CN107919548B - electrical connector - Google Patents

Abstract

An electrical connector includes an insulating body, a terminal module mounted on the insulating body, and a cover. The terminal module includes a plurality of support terminals arranged in a row along the length direction of the insulating body and a plurality of differential signal terminal pairs and a plurality of grounding terminals arranged in another row along the length direction. A differential signal terminal pair is arranged between any two adjacent grounding terminals. Each grounding terminal corresponds to a support terminal along the height direction perpendicular to the length direction, at least some of the differential signal terminal pairs correspond to a support terminal along the height direction, and the differential signal terminal pairs and support terminals corresponding to each other along the height direction are spaced apart from each other and electrically separated. The cover is assembled to the plurality of support terminals and can pivot relative to the insulating body. Thereby, an electrical connector is provided that enables the cover to have better supporting force.

Description

electrical connector

technical field

The present invention relates to a connector, and also relates to an electrical connector suitable for high-frequency signal transmission.

Background technique

After the existing electrical connector (especially the existing electrical connector suitable for high-frequency signal transmission) provided with a cover is fixed on the circuit board, the existing electrical connector only provides the above-mentioned The required support for the cover. However, the supporting force provided by the existing electrical connectors for the cover is gradually insufficient, so there is a need for further improvement.

Therefore, the inventor believes that the above-mentioned defects can be improved, devoted himself to research and combined with the application of theories, and finally proposed an invention with reasonable design and effective improvement of the above-mentioned defects.

Contents of the invention

An embodiment of the present invention is to provide an electrical connector, which is used to improve the possible problems of the existing electrical connector.

The embodiment of the present invention discloses an electrical connector. The electrical connector includes: an insulating body; a terminal module installed on the insulating body, and the terminal module includes: a plurality of supporting terminals along the insulating body; A length direction of the body is arranged in a row; and a plurality of differential signal terminal pairs and a plurality of ground terminals are arranged in another row along the length direction, and one of the ground terminals is arranged between any two adjacent ground terminals. Differential signal terminal pairs; wherein, each of the ground terminals corresponds to one of the support terminals along a height direction perpendicular to the length direction, and at least some of the differential signal terminal pairs of the plurality of differential signal terminal pairs are each Corresponding to one of the support terminals along the height direction, and the pair of differential signal terminals and the support terminals corresponding to each other along the height direction are arranged at intervals and electrically separated from each other; and a cover, assembled on multiple There are two supporting terminals, and the cover can pivot relative to the insulative body with the position assembled to the supporting terminals as an axis.

Preferably, each pair of differential signal terminals includes two differential signal terminals, at least one of the differential signal terminals in each pair of differential signal terminals corresponds to one of the supporting terminals along the height direction, and The differential signal terminals and the support terminals corresponding to each other along the height direction are arranged at intervals and electrically separated from each other.

Preferably, the electrical connector is used to detachably connect a flexible conductor, wherein each of the support terminals includes a fastening portion, and the cover is assembled to a plurality of the fastening portions; each Each of the differential signal terminals includes a signal conduction portion, each of the ground terminals includes a ground conduction portion, and the plurality of signal conduction portions and the plurality of ground conduction portions are used to abut against the flexible conductor multiple electrical contacts of the material.

Preferably, the insulating body is recessed to form a receiving groove, which is used to accommodate the parts of the flexible conductive material provided with a plurality of the electrical contacts; and the insulating body is recessed at the bottom of the receiving groove A plurality of buffer slots are formed, and a plurality of the signal conduction parts and a plurality of the ground conduction parts are respectively partly accommodated in the plurality of buffer slots, and each of the signal conduction parts is partly self-contained from the accommodated The buffer groove protrudes to the receiving groove, and each of the signal conducting parts forms a gap with the bottom of the accommodated buffer groove; when the electrical connector is connected to the flexible conductor and the When the cover body is press-fitted on the flexible conductive material, the differential signal terminals and the support terminals corresponding to each other along the height direction, the signal conducting part and the fastening part included in it are respectively facing away from each other Elastic displacement in the direction of .

Preferably, each of the differential signal terminals includes a signal fixing portion away from the signal conducting portion, each of the ground terminals includes a ground fixing portion away from the ground conducting portion, and a plurality of the signal The fixing part and the plurality of grounding fixing parts are used for fixing on a circuit board.

