JPH0562043U - Capillary for wire bonding - Google Patents

Abstract

(57) [Abstract] [Purpose] In a capillary for wire bonding, to improve the bondability even if the pressure bonding ball diameter is small. [Arrangement] In the lower part, a radius (R) is attached to the lower end of the through hole, and an angle θ formed by a straight line connecting the upper end and the lower end of the through hole and an extension line of the inner peripheral surface of the through hole is 30 ± 5 °, The lower end surface is flat and has a vertical cross-sectional shape that is inclined so as to become higher toward the outside.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a wire bonding capillary, and more particularly to a wire bonding capillary provided with a through hole.

[0002]

[Prior Art]

 In the manufacture of semiconductor devices, a thin conductive wire, that is, a wire made of gold or aluminum is used to connect the electrode of the semiconductor element and the electrode of the lead of the package. The shape was performed using a capillary as shown in FIGS. 14 (A) to 14 (C).

The capillary of FIG. 14 (A) has a vertical cross-sectional shape in which the lower end of the through hole is composed of two straight lines, and the lower end of the through hole of the capillary of FIG. R) has a curved portion, and the lower end surface has a vertical cross-sectional shape perpendicular to the center axis. The capillary of FIG. 14C has a rounded lower end of the through hole. It has a vertical cross-sectional shape in which a curved portion and a straight portion are connected.

[0004]

[Problems to be solved by the device]

 By the way, according to the conventional capillary for wire bonding, the bondability is not necessarily good when the diameter of the pressure bonding ball is as small as 70 to 80 μm. This point will be described in detail below. 2 (A) to (D) more specifically show other examples of conventional capillaries, and FIG. 3 shows the pressure bonding ball diameters of these capillaries (A), (B), (C), (D). And the slip amount integral value are shown. As will be described later, the larger the integrated value of the slip amount, the better the bondability, and the wire bonding capillaries (A), (B) and (D) shown in FIGS. 2 (A), (B) and (C) are Since the integrated value of the slip amount is not so large, the bondability is not good. However, it can be said that the wire bonding capillary (C) shown in FIG. 2 (C) has a relatively large integrated value of the amount of slip and therefore has good bondability.

That is, it can be said that the capillary having the lower end portion of the capillary formed by a straight line forming an angle θ of 30 ° with the extension war of the inner peripheral surface of the through hole in the lower longitudinal cross-section has a relatively good joint property. However, even with the wire-bonding capillary (C), the value of the integrated value of the amount of slip could not be sufficiently increased when the pressure bonding ball diameter was small. Therefore, there is a problem that it is difficult to cope with the reduction of the pressure bonding ball diameter due to the increase in the number of pins of the semiconductor element.

The present invention has been made to solve such a problem, and an object of the present invention is to provide a capillary for wire bonding, which can obtain good bondability even if the diameter of the pressure bonding ball is small.

[0007]

[Means for Solving the Problems]

 In the wire bonding capillary of the present invention, the lower part is provided with a radius (R) at the lower end of the through hole, and the angle θ formed by the straight line connecting the upper and lower ends of the through hole and the extension line of the through hole inner peripheral surface is It is characterized in that the lower end surface is flat at 30 ± 5 ° and has a vertical cross-sectional shape that is inclined so as to become higher toward the outside.

[0008]

[Action]

 According to the wire bonding capillary of the present invention, as is clear from the pressure-bonded ball diameter / slip amount integrated value relationship diagram shown in FIG. 3, when the wire pressure-bonded ball diameter is as small as 67 to 85 μm, the conventional The type of capillaries (A) to (D) has a larger integrated value of the amount of slip, and the bondability is better. Therefore, it becomes easy to cope with the reduction of the diameter of the pressure bonding ball.

