Electrical connectors for circuit panels

Disclosed is a connector module for making electrical contact between two essentially parallel boards which include contact pads on the edges. The connector includes at least one conductive member adapted to extend from a pad on one board to a corresponding pad on the other board. The connector also includes an insulating support member formed to extend from the top of one board, around the edge of that board, and to the top of the other board. This support member fixes the distance between the boards, permits the conductive members to make electrical contact for test purposes prior to clamping, and provides an appropriate clamping force for the connection to the first board.

BACKGROUND OF THE INVENTION 
This invention relates to providing electrical connection between planar, 
essentially parallel, components. 
In many electronic interconnect systems, it is necessary to provide 
electrical connection between essentially parallel surfaces of different 
components. These components can be at least two printed circuit boards 
representing different levels of interconnection in the system or can be a 
printed circuit board and some other type of component such as a display 
panel. As an example of the latter, ac plasma panel displays require 
electrical connection between glass covers and substrates and a printed 
circuit board so that the display can be appropriately addressed. In 
particular, a glass cover and glass substrate enclose a gas which is 
capable of being ionized when a bias is supplied to electrodes which are 
also formed on the substrate and cover. Contact pads are also protided on 
the facing surfaces of the substrate and cover, but outside the gas 
envelope, and are electrically connected to a printed circuit board which 
includes the necessary components for addressing the electrodes. 
Several types of connectors have been proposed for providing electrical 
interconnection between parallel surfaces of a printed circuit board and 
another board or display component. These connectors are usually in the 
form of an elastomeric material consisting of alternating layers of 
conducting and nonconducting rubber (See, e.g., Connectors and 
Interconnection Handbook, Vol. 2, pp. 4-26 to 4-30 (Fort Washington Pa. 
Electronic Connector Study Groups, 1979)) or spring contacts (See, e.g., 
TKC Printed Circuit Connectors Catalog, Vol. 2, pp. 1-6, (Huntington Beach 
Calif., Ken Fleck Association, 1983)) which are placed between facing 
surfaces of the parallel components so as to interconnect corresponding 
contact pads. The parallel components and connectors are usually clamped 
together by screws running through holes in the components and a holder 
for the connector. 
Such connectors are generally adequate for most applications. However, many 
problems exist, especially in the connection of plasma displays. For 
example, it is desirable to be able to provide a fairly stable connection 
between the cover, substrate and printed circuit board so that the device 
can be tested prior to actual clamping. Since the glass covers and 
substrates are fragile, some means is usually needed to prevent the 
clamping action from breaking these elements. It is also necessary in 
plasma displays to provide connection between the top of the substrate and 
the top of the printed circuit board (i.e. two non-facing surfaces). 
Some connectors have been proposed to deal with some of the problems 
involved. For example, it has been proposed for LCD displays to provide a 
connector which includes a conductive member extending to the top surface 
of the display with an insulating support positioned on the opposite 
(bottom) surface of the display (See TKC Catalog cited above). Such a 
connector provides electrical contact from the top of the display to the 
printed wiring board. However, the contact force is apparently dependent 
upon the thickness of the display, and no provision is made for a padding 
element which would probably be required for use in conjunction with 
additional clamping which is desirable for a glass cover or substrate in a 
plasma display. It has also been proposed to provide electrical connection 
in a plasma display panel by means of a flexible circuit member extending 
between the glass and printed circuit board and mechanically attached 
thereto by spring clips on the edges of the glass and board (See, e.g., 
Bilsback et al. "Plasma Panel Display Presents Unique Packaging Problems," 
Electronic Packaging and Production, pp. 132-134 (March 1984)). Since the 
conductive element is a flex circuit, the distance between the glass and 
board must be fixed by some additional means. Also, padding elements which 
are not an integral part of the connector are required to prevent breakage 
of the glass and provide the appropriate contact force between tne 
conductive element and the glass or board. 
