Patent Application
20060042829
1. Field of the Invention
This invention relates to a transmission circuit board structure, a transmission circuit board, and a connector having the same.
2. Description of the Related Art
In a high speed transmission, such as a 3 giga (3 G) transmission or a transmission beyond 3 giga, a conductor (resistance) loss of a signal line forming a transmission line and a dielectric loss by a dielectric material around the signal line become too large to disregard. Therefore, the structure around the signal line is required to be improved. In a high speed transmission connector having a long transmission path, a transmission circuit board and an insert are used to minimize these losses. For example, the employment of the insert is disclosed in Patent Documents 1 and 2.
In Patent Document 1 and 2, as shown in
PATENT DOCUMENT 1: Japanese Patent Application Kokai Number 2001-510627.
PATENT DOCUMENT 2: Japanese Patent Application Kokai Number 2004-87348.
In Patent Documents 1 and 2, however, a resin is used, as an insert material, around the signal lines. Since the dielectric rate (ε r) and dielectric loss (tan δ) are large, the transmission degradation (attenuation) is produced. This problem is an obstacle to the high speed transmission, especially the transmission employing the differential pair and, therefore, must be solved.
Therefore, one of the objectives of the present invention is to provide a transmission circuit board structure that solves the above problem, a circuit board having such a structure, and a connector having such circuit boards.
According to an aspect of the present invention, a transmission circuit board structure comprises at least one signal layer formed by a plurality of signal lines arranged side by side, at least one ground layer provided in parallel to the signal layer and extending in an area of the signal layer, and an insulation layer provided between the signal and ground layers.
The ground layer is formed of a ground plate made of a sheet metal. The transmission circuit board structure further comprises a support member made of a dielectric material, formed integrally with said signal lines to support the signal lines, and having at least one connection member, which abuts against the ground plate at a position where the insulation layer made by an air space is produced between the signal lines and the ground plate.
Since the air layer exists between the respective signal lines and the ground layer, the dielectric rate (δ r) thereof is approximately 1 and dielectric loss (tan δ) thereof is approximately 0, which is preferable for the high speed transmission. Each of the signal lines is formed by an elongated piece made of a thin sheet metal, which is in parallel to the ground plate. The surface of the sheet metal is generally smooth, which is suitable for a high speed transmission and secures a large transmission area. Also, since the signal lines are formed thin, the transmission board can be made thin.
Since a plurality of the signal layers and the ground layers can be provided reciprocally, the ground property or the shield property is secured. The connection member extends in a direction perpendicular to the signal lines in the same signal layer. The support member is positioned at a center of the transmission circuit board structure in a thicknesswise direction of the transmission circuit board structure and the signal and ground layers are symmetrically provided in this order on both sides of the support member.
The support member extends only in an area of the connection member and adjacent two layers of the signal layers provide the insulation layer of the air space therebetween in whole area other than the area of the connection member. Accordingly, the whole area between the adjacent signal layers is occupied by the air space except for the area where the support member exists, which is also suitable for the high speed transmission. The support member supports the ground plate at a center of the transmission circuit board structure in a thicknesswise direction of the transmission circuit board structure and holds the signal lines on both outsides of the ground plate such that the air space is provided between the signal lines and the ground plate.
Corresponding two of the signal lines, one each provided in either of two of the adjacent signal layers, make a pair. If the two corresponding signal lines making the pair are located at the same position when seen in a thicknesswise direction of the transmission circuit board structure, it is preferable for the differential pair. If the two corresponding signal lines are located at shifted positions when seen in a thicknesswise direction of the transmission circuit board structure, it is applicable as a single end without cross-talk.
When the support member is limited only in the area of the connection member and air space is provided between the adjacent signal layers in whole area except for the area the support member exists, it is desirable to increase the efficiency of the high transmission that each of the signal line has a first width in a first range where the each of the signal lines is supported by the support member and a second width in a second range where the air space exists between the adjacent signal layers, wherein the first width is set smaller than the second width such that characteristic impedances of the signal line in the first and second ranges become equal to each other.
According to another aspect of the present invention, a board having the above-described transmission circuit board structure is used to provide a transmission circuit board by bringing the signal lines and the ground plate into electrical contact with a corresponding connection portion provided on the surface of the board along the verge of the board.
According to still another aspect of the present invention, a plurality of the transmission circuit boards are held in parallel to each other by a retainer at a predetermined interval to provide a transmission circuit board connector.
Since the air layer exists between the respective signal layer and the ground layer, the dielectric rate (ε r) thereof is approximately 1 and dielectric loss (tan δ) thereof is approximately 0, which is preferable for the high speed transmission, especially for the transmission of differential pair type.
Embodiments of the present invention will now be described with reference to the accompanying drawings.
