Electrical connector with conductive plastic features

CROSS-REFERENCES TO RELATED APPLICATIONS

Not Applicable.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not Applicable.

Reference to Microfiche Appendix

Not Applicable

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates generally to electrical connectors and more specifically to high speed electrical connectors.

2. Description of Related Art

Electrical connectors are widely used in the manufacture of electronic systems because they allow the system to be built in separate pieces that can then be assembled. Board-to-board connectors are widely used because sophisticated electronic systems are usually fabricated on multiple printed circuit boards. To assemble the electronic system, the printed circuit boards are electrically connected.

In the description that follows, the invention will be illustrated as applied to a board to board connector. In particular, the invention will be illustrated in connection with a backplane-daughter card interconnection system. Many electronic systems, such as computer servers or telecommunications switches are built using a backplane and multiple “daughter” cards. In such a configuration, the active circuitry of the electronic system is built on the daughter cards. For example, a processor might be built on one daughter card. A memory bank might be built on a different daughter card. The backplane provides signal paths that route electrical signals between the daughter cards.

Generally, electrical connectors are mounted to both the backplane and the daughter card. These connectors mate to allow electrical signals to pass between the daughter card and the backplane.

Because the electronic systems that use a backplane-daughter card configuration usually process much data, there is a need for the electrical connectors to carry much data. Furthermore, this data is generally transmitted at a high data rate. There is simultaneously a need to make the systems as small as possible. As a result, there is a need to have electrical connectors that can carry many high speed signals in a relatively small space. There is thus a need for high speed-high density connectors.

Several commercially available high-speed, high density electrical connectors are known. For example, U.S. Pat. No. 6,299,483 to Cohen et al. entitled High Speed High Density Electrical Connector is one example. Teradyne, Inc., the assignee of that patent, sells a commercial product called VHDM®. Another example may be found in U.S. Pat. No. 6,409,543 to Astbury, et al. entitled Connector Molding Method and Shielded Waferized Connector Made Therefrom. Teradyne, Inc., the assignee of that patent, sells a commercial product called GbX™. The foregoing patents arc hereby incorporated by reference.

Both of the above-described electrical connectors employ insert molding construction techniques, at least for the daughter card connectors. Subassemblies, called wafers, are formed around individual columns of signal contacts. The wafers are formed by molding a dielectric material around the metal signal contacts. The wafers are then stacked side by side to make a connector of the desired length.

One of the difficulties that results when a high density, high speed connector is made in this fashion is that the electrical conductors can be so close that there can be electrical interference between adjacent or nearby signal conductors. To reduce interference, and to otherwise provide desirable electrical properties, metal members are often placed between or around adjacent signal conductors. The metal acts as a shield to prevent signals carried on one conductor from creating “cross talk” on another conductor. The metal also impacts the impedance of each conductor, which can further contribute to desirable electrical properties.

Generally, the metal members are made from separate pieces of metal that are added to the connector. However, it has also been suggested that a metal coating be applied to the connector. Also, in some connectors, the base material of the housing is formed of metal, usually as a die cast part. Then, insulative members are inserted to preclude the signal conductors of the connector from being shorted by the metal housing.

A drawback of forming the shields from separate pieces of metal is that additional pieces are required to assemble the connector. The additional pieces increase the cost and complexity of manufacturing the connector. In some cases, shield pieces are stamped and formed to create tabs or projections that extend between adjacent signal conductors. This configuration reduces the number of separate pieces because the projections stay attached to the sheet, so only one additional piece is required. However, a drawback of forming a sheet with projections extending from it is that forming the projection leaves a hole in the sheet. Thus, while the projection increases shielding between signal conductors that are adjacent along a line running in one direction, leaving a hole in the shield sheet decreases shielding between signal conductors that are adjacent along a line running in an orthogonal direction. A further drawback of stamping and forming projections from a single shield member is that it is difficult to form projections that have bends or corners—which are often needed to follow contours of signal contacts in some connectors, such as right angle connectors.

