JP2002093827A - Die bonder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a die bonder that can speedily operate a bonding arm, when picking up a die, will not give shock loads to the die at that time, for preventing the die from being damaged. SOLUTION: When the die 6 is to be picked up, a head section 16b at the tip of the bonding arm is descended speedily, while a collet 18b is been pulled upward by a plunger shaft 31b. Then, the collet 18b stops before coming into contact with the die 6. After that, a solenoid 32b is energized by a prescribed, current in the opposite direction, the plunger shaft 31b is allowed to project so that shock is not given to the die 6, and the collet 18b is allowed to project downward. Then, a current value is increased, and a prescribed pickup load is given to the die 6, thus speedily lowering the head section 16b, without giving shocks to the die 6.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a die bonder for adsorbing a semiconductor die and mounting it at a predetermined position, and more particularly to a die bonder capable of high-speed operation.

[0002]

2. Description of the Related Art A semiconductor die (hereinafter referred to as a die) is made of a wafer having a size of 6 inches or 8 inches, and then cut into a rectangular shape to obtain a final product. Its size is
The shape varies from a square shape ranging from □ 0.2 mm to □ 30 mm, or a horizontally long strip shape depending on the case. The dies are placed and adhered one by one on a lead frame by a die bonder. Thereafter, each die is wire-bonded to a lead and molded, and then the lead frame is cut and lead molded for each die unit. After the characteristic inspection, the product is stored in a tape pocket by a taping device. This is usually taken I
This is a post-process in manufacturing semiconductor products such as C. The die bonder is a device that picks up dies, each of which is cut into a rectangular shape from a wafer, one by one, and places the dies at predetermined positions on a lead frame. This will be described in detail with reference to FIG. FIG. 6 is a perspective view of the die bonder 1 centering on the pick and place unit 2.

[0006] The dies 6 in the wafer 4 cut in a lattice shape are picked up one by one by the pick and place unit 2 while being attached to the adhesive sheet 3, and the lands of the lead frame 7 which are fed at a constant pitch are picked up. It is placed on the unit 8. The upper part of the die 6 to be picked up and the die 6
A camera is installed above the land portion 8 on which is mounted (not shown). The former camera recognizes the position of the die 6 to be picked up and adjusts the position of the adhesive sheet 3 together. On the other hand, the latter camera recognizes the position of the land portion 8 and adjusts to the position,
This is for correcting the position of the die 6 during transportation.

Accordingly, the pick and place unit 2
With regard to, operation in the X-axis (left-right) direction is possible together with the Y-axis (front-back) direction and the Z-axis (vertical) direction. Note that X
Although illustration is omitted in the axial direction, it is necessary to correct the position in the left-right direction while the die 6 is being conveyed.
Looking at the drive unit in the Y-axis direction, the nut unit 12 moves back and forth as the ball screw 11 connected to the rotation shaft of the motor 9 is used as a drive source. Further, a guide rod 13 is arranged in parallel with the ball screw 11, and the nut portion 12 can move straight without rattling.

On the other hand, an LM guide (straight running guide) 14 is disposed on the nut portion 12 which operates in the Y-axis direction.
Along the guide 14, the bonding arm 15 and the head 16 located at the tip thereof move up and down. In addition, a motor (not shown) provided on the back of the connecting arm 17 also serves as a driving source for this vertical movement. Although the operation in the X-axis direction is not shown as described above,
A method is generally adopted in which the entire pick and place unit 2 shown is moved left and right by a motor on a slide unit movable in the axial direction.

Subsequently, the manner in which the die is picked up by the die bonder will be described in detail with reference to FIG. FIG.
(A)-(d) is an enlarged front view (partial sectional drawing) of the head part 16. FIG. First, the overall structure will be described with reference to FIG. The cylindrical collet 18 is passed through a hole provided in the L-shaped mounting plate 19 and can move up and down smoothly. A spring stopper 21 is provided below the collet 18, and a compression spring 2 is provided between the lower surface of the L-shaped mounting plate 19 and the spring stopper 21 and on the outer periphery of the collet 18.
2 is inset. Therefore, the collet 18 is always pressed downward by the force of the spring. Meanwhile, collet 18
The upper and lower stoppers 23 are provided above the
Unless an external force is applied from below, the collet 18 is in a state where the upper and lower stoppers 23 are in contact with the upper surface of the L-shaped mounting plate 19. The collet 18 has a suction hole extending from the upper end to the lower end, and an air tube 24 connected to the upper end is connected to a vacuum suction device (not shown).

