JPS6256657B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a variable load mechanism in a wire bonder for wire bonding semiconductor components.

Wire bonding work is done on bonding surface 2.
When connecting points with wires, the following three bonding conditions are used in most cases. The first is when the first bond point is a pellet and the second bond point is a lead, the second is when the first bond point is a lead and the second bond is a pellet, and the third is when the first bond point is a lead and the second bond point is a pellet. This is a case where both the point and the second bond point are leads. In this case, since the bonding conditions for pellets and leads are different, optimal bonding cannot be achieved unless the bonding load is changed.

Conventionally, as shown in Japanese Patent Application Laid-open No. 53-60569, in a device in which the vertical movement of a capillary is driven by a cam, the tension of the bonding load spring is controlled by the tension of the arm driven by the two-stage load cam. A mechanism is known in which the first bond point and the second bond point are made variable depending on the stroke. however,
In this mechanism, the load at the first bond point and the second bond point can be changed, but the load at the first bond point and the second bond point will be constant at the set load, so the first bond point will always be Pellet (or lead): The second bonding point must always be a lead (or pellet) for bonding. As described above, since the load cannot be set for each bonding point, there are disadvantages in that the samples that can be bonded are limited and the bonding order is also limited. Furthermore, in the case where three bonding conditions are combined in one sample as described above, bonding must be carried out in two or three steps, which has the disadvantage of poor workability.

These drawbacks can be overcome by using a wire bonder that controls the vertical movement of the capillary by measuring the amount of rotation of the motor with an encoder, as disclosed in, for example, Japanese Patent Application Laid-Open No. 54-154273. In this structure, the motor is further rotated after the capillary contacts the bonding surface, and the bonding load is changed by controlling the amount of rotation of this motor. In this way, the bonding load can be arbitrarily set for each bond point. However, the magnitude of the bonding load is determined by the amount of extension and the spring constant of the bonding load spring. However, due to the bonding speed, it is not preferable to increase the rotation amount of the motor to increase the elongation of the spring due to load changes, so it is necessary to increase the spring constant. When the spring constant is increased,
Even a slight elongation causes a large change in load, but the following drawbacks occur. In other words, if the bonding part is floating from the sample stage of the frame feeder due to warping of the lead frame, etc., the position where the capillary contacts the bonding surface and the load of the capillary applied to the bonding surface will cause the warpage. The amount of extension of the spring changes by the difference in the lowered position of the capillary to compensate for this, so if the spring constant is large, the actual applied load will be smaller than the predetermined setting amount. Because of this variation in load, bondability deteriorates.

The present invention was made in view of the above-mentioned drawbacks of the prior art, and it is an object of the present invention to provide a load variable mechanism for a wire bonder that can set the best bonding load for each bonding point.

Hereinafter, the present invention will be explained with reference to illustrated embodiments.

FIG. 1 is a partially sectional side view showing an embodiment of the apparatus according to the present invention, and FIG. 2 is a sectional view taken along the line 2--2 in FIG. A bonding arm 11 holding a capillary 10 at one end is rotatably attached to a support shaft 1 via a bearing 14 to a head frame 13 fixed to an XY feeder 12 that moves in the XY direction.
It is fixed at 5. A cylindrical portion 13a concentric with the support shaft 15 projects inward from the head frame 13, and a drive block 17 is rotatably mounted via a bearing 16. The driving block 17 includes an insulating block 19 holding a contact rod 18.
is fixed, and the bonding arm 11 is attached to the support shaft 15.
The contact rod 18 is biased counterclockwise by a spring 22 applied to the hook 20 of the drive block 17 and the hook 21 of the drive block 17. Further, a clamp arm 24 holding a clamper 23 is fixed to the drive block 17. The clamp arm 2
4 has a boss 26 fixed thereto facing the upper surface of the bonding arm 11 and having a contactor 25 slidably provided thereon. The contactor 25 is urged toward the bonding arm 11 by a spring 27, and the pressure can be adjusted by turning a screw 28 screwed into a boss 26.

A rotary encoder 3 is installed in the head frame 13.
0 is fixed, and the output shaft of this motor 31 has a male screw 3 that is rotatably supported on the head frame 13 via a bearing 32 at one end.
3 and joint 34. A female thread block 35 is screwed into the male thread 33,
A bearing 37 attached to a pin 36 fixed to the female thread block 35 is slidably fitted into a vertical groove 13b provided in the head frame 13 so that the female thread block 35 can move vertically but not rotate. There is. Further, a pin 39 to which a bearing 38 is attached is fixed to the female thread block 35, and the bearing 38 is held between two connecting pins 41 and 42 fixed to a drive arm 40 fixed to the drive block 17. There is.

Further, a spool lever 50 is attached to the head frame 13.
is fixed, and a spool 52 around which a wire 51 is wound is attached to the end of the spool lever 50. The wire 51 wound around the spool 52 is inserted into the capillary 10 through the guide pipe 53 and the clamper 23. Further, the lead frame 61 with pellets 60 attached thereto is guided and transported by a frame feeder 62.

Next, the operation of this apparatus having such a configuration will be explained with reference to FIG. Before wire connection, as shown in FIG. 3a, the capillary 10 is located above the bonding surface, and the tip of the wire 51 protrudes from the tip of the capillary 10. In this state, the bonding arm 11 is brought into contact with the contact rod 18 by the biasing force of the spring 22, and the contactor 25 is separated from the bonding arm 11. And XY
When the head frame 13 is moved on a plane by the feeder 12 and the capillary 10 is positioned above the first bond point, the motor 31 rotates. The rotation of the motor 31 causes the female screw block 35 to move upward in the direction of arrow A. Since the drive arm 40 is fixed to the drive block 17, when the female screw block 35 moves upward in the direction of arrow A, the drive block 17 moves the bearing 38, the connecting pins 41 and 42, and the drive arm 4.
0, the clamper 23 attached to the contact rod 18 and the clamp arm 24 descends. When the contact rod 18 is lowered, the bonding arm 11 is rotated in the direction B about the support shaft 15 while being in pressure contact with the contact rod 18 due to the biasing force of the spring 22, and the capillary 10 is lowered.

