[0001] The present invention relates to an electrical connector according to the preamble
of claim 1.
[0002] This invention relates to an electrical article such as a connector and more particularly
a method of assembling thereto a filter of a tape, laminated construction, by mounting
the tape filter on portions of the exterior surface of the connector housing.
[0003] The increasing use of high speed digital pulses for communication has led to the
use of sensitive components to receive and manipulate such signals. This sensitivity
has in turn made the components vulnerable to unwanted frequencies transmitted thereto
on the same signal paths as the wanted signal frequencies. To solve the problem caused
thereby, a number of developments have led to patents that purport to filter out unwanted
frequencies utilizing electrical connectors as the vehicle for accommodating appropriate
filters having appropriate characteristics. U.S. Patent No. 4,695,115 is drawn to
a telephone connector with bypass capacitor and teaches the use of capacitors built
into the connector to filter out unwanted frequencies from signals carried on signal
contacts of a connector. There, the filters are termed "tombstone capacitors" and
means are provided for interconnecting such capacitors between the signal paths and
grounding paths. As will be discerned, the filters occupy a considerable volume of
the total volume of the connector.
[0004] U.S. Patent No. 4,772,224 represents a modular electrical connector which includes
capacitors and additionally, ferrite inductors to provide filtering. As with Patent
No. 4,695,115, the filter elements take up considerable volume of the device, particularly
in terms of the height of the device from a printed circuit board or part of the assembly
served by the filtered connector.
[0005] Accordingly, it is an object of the present invention to provide a connector having
a filter that adds minimally to the packaging dimensions of the connector. It is a
further object to provide the combination of multi-pin electrical connector in conjunction
with a thin tape filter disposed on the exterior surface of the connector housing
in an unobtrusive way, generally conforming to the shape of the exterior surfaces
while innocuously traversing openings thereinto. It is a still further object to provide
a simple, and readily manufacturable filter construction that adapts itself to use
on connectors and other electrical articles such as printed circuit boards and transmission
cable.
[0006] The invention provides an electrical connector as defined in claim 1 and a method
of applying a filter element as defined in claim 6. Preferred embodiments are defined
in the dependent claims.
[0007] In accordance with the present invention, there is provided a filter assembly consisting
essentially of one or more thin foil signal electrodes and one or more grounding electrodes
separated by a thin coating of dielectric material with the area of the electrodes,
in conjunction with the dielectric constant of the material and the spacing between
electrodes, selected to provide a capacitance effectively filtering out unwanted frequency
components and allowing desired frequency components to pass through signal transmission
circuits. The unwanted frequency components are in essence grounded by the filter
through a connection to a grounding means. The filter may include the electrodes and
dielectric material laminated together, or additionally, a thin dielectric film utilized
as a carrier to hold the assembly of electrodes and dielectric material in a position
for manufacturing and application.
[0008] In one embodiment, the present invention achieves the foregoing objectives through
the use of an electrical connector having a plastic housing with an exterior surface
essentially of a conventional configuration. The connector includes signal contacts
carried by the housing with post portions extending from the bottom of the housing
and a grounding contact, including a shield structure over the front or mating face
of the connector, with post portions extending down from the bottom or mounting face
of the connector, the post portions to be inserted into respective apertures of the
printed circuit board of a circuit assembly being soldered thereto. Signals transmitted
to the connector by a mating connector are carried by their signal contacts to signal
traces on the circuit assembly through printed circuit board conductive traces extending
from connections with the contacts at the apertures, to components within the assembly
that receive and utilize such signals for communication purposes. The combination
is disclosed in U.S. Patent Application Serial No. 07/971,028 filed November 3, 1992.
[0009] In combination with the connector, which may be in the form of a telephone receptacle
that mates with a telephone connector plug, the electrodes of the filter, both signal
and ground, have holes therein through which are fitted the contacts of the connector,
suitably terminated thereto such as by solder joints, with the filter tape lamination
being thereafter folded around from the bottom of the connector housing, over the
back and top of the housing with the grounding electrode being joined to the shielding
and grounding of the connector as by solder. An insulative layer is provided over
the portions of the electrodes except at the soldering sites, such as by spraying
of a polymeric coating thereover or lamination to a polymeric film.
