JP3061092B2 - Noise filter block with varistor function - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a noise filter block for removing high frequency noise in a plurality of signal lines. More specifically, the present invention relates to a noise filter block with a varistor function suitable for being incorporated in a connector or the like and capable of absorbing a surge voltage.

[0002]

2. Description of the Related Art In digital equipment such as computers, there is a problem that when high-frequency noise is mixed in a signal line, malfunctions are liable to occur, and unnecessary electromagnetic waves which may cause a failure in other electronic equipments are radiated from wiring. is there. For this reason, a noise filter that removes high-frequency noise using a capacitor element is frequently used in a signal line. A noise filter block for removing high-frequency noise in a plurality of signal lines may be one in which through capacitors are arranged in a plurality of mounting holes formed in a metal ground plate or a shield case by soldering, or a printed circuit. 2. Description of the Related Art A device in which a chip capacitor is mounted on a substrate by soldering is known.

On the other hand, since a surge voltage may be applied to this type of signal line in addition to the incorporation of high-frequency noise, conventionally, high-frequency noise has been removed and, at the same time, "high-frequency and surge absorption" capable of absorbing surge voltage has been proposed. A "filter" has been disclosed (JP-A-1-102874). In this filter, an elongated signal line for transmitting an electric signal is provided on one surface of a flat plate made of a dielectric material having capacitive and varistor characteristics, and a ground electrode is provided on almost the entire other surface, and the signal line and the ground are provided. A distributed constant type capacitor and a varistor are formed between the electrodes.

[0004]

However, in the noise filter block using the feedthrough capacitor, when a plurality of feedthrough capacitors are mounted on the ground plate,
The noise filter block becomes thicker by the length of the feedthrough capacitor, making it difficult to make it thinner.Moreover, the mounting holes must be spaced from each other in accordance with the outer diameter of the feedthrough capacitor, and the narrow pitch of the signal line When a temperature cycle test is carried out in a state where the connector is incorporated in the connector, stress is generated in the connector pin, which is a terminal, due to the difference in the coefficient of thermal expansion between the insulating resin of the connector and the ground plate. Cracking or the like may occur in the feedthrough capacitor through which the pin is inserted, and there is a problem that the range in which the capacitance of the feedthrough capacitor can be obtained is narrowed and limited. In addition, the noise filter block using a chip capacitor has insufficient performance in removing high-frequency noise due to the layout of the printed pattern on the substrate and the structure of the ground electrode.

Further, the "high-frequency and surge absorbing filter" disclosed in Japanese Patent Application Laid-Open No. Hei 1-102874 requires a dielectric such as a ceramic substrate not only as a capacitor but also as a varistor at the same time. In order to obtain the effect of (1), the structure and composition of the ceramic substrate must be strictly defined, and the range in which the capacitance can be obtained is limited as in the case of the feedthrough capacitor. Therefore, there is a problem that a ferrite plate or a ferrite bead is required.

An object of the present invention is to provide a noise filter block which can be reduced in size by making the overall shape thinner and narrowing the pitch between signal lines, and which is free from cracks even when a temperature cycle test is performed. It is in. Another object of the present invention is to provide a noise filter block with a varistor function that has a simple structure, a wide range of obtaining capacitance, can sufficiently remove high-frequency noise, and can also absorb a surge voltage.

[0007]

A configuration of the present invention for achieving the above object will be described with reference to FIG. 1 corresponding to an embodiment. The noise filter block 10 having a varistor function according to the present invention includes an insulating substrate 11 in which a plurality of terminal insertion holes 12 are provided at predetermined intervals, and an inner electrode on the inner surface of the hole on the surface of the peripheral edge of the hole of the substrate 11. 12a, a signal electrode 14 formed continuously on the surface of the substrate 11, a first ground electrode 16 formed on the surface of the substrate 11 with a predetermined insulating gap 15 therebetween, and an inner electrode on the inner surface of the hole 12. A second ground electrode 17 formed on the back surface of the substrate 11 with a predetermined insulating gap 18 therebetween and electrically connected to the first ground electrode 16
And a pair of terminal electrodes 19b and 19c provided at both ends of the bare chip 19a by the signal electrode 14 and the first ground electrode 16 respectively.
And a pair of terminal electrodes 29b and 29c provided at both ends of the bare chip 29a are connected to the signal electrode 14, respectively. And a chip varistor 29 erected between the signal electrode 14 on the substrate surface and the first earth electrode 16 so as to be connected to the first and second earth electrodes 16 respectively.