Preferably, the electrical connector further includes two positioning pieces installed on the insulating body, and the two positioning pieces are respectively adjacent to opposite sides of the cover, and the cover contains two Each positioning part includes a matching positioning part, and the two positioning parts of the cover are respectively detachably engaged with the matching positioning parts of the two positioning parts.

Preferably, each of the differential signal terminals corresponds to one of the supporting terminals along the height direction.

Preferably, each supporting terminal is electrically connected to adjacent supporting terminals through a conductor.

Preferably, the terminal module includes a plurality of connecting segments integrally connected to the plurality of grounding terminals, and each of the grounding terminals is integrally connected to the corresponding terminals along the height direction through one connecting segment. The support terminal.

Preferably, at least part of each connecting section is accommodated in the insulating housing.

Preferably, the ground terminals and the supporting terminals corresponding to each other along the height direction are arranged at intervals and electrically separated from each other.

Preferably, the appearances of the plurality of support terminals are the same, and the appearances of the plurality of differential signal terminals and the plurality of ground terminals are the same.

To sum up, the electrical connector disclosed in the embodiment of the present invention can increase the supporting force required by the cover body by providing support terminals separated from the differential signal terminal pair, so as to avoid the electrical connector being installed with flexible conductive materials. When pulling, the electrical connection between the electrical connector and the flexible conductive material is unstable or separated from each other due to pulling.

In order to enable a further understanding of the features and technical content of the present invention, please refer to the following detailed description and accompanying drawings of the present invention, but these descriptions and accompanying drawings are only used to illustrate the present invention, rather than to the protection scope of the present invention make any restrictions.

Description of drawings

FIG. 1 is a three-dimensional schematic diagram of an electrical connector of the present invention fixed on a circuit board and installed with a flexible conductive material.

FIG. 2 is an exploded schematic diagram of FIG. 1 .

FIG. 3 is a three-dimensional schematic view of Embodiment 1 of the electrical connector of the present invention.

FIG. 4 is an exploded schematic diagram of FIG. 3 .

FIG. 5 is an exploded schematic view from another perspective of FIG. 3 .

FIG. 6 is a schematic cross-sectional view along the line VI-VI of FIG. 3 .

FIG. 7 is a schematic cross-sectional view of FIG. 3 along section line VII-VII.

FIG. 8 is a schematic cross-sectional view of the electrical connector of FIG. 6 when the flexible conductive material is inserted.

FIG. 9 is a schematic cross-sectional view of the electrical connector of FIG. 7 when a flexible conductive material is inserted.

FIG. 10 is a schematic perspective view of a variant of FIG. 3 .

FIG. 11 is a three-dimensional schematic diagram of Embodiment 2 of the electrical connector of the present invention.

FIG. 12 is an exploded schematic diagram of FIG. 11 .

FIG. 13 is a schematic perspective view of a variant of FIG. 11 .

FIG. 14 is a schematic rear view of Embodiment 3 of the electrical connector of the present invention.

Detailed ways

[Example 1]

Please refer to Figures 1 to 10, which are the first embodiment of the present invention. It should be explained first that this embodiment corresponds to the relevant quantities and shapes mentioned in the accompanying drawings, and is only used to specifically illustrate the implementation of the present invention. In order to facilitate the understanding of the content of the present invention, it is not used to limit the protection scope of the present invention.

As shown in Figures 1 and 2, this embodiment discloses an electrical connector 100, especially an electrical connector 100 suitable for high-frequency signal transmission. The above-mentioned electrical connector 100 is used to be fixed on a circuit board in this embodiment 300 and can be used to detachably connect a flexible conductor 200. Wherein, the flexible conductive material 200 is, for example, a flexible flat cable (Flexible Flat Cable, FFC) or a flexible printed circuit (Flexible Printed Circuit, FPC), but is not limited thereto.

