JPH0139211B2 - - Google Patents

Abstract

PURPOSE:To control the height of a loop when a ball is to be formed at wire bonding by a method wherein generation of a spark is repeated periodically applying an AC voltage. CONSTITUTION:A ball is formed to a gold wire applying AC voltage, and when a chip 5 formed on a frame 4 and a lead 6 are connected with a wire 7, the wire 7 is bent to form the loop of height (l). Because height (l) of the loop is enlarged nearly linearly in proportion to the increase of the number of times of the sparks, to keep height (l) of the loop at the desired value, the frequency value to be selected can be decided, and when frequency is decided, how many times the sparks are to be generated, and accordingly to control applying time of the voltage at what value is decided, and the value of height (l) of the loop can be set at the previously set value as occasion demands.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a wire bonder used for semiconductors. When joining a chip formed on a frame and a lead with a gold wire, a voltage is applied to the tip of the gold wire to form a ball at the tip, and this ball is applied to the part to be joined to join. When bonding is complete, a loop is formed between the chip and the leads. If the height of the loop is too high, it will take up wasted space, which is an obstacle to miniaturization, and if it is too low, it may cause a collision accident. When the object to be bonded changes, this height must be changed to an appropriate value depending on the object to be joined.

In view of the above, the present invention provides a method for artificially controlling the height of a loop based on experimental results, and will be described in detail below with reference to the drawings.

Figure 1 is an explanatory diagram of the conventional method of making a ball at the tip of a gold wire.A torch rod 3 is placed at the tip of a gold wire 2 that has passed through a hole provided in a tool 1, with an interval of about 0.2 mm. Then, a DC voltage of about 1000 volts is applied between the tool 1 and the torch rod 3. In this case, a capacitor C was charged with a DC power source E through a charging resistor _R1 , and this was discharged between the gold wire ₂ and the torch rod 3 through a discharging resistor R2, and a ball was created with just one spark.

Figure 2 shows a ball made of gold wire as described above.
A chip 5 formed on a frame 4 and a lead 6 are connected by a wire 7, and the wire 7 is bent at an apex 8 to form a loop having a height l.

Here, the point 8 where the wire 7 is bent corresponds to the vicinity where when the wire 7 is heated to form a ball, recrystallization occurs where it melts, and where the recrystallization progresses and ends.

By the way, the height l of the loop is desired to be an appropriate value, so if the length of recrystallization can be controlled as a means to achieve this, the height l can be adjusted accordingly.
In the present invention, it has been experimentally confirmed that the height l of the loop changes by applying an alternating voltage as a control means when making the ball and periodically repeating sparks. It is.

Figure 3 shows the experimental results of determining the relationship between the number of sparks and the loop height l using a gold wire with a diameter of 30 microns.As the number of sparks increases, the loop height l increases almost linearly. It can be seen that becomes larger.

Based on this experimental result, it is determined how much frequency should be selected in order to make the loop height l the desired value in a certain period of time, and once the frequency is determined, how many times should sparks be generated? , Therefore, it is determined how much the application time should be controlled, and in any case, the time can be easily controlled, so it is possible to set the value of the loop height l to a preset value as necessary, Extremely convenient for wire bonding work.

[Brief explanation of drawings]

Figure 1 is an explanatory diagram of the conventional method of creating a ball at the tip of a gold wire. FIG. 2 is an explanatory diagram of the loop. Figure 3 shows the experimental results. 1... Tool, 2... Gold wire, 3... Torch rod, 4... Frame, 5... Chip, 6... Lead, 7... Wire.

Claims (1)

[Claims] 1. In a wire bonder that performs bonding by forming a ball at the tip of a gold wire, control is applied so that an alternating current voltage of an appropriately determined frequency is applied to the gold wire for a preset predetermined time or number of times. A method for controlling the height of a loop in a wire bonder characterized by forming a ball at the tip.