[0008]

A signal line P such as a connector pin is inserted into a plurality of terminal insertion holes 12, these signal lines P are respectively connected to signal electrodes 14 on the substrate surface, and a second ground electrode 17 on the rear surface of the substrate. To the earth electrode of the earth shield case. Since a large capacitance can be obtained in a small space by the chip capacitor 19, the noise filter block 10 can be reduced in size and thickness, and the residual inductance generated on the ground side after being mounted on the connector by the block 10 can be extremely reduced. Therefore, high-frequency noise of a signal passing through each signal line can be collectively and reliably removed. When a surge voltage is applied to the signal line P, the signal varistor 29 and the signal electrode 14 and the ground electrode 16,
17 conducts, a surge current flows to the earth electrode of the shield case via the earth electrodes 16 and 17, and the signal line P
Protect electronic devices connected to

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, embodiments of the present invention will be described in detail with reference to the drawings. 1 to 4 show a noise filter block 10 having a varistor function according to a first embodiment of the present invention. As shown in FIGS. 1 to 4, a glass epoxy substrate 11 which is an insulating substrate
Using a copper-clad laminate having thin copper foils adhered to both sides of the substrate as a starting material, unnecessary portions were removed by etching to form the signal electrode 14 and the first and second ground electrodes 16 and 17. That is, four terminal insertion holes 12 are provided at the center of the copper-clad substrate 11, and ten through holes 13 are provided at equal intervals near both ends of the substrate 11. The inner surface of each of the hole 12 and the through hole 13 is formed by copper plating on the inner surface electrode 1.
2a and 13a were formed.

On the surface of the substrate 11, a circular signal electrode 14 centering on the hole 12 and the first ground electrode 1
6 is printed with a resist leaving a gap 15, and on the back surface of the substrate 11, a second resist is left leaving a gap 18 around the hole 12.
A resist was printed on each of the ground electrodes 17. The copper foil in the gaps 15 and 18 was removed by etching. As a result, the signal electrode 14 is formed on the peripheral surface of the hole of the substrate 11 so as to be continuous with the inner electrode 12a on the inner surface of the hole 12, and the first ground electrode 16 is connected to the signal electrode 14a.
And a predetermined insulating gap 15 from the electrode 14 is formed. A second ground electrode 17 is provided on the back surface of the substrate 11.
Surrounds the inner electrode 12a on the inner surface of the hole 12 and
a with a predetermined insulating gap 18 therebetween, and the second ground electrode 17 is formed on the inner surface electrode 13 of the inner surface of the through hole 13.
a, and was electrically connected to the first ground electrode 16.
Signal electrode 14 and first ground electrode 16 on the surface of substrate 11
Between each of the signal electrodes is a chip capacitor 19.
And chip varistors 29 are installed one by one. The chip capacitor 19 is mounted by soldering a pair of terminal electrodes 19b and 19c provided at both ends of the bare chip 19a to the signal electrode 14 and the first ground electrode 16, respectively. The chip capacitor 19 is a chip-type multilayer ceramic capacitor, and includes a bare chip 19a.
Is a sintered body obtained by alternately laminating an internal electrode and a barium titanate-based or lead-based dielectric layer, followed by firing. The terminal electrodes 19b and 19c are formed by applying a conductive paste containing Ag to both end surfaces of the bare chip and then baking the solder paste. The surface of the terminal electrodes is plated with solder.

