JPS5931036A - Wire bonding stopping circuit - Google Patents

Abstract

PURPOSE:To prevent the bonding pad part of the title device from a mis-striking by a method wherein the gold wire short-circuit condition between the tip of a capillary and a spark electrode, and the condition that the sending out quantity of the gold wire from the tip of the capillary is small are detected, and action of a bonding arm is stopped. CONSTITUTION:The wire bonding stopping circuit is constructed of a discharge current detecting circuit 1, a delay circuit 2, a signal comparing circuit 3, and a prohibiting signal generating circuit 4. The discharge current detecting circuit 1 is the circuit to detect existence of a current to flow to a spark discharge circuit 5, and to convert the current into a pulse signal. The discharge current circuit 5 is constructed of a high voltage DC electric power source 6, a switch 7, a resistor 8, a wire clamping means 9, the gold wire 10, and the spark electrode 11. The gold wire short-circuit condition between the tip of the capillary 13 and the spark electrode 11, and the condition that the sending out quantity of the gold wire 10 from the tip of the capillary 11 is small are detected by the circuit thereof, and action of the bonding arm 14 is stopped.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a wire bonding stop circuit, and more particularly to a wire bonding stop circuit used in an automatic wire bonding apparatus that utilizes a switching discharge.

In the production of semiconductor integrated circuit (IC) components, speeding up the bonding process, which connects the bonding pads of IC chips and the pin terminals of lead frames using metal lead wires, is an extremely important issue due to the mass production of IC components. be.

To solve this problem, automatic wire bonding devices have recently been widely adopted in IC manufacturing lines.

In this bonding process, it is essential to melt the tip of a metal lead wire, such as a gold wire, to form a gold ball with a diameter of 80-110 μm, and for this purpose an electrical spark discharge between the gold wire and the spark electrode is required. Gold metal forming methods are widely practiced.

This gold metal increases the surface area for thermocompression bonding with the IC chip's bonding band and prevents cracks from occurring in the pad due to mechanical impact during wire ending. Acts as a buffer.

The 1-pond cycle of automatic wire ending equipment consists of the following first to third main steps.

(1) Feed out a specified length of gold wire from the tip of the gear pillar. (Gold wire delivery process) (2) After placing the silicone electrode at the tip of the gold wire,
A term used to melt the tip of a gold wire using spark discharge to form a gold ball of a specified diameter. (Gold ball forming step) (3) After placing the capillary on the pad portion of the IC chip, the pad portion and the gold ball portion are bonded by thermocompression.

(Thermocompression bonding process) Conventional automatic wire bonding equipment using spark discharge performs bonding work at a bonding speed of about 02 to 04 seconds/bonding cycle, but the amount of gold wire sent out from the capillary exceeds the set value. The spark electrode was too long and the gold wire was short-circuited, and a gold ball was often not formed at the tip of the gold wire.

Conventional bonding equipment has a function to detect short-circuit conditions between the gold wire and the spark electrode, so the thermocompression bonding process is started before a gold ring of a predetermined diameter is formed at the tip of the gold wire. Since the tip of the pad directly hits the pad part, there is a problem in that IC parts with continuous bonding defects are manufactured while cracking the pad part.

In order to overcome these drawbacks, the present invention provides a wire bonding stop circuit that stops the thermocompression bonding process when the gold wire comes into contact with the slit electrode.

DESCRIPTION OF THE PREFERRED EMBODIMENTS A detailed explanation will be given below according to the embodiments of the present invention shown in FIGS. 1 to 3.

The wire bonding stop circuit according to the embodiment of the present invention includes a discharge current detection circuit 1, a delay circuit 2, a signal comparison circuit 3, and an inhibition signal generation circuit 4. The discharge current detection circuit 1 is a circuit that detects the presence or absence of a current flowing through the spark discharge circuit 5 and converts it into a pulse signal. The discharge current circuit 5 includes a high voltage DC power supply (for example, 550 V) 6, a switch 7, a resistor 8, a wire clamping means 9, a gold wire 10,
It is formed from 1 no.

The gold wire 10 is fed out vertically (biaxially) from the wire reel 12 and guided into the needle hole of the capillary 13. The capillary 13 is integrated with the bonding arm 14 and the drive circuit 1
It is moved in the z-axis direction by the output signal (K) of No. 5. The wire clamping means 9 is connected to the gold wire 1 by the driving circuit 16.
0 and also acts as a switch for the discharge circuit 5.

