JPH11135574A - Collet for ultrasonic bonding and bonding method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To mount a chip without tilting in a collet that is welded by lifting a chip with bump, mounting it on a wiring part or the like, and applying ultrasonic vibration. SOLUTION: A suction hole 5 is opened at the central part of a body part 1, and its lower surface is flat as a chip suction surface 4. The body part 1 has a root part where the outer shape of a traverse cross section outer shape is square and a tip part where a traverse cross section outer shape is rectangular, and a pair of chip pressers 3 with an inclined surface 6 is branched in a chevron shape. A slide sleeve 2 is engaged to the body part 1. When a chip 7 is subjected to vacuum suction and lifted, the center of a collet normally deviates from that of the chip (a). When the chip 2 is lowered, the chip presser 3 touches the ridge on the reverse side of the chip and a position for the collet of the chip is corrected (b). In this state, the chip is mounted on the upper part of a wiring part or the like and ultrasonic vibration is applied, thus welding a bump 8.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic bonding collet and a bonding method using the same, and more particularly to a collet for ultrasonically bonding a semiconductor chip having metal bumps on inner leads by a face-down method. And a bonding method using the same.

[0002]

2. Description of the Related Art In recent years, as consumer electronic devices have become smaller and lighter, there has been a strong demand for smaller and thinner semiconductor devices mounted in the electronic devices. Is manufactured by mounting a semiconductor chip (hereinafter, referred to as a chip) on a lead frame, a substrate, or the like, electrically connecting an electrode of the chip with a lead or a wiring portion, and sealing with a resin or the like. . In order to reduce the size and thickness of a semiconductor device, it has been frequently used to directly connect a semiconductor chip to an inner lead or a wiring portion via a bump instead of a mounting method using wire bonding. I have.

For bump connection, a method of welding solder bumps by a reflow method is known. As a more efficient method, bumps are applied by applying ultrasonic vibration, which is proposed in Japanese Patent Application Laid-Open No. 1-244630. There is a method of welding. In the ultrasonic application method, ultrasonic vibration is transmitted to a chip in a horizontal direction through a collet. For this reason, it is necessary to hold the ridge on the back surface of the chip with a collet. Particularly, the ultrasonic vibration can be efficiently transmitted to the chip by holding the ridge in the direction perpendicular to the ultrasonic vibration direction. A conventional collet and a bonding method using the same will be described with reference to the drawings.

FIG. 6B is a plan view of the conventional pyramid collet as viewed from the tip side, and FIG.
It is sectional drawing in a line. FIG. 7 is a cross-sectional view and a plan view for explaining the relationship between the collet and the chip during ultrasonic bonding in the pyramid collet shown in FIG. 8 (a) and 8 (b) are a cross-sectional view of a conventional two-sloped surface collet and a plan view as viewed from the tip side, and FIG. 9 is an ultrasonic bonding of the two-sloped surface collet shown in FIG. It is a sectional view and a plan view for explaining the relationship between the collet and the chip at the time. As shown in FIG. 6, the pyramid collet 20 has a suction hole 22 for evacuation at the center, and has four inclined surfaces 21 inside the tip. Then, at the time of bonding, as shown in FIG. 7, the chip 23 having the bumps 24 is attracted and sucked by the pyramid collet 20.
It is held and lowered onto the substrate 25 having the wiring portion 26, and the bump 24 of the chip is positioned on the wiring portion 26. Thereafter, the ultrasonic wave is applied such that two sides of the square are perpendicular to the ultrasonic vibration direction in plan view of the collet tip. However, since the tip 23 is not limited to a square, and even if it is designed to be a square, it does not become a perfect square due to the accuracy of dicing, so that the short side of the tip 23 is perpendicular to the ultrasonic vibration direction [FIG. In a1) and (a2)], since the contact line 27 between the inclined surface and the corner of the chip is perpendicular to the ultrasonic vibration direction, the ultrasonic vibration can be efficiently transmitted to the chip. In the case of being perpendicular to the vibration direction [FIGS. 7 (b1) and 7 (b2)], the contact line 27 between the inclined surface and the corner of the chip becomes parallel to the ultrasonic vibration direction, and the ultrasonic vibration cannot be transmitted efficiently.

In order to prevent the ultrasonic bonding conditions from being influenced by the shape of the chip, a two-sided inclined plane collet shown in FIG. 8 is sometimes used. That is, as shown in FIG. 9, the ultrasonic vibration is applied vertically to the inclined surface 31 inside the collet tip in a plan view. In the case of this collect, the short side of the tip 33 is perpendicular to the ultrasonic vibration direction [FIG.
(A1) and (a2)], even when the long side of the chip is perpendicular to the ultrasonic vibration direction [FIGS. 9 (b1) and (b2)], the contact line segment 37 between the inclined surface and the corner of the chip is Since the direction becomes perpendicular to the ultrasonic vibration direction, the ultrasonic vibration can be efficiently transmitted to the chip 33.

