Active solid-state devices (e.g. – transistors – solid-state diode – Combined with electrical contact or lead – Chip mounted on chip
Reexamination Certificate
2001-11-20
2004-02-17
Whitehead, Jr., Carl (Department: 2813)
Active solid-state devices (e.g., transistors, solid-state diode
Combined with electrical contact or lead
Chip mounted on chip
C257S723000, C438S107000, C438S109000
Reexamination Certificate
active
06693362
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to a multichip module and, more particularly, to a multichip module having LSI chips mounted on a wiring substrate of a composite structure.
In regard to a multichip module having LSI chips mounted on a wiring substrate, there are such requirements that the LSI chips be densely mounted, have high operating frequencies, be mounted in an arrangement that is easy to repair, and have a good heat radiation property.
In addition, there is a trend that LSI chips will have a micronized pattern and have narrowly pitched electrodes in the future. Accordingly, a wiring substrate on which these LSI chips are mounted needs to have a structure that can accommodate these LSI chips.
2. Description of the Related Art
A conventional chip module
10
comprises an LSI-chip-mounting wiring substrate
11
, and an LSI chip
20
mounted thereon, as shown in FIG.
1
. The LSI-chip-mounting wiring substrate
11
comprises a rigid substrate
12
formed of a glass epoxy and having a core material therein, built-up layers
13
and
14
formed on the upper and under surfaces of the rigid substrate
12
, bumps
15
formed on the undersurface of the built-up layer
14
, and an LSI chip-mounting part
16
provided on the upper surface of the built-up layer
13
. The LSI chip
20
is mounted on the LSI-chip-mounting part
16
in a flip-chip form. The chip module
10
is mounted on a motherboard
30
.
Since the chip module
10
employs a buildup method, the manufacture of the LSI-chip-mounting wiring substrate
11
does not exhibit a good yield. Additionally, due to a relatively low degree of evenness of the surface of the rigid substrate
12
, an L/S (line/space) of a wiring pattern of the LSI-chip-mounting part
16
is limited to approximately 25/25 &mgr;m not narrow enough to cope with electrodes of the LSI chip to be narrowly pitched.
Inventors of the present invention proposed a multichip module solving the above-mentioned problems. Japanese Laid-Open Patent Application No. 2000-353765 describes this multichip module. As shown in
FIG. 2
, this multichip module
40
comprises an LSI-chip-mounting wiring substrate
41
, and LSI chips
45
and
46
mounted thereon in a flip-chip form. The multichip module
40
is mounted on the motherboard
30
.
The LSI-chip-mounting wiring substrate
41
has a composite structure comprising a rigid substrate
42
formed of a glass epoxy and having a core material therein, and a flexible substrate
43
bonded on the upper surface of the rigid substrate
42
. An LSI-chip-mounting part
44
is formed on the upper surface of the flexible substrate
43
.
The flexible substrate
43
is manufactured by sputtering and etching on a surface of a glass board having a high degree of evenness, which are eventually removed from the glass board.
Since the LSI-chip-mounting wiring substrate
41
is manufactured by bonding the flexible substrate
43
manufactured independently of the rigid substrate
42
on the upper surface of the rigid substrate
42
, the manufacture of the LSI-chip-mounting wiring substrate
41
exhibits an improved yield, compared with the chip module
10
employing the buildup method. Additionally, an L/S of a wiring pattern of the LSI-chip-mounting part
44
becomes smaller than approximately 25/25 &mgr;m, narrow enough to cope with electrodes of the LSI chip to be narrowly pitched.
In the multichip module
40
, however, the LSI chips
45
and
46
can be mounted only on the upper surface of the LSI-chip-mounting wiring substrate
41
; thus, it is difficult to mount the LSI chips densely enough.
SUMMARY OF THE INVENTION
It is a general object of the present invention to provide an improved and useful multichip module in which the above-mentioned problems are eliminated.
A more specific object of the present invention is to provide a multichip module which can have LSI chips mounted densely enough on a wiring substrate.
In order to achieve the above-mentioned objects, there is provided according to one aspect of the present invention a multichip module comprising:
a rigid substrate including a core material and having an opening;
a thin film fixed on an upper surface of the rigid substrate so as to be electrically connected to the rigid substrate and to close the opening, the thin film having an upper chip mounting part on an upper surface thereof and an under chip mounting part on an under surface thereof;
a first chip mounted on the upper chip mounting part; and
a second chip mounted on the under chip mounting part so as to be located in the opening,
wherein the rigid substrate and the thin film form a wiring substrate having a composite structure.
According to the present invention, the chips are mounted not only on the upper surface of the thin film but also on the under surface thereof. Thus, the chips are densely mounted on the wiring substrate.
The distance between the chip mounted on the upper surface of the thin film and the chip mounted on the under surface thereof becomes as extremely short as the thickness of the thin film. In a case where the upper and under chips are semiconductor chips, a delay of a signal transmitted between the upper and under semiconductor chips becomes so small that the delay can be ignored. This enables operating frequencies of the semiconductor chips to be increased. In another case where one of the chips is a semiconductor chip, and the other is a chip capacitor, inductance between the semiconductor chip and the chip capacitor becomes extremely small so as to make a full use of the chip capacitor; this enables elimination of high-frequency noises.
Additionally, in the multichip module according to the present invention, the thin film may comprise a first electrode pad formed on the upper chip mounting part, a second electrode pad formed on the under chip mounting part, and a via hole connecting the first electrode pad and the second electrode pad.
According to the present invention, bumps of the chip mounted on the upper chip mounting part of the thin film and bumps of the chip mounted on the under chip mounting part thereof are electrically connected to each other by way of the via hole formed in the thin film. This makes a delay of a signal transmitted therebetween so small that the delay can be ignored, and consequently, enables operating frequencies of the semiconductor chips to be increased. Thereby, the upper and under chips can function as one large-sized chip having functions of both the upper and under chips. Therefore, the cost of manufacturing the chips can be lowered while the performance of the chips is maintained.
Additionally, the multichip module according to the present invention may further comprise:
a lid joined to the upper surface of the rigid substrate so that the lid contacts and covers the first chip; and
a sealing member covering the second chip located in the opening.
According to the present invention, the lid and the sealing member protect the chips. Also, the lid encourages heat radiation so as to effectively cool the chip.
Additionally, in the multichip module according to the present invention, the first chip may produce a larger amount of heat than the second chip.
According to the present invention, the chip mounted on the upper surface of the thin film can be effectively cooled.
In order to achieve the above-mentioned objects, there is also provided according to another aspect of the present invention a printed board unit comprising:
a printed board; and
a multichip module mounted on the printed board via at least one bump, the multichip module including:
a rigid substrate including a core material and having an opening, the bump being formed on an under surface of the rigid substrate;
a thin film fixed on an upper surface of the rigid substrate so as to be electrically connected to the rigid substrate and to close the opening, the thin film having an upper chip mounting part on an upper surface thereof and an under chip mounting part on an under surface thereof;
a first chip mounted on the upper chip mo
Seyama Kiyotaka
Yamada Hiroshi
Yamamoto Haruhiko
Berezny Nema
Jr. Carl Whitehead
LandOfFree
Multichip module having chips mounted on upper and under... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Multichip module having chips mounted on upper and under..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Multichip module having chips mounted on upper and under... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3302252