It is, therefore, a primary object of the invention to provide an integral 
connector structure for making electrical contact between contact pads of 
different components with essentially parallel surfaces. 
SUMMARY OF THE INVENTION 
This and other objects are achieved in accordance with the invention which 
in one aspect is an electrical connector including an insulating support 
member comprising at least two contiguous U-shape portions. As least one 
of the portions defines a slot suitable for insertion therein of an 
electronic component having essentially planar major surfaces with contact 
pads on at least one surface. A conductive member is attached to the 
insulating support member and extends over a surface of at least one of 
the U-shaped portions. 
In accordance with another aspect, the invention is an electronic assembly 
comprising at least two components, each having essentially planar major 
surfaces with contact pads formed on at least one surface. The components 
are in a spaced relationship having their major surfaces essentially 
parallel. Connectors are provide coupling the pads on the surface of one 
component to corresponding pads on the other component. The connectors 
each comprise an insulating support member having at least two contiguous 
U-shaped portions. One of the portions is clamped around an edge of one of 
the components. The connectors further include conductive members attached 
to the insulating support member and extending from a pad on one component 
to a corresponding pad on the other component.

DETAILED DESCRIPTION OF THE INVENTION 
FIG. 1 illustrates an electronic assembly including components having 
essentially planar major surfaces with contact pads formed on at least one 
surface of each component, where the components are spaced apart having 
their major surfaces essentially parallel to each other and electrical 
connection provided between corresponding pads on at least two components. 
In this example, the assembly is a plasma panel display which includes two 
glass panels, 10 and 11, typically referred to as the substrate and cover, 
respectively, which are spaced apart to form a gap including an ionizable 
gas sealeo therein. This sealed unit is referred to as a "display panel". 
Each panel includes electrodes formed on the major surface in the gap to 
selectively ionize the gas and produce the display. (For a detailed 
discussion of a plasma display, see for example U.S. Pat. No. 4,554,537 
issued to Dick.) The panels also each include a series of contact pads, 
e.g., 12 and 16, formed near at least one edge of the major surface facing 
the other panel. (Thus, in FIG. 1, only the pads on the cover panel, 11, 
are directly visible, but similar rows of pads, e.g., 16 are formed near 
the edges of the substrate, 10, at right angles to those of the cover.) 
The substrate and cover are bonded together by standard techniques. 
The display panel is positioned in a spaced relationship with a printed 
circuit board, 14, so that the major surfaces of each are essentially 
parallel. The board, 14, includes various electronic components thereon 
which provide the drive circuitry for the plasma panel display. These 
components are electrically connected to contact pads formed near the 
edges of the board on the major surface facing the display panel. Thus, 
these pads are not directly visible in the view of FIG. 1, but groups of 
such pads, are shown in phantom in the figure for purposes of 
illustration, and FIG. 4 gives an enlarged view of a portion, 60, of the 
board which is broken away for purposes of showing one group of pads such 
as 15. It will be noted that the pads are staggered for the purpose of 
providing a high density connection. 
Typically, the cover measures approximately 11 inches.times.7 inches and 
the substrate measures approximately 12 inches.times.6 inches and each is 
approximately 0.12 inch thick. The printed circuit board is a standard 
type made of epoxy-glass with tin-lead plated copper conductors and 
measuring approximately 12 inches.times.7 inches and 0.06 inch thick. The 
substrate panel, 10, is typically placed approximately 0.25 inch from the 
surface of the printed wiring board. In a typical example, the contact 
pads on an edge of the glass panel are spaced approximately 0.030 inch 
from center-to-center in groups of 32. The pads are usually made of an 
appropriate conductive material and measure approximately 0.10 
inch.times.0.02 inch with a thickness of 0.003 inch. 
It will thus be appreciated that it is desired to form electrical 
connections between the pads on the display panel and corresponding pads 
on the printed circuit board. At the same time, it is desired to fix the 
distance between the display panel and board by some support means. 
