JPH0430615A - Noise filter - Google Patents

Abstract

PURPOSE:To provide an attenuation characteristic of a broad band at a comparatively low frequency pass characteristic regardless of thin profile and small sized configuration by replacing alternately the arrangement of two spiral electrodes opposite to each other with a plate dielectric body inserted in between on the front and rear sides of the dielectric body so that adjacent and opposed spiral electrodes are necessarily 2nd electrodes even at any position of 1st spiral electrodes. CONSTITUTION:The noise filter is formed by forming a spiral electrode to both sides of a plate dielectric body 11, and a structure of a laminator may be adopted as shown in cross sectional figure cut along the spiral electrode, in which two dielectric bodies 11 or over are overlapped via an intermediate plate dielectric body (insulator) 12. Each inner end of both the spiral electrodes 1, 2 of a 1st layer is connected with an inner end of both the spiral electrodes 1, 2 of a 2nd layer via a throughhole provided to an intermediate plate dielectric body 12. In such a case, the electrodes are so arranged that a 1st spiral electrode 1 is opposite to a 2nd spiral electrode 2 without fail in any position of the noise filter through the intermediate plate dielectric body 12.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a noise filter applied to power supply circuits, signal passing circuits, etc. in various electronic devices such as computers that handle dental signals.

(Prior Art) In electronic equipment such as computers that handle digital signals, noise filters are used in power supply circuits and signal passing circuits.

As an example of such a conventional noise filter, the first
As shown in Figure 4, a plate-shaped dielectric material 11 such as ceramic
Two spiral electrodes 1.2 are arranged facing each other on both sides of the , one spiral electrode 1 is inserted into a power supply circuit or a signal passing circuit via a terminal 5.7 as a current carrying conductor, and the other spiral electrode 2 is inserted as a grounding conductor. An arbitrary one end is grounded via the terminal 6, and a potential difference is generated between two parallel wires sandwiching the plate-shaped dielectric 11 to form a distributed capacitance. It is known that it forms an inductance.

(The problem to be solved by the invention) However, in such a conventional noise filter, as shown in the cross-sectional view of FIG. However, due to the capacitance C2 that also exists between the adjacent conductors 14, the AC component from the outermost conductor to the innermost conductor, especially high Since frequency components pass through, it was not possible to obtain good attenuation characteristics over a high frequency band.

(Means for Solving Problems) Therefore, the noise filter of the present invention was devised to solve such problems, and includes first noise filters arranged facing each other on both sides of a plate-shaped dielectric material. Spiral electrode and second
The spiral electrode is cut one turn at a time, and the cut portion is connected to the opposite spiral electrode through a penetrating conductor such as a through hole provided in the plate-like dielectric material. The configuration is such that the arrangement is alternately changed so that the adjacent and opposing spiral electrodes always become the second electrodes at any position of the first spiral electrode, and when either one of the spiral electrodes is energized. It can be used as a 3-terminal normal mode noise filter with the other spiral electrode as a conductor and the other spiral electrode as a ground conductor, or as a 41-terminal common mode noise filter with both spiral electrodes as a current-carrying conductor.

A low-pass filter having good attenuation characteristics over a wide band is obtained by the distributed capacitance formed between the two spiral electrodes and the inductance of each spiral electrode.

(First Embodiment) As shown in the assembly diagram of FIG. 1 and the perspective view of FIG. spiral electrode 2
As is clear from the enlarged view of Fig. 3, two through holes 3 are formed at the cut positions.
．． The front and back electrodes 1.2 are alternately connected through the electrodes 4.

Such a spiral electrode 1.2 and a through hole 3
．． 4 may be formed by known techniques such as photo-etching or screen printing.

As is clear from FIG. 4, which shows the connection state through the through hole 3.4 by cutting along the opposing spiral electrodes, both spiral electrodes 1 and 2 are arranged with the front and back sides alternately every turn. It's being replaced.

Furthermore, as is clear from the cross-sectional view of FIG. The spiral electrode 2 is configured so as to be a spiral electrode 2.

When used as a normal moat noise filter, three connection terminals 5, 6 and 7 are provided on one end surface of the plate-shaped dielectric 11 for connection to an external circuit. The outer end of the first spiral electrode 1 is connected to the terminal 7, and the connecting conductor 9 formed on the inner end of the first spiral electrode 1 and the bonding wire or insulating film is connected to the terminal 7. The terminal 6 is connected to the outer end of the second spiral electrode 2 on the back side.

In addition, when used as a common mode noise filter, a connecting terminal 8 is provided in addition to the connecting terminals 5, 6, 7, and the terminal 5 is provided with an outer side of the first spiral electrode 1. The terminal 7 is connected to the inner end of the first spiral electrode 1 via the bonding wire 9, and the terminal 6 is connected to the outer end of the second spiral electrode 2 on the back side. The terminal 8 is connected to the inner end of the second spiral electrode 2 on the back side via a bonding wire.

