CN108288532B

CN108288532B - Common mode filter

Info

Publication number: CN108288532B
Application number: CN201711315228.XA
Authority: CN
Inventors: 李相汶; 朴成珍; 权赫重; 宋河润; 马成龙
Original assignee: Samsung Electro Mechanics Co Ltd
Current assignee: Samsung Electro Mechanics Co Ltd
Priority date: 2017-01-09
Filing date: 2017-12-12
Publication date: 2021-04-27
Anticipated expiration: 2037-12-12
Also published as: CN108288532A

Abstract

The invention provides a common mode filter. The common mode filter includes a filter section and an electrostatic protection section provided on the filter section. The electrostatic protection unit includes: a first discharge electrode and a second discharge electrode spaced apart from each other; a discharge layer disposed between the first discharge electrode and the second discharge electrode; and a first insulating layer covering an upper surface of the discharge layer and including flat first insulating particles and spherical second insulating particles.

Description

Common mode filter

This application claims the benefit of priority of korean patent application No. 10-2017-0018265 filed on korean intellectual property office at 2/9.2017 and korean patent application No. 10-2017-0002893 filed on korean intellectual property office at 1/9.2017, the disclosures of which are incorporated herein by reference in their entireties.

Technical Field

The present disclosure relates to a common mode filter.

Background

With the advance of technology, electronic devices such as mobile phones, home appliances, PCs, PDAs, LCDs, and the like have been changed from analog type devices to digital type devices, and tend to have increased processing speeds due to an increase in the amount of data required to be processed. In line with this, USB 2.0, USB 3.0, and high-definition multimedia interface (HDMI) have become widespread as high-speed signal transmission interfaces, and have been used in digital devices such as personal computers and digital high-definition (HD) televisions.

Unlike single-ended transmission systems commonly used in the art, such high-speed interfaces employ a differential signaling system that transmits a differential signal (differential mode signal) using a pair of signal lines. However, high speed digitizing electronics are sensitive to external stimuli, resulting in frequent signal distortion due to high frequency noise.

A switching voltage generated in the circuit, power supply noise included in the source voltage, unnecessary electromagnetic signals, electromagnetic noise, and the like cause abnormal voltage and noise, and a Common Mode Filter (CMF) is used to prevent such abnormal voltage and high frequency noise from being introduced into the circuit.

Disclosure of Invention

An aspect of the present disclosure may provide a structure capable of preventing a leakage current from being generated in an insulating layer when an overvoltage such as static electricity is applied in a common mode filter including an electrostatic protection portion.

According to an aspect of the present disclosure, a common mode filter may include: a filter part and an electrostatic protection part disposed on the filter part, wherein the electrostatic protection part includes: a first discharge electrode and a second discharge electrode disposed to be separated from each other by a predetermined distance; a discharge layer disposed between the first discharge electrode and the second discharge electrode; and a first insulating layer disposed to cover an upper surface of the discharge layer and including flat first insulating particles and spherical second insulating particles.

According to another aspect of the present disclosure, a common mode filter may include: a filter part and an electrostatic protection part disposed on the filter part, wherein the electrostatic protection part includes: a first discharge electrode and a second discharge electrode disposed to be separated from each other by a predetermined distance; a discharge layer disposed between the first discharge electrode and the second discharge electrode; and an insulating layer disposed under the discharge layer and the first and second discharge electrodes and including flat first insulating particles and spherical second insulating particles.

Drawings

The above and other aspects, features and advantages of the present disclosure will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which:

fig. 1 is a schematic perspective view of a common-mode filter according to an exemplary embodiment of the present disclosure;

FIG. 2 is a sectional view taken along line I-I' of FIG. 1;

FIG. 3 is a schematic enlarged sectional view of portion "A" of FIG. 2;

fig. 4A and 4B are schematic cross-sectional views illustrating shapes of first insulating particles and second insulating particles;

fig. 5 is a Scanning Electron Microscope (SEM) picture of a cross section of the electrostatic protection portion;

FIG. 6 is an enlarged picture of portion "B" of FIG. 5;

FIG. 7 is an enlarged picture of portion "C" of FIG. 5;

FIG. 8 is an enlarged picture of portion "D" of FIG. 5; and

fig. 9 is a schematic enlarged view of a portion "a'" corresponding to the portion "a" of fig. 2 in a common mode filter according to another exemplary embodiment of the present disclosure.