Turning to the description of the pickup operation, first,
The head unit 16 moves so that the collet 18 is positioned 20 to 30 mm above the aligned die 6 (up end). (Not shown) (a) Thereafter, the descent is started, and the tip of the collet 18 contacts the die 6 on the adhesive sheet 3. (B) Further, the head portion 16 slightly descends, and the compression spring 2
2 deflects and applies a pressing load (hereinafter referred to as a pickup load, usually 50 g to 100 g) to the die 6. Then, the tip of the collet 18 starts suction. (C) Although this is a typical example, the pressure-sensitive adhesive sheet 3 is placed on a stage 26, and a needle 27 that can move up and down and pushes the center of the die 6 is provided in the stage 26. When the needle 27 and the head 16 rise slightly at the same time, the die 6 rises while being sandwiched between them, and most of the adhesive sheet 3 is peeled off from the lower surface of the die 6. (D) Thereafter, the head portion 16 continues to rise, and the collet 18 conveys the die 6 peeled from the adhesive sheet 3. Then, the needle 27 goes down and returns to the original position.

FIG. 8 is a graph showing the movement of the head section 16 just described. This illustrates a process in which the head unit 16 descends / adsorbs from the rising end when the die 6 is sucked, and reaches the rising end again. The horizontal axis represents the elapsed time, and the vertical axis represents the height position of the head.

[0009]

However, the conventional die bonder described above has the following problems. The problem is the process from (a) to (b) shown in FIG. This timing or period is additionally shown in the graph of FIG. That is, the tip of the collet 18 comes into contact with the die 6 shortly before the head portion 16 reaches the lowering end. However, as can be seen from the graph, during this time, the head unit 16 is descending at a high speed. Therefore, when the collet 18 contacts the die 6, the die 6
A large impact load is applied to the die 6 and the die 6 is damaged by the impact load.

Therefore, it is necessary to temporarily decelerate the head portion 16 before the collet 18 contacts the die 6 and to make contact during the deceleration period in a state where the impact load at the time of contact is reduced. FIG. 9A shows an operation graph in this case. In order to prevent the die 6 from being damaged, the head unit 16 is normally moved down in this manner. As a result, an extra cycle time for picking up the die 6 is required for the deceleration. FIG. 9B is a graph showing a change in load applied to the die 6 during the operation. As can be seen, even if the collet 18 came into contact with the die 6 during the deceleration period, the impact load at that time instantaneously increased, and reached twice or more the pickup load. This occurred because the weight of the collet 18 and the compression spring load collided with the die 6 while maintaining a certain speed, and could not be avoided. In addition, if an impact load more than this is applied, the die 6 may be damaged, so that the speed during deceleration cannot be increased any more.

In recent years, with regard to cycle time (pick and place of one die), there has been an increasing demand for further shortening the cycle time, and a die bonder has to be provided to meet the demand. The cycle time, which was about 0.35 seconds / die in the past, is faster than 0.2-0.25 seconds / die.
Shorter dies and may even be less than 0.2 seconds / die in the near future. However, the above-described deceleration operation has a slight length of about 0.5 mm in vertical stroke, but the lowering speed during that period is as small as several tenths as compared with the high-speed lowering operation. Therefore, the cycle time is 0.
In the case of a die bonder of 2 to 0.25 seconds / die, this deceleration operation alone took about 0.03 seconds. Until now, the deceleration operation when picking up the die 6 has been described, but this is also necessary when placing the die 6 on the lead frame 7. The reason for this is the same as during pickup, in order to prevent the die 6 from being damaged.

