Semiconductor device and method of making the same

Details Semiconductor device and method of making the same Semiconductor device and method of making the same

2002-01-23

2003-06-17

Clark, Sheila V. (Department: 2815)

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

Lead frame

With structure for mounting semiconductor chip to lead frame

C257S787000, C438S124000, C438S123000

Reexamination Certificate

active

06580161

ABSTRACT:

TECHNICAL FIELD
The present invention relates to a resin-packaged surface-mounting semiconductor device and a method of making the same.
BACKGROUND OF THE INVENTION
FIGS. 14A-14C
are sectional views illustrating the process steps of a prior art method for making a semiconductor device Y
1
. First, as shown in
FIG. 14A
, a semiconductor chip
8
is mounted on a conductor frame
9
, and electrodes
80
a
,
80
b
respectively provided on the upper and the lower surfaces of the semiconductor chip
8
are electrically connected to a pair of lead portions
90
of the conductor frame
9
via a wire or a conductive adhesive. The conductor frame
9
, which is generally called a lead frame, may be formed by punching or etching a metal plate of copper for example. The conductor frame
9
is formed with thin-walled etched portions
92
a
,
92
b
at each of the lead portions
90
. The etched portions
92
a
,
92
b
are provided by etching the lead portions
90
from the lower surfaces
91
a
to a predetermined depth to form recesses
93
a
,
93
b.
Subsequently, as shown in
FIG. 14B
, a resin package
81
for sealing the semiconductor chip
8
and the wire W is formed. At this time, the resin package
81
is formed so that the lower surface
91
a
of each lead portion
90
is partially exposed at the bottom surface
81
a
of the resin package
81
and the thin-walled etched portions
92
b
project outward from the side surfaces
81
b
of the resin package
81
. Then, each of the lead portions
90
is cut at the position indicated by a reference sign n
1
in FIG.
14
B.
The semiconductor device Y
1
as shown in
FIG. 14C
is obtained by the above-described process steps. In the semiconductor device Y
1
, conductors
90
A, each of which has formed a part of each lead portion
90
, are partially exposed at the bottom surface
81
a
of the resin package
81
, thereby providing terminals
94
for surface-mounting. Thus, the semiconductor device Y
1
can be surface-mounted to a predetermined position by reflow soldering.
In the above-described method, each lead portion
90
is cut at the thin-walled etched portion
92
b
. Therefore, the cutting operation can be performed more properly and easily than in the case where the lead portion
90
is cut at a thick-walled portion. Moreover, the etched portion
92
a
is also provided at the lower surface
91
a
of each lead portion
90
. Therefore, in the semiconductor device Y
1
finally obtained, the upper surface
91
b
of each conductor
90
A has an area sufficient for connecting the semiconductor chip
8
or bonding of the wire W whereas each terminal
94
has a predetermined configuration and an area which is smaller than that of the upper surface
91
b.
The prior art semiconductor device Y
1
still has room for improvement. For example, as shown in
FIG. 14C
, when the semiconductor device Y
1
is mounted to a mother board
95
for making a certain equipment or apparatus, a test is carried out for checking whether the solder bonding between the terminals
94
of the semiconductor device Y
1
and terminals
95
a
of the mother board
95
has been properly performed. To perform the test relatively easily, the state of solder H used for the mounting can be visually checked with naked eyes or using an image capturing means such as a camera.
However, in the prior art semiconductor device Y
1
, each terminal
94
is located inward from the outer edge of the bottom surface
81
a
of the resin package
81
. Therefore, the solder H applied between the terminals
94
and the terminals
95
a
exists only between the terminals in the mounting step by reflow soldering, and it is difficult to visually check the solder H from the outside. In the semiconductor device Y
1
, an end surface
96
of each conductor
90
A is exposed at the side surface
81
b
of the resin package
81
. However, the end surface
96
is separated from the bottom surface la of the resin package
81
by a predetermined height h. Therefore, in the mounting step by reflow soldering, it is unlikely that part of the solder H interposed between the terminals
94
and
95
a
rises up to the end surface
96
to provide a solder fillet. In this way, in the prior art semiconductor device Y
1
, a test for solder bonding cannot be conveniently carried out because the existence or state of the solder H cannot be visually checked.
FIG. 15
is a sectional view showing another prior art semiconductor device Y
2
. In the semiconductor device Y
2
, each conductor
90
A includes a terminal
94
which reaches the outer edge of the bottom surface
81
a
of the resin package
81
. Thus, the conductor
90
A has an end surface
96
which is exposed at the side surface
81
b
of the resin package
81
as connected to the terminal
94
. With this structure, when the terminal
94
is bonded to a terminal
95
a
of a mother board
95
by reflow soldering for example, part of the solder H can rise up to the end surface
96
to form a solder fillet Hf existing outside of the resin package
81
. The presence of the solder fillet Hf facilitates the test for solder bonding. Specifically, it is possible to visually check, from the outside, whether the solder bonding is properly performed.
However, in the semiconductor device Y
2
, the portion of a conductor frame to be cut for providing each conductor
90
A is not subjected to etching, thereby having a thickness t which is larger than that in the semiconductor device Y
1
. Therefore, the cutting operation is not easy, which may cause improper cutting of the conductor frame.
The present invention is conceived under the circumstances described above. An object of the present invention is to provide a semiconductor device which can be easily manufactured and which makes it possible to easily check the appropriateness of the surface-mounting when the semiconductor device Y
2
is surface-mounted to a predetermined position via solder and, to provide a method for making such a semiconductor device.
DISCLOSURE OF THE INVENTION
According to a first aspect of the present invention, a semiconductor device is provided. The semiconductor device comprises: a plurality of conductors each of which includes a first surface, a second surface opposite to the first surface, and a thickness defined between the surfaces, and a thin-walled end portion retreating from the first surface toward the second surface and having a side surface connected to the second surface; a semiconductor chip having a plurality of electrodes electrically connected to the plurality of conductors, respectively; and a resin package for sealing the conductors and the semiconductor chip while exposing, for each conductor, the side surface of the thin-walled end portion and at least a part of the second surface connected to the side surface.
Preferably, at least one of the conductors is formed with an additional thin-walled end portion retreating from the second surface toward the first surface and surrounded by the resin package.
According to a second aspect of the present invention, a method of making a semiconductor device is provided. The method includes the steps of: mounting a semiconductor chip including a plurality of electrodes onto a conductor frame including a plurality of lead portions, each of the lead portions including a first surface, a second surface opposite to the first surface, and a thickness defined between the surfaces, and a thin-walled portion retreating from the first surface toward the second surface; electrically connecting the plurality of electrodes to the plurality of lead portions, respectively; forming a resin package for sealing the lead portions and the semiconductor chip while exposing the second surface of each lead portion so that the thin-walled portion projects outward; and cutting the thin-walled portion projecting from the resin package outside the resin package.
Preferably, in the resin sealing step, the resin package is formed so that the thin-walled portion of each lead portion extends from inside to outside the resin package.
Preferably, at least one of the lead portion

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