Electrical connectors – Preformed panel circuit arrangement – e.g. – pcb – icm – dip,... – With provision to conduct electricity from panel circuit to...
Reexamination Certificate
2000-04-28
2003-04-01
Abrams, Neil (Department: 2839)
Electrical connectors
Preformed panel circuit arrangement, e.g., pcb, icm, dip,...
With provision to conduct electricity from panel circuit to...
C439S957000
Reexamination Certificate
active
06540527
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a method and apparatus for reworking an electronic circuit on a printed circuit board. More particularly, this invention relates to a method for producing an adapter for use with an LGA device, a rework adapter for use with an LGA device, and a method for reworking a circuit containing an LGA device to provide a desired circuit.
BACKGROUND OF THE INVENTION
Manufacturers that are involved in the design and fabrication of printed circuit boards may, under some circumstances, find it necessary to modify newly designed printed circuit boards in order to implement engineering improvements. Over the years, various rework techniques have been proposed for use with printed circuit boards.
These proposed techniques are often specialized in that they are suited for use with particular types of printed circuit boards and circuit board components. Accordingly, some of the techniques proposed in the past are appropriate for use with certain component types but may be ineffective for use with other types of components.
For example, referring generally to
FIGS. 1 and 2
, an exemplary printed circuit board modification procedure will now be described. Referring first to
FIG. 1
, a circuit board assembly
10
includes an electronic device
12
mounted to a circuit board
14
. Circuit board
14
includes a plurality of pads
16
, and surface traces connect the pads
16
to a plurality of vias
18
. Electronic device
12
is provided with a plurality of pins or leads
28
, which provide for electrical coupling with selected pads
16
on the circuit board
14
.
A modification can be made to such a printed circuit board in two stages. The first stage can be considered “pin isolation,” wherein a pin of an electronic device is isolated from a circuit on the printed circuit board. This stage is illustrated in
FIG. 1
, wherein a surface trace cut isolates a surface mount pad from a via hole that is connected to the rest of the circuit. More specifically, a surface trace cut
20
is made in order to isolate a surface mount pad
16
from a via
18
. The surface trace cut
20
therefore provides an accessible connection
22
to which a modification can be made (as shown in FIG.
2
). A surface trace cut
24
, however, is hidden beneath electronic device
12
. Accordingly, surface trace cut
24
provides an inaccessible connection
26
.
Referring now to
FIG. 2
, the second stage is illustrated. In this stage, which can be considered a “circuit re-connection” stage, a pin of an electronic device is connected to another circuit using a wire. Specifically, a wire
30
is connected to a pin or lead
28
of electronic device
12
by means of a soldered connection
32
. An opposite end
34
of wire
30
is provided for connection to an external circuit. Similarly, a second wire
36
is connected to another pin or lead of electronic device
12
at a soldered connection
38
. An opposite end of wire
36
is provided with an end
40
for connection to an external circuit.
Pin isolation for an electronic device such as device
12
is usually a straight forward procedure and the manner in which circuit re-connection is made depends primarily on the accessibility of the surface trace being cut or on the accessibility of the pin that is to be isolated. For example, if a trace is not readily accessible (e.g., for making the surface trace cut
24
illustrated in FIG.
1
), then an electronic device such as device
12
is first removed from the printed circuit board so that the trace can be accessed, and the device can be subsequently reinstalled. Nevertheless, an inaccessible connection such as connection
26
can be overcome by connecting a wire directly to the exposed lead of the device such as at soldered connection
38
.
It will be appreciated, therefore, that the modification procedure illustrated in
FIGS. 1 and 2
is suitable for use with devices such as device
12
that have pin-type leads, but that the modification will not be adequate for use with electronic devices of the type where the pins or leads of the device are not accessible. Accordingly, there remains a need for an adapter and method for use with electronic devices which have leads that are not easily accessible. More specifically, there remains a need for an adapter and method that can be used with land grid array (LGA) devices.
An LGA adapter should be fabricated and prepared for use easily, quickly and with standard laboratory equipment. Accordingly, there remains a need for an improved method for producing an adapter for use with an LGA device, an approved rework adapter for use with an LGA device, and an improved method for reworking a circuit containing an LGA device to provide a desired circuit.
SUMMARY OF THE INVENTION
This invention provides a method for producing an adapter for use with an LGA device. The method includes providing a flexible substrate having a conductive base layer. The method also includes forming a plurality of vias extending through openings defined in the flexible substrate, defining on the flexible substrate a plurality of conductive pads electrically connected to the vias, and further defining on the flexible substrate a plurality of conductive paths extending between adjacent conductive pads. Spaces are defined between the conductive pads and the conductive paths to prevent direct contact between the conductive pads and the conductive paths. The method further includes the step of retaining the conductive base layer, thereby maintaining electrical contact between the conductive pads and the conductive paths.
This invention also provides an adapter for use with an LGA device. The adapter includes a flexible substrate having a conductive base layer. Vias extend through openings defined in the flexible substrate. The adapter also includes conductive pads electrically connected to the vias. The conductive paths of the adapter extend between adjacent conductive pads. Spaces are defined between the conductive paths and the conductive pads to prevent direct contact between the conductive pads and the conductive paths. The conductive base layer maintains electrical contact between the conductive pads and the conductive paths.
This invention further provides a method for reworking a circuit containing an LGA device to provide a desired circuit. The method includes providing an adapter including a flexible substrate having a conductive base layer, vias extending through openings defined in the flexible substrate, conductive pads electrically connected to the vias, and conductive paths extending between adjacent conductive pads, spaces being defined between the conductive paths and the conductive pads to prevent direct contact between the conductive pads and the conductive paths. The conductive base layer maintains electrical contact between the conductive pads and the conductive paths. The method also includes the step of selecting a desire circuit. Further included in the method is the step of removing a portion of the conductive base layer from the flexible substrate such that the remaining portion of the conductive base layer, together with selected ones of the conductive pads and the conductive paths, defines the desired circuit.
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patent: 5683256 (1
Abrams Neil
RatnerPrestia
Rode Lise A.
Starr Mark T.
Unisys Corporation
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