Electricity: conductors and insulators – Anti-inductive structures – Conductor transposition
Reexamination Certificate
1999-03-29
2001-07-03
Reichard, Dean A. (Department: 2831)
Electricity: conductors and insulators
Anti-inductive structures
Conductor transposition
C174S034000, C361S818000, C361S816000
Reexamination Certificate
active
06255582
ABSTRACT:
FIELD OF THE INVENTION
This invention relates generally to methods and apparatus for connection two circuit elements via a flex cable, and more specifically to methods and apparatus for connecting a ground shield plane of a flex cable to a grounding pad on circuit element comprising a printed wire board or a metal chassis to provide effective EMI/ESD grounding by the ground shield plane of the flex cable.
BACKGROUND OF THE INVENTION
State of the art electrical circuit designs require improved EMI and ESD suppression. To achieve this in an arrangement in which one or more electrical components are mounted external to a printed wire board or chassis and connected via a flex cable requires that the flex cable include a ground plane separate from and insulated from the conductive traces of the cable and that this ground plane be effectively connected to a grounding pad on the printed wire board.
FIG. 1
illustrates a prior art flex cable arrangement in which the component mounted to pads
12
on flex cable
10
are provided with ground only through a separate set of traces
11
. This arrangement may provide ineffectual EMI/ESD shielding.
FIGS. 2 and 3
illustrate a prior art flex cable shield grounding arrangement. Flex cable
20
has conductive cable traces
24
extending between component connection points
22
and a connector region
20
A which is inserted into a flex cable connector
40
mounted on printed wire board
31
.
FIG. 3
illustrates the structure of the flex cable and the grounding structure
21
to ground the copper shielding layer
26
to a grounding pad
32
on a printed wire board
31
. A plated through hole
30
extends through the various layers of the flex cable, i.e. stiffener
28
, polyamide
27
, copper layer
26
, polyamide
25
, traces
24
, and polyamide
23
. The plated through hole contacts copper shielding layer
26
and, together with screw
29
, provides a conductive connection to grounding pad
32
. This ground arrangement may not provide sufficient EMI/ESD shielding for many flex cable applications and also requires extra steps in cable manufacture and assembly of the cable into the final product.
OBJECTS OF THIS INVENTION
It is the principal object of this invention to provide an improved method and apparatus for connecting a ground shield plane of a flex cable to a grounding pad on a circuit element comprising a printed wire board or metal chassis to provide effective EMI/ESD grounding of the ground shield plane of the flex cable.
FEATURES AND ADVANTAGES OF THIS INVENTION
This invention features a method for connecting the shielding ground plane of a flex cable to a grounding pad on a circuit element comprising a printed wire board or metal chassis to which the flex cable is connected. For purposes of this discussion, a printed circuit board will be used as the circuit element. A flex cable connector is mounted on the printed wire board at a prearranged location. The printed wire board has formed thereon a grounding pad positioned adjacent to the flex cable receiving portion of the flex cable connector. The flex cable has formed thereon adjacent to the connector end thereof an access window in the flex cable layers overlying the shielding ground plane sized to allow sufficient connection to the shielding ground plane of the flex cable. The connector end of the flex cable is inserted into the flex cable connector on the printed wire board. The access window in the flex cable is placed over the grounding pad to make an electrical connection between the grounding pad and the shielding ground plane of the flex cable across substantially the entire area of the access window.
This provides a more effective grounding of the EMI/ESD shielding layer and thus more effective EMI/ESD shielding of the conductive traces of the cable and the component mounted on the flex cable.
Preferrably the method further comprising forming a layer of conductive adhesive material in the access window in the flex cable layers or on the grounding pad on the printed wire board. In this embodiment, the flex cable and the printed wire board are pressed together where the layer of conductive adhesive has been formed to adhere the exposed ground plane of the flex cable to the grounding pad and to provide electrical connection between the grounding pad and the shielding ground plane of the flex cable.
Other objects, features and advantages of this invention will be apparent from a consideration of the detailed disclosure, claims and drawing figures.
REFERENCES:
patent: 3612744 (1971-10-01), Thomas
patent: 4184729 (1980-01-01), Parks et al.
patent: 4644092 (1987-02-01), Gentry
patent: 4845311 (1989-07-01), Schreiber et al.
patent: 5448020 (1995-09-01), Pendse
patent: 5669775 (1997-09-01), Campbell et al.
Bonville Curtis Allen
Miller William Michael
Hewlett--Packard Company
Reichard Dean A.
Walkenhorst W. David
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