JPS5919463B2 - wire bonding method - Google Patents

Abstract

PURPOSE:To bond a wire in the best condition while calculating the supersonic wave output values of respective bonding points by inputting the optimum values of the supersonic oscillation outputs for driving the vibrating direction of the horn of a supersonic pressing device into a microcomputer. CONSTITUTION:A ratio of a reference oscillation output value for bonding a wire in the best condition when the bending direction of the tail of the wire at the time of bonding is matched to a Y-axis direction to a reference oscillation output value for bonding the wire in the best condition when the bending direction of the tail is matched to an X-axis direction is prepared, the best oscillation output value of the bonding point at a certain position is prepared as a predetermined function, and they are stored in a computer beforehand. The oscillation output of the best bonding calculated by the computer 11 is outputted by a supersonic oscillator 12 to vibrate a horn 5. Since it is a supersonic vibration calculated by the computer, uniform bonding can be performed.

Description

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

In the manufacture of semiconductors, integrated circuit devices, etc., there is work to connect pads on pellets and external leads with wires, and ultrasonic wire bonding methods and ultrasonic thermocompression wire bonding methods are known as methods for this wire connection. ing.

In this method, it is necessary to match the direction in which the wire extends and the direction in which the wedge vibrates so that the wire does not escape from the lower end of the wedge used to press the wire against the bonding point. Therefore, recently, in order to eliminate the need to consider such directionality, a wire has been inserted into a cylindrical capillary instead of a wedge.

FIG. 1 is a schematic side view of a wire bonding apparatus using a capillary, and FIG. 2 is a plan view and a side view showing a bonding state. As shown in FIG. 1, a capillary 3 is disposed above a sample stage 2 on which a sample 1 is positioned and mounted. The capillary 3 is attached to the tip of a horn 5 that is driven up and down by a bonding head 4, and the bonding head 4 is moved on the XY plane by an XY table 6. Further, the wire T is guided from the spool 8 to the lower surface of the tip of the capillary 3 through a clamper 9 that moves up and down with the horn 5 and a guide hole of the capillary 3.
Therefore, by operating the Chessman 10 to move the XY table 6 and aligning an arbitrary fixed point on the sample 1 with a mark projected on the monitor (not shown) using a camera (not shown) fixed on the bonding head 4, the sample A microcomputer (not shown) automatically calculates the bonding position from the amount of deviation of 1, and thereafter all bonding points are automatically bonded according to the operation shown in FIG. That is, the XY table 6 moves and the capillary 3
is located above the first bond point a4, the capillary 3 is lowered by the drive of the bonding head 4 and is grounded at the first bond point a4, and the horn 5 oscillates ultrasonic waves to connect the wire T to the first bond point a. At the same time, the clamper 9 opens.

Next, the capillary 3 is raised by the drive of the bonding head 4, and the second bond point b is moved by the movement of the XY table 6.
Located above 1. Subsequently, the capillary 3 and clamper 9 are lowered by driving the bonding head 4 and grounded at the second bond point B, and the horn 5 oscillates ultrasonic waves to bond to the second bond point B. Next, the capillary 3 rises slightly, and then the wire 7 is held by the clamper 9, the XY table 6 is moved to the rear of the lube formed by the wire 7, and the wire 7 is cut near the second bond point b1. . As a result, under the bottom surface of the tip of the capillary 3, a wire 7 is bent in the direction of the bottom surface of the capillary 3.
The tail of is extended. Finally, the bonding head 4 is driven to raise the capillary 3, and the XY table 6 is further driven to move the capillary 3 to the next first bonding point. This operation is repeated to complete bonding. In this way, by using the capillary 3, bonding can be performed using ultrasonic waves without rotating the sample stage 2.

Now, the vibration direction of the ultrasonic wave is the axis of the horn 5, that is, the Y direction, and the bending direction of the tail and the loop direction connecting the first bond point a and the second bond point b to which the wire is connected coincide with this Y direction. If this is the case, the ultrasonic oscillation output will be effectively transmitted to the bond portion of the wire 7 for the first pound to the first bond a and the second bond to the second bond point b, and good bonding will be performed. However, as is clear from Fig. 2a, there are various loop directions, and it is better to bend the tail so that it approximates the loop direction as much as possible. When bonding is performed with a constant reference oscillation output as shown in FIG. For this reason, the conventional method using a capillary has the disadvantage that it can only be applied to a limited number of samples. The present invention has been made in view of the above-mentioned drawbacks of the prior art, and it is an object of the present invention to provide a wire bonding method that can perform the best bonding in any tail bending direction or loop direction.

