Electrical connectors – Electromagnetic or electrostatic shield – Shielding individually surrounding or interposed between...
Reexamination Certificate
2000-07-10
2001-03-06
Bradley, Paula (Department: 2833)
Electrical connectors
Electromagnetic or electrostatic shield
Shielding individually surrounding or interposed between...
C439S082000
Reexamination Certificate
active
06196876
ABSTRACT:
1. FIELD OF THE INVENTION
The present invention relates to an assembly comprising at least one connector and a board, each connector being connected to a predetermined side of said board and comprising at least one signal contact member fitted in a hole of the board, the connector comprising electrically conductive connector shielding means to shield each signal contact member.
2. PRIOR ART
Such an assembly is known from U.S. Pat. No. 4,874,319, which is assigned to the Applicant of the present Patent Application and describes a connector-board connection to reduce the adverse effects of electromagnetic radiation generated by signal contact members extending from the connector into the board. The known connector comprises a series of leaf-type spring ground contacts positioned on opposite sides of the signal contact members within the connector. A right-angle connection is present between the connector and the board. To establish this right-angle connection, the signal contact members and the leaf-type spring ground contacts each extend from the rear side of the connector and are bend over 90°. However, the signal contact members extend, unshielded, through corresponding through-holes in the board and are not entirely shielded. When very high frequencies, e.g. within the frequency range from 50 MHz to 15 GHz, are used they still act as antennas radiating undesired electromagnetic radiation.
U.S. Pat. No. 4,697,858 discloses connections between a backplane and several printed circuit boards (pcb's) (FIG. 5). One side of the backplane carries several chip elements each having several terminals. For example as shown in FIG. 7, some of those chip terminals are connected to inner bus lines within the backplane through blind holes reaching as deep as the depth of the corresponding bus lines. Other chip terminals are connected to an inner ground plane through blind holes reaching as deep as the depth of that inner ground plane. Still other signal carrying chip terminals are connected to signal pins extending from the pcb's by means of signal contact members extending entirely through the backplane. These signal contact members extend from connectors accommodating the pcb's and being arranged at the side of the backplane opposite the side carrying the chip elements. None of said connectors is shielded and the signal contact members extend unshielded through said backplane. The bus line within the backplane is situated between two separate ground planes in order to establish a well defined impedance level. No EMC protective measures are provided for.
The present invention starts from the problem that in existing equipment signal contact members of a connector connected to a board, e.g. a pcb or a backplane, extend entirely through plated through-holes and generate electromagnetic radiation also at the opposite side of the board. This will be explained referring to FIG.
1
.
FIG. 1
shows a connection between a connector
42
and a board
41
, e.g. a pcb or a backplane. One signal contact member
43
is schematically shown extending from the connector
42
through a plated through-hole
40
. It is to be understood that “signal contact member” is to be conceived as referring to those contact members of the connector
42
that are intended to carry signals during operation, i.e. the not-ground members.
The connector
42
is provided with an electrically conductive layer
47
to shield contact member
43
. Therefore, connector
42
is suited as coaxial connector.
In existing connector-board connections each signal contact member
43
extends from the through-hole
40
at the side of the board
41
opposite the connector
42
or at least reaches the other side of the board
41
, as shown in FIG. 16 of International Patent Application WO-NL-94/00075 filed on Apr. 12, 1994, by the Applicant of the present Patent Application. Since the end part of the signal contact member
43
extending from the board
41
is not shielded it acts like an antenna and radiates electromagnetic radiation which might induce cross-talk or affect adjacent circuit elements.
SUMMARY OF THE INVENTION
The object of the present invention is to provide an assembly of a board and at least one connector in which each signal contact member of each connector is prevented from radiating any undesired electromagnetic radiation to the outside world.
To reach this object the assembly according to the invention is characterized in that said connector shielding means comprises a shielded connector housing enclosing each contact member, that each hole is provided with an electrically conductive layer on its inside surface, and that the board, except in areas where connectors are fitted to the board, is provided with a first continuous electrically conductive layer on one side and a second continuous electrically conductive disposed in opposed relation to the first electrically conducting layer, each of the shielded connector housings being electrically connected to one of said layers, in order to prevent electromagnetic radiation generated by any of said signal contact members from propagating to the outside world. By the application of these measures all shielding of the individual connectors and the electrically conductive layers on both sides of the board provide a substantially leakproof shield against electromagnetic radiation from the contact members. When the connectors have a coaxial or twinaxial function, such function is retained. By the application of the electrically conductive layer on the inside surface of each hole contact areas for connecting the signal contact members to other circuit elements, e.g. by means of a signal layer within the board, are provided.
Preferably, the board comprises at least one electrically conductive blind hole and at least one signal layer electrically connected to said conductive blind hole, each signal contact member being fitted in a corresponding blind hole.
If required, one of said electrically conductive layers may be covered with an insulating layer, e.g. to protect said layer from engaging other metal parts carrying a certain voltage.
In one embodiment of the assembly according to the invention a first connector is connected to one side of the board and a second connector is connected to the opposite side of said board and one contact member of the first connector is fitted in a first hole and one contact member of the second connector is fitted in a second hole, the first and second holes being aligned with each other. Since connectors may be connected to the board opposite to each other and with aligned contact members package density may be increased.
In such an embodiment, a ground layer may also be provided within the board, separating the first and second holes.
Said first and second holes may be parts of one electrically conductive through-hole in such a way that said contact member of the first connector is electrically connected to said contact member of the second connector.
Each contact member may carry a signal in the frequency range of 50 MHz to 15 GHz. The assembly according to the invention provides excellent shielding against the antenna action of each contact member, even in this range of frequencies.
Each blind hole may have a depth less than 1.5 mm and a diameter less than 1.2 mm. These dimensions may be obtained with current manufacturing methods and allow for the application of blind holes in pcb's which usually have a thickness of about 1.6 mm or more. Moreover, these dimensions stimulate the progress of miniaturization in connector technology which is becoming more and more important but which demands increasing countermeasures against the adverse effects of the antenna action of signal carrying contact members, especially in high frequency applications.
Preferably, each signal contact member is fitted to its corresponding hole by means of a press-fit connection. Such a connection offers great manufacturing advantages. However, alternatively, each signal contact member may be fitted to its corresponding hole by means of a solder connectio
Berg Technology Inc.
Bradley Paula
Hamilla Brian J.
Page M. Richard
Ta Tho D.
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