Detailed Description

Exemplary embodiments of the present disclosure will now be described in detail with reference to the accompanying drawings.

Fig. 1 is a schematic perspective view of a common mode filter according to an exemplary embodiment of the present disclosure, fig. 2 is a sectional view taken along line I-I' of fig. 1, and fig. 3 is a schematic enlarged sectional view of a portion "a" of fig. 2.

A structure of a common mode filter 100 according to an exemplary embodiment of the present disclosure will be described with reference to fig. 1 to 3.

In the case of the common mode filter according to the present disclosure, in the drawings, a width direction of the common mode filter is defined as an "X" direction, a length direction of the common mode filter is defined as a "Y" direction, and a thickness direction of the common mode filter is defined as a "Z" direction.

The common mode filter 100 according to an exemplary embodiment of the present disclosure includes a body 101 and a plurality of

outer electrodes

151, 152, 153, 154 and a ground electrode 160 disposed on an outer surface of the body 101.

The

external electrodes

151, 152, 153, and 154 may include a first external electrode 151, a second external electrode 152, a third external electrode 153, and a fourth external electrode 154, and the first external electrode 151, the second external electrode 152, the third external electrode 153, and the fourth external electrode 154 may be disposed to be separated from each other. The ground electrode 160 may also be disposed to be separated from the

outer electrodes

151, 152, 153, and 154.

For example, the

outer electrodes

151, 152, 153, and 154 may be disposed on opposite sides of the body 101 in the width direction (X direction), and the ground electrode 160 may be disposed on opposite sides of the body 101 in the length direction (Y direction).

As shown in fig. 1, the

external electrodes

151, 152, 153, and 154 may be disposed on the upper surface of the body 101, but are not limited thereto, and may also be disposed on the side surfaces of the body 101.

The

external electrodes

151 and 152 and the ground electrode 160 may be formed by forming

metal posts

151a, 152a and 160a, respectively, and plating

layers

151b, 152b and 160b on the surfaces of the

metal posts

151a, 152a and 160a, respectively, but are not limited thereto. In fig. 1 to 3, only the sections of the first and second

external electrodes

151 and 152 are shown, but the third and fourth

external electrodes

153 and 154 may also have the same structure as that of the first and second

external electrodes

151 and 152.

The

metal pillars

151a, 152a, and 160a may be formed of a metal having excellent conductivity (e.g., copper, silver, gold, palladium, nickel, etc.), but are not limited thereto. Similar to the

metal posts

151a, 152a, and 160a, the

plating layers

151b, 152b, and 160b may also be formed of a metal having excellent conductivity. The

metal posts

151a, 152a, and 160a may be formed on the discharge electrode 171 as described below. Some of the discharge electrodes 171 may be disposed between the connection electrode 155 and the

outer electrodes

151, 152, 153, and 154, but are not limited thereto.

The

outer electrodes

151, 152, 153, and 154 are connected to the

coils

121 and 122 as described below to input or output signals. The ground electrode 160 discharges static electricity introduced into the

outer electrodes

151, 152, 153, and 154. The ground electrode 160 may also be formed on the filter part 120, similar to the

outer electrodes

151, 152, 153, and 154. The ground electrode 160 is not generally electrically connected to the

coils

121 and 122, and as shown in fig. 1, the ground electrode 160 may be formed between the

outer electrodes

151, 152, 153, and 154.

The main body 101 includes a magnetic substrate 110, a filter portion 120, and an electrostatic protection portion 130.

In fig. 1 and 2, the electrostatic protection part 130 is illustrated as being disposed on the filter part 120, but is not limited thereto, and the electrostatic protection part 130 may be disposed in another portion of the body 101 under the condition that the electrical connection relationship between the electrostatic protection part 130 and the external electrode or the ground electrode is the same.

The magnetic substrate 110 is located at the lowermost layer of the common mode filter 100 and exhibits magnetism. The magnetic substrate 110 may include at least any one of metal, polymer, and ceramic as a material exhibiting magnetism. For example, the magnetic substrate 110 may be a ferrite substrate, but is not limited thereto.