A drawback of coating metal onto a plastic is that there are no combinations of readily available and inexpensive metals and plastics that can be used. Either the metal does not adhere well to the plastic or the plastic lacks the desired thermal or mechanical properties needed to make a suitable connector. A further drawback of coating metal onto plastic is that available plating techniques are not selective. The portions of the connector housing which should not be conductive must be masked before the coating is applied. For example holes in the housing that hold signal contacts are often filled with plugs before coating, which are then removed after coating. A drawback of manufacturing connectors using a die cast metal housing is the complexity arising from the use of insulative inserts. Further, there is a limit to how thin features on a die cast part can be made. Generally, a die cast housing will have thicker parts. Using thicker housing parts is generally undesirable because it reduces the overall density of the connector. Die cast metals are more expensive than typical plastic parts.

It would be highly desirable to provide a connector with desirable electrical properties that is easy to manufacture and provides a high signal density.

BRIEF SUMMARY OF THE INVENTION

With the foregoing background in mind, it is an object of the invention to provide a high speed, high density electrical connector that is easy to manufacture.

The foregoing and other objects are achieved in an electrical connector that is molded from different types of material to form at least two regions of distinct electrical properties. One region is formed from material filled with conducting material to alter the electrical properties.

In a preferred embodiment, an electrical connector having electrical conductors in a plurality of rows is provided, wherein each of the plurality of rows includes a housing and a plurality of electrical conductors. Each electrical conductor has a first contact end connectable to a printed circuit board, a second contact end and an intermediate portion therebetween that is disposed within the housing. The housing includes a first region surrounding each of the plurality of electrical conductors, the first region made of insulative material and extending substantially along the length of the intermediate portion of the electrical conductors. The housing also includes a second region adjacent the first region and extending substantially along the length of the intermediate portion of the electrical conductors. The second region is made of a material with a binder containing conductive fillers.

BRIEF DESCRIPTION OF THE DRAWINGS

Additional objects, advantages, and novel features of the invention will become apparent from a consideration of the ensuing description and drawings, in which—

FIG. 1

is a sketch of an electrical connector as known in the prior art;

FIG. 2

is a sketch of a wafer of the electrical connector of

FIG. 1

;

FIG. 3

is a sketch of the wafer of

FIG. 2

at a stage in its manufacture;

FIGS. 4A and 4B

are cross sectional views of different embodiments of a wafer of an electrical connector made according to the invention;

FIG. 5

is a schematic illustration of a molding machine suitable for use in making a connector according to the invention;

FIG. 6

is a sketch of a prior art backplane connector; and

FIGS. 7A and 7B

are views of a backplane connector made according to the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to

FIG. 1

, a two piece electrical connector

100

is shown to include a backplane connector

105

and a daughtercard connector

110

. The backplane connector

105

includes a backplane shroud

102

and a plurality of signal contacts

112

, here arranged in an array of differential signal pairs. In the illustrated embodiment, the signal contacts are grouped in pairs, such as might be suitable for manufacturing a differential signal electrical connector. A single-ended configuration of the signal contacts

112

is also contemplated in which the signal conductors are evenly spaced. In the prior art embodiment illustrated, the backplane shroud

102

is molded from a dielectric material. Examples of such materials are liquid crystal polymer (LCP), polyphenyline sulfide (PPS), high temperature nylon or polypropylene (PPO). All of these are suitable for use as binder materials in manufacturing connectors according to the invention.

The signal contacts

112

extend through a floor

104

of the backplane shroud

102

providing a contact area both above and below the floor

104

of the shroud

102

. Here, the contact area of the signal contacts

112

above the shroud floor

104

are adapted to mate to signal contacts in daugthercard connector

110

. In the illustrated embodiment, the mating contact area is in the form of a blade contact.

A tail portion of the signal contact

112

extends below the shroud floor

104

and is adapted to mating to a printed circuit board. Here, the tail portion is in the form of a press fit, “eye of the needle” compliant contact. However, other configurations are also suitable such as surface mount elements, spring contacts, solderable pins, etc. In a typical configuration, the backplane connector

105

mates with the daughtercard connector

110

at the blade contacts and connects with signal traces in a backplane (not shown) through the tail portions which are pressed into plated through holes in the backplane.

