JP2527531B2 - Wire bonding equipment - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bonding technique, and more particularly to a technique effective when applied to a wire bonding process in assembling a semiconductor device.

[0002]

2. Description of the Related Art In order to achieve electrical connection between a pellet and an external terminal, it is conceivable to perform wire bonding as described below.

That is, a wire made of gold (Au) or the like is inserted into a capillary, the tip of the wire protruding from the tip of the capillary is melted by, for example, an electric torch, and a ball is formed by the surface tension of the melted portion. The ball is pressed against the bonding pad of the pellet that has been heated to a predetermined temperature in advance while applying ultrasonic vibration to perform thermocompression bonding.

Next, while moving the capillary, the wire is pulled out from the tip of the capillary to form a loop, and the loop end is pressed against a bonding post of an external terminal such as a lead frame which is heated to a predetermined temperature in advance. After applying ultrasonic vibration for thermocompression bonding, move the capillary with the wire clamped in the capillary, disconnect the wire from the crimping part, and achieve electrical connection with a pair of bonding pads and bonding posts. It is something.

On the other hand, the bonding pads provided on the pellets tend to be miniaturized and densified as the semiconductor devices become highly integrated and highly densified, and in order to prevent the mutual interference of the bonding parts. The ball diameter is becoming finer.

Further, as the cost of the semiconductor device is lowered, the material of the wire used for bonding is being changed from expensive one such as gold (Au) to inexpensive one such as copper (Cu).

However, in the wire bonding as described above, since the pressing load applied to the capillary at the time of forming the joint is constant, the load acting on the crushing of the ball at the initial stage of the pressing operation and the load at the time of applying ultrasonic waves are different. However, the initial deformation of the ball cannot be adjusted according to the change in the wire material and the ball diameter, and the pressing load is insufficient when ultrasonic waves are applied, resulting in damage to the pellet.

Further, in the initial stage when the ball is pressed against the bonding pad on the pellet, the ball and the bonding pad are in point contact with each other, so that a large pressing force is locally applied to the bonding pad, which is harder than gold (Au). The present inventor has found that there is an inconvenience that the bonding pad is damaged when a wire made of, for example, copper (Cu) is cost-effective.

Documents that describe wire bonding technology in detail include Industrial Research Institute Co., Ltd., 19
Issued November 15, 1982, "Electronic Materials" November 1982 issue, separate volume, P16
There are 3 to P168.

In Japanese Patent Laid-Open No. 57-155739, a bonding tool presses a member to be bonded via a wire with a load larger than the optimum load for wire connection, and when the vibration of the bonding tool is damped, the load is applied. Is disclosed to reduce the wire connection optimum load. In this case, the large load for damping the vibration and the optimum load for wire connection are different from each other, and a constant load is applied to each load.

[0011]

SUMMARY OF THE INVENTION An object of the present invention is to provide a bonding technique capable of highly reliable wire bonding without damaging the bonding position even if the wire material or the ball diameter changes. Especially.

The above and other objects and novel features of the present invention will be apparent from the description of this specification and the accompanying drawings.

[0013]

The outline of the representative one of the inventions disclosed in the present application will be briefly described as follows.

That is, the wire bonding apparatus of the present invention has a bonding arm for performing a bonding operation at a first position and a second position with respect to a wire, and a bonding load pattern generation unit, and the bonding load pattern generation unit. The optimum bonding load pattern is generated according to the wire material and the wire tip ball diameter, and a load corresponding to the load pattern is applied to the bonding arm.

In the wire bonding apparatus of the present invention, the ball at the tip of the wire is pressed to the first position and the loop end of the wire is pressed to the second position, which comprises an initial crushing process and a crimping process. A bonding arm that performs an operation, a voice coil that applies a bonding load of the bonding arm to the first position and the second position, and an initial crushing process and crimping in the bonding operation of at least one of the first position and the second position. And a bonding load pattern generation unit that changes the bonding load in at least one of the processes.