The filter section 120 is provided on the magnetic substrate 110.

The filter part 120 includes a first coil 121 and a second coil 122. In addition, the filter part 120 may include a coil magnetic layer 142.

Both end portions of the first coil 121 may be electrically connected to the first and second

external electrodes

151 and 152, respectively, and both end portions of the second coil 122 may be electrically connected to the third and fourth

external electrodes

153 and 154, respectively.

The first and

second coils

121 and 122 may have a shape in which spiral electrode patterns are wound in the same direction.

Since the first and

second coils

121 and 122 have a shape in which electrode patterns are wound in the same direction, when signals flow in the first and

second coils

121 and 122, the first and

second coils

121 and 122 function as resistors for common mode signals for reducing common mode noise.

The first coil 121 includes

first electrode patterns

121a and 121b, and the second coil 122 includes

second electrode patterns

122a and 122 b.

The

first electrode patterns

121a and 121b are disposed in a spiral form and may be formed to include a metal having excellent conductivity. For example, the

first electrode patterns

121a and 121b may be formed of silver (Ag), palladium (Pd), aluminum (Al), nickel (Ni), titanium (Ti), gold (Au), copper (Cu), platinum (Pt), or an alloy thereof. The

first electrode patterns

121a and 121b may be formed using a plating method, a printing method, a photolithography method, or the like.

The

second electrode patterns

122a and 122b are provided in a spiral form and may be formed to include a metal having excellent conductivity. For example, the

second electrode patterns

122a and 122b may be formed of silver (Ag), palladium (Pd), aluminum (Al), nickel (Ni), titanium (Ti), gold (Au), copper (Cu), platinum (Pt), or an alloy thereof. The

second electrode patterns

122a and 122b may be formed using a plating method, a printing method, a photolithography method, or the like.

The first and

second electrode patterns

121a and 122a may be formed to be adjacent to each other on the same layer and may not overlap each other, but is not limited thereto. For example, the first electrode pattern 121a and the second electrode pattern 122a may be formed on different layers.

The first and

second electrode patterns

121b and 122b may be formed to be adjacent to each other on the same layer and may not overlap each other, but is not limited thereto. For example, the first electrode pattern 121b and the second electrode pattern 122b may be formed on different layers.

The first electrode pattern 121a is wound from the outside to the inside, and the first electrode pattern 121b is wound from the inside to the outside. The inner end portions of the

first electrode patterns

121a and 121b may be electrically connected through the conductive via 125.

The

outer electrodes

151, 152, 153, and 154 and the

coils

121 and 122 may be electrically connected by a connection electrode 155, but are not limited thereto, and may also be electrically connected by any other method.

The

outer electrodes

151, 152, 153, and 154 input signals to the

coils

121 and 122 and output signals from the

coils

121 and 122. Meanwhile, when the coil magnetic layer 142 is positioned on the filter part 120, the

external electrodes

151, 152, 153, and 154 may be formed on the coil magnetic layer 142.

The filter part 120 may include a coil insulating layer 141. The coil insulating layer 141 may be disposed to surround the first and

second coils

121 and 122. The coil insulating layer 141 may insulate the first and

second coils

121 and 122 from the magnetic substrate 110, and insulate the first and

second coils

121 and 122 from the coil magnetic layer 142 and the magnetic material filling the trench 143 as described below. The coil insulating layer 141 may be formed on the magnetic substrate 110. As the material of the coil insulating layer 141, a polymer resin having excellent electrical insulating properties and processability may be used. For example, epoxy resin, polyimide resin, or the like can be used as the material of the coil insulating layer 141.

The coil magnetic layer 142 may be formed on the coil insulating layer 141. The coil magnetic layer 142 forms a closed magnetic path together with the magnetic substrate 110. The magnetic coupling of the first coil 121 and the second coil 122 can be enhanced by the coil magnetic layer 142 and the magnetic substrate 110 collectively forming a magnetic flux. The coil magnetic layer 142 may be a ferrite sheet.

Further, the trench 143 filled with the magnetic material may be disposed in a central portion of the coil insulating layer 141. When the trench 143 filled with the magnetic material is included in the central portion of the coil insulating layer 141, the magnetic substrate 110, the coil magnetic layer 142, and the trench 143 form a closed magnetic circuit.