The backplane shroud

102

further includes side walls

108

which extend along the length of opposing sides of the backplane shroud

102

. The side walls

108

include grooves

118

which run vertically along an inner surface of the side walls

108

. Grooves

118

serve to guide the daughter card connector

110

into the appropriate position in shroud

102

. Running parallel with the side walls

108

are a plurality of shield plates

116

, located here between rows of pairs of signal contacts

112

. In a presently preferred single ended configuration, the plurality of shield plates

116

would be located between rows of signal contacts

112

. However, other shielding configurations could be formed, including having the shield plates

116

running between the walls of the shrouds, transverse to the direction illustrated. In the prior art, the shield plates are stamped from a sheet of metal.

Each shield plate

116

includes one or more tail portions, which extend through the shroud base

104

. As with the tails of the signal contacts, the illustrated embodiment has tail portions formed as an “eye of the needle” compliant contact which is press fit into the backplane. However, other configurations are also suitable such as surface mount elements, spring contacts, solderable pins, etc.

The daughtercard connector

110

is shown to include a plurality of modules or wafers

120

that are supported by a stiffener

130

. Each wafer

120

includes features which are inserted into apertures (not numbered) in the stiffener to locate each wafer

120

with respect to another and further to prevent rotation of the wafer

120

.

Referring now to

FIG. 2

, a single wafer is shown. Wafer

120

is shown to include dielectric housings

132

,

134

which are formed around both a daughtercard shield plate (

10

,

FIG. 3

) and a signal lead frame. As described in the above-mentioned U.S. Pat. No. 6,409,543, wafer

120

is preferably formed by first molding dielectric housing

132

around the shield plate, leaving a cavity. The signal lead frame is then inserted into the cavity and dielectric housing

134

is then overmolded on the assembly to fill the cavity.

Extending from a first edge of each wafer

120

are a plurality of signal contact tails

128

, which extend from the signal lead frame, and a plurality of shield contact tails

122

, which extend from a first edge of the shield plate. In the example of a board to board connector, these contact tails connect the signal conductors and the shield plate to a printed circuit board. In the preferred embodiment, the plurality of shield contact tails and signal contact tails

122

and

128

, respectively, on each wafer

120

are arranged in a single plane.

Here, both the signal contact tails

128

and the shield contact tails

122

are in the form of press fit “eye of the needle” compliants which are pressed into plated through holes located in a printed circuit board (not shown). In the preferred embodiment, it is intended that the signal contact tails

128

connect to signal traces on the printed circuit board and the shield contact tails connect to a ground plane in the printed circuit board. In the illustrated embodiment, the signal contact tails

128

are configured to provide a differential signal and, to that end, are arranged in pairs.

Near a second edge of each wafer

120

are mating contact regions

124

of the signal contacts which mate with the signal contacts

112

of the backplane connector

105

. Here, the mating contact regions

124

are provided in the form of dual beams to mate with the blade contact end of the backplane signal contacts is

112

. The mating contact regions are positioned within openings in dielectric housing

132

to protect the contacts. Openings in the mating face of the wafer allow the signal contacts

112

to also enter those openings to allow mating of the daughter card and backplane signal contacts.

Provided between the pairs of dual beam contacts

124

and also near the second edge of the wafer are shield beam contacts

126

. Shield beam contacts are connected to daughter card shield plate

10

(

FIG. 3

) and are preferably formed from the same sheet of metal used to from the shield plate. Shield beam contacts

126

engage an upper edge of the backplane shield plate

116

when the daughter card connector

110

and backplane connector

105

are mated. In an alternate embodiment (not shown), the beam contact is provided on the backplane shield plate

116

and a blade is provided on the daughtercard shield plate between the pairs of dual beam contacts

124

. Thus, the specific shape of the shield contact is not critical to the invention.

FIG. 3

shows a wafer at an intermediate step of manufacture. The shield plate

10

is shown still attached to a carrier strip

310

. In a preferred embodiment, shield plates will be stamped for many wafers on a single sheet of metal. A portion of the strip of metal will be retained as a carrier strip. The individual components can then be more readily handled. When manufacturing is completed, the finished wafers

120

can then be severed from the carrier strip and assembled into daughter card connectors.

In

FIG. 3

, dielectric housing

132

is shown molded over a shield. Insert molding is known in the art and is used in the connector art to provide conductors within a dielectric housing. In this prior art connector, dielectric material is molded over the majority of the surface of shield

10

. Additionally, the dielectric is largely on the upper surface of shield, leaving the lower surface of the shield exposed.

