JPH0196938A - Capillary for wire bonding - Google Patents

Abstract

PURPOSE:To enable a highly reliable stitch bonding to be made by providing the first and second press parts in the direction of outer periphery of tip surface of capillary, by allowing the first wire press part to protrude toward the part to be bonded as compared with the second wire press part, and by setting the slope angle of the second wire press part surface to an angle exceeding 15 degrees in reference to the main surface of the part to be bonded. CONSTITUTION:A wire 5 is stitch-bonded to the second part to be bonded 4 after bonding. The wire 5 is pressed at the first and second wire press parts 21 and 22 and is crushed so that a thick part 25 and a thin part 20 are produced. Also, the thin part 26 is made to be wider than the thick part 27. The second part to be bonded 4 is heated on this stitch bonding and supersonic vibration is applied to a capillary 6 horizontally to perform thermal contact bonding which also uses supersonic. Thus, an alloy layer of Au-A1 16 is produced. And the wire 5 is cut at the edge of a wire delivery hole 7 of the thin part 26.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a capillary that allows highly reliable wire bonding when manufacturing a concentrator circuit, etc. [Prior Art] For example, a power transistor The first bonded portion 2 consisting of the A1 electrode on the step 1 and the second bonded portion 4 consisting of the AI'lE electrode of the driving monolithic IC chip 3 may be connected by a wire 5 made of a thin Au wire. . When performing this type of wire bonding, as shown in Part 94, it is necessary to attach a 1. A ball 8 is formed using a gas spark or a hydrogen flame. Here, the diameter of the ball 8 is two to three times the diameter of the wire 8.

Next, as shown in FIG. 9 CB+, the ball 8 is pressed against the first bonding target portion 2 of the power transistor TEP 1 by the tip pressurizing surface 9 of the capillary 6. At this time, the first bonded portion 2 is heated, and ultrasonic vibrations are applied to the capillary 6 in a direction parallel to the surface of the first bonded portion 2. thus,
By using thermocompression bonding and ultrasonic bonding in combination, a first bonding portion 10 is formed in which a wire 5 is connected in a nail-head shape to the first bonded portion 2 .

Next, as shown in FIG. 9(C), the capillary 6 is raised while letting out the wire 5, and the capillary 6 is pulled wide so that the capillary 6 is pulled out toward the second bonding target portion 4 on the monolithic IC chip 6. and move.

Subsequently, as shown in FIG. 9 [F], the wire 5 is connected to the pressure surface 9 of the gear pillar 6 against the second bonding target portion 4.
The wire 5a is crushed and connected to the second bonded portion 4. As a result, the second bonding portion 11 is formed.

At this time, the second bonded portion 4 is heated, and the capillary 6 is subjected to ultrasonic vibrations as described above.

Finally, as shown in Fig. 9 (■), the capillary 6 is raised to a predetermined height, the wire 5 is fixed so that it does not come out from the gear pillar IJ 6, and the capillary 6 is further raised to cut the wire 5. do.

Usually, the bonding that forms the first bonding part 10 is called t-ball bonding, and the bonding that forms the second bonding part 11 is called stitch bonding.

[Problems to be Solved by the Invention] Incidentally, the tip end surface 9 of the conventional capillary 6 is formed as shown in an enlarged view in FIG. That is, the tip surface 9 of the capillary 6 made of a tapered tube has the bonded portion 4 outside the chamfered portion 12 at the outlet of the wire feeding hole 7.
It has a wire pressurizing part 13 having an inclination angle of 7 degrees of phase change with respect to the main surface of the capillary, and has a chamfered part 14 between the capillary side surface 15 and the tip surface 9 on the outside thereof.

When the tip surface 9 of the capillary 6 is formed as shown in FIG. 10, the first bonding part 10 by ball bonding shown in FIG.
It was difficult to obtain the second bonding portion 11 by stitch bonding shown in FIG. 1 with high reliability.

This will be explained in detail next.

When an Au-based thin lead wire is connected to an Al-based electrode, an Au layer consisting of AuA12'P AuAl is formed at the bonding interface.
It is well known that -A1 alloy layers are formed. FIG. 11 shows a wire 5 made of thin Au wire attached to a second bonded part 4 made of an AI electrode using a conventional gear villa 1J6Y.
The second bonding portion 11 obtained by YK-uniform bonding is shown. An Au-Al alloy layer 16 is formed in this second bonding portion 11 . A semiconductor device having such a second bonding portion 11 was subjected to a high temperature storage test (200° C.).

