JPH0141023B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a bonding method and apparatus for suspending a wire between an IC pellet and a lead.

To bond between the pads and leads of an IC chip, use a bonding tool (for example, a cavity for ball bonding for gold wire, or a stitch bonding tool for aluminum wire) installed at the tip of the bonding arm of the bonding device. The wire is held with a wedge) and brought into contact with the surface of the target pad or lead, a part of the wire is crushed with a bonding tool, and the wire is crimped by thermal compression or welded by the action of ultrasonic waves.

For example, a case will be described in which a ball 3 formed at the tip of a wire 2 is bonded to a pad 5 of an IC pellet 4 using a cavity 1 as shown in FIG. 6 is a lead to be connected to pad 5.

First, the cavity 1 is positioned at a certain height directly above the pad 5 as shown in FIG. At this time, a ball 3 is formed at the tip of the wire 2. t ₀ is the height of the ball 3 at the portion protruding from the lower end 7 of the cavity 1 . Next, the cavity 1 is lowered to bring the ball 3 into contact with the pad 5 as shown in FIG.
t ₁ is the amount of crushing, and t ₂ is the thickness of the flat portion 8.
This squeezing action provides a pressing force necessary to fix the wire 2 to the pad 5, and also forms a flat portion 8 to ensure a sufficient contact area for electrical contact. Thereafter, the cavity 1 is moved upward and horizontally to position it above the lead 6 to be bonded, as shown in FIG. The wire 2 is crushed to form a flat part 9 and fixed to the lead 6, the wire 2 is pulled and cut from the end of the flat part 9, and then the cavity 1 is raised to complete one bonding process. Thereafter, a ball 3 is formed at the tip of the wire 2 using a torch, and the state shown in FIG. 1 is returned to for the next bonding. t′ ₀ is the diameter of wire 2, t′ ₁ is the amount of compression,
t′ ₂ is the thickness of the flat portion 9.

In addition to the above-mentioned cavity bonding,
For example, even in the case of wedge bonding (used for Al wire), a portion of the wire 2 is crushed in order to obtain pressing force and contact area.

In either case, there is a suitable and preferable range for the pressing force and the thicknesses t ₂ and t' ₂ of the flat portion 8. For example, if the pressing force is too small, the pressure necessary for fixation will not be produced and the contact area will be insufficient, while if the pressing force is too large, the pads 5 and pellets 4 will be damaged.

A conventional example of this type of bonding apparatus is shown in FIG. Reference numeral 10 denotes an ultrasonic transducer, which is swingably supported on a frame 11 by pins 12. 13 is a horn, with a cavity 1 at the tip.
is provided and also functions as a bonding arm. A lever 14 is provided at the other end of the vibrator 10, and a roller 15 provided at the end is connected to a cam 16.
A counterclockwise moment is applied by the spring 17 so as to make contact with. 18 is a reel for the wire 2; 19 is a clamp for gripping and cutting the wire 2; 20 is a half clamp for pulling up the ball and bringing it into contact with the lower end 7 of the cavity 1; 21 is a ball 3 (first It is a torch for making a torch (see Figure), and is rotatable around a vertical axis 22. 23 is a position detection device;
The deviation of the pellet 4 and each pad 5 (FIG. 1) from the standard position is detected. Depending on the detected value of this deviation, the frame 11 or the pellet 4 is moved horizontally in the X or Y direction to adjust the relative position between the cavity 1 and the pad 5 of the pellet 4 for alignment.

In such a conventional device, the vertical movement of the cavity 1 is determined by the shape of the cam 16, and cams must be prepared and replaced for different vertical patterns corresponding to different types of pellets 4. Furthermore, there is a drawback that it is not possible to accommodate errors in dimensions such as the thickness of the pellet 4, the diameter of the ball 3, and the diameter of the wire 2, so that appropriate pressing force and contact area cannot be obtained.

Also, instead of using the cam 16, there is a system that uses a screw shaft driven by a motor equipped with an encoder to move the bonding arm up and down.
By simply regulating the amount of overrun descent of the elevating frame after the cavity 1 contacts the pad 5,
Since there is no restriction on the amount by which the bonding arm is pressed by a spring (for example, spring 17) that biases it, there is a risk that the pressing force may be too large or too small, or that the contact area may be too large or too small.

Further, if the size of the ball 3 is too small, proper bonding cannot be performed, but this abnormality is not discovered, resulting in defective bonding.

The inventors have conducted repeated research to improve these drawbacks, and have focused on the fact that pressing force, contact area, etc. are related to the amount of crushing, and have come up with the present invention.

The present invention is a bonding method that is less affected by dimensional errors such as wire diameter and ball diameter, is easy to adjust even when pellet types and wire types are different, and can reliably perform highly reliable bonding. The purpose of this invention is to provide a device for the same.

A second object of the present invention is to provide a bonding method and apparatus that can prevent defective bonding by detecting an undersized ball or wire diameter by utilizing this squeezing amount detection. be.

In the present invention, a wire is bonded to an object by crushing a part of the wire at the lower end of a bonding tool provided at the tip of a bonding arm that is rotatably supported around a horizontal axis on a lift frame that can be raised and lowered. In the bonding method, a downward pressing force is applied to the bonding tool; after the elevating frame is lowered and a part of the wire comes into contact with the object, it continues to descend against the pressing force; , stopping the lowering after a predetermined distance from the point of contact, detecting the amount of crushing while crushing a part of the wire with the pressing force, and stopping the crushing operation when the predetermined amount of crushing is reached. A bonding method and apparatus for the same.

Embodiments of the present invention will be described using the drawings.

In FIG. 3, the elevating frame 24 is held movable up and down along the elevating guide 25 of the frame 11, and a female threaded portion 26 formed integrally with the elevating frame 24 is screwed into a threaded shaft 27. , and is driven up and down by a pulse motor 28 or a motor using an encoder. An ultrasonic transducer 10 is fixed to a swinging frame 30 which is rotatably supported by a pin 29 which is a horizontal axis in the lifting frame 24, and a capillary which is a bonding tool is attached to the tip of a horn 13 which acts as a bonding arm. 1 is provided. 31
is a leaf spring fixed to the lifting frame 24,
A counterclockwise moment is constantly applied to the swing frame 30 via the eccentric pin 32, and a downward pressing force is applied to the capillary 1 as a pressing force applying mechanism. By adjusting the eccentricity of the eccentric pin 32, the force of the leaf spring 31 can be adjusted. 33
is a stopper made of an electromagnet, which determines the lowest position of the capillary 1 relative to the lifting frame 24.

34 is a magnet sensor, and the swing frame 30
An output signal is sent to the control mechanism 37 in accordance with the relative distance between the permanent magnet and the chip 36 provided on the lever 35 attached to the lever 35, that is, the amount of deviation l of the center of the chip 36 with respect to the center of the magnet sensor 34. It's summery. That is, an output signal corresponding to the displacement of the capillary 1 in the vertical direction is sent to the control mechanism 37, and the capillary 1 relative to the vertical frame 24 is
It acts as a displacement detection mechanism that detects the vertical displacement of.

Therefore, the swing frame 30 is moved to the stopper 33.
When the capillary 1 is in contact with the lifting frame 24, that is, when the capillary 1 is at the lowest position with respect to the elevating frame 24, the amount of deviation l is not zero but a certain positive value _l0 . That is, a positive output signal is output at that position.

Cams 38 and 39 operate the clamp 19 and the half clamp, respectively, and are driven by pulse motors.

The operation will be explained with reference to FIGS. 4 and 5.

FIG. 4 is a schematic explanatory diagram, and the size of the ball 3 is shown exaggerated. First, assume that the capillary 1 is initially located at a height h above the pellet 4 directly above the pad 5 to be bonded, as shown in FIG. 4a. In FIG. 5, A is the time axis, and the time point in FIG. 4a above is indicated by _T1 . B is a lifting guide 25 of the lifting frame 24;
The vertical displacement is 0 at _T1 .
A dotted line B' indicates the vertical displacement of the capillary 1 with respect to the vertical guide 25. C indicates the relative deviation of the chip 36 with respect to the magnetic sensor 34, and is l ₀ at T ₁ . D is the height t of the portion of the ball 3 protruding from the lower end 7 of the capillary 1, which is t ₀ before being crushed and the thickness t ₂ of the flat part 8 after being crushed (squeezed amount = t ₂ ). show. During that time, when the amount of squeezing is e, the amount is t=t ₀ −e. At T ₁ , t ₀ and the amount of crushing is e=
It is 0. E is the deflection of the leaf spring 31, and an initial set of S ₀ is given. At _T1 , the initial set remains _S0 . F indicates energization for horizontal movement of capillary 1, T ₁
It is OFF. G indicates the excitation of the stopper 33, which is an electromagnet, and is OFF until reaching _T1 .