When using a ceramic substrate as the plate-shaped dielectric 11 formed by such two spiral electrodes 1.2,
Ceramic substrate, crystallized glass ceramic, alumina glass ceramic, BSB (BaSn (BO,)
l) It is advantageous to use a low temperature sintered ceramic substrate such as a series ceramic. That is, such a low-temperature sintered ceramic substrate has a sintering temperature of 900-t, too°C.
Since metals such as gold and silver, which are low-resistance conductors, do not deteriorate during sintering, the manufacturing process is simple because two spiral electrodes can be pre-formed before sintering. This makes it possible to reduce manufacturing costs.

Note that a high-temperature sintered ceramic substrate may be used as the plate-shaped dielectric 11 formed by the two spiral electrodes 1.2. In that case, the two spiral electrodes 1.2 may be formed on a ceramic substrate that has been sintered in advance.

(Operation) When applying the noise filter of the present invention to a circuit in which common mode noise is to be suppressed, as shown in the equivalent circuit diagram of Figure 6a, it is necessary to Connect terminals 5 and 7 to create the first spiral i! T!
pi is inserted as a current-carrying conductor, and the terminal 6 is grounded to make the second spiral electrode 2 a grounding conductor.

In addition, when applied to a circuit that should suppress normal mode noise, as shown in the equivalent circuit diagram in Figure 6,
Terminals 5.7 and 6. are connected in the middle of the power supply circuit and signal passage circuit.
8 to connect the two spiral electrodes 1.2 as current-carrying conductors.

Then, a potential difference is effectively generated between the two parallel spiral electrodes 1.2 to form a distributed capacitance, and
Due to the inductance of the spiral electrode serving as a current-carrying conductor, it can operate as a low-pass filter that effectively suppresses noise, and a pseudo-distributed constant type noise filter can be obtained.

(Second Embodiment) In the embodiment shown in FIGS. 1 to 4, there is one noise filter in which spiral electrodes are formed on both sides of the plate-shaped dielectric 11. As shown in FIG. 7, which is a cutaway view, it is possible to form a laminate in which two or more sheets are stacked with an intermediate plate-shaped dielectric (insulator) 12 interposed therebetween.

The inner ends of both spiral electrodes 1.2 of the first layer are interconnected with the inner ends of both spiral electrodes 1.2 of the second layer through through holes provided in the intermediate plate-shaped dielectric 12. Connect to.

In this case as well, the first spiral electrodes 1 facing each other via the intermediate plate-shaped dielectric 12 are arranged so as to always become the second spiral electrodes 2 at any position.

(Third Embodiment) The noise filter of this invention can be made by thin film printing technology.

As shown in FIG. 8, (1) Connecting terminals 5.6 are formed on the side surface of the insulating substrate 13, and the first layer of spiral electrodes 1a and 2a, cut at each turn, are coated with conductive paint on the surface. (2) Leave the cut part to form the spiral electrode 1a.

A first layer of dielectric material 14 is printed so that the ends of electrodes 2a are exposed, and (3) each of the first layer of spiral electrodes 1a and 2a is printed on this first layer of dielectric material 14. The second layer of spiral electrodes 1b and 2b are printed with conductive paint so as to be continuous with the ends, so that they are continuous with the first layer of spiral electrodes 1a and 2a, and (4) the second layer becomes a current-carrying conductor. A second dielectric layer 15 is printed so that the inner edge of the spiral electrode 1b is left and the edge is exposed. (5) On this second layer dielectric 13, the exposed A conductor 9 for connecting between the inner end of the spiral electrode 1b and the terminal 7 is printed with conductive paint.

Through these steps (1) to (5), a thin film noise filter can be made.

(Fourth Embodiment) The noise filter of the present invention can be made in multiple layers using Fs film printing technology.

As shown in FIG. 9, (1) Connecting terminals 5.6 are formed on the side surface of the insulating substrate 13, and the first layer of spiral electrodes 1a and 2a are coated with conductive paint on the surface, with each turn being cut. (2) Leaving the cut part, each spiral electrode 1a,
A first layer of dielectric material 14 is printed so that the ends of electrodes 2a are exposed, and (3) each of the first layer of spiral electrodes 1a and 2a is printed on this first layer of dielectric material 14. The second layer spiral electrodes tb, 2b are printed with conductive paint so as to be continuous with the end portions, so that they are continuous with the first layer spiral electrodes 1a, 2a, and the spiral electrodes 1.2 are directed from the outside to the inside. (4) Print a second layer of dielectric material 15 so that each inner end of each spiral electrode 1.2 of this second layer is left exposed, and (5) ) This 27th! On the eye dielectric 15, print a conductor 9 directed outward from each inner end of the second layer spiral electrode 1.2 with conductive paint 6) Leave the outer end of this conductor 9 and (7) On top of this third layer dielectric 16, each outer end of the second layer spiral electrode 1.2 is printed. The third layer spiral electrodes 1c and 2c are cut every turn so that they are continuous.
(8) Print a fourth layer of dielectric material 17 so that the ends of each spiral electrode 1c, 2c of the third layer are exposed, leaving the cut portions, (9) ) On this fourth layer dielectric material 17, fourth layer spiral electrodes 1d and 2d are printed with conductive paint so as to be continuous with each end of the third layer spiral electrodes 1c and 2c. Continuous with the third layer spiral electrodes 1c and 2c, (10) Fourth layer spiral electrode 1d serving as a current-carrying conductor.
(11) Print the fifth layer dielectric 18 so that the inner edge of the spiral electrode 1d is exposed, leaving the inner edge of the spiral electrode 1d exposed. A conductor 9 for connecting between the inner end and the terminal 7 is printed with conductive paint.