Tabs

322

on the shield plate are visible because dielectric housing

132

is molded to leave windows

324

around tabs

322

. Likewise, holes

22

and

24

are visible because no dielectric housing has been molded around them.

Various features are molded into dielectric housing

132

. Cavity

350

bounded by walls

352

is left generally in the central portions of the housing

132

. Channels

324

are formed in the floor of cavity

350

by providing closely spaced projecting portions of dielectric housing. Channels

324

are used to position signal conductors. Also, openings

326

are molded to allow a mating contact area for each signal contact. The front face of dielectric housing

132

creates the mating face of the connector and contains holes to receive the mating contact portion from the backplane connector, as is known in the art. The walls of opening

326

protect the mating contact area.

To complete the manufacture of the prior art connector shown in

FIG. 3

, a signal lead frame is inserted into cavity

350

. Cavity

350

is then filled with additional dielectric material to form dielectric housing

134

, thereby locking the signal conductors into the wafer. Holes

22

and

24

represent openings through which stabilizers, sometimes called “pinch pins,” can be inserted into the part as dielectric housing

134

is being molded. The pinch pins hold the signal lead frame in place as the part is being molded.

According to the invention, a similar molding process will be used. However, different types of material will be used in molding the housing pieces of each wafer. In particular, in addition to the dielectric material used in the prior art, a material with different electromagnetic properties is used to form a portion of the housing for the wafer. In particular, portions of the housing will be formed from material that selectively alters the electrical properties of the housing, thereby suppressing cross talk, altering the impedance of the signal conductors or otherwise imparting desirable electrical properties to the connector. In the preferred embodiment, some portion of the material used to mold the connector housing will be an insulator and some portion will have a higher conductivity.

In accordance with the preferred embodiment, prior art molding material will be used to create the portions of the connector housing that need to be non-conducting to avoid shorting out signal contacts or otherwise creating unfavorable electrical properties. Also, in the preferred embodiment, those portions of the connector housing for which no benefit is derived by using a material with different electromagnetic properties are also made from prior art molding materials, because such materials are generally less expensive and mechanically stronger than the electromagnetic materials to be described below.

Prior art electrical connector molding materials are generally made from a thermoplastic binder into which non-conducting fibers are introduced for added strength, dimensional stability and to reduce the amount of higher priced binder used. Glass fibers are typical, with a loading of about 30% by volume.

In a preferred embodiment of the invention, electromagnetic fillers are used in place of or in addition to the glass fibers for portions of the connector housing. The fillers can be conducting or can be ferroelectric, depending on the electrical properties that are desired from the material.

To simulate a metal shield insert, it is preferable that a conducting filler be used. Examples of suitable conducting fillers are stainless steel fibers, carbon fibers, nanotube material, carbon flake or nickel-graphite powder. Blends of materials might also be used.

In a preferred embodiment, the binder is loaded with conducting filler between 10% and 80% by volume. More preferably, the loading is in excess of 30% by volume. Most preferably, the conductive filler is loaded at between 40% and 60% by volume.

When fibrous filler is used, the fibers preferably have a length between 0.5 mm and 15 mm. More preferably, the length is between 3 mm and 11 mm. In one contemplated embodiment, the fiber length is between 3 mm and 8 mm.

In one contemplated embodiment, the fibrous filler has a high aspect ratio (ratio of length to width). In that embodiment, the fiber preferably has an aspect ratio in excess of 10 and more preferably in excess of 100.

Filled materials can be purchased commercially, such as materials sold under the trade name Celestran® by Ticona. Or, suitable material could be custom blended as sold by RTP Company.

Preferably, the binder material is a thermoplastic material that has a reflow temperature in excess of 250° C. and more preferably in the range of 270-280° C. LCP and PPS are examples of suitable material. In the preferred embodiment, LCP is used because it has a lower viscosity. Preferably, the binder material has a viscosity of less than 800 centipoise at its reflow temperature without fill. More preferably, the binder material has a viscosity of less than 400 centipoise at its reflow temperature without fill.

The viscosity of the molding material when filled can not be made arbitrarily high. Preferably, the material has a viscosity low enough to be molded with readily available molding machinery.

