JPS61123148A - Wire bonding method - Google Patents

Abstract

PURPOSE:To make vibration of capillary small and execute good bonding process by previously setting the standard acceleration characteristic and moving a capillary with the same acceleration characteristic as the reference acceleration characteristic. CONSTITUTION:A capillary 6 is driven with a constant acceleration characteristic by the wire bonding method wherein the bonding lead is extended by moving the capillary 6 between the electrode and external lead of semiconductor element. A central processing unit 1 has the reference moving distance L, a reference target number of times of renewal N required for movement in distance L and a capillary moving function f(t) as the reference data in the memory 2. A number of renewal pulses DELTAli of pulse encoder 7 is obtained from the target number of renewals N, moving function f(t) and moving distance l and the target position is renewed according to such value. Thereby, the capillary 6 can be moved with optimum acceleration characteristic.

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 movement of a bonding capillary (hereinafter simply referred to as a capillary) is performed using digital 1tll wJL in order to cope with various bonding conditions. The advantage of a digital bonder is that it is possible to expand and contract the vertical movement distance of the capillary, which was not possible with conventional cam-type bonders, and it is possible to control the shape of the wire loop during bonding. FIG. 6 is an explanatory diagram showing an am-like movement locus of a capillary in a digital bonder. The capillary at origin A descends at high speed and reaches point 8. Next, the ball is pressed against the pellet surface after reaching the pellet surface at a low speed. Next, when a predetermined bonding time has elapsed, the capillary moves toward the second bonding point while rising toward point D.

The capillary rising distance (Hco) at this time is determined by predicting the required wire amount Qco from the horizontal distance between the first bonding point and the second bonding point (XY in Figure 7) and the so-called loop height β). Determined by Therefore, when the horizontal distance XY increases by ΔXY, the amount of wire must also be increased to ff1co-, as shown in FIG. 7, and the capillary rising distance must also be increased to Hco', as shown in FIG.

When the capillary reaches point D, it descends again, and then moves to the origin G after the second bonding process (stitch bonding) to complete the installation of the bonding line. The movement trajectory of such a capillary, which is also important, is the part where the moving distance needs to be changed depending on the XY distance, that is, the C
-+D (C→D-) and D-E (D→E-). Conventional digital bonders can respond to changes in moving distance, but they do not consider moving speed, and as shown in Figure 8, even if the moving distance is long from C-40 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 differs depending on the moving distance of the capillary, the capturing state of the capillary also changes each time. As a result, it was not possible to obtain the desired bonding strength or wire loop shape.
It is not possible to perform a good bonding process.

[Purpose of the invention]

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

(Summary of the Invention) The present invention prevents capillary vibration by setting standard acceleration characteristics in advance and moving the capillary with the same acceleration characteristics as the standard acceleration characteristics according to the moving distance of the capillary. This is a wire bonding method that can be made small and perform good bonding processing.

[Embodiments of the invention]

Hereinafter, one embodiment of the present invention will be described with reference to the relevant aspects.

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. A predetermined signal is supplied to the central processing unit 1 from the memory section 2. Memory section 2
includes standard trajectory data 2a, moving distance (l data 2b,
Current position (EXPT) 7”-Y2c, target position (TAR)
G) Data 2d, deviation 1 (HEN) data 2e, and target update data (Δffi+>2f) are stored.

The output of the central processing unit W1 is supplied to the servo amplifier 5 together with the output of a tacho generator 4 attached to the motor 3. Servo amplifier 5 is capillary 6
It is connected to a motor 3 that drives the. A pulse train proportional to the motor rotation angle is supplied to a pulse counter 8 via a rotary square 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 controlled 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 according to the following principle. One electric power for the motor 3Ab' is supplied by the servo amplifier 5, and the tachogenerator 4 generates a voltage proportional to the rotational speed of the motor 3. The rotary pulse encoder 7 generates a force pulse proportional to the rotation direction and rotation angle of the motor 3. The voltage output from the tachogenerator 4 is directly negatively fed back to the servo amplifier 5, forming 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 outputs WJf at a predetermined time.
The contents of the pulse counter 8 are read at intervals of lIl, the difference from the previous count value is calculated, and this difference is added to the old current position data 2C (hereinafter referred to as EXPT) in the memory section 2. By "subtracting" the new current position of the capillary 6, the target position data 2d includes the capillary 6.
target position data (hereinafter referred to as TARG) is stored, and the central processing unit 1 uses this TARG and the new EX
, PT, and stores this in the memory unit 2 as a deviation value (hereinafter referred to as HEN). Then, the central numbing device M1 obtains an analog output according to HEN by a predetermined calculation so that HEN-, TARG-EXPT=0, and outputs it to the servo amplifier 5.