As shown in Figure 3, the electrical connector 100 includes an elongated insulating body 1, a terminal module 2 installed on the insulating body 1, a cover 3 that can pivot relative to the insulating body 1, and is installed on the insulating body 1. Two positioning parts 4 of the body 1 . Wherein, the insulating body 1 defines a length direction L, a height direction H, and a width direction W perpendicular to each other, which are used to assist in explaining the structure of the electrical connector 100 . As shown in Figures 4 to 7, the insulating body 1 is recessed to form a receiving groove 11, so that the top surface of the insulating body 1 is roughly U-shaped, and the receiving groove 11 is used to accommodate the flexible conductive material 200. There are multiple electrical contacts (such as the front end of the flexible conductive material 200 in FIG. 2 ). Wherein, the insulating body 1 is recessed with a plurality of elongated buffer grooves 12 at the groove bottom 111 of the receiving groove 11, each buffer groove 12 is substantially parallel to the width direction W, and the plurality of buffer grooves 12 are along the The length directions L are arranged in a row. Moreover, the insulating body 1 is formed with a penetrating conductive terminal groove 13 along the width direction W from each buffer groove 12, and the insulating body 1 is formed with a plurality of supporting terminal grooves 14 in a penetrating shape, and the above-mentioned multiple The supporting terminal slots 14 correspond to the plurality of conductive terminal slots 13 along the height direction H, respectively. In addition, the insulating body 1 is formed with a positioning groove 15 at opposite ends along the length direction L, and the two positioning grooves 15 communicate with the receiving groove 11 respectively.

The terminal module 2 includes a plurality of support terminals 21a, 21b arranged in one row along the length direction L, and a plurality of differential signal terminals 22 and a plurality of ground terminals 23 arranged in another row along the length direction L. Wherein, the plurality of supporting terminals 21a, 21b are respectively disposed in the plurality of supporting terminal slots 14 of the insulating body 1, and the plurality of differential signal terminals 22 and the plurality of grounding terminals 23 are respectively disposed in the insulating body 1. There are a plurality of conductive terminal slots 13, and two differential signal terminals 22 (also called a differential signal terminal pair 20) are arranged between any two adjacent ground terminals 23.

Further, each ground terminal 23 corresponds to a supporting terminal 21a along the height direction H, and the terminal module 2 includes a plurality of connecting sections 24 integrally connected to the plurality of ground terminals 23, each ground terminal 23 are integrally connected to supporting terminals 21 a corresponding to each other in the height direction H through a connecting section 24 . In this embodiment, the integrally connected ground terminal 23 , connecting segment 24 , and supporting terminal 21 a are formed by stamping a single metal sheet, but it is not limited thereto. And at least a part of each connecting segment 24 is accommodated in the insulating housing 1 .

Moreover, among the plurality of differential signal terminals 22, at least some of the differential signal terminals 22 each correspond to a support terminal 21b along the height direction H, and the differential signal terminals 22 and support terminals corresponding to each other along the height direction H 21b are arranged at intervals and electrically separated from each other. However, although the supporting terminals 21a and 21b in this embodiment are spaced apart and electrically separated from each other, the present invention is not limited thereto. For example, in an unillustrated embodiment, the support terminals can be electrically connected and grounded with conductors (such as wires) or other means, so as to provide shielding effect for the above-mentioned differential signal terminals.

In this embodiment, the terminal module 2 is such that each differential signal terminal 22 corresponds to one support terminal 21b along the height direction H, but it is not limited thereto. For example, as shown in FIG. 10, a pair of adjacent differential signal terminals 22 can only use one of the differential signal terminals 22 to correspond to a supporting terminal 21b along the height direction H; or, in another not-shown implementation In an example, the plurality of differential signal terminals can be selected according to the needs of the designer, and some of the differential signal terminals correspond to a support terminal along the height direction.

As shown in Figures 6 and 7, looking at the detailed structure of the terminal module 2, each support terminal 21a, 21b includes a support portion 211 disposed in the corresponding support terminal slot 14 and opposite from the above support portion 211. A fastening portion 212 and an exposed portion 213 extending from both ends. Wherein, as shown in FIG. 6 , the support portion 211 of the support terminal 21 b is preferably formed with at least one barb 2111 embedded in the corresponding support terminal groove 14 , so that the support terminal 21 b can be stably installed on the insulating housing 1 . Also as shown in FIG. 7 , in this embodiment, the support terminal 21 a has been connected to the ground terminal 23 through the connection section 24 , so there is no need to form barbs, but it is not limited thereto. For example: in an unillustrated embodiment, the supporting terminals can also form barbs, so that the supporting terminals can be more stably installed in the supporting terminal slots. As shown in FIG. 6 and FIG. 7 , the plurality of fastening portions 212 are generally located in the receiving groove 11 and directly above the buffer grooves 12 . Each exposed portion 213 is away from the corresponding fastening portion 212 and exposed outside the insulating housing 1 .

