JPH11195670A - Wire bonding device and method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a wire bonding device and method, wherein an accurate bonding operation is carried out through the bonding device of simple structure without causing a short circuit between adjacent pads. SOLUTION: A bonding device is equipped with a first vibrator 20 which oscillates supersonic waves, a first horn 22 whose base end is connected to the first vibrator 20 and which transmits supersonic vibrations along its rod main body, and a capillary 24 provided with a through-hole and fixed to the tip of the first horn 22. The bonding device is also equipped with a second vibrator 40 which functions the same as the first vibrator 20, and a second horn 42 whose base end is connected to the second vibrator 40 and which is formed like a rod so as to be gradually decreased in diameter towards its tip connecting its tip to the tip of the first horn 22 at a right angle and transmits ultrasonic vibrations along its rod main body. By this setup, the capillary 24 can be switched in the direction of vibrations corresponding to the direction in which the pads are arranged.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wire bonding apparatus, and more particularly to a wire bonding apparatus and a wire bonding method for performing accurate bonding to all objects to be bonded with a simple structure.

[0002]

2. Description of the Related Art In manufacturing a semiconductor device, a semiconductor chip (semiconductor element) is mounted on a lead frame, and external leads of the lead frame are bonded to the semiconductor chip. The bonding method mainly includes a wire bonding method and a wireless bonding method. As the wire bonding method, an ultrasonic bonding method using ultrasonic waves and an ultrasonic thermocompression bonding method using both heat and ultrasonic waves are widely used. ing. Hereinafter, a wire bonding apparatus that performs wire bonding by an ultrasonic thermocompression bonding method will be described as an example of a conventional wire bonding apparatus with reference to the drawings.

A conventional wire bonding apparatus mounts a lead frame and moves freely in an XY plane.
The stage includes a bonding head unit (see FIG. 5) for wire bonding the lead frame and the semiconductor chip. FIG. 4 is a perspective view showing the ultrasonic horn 14 of the conventional wire bonding apparatus 10 and the semiconductor chip 16 wire-bonded by the ultrasonic horn 14. The conventional wire bonding apparatus 10 includes a bonding arm 18 that can move up and down, and the bonding arm 18 includes an ultrasonic horn 14 that bonds a wire to a pad 19 of a semiconductor chip 16.

FIG. 5 is a side view showing the structure of the ultrasonic horn. The ultrasonic horn 14 includes a vibrator (hereinafter, referred to as a first vibrator) 20 that oscillates ultrasonic vibration and a rod-shaped body connected to the first vibrator 20 at a base end and extending in a vibration direction of the ultrasonic vibration. A horn (hereinafter, referred to as a first horn) 22 that is formed and propagates ultrasonic vibrations along the rod-like body, and a capillary 24 that is attached to the tip of the horn and has a through hole
And The first vibrator 20 is connected to an ultrasonic oscillator (not shown) so that ultrasonic waves are transmitted.
A bonding wire (hereinafter simply referred to as a wire) 26 for bonding to a bonded object such as a pad is passed through the capillary 24 in a vertical direction and sent out from the capillary tip (lower end) 21. 2
The material of No. 6 is, for example, gold. Above the capillary 24, a clamper 28 for controlling the sending speed of the wire 26 is provided. In addition, the capillary tip 21
Is designed to function as an electric torch tip which melts and solidifies the tip of the wire with a spark to form a ball.

The XY stage (not shown) has a heater block (not shown) having a heating mechanism using a heater. A so-called heat piece (not shown) manufactured according to the shape of the die pad of the lead frame 32 and the shape of the external lead 33 is attached to the upper surface of the heater block. The XY stage includes a driving unit (not shown) for moving the stage in the XY plane, and an XY stage.
A storage unit (not shown) for storing coordinates on the Y stage.

The semiconductor chip 16 has a generally square or rectangular planar outer shape. A large number of pads 19 are formed along the periphery of the surface to be bonded to which the wire 26 is bonded.
They are arranged in the X direction along the axis and in the Y direction along the Y axis (see FIG. 4). The interval (pitch) between adjacent pads is equal in each of the X direction and the Y direction.

A method for performing wire bonding using the wire bonding apparatus 10 will be described below. First, X-
The lead frame 32 is held on the Y stage, the lead frame 32 is heated to a predetermined temperature by the heater block, and the semiconductor chip 16 is bonded to a mounting position on the lead frame 32. Next, a semi-ball-shaped ball portion (not shown) is formed at the tip of the wire. Subsequently, while the wire 26 is ultrasonically vibrated, the capillary tip 21 is positioned with respect to one pad, and the tip of the wire is pressed against the pad to generate frictional heat. To the pad. Further, the wire 26 is pressed and welded to the external lead corresponding to the pad while vibrating, and then the wire 26 is
Disconnect. Hereinafter, similarly, all pads of the semiconductor chip 16 are joined to external leads corresponding to each pad. Thus, the semiconductor chips are sequentially wire-bonded on the lead frame 32.

[0008]

By the way, in the conventional wire bonding apparatus, when performing wire bonding,
The capillary is vibrated only in the Y direction. For this reason,
Pads arranged along the X direction (hereinafter simply referred to as X direction arranged pads) and pads arranged along the Y direction (hereinafter simply referred to as Y direction arranged pads) are welded. The diameter and shape of the resulting ball-shaped welded portion (hereinafter simply referred to as welded ball) is different, and it is not possible to perform uniform bonding over all pads. The problem caused by this will be described in detail below with reference to FIG. Since the capillary is welded by vibrating in the Y direction, the planar size of the welded ball is an elliptical shape long in the Y direction. Therefore, the long width of the welded ball is formed in the X direction array pad 19A in a direction orthogonal to the array direction,
The direction arrangement pads 19B are formed in the same direction as the arrangement direction. Therefore, the welding balls protruding from the pad are adjacent to each other, for example, the pads 19B1, 19B.
There is a problem that the welded balls 2 are often short-circuited due to contact with each other. Since semiconductor chips tend to be smaller and smaller in pitch, it is important to solve this problem. This problem has occurred not only in the ultrasonic thermocompression bonding method but also in the ultrasonic bonding method.

[0009] A new type of wire bonding apparatus that takes this measure is disclosed in Japanese Patent Application Laid-Open Nos. 09-213755 and 06-2.
68033 and JP-A-04-372146. In Japanese Patent Application Laid-Open No. 09-213755, the ultrasonic horn has another vibrator between the first horn and the first horn, which vibrates the first horn by bending it in the Y direction (see FIG. 7). In Japanese Unexamined Patent Publication No. 06-268033, the ultrasonic horn includes a piezoelectric element (piezo-electron) that vibrates the first horn in the Y direction. JP-A-04-372146
Has a mechanism in which the center line of the first horn of the ultrasonic horn coincides with the center line of the capillary, and the first horn has torsional vibration.

[0010] However, in JP-A-09-213755 and JP-A-06-268033, it is presumed that the mechanism for vibrating the first horn in the Y direction can be further improved. There was a disadvantage that the capillary could not be vibrated in the Y direction. In view of the circumstances as described above, an object of the present invention is to provide a wire bonding apparatus and a wire bonding method for performing accurate bonding to all the objects to be bonded with a simple configuration and without causing a short circuit between adjacent welded balls. It is to provide.

[0011]

In order to achieve the above object, a wire bonding apparatus according to the present invention comprises a vibrator for oscillating ultrasonic vibration and a vibrator at a base end (hereinafter referred to as a first vibrator). ), A horn (hereinafter, referred to as a first horn) that is formed as a rod extending in the vibration direction of the ultrasonic vibration and propagates the ultrasonic vibration along the rod, and attached to the tip of the horn, A wire having a capillary having a through-hole, and a wire bonded through the capillary through-hole, the tip of the wire being pressed against a member to be welded while ultrasonically oscillating a bonding wire passing through the hole of the capillary to generate frictional heat and joining to the member to be joined. In the apparatus, another vibrator that oscillates ultrasonic vibration (hereinafter referred to as a second vibrator) is connected to the second vibrator at the base end, and the vibration direction of the ultrasonic vibration while reducing the diameter toward the front end Extending to the tip Another horn (hereinafter, referred to as a second horn) that is formed as a rod-like body connected to the distal end of the first horn in a direction intersecting with the distal end of the first horn and that transmits ultrasonic vibrations along the rod-like body. ).

[0012] Preferably, the second horn extends in the same direction as the first horn, and is curved and connected at its distal end toward the distal end of the first horn. In this case, the angle between the distal end of the first horn and the distal end of the second horn is almost a right angle in many cases.

In the present specification, the vibration direction of the ultrasonic vibration is
It means the amplitude direction of the vibration given by the first and second vibrators.
Also, while reducing the diameter toward the distal end means that only the distal end may be reduced in diameter as long as the capillary vibrates ultrasonically. The material of the wire is, for example, gold or aluminum. In the case of gold, wire bonding is performed by an ultrasonic thermocompression bonding method in which an object to be bonded is heated and then wire-bonded. Aluminum has a low melting point,
There is no need for heating, and it is performed by an ultrasonic bonding method. With the wire bonding apparatus according to the present invention, the amplitude direction of the vibration of the capillary can be switched so that it can be selected according to the surface to be bonded of the bonded body, and the vibration can be simultaneously performed in both directions. . Therefore, the size and shape of the welded ball can be changed according to the arrangement direction of the pads on the semiconductor substrate.

In a first aspect of the present invention, a wire bonding apparatus according to the present invention is used to wire a semiconductor chip having objects to be bonded arranged in the X and Y directions in an XY plane. In a bonding method, a bonded object arranged in the Y direction is wire-bonded to one of the first horn and the second horn by vibrating the capillary in the Y direction, and the other is arranged in the Y direction. The bonded body is characterized in that the capillary is vibrated in the X direction by the other side to perform wire bonding.
The bonded object is, for example, a pad.

According to the method of the first invention, the lengths of the welding balls formed on the X-direction arrangement pads and the Y-direction arrangement pads are:
Since all are formed in a direction orthogonal to the arrangement direction, adjacent welded balls do not come into contact with each other.

[0016] A wire bonding method according to a second invention method of the present invention uses a wire bonding apparatus according to the present invention, and uses a wire bonding apparatus according to the present invention and has semiconductors having objects to be bonded arranged in the X direction and the Y direction in an XY plane. A method of wire bonding to a chip, characterized in that the capillary is vibrated by the first and second horns so that the tip of the capillary draws a substantially circular locus, thereby performing wire bonding.

According to the second aspect of the present invention, since the tip of the capillary draws a circle, the plane size of the welding ball formed on the pad is circular. Therefore, adjacent welded balls do not come into contact with each other.

[0018]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. Embodiment 1 This embodiment is an example in which the first invention method is carried out using a suitable wire bonding apparatus of the present invention. In the wire bonding apparatus 36 of the present embodiment, the bonding arm further includes a second ultrasonic horn as compared with the conventional wire bonding apparatus 10. FIG. 1 is a partial perspective view showing the ultrasonic horn and the second ultrasonic horn of the wire bonding apparatus of the present embodiment, and a semiconductor chip subjected to wire bonding. In FIG. 1, the same components as those in FIG. 5 are denoted by the same reference numerals, and description thereof will be omitted.

FIGS. 2A and 2B are a plan view and a perspective view taken along the line II, respectively, showing the ultrasonic horn and the second ultrasonic horn of the wire bonding apparatus 36. The second ultrasonic horn 38 has a second vibrator 40 having the same configuration and function as the first vibrator 20, and is connected to the second vibrator 40 at the base end, and the ultrasonic vibration is performed while reducing the diameter toward the distal end. Is formed as a rod-like body extending in the vibration direction of the first horn 22 and connected to the distal end of the first horn 22 in a direction substantially orthogonal to the distal end of the first horn 22 at the distal end. And a second horn 42 that propagates. The second horn 42 extends in the same direction as the first horn 22, and is formed in a gentle arc toward the front end of the first horn 22 at the front end, and is connected. First vibrator 20 and second vibrator 4
0 indicates that the vibration can be switched ON and OFF, respectively, and the capillary 24 can vibrate in any of the X direction and the Y direction. It is also possible to draw a trajectory of a shape. In addition, the wire bonding apparatus 36 includes an imaging device (not shown) for positioning above the XY stage.

A method of performing wire bonding to a lead frame using the wire bonding apparatus 36 will be described below. First, as in the conventional case, the lead frame 32 was held on the XY stage, the lead frame 32 was heated to a predetermined temperature by the heater block, and the semiconductor chip 16 was bonded to the mounting position on the lead frame 32.
Next, a self-teach for setting a pad position, a bonding position of an external lead corresponding to the pad, and setting various conditions necessary for wire bonding was performed as follows. First, for each pad, the XY stage is manually moved while visually monitoring the image on the XY stage by the image pickup device, and the pad position and the external lead are moved to the reference position shown on the monitor screen. The respective substantially center positions with respect to the bonding position are positioned, and the coordinates are stored in the storage unit. The reference position is a position where the tip of the wire contacts when the capillary 24 is lowered, and is stored in the storage unit in advance. Further, each pad is distinguished into the X-direction arrangement pad 19A or the Y-direction arrangement pad 19B by the self-teach, and the fact is stored in the storage unit.

Next, a ball portion (not shown) was formed at the tip of the wire. In the present embodiment, a gold wire is used as the wire 26. Subsequently, one pad of the X-direction array pad 19A is positioned with respect to the capillary tip 21 based on the coordinates stored in the storage unit, and the ultrasonic horn 14
, The ball portion is pressed against the pad while vibrating the capillary 24 in the Y direction to generate frictional heat, and the ball portion is welded by the heat of the lead frame and the frictional heat. Further, the wire 26 was pressed and welded to the external lead corresponding to the pad while vibrating (exciting), and subsequently cut by the clamper 28. Hereinafter, all the X direction arrangement pads 19
The same was done for A and the corresponding external leads. Next, a ball portion is formed on the capillary tip 21 for the Y-direction array pad 19B in the same manner as described above, the capillary tip 21 is positioned with respect to one of the Y-direction array pads 19B, and the second ultrasonic horn 38 The ball portion was pressed against the pad while vibrating the capillary 24 in the Y direction to generate frictional heat, and the ball portion was welded. Further, similarly to the case of the X direction arrangement pad 19A, the wire 26 was welded to the external lead corresponding to this pad and cut. Hereinafter, the same operation is performed for all the Y-direction arrangement pads 19B and the corresponding external leads, and the state shown in FIG. 1 is realized.

According to the present embodiment, the pad 1 in the X direction is arranged.
The length directions of the weld balls formed on the 9A and Y-direction arrangement pads 19B are all orthogonal to the arrangement direction (see FIG. 1). Therefore, the adjacent welding balls do not come into contact with each other.

Embodiment 2 This embodiment is an example in which the second invention method is carried out using the wire bonding apparatus 36 of Embodiment 1. FIG.
1 is a partial perspective view of a semiconductor chip which has been wire-bonded in the present embodiment. 3, the same components as those in FIG. 1 are denoted by the same reference numerals, and the description thereof will be omitted.

In the present embodiment, similar to the first embodiment,
First, the semiconductor chip 16 was bonded on a predetermined position of the lead frame 32. Next, a ball portion was formed at the tip of the wire. Subsequently, one pad is positioned with respect to the capillary tip 21, and the ultrasonic wave horn 14 and the second ultrasonic horn 38 are used to vibrate the capillary 24 so that the capillary tip 21 draws a circle, and the ball portion is placed on the pad. When pressed, frictional heat was generated, and the ball portion was melted and fixed by the heat of the lead frame and the frictional heat. Further, the wire 26 was pressed and welded to the external lead corresponding to the pad while vibrating, and the wire 26 was cut by the clamper 28. Hereinafter, the same operation is performed for all the pads and the corresponding external leads, and the state shown in FIG. 3 is realized.

In the present embodiment, since the tip 21 of the capillary draws a circle, the welding ball 44 formed on the pad 19 is formed.
All have a perfect circular shape and the same outer diameter. Therefore,
Adjacent welded balls do not come into contact with each other,
The weld ball does not protrude from the pad 19.

[0026]

According to the present invention, the second vibrator that oscillates ultrasonic vibration, the base end is connected to the second vibrator, extends in the vibration direction of the ultrasonic vibration, and the first horn extends at the tip end. And a second horn which is formed as a rod-like body connected to the distal end of the first horn in a direction intersecting the distal end of the first horn, and which propagates ultrasonic vibrations along the rod-like body. Thereby, the vibration direction of the capillary can be switched, and the vibration direction can be selected according to the surface to be bonded of the body to be bonded. Therefore, the size and shape of the welded ball can be changed according to the arrangement direction of the surfaces to be joined.

According to the first invention method, the pads arranged in the X direction on the XY plane are made to vibrate the capillary in the Y direction by either the first horn or the second horn. Wire bonding is performed on the pads arranged in the Y direction by vibrating the capillary in the X direction by the other. As a result, the entire width of the welded ball formed on the pad is formed in a direction orthogonal to the arrangement direction. Therefore, the adjacent welding balls do not come into contact with each other.

Furthermore, according to the second invention method, the capillary is vibrated by the first and second horns in the XY plane so that the capillary tip traces a substantially circular locus, thereby performing wire bonding. As a result, the tip of the capillary draws a circle, so that all the welding balls formed on the pad are circular and have the same plane dimensions of the same diameter. Therefore, the adjacent welding balls do not come into contact with each other, and the welding balls do not protrude from the pad.

[Brief description of the drawings]

FIG. 1 is a partial perspective view showing an ultrasonic horn and a second ultrasonic horn of a wire bonding apparatus according to a first embodiment, and a semiconductor chip subjected to wire bonding.

FIGS. 2A and 2B are respectively an ultrasonic horn and a second ultrasonic horn of the wire bonding apparatus according to the first embodiment;
It is the top view of the ultrasonic horn, and the side view seen from arrow II.

FIG. 3 is a partial perspective view of a semiconductor chip wire-bonded in a second embodiment.

FIG. 4 is a perspective view showing an ultrasonic horn and a wire-bonded semiconductor chip of a conventional wire bonding apparatus.

FIG. 5 is a side view showing a configuration of an ultrasonic horn of a conventional wire bonding apparatus.

[Explanation of symbols]

Reference numeral 10: wire bonding apparatus, 12: bonding head section, 14: ultrasonic horn, 16: semiconductor chip, 18: bonding arm, 19, 19B1,
19B2 ... pad, 19A ... X direction arrangement pad, 1
9B: Y direction arrangement pad, 20: First vibrator, 21
… Capillary tip, 22… First horn, 24… Capillary, 26… Wire, 28… Clamper, 32…
... lead frame, 33 ... external lead, 36 ... wire bonding device, 38 ... second ultrasonic horn, 40
... Second vibrator, 42... Second horn, 44.

Claims (5)

[Claims] 1. A vibrator that oscillates ultrasonic vibration, and a rod-shaped body connected to a vibrator (hereinafter, referred to as a first vibrator) at a base end and extending in a vibration direction of the ultrasonic vibration. (Hereinafter, referred to as a first horn) that propagates ultrasonic vibration along the horn, and a capillary that is attached to the tip of the horn and has a through-hole. In a wire bonding apparatus that generates frictional heat by pressing the tip of a wire against an object to be bonded while oscillating the sound, another vibrator that oscillates ultrasonic vibration (hereinafter referred to as a second vibrator) ), Connected to the second vibrator at the base end, extended in the vibration direction of the ultrasonic vibration while reducing the diameter toward the front end, and moved in the direction intersecting the front end of the first horn at the front end. A rod connected to the tip of one horn Formed Te, another horn which propagates ultrasonic vibration along the rod-like body (hereinafter, referred to as a second horn) and a wire bonding apparatus characterized by comprising a. 2. The second horn extends in the same direction as the first horn, curves at the tip toward the tip of the first horn,
The wire bonding apparatus according to claim 1, wherein the wire bonding apparatus is connected. 3. The wire bonding apparatus according to claim 2, wherein the angle between the tip of the first horn and the tip of the second horn is substantially a right angle. 4. A method for performing wire bonding to a semiconductor chip having objects to be bonded arranged in an X direction and a Y direction in an XY plane using the wire bonding apparatus according to claim 3. The first horn or the second horn
Wire bonding by vibrating the capillary in one of the horns in the Y direction to perform wire bonding, and performing wire bonding by vibrating the capillary in the X direction by the other to the bonded objects arranged in the Y direction. Method. 5. A method for performing wire bonding to a semiconductor chip having objects to be bonded arranged in an X direction and a Y direction in an XY plane using the wire bonding apparatus according to claim 3, A wire bonding method, characterized in that the capillary is vibrated by the first and second horns so that the tip of the capillary draws a substantially circular trajectory to perform wire bonding.