When filled, the molding material preferably has a viscosity below 2000 centipoise at its reflow temperature and more preferably a viscosity below 1500 centipoise at its reflow temperature. It should be appreciated that the viscosity of the material can be decreased during molding operation by increasing its temperature or pressure. However, binders will break down and yield poor quality parts if heated to too high a temperature. Also, commercially available machines are limited in the amount of pressure they can generate. If the viscosity in the molding machine is too high, the material injected into the mold will set before it fills all areas of the mold.

In connectors for which the conductive plastic material is molded to act as a shield, preferably, the binder is filled to provide a surface resistivity of less that 10

5

Ω/sq. More preferably, the surface resistivity is less than 10

2

Ω/sq. Resistivity might also be expressed as a bulk or volume resistivity. Preferably, the volume resistivity is less than 10 Ω-cm and more preferably less than 1 Ω-cm and more preferably less than 0.8 Ω-cm.

The use of plastics filled with electromagnetic materials for a portion of the connector housing allows electromagnetic interference between signal conductors to be reduced. In a preferred embodiment, housing

132

is molded with materials that contains conductive filler. If sufficiently conductive, the conductive filler acts like an extension of the shield plate

10

. Even if not fully conductive, the filled plastic can absorb signals radiating from the signal conductors that would otherwise create crosstalk.

FIG. 4

shows a portion of wafer

120

that has been molded with two types of material according to the invention. In

FIG. 4A

, housing

132

is shown formed from a material with conductive filler. Housing

134

is formed from an insulator with little or no conductive fillers.

Housing

132

is electrically in contact with shield

10

, which will preferably be grounded in a connector system. Therefore, housing

132

is preferably grounded. To increase the electrical connection between housing

132

and shield plate

10

, projections can be provided from shield plate

10

.

FIG. 4A

shows, as an example, tab

460

bent out of the plane of shield plate

10

and projecting into housing

132

.

If sufficiently conductive, housing

132

acts as an extension of shield

10

. Projections

414

A,

414

B . . . are positioned between adjacent signal conductors used to carry different signals. They therefore provide shielding between the signal conductors. Significantly, because projections

414

A,

414

B . . . are molded from plastic, they can be in almost any shape and can follow the contours of the signal conductors

410

A,

410

B . . . through the connector.

In the embodiment of

FIG. 4A

, wafer

120

is designed to carry differential signals. Thus, each signal is carried by a pair of signal conductors. And, preferably, each signal conductor is closer to the other conductor in its pair than it is to a conductor in an adjacent pair. For example, a pair of signal conductors

410

A and

410

B carry one differential signal and signal conductors

410

C and

410

D carry another differential signal. Thus, projection

414

B is positioned between these pairs to provide shielding between the adjacent differential signals.

Projection

414

A is at the end of the column of signal conductors in wafer

120

. It is not shielding adjacent signals in the same column. However, having shielding projections at the end of the row helps prevent cross-talk from column to column.

To prevent signal conductors

410

A,

410

B . . . from being shorted together through conductive housing

132

, a second molding step is used to create insulative portions such as

450

A and

450

B in the housing. Once the signal conductors arc inserted, further dielectric material is molded over the part to finish housing

134

.

FIG. 4B

shows an alternative implementation of wafer

120

′. Wafer

120

′ is designed for single ended signals. Therefore, a projection, such as

414

B,

414

C,

414

D . . . is positioned between adjacent signal conductors, which are relatively uniformly spaced. In

FIG. 4B

, insulative portions

452

A,

452

B . . . are molded between the projections

414

B,

414

C,

414

D . . . to ensure that the signal conductors are not shorted to the conducting portions of the housing.

FIG. 5

is a simplified sketch of a machine to make a connector according to the invention. Molding machine

500

is a two-shot molding machine, generally as known in the art. Such machines arc used for things such as molding knobs, toohbrushes or buttons in two colors of plastic.

Molding machine

500

has three molding chambers

510

A,

510

B and

510

C. Each molding chamber is made of a lower chamber, such as

512

A, and an upper chamber, such as

514

A. Upper chamber

514

A is moveable, allowing the upper and lower chamber to separate. As is traditional in the molding art, mold pieces separate to allow removal of molded parts or to place conducting members into the chamber to prior to injection of molding material to insert mold the conducting members into the molding material.

