JP2000286587A - Electromagnetic shield structure at connector part with external cable - Google Patents

Abstract

PROBLEM TO BE SOLVED: To block electrical coupling of high frequency noise and to shield from a radiation electromagnetic field propagating through the air or a board by arranging a conductor, all solid patterns and via holes while being spaced apart so that they are not connected directly with an internal circuit and not connected with the circuit of filter and connector. SOLUTION: A printed board 100 is secured to box shape 11 screw holes by means of screws thus connecting a solid pattern 106 on the surface side surface layer rigidly with the box shape 111. The box shape 111, the solid pattern 106 on the surface side surface layer, second and third solid patterns 108, 109, and a rear surface layer solid pattern 110 are arranged while being spaced apart by a specified distance without being connected directly with the internal circuit 102. Furthermore, the box shape 111, the solid pattern 106 on the surface side surface layer, the second and third solid patterns 108, 109, and the rear surface layer solid pattern 110 are arranged not to be connected with the circuit of a connector 101 and a filter 103.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electromagnetic shield structure of a connector for connecting an external cable in an electronic device having a circuit for generating high-frequency noise such as a digital circuit and having an external cable connected thereto. .

[0002]

2. Description of the Related Art Generally, a cable externally connected to an electronic device has a shield structure independent of a signal line and a return ground in consideration of suppression of electromagnetic noise radiation.
Many are connected to the frame ground of the electronic device itself.

However, cables such as earphones, microphones, and DC power output of an AC adapter are independent of a signal path, such as those having no shield structure to reduce costs and those using a shield conductor as a return ground. Many are not shielded by conductors connected to the frame ground.

When such a cable is connected to an electronic device such as a digital circuit having a circuit that generates switching noise, if the switching noise generated inside the electronic device leaks to a signal line or a return ground of the connected cable, the aforementioned As described above, since there is no shield structure of the conductor connected to the frame ground, noise may be radiated from the cable.

[0005] As an example of suppressing electromagnetic noise radiation from a connected cable, a method of attaching a ferrite core to the cable may be adopted. Although this ferrite core has a large effect of suppressing electromagnetic noise, the appearance of the cable tends to be impaired, and the cable routing tends to be poor. It is desirable to take countermeasures inside the electronic device without attaching an external connection cable such as a ferrite core, so that a filter should be inserted between the internal circuit of the electronic device and the connector circuit that connects the external cable to prevent leakage of high-frequency noise. Often employs a blocking method. In some cases, the connector circuit after the filter is shielded.

An example of noise leakage suppression by a conventional filter and shield structure will be described with reference to FIGS.

FIG. 11 is a plan view of the printed circuit board 200 as viewed from the front side. FIG. 12 is a sectional view taken along line AA of FIG. 11, and FIG. 13 is a sectional view taken along line BB of FIG.

Reference numeral 201 denotes a connector for connecting an external cable, and its signal and return ground lines correspond to a pattern 204, a filter 203, and a pattern 205, respectively.
Through to the internal circuit 202 having a built-in noise source. A ground pattern 206 is provided on the surface layer on the front side of the printed circuit board in a range surrounding the filter 203 from the connector 201.
The ground pattern is also provided in the second layer, the third layer, and the rear surface layer thereunder so that the ground pattern 206 has substantially the same range. 208 is a ground pattern of the second layer, 209 is a ground pattern of the third layer, and 210 is a ground pattern of the back surface layer. 20
The ground patterns 6, 208, 209 and 210 are connected to each other by a plurality of via holes 207. The filter 203 is of a three-terminal type, and its ground terminal is connected to a ground pattern 206 on the surface layer on the front side of the substrate.

In the area of the internal circuit 202, the front surface layer and the back surface layer are mainly used for component mounting and signal wiring, the second layer is used for the power supply wiring layer 212, and the third layer is used for the ground layer 213.