When exposed to air for 20 hours, as shown in Figure 12, <Au-A
The Al alloy layer 16 grows, and almost the entire second bonding part 11 becomes the Al-Au alloy layer 16. As a result, Au
-A1 alloy 7) A crack develops between the <Au layer based on the Aual wire 16 and the γ of the second bonding part 11.
- You may be in a flat state or a state close to this. Note that, since the first bonding part 10 is formed by pole bonding, it is much thicker than the second bonding part 11, and has a thickness of 0.5 mm. Highly reliable connection.

By the way, the applicant has reported that Au
- When the growth of the A1 alloy layer 16 was investigated, it was found that the thickness was 10βm.
It was found that the growth rate is rapid up to a certain point, but the growth after that becomes slower. Furthermore, if an Au layer remains on the Au-A1 alloy layer 16 based on the wire 5 as shown in FIG.
As shown in the figure, it was also found that if no AuM remained in the soil of the Au-Al alloy layer 16, connection failures would occur more frequently.

The inclination angle of the wire blade pressure part 16 on the tip surface 9 of the capillary 6 shown in FIG. 10 was increased so that the maximum thickness of the second pounding part 11 exceeded 10 μml'. L
However, when the inclination angle is increased.

radial direction C crushing direction of the wire 5 by the wire pressurizing section 16)
The pressing force became weak and the connection became incomplete.

Although we have just described the connection of Au wires to AIRI, similar problems arise when other metals are incorporated into one alloy layer. ! Ta. Similar problems occur not only in heating for high-temperature storage tests, but also in heating for other purposes.

Therefore, an object of the present invention is to provide a capillary capable of performing highly reliable stitch bonding.

[Means for solving problems]

To solve the above problems and achieve the above object, the present invention will be described with reference to the reference numerals in the drawings showing the embodiments. 12, and has a hole 7' for feeding out the wire 5 in the center of the tip surface 12, and is configured to perform at least stitch bonding. A first wire pressure section 21 and a second wire pressure section 2 are provided on the tip surface 12.
2, the first wire pressure section 21 is disposed near the hole 7 and protrudes toward the bonded portion 4 from the second wire pressure section 22;
The second wire pressurizing part 22 is provided at a position farther from the hole 7 than the first wire pressurizing part 21, and the second wire pressurizing part 22 is placed at a position farther away from the hole 7 than the first wire pressurizing part 21, and A stepped portion 23 is provided between the first wire pressing portion 21 and the second wire pressing portion 22 so that the first wire pressing portion 21 and the second wire pressing portion 22 are spaced apart from each other.
The inclination angle of the straight line connecting the end of the main part of the wire pressurizing part 22 closer to the hole 7 and the end farther from the hole 7 with respect to the main surface of the bonded part 4 is 15 degrees or less, The angle of inclination of the straight line connecting one end and the other end of the main portion of the stepped portion 23 with respect to the main surface of the bonded portion 4 is 1.
The present invention relates to a capillary for wire bonding characterized in that the angle is set larger than 5 degrees.

[For production]

The first wire pressure section 21 in the above invention has a stepped section 26.
Since it protrudes through the wire, it has a function like a spacer for determining the distance between the second wire pressurizing part 22 and the bonded part 4.

Therefore, when stitch bonding is performed, a bonding portion 11 having a wall thickness greater than the protrusion amount of the first wire pressurizing portion 21 is generated on the bonded portion 4 . If the thickness of the bonding portion 11 is kept within a predetermined range, the necessary wire pressing force can be obtained, and the necessary connection strength and reliability can be obtained.

〔Example〕

Next, a capillary according to an embodiment of the present invention and a wire bonding method using the same will be explained with reference to FIGS. 1 to 7. However, in FIGS. 1 to 7, parts that are substantially the same as those in FIGS. 8 to 12 are given the same reference numerals, and their explanations will be omitted.

In this embodiment, the tip surface 9 of the capillary 6 has a first groove so as to surround the chamfered portion 12 at the outlet of the wire feeding hole 7.
A wire pressure section 21 is provided.

A second wire pressure section 2 is provided on the outside of this via a stepped section 23t/
2 is provided, and furthermore, a chamfered portion 14 between the side surface portion 15 and the second wire pressurizing portion 22 is provided on the outside thereof.

Wire feeding hole 7, chamfered portion 12, first wire pressing portion 211 step portion 23. Second wire pressure section 22. The chamfered portions 14 are arranged concentrically as shown in FIG.

