Reexamination Certificate
1998-01-30
2001-10-30
Chaudhuri, Olik (Department: 2814)
C257S780000, C257S783000
Reexamination Certificate
active
06308938
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a semiconductor integrated circuit device which has a ball grid array structure, package particularly to a semiconductor integrated circuit device having reliable on connections between the semiconductor integrated circuit device and a printed-wiring board on which the semiconductor integrated circuit device is mounted. Further, the present invention relates to a semiconductor integrated circuit device which is thin and has a high bending stiffness.
2. Discussion of Background
In recent years, the number of pins used in a semiconductor integrated circuit device has been increasing. Therefore, a package (hereinbelow, referred to as BGA
20
package) having a ball grid array structure is conventionally used, wherein conductive terminals having a spherical-shape, as an external connection terminal, are formed in a grid array. Such a BGA package is paid attention to because this package can satisfy increasing requirements for the packages, such as an increment in the number of pins, miniaturization, and a thin body.
FIGS. 9 and 10
respectively show structures of conventional BGA packages. The BGA package shown in
FIG. 9
has a conductive pad provided on a principal surface of semiconductor chip
1
electrically connected to a conductors
6
through a conductive adhesive
9
at one surface side of a carrier base
3
, and external output terminals
8
are provided on the conductor
6
at the other surface side of the carrier base
3
.
On the other hand, the BGA package shown in
FIG. 10
has a bonding pad provided on a principal surface of semiconductor chip
1
electrically connected to conductors
6
through bonding wires
7
to one surface side of a carrier base
3
, and external output terminals
8
are provided on the conductor
6
at the other surface side of the carrier base
3
.
In
FIGS. 9 and 10
, numeral
2
designates a die pad, and numeral
5
designates a sealing resin layer.
However, it has been pointed out recently that there is a problem of reliability on connection between such a BGA package and a printed-wiring board on which the BGA package is mounted. For example, in Nikkei Electronics (vol. 1997.7.28 (No. 695), pages 19 through 20), it is reported that because of a difference between a coefficient of thermal expansion of a semiconductor chip made of silicon
1
and that of an interposer (hereinbelow, referred to as carrier base) on which the semiconductor chip is directly installed, the largest deformation occurs at a central portion of BGA package, corresponding to a lower portion of the semiconductor chip
1
, after a heat cycle test is conducted, and therefore solder balls connecting the package to a printed-wiring board, in which the package is equipped with, are apt to break by fatigue.
Specifically, as shown in
FIG. 11
, there was a phenomenon that a central portion at a side other than the side in which a semiconductor chip
1
is provided (namely, at the side in which external connection terminals
8
are provided) cambers when a carrier base
3
has a larger coefficient of thermal expansion than that of the semiconductor chip
1
. The external connection terminals
8
of solder balls in the central portion receive a large load, therefore, that a crack is caused at an interface between the solder balls
8
in the central portion and the printed-wiring board
10
or in the solder balls
8
themselves. Thus the package was destroyed.
On the other hand, in order to evade affects of thermal stress caused by the difference between the coefficient of thermal expansion of the carrier base
3
and that of the printed-wiring board
10
, it was proposed to use fiber-reinforced plastics for the carrier base
3
. However, when the carrier base
3
made of fiber-reinforced plastics was used, the deformation of the central portion of BGA package caused by the difference of the coefficients of thermal expansion became large, whereby a problem of reliability of connections against deformation became conspicuous.
In the next approach, a ceramic was used for the carrier base
3
, sacrificing the effects of thermal stress caused by the difference between the coefficient of thermal expansion of the carrier base
3
and that of the printed-wiring board
10
. In this case, the difference between the coefficient of thermal expansion of the semiconductor chip
1
and that of the carrier base
3
was small and the deformation of the BGA package at the central portion thereof caused by the difference between the thermal coefficients became small. However, the deformation can not completely be eliminated and problems such as cracks and breakage in the solder balls
8
have been still existed though the extent of each problem was different.
SUMMARY OF THE INVENTION
The present invention is to solve the above mentioned problems inherent in the prior art. It is an object of the present invention to provide a semiconductor integrated circuit device comprising a BGA package having a high reliability of connection to a printed-wiring on which the package is mounted during heat cycling.
It is another object of the present invention to provide a semiconductor integrated circuit device comprising a BGA package which is thin and has a stiffness strong enough to bear a bending stress.
According to a first aspect of the present invention, there is provided a semiconductor integrated circuit device comprising a semiconductor chip having a plurality of connection pads; a plurality of conductors electrically connected to the plurality of connection pads; and a plurality of external connection terminals of a spherical-shape corresponding respectively to the plurality of conductors, further comprising: a sealing resin layer surrounding a periphery of the semiconductor chip; a carrier base; a reinforcement base, characterized by the semiconductor chip and the sealing resin layer form a core material, the carrier base and the reinforcement base are skin materials, the core material and the skin materials constitute a sandwich structure, the connections of conductors with the connection pads are provided in one surface of the carrier base, the conductors are provided in the other surface of the carrier base, and the external connection terminals are provided in the other surface of the carrier base.
According to a second aspect of the present invention, there is provided a semiconductor integrated circuit device according to the first aspect of the invention, wherein the plurality of connection pads in the semiconductor chip and the plurality of conductors are connected electrically by bending wires, and the semiconductor chip is equipped with by adhering to the surface of the carrier base interposing a die pad which is provided in the carrier base.
According to a third aspect of the present invention, there is provided a semiconductor integrated circuit device according to the first aspect of the invention, wherein the plurality of connection pads in the semiconductor chip and the plurality of conductors are connected electrically interposing conductive adhesive only.
According to a fourth aspect of the present invention, there is provided a semiconductor integrated circuit device according to the first aspect of the invention, wherein the plurality of conductors provided on the other surface of carrier base are arranged in the form of grid array having a plurality of rows and plurality of columns.
According to a fifth aspect of the present invention, there is provided a semiconductor integrated circuit device according to the first aspect of the invention, wherein the reinforcement base is embedded in the sealing resin layer.
According to a sixth aspect of the present invention, there is provided a semiconductor integrated circuit device according to the first aspect of the invention, wherein a distance from a center plane with respect to the thickness direction of semiconductor chip to the reinforcement base is the same as a distance from the center plane to the carrier base.
According to a seventh aspect o
Chaudhuri Olik
Leydig, Voit & Mayer,Ltd.
Mitsubishi Denki & Kabushiki Kaisha
Wille Douglas A.
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