The coil magnetic layer 142 and the trenches 143 may be formed as a magnetic resin composite or a ferrite sheet including a magnetic material and a resin material. The magnetic powder makes the coil magnetic layer 142 and the groove 143 exhibit magnetism, and the resin material serves to enhance chargeability and dispersibility of the magnetic material in the coil magnetic layer 142 and the groove 143. Here, the magnetic powder may include ferrite. Alternatively, the coil magnetic layer 142 and the groove 143 may also be formed by stacking and pressing magnetic sheets.

The electrostatic protection part 130 may be provided on the filter part 120. Here, if the electrostatic protection part 130 is disposed in another position of the main body 101, the upper cover part may be disposed on the filter part 120.

The electrostatic protection portion 130 includes discharge electrodes 171 and a discharge layer 172 provided between the adjacent discharge electrodes 171. The discharge electrode 171 may be disposed to be electrically connected to at least one of the outer electrodes and the ground electrode.

The discharge layer 172 is a material having a property of mainly exhibiting high resistance, but when a surge S having a high voltage is introduced, the resistance of the material rapidly decreases. The discharge layer 172 may be disposed between the

outer electrodes

151, 152, 153, and 154 and the ground electrode 160.

The discharge layer 172 may be a resin including metal particles. The metal particles may extend in one direction. According to the discharge layer 172, when the voltage is lower than a predetermined value, the current between the metal particles may be insulated by the resin, but when the voltage is equal to or higher than the predetermined value, the current flows between the metal particles along the metal particles. Such a predetermined value may be a turn-on voltage (or reference voltage).

The discharge layer 172 may be printed in a screen printing manner. Here, after a mask including an opening corresponding to a position where the discharge layer 172 is to be formed is disposed on the

outer electrodes

151, 152, 153, and 154 and the ground electrode 160, the discharge layer 172 may be applied to the inside of the opening. Here, the discharge layer 172 may exist as a liquid having fluidity. After printing, the discharge layer 172 may be cured at an elevated temperature.

The metal columns forming the

external electrodes

151, 152, 153, and 154 and the ground electrode 160 may serve to prevent the discharge layer 172 from flowing into other portions during a process of forming the discharge layer 172.

In order to maintain the proper shape of the discharge layer 172, insulating particles may be included in the resin. For example, the insulating particles included in the discharge layer 172 may be inorganic insulating particles, and may include spherical SiO₂And (3) granules.

An upper insulating layer 181 is disposed on the discharge electrodes 171 and the discharge layers 172 to cover the discharge electrodes 171 and the discharge layers 172. In addition, a lower insulating layer 182 may be disposed under the discharge electrodes 171 and the discharge layer 172. Specifically, the upper insulating layer 181 may cover the upper surface and the side surfaces of the discharge layer 172, and the lower insulating layer 182 may cover the lower surface of the discharge layer 172. The upper insulating layer 181 and the lower insulating layer 182 may be ABF (Ajinomotor build-up film), but are not limited thereto.

The upper insulating layer 181 includes first insulating particles 191 and second insulating particles 192. The first insulating particles 191 are flat and the second insulating particles 192 are spherical.

Fig. 4A is a schematic cross-sectional view showing the shape of a flat first insulating particle, and fig. 4B is a schematic cross-sectional view showing the shape of a spherical second insulating particle. Referring to fig. 4A and 4B, when the length of the short axis of the first and second insulating

particles

191 and 192 is a and the length of the long axis thereof is c, the c/a of the first insulating particles 191 may be 2 or more and the c/a of the second insulating particles 192 may be 1 to 1.99.

If the c/a of the first insulating particles 191 is less than 2, the effect of suppressing the development of cracks as described below is reduced, thereby increasing leakage current. In addition, when c/a of the second insulating particles 192 exceeds 1.99, it is difficult for the upper insulating layer 181 to have a proper shape when formed.

The magnetic capping layer 175 is disposed on the upper insulating layer 181. The magnetic capping layer 175 may include a magnetic material, for example, the magnetic capping layer 175 may be a ferrite sheet. Since the magnetic capping layer 175 includes a magnetic material, the impedance characteristic of the common mode filter 100 may be enhanced.

