Electricity: conductors and insulators – Conduits – cables or conductors – Preformed panel circuit arrangement
Reexamination Certificate
2002-03-27
2003-10-07
Talbott, David L. (Department: 2827)
Electricity: conductors and insulators
Conduits, cables or conductors
Preformed panel circuit arrangement
C174S260000, C029S852000, C029S853000
Reexamination Certificate
active
06630631
ABSTRACT:
FIELD
Embodiments of the present invention relate to printed circuit board (PCB) technology and more particularly to interconnecting a component with a PCB.
BACKGROUND
Within the electronics industry there is a continuing effort to increase device density and speed. As device density increases, the number of interconnections per square inch of an electronic component may increase accordingly. To accommodate an increased number of interconnections, some electronic components are packaged in a ball grid array (BGA) package with an array of solder balls formed on a bottom surface. As illustrated in
FIG. 1
, a BGA component
110
may be interconnected with a printed circuit board (PCB)
120
by aligning an array of solder balls
112
having an array pitch “P” with a corresponding array of contact pads, such as contact pads
122
and
124
, formed on a top surface of the PCB
120
. The solder balls
112
may be reflowed to make electrical connections between the solder balls
112
and the contact pads
122
and
124
. A layer of solder mask
160
may prevent solder from wicking to adjacent contact pads during reflow.
Typically, the PCB
120
has numerous layers of conductive traces to route signals from the BGA component
110
to other electronic components mounted on both sides of the PCB
120
. The PCB
120
may also have a number of vias to route signals from contact pads to the signal routing layers. For example, a signal may travel from the solder ball
112
to the contact pad
122
and through a via
130
to a conductive trace on a bottom surface signal routing layer. The via
130
is typically formed by drilling a hole through the contact pad
122
and plating the drilled hole with a plating material
132
. For example, a hole having a diameter D
1
from 10-16 mils may be drilled through a contact pad having a diameter D
3
from 18-24 mils. To make efficient use of the signal routing area on the PCB
120
beneath the BGA component
110
, one or more conductive traces may be routed between adjacent contact pads
122
and
124
.
However, as device density increases, the BGA array pitch may shrink and the contact pads may occupy a larger percentage of signal routing area beneath the BGA component which may prevent signal routing between adjacent contact pads. One approach to increase the signal routing area is to reduce the diameter of the contact pads. However, as contact pad diameter decreases, it may become more difficult to drill a via hole through the contact pad due to drill wander and tolerance errors in the drilling process. Errors in the drilling process may lead to non-uniformity in contact pad configuration, which may result in manufacturing errors during assembly of the PCB, and may ultimately lead to scrapping the PCB. Another approach to increase signal routing area is to reduce the width and spacing of conductive traces. However, this approach may require more complicated manufacturing processes which may increase overall PCB cost.
REFERENCES:
patent: 5399898 (1995-03-01), Rostoker
patent: 5880030 (1999-03-01), Fang et al.
patent: 6020561 (2000-02-01), Ishida et al.
patent: 6274821 (2001-08-01), Echigo et al.
patent: 6335565 (2002-01-01), Miyamoto et al.
“Ball Grid Array (BGA) Packaging”, Intel 2000 Packaging Databook, Chapter 14, 2000.
“The Chip Scale Package (CSP)”, Intel 2000 Packaging Databook, Chapter 15, 2000.
Burgess, Larry W. Introducing Via-In-Pad Blind Via Technology to Any PCB Multilayer Fabricator, Technical Paper S15-2-1, IPC Printed Circuits Expo, San Jose, CA, Mar. 1997.
Wessel, Richard “Polymer Thick Film Via Plug for PCB's and Packaging Applications” Technical Paper S17-4-1, IPC Printed Circuits Expo, Long Beach, CA, Apr. 1998.
Dishongh Terrance J.
McCormick Carolyn R.
Intel Corporation
Norris Jeremy
Talbott David L.
Travis John F.
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