Universal clamping mechanism

Details Universal clamping mechanism Universal clamping mechanism

2001-02-01

2004-03-02

Eley, Timothy V. (Department: 3724)

Metal working

Means to assemble or disassemble

Means to assemble electrical device

C029S831000, C029S840000, C029S739000

Reexamination Certificate

active

06698088

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates generally to integrated circuit packages. More specifically, the invention relates to the clamping of lead frames during the manufacturing of a Leadless Leadframe Package.
BACKGROUND OF THE INVENTION
An integrated circuit (IC) package encapsulates an IC chip (die) in a protective casing and may also provide power and signal distribution between the IC chip and an external printed circuit board (PCB). An IC package may use a metal lead frame to provide electrical paths for that distribution. During the process of die attach and wire bonding for conventional semiconductor packages, the semiconductor lead frame or substrate material rests on a base block during the epoxy dispensing, die attaching, and wire bonding processes. During these processes the frame or substrate needs to be held down firmly to a heater block by a vacuum, a clamp, or both.
To facilitate discussion,
FIG. 1
is a top view of a lead frame panel
100
made up for a plurality of lead frames that may be used in the prior art. The lead frame may comprise leads
108
, die attach pads
112
, ties
116
for supporting the die attach pads
112
and leads
108
, and a skirt
120
for supporting the plurality of leads
108
and ties
116
. The lead frame panel
100
may be etched or stamped from a thin sheet of metal.
FIG. 2
is a cross sectional view of the lead frame panel
100
shown in
FIG. 1
, along cut lines
2
—
2
, attached to a lead frame base tape
204
, which is mounted on a base block
208
used in the prior art. The base block
208
has a plurality of holes
212
, through which a vacuum is applied to the lead frame base tape
204
to hold the lead frame
100
and the lead frame base tape
204
to the base block
208
. A top clamp
216
may also be used to hold the lead frame
100
and lead frame base tape
204
to the base block
208
. Preferably, the holes
212
are positioned at the die attach pads
112
, not between the die attach pads
112
and the ties
116
or at the ties
116
. As a result, a base block with a configuration of holes for one type of lead frame may not be useful in clamping another type of lead frame.
FIG. 3
is a cross sectional view of another type of lead frame
300
mounted on the base block
208
that is used in FIG.
2
. Tape
304
is placed across the leads, die attach pads
312
, the ties
308
, and skirt
320
of the lead frame
300
. The tape
304
and lead frame
300
are placed on the base block
208
. Two vacuum holes
212
are under parts of the tape
304
connected to die attach pads
312
and two vacuum holes
212
are under tape
304
that is next to a gap between a lead
308
and a die attach pad
312
. Placing a lead
308
or gap over a vacuum hole
212
may cause the lead frame to float or bounce during the wire bonding process. As a result, the vacuum provided through the base block
208
, even in combination with a clamping
316
may not be sufficient to secure the lead frame during the wire bonding and die attach process.
It is desirable to provide a universal base block that is able to secure different lead frame configurations.
SUMMARY OF THE INVENTION
To achieve the foregoing and other objects and in accordance with the purpose of the present invention, a variety of techniques is provided for processing a lead frame. Generally, a first surface of a lead frame base tape is placed on a first surface of the lead frame. A second surface of the lead frame base tape is placed on a first surface of a porous block. A vacuum is placed on a second surface of the porous block.
Another aspect of the invention provides a device for processing lead frames, comprising a porous block with a first side and a second side, and a vacuum system connected to the first side of the porous block.
These and other features of the present invention will be described in more detail below in the detailed description of the invention and in conjunction with the following figures.


REFERENCES:
patent: 3667103 (1972-06-01), Petree
patent: 3704504 (1972-12-01), Koegler
patent: 3755048 (1973-08-01), Schubert
patent: 3930295 (1976-01-01), Rose
patent: 4037830 (1977-07-01), Poluzzi et al.
patent: 4906011 (1990-03-01), Hiyamizu et al.
patent: 5651180 (1997-07-01), Himmel et al.
patent: 04085996 (1992-03-01), None

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