[0010] The invention contemplates application for a broad range of connectors, including
at least one signal contact and at least one grounding contact with separate tape
structures for separate signal contacts in accordance with the size of the capacitor
required or with a common ground and separate electrodes for separate signal contacts.
The invention also contemplates, in certain applications, a lamination having a common
grounding electrode with separate signal electrodes for the filter capacitor. The
filter of the invention being as mentioned tape-like and laminated is, in all events,
made quite thin and flexible so as to be foldable over the pressed against substantially
flat portions of the outside surface of the connector housing and attached thereto
as by adhesive or bonding or structures intended to hold the filter in place on the
housing so that the connector/filter assembly can be handled as one element. The filter
tapes may be mechanically secured to the connector housing by means of the solder
joints with signal and ground contacts of the connector, and optionally further secured
by a plastic covering thereover assembled to the connector after soldering. Through
this technique, the volumetric change by adding the filter is minimized and the invention
is adaptable to existing connector designs, being added thereto in a straightforward
assembly technique.
[0011] The filter of the present invention can also be utilized with other electrical articles
such as printed circuit boards, where the signal and ground electrodes could be soldered
directly to exposed contact pads of the boards's signal and ground traces, for example.
The filter could also be used around a length of shielded signal transmission cable.
[0012] The method of the present invention includes the steps of providing a tape filter
for a particular selected connector, electrically connecting each signal electrode
with a portion of corresponding signal terminal of the connector extending from the
connector housing or at least exposed along the surface of the housing, wrapping the
tape filter along outer surfaces of the connector so that it is disposed adjacent
the surfaces thereof, and electrically connecting each ground electrode with a ground
shell or shield of the connector.
[0013] The present invention will now be described by way of example with reference to the
accompanying drawings in which:
FIGURE 1 is an isometric view showing an electrical connector positioned above two
representative tape filters of the present invention prior to an assembly thereof;
FIGURE 2 is a view of the elements of FIG. 1 in partial assembly;
FIGURE 3 is a side, elevation and partially sectioned view of the end of the filter
as connected to a contact of the connector;
FIGURE 4 is an isometric view of the connectors of FIGS. 1 and 2 in the fully assembled
condition;
FIGURE 5 is an isometric view of the end of the filter and the connection to the ground
circuit of the connector;
FIGURE 6 is a side and elevation view of the connector and filter of FIG. 1;
FIGURE 7 is a side and elevation view of the connector just prior to complete assembly;
FIGURE 8 is a side and elevation view of the connector as shown in FIG. 4; and
FIGURE 9 is a plan view of an alternate embodiment of tape filter showing a pair of
signal electrodes.
[0014] Referring now to FIG. 1, an electrical article such as connector assembly 10 is shown
to include a connector 12 and a pair of filters 32 and 32' prior to assembly of connector
and filters. The connector 12 may be taken to be a modular telephone receptacle jack
of a well-known type mountable to a printed circuit board (not shown) at a board connection
or mounting face 25. Connector 12 receives into a cavity at a mating face 29, a modular
telephone plug (not shown) connected to telephone cable to interconnect such cable
and the signals carried thereon through the connectors to the circuit board, telephone
receiver, facsimile receiver, and/or computer. The signals transmitted through the
plug and jack connectors to the circuit receiving signals may carry unwanted frequencies
that find their way onto the cable through radiation of fields, induction, leakage
from other circuits and the like. It is these unwanted frequency components that can
cause error, particularly with respect to the interpretation of digital 1 and O information
that makes up digital transmission. It is the purpose of the present invention to
filter out the unwanted frequencies while allowing the frequencies that constitute
the proper signal representations, namely, voltage levels, to pass through the connector
and into the circuit and apparatus receiving such signals.
[0015] Construction of a connector like connector 12 is relatively well known, and includes
a plastic housing 14 having on the face thereof a shielding and grounding structure
16 that includes posts 18 extending from the bottom of the connector as shown in FIGS.
