JPH0566731B2 - - Google Patents

Description

[Detailed description of the invention] [Technical field of invention] The present invention relates to a wire bonding method.

[Technical background of the invention]

In recent years, so-called digital bonders have been developed in which the vertical drive of a bonding capillary (hereinafter simply referred to as a capillary) is digitally controlled in order to accommodate various bonding conditions. The advantage of the digital bonder is that it is possible to extend and contract the vertical movement distance of the capillary, which was impossible with conventional cam-type bonders, and that the shape of the wire loop during bonding can be controlled. FIG. 6 is an explanatory diagram showing a standard movement locus of a capillary in a digital bonder. The capillary at origin A descends at high speed and reaches point B. Next, after reaching the pellet surface at a low speed, the ball is pressed against the pellet surface. Next, when a predetermined bonding time has elapsed, the capillary moves toward the second bonding point while rising toward point D.
The rising distance of the capillary (H _CD ) at this time is the first
The required wire amount l _CD is predicted and determined from the horizontal distance between the bonding point and the second bonding point (XY→ in FIG. 7) and the so-called loop height (l).
Therefore, if the horizontal distance XY→ increases by ΔXY, the wire length will also increase to l _CD ' as shown in Figure 7, and the capillary's rising distance will also increase as shown in Figure 6.
It is necessary to make it as long as H _CD ′. The capillary is D
When it reaches the point, it descends again, and after the second bonding process (state bonding), it moves to the origin G and completes the erection of the bonding line. The most important trajectory among these capillary motion trajectories is
The parts where the movement distance needs to be changed according to the distance of XY→, namely C→D (C→D'), D→E (D→
E′). Conventional digital bonders can respond to changes in moving distance, but they do not take into account moving speed, and as shown in Figure 8, even if the moving distance is long from C→D to C→D'. Try to move them in the same amount of time. In other words, as the moving distance changes, the acceleration of the capillary also changes.

[Problems with background technology]

In such a conventional wire bonding method, since the acceleration varies depending on the moving distance of the capillary, the vibration state of the capillary also changes each time. As a result, a predetermined bonding strength and wire loop shape cannot be obtained, and a good bonding process cannot be performed.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a wire bonding method that can perform a good bonding process by reducing the drive of a capillary.

[Summary of the invention]

In the present invention, a standard acceleration characteristic is set in advance, and the capillary is moved with the same acceleration characteristic as the standard acceleration characteristic according to the moving distance of the capillary, thereby reducing the vibration of the capillary and achieving a good performance. This is a wire bonding method that can perform bonding processing.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is an explanatory diagram showing a schematic configuration of a wire bonding apparatus used in the method of the present invention. 1 in the figure is a central processing unit. The central processing unit 1 is supplied with a predetermined signal from the memory section 2 . The memory unit 2 contains standard trajectory data 2a, movement distance (l) data 2c, target position (TARG) data 2d, deviation value (HEN) data 2e,
Target update data (Δl _i ) 2f is described.
The output of the central processing unit 1 is supplied to the servo amplifier 5 together with the output of a tachogenerator 7 attached to the motor 3. The servo amplifier 5 is connected to a motor 3 that drives a capillary 6. The pulse train proportional to the motor rotation angle is
The signal is supplied to a pulse counter 8 via a rotary pulse encoder 7. The pulse counter 8 is configured to output a predetermined signal to the central processing unit 1. That is, in this wire bonding apparatus 10, the vertical movement direction of the capillary 6 is suppressed by the rotation direction of the motor 3, and the movement distance is proportional to the rotation angle of the motor 3.

The capillary 6 is driven by the following principle. Power to the motor 3 is supplied by a servo amplifier 5, and a tachogenerator 4 generates a voltage proportional to the rotational speed of the motor 3. The rotary pulse encoder 7 generates pulses proportional to the rotation direction and rotation angle of the motor 3. The voltage output from the tacho generator 4 is sent to the servo amplifier 5.
is provided with negative feedback directly to constitute an independent servo loop. The pulse counter 8 counts the pulse train sent from the pulse encoder 7 while distinguishing its rotational direction. The central processing unit 1 reads the contents of the pulse counter 8 at predetermined time intervals, calculates the difference from the previous count value, and converts this difference into old current position data 2c (hereinafter referred to as EXPT) in the memory section 2. By adding (subtracting) to , the new current position of the capillary 6 is determined. On the other hand, the target position data 2d stores the target position data (hereinafter referred to as TARG) of the capillary 6, and the central processing unit 1 calculates the difference between this TARG and the new EXPT, and uses this as the deviation value. (hereinafter referred to as HEN) in the memory unit 2. Then, the central processing unit 1 sets the
An analog output corresponding to HEN is obtained by a predetermined calculation and outputted to the servo amplifier 5. Therefore, when the capillary 6 is in a stopped state,
TARG≒EXPT, and if you want to move the capillary 5, you just need to change TARG. Note that the units of all the data mentioned above, including the moving distance, such as TARG, EXPT, HEN, etc., are not units of length but pulse encoder 7.
This is the number of pulses with the minimum resolution as the capillary displacement per unit pulse emitted by.