In this way, the capillary 10 descends and the third
As shown in Figure b, the moment the capillary 10 hits the bonding surface, the contact rod 18 is slightly separated from the bonding arm 11, and as a result, the bonding arm 11 and the contact rod 18 are no longer electrically conductive.
The height of the bonding surface is detected. In this state, the contact 25 is still separated from the bonding arm 11. Therefore, the pressing force with which the capillary 10 presses the bonding surface is the biasing pressure (first load) by the spring 22. Therefore, if a small bonding load (first load) is sufficient at the first bonding point, the wire 51 is bonded to the first bonding point using the capillary 10 in this state. If the bonding load at the first bonding point requires a larger load than the first load, the contact rod 18 is attached to the bonding arm 1.
By presetting the count number of the rotary encoder 30 based on a detection signal distant from 1, that is, a signal when the capillary 10 is in contact with the bonding surface, the motor 31 is further rotated by the preset rotation amount. As a result, as shown in FIG. 3c, the drive block 17 further rotates in the direction B while the capillary 10 remains in contact with the first bonding point, and the contact 25 descends and contacts the bonding arm 11, causing the stopper portion of the contact 25 to come into contact with the bonding arm 11. A gap is opened between the stopper portion 25a and the stopper portion 26a of the boss 26, and the biasing pressure (second load) of the spring 27 is applied to the bonding arm 11, that is, the capillary 10. The pressing force on the capillary 10 at this time is the first load by the spring 22 and the spring 2
This is the load obtained by adding the second load of 7. The amount of rotation of the motor 31 for applying the second load is determined by the amount of clearance between the bonding arm 11 and the contact 25.

After bonding the first bond point, motor 3
1 rotates in the opposite direction to the above, and the capillary 10 rises. This amount of increase is determined by the distance (wire length) to the second bond point. Subsequently, in the same manner as described above, the capillary 10 is moved in a plane by the XY feeder 12 and positioned above the second bond point. Next, the motor 31 rotates and the capillary 10
is lowered, and the second bond point is bonded to the second bond point in the state shown in FIG. 3b or 3c, as described above, depending on the bonding conditions of the second bond point. This completes the wire connection work. Then, when moving on to the next connection operation, the capillary 10 rises, but at this time the clamper 23 closes and cuts the wire 51. Here, the above-mentioned capillary 1
0. The vertical amount of the clamper 23, that is, the amount of rotation of the motor 31, is measured and controlled by the rotary encoder 30.

In the above embodiment, the contactor 25 biased by the spring 27 is attached to the clamp arm 24, but the contactor 25 may be attached to a portion of the drive block 17 by extending a portion thereof. Although the contactor 25 is disposed above the bonding arm 11 and the contact rod 18 is disposed so as to be in pressure contact with the lower surface of the bonding arm 11, the bonding arm 11 is extended to the other side of the support shaft 15, and this extension is Contact 25 below the
Further, the contact rods 18 may be respectively disposed so as to be in pressure contact with the upper surface of the extending portion. Also, the support shaft 15
was attached to the head frame 13, but the drive block 17
It may be rotatably mounted on the Further, the drive block 17 is not limited to swinging, but may be configured to be vertically movable. Further, the height of the bonding surface may be detected by an optical detection method using a photo sensor or a sonic detection method using a microphone. Also, the rotary encoder 30 measures the vertical amount of the capillary 10.
A linear encoder or the like may be used instead.

As is clear from the above explanation, according to the variable load mechanism in the wire bonder of the present invention, the load of the contactor biased by the spring is applied to the bonding arm by the rotation of the motor after the capillary hits the bonding surface. Since the magnitude of the load can be freely set for each bonding point, good bonding can be performed on a wide variety of samples. Furthermore, since the spring constant of the bonding load spring that acts when the capillary is in contact can be made small, even if the bonding part is floating due to warping of the frame, etc., the variation in the bonding load is extremely small, and bondability is improved.

[Brief explanation of the drawing]

Fig. 1 is a partially sectional side view showing an embodiment of the variable load mechanism according to the present invention, and Fig. 2 is a 2-2 in Fig. 1.
The line sectional views and FIGS. 3A, 3B, and 3C are explanatory views of the operation. 10... Capillary, 11... Bonding arm, 17... Drive block, 24... Clamp arm, 25... Contact, 27... Spring, 30...
...Rotary encoder, 31...Motor, 51
...Wire.

Claims (1)

[Claims] 1. A bonding arm that holds a capillary through which a wire is inserted and is swingably provided; a drive block that swings this bonding arm;
In the wire bonder, the wire bonder includes a motor with an encoder that swings or moves the drive block up and down, and a contact for varying the load disposed opposite to the bonding arm, wherein the contact swings the bonding arm. The drive block or a member integrated with the drive block is movable up and down, and is biased toward the bonding arm by a spring. A load on a wire bonder that is located a certain distance away from the bonding arm and is arranged so that the capillary comes into contact with the bonding arm by swinging or vertical movement of the drive block due to the rotation of the motor after the capillary comes into contact with the bonding surface. Variable mechanism.