[0006]

In the pyramid collet shown in FIG. 6, when the long side of the chip is perpendicular to the ultrasonic vibration direction, the ultrasonic vibration cannot be transmitted efficiently. On the other hand, the two-sloped-surface collet shown in FIG. 8 has a problem that it is difficult to hold the chip horizontally when picking up the chip. The reason will be described with reference to FIG. 10 which is a cross-sectional view showing a process of picking up chips using a conventional two-sloped collet. The center line offset occurs between the collet 30 and the chip 33 when the collet descends due to the chip recognition accuracy, the collet horizontal positioning accuracy, and the axis displacement in the collet descending direction (FIG. 10A). Due to the center line offset, the tip 33 is first placed on one of the two inclined surfaces 31 inside the collet tip.
One ridge on the back surface contacts (FIG. 10B). After this,
When the chip 33 is vacuum-sucked, the chip
The chip 33 is held obliquely with the ridge of the back surface as a fulcrum and held by the collet 30 (FIG. 10C). Accordingly, the chip 33 is mounted on the wiring portion on the substrate while being slanted, and a bump that cannot be connected to the wiring portion in the chip surface occurs. SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems, and an object of the present invention is to provide an ultrasonic bonding collet and an ultrasonic bonding method capable of holding a chip horizontally and bonding efficiently. It is to provide a bonding method.

[0007]

SUMMARY OF THE INVENTION An ultrasonic bonding collet according to the present invention has a suction hole at the center and a flat suction surface at the front end, and two opposed ridges on the back surface of the chip. And a chip holder having an inclined surface capable of holding the chip in contact with the main body. The chip holder is configured to be able to operate the chip holder independently of the suction operation of the main body.

Further, the bonding method of the present invention
(1) A collet having a main body having a suction hole opened and a tip part formed as a flat suction part and a chip holder having an inclined surface capable of contacting two opposing ridges on the back surface of the chip is lowered. A step of sucking and holding the semiconductor chip with metal bumps that are reversely aligned by the sucking unit;
(2) raising, moving, and lowering the collet, and mounting the semiconductor chip on the inner leads of the lead frame or on the wiring portion of the wiring board in such a manner that the metal bumps contact the inner leads; (3) With the inclined surface of the chip holder pressed against two ridges on the back surface of the semiconductor chip, ultrasonic vibration is applied in the horizontal direction by the collet to apply the metal bump to the inner lead or the wiring portion. Welding step.

[Operation] In the case of using the ultrasonic bonding apparatus of the present invention, the chip can be always arranged horizontally on the wiring portion or the like because the chip is sucked and held on the flat chip suction surface. Therefore, it is possible to prevent the occurrence of unconnected bumps caused by bonding the chip in an inclined state. Further, since the ultrasonic vibration can be applied in a state where two opposing ridges on the back surface of the chip are pressed by the chip pressing, the ultrasonic vibration energy can be efficiently transmitted from the collect to the chip.

[0010]

Embodiments of the present invention will be described with reference to the drawings. [First Embodiment] FIG. 1 (b) is a plan view of an ultrasonic bonding collet according to a first embodiment of the present invention as viewed from the front end side, and FIG. It is sectional drawing in the -A 'line. As shown in FIG. 1, a suction hole 5 is formed in the center of the main body 1, and the lower surface of the tip portion is flat as a chip suction surface 4. Main unit 1
Has a root portion having a square cross-sectional outer shape and a tip portion having a rectangular cross-sectional outer shape, and a pair of tip holders 3 each having an inclined surface 6 are branched from the middle of the tip portion. . The two inclined surfaces 6 are formed so as to face each other with the main body 1 as a center, and the pair of chip holders 3 has an “eight” shape.

The slide sleeve 2 is formed in a ring shape having a square cross section and a square hole formed therein. The slide sleeve 2 surrounds the outside of the main body 1, contacts the inside of the main body 1, and contacts the main body 1. Slide up and down as a guide. The tip of the slide sleeve 2 hits the outer side of the tip holder 3 from above and pushes it inward. The material of the tip holder 3 and the slide sleeve 2 of the main body 1 is ceramic,
It is a simple substance such as a cemented carbide or a hard resin, or a combination thereof.