Hereinafter, the present invention will be explained with reference to illustrated embodiments.

FIG. 3 is a schematic explanatory diagram of an ultrasonic oscillator used in the method of the present invention, and FIG. 4 is a diagram for explaining an example of a calculation formula used in the method of the present invention. In FIG. 3, 11 is a microcomputer, and 12 is an ultrasonic oscillator that outputs ultrasonic oscillation output to the horn 5 according to instructions from the microcomputer 11. Now, the first bond point A shown in FIG. 2a,
The case of bonding to the second bond point b1 will be explained. As shown in FIG. 4, the center point of the sample 1 is taken as the origin 0, and the bending direction of the tail when bonding to the first pound point a1 with respect to the Y axis is α;. The bending direction α of the tail is automatically calculated by a computer according to the direction in which the capillary is moved to cut the wire, that is, the direction in which the capillary is moved. Alternatively, if the tail is cut vertically, the bending of the tail can be avoided by moving the capillary so that the tail touches the edge of a sample holder, etc. that is holding the sample. This is determined by the direction in which the capillary is moved to create this tail bend. Then, the reference oscillation output value that allows the best bonding to be performed when the tail bending direction is zero, that is, coincides with the Y direction, is the reference oscillation output value that allows the best bonding to be performed when the tail bending direction α is 9σ, that is, coincides with the X direction. Assuming that the oscillation output value is Px and the ratio of the two is A, the following equation holds true.

As mentioned above, since PY and PX are values determined by experimental values, the constant A is naturally determined.

Therefore, the best oscillation output value P at the first bond point a1
a, is as shown in the following equation.

(Substituting (1st) into 2nd and rearranging, becomes.

In this way, Pal is expressed as a function of α; as is clear from the three components.

Therefore, if l of the constant PY, A (or Px) is stored in advance in the computer, all that is left is the tail bending direction α1.
As a result, the best bonding oscillation output calculated by the microcomputer 11 shown in FIG. 3 based on the three components is outputted by the ultrasonic oscillator 12, and the horn 5 vibrates. , the direction in which the capillary 3 moves is determined by the value stored in advance in the microcomputer, so it is determined which point is to be bonded.In this way, the best bonding point is determined at the first bonding point a1. Next, the best bonding oscillation output Pbl at the second bond point b1 is given by β1 in the direction connecting the first bond point a1 and the second bond point b1, that is, the lube direction.
The following equation is exactly the same as that of the third generation.

Here, β1 is determined by the coordinates of a1 and b1, and is a value stored in the microcomputer in advance, so Pbl is calculated by the microcomputer 11 based on the 4 components as described above. , tail bending direction α; and loop direction β; are expressed as θ as a function of angle, then the best oscillation output P at the bond point is given by the following general formula.

Furthermore, the bonding point A2'A3l\B29b3l6 is also given by the above equation.

As is clear from the above explanation, the ultrasonic oscillation output value that indicates the best bonding state when the direction of the wire extending from the capillary is the vibration direction of the horn and the direction perpendicular to this is input into the microcomputer in advance. Then, the microcomputer calculates the ultrasonic oscillation output value for the best bonding at each bond point based on the tail direction and loop direction determined by the microcomputer's instructions, and the horn vibrates based on this calculated value. Since the bonding is carried out using the same method, uniform bonding can be obtained.

[Brief explanation of drawings]

Fig. 1 is a schematic side view of the wire bonding device, Fig. 2 shows the bonding state, a is a plan view, b is a side view,
FIG. 3 is a schematic explanatory diagram of an ultrasonic oscillator used in the method of the present invention, and FIG. 4 is a diagram for explaining an example of a calculation formula used in the method of the present invention. 1: Sample, 3: Capillary, 5: Horn, 7 Rewire,
11: Microcomputer, 12: Ultrasonic oscillator, A
l, a2, a3...: first bond point, B,, b2, b
3...: second bond point, α1, α2, α3...: tail bending direction, β1, β2, β3...: lube direction.

Claims (1)

[Claims] 1. By inputting in advance into the microcomputer the respective ultrasonic oscillation output values that provide the best bonding state in each case where the direction of the wire extending from the lower surface of the capillary tip is the vibration direction of the horn and the direction perpendicular to this, The microcomputer calculates the bonding ultrasonic oscillation output value at each bond point according to the tail bending direction and loop direction predetermined by the microcomputer's instructions, and the horn vibrates according to the calculated value to A wire bonding method characterized by bonding points.