Active solid-state devices (e.g. – transistors – solid-state diode – Housing or package – For plural devices
Reexamination Certificate
2000-02-24
2002-06-25
Potter, Roy (Department: 2822)
Active solid-state devices (e.g., transistors, solid-state diode
Housing or package
For plural devices
C257S701000, C257S731000
Reexamination Certificate
active
06410983
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to semiconductor devices and, more particularly, to a semiconductor device having a plurality of multi-chip modules connected to each other, each of the multi-chip modules having a plurality of input/output terminals.
2. Description of the Related Art
Recently, in the electronic equipment field, a multi-chip module (MCM) has been put into practice. The MCM comprises a thin-film circuit board which can achieve a high-density wiring and functional parts mounted on the thin-film circuit board.
FIG. 1
is a perspective view of a conventional multi-chip module (MCM). The conventional MCM
1
shown in
FIG. 1
comprises an MCM board
2
, a plurality of functional parts
3
and a plurality of input/output pins
4
. The functional parts
3
include a CPU chip for processing data, a cache memory chip for temporarily storing processed data and an interface LSI chip for controlling the input and output of signals in the MCM
1
.
Generally, the MCM board
2
of the MCM
1
has a size of a few square centimeters. The MCM board
2
is made of a ceramic material. A thin-film multi-layered circuit is formed on the ceramic material. The functional parts
3
are mounted on the MCM board
2
by means of bump connections, which enables high-density connections. The bumps are made from solder or gold. Each of the bumps has a ball-like shape having a diameter of tens of micrometers. Accordingly, a part having terminals arranged in a grid with a pitch of hundreds of micrometers can be mounted.
According to the above-mentioned structure, a wiring pattern between the MCM board
2
and the functional parts
3
can be made short so as to increase the signal transmission throughput. Thus, the MCM
1
has become popular in the electronic equipment field in which computers requiring a high-speed operation are included.
FIG. 2
is a perspective view of a printed circuit-board unit having a plurality of MCMs
1
shown in FIG.
1
. In
FIG. 2
, the printed circuit-board unit
11
comprises a motherboard
12
, a plurality of MCMs
1
, a plurality of memory sockets
13
for mounting RAMs, and a plurality of I/O connectors
14
for connecting input/output cables. It should be noted that each of the MCMs
1
shown in
FIG. 2
has a height greater than that shown in
FIG. 1
since each of the MCMs
1
is usually provided with a heat sink mounted on the functional parts
3
.
The printed circuit-board unit
11
is used as a brain of a computer system that requires high-speed data processing. As mentioned above, as computer systems have come to require a high-level function, the number of MCMs used in the printed circuit-board unit has been increasing.
If there is an MCM that satisfies a whole function alone, there is no need to provide the interconnection between the MCMs. However, in practice, such a large MCM is not favored due to low yield rates and large investment required for the manufacturing facility.
FIG. 3
is a side view of a part of the printed circuit board unit
11
shown in FIG.
2
. As shown in
FIG. 2
, wiring patterns
26
and
27
are formed between the MCM
1
-
1
and the MCM
1
-
2
mounted on the motherboard
12
so as to interconnect the MCMs
1
-
1
and
1
-
2
. The wiring patterns
26
and
27
are formed in a thick-film wiring layer formed on the motherboard
12
. The signal transmission throughput between the MCMs
1
-
1
and
1
-
2
is a major factor in determining the processing capability of the system. Accordingly, lengths of the wiring patterns
26
and
27
are preferably as short as possible so as to achieve a quick signal transmission.
The path of each of the wiring patterns
26
and
27
extends between a terminal of the interface LSI chip
20
-
1
of the MCM
1
-
1
and a terminal of the interface LSI chip
20
-
2
of the MCM
1
-
2
. Each of the wiring patterns
26
and
27
routes one of bumps
23
-
1
of the interface LSI chip
20
-
1
, a thin-film multi-layer circuit
25
-
1
, a through hole
28
-
1
of a ceramic board
24
-
1
, one of the input/output pins
4
-
1
, the thin-film multi-layer circuit
25
of the motherboard
12
, one of the input/output pins
4
-
2
, a through hole
28
-
2
of a ceramic board
24
-
2
, a thin-film multi-layer circuit
25
-
2
and one of the bumps
23
-
2
of the interface LSI chip
20
-
2
.