Through these steps (1) to (11), a multilayer thin film noise filter can be manufactured.

(Fifth Embodiment) In the first to fourth embodiments described above, the noise filter of the present invention is constructed as a component, but it is mounted on a substrate such as a printed wiring board or an IC card board. It may also be formed as a pattern.

That is, as shown in FIG. 10, a printed wiring board 20 on which an electronic component 21 is mounted or a board itself such as a C card board is used as a plate-like dielectric material, and first
As explained in the example above, two spiral electrodes 1.
2 as an IMI or a plurality of sets, or the printed wiring board 20 or the IC card board itself is used as an insulating substrate, as described in the second to fourth embodiments, i1m! Depending on the printing technique, one or more sets of two spiral electrodes 1.2 may be formed.

Furthermore, as shown in FIG. 11, an assembly 22 in which a plurality of noise filters are formed on one dielectric substrate can be mounted on the printed wiring board 20 in the same way as other components.

(Other Examples) (A) In addition to ceramic, plastic, glass, barium titanate, fluororesin, mica, etc. are used as the plate-shaped dielectric 11, and a first spiral is arranged on both the front and back surfaces of the plate-shaped dielectric 11. The electrode 1 and the second spiral electrode 2 are cut every turn or every odd turn, and the front and back electrodes are alternately connected through through holes 3.4 provided at the cut positions.

(B) As a means of increasing the capacitance between two spiral electrodes, it is possible to reduce the thickness by using a material with a high dielectric constant for the plate dielectric 11, to increase the width of each spiral electrode, or to increase the capacitance between two spiral electrodes. As shown in the cross-sectional view of FIG.
The capacitance can be increased by roughening both the front and back surfaces of the dielectric plate 11 to increase the substantial surface area, or as shown in the cross-sectional view of FIG. 1
5 is provided, and a spiral electrode 1.2 is formed in a spiral groove 19 formed between the protrusions 15 to increase capacitance.

(C) As a means of increasing the inductance of the spiral electrode, it is sufficient to add a magnetic material to the spiral electrode or to mix a magnetic material into the dielectric material.

(D) As the dielectric material forming the spiral electrode, in addition to a flat dielectric material, dielectric materials having other shapes such as a cylindrical shape and a rectangular tube shape can also be used.

(E) The noise filter package may be a leaded package conventionally used in ceramic capacitors or the like, or a leadless chip-like package suitable for surface mounting.

(Effects) As explained above, in the noise filter of the present invention, the arrangement of the front and back sides of two spiral electrodes facing each other through a plate-like dielectric material is alternately switched for each turn.
At any position of the spiral electrode, the adjacent and opposing spiral electrode is always the second electrode, so it can be used as a 3-terminal normal mode filter or as a 4-terminal common mode filter. - By using it as a noise filter, it is possible to obtain a pseudo-distributed constant type noise filter that has a relatively low-pass property and wideband attenuation characteristics despite being thin and compact.

[Brief explanation of the drawing]

FIG. 1 is an assembly diagram showing one embodiment of the noise filter of the present invention, FIG. 2 is a perspective view of one embodiment of the noise filter of the present invention, and FIG. 3 is an enlarged view of the main parts. FIG. 4 is a cross-sectional view taken along the spiral electrode, FIG. 5 is a cross-sectional view taken along a plane perpendicular to the spiral electrode, and FIG. and b are equivalent circuit diagrams used to explain how to use the noise filter of the present invention, FIG. 7 is a cross-sectional view of the second embodiment taken along the spiral electrode, and FIG. 8 is a cross-sectional view of the second embodiment. , FIG. 9 is a perspective view showing the third embodiment in the order of manufacturing steps, FIG. 9 is a perspective view showing the fourth embodiment in the order of manufacturing steps, FIGS.
The figure is a perspective view of the fifth embodiment, FIGS. 12 and 13 are sectional views of other embodiments, and FIG. 14 is a conventional noise filter.
The configuration diagram of the filter, FIG. 15, is a cross-sectional view thereof,
Identical parts are represented by the same reference numerals throughout the figures. 1.2...Spiral electrode 3.4...Through hole 5.6.7.8...Connection terminal 11.12.14.15.16...Plate dielectric 13.
... Insulating substrate No. 1N No. 2N No. 3

Claims (1)

[Claims] (1) At least two spiral electrodes arranged oppositely on both sides of a dielectric are cut, and the front and back sides of each spiral electrode are connected to the spiral electrode on the opposite side via a conductor penetrating the dielectric at the cut site. 1. A noise filter characterized in that the arrangement of the first spiral electrodes is alternately changed so that an adjacent and opposing electrode becomes a second spiral electrode at any position of the first spiral electrode.