[0009]

【Example】

 Hereinafter, the wire bonding capillary of the present invention will be described in detail with reference to the illustrated embodiment. 1 (A) and 1 (B) show one embodiment of the wire bonding capillary of the present invention, in which (A) is a partially cutaway front view and (B) is an enlarged vertical sectional view showing a lower end portion. is there. In the drawing, reference numeral 1 denotes a capillary having a diameter of, for example, 1.588 mm and a lower portion formed into a conical shape, and a tip angle of a lower portion of the conical shape is, for example, about 20 °.

Reference numeral 2 denotes a through hole having a diameter of about 0.046 mm, and 2 a denotes an inner peripheral surface of the through hole 2. Reference numeral 3 denotes a lower end surface of the capillary 1, which is formed to be flat, but is inclined so as to be higher toward the outside, and the inclination angle thereof is 8 °, for example.

Between the inner peripheral surface 2 a of the through hole 2 and the lower end surface 3, a radius of, for example, 0. A curved portion 4 of 03 mm or 0.02 mm is interposed. That is, a portion 4 having a radius R of 0.03 or 0.02 mm is provided at the lower end of the through hole 2 and is connected to the lower end surface 3.

Reference numeral 5 denotes an upper end of the R-attached portion 4, 6 denotes a lower end of the R-attached portion 4, and also a lower end of the capillary 1. The difference in height between the upper end 5 and the lower end 6 is such that the size of R is 0. When it is 030 mm, it is 0.0232 mm, and when the size of R is 0.02 mm, it is 0.0179 mm. The distance of the lower end 6 from the center of the through hole 2 is 0.068 mm.

In the vertical cross section of the lower end portion of the capillary 1, an angle θ formed by a straight line connecting the upper end 5 and the lower end 6 and an extension line of the inner peripheral surface 2 a of the through hole 2 is 30 ° ± 5. The outer end of the lower end surface of the capillary 1 may not be rounded (R), but may be rounded (R) of about 0.02 mm as shown by a chain double-dashed line.

In the present invention, the diameter of the through hole 2 and the radius R of the rounded portion 4 are changed according to the size of the ball diameter of the pressure bonding ball for ball bonding, but the angle θ is 30 ±. It is 5 °.

According to the capillary of the present invention, as shown in FIG. 3, in the case of a small pressure bonding ball diameter of 0.80 μm or less, which type of conventional capillary ((A) to (D) shown in FIG. This is because the integrated value of slip amount is higher than in A) to (D), and the bondability is improved. Even when the crimping ball diameter is 80 to 90 mm, only the capillary of FIG. 2 (C) is better than the capillary of the present invention, and a relatively good bonding property can be obtained, so that the crimping ball diameter is wide. It can be said that it can respond.

Incidentally, FIG. 3 described above is obtained by simulating the case where the initial ball is compressed and deformed by the capillary using the rigid-plastic finite element method. From FIG. 3, the following can be said. .. That is, as shown in the capillary (C) shown in FIG. 2 (C), the smaller the angle θ is, the better the bonding property is. Further, as shown in FIG. 2 (D), the portion contacting the ball 9 at the lower end is rounded. It can be said that the capillaries have extremely bad joints.

However, the shape of the capillary 2 cannot be determined by considering only the bondability. The reason is that the relationship between the crimping ball diameter and the joining load cannot be ignored. Figure 4 shows the relationship. The following can be said from FIG. The capillary (C) with an angle θ of 30 ° shown in FIG. 2 (C) requires 1.5 to 1.8 times as much joining load as that shown in FIG. 2 (D). That is, if the angle θ is small, a large joining load is required to crush the ball. This requires a large amount of ultrasonic wave output, and causes a large damage to the film made of aluminum or the like to which the wire is bonded, which is not preferable.

However, the wire bonding capillary 1 of the present invention can enjoy both the advantages of the capillary (C) and the advantages of the capillary (D). That is, as is apparent from FIG. 4, the capillaries of the present invention have a larger bonding load than those of the capillaries (D), but a smaller bonding load than the capillaries (C) and (A), and the capillaries (B). Therefore, it is possible to improve the bondability with a comparatively small load, and therefore, the capillary 1 of the present invention can be said to be preferable as a whole.