Fig. 5 is a Scanning Electron Microscope (SEM) image of a cross section of the electrostatic protection portion. Fig. 6 is an enlarged picture of a portion "B" of fig. 5, fig. 7 is an enlarged picture of a portion "C" of fig. 5, and fig. 8 is an enlarged picture of a portion "D" of fig. 5.

In the case where static electricity having a high voltage or an overvoltage is applied to the electrostatic protection portion a plurality of times, as in part B' of fig. 6, cracks are formed in the insulating layer connected to the discharge layer portion where metal particles such as aluminum particles included in the discharge layer are excessively agglomerated.

Such cracks propagate along the insulating layer, as in section C 'of fig. 7, and reach the ferrite sheet located on the insulating layer, as in section D' of fig. 8.

In the case of the related art, when a high voltage (for example, a voltage of 8 kv) is applied to the electrostatic protection portion, the insulating layer and the magnetic cover layer provided on the discharge layer are deteriorated and damaged. In order to prevent such a phenomenon, in the related art, the thickness of the discharge layer is reduced and the thickness of the insulating layer is increased, but the durability of the electrostatic protection portion still has a problem.

In addition, the magnetic material generally used as the magnetic coating layer is a material having a specific resistance value (specific resistance value) with respect to an insulating material>10¹⁶Ω cm) has a value of about 10⁶Ferrite pieces of low specific resistance value of Ω cm. Thus, when it happensWhen the electrostatic protection portion is broken down by the dielectric damaged by the overvoltage, a leakage current flows to the magnetic coating layer through the crack.

However, in the common mode filter 100 according to the exemplary embodiment of the present disclosure, since the flat first insulating particles 191 and the spherical second insulating particles 192 are included in the upper insulating layer 181, propagation of cracks in the upper insulating layer 181 is prevented, thereby preventing generation of a leakage current.

Table 1 below shows the measurement of the leakage current according to the content of the first insulating particles 191 with respect to the total content of the first insulating particles 191 and the second insulating particles 192 in the upper insulating layer 181.

[ Table 1]

The leakage currents shown in table 1 represent average values of leakage currents measured at voltages of 5V after applying a voltage of 8kV 10 times to 100 pieces of electrostatic protection parts manufactured according to the content of the first insulating particles, respectively.

Referring to table 1, it can be seen that the leakage current decreases as the content of the flat first insulating particles 191 increases. Specifically, it can be seen that when the content of the first insulating particles 191 is 40 vol% or more, the leakage current is reduced to about a 1/100 level as compared to the case where the content of the first insulating particles 191 is less than 40 vol%. Accordingly, in the upper insulating layer 181, the first insulating particles 191 may be included in an amount equal to or greater than 40 vol% with respect to the total content of the first insulating particles 191 and the second insulating particles 192.

However, if the content of the flat first insulating particles 191 is greater than or equal to 90 vol%, the dispersibility of the insulating particles of the upper insulating layer 181 is deteriorated and the leakage current is rather increased. Here, however, an increase in the increased leakage current is relatively small compared to a leakage current value that varies based on a content of 40 vol% as a starting point in the content of the first insulating particles 191. Accordingly, in the upper insulating layer 181, the first insulating particles 191 may be included in an amount equal to or less than 80 vol% with respect to the total content of the first insulating particles 191 and the second insulating particles 192.

The first insulating particles 191 and the second insulating particles 192 may be inorganic insulating particles, for example, SiO₂。

Fig. 9 is a schematic enlarged cross-sectional view of a portion "a'" corresponding to the portion "a" of fig. 2 in a common mode filter according to another exemplary embodiment of the present disclosure.

Components of a common mode filter according to another exemplary embodiment of the present disclosure are the same as those of the common mode filter according to the above-described exemplary embodiment of the present disclosure, except for the lower insulating layer.

Referring to fig. 9, in a common mode filter according to another exemplary embodiment of the present disclosure, first insulating particles 191 ' and second insulating particles 192 ' may be included in a lower insulating layer 182 '.

The lower insulating layer 182' is disposed in contact with the coil magnetic layer 142 including ferrite pieces.