Further, in assemblying the plasma panel display, it is convenient to have 
some way of connecting a printed circuit board to the display panel for 
testing purposes in such a way that it is easily disconnected if there is 
a defect. It is also convenient to be able to disassemble a printed 
circuit board from a completed display panel without disturbing the 
connections between the connectors and the display panel in the event that 
a defect appears some time after assembly. 
The necessary electrical contact between the pads on the display panel and 
those on the printed circuit board is provided by two forms of a connector 
in accordance with the invention. One form, shown, for example as element 
20, connects the pads on the substrate to the pads on the board, while the 
other form, shown for example as element 30, connects the pads on the 
cover to corresponding pads on the board. 
FIG. 2 illustrates, in cross-section, one of the connectors, 20, of FIG. 1, 
when the elements are fully assembled. The same elements in the two 
figures are similarly numbered. Each connector includes a plurality of 
conductive strips or springs, in this example, 64, which extend from a 
contact pad, e.g., 16, on the top surface of the substrate panel, 10, to a 
corresponding pad, e.g., 15, on the top surface of the printed circuit 
board 14. One of these conductive strips is illustrated as 21 in FIG. 2 
and an adjacent strip is illustrated as 22 in phantom. It will be noted 
that the strip is formed in a generally S-shaped configuration to extend 
around the edge of the substrate to the top of the printed wiring board. 
In this example, each strip is blade of stainless-steel plated with 
tin-lead and is approximately 1.3 inches long, 0.014 inch wide and 0.010 
inch thick. Of course, other conductive material may be used. 
The conductive strips are mechanically attached to an integral, insulating 
support member, 23, which also extends from the top surface of the 
substrate, 10, to the top surface of the printed wiring board 14. The 
support is also generally S-shaped or may be considered, for purposes of 
discussion, to comprise two contiguous U-shaped portions, 24 and 25. The 
top U-shaped portion, 24, clips onto the edge of the substrate and 
supports the strip so that the strip makes contact with the pad, 16, on 
the top of the substrate. Prior to clamping of the connector in this 
embodiment with screws 26 and 29 as discussed below, the strip makes 
contact to the pad by spring forces. Subsequent to clamping, the contact 
force is essentially independent of the thickness of the substrate. It is 
also possible to make the contact force independent of the substrate 
thickness prior to clamping if the slot is made narrower than the 
substrate. A further advantage of this portion, 24, is that a fairly rigid 
contact is formed with the substrate pads prior to final clamping of the 
structure. Thus, the substrate panel can be electrically tested and the 
contacts easily removed if any defect occurs. The bottom portion, 25, of 
the support member, 23, serves in part as a guide for the conductive 
strips to make contact with the printed circuit board pads. Further, since 
the support is a rigid structure, this portion, 25, also fixes the 
distance between the substrate and the board when the components are fully 
assembled. 
Each individual strip, 21, is inserted within a groove in the support 
member, 23, and separated from an adjacent strip, 22, by reans of a rib 
portion, 50, extending over the surface of the member, 23. The strips are 
typically attached to the support member by heating the surface to deform 
the rib portions until they extend over the strips. In this example, the 
support member was a molded plastic. The inside dimension, A, of the upper 
portion, 24, measured approximately 0.20 inch, while the outer dimension, 
B, of the lower portion, 25, measured approximately 0.18 inch. The total 
length of the two portions in the cross-sectional view of FIG. 2 was 
approximately 0.60 inch. The connector was built to accommodate 64 
conductive strips, 21 and 22, and had a longitudinal dimension 
(perpendicular to the plane of FIG. 2) of approximately 2.1 inches. 
As shown in FIGS. 1 and 2, the connector, 20, is clamped to the substrate, 
10, by means of a screw, 26, threaded through a top plate, 27, which is 
placed on the top of portion 24. The screw extends through the slot 
portion of the connector adjacent to the edge of the substrate and through 
a nut plate, 28, which is placed adjacent to the bottom of portion, 24. 
