Metal fusion bonding – Process – Plural joints
Reexamination Certificate
2001-04-27
2003-09-16
Elve, M. Alexandra (Department: 1725)
Metal fusion bonding
Process
Plural joints
C228S212000, C228S049500, C228S110100
Reexamination Certificate
active
06619535
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field
The present invention relates to a working method and apparatus for holding by suction a work object (for example, a semiconductor component such as an IC chip) to be placed on a work stage, moving the work object to a specified position, regulating the object in position, and thereafter subjecting the work object to specified work (for example, bump bonding work of bumps formed on an IC chip), and in particular, to a bump bonding working method and apparatus for holding by suction a work object of, for example, a semiconductor component such as an IC chip in which a semiconductor device is formed, to be placed on a work stage, moving the semiconductor component to a specified position, regulating the component in position, and thereafter subjecting the component to specified work such as bump bonding work of a bump that serves as a protruding electrode formed on an electrode of, for example, a semiconductor component: and an IC chip obtained through the processes.
2. Description of Related Art
Regarding semiconductor components such as the so-called IC chips and the like in which semiconductor elements having an integrated circuit are formed, in accordance with the miniaturization of electronic components, the compacting of a circuit board, increasing integration density, and increasing mounting density on a circuit board, there is frequently adopted the so-called surface mounting for collecting electrodes on a surface to be mounted on a circuit board, electrically connecting face to face the electrodes to corresponding electrodes and conductor lands of the circuit board and concurrently bonding them together into an integrated body with solder or adhesive for mounting.
It has already been known to form metal bumps on the electrodes of an IC chip for this surface mounting and easily achieve individual electrical connections with the circuit board. The present applicant has previously provided and put into practical use a bump bonding method by means of a wire bonding method as a method for forming a metal bump.
The outline of this method will be explained with reference to FIG.
14
and
FIGS. 5A through 5D
. Using an IC chip
1
as a work object, this work presses a metal wire
3
against an electrode
2
of a surface
1
a
thereof with ultrasonic vibrations applied to the wire for the achievement of metallic bond as shown in
FIGS. 5A through 5D
and separates the succeeding metal wire
3
from a bonded metal lump
3
a
formed through the above process by tearing off or cutting by pushing the metal wire
3
, forming a metal bump
4
on the electrode
2
.
Specifically,
FIG. 14
is a perspective view of a bump bonding apparatus for forming a bump on the IC chip
101
with a gold wire
113
.
In
FIG. 14
, the IC chip
101
supplied from a tray
110
is held by suction by a suction nozzle
1111
, thereafter moved by the suction nozzle
111
and fixed to an IC chip placement surface or, for example, the upper surface of a stage
151
that has a raised temperature. A capillary
112
is constructed so as to be held by an ultrasonic wave supply unit and receive ultrasonic waves, and a gold bump is formed on the electrode of the IC chip
101
by the capillary
112
through which the gold wire
113
is positioned. The IC chip
101
that has undergone bump formation in the required portions is held by suction by the suction nozzle
111
and stored in another tray
110
a.
FIGS. 5A through 5D
are process charts showing the bump forming process performed by the aforementioned conventional bump bonding apparatus.
First of all, in the process of
FIG. 5A
, a gold wire
3
is put through the capillary
34
, and the tip of the gold wire
3
is sparked, forming a spherical ball portion
3
a
at the tip.
Next, in the process of
FIG. 5B
, the capillary
34
is lowered to press the spherical ball portion
3
a
located at the tip against the electrode
2
of the IC chip
1
. At this time, ultrasonic waves are applied to bond the gold wire
3
to the electrode
2
(first bonding).
Next, in the process of
FIG. 5C
, the capillary
34
is moved up and moved down again while being controlled so as to move in a loop form. As shown in the process of
FIG. 5D
, the capillary
34
presses the gold lump that has undergone the first bonding, cutting the gold wire
3
(second bonding).
The following will describe in detail the position regulating section of the IC chip
1
of the aforementioned conventional bump bonding apparatus.
FIGS. 6
,
15
A,
15
B and
15
C are a flowchart of a position regulating operation and plan views of the position regulating section of the IC chip
1
.
As shown in
FIG. 15A
, the position regulating section of the bump bonding apparatus is constructed of a stage
151
provided with four suction holes
157
and an L-figured position regulating pawl
152
that can move in XY-directions. The IC chip
1
is moved on the suction holes
157
of the stage
151
by the position regulating pawl
152
and regulated in position on the stage
151
while being sucked by vacuum. Describing this operation based on the flowchart, as shown in
FIG. 13
, suction is first turned on by a vacuum pump to start suction (step S
51
), and the IC chip
1
held by suction by the suction nozzle
111
is placed on the stage
151
of the bump bonding apparatus. The IC chip
1
is sucked by the suction holes
157
(step S
52
, see FIG.
15
A), and the position regulating pawl
152
is moved on the stage
151
to regulate in position the IC chip
1
by means of a constant suction force (step S
53
, see FIG.
15
B). That is, in this
FIG. 15B
, the IC chip
1
is first moved leftward by the position regulating pawl
152
and thereafter moved upward to perform positioning, and the IC chip
1
is held by suction by the four suction holes
157
. Subsequently, after the IC chip
1
is positioned, the position regulating pawl
152
is moved back from the position of the solid line to the position of the one-dot chain line (step S
53
, see FIG.
15
C), release regulation is performed (Step S
54
), and thereafter the IC chip
1
is bonded, according to the conventional practice (Step S
55
).
In attempting to further increase the speed and quality in practically using this wire bonding method and apparatus, the present applicant has found visible minute scratches on a surface
1
b
that belongs to the IC chip
1
and is located opposite from the mounting surface
1
a
on which the metal bumps
4
are formed for the bonding onto a circuit board or the like. Since the surface is to be noticed as the identification surface of the manufacturer name, article number, specifications and so on, such scratches are concerned with the quality in terms of the external appearance although the scratches lead to no functional defect. Depending on the size and depth of the scratches, it can be considered that the scratches would become the cause of chipping and cracking due to an impact or the like at the time of handling in various stages, and this has became an important issue.
The present inventor and others have conducted various experiments in order to solve this issue and discovered the following facts. To the stage
151
are adhering foreign objects such as processing dust occurring when dicing is performed for separation into individual IC chips
1
, chipped segments generated during processing, conveying and various handling processes, dust in the air and so on, each having a particle diameter of two to several tens of micrometers. The processing dust and chip dust as described above are often hard substances of the grindstone that has performed dicing and those of the processed IC chips, having hardness equivalent to that of the IC chip
1
. Therefore, when the IC chip
1
is regulated in position by being pushed from the placement position to the work position in a state in which it is sucked onto the work stage
151
, the IC chip suffers scratches while being brought in strong abrasive contact with the foreign objects, occasionally causing chipping and cracking. That is,
Imanishi Makoto
Kanayama Shinji
Katano Ryoichiro
Mae Takaharu
Yonezawa Takahiro
Elve M. Alexandra
McHenry Kevin
Wenderoth , Lind & Ponack, L.L.P.
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