Metal fusion bonding – Process – With condition responsive – program – or timing control
Reexamination Certificate
1999-04-13
2001-02-20
Ryan, Patrick (Department: 1725)
Metal fusion bonding
Process
With condition responsive, program, or timing control
C228S103000, C228S010000, C228S004500, C228S180500
Reexamination Certificate
active
06189765
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an apparatus and a method for detecting a double wire bonding; and, more particularly to the apparatus and the method capable of detecting a double bonding error when a wire ball is in contact with a previously formed wire loop.
DESCRIPTION OF THE PRIOR ART
FIG. 1
shows an exemplary structure illustrating a conventional wire bonding apparatus.
A wire spool
101
winds a wire, a guide
103
is for guiding the wire drawn from the wire spool
101
and a wire loop control unit
102
includes a sensor
104
for sensing whether the wire guided by the guide
103
exists at present.
A wire extractor
105
provides the wire with a tensile force and a wire clamp
106
clamps a wire position moved through the extractor
105
, and a capillary
107
is positioned in a lower part of the wire clamp
106
and performs a wire bonding between a pad and a lead, and a transducer
108
drives the capillary
107
.
Conventionally the lead frame having a structure of a complicated wire connection has been designed. Thus, because coordinates for connecting the lead and the pad acts as an important parameter, it is important to accurately connect the pad and the lead depending on coordinates established by a processor connected to the wire bonding apparatus, in a semiconductor assembly. When an arrangement sequence of pads and lead frames is established and then a wire bonding process is programmed, the wire bonding apparatus performs the wire bonding between the pad and the lead according to the programmed wire bonding process.
When the wire bonding apparatus performs the wire bonding process, a position arrangement of lead frames must be accurately accomplished so that the wire can be accurately connected at a bonding position of the pad and the lead.
However, unstable elements of a manufacturing process, such as a position error of bonding material and an error of the lead frame arrangement by an unskilled workman, may result in the lead frame being reloaded, and errors of the wire bonding apparatus such as an index error, a wire break and so on, may result in work manipulation mistakes.
Because of those errors as described above, the case where a position for the wire bonding of the pad and the lead is beyond an allowance error may occur. According to the work manipulation mistakes, the case where the lead frame is not positioned at the accurate coordinate may occur. Thus, due to these errors and work manipulation mistakes, a bonding coordinate different from the coordinate established by the processor may be set on a display and a camera for monitoring a wire bonding state may not sense the wire bonding state.
Furthermore, the wire bonding can be carried out once more at the same coordinate of the pad on which the wire bonding has been previously performed and consequently, there is a problem in that a double wire bonding may occur.
Because the wire bonding apparatus itself may not detect errors of the wire bonding. Such a problem may occur resulting in the producing a small or large amount of bad products in a production process.
SUMMARY OF THE INVENTION
Therefore, an object of the present invention is to provide an apparatus and a method for detecting a double bonding error that a wire ball is in contact with a wire loop previously formed between a pad and a lead, by using the position of the wire ball and comparing a reference voltage with the voltage on a wire when the wire ball is in contact with either the pad or the wire loop.
In accordance with a first aspect of the present invention, there is provided a wire bonding apparatus having a wire spool for providing a wire, a high voltage torch for forming a wire bonding ball on an end of the wire, a capillary for determining a position of the wire bonding ball and x,y and z-axis drivers for moving the capillary, the wire bonding apparatus comprising: a first means for applying a voltage to the wire and for forming a closed loop through the voltage applied wire and the wire bonding ball; and a second means for detecting a double bonding error using a voltage signal from the closed loop and present position of the wire bonding ball on a z-axis.
In accordance with a second aspect of the present invention, there is provided a wire bonding apparatus comprising: a bonding means for forming a wire bonding ball from a wire fed from a wire spool and for bonding the wire between a pad and a lead of a semiconductor device; a voltage supplying means for applying a voltage to the wire; a first comparing means for comparing a predetermined voltage with the voltage applied to the wire when the wire bonding ball formed by the bonding means is in contact with either the pad or a wire loop which is previously formed at a preceding wire bonding process; a detector for providing height of the wire bonding ball at a present position; a second comparing means for comparing a predetermined height with a present height of the wire bonding ball in response to an output from the first comparing means in order to prevent a double wire bonding from being generated; and a driving means for moving position of the wire bonding ball when the height of the wire bonding ball is more than the predetermined height.
In accordance with a third aspect of the present invention, there is provided a method for detecting a double wire bonding, comprising steps of: descending a capillary to form a wire bonding ball on an end of a wire and perform a wire bonding; determining whether a voltage applied to the wire exists, comparing the applied voltage with a reference voltage and outputting a compared result signal in a first comparator; determining whether the compared result signal is either a low level signal or a high level signal; performing a normal wire bonding if the compared result signal is the high level signal; and receiving the present position of the wire bonding ball if the compared result signal is the low level signal and detecting a double bonding error when the wire bonding ball has been contacted to either the pad or a wire loop in a second comparator.
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Hyundai Electronics Industries Co,. Ltd.
Jacobson Price Holman & Stern PLLC
Johnson Jonathan
Ryan Patrick
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