Electrical connectors – Preformed panel circuit arrangement – e.g. – pcb – icm – dip,... – For receiving coaxial connector
Reexamination Certificate
2002-02-15
2004-01-27
Ta, Tho D. (Department: 2833)
Electrical connectors
Preformed panel circuit arrangement, e.g., pcb, icm, dip,...
For receiving coaxial connector
C439S581000
Reexamination Certificate
active
06682354
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to connectors for attaching electrical cable to a circuit board. More particularly, the present invention provides a method and apparatus for easily and securely attaching an electrical cable to a circuit board.
BACKGROUND OF THE INVENTION
One problem encountered in a variety of industries today is the connection of an electrical cable to a circuit board. Circuit boards typically comprise some form of electric circuitry and can be used in a variety of conventional devices and processes. Circuit boards are typically made of a combination of materials such as metal traces positioned on relatively delicate substrate material, where the substrate material is often referred to as a dielectric. The electrical cables that need to be attached to the delicate circuit boards are often inflexible. The inflexibility of the cable and delicate nature of the circuit board make it difficult to create a connection between the cable and the circuitry on the circuit board that is mechanically and electrically secure.
This problem is particularly apparent in the field of antennas. Antennas, and particularly cellular antennas mounted on a pole at a base station, often have spatial constraints that make it desirable to construct an antenna of compact size. Aesthetic and environmental concerns can also control the size and shape of the antenna, which in turn impact the construction and assembly of the components within the antenna. The difficulty of assembling the antenna components in a small area is further complicated by physical constraints that ensure the components function properly. This difficulty is particularly acute in that portion of the assembly process where a power cable is connected to the dielectric circuit board within the antenna. Typically, an intermediate coaxial cable is used to connect an external power cable and the circuit board. Because the intermediate power cable is relatively short and stiff, it is difficult to achieve a secure connection with the circuit board. One common problem resulting from poor connections is degradation of the electrical signal caused by stresses in the connection between the power cable and the circuit board. In some instances the dielectric circuit board will crack or break because of its delicate nature.
PRIOR ART
The key to solving these problems lies in the design of the connector and how the connector is attached to the intermediate power cable and the dielectric circuit board. Existing connectors are difficult to work with in confined spaces and often produce connections with undue stresses that adversely affect the antenna. Attempts have been made to manufacture better connectors. Examples of more complex connectors are illustrated in U.S. Pat. No. 4,737,111, entitled “RF Connector for Use In Testing a Printed Circuit Board,” and U.S. Pat. No. 6,106,304, entitled “Cable Connecting Head for Connecting to an Integral Circuit Board.” However, there are limitations with the designs taught in these patents. First, the connectors do not facilitate simple and secure connection of the two conductors of a coaxial cable to a circuit board. Typically, it is necessary to solder the outer conductor to the circuit board ground and to solder the inner conductor to a trace connected to the circuit. The connector designs of the prior art do not allow for easy access to the outer and inner conductor for soldering. Second, the prior art connectors are expensive in that they require modification of the circuit board (drilling holes) and machining of a complex connector device. These additional costs make the designs prohibitive. Third, the designs taught in these two patents require turning and manipulation of the connector device to attach it to the circuit board. Maneuvering the connector device is difficult given the compact structure of cellular antennas.
Two other types of connectors that are generally used for this type of application are illustrated in
FIGS. 1
,
2
, and
3
. The connector shown in
FIG. 1
is an example of a standard connector. The standard connector
2
connects intermediate cable
3
to circuit board
1
. The intermediate cable
3
is then connected to an external power cable (not shown) via a DIN connector
4
. The DIN connector is attached to the antenna tray
5
, usually with rivets
6
. The intermediate cable
3
comprises an outer conductor
7
and an inner conductor
8
. The intermediate cable
3
is inserted into the distal hole
9
of the standard connector
2
such that the inner connector
8
protrudes from the proximal side of the standard connector
2
. The outer conductor
7
can be soldered to the standard connector
2
and the inner conductor
8
can be soldered to the circuit board
1
at the microstrip trace line
10
. The standard connector
2
also comprises two top stubs
11
and
12
and two bottom stubs
11
′ and
12
′ (not shown). The connector
2
is typically soldered to the circuit board
1
at stubs
11
,
11
′,
12
, and
12
′.
The other type of conventional connector is called a clamp nut connector. An exemplary clamp nut connector, as manufactured by Amphanol Connectors, Inc. in Allentown, Pa., is shown assembled in FIG.
3
and unassembled in FIG.
2
. The clamp nut connector
20
comprises a clamp nut
21
, a threaded nut sleeve
22
, a ferrule
23
, and a connector assembly
24
. The process for connecting the intermediate cable
25
with a clamp nut connector differs somewhat from the process for a standard connector. With the clamp nut connector, the intermediate cable
25
is fed through the clamp nut
21
and the threaded nut sleeve
22
. The ferrule
23
is then attached to the end of the intermediate cable
25
and soldered to the cable's outer conductor
26
. The connector assembly
24
is inserted onto the edge of a circuit board
33
such that upper stubs
29
and
32
rest on the top of the circuit board
33
and the lower stubs
30
and
31
are beneath the circuit board
33
. Each stub
29
,
30
,
31
, and
32
is soldered to the circuit board
33
securing the connector assembly
24
. The ferrule
23
is then inserted into the connector assembly and secured by tightening the clamp nut
21
. Finally, the inner conductor
27
can be soldered to the circuit board
33
. The problem with the clamp nut connector is that it requires the machining of several more parts than the standard connector. These additional parts add to the cost of the connector and also add additional steps to the antenna assembly process. Furthermore, manipulation of the clamp nut
21
in the confined space of an antenna system also causes unwanted movement and stress on the solder connections with the circuit board
33
.
The rigid nature of the intermediate cable
3
,
25
causes stresses in the various solder points of the connection. These stresses can be exacerbated by the fact that the shape of the standard connector
2
and the clamp nut connector
20
make it difficult to form secure solder joints. The resulting stresses can adversely affect the performance of the antenna. In an ideal antenna manufacturing process, the first two steps would involve attaching the DIN connector
4
to the antenna tray
5
and attaching the intermediate cable
3
,
25
to the DIN connector
4
. Then later in the manufacturing process, the intermediate cable
3
,
25
would be attached to the circuit board
1
,
33
via a connector.
Using a standard connector
2
or a clamp nut connector
20
, the actual antenna manufacturing process occurs in the reverse order of the ideal process. The structure of the conventional connectors and the compact spatial constraints of cellular antennas require that the intermediate cable
3
,
25
be connected to the circuit board
1
,
33
first. Subsequently, the intermediate cable
3
,
25
is bent and fed into the cylindrical opening of the DIN connector
4
. The process of bending the intermediate cable
3
,
25
and attaching it to the DIN connector
4
, increases the problems associated with stresses accumulating in the
Carson James C.
Phillips Sara
EMS Technologies Inc.
Harvey James R.
King & Spalding LLP
Ta Tho D.
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