In some head structures, a means for applying a pickup load to the collet uses a solenoid and a plunger shaft instead of a spring.
This is because a plunger shaft that can be moved in and out of the solenoid is fitted into the solenoid, and a magnetic attraction is generated by energizing the solenoid, and a predetermined force (hereinafter referred to as thrust) is generated according to the magnitude and direction of the current. And call it smoothly). In FIG.
An example of the head section 16a using these will be described. Collet 1
8a can move up and down smoothly, and the backing plate 28 is fixed to the upper part. On the other hand, the solenoid 32 is fixed to the head 16a in the direction in which the plunger shaft 31 moves up and down. FIG. 10A shows the plunger shaft 31.
The power supply line 33 of the solenoid 32 is energized so as to protrude downward with a certain thrust, and the vertical stopper 23a is pressed against the upper surface of the L-shaped mounting plate 19a.
That is, the plunger shaft 31 is constantly pushing down the collet 18a with a constant thrust instead of the compression spring. (See FIG. 7 (d) for comparison.)

When the die 6 is sucked, the head portion 16a descends in a state shown in FIG. 10A or in a state in which the plunger shaft 31 has escaped upward as shown in FIG. Contact. However, in both cases, as in the case of the head unit 16 using a compression spring, unless the descent speed of the head unit 16a is reduced before contact with the die 6, the impact load at the time when the collet 18a hits is used. The die 6 is damaged.

That is, in the conventional structure of the head portion,
When picking up or placing the die with the lowering operation, before the collet contacts the die or before the sucked die hits the mounting surface, the lowering operation must be performed to minimize the collision load of the collet. They had to decelerate once and make contact in a decelerated state. This has been a bottleneck in operating the die bonder at high speed, and it was necessary to solve this.

[0015]

Accordingly, the present invention is a die bonder proposed to solve the above-mentioned problems. First of all, the head part at the tip of the bonding arm has a collet that can move up and down and adsorbs the semiconductor die at the tip, a plunger shaft that engages with the collet, and a pair with the plunger shaft and the head part A fixed solenoid is provided, and the collet is moved up and down by a predetermined amount while changing the magnetic attraction force of the plunger shaft according to the magnitude of the current supplied to the solenoid, and when the bonding arm descends and sucks the die,
When the bonding arm reaches the lower end, the collet does not come into contact with the die, and thereafter, the current supplied to the solenoid is set to a predetermined value, and the collet descends and comes into contact with the die. In some of the features, the collet and the plunger shaft take a form to be engaged via a connecting bar.

In addition, when the bonding arm is lowered and the die sucked by the collet is placed at a predetermined position, the collet contacts the die when the bonding arm reaches the lower end. Instead, the current flowing through the solenoid is set to a predetermined value, and the collet descends to contact the die with a predetermined mounting surface. Also, when the bonding arm is lowered to suck or place the die, the bonding arm does not decelerate just before the lower end. As a result of having these features, when sucking or placing the die,
High-speed operation is possible without damaging the die.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a die bonder according to the present invention will be described below in detail with reference to the accompanying drawings. The same components as those of the conventional example are denoted by the same reference numerals as those of the conventional example.

[0018]

Embodiment 1 FIG. 1 is a front view (partial cross section) of a head section showing Embodiment 1 of the present invention. First, this configuration will be described. A counterbore is provided at the upper end of the collet 18b, into which a connecting bar 36 is inserted.
7 are engaged. The upper part of the connection bar 36 is engaged with the plunger shaft 31b. When a predetermined current flows through the power supply line 33b of the solenoid 32b,
The plunger shaft 31b moves in and out with a predetermined thrust. Accordingly, the collet 18b smoothly moves up and down accordingly. The upper end of the collet 18b is moved upward and downward by the upper and lower stoppers 23b.
And the descending end is the position shown in FIG. Although not shown, an air tube is connected to the side of the collet 18b (in the direction of the back side of the paper), and is connected to an internal suction hole communicating with the die suction surface at the tip.

