JP2539963B2 - Wire bonding apparatus and wire bonding method - Google Patents

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 a wire bonding method for connecting a semiconductor chip and an object to be connected such as an external lead with a fine metal wire.

[0002]

2. Description of the Related Art FIGS. 4 and 5 show, for example, Japanese Patent Laid-Open No. 61-113250.
FIG. 3 is a schematic side view of a conventional wire bonding apparatus and an explanatory view showing a wire bonding method in the order of operation, which is disclosed in Japanese Patent Publication No. In FIG. 4, reference numeral 1 is a wire bonding apparatus, which is configured as follows. The capillary 2 is provided with a clamp means 3 for sandwiching the wire 6 thereabove, and a bobbin 7 which is arranged on the upper part and which feeds and supplies the wire 6. Reference numeral 8 is a guide for the wire 6.

A wire 2 is passed through the capillary 2 and is moved up and down by an up / down moving means (not shown). The clamp means 3 is moved up and down by a vertically moving means (not shown), and the wire 6 is clamped and released by an opening / closing means (not shown).

Next, a wire bonding method using the wire bonding apparatus 1 will be described with reference to FIG. First, in FIG. A, the clamp means 3 clamps the wire 6, and the tip of the wire 6 is taken out from the lower portion of the capillary 2 to form a sphere 6a. The lead frame 5 is fixed on a stage (not shown), and the semiconductor chip 4 is fixed on the lead frame. 4a is an electrode of the chip 4, 5a is an external lead, and 5b is an electrode portion. The electrode 4a is located directly below the capillary 2.

Continuing, as shown in FIG.
After the pinching is released, the capillary 2 is lowered and pressed against the electrode 4a and heated to press the tip of the wire 6 to the electrode 4a.
Then, the capillary 2 is raised, and the stage is moved to move the capillary 2 and the clamp means 3 relatively in parallel to the stage as shown in FIG.
It is located above the electrode portion 5b of 5a. By this movement, the wire 6 is paid out by a predetermined length.

After that, the capillary 2 is lowered, and the wire 6 is clamped by the clamp means 3 as shown in FIG.
The clamp means 3 is lowered together with the capillary 2, and the capillary 2 is pressed against the electrode portion 5b and heated to press the wire 6 in the middle to the electrode portion 5b.

Subsequently, as shown in Fig. E, the clamping of the clamping means 3 is released, and the ascending of the capillary 2 is started. As shown in FIG. F, the wire 6 is clamped by the clamp means 3 while the capillary 2 is being raised. Further, the clamp means 3 is raised together with the capillary 2 as shown in FIG. As a result, the wire 6 is cut from above the pressure-bonded portion to the electrode portion 5b, and the chip 4 and the external lead 5a are wire-bonded.

Finally, as shown in Fig. H, the tip of the wire 6 is heated by the hydrogen torch 9, and as shown in Fig. I, the tip of the wire 6 is formed into a sphere 6a, which is completed.

The clamping timing of the clamp means 3 is adjusted by a so-called matching cam using two cams, and the length of the wire 6 and the rising height of the capillary 2 are taken into consideration while the capillary 2 is descending. I try to pinch it.

When the capillary 2 is raised in the state shown in FIG. 5C, the wire 6 may bend between itself and the clamp means 3 as shown in FIG. 6 to cause slack 6d. this is,
This is because the wire 6 is extremely fine and soft and is pushed up by the frictional resistance in the capillary 2. Therefore, the slack of the proper loop 6b formed by using the entire length H of the wire 6
The short loop 6c is shortened by 6d. This short loop
At 6c, the middle portion comes into contact with the corner of the semiconductor chip 4 and short-circuits. Further, as shown in FIG. 7, the wire 6 may be strongly pulled by the short loop 6c, and may be bent and cut on the connection portion of the electrode 4a.

Further, since the wire 6 is strongly clamped by the clamp means 3, the wire 6 made of gold fine wire or aluminum fine wire is used.
In addition, the constriction may cause a constriction with a reduced cross section. FIG. 8 is a plan view showing the state in which the constriction is located in the loop of the wire 6. 6e is this constriction.

[0012]

In the conventional wire bonding apparatus 1 and wire bonding method as described above, the loop of the wire 6 formed by wire bonding between the first and second bond points becomes a short loop 6c. However, there is a problem in that the loop may come into contact with a corner of the semiconductor chip 4 and short-circuit, or the wire may be bent and cut on the connection portion of the electrode 4a. Further, since the wire 6 is rapidly and strongly clamped by the clamp means 3, there is a problem that a constriction 6e may occur.

Further, when the wire 6 is clamped by the clamp means 3 in the state of FIG. 5D, there is a variation in the clamping completion time, so that the length of the wire 6 forming the loop can vary, and the length can be uniform. There is a problem that it is difficult to obtain a proper loop shape.

The present invention has been made in order to solve such a problem, and a wire between the first bond point and the second bond point is formed in a proper loop, and the loop is connected to one of the connected points on the way. (EN) A wire bonding apparatus and a wire bonding method which do not contact an object or cut a wire on a connection portion of a first bond point, and which does not cause a constriction due to strong clamping of a wire by a clamper means. The purpose is to get.

[0015]

A wire bonding apparatus and a wire bonding method according to the present invention perform a wire bonding cycle operation while a wire is always clamped by a clamper to lower a capillary at an initial stage of a process. At the predetermined height position, the wire is slipped and pulled down weakly, and in the process after the connection at the first bond point, the clamper holds the wire and clamps the wire. And the clamper are moved above the second bond point, and the completion of the descent of the capillary onto the second bond point is delayed with respect to the completion of the descent of the clamper. After the connection at the second bond point, the capillary started to rise, and the clamper started to rise later than this.

[0016]

In the present invention, the wire is always clamped by the clamper, and damage caused by impact applied to the wire is eliminated by repeating clamping and opening. Further, there is no variation in the time until the wire is clamped, the slack of the wire between the clampers due to the rise of the capillary after the connection at the first bond point is eliminated, and the wire below the cavity is made to have a predetermined length. The wire loop can be formed into an appropriate shape by the connection at the second bond point, the middle part of the loop contacts one object to be connected, or the wire is pulled and cut on the connection part at the first bond point. Disappears.

[0017]

1 is a schematic block diagram of an embodiment of a wire bonding apparatus according to the present invention. The wire bonding device 10 is configured as follows. A bonding head body 11 is fixed on the XY table 12. The XY table 12 is moved in the X-axis direction by an X-axis electric motor 13 via X-axis drive transmission means (not shown),
Further, it is moved in the Y-axis direction by the Y-axis electric motor 14 via Y-axis drive transmission means (not shown). The capillary 2 is attached to the tip of the ultrasonic horn 15,
Reference numeral 15 is an intermediate portion of the head body 11 which is rotatable via a support pin 16.
Supported by. A clamper 17 for sandwiching the wire 6 is attached to the tip of a support arm 18, and the support arm 18 is rotatably supported by the head body 11 via a support pin 19 at an intermediate portion. Reference numeral 20 is a first Z-axis electric motor, which is a first vertical movement transmission means 21.
It is connected to the rear end part of the ultrasonic horn 15 via and is moved up and down. As a result, the ultrasonic horn 15 is rotated around the support pin 16 to move the capillary 2 up and down. A second Z-axis electric motor 22 is connected to the rear end portion of the support arm 18 via the second vertical movement transmission means 23 and is moved up and down. As a result, the support arm 18 is rotated about the support pin 19 and the clamper 17 is moved up and down. First and second vertical movement transmission means 21
And 23 are configured, for example, as follows. A lower end portion of a link 26 is connected to a connecting body 24 fixed to shaft ends of the electric motors 20 and 22 via a connecting pin 25. Link
Reference numeral 26 is connected to the rear end of the ultrasonic horn 15 and the rear end of the support arm 18 via rollers 27 at the upper end.

Next, 28 is a guide body which is attached to the head main body 11 and guides the wire 6, and 29 is a wire spool around which the wire 6 is wound and which is pulled out. Reference numeral 30 is a torch such as hydrogen for forming the spherical body 6a of the wire 6 in the lower portion of the capillary 2.

The clamper 17 is shown in FIG. Reference numeral 31 is a fixed piece, and 32 is a movable piece rotatably supported by the fixed piece 31 via a support shaft 33, and the wire 6 is passed vertically between them. 34 is an exciting coil and 35 is a yoke. When the exciting coil 34 is energized, the movable iron piece portion at the rear end of the movable piece 32 is attracted,
The movable piece 32 is closed and the wire 6 is clamped. When the power supply is cut off, the movable piece 32 is opened by the return spring (not shown). By switching the current to the exciting coil 34 between two levels, weak and strong,
The clamping force is that the wire 6 can be pulled out smoothly and the first step is weak clamping and the wire 6 is fixed (not deformed).
The strong clamping of the second step is performed.

Returning to FIG. 1, 40 is a stage which adsorbs the lead frame 42 on the upper part thereof, and the semiconductor chip 41 is fixed on the lead frame 42. 41a is an electrode of the chip 41, which forms the first bond point. 42b is an electrode portion of the external lead 42a of the lead frame 42.

A wire bonding method using the wire bonding apparatus 10 will be described with reference to FIG. Clamper
No. 17 performs a clamping operation during all the steps. In the steps shown in A and B, the wire 6 is clamped in a weak first step, and in the steps shown in C to H, the wire 6 is fixed. Strong holding held (however, the wire 6 is not deformed,
Hatched). First, in FIG.
The clamper 17 clamps the wire 6 in the first stage, and the tip of the wire 6 is taken out from the lower portion of the capillary 2 to form a sphere 6a. The capillary 2 and the clamper 17 are located above the electrode 41a.

Subsequently, as shown in FIG. B, the capillary 2 is lowered and the clamper 17 is clamped at the switching position h of the force.
Descend to height. Capillary 2 is electrode 41a of chip 41
When it descends to the upper position, the ultrasonic horn 15 oscillates ultrasonic waves to perform the first bonding. Clamper during this bonding
Switch the clamping force of 17 to the 2nd step. When the bonding is completed, the capillary 2 is raised to the height h ₁ as shown in FIG. This h1 is the length necessary for connecting the wire 6 with a proper loop. h becomes h ₁ + h ₂ .

Next, as shown in FIG. D, the capillary 2 and the clamper 17 are connected to the electrode section in the Y-axis direction by the XY table 12.
42b Moves upward, and at the same time, descends. At this time, as shown in FIG. E, the clamper 17 completes the descent to the predetermined position faster than the capillary 2. The height h ₂ of the clamper 17 in this state is the sum of the distances h ₃ and h ₄ . Wire 6
Is extruded below the capillary 2, and the length of the wire bending portion 6f is the length h ₁ required for connection with a proper loop added with h ₄ .

Next, as shown in FIG. F, the capillary 2 is lowered onto the electrode portion 42b of the external lead 42a, ultrasonically oscillated by the ultrasonic horn 15, and second bonding is performed to form the loop 6b of the wire 6. The distance between the capillary 2 and clamper 17 is h
_2, and it has not bend the wire 6 between the both. In E Figure, even if slack in the wires 6 between the clamper 17 and the capillary 2 is generated by only the capillary 2 is lowered h ₄ length can be extended slack.

Subsequently, as shown in FIG. 6G, the capillary 2 is raised to a height where the wire 6 has a protruding length m, and then the clamper 17 is also started to rise. This protrusion length m is
The length is necessary to form the sphere 6a on the wire 6.
Thus, the wire 6 is cut off on the second bonding portion. Further, as shown in the diagram H, the clamper 17 and the cavity 2
And are elevated while keeping an equal distance, and the torch 30 forms the sphere 6a on the wire 6.

As described above, one cycle of wire bonding is performed by a series of operations.

Although the semiconductor chip 41 and the external lead 42a are wire-bonded in the above embodiment, the present invention is not limited to this and can be applied to wire-bonding an object to be connected such as between other kinds of electronic components. Is.

Further, in the above embodiment, the mechanism using the electric motor as the driving source is used as the vertical movement driving means for the capillary 2 and the clamper 17, but the present invention is not limited to this. Good.

[0029]

As described above, according to the present invention, the wire is always clamped by the clamper during the bonding cycle operation, and the clamper is made to have a weak clamping force before the first bonding in the initial stage of the process. Since a strong clamping force is applied thereafter, the impact of the clamping is eliminated and abnormal wire deformation is eliminated. Further, at the time of the second bonding, since the timing of the completion of the lowering of the capillary is delayed with respect to the completion of the lowering of the clamper to the predetermined height position, an appropriate loop of the wire can be formed and the connection can be made. The intermediate portion does not contact with one of the objects to be connected and short-circuited, or the wire is not cut on the first bonding portion. Further, after the second bonding, the start of the rise of the clamper is delayed with respect to the start of the rise of the capillaries so that the rise of the capillaries is not stopped halfway, so that a wire protrusion with a stable length can be formed below the capillaries. , 1 cycle time of wire bonding is shortened. In this way, the quality and productivity of wire bonding are improved.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an embodiment of a wire bonding apparatus according to the present invention.

FIG. 2 is a perspective view of the clamper shown in FIG.

FIG. 3 is an operation explanatory diagram of a wire bonding method by the apparatus of FIG.

FIG. 4 is a configuration diagram of a main part of a conventional wire bonding apparatus.

5 is an operation explanatory view of a wire bonding method by the apparatus of FIG.

FIG. 6 is an explanatory view showing a loop formation of a wire between the first and second bonding portions by a conventional method.

FIG. 7 is an explanatory diagram showing a wire bending accident on the first bonding portion in the case of the short and small loop of the wire of FIG. 6;

FIG. 8 is a plan view showing a constricted portion formed on a wire when the clamp means is clamped by a conventional method.

[Explanation of symbols]

 2 Capillary 6 Wire 6a Sphere 6b Appropriate loop 11 Bonding head body 12 XY table 15 Ultrasonic horn 17 Clamper 18 Support arm 20 1st Z axis electric motor 21 1st vertical movement transmission means 22 2nd Z axis electric motor 23 2nd Vertical movement transmission means 29 Wire spool 41 Semiconductor chip 42 Lead frame 42a External lead

Continuation of the front page (56) References JP-A-50-55265 (JP, A) JP-A-55-138245 (JP, A) JP-A-63-124435 (JP, A) JP-A-2-45943 (JP , A) JP 60-57223 (JP, B2)

Claims (2)

(57) [Claims] 1. An ultrasonic horn, which is vertically movably supported by a bonding head body on an XY table, is fixed to the tip of the ultrasonic horn, and is raised and lowered by a first vertical movement drive means. A capillary having a wire penetrating from above, fixed to the tip of a support arm arranged above the capillary and vertically movably supported by the bonding head main body, and moved up and down by a second vertical movement drive means. The wire pulled out from the upper wire spool is passed through and a clamper for guiding the capillary is provided. This clamper can be switched to a two-step clamping force of weak and strong, and is always The wire is clamped, and in the bonding cycle operation, the above-mentioned until the capillary in the initial stage descends to the first bond point of the connected object. The wire bonding apparatus is characterized in that the clamper clamps the wire with a weak clamping force and is switched to a strong clamping force after the first bonding to continue the clamping of the wire. 2. A wire is sandwiched by a clamper at a predetermined height position with a weak clamping force, a capillary is positioned below the clamper at a predetermined distance, and a wire sphere is formed below the capillary. The first step of bringing the capillary to a position above the first bond point of the object to be connected, and the clamper holding the wire with a weak holding force are lowered to a predetermined position,
The second step of lowering the capillary to the first bond point and performing the first wire bonding, and switching the clamper to a strong clamping force during the first wire bonding, and after the first bonding, the wire forms an appropriate loop in the capillary. A third step of raising to a height corresponding to the length required to
A fourth step in which the capillary and the clamper are horizontally moved to a position above the second bond point, and at the same time, both are lowered to delay the completion timing of the descent of the capillary to the second bond point relative to the completion of the descent of the clamper to the predetermined height position. Then, the fifth step of performing the second bonding while the capillary is lowered to the second bond point, and the raising of the capillary after the second bonding is started, and the clamper is raised when the wire extends below the capillary for a predetermined length. Starting the sixth step of cutting the wire on the second bonding part, and the sixth step of setting the capillary and clamper.
A wire bonding method according to the seventh step of forming a sphere on a wire that has risen to a predetermined height position while maintaining the distance of the step and has come out from the lower part of the capillary.