Material or article handling – Device for emptying portable receptacle
Reexamination Certificate
2000-11-08
2003-05-13
Bratlie, Steven A. (Department: 3652)
Material or article handling
Device for emptying portable receptacle
C414S411000, C414S416060, C156S345420, C156S583200
Reexamination Certificate
active
06561743
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a pellet picking method and a pellet picking apparatus used preferably in semiconductor device fabrication and more particularly, to a pellet picking method and a pellet picking apparatus for picking up one or more pellets arranged on an adhesive sheet with a collet, where the pellet or pellets is/are usually formed by separation of a wafer through scribing or sawing.
2. Description of the Related Art
Semiconductor pellets are typically formed by cutting or separating a semiconductor wafer with a specific diameter such as 6 or 8 inches into pieces. The pellets are typically rectangular or square. Semiconductor devices and/or elements or semiconductor integrated circuits are formed in the corresponding areas of the wafer to the pellets and therefore, they are formed in each of the pellets. Semiconductor pellets will be often called simply “pellets” hereinafter.
The pellet has a variety of shapes and sizes. For example, the pellet has an approximately square shape of 0.5 mm×0.5 mm to 30 mm×30 mm. The pellet may have an elongated, strap-like shape. The square pellet may be formed by separating the wafer into strap-shaped parts in a step and by separating each of the strap-shaped parts into square pieces in another step.
The above-described separation process of the wafer or its strap-shaped part is typically performed in the following way.
The wafer itself or the strap-shaped part is adhered onto an adhesive sheet and then, it is cut by using an edged tool such as a dicing saw on the sheet, thereby forming the pellets. The sheet is usually stretched or spread on a circular support ring with almost no looseness. In this separation process, the cutting blade of the tool is lowered to penetrate the wafer or the strap-shaped part and then, it is lowered into the sheet to create a trench with about one-third to one-second (⅓ to ½) of the thickness of the sheet. The thickness of the sheet is typically approximately 0.1 mm.
Subsequently, the wafer or the strap-shaped part thus formed is mounted on a pellet picking apparatus. At this time, the wafer or the strap-shaped part is kept adhered on the sheet while they are mounted on the apparatus along with the support ring. Then, the apparatus picks up or separates the pellets from the sheet one by one. If the apparatus is built in a die or pellet bonding apparatus, each of the pellets thus separated is bonded to the specific land of a leadframe If the apparatus is not built in a die or pellet bonding apparatus, the pellets thus separated are placed in respective pockets of a tray.
Next, a most popular pellet picking method will be explained with reference to
FIGS. 1 and 2
and
FIGS. 3A
to
3
D. In this method, the pellet on the adhesive sheet is pushed up by the needles by way of the sheet, thereby detaching the pellet from the sheet. Then, the pellet thus detached is picked up by the suction collet.
FIGS. 1 and 2
schematically show a prior-art pellet picking apparatus
100
, which performs the most popular pellet picking method described above. In
FIGS. 1 and 2
, an adhesive sheet
101
on which a semiconductor pellet
103
is adhered is also shown. Needless to say, a lot of pellets
103
are adhered onto the sheet
101
. However, only one of the pellets
103
is shown for the sake of simplification and facilitation in understanding.
The basic configuration of the prior-art pellet picking apparatus of this type has been already known and therefore, its detailed explanation is omitted here. An example of the basic configuration of the apparatus is disclosed in the Japanese Non-Examined patent publication No. 4-12549 published in 1992. This apparatus is comprised of a wafer table on which an adhesive sheet with a semiconductor wafer (which have been separated into pellets) is placed, an X-Y table for moving horizontally the table along the X and Y directions, a pushing-up needle located under the table and movable vertically by an actuator, a vacuum-suction collet located over the table and movable horizontally and vertically by an actuator, an optically recognition means (e.g., a video camera) for recognizing the position and shape of the pellets on the adhesive sheet, and a controller for controlling the operation of the wafer table, the X-Y table, the needle, the collet, and the optically recognition means. The sheet with the wafer is stretched or spread on a circular support ring. The sheet is placed on the wafer table along with this ring.
The pellets located on the sheet in the form of wafer are placed on the wafer table in such a way that the needle can touch the pellets by way of the opening of the wafer table. Then, the pellets are successively pushed up by the needle while they are held by the collet, thereby detaching successively the pellets from the sheet. Subsequently, the pellets thus detached are successively transported to their specific positions with the collet.
As shown in
FIGS. 1 and 2
, the prior-art pellet picking apparatus
100
comprises a table
105
, one needle
102
a
and four needles
102
b
which are arranged to be movable upward and downward in the table
105
, and a cylindrical suction collet
104
provided over the table
105
.
The table
105
has a hole
106
a
for accommodating vertically the needle
102
a
and four holes
106
b
for individually accommodating vertically the needles
102
b
. The hole
106
a
is located at the center of the upper surface
105
a
of the table
105
. The four holes
106
b
are regularly arranged in the vicinity of the central hole
105
a
so as to surround the same. The needles
102
a
and
102
b
are fixed to a driving mechanism (not shown) for making their vertical motion (which is along the Z-axis).
The collet
104
is fixed to a driving mechanism (not shown) for making its vertical motion (which is along the Z-axis) and its horizontal motion (which is along the X-Y plane). The collet
104
has a suction or absorption end
104
a
. The collet
104
is located over the table
105
in such a way that the suction or absorption end
104
a
is opposed to the upper surface
105
a
of the table
105
. The collet
104
is connected to a vacuum generator (not shown), thereby enabling the collet
104
to generate a suction or absorption force at the end
104
a .
The prior-art pellet picking apparatus
100
operates in the following way.
First, as shown in
FIG. 2
, the adhesive sheet
101
, on which the pellet
103
has been adhered, is moved horizontally (i.e., along the X-Y plane) while the collet
104
is kept apart from the pellet
103
, thereby making positional alignment of the pellet
103
with respect to the table
105
. The sheet
101
has been stretched or spread on a circular support ring and is placed on the X-Y stage (not shown) Thus, the sheet
101
is optionally moved along the X-Y plane by driving the X-Y stage for the positional alignment.
If the pellet picking apparatus
100
is applied to the die-or pellet bonding apparatus, the positional alignment of the sheet
101
is realized at high accuracy by visual recognition with a camera or cameras provided over the pellet
103
. This is to place the pellet
103
onto the land of a leadframe at high accuracy in the pellet bonding apparatus.
Next, as shown in
FIG. 3A
, the collet
104
is lowered until the suction end
104
a
is contacted with the surface of the pellet
103
, in which the air in the collet
104
is being exhausted by the vacuum generator to generate a suction force at the end
104
a
. Thus, the pellet
103
is held by the collet
104
due to the suction force. The state at this stage is shown in FIG.
3
A.
Subsequently, as shown in
FIG. 3B
, the four peripheral needles
102
a
are moved upward simultaneously to push the peripheral area of the pellet
103
up. At this time, the collet
104
is moved upward to be synchronous with the motion of the pellet
103
without separating the pellet
103
. Thus, the adhered area of the periphery of the pellet
103
begins to be detached from the a
Bratlie Steven A.
Choate Hall & Stewart
Nec Machinery Corporation
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