Next, the pulse motor 28 is driven to lower the elevating frame 24. At first, we made a high-speed descent,
When the lower end of the ball 3 approaches the top of the pad 5 (for example, about 0.2 mm), the speed is changed to low. This switching point is defined as _T2 , and the downward displacement Z at this time is measured downward and has Z= _Z1 . During the maximum descent, the horn 13 swings to prevent the capillary 1 from unnecessarily vibrating, as shown in FIG. 5G, by exciting the stopper 33 and attracting it to prevent vibration.

Then, the lowering speed is set to a low speed, and the ball 3 descends further, and the time point at which the lower end of the ball 3 contacts the pad 5 as shown in FIG. 4b is defined as _T3 . The downward displacement at this time is Z=
If Z ₀ , then Z ₀ = h−t ₀ . From this point of contact, scrubbing is started in the scrub-type thermocompression bonding method, and application of ultrasonic waves is started in the ultrasonic bonding method.

If the ball 3 continues to descend further, the ball 3 has already contacted the pad 5, so the capillary 1 does not descend and remains at the same height as indicated by the dotted line B', but the elevating frame 24 continues to descend as indicated by the solid line B. Then, the deviation l of the chip 36 gradually increases, and the output signal also increases accordingly. A contact time T ₃ is detected at the start of this increase, and counting of the number of pulses of the pulse motor 28 is started, and the amount of downward displacement after time T ₃ is determined from the counted number.

Next, by counting the corresponding set number of pulses, it is determined that the displacement amount _{Z 3 (} that is, Z ₃ = Z ₀ + Z _L ) has been reached, which is a predetermined downward distance Z _L from the contact point T 3 . It is detected and the lowering of the elevating frame 24 is stopped.

That is, a stop distance setting mechanism is formed by a displacement detection mechanism that detects the counting start time, a pulse counter, a stop pulse number setting mechanism control mechanism 37, and the like.

This stopping point is defined as _T5 . At this time, leaf spring 3
1 is the maximum deflection _S2 . The apparent deflection is S ₂ −S ₀ . The amount of descent Z _L after the contact point _T3 is determined by the set number of pulses of the corresponding counter, but it also depends on the material of the wire 2, the size of the ball 3, the set amount of the crushing amount e, the preferred value of the pressing force, etc. are selected taking into consideration. The amount of deviation is l=l ₂ .

At this point, the elevating frame 24 stops, but the ball 3 is crushed by the restoring force of the leaf spring 31. In FIG. 5D, the amount of crushing e is indicated by the distance between the horizontal line at t=t ₀ and the solid line D. In addition, as the ball 3 is crushed, the amount of deviation l decreases again, but the return deviation amount L, which is the decrease value from the maximum value l ₂ of the amount of deviation, is the horizontal line of l = l ₂ in Fig. 5C. It is indicated by the distance from solid line C. Since the return displacement amount L is proportional to the squeezing amount e, the squeezing amount e can be determined by detecting the return displacement amount L based on the output signal. The deflection S of the leaf spring 31 decreases again.

As shown in Fig. 4 d, in order to detect that the squeezing amount e has reached the predetermined squeezing amount t ₁ (see Fig. 1) using the set value L ₁ of the return displacement amount L, and to stop the squeezing operation. , stop scrubbing, stop applying ultrasonic waves, or raise the lifting frame 24 at high speed. The time point when the return deviation amount L reaches the set value _L0 is defined as _T6 . At this time, the amount of deviation is l=l ₁ (that is, l ₁ =l ₃ -L ₁ ), and the amount of deflection of the leaf spring 31 is S=S ₁ .

At time _T6 , the amount of pressing reaches a predetermined set value _t1 , and bonding is completed with appropriate pressing force and contact area.

In this way, the displacement detection mechanism, return deviation amount setting mechanism, control mechanism 37, and the like form a crushing amount setting mechanism.

This preferable set value t ₁ of the amount of squeezing e is selected depending on the material of the wire 2, the size of the ball 3, the preferable value of the pressing force, the preferable value of the contact area, etc.

The stopper 33 is energized at the start of high-speed ascent to prevent vibration of the capillary 1. During the ascent, the lower end ₇ of the capillary 1 leaves the upper end of the ball 3 (flat portion 8) at time T7, and the amount of deviation l returns to _l0 , and the amount of deflection S of the leaf spring 31 returns to _S0 . It continued to climb at high speed, and at an appropriate point, it started moving horizontally, and reached the position shown in Figure 4 e.
The state will be as follows. This point is designated as _T8 .

