Electrical connectors – Preformed panel circuit arrangement – e.g. – pcb – icm – dip,... – With mating connector which receives panel circuit edge
Reexamination Certificate
2000-01-24
2001-05-22
Donovan, Lincoln (Department: 2839)
Electrical connectors
Preformed panel circuit arrangement, e.g., pcb, icm, dip,...
With mating connector which receives panel circuit edge
C439S059000
Reexamination Certificate
active
06234807
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field
This invention relates in general to improved interfaces between pin connectors and printed circuit boards, and in particular to improved printed circuit boards. Still more particularly, the invention relates to an improved tab design for printed circuit board connector edges.
2. Description of the Prior Art
As the designs of computer processors and other supporting hardware become increasing complex, so too are the physical designs of the printed circuit boards, such as mother boards and daughter boards, that they utilize. For example, in circuit boards that contain advanced, high-speed, impedance-controlled channels, it is difficult to match impedances at the connector interfaces. Generally, impedance has two aspects: resistance and reactance. Resistance impedes current by converting electrical energy to heat and is always greater than zero. Reactance impedes current, but varies with frequency and can be positive or negative. The electrical characteristics of the connectors and the associated via patterns on circuit boards tend to present highly inductive influences on the signal lines. These inductive influences create discontinuities in the line impedance which, in turn, cause reflection noise on the signal lines, thereby degrading the overall quality of the signals.
Although the size of the edge tabs on daughter cards can be increased to compensate for the effects of the impedance discontinuities, there are several mechanical factors which limit the extent to which the size of the edge tabs may be increased. As shown in
FIG. 1
, the first limitation is the mechanical requirement that “vertical” (top to bottom) plated pathways
11
be provided for the mother board connector pins (not shown) which mate to the “upper” row
13
of contacts
15
. The plated pathways
11
allow the connector pins to slide from the beveled perimeter edge
17
of the daughter card
19
up to the contact areas on the upper edge tabs (indicated schematically at
21
) without grinding on the bare fiberglass substrate
23
of the daughter card
19
. Such grinding would lead to premature wear of the connector pins which, in turn, would cause intermittent electrical contacts and short circuits between the signal wires passing through the connector.
The “lower” row
25
of contacts
27
are touched by the connector pins at areas
29
. The lower row contacts
27
are typically used for signal line connections and have a size limitation in the “horizontal” direction (left to right in FIG.
1
). The lower edge contacts
27
require a safety buffer
31
of about
5
mils from the plated pathways
11
between each signal contact
27
. Violating this minimum distance for buffer gaps can cause short circuits between the pathways, thereby shorting the upper row of reference contacts
15
.
The second limiting factor is the electrical effect of the capacitive pad area on the actual connector pin contact area. Increasing the signal pad area upward, or in the vertical direction, has diminishing returns. The farther away the capacitive area is from the pin contact area, the less effect it will offer in compensating for the impedance mismatch at the connector interface. Thus, an improved printed circuit board card edge design which overcomes the limitations of the prior art is needed. It would be desirable to provide an improved printed circuit board card edge design which has sufficient contact area without resulting in inductive effects.
SUMMARY OF THE INVENTION
A printed circuit board connector edge tab design allows for increased contact area while bypassing previously restrictive mechanical limitations. The enlarged edge tabs create a larger local capacitance at the connector interface. This serves to balance out the inductive effects of the connector and results in a lower overall channel impedance at the interface. The invention replaces the prior art plated pathway to the upper row of tabs with wider tabs on the lower row. The edges of the lower row tabs are spaced such that each of the connector pins destined for the upper row straddle two of the lower tabs as they travel upward. This design prevents the pins from contacting the fiberglass substrate of the board while it traverses the lower row of tabs. The absence of the prior art plated pathways allows each of the lower row tabs to be expanded into the space formerly occupied by the pathways. This design also allows the increased capacitive area of the edge tabs to be located in very close proximity to the connection area between the connector pins and the edge tabs.
Accordingly, it is an object of the present invention to provide improved interfaces between pin connectors and printed circuit boards.
It is an additional object of the present invention to provide improved printed circuit boards.
Still another object of the present invention is to provide an improved tab design for printed circuit board connector edges.
The foregoing and other objects and advantages of the present invention will be apparent to those skilled in the art, in view of the following detailed description of the preferred embodiment of the present invention, taken in conjunction with the appended claims and the accompanying drawings.
REFERENCES:
patent: 3399372 (1968-08-01), Uberbacher
patent: 5259768 (1993-11-01), Brunker et al.
patent: 5277591 (1994-01-01), Feleman et al.
patent: 5403208 (1995-04-01), Feleman et al.
patent: 5522737 (1996-06-01), Brunker et al.
patent: 5730609 (1998-03-01), Harwath
patent: 5772448 (1998-06-01), Ekrot et al.
patent: 5853303 (1998-12-01), Brunker et al.
patent: 5865631 (1999-02-01), Berto et al.
patent: 5919049 (1999-07-01), Petersen et al.
patent: 5944541 (1999-08-01), Payne
Amini Kamran
Diepenbrock Joseph Curtis
Evans Robert J.
Scollard Mike L.
Tran Marcel B.
Dillon Andrew
Donovan Lincoln
Grosser George E.
International Business Machines - Corporation
Le Thanh-Tam
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