Active solid-state devices (e.g. – transistors – solid-state diode – Combined with electrical contact or lead – Die bond
Reexamination Certificate
2002-06-11
2003-11-18
Thomas, Tom (Department: 2811)
Active solid-state devices (e.g., transistors, solid-state diode
Combined with electrical contact or lead
Die bond
C257S679000, C257S669000, C257S672000, C257S673000, C257S676000, C257S778000, C257S784000, C257S782000, C257S779000, C257S786000, C257S780000, C438S612000, C438S123000, C264S272170
Reexamination Certificate
active
06650020
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention generally relates to a resin-sealed semiconductor device in which a die pad portion having a semiconductor element mounted thereon is exposed from a sealing resin, and a manufacturing method thereof. More particularly, the present invention relates to a resin-sealed semiconductor device preventing generation of resin voids within a sealing resin, and a manufacturing method thereof.
Recent reduction in size of electronic equipments requires high-density packaging of semiconductor components such as a resin-sealed semiconductor device. In response to such a requirement, the semiconductor components are increasingly reduced in size and thickness. In addition to such a trend, semiconductor devices having an increased number of pins are increasingly produced. Accordingly, there is a demand for a small, thin, high-density resin-sealed semiconductor device.
Hereinafter, a conventional resin-sealed semiconductor device having a die pad portion exposed from a resin will be described.
FIGS. 11A
to
11
C show a conventional resin-sealed semiconductor device.
FIG. 11A
is a plan view,
FIG. 11B
is a bottom view, and
FIG. 11C
is a cross-sectional view taken along line A-A
1
in FIG.
11
B.
As shown in
FIGS. 11A
to
11
C, a semiconductor element
102
is mounted on a die pad portion
101
of a lead frame. The semiconductor element
102
is electrically connected to inner lead portions
103
by thin metal wires
104
. The semiconductor element
102
on the die pad portion
101
and the inner lead portions
103
are sealed with a sealing resin
105
. The side surface of the sealing resin
105
is flush with the terminal ends of the inner lead portions
103
. The bottom surface of the die pad portion
101
is exposed from the sealing resin
105
. The tips of the inner lead portions
103
are exposed as external terminals
106
.
Hereinafter, a method for manufacturing the conventional resin-sealed semiconductor device will be described.
FIGS. 12A
to
12
D are cross-sectional views illustrating the steps of the method for manufacturing the conventional resin-sealed semiconductor device using a lead frame.
As shown in
FIG. 12A
, a lead frame is first prepared. The lead frame has a frame portion, a rectangular die pad portion
101
provided within the frame portion, for mounting a semiconductor element thereon, suspended lead portions for supporting the die pad portion
101
, and beam-like inner lead portions
103
to be electrically connected to the semiconductor element mounted on the die pad portion
101
by connecting means such as thin metal wires.
As shown in
FIG. 12B
, a semiconductor element
102
is then bonded to the die pad portion
101
of the lead frame by an adhesive such as silver paste (die bonding step).
As shown in
FIG. 12C
, electrode pads (not shown) on the surface of the semiconductor device
102
mounted on the die pad portion
101
are respectively connected with the tips of the inner lead portions
103
of the lead frame by thin metal wires
104
(wire bonding step).
As shown in
FIG. 12D
, with a sealing sheet in close contact with the lead frame, the die pad portion
101
, the semiconductor element
102
and the inner lead portions
103
are sealed with a sealing resin
105
. In the illustrated example, the sealing step is conducted with the sealing sheet in close contact with the bottom surface of the lead frame. Therefore, the die pad portion
101
, the suspended lead portions, the semiconductor element
102
, the inner lead portions
103
and the connection regions of the thin metal wires
104
are sealed except the bottom surface of the die pad portion
101
and the bottom surface of each inner lead portion
103
. As a result, the bottom surface of the die pad portion
101
is exposed from the bottom surface of the sealing resin
105
.
In the conventional resin-sealed semiconductor device and the manufacturing method thereof, a semiconductor element is first mounted on a lead frame and electrical connection thereof is then conducted using thin metal wires. The subsequent resin sealing step is conducted with a sealing sheet in close contact with the bottom surface of the lead frame. In the resin sealing step, however, the air may be introduced into the interface between the sealing sheet and the die pad portion and the inner lead portions of the lead frame. In this case, this air is trapped at the interface without being forced to air vents formed in a mold. As a result, the air is trapped at the end of the die pad, whereby resin voids are generated in the sealing resin near the die pad portion. Recently, such a phenomenon often occurs in the resin sealing step using both a multi-pin, high-density lead frame having leads arranged at smaller intervals and a sealing sheet. This is extremely problematic in manufacturing a resin-sealed semiconductor device having a die pad portion exposed from a resin.
Resin voids thus produced in the sealing resin would generate cracks within the resin during operation in the heating environment, hindering mounting of the resin-sealed semiconductor device on a circuit board. This is not preferable in terms of reliability.
SUMMARY OF THE INVENTION
The present invention is made to solve the above conventional problems, and it is an object of the present invention to provide a resin-sealed semiconductor device having a die pad portion exposed from a sealing resin and a manufacturing method thereof, which prevent generation of resin voids within a sealing resin.
According to one aspect of the present invention, a resin-sealed semiconductor device includes a die pad portion for mounting a semiconductor element thereon, a semiconductor element mounted on the die pad portion and having electrodes, a plurality of lead portions arranged with their respective tips facing the die pad portion, thin metal wires for connecting the electrodes of the semiconductor element to the lead portions, and a sealing resin for sealing the die pad portion, the semiconductor element, the lead portions and connection regions of the thin metal wires except a bottom surface of the die pad portion and respective bottom surfaces and terminal ends of the lead portions. The terminal ends of the lead portions are approximately flush with a side surface of the sealing resin. The die pad portion has a first recess formed in an outer periphery of the bottom surface thereof.
Preferably, the resin-sealed semiconductor device further includes suspended lead portions for supporting the die pad portion.
Preferably, the die pad portion has an upward projecting support portion for supporting the semiconductor element. A second recess is provided at a region of the bottom surface of the die pad portion that corresponds to the support portion. The first recess formed at the bottom surface of the die pad portion is a groove-like recess extending from an outer end of the bottom surface of the die pad portion to the second recess.
Preferably, at least the lead portions include first lead portions arranged with their respective tips facing the die pad portion, and second lead portions extending so that their respective tips are located at a position closer to the die pad portion than are the tips of the first lead portions.
Preferably, respective bottom surfaces of the first lead portions and respective bottom surfaces of the second lead portions form land electrodes. The land electrodes are arranged in at least two rows in a bottom surface region of the sealing resin when viewed two-dimensionally.
According to another aspect of the present invention, a method for manufacturing a resin-sealed semiconductor device includes the steps of: preparing a lead frame having a die pad portion provided within a frame portion formed from a metal plate, for mounting a semiconductor element thereon, a plurality of lead portions arranged with their respective tips facing the die pad portion and their respective terminal ends connected to the frame portion, and a sealing sheet attached in close contact with respective bottom surfaces of the l
Minamio Masanori
Yamada Yuichiro
Im Junghwa
Matsushia Electric Industrial Co., Ltd.
Thomas Tom
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