JPH0691133B2 - Ultrasonic wire bonding method - Google Patents

Description

Description: FIELD OF THE INVENTION This invention relates to ultrasonic wire bonding methods.

[Technical background of the invention and its problems]

BACKGROUND ART An ultrasonic wire bonding apparatus that applies ultrasonic waves to a capillary for wire bonding when a bonding wire inserted in a capillary is transferred to a bonding position for bonding is the mainstream of wire bonding apparatuses currently in practical use.

When wire bonding of a semiconductor, an integrated circuit, a hybrid circuit board, etc. is performed by this ultrasonic wire bonding apparatus, there are some defects such as chipping of the IC pellet and insufficient bonding strength.

[Object of the Invention]

The present invention has been made in view of the above points, and relates to an ultrasonic wire bonding method for reducing damage to IC pellets, shortening the bonding time, and performing efficient bonding.

[Outline of Invention]

According to the present invention, when ultrasonic waves are applied to a capillary for guiding a bonding wire to a bonding position for wire bonding, the rising envelope characteristic of the ultrasonic oscillator output current waveform of the ultrasonic wave applied to the capillary is changed. A wire bonding method is obtained.

Example of Invention

Next, an embodiment of the method of the present invention will be described with reference to the drawings. FIG. 1 shows an outline of the ultrasonic wire bonding apparatus. That is, the article to be bonded, for example, the lead frame (1) is conveyed from a magazine (not shown) and stopped at the bonding position (2). A heating device such as a heater block (3) is provided below this position, and the lead frame (1) stopped at the bonding position (2) is heated to a predetermined temperature, for example, 250 ° C. Semiconductor pellets such as IC pellets (4) are previously mounted on the lead frame (1) by a mounter (not shown). On the other hand, a bonding head (6) is placed on the XY table (5), and a bonding arm (7) is provided so as to project from this head (6), and a capillary (8) is provided at the tip of this arm (7). ) Is attached. A spool (10) around which a bonding wire (9) is wound is installed on the bonding head (6), and the bonding wire (9) from the spool (10) is guided through a guide (11) into a capillary (8). Will be guided to. An ITV camera (12) is fixed to the bonding head (6) on the XY table (5) to form a wire bonding device. Although these are wire bonding devices having a well-known configuration, the present invention operates the bonding arm (7) as an ultrasonic horn so that the ultrasonic horn oscillator (13) has a rising envelope characteristic of the ultrasonic oscillator output current waveform. Is made variable. That is, the rising envelope characteristic is set to be appropriately variable according to the state of the surface to be bonded. Therefore, when there are a large number of wire bonding points, the bonding position order is programmed. However, in accordance with this program, the rising envelope characteristics suitable for each bonding position are selected and set in advance, so that optimum conditions can be set for each wire bonding. The best bonding strength can be obtained.

A concrete example of this is shown in FIG. FIG. 2 (A) shows an example of displacement change of the capillary (8) in the Z-axis direction. In FIG. 2 (A), during displacement cd-f, f-g during bonding during displacement shown in FIG. ), The rising envelope (22) of the output current waveform (21) of the ultrasonic oscillator (13) is selected according to the bonding position. An example of the configuration of the ultrasonic oscillator having such a function is as shown in FIG. That is, the output of the ultrasonic oscillator (31) is connected to the multiplier (32) via the output / time adjustment circuit (32). The output of the pulse wave generator (34) is connected to the multiplier (33) through an integrating circuit (35).

The output of the multiplier (33) is connected to the output terminal via the amplifier (36), and a part of the output of the amplifier (36) is fed back to the oscillator (31) via the phase lock circuit (37). Has been done. That is, the output of the ultrasonic oscillator (31) is controlled by the output time adjusting circuit (32) so as to be output as shown in the waveform (41) of FIG.
Supply to 3). On the other hand, the pulse signal is output from the pulse wave generator (34) to the integrating circuit (35). In this circuit (35), the resistance (R) is adjusted to output the waveform (42) shown in FIG. 4 whose rise characteristic is controlled to a desired value to the multiplier (33), and the output to the multiplier (33) The rising envelope (44) of the ultrasonic oscillation output current waveform shown by the waveform (43) in FIG. 4 is controlled by the waveform (42) to obtain the ultrasonic oscillation output signal. A signal obtained by amplifying this signal to a desired value suitable for ultrasonic bonding is obtained at the output. It is fed back to a part of this output signal. The phase of the feedback path is controlled by the phase synchronization circuit (37) and input to the oscillator (31). In this way, a desired rising envelope ultrasonic output is obtained. With this ultrasonic output, the bonding arm (7) is ultrasonically vibrated, and ultrasonic wire bonding is performed at the bonding position by the capillary (8).

〔The invention's effect〕

As described above, according to the method of the present invention, it is possible to prevent the pellets from being broken by ultrasonic wire bonding and to apply the ultrasonic waveform suitable for each wire bonding, so that the bonding strength is good and the rising envelope is selected. This has the effect of enabling high-speed bonding.

[Brief description of drawings]

1 is a perspective view of a bonding apparatus for explaining an embodiment of the method of the present invention, FIG. 2 (A) is a displacement diagram of a capillary in the wire bonding operation of FIG. 1, and FIG. 2 (B).
3A is an ultrasonic output waveform diagram in the bonding period of FIG. 3A, FIG. 3 is a circuit configuration diagram for obtaining the waveform of FIG. 2B, and FIG. 4 is a diagram for explaining the operation of the circuit of FIG. It is a waveform diagram. 21 …… Ultrasonic oscillator output current waveform, 22 …… Rising envelope of ultrasonic output oscillation.

Claims (3)

[Claims] 1. When applying ultrasonic waves to a capillary for guiding a bonding wire to a bonding position for wire bonding, a rising envelope characteristic of an ultrasonic oscillator output current waveform of the ultrasonic wave applied to the capillary is changed. An ultrasonic wire bonding method characterized by the above. 2. The ultrasonic wire bonding method according to claim 1, wherein the control of the rising envelope characteristic of the ultrasonic oscillator output current waveform is selected according to the material of the surface to be bonded. 3. The ultrasonic wire bonding method according to claim 1, wherein the control of the rising envelope characteristic of the ultrasonic oscillator output current waveform is preprogrammed in the same manner as the bonding position program. .