Electrical connectors – Electromagnetic or electrostatic shield – Multi-part shield body
Reexamination Certificate
2000-02-03
2001-09-25
Donovan, Lincoln (Department: 2832)
Electrical connectors
Electromagnetic or electrostatic shield
Multi-part shield body
C439S108000
Reexamination Certificate
active
06293827
ABSTRACT:
This invention relates generally to electrical connectors for electronic systems and more particularly to electrical connectors for high speed, high density systems.
Electrical connectors are used in many electronic systems. It is generally easier and more cost effective to manufacture a system on several printed circuit boards which are then joined together with electrical connectors.
A traditional arrangement for joining several printed circuit boards is to have one printed circuit board serve as a backplane. Other printed circuit boards, called daughter boards, are connected through the backplane.
A traditional backplane is a printed circuit board with many connectors. Conducting traces in the printed circuit board connect to signal pins in the connectors so that signals may be routed between the connectors. Other printed circuit boards, called “daughter boards” also contain connectors that are plugged into the connectors on the backplane. In this way, signals are routed among the daughter boards through the backplane. The daughter cards often plug into the backplane at a right angle. The connectors used for these applications contain a right angle bend and are often called “right angle connectors.”
Connectors are also used in other configurations for interconnecting printed circuit boards, and even for connecting cables to printed circuit boards. Sometimes, one or more small printed circuit boards are connected to another larger printed circuit board. The larger printed circuit board is called a “mother board” and the printed circuit boards plugged into it are called daughter boards. Also, boards of the same size are sometimes aligned in parallel. Connectors used in these applications are sometimes called “stacking connectors” or “mezzanine connectors.”
Regardless of the exact application, electrical connector designs have generally needed to mirror trends in the electronics industry. Electronic systems generally have gotten smaller and faster. They also handle much more data than systems built just a few years ago. To meet the changing needs of these electronic systems, some electrical connectors include shield members. Depending on their configuration, the shields might control impedance or reduce cross talk so that the signal contacts can be placed closer together.
An early use of shielding is shown in Japanese patent disclosure 49-6543 by Fujitsu, Ltd. dated Feb. 15, 1974. U.S. Pat. Nos. 4,632,476 and 4,806,107—both assigned to AT&T Bell Laboratories—show connector designs in which shields are used between columns of signal contacts. These patents describe connectors in which the shields run parallel to the signal contacts through both the daughter board and the backplane connectors. Cantilevered beams are used to make electrical contact between the shield and the backplane connectors. U.S. Pat. Nos. 5,433,617; 5,429,521; 5,429,520 and 5,433,618—all assigned to Framatome Connectors International—show a similar arrangement. The electrical connection between the backplane and shield is, however, made with a spring type contact.
Other connectors have the shield plate within only the daughter card connector. Examples of such connector designs can be found in U.S. Pat. Nos. 4,846,727; 4,975,084; 5,496,183; 5,066,236—all assigned to AMP, Inc. An other connector with shields only within the daughter board connector is shown in U.S. Pat. No. 5,484,310, assigned to Teradyne, Inc.
Another modification made to connectors to accommodate changing requirements is that connectors must be much larger. In general, increasing the size of a connector means that manufacturing tolerances must be much tighter. The permissible mismatch between the pins in one half of the connector and the receptacles in the other is constant, regardless of the size of the connector. However, this constant mismatch, or tolerance, becomes a decreasing percentage of the connector's overall length as the connector gets larger. Therefore, manufacturing tolerances must be tighter for larger connectors, which can increase manufacturing costs. One way to avoid this problem is to use modular connectors. Teradyne Connection Systems of Nashua, N.H., USA pioneered a modular connector system called HD+®, with the modules organized on a stiffener. Each module had multiple columns of signal contacts, such as 15 or 20 columns. The modules were held together on a metal stiffener.
An other modular connector system is shown in U.S. Pat. Nos. 5,066,236 and 5,496,183. Those patents describe “module terminals” with a single column of signal contacts. The module terminals are held in place in a plastic housing module. The plastic housing modules are held together with a one-piece metal shield member. Shields could be placed between the module terminals as well.
A state of the art modular electrical connector is shown in U.S. Pat. Nos. 5,980,321 and 5,993,259 (which are hereby incorporated by reference). That patent shows a plurality of modules, each assembled from two wafers, held together on a metal member, called a “stiffener.” The assignee of those patents, Teradyne, Inc, sells a commercial embodiment under the name VHDM.
FIG. 1
is reproduced from U.S. Pat. No. 5,980,321.
FIG. 1
shows an example of a “right angle” connector. It is used to connect a backplane
110
to a daughter card
112
. The daughter card portion of the connector is made from two pieces—a ground wafer
166
and a signal wafer
168
.
Signal wafer
168
contains a plurality of signal contacts. A housing
172
is molded around the contacts to hold them together. Ground wafer
166
is made from a one-piece metal plate. Plastic is molded around the plate to form an insulative portion
170
.
FIG. 1
shows an exploded view of a module
154
. In use, the signal wafer and ground wafers are securely fastened to each other. Mating regions
158
of the signal contacts are inserted into the insulative portion
170
and are thereby protected.
The module
154
is attached to a support member, which in
FIG. 1
is shown as a metal stiffener
156
. The metal stiffener
156
contains features
160
A,
162
A and
164
A that receive complementary features on module
154
. Those features are illustrated as
160
B,
162
B and
164
B and are formed from the plastic used in molding signal wafer
168
. For simplicity,
FIG. 1
shows a single module
154
. In use, many modules would likely be assembled to a support member to form a connector that would typically be several inches long.
The daughter card connector
116
mates with a pin header
114
. Pin header
114
contains parallel columns of signal contacts
122
that engage with the signal contacts at their mating ends
158
. In use, the connection between daughter card connector
116
and pin header
114
is separable. This separable connection allows daughter cards to be easily installed and removed from a backplane system.
FIG. 1
shows that pin header
114
contains backplane shields
128
between adjacent columns of pin. While backplane shields
128
improve electrical performance, not all connectors need or use shielding in the backplane connector.
Another variation of a modular connector is described in U.S. patent application Ser. No. 09/199,126 (which is hereby incorporated by reference). The assignee of that application, Teradyne, Inc, sells a commercial embodiment under the name HSD. That application also shows a connector in which modules, each assembled from two wafers, are held together on a metal stiffener. These wafers differ from the wafers shown in the U.S. Pat. Nos. 5,980,321 and 5,993,259 in that these wafers have signal contacts with non-uniform spaces. In particular, the signal contacts are arranged in pairs. Each pair carries one differential signal. A differential signal is represented as the difference in voltage levels between two conductors. Differential signals are often used at high speeds because they are much less susceptible to noise than single ended signals. In an ideally balanced pair, noise affects both conductors in the pair the same. Therefore, the difference between the pair of
Donovan Lincoln
Teradyne Legal Dept.
Teradyne, Inc.
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