Ground patterns 206, 208, 20
Although the internal circuit 202 does not exist in the regions 9 and 210, the third ground layer 213 and the ground pattern 209 in the region of the internal circuit 202 are integrally connected. Reference numeral 211 denotes a shield case,
1 and the side of the range of the pattern 204 and the upper side thereof are connected to the ground pattern 206. Printed circuit board 2
00 is a screw 21 through a screw hole 214 provided in each of the ground pattern areas 206, 208, 209 and 210.
5, and is fixed to the boss 216 of the housing, and the ground pattern 210 on the back surface layer is connected to the boss 216, that is, the housing. The hole 214 through which the screw 215 passes is a copper through-hole, and is the same as the via hole 207, 206, 20.
The ground patterns 8, 209 and 210 are connected.

With such a configuration, the filtering effect of the filter 203 on the high frequency noise transmitted through the signal and return ground lines and the shielding effect of the shield case 211 on the electromagnetic noise propagating in the air are obtained, and the high frequency noise applied to the connector 201 is obtained. Leakage is reduced.

[0012]

In the above arrangement, the housing is fixed to the boss 216 by the screw 215, so that
The ground patterns 6, 208, 209, and 210 and the shield case 211 are connected to the housing, and their conductors are expected to have the same zero potential as the housing.

However, 206, 208, 209, 210
Each ground pattern and any point on the shield case 211 have an impedance that increases with an increase in the distance from the connection point with the boss 216 of the housing. The drop causes a noise potential.

On the other hand, high frequency noise is present in the third ground layer 213 in the region of the internal circuit 202 due to the switching operation of the digital circuit, and the high frequency noise is transmitted to the ground pattern 209 integrated with the ground layer 213. The high-frequency noise transmitted to the ground pattern 209 is adjacent to the ground pattern 209, 206, 20.
8, 210, and also flows to the boss 216 of the housing as a high-frequency noise current through these conductors. The high-frequency noise filtered by the filter 203 flows from the ground terminal of the filter 203 to the ground pattern 206 as a noise current, and is directed toward the boss 216 of the housing through the ground patterns 206, 208, 209, and 210 and the shield case 211 as described above. Flows. 206, 208,
When a high-frequency noise current flows through each of the ground patterns 209 and 210 and the shield case 211, a high-frequency noise potential is generated in each conductor due to the voltage drop as described above. 2
Since each of the ground patterns 06, 208, 209, and 210 and the circuit of the shield case 211 and the connector 201 are at a very short distance, high-frequency noise is induced in the circuit of the connector 201 by electrostatic coupling or electromagnetic coupling. The high-frequency noise potential generated in the portion of the ground pattern 206 to which the ground terminal of the filter 203 is connected is
There is also a path that is transmitted to the circuit of the connector 201 through 3.

As described above, when high-frequency noise is transmitted to the circuit of the connector 201, in the case of an external cable that does not have a shield structure of the conductor connected to the frame ground, the high-frequency noise of the connector 201 is transmitted to the external cable as it is. Then, electromagnetic waves are radiated to the outside of the electronic device using the conductor of the external cable as an antenna.

Even if the filter 203 has the filtering performance of the high frequency noise transmitted through the signal line and the return ground line and the shielding performance of the shield case 211 against the high frequency noise due to the radiated electromagnetic field propagating in the air, as described above, the filter 203 has another function. Leakage of high-frequency noise along the path may result in an insufficient overall high-frequency noise suppression effect.

The present invention has been made in view of the above problems, and has a simple structure which prevents electric coupling of high-frequency noise and shields from a radiation electromagnetic field propagating in the air or in a substrate.
An object of the present invention is to provide an electromagnetic shield structure of an external cable connection connector part having excellent electromagnetic noise leakage suppression performance.

[0018]

In order to achieve the above object, an external cable connecting connector according to the present invention comprises:
An electromagnetic shield structure is formed by a part of the housing and the solid pattern and via hole provided on the printed circuit board to surround the connector circuit after the filter and the connector circuit after the filter from the electromagnetic waves propagating in the air or inside the board. Shield.

