JPH01179333A - Bonding pressure adjusting apparatus for semiconductor - Google Patents

Abstract

PURPOSE:To execute an adjusting operation quickly and easily and to relax an impulse force by a method wherein a bonding pressure is adjusted by chang ing the initial length of a tension spring, the tension spring exerts a reaction force against a thrust force of an air cylinder in accordance with the displace ment of a bonding-tool holding block and the reaction force is increased in proportion to the displacement. CONSTITUTION:When a bonding pressure is to be adjusted in accordance with the kind of an IC chip (m) or a lead frame RF, it is adjusted by changing the initial length of a tension spring 32 while a rotary operation knob 24 is turned. While an air cylinder 3 is elongated and its piston rod 3a is lowered, a bonding tool 10 is lowered together with a bonding-tool holding block 5. The lowered tool 10 connects an aligned inner lead part IR to a bump (b). In this case, when the holding block 5 is displaced as the cylinder 3 is elongated, the tension spring 32 is elongated by the displaced amount, and exerts a reaction force against a thrust force of the cylinder 3. Accordingly, the speed of a stroke movement of the cylinder 3 is decreased gradually; an impulsive force to be exerted on the IC chip (m) is relaxed.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a semiconductor bonding apparatus for mounting an IC chip onto a lead frame using a wireless bonding method, and in particular to a technique for adjusting the pressing force of a bonding tool.

<Prior art> The wireless bonding method is, for example, after aligning the bumps of an IC chip placed on a bonding stage and the inner lead portions of a lead frame, by lowering the glue onto the bonder by driving an air cylinder. By joining the bump and the inner lead part between the bonding stage and the bonding tool, the I
This method connects all the electrodes of the C chip to the inner lead portion at the same time.

The bonding pressure applied by the bonding tool needs to be precisely adjusted depending on various conditions such as the type of IC chip and the number of bumps.

Conventionally, this bonding pressure was adjusted as follows.

The thrust of the air cylinder was adjusted to match the bonding pressure to the required pressure by operating a pressure regulator while watching a pressure gauge installed in the compressed air supply system to the air cylinder.

<Problems to be solved by the invention> However, it is not only troublesome to operate the regulator while looking at the pressure gauge, but also because the precision of the pressure gauge and the adjustment precision of the regulator are low, making it difficult to adjust the bonding pressure accurately to the required bonding pressure. It was very difficult to adjust the bonding pressure, and it was necessary to repeat the adjustment work, which required a great deal of time and effort.

In addition, in the case of a single-acting air cylinder, when the number of bumps is small, the thrust of the air cylinder is adjusted to 0.5, for example.
If the piston was lowered to about 4 kg/c4, the piston movement speed would drop significantly, which would not only reduce the workability of bonding, but also prevent smooth stroke movement, which could lead to defects in the bonding itself. .

For smooth stroke movement, the minimum setting is 1, for example.
A thrust of approximately 1 kg/cm is required, but this not only increases the moving speed of the piston and causes excessive bonding pressure relative to the number of bumps, but also causes damage to the IC chip at the moment when pressure is first applied. There was a risk of applying impact force and damaging the IC chip.

In the case of a double-acting air cylinder, it is driven by the differential pressure between the inlet and outlet sides, so there is no impact problem as mentioned above.
Since the pressure must be adjusted using two regulators, one on the inlet side and the other on the outlet side, there is a problem in that the workability of adjustment is significantly reduced.

An object of the present invention is to make it possible to finely adjust the bonding pressure with a simple operation and to avoid applying impact force to the IC chip.

<Means for Solving the Problems> In order to solve the above problems, the present invention has the following configuration. That is, the semiconductor bonding pressure regulating device according to the present invention includes: an air cylinder whose thrust is fixed at a predetermined constant value; a bonding tool holding block attached to the piston rod of the air cylinder; and one end attached to the tool holding block. A tension spring that is attached to the air cylinder and applies a reaction force to the thrust of the air cylinder; and an initial length adjustment mechanism that attaches the other end of the tension spring to change the initial length of the tension spring. be.

<Effect> The effects of the configuration of the present invention are as follows.

When the bonding tool holding block is displaced due to the operation of the air cylinder during bonding, the tension spring is expanded by the amount of displacement and provides a reaction force to the thrust of the air cylinder. The closer the bonding tool is to the joint to the chip, the more the tension spring stretches and the more the reaction force increases. Therefore, the speed of the stroke movement of the air cylinder is gradually reduced to reduce the impact force on the tip.