1 and 2 for connection to circuits of the board. Housing 14 includes a series of grooves
20 that extend from the top and through selected rearwardly projecting portions. Grooves
20 contain sets of signal contacts 22 and 24, offset as shown in FIG. 1, with the
contacts ending in posts 28,26 coextending below the bottom surface or mounting face
25 to be terminated to conductive traces of the board, along with the grounding post
18 of shield 16. The front ends of contacts 22 and 24 (not shown) are formed to extend
into the plug- receiving cavity at mating face 29 to receive portions of contacts
of the mating plug connector connected to signal cable. Housing 14 includes a resilient
mounting fastener 30 also extending from the bottom or mounting face 25 of the connector
that plugs into a corresponding aperture of the circuit board served by the connector.
The fastener 30 is shown in more detail in FIGS. 6 to 8 to include an interior slot,
a barbed edge 31 that will latch and lock the connector housing 12 to the board prior
to soldering posts 18, 26, and 28 to the board.
[0016] The shielding structure 16 includes opposed side portions 15 and at the top thereof
a portion 17 as shown in FIGS. 1, 2, 4 and 5 and, as shown in FIGS. 4, 5, and 8 is
folded down against the top surface of housing 12. As can also be discerned from the
various figures, the housing 12 has an exterior surface comprised of a top, rear,
sides, and a bottom. The top and sides represent relatively flat planar surfaces,
the rear also containing flat surfaces as well as the reliefs as shown in the various
figures.
[0017] In accordance with the invention, representative filters are included for two of
the six signal contacts, the filters being shown carried by two filter elements 32
and 32'; it being understood that all six signal conductors can be filtered in the
manner to be described. As can be seen in FIG. 1, the filter element 32 includes an
upper electrode 34 and a lower electrode 38. A substrate of dielectric material 36
is provided therebetween in the manner shown in FIG. 3. At the forward end of the
element 32 is a finger 35 of upper electrode 34 defining a signal connection section,
apertured as at 37 with the aperture aligned to receive the inner post 28 inserted
therethrough and soldered thereto as by a solder fillet S as shown in FIG. 3. At the
rear is a grounding finger 39 of lower electrode 38 defining a ground connection section
that is soldered to ground shielding structure 16 in final assembly. Posts 26,28 defining
signal connection sites spaced from each other, and top portion 17 of shield 16 defines
a ground connection site remote from all signal connection sites. Finger 35 is shown
laterally staggered and otherwise electrically separated from the other filter element
32' to allow clearance and nonengagement with a post 26 extending therepast for termination
to electrode 34' of element 32', noting the finger 35' and aperture 37' associated
with post 26. Element 32' also includes a grounding finger 39'.
[0018] Each of the filter elements is comprised then of an upper electrode 34 and a lower
electrode 38 separated by a substrate 36 of dielectric material. Such an element can
be formed such as by first laminating respective layers of conductive material to
respective surfaces of a sheet of the dielectric material, after which an etching
process defines the boundaries of the respective electrodes, in which process a plurality
of such tape filters can conveniently be fabricated. Preferably outwardly facing surfaces
of the electrodes have an insulative covering after etching, such as by spraying with
a polymer paint or by lamination to a polymeric film except at soldering sites of
the electrodes. The individual electrodes 34,34', one for each of the signal contacts
associated with one post 28 and one for each signal contact associated with one post
26 and with common grounding electrodes 38 and 38', have areas selected in conjunction
with the particular dielectric material having a particular dielectric constant and
the thickness of the coating 36 to provide a desired capacitance associated with each
signal contact and, in essence, connecting each signal contact through the capacitive
material to ground through the common ground electrode 38. As is well known, capacitance
is a function of area of electrode, dielectric constant of the dielectric material,
and the spacing between electrodes with capacitance values decreasing as the space
between electrodes is increased and with capacitance increasing with the dielectric
value increasing.
[0019] In accordance with one embodiment of the invention, the electrodes were formed of
foils each on the order of about 0.0014 inches thick, with the substrate on the order
of 0.002 inches thick, the package thus formed being on the order of 0.005 inches
thick. A film of polymeric material such as PHEOPLEX LC 40 acrylic emulsion adhesive
sold by Rohm and Haas, Inc., Philadelphia, PA having a matrix of acrylic polymer with
barium titanate filler homogeneously dispersed therein on the order of about fifty
percent by weight, with particle size of about one micron, was employed for the dielectric
material. The conductive layers were of half-ounce copper which were joined to the
sheet of dielectric material with a three-ply heat and pressure laminating machine.
