Active solid-state devices (e.g. – transistors – solid-state diode – Lead frame
Reexamination Certificate
1999-04-27
2001-01-23
Clark, Sheila V. (Department: 2815)
Active solid-state devices (e.g., transistors, solid-state diode
Lead frame
C257S676000, C257S670000, C257S787000
Reexamination Certificate
active
06177718
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a resin-sealed semiconductor device.
A resin-sealed semiconductor device is a device having a semiconductor chip (IC) package made of molding resin. The resin-sealed semiconductor device is inexpensive and excels in mass-productivity. Therefore, it is most generally developed and manufactured in the field of semiconductor devices.
FIG. 1
is a plan view of a conventional resin-sealed semiconductor device.
FIG. 2
is a sectional view, taken along line II—II in FIG.
1
.
FIG. 3
is a sectional view, taken along line III—III in FIG.
1
.
A semiconductor chip
11
is mounted on a die-pad
10
. The chip
11
is secured to the die-pad
10
with electrically conductive adhesive
12
such as silver paste. Tie-bars
17
tie the die-pad
10
to a lead frame in the course of manufacturing a resin-sealed semiconductor device. A plurality of leads
13
are arranged around the die-pad
10
. Bonding wires
14
connect the leads
13
to the electrodes (pads)
15
of the semiconductor chip
11
. Resin
16
covers the semiconductor chip
11
. Those parts of the leads
13
, which are in the resin
16
, are called inner leads. Those parts of the leads
13
, which are outside the resin
16
, are called outer leads.
The die-pad
10
, leads
13
and tie-bars
17
are made of metal such as copper, copper alloy or iron-nickel alloy (Fe—42Ni). The distal portion (bonding portion) of each lead (inner lead)
13
is plated with metal such as gold or tin. The bonding wires
14
are made of metal such as copper, copper alloy or gold. The electrodes
15
of the semiconductor chip
11
are made of metal such as aluminum.
The leads (outer leads)
13
are made in the form of a Gull-wing so as to easily contact the wires provided on a printed circuit board. The tie-bars
17
is used to tie the die-pad
10
to the lead frame in the course of manufacturing the resin-sealed semiconductor device. Those parts of the tie-bars, which are outside the resin
16
, are therefore finally removed. Hence, the tie-bars
17
will exists in the resin
16
only.
The die-pad
10
is fixed at the ground potential in order to stabilize the operation of the integrated circuit provided within the semiconductor chip
11
. A method of fixing the die-pad
10
at the ground potential is known, in which one of the leads
13
and the die-pad
10
are connected to each other and the ground potential is applied to this lead
13
.
In this case, however, the ground potential is applied from the lead
13
to the die-pad
10
. Due to the resistance components of the leads, bonding wires and die-pad, it is difficult to stabilize the entire lower surface of the semiconductor chip
11
at the ground potential.
Further, since one of the leads
13
must be used to set the die-pad
10
at a specific potential, the semiconductor device needs to have more pins (outer leads) than otherwise. Still further, since the lead (outer leads) are bent in Gull-wing form, there is limit to miniaturization and thickness reduction of the semiconductor device.
BRIEF SUMMARY OF THE INVENTION
The object of this invention is to provide a resin-sealed semiconductor device which has a novel structure and which can be made small and thin, to reliably set the entire lower surface of a semiconductor chip at the ground potential by means of a novel method of setting the potential of a die-pad, and to increase the mount strength of a semiconductor device with respect to a printed circuit board.
A resin-sealed semiconductor device according to the present invention comprises: a die-pad; a semiconductor chip arranged on the die-pad; a tie-bar having a first end and a second end, the first end combined with the die-pad; a lead having a first end and a second end; a resin block covering up the die-pad, the semiconductor chip, the tie-bar and the lead and having an upper surface, a lower surface and sides. The second end of the tie-bar and the second end of the lead are exposed at the lower surface of the resin block. The surfaces of the tie-bar and lead, which are exposed outside the resin block, lie in substantially the same plane as at least the lower surface of the resin block.
A lead frame for use in a resin-sealed semiconductor device, according to this invention, comprises: a main body; a die-pad for supporting a semiconductor chip; a tie-bar having a first end and a second end, the second combined with the main body; and a lead having a first end arranged near the die-pad and a second end combined with the main body. The die-pad, the tie-bar and the lead are depressed. The first end of the lead is located closer to the main body than to the die-pad. The second end of the tie-bar and the second end of the lead lie in a plane defined by the main body.
A method of manufacturing a resin-sealed semiconductor device, according to the invention, comprises the steps of: depressing a die-pad, tie-bar and lead of a lead frame; securing a semiconductor chip on the die-pad of the lead frame; connecting the lead and the semiconductor chip; applying resin by means of a resin-molding process, forming a resin block and covering the die-pad, tie-bar and lead of the lead frame; and cutting the tie-bar and the lead, thereby exposing one end of the tie bar and one end of the lead, at a lower surface of the resin block, and thereby setting surfaces of the tie-bar and lead, which are exposed outside the resin block, in substantially the same plane as at least the lower surface of the resin block.
A method of manufacturing a resin-sealed semiconductor device, according to the invention, comprises the steps of: depressing a lead of a lead frame which also has a die-pad and a tie-bar; securing a semiconductor chip on the die-pad of the lead frame; connecting the lead and the semiconductor chip; applying resin by means of a resin-molding process, forming a resin block and covering the die-pad, tie-bar and lead of the lead frame; and cutting the tie-bar and the lead, thereby exposing one end of the tie bar and one end of the lead, at a lower surface of the resin block, and thereby setting surfaces of the tie-bar and lead, which are exposed outside the resin block, in substantially the same plane as at least the lower surface of the resin block.
A method of manufacturing a resin-sealed semiconductor device, according to this invention, comprises the steps of: depressing a die-pad and tie-bar of a first lead frame; depressing a lead of a second lead frame; securing a semiconductor chip on the die-pad of the first lead frame; placing the first and second lead frames, one upon the other; connecting the lead and the semiconductor chip; applying resin by means of a resin-molding process, forming a resin block and covering the die-pad, tie-bar and lead of the lead frame; and cutting the tie-bar and the lead, thereby exposing one end of the tie bar and one end of the lead, at a lower surface of the resin block, and thereby setting surfaces of the tie-bar and lead, which are exposed outside the resin block, in substantially the same plane as at least the lower surface of the resin block.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.
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paten
Clark Sheila V.
Kabushiki Kaisha Toshiba
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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