That is, the coil magnetic layer 142 is disposed between the filter part 120 and the electrostatic protection part 130 and is in contact with the lower insulating layer 182 ', and therefore, if an overvoltage is applied to the electrostatic protection part 130 to thereby cause a crack in the lower insulating layer 182', a leakage current may flow to the coil magnetic layer 142, which is a ferrite sheet, through the crack.

However, in the common mode filter according to another exemplary embodiment of the present disclosure, since the lower insulating layer 182 'includes the flat first insulating particles 191' and the spherical second insulating particles 192 ', propagation of cracks in the lower insulating layer 182' may be prevented, thereby preventing generation of leakage current.

As described above, in the common mode filter according to the exemplary embodiments of the present disclosure, since the insulating layer disposed on the discharge electrode and the discharge layer includes the flat first insulating particles and the spherical second insulating particles, when an overvoltage such as static electricity is applied, a leakage current may be prevented from being generated in the insulating layer.

While exemplary embodiments have been shown and described above, it will be apparent to those skilled in the art that modifications and variations can be made without departing from the scope of the invention as defined in the appended claims.

Claims

1. A common-mode filter comprising:

a filter part and an electrostatic protection part arranged on the filter part,

wherein the electrostatic protection part includes:

a first discharge electrode and a second discharge electrode spaced apart from each other;

a discharge layer disposed between the first discharge electrode and the second discharge electrode and covering a portion of an upper surface of the first discharge electrode and a portion of an upper surface of the second discharge electrode; and

and a first insulating layer covering an upper surface of the discharge layer and including flat first insulating particles and spherical second insulating particles.

2. The common mode filter according to claim 1, wherein c/a of the first insulating particles is equal to or greater than 2 and c/a of the second insulating particles is 1 to 1.99, where a is a length of a short axis of the first insulating particles and the second insulating particles and c is a length of a long axis of the first insulating particles and the second insulating particles.

3. A common-mode filter according to claim 1, wherein in the first insulating layer, the first insulating particles are included in an amount equal to or more than 40 vol% with respect to a total content of the first insulating particles and the second insulating particles.

4. A common-mode filter according to claim 1, wherein in the first insulating layer, the first insulating particles are included in an amount equal to or less than 80 vol% with respect to a total content of the first insulating particles and the second insulating particles.

5. A common-mode filter according to claim 1 further comprising a magnetic cover layer disposed on the first insulating layer.

6. A common-mode filter according to claim 1,

the filter part further includes a coil magnetic layer provided between the filter part and the electrostatic protection part, and

the electrostatic protection portion includes a second insulating layer disposed under the discharge layer and the first and second discharge electrodes, and including flat first insulating particles and spherical second insulating particles.

7. A common-mode filter according to claim 1, wherein the first and second insulating particles are made of SiO₂And (4) forming.

8. The common mode filter according to claim 6, wherein the first insulating layer covers an upper surface and a side surface of the discharge layer, and the second insulating layer covers a lower surface of the discharge layer.

9. A common-mode filter according to claim 5 wherein the magnetic cover layer is a ferrite sheet.

10. A common-mode filter according to claim 6 wherein the coil magnetic layers are ferrite plates.

11. A common-mode filter comprising:

a filter part and an electrostatic protection part arranged on the filter part,

wherein the electrostatic protection part includes:

an insulating layer disposed under the discharge layer and the first and second discharge electrodes and including flat first insulating particles and spherical second insulating particles.

12. The common mode filter according to claim 11, wherein c/a of the first insulating particles is equal to or greater than 2 and c/a of the second insulating particles is 1 to 1.99, where a is a length of a short axis of the first insulating particles and the second insulating particles, and c is a length of a long axis of the first insulating particles and the second insulating particles.

13. A common-mode filter according to claim 11, wherein the first insulating particles are included in the insulating layer in an amount equal to or more than 40 vol% with respect to a total content of the first insulating particles and the second insulating particles.

14. A common-mode filter according to claim 11, wherein in the insulating layer, the first insulating particles are included in an amount equal to or less than 80 vol% with respect to a total content of the first insulating particles and the second insulating particles.

15. A common-mode filter according to claim 11, wherein the filter section further comprises a coil magnetic layer disposed between the filter section and the insulating layer.

16. A common-mode filter according to claim 15 wherein the coil magnetic layers are ferrite plates.