Electricity: electrical systems and devices – Housing or mounting assemblies with diverse electrical... – For electronic systems and devices
Reexamination Certificate
2002-09-30
2003-11-11
Martin, David (Department: 2841)
Electricity: electrical systems and devices
Housing or mounting assemblies with diverse electrical...
For electronic systems and devices
C361S777000, C361S803000, C257S692000, C257S691000, C257S723000, C174S255000, C174S260000
Reexamination Certificate
active
06646888
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to a printed circuit board having at least one pad on which a surface mounted device can be mounted. Particularly, the present invention relates to a pad arrangement on a printed circuit board for applying reworks or engineering changes to an electronic circuits to be formed on said circuit board.
2. Description of the Related Art
The majority of electronic devices are now packaged with their electronic components mounted on printed circuit boards (PCB). PCBs have electrically conductive paths that are often connected to electrically conductive pads upon which surface mounted devices (SMDs) can be mounted. Typically, these SMDs are resistors or capacitors. However, SMDs can also be inductors, jumpers, i.e., a removable wire or small plug whose presence or absence is used to determine some aspect of hardware configuration, or other electrical components known to those of ordinary skill in the art.
Generally, the electrical element of an SMD is carried within a ceramic or plastic package having two conductive end portions that are connected internally to the electrical element and a nonconductive center portion. To permanently connect the SMD electrically to the PCB, its conductive end portions are soldered to appropriately spaced conductive pads provided on the surface of the PCB.
Problems can arise, whenever changes to the layout of the electronic circuit get necessary. May it because of reworks or engineering changes, e.g., due to design requirements or the desire to substitute one SMD for another, the size of an SMD might change. In order to avoid a potentially costly redesign of the PCB layout some arrangements could be made.
U.S. Pat. No. 5,303,122 by Clifford G. Adams, Jr. et. al., assigned to Ford Motor Company, filed May 19, 1993, issued Apr. 12, 1994, “Printed circuit board having a commonized mounting pad which different sized surface mounted devices can be mounted”, discloses a printed circuit board having a unique commonized pad upon which different sized surface mounted devices can be mounted. The preferred form of the commonized pad comprises two electrically conductive pads, each having a tapered portion that electrically connects a narrow portion to a wide portion. The present invention is advantageous over known pads in that it (1) allows for using different sizes of surface mounted devices without redesign and (2) it does not require wasting what might otherwise be antiquated inventory or continuation of an old process to use up what would be antiquated inventory.
In some cases it is more than a question of the size of a SMD. Additional, wires might be required to be connected to the PCB or an additional electrical connection from one surface of the PCB to the other surface may be needed. For this case simple pad arrangements were introduced that would only be used in case of a rework or an engineering change.
Such a pad arrangement
100
is depicted in FIG.
1
. As it can be seen from
FIG. 1
, there is a first conductive pad
102
and a second conductive pad
104
. The first conductive pad
102
is formed by a basically rectangularly shaped central portion
106
having truncated corners and a rectangularly shaped extension
108
being provided for receiving a via
110
connecting the first conductive pad
102
to a respective pad (not shown) on the opposite surface of a PCB (not shown). The second conductive pad
104
comprises tree basically rectangularly shaped conductive portions
120
,
122
and
124
being connected to each other by two trapezoidal conductive portions
126
and
128
, all together forming basically an annulus running approximately half around the first conductive pad
102
. The second conductive pad
104
further comprises in one of the trapezoidal conductive portions
128
a via
130
connecting the second conductive pad to a ground line (not shown) provided in the PCB.
OBJECT OF THE INVENTION
Starting from this, the object of the present invention is to provide a pad arrangement on a printed circuit board that allows flexibly applying reworks or engineering changes to an electronic circuits to be formed on said circuit board.
BRIEF SUMMARY OF THE INVENTION
The foregoing object is achieved by a pad arrangement as laid out in the independent claims. Further advantageous embodiments of the present invention are described in the sub claims and are taught in the following description.
According to the present invention a pad arrangement is provided for applying reworks or engineering changes to an electronic circuits to be formed on the circuit board, the pad arrangement comprising a first signal pad for being electrically connected to a first signal line, a second signal pad for being electrically connected to a second signal line, a ground pad being connected to a ground line provided on the circuit board, and a voltage pad being connected to a supply voltage line provided on the circuit board, whereby the pads are arranged in proximity to each other for facilitating a placement of electronic devices between at least two of the pads.
In a preferred embodiment according to the present invention the group of two signal pads, a ground pad and a voltage pad is substantially being arranged in the edges of a square, whereby in a refinement the ground pad and the voltage pad are arranged next to each other.
In order to reduce the inductance on the PCB the connection between the ground pad to the ground line and between the voltage pad to the voltage line are formed basically on the edge of the respective pad which is closest to the respective other of both pads.
According to another embodiment of the present invention the ground pad extends on the respective surface of the circuit board basically around the adjacent signal pad forming further areas for soldering electrical elements onto. In a refinement the ground pad even extends further to the opposite side of the second signal pad, providing an additional shielding from electrical interferences and more possibilities for connecting surface mounted devices (SMD) and electrical wires, such as coaxial cable, to the pads and in particular to the ground pad. A coaxial cable is a kind of cable having a solid central conductor surrounded by an insulator, in turn surrounded by a cylindrical shield woven from fine wires. It is used to carry high frequency signals, in the area of radio frequencies. The shield is usually connected to electrical ground to reduce electrical interference. In the present case the shield may be connected to a portion of the ground pad.
In order to provide further flexibility and to allow a connection from one surface of the PCB to the other, the pad arrangement further comprises in another embodiment a third signal pad being electrically connected to the first signal pad, a fourth signal pad being electrically connected to the second signal pad, another ground pad being connected to a ground line provided on the circuit board, and another voltage pad being connected to a supply voltage line provided on the circuit board, whereby the pads are placed on the opposite surface of the PCB and are again arranged in proximity to each other for facilitating a placement of electronic devices between at least two of the pads. To improve crosstalk behavior, the connection between the first signal pad to the third signal pad and between the second signal pad to the fourth signal pad are formed basically on the edge of the respective pad which is furthest away from the respective other of both pads.
The pad arrangement in accordance with the present invention is placed as prevention of costly and time consuming modifications of cards or PCBs because of potential reworks and engineering changes. It is advantageously applied in order to get connectivity between the front and back side of double side mounted cards and PCBs. In addition, with embedded wires placed in an intermediate layer of the PCB, the pad arrangement according to the present invention may be used, to tunnel blockages or get in t
Cwik Manfred
Pross Harald
Schrottenholzer Rene Frank
Augspurger Lynn L.
Bui Hung
International Business Machines - Corporation
Martin David
LandOfFree
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