The chip varistor 29 is constructed by a pair of terminal electrodes 29 provided at both ends of the bare chip 29a.
b, 29c are soldered to the signal electrode 14 and the first ground electrode 16, respectively. The chip varistor 29 is a chip-type multilayer ceramic varistor, and the bare chip 29a is a sintered body obtained by alternately stacking internal electrodes and zinc oxide-based varistor layers and then firing. Terminal electrodes 29b and 29c are terminal electrodes 19b and 19c.
It is formed similarly to

A case will be described in which the noise filter block 10 having the varistor function configured as described above is built in, for example, a connector (not shown). Four connector pins P (FIG. 1), which are signal lines, are inserted into the four terminal insertion holes 12, respectively, and these connector pins P are inserted into the inner electrode 12a, and the second ground electrode 1 on the rear surface of the substrate 11 is inserted.
7 are electrically connected to an earth shield case (not shown) by soldering. The connector pin P includes the inner electrode 12a, the signal electrode 14, and the chip capacitor 1.
9 or the ground electrode 16, 1 via the chip varistor 29.
7 is connected. Since a large capacitance can be obtained in a small space by the chip capacitor 19, the noise filter block 10 can be reduced in size and thickness, and the residual inductance generated on the ground side after being mounted on the connector by the block 10 can be extremely reduced. Therefore, high-frequency noise of a signal passing through each signal line can be collectively and reliably removed. When a surge voltage is applied to the signal line P by the chip varistor 29, the signal electrode 14 and the ground electrode 16,
17 conducts, a surge current flows to the earth electrode of the shield case via the earth electrodes 16 and 17, and the signal line P
Protect electronic devices connected to

FIGS. 5 to 8 show a noise filter block 20 having a varistor function according to a second embodiment of the present invention. 1 to 4
The same reference numerals indicate the same components. The characteristic configuration of this example is that, instead of providing the through holes 13 of the first embodiment, end surface electrodes 21 are formed on both end surfaces of the insulating substrate 11, and the first ground electrode 16 and the second ground electrode 17 are That is, it is electrically connected via the end face electrode 21 instead of the electrode 13a. In this example, an alumina ceramic substrate was used as the insulating substrate 11. Four terminal insertion holes 12 were provided at equal intervals in the center of the substrate 11 as in the first embodiment. Inner electrodes 12a were formed on the inner surfaces of the holes 12 by through-hole printing. The signal electrode 14 and the first ground electrode 16 are formed on the surface of the substrate 11 by using Ag or Ag / P.
The conductive paste containing d or the like was formed by screen printing. That is, the signal electrode 14 is formed in a circular shape on the peripheral surface of the hole of the substrate 11 so as to be continuous with the inner electrode 12a on the inner surface of the hole 12, and the first ground electrode 16 surrounds the signal electrode 14 and The electrode 14 was formed with a predetermined insulating gap 15 therebetween.

The second ground electrode 17 was formed on the back surface of the substrate 11 by screen printing the same conductive paste as described above. Further, the end face of the substrate 11 was coated with a conductive paste to form a baked end face electrode 21. As a result, the second ground electrode 17 surrounds the inner electrode 12a on the inner surface of the hole 12 and is formed with a predetermined insulating gap 18 from the electrode 12a.
It was electrically connected to the ground electrode 16. A chip capacitor 19 and a chip varistor 29 are provided between the signal electrode 14 and the first ground electrode 16 on the surface of the substrate 11 as in the first embodiment. This noise filter block 2
The method of use and the characteristics of 0 are the same as those in the first embodiment, so that the repeated description will be omitted.

In the above example, a glass epoxy substrate and an alumina ceramic substrate are shown as insulating substrates, but any other insulating substrate having heat resistance and high mechanical strength may be used. The shape of the signal electrode is not limited to a circle, but may be another shape such as a square or an ellipse.
Also, the chip capacitor and the chip capacitor are provided one for each signal electrode, but this number is merely an example, and two or more chip capacitors may be provided according to the frequency range to be removed.
More than one capacitor may be provided, or the capacitance may be changed according to the frequency range to be removed. Also, two or more chip varistors may be provided according to the required surge withstand capability. Furthermore, the number of terminal insertion holes or the number of through holes is an example, and is not limited to the above example.