The portion, 25, of the connector is clamped to the board, 14, by means of 
screw 29 which is threaded through the board, the bottom of portion 25, 
and through the portion of nut plate 28 which extends into the slot of 
portion 25. The top plate and nut plate are typically made of steel and 
extend the length of the portions of the substrate and board which include 
the contact pads. This length is typically approximately 7 inches. The 
thickness of the plates is approximately 0.05 inch. The width of top plate 
27 is approximately 0.32 inch, and that of nut plate 28 is approximately 
0.42 inch. 
A further advantage of the insulating support member, 23, is that it 
provides padding between the plates, 27 and 28, and the glass panel to 
prevent breakage due to clamping. Thus, no additional elements are 
necessary to protect the glass. 
FIG. 3 illustrates, in cross-section, another embodiment of the connector 
of the present invention which is useful for connecting the pads, such as 
12, on the cover, 11, to corresponding pads, such as 17, on the surface of 
the printed circuit board, 14. This connector also includes conductive 
strips or springs, e.g., 31, extending from pads, e.g., (12) on the cover 
to pads, e.g., (17) on the board. However, it is apparent that since the 
pads are on surfaces of the cover and board which face each other, the 
strips are shorter and do not extend around the edge of the panel. In this 
example, each strip is approximately 0.7 inch long with the same width and 
thickness as the conductive strip 21 of connectors 20. Again, the 
connector accommodates several strips (64) one additional strip being 
shown in phantom as 32 for contacting adjacent pads (not shown). 
The connector, 30, also includes an integral insulating support member, 33, 
which extends from the top of the cover, 11, around the edge of said cover 
and to the top surface of the board, 14. Again, it is useful for purposes 
of illustration to consider the support as comprising two contiguous 
U-shaped portions, 34 and 35. The upper portion, 34, includes a slot which 
clips onto the edge of the cover 11 and provides a clamping force thereto 
to hold the connector in place even before final clamping. This permits 
testing of the components on the cover with easy removal of the connectors 
if any defect is discovered. The other portion, 35, provides a guide for 
the conductive strips, (e.g., 31 and 32), which are attached thereto, as 
before, by deforming the rib portions, e.g., 51, of the insulating member 
which separate the strips. Since the support member is a fairly rigid 
structure, portion 35 also fixes the distance between the cover, 11, and 
board 14, which in this example is approximately 0.38 inch. In this 
example, the dimension, C, of the slot of the upper portion 34 is 
approximately 0.26 inch. The outer dimension, D, of the portion, 35, is 
approximately 0.30 inch. As before, the longitudinal dimension 
(perpendicular to the plane of FIG. 3) of the support is approximately 2.1 
inches to accommodate several conductive strips. The length of the 
insulating support (in the plane of FIG. 3) is approximately 0.57 inch. 
As in the case of connectors of FIG. 2, the connectors, 30 of FIG. 3, are 
finally clamped to the panel, 11, by means of a screw, 36, threaded 
through a top plate 37 and extending along the edge of the panel through a 
nut plate 38. The connector is clamped to the board, 14, by a screw, 39, 
extending through the board, through a portion of the bottom of the 
connector and through nut plate 38. (See also FIG. 1) 
Again, the support, 33, also provides padding between the plates 37 and 38 
and the glass panel, 11. 
While the invention is most advantageously applied to plasma display panels 
as described above, it should be apparent that the invention may be 
utilized wherever it is desired to electrically connect two components 
having essentially planar, major surfaces where the surfaces are 
essentially parallel and there are contact pads on at least one surface 
near the edge. For example, both components could be printed circuit 
boards. 
Various additional modifications will become apparent to those skilled in 
the art. All such variations which basically rely on the teachings through 
which the invention has advanced the art are considered within the scope 
of the invention.