Therefore, when capillary 6 is in a stopped state, TAR
G4EXPT, and if you want to move the capillary 5, you only need to change TARG. It should be noted that all the data mentioned above including the travel distance, that is, T
The unit of ARG%EXPT, )(EN, etc. is not a unit of length, but the number of pulses with the minimum resolution being the capillary displacement per unit pulse emitted by the pulse encoder 7.

Next, the case where the capillary 6 is moved by a predetermined distance β is described as a second case.
This will be explained with reference to the figures. It is assumed that the moving distance 2 is given to the memory section 2. The central processing unit 1 calculates the number of updates n of the target position from the moving distance λ given by the moving distance data 2b of the memory section 2 using the method described below, and calculates the number of update pulses Δxt (i-1 to n ) is calculated 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. 3, and ΔC1 is calculated based on this function. Ru.

For simplicity, FIG. 4 shows the case where the velocity change of the capillary 6 is made into a triangular wave as the above-mentioned rJA number. Therefore, the calculation result of Δλi satisfies the following equation.

! =ΣΔ/i, lΔ7/i−Δ1i−11=k (7
After completing this calculation, the central processing unit 1 sequentially reads the target update data Δe; from the target update data 2f starting from i = 1 at intervals of a predetermined target value update time T, and adds this to TARG. To go. (Here, the moving distance 2 and the update data Δe1 are data including the moving direction.

) Then, the update of TARG is finished when the time nT has elapsed, and the movement of the capillary 6 is completed by waiting for EXPT"FTARG. 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, as standard trajectory data, the standard moving distance ri, the standard target update number N required to move the distance, and the capillary moving number wJ (t) in the memory unit 2. . Changes in capillary displacement, velocity, and acceleration over time on this standard trajectory are shown by solid lines in FIGS. 5(A) to 5(C). The locus function f(1) is generally arbitrary, but for the sake of simplicity, the case where it is a triangular wave velocity is shown here as well. The standard movement distance usually means the maximum movement range of the capillary 6, and the standard target update number N is the function f (t
), the distance 111L was experimentally moved, and vibration and other elements were measured, and the optimum value was adopted.

Moving distance! 2 (<L), the moving acceleration characteristic of the capillary 6 is set to be the same as the acceleration characteristic determined by the standard trajectory data, which means that the capillary moving speed change with respect to the moving distance 111λ is shown in FIG. As shown by the broken line,
The aim is to make the velocity change similar to that of the standard trajectory data. On the other hand, the capillary movement distance e given the standard movement distance is the integral value of the capillary velocity change shown by the solid line and the broken line in FIG. It can be obtained using the following formula.

n = , f”7 and according to this TARG
By updating , 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.

(Effects of the Invention) As explained above, according to the wire bonding method according to the present invention, it is possible to perform a good bonding process by reducing the capillary movement.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram showing the schematic configuration of the wire bonding apparatus 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. 4 is an explanatory diagram showing the relationship between capillary velocity and time. FIG. 5 (A) is an explanatory diagram showing the relationship between capillary displacement and time. FIG. 5 (B) is an explanatory diagram showing the relationship between capillary velocity and time. An explanatory diagram showing the relationship between velocity and time, FIG. 5 (C) is an explanatory diagram showing the relationship between capillary acceleration and time, and FIG.
FIG. 7 is an explanatory diagram showing a trajectory of a capillary during wire bonding, FIG. 7 is an explanatory diagram showing a wire loop formed by movement of the capillary, and FIG. 8 is an explanatory diagram showing changes in acceleration of the capillary. 1... Central processing unit, 2... Memory section, 3...
Motor 4...Tachogenerator, 5...Servo amplifier, 6...Capillary, 7...Pulse encoder,
8... Pulse counter, 10... Wire bonding device.

Claims (1)

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