JP2748770B2 - Wire bonding method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wire bonding method for connecting an electrode pad of a semiconductor chip and an inner lead of a lead frame with a metal wire in a manufacturing process of a semiconductor device.

[0002]

2. Description of the Related Art FIGS. 2A to 2D are views showing a lead frame and a semiconductor chip in order of steps for explaining an example of a conventional wire bonding method. Conventionally, in this type of wire bonding method, first, as shown in FIG. 2A, a ball 3 is formed at the tip of a metal wire 2 protruding from a capillary 1 by an electric spark or the like.
The capillary 1 is lowered. Next, as shown in FIG. 2B, the first bonding is performed by pressing the ball 3 against the electrode pad 5 on the semiconductor chip 4. Next, the capillary 1 is raised and moved to a predetermined position of the inner lead 6.

[0003] Then, as shown in FIG. 2 (c), the capillary 1 is lowered again, and the metal wire 2 is pressed against the inner lead 6 to perform the second bonding. next,
As shown in FIG. 2C, the clamper 7 is closed, the metal wire 2 and the capillary 1 are simultaneously raised, and the metal wire 2
Disconnect. Then, as shown in FIG. 2A again, the ball 3 is formed again at the tip of the metal wire 2 to prepare for the first bonding on the next electrode pad 5.

The above operation is repeated to connect the plurality of electrode pads 5 on the semiconductor chip 4 and the plurality of inner leads 6 around the semiconductor chip 4 with the metal wires 2.

[0005]

However, in this conventional bonding method , organic substances often adhere to the plating surfaces of the electrode pads and the inner leads. For this reason, there is a problem that the formation of the alloy on the bonding surface is hindered, the bonding strength is reduced, and the bonding yield is reduced.

Particularly, in a semiconductor device using a multi-layer lead frame corresponding to recent high integration and high density, it is possible to avoid adhesion of a trace amount of an organic substance such as a low molecular component from an adhesive in manufacturing a lead frame. Therefore, this problem has become prominent.

An object of the present invention is to form a good alloy even if the joint surface between an electrode pad and an inner lead is contaminated,
An object of the present invention is to provide a wire bonding method capable of performing connection having a bonding strength.

[0008]

According to one aspect of the present invention, there is provided a wire bonding method for connecting an electrode pad of a semiconductor chip to an inner lead portion of a lead frame on which the semiconductor chip is mounted by using a metal wire. Contacting a bonding tool with a bonding surface at a bonding position of at least one of the electrode pad and the inner lead, and performing an operation of rubbing the tool and the bonding surface with each other; Pressing the wire against the joint surface with the tool. Further, another wire bonding method is characterized in that an ultrasonic signal is superimposed on the above-mentioned aligning operation.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described with reference to the drawings. FIGS. 1A to 1C are views showing a lead frame and a semiconductor chip for explaining an embodiment of a wire bonding method according to the present invention in the order of steps. This wire bonding method is characterized by adding a process operation of cleaning the bonding surfaces of the electrode pads and the inner leads with the metal wires before performing ball forming and connection.

That is, first, as shown in FIG. 1A, the clamper 7 is closed with the wire 2 inserted into the capillary 1. Next, as shown in FIG. 1B, the capillary 1 is lowered onto the electrode pad 5, and the capillary 1 is pressed against the electrode pad with a weight of 10 to 50 g.
In this state, the capillary 1 and the electrode pad 5 are scrubbed several times by an XY stage (not shown) on which a lead frame is mounted.
Foreign matter composed of organic substances and the like attached to the upper surface is removed.

The scrub operation at this time depends on the material of the electrode pad and the thickness of the adhered foreign matter, but it is sufficient that the amplitude is about 5 μm and the number of times is 2 to 5 times. The bottom surface of the capillary 1 is roughened in order to enhance the cleaning effect.

Next, as shown in FIG. 1 (c), the capillary 1 is moved and brought into contact with the plating surface on the inner lead 6 to apply a load. Then, the capillary 1 is scrubbed to remove the adhered foreign matter. In this case, it is desirable that the weight is 50 to 150 g, the scrub amplitude is about 5 μm , and the number of times is 2 to 5 times. Further, a wiper such as a grindstone may be arranged in the middle of the moving path of the capillary 1 so as to wipe off foreign matter that moves to the capillary 1.

Next, as described in the conventional example, the clamper 7 is opened, the metal wire 2 is projected from the capillary 1 to form the ball 3 at the tip, and the first ball is formed in the same manner as in the prior art.
Bonding and second bonding are performed. At this time, since the foreign matter on the electrode pad 5 and the inner lead 6 has been removed , the alloy is easily formed on the bonding surface. next,
Also, as in the conventional method, the clamper 7 is closed, the metal wire 2 and the capillary 1 are simultaneously raised to cut the metal wire 2, and then, as shown in FIG. 2 is stopped at a position where the tip ends stay in the capillary 1 to prepare for removal of foreign matter from the next electrode pad and inner lead.

In this embodiment, foreign matter is removed for each electrode pad and each inner lead. However, immediately before wire bonding, all electrode pads and inner leads may be cleaned for each chip. This method can also be easily realized by repeating FIGS. 1A to 1C using the same mechanism as a normal wire bonding apparatus.

In the embodiment described above, the foreign matter is removed by several scrubbing movements by moving the XY stage. However, in the wire bonding apparatus provided with a capillary for applying ultrasonic vibration, the scrubbing movement is performed. In addition to this, if ultrasonic vibrations are applied to the capillary to remove foreign matter, the cleaning effect can be further improved. In this case, the cleaning effect obtained by the scrubbing exercise in the above-described embodiment can be made substantially the same, and the time required for the scrubbing exercise can be reduced.

[0016]

As described above, according to the present invention, the capillary is brought into contact with the electrode pads and the inner leads to perform a scrub operation to remove foreign matter on the bonding surface, thereby inhibiting the formation of an alloy on the bonding surface. Therefore, there is an effect that bonding strength is secured.

[Brief description of the drawings]

FIG. 1 is a view showing a lead frame and a semiconductor chip in order of process for explaining one embodiment of a wire bonding method of the present invention.

FIG. 2 is a diagram illustrating a lead frame and a semiconductor chip in order of process for describing an example of a conventional wire bonding method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Capillary 2 Metal wire 3 Ball 4 Semiconductor chip 5 Electrode pad 6 Inner lead 7 Clamper

Claims (2)

(57) [Claims] 1. A wire bonding method for connecting an electrode pad of a semiconductor chip to an inner lead portion of a lead frame on which the semiconductor chip is mounted by using a metal wire, wherein a bonding position of at least one of the electrode pad and the inner lead is set. Contacting a bonding tool with the bonding surface, performing an operation of rubbing the tool and the bonding surface with each other, and pressing the metal wire against the bonding surface with the tool after the step. A wire bonding method comprising: 2. The wire bonding method according to claim 1, wherein an ultrasonic signal is superimposed on the aligning operation.