[0016]

In the wire bonding apparatus having the above structure, a plurality of bonding loads are applied to the bonding arm by the bonding load pattern generation unit, and the bonding operation is performed while changing the bonding load. Further, the bonding operation is performed while changing the bonding load in at least one of the initial collapse process and the pressure bonding process in the bonding operation.

Therefore, wire bonding can be performed even if the ball diameter at the tip of the wire is small, and wire bonding can be performed using wires of various materials such as a material having a relatively high hardness.

[0018]

Embodiments of the present invention will be described below in detail with reference to the drawings.

(Embodiment 1) FIG. 1 is a side view showing the configuration of a thermocompression bonding wire bonding apparatus in which ultrasonic bonding according to an embodiment of the present invention is added.

On the XY table 10, a bonding head 20 which is movable in a plane perpendicular to the paper surface of FIG. 1 is positioned, and a bonding arm 30 is centered on a fulcrum 31 in the paper surface of the bonding head 20. It is rotatably held.

The bonding head 20 shown in the figure
Is only a part particularly relevant to the present invention. The actual bonding head 20 includes a vertically moving mechanism of a bonding arm, a drive mechanism of a wire clamper, an electric discharge machining mechanism for making the tip of the bonding wire spherical.

A horn 40 is provided at one end of the bonding arm 30, and ultrasonic vibration generated by an oscillator 41 driven by an ultrasonic oscillating source 42 is transmitted to a capillary 50 fixed to the tip of the horn 40. It The capillary 50 performs thermocompression bonding wire bonding, and the ultrasonic bonding is further applied by the wire bonding apparatus of this embodiment.

A wire 61 supplied from a spool 60 is inserted into the capillary 50, and the wire 61 is fixed in a timely manner by a clamp 62 provided between the spool 60 and the capillary 50.

A frame feeder 70 is located below the capillary 50, and FIG. 2A is a plan view of the frame feeder 70 as seen from the direction of line II-II.

On the frame feeder 70, a plurality of pellets 90 fixed on a lead frame 80 which is successively moved by the frame feeder 70 in a direction perpendicular to the paper surface.
And the lead frame 80, the plurality of bonding pads 91 (first position) provided on the pellet 90, and the bonding posts 8 on the lead frame 80.
1 (the second position) is bonded by the wire 61 inserted through the capillary 50. The bonding pad 91 and the bonding post 81 are members to be bonded.

A load spring 32 is provided at the other end of the bonding arm 30, and the rotational force applied to the bonding arm 30 is adjusted by the screw 33.

Further, the fulcrum 3 of the bonding arm 30
1 and the load spring 32 are fixed to a core 101 which is moved vertically by a voice coil 100 and generates a turning force in the bonding arm 30. The core 101 generates a turning force in the same direction as or opposite to the load spring 32. By
The bonding load of the wire 61 to the bonding pad 91 of the wire 61 by the capillary 50 or the bonding post 81 in the lead frame is adjusted in the bonding operation.

The voice coil 100 is connected to the voice coil driving unit 102 controlled by the bonding load pattern generation unit 103, and has a structure in which bonding loads based on various bonding load patterns are applied to the capillary 50 during bonding.

The XY table 10, the ultrasonic oscillating source 42 and the bonding load pattern generator 103 are connected to the main body controller 110 so as to control the entire apparatus.

Next, the operation of this embodiment will be described.

First, the tip portion of the wire 61 inserted into the capillary 50 is melted by an electric torch (not shown) and surface tension causes a ball 61a to be formed on the tip portion of the wire 61 as shown in FIG. 2 (b). It is formed.

Next, the XY table 10 is appropriately driven so that the tip of the capillary 50 is the target bonding pad 91.
Positioned just above.

Next, the voice coil 100 and the core 10
1, the rotational force against the rotational force of the load spring 32 is reduced, the bonding arm 30 is rotated counterclockwise in FIG. 1, the capillary 50 is lowered onto the bonding pad 91, and the wire 61 is moved. The ball 61a formed at the tip portion is pressed against the bonding pad 91 and thermocompression bonded, and at the same time, ultrasonic vibration is transmitted to the capillary 50 via the horn 40, and wire bonding by ultrasonic vibration is added. In this way, the voice coil 100 changes the pattern of the bonding load in cooperation with the load spring 32.