The first wire pressing section 21 is formed approximately parallel to the main surface of the bonded portion 4 made of the A1 electrode, and the second wire pressing section 22 is approximately It has a degree of slope. The stepped portion 23#-tM between the first wire pressing surface 21 and the second wire pressing surface 22 has an inclination angle of approximately 45 degrees with respect to the bonding portion 4, and the vertical component is approximately 15 μm. It is. Therefore, the first wire pressing section 21 protrudes downward by 15 μm from the inner circumferential end of the second wire pressing section 22. First wire pressure section 21
The radial width WI of the second wire pressing section 22 is approximately 10 μm, and the radial width sW of the second wire pressurizing portion 22 is approximately 50 μm. Note that the width WI is 10 to 20 μm, and the width W2 is 240 to 60 μm.
It is desirable to set it to about m. Just to be sure, if we divide the width of the stepped portion 26 in the radial direction by Ws, then (Wl + Ws) /
It is preferable to set Wz to about 1/6 to 2/3, and 11
It is more preferable to set it to about 5 to 1/2. Considering Wz in relation to the diameter of the wire 5.

W! /D'! +' It is preferable to set it to 1-2.

Next, a method of performing wire bonding similar to that shown in FIG. 8 using this capillary 6 and a bonding state will be described.

The wire bonding method is the same as the conventional method.

The thickness 3 consisting of the A1 electrode of the transistor chip 1
~5μm first bonded part 2 with a diameter of 30μm
A wire 5 made of thin Au wire is ball-bonded. FIG. 7 shows the state after ball bonding. The balls are connected to the first and second wires 7 on the tip surface 9 of the capillary 6)
Since it is pressed by the zero pressure parts 21 and 22, the annular #1124 is slightly reduced corresponding to the first wire pressing surface 21. Although the annular groove 24 portion of the first bonding portion 10 is thinner than other portions, the first bonding portion 10 based on the ball 2 to 6 times the diameter of the wire 5 is connected to the second bonding portion 11. Since it is thicker than #124, there is almost no reduction in connection strength due to #124.

Next, the capillary 6 is moved between the second bonded parts 4 made of AIti with a thickness of 3 to 5 μm of the IC chip 3 as shown in FIG. Stitch bond the wire 5 to 4.

The wire 5 is pressed by the first and second wire pressurizing parts 21, 22, and a thick part 25 with a thickness of 15 μm or more and a thick part 15 μm thicker than this are pressed.
It collapses into 5 so that a 5 μm thin wall portion 26 is formed. NaH
1. The thinner part 26 is wider than the thicker part 27. At the time of this stitch bonding, the second bonded portion 4 is heated at the cutting edge, and horizontal ultrasonic vibration is applied to the capillary 6, so that ultrasonic thermocompression bonding is performed. Therefore, an Au--Al alloy layer 16 is formed as shown in FIG.

Thereafter, the wire 5 is cut in a conventional manner. The wire 5 is cut at the end of the thin portion 26 on the wire feeding hole 7 side, as shown in FIG.

This embodiment has the following advantages.

+I+ Because there is a level difference of about 15 μm between the first wire pressure section 21 and the second wire pressure section 22.

Thick part 25y in second bonding part 11! - You can definitely get it. For this reason, high temperature storage tests (200℃,
Even if left for 20 hours, the Au-
The Au layer 5a can be left on top of the A1 alloy layer 16, and the incidence of connection failures is reduced.

(21) Since the inclination angle of the second wire pressurizing portion 22 is 7 degrees, the wire 5 can be sufficiently suppressed in the radial direction. Therefore, good stitch bonding is achieved.

[Modified example]

The present invention is not limited to the above-described embodiments, but can be modified, for example, as follows.

(II) It is preferable that the inclination angle of the second wire pressurizing part 22 with respect to the bonded part 4 is 15 degrees or less.
It has been confirmed that a range of <, 5 to 10 degrees is more preferable. If it exceeds 15 degrees, the pressure will be insufficient and good stitch bonding will not be possible. In the embodiment, this angle was set to 7 degrees, but it can be varied within the above range.

(2) The angle of the step portion 23 with respect to the bonding target portion 4 needs to be larger than the angle of the second wire pressurizing portion 22, that is, larger than 15 degrees, in order to obtain the necessary step with a small area. , preferably in the range of 60 to 60 degrees. Although the angle is set at 45 degrees in the embodiment, it may be changed as appropriate within the above range.

