Metal fusion bonding – Means to apply vibratory solid-state bonding energy to work
Reexamination Certificate
1999-05-27
2001-10-16
Nelms, David (Department: 2818)
Metal fusion bonding
Means to apply vibratory solid-state bonding energy to work
C438S014000
Reexamination Certificate
active
06302312
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a bonding apparatus and method for performing a scrubbing operation during bonding.
2. Prior Art
Performing a scrubbing operation by applying vibrations to a bonding tool during bonding is known in the past. This type of scrubbing operation is disclosed in, for example, Japanese Patent Application Laid-Open (Kokai) Nos. S60-70736 and S62-249437 (hereinafter referred to as Prior Art 1), Japanese Patent Application Laid-Open (Kokai) No. S63-239834 (hereinafter referred to as Prior Art 2), and Japanese Patent Nos. 2,530,224 and 2,565,009 (hereinafter referred to as Prior Art 3).
In Prior Art 1, before a bonding operation is executed, the regions to be joined on a lead frame are scrubbed by a scrubbing device which is a separate device from a bonding apparatus. The scrubbing operation is performed by applying ultrasonic vibrations to the ultrasonic horn of the bonding apparatus. Thus, since a scrubbing device is required in addition to the bonding apparatus, there is a major increase in the total cost of the bonding system as well as an increase in installation space. Also, since the scrubbing operation is performed by applying ultrasonic vibrations to an ultrasonic horn, only a reciprocal scrubbing operation in the direction of the axis of the ultrasonic horn can be performed.
In Prior Art 2, a piezoelectric element is provided on an ultrasonic horn, and the scrubbing operation is performed by applying voltage to the piezoelectric element so that the piezoelectric element oscillates. Since a piezoelectric element is thus provided on the ultrasonic horn of the bonding apparatus in Prior Art 2, there is no major increase in apparatus cost or increase in installation space as in Prior Art 1; however, a separate piezoelectric element and a drive circuit for driving the piezoelectric element are required. As a result, a corresponding increase in costs is inevitable in this Prior Art 2. Also, since the scrubbing operation is in the direction of expansion and contraction of the laminated piezoelectric element, only a linear reciprocal scrubbing operation in the direction of extension of the ultrasonic vibrations is performed just as in Prior Art 1.
In contrast, with Prior Art 3, the scrubbing operation is performed by a bonding tool provided on an XY table which is moved by, for instance, a DC motor and is a part of the bonding apparatus installed from the outset. Accordingly, there is no increase in apparatus cost, nor is there any increase in installation space. Also, since the scrubbing operation is carried out by driving the XY table, the scrubbing operation can be performed in a square pattern, a rectangular pattern, an elliptical pattern, a linear reciprocating pattern, or any other desired pattern. In other words, it is possible to select the scrubbing operation that is best-suited to the intended object.
However, the Prior Art 3fails to disclose the control of the DC motor which drives the XY table though it teaches that the DC motor is controlled by a control circuit.
Accompanying
FIG. 3
shows the control circuit for the DC motor of the Prior Art 3. In the
FIG. 3
, the DC motor
2
that drives the XY table
1
is controlled by a position sensor
3
that reads the position of the rotary shaft of the DC motor
2
, the control circuit
10
includes a drive circuit of the DC motor
2
, and a computer
4
controls the control circuit
10
.
More specifically, a pulse train command
4
a
from the computer
4
is inputted to a position comparison circuit
11
and becomes a current command via a speed comparison circuit
12
, an adder
13
, and a drive circuit
14
, thus driving the DC motor
2
and moving the XY table
1
.
The movement of the rotary shaft of the DC motor
2
driven by the current command is detected by the position sensor
3
. The output signal
3
a
of the position sensor
3
is converted into a speed signal
15
a
by a speed conversion circuit
15
, after which it is inputted in the speed comparison circuit
12
so as to stabilize the control system. The output signal
3
a
of the position sensor
3
is also converted into a pulse by a pulse conversion circuit
16
, after which it is inputted to the position comparison circuit
11
. When the number of pulses of the input signal
16
a
becomes the same as the number of the pulse train command
4
a
from the computer
4
, the operation to control the DC motor
2
is completed.
So as to stop the DC motor
2
at a specific location between pulses, the output signal
3
a
from the position sensor
3
is inputted to a clamp circuit
17
, and a clamp signal
17
a
from the clamp circuit
17
is inputted to the adder
13
. This will be explained with reference to FIG.
4
.
FIG.
4
(
a
) shows the one-pulse movement of the rotary shaft of the DC motor
2
caused by the pulse train command
4
a
of the computer
4
. Here, “one-pulse movement” means that if the rotary shaft was within range A between pulses P
1
and P
2
, for example, it has moved to range B between pulses P
2
and P
3
as a result of one pulse (from pulse P
2
to P
3
) of movement. However, the position of the rotary shaft of the DC motor
2
cannot be fixed in this state.
Accordingly, as shown in FIG.
4
(
b
), the clamp circuit
17
controls the rotary shaft of the DC motor so that the rotary shaft stops in the centers A
1
, B
1
, and so on; in other words, the rotary shaft stops between pulses P
1
and P
2
, between pulses P
2
and P
3
, and so on. More specifically, if the rotary shaft is stopped at the position of the center A
1
and is moved one pulse, it will be moved to the position of the center B
1
. FIG.
4
(
b
) shows the serrated output signal
3
a
produced by an encoder of the position sensor
3
. This output signal
3
a
is the product of converting the distance from a given pulse to the next pulse (the amount of movement) to an electrical quantity.
Usually, the DC motor
2
stops between pulses or at the intermediate point of two pulses. Thus, when the output signal
3
a
is expressed as voltage, the distance from the leading edge of a pulse to the leading edge of the next pulse is expressed from a positive voltage +V to a negative voltage −V or vice versa, with the center being 0 V. For instance, if the motor is actuated in a state in which it is stopped with the output signal
3
a
at 0 V, and if the stopping position after actuation is not the 0 V position, then a voltage corresponding to this discrepancy is added to the adder
13
as the clamp signal
17
a
from the clamp circuit
17
, and the output of the adder
13
is compensated so that the output signal
3
a
will be at the 0 V position; as a result, the motor stops at its intended position.
Since the operation of the DC motor
2
is controlled by the pulse train command
4
a
that is supplied by the computer
4
, when the scrubbing operation is performed by controlling the XY table
1
as in the Prior Art 3, the scrubbing operation is also performed in one-pulse operational units just as in normal operation. In other words, since the resolution (such as 2.5 &mgr;m per pulse) is fixed in the control of an ordinary XY table
1
, the scrubbing operation is performed only in these units, and the operation finer than one pulse that is required for the scrubbing operation cannot be carried out.
SUMMARY OF THE INVENTION
Accordingly, the object of the present invention is to provide a bonding apparatus and method which can make a driving control of the XY table in units smaller than the one-pulse units with which the XY table is driven for an ordinary bonding operation, thus allowing free setting of the amplitude and frequency of the scrubbing operation and good bonding to be carried out.
The above object is accomplished by a unique structure for a bonding apparatus that comprises an XY table having a bonding tool, a drive means (motor) for driving the XY table, a control circuit for controlling the drive means in drive amounts based on the units of resolution of the drive means, a position
Hayashi Hijiri
Takahashi Kuniyuki
Berry Renee R
Kabushiki Kaisha Shinkawa
Koda & Androlia
Nelms David
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