FIGS. 3 (b) and 4 (a), (b) are graphs showing some examples of the bonding load pattern and ultrasonic vibration application timing at this time, and the vertical axis represents The bonding load and the strength of ultrasonic vibration are taken, and the horizontal axis shows time.

Further, FIG. 3A shows a bonding load pattern by a possible wire bonding apparatus. In this case, after the bonding load sharply decreases due to the initial collapse of the balls 61a, the bonding load remains almost constant regardless of whether or not ultrasonic vibration is applied. 4 (a),
It is shown that in the wire bonding apparatus of the present embodiment shown by (b), the bonding load can be adjusted independently of the initial crushing of the ball 61a, that is, the initial crushing process and the ultrasonic vibration application, that is, the crimping process. .

As a result, for example, when the diameter of the ball 61a is small, as shown in the graph of FIG. 4 (a), the bonding load that acts when the ball 61a is initially crushed is set to be relatively small, and Prevents excessive plastic deformation, increases the bonding load when ultrasonic vibration is applied, and causes the ultrasonic vibration to act efficiently on the bonding part, resulting in damage to the bonding pad due to insufficient bonding load and bonding strength The drop is prevented.

Further, for example, the wire 61 is made of copper (Cu).
If it is composed of a relatively hard material such as
As shown in the graph of (b), in order to sufficiently perform the initial plastic deformation of the ball 61a, the bonding load is set to be relatively large, and the bonding load is gradually reduced when the ultrasonic vibration is applied. It is possible to prevent an excessive force from being applied to 91 and enable wire bonding using a wire 61 made of a relatively hard material such as copper.

As described above, after the bonding is performed on the bonding pad 91, the capillary 50 is raised and the XY table 10 is appropriately driven to pull out the wire 61 to form a loop, and the capillary 50 is connected to the lead frame 80. Upper bonding post 81
Moved directly above.

Next, the capillary 50 is lowered, the side surface of the wire 61 is pressed against the bonding post 81 by the tip of the capillary 50, and ultrasonic vibration is applied to the capillary 50 via the horn 40, so that the loop end is reached. Are crimped onto the bonding post 81.

Next, the capillary 50 is raised while the wire 61 is fixed to the side of the capillary 50 by the clamp 62, and the wire 61 is torn off near the crimping portion, that is, near the loop end, and the wire between the pair of bonding posts 81. Bonding is achieved.

By repeating the above-described series of bonding operations, the wire bonding between the plurality of bonding pads 91 and the bonding posts 81 is performed by the balls 6.
It is performed with high reliability without being affected by the diameter of 1a and the material of the wire 61.

As shown in FIGS. 3 and 4, the ball and the loop end first undergo the initial crushing process, and then the crimping process with ultrasonic vibration applied to complete the bonding operation.

(Embodiment 2) Further, FIG. 2C shows a wire bonding method which is another embodiment of the present invention, in which the tip end of the wire 61 is formed as shown in FIG. 2B. Before bonding the ball 61a to the bonding pad 91 on the pellet 90, the lead frame 80
The first embodiment is that the lower part of the ball 61a is flattened by being pressed to the preliminary striking position 82 (third position) where the shock absorbing layer 83 is provided in the vicinity of the bonding post 81 of FIG.
Others are the same as the first embodiment.

That is, by flattening the lower portion of the ball 61a prior to bonding to the bonding pad 91, when the wire 61 is made of a material having a relatively high hardness, such as copper (Cu), ,
The bonding pad 91 and the ball 61a having high hardness are prevented from making point contact, and
Is prevented from being damaged by the balls 61a.

In this case, the shock absorbing layer 83 is made of, for example, a layer made of aluminum, adheres to the ball 61a when the ball 61a is pressed to the preliminary striking position 82, and acts as the shock absorbing layer even at the bonding portion of the bonding pad 91. Fulfill.

Although the invention made by the present inventor has been specifically described based on the embodiments, the invention is not limited to the embodiments and various modifications can be made without departing from the scope of the invention. Needless to say.

For example, the third position can be the electric torch surface. Of course, it is also effective when used as a thermocompression bonding wire bonding that does not use ultrasonic waves.

[0048]

Advantageous effects obtained by typical ones of the inventions disclosed in the present application will be briefly described.
It is as follows.

(1). Since it becomes possible to realize a bonding load application pattern that is optimum for the ball diameter and wire material, highly reliable wire bonding can be performed without damaging the bonding portion.

(2) As a result of the above (1), wire bonding with a smaller diameter ball formed on the tip of the wire is possible, and wire bonding can be performed on a fine bonding portion.

(3) As a result of the above (1) and (2), wire bonding using a wire made of a cheaper material is possible, and the cost of the semiconductor device can be reduced.

(4). As a result of the above (3), miniaturization and high integration of the semiconductor device can be realized.

[Brief description of drawings]

FIG. 1 is a side view of a wire bonding apparatus that is an embodiment of the present invention.

2A is a plan view of a portion indicated by a line II-II in FIG. 1, FIG. 2B is an enlarged view of a tip portion of a capillary, and FIG. It is a figure which shows the Example of.

FIG. 3A is a diagram showing a possible bonding load pattern of a wire bonding apparatus, and FIG. 3B is a diagram showing a bonding load pattern of a wire bonding apparatus according to an embodiment of the present invention.

4A and 4B are diagrams showing a bonding load pattern of a wire bonding apparatus according to an embodiment of the present invention.

[Explanation of symbols]

 10 XY table 20 Bonding head 30 Bonding arm 40 Horn 50 Capillary 70 Frame feeder 80 Lead frame 81 Bonding post (2nd position) 82 Preliminary striking position (3rd position) 83 Shock absorbing layer 90 Pellet 91 Bonding pad (1st position) Position) 100 voice coil 101 core 102 voice coil drive unit 103 bonding load pattern generation unit 110 main body control unit

Claims (6)

(57) [Claims] 1. A wire bonding apparatus for electrically connecting a first position and a second position of a member to be bonded by a wire made of a conductor, the wire bonding device comprising: A bonding arm for performing a bonding operation to the second position, and bonding
A load pattern generator, and the bonding load pattern
Wire material and wire tip ball diameter
Generate an optimal bonding load pattern according to
The load corresponding to the load pattern is applied to the bonding arm.
A wire bonding device characterized by applying to a wire. 2. A wire bonding apparatus for electrically connecting a first position and a second position of a member to be bonded with a wire made of a conductor, the device having a capillary for guiding the wire, A bonding arm for pressing a ball at the tip of the wire to the first position and a loop end of the wire to the second position to perform a bonding operation including an initial crushing process and a crimping process; And a voice coil for applying a bonding load of the bonding arm to the second position, and an initial crushing process in a bonding operation of controlling at least one of the first position and the second position by controlling the voice coil. And a bonding load pattern for changing the bonding load in at least one of the crimping process A wire bonding apparatus comprising: a wire generation unit. 3. A bonding spring for applying a constant bonding load to the bonding arm, wherein the bonding load pattern generation unit changes the bonding load on the member to be bonded in cooperation with the load spring. The wire bonding apparatus according to claim 2, wherein 4. The bonding load pattern generation unit is configured to change the bonding load in the initial collapse process in the bonding operation at each of the first position and the second position. 2. The wire bonding device according to 2 or 3. 5. The bonding load pattern generation unit is configured to change the bonding load in the crimping process in the bonding operation at each of the first position and the second position.
Alternatively, the wire bonding apparatus described in 3. 6. The bonding load pattern generation unit is configured to change a bonding load in each of the initial crushing process and the crimping process in each bonding operation at the first position and the second position. The wire bonding device according to claim 2 or 3, characterized in that: