Active solid-state devices (e.g. – transistors – solid-state diode – Combined with electrical contact or lead – Die bond
Reexamination Certificate
1996-12-03
2001-03-13
Chaudhuri, Olik (Department: 2814)
Active solid-state devices (e.g., transistors, solid-state diode
Combined with electrical contact or lead
Die bond
C257S785000, C228S006200, C228S008000, C228S102000, C228S180210
Reexamination Certificate
active
06201306
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a push-up pin of a semiconductor element pushing-up device in a die bonding apparatus, a semiconductor element pushing-up device in a die bonding apparatus, and a method for separating a semiconductor element in a semiconductor element pushing-up device of a die bonding apparatus.
2. Description of the Related Art
The process for bonding a semiconductor element obtained by subjecting a semiconductor substrate to the dicing process on a lead frame in the method of manufacturing a semiconductor device is called a die bonding process.
The conventional die bonding apparatus is shown in FIG.
1
.
The die bonding apparatus is mainly constructed by a portion for taking up one semiconductor element, a portion for moving the taken-up semiconductor element onto a lead frame, and a portion for carrying the lead frame.
The portion for taking up the semiconductor element includes a wafer ring
2
for fixing a semiconductor substrate
1
obtained after semiconductor elements are subjected to the dicing process with the semiconductor substrate attached to the adhesive sheet, an XY table
3
for carrying the wafer ring
2
, a camera
4
set above the XY table
3
, and a semiconductor element pushing-up device
30
disposed below the XY table and used for pushing up the semiconductor element from the rear surface side of the adhesive sheet by use of a pin or pins so as to separate the semiconductor element from the adhesive sheet.
The portion for moving the semiconductor element onto the lead frame
12
includes an element suction head
10
for taking up the semiconductor element separated from the adhesive sheet and moving the semiconductor element to a position correcting stage
11
, and the position correcting stage
11
for correcting the position of the semiconductor element, and a bonding head portion
8
for holding the semiconductor element by use of a collet and carrying the semiconductor element from the position correcting stage
11
onto the lead frame.
The portion for carrying the lead frame includes a lead frame supplying portion
5
for supplying a lead frame, a lead frame carrying portion
6
, a paste supplying portion
7
for supplying adhesive onto the lead frame, and a lead frame receiving portion
9
.
The portion for taking up the semiconductor element is explained in more detail with reference to
FIGS. 2A
,
2
B, and
3
A to
3
D.
FIG. 2A
is an enlarged top plan view showing the semiconductor substrate
1
on the semiconductor element pushing-up device
30
, and
FIG. 2B
shows a cross section taken along the line IIB—IIB of FIG.
2
A and the construction of peripheral devices of the semiconductor element pushing-up device
30
.
FIGS. 3A
to
3
D are cross sectional views for illustrating the operation of the semiconductor element pushing-up device
30
.
The semiconductor element pushing-up device
30
includes a backup holder
15
, push-up pins
17
, pin holder
19
, pin holder driving device
31
, control device
32
, and vacuum device
20
.
The backup holder
15
is a vacuum chamber having through holes
18
formed in the upper surface thereof
16
and vacuum suction force is applied to an adhesive sheet
14
on the upper surface of the backup holder
15
by use of the vacuum device
20
connected to the vacuum chamber so as to fixedly hold the adhesive sheet
14
on the upper surface thereof.
Semiconductor elements
13
are attached to the adhesive sheet
14
.
The pin holder
19
capable of receiving a plurality of push-up pins
17
is inserted into the vacuum chamber of the backup holder
15
and the pin holder
19
is driven in the vertical direction by the driving device
31
shown in FIG.
2
B.
The control device
32
controls the operation of the driving device
31
to drive the pin holder
19
in the vertical direction.
As shown in
FIGS. 3A
to
3
D, if the pin holder
19
is moved upwardly in the state shown in
FIG. 3A
, the push-up pins
17
pass through the through holes
18
formed in the upper surface of the backup holder
15
to push up the semiconductor element
13
on the adhesive sheet
14
(FIG.
3
B).
Since the adhesive sheet
14
is fixedly held on the backup holder
15
by vacuum suction force, the semiconductor element
13
is separated from the adhesive sheet
14
and taken up by suction of the element suction head
10
(FIG.
3
C).
After this, the pin holder
19
is moved downwardly and the vacuum suction is released.
Then, a new semiconductor element
13
is placed on the backup holder
15
with the adhesive sheet
14
disposed therebetween in such a position that it can be taken up by suction of the semiconductor element suction head
10
(FIG.
3
D).
Generally, the bonding force between the semiconductor element
13
and the adhesive sheet
14
depends on the property of the adhesive of the adhesive sheet
14
and the area of the semiconductor element
13
. However, in the above-described conventional element pushing-up device
30
, the conditions of the shape of the tip end portion of the push-up pin
17
, the traveling distance in the vertical direction, the moving speed, and the vacuum suction pressure are kept constant irrespective of the above factors.
Recently, the adhesive strength between the semiconductor element
13
and the adhesive sheet
14
increases with an increase in the area of the semiconductor element
13
and it becomes difficult to separate the semiconductor element
13
from the adhesive sheet
14
under the constant condition as in the conventional case.
Therefore, in order to separate the semiconductor element
13
from the adhesive sheet
14
, it is necessary for the push-up pins
17
to push up the semiconductor element
13
with extremely large force. In this case, there occurs a problem that the adhesive strength between the adhesive and the rear surface of the semiconductor element
13
becomes larger than the adhesive strength between the adhesive and the adhesive sheet
14
by application of the above force, and adhesive is left behind on the rear surface of the semiconductor element
13
which is separated from the adhesive sheet
14
or the adhesive sheet
14
is broken and left behind on the rear surface of the semiconductor element
13
.
The above phenomenon is explained more in detail below.
FIG. 4
is a side view showing the push-up pin
17
of the conventional element pushing-up device
30
.
The push-up pin
17
has a cylindrical portion
17
a
to be engaged into the pin holder
19
, a conical coupling portion
17
b,
and a tip end portion
17
c
having a curved surface with the radius R of curvature.
The angle &thgr; of circumference of a sector formed by a curved surface portion of the tip end portion
17
c
on a cross section taken along a line passing the central axes of the above portions is less than 180°.
FIG. 5
is an enlarged view showing a state in which the push-up pin
17
pushes up the semiconductor element
13
. The push-up pin
17
pushes up the semiconductor element
13
while expanding the adhesive sheet
14
and adhesive
23
.
In
FIG. 5
, since the adhesive sheet
14
and adhesive
23
are disposed between the tip end portion
17
c
of the push-up pin
17
and the rear surface of the semiconductor element
13
in an A zone, the adhesive sheet
14
and adhesive
23
are difficult to expand. On the other hand, since the adhesive sheet
14
and adhesive
23
are not set in contact with the rear surface of the semiconductor element
13
in a B zone, they can easily expand in the B zone than in the A zone.
Thus, the adhesive sheet
14
and adhesive
23
cannot expand equally in the A zone and in the B zone.
As a result, as shown in
FIG. 5
, the adhesive sheet
14
and adhesive
23
become extremely thin particularly on the boundary line S between the tip end portion
17
c
and the conical coupling portion
17
b.
Therefore, the coupling strength between the adhesive
23
on the tip end portion
17
c
and the adhesive
23
on the conical coupling portion
17
b
or the coupling strength between the adhesive
2
Kurosawa Tetsuya
Sasaki Shigeo
Chambliss Alonzo
Chaudhuri Olik
Finnegan Henderson Farabow Garrett & Dunner L.L.P.
Kabushiki Kaisha Toshiba
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