JPH0917821A - Capillary for bonding - Google Patents

Abstract

(57) [Summary] [Object] To provide a bonding capillary having a simple structure, which can improve the number of continuous bondings until an abnormality occurs in the wireless bonding method and the wire bonding method. [Structure] By forming a groove 11 on the outer surface of the capillary 1 and making the outer surface uneven, the surface area is larger than the reference surface area when the outer surface is a smooth surface having no unevenness unlike conventional capillaries. It is possible to increase the size and shorten the coarsening region of the crystal structure of the wire immediately above the ball in the bonding operation.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bonding capillary having excellent heat dissipation characteristics, which is used when connecting an IC chip and a substrate or an IC chip and an external lead.

[0002]

2. Description of the Related Art Conventionally, in mounting a semiconductor device, a bonding method for connecting an IC chip and a substrate or an IC chip and an external lead by using a wire made of a metal such as Au, Ag, Pb-Sn, Al or Cu. Is used. As this method, a wireless bonding method using a bump formed of a wire as a connecting material and a wire bonding method using a wire are known.

First, a wireless bonding method using bumps will be described with reference to FIG. First, as shown in FIG. 3A, the tip of the wire 2 which is conducted to the wire conducting path 1a of the capillary 1 and led out from the tip lead-out port 1b is heated and melted by using the torch 3 to form the ball 4. Next, as shown in FIG. 2B, the capillary 1 is lowered and the ball 4 is pressure-bonded to the tip surface 1c of the capillary 1. As a result, the ball 4 is pressure-bonded onto the Al electrode 6 formed on the IC chip 5. Further, as shown in (c), the wire 2 is torn off above the pressure-bonded ball 4 by pulling up the capillary 1 and the wire 2, and the bump 8 is formed with the wire neck portion 7 left. Then, as shown in (d), the flux is applied to the bumps 8 and the IC chip 5 and the substrate 9 are subjected to the reflow process.
Are connected to the respective electrodes 6 and 10 via bumps 8.

Next, although a wire bonding method using a wire is not shown, the ball 4 is pressure-bonded as shown in FIGS. 3 (a) and 3 (b) in the same manner as the wireless bonding method described above. In the step shown in the figure, only the capillary 1 is moved to guide the wire 2 in a loop shape to an external lead (not shown), and the wire 2 is crimped and then cut. This is a bonding method in which the IC chip 5 and the external lead (not shown) are connected via the loop wire.

In any of the bonding methods
In addition, the capillary 1 holds the molten metal balls 4
Continuously perform the crimping operation on the tip surface 1c of the capillary 1.
Therefore, the temperature of the capillary 1 rises. Because of this
The capillary 1 is usually ceramic in consideration of heat resistance strength.
Made of aluminum, and in consideration of heat dissipation, Al _Two
O_ThreeIs often used. However, the capillary material
When these ceramics are used for quality, the bond
The temperature of the capillary 1 rises as you perform the
In line with this, the wire bonding method
-2 is pulled and the ball 4 is cut to form the bump 8.
At the time, the neck part which is the rest of the wire part just above the ball 4
7, the so-called wire neck length begins to increase,
There is a problem that continuous operation cannot be performed. See you again
The wire bonding method weakens the waist strength of the wire,
If the wire stretched in a loop shape is sagging or bending,
Have the problem of coming.

On the other hand, as a means for preventing the temperature rise of the capillaries, the applicant of the present invention proposed in JP-A-6-196522 to provide the capillaries with water cooling or air cooling means. These means are structures intended to be provided with cooling means such as a pipe structure using water or air as a refrigerant. However, in the structure provided with these refrigerant pipes and the like, although there is a cooling effect of the capillaries, there is a problem that the structure becomes complicated and expensive, and the capillaries that operate at high speed are prone to failure. There is.

[0007]

The present invention has been made in view of such conventional circumstances, and its object is to compare the structure of the capillary with a structure in which a refrigerant pipe or the like is attached to the capillary. Although it has a simple structure, it can improve the number of continuous bonding until the wire neck length starts to vary in the wireless bonding method, and in the wire bonding method, the wire stretched in a loop shape is sagged or bent. It is to provide a capillary for bonding which can improve the number of continuous bondings before starting.

[0008]

DISCLOSURE OF THE INVENTION In order to achieve the above-mentioned object of the present invention, the present inventors have found that it is effective to shorten the coarse region of the crystal structure of the wire immediately above the ball. Based on the above, the present invention has been accomplished as a result of intensive studies.
That is, as disclosed in Japanese Patent Application Laid-Open No. 6-196522, in the method of producing a ball in a substantially hemispherical concave portion formed on the inner surface of the outlet of the capillary, the amount of heat transferred to the capillary is large, It is effective to attach a cooling means such as a pipe structure using the refrigerant as a refrigerant. However, in a normal ball forming method of forming a ball outside the capillary (the tip surface), the structure adopted by the present invention makes the ball The inventors have found that it is possible to shorten the coarsened region of the crystal structure of the wire immediately above and thereby achieve the above-mentioned problems, and have reached the present invention.

That is, the first invention of the present application (claim 1) is an IC chip bonding capillary characterized in that the surface area of the outer surface of the capillary is increased by making the outer surface of the capillary uneven. Further, in the first invention, the surface area of the outer surface of the capillary is 1.5 to 10
It is more preferable to double the size (claim 2). Furthermore, in the first invention, it is more preferable that the irregular shape of the outer surface of the capillary is a groove shape (claim 3).

A second invention of the present application (claim 4) is characterized in that the outer surface of the capillary is coated with a metal.
A capillary for chip bonding.

[0011]

Although ceramics is used as the material of the capillary used in the present invention, it is preferable that the material has excellent thermal conductivity. Therefore, Al ₂ O ₃ is preferably used. The first invention of the present application is to increase the surface area of the outer surface of the capillary by making the outer surface of the capillary uneven, and preferably to increase it by 1.5 to 10 times. Here, the surface area of the outer surface is a surface area based on the outer surface of the capillary made of ceramic as a smooth surface. In other words, increasing the surface area of the outer surface is based on the surface area when the outer surface of the capillary made of ceramics is a smooth surface having no uneven shape on the outer surface like a conventional capillary,
It means making it larger than the reference surface area.

By making the surface area of the capillary having such a structure, in the wireless bonding method, it is possible to increase the number of continuous bondings until the variation in the wire neck length starts to occur, and in the wire bonding method, the number of continuous bonding is increased. It is possible to improve the number of times of continuous bonding until the set wire starts to sag or bend, and it is possible to achieve the above-described object of the present application. Further, it is not clear why the number of continuous bondings can be increased by adopting the above-mentioned configuration, but in each bonding cycle, the heat once absorbed by the capillaries in the time from the end of the pressure bonding of the ball to the start of the next pressure bonding. Since it is possible to shorten the area of coarsening of the crystal structure of the wire immediately above the ball, the advantageous effect for the problem of the present application was obtained. it is conceivable that.

Here, when the surface area of the outer surface is 1.5 times or more, there is an effect that the number of continuous bondings, which is the subject of the present application, is significantly improved. Further, when the surface area of the outer surface is 10 times or less, there is no problem that the strength of the capillary is lowered due to the deepening of the uneven shape or the number of grooves, so that the surface area of the outer surface of the capillary is 1.5 to 10 It is preferable to double the size. Furthermore, achieving the subject of the present application,
In addition, the surface area of the outer surface is preferably 2.0 to 10 times in order to prevent the strength of the capillary from decreasing.

As a method of forming the uneven shape, a curved surface which is the outer surface of a normal capillary and does not have the uneven shape is used as a reference surface, and a groove is engraved in the reference surface, or a heat dissipation portion is attached to the reference surface. There is a way. In the present invention, the surface area of the outer surface is calculated based on the area of the reference surface. As a method of engraving the grooves, as shown in FIG. 1, grooves 11 and 11 parallel to each other are formed on the outer surface of the capillary 1.
It is possible to exemplify forming a large number of ... And forming a groove 12 in a spiral shape on the outer surface of the capillary 1 as shown in FIG. By forming such a groove, it is possible to easily adjust the increased surface area of the outer surface of the capillary 1 from the depth and length of the groove, and it is possible to evenly dissipate the heat radiation portion to the surroundings.

The second invention of the present application is to coat the outer surface of the capillary with a metal component. The metal component to be coated may be any of Cu, Al, Ni, etc., but it is preferable to use a metal having a higher melting point than the metal wire. As a coating method, electroless plating, vapor deposition, sputtering or the like can be used, but it is practically preferable to use electroless plating. It is not clear why the number of continuous bondings can be increased by adopting the above-mentioned configuration, but as in the first invention described above, in each bonding cycle, the time from the end of pressure bonding of the ball to the start of the next pressure bonding is reduced. The heat once absorbed in the capillaries can be mainly released, which makes it possible to shorten the coarse area of the crystal structure of the wire immediately above the ball, which is advantageous for the problems of the present application. It is considered that such an effect was obtained.

[0016]

The present invention will now be described by way of examples, which should not be construed as limiting the invention. (Example 1) As shown in FIG. 1, an Al ₂ O ₃ capillary is formed with an appropriate number of grooves parallel to the circumferential direction perpendicular to the axis of the capillary, and the depth and number of each groove are adjusted. Then, the outer surface of the capillary was adjusted to be 1.3 times as large as the surface area (reference surface area) in the case of a smooth surface having no uneven shape. The following wireless bonding test and wire bonding test were performed using the capillary thus configured and a 10 wt ppm Y-containing gold alloy wire having a diameter of 30 μm.

(Wireless Bonding Test) FIG. 3
Metal balls were formed as in (a) to (c). At this time, bumps were continuously formed on the IC chip by pressure bonding with a capillary of this example for 30 milliseconds under a load of 60 g while applying an ultrasonic wave output of 0.47 W. FIG.
Repeating each cycle of (c), the state in which the wire neck length is the same as the ball diameter due to the temperature rise of the capillary is regarded as an abnormal neck, and the number of continuous bondings until the abnormal neck occurs Was measured. Table 1 shows the measurement results.

(Wire bonding test) FIG. 3 (a)-
Up to (b), the ball was crimped in the same manner as in the wireless bonding test method, and in the step shown in (c), only the capillary of this example was moved to guide the wire in a loop shape to the external lead and crimped. Disconnected. In this way, the IC chip and the external leads were continuously bonded with wires. Repeat each cycle, lean on the loop stretched as the temperature of the capillary rises,
The number of times of continuous bonding until the occurrence of bending and the occurrence of short circuit abnormality was measured. Table 1 shows the measurement results.

(Examples 2 to 11) A wireless bonding test and wire bonding were carried out in the same manner as in Example 1 except that the irregularities on the capillary surface and the surface area ratio of the outer surface to the reference surface area were set as shown in Table 1. The test was conducted. Table 1 shows the measurement results.

(Examples 12 to 16) 5 wt% Sn-95 wt% Pb having a diameter of 40 μm was used as the type of wire, the surface area ratio of the capillary was as shown in Table 1, and the wireless bonding test and wire bonding were performed. In the test, the test was performed in the same manner as in Example 1 except that the bonding conditions were such that an ultrasonic output of 0.58 W was applied and a load of 28 g was applied for 15 milliseconds for each of the capillaries of Examples. Table 1 shows the measurement results.

(Example 17) An Al ₂ O ₃ capillary was coated with Ni by electroless plating. For Ni electroless plating, adjust the pH of the Ni bath to pH 4 to 5, and set the temperature to 90 to 100 ° C.
It was carried out by heating to 100 ° C. and using hypophosphite as a reducing agent.
A capillary with this structure and a 1 μm diameter 30 μm
Example 1 using 0 wt ppm Y-containing gold alloy wire
The same tests as the wireless bonding test and the wire bonding test adopted in 1. were performed. The measurement results are shown in Table 2.
Shown in

(Embodiment 18) A capillary is used in Embodiment 17.
The same type of wire and the bonding conditions in the wireless bonding test and the wire bonding test as in Example 12 were used. Table 2 shows the measurement results.