Since the conductor constituting the shield structure is arranged separately from the high frequency noise source and is not connected to the ground terminal of the filter, no high frequency noise current flows through the conductor. . Moreover, since a part of the shield structure is the housing itself, both the solid pattern and the via hole provided on the printed circuit board, which are the other components, have the same zero potential as the housing.

Therefore, even if there is electrostatic coupling or electromagnetic coupling between the circuit of the conductor forming the shield structure and the connector after the filter, the conductor forming the shield case is affected by high frequency noise as described above. Since there is no current or potential, high frequency noise is not induced in the circuit of the connector after the filter.

The connector circuit for connecting an external cable having such a shield structure is useful for constructing a favorable electromagnetic environment in which high-frequency noise does not leak to the connected external cable to cause unnecessary radiation.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention according to claim 1 of the present invention is a multilayer or double-sided printed circuit board on which an internal circuit including a portion that generates high-frequency switching noise by a digital signal is mounted, and the printed circuit board is housed. A metal or resin-treated housing, an external cable connection connector mounted on the front side of the printed circuit board and connecting peripheral devices, and the printed circuit board inserted between the internal circuit and the connector. The filter mounted on the front side of the board, the front side solid pattern provided on the front side surface layer of the printed circuit board and surrounding the connector and the filter, and the printed circuit board positioned in a range matching the shape of the front side solid pattern. A solid pattern provided on one or more of the back surface layer and the inner layer, and the front surface solid pattern and the back surface layer or A via hole for connecting all of the solid patterns provided on the layer; a side and an upper side of a circuit area of the connector or a range from the connector to the filter are surrounded by a box-shaped conductor; an open surface of the conductor Most of the end facing the printed circuit board on the side is in contact with the front surface solid pattern without any gap and ensuring electrical connection, and is provided on the conductor, the front surface solid pattern, and the back surface layer or inner layer. An external cable connecting connector, wherein all of the solid patterns and the via holes are arranged so as to be apart from each other without directly connecting to the internal circuit, and are not connected to the circuit of the filter and the connector. The electromagnetic shield structure of the section makes it difficult for high-frequency noise generated in the internal circuit to leak to the external cable connected to the connector. To realize electronic devices with low radiation.

According to a third aspect of the present invention, the conductor is formed as a part of a housing.
The electromagnetic shield structure of the external cable connection connector part according to claim 1, wherein the shield structure is formed by using a part of a housing, so that the connector is small and thin, and is capable of removing high-frequency noise generated in an internal circuit. An electronic device with low electromagnetic radiation that does not easily leak to an external cable connected to the computer.

An embodiment of the present invention will be described below with reference to FIGS.

(Embodiment 1) FIG. 1 is a plan view showing an electromagnetic shield structure of an external cable connection connector according to a first embodiment of the present invention. FIG. 2 is a sectional view taken on line AA of FIG.
FIG. 3 is a cross-sectional view of FIG. FIG.
FIG. 5 is a pattern diagram of the second or third layer of the printed circuit board seen through from the same direction as FIG. 1, and FIG. 5 is a pattern diagram of the back surface layer. These are shown in the case where they are configured using a printed circuit board 100 having a four-layer structure.

Reference numeral 101 denotes a connector for connecting an external cable, which is mounted on the surface layer of the printed circuit board. Reference numeral 102 denotes an internal circuit including a portion that generates high-frequency noise, and is mounted and patterned using all four layers of the printed circuit board. Reference numeral 103 denotes a filter, which shows a state in which a 3-line common mode filter is mounted on the surface layer on the front side of the printed circuit board. Each terminal of connector 101 and filter 1
Each terminal on one side of 03 has a pattern 1 so that the wiring is shortest.
04 is connected. Each terminal on the opposite side of the filter 103 is connected to the internal circuit 102 by a pattern 105. The connector 101, the pattern 104, the filter 103, the pattern 105, and the internal circuit 102 are arranged substantially in a straight line.