[0020] The lamination thus formed was found to have a capacitance varying between 400 and
480 picofarads when the individual electrodes were on the order of 0.200 inches wide
and 1 inch in length. The resulting capacitance provided an attenuation beginning
at on the order of several dB insertion loss at slightly less than 10 Mhz rising to
on the order of 12 to 15 dB at around 100 MHz and peaking for the 400 picofarad capacitance
at about 34 dB at around 250 MHz. The 480 picofarad sample had an insertion loss at
slightly less than 30 dB at a frequency of around 200 to 300 MHz. The use of an appropriate
amount of barium titanate in the polymer further provides a voltage withstanding of
1000 volts of greater, needed for certain FCC requirements.
[0021] Alternatively a pair of opposing foils of anodized aluminum could be utilized, laminated
to a sheet of the barium titanate-filled polymer; or a coating of barium titanate-filled
polymer may be screen printed or sprayed onto one sheet of foil as the other foil
sheet is then laminated thereonto; and then after application of masking of appropriate
geometry, the foil sheets are etched in conventional manner to result in a structure
similar to the etched electrode structure described above, after which dielectric
coating such as 350 CC epoxy sold by Mavidon Corp., Palm City, FL, may be applied
to one or both electrode outer surfaces. The tape filters may then be cut from the
sheet of dielectric material.
[0022] The filters 32 and 32' were in turn laminated with a thin insulating film therebetween
(not shown) electrically isolating electrode 38 from electrode 34', in the fashion
shown in FIG. 2 with the various separate electrodes soldered to the various contacts
22 and 24 at respective post portions 26 and 28. The lamination was folded around
from the bottom of the connector housing 14, up the back, resting on the flat surfaces
thereof, and across the top in the manner shown in FIG. 7, traversing grooves 20 and
18 seen in FIGS. 1 and 2 and being disposed between raised lips 41 of housing 12 for
protection against the side edges being snagged and the filters becoming dislodged
or otherwise stressing the solder termination joints. The filter elements 32,32' are
shaped and dimensioned such that the signal connection sections defined by fingers
35,35' are staggered with respect to each other and are adjacent respective signal
connection sites (posts 26,28); ground connection sections defined by fingers 39,39'
are staggered with respect to each other and are adjacent the ground connection site
defined by top portion 17 of shield 16.
[0023] With the end of the elements 32 and 32' folded down against the upper surface, the
projection 17 was then folded down over the top of the fingers 39 and 39' of the filters
in the manner shown in FIG. 8 and in the manner shown in FIG. 5. As can be seen in
FIG. 5, a solder fillet S' interconnects finger 39 of electrode 38 to projection 17
and thus to shielding structure 16 and the fillet solder S" connects the finger 39'
to electrode 38' of the element 32' to the same grounding structure. In this fashion,
two filter elements such as 32 and 32' may be folded as shown and terminated to the
grounding structure. It may be desired after soldering, for a plastic covering to
be molded over the filter tapes for protection thereof, or alternatively a premolded
plastic cover to be secured to the connector over the filter tapes by conventional
methods to protect the filter tapes.
[0024] The invention contemplates additional elements such as 32 that may be individually
grounded rather than commonly grounded as shown and terminated by using fingers such
as 39 and 39' appropriately. The invention also contemplates that where necessary
to achieve a desired capacitance, the area of the electrodes, such as electrodes 34,
may be increased for a given signal contact with additional elements provided for
the remaining signal electrodes. Also contemplated is the use of additional area achieved
by providing electrodes 40 extending over the sides of the housing in the manner shown
in phantom in FIG. 8, such additional area providing an increased capacitance for
the device.