Next, a bonding method using the ultrasonic bonding collet of the present embodiment will be described with reference to FIGS. The position of the chip 7 with the bumps 8 in a state of being reversely aligned and affixed on the UV tape 10 is confirmed by an outer shape recognition device (not shown), and the main body 1 of the collet is lowered from above the chip 7, The chip suction surface 4 is brought into contact with the back surface (FIG. 2A). The UV tape was previously irradiated with ultraviolet rays to reduce the adhesive force. Next, the chip 7 is lifted by elevating the collet after vacuuming the back surface of the chip 7 by vacuuming through the suction hole 5 [FIG.
(B)]. At this time, the back surface of the chip 7 is vacuum-sucked to the flat chip suction surface 4, so that the chip 7 is always picked up horizontally. At this time, there is an offset between the center line of the normal chip 7 and the center line of the collet body 1 [FIG. 3 (a)]. Then, when the slide sleeve 2 is lowered and the end of the chip holder 3 is moved to close to the center point side, the inclined surface 6 hits the ridge on the back surface of the chip 7, and the chip has a position where the center line coincides with the collet body 1. The chip 7 continues to be sucked and is held by the inclined surface 6 of the chip holder 3 [FIG.
(B)]. This centering operation of the chip is performed during the movement of the collect.

While the chip is being sucked and held, the collet is moved, the position of the mounting portion 13 of the wiring portion 12 on the substrate 11 is confirmed by a recognition device (not shown), the collet is lowered, and the bump of the chip 7 is lowered. 8 is brought into contact with the mounting portion 13 on the substrate 11 (FIG. 2C). Then, while the two ridges on the back surface of the chip 7 are sandwiched by the chip holder 3, ultrasonic vibration is applied to the collet in the horizontal direction using the ultrasonic generator 14 to weld the bumps 8 (FIG. 2D). ].

[Second Embodiment] FIG. 4B is a plan view of an ultrasonic bonding collet according to a second embodiment of the present invention, as viewed from the tip end side, and FIG. Is a sectional view taken along line AA ′. As shown in FIG.
A suction hole 5 is formed in the center of the main body 1, and the lower surface of the tip portion is flat as a chip suction surface.
The main body 1 has a root portion having a square cross-sectional outer shape and a tip portion having a rectangular cross-sectional outer shape.

The slide sleeve 2 has a ring-shaped root portion having a square cross section and a square hole formed therein, and a pair of tip holders 3 extending downward from the lower end of the root portion. doing. The base of the slide sleeve 2 surrounds the outside of the main body 1, and the inside touches the inside and slides up and down using the guide as a guide. Tip holder 3
Has an inclined surface 6, and the two inclined surfaces 6
Is formed in the shape of an “eight” with the center as the center.

The bonding method using the ultrasonic bonding apparatus according to the second embodiment is almost the same as that of the first embodiment shown in FIG. That is, the position of the chip with bumps, which has been inverted and aligned and adhered to the UV tape, is checked with an outer shape recognition device, the main body 1 of the collet is lowered from above the chip, and the suction surface 4 is brought into contact with the back surface of the chip. [See FIG. 2 (a)]. Next, after the vacuum is evacuated from the suction hole 5 to vacuum-suction the back surface of the chip, the collet is raised to lift the chip (see FIG. 2B).

The collet is moved while the chip is being sucked, the position of the mounting portion of the wiring portion on the substrate is confirmed by a recognition device, the collet is lowered, and the bump of the chip is brought into contact with the mounting portion on the substrate [FIG. 2 (c)]. Then, ultrasonic vibrations are applied to the collet in the horizontal direction while holding the rear edge of the chip 7 by the chip holder 3 to weld the bump [FIG. 2 (d)].

Also in this embodiment, the centering of the chip is performed during the transportation of the chip to the bonding point after the chip is picked up. That is, when the chip is picked up, there is usually an offset between the center line of the chip 7 and the center line of the collet body 1 [FIG.
(A)]. Then, the slide sleeve 2 is lowered, and the inclined surface 6 of the chip holder 3 is pressed against the ridge on the back surface of the chip 7. As a result, the chip slides horizontally to a position where its center line coincides with that of the collet body 1, and the chip 7 is held by the inclined surface 6 of the chip holder 3 [FIG.
(B)].

Although the preferred embodiments have been described above, the present invention is not limited to these examples, and can be appropriately modified without departing from the gist of the invention. For example, in the above embodiment, the bump of the chip is bonded to the wiring portion on the substrate, but the present invention is also applicable to the case of bonding to the inner lead of the lead frame. In the description of the above embodiment, the centering of the chip with respect to the collet is performed during the transportation of the chip. However, before the chip is lifted from the UV tape, or after the chip is once lifted, the position correction prepared in advance is performed. The slide sleeve may be lowered on the position correction plate placed on the plate. With this configuration, the centering of the chip can be performed stably without causing the accident of the chip dropping.