In
The connection members 12 are a plurality of protrusions, which are provided on both sides of the plate member 11 at a certain interval and extend in parallel to each other in a vertical direction or a longitudinal direction of the plate member 11. A plurality of projections 13 are integrally formed on the respective connection members 12 at a certain interval in the longitudinal direction of the connection members 12. Each of the projections 13 is cylindrical and has a height of δ. The top side of the projection 13 is flat and used as a abutting face 13A, which abuts against the ground plate 30. That is, all the abutting faces 13A of the projections 13 provided on the respective connection members 12 on both the sides of the support member 10 are flush with each other.
The signal lines 20 are held on both sides of the plate member 11 at the same locations viewed in a thichknesswise direction of the plate member 11. Namely, the signal lines form two layers. The respective signal lines 20 are stripes or elongated pieces made of a sheet metal and extend in a horizontal direction (a direction perpendicular to the direction where the connection members 12 extend) between the respective adjacent projections 13. The signal lines 20 cross the respective connection members 12 between the adjacent projections 13 and are flush with the connections members 12 at the crossing points. Accordingly, the projections 13 project from the flush level by a height of δ. It is preferable that the signal lines 20 are integrally formed with the support member 10 with the connection members 12. The abutting faces 13A of the projections 13 are located above the level, by a height of δ, which includes the face of the signal lines 20 and the face of the connection members 12 at the crossing points.
The ground plates 30 made of a flat sheet metal with an appropriate dimension are fixed to both sides of the support member 10. The inside surfaces of the ground plates 30 are brought into contact with the abutting faces 13A of the projections 13 and maintain a constant distance from the signal lines 20, that is, a distance δ equal to the height δ of the projections 13. Consequently, the signal lines 20 are everywhere spaced from the ground plates 30 by the distance δ. Thus, since an air layer is produced between the respective signal lines 20 and the ground plates 30, the dielectric rate (ε r) thereof is approximately 1 and dielectric loss (tan δ) thereof is approximately 0.
Such a transmission circuit board as has a structure where the air layer exists between the signal lines 20 and the ground plates 30, is suitable for the high speed transmission. Especially, in the embodiment shown in
In
In
In the second embodiment, too, the signal lines 20 form two layers. The air layer exists not only between the signal layer and the ground plate but also between the two signal layers except for the area where connection members 12 exist. Accordingly, the dielectric rate (ε r) becomes closer to 1 and the dielectric loss (tan δ) approach to 0 infinitely. This effect increases when the connection members are made slimmer and the adjacent connection members 12 are spaced greater. A pair of corresponding signal lines 20 can be shifted from each other to use as the single-end application. In this case, as shown in
In the first and second embodiments, the signal lines forming the signal layers are held on both the sides of the support member of a dielectric material or the connection member of the support member, and the ground plates forming the ground layers are provided outside the signal layers. In the third embodiment, the ground plate is provided in the center and the signal layers are provided on both the sides of the ground plate.
In
In the third embodiment, the projections 13 of the connection members 12 can be omitted. However, the projections 13 may provided to prevent the signal lines 20 from touching other members when the board is accommodated in or fixed to the members.
In the fourth embodiment, an example, in which the board structure described in the first to third embodiments is incarnated to a transmission circuit board, is described. In
In
A plurality of the projections 13 with the abutting faces 13A are provided in the support member 10 between the adjacent signal lines 20. A plurality of plug-in projections 43 having a height larger than that of the projections 13 are provided in the support member 10 at suitable positions. Some of the plug-in projections 43 are hung over the signal lines 20 to increase the support strength for the signal lines 20. The support member 10 has various flange portions 14 at the peripheries of the board to reinforce the board and connect the board to other similar board. The flange portions 14 are plugged in retainers (connection members), not shown, to hold a plurality of boards, thereby to assemble a connector apparatus.
The ground plates 30 are installed on both the sides of the support member 10. The ground plates 30 have an outline, which stays inside the various flange portions 14. Also, the ground plates 30 have holes 31, which are plugged in the plug-in projections 43 of the support member 10. Further, the ground plates 30 have terminal portions 32 and 33, which adjoin to the ends of the rows of the contact lands 41A and 42A of the connection portions 41 and 42.
In
A plurality of such boards are held by a retainer (not shown) to provide an intermediate connector. The connection portions 41 and 42 at the two edge portions of the board unable the connection with two apparatuses. The present invention is not limited to the embodiments and various variations are possible. For example, the support member and the connection members may be separate instead of being made integrally. The connection members may be formed integrally with the ground plates such that when the connection members abut against the support member, the ground plates are spaced from the signal lines. Also, separate connection members may be provided between the ground plates and the support members. Further, the connection members may be installed to the edge portion of the support member.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2004-251396 | Aug 2004 | JP | national |