(Comparative Example 1) Example 1 except that the outer surface of the Al ₂ O ₃ capillary was not formed to have an uneven shape.
A wireless bonding test and a wire bonding test were performed in the same manner as in. The measurement results are shown in Table 3.

(Comparative Example 2) A wireless bonding test and a wire bonding test were conducted in the same manner as in Example 1 except that the type of wire, the shape of the outer surface of the capillary and the surface area ratio were as shown in Table 3. The measurement results are shown in Table 3.

[0025]

[Table 1]

[0026]

[Table 2]

[0027]

[Table 3]

From the above measurement results, a comparative example in which the outer surface of the capillary is not made uneven and the surface area is the reference surface area (that is, the surface area magnification is 1.0 times) and the outer surface of the capillary is not coated with metal is as follows: Wire is 5S
In the case of n-95Pb solder, the number of continuous bondings is about 3 × 10 ⁴ times until an abnormal neck occurs in wireless bonding and a short circuit abnormality occurs in wire bonding. It can be seen that in the case of the contained gold alloy, the number of times of continuous bonding is about 3 × 10 ⁵ times.

On the other hand, in the embodiment of the first invention of the present application in which the outer surface of the capillary is made uneven to increase its surface area, the wire is made of Sn-Pb solder or Y-containing gold alloy, respectively, and is wireless. It can be seen that the number of continuous bondings until the abnormal neck occurs in the bonding and the short circuit abnormality occurs in the wire bonding is almost doubled as compared with the comparative example. In addition, among them, in the examples in which the surface area is increased by 1.5 to 10 times, the number of times of continuous bonding is increased, and in the embodiment in which the surface area is increased by 2.0 to 10 times, the number of times of continuous bonding is increased. It can be seen that it will increase further.

In addition, in the embodiment of the second invention of the present invention in which the outer surface of the capillary is coated with a metal, the number of times of continuous bonding in each of the cases where the wire is Sn-Pb solder and the Y-containing gold alloy is It can be seen that the number increases three times or more as compared with the comparative example.

[0031]

As described above, the bonding capillary according to the present invention has a novel structure in which the outer surface is made to have an uneven surface to increase the surface area in the first invention and the second surface is coated with a metal. Therefore, in the bonding work, it is possible to shorten the coarse area of the crystal structure of the wire immediately above the ball, and in the wireless bonding method, it is possible to improve the number of continuous bondings until the wire neck length starts to vary.
In the wire bonding method, it is possible to improve the number of times of continuous bonding until the wire stretched in a loop shape starts to sag or bend. Therefore, it can be implemented at low cost without adopting a complicated structure such as a cooling means for the capillaries, and does not affect the high-speed operation of the capillaries at all, so that a highly reliable semiconductor device can be manufactured at low cost. It has been possible to provide a capillary for IC chip bonding which is extremely useful for the purpose.

[Brief description of the drawings]

FIG. 1 is an enlarged front view of essential parts showing an embodiment of a bonding capillary according to the present invention.

FIG. 2 is an enlarged sectional view of an essential part showing another embodiment of the bonding capillary according to the present invention.

FIG. 3 is a simplified diagram showing an outline of a wireless bonding method using bumps.

[Explanation of symbols]

 1: Capillary 11, 12: Groove 2: Wire 4: Ball 5: IC chip 7: Wire neck part 8: Bump

Front Page Continuation (72) Inventor Shin Takaura 8-5-1 Shimorenjaku, Mitaka City, Tokyo Tanaka Denshi Kogyo Co., Ltd. Mitaka Factory (72) Inventor Hideyuki Akimoto 8-5-1 Shimorenjaku, Mitaka City, Tokyo Tanaka Denshi Industrial Co., Ltd. Mitaka factory

Claims (4)

[Claims] 1. A capillary for IC chip bonding, wherein the surface of the outer surface of the bonding capillary is increased by making the outer surface of the capillary irregular. 2. The capillary for IC chip bonding according to claim 1, wherein the surface area of the outer surface is increased by 1.5 to 10 times. 3. The capillary for an IC chip bondig according to claim 1, wherein the uneven shape is a groove shape. 4. A capillary for bonding, wherein the outer surface of the capillary is coated with a metal, and the capillary for bonding an IC chip.