Reference numeral 106 denotes a solid pattern provided on the front side surface layer, and is disposed so as to surround the area from the connector 101 to the filter 103. 108 is the second layer, 109
Is a solid pattern provided on the third layer and 110 is a solid pattern provided on the back surface layer, respectively, so that they are substantially in the same range as the solid pattern 106 on the front surface layer. Reference numeral 107 denotes a via hole which connects the solid pattern 106 on the front surface layer, the solid pattern 108 on the second layer, the solid pattern 109 on the third layer, and the solid pattern 110 on the rear surface, and the area of the connector 101 and the pattern 104 and the internal circuit 102. Plural and as many as possible are arranged between the areas.

Reference numeral 111 denotes a box shape formed by a part of a housing made of a metal or a resin subjected to a conductive treatment of an electronic device.
A side and an upper part of a range from the connector 101 to the filter 103 are surrounded. The side wall of the box shape 111 is located on the solid pattern 106 on the front surface layer, and most of the end portions of the side wall face the solid pattern 106 on the front surface layer without gap and are electrically connected. As one of the methods, there is a method of obtaining a stable connection by sandwiching a conductive elastic body or a metal leaf spring commonly called a gasket between the solid pattern 106 and the box shape 111 on the front surface layer.

Then, the printed circuit board 100 is
2 and 113, a screw hole 114 provided in a box shape 111,
115 and fix it with a screw.
6 and the box shape 111 are strongly connected. Here, the holes 116 and 117 of the printed circuit board 100 through which the screws 112 and 113 pass are formed as copper through holes, and like the via hole 107, the solid pattern 106 on the front surface side, the solid pattern 108 on the second layer, and the solid pattern 109 on the third layer 109 are formed. The back surface solid pattern 110 is connected.

In FIG. 1, the box shape 111 shows only the side wall excluding the top surface. The box shape 111, the solid pattern 106 on the front side surface layer, the solid pattern 108 on the second layer, and the third
Layer solid pattern 109 and back surface solid pattern 110
Are arranged at a certain distance without being directly connected to the internal circuit 102. Further, a box shape 111, a solid pattern 106 on the front surface layer, a solid pattern 108 on the second layer, a solid pattern 109 on the third layer, and a solid pattern 11 on the back surface layer
0 is set so as not to be connected to the circuit of the connector 101 and the filter 103.

FIG. 6 and FIG. 6 are equivalent circuits showing circuit connection in the above-described configuration, a path through which switching noise generated in a digital circuit propagates as electromagnetic wave noise, and a path through which electromagnetic noise is transmitted by electrostatic coupling or electromagnetic coupling between circuits. FIG.

In FIG. 6, a connector 101, an internal circuit 102, a filter 103, a pattern 104, a pattern 1
05 is the same as FIGS.

Reference numeral 51 denotes a housing of the electronic device, which covers the entire range from the internal circuit 102 to the connector 101. Reference numeral 52 denotes a shield conductor, which is a box shape 111 in FIGS.
All of the layer solid pattern 108, the third layer solid pattern 109, the back surface solid pattern 110, and the via hole 107 are shown as one.

The shield conductor 52 surrounds the area from the connector 101 to the filter 103,
1 and is electrically at the same potential as the housing 51. Although not shown in FIGS. 1 to 5, the internal circuit 102
The inner ground 54 is connected to the housing 51 through 56 paths.

Reference numeral 57 denotes an external cable connected to the connector 101. Reference numeral 58 denotes a path of an electromagnetic wave propagating from the internal circuit 102 in the air or in the substrate. Reference numeral 59 denotes a path of electromagnetic coupling or electrostatic coupling between the internal circuit 102 and the shield conductor 52. Numeral 60 indicates a path of electromagnetic coupling or electrostatic coupling between the shield conductor 52, the connector 101 and the pattern 104.

FIG. 7 is an equivalent circuit showing only a propagation path related to electromagnetic noise in FIG. 6, and a path passing through the filter 103 is omitted.

