Active solid-state devices (e.g. – transistors – solid-state diode – Combined with electrical contact or lead – Solder wettable contact – lead – or bond
Reexamination Certificate
2003-02-21
2004-04-06
Nelms, David (Department: 2818)
Active solid-state devices (e.g., transistors, solid-state diode
Combined with electrical contact or lead
Solder wettable contact, lead, or bond
Reexamination Certificate
active
06717277
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
The present invention relates generally to electronic circuit packages and methods of fabrication therefor, and more particularly, to integrated circuit packages having bond pads that are directly connected with vertically-oriented conductive layers, rather than with vias or horizontally-oriented conductive layers.
BACKGROUND OF THE INVENTION
Signals, power, and ground typically are routed to and from an integrated circuit (IC) through conductive bond pads on the bottom of the IC, which mate with complementary bond pads on the top surface of an IC package. This is common for ICs that use ball grid array (BGA) (e.g., “flip chips”) and land grid array (LGA) interconnection technologies. Alternatively, wire bonds are often used to electrically connect an IC and an IC package.
FIG. 1
illustrates a cross-sectional view of an electronic assembly that includes an IC
102
and package
104
in accordance with the prior art. Bond pads
106
on the bottom surface of IC
102
electrically connected to complementary bond pads
108
on the top surface of IC package
104
using solder bumps or balls
110
. The IC package bond pads
108
are, in turn, electrically connected to vias
112
. Vias
112
are plated and/or filled holes in the package's dielectric layers, which are used to interconnect various conductive layers
114
within the package
104
, and/or connectors
108
,
116
on the top and/or bottom surfaces, respectively, of the package
104
.
Package
104
is electrically connected to a socket
118
or interposer (not shown), through soldered or pinned connectors
116
. Socket
118
, in turn, is electrically connected to a printed circuit (PC) board
122
using pinned or soldered connections. Alternatively, package
104
can be connected directly to PC board
122
without the use of an intermediate socket or interposer. Using prior art technologies, input/output (I/O) signals, power, and ground are supplied from PC board
122
to IC
102
through socket
118
, connectors
116
, conductive layers
114
, vias
112
, pads
108
, and solder balls
110
.
FIG. 2
illustrates a top view of an IC package, which includes multiple rows of pads
202
,
204
in accordance with the prior art. Pads
204
within a center region
206
of the package typically are allocated to power and ground. In contrast, pads
202
within a peripheral region
208
typically are allocated to I/O signals.
Current packaging technologies are limited in the location and number of pads
202
that can be dedicated to I/O signals because of the need to separately fan out, through vias and traces, each I/O signal from the IC pad pitch to the package pad pitch. In current flip chip packages, only the outer few rows of pads
202
can be dedicated to I/O signals. Thus, for example, in a package having 40×40 rows of pads, only about 300 pads can be dedicated to I/O signals, while about 1300 pads can be dedicated to power and ground. In order to increase the number of I/O signals that can be fanned out, it is necessary to use finer design rules (e.g., smaller line spacing and pad pitches), increase the size of the IC, and/or increase the number of package layers. Using finer design rules translates to more expensive materials and manufacturing techniques.
IC package size and package layer increases are undesirable in many applications, because the consumer-driven trend within industry is to reduce the size of electronic systems. Accordingly, what are needed are package designs that enable higher I/O counts without increases in IC sizes, package layer counts or finer package design rules.
In addition to issues relating to limited numbers of I/O signals, noise in the power and ground lines increasingly becomes a problem with current IC package designs. This is primarily due to escalating circuit frequencies, which result in increased high frequency transients. To reduce such noise, capacitors known as decoupling capacitors are often used to provide a stable signal or stable supply of power to the circuitry. Decoupling capacitors are also used to suppress unwanted radiation, to dampen voltage overshoot when an electronic device (e.g., a processor) is powered down, and to dampen voltage droop when the device powers up.
Decoupling capacitors are generally placed as close as practical to a die load in order to increase the capacitors' effectiveness. Often, the capacitors are surface mounted to the die side or land side of the package upon which the die is mounted, or embedded within the package itself. Referring again to
FIG. 1
, die side capacitors
130
(“DSC”) and land side capacitors (not shown) (“LSC”) are mounted on IC package
104
in accordance with the prior art. DSCs
130
, as their name implies, are mounted on the same side of the package
102
as the IC
102
. In contrast, LSCs are mounted on the opposite side of the package
104
as the IC
102
. Embedded chip capacitors (not shown) (“ECC”) can be embedded within the package
104
and electrically connected to package planes and/or pads through conductive vias.
When a “first level” voltage droop occurs, the electrically closest, off-chip capacitors (e.g., ECCs, if they are available) will respond first to supply the current needed to bolster the die voltage. When the charge stored within these first level capacitors begins to deplete, a “second level” voltage droop occurs, and other off-chip capacitors (e.g., DSCs and/or LSCs) will respond, if they are available.
The capacitors' terminals are connected to the integrated circuit load through conductive structures (e.g., pads, vias, and power or ground planes), thus enabling the capacitors
130
to provide decoupling capacitance to the integrated circuit. Connection of the capacitors
130
to the load and to each other through the package's conductive structures results in “vertical” and “lateral” inductances to exist in the supply and return loop between the capacitors
130
and the IC load. These vertical and lateral inductances tend to slow the response time of off-chip capacitors, which may cause the first and second level voltage droops to be unacceptably low.
Vertical inductance issues can be addressed by placing off-chip capacitors
130
as electrically close as possible to the die load, such as by using ECCs, which typically can be placed closer to the load than surface mounted capacitors. Similarly, lateral inductance issues can be addressed by placing adjacent capacitors as close as possible to each other.
As the frequencies and edge rates of electronic devices continue to advance, there is an increasing need for higher levels of decoupling capacitance. However, increasing the numbers of discrete decoupling capacitors typically results in increased package sizes. Therefore, what are needed are packages that can provide higher levels of decoupling capacitance, without increased package sizes, and at reduced inductance levels.
REFERENCES:
patent: 6031282 (2000-02-01), Jones et al.
patent: 6495912 (2002-12-01), Huang et al.
patent: 6556453 (2003-04-01), Figueroa et al.
Chung Chee-Yee
Figueroa David G.
Sankman Robert L.
Intel Corporation
Le Thao P.
Nelms David
Schwegman Lundberg Woessner & Kluth P.A.
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