Semiconductor device manufacturing: process – Packaging or treatment of packaged semiconductor – Metallic housing or support
Reexamination Certificate
1999-07-27
2001-05-01
Picardat, Kevin M. (Department: 2823)
Semiconductor device manufacturing: process
Packaging or treatment of packaged semiconductor
Metallic housing or support
C438S106000, C438S110000, C438S118000, C438S121000
Reexamination Certificate
active
06225146
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a lead frame for a semiconductor device mounting a semiconductor chip such as a semiconductor integrated circuit chip and a transistor, a method of manufacturing the lead frame, a semiconductor device and a method of manufacturing the semiconductor device. More particularly, it relates to improvement in reliability and application to multi-pin devices.
A conventional lead frame will be described with reference to drawings.
FIG. 27
is a plan view for showing the structure of the conventional lead frame. As is shown in
FIG. 27
, the conventional lead frame includes a rectangular outer frame
110
; a rectangular die pad
101
disposed at substantially the center of an area surrounded with the outer frame
110
for mounting a semiconductor chip; first inner leads
102
, second inner leads
103
, third inner leads
104
and fourth inner leads
105
electrically connected with the semiconductor chip mounted on the die pad
101
through connecting means such as metal wires; first outer leads
106
, second outer leads
107
, third outer leads
108
and fourth outer leads
109
respectively formed continuous with the first inner leads
102
, the second inner leads
103
, the third inner leads
104
and the fourth inner leads
105
for connection with external terminals; a dam bar
111
for connecting and fixing the first outer leads
106
, the second outer leads
107
, the third outer leads
108
and the fourth outer leads
109
; and tie-bars
113
for connecting the corners of the outer frame
110
with the corresponding corners of the die pad
101
. In this manner, the die pad
101
is supported by the tie-bars
113
in the conventional lead frame.
The conventional lead frame is manufactured through procedures as is shown in FIGS.
28
(
a
) and
28
(
b
). FIGS.
28
(
a
) and
28
(
b
) are partial plan views for showing the manufacturing procedures for the conventional lead frame, wherein merely the upper right portion of the lead frame is shown.
First, as is shown in FIG.
28
(
a
), a metal plate
114
is etched or pressed, thereby forming, in the metal plate
114
, the die pad
101
, the tie-bars
113
, the inner leads
102
through
105
(among which the inner leads
103
and
104
are not shown) connected with the die pad
101
, the outer leads
106
through
109
(among which the outer leads
107
and
108
are not shown) formed continuous with the inner leads
102
through
105
for connection with external terminals, the outer frame
110
, and the dam bar
111
for connecting and fixing the outer leads
106
through
109
. Thus, a lead frame body
115
is formed. At this point, every two inner leads are connected with each other at their tips among the inner leads
102
through
105
.
Then, as is shown in FIG.
28
(
b
), the tips of the inner leads
102
through
105
of the frame body
115
are cut off (a tip cutting procedure), so that the inner leads
102
through
105
can be separated from the die pad
101
and independent of one another. After the procedure shown in FIG.
28
(
a
) and before the procedure shown in FIG.
28
(
b
), a plating procedure for plating the lead frame body
115
can be carried out. In the procedure shown in FIG.
28
(
b
), since every two inner leads are connected with each other among the inner leads
102
through
105
in the previous procedure, the connected tips are cut off.
Next, a semiconductor device using the conventional lead frame will be described.
FIG. 29
is a plan view of a conventional semiconductor device, and
FIG. 30
is a sectional view taken on line XXX—XXX of FIG.
29
.
As is shown in
FIGS. 29 and 30
, a semiconductor chip
116
is bonded onto the die pad
101
supported by the tie-bars
113
, and the first inner leads
102
, the second inner leads
103
, the third inner leads
104
and the fourth inner leads
105
are disposed in the vicinity of respective sides of the semiconductor chip
116
, namely, a first side
116
a
, a second side
116
b
, a third side
116
c
and a fourth side
116
d
, respectively. Electrode pads
117
of the semiconductor chip
116
are electrically connected with the inner leads
102
,
103
,
104
and
105
through metal wires
118
. Then, the semiconductor chip
116
, the die pad
101
, the tie-bars
113
, the inner leads
102
,
103
,
104
and
105
and the metal wires
118
are sealed with a sealing resin
119
, so that the first outer leads
106
, the second outer leads
107
, the third outer leads
108
and the fourth outer leads
109
can be protruded from the sealing resin
119
. Ultimately, the dam bar
111
is cut off, the outer frame
110
is removed, and the outer leads
106
,
107
,
108
and
109
are formed into desired shapes. Thus, the semiconductor device is completed.
In the plan view of
FIG. 29
, the sealing resin
119
is shown as a transparent substance, and merely the outline thereof is shown.
However, the conventional lead frame and the conventional semiconductor device using the lead frame have the following problems:
First, when the lead frame is used for a semiconductor device, the outer leads are protruded from the side faces of the semiconductor device as external terminals. Therefore, there is a limit in compactness in the packaging area.
Second, even when the inner leads and the outer leads are formed with small pitches therebetween and a semiconductor chip having a large number of electrode pads is mounted, there is a limit in application to multi-pin devices. Actually, the applicable number of pins is limited to approximately
160
.
Third, since the lead frame includes the dam bar, the procedure for cutting off the dam bar and forming the outer leads into desired shapes is indispensable after the resin sealing procedure in the manufacture of a semiconductor device. Therefore, there is also a limit in decreasing the manufacturing procedures for the semiconductor device.
SUMMARY OF THE INVENTION
The object of the invention is providing a lead frame, a method of manufacturing the lead frame, a semiconductor device and a method of manufacturing the semiconductor device, which can attain a compact packaging area, can be applied to multi-pin devices and can simplify manufacturing procedures, by adopting a structure of a lead frame suitable to disposing exposed external terminals on a bottom of a semiconductor device.
The lead frame of this invention for use in manufacturing a semiconductor device including a semiconductor chip comprises an outer frame; supporting leads connected with the outer frame; inside inner leads which are independent of one another, whose tips are disposed within or in the vicinity of an area for the semiconductor chip and whose ends are disposed at outside of the area for the semiconductor chip and are separated from the outer frame; and an insulator fixed on top faces of the supporting leads and the inside inner leads, wherein the inside inner leads are supported by the supporting leads through the insulator.
In this lead frame, the ends of the inside inner leads are separated from the outer frame. Therefore, in manufacturing a semiconductor device by using this lead frame, a cutting procedure for separating the inside inner leads from the outer frame is not required to be conducted after resin sealing. Specifically, the outer frame can be removed with ease by separating an outer frame from the supporting lead close to the outer frame. Accordingly, the resultant semiconductor device is free from burrs, which are formed on the side faces of the sealing resin through the conventionally required cutting procedure for the outer frame, and thus, a so-called burr-less semiconductor device having an accurate shape can be obtained. A “burr” herein means a rigid filler and the like of the sealing resin remaining without being cut and extending outward from the obtained package, and is an unnecessary part for the resin sealing. Also, external terminals can be two-dimensionally disposed by using the back faces of the inside inner leads as the external terminals, and hence, a high packaging
Minamio Masanori
Nomura Toru
Oga Akira
Yamaguchi Yukio
Collins D. M.
Matsushita Electronics Corporation
McDermott & Will & Emery
Picardat Kevin M.
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