The spark electrode 11 is rotated about the z-axis by a drive circuit 17 and placed directly below the capillary 13. The gap t1 between the tip of this capillary 13 and the spark electrode 11
can be determined accurately to a set value (for example, about 1.0 to 1.2 mm).

The discharge current detection circuit 1 includes, for example, a photocanola circuit 18 and a waveform shaping circuit 19. The photocazolar circuit 18 includes a light emitting element 20 and a light receiving element 2. The voltage dropped across the resistor 8 causes the light emitting element 20 to emit light, which is incident on the light receiving element 21. The waveform shaping circuit 19 includes, for example, a transistor 22 and an interface (5) 23, and amplifies and shapes the waveform of the signal input from the light receiving element 21.

The delay circuit 2 is formed by monostable multivibrator circuits 24, 25, each having a time constant circuit 26, 27, and which, by the signal output from the inverter 23, generates a pulse signal after a corresponding time Tl during the pulse of this output signal. Output. The time constant circuit 26 has a time constant T2 that is equal to or larger than the width of the output signal output from the inverter 23.

The signal comparison circuit 3 includes an inverter 28 and an AND logic circuit 29
When the inverter 23 outputs a pulse signal having a predetermined pulse, it outputs an i+ pulse signal.

The prohibition signal generation circuit 4 is composed of a JK Frizzo Frozzo 30, a gate circuit 31, a delay circuit 32, and a comparison circuit 3.
? of capillary 13 in response to the output signal of Outputs a prohibition signal to stop the landing operation. The JK Frinoproflozzo 30 receives a timing signal from the timing signal generation circuit 33 through the delay circuit 32, and periodically resets the b output terminal to the ``HII level (6)''.

Next, the operation according to the embodiment of the present invention will be explained with reference to the timing diagram of FIG.

First, a timing signal (
When A) is output, the drive circuit 16 causes the wire clamping means 9 to clamp the gold wire 10.

(FIG. 2(A)) Next, when the timing signal (B) is output from the timing signal generating circuit 33, the spark electrode 11 is placed directly below the capillary 13 by the drive circuit 17. (Figure 2 (B)) Normally, the diameter of the bonding wire is 20 mm.
~30 μm gold wire 10 is used, and the distance t1 between the tip of the capillary 13 and the spark electrode 11 is, for example, 1~2 mm1.
set at the same time. Also, the DC power supply 6 of the discharge circuit 5 is 550V.
For example, the spark gap t3 between the tip of the gold wire 10 and the sliding electrode 11 is set to about 0.15 to 0.2 mm.

The JK flip-flop 30 receives the timing signal (C) of the timing signal generation circuit 33 during the previous bonding cycle.
), the Q output terminal is held at the °°H'' level state. Also, one input terminal of the AND logic circuit 34 is held at the N level until the next timing signal is output.
It is maintained at LI+ level state.

Next, a timing signal (
When E) is output, the switch 7 is closed for, for example, 20 to 30 milliseconds, and the discharge circuit 5 is completed.

This generates spark discharge in the gap t3, melting the tip of the gold wire 10. The molten gold wire becomes the pole 10a at a height of 72 at which the cis-spark discharge is sustained due to surface tension.
(for example, about 0.5 rnm) and then stops.

In this normal spark state, the waveform shaping circuit 19 operates for a predetermined period TI (for example, 25 to 30 milliseconds).
The output signal from the in/output 23 is outputted from the delay circuit 2. (Fig. 2 (F))
The pulse signal (G) is output after a time T2 which is longer than the period Tl and shorter than the control signal (E) of the switch 7. (Fig. 2 (G)) The states of these pulse signals (G) and (F) are compared, and the spark period TI during which the nof width of the output signal (F) of the waveform shaping circuit 19 is normal
If it is within the range, the H11 level signal is output (Fig. 2 (H)) When the HII level signal is input to the JK fritz flop 30, the output signal (I) of the Q output terminal changes to the L level state. The output signal (J) of the gate circuit 34 is "L" and is input to the AND logic circuit 34 (FIG. 2(I)). (Figure 2 (J) (
K)) Therefore, a thermocompression bonding process to the pad portion is performed.

