inductance L is 1 μH.
FIG. B2 indicates that the resistance R of the circuit is 300Ω.
Shows the frequency characteristic of the resistance component R2 of the real part when the inductance L is 1 μH. C2 is a circuit resistance R of 300
Ω indicates the frequency characteristic of the imaginary part reactance component X2 when the circuit inductance L is 1 μH. D2 has a circuit resistance R of 300Ω and a circuit inductance L of 2μ.
The frequency characteristic of the impedance Z2 at the time of H is shown. E2
Shows the frequency characteristic of the resistance component R2 of the real part when the circuit resistance R is 300Ω and the circuit inductance L is 2 μH. F2 indicates the frequency characteristic of the imaginary part reactance component X2 when the circuit resistance R is 300Ω and the circuit inductance L is 2 μH.

As is clear from FIGS. 2 and 3, in the low frequency region, the impedance value of the coil portion having a low impedance value is dominant, and the impedance value between the two terminals is determined. When the impedance value exceeds the resistance of the circuit, the impedance value between the two terminals is dominated by the resistance component of the real part, and converges to the value of the resistance component of the real part.

It is also possible to change the rise of the impedance value with the frequency characteristic of the impedance value depending on the inductance value.

When the impedance element is manufactured by using a magnetic material such as ferrite for the core, the reactance component decreases as the frequency increases, and the loss increases at the same time.

As a result, the frequency characteristic of the impedance value shows a change similar to the frequency characteristic of the above-described parallel circuit of the pure inductance L and the resistor R. However, in order to obtain a desired frequency characteristic, the frequency characteristic is controlled mainly by the loss characteristic of the material, and the others are less in the degree of freedom due to the number of turns of the spiral coil and the inductance value by adjusting the shape. Is not necessarily obtained.

However, when a resistor is connected in parallel with the so-called air-core inductance without using a magnetic material as the inductance element, the component of the real part of the impedance in the high-frequency region has the effect of being connected in parallel with the resistor. And the component of the real part of the impedance can be controlled, and the resistance value in the high frequency region can be controlled very easily.

However, it is not preferable to newly add a resistance element in terms of increasing the number of steps in downsizing components and performing surface mounting work. If a resistance element can be formed on the surface of a bobbin of an inductance element, an extremely practical impedance element can be provided.

[0024]

An embodiment of the present invention will be described.

As a ceramic powder, a titania-based powder was prepared. A polyvinyl alcohol-based binder was mixed with the powder, and the mixture was granulated with a spray drier to prepare a powder for press molding.

As shown in FIG. 4, a ceramic bobbin 1 having an I-shaped cross section was formed by a mechanical press, and the formed body was fired in the atmosphere at 1350 ° C. for 2 hours. Silver paste was applied to both ends of this sintered body, and baking was performed at 500 ° C. for 30 minutes in the air to form silver-baked terminals 2. Next, a 50 μm-diameter covered conductive wire 3 was
A sample A was obtained by winding the wire for 00 turns and applying the solder 4 to the terminal 2 at both ends of the conductor 3.

Next, when a tantalum film was sputtered on the surface of the bobbin to make it conductive, the electric resistance between the terminals was measured, and an average resistance of 300Ω was shown between the terminals. The bobbin provided with the same winding as that of the sample A was used as a sample B.

Further, the bobbins after silver baking were heat-treated at 800 ° C. for 30 minutes and 120 minutes while flowing a mixed gas of nitrogen and several percent hydrogen at a flow rate of several liters / minute in an annular furnace.

When the electric resistance at both ends was measured, the average values showed resistance values of 780 Ω and 510 Ω, respectively. These were also wound in the same manner as Sample A, and Samples C and D were obtained.

When the inductance at 100 kHz was measured for each of them using an impedance bridge, values of 0.9 to 1.2 μH were shown in almost the same manner.

The frequency characteristics of the impedance of the multilayer inductor manufactured as described above were evaluated using a YHP impedance analyzer HP4191A.
The results of Sample A, Sample B, Sample C, and Sample D are shown in FIGS. 5, 6, 7, and 8, respectively.