The area from the connector 101 to the filter 103 is surrounded by the shield conductor 52 and is shielded from electromagnetic waves generated in the internal circuit 102 and propagated in the air or in the board. Further, since electromagnetic or electrostatic coupling with the internal circuit 102 is also shielded, there is no direct influence of electromagnetic noise from the internal circuit 102.

Electromagnetic noise is induced from the internal circuit 102 to the shield conductor 52 by the electromagnetic wave path 58 and the electromagnetic coupling or electrostatic coupling path 59, but the shield conductor 52 is strongly connected to the housing 51 by the path 53 as described above. Therefore, the induced electromagnetic noise is grounded to the housing 51, and almost no potential of the electromagnetic noise appears on the shield conductor 52.

Further, the shield conductor 52 is connected to the internal circuit 102.
The path 59 for electromagnetic coupling or electrostatic coupling with the internal circuit 102 is loosely coupled, while the connection path 53 between the shield conductor 52 and the housing 51 is tightly coupled. Therefore, it can be understood from the equivalent circuit of FIG. 7 that the potential of the electromagnetic noise hardly appears on the shield conductor 52 and the electromagnetic noise current flowing when grounded to the housing 51 is small.

Therefore, the shield conductor 52 and the connector 1
Even when the electromagnetic coupling or the electrostatic coupling path 60 of the pattern 01 and the pattern 104 is tightly coupled, no electromagnetic noise is induced in the circuit of the connector 101 from the shield conductor 52.

In addition to the above configuration, if a filter having a necessary and sufficient filtering characteristic is used for the filter 103, high-frequency noise does not leak to the external cable 57 connected to the connector 101 and unnecessary radiation is prevented. It is possible to build a simple electromagnetic environment.

Up to this point, an example in which the printed circuit board 100 having a four-layer structure is used has been described as the first embodiment.
In the case where high-density mounting is not required for the internal circuit 102, the same configuration can be obtained even by using a printed circuit board having a double-sided structure that is less expensive than a four-layer structure.

FIG. 8 shows a case where the printed circuit board in FIG. The difference from the four-layer structure in FIG. 2 is that the second layer solid pattern 108 and the third layer solid pattern 109 are not provided, and the other configurations are exactly the same.

Even if there is no solid pattern due to the inner layer, the shield conductor 52 surrounding the circuit of the connector 101 of FIG. 6 can be constituted by the box shape 111, the solid pattern 106 on the front surface layer, the solid pattern 110 on the rear surface layer, and the via hole 107. The same shielding effect as in the case of the four-layer structure can be obtained.

1 to 8, the filter 103 has a box shape 1
However, in order to achieve the object of the present invention,
It is not necessary to limit the arrangement of the filter 103 to the inside of the box shape 111. FIG. 9 shows the arrangement of the filter 103 in a box shape 111.
Is formed by cutting out the side wall of the box shape 111 in accordance with the outer shape of the filter 103, and the other configuration is exactly the same as that of FIGS. With this arrangement of the filter 103, the filter 1
03 between the input terminal side and the output terminal side
, The solid pattern 106 on the front surface layer, the solid pattern 108 on the second layer, the solid pattern 109 on the third layer, the solid pattern 110 on the rear surface layer, and the via hole 107 can be spatially separated.

As a result, the spatial electric coupling between the input terminal and the output terminal of the filter 103 is shielded, and the filtering performance of the filter 103 is improved. Therefore, when the filter 103 is disposed, the electromagnetic noise shielding effect is
It is better than the case of FIGS.

Next, FIG. 10 shows the arrangement of the filter 103 outside and close to the side wall of the box shape 111, and the other configuration is exactly the same as that of FIGS. By placing the filter 103 in the immediate vicinity of the side wall of the box shape 111 and minimizing the dimension of the pattern 104 located outside the box shape 111, the pattern 104 is prevented from being exposed to the electromagnetic noise generated in the internal circuit 102. 1 to 8
The same electromagnetic shielding effect as in the case of is obtained. This is performed when the filter 103 cannot be arranged inside the box shape 111.