5 (A) to 5 (E) show the cross-sectional shape of the ball when wire-bonding with each capillary, and FIGS. 5 (A) to 5 (D) show the conventional capillaries shown in FIG. The shapes of (A) to (D) are shown, and FIG. 5 (E) shows the case of the capillary of the present invention.

FIG. 6 shows the relationship between the initial ball thickness and the pressure bonding ball diameter (obtained by simulation) when the wire bonding capillary of the present invention is used, with the initial ball diameter as a parameter. The following can be said from FIG. From the experiments conducted so far, the shear strength per unit area of Au and Au-Al alloys is about 89 to 98 and 108 to 128 N / mm ² , respectively, and in order to obtain a shear strength of 0.4 N, It is necessary that the pressure bonding ball diameter is 72 to 76 μm and the alloy diameter is 63 to 69 μm. Therefore, when the alloy diameter of 63 μm is satisfied, the pressure bonding ball diameter needs to be about 78 μm. When the initial ball is 68 ± 2 μm, the pressure ball diameter is 86 ± 8 μm and the ball thickness is 18 ⁺⁸ _-5 μm. Seems good.

FIG. 7 shows the pressure bonding ball diameter and the bonding rate (the ratio of the wire to the wire bonded wire). The uppermost curve shows the case of the capillary of the present invention, and (A) shows FIG. 2 (A). 2A shows the case of the capillary (A), and FIG. 2B shows the case of the capillary (B) of FIG. 2B. It will be understood from this that the capillary 1 of the present invention is good. Fig. 8 shows the relationship between the pressure bonding ball diameter and the alloy diameter, Fig. 9 shows the relationship between the bonding load (impact load) and the pressure bonding ball diameter, and Fig. 10 shows the relationship between the pressure bonding ball diameter and the pressure bonding ball shear strength. Show. In the drawings, 0.62 μm of the present invention and 1.1 μm of the present invention refer to the case where the capillary 1 of the present invention is used by applying ultrasonic waves, and the ultrasonic amplitude is 0.62 μm, 1 The case of 1 μm is shown.

From the above, it is understood that the capillary 1 of the present invention crushes the ball with a smaller load than the other capillaries, and it can be said that there is almost no difference in the shear strength of the crimped ball if the ball diameter is the same. It can be seen that the shear strength of the pressure-bonded ball increases substantially in proportion to the diameter of the compression ball regardless of the amplitude of the capillary tip amplitude, and that the strength is superior to the case where no ultrasonic wave is applied.

The reason why the strength is better when ultrasonic waves are applied is because the Au—Al contact surfaces are entirely bonded by the ultrasonic waves, and a tip amplitude of 0.62 μm is sufficient. Then, when an ultrasonic wave having an amplitude of 0.62 μm was applied, 100% bonding was achieved in the case of the capillary 1 of the present invention within the conditions shown in the figure. That is, the bonding rate (the ratio of the wires that could be bonded to the wire bonded wire) was 100%. Also, it has been confirmed that when the ultrasonic amplitude is about 0.62 μm, there is almost no effect on the ball shape.

By the way, the effect of the present invention has been confirmed by the slip amount and the slip integrated value by the simulation shown in FIG. 3. The slip amount and the integrated value thereof were obtained as follows. .. The velocity distribution in the radial direction of only the portion where Au-Al is in contact with the material flow velocity at each calculation step during wire deformation is calculated. The velocity is integrated over time to obtain the slip amount. Since the deformation of the Al film is not taken into consideration, this slip amount is the amount of Au slipped with respect to the Al film. On the other hand, as shown in FIG. 11 for explaining the bonding mechanism, when Au is deformed on the Al film (the upper part in the figure is before deformation, the lower part is after deformation, and a, b and c are respectively It is believed that the newly formed surfaces on the Au and Al films come into contact with each other to perform the bonding. Therefore, we thought that this slip amount correlates with the amount of new surface generation, and we thought that we could evaluate the bondability with a large or small amount of slip.

