JPH0831492B2 - Head control method for wire bonding apparatus - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a head control method for a wire bonding apparatus in which electrodes of a semiconductor chip and leads are connected by a conductor wire (wire) in a manufacturing process of a semiconductor device. is there.

[Conventional technology]

FIG. 2 is a process diagram showing a process of a normal wire bonding apparatus. In the figure, 20 is a wire corresponding to a conductor wire, 21 is a clamper, 22 is a capillary, 23 is a ball,
24 is a semiconductor chip, and 25 is a lead frame.

At the start of bonding, the ball 23 is formed at the tip of the wire 20 as shown in FIG. From this state, the capillary 22 descends, and bonding is performed at the junction point p1 on the semiconductor chip 24 in the state shown in FIG. Further, the wire 20 is paid out from a wire spool (not shown) when the capillary 22 descends. next,
The capillary 22 after bonding rises to a predetermined height and moves to the lead frame 25 side as shown in FIG. Then, the capillary 22 descends again, lands on the joint point p2 on the lead 25, and performs bonding ((d) in the same figure). Subsequently, the bonding arm (not shown) ascends and stops together with the capillary 22, and the clamper 21 for holding the wire is closed and the wire 20 is torn off ((e) in the figure). Then, the tip of the wire 20 that has been torn off is heated by electric discharge or the like to form a ball 23 as shown in FIG. After that, the clamper 21 is opened, and the same operation is repeated from the initial state shown in FIG.

Next, conventional problems in the above steps will be described. First, in FIG. 2 (c), the rise of the capillary 22 is
It is necessary to pull out the wire from the joining point p1 to a required predetermined length so that a proper wire loop can be joined from each joining point. Also in FIG. 6E, it is necessary to determine the stop position of the bonding arm so that the wire length protruding from the capillary 22 becomes a predetermined length. This is because the diameter of the ball formed in the step of FIG.

In order to operate these operations stably, it is proposed to teach and store the lower surface height in advance along the junction point of the semiconductor chip 24 and the lead 25, and control the bonding arm while referring to this data at the time of bonding. ing.

FIG. 3 is an external view showing a configuration of a conventional device disclosed in Japanese Patent Laid-Open No. 57-183047. In the figure, 13 is a height detector, 14 is a bonding tool, 15 is an XY table, 16 is a position detector, 17 is a speed detector, 18 is a bonding control unit, 19 is a motor, and 20 is a first height storage unit. , 21 is a second height storage unit, and 22 is a pellet.

Next, the operation will be described. The height detector 13 attaches the bonding tool 14 to the pellet 22 before bonding.
It is mounted on the XY table 15 in such a positional relationship as to point to the same position as, and detects the height of the pad and lead before bonding in synchronization with bonding. The detected heights are stored in the first height storage unit 20 one after another for each bonding point.
When the bonding is completed, the data is transferred to the second height storage unit 21 and the speed profile of the bonding tool is generated based on the held data of the height of the bonding point. The position detector 16 indicating the current speed and the speed detector 17 indicating the current speed are used as feedback signals for the motor 19
Control.

[Problems to be Solved by the Invention]

A conventional head control method for a wire bonding apparatus is
The height of the joining point is taught and stored in advance, and the adjustment during the actual bonding operation is dealt with by manually changing the data. However, at the time of actual bonding, due to factors such as uneven base height of the chip transfer device, unevenness of lead pressing, and chip inclination, the height of the bonding point at the time of teaching and at the time of actual operation always matched. Not necessarily in a state,
There was variation in the height of each junction. On the other hand, in the conventional method, the height cannot be corrected in real time during the actual bonding, and as a result, the loop shape is deformed, the ball diameter is destabilized, and the reliability of the bonding state due to the pressure change Was causing a decline. Further, there is a drawback that productivity is not improved because the work of previously teaching and storing the height of the joining point is performed.

The present invention has been made to solve the above-mentioned drawbacks, and an object of the present invention is to obtain a head control method for a wire bonding apparatus for achieving ultra-high-speed wire bonding and realizing highly reliable bonding. .

[Means for solving the problem]

A head control method of a wire bonding apparatus according to the present invention detects a latest landing position of a bonding tool at a bonding point of an electrode or a lead at the time of bonding and stores it as a lower surface position, and the bonding after bonding is performed based on this lower surface position. It controls the movement of the tool and pulls out a certain amount of wire.