Furthermore, each of the differential signal terminals 22 includes a signal mounting portion 221 disposed in the corresponding conductive terminal groove 13 and a signal conducting portion 222 and a signal fixing portion 223 extending from opposite ends of the signal mounting portion 221 respectively. . Each ground terminal 23 includes a ground mounting portion 231 disposed in the corresponding conductive terminal slot 13 , and a ground conducting portion 232 and a ground fixing portion 233 respectively extending from opposite ends of the ground mounting portion 231 .

Wherein, each of the above-mentioned signal installation parts 221 is preferably formed with at least one barb 2211 embedded in the corresponding conductive terminal slot 13 , so that the differential signal terminal 22 can be firmly installed on the insulating housing 1 . Each ground mounting portion 231 is preferably formed with at least one barb 2311 embedded in the corresponding conductive terminal slot 13 , so that the ground terminal 23 can be firmly installed on the insulating housing 1 .

The plurality of signal conduction portions 222 and the plurality of ground conduction portions 232 are used to abut against a plurality of electrical contacts (not shown in the figure) of the flexible conductive material 200 . The plurality of signal conducting parts 222 and the plurality of grounding conducting parts 232 are partly accommodated in the plurality of buffer slots 12 of the insulating body 1, and a part of each signal conducting part 222 protrudes from the accommodated buffer slot 12 to the receiving position. A gap G is formed between the groove 11 and the groove bottom 121 of the buffer groove 12 accommodated therein. Similarly, a part of each grounding conductive portion 232 protrudes from the received buffer tank 12 to the receiving tank 11 , and forms a gap G with the tank bottom 121 of the received buffer tank 12 .

Therefore, when the electrical connector 100 is connected to the flexible conductor 200 and the cover body 3 is pressed onto the flexible conductor 200, as shown in Figures 8 and 9, the differences along the height direction H correspond to each other The signal terminal 22 and the supporting terminal 21b, the signal conducting part 222 and the fastening part 212 respectively included in the signal terminal 222 and the fastening part 212 are respectively elastically displaced toward directions away from each other (downward and upward in FIG. 8 ), and mutually along the height direction H. Corresponding to the ground terminal 23 and the support terminal 21a, the ground conducting portion 232 and the fastening portion 212 respectively included in the grounding terminal 23 and the fastening portion 212 are elastically displaced toward directions away from each other (downward and upward as shown in FIG. 9 ).

Furthermore, each signal fixing portion 223 is away from the corresponding signal conducting portion 222 and exposed outside the housing 1 , and each ground fixing portion 233 is away from the corresponding grounding conducting portion 232 and exposed outside the housing 1 . The plurality of signal fixing portions 223 and the plurality of grounding fixing portions 233 are used for fixing (such as soldering) on the circuit board 300 (as shown in FIG. 1 ), so that the differential signal terminals 22 and the ground terminals 23 can be electrically connected to the circuit board. 300.

As shown in Figures 4 to 7, the cover body 3 is assembled to the above-mentioned multiple support terminals 21a, 21b, and the cover body 3 can take the position assembled to the plurality of support terminals 21a, 21b as the axis, and relative to the insulating body 1 pivot. Wherein, the cover body 3 includes a long plate portion 31, a rod portion 32 connected to the long side of the plate portion 31, and two positioning portions 33 respectively located on the two short sides of the plate portion 31. . The rod portion 32 of the cover body 3 is fastened to the fastening portion 212 of the plurality of support terminals 21a, 21b. From another perspective, the above-mentioned rod portion 32 is generally located below the fastening portion 212, and the signal conducting portion 222 is connected to the fastening portion 212. above the ground conducting portion 232 .

As shown in Fig. 1, Fig. 3 to Fig. 5, the two locating members 4 are respectively adjacent to the opposite sides of the above-mentioned cover body 3 (such as the two short sides of the plate portion 31), the two locating members of this embodiment 4 are two positioning slots 15 installed in the insulating body 1 respectively, and each positioning member 4 is preferably formed with a barb 42 embedded in the corresponding positioning slot 15 . Wherein, parts of the above-mentioned two positioning members 4 are used to be welded to the above-mentioned circuit board 300 , so that the electrical connector 100 can be stably arranged on the circuit board 300 .

