Active solid-state devices (e.g. – transistors – solid-state diode – Lead frame – With separate tie bar element or plural tie bars
Reexamination Certificate
2003-01-15
2004-12-28
Lebentritt, Michael S. (Department: 2824)
Active solid-state devices (e.g., transistors, solid-state diode
Lead frame
With separate tie bar element or plural tie bars
C257S666000, C257S667000, C257S690000, C257S696000
Reexamination Certificate
active
06836004
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a lead frame, and a method for producing a semiconductor device and a method for inspecting the electrical properties of a small device using the lead frame.
2. Background Art
Resin-sealed semiconductor devices using a lead frame are widely used as inexpensive small-pin IC packages, whose pin counts and package sizes vary greatly.
FIG. 9
is a perspective plan view of a device employing a conventional SOP (Small Outline Package) type package, the view showing how the IC chip is mounted on the lead frame and molded with resin. In the figure, reference numeral
22
denotes a package made up of a semiconductor chip molded with resin, and
23
denotes a lead frame having the package
22
mounted thereon forming a single unit. The lead frame
23
includes a die pad
24
, leads
25
, suspension leads
26
, and tie bars
27
. A semiconductor chip
28
is bonded onto the die pad
24
by means of die bonding. The leads
25
include inner leads
25
a
disposed within the package and outer leads
25
b
extending from the inner leads
25
a
to the outside of the package. The inner leads
25
a
are connected to electrode pads
29
on the semiconductor chip
28
through wires
30
. On the other hand, the ends of the outer leads
25
b
extending from the inner leads
25
a
are connected to a framework
31
. Furthermore, the suspension leads
26
are provided between the semiconductor chip
28
and the framework
31
such that they intersect the outer leads
25
b
and thereby function to, when the package
22
is molded with resin, prevent the resin from flowing to the outer leads
25
b
. The suspension leads
26
extend in parallel with the longitudinal direction of the die pad
24
, and both of their ends are connected to the framework
31
so that the suspension leads
26
function to support the die pad
24
.
Description will be made below of a method for manufacturing a semiconductor device using the lead frame shown in FIG.
9
. First of all, the semiconductor chip
28
is mounted on the die pad
24
and connected to the inner leads
25
a
through the wires
30
using the wire bonding method. Subsequently, the die pad
24
, the inner leads
25
a
, the semiconductor chip
28
, and the wires
30
are sealed with resin using the transfer molding method to form the package
22
. The actual lead frame has a structure in which, for example, a plurality of devices
32
are disposed alongside of one another in the longitudinal direction of a lead frame
33
, as shown in FIG.
10
. Each device
32
is arranged such that the longitudinal direction of outer leads
34
and that of the lead frame
33
are in parallel with each other. Then, in
FIG. 9
, the tie bars
27
and the tip of the outer leads
25
b
, and the suspension leads
26
are cut, and the outer leads
25
b
are bent in a predetermined shape, completing a resin-sealed semiconductor device. FIG.
11
(
a
) is a plane view of a completed resin-sealed semiconductor device, while FIG.
11
(
b
) is a side view.
Conventionally, the electrical properties of each individual semiconductor device cut off as described above is inspected independently by connecting an electrode terminal to each lead. However, this means that it is necessary to set each semiconductor device at a predetermined inspection position for measurement one at a time, which requires considerable time. In addition, since each semiconductor device is small and therefore difficult to handle, JAM is likely to occur due to dropping at the time of inspection or transfer of the device. Furthermore, it is necessary to prepare an inspecting aid(s) for each package size, incurring a cost.
The present invention has been devised in view of the above problems. It is, therefore, an object of the present invention to provide a lead frame with which electrical property inspection (of a each device) can be efficiently carried out, and a method for manufacturing a semiconductor device using the lead frame.
Another object of the present invention is to provide a method for efficiently inspecting the electrical properties of a small device.
Other objects and advantages of the present invention will become apparent from the following description.
SUMMARY OF THE INVENTION
According to one aspect of the present invention, a lead frame comprises a plurality of framework assemblies. Each framework assembly includes a framework, a suspension lead whose both ends are connected to said framework, a die pad which is supported by the suspension lead and on which a semiconductor chip is mounted, a plurality of inner leads whose front ends are connected to electrodes on the semiconductor chip through wires, a plurality of outer leads extending from back ends of the plurality of inner leads toward outside of the semiconductor chip, wherein front ends of the plurality of outer leads are connected to no other portions and leave in a free state, a first tie bar located near the plurality of inner leads across the plurality of outer leads, wherein both ends of the first tie bar are connected to the framework, a second tie bar located near the front ends of the plurality outer leads across the plurality of outer leads, wherein both ends of the second tie bar are connected to the framework, and a lead support protruding from the framework's surface facing to the front ends of the plurality of outer leads to the front ends of them and having a rectangular shape whose long sides are in parallel with a direction in which the plurality of outer leads are disposed alongside of one another and whose length is approximately equal to a length of space occupied by all of the plurality of outer leads. The plurality of framework assemblies are disposed alongside of one another in a direction perpendicular to a direction in which the plurality of outer leads extend. A distance between close-set outer leads of each two neighboring frameworks is substantially n times a pitch of the plurality of outer leads of each framework, wherein n is an integer.
According to another aspect of the present invention, in a method for manufacturing a semiconductor device, a lead frame is prepared. The lead frame comprises a plurality of framework assemblies. Each framework assembly includes a framework, a suspension lead whose both ends are connected to the framework, a die pad which is supported by the suspension lead and on which a semiconductor chip is mounted, a plurality of inner leads whose front ends are connected to electrodes on the semiconductor chip through wires, a plurality of outer leads extending from back ends of the plurality of inner leads toward outside of the semiconductor chip, wherein front ends of the plurality of outer leads are connected to no other portions and leave in a free state, a first tie bar located near the plurality of inner leads across the plurality of outer leads, wherein both ends of the first tie bar are connected to the framework, a second tie bar located near the front ends of the plurality outer leads across the plurality of outer leads, wherein both ends of the second tie bar are connected to the framework; and a lead support protruding from the framework's surface facing to the front ends of the plurality of outer leads to the front ends of them and having a rectangular shape whose long sides are in parallel with a direction in which the plurality of outer leads are disposed alongside of one another and whose length is approximately equal to a length of space occupied by all of the plurality of outer leads. The plurality of framework assemblies are disposed alongside of one another in a direction perpendicular to a direction in which the plurality of outer leads extend. A distance between close-set outer leads of each two neighboring frameworks is substantially n times a pitch of the plurality of outer leads of each framework, wherein n is an integer. Then, in the method for manufacturing the semiconductor device, the semiconductor chip is mounted on the die pad. Between the electrodes on the semicond
Michii Kazunari
Semba Shinji
Shinonaga Naoyuki
Lebentritt Michael S.
Menz Douglas M
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