Subsequently, (a) to (e) shown in FIGS.
A method of adsorbing the die 6 by the die bonder having the head portion 16b will be described with reference to FIG. (A) The head unit 16b moves so that the collet 18b is positioned 20 to 30 mm above the aligned die 6 (upward end). At this time, a predetermined current is supplied to the power supply line 33b such that the plunger shaft 31b projects from the solenoid 32b. Therefore, the upper and lower stoppers 23b are in a state of contacting the L-shaped mounting plate 19b. (B) A predetermined current is applied to the solenoid 32b in a direction opposite to that of (a) so that the plunger shaft 31b is drawn. As a result, the collet 18b is held with the upper and lower stoppers 23b abutting on the upper end stopper 38. At the same time, the head 16b descends at a high speed and stops just before the tip of the collet 18b contacts the die 6. This corresponds to the lower end of the head section 16b. The figure shows the state at this time. (C) Thereafter, a predetermined current is supplied to the solenoid 32b so that the plunger shaft 31b projects again with a predetermined thrust. The result is the state shown in (c), and at the same time, the tip of the collet 18b starts suction. At this time, the upper and lower stoppers 23b do not contact the L-shaped mounting plate 19b or the upper end stopper 38, and the collet 18b presses the die 6 with a constant thrust. That is, a state in which a predetermined pickup load is applied to the die 6. (D) In this state, the needle 27 and the head portion 16b slightly rise while sandwiching the die 6. Then, most of the adhesive sheet 3 is peeled off from the lower surface of the die 6. (E) Thereafter, the head portion 16b continues to rise, and the collet 18b conveys the die 6 peeled from the adhesive sheet 3.
Then, the needle 27 goes down and returns to the original position.

FIG. 4A is a graph showing the movement of the head 16b. This graph illustrates a process in which the head portion 16b descends / adsorbs from the rising end when the die 6 is sucked, and reaches the rising end again. As can be seen at a glance, the trajectory is almost the same as the one described above with reference to FIG. FIG. 4B is a graph showing a change in load applied to the die 6 during the operation.

Here, referring to FIGS. 1 to 4 again, and comparing with FIGS. 7 to 9 shown in the conventional example, specific height dimensions and load values will be described, and the operation of the present invention will be described. Summarize the effects. First, in the process from FIG. 1A to FIG.
The head part descends at high speed and stops without deceleration halfway. Therefore, the required time during this period is shorter than in the conventional example. Specifically, the typical value of the prior art is that the high-speed descent stroke is about 20 mm and the descent speed at that time is about 5 mm.
00mm / sec, deceleration descent stroke is about 0.3mm
The descending speed at that time was about 10 mm / sec. Accordingly, it took about 0.03 seconds for the deceleration descent time. This is because such a deceleration was necessary to reduce the impact load when the collet contacts the die.
However, in the case of the head portion of the present invention, the inventor first sandwiched the upper and lower stoppers in the state of FIG.
The stroke of the collet up and down was about 2 mm. When the head stops at the lower end (see FIG. 1B), there is a gap of about 0.5 mm between the tip of the collet and the upper surface of the die. Here, when a reverse current is applied to the solenoid, the collet projects about 0.3 mm therefrom and comes into contact with the die. The time for this collet to protrude is 2-3
Very short, m seconds. As a result, the head section of the present invention almost eliminates the time required for the conventional deceleration operation of about 0.03 seconds.

Next, the impact load applied to the die when the present invention is used will be described. As described above, the thrust of the plunger shaft can be set by the magnitude of the current supplied to the solenoid. However, the protruding speed hardly changes due to the difference in the thrust. Therefore, when a current in the reverse direction is applied to the solenoid, first, a current is applied so that only the load of the collet itself (several tens of grams) is applied to the die. In this state, the collet is brought into contact with the die, and then the current value is reduced. It can be increased stepwise to increase the pickup load (50 to 100 g). Therefore, the collet contacts the die without applying any collision load to the die, and thereafter, the collet applies an appropriate pickup load to the die.