[Action]

Since a certain amount of wire is pulled out based on the latest landing position, the ball can be stably formed.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram of a wire bonding apparatus for carrying out a head control method showing an embodiment of the present invention. In the figure, 1 is a lower surface detector that detects the grounding of a bonding point, 2 is a position detector such as an encoder that detects the vertical position of a bonding arm, and 3 is a count signal of the position detector (measurement)
Then, the present value counter 4 for holding the present height of the bonding arm 4 is provided with the output signal from the lower surface detector 1,
This is a lower surface position register that holds the count value of the current value counter 3 at that time. Here, the lower surface position register 4 is composed of two registers for holding the lower surface position data of the pad and the lower surface position data of the lead, and switches the two registers according to the grounding of the pad and the lead. Reference numeral 5 denotes a subtracter for subtracting the value of the lower surface position register 4 from the current value counter 3, and the resulting value indicates the relative displacement amount of the bonding arm from the detected lower surface position reference. Reference numeral 6 is a comparator for comparing and judging whether or not the bonding arm has reached the target position of the operation switching point. Here, the output of the comparator 6 is input to the sequence controller 8 and serves as a trigger for operating the sequence.
As a result, the series of bonding steps shown in FIG. 2 are sequentially executed according to the instruction of the sequence controller 8.
Reference numeral 7 is a target value buffer for storing the switching point position of the operation from the sequence control unit, 9 is operation start and stop from the sequence control unit 8 to the speed control unit 11 for controlling the vertical movement of the mechanical drive unit 10 and the bonding head, and It is an output buffer that stores control data for instructing switching of the lower surface position register. The mechanical drive unit 10 controls the current of a solenoid or a linear motor for opening and closing a clamper or the like. The speed controller 11 controls the drive motor 12 by moving the head up and down by a predetermined amount to generate a speed profile for descending to the joining point and wire looping.

Next, the operation of this embodiment will be described. The sequence control unit 8 stores a wire bonding sequence program in advance, and the target buffer 7 and the output buffer 9 have 1
The data of the step is held. The mechanical driver unit 10 operates according to the content of this data, and the mechanism of the bonding tool is maintained in a desired state. Then, the speed controller 11 is also activated, and the bonding tool descends toward the first bonding point (pad). At this time, as the lower surface position register 4, the register on the pad side is selected and the sequence is started in accordance with the displacement amount based on the height of the adjacent pad previously held, and the bonding tool is controlled. Next, when the capillary lands on the junction point of the pad and the lower surface detector 1 is activated, the contents of the register are updated to the current height of the pad. Is started. Therefore, in the loop formation after the first bonding point bonding, a constant amount of wire can be pulled out. Next, when the bonding tool pulls out the wire and reaches the top of activation, the lower surface position register 4 is switched to the register on the read side, and the previously held lead height is used as a reference. Then, the sequence is started, and the bonding tool is lowered toward the second bonding point (lead). When the capillary lands on the lead, the contents of the lower surface position register 4 are updated to the lead landing height. The subsequent sequence is started based on the latest lead landing height. Therefore, it is possible to always keep the desired value of the tail length after the second bonding point bonding, and it is possible to form a stable ball. After ball formation, the sequence control unit 8 returns to the desired step and repeats the same sequence.

As described above, the method of controlling the head of the wire bonding apparatus according to the present embodiment switches the speed control of the head and sets the operation timings of various mechanisms associated with the head, such as the clamper, to the relative height position with reference to the height of the bonding point. It can be generated based on the sequence, and the sequence can be sequentially advanced.

In addition, since the bonding head can be controlled in real time by adapting to the fluctuating height of the bonding point during actual bonding, the wire loop shape and bonding conditions can always be kept in the optimum state, and the head is wasted. It is possible to shorten the soft landing time. Therefore, the reliability of wire bonding and the productivity are significantly improved, and as a result, the product reliability and the yield of the semiconductor device can be improved.

〔The invention's effect〕

As described above, the present invention includes means for detecting the landing of the bonding tool at the bonding point of the electrode or the lead at the time of bonding and reading the position of the bonding tool at that time, and performing the vertical movement of the bonding tool after wire bonding. Because it controls in real time based on the latest landing position, due to factors such as tip inclination,
Even if there are variations in the height of each joining point, stable bonding can be achieved.

In addition, because the vertical movement of the bonding tool is controlled in real time, the loop shape can be
It does not cause instability of the ball diameter and decrease in reliability of the joining state due to pressure fluctuation. Further, since there is no work of teaching and storing the height of the joining point in advance, the productivity can be improved.

[Brief description of drawings]

FIG. 1 is a block diagram of a wire bonding apparatus showing an embodiment according to the present invention, FIG. 2 is a process drawing of normal wire bonding, and FIG. 3 is an external view showing a conventional apparatus. 1 ... bottom detector, 2 ... position detector, 3 ... current value counter, 4 ... bottom position register, 5 ... subtractor, 6 ...
Comparator, 7 Target value buffer, 7 Target value buffer, 8 Sequence control unit, 9 Output buffer, 10
...... Mechanical drive section, 11 …… Speed control section, 12 …… Drive motor.

Claims (2)

[Claims] 1. A wire bonding apparatus for connecting an electrode of a semiconductor chip and an external lead with a conductor wire, the step of detecting landing of the bonding tool at a bonding point of the electrode or the lead at the time of bonding, and the bonding tool at that time. A head for a wire bonding apparatus including a step of reading a position and storing the latest read value as a lower surface position, and a step of controlling the operation of a bonding tool after bonding based on the lower surface position to pull out a certain amount of wire. Control method. 2. A head control method for a wire bonding apparatus according to claim 1, wherein a fixed amount of wire is an amount necessary for ball formation.