[0025] The invention contemplates a use with one signal contact and one ground contact or
with two, four, or six contacts. For example, FIG.9 is an alternate embodiment of
tape filter 80 adapted to filter two contacts by means of one tape structure. Tape
filter 80 is shown having two signal electrodes 82,84 on a common side of the dielectric
substrate, separated by a gap 86. A single common ground electrode 88 is disposed
across the opposed surface of the substrate. Each of the signal electrodes 82,84 have
respective fingers 90,92 extending to traverse the axis of the corresponding signal
terminals of the connector (not shown), with the terminals received through respective
apertures 94,96 through the fingers 90,92 and soldered thereto, upon assembly of the
tape filter to the connector. Ground electrode 88 is shown to include grounding fingers
98 extending beyond the extent of signal electrodes 82,84 for soldering to a ground
shield of the connector (not shown).
[0026] Various layouts utilizing various portions of the exterior area of the housing may
be employed with adequate areas for the desired capacitance as indicated. Having now
described the invention to enable a preferred practice thereof, claims are appended
intended to define what is inventive.
ADVANTAGES OF THE INVENTION:
[0027] An advantage of the present invention is to provide an electrical connector with
a tape filter. Another advantage of the invention is to mount the tape filter along
an exterior surface of the connector housing connecting one electrode of the tape
filter to a signal contact of the connector and the other electrode of the tape filter
is connected to a shield member on the housing.
1. An electrical connector assembly (10) comprising a dielectric housing (14) having
electrical contacts (22,24) secured therein and including posts (26,28) extending
outwardly from a mounting surface (25), a shield member (16) mounted on said housing
(14), and a filter element (32,32') electrically connected to at least one of said
posts (26,28), characterized in that:
said filter element (32) includes electrodes (34,38) separated by a dielectric material
(36), one of said electrodes (34) being electrically connected to said one of said
posts (26,28), said filter element (32) extending along a section of said dielectric
housing (14) and being electrically connected to said shield member (16).
2. An electrical connector assembly as claimed in claim 1, characterized in that said
filter element (32) includes a contact finger (35) electrically connected to said
post.
3. An electrical connector assembly as claimed in claims 1 or 2, characterized in
that said filter element (32) includes a ground finger (39) electrically connected
to said shield member (16).
4. An electrical connector as claimed in any of claims 1-3, characterized in that
said shield member (16) has a top portion (17) bent into engagement with said housing
(14).
5. An electrical connector assembly as claimed in any of claims 1-4, characterized
in that said housing (14) has flat surfaces along the back and top thereof, said filter
element (32) extending along said flat surfaces.
6. A method of applying a filter element (32) to an electrical article (12) of the
type having a dielectric housing (14) having first and second faces (25,29) and at
least one signal contact member (22,24) having first and second contact sections exposed
respectively at said first and second faces for defining a signal transmission circuit
between corresponding electrical conductors for signal transmission therebetween,
and further having a grounding means (16) having a portion at least exposed along
an outer surface of the housing remote from said first face (25), said article having
a known configuration and outer surface topography, characterized by the steps of:
providing with respect to each said signal contact (22,24) of said article, a filter
element (32) having at least one signal electrode (34) for connection to a respective
said signal transmission circuit and having a ground electrode (38) for connection
to the grounding means (16) with said filter electrically disposed therebetween and
defined by dielectric material (36) having characteristics to transmit the unwanted
signal frequency components from said signal transmission circuit to said grounding
means (16), said filter having a thin flat configuration and being sufficiently flexible
to be formed into a selected shape and further having a two dimensional shape selected
to correspond with those portions of the exterior surface of said electrical article
(12) extending between said first face (25) and said exposed portion of said grounding
means (16);
joining said signal electrode (34) proximate a first portion of said filter element
to an exposed portion (28) of a respective said signal contact (22);
pressing said filter member (32) against and along said exterior surface portions
of said housing (14) of said electrical article; and
joining said ground electrode (38) proximate a second portion of said filter element
remote from said first portion to an exposed portion (17) of said grounding means
(16),
whereby said filter element (32) extends over portions of said flat surface to conform
at least in part to the geometry of an exterior surface of the electrical article
(12) containing said signal transmission circuits, thereby minimizing the volume of
the filter element/article combination while filtering a preexisting electrical article
without modification thereof being necessary.
7. The method of claim 6, characterized in that said joining steps comprise soldering.
8. The method of claims 6 or 7, characterized in that said exposed portion (17) of
said grounding means (16) is bent into engagement with said housing after said ground
electrode (38) is joined to said exposed portion (17).