Even though the speed of the air cylinder gradually decreases, the initial speed is high, so it is possible to stroke faster than when the stroke is made at a constant low speed from the beginning without any reaction force, and the bonding work is faster. You don't have to reduce your sexuality too much.

Further, the bonding pressure is adjusted by adjusting the reaction force against the thrust of the air cylinder by changing the initial length of the tension spring. That is, there is no need to adjust the regulator in the compressed air supply system of the air cylinder.

Since the operation of the initial length adjustment mechanism that controls the change of the initial length of the tension spring is simply a length adjustment, it is much easier than operating the regulator while looking at the pressure gauge.

Further, the adjustment accuracy is high, and it is easy to finely adjust the reaction force and thus the bonding pressure.

<Example> Hereinafter, an example of the present invention will be described in detail based on the drawings.

FIG. 1 is a partially broken sectional view showing the structure of a bonding tool drive unit in a semiconductor bonding apparatus, FIG. 2 is a partially broken side view thereof, and FIG. 3 is a partially broken plan view thereof.

As shown in these figures, a pair of left and right guide rails 77 on which the lead frame RF (see FIG. 5) is placed and guided.
The central location between them is defined as the bonding location BP. A bonding stage unit A is arranged below the bonding point BP (Figs. 4 and 5).
(see figure), at the position above the bonding point BP,
A bonding tool drive unit) B is provided facing the bonding tool drive unit I-A.

First, the specific structure of the bonding tool drive unit B will be explained.

An air cylinder 3 is vertically attached to a fixed frame 1 via a pair of upper and lower brackets 2. Air Siri,
A bonding tool holding block 5 is attached to the piston rod 3a of the bonder 3 via a floating joint 4.

The compressed air supply system of the air cylinder 3 is equipped with a pressure gauge and regulator as in the conventional example, but once the thrust of the air cylinder 3 is adjusted to a required constant value using these, as long as the thrust does not fluctuate, The thrust force of the air cylinder 3 is not adjusted by the regulator, and the thrust force of the air cylinder 3 is always fixed at a constant value.

As shown in FIG. 1, the bonding tool holding block 5 includes a tool holding plate 6 whose one end is directly attached to the floating joint 4, and a tool holding plate 6 that is inserted through the other end of the tool holding plate 6 and fixed with a nut 7. Tool base 8
The bonding tool 10 is detachably supported at the lower part of the tool base 8.

Note that the bonding tool 10 includes a heater (not shown).
is built-in.

The lower end of the bonding tool 10 is located directly above the bonding point BP, and is also located directly above the bonding point BP.
(see figure). The bonding tool IO is designed to be replaced with another compatible bonding tool when the size of the IC chip m changes.

As shown in FIG. 3, a pair of side plate blocks 18 are attached to both sides of the fixed frame 1.

This side plate block 18 includes a mounting board portion 18a, a side plate portion 1
8b, a rising piece 18C protruding from the side plate portion 18b
It is composed of a mounting plate part 18d and a reinforcing plate part 18e that protrude from the side plate part 18b in a state parallel to the second mounting board part 18a.

A horizontal upper plate 19 is hung between the upper surfaces of both rising pieces 18c, and a screw-type initial length adjustment mechanism 2 is attached to this horizontal upper plate 19.
0 is attached.

As shown in FIG. 2, the initial length adjustment mechanism 20 includes a vertically long cylindrical nut 21 having a flange portion 21a fixed to the horizontal upper plate 19, and a relatively long bolt screwed into the cylindrical nut 21. 22, and the spring receiver attached to the lower end of the bolt 22 in a relatively rotating state is connected to the block 23 and the cylindrical NAND 2.
1 and is rotatably fitted onto the outside of the bolt 22 and fixed to the upper end 22a of the bolt 22. 25 is a screw for preventing rotation of the rotation operation knob 24.

A scale 26 is attached to the outer peripheral surface of the cylindrical nut 21.
The scale 26 is read at the lower edge 24a of the rotary operation knob 24.

The spring receiver block 23 includes a cylindrical body 28 that is fitted onto the bolt 22 and supported by a flange 22b at the lower end of the bolt 22 via a bearing 27, and a nut member 29 that is screwed onto the lower end of the cylindrical body 28. A U-shaped spring receiver fixed to the lower surface of the nut member 29 is composed of a seat plate 30.

