Active solid-state devices (e.g. – transistors – solid-state diode – Housing or package – For plural devices
Reexamination Certificate
2001-01-17
2002-10-08
Talbott, David L. (Department: 2827)
Active solid-state devices (e.g., transistors, solid-state diode
Housing or package
For plural devices
C257S724000, C257S706000, C257S720000, C257S696000, C257S738000, C257S780000, C257S779000, C257S777000
Reexamination Certificate
active
06462412
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a high-density laminate-type semiconductor apparatus having a plurality of semiconductor devices mounted on a plurality of flexible substrates. In particular, the present invention relates to a laminate-type semiconductor apparatus using a plurality of foldable flexible substrates. The present invention is utilizable as an assembly structure of a variety of semiconductor apparatuses such as a MOSFET, MISFET and other field-effect transistors, for example, and yet, the present invention can also be utilized as a practical technique for fabricating a laminate-type semiconductor apparatus by way of using a plurality of foldable flexible substrates.
2. Description of the Related Art
Because of the demand for further downsizing and higher density, higher density mounting of component parts has thus been demanded for electronic apparatuses using semiconductor apparatuses. To achieve this, in semiconductor apparatuses being a constituent of the electronic component parts, there are such proposals with regard to so-called “chip-size-package (CSP)” or “multi-chip-module (MCM)” each having such a size substantially equivalent to that of a semiconductor apparatus, or such a laminate-type semiconductor package comprising plural elements laminated in the height direction for contraction of the mounting area, for example. The above-cited packages have already been provided for practical services.
There are various proposals with regard to the laminate-type semiconductor apparatus using a foldable flexible substrate having various semiconductor devices mounted thereon, which is laminated on predetermined areas of the folded substrate, and yet, this apparatus has actually been provided for practical use. It should be noted that the terms “foldable” mentioned in the present specification implies that the above-cited laminate-type semiconductor devices can be processed via lamination by allowing desired areas to be superposed with each other. In this case, clear fold is not always required, but insofar as lamination can be effected, and yet, insofar as flexibility is retained, even such a substrate with curved form, plate-form, tape-form or sheet-form may also be used. With regard to the laminate-type semiconductor-device mounted apparatus, refer to the Japanese Patent Application Laid-Open Publication No. HEISEI-11-135715/1999, for example.
There is such a proposal on a conventional laminate-type semiconductor apparatus or a semiconductor package as the one shown in
FIG. 3
via a lateral sectional view.
According to the above-cited conventional laminate-type semiconductor apparatus, a plurality (four, in this case) of semiconductor elements comprising a first device
3
, a second device
4
, a third device
4
, and a fourth device
30
, are laminated in the vertical direction of FIG.
3
. As shown in
FIG. 4
via a development view, the first device
3
, the second device
4
, the third device
5
, and the fourth device
30
, are mounted on edge portions of crossed members of a cross-form flexible substrates before being folded into an assembly, whereby forming a laminated structure by way of superposing four devices one after another like the one shown in FIG.
3
. The development view shown in
FIG. 4
is illustrative of a position at which back surface shown in
FIG. 3
corresponding to an externally-connected terminal disposing area
6
is visible on the upper side.
Detail of the development view shown in
FIG. 4
will be described below. Initially, by way of utilizing a plurality of substrates made of polyimide resin, a plurality of flexible substrates foldable as a whole are assembled as shown in
FIG. 4
via the development view. In this conventional example, the flexible substrates are assembled into a crossed formation. The center portion of the crossed substrates is determined as the externally-connected terminal disposing area
6
for accommodating an externally connected terminal
7
as shown in FIG.
3
. Next, originating from the center portion, four of the semiconductor-device mounting areas
61
,
62
,
63
, and
64
, are independently formed via foldable wiring distributing areas
11
,
12
,
13
, and
50
, respectively, to complete formation of a wiring substrate
2
. Individual semiconductor devices are mounted on respective semiconductor-device mounting areas
61
,
62
,
63
, and
64
formed on the wiring substrate
2
. More particularly, the above-referred semiconductor devices comprising the first device
3
, the second device
4
, the third device
5
, and the fourth device
30
, are mounted on the corresponding semiconductor-device mounting areas
61
,
62
,
63
, and
64
. This completes such a semiconductor apparatus having a plurality of semiconductor devices
3
,
4
,
5
, and
30
mounted on the back-surface side (inside of the apparatus) of the externally-connected terminal disposing area
6
.
Reference codes “a”, “b”, “c”, and “d” shown in
FIG. 4
respectively designate connecting parts between respective semiconductor-device mounting areas
61
,
62
,
63
and
64
and wiring extended areas
11
,
12
,
13
and
50
.
In terms of such a semiconductor package comprising a laminated assembly of semiconductor devices laminated on a polyimide substrate, introduction of module structure has recently been promoted in the assembly of memory devices and also in the assembly of logic devices and memory devices. Because of this, the number of laminated layers tends to become greater. However, as the number of laminated layers increases, thermal radiation generated by individual elements becomes a critical problem. In the above-cited conventional laminate-type package, the laminate-type structure has the substrate
2
which is developed as shown in FIG.
4
. On the other hand, as shown in
FIG. 3
, when forming a laminate-type package by serially laminating the first device
3
, the second device
4
, the third device
5
, and the fourth device
30
, individual lamination causes thermal radiation to grow to necessitate any counter-measure to deal with this problem.
Further, whenever laminating semiconductor devices on a flexible substrate, a problem may be generated by effect of folding stress via a folding process. For example, when forming a laminate-type package by way of folding a flexible polyimide substrate, because of the folding stress via the folding process, leveling effect can hardly be achieved throughout the above-referred externally-connected terminal disposing area
6
, thus raising such a problem. Because of this, in order to improve effect of connection between the externally-connected terminal disposing area
6
and the substrate for accommodating it via a soldering process, it has thus been necessary to implement any measure to ensure leveling effect, in other words, improve the parallelism.
As was described above, in the conventional laminate-type semiconductor apparatuses, in order to achieve higher density of such a package mounted with laminated semiconductor devices, a laminate-type structure is formed by way of folding a flexible substrate which is made of a flexible polyimide plate or a polyimide tape, for example. However, when a number of semiconductor devices are laminated, it is quite difficult to suppress amount of heat generated by respective semiconductor devices to damage operating function of the package itself. On the other hand, in the case of lamination of semiconductor devices on a flexible polyimide substrate such as a flexible polyimide plate or a polyimide tape, for example, via a folding process, it had thus been necessary to implement any measure to level off the substrate before mounting semiconductor devices on the substrate via a soldering process, and yet, it had thus been necessary to fully ensure strength of the connected effect between them.
SUMMARY OF THE INVENTION
The object of the present invention is to fully solve the above-referred technical problems by way of providing a novel semiconductor apparatus which is free from incurrin
Kamei Shigeki
Takagi Saeko
Rader & Fishman & Grauer, PLLC
Talbott David L.
Thai Luan
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