As shown in FIG. 5, ZA indicates the frequency characteristic of the impedance ZA of the sample A when no resistance element is added. RA indicates the frequency characteristic of the resistance component RA of the real part of the sample A when no resistance element is added. XA indicates the frequency characteristic of the reactance component XA of the imaginary part of the sample A when no resistance element is added.

As shown in FIG. 6, ZB indicates the frequency characteristic of the impedance ZB of the sample B. RB indicates the frequency characteristic of the resistance component RB of the real part of the sample B. XB indicates the frequency characteristic of the reactance component XB of the imaginary part of the sample B.

As shown in FIG. 7, ZC indicates a frequency characteristic of the impedance ZC of the sample C. RC indicates the frequency characteristic of the resistance component RC of the real part of the sample C. XC indicates the frequency characteristic of the reactance component XC of the imaginary part of the sample C.

As shown in FIG. 8, ZD indicates the frequency characteristic of the impedance ZD of the sample D. RD indicates the frequency characteristic of the resistance component RD of the real part of the sample D. XD indicates the frequency characteristic of the imaginary part reactance component XD of the sample D.

In FIG. 5, the impedance value of the sample A in the high frequency region (> 50 MHz), which corresponds to the case where no resistive element is added, has a high ratio of the reactance component.
No favorable frequency characteristics are shown in terms of noise absorption characteristics.

On the other hand, in the case of the samples B, C, and D shown in FIGS. 6, 7, and 8, the impedance values in the high frequency region almost converge to the values of the added resistive elements. Is controlled by

Further, the imaginary part of the impedance is remarkably attenuated in the high frequency region and becomes almost only the real part, showing favorable frequency characteristics with respect to noise absorption and occurrence of phase delay or distortion to a signal.

From this, it has been proved that the frequency characteristic of the impedance value in the high frequency region can be controlled extremely easily in manufacturing. Further, it was confirmed that a conductive layer was formed on the element surface by heat treatment in a reducing atmosphere from Samples C and D, and that this could be used as a resistance element, and that the resistance value could be controlled by heat treatment conditions.

[0040]

As described above, according to the present invention, it is possible to easily control an impedance value to a target value in a specific high-frequency region for an impedance element, which is an SMD component having many restrictions on the shape and size, and a method for manufacturing the same. It has become possible to provide a device that can be manufactured and a method for manufacturing the same.

[Brief description of the drawings]

FIG. 1 is a diagram showing a parallel circuit including an inductance L and a resistance R.

FIG. 2 shows that the value of the inductance L of the circuit is 1 μH or 2 μH.
FIG. 9 is a diagram showing the frequency characteristics of the impedance Z1 between both terminals of the circuit, the resistance component R1 of the real part thereof, and the reactance component X1 of the imaginary part thereof when μH is set and the value of the resistance R of the circuit is 500Ω.

FIG. 3 shows a case where the value of the inductance L of the circuit is 1 μH or 2 μH and the value of the resistance R of the circuit is 300Ω.
The figure which shows the frequency characteristic of impedance Z2 between each both terminals, the resistance component R2 of the real part, and the reactance component X2 of the imaginary part.

FIG. 4 is a perspective view showing a sample A.

FIG. 5 is a diagram illustrating frequency characteristics of a sample A;

FIG. 6 is a diagram illustrating frequency characteristics of a sample B;

FIG. 7 is a diagram illustrating frequency characteristics of a sample C;

FIG. 8 is a diagram illustrating frequency characteristics of a sample D;

[Explanation of symbols]

 1 bobbin 2 terminal 3 conductor 4 solder

Claims (2)

[Claims] 1. An inductance element in which a winding is applied to a bobbin formed by molding and firing a non-magnetic ceramic, wherein a coating made of a conductive substance formed on a surface of the bobbin is parallel to both ends of the winding. An impedance element characterized by being connected to. 2. A method for manufacturing an impedance element according to claim 1, wherein the surface of the bobbin is partially reduced to form a layer having a predetermined conductivity.