In the illustrated embodiment, the lower chambers

512

A,

512

B and

512

C are identical. Each lower chamber has a mold cavity that has the same contour as the lower portions of the part to be molded. Upper chamber

514

A is shaped to mate with any of the lower chambers and form a mold cavity that ha contour matching the desired contour of the part being molded after one type of molding material has been applied. For example, in the case of a wafer as shown in

FIG. 4

, mold chamber

510

A has a contour that matches shield

10

with housing

132

molded on it—but without housing

134

in place.

Mold chamber

510

B has a contour that matches the upper surface of housing

132

with inserts

450

A and

450

B in place.

Mold chamber

510

C has a contour that matches the contour of the finished part. To provide this result, upper chamber

514

B will have a different shape than upper chamber

514

A. In the example of

FIG. 4

, mold chamber

510

C will have a contour that matches the contour of the finished wafer

120

with a shield

10

, housing

132

and

134

in place.

Molding machine

500

includes feed systems

520

A,

520

B and

520

C. As in a conventional molding machine, each of the feed systems provides molding material into a mold cavity. In a preferred embodiment that uses a thermoplastic material as a binder, each feed system includes a hopper of materials in pellet form.

In this preferred configuration, material is dispensed from the hopper and heated to a liquid state. The feed system then injects the liquid material into the mold cavity. For example, and auger screw can be used to provide the required force to inject the material. In

FIGS. 4

5

, the material passes through nozzles

522

A,

522

B or

522

C into a respective mold chamber

510

A,

510

B or

510

C.

In the mold cavity, the material rapidly cools to below its set point. The mold can then be opened. Parts molded in chamber

510

A and

510

B are only partially complete. To finish molding parts from chamber

510

A, the partially finished part is left in lower chamber

512

A. Lower chamber

512

A is then moved below upper chamber

514

B. Thus, the partially molded part is in chamber

510

B. Additional material can be added to the part. The partially finished part can then be rotated below upper chamber

514

C to complete the operation.

In the illustrated embodiment, lower mold chamber

512

A is mounted on a moving member and moves with the partially molded part into position to form mold chamber

510

B. Here, lower mold chamber

512

A rotates on a turntable-like device. However, other forms of moving members could be used.

For example, a moving member that provided linear motion might be preferred. A shuttle is a suitable moving member that provides linear motion. In some cases, a shuttle-type arrangement would be preferable. Where wafers are formed on carrier strips, it is preferable that the parts move in a straight line so that a “reel to reel” manufacturing line can be set up. In such a line, numerous shield plates would be stamped from a long strip of metal. As part of the stamping, a carrier strip would be left and each of the shield plates would be attached to the carrier strip. The strip would be wound on a reel. The reel would feed shields one at a time into chamber

510

A. For each cycle of the molding machine, a new shield would be fed into chamber

510

A and a finished part would emerge from chamber

510

B. The finished parts, still on their carrier strips, could then be wound on another reel.

In the illustrated embodiment, feed system

520

A feeds molding material filled with conducting fibers. Depending on the length of fibers used in the filler and the filler content in the binder, such a material is likely to have a higher viscosity than materials traditionally used to mold connector housings. Consequently, greater pressure might be required.

Feed system

520

A must generate sufficient force to inject the filled material. In practice, empirical data is gathered to determined the appropriate settings for molding machine

500

. However, it is expected that the feed system providing conductor filled plastic will deliver material at a higher pressure.

Furthermore, nozzle

522

A, which delivers the conductor filled plastic at higher pressure will have a larger orifice. Furthermore, the combination of higher pressure and conductive fillers, which could be abrasive, is likely to cause additional wear in feed system

520

A. To counteract these problems, nozzle

522

A is preferably made of a hardened material, such as carbide steel.

Other parts of molding machine

500

exposed to the conductor filled plastic are also likely to experience excessive wear and can likewise be made of hardened materials and might be made easily replaceable. For example, carbide mold inserts might be used to reduce wear and also to allow easy replacement.

Turing to

FIGS. 6 and 7

, an example of application of the invention to a backplane connector is shown.

FIG. 6

shows a prior art backplane connector

605

. Backplane connector

605

has a shroud

610

. To enhance shielding, shroud

610

is die cast of metal.