In the reports so far, this slip amount is compared by the change in the slip amount at a point at a certain distance from the center of the crimp ball, or the slip amount corresponding to a certain crimp ball diameter is distributed in the radial direction. Was represented. This time, it was used after being integrated as shown in FIG. 12 so that the difference in the capillary shape can be easily expressed. Regarding the method of evaluating the bondability based on the amount of slip, the 42nd Plastic Working Federation Lecture Meeting (199.9.125-27 Sapporo) Proceedings 687-690, “Au-Al Bondability by Au Ball Deformation Analysis” "Evaluation" and so on.

FIG. 13 is a relationship diagram of the pressure bonding ball diameter and the bonding rate of each capillary. In this figure, the X and + marks are prototypes (material single crystal ruby) according to the present invention, and the others are conventional ones. As is clear from this figure, according to the capillary of the present invention, the bonding rate is 100% or close to it in the pressure bonding ball diameter range of 90 to 70 μm, and it is clear that it can greatly contribute to the improvement of the yield.

[0027]

[Effect of the device]

 As is clear from the above description, according to the wire bonding capillary of the present invention, as shown in FIG. 3, when the wire crimping ball diameter is as small as 67 to 85 μm, the conventional capillary ( The integrated value of the amount of slippage is larger than any of A) to (D), and the bondability is improved. Therefore, it becomes easy to cope with the reduction of the diameter of the pressure bonding ball.

[Brief description of drawings]

1A and 1B show an embodiment of a wire bonding capillary of the present invention, FIG. 1A is a front view, and FIG. 1B is an enlarged vertical cross-sectional view of a main part.

FIG. 2A to FIG. 2D are enlarged vertical cross-sectional views showing the lower shape of each conventional capillary for which data is to be obtained.

FIG. 3 is a relationship diagram of a pressure-bonded ball diameter and an integrated value of slip amount.

FIG. 4 is a relationship diagram of a pressure bonding ball diameter and a bonding load.

5A to 5E are cross-sectional views of pressure-bonded balls formed by the capillaries.

FIG. 6 is a diagram showing the relationship between the ball thickness and the pressure-bonded ball diameter according to the capillary of the present invention.

FIG. 7 is a relationship diagram of a pressure bonding ball diameter and a bonding rate by each capillary.

FIG. 8 is a relationship diagram of a pressure bonding ball diameter and an alloy diameter by each capillary.

FIG. 9 is a relational view of the bonding load and pressure bonding ball diameter of each capillary.

FIG. 10 is a relationship diagram of a pressure bonding ball diameter / shear strength by each capillary.

FIG. 11 is an explanatory view of a joining mechanism.

FIG. 12 is an explanatory diagram of calculation of integral of slip amount.

FIG. 13 is a relationship diagram of a pressure bonding ball diameter and a bonding rate by each capillary.

14A to 14C are enlarged vertical cross-sectional views showing a main part of another conventional example.

[Explanation of symbols]

1 Capillary for Wire Bonding 2 Through Hole 2a Inner Surface of Through Hole 3 Lower End Surface 4 Part with R (R) 5 Upper End of Part with R (R) 6 Lower End of Part with R (R) 7 The extension line θ of the inner peripheral surface of the through hole The angle formed by the straight line connecting the upper end 5 and the lower end 6 and the extension line of the inner peripheral surface of the through hole

Claims (1)

[Scope of utility model registration request] 1. A wire bonding capillary having a through hole, wherein a lower portion is provided with a round (R) at a lower end portion of the through hole, and a straight line connecting the upper end and the lower end of the round and a through hole inner peripheral surface. The capillary for wire bonding is characterized in that the angle θ formed with the extension line is 30 ± 5 °, and the lower end surface is flat and has a vertical cross-sectional shape that is inclined so as to become higher toward the outside.