[0023]

Embodiment 2 Next, another embodiment of the present invention will be described with reference to FIG. The difference from the first embodiment described above is that the solenoid 32c and the plunger shaft 31
c is set horizontally. In addition, the plunger shaft 31c and the collet 18c are connected by an L-shaped bar 39. The L-shaped bar 39 is rotatable about a fulcrum, and both ends thereof are plunger shafts 31.
c and the collet 18c. Therefore, when the plunger shaft 31c moves left and right, the collet 1
8c, the collet 18c moves up and down without twisting or backlash. FIG. 5A shows a state in which the plunger shaft 31c protrudes, and the upper and lower stoppers 23c of the collet 18c abut the L-shaped mounting plate 19c. (B), the plunger shaft 31c is retracted and the collet 18c
The upper and lower stoppers 23c are in contact with the upper end stopper 38c.

When the die is lowered and sucked using the head portion 16c having this structure, the operation of the collet 18c and the positional relationship between the tip of the collet 18c and the die are the same as those of the first embodiment described above. . Before the head portion 16c stops at the lower end, the collet 18c is pulled up by the plunger shaft 31c.
Make a gap between the tip of c and the die. afterwards,
By applying an appropriate reverse current to the solenoid 32c, the collet 18c is pushed down by an appropriate thrust and brought into contact with the die, and then a pickup load is applied.

As a result, unlike the conventional example, when the die is moved down and sucked, the deceleration operation of the head portion is not required, and high-speed operation is possible. Pickup load can be applied.

Finally, a few points are supplemented. In the detailed description, the operation and effect when the head unit of the present invention picks up the die has been mainly described, but the same operation and effect applies to the case where the die is mounted on the lead frame. . In other words, when placing the die, the collet sucks the die and retracts the plunger shaft.
The head is lowered at high speed and stopped just before the die contacts the lead frame. Thereafter, a current of an appropriate value in the opposite direction is supplied to the solenoid, and the die is brought into contact with the lead frame while a small load is applied to the die. Then, the pressing force against the lead frame is increased by gradually increasing the current value. Thus, when the die is mounted, the head does not need to be decelerated and need only be moved down at a high speed, so that the mounting time can be shortened as in the case of picking up. This has a double effect when picking and placing one die (so-called cycle time). Specifically, the numerical value can be reduced from about 0.25 seconds to about 0.19 seconds. When the die is placed, no impact load is applied to the die, and the die is not damaged. Thereafter, the load for pressing the die against the lead frame can be set arbitrarily (depending on the current value flowing through the solenoid). When the die is bonded to the lead frame with a resin, the pressing load usually has to be delicately controlled. However, the structure of the present invention makes the control easy and very effective.

In the description of the first embodiment, the stroke at which the collet can move up and down in the head portion is set to about 1 mm (see FIG. 1A). This dimension can be increased to about 2 mm, for example, by changing the upper end stopper. If the collet is pushed down with a predetermined thrust after the head is stopped at a high speed after the head descends at a high speed, suction from thin dies to relatively thick dies can be performed without problems. can do. This is because, with the structure and operation using the plunger shaft of the present invention, an appropriate thrust that does not damage the die can be applied to each die regardless of the magnitude of the vertical stroke.

Further, in the above description, the plunger shaft and the collet are engaged via the connecting bar or the L-shaped bar, but they may be directly engaged without any intervention on the way. In this case, the arrangement of the plunger shaft and the solenoid is limited to the vertical direction only, but there is no difference from the operation and effect of the present invention described above.

[0029]

As described above, according to the die bonder of the present invention, when the die is sucked, the plunger shaft is pulled in to release the collet upward, and the head portion descends at a high speed, and the collet is removed. Stop before touching the die. Thereafter, a predetermined current in the opposite direction is applied to the solenoid, so that the collet contacts the die with a small load. After that, by increasing the current value, a predetermined pickup load can be applied to the die. This eliminates the need for the head portion to decelerate before stopping by stopping at a high speed, and further high-speed operation of the die bonder becomes possible. In addition, since a large impact load is not applied to the die at the time of pickup, the expensive die is not damaged.