Shields

616

may make direct electrical contact to the metal housing, as both are intended to be connected to ground in operation. However, signal conductors

612

would be shorted out if inserted directly into the metal housing. Insulative spacer member

620

is inserted into shroud

610

to prevent signal conductors

612

from being shorted out by the conducting housing of backplane connector

605

.

The implementation shown in

FIG. 6

has the drawback of being made of relatively expensive die cast parts and has separate pieces that add cost to the assembly operation. Using the molding technique according to the invention, a connector providing similar performance can be achieved at a lower cost.

FIG. 7A

shows a portion of backplane connector

605

in cross section. Housing

632

is molded of conventional connector molding material. For example, the thermoplastic PPS filled to 30% by volume with glass fiber might be used.

In molding housing

632

a recessed area is left for housing

634

. However, the recessed area includes lands

710

(

FIG. 7B

) that contain areas for receiving signal conductors

612

.

In a second molding step, the recessed area is filled with molding material with conductive filler. Examples of the materials and fillers that might be used for housing

634

are given above.

FIG. 7A

shows a projection

650

from shield

616

into the conductive portion

634

. The projection enhances the electrical conductivity between the shield and the conducting plastic portions. The projection could be in any convenient form, such as a tab or a bend in the shield.

FIG. 7B

shows a top view of the portion of backplane connector

605

shown in FIG.

7

A. Lands

710

are visible in this view. Also, it can be seen that housing

634

is in contact with shields

616

, grounding housing

634

through the ground contacts of shields

616

.

Alternatives

Having described one embodiment, numerous alternative embodiments or variations can be made.

For example, it was described that parts being molded with molding material with different electrical properties are moved from molding station to molding station. It is possible that the parts could be stationary at a molding station with two different material inlets.

As another example, the invention was described as applied to a backplane-daughter card connector. Conductive features might be built into connectors in any configuration, such as stacking connectors or other board to board connectors or in phone jacks or cable connectors. Moreover, the invention was illustrated as applied to both the backplane and daughter card pieces of the connector. It could be used with either or both.

Also, a two step molding operation is described in connection with the backplane connector and a three step operation is described in connection with daughter card wafers

120

. Other types of molding operations might be used. A single step molding might be used in cases where the entire housing is to be conducting. Alternatively, three or more molding steps might be performed. Such a process might be employed where the finished shape of the part is more complicated than can be molded in two steps or where materials with more than two different properties are required in the finished product.

Further, it was shown in

FIG. 4A

that a conductive housing is molded and then an insulative housing is molded. Thereafter, the signal contacts are inserted and a second insulative layer is applied to lock the signal contacts into place. Application of the second insulative layer could be done as a true molding operation using a mold with a cavity shaped to match the desired final contour of the part. Alternatively, a simpler form of “molding” might be used in which the first two operations leave a cavity. Once the signal contacts are inserted into this cavity the second insulative layer is “molded” by putting material into this cavity and leveling it off to leave a smooth upper surface. In this process, a full cavity mold is not required to shape the final part.

FIG. 5

shows a molding machine that has two mold chambers operating simultaneously. For each cycle of the molding machine, a part is being molded with the first type material and another part is being molded with the second type of material. One complete part can therefore emerge from mold chamber

510

B each cycle. As shown, there is no loss of efficiency from having a two step molding operation. It would be possible, however, to manufacture parts with molding steps done sequentially rather than simultaneously. Sequential molding equipment might be lower cost, but would have lower throughput.

Also, it should be appreciated that preferred lengths and aspect ratios of fibers are described. It should be appreciated that all fibers in a batch will not have precisely uniform properties. Thus, when reference is made to an upper or lower limit on properties of fibers or other materials, it should be appreciated that not every fiber will meet this limit. Rather, the limits should be interpreted as meaning that most of the fibers meet that limitation.

While the invention has been particularly shown and described with reference to the preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the invention.

Number	Name	Date	Kind
4195272	Boutros	Mar 1980	A
4276523	Boutros et al.	Jun 1981	A
4682129	Bakermans et al.	Jul 1987	A
4761147	Gauthier	Aug 1988	A
5551893	Johnson	Sep 1996	A
6174203	Asao	Jan 2001	B1
6364711	Berg et al.	Apr 2002	B1

Electrical connector with conductive plastic features

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US Referenced Citations (7)