Method of making semiconductor device

Details Method of making semiconductor device Method of making semiconductor device

2003-09-17

2004-09-14

Nelms, David (Department: 2818)

Semiconductor device manufacturing: process

Packaging or treatment of packaged semiconductor

Metallic housing or support

C438S112000, C438S691000, C438S754000, C257S676000, C257S690000, C257S787000

Reexamination Certificate

active

06790711

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a semiconductor device and a manufacturing method thereof, and more particularly, relates to a semiconductor device using a lead frame as a wiring base member and a manufacturing method thereof.
2. Description of the Background Art
Under the background of high density integration of semiconductor chins, it has been increasingly popular to use a ball grid array (hereinafter referred to as BGA) type semiconductor device in which an external lead is arranged over a surface. Generally, in the BGA type semiconductor device, a printed circuit board as a wiring base is popularly used. Since such a convention BGA type semiconductor device is, however, high-priced, a BGA type semiconductor device using a low-priced lead frame as a wiring base member has been practically used.
A semiconductor device using a conventional lead frame as a wiring base member is hereinafter described with reference to the accompanying drawings.
FIG. 11A
is a sectional view showing a construction of a conventional BGA type semiconductor device disclosed in the Japanese Laid-Open Patent Publication (unexamined) No. Hei 11-74404, and
FIG. 11B
is a bottom view of the semiconductor device shown in FIG.
11
A.
FIG. 12A
is a plan view showing a lead frame used in the convention BGA type semiconductor device and arranged in a single line.
FIG. 12B
is a sectional view taken along the line XIIb—XIIb indicated by the arrows in FIG.
12
A.
FIG. 12C
is a sectional view taken along the line XIIc—XIIc indicated by the arrows in FIG.
12
A.
In
FIGS. 11A
,
11
B,
12
A,
12
B and
12
C, the conventional BGA type semiconductor device uses a lead frame
50
as a wiring base member, and a semiconductor chip
1
provided with a pad electrode is mounted on a die pad
2
with a junction material
3
. The semiconductor device has solder ball mounting portion (hereinafter referred to as external electrode portion)
4
. A lead electrode
5
, of which an inside end portion is radially arranged the die pad
2
, and a pad electrode of the semiconductor chip
1
are connected to each other through a connection lead
6
and sealed with a resin layer
7
. Portions
4
a
and
4
b
continued underneath the lead electrode
5
are made thin by etching except the external electrode portion
4
. Accordingly, the die pad
2
, the external electrode portion
4
and a suspension lead
8
for supporting the die pad
2
are exposed on the same surface as the under surface of the seal resin layer
7
. A solder ball
9
is mounted on the external electrode portion
4
, and an end of the lead electrode
5
and that of the suspension lead
8
are finally cut along the resin seal line
7
a.
A manufacturing method is hereinafter described with reference to
FIGS. 11
to
13
.
FIGS. 13A
,
13
B and
13
C are explanatory views showing a manufacturing method of the conventional BGA type semiconductor device.
FIG. 13A
is a sectional view of the lead frame shown in FIG.
12
C.
FIG. 13B
is a sectional view showing molds applied at the time of sealing with the seal resin layer.
FIG. 13C
is a sectional view showing an assembling step before mounting of the soldering ball has been completed.
First, the lead frame
50
shown in
FIGS. 12A
,
12
B and
12
C is manufactured. More specifically, after forming a resist film on the upper surface
50
a
and the under surface
50
b
of the lead frame
50
and patterning it, as shown in
FIG. 12A
the lead frame is etched from the upper surface
50
a
and the under surface
50
b
. Thus, the die pad
2
, the external electrode portion
4
, the lead electrode
5
, the suspension lead
8
and a dam bar
50
c
are formed to continue across openings
50
d
and
50
e
. Then, after forming a resist film on the under surface
50
b
of the lead frame
50
, except the portions
4
a
and
4
b
on the underside of the lead electrode
5
, the portions
4
a
and
4
b
are formed by half etching.
Subsequently, the semiconductor chip
1
provided with the pad electrode is mounted on the die pad
2
by applying the junction material
3
. The pad electrode of the semiconductor chip
1
and the inside end of the electrode
5
are then connected through the connection lead
6
. Then, as shown in
FIG. 13B
, after mounting a lower mold
10
in contact with the die pad
2
and the external electrode portion
4
, an upper mold
11
is positioned on the resin seal line
7
A and mounted on the upper surface of the lead frame
50
. After tightening the two molds
10
and
11
, the semiconductor chip
1
, the die pad
2
, the lead electrode
5
and the connecting lead
6
are sealed with the seal resin layer
7
by transfer molding. Thereafter, when removing the upper mold
11
and the lower mold
10
, a non lead type semiconductor devices before mounting the solder ball
9
, is obtained as shown in FIG.
13
C.
Then, by applying a soldering paste to the external electrode portion
4
, the solder ball
9
is mounted on the external electrode potion
4
. When the lead electrode
5
protruding from the resin sealing line
7
a
, and the seal resin layer
7
getting into the underside portions
4
a
and
4
b
of the lead electrode
5
, made thin by half etching, are cut along the resin seal line
7
a
with a cutter, the conventional BGA type semiconductor device shown in
FIGS. 11A and 11B
is obtained.
In the mentioned semiconductor device using the conventional lead frame as the wiring base member, since the die pad
2
, the external electrode portion
4
, the lead electrode
5
, the suspension lead
8
and dam bar
50
c
continue across the openings
50
d
and
50
e
, when sealed with the seal resin layer
7
after mounting the two molds
10
and
11
, the molten resin, having a low viscosity, also flows into the opening portion
50
d
. As a result, there has been a problem that the molten resin intrudes into a small space between contact surfaces, where the die pad
2
, the external electrode portion
4
, the suspension lead
8
are in contact with the lower mold
10
, and comes to form a thin resin film (hereinafter referred to as thin burr).
It is certainly possible to prevent the formation of the thin burr between the external electrode portion
4
and the lower mold
10
if a contact pressure between the external electrode portion
4
and the lower mold
10
is large. However, the lead electrode
5
is made thin by etching and supported like a cantilever at a part held between the lower mold
10
and the upper mold
11
at the position of the resin seal line
7
a
. Therefore, if the external electrode portion
4
is pressed by the lower mold
10
, the lead electrode
5
is deformed by the pressure. As a result, it has been heretofore impossible to secure a contact pressure preventing the formation of the thin burr between the external electrode portion
4
and the lower mold
10
.
The formation of the thin burr varies depending on the degree of roughness in surface finishing (hereinafter referred to as surface roughness) of the contact surface where the die pad
2
and the external electrode portion
4
are in contact with the lower mold
10
. Generally, the thin burr does not adhere to any die or mold having good surface roughness, but adheres to the die pad
2
, the external electrode portion
4
, etc. having poor surface roughness. Therefore, it is necessary to remove the thin burr adhered, for example, to the external electrode portion
4
. To remove the thin burr, hydraulic pressure trimming, chemical trimming, chemical and hydraulic pressure trimming, etc. are performed, and after removing the thin burr, it is necessary to perform treatments such as washing, drying, etc., and as a result manufacturing cost is high.
There has been another problem with the lead electrode
5
protruding from the resin seal line
7
a
, the seal resin layer
7
gets into the portions
4
a
and
4
b
made thin by half etching, and the suspension lead
8
, cut using a cutter along the resin seal line
7
a
. Therefore, it is easy to cause a failure in cutting th

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