The axis of the screw shaft portion of the tool base 8 in the bonding tool holding block 5 that is fixed with the nut 7 is
It coincides with the axis of the bolt 22 in the upper initial length adjustment mechanism 20. A seat plate 31 is fixed to the U-shaped spring receiver at the upper end of the screw shaft portion of the tool base 8, and the pair of upper and lower opposing spring receivers extends between the seat plates 30 and 31.
A tension spring 32 is provided to provide a reaction force to the thrust of the air cylinder 3. 33.34 is tension spring 3
In order to hang the upper and lower hook parts of 2, the spring holder is a seat plate 30.
．． This is the pin inserted into 31.

Guide plotters 35, 36 (see Fig. 2) are attached to the upper and lower sides of the mounting plate portion 18d (see Fig. 3) of each side plate block 18, and each guide rod is slidably inserted into both guide plotters 35, 36. The lower end of the bonding tool holding block 5 is inserted into the tool holding temporary 6 and fixed by a nand 38.

A cooling fan motor 39 is attached to the back surface of the fixed frame 1, and ventilation holes 1a are formed in the fixed frame 1 at corresponding locations.

Air cylinder 3. Tension spring 32. guide block 35,
36. A casing 40 that covers the guide wand 3 and the like is attached to both side plate blocks 18. casing 40
A number of air intake holes (not shown) are formed at the bottom of the .

As shown in FIG. 1, the inner side of the lead frame RF is placed on the side of the bonding tool drive unit B in the Y direction perpendicular to the length direction (X direction) of the guide rail 77 that guides the placement of the lead frame RF. The lead part JR and the IC chimbu m on the bonding stage 72, which will be described later.
A microscope 41 is disposed for photographing the relative positional relationship between the two. The image taken by this microscope 41 is configured to be displayed on a monitor display (not shown).

In order to cope with the fact that the microscope 41 is disposed offset in the Y direction with respect to the bonding point BP, a reflecting mirror unit 42 is provided to send light from the bonding point BP to the microscope 41. . This reflecting mirror unit 42 is a first reflecting mirror 4 located directly above the bonding point BP and having a reflecting surface facing downward at 45 degrees.
3 and 45 located directly below the microscope 41 and facing upward.
a second reflecting mirror 44 having a reflective surface of
3.44, and a reflecting mirror holding frame 45 for holding the mirror.

Since the reflecting mirror unit 42 is located directly below the bonding tool 10, it is necessary to evacuate the reflecting mirror unit 42 when the bonding tool 10 descends. For this reason, a link mechanism (not shown) that swings in conjunction with the raising and lowering of the tool holding plate 6 is attached to the fixed frame 1, and an end of the link mechanism is connected to the reflector holding frame 45.

Next, the structure of the bonding stage unit A will be explained based on FIGS. 4 and 5. FIG. 4 is a partially broken front view, and FIG. 5 is a partially broken side view.

49 is an X-table that moves while being guided by an X-direction rail 51 fixed to a fixed base 50; 52 is an X-direction stepping motor that drives the X-table 49;

Further, 53 is a ball screw nut attached to the X table 49, 54 is a screw shaft, and 55 is a screw shaft 54.
The bearing portion 56 is a coupling that connects the screw shaft 54 and the output shaft of the X-direction stepping motor 52.

57 is a Y table that moves guided by a Y direction rail 58 fixed to the X table 49; 59 is a Y table 57;
This is a Y-direction stepping motor that drives the

Further, 60 is a nut of a pole screw attached to the Y table 57, 61 is a screw shaft, and 62 is a screw shaft 61.
The bearing portion 63 is a coupling that connects the screw shaft 61 and the output shaft of the Y-direction stepping motor 59.

X direction stepping motor 52. The Y-direction stepping motor 59 is configured to be driven by an X-Y twist (not shown).

A stage box 64 is attached to the upper surface of the Y table 57, and a Z direction stepping motor 65, a Z
A block 66 and a pole screw for raising and lowering this Z block 66 are built-in. A screw shaft 67 of the ball screw is vertically supported, and a nut 68 thereof is fixed to the Z block 66. Z direction stepping motor 65
The output gear 69 is a driven gear 70 at the lower end of the screw shaft 67.
It meshes with the 71 is a guide rail of the Z block 66.

A bonding stage 72 is fixed to the upper surface of the Z block 66, and a vacuum suction path 73 formed inside the bonding stage 72 opens to the upper surface of the bonding stage 72 directly below the bonding location BP to form the vacuum suction lower 4. There is. The other end of the vacuum suction path 73 is connected to a vacuum suction pipe 75.