Consideration is made to the length of the wiring patterns
26
and
27
with respect to a direction (vertical direction) of the height of the MCMs
1
-
1
and
1
-
2
and a direction (horizontal direction) parallel to the mounting surface of the motherboard
12
. With respect to the vertical direction, a length of each of the through holes
28
-
1
and
28
-
2
of the ceramic boards
24
-
1
and
24
-
2
must be a few millimeters, which is equal to the thickness of each of the ceramic boards
24
-
1
and
24
-
2
, respectively. A length of each of the input/output pins
24
-
1
and
24
-
2
must be a few millimeters when a pin grid array (PGA) is used to absorb a distortion generated in the mounting structure between the motherboard
12
and each of the MCMs
1
-
1
and MCM
1
-
2
.
With respect to the horizontal direction, the path distance between the input/output pins
4
-
1
of the MCM
1
-
1
and the input/output pins
4
-
2
of the MCM
1
-
2
to be connected to each other is determined by the wiring rule of the motherboard
12
. If a distance between the terminal of the interface LSI chip
20
-
1
is far from the input/output pins
4
-
1
to be connected as shown in
FIG. 3
, a long wiring path must be provided.
As mentioned above, in the structure shown in
FIG. 3
, the wiring path between the MCM
1
-
1
and the MCM
1
-
2
must always extend through the motherboard
12
. Accordingly, the length of each of the wiring patterns
26
and
27
cannot be shorter than a predetermined length.
In order to reduce the length of the wiring path between the MCMs, a structure in which the MCMs are interconnected by a flexible wiring board
30
as shown in
FIG. 4
has been suggested. The flexible wiring board
30
shown in
FIG. 4
is a flexible board having a high-density wiring structure formed by thin-film multi layered circuits.
In
FIG. 4
, each of the wiring patterns
26
and
27
shown in
FIG. 3
corresponds to a total of a wiring pattern
32
-
1
connecting the interface LSI chip
20
-
1
to the flexible circuit board
30
, a wiring pattern
32
-
2
connecting the the interface LSI chip
20
-
2
to the flexible circuit board
30
and a wiring pattern
31
extending through the flexible wiring board
30
.
The length of the wiring pattern connecting the interface LSI chips
20
-
1
and
20
-
2
does not include the lengths of the through holes
28
-
1
and
28
-
2
of the ceramic boards
24
-
1
and
24
-
2
and the lengths of the input/output pins
4
-
1
and
4
-
1
that exist in the structure shown in FIG.
3
. Thus, a length of the wiring path along the vertical direction is reduced by a few millimeters.
In the horizontal direction, there is no need to provide the wiring path from the terminal of the each of the interface LSI chips
20
-
1
and
20
-
2
to the respective one of the input/output pins
4
-
1
and
4
-
2
and the wiring path corresponding to the path in the motherboard
12
. Accordingly, the wiring path is shortened by tens of millimeters.
In the structure shown in
FIG. 4
, the wiring pattern
32
is newly added. However, since the eliminated length of the wiring path extending in the motherboard
12
as shown in
FIG. 3
is greater than the newly provided wiring pattern
32
, the lengths of wiring patterns shown in
FIG. 4
are shorter that that shown in FIG.
3
.
However, there is a demand for further increasing the processing throughput due to continuous increase in the processing speed of computer systems. In order to further increase the processing throughput, it is required to further shorten the wiring patterns interconnecting the MCMs.
SUMMARY OF THE INVENTION
It is a general object of the present invention to provide an improved and
Moriizumi Kiyokazu
Osawa Satoshi
Armstrong Westerman & Hattori, LLP
Fujitsu Limited
Potter Roy
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