[0020]

As described above, the ultrasonic bonding collet of the present invention comprises a main body having a flat chip suction surface and a pair of chip holders capable of holding two opposing edges on the back surface of the chip. The bonding method using this method is to perform the ultrasonic bonding while holding and holding the two ridges on the back surface of the chip with the chip holder while holding and holding the flat suction surface. The following effects can be simultaneously enjoyed. Since the chip can always be mounted on a wiring board or the like in a horizontal state, occurrence of unconnected bumps can be prevented. Ultrasonic vibration energy can be applied to the chip in a state where two ridges in a direction perpendicular to the ultrasonic vibration direction are sandwiched, so that highly reliable bonding can be performed.

[Brief description of the drawings]

FIG. 1 is a sectional view and a suction side plan view showing a first embodiment of an ultrasonic bonding collet of the present invention.

FIG. 2 is a sectional view in the order of steps for explaining a bonding method using the ultrasonic bonding collet according to the first embodiment of the present invention.

FIG. 3 is a sectional view in the order of steps for explaining the operation of the ultrasonic bonding collet according to the first embodiment of the present invention.

FIG. 4 is a sectional view and a suction side plan view showing a second embodiment of the ultrasonic bonding collet of the present invention.

FIG. 5 is a sectional view in the order of steps for explaining the operation of the ultrasonic bonding collet according to the second embodiment of the present invention.

FIG. 6 is a cross-sectional view of a conventional pyramid collet and a plan view of a collet tip side.

FIG. 7 is a cross-sectional view showing a state of ultrasonic bonding using a conventional pyramidal collet and a plan view of a collet tip side.

FIG. 8 is a cross-sectional view of a conventional two-sloped surface collet and a plan view of the front end of the collet.

9A and 9B are a cross-sectional view and a plan view of a collet tip side showing a state of ultrasonic bonding using a conventional two-sloped surface collet.

FIG. 10 is a cross-sectional view for explaining a problem at the time of chip pickup using a conventional two-sloped collet.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Main body part 2 Slide sleeve 3 Chip holder 4 Chip suction surface 5 Suction hole 6 Inclined surface 7 Chip 8 Bump 9 Wafer ring 10 UV tape 11 Substrate 12 Wiring unit 13 Mounting unit 14 Ultrasonic generator 20 Pyramid collet 21, 31 Incline Surface 22, 32 Suction hole 23, 33 Chip 24, 34 Bump 25, 35 Substrate 26, 36 Wiring part 27, 37 Contact line of inclination and corner of chip 38 UV tape

Claims (6)

[Claims] 1. A main body having a suction hole in the center and a flat suction surface at a front end, and an inclined surface capable of holding the chip by contacting two opposing ridges on the back surface of the chip. And a tip holder having the same, and wherein the tip holder can be operated independently of the suction operation of the main body. 2. A main body having a suction hole in the center and having a flat suction surface at a front end, and an eight-shaped cross section in a sectional view from the vicinity of the front end of the main body to the outside. A pair of chip holders made lower than the surface, and the chip holder, which is externally fitted to the main body part so as to be vertically movable, is pressed from above to narrow its spread and contact the chip holder with the ridge on the back surface of the chip. A collet for ultrasonic bonding, comprising: a slide sleeve that can be used. (1) A main body having a suction hole opened and a tip portion formed as a flat suction portion, and a chip holder having an inclined surface capable of contacting two opposing ridges on the back surface of the chip. A step of lowering the collet to suck and hold the semiconductor chip with the metal bumps that have been inverted and aligned by the suction unit; and (2) raising, moving, and lowering the collet so that the semiconductor chip is brought into contact with the metal bumps. Placing on the inner lead or the wiring portion in a state of contacting the inner lead of the lead frame or the wiring portion of the wiring board; and (3) the inclined surface of the chip holder is formed on two ridges on the back surface of the semiconductor chip. In the pressed state, applying ultrasonic vibration in a horizontal direction by the collet to weld the metal bump to the inner lead or the wiring portion;
A bonding method comprising: 4. The semiconductor device according to claim 3, wherein, during the step (2), the inclined surface of the chip holder is pressed against the ridge on the back surface of the semiconductor chip to correct the position of the chip with respect to the collet. Bonding method. 5. The semiconductor device according to claim 1, wherein the chip retainer is branched from the main body part to the outside from the middle thereof, and when the chip retainer is pressed against a back edge of the semiconductor chip,
4. The bonding method according to claim 3, wherein a slide sleeve provided vertically movably outside the main body is lowered to narrow the spread of the chip holder by the slide sleeve. 6. The tip holder is a pair of protrusions formed at a lower end portion of a slide sleeve body movably provided on the outside of the main body part so as to be vertically movable, and having an inclined portion inside. 4. The bonding method according to claim 3, wherein the slide sleeve is lowered when the semiconductor chip is pressed against the back edge of the semiconductor chip.