JP2676446B2 - 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 in which a wire is laid between a semiconductor component (IC chip) and a lead for bonding connection.

[0002]

2. Description of the Related Art Conventionally, in order to make a bonding connection between a pad of an IC chip and a lead using a wire bonding apparatus of this kind, a wire is provided by a capillary as a bonding tool provided at the tip of a bonding arm. It is held and brought into contact with the surface of a pad or a lead as an object, and a part of a wire having a ball formed at the tip is crushed by using the capillary to be welded by thermocompression bonding.
At this time, ultrasonic vibration may be simultaneously applied to the tip of the wire.

In this wire bonding apparatus, as shown in FIG. 2, a bonding arm 1 composed of a holding frame 1a and a horn 1b can swing about a shaft center of a support shaft 3 together with a swing arm 2. The bonding arm 1 is firmly fitted to the support shaft 3, and the swing arm 2 is swingably fitted to the support shaft 3. Note that an ultrasonic vibrator (not shown) for exciting the horn 1b is incorporated in the holding frame 1a. A solenoid 4a and an electromagnetic attraction piece 4b are fixed to the swing arm 2 and the holding frame 1a, respectively, in correspondence with each other. When swinging the bonding arm 1, a power source (not shown) for the solenoid 4a is provided. Then, the bonding arm 1 and the swing arm 2 are fixed to each other and coupled by generating an attractive force between this and the electromagnetic attraction piece 4b. A magnet 5a and a coil 5b are attached to the swing arm 2 and the holding frame 1a in front of the electromagnetic attraction means. The magnet 5a and the coil 5b generate an attraction force for urging the tip 1c of the bonding arm 1 at the time of bonding, that is, the portion holding the capillary 36 (shown in FIG. 5) as a bonding tool downward in FIG. Constitutes a means.

As shown in FIG. 3, a support shaft 6a is provided at the rear end side of the swing arm 2, and the arm side cam follower 6 and the swing base 9a are rotatable around the support shaft 6a. Has become. A bearing guide 9b is fixed at one end to the swing base 9a.
A preload arm 9a is rotatably attached to the other end of b via a support pin 9e. A support shaft 7a is provided at a free end of the preload arm 9d, and a cam follower 7 is rotatably attached to the support shaft 7a. And
A preload spring 9f, which is a tension spring, is bridged between the tip of the preload arm 9a and the tip of the swing base 9a, and the arm side cam followers 6 and the cam followers 7 have an outer periphery of a cam 8 formed in a substantially heart shape. It is pressed against the cam surface which is the surface. The two contact points of the arm side cam follower 6 and the cam follower 7 with respect to the cam 8 are located with the center of rotation of the cam 8 in between.

A frame structure is formed by the swing base 9a, the bearing guide 9b, and the preload arm 9d, which is generically referred to as a swing frame 9. A bearing guide 9b as a component of the swing frame 9 is in contact with an outer ring of a radial bearing 11 attached to a cam shaft 12 fitted with a cam 8. The cam 8 is
The motor 13 rotates by the torque applied to the cam shaft 12.

Here, a support mechanism including the above-mentioned support shaft 3 for swingably supporting the bonding arm 1 will be described with reference to FIG.

As shown in FIG. 4, the support mechanism has a support shaft 3 and a radial bearing 21 and a thrust bearing 22 incorporated in a pair of brackets 20 provided on a frame on an XY table (not shown). It is held and swingable. Further, the pressurizing plate 23 applies a pressurizing force F in the direction of the rotation center axis to the support shaft 3 to prevent rattling of the capillaries due to the rotation of the support shaft 3. The pressurizing force F is applied by a spring member or the like (not shown).

Further, as shown in FIG. 4, a shaft 24a of a rotary encoder 24 as a position detecting means and a support shaft 3 are connected to one of the brackets 20 by a connecting means (not shown). This rotary encoder 2
A pulse train corresponding to the rotation angle is output from 4 and counted by the control means such as a microcomputer (not shown) to calculate the movement amount of the tool.

Next, the operation of the wire bonding apparatus having the above structure will be described according to the procedure of the bonding work.

As shown in FIGS. 2 to 6, I which is die-bonded by the paste 32 onto the island 37 of the lead frame 31 placed on the bonding stage 30.
Pad 34a which is the first bonding point of C chip 34
₁ above, the capillary 36 the ball is formed at the tip of the wire 33 is positioned by movement of the XY table on the basis of the information from the support shaft 3 such as an imaging device (not shown) the support mechanism including. Along with this positioning, the bonding arm 1 is swung by the arm driving means including the cam 8 and the motor 13 to lower the capillary 36 and crush the ball to the pad 34a ₁ to perform thermocompression bonding. After this bonding connection, the wire 33 is connected to the lead 31a ₁ which is the second bonding point, and a series of bonding operations are performed. The above bonding work is performed by wire bonding to the pads and leads on all the IC chips 34, and next IC chips 34 and leads 31
The same operation is repeated for a. The IC chip 34 and the like formed by the above steps are sealed with a resin 35 as shown by the chain double-dashed line in FIG. 5 to form a semiconductor component.

[0011]

By the way, as shown in FIGS. 5 and 6, when the IC chip 34 is welded onto the island 37 by the paste 32 in the die bonding process, as shown in FIG. May be inclined and welded. When wire bonding is performed on the lead frame 31 on which the IC chip 34 is arranged by using a conventional device, the capillary 36 descends and the pad 34a ₁ (34a) serving as the first bonding point is formed.
_When it touches ₂ ), a touch sensor (not shown) detects that it touches the pad. And this pad 3
The height position when the capillary comes into contact with 4a ₁ (34a ₂ ) is determined by a rotary encoder (Fig.
(Shown in FIG. 2). Then, after the ball formed at the tip of the wire 33 at the first bonding point is crushed by thermocompression bonding, the capillaries 36 are subjected to self-teaching in which conditions are set using the pad 34a ₁ as the first bonding point as a reference point. In order to achieve a predetermined loop height Hc in a process such as time, the lead 31a ₁ which is the second bonding point is bonded and bonded according to a predetermined wire loop control. Also, when the IC chip 34 is bonded to the pad 34a ₂ located at a high position, the capillary 33 is bonded to this first bonding point and then used as a reference point for the capillary 33 to realize a constant loop height Hc. According to the control, it is bonded and connected to the lead 31a ₂ which will be the next second bonding point.

In recent years, semiconductor parts formed by such wire bonding have a tendency to be made thinner.
As a result, it is required that the absolute height H of the wire from the lead surface formed by the wire loop be low and that the height of each wire be uniform.

However, in the conventional apparatus, even if the IC chip 34 is inclined and welded when it is die-bonded onto the island 37, it is assumed that the apparatus is always in a flat state and the first bonding point is set. Since the wire loop is controlled so as to have a constant height Hc as the reference point, the absolute height H for the sealing molding by the resin 35 which is thinned as shown by the chain double-dashed line in FIG. However, there is a drawback in that the wire 33 protrudes, resulting in defective bonding. Also, in this type of device,
Since each process such as wire bonding is often automated, when the wire 33 is not within the range of the absolute height H, the frame is grasped by a robot arm or the like or resin sealing is performed. Wire 3 during the process
There is a drawback in that it may come into contact with 3.

Therefore, the present invention has been made in view of the above-mentioned drawbacks of the prior art. Even when the surface of the IC chip is not a flat surface, the wire loop height is low and the height is substantially uniform. It is an object of the present invention to provide a wire bonding method capable of achieving thinness and improving bonding accuracy.

[0015]

In a wire bonding method according to the present invention, a bonding arm holding a bonding tool having a wire inserted therein is swingably supported by a supporting mechanism, and the bonding tool is bonded by the swing. In a wire bonding method for contacting and separating an object with each other to perform wire bonding, at least positions of a first bonding point and a second bonding point are respectively detected by a position detecting means for detecting a position of the bonding tool, and from the position, A distance to a predetermined target position is calculated by the control means, and a substantially uniform loop height is formed between the first bonding point and the second bonding point based on the calculated result. It was done. Further, in the wire bonding method according to the present invention, a bonding mechanism holding a bonding tool having a wire inserted therein is swingably supported by a supporting mechanism, and the swinging moves the bonding tool to and from a bonding target. In the wire bonding method in which the wire bonding is performed, a step of setting the absolute height H of the wire loop and storing it in the storage means, and a reference point which is a reference position in advance by the position detection means for detecting the position of the bonding tool are set. The step of obtaining and storing in the storage means and the absolute height H by obtaining the distance from the reference point to a predetermined target position of the semiconductor component
The distance Ha between the target position and the pad of the semiconductor component, which is the first bonding point, is calculated by the control means and stored in the storage means. The loop height of the wire connecting between the first bonding point and the second bonding point forms a substantially uniform loop height based on the difference from the pad of the semiconductor component.

[0016]

Next, an embodiment of a wire bonding apparatus according to the present invention will be described with reference to the drawings. The wire bonding apparatus is configured in substantially the same manner as the conventional apparatus shown in FIGS. 2 to 6 except for the portions described below, and therefore the description of the entire apparatus is omitted.

FIG. 1 shows an IC in the die bonding process.
When the chip 34 is welded onto the island 37 by the paste 32, a wire loop is formed within the height of the resin encapsulation 35 even when the IC chip 34 is inclined and welded. .

First, at the time of self-teaching for setting conditions and the like, an absolute height H from a lead in which a wire loop is formed in a storage means in a control circuit (not shown), and an IC chip 34.
The coordinate position of each pad is set and stored. The absolute height H is arbitrarily set by an external operating means (not shown) based on data such as a predetermined height of the resin 35. Then, the capillary 36 is moved by the movement of the XY table (not shown), and the lead frame 3 shown in FIG.
The leads 31a ₁ and 31a ₂ of _No. 1 are touched (touched) by a tool, and the height is detected by the output of the rotary encoder 24 as the position detection means in FIG. 4 and stored in the storage means. This is the reference point.

Next, the XY table is moved to move the capillary 36 to the center C of the IC chip 34 shown in FIG. 1 and a tool is touched on the center C to store the position (height) thereof. This position is the height from the reference point, and this height is obtained from the output from the rotary encoder 24 in FIG. The difference Ha is calculated from the obtained values of the reference point C and the absolute height H and stored in the storage means.

Next, the capillary 36 is moved up and moved from the reference point C to be the pad 34 which becomes the first bonding point.
The height position of the pad is determined by moving and lowering it to the position a ₁ . From the obtained value, ΔH ₁ which is the difference from the reference point C is obtained. Similarly, ΔH ₂ which is the difference between the other pad 34a ₂ having a different height position and the reference point C is also obtained and stored in the storage means. By such a method, the difference between all the pads and the reference point C is obtained and stored in the storage means.

The wire bonding process after the above conditions are set will be described. First, after wire bonding to the pad 34a ₁ which is the first bonding point shown in FIG. 1, the control means (not shown) is a storage means. The wire loop height is calculated as Ha + ΔH based on the information from
Perform loop control so that it becomes ₁ . A wire loop control method for controlling the wire to be bent at a position where the wire loop height is Ha + ΔH ₁ has already been proposed in, for example, Japanese Patent Application Laid-Open No. 53-26668 and Japanese Patent Publication No. 1-26531. The method can be adopted and will not be described in detail here. The pad 3 is controlled by such loop control.
Lead 3 as the second bonding point corresponding to 4a ₁
Bonding connection to 1a ₁ is made.

On the other hand, for the pad 34a ₂ located higher than the center point C, the wire loop height is Ha-ΔH.
Loop control is performed so that it becomes ₂ . By such a method, the loop height of the wire connected to each pad and each lead can be kept substantially uniform.

Although the islands 37 arranged on the lead frame 31 have the same height in this embodiment, the upper surfaces of the leads may be provided even if the lead frame 31 and the island 37 have different heights. IC as a reference point
Since the center height of the tip 34 is obtained, the loop height can be easily obtained. Further, in this embodiment, the height of the center C of the IC chip 34 is obtained, but for example, the height of the pad 34a ₁ which is the first bonding point is obtained, and the absolute height from the target lead which is the target is obtained based on this. You may make it loop-control so that it may become H. By doing so, it becomes possible to make the loop height uniform without obtaining the height of the center C of the IC chip 34. Further, although the cam type is used as the means for driving the bonding arm, a linear drive type can also be used.

[0024]

As described above, according to the present invention, even if the surface of an IC chip as a semiconductor component is not flat, the height of the wire loop is made low and the height is made substantially uniform to reduce the thickness. And the bonding accuracy can be improved.

[Brief description of the drawings]

FIG. 1 is a diagram showing a state in which a wire loop is performed at a uniform height even when an IC chip is tilted and welded by a wire bonding apparatus according to the present invention.

FIG. 2 is a side view including a partial cross section of a main part of the wire bonding apparatus.

FIG. 3 is a sectional view taken along line AA of FIG. 2;

FIG. 4 is a cross-sectional view taken along the line BB in FIG.

FIG. 5 is an explanatory view showing a state of wire bonding using the wire bonding apparatus shown in FIGS. 2 to 4.

FIG. 6 is a diagram showing a state in which wire bonding is performed by a conventional method.

[Description of sign]

 1 bonding arm 2 swing arm 3 support shaft 6 arm side cam follower 7 cam follower 8 cam 9 swing frame 13 motor 33 wire 34 IC chip 35 resin 37 island

Claims (4)

(57) [Claims] 1. A wire bonding is carried out by swingably supporting a bonding arm holding a bonding tool having a wire inserted therethrough by a supporting mechanism and bringing the bonding tool into and out of contact with an object to be bonded. In the wire bonding method, the position detecting means for detecting the position of the bonding tool detects at least the positions of the first bonding point and the second bonding point respectively, and the control means measures the distance from the position to a predetermined target position. Calculate and obtain,
A wire bonding method characterized in that a substantially uniform loop height is formed between the first bonding point and the second bonding point based on the calculated result. 2. A bonding arm for holding a bonding tool having a wire inserted therein is swingably supported by a supporting mechanism, and the swing causes the bonding tool to come into contact with and separate from an object to be bonded to perform wire bonding. In the wire bonding method, a step of setting an absolute height H of the wire loop and storing it in a storage means, and a reference point serving as a reference position is previously obtained by the position detection means for detecting the position of the bonding tool and stored in the storage means. A step of obtaining a distance from the reference point to a predetermined target position of the semiconductor component, calculating a distance Ha from the absolute height H by the control means, and storing the distance Ha in the storage means; And a step of obtaining a difference between the first bonding point and the pad of the semiconductor component, the distance Ha The wire is characterized in that the loop height of the wire connecting between the first bonding point and the second bonding point forms a substantially uniform loop height based on the difference from the pad of the semiconductor component. Bonding method. 3. The target position of the semiconductor component is the center of the semiconductor component.
The wire bonding method described in. 4. The wire bonding method according to claim 1, wherein the target position of the semiconductor component is a pad of the semiconductor component.