After that, while continuing to move horizontally, the elevating frame 24
is lowered again, and when the lead 6 reaches the position directly above the bonding position T ₉ , the lowering speed is switched to low speed, and after that, a part of the lead 6 is crushed in the same process as the crushing process of the ball 3 described above. Perform bonding while doing so. In this case, the preferred amount of compression t' ₁ (see FIG. 1) is determined by the diameter of the wire 2, the required pressing force, the required contact area, etc.

After bonding is completed, the wire 2 is cut from the end of the bonding point by moving the clamp 19 upward, the capillary 1 is raised, and the clamp 19
With the wire 2 protruding a predetermined length from the lower end 7 of the capillary 1, the capillary 1 is positioned directly above the next pad, and the torch 21 is used to form the ball 3. The ball 3 may be formed before reaching directly above the pad.

Frame 1 is used to move capillary 1 directly above a predetermined pad and a predetermined lead.
1 or pellets 4 may be placed on an XY table and relative movement in the X or Y direction within a horizontal plane may be performed.

The control mechanism 37 includes the following abnormality detection mechanism. That is, a timer is provided that starts when the lower end of the ball 3 contacts the pad 5 when the lifting frame 24 is lowered, and is sufficient to provide an appropriate amount of compression for the stroke of the ball 3 and the lifting frame 24 in a normal state. A certain amount of squeezing time is set, and an abnormal signal is generated when the amount of wire squeezing detected by the displacement detection mechanism using the magnetic sensor 34 does not reach the predetermined amount of squeezing even after this predetermined squeezing time has elapsed. , the bonding operation is stopped by this abnormal signal.

Since this embodiment is configured and operates as described above,
Squeezing amount e of a part of the ball 3 or wire 2
can be regulated by the crushing amount setting mechanism, so the optimal crushing amount can be obtained without being affected by errors in wire diameter, ball diameter, etc., and the pressing force and contact area can be set in a preferable range.
Good and reliable bonding can be performed. Furthermore, even if the pellet 4, lead 6, and wire 2 are changed and the working conditions change, the optimal crushing amount _t1 can be easily set accordingly, and bonding can be performed with good workability.

By adjusting the eccentricity of the eccentric pin 32, the optimal force of the leaf spring 31 can be selected.

Furthermore, since the above-mentioned abnormality detection mechanism is provided, if the dimensions of the ball 3 are too small, the crushing operation will stop before reaching the predetermined amount of crushing, so the timer will stop at the predetermined setting point. Even if , the squeezing amount detection value does not reach the predetermined squeezing amount. In this case, the abnormality detection mechanism stops the bonding operation based on the abnormality signal.
Thereby, it is possible to detect that the ball 3 is too small in size, and to prevent conduction failure or peeling off due to insufficient contact area of the ball 3.

If the time from contact point T ₃ to the lowest position Z = Z ₂ is extremely short compared to the deformation speed of crushing, crushing is considered to start from time T ₅ as explained above, but if T ₃ and If the crushing is started between T ₄ , e.g. T ₄ , the capillary 1 will be
Instead of B', the tip 36 is displaced as shown by the two-dot chain line B''. At that time, the movement of the tip 36 becomes as shown by the two-dot chain line C' in _FIG.
and T ₅ is the distance between the solid line C and the two-dot chain line C', and between T ₅ and T ₆ it is the distance between the horizontal line of l=l ₂ and the two-dot chain line C'. e', which corresponds to the amount of squeezing e, is the distance between the horizontal line at t= _t0 and the two-dot chain line D' in FIG. 5D. The deflection of the leaf spring 31 is indicated by a two-dot chain line E' instead of the solid line E in FIG. 5E.

The return displacement amount L' corresponding to the squeezing amount e' cannot be determined only from the actually measured detected value because the displacement amount l does not reach the maximum _l2 . Therefore, it is sufficient to calculate l ₂ from the stopping distance set value Z _L by geometric calculation, and then subtract the detected value of the two-dot chain line C' from l ₂ , and that L' becomes the return deviation amount set value L'. It is only necessary to know that the squeezing amount e′ has reached the squeezing amount set value t 1 when the squeezing amount e′ has reached the squeezing amount set value t ₁ .

The above is an example of capillary bonding, but the same applies to wedge bonding.

The pressing force applying mechanism is not limited to the leaf spring 31, and any mechanism that changes the pressing force depending on displacement may be used. For example, a moving coil may be used to apply a pressing force depending on the displacement. In this case, the pressing force can be changed by changing the applied voltage. For example, if the applied voltage is strengthened when the lifting frame 24 is rapidly lowered, it will be pressed strongly against the stopper 33, so that vibration of the bonding arm such as the horn 13 can be prevented. Therefore, there is no need for the stopper 33 to be an electromagnet, and it may be a simple solid piece, resulting in a simple structure.