Further, it is not so difficult to convert the head portion of the conventional die bonder into the structure of the present invention, and at the same time, the conversion cost is small.

[Brief description of the drawings]

FIG. 1 shows a head unit according to a first embodiment of the present invention.
Front view (1) showing a state of sucking a die

FIG. 2 is also a front view showing the state (2).

FIG. 3 is also a front view showing the state (3).

FIG. 4A is a graph showing the elevating operation of the head unit when the die is attracted by the head unit according to the first embodiment of the present invention. FIG.

FIG. 5 is a front view showing a head unit according to a second embodiment of the present invention.

FIG. 6 is a perspective view of a general die bonder centering on a pick and place unit.

FIG. 7 is a front view showing a state where a die is sucked by a conventional head unit using a compression spring.

FIG. 8 is a graph showing the elevating operation of the head unit in the case where the conventional head unit using a compression spring does not decelerate at the time of descent when sucking the die.

FIG. 9A is a graph showing the elevating operation of the head unit when decelerating at the time of descent when the die is sucked by the conventional head unit using a compression spring. Graph showing changes in load

FIG. 10 is a front view showing a conventional head unit using a plunger shaft and a solenoid.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Die bonder 2 Pick and place unit 3 Adhesive sheet 4 Wafer 6 Die 7 Lead frame 8 Land 9 Motor 11 Ball screw 12 Nut 13 Guide rod 14 LM guide 15 Bonding arm 16, 16a, 16b, 16c Head 17 Connection arm 18 , 18a, 18b, 18c Collet 19, 19a, 19b, 19c L-shaped mounting plate 21 Spring stopper 22 Compression spring 23, 23a, 23b, 23c Vertical stopper 24 Air tube 26 Stage 27 Needle 28 Backing plate 31, 31b, 31c Plunger shaft 32, 32b, 32c Solenoid 33, 33b Power supply line 36 Connecting bar 37 Pin 38, 38c Upper end stopper 39 L-shaped bar

Claims (4)

[Claims] 1. A die bonder for adsorbing a semiconductor die and mounting the die at a predetermined position, a head portion of a bonding arm includes a collet which can move up and down and adsorbs the semiconductor die at a tip, and a plunger which engages the collet. A shaft, and a solenoid that is paired with the plunger shaft and fixed to the head portion. The collet is moved up and down by a predetermined amount while changing the magnetic attraction force of the plunger shaft according to the magnitude of a current supplied to the solenoid. When the bonding arm descends and sucks the semiconductor die, the collet does not contact the die when the bonding arm comes to the descending end, and thereafter, the energizing current value of the solenoid is set to a predetermined value. A die bonder wherein a collet descends and contacts a semiconductor die. 2. A die bonder for adsorbing a semiconductor die and placing the semiconductor die at a predetermined position, wherein a head portion of the bonding arm is vertically movable and a collet which adsorbs the semiconductor die at a tip and one end engages the collet. A connection bar, a plunger shaft engaged with the other end of the connection bar, and a solenoid paired with the plunger shaft and fixed to the head portion, wherein the plunger is driven by the magnitude of a current supplied to the solenoid. The collet is moved up and down by a predetermined amount while changing the magnetic attraction force of the shaft, and the bonding arm is lowered to suck the semiconductor die. When the bonding arm reaches the lower end, the collet does not contact the die. Thereafter, the energizing current value of the solenoid is set to a predetermined value, and the collet descends and contacts the semiconductor die. Die bonder which is characterized in that. 3. When the bonding arm is lowered and the semiconductor die sucked by the collet is mounted at a predetermined position, the semiconductor die contacts the mounting surface when the bonding arm reaches the lower end. 3. The die bonder according to claim 1, wherein the current flowing through the solenoid is set to a predetermined value, and the collet is lowered to bring the semiconductor die into contact with a predetermined mounting surface. 4. A die bonder according to claim 3, wherein said bonding arm does not decelerate immediately before a lowering end when said bonding arm is lowered to attract or mount said semiconductor die.