On the other hand, while the switch signal (E) is at H''' level, the timing signal (C) from the timing signal generation circuit 33 is input to the delay circuit 32, and after a predetermined period of time, the output terminal of the JK flip-flop 300 is reset to H' level. be done. (FIGS. 2C and 2D) Next, considering the case where the gold wire 10 comes into contact with the spark electrode 1, a short circuit current flows through the discharge circuit 5 while the switch 7 is on. Therefore, waveform shaping circuit 1
The output signal (F) of 9 outputs a "H" level signal for more than the T1 period. (Figure 2 (F) dotted line waveform) When a signal is input, the delay circuit 2 always outputs a signal after the T2 period (9). Therefore, the comparator circuit 3 outputs the switch signal (E
) is held at the ``L++'' level during the ``H'' level period, and accordingly, the state of the Q output terminal of the JK frizzo flop circuit 30 is also held at the ``H'' level.

Next, the timing signal generation circuit 33 inputs the IIHI+ level signal to one input terminal of the AND logic circuit 34, so the AND logic circuit 34 and the drive circuit 15 input the IIHI+ level signal.
A II level prohibition signal is output. Therefore, the bonding arm 14 stops operating, and the i<? The thermocompression bonding process to the radius part is completely prevented. The drive circuit 15 maintains its state until a release signal (0) is input. AN
After the D logic circuit 34 outputs the prohibition signal, one input terminal becomes the "LIT" level state, and the AND logic circuit 34 again
The output terminal returns to the t+Lu level state.

Next, considering the case where the distance between the tip of the gold flJ10 and the spark electrode 11 is 22 or more, no spark discharge occurs during the ON period of the switch 7, and no discharge current flows through the discharge circuit 5. The output signal (F') of the waveform shaping circuit 19 is held at the "L" level, and the output signal (10) (G) of the delay circuit 2 is also held at the "L" level. Therefore, the output signal (H) of the comparator circuit 3 also becomes the II LI+ level state, which causes the Q signal of the JK Frizzo 30 to change the 6'' level level.Then, one input from the timing signal generation circuit 33 to the AND logic circuit 34. When the timing signal (C) is input to the terminal, the AND logic circuit 34 outputs an inhibit signal of "H11 level" to the drive circuit 15, and stops the operation of the bonding arm 14. After that, a reset signal (D) is outputted from the delay circuit 32, and the Q output terminal of the JK flip flop 30 is held at the '°H' level, waiting for a signal to be input to the clock terminal CK in the next bonding cycle. .

In the embodiment of the present invention, each timing signal is generated using a timing signal generation circuit 33 using a digital circuit, but it is also possible to generate each timing signal by mechanical means having a control disk with a slit and a detector attached to a rotating shaft. It is.

As explained above, the wire winding stop circuit according to the present invention can similarly detect a gold wire short-circuit condition between the capillary tip and the snowdrop electrode and a condition in which the amount of gold wire delivered from the capillary tip is small. Since the operation of the bonding arm is stopped, it is completely prevented that the tip of the capillary directly hits the bonding pad portion of the semiconductor electronic component.

Therefore, the automatic bonding operation is performed without a gold ball being formed at the tip of the gold wire, and the accident of continuously manufacturing defective IC parts is eliminated. The wire bonding stop circuit according to the invention can be used in fully automatic bonding equipment operating at high speeds to enable wire bonding operations with very high manufacturing yields.

[Brief explanation of the drawing]

FIG. 1 is an embodiment of a wire bonding stop circuit according to the present invention. FIG. 2 is an operational timing diagram for an embodiment of the present invention. 1... Discharge current detection circuit, 2... Delay circuit, 3...
- Comparison circuit, 4... prohibition signal generation circuit. Procedural Amendment (Mutsu) Showa Renki January 14th, Director General of the Patent Office, 1, Indication of Case, 1982 Patent Application No. 140962, 2, Title of Invention: Wire Ponting Stop Circuit 3, Person Making Amendment Related Patent Application Personnel Office (105) 1-7-12 Toranomon, Minato-ku, Tokyo Address (105) 1-7-12 Toranomon, Minato-ku, Tokyo
No. 5, “Detailed Description of the Invention” column 191- in the specification subject to amendment

Claims (3)

[Claims] (1) A discharge current detection circuit that outputs a first pulse signal corresponding to the discharge period when a discharge current flows between the spark electrode and the bonding metal wire, and when the first pulse signal is generated. a delay circuit that outputs a second pulse signal after a predetermined period of time has elapsed; a comparison circuit that compares the pulse width of the first pulse signal with the delay time; - A wire bonding stop circuit including a bath prohibition signal generation circuit that outputs a signal to stop the thermocompression bonding process between the grading portion and the bonding metal wire. (2) The wire ending and stopping circuit according to claim 1, wherein the delay circuit comprises a plurality of monostable multivibrators. (3) The wire pounding stop circuit according to claim 1, wherein the delay time is 3 milliseconds or more.