Although FIGS. 1 to 10 show the case where the box shape 111 is formed by a part of the housing, the box shape is formed by applying a conductive treatment to metal or resin separately from the housing. Can be configured in the same manner as when it is formed as a part of the housing. This method uses box shape 1
By manufacturing the mold 11 separately from the housing, the degree of freedom in manufacturing the molds and determining the specifications of the shape and the like is increased, and there is an effect that the manufacturing becomes easy.

The embodiment shown in FIGS. 1 to 10 has a configuration in which a connector for a three-terminal mini-plug is used as the connector 101. However, a connector for a standard plug, a power connector, and the like are used as they are. Applicable, 3 more
The electromagnetic shield structure of the connector part for connecting an external cable according to the present invention can be applied to two or four or more terminals in accordance with the number of terminals.

[0050]

As described above, according to the present invention, a box shape formed by a part of a housing or a box shape formed separately from the housing and fixedly connected to the housing, a solid pattern of a printed circuit board, and a via hole are provided. And shield the circuit of the connector after the filter from electromagnetic waves propagating in the air or inside the board, and then connect the box shape used for the shielding, the solid pattern of the printed circuit board, and the via hole directly to the high-frequency noise source. In addition to the structure that is strongly connected to the housing without connecting to the ground terminal of the filter, and using a filter with necessary and sufficient filtering performance, the circuit of the connector for external cable connection is In addition to being shielded from electromagnetic waves due to high-frequency noise that propagates in the air and inside the board, it can not only directly induce electromagnetic noise from internal circuits, but also shield Connect a cable that does not receive electromagnetic noise induced by indirect electrostatic or electromagnetic coupling through the body and does not have a shielded structure of conductors connected to the frame ground, such as microphones, earphones, and external power supplies. However, leakage of high-frequency noise to the cable can be suppressed to a level that does not cause a problem, and a favorable electromagnetic environment can be constructed.

[Brief description of the drawings]

FIG. 1 is a schematic plan view showing an electromagnetic shield structure of a jack portion for connecting an external cable according to an embodiment of the present invention.

FIG. 2 is a sectional view taken along line AA of FIG. 1;

FIG. 3 is a sectional view taken along line BB of FIG. 1;

FIG. 4 is a pattern diagram of a second or third layer of the printed circuit board seen through from the same direction as FIG. 1;

FIG. 5 is a surface pattern diagram of the back surface of the printed circuit board seen through from the same direction as FIG. 1;

FIG. 6 is a diagram showing a circuit showing the connection relationships shown in FIGS. 1 to 5 and an equivalent circuit of electromagnetic wave propagation and electromagnetic coupling or electrostatic coupling.

FIG. 7 is a diagram showing an equivalent circuit of only a propagation path related to the electromagnetic noise of FIG. 6;

FIG. 8 is a cross-sectional view when the printed circuit board of FIG. 2 is replaced with a double-sided printed circuit board;

FIG. 9 is a schematic plan view showing the arrangement of the filter 103 in FIG.

FIG. 10 shows a case where the arrangement of the filter 103 in FIG.
Schematic configuration diagram outside and close to the side wall

FIG. 11 is a schematic plan view showing a conventional electromagnetic shield structure of a jack portion for connecting an external cable.

FIG. 12 is a sectional view taken along line AA of FIG. 11;

FIG. 13 is a sectional view taken along line BB of FIG. 11;

[Explanation of symbols]

Reference Signs List 51 housing 52 shield conductor 53 shielding and surrounding the connector section 53 a path connecting 51 and 52 54 a ground in internal circuit 102 55 a digital circuit 56 in internal circuit 102 a path connecting 51 and 54 57 External cable 58 Propagation path of electromagnetic wave radiated from internal circuit 102 59 Path of electromagnetic or electrostatic coupling between internal circuits 102 and 52 60 Circuit of connector 101 and patterns 104 and 5
2 Electromagnetic coupling or electrostatic coupling path 100, 200 Printed circuit board 101, 201 Connector 102, 202 Internal circuit 103, 203 Filter 104, 204 pattern 105, 205 pattern 106, 206 Solid pattern 107, 207 via hole provided on surface layer 108, 208 Second layer solid pattern 109, 209 Third layer solid pattern 110, 210 Back surface solid pattern 111, 211 Shield case 112, 113, 215 Screw 114, 115, 214 Screw hole 116, 117 Copper through hole in shield case Hole 212 Second power supply wiring layer in internal circuit area 213 Third ground layer in internal circuit area 216 Boss of housing

Claims (4)

[Claims] 1. A multilayer or double-sided printed circuit board on which an internal circuit including a portion that generates high-frequency switching noise by a digital signal is mounted, a case in which a metal or resin housing the printed circuit board is subjected to conductive processing, An external cable connection connector mounted on the front side of the printed circuit board for connecting peripheral devices, a filter inserted between the internal circuit and the connector and mounted on the front side of the printed circuit board, and a front side of the printed circuit board; A surface side solid pattern surrounding the connector and the filter provided on the surface layer, and provided on one or more of the back surface layer and the inner layer of the printed circuit board located in a range according to the shape of the surface side solid pattern. Connecting the solid pattern, the solid pattern on the front surface layer and all the solid patterns provided on the rear surface layer or the inner layer. A via hole, a side and an upper side of a range of the circuit of the connector or a range from the connector to the filter are surrounded by a box-shaped conductor, and an end of the open surface side of the conductor facing the printed circuit board is provided. Most are in contact with the front surface solid pattern without any gaps and electrical connection can be ensured, and the conductor and the front surface solid pattern and all of the solid patterns provided on the back surface layer or inner layer and the via hole are An electromagnetic shield structure for an external cable connection connector portion, wherein the electromagnetic shield structure is arranged so as not to be directly connected to an internal circuit but to be separated from the internal circuit and not to be connected to a circuit of the filter and the connector. 2. A multilayer or double-sided printed circuit board on which an internal circuit including a portion for generating high-frequency switching noise by a digital signal is mounted; a housing for accommodating the printed circuit board made of metal or resin which is subjected to conductive processing; An external cable connection connector mounted on the front side of the printed circuit board for connecting peripheral devices, a filter inserted between the internal circuit and the connector and mounted on the front side of the printed circuit board, and a front side of the printed circuit board; A surface side solid pattern surrounding the connector and the filter provided on the surface layer, and provided on one or more of the back surface layer and the inner layer of the printed circuit board located in a range according to the shape of the surface side solid pattern. Connecting the solid pattern, the solid pattern on the front surface layer and all the solid patterns provided on the rear surface layer or the inner layer. A via hole, a side and an upper side of a range of the circuit of the connector or a range from the connector to the filter are surrounded by a box-shaped conductor, and an end of the open surface side of the conductor facing the printed circuit board is provided. Most are in contact with the front surface solid pattern without any gaps and electrical connection can be ensured, and the conductor and the front surface solid pattern and all of the solid patterns provided on the back surface layer or inner layer and the via hole are An electronic device having a connector portion for connecting an external cable, wherein the electronic device is arranged not to be directly connected to an internal circuit but to be separated from the internal circuit and not to be connected to a circuit of the filter and the connector. 3. The method according to claim 1, wherein the conductor is formed as a part of a housing, or the conductor is a separate piece from the housing and is made of metal or resin subjected to conductive treatment. The electromagnetic shield structure of the external cable connection connector according to claim 2. 4. The method according to claim 1, wherein the conductor is formed as a part of a housing, or the conductor is a separate piece from the housing and is made of a metal or a resin subjected to a conductive treatment. An electronic device comprising the external cable connection connector according to claim 2.