Next, in the semiconductor bonding apparatus of this embodiment,
The work procedure for adjusting the bonding pressure will be explained.

The thrust force of the air cylinder 3 in the bonding tool drive unit (B) is always fixed at a constant value. Adjustment of the bonding pressure according to the type of IC chip m or lead frame RF is performed by changing the initial length L of the tension spring 32 for applying reaction force by rotating the rotary operation knob 24.

That is, when the rotation operation knob 24 of the screw-type initial length adjustment mechanism 20 is rotated, the bolt 22 rotates integrally with the rotation operation knob 24, and the bolt 22 moves up and down to be screwed into the cylindrical nut 21. Move along the direction.

When the rotation knob 24 is rotated clockwise, the bolt 22 moves upward while rotating. Since the cylindrical body 28 is supported by the flange portion 22b at the lower end of the bolt 22 via the bearing 27, it does not rotate but rises. Along with this, Oak]・Component 29. In the spring receiver, the seat plate 30° pin 33 also rises. Since the air cylinder 3 is at the end of its contraction stroke and remains stationary during the bonding pressure adjustment operation, the bonding tool holding block 5. The position of the pin 34 of the seat plate 31 of the spring receiver is also locked.

Therefore, when the pin 33 rises due to the rise of the bolt 22, the tension spring 32 is stretched and its initial length increases. As the initial length increases, the reaction force against the thrust of the air cylinder 3 also increases.

Conversely, when the rotary operation knob 24 is rotated counterclockwise, the tension spring 32 contracts and its initial length decreases, so that the reaction force also decreases.

The bonding tool 10 descends to the bonding point BP by the extension drive of the air cylinder 3, and connects the inner lead portion IR of the lead frame RF and the bump b of the IC chip m.
The relationship between the initial length and the bonding pressure Po and the pressure decrease F is illustrated as follows, where P is the bonding pressure when bonding and F is the pressure decrease due to the reaction force of the tension spring 32 at that point. The result will be as shown in Figure (A).

Here, Po is the bonding pressure when the tension spring 32 is removed. The bonding pressure P is P=P, -F. Note that Lo is the free length of the tension spring 32.

The pressure value to which the bonding pressure P is adjusted is determined by the scale 26 of the cylindrical nut 21 and the lower edge 24 of the rotary operation knob 24.
Judgment is made based on the positional relationship with a.

The initial length adjustment mechanism 20 is a screw type, and the amount of displacement of the bolt 22 and the amount of change in the initial length of the tension spring 32 are very small compared to the amount of rotation of the rotation operation knob 24. Therefore, even when finely adjusting the initial length L, the rotation operation knob 2
4 can be rotated a lot, and its operability is good.

Next, the bonding operation will be explained.

The heater in the bonding tool holding block 5 is constantly energized, and the bonding tool 10
．． The bonding stage 72 is controlled to a predetermined temperature.

In addition, a cooling fan motor 39 is constantly driven, and cooling air flows into the casing 40 from the air intake provided at the bottom of the casing 40, causing the tension spring 3
2. After removing heat from the air cylinder 3 and its surrounding parts, the ventilation hole 1a of the fixed frame 1 and the fan motor 3
It is exhausted through 9.

In this way, the air cylinder 3. Since the tension spring 32 is cooled, there is no linear expansion due to heat conduction from the heater, and the origin position of the bonding tool 10 can always be maintained at a constant position. Fluctuations can be prevented.

The inner lead portion IR is attached to the guide surface 7 of the guide rail 77 by the lead frame holding plate 78 on both side edges of the lead frame RF set at the bonding point BP.
7a.

I with bump b that has been pre-aligned in the X, Y and θ directions at a pre-alignment section (not shown)
The C chip m is suctioned by a traverse arm (not shown) and placed on the vacuum suction lower 4 of the bonding stage 72 as shown in FIG. 7(A). place Open the 11i1 magnetic valve installed in the vacuum suction pipe 75, apply negative pressure to the vacuum suction lower 4 through the vacuum suction path 73, and place the IC chip m face up on the bonding duster and shifter 2. Holds by adsorption. The suction and holding is the vacuum suction pipe 7.
When detected by a pressure gauge (not shown) installed at 5, the suction by the traverse arm is released and the traverse arm returns to the pre