Each positioning component 4 includes a matching positioning portion 41 , and the two positioning portions 33 of the cover 3 are detachably engaged with the matching positioning portions 41 of the two positioning components 4 . Furthermore, when the cover body 3 is roughly located in the receiving groove 11 and is pressed against the flexible guide material 200, the two positioning portions 33 of the cover body 3 are respectively engaged with the matching positioning portions 41 of the above-mentioned two positioning members 4, thereby The relative position of the cover body 3 and the insulating body 1 is maintained. Furthermore, the positioning portion 33 in this embodiment is described as a protrusion, and the matching positioning portion 41 is a groove corresponding to the protrusion, but the present invention is not limited thereto. For example: in an unillustrated embodiment, the positioning portion may be a groove, and the matching positioning portion is a protrusion corresponding to the groove.

According to the above, the electrical connector 100 disclosed in this embodiment can meet the requirements of high-frequency signal transmission, by providing the supporting terminal 21b separated from the differential signal terminal 22, the supporting force required by the cover body 3 can be increased. In order to prevent the electric connector 100 and the flexible conductive material 200 from being unstable or separated from each other due to pulling or collision when the flexible conductive material 200 is installed on the electrical connector 100 . Moreover, when the supporting terminal 21 b of this embodiment is under force, it will not affect the corresponding differential signal terminal 22 .

Furthermore, when the electrical connector 100 is connected to the flexible conductive material 200 and the cover body 3 is pressed against the flexible conductive material 200, the signal conducting part 222 and the fastening part 212 can elastically displace in directions away from each other. And there is a restoring force, so as to enhance the connection stability with the flexible conductive material 200 .

[Example 2]

Please refer to Figures 11 to 13, which are the second embodiment of the present invention. This embodiment is similar to the above-mentioned first embodiment, and the same parts will not be repeated. The difference between the two embodiments mainly lies in: the terminals of this embodiment The module 2 does not include the connection section 24 described in the first embodiment, so that the ground terminals 23 and the support terminals 21 a corresponding to each other along the height direction H are spaced apart and electrically separated from each other.

More specifically, as shown in FIG. 11 and FIG. 12 , the appearances of the plurality of support terminals 21 a and 21 b are the same, and the appearances of the plurality of differential signal terminals 22 and the plurality of ground terminals 23 are also the same. Accordingly, the arrangement order of the plurality of support terminals 21a, 21b in this embodiment can be changed arbitrarily according to the needs of the designer, and the arrangement order of the plurality of differential signal terminals 22 and the plurality of ground terminals 23 in this embodiment can also be changed according to the design. According to the user's needs, it can be changed arbitrarily.

In this embodiment, the terminal module 2 is such that each differential signal terminal 22 corresponds to one support terminal 21b along the height direction H, but it is not limited thereto. For example, as shown in FIG. 13, a pair of adjacent differential signal terminals 22 can only use one of the differential signal terminals 22 to correspond to a support terminal 21b along the height direction H; or, in another not-shown implementation In an example, the plurality of differential signal terminals can be selected according to the needs of the designer, and some of the differential signal terminals correspond to a support terminal along the height direction.

However, although the support terminals 21a and 21b in this embodiment are spaced apart and electrically separated from each other, the present invention is not limited thereto. For example, in an unillustrated embodiment, the supporting terminals can be electrically connected and grounded using conductors (such as wires) or other means, so as to provide shielding effect for the differential signal terminals.

[Embodiment three]

Please refer to Figure 14, which is the third embodiment of the present invention. This embodiment is similar to the above-mentioned first and second embodiments, and the same parts will not be repeated. The difference between the above-mentioned embodiments mainly lies in: the adjacent Two differential signal terminals 22 (or two differential signal terminals 22 located between any two adjacent ground terminals 23) form a differential signal terminal pair 20, and the differential signal terminal pair 20 corresponds to A support terminal 21b.

In addition, the terminal module 2 of the present embodiment may include the connection section 24 as in the first embodiment, so as to electrically connect the support terminal 21 a to the ground terminal 23 , but it is not limited thereto. In an embodiment not shown, the terminal module 2 may also not include the connection section 24 as in the second embodiment, so that the supporting terminal 21 a is electrically separated from the grounding terminal 23 .

