Semiconductor device

Details Semiconductor device Semiconductor device

1998-10-07

2001-07-17

Lee, Eddie C. (Department: 2815)

Active solid-state devices (e.g., transistors, solid-state diode

Combined with electrical contact or lead

Beam leads

C257S696000, C257S692000, C257S687000, C257S734000, C257S736000, C257S787000

Reexamination Certificate

active

06262482

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to a semiconductor device having a structure achieved by bonding inner leads to a semiconductor element internally provided at a package.
The memory capacities in semiconductor devices such as memory units have been increasing, as in 16 Mb DRAM and 64 Mb DRAM in recent years, which has resulted in an increase in the size of the semiconductor element (chip) which is internally provided at the package. At the same time, there is a need for miniaturization of semiconductor devices to facilitate high density mounting in electrical products, and thus, a large semiconductor element must be mounted in a small package. As a means for achieving this, LOC (Lead On Chip) semiconductor devices having a structure achieved by using double-sided adhesive tape to directly bond inner leads to a front surface of a semiconductor element and packaging this with resin have been proposed.
FIG. 17
is a plan view illustrating the internal structure of an LOC semiconductor device
100
in the prior art.
FIG. 18
is a cross section along line D_D in
FIG. 17. A
plurality of inner leads
104
are bonded using a double-sided adhesive tape
103
having an insulating property at a front surface of a semiconductor element (chip)
102
covered by a package
101
. The inner leads
104
are each electrically connected with an electrode pad
105
provided at the front surface of the semiconductor element
102
via a wire
106
such as a metal wire. In addition, the assembly is sealed (molded) with liquid resin inside a forming die in a state in which the inner leads
104
are bonded to the front surface of the semiconductor element
102
to achieve a structure having the semiconductor element
102
internally provided in the package
101
. With the semiconductor device
100
having such an LOC structure, which does not require a die bat or the like for supporting the semiconductor element
102
unlike conventional packages, a relative increase can be achieved in the rate of the volume occupied by the semiconductor element
102
in the package
101
to realize miniaturization and high density mounting. Ultimately, with a semiconductor device
100
having the LOC structure, the ratio of the volume occupied by the semiconductor element
102
within the package
101
can be increased up to a maximum of approximately 90%.
However, in a semiconductor device having the LOC structure, the semiconductor element may be sometimes caused to move vertically within the forming die by the pressure of the liquid resin used for sealing and the like, resulting in the semiconductor element being placed at a position offset from the center inside the package. Such a misalignment of the semiconductor element is referred to as a chip shift. In the case of a semiconductor device having a so-called TSOP (Thin Small Outline Package) structure which employs a thin package, in particular, misalignment of the semiconductor element (chip shift) is problematic, since it may cause exposed wires and forming defects such as incomplete sealing of the package, which, in turn, will result in a reduction in the moisture resistance and the like.
SUMMARY OF THE INVENTION
Accordingly, an object of the present invention, which has been completed by addressing the problem of the semiconductor device in the prior art discussed above, is to provide a new and improved semiconductor device with which the pressure of the liquid resin or the like do not cause the semiconductor element to move vertically within the forming die during the sealing process.
Another object of the present invention is to provide a new and improved semiconductor device with which the semiconductor element can be internally provided at the center inside a package to eliminate problems such as exposed wires and forming defects, attributable to misalignment of the semiconductor element.
Yet another object of the present invention is to provide a new and improved semiconductor device with which exposed wire and forming defects attributable to misalignment of the semiconductor element can be prevented even in a semiconductor device employing a thin package such as, in particular, a semiconductor device with the TSOP structure.
In order to achieve the objects described above, in a first aspect of the present invention, a semiconductor device constituted by bonding a plurality of inner leads at a front surface of a semiconductor element covered by a package, which is characterized in that a bent portion is formed at some of the plurality of inner leads with the front end of the bent portion exposed at a front surface of the package, is provided.
In this semiconductor device, since the front ends of the bent portions formed at some of the inner leads are exposed at the front surface of the package, the semiconductor element can be prevented from moving toward the package front surface within the forming die by the bent portions even when the pressure of the liquid resin or the like is applied to the semiconductor element during the resin sealing process. Thus, this semiconductor device, in which the semiconductor element can be internally provided at the center of the package is free of problems such as exposed wire and forming defects caused by misalignment of the semiconductor element.
In addition, it is desirable that the inner leads at which the bent portions are formed not be electrically connected with the semiconductor element in the semiconductor device. This will ensure that the problem of an electrical signal erroneously input to the semiconductor element through the front ends of the bent portions exposed at the front surface of the package does not occur. Furthermore, the bent portions may each be formed by branching out from an inner lead that is not electrically connected with the semiconductor element. In this case, it is desirable that the inner leads having the bent portions be bonded to the front surface of the semiconductor element, since this will ensure that the bent portions are firmly secured to the front surface of the semiconductor element. Moreover, a supporting piece which is exposed parallel to the front surface of the package may extend at the front end of each bent portion. By providing such a supporting piece extending at the front end of the bent portion, the front surface of the supporting piece can be firmly placed in tight contact with the inner surface of the forming die during the resin sealing process so that the semiconductor element can be prevented from moving toward the package front surface within the forming die with a high degree of reliability. It is desirable that a double-sided adhesive tape be applied onto the front surface of the supporting piece in this case, since it will bond the front surface of the supporting piece to the inner surface of the forming die during the resin sealing process to prevent the semiconductor element from moving toward the package front surface within the forming die with an even higher degree of reliability.
In a second aspect of the present invention, a semiconductor device constituted by bonding a plurality of inner leads at a front surface of a semiconductor element covered by a package, which is characterized in that a bent portion is formed at some of the plurality of inner leads with the front end of the bent portion exposed at a first front surface of the package and in that each inner lead having the bent portion is bent within the package with the front end of the bent inner lead being exposed at a second front surface of the package is provided.
In this semiconductor device, in which the front ends of the bent portions formed at some of the inner leads are caused to be exposed at the first front surface of the package and the inner leads having the bent portions are bent with their front ends exposed at the second front surface of the package, the semiconductor element can be prevented from moving toward the first front surface of the package with the bent portions and the semiconductor element can also be prevented from moving toward the se

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