(31 When stitch-bonding the wire 5 with a diameter of 30 μm, the thickness of the thick portion 25 is set to 15 to 20 μm, and the thickness of the thin portion is set to approximately 6 to 5 μm.

Good wire bonding is possible. Therefore.

It is preferable that the step difference V between the first wire pressure section 21 and the second wire pressure section 22 be approximately 10 to 20 μm. That is, it is preferable that the level difference is about 1/3 to 2/3 of the width of the wire 5.

(4) The first wire pressurizing portion 21 may have a shape without a flat surface. That is, the stepped portion 23, the first wire pressure surface 21, and the chamfered portion 12a are combined to form a protruding portion having a semicircular cross section;
Alternatively, it may be a quadratic curved protrusion. Further, the first wire pressurizing portion 21 may also have an appropriate steep angle with respect to the bonding target portion 4.

(5) This is convenient for wire bonding when the bonded portion 4 is made of AI and the wire 5 is made of cancer.

It is also applicable to other metal combinations where similar problems occur. Further, even if there is no problem due to the alloy, it is possible to obtain a thick wall portion 25yill with a thickness greater than a predetermined value, making it possible to perform good wire bonding.

〔Effect of the invention〕

As described above, according to the present invention, a capillary capable of performing highly reliable wire bonding can be provided.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing a capillary according to an embodiment of the present invention at a portion corresponding to line I-1 in FIG. 2. FIG. 2 is a bottom view showing the tip of the capillary shown in FIG. 1. FIG. 6 is a sectional view showing a state in which stitch bonding is performed using the capillary of FIG. 1. FIG. 4 is a plan view showing a second bonding portion using the capillary of FIG. 1; FIG. 5 is a sectional view of the second bogging portion by the capillary of FIG. 1. FIG. 6 is a sectional view showing the state of the item shown in FIG. 5 after being subjected to a high-temperature fIt test, and FIG. 7 is a sectional view showing the first bonding portion by the sheep yabbirari in FIG. 1. FIG. 8 is a front view showing a part of a semiconductor device that performs wire bonding. Figure 9 (At(Bj(C)Ω) is a cross-sectional view for explaining the wire bonding method step by step. Figure 10 is a cross-sectional view showing stitch bonding using a conventional capillary. Figure 11 is a cross-sectional view showing stitch bonding using a conventional capillary. Fig. 12 is a sectional view showing the state of the stitch bonding part shown in Fig. 11 after being subjected to a high-temperature storage test. 2...first bonded part, 4...second part 5... wire, 6... capillary, 7... wire feeding hole, 10-... first bonding part, 11... second bonding part,
21... First wire pressure section, 22... Second wire pressure section, 26... Step portion. Agent Nori Takano Figure 1 Figure 8 Figure 8 Figure 9 (C) (D)] 1 (E) Procedural amendment (voluntary) December 30, 1988 1, 7 IG indication Showa 62 years Registration Liver III No. 25507
No. 2 No. 2, Title of the invention Wire bonding capillary 3, Relationship to the case to be amended Applicant residence fat 3-4 No. 6, Kitano 3-chome, Niiza City, Saitama Prefecture
, Agent 5, Date of amendment order Voluntary 6, Number of inventions increased by amendment + 11 Add ``as shown in Figure 9 Ω'' after ``for example'' on page 2, line 18 of the specification.

Claims (1)

[Scope of Claims] [1] It has a tip end surface (12) for pressing the wire (5) toward the bonding target part (4), and the tip end surface (1
2) has a hole (
7) and is configured to perform at least stitch bonding, the tip surface (12) having a first wire pressurizing part (21) and a second wire pressurizing part (21). a portion (22), and the first wire pressing portion (21) is disposed near the hole (7) and is located closer to the bonded portion (22) than the second wire pressing portion (22). 4) protrudes toward
The second wire pressurizing part (22) is provided at a position farther from the hole (7) than the first wire pressurizing part (21), and the second wire pressurizing part (22) The first wire pressure section (21) is spaced apart from the bonding region (4) more than the first wire pressure section (21).
and the second wire pressure section (22).
3) is provided, and the hole (7) in the main part of the second wire pressurizing part (22) is provided.
) and the end far from the hole (7), the inclination angle of the straight line connecting the end near the hole (7) with respect to the main surface of the bonded part (4) is 15 degrees, and the main part of the step part (23) A capillary for wire bonding, characterized in that an inclination angle of a straight line connecting one end and the other end with respect to the main surface of the bonded portion (4) is set to be larger than 15 degrees.