[0016]

As described above, according to the present invention, the following excellent effects can be obtained. (a) Since a chip capacitor is used instead of the conventional feedthrough capacitor as the capacitor element, the pitch between signal lines can be narrowed, and the noise filter block can be reduced in size and thickness. Becomes possible. (b) Even if a load is applied to the terminals such as connector pins after mounting on the connector, etc., the chip capacitor as the capacitor element and the chip varistor as the surge absorbing element are not directly loaded, so these chip electronic components are damaged. I will not let you. Further, even when the temperature cycle test is performed, no cracks or the like occur.

(C) Since a chip capacitor is mounted, the capacitance acquisition range is wider than that of a conventional feedthrough capacitor, and high-frequency noise can be sufficiently removed. And chip capacitors for low frequency use, it is possible to take measures against noise in a wide frequency range. (d) First and second surfaces on the front and back surfaces of the insulating substrate, respectively.
Since the ground electrode is provided and both ground electrodes are electrically connected to each other by the end face of the board or through holes, when it is mounted on a grounding shield case such as a connector, the shielding effect is high and the residual inductance generated on the ground side is suppressed. And has an excellent high-frequency removing effect. (e) Since a chip varistor is mounted, when a surge voltage is applied to the signal line, the surge current flows to the ground electrode of the shield case to protect the electronic device connected to the signal line. (f) In particular, the filter block of the present invention performs noise removal and surge absorption with dedicated chip electronic components, respectively.
The design and manufacture for obtaining the desired effect are simple, and both functions can be reliably performed without a complicated structure.

[Brief description of the drawings]

FIG. 1 is a sectional view of a noise filter block with a varistor function according to a first embodiment of the present invention, taken along line AA of FIG. 2;

FIG. 2 is a plan view thereof.

FIG. 3 is an external perspective view thereof.

FIG. 4 is an external perspective view of the inverted appearance.

5 is a sectional view of the noise filter block with a varistor function according to a second embodiment of the present invention, taken along line BB of FIG. 6;

FIG. 6 is a plan view thereof.

FIG. 7 is an external perspective view of the same.

FIG. 8 is a perspective view of the inverted appearance.

[Explanation of symbols]

 P connector pin (signal line) 10, 20 noise filter block with varistor function 11 insulating substrate 12 terminal insertion hole 12a, 13a inner electrode 13 through hole 14 signal electrode 15, 18 insulating gap 16 first ground electrode 17 second Ground electrode 19 Chip capacitor 19a Bare chip 19b, 19c Terminal electrode 21 End electrode 29 Chip varistor 29a Bare chip 29b, 29c Terminal electrode

Claims (3)

(57) [Claims] An insulating substrate (11) having a plurality of terminal insertion holes (12) provided at predetermined intervals, and an inner surface of the hole (12) in a surface of a peripheral edge of the hole of the substrate (11). A signal electrode (14) formed continuously with the inner electrode (12a) of the substrate, and a signal electrode (14) formed on the surface of the substrate (11) with a predetermined insulating gap (15) therebetween. A first ground electrode (16), an inner electrode (12a) on the inner surface of the hole (12) and a predetermined insulating gap (1
8) A second ground electrode (17) formed on the back surface of the substrate (11) and electrically connected to the first ground electrode (16)
And a pair of terminal electrodes (19b, 19b,
19c) is connected to the signal electrode (14) and the first ground electrode (16) so as to be connected to the signal electrode (14) and the first ground electrode (16), respectively. And a pair of terminal electrodes (29b, 29b) provided at both ends of the bare chip (29a).
29c) is connected to the signal electrode (14) and the first ground electrode (16) on the surface of the substrate (11) so as to be connected to the signal electrode (14) and the first ground electrode (16), respectively. A noise filter block with a varistor function including a chip varistor (29) installed between the two. 2. A plurality of through holes (1) in an insulating substrate (11).
3), a first ground electrode (16) and a second ground electrode (1) are provided.
2. The noise filter block with a varistor function according to claim 1, wherein said 7) is electrically connected via an inner surface electrode (13a) of said through hole (13). 3. An end face electrode (21) is formed on an end face of an insulating substrate (11), and a first earth electrode (16) and a second earth electrode (17) are electrically connected via the end face electrode (21). Claim 1 connected to
Noise filter block with varistor function described.