According to the present invention, reliable and reliable bonding can always be performed with appropriate pressing force and contact area without being affected by errors in wire diameter, ball diameter, or variations in wire material. It is possible to provide a bonding method and a bonding apparatus that can easily set optimum conditions depending on the type, wire material, size, ball size, etc., and can achieve extremely great practical effects.

[Brief explanation of drawings]

Figures 1a, b, c, and d are explanatory diagrams of bonding processes, Figure 2 is a front view of a conventional bonding device, and Figure 3 is a partially sectional front view of a bonding device according to an embodiment of the present invention. Figures 4a, b, c, d, and e are explanatory diagrams showing the operating steps, and Figure 5 is a diagram showing the operation of each part during the process. 1... Capillary, 2... Wire, 3... Ball, 4... Pellet, 5... Pad, 6... Lead, 7... Lower end, 8... Flat part, 9... Flat part, 10... Vibrator, 11...Frame, 12...
...Pin, 13...Horn, 14...Lever, 15
...Roller, 16...Cam, 17...Spring, 18
... Reel, 19 ... Clamp, 20 ... Half clamp, 21 ... Torch, 22 ... Vertical axis, 2
3...Position detection device, 24...Elevating frame, 2
5...Lifting guide, 26...Female thread part, 27...
Screw shaft, 28...Pulse motor, 29...Pin,
30... Swing frame, 31... Leaf spring, 32...
...Eccentric pin, 33...Stopper, 34...Magnetic sensor, 35...Lever, 36...Tip, 3
7...Control mechanism.

Claims (1)

[Claims] 1. Targeting the wire by crushing a part of the wire at the lower end of a bonding tool provided at the tip of a bonding arm that is rotatably supported around a horizontal axis on a lift frame that can be raised and lowered. In a bonding method for bonding to an object; a downward pressing force is applied to the bonding tool; after the elevating frame is lowered and a part of the wire comes into contact with the object, while still resisting the pressing force; Continues to descend, stops descending after a predetermined distance from the point of contact, detects the amount of crushing while crushing a part of the wire with the pressing force, and stops the crushing operation when the predetermined amount of crushing is reached. A bonding method characterized by forcing. 2. A bonding method in which a part of the wire is crushed and bonded to the target object using the lower end of a bonding tool installed at the tip of a bonding arm that is rotatably supported around a horizontal axis on a lift frame that can be raised and lowered. A downward pressing force is applied to the bonding tool; After the elevating frame is lowered and a part of the wire comes into contact with the object, it continues to descend against the pressing force and the contact is made. The descent is stopped after a predetermined distance from the point of contact, and the amount of crushing is detected while crushing a part of the wire by the pressing force; A bonding method characterized by determining that an abnormality has occurred and stopping the bonding operation when the amount of compression is not reached. 3 A bonding device that crushes a portion of the wire at the lower end of the bonding tool provided at the tip of the bonding arm that is rotatably supported around a horizontal axis on a lift frame that can be raised and lowered to bond the wire to the target object. a pressing force applying mechanism that applies a downward pressing force to the bonding tool; and a displacement detection mechanism that detects vertical displacement of the bonding tool relative to the lifting frame; when the lifting frame is lowered; a stopping distance setting mechanism that detects the point in time when the wire contacts the object and then stops the descending movement of the lifting frame when the wire descends a predetermined distance; after the point of contact, a force from the pressing force applying mechanism is applied; A bonding device comprising a crushing amount setting mechanism that detects the crushing amount of a wire to be crushed by a variable displacement detection mechanism and stops the crushing movement when a predetermined crushing amount is reached. 4 A bonding device that crushes a portion of the wire and bonds the wire to the target object using the lower end of a bonding tool installed at the tip of a bonding arm that is rotatably supported around a horizontal axis on a lift frame that can be raised and lowered. a pressing force applying mechanism that applies a downward pressing force to the bonding tool; and a displacement detection mechanism that detects vertical displacement of the bonding tool relative to the lifting frame; when the lifting frame is lowered; a stopping distance setting mechanism that detects the point in time when the wire contacts the object and then stops the descending movement of the lifting frame when the wire descends a predetermined distance; after the point of contact, a force from the pressing force applying mechanism is applied; Abnormality detection in which the amount of crushing of the wire to be crushed is detected by the displacement detection mechanism and the bonding operation is stopped when the detected amount of crushing does not reach a predetermined amount of crushing even after a predetermined time has elapsed from the point of contact. A bonding device characterized by comprising a mechanism.