Next, a case in which the capillary 6 is moved by a predetermined distance l will be explained with reference to FIG. The moving distance l is
It is assumed that the memory section 2 is provided with the following information. The central processing unit 1 calculates the number of updates n of the target position from the moving distance l given by the moving distance data 2b of the memory unit 2 using the method described below, and calculates the number of update pulses Δl _i (i=1 to n) is determined and stored as target update data in the target update data 2f as shown in FIG. Normally, the movement trajectory of the capillary 6 is controlled by a function f(t), such as a cycloidal curve, with smooth start and end points, as shown in FIG.
Δli is calculated based on this function. Figure 4 shows the capillary 6 as a function of the above for simplicity.
This shows the case where the velocity change is a triangular wave.
Therefore, the calculation result of Δli satisfies the following equation.

l = _o 〓 ⁱ⁼¹ Δl _i , | Δl _i - Δl _i-1 | = k (acceleration) After completing this calculation, the central processing unit 1 updates the target update data Δli at intervals of a predetermined target value update time T. are sequentially read from the target update data 2f starting from i=1 and added to TARG. (Here, the moving distance l and the updated data Δli are data including the moving direction.) Then, at the time point when time nT has elapsed,
After updating TARG, wait until EXPT≒TARG, and move the capillary 6 to completion. In this way, the capillary 6 can be moved along a desired trajectory.

Next, a method of driving the capillary 6 with constant acceleration/deceleration characteristics will be described.

The central processing unit 1 has a standard movement distance L, a standard target update number N required to move the distance L, and a capillary movement function f(t) in the memory unit 2 as standard trajectory data. Figure 5A shows the temporal changes in capillary displacement, velocity, and acceleration of this standard trajectory.
-C are indicated by solid lines. The locus function f(t) is generally arbitrary, but for the sake of simplicity, the case where it is a triangular wave velocity is shown here as well. Standard travel distance L
usually means the maximum movement range of the capillary 6, and the standard target update number N is the optimum value that is adopted as the result of experimentally moving the distance L using the function f(t) and measuring vibration and other elements. Ru. Movement distance l (<L)
The fact that the moving acceleration characteristic of the capillary 6 is the same as the acceleration characteristic determined by the standard trajectory data, regardless of the length of This is to make it similar to the speed change of .
On the other hand, since the standard travel distance L and the given capillary travel distance l are the integral values of the capillary speed changes shown by the solid line and the broken line in FIG. 5B, the target number of updates for the travel distance l is determined by the following formula You can get it at

n=√l/L×N Below, the target number of updates n obtained from the above formula,
The number of update pulses Δli (i=1 to n) described above is determined from the trajectory function f(t) and the moving distance l, and according to this,
By updating TARG, the capillary 6 can always be moved with optimal acceleration characteristics.

It goes without saying that the present invention is not applied by specifying which trajectory among the movement trajectories of the capillary shown in FIG. 6. In reality, it is possible to control all trajectories according to a single standard trajectory data, or it is also possible to individually set standard trajectory data for each trajectory. Furthermore, it is also possible to prepare a plurality of standard locus data and select any standard data for each locus.

〔Effect of the invention〕

As explained above, according to the wire bonding method according to the present invention, it is possible to reduce the vibration of the capillary and perform a good bonding process.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram showing the schematic configuration of the wire bonding device used in the present invention, Fig. 2 is an explanatory diagram showing the number of update pulses for each update, and Fig. 3 is an explanatory diagram showing the relationship between capillary displacement and time. FIG. 4 is an explanatory diagram showing the relationship between capillary speed and time, FIG. 5A is an explanatory diagram showing the relationship between capillary displacement and time, and FIG. 5B is an explanatory diagram showing the relationship between capillary velocity and time. FIG. 5C is an explanatory diagram showing the relationship between capillary acceleration and time. FIG. 6 is an explanatory diagram showing the trajectory of the capillary in wire bonding. FIG. FIG. 8 is an explanatory diagram showing the wire loop thus formed, and FIG. 8 is an explanatory diagram showing changes in the acceleration of the capillary. 1... central processing unit, 2... memory section, 3...
Motor, 4...Tachometer generator, 5...Servo amplifier, 6...Capillary, 7...Pulse encoder, 8...Pulse counter, 10...Wire bonding device.

Claims (1)

[Claims] 1. In a wire bonding method in which a capillary is moved between an electrode part and an external lead of a semiconductor element to construct a bonding line, a standard driving trajectory of a capillary that moves between an electrode part and an external lead is set in advance, and the actual The driving trajectory of the capillary is compared with the standard driving trajectory, and the capillary is moved along the actual driving trajectory with an acceleration characteristic equal to the standard acceleration characteristic of the capillary in the standard driving trajectory. Wire bonding method.