The above descriptions are only preferred feasible embodiments of the present invention, and are not intended to limit the protection scope of the present invention. All equivalent changes and modifications made according to the claims of the present invention shall fall within the protection scope of the present invention.

Claims (12)

1. a kind of electric connector, which is characterized in that the electric connector includes:

One insulating body；

One terminal module is installed on the insulating body, and the terminal module includes:

Multiple support terminals, the length direction along the insulating body are in line；And

Multiple difference signal terminals pair and multiple ground terminals, line up another row along the length direction, and any two are adjacent The ground terminal between be provided with the difference signal terminal pair；

Wherein, each ground terminal corresponds to a support end along a short transverse of the vertical length direction Son, multiple difference signal terminals the wherein at least part difference signal terminal to each corresponding along the short transverse In the support terminals, and along the mutual corresponding difference signal terminal pair of the short transverse and the support end Son is intervally installed and electrically isolated；And

One lid, is connected to multiple support terminals, and the lid can be to be connected to the portions of multiple support terminals Position is axis, and is pivoted relative to the insulating body.

2. electric connector as described in claim 1, which is characterized in that each difference signal terminal is to including two difference Signal terminal, difference signal terminal described in at least one of which of each difference signal terminal centering is along the short transverse Corresponding to the support terminals, and along the mutual corresponding difference signal terminal of the short transverse and the support Terminal is intervally installed and electrically isolated.

3. electric connector as claimed in claim 2, which is characterized in that it is soft that the electric connector is used to energy isolatedly connected one Lead material, wherein each support terminals include an engaging portion, and the lid is connected to multiple engaging portion；Often A difference signal terminal includes a signal transduction portion, and each ground terminal includes a ground connection conducting part, and Multiple signal transduction portions and multiple ground connection conducting parts are used to be connected to the soft multiple electrical contacts for leading material.

4. electric connector as claimed in claim 3, which is characterized in that the insulating body is recessed to be formed with a container, uses To accommodate the soft position led material and be equipped with multiple electrical contacts；And the insulating body is in the slot of the container Bottom is recessed to be formed with multiple dashpots, and multiple signal transduction portions and multiple ground connection conducting parts are partially placed in more respectively The part of a dashpot, each signal transduction portion protrudes out to the container from the dashpot accommodated, and And each signal transduction portion and the slot bottom of the dashpot accommodated are formed with a gap；When the electric connector connects It is described it is soft lead material and the lid be pressed on it is described soft when leading material, along the mutual corresponding difference of the short transverse Signal terminal and the support terminals, it includes the signal transduction portion and the engaging portion be respectively facing side away from each other To elastic displacement.

5. electric connector as claimed in claim 3, which is characterized in that each difference signal terminal includes far from described The one signal fixed part in signal transduction portion, each ground terminal include that the ground connection far from the ground connection conducting part is fixed Portion, and multiple signal fixed parts and multiple ground connection fixed parts are for fixing on a circuit board.

6. electric connector as described in claim 1, which is characterized in that the electric connector further comprise be installed on it is described Two locating pieces of insulating body, and two locating pieces are adjacent to the two opposite sides of the lid, the lid respectively Comprising there are two positioning region, each locating piece includes a cooperation positioning region, and two position portions of the lid It can not be sticked in the cooperation positioning region of two locating pieces discretely.

7. electric connector as claimed in claim 2, which is characterized in that each difference signal terminal is along the short transverse Corresponding to the support terminals.

8. electric connector as described in claim 1, which is characterized in that each support terminals by a conductor with it is adjacent The close support terminals are electrically connected.

9. such as electric connector described in any item of the claim 1 to 8, which is characterized in that the terminal module includes difference Multiple linkage sections of multiple ground terminals are integrally connected to, and each ground terminal passes through a linkage section And it is integrally connected to along the mutual corresponding support terminals of the short transverse.

10. electric connector as claimed in claim 9, which is characterized in that at least part of each linkage section is contained in institute It states in insulating body.

11. the electric connector as described in any one of claim 2 to 8, which is characterized in that corresponded to each other along the short transverse The ground terminal and the support terminals be intervally installed and electrically isolated.

12. electric connector as claimed in claim 11, which is characterized in that the external form of multiple support terminals is all identical, and And multiple difference signal terminals are all identical as the external form of multiple ground terminals.