Electricity: measuring and testing – Fault detecting in electric circuits and of electric components – Of individual circuit component or element
Reexamination Certificate
2002-07-19
2004-11-30
Zarneke, David (Department: 2829)
Electricity: measuring and testing
Fault detecting in electric circuits and of electric components
Of individual circuit component or element
C324S1540PB, C174S261000
Reexamination Certificate
active
06825679
ABSTRACT:
BACKGROUND OF THE INVENTION
Wireless test fixtures, when used in combination with in-circuit testers for target printed circuit boards (PCBs), allow for quick and accurate testing of PCBs by providing the necessary electrical and mechanical connections between points of interest on the target PCB with the testing interface of the particular tester being used. A simplified diagram of one such wireless fixture
100
is shown in
FIG. 1. A
target PCB
105
, typically populated with electronic components
107
, is held in a stable fashion by a target board support
130
. A plurality of probes
135
make contact at one end with points of interest on the target PCB
105
to be tested. The other end of each probe
135
makes contact with electrical contact points on one side of a fixture PCB
110
. On the opposite side of the fixture PCB
110
are another set of electrical contact points, each of which is associated with a pin
120
. The pins
120
are utilized to connect various points of the fixture PCB
110
, with a testing interface
115
of the tester, shown without detail in FIG.
1
.
Thus, the fixture PCB
110
is employed as a way of mechanically customizing the testing interface
115
for any particular target PCB
105
. Typically, significant forces are applied to one or both sides of the fixture PCB
110
by way of the probes
135
and the pins
120
. To prevent inordinate flexing of the fixture PCB
110
under such forces, structural elements, such as spacers
140
and fixture adapter
125
, are employed. These structural elements may predominantly reside on the upper or lower side, or both, of the fixture PCB
110
.
Some such structural elements may make direct contact with the fixture PCB
110
over a significant portion of the fixture PCB
110
. For example, the fixture adapter
125
may contain a number of holes (not shown in
FIG. 1
) through which the pins
120
protrude to make contact with the fixture PCB
110
. Areas of the top of the fixture adapter
125
not occupied by the pins
120
therefore make direct contact with the fixture PCB
110
to provide mechanical support. In other wireless test fixture designs, a structural element may reside atop the fixture PCB
10
, making direct contact with much of the top side of the fixture PCB
110
for support.
Unfortunately, such contact has been shown to cause problems when changes to the connections embodied in the fixture PCB
110
are required. These changes are often necessitated by modifications in test strategy, causing a change in the number of points of interest to be checked or a modification in how the points of interest are tested. Also, design modifications made to the target PCB
105
may cause a change of location in the points of interest on the target PCB
105
. As a result of these modifications, commensurate changes in the location or number of the probes
135
, or in how the probes
135
are connected to the pins
120
, are required. In such cases, changes in the electrical connections implemented within the fixture PCB
110
are necessary.
The changes in the fixture PCB
110
are normally implemented in part by way of one or more standard, round, insulated wires, such as small-gauge wire-wrap wires. With respect to the wireless fixture
100
, such wires, when residing on the bottom side of the fixture PCB
110
, are compressed between the fixture PCB
110
and the fixture adapter
125
, potentially causing bending of the fixture PCB
110
. For variants of test fixtures with structural elements in contact with the top of the fixture PCB
110
, wire-wrap wires existing on the top of the fixture PCB
110
would create similar problems. If the fixture PCB
110
is not maintained sufficiently flat within certain limits, the probes
135
and pins
120
may not make sufficient contact with the fixture PCB
110
in the proper locations, causing undesirable disconnections between the testing interface
115
and the target PCB
105
. Also, physical damage to the wires implementing the changes may occur. Such damage is exacerbated in situations where two of the wires cross, as the insulation between the two wires may be compromised, causing a short circuit between those wires.
The wires also potentially cause obstruction of the points on the fixture PCB
110
at which the probes
135
and the pins
120
make contact. This problem may be remedied by gluing the wires to the side of the fixture PCB
110
to restrict the movement of the wires, but such a task is rather time-consuming.
Therefore, from the foregoing, a new structure and method that allows for low-profile, low-movement implementations of circuit changes on a printed circuit board would be advantageous.
SUMMARY OF THE INVENTION
Embodiments of the present invention, to be discussed in detail below, represent a structure and method that allow circuit changes to be made to a printed circuit board that occupy an insignificant amount of space above the board, and are essentially stationary. Where two previously unconnected points on a side of the printed circuit board must be connected, electrically conductive tape is applied to the side of the printed circuit board to define a contiguous path between the two points.
Electrically conductive tape is often backed with an adhesive, thus restricting the movement of the tape when applied to the board with the adhesive. Also, conductive tape is typically quite thin compared to the type of wire normally used for such PCB circuit changes, thus occupying less space above the board compared to that wire so that mechanical tolerance problems due to bending of the printed circuit board are significantly reduced.
Other aspects and advantages of the invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention.
REFERENCES:
patent: 2808352 (1957-10-01), Coleman et al.
patent: 4724383 (1988-02-01), Hart
patent: 5060370 (1991-10-01), Scales et al.
patent: 5829127 (1998-11-01), Hagner
patent: 3943261 (1991-07-01), None
patent: 0 113 820 (1983-11-01), None
patent: 2 111 759 (1982-12-01), None
patent: 56008891 (1981-01-01), None
King Philip N
Willard Stephen
Tang Minh N.
Zarneke David
LandOfFree
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