JPH0457100B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a wire bonding method, and more particularly to a method for detecting a sample surface in an automatic wire bonding process.

[Conventional technology]

The apparatus shown in the front view of FIG. 3 is used for automatic wire bonding, and in the figure, 31 is a bonding head, 32 is a clamper, 33 is a bonding arm, 34 is a capillary, 35 is a contact terminal, and 36 is a bonding arm. The contact points are shown respectively. FIG. 4 is an enlarged front view of the bonding arm 33, and numeral 37 indicates a sample on which a wire is bonded.

The illustrated capillary 34 is a means for bonding a gold wire, and a ball is made at the tip of this gold wire, and this ball is pressed against the surface of the sample 37, and the ball is bonded to the sample 37 by eutectic. The gold wire is thereby bonded to the surface of the sample 37. To this end, the bonding head 31 and the bonding arm 33 undergo a movement indicated by the arrow in the figure.

[Problems to be solved by the invention] According to the conventional wire bonding method, the capillary 37 is connected to the sample surface (die surface and lead surface).
When the contact terminal 35 contacts the bonding arm 33 and descends in the same way as the bonding arm 33, the contact terminal 35 contacts the bonding arm contact 36.
By moving away from the sample surface, the sample surface (die surface, lead surface) was detected, and the necessary load was applied to connect the gold wire sphere and the sample surface. However, when the contact terminal 35 leaves the bonding arm contact 36 (indicated by δ in the figure), in reality the capillary 34 has already collided with the sample surface, and before the load is applied to bond the gold wire and the sample surface. An impact load is occurring. This means that bonding head 3
This is because the system for driving the sample 1 up and down and the system for detecting whether the contact terminal is in contact with the sample surface are connected to separate drive systems and are moved by separate signals. For this reason, there is a problem that variations occur in bonding, particularly in the formation of a eutectic between the gold wire sphere and the sample surface.

[Means for solving problems]

The present invention provides a wire bonding method that solves the above-mentioned problems.In the method of wire bonding to a sample surface, when the capillary supporting the wire reaches a predetermined distance from the sample surface, Speed control is automatically performed to allow the capillary to approach the sample at a controlled constant speed, and when the capillary touches the sample surface, a collision with the sample surface is detected by the change in uniform speed, and the load for bonding is detected. This is done by an automatic wire bonding method characterized by applying pressure to the wire, then moving the wire to the next sample surface and repeating the above operation.

[Effect]

In the above method, the capillary is lowered using the same drive system, and whether or not the capillary hits the sample surface is detected by minute changes in the bonding arm descending speed.The signal is immediately applied to the drive system to perform wire bonding. It is something.

〔Example〕

Embodiments of the present invention will be described in detail below with reference to the drawings.

The system of the invention is shown in the block diagram of FIG.
In the same figure, 7 is a voltage application time designation circuit for applying wire pressure for bonding;
is an applied voltage specification circuit for applying wire pressure for bonding, 9 is a collision judgment constant (speed, ΔV) to the sample, 10 is a ΔV comparator for V _E and V _R , and 11 is for motor drive. Power amplifier, 12 is Z
Axis (vertical direction) motor drive circuit, 13 is a linear encoder provided in the bonding head, 14 is a smoother, 15 is a differential circuit, 16 is a specified search speed (V _R ) designating circuit, 17 is the actual lowering of the bonding arm The speed of time (V _E ) and
A comparator with _VR is shown, respectively.

In the above system, a position error signal is obtained from the A-phase and B-phase output signals of the linear encoder 13, and this signal is differentiated by a smoother 14 and a differentiator circuit 15 to generate a speed signal. The linear encoder 13 obtains information about the capillary 23, and the greater the movement of the capillary, the greater the number of sine waves output. In order to detect which direction the capillary has moved up or down, obtain two phase signals, A phase and B phase, which are different in phase and are shifted by 90 degrees, for example.
Next, the smoother 14 processes the A and B phases to obtain a continuous smooth signal, which is differentiated and converted into speed information. This speed signal is compared with the search speed specified at the beginning to ensure that the speed is always constant. That is, the motor drive power amplifier 11 uses the V _E and V _R comparator 17 to lower the motor drive voltage when V _E > V _R , and to increase the motor drive voltage when V _E < V _R. , thereby always V _E
= V _R . Then, in the comparator 10, the difference between V _{E and V R is} compared with the collision determination constant ΔV specified by the collision determination constant 9 against the sample, and V _E
When the difference between and V _R is greater than or equal to ΔV, an applied voltage for wire pressurization for bonding specified by circuit 8 is applied for a period of time specified by circuit 7.

The method of the present invention will be explained with reference to FIG. The upper graph in FIG. 2 shows the Z-axis (vertical direction) operation timing, and the lower part shows the sample, that is, the semiconductor chip 21, the leads 22, and the capillary 23, and the relationship between the die surface of the semiconductor chip 21 and the surface of the leads 22 is shown. The capillary 23 is the same as the conventional example. In actual bonding, the capillary is rapidly lowered from a position, but constant velocity control is performed from a position (search level) several hundred microns above the position where collision with the die surface is predicted (bond level).
In the graph, the slope of the line with respect to the horizontal plane indicates the speed of the capillary 23, and the steeper the slope, the higher the speed.

When the capillary collides with the die surface, that is, when the capillary reaches the position, the constant velocity control changes, so the collision with the die surface is detected from the amount of change in speed, and the gold wire ball is eutectic on the die surface. Apply the necessary load P for this purpose. Thereafter, the capillary reaches the position via the position .
This position corresponds to the position described above, and then the speed control and pressurization operations described above are performed on the surface of the lead 22. In this way, constant velocity control is performed between positions, and when a change in constant velocity is detected at a position, a signal to apply a load is immediately issued via the CPU, and a mechanical load application operation is performed.

〔Effect of the invention〕

As explained above, according to the present invention, the magnitude of the collision load can be freely changed by changing the speed amount for detecting a collision (specimen collision determination constant ΔV) and the specified search speed _VR . , a stable load is applied to bond the gold wire and the sample surface, which has the effect of preventing variations in wire bonding.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of a system implementing the method of the present invention, Fig. 2 is a graph showing the operation of wire bonding, showing the semiconductor chip, leads, capillary, and gold wire, and Fig. 3 is a diagram of conventional wire bonding. FIG. 4, a front view of the apparatus, shows the bonding arm of FIG. 3. In the figure, 7 is an applied voltage application time specification circuit for applying wire pressure for bonding, 8 is an applied voltage specification circuit for applying wire pressure for bonding, and 9 is a constant for determining collision with the sample. , 10 is
ΔV comparator for the difference between V _E and V _R , 11 is a motor drive power amplifier, 12 is a Z-axis motor drive circuit, 13 is a linear encoder, 14 is a smoother, 15 is a differentiation circuit, 16 is a specified search speed generation circuit, 17
denote V _E and _VR comparators, 21 a semiconductor chip, 22 a lead, 23 a capillary, and 24 a gold wire, respectively.

Claims (1)

[Claims] 1 When the capillary supporting the wire reaches a predetermined distance from the sample surface, constant velocity control is performed to bring the capillary closer to the sample at a constant velocity, and the change in the speed of the capillary prevents the capillary from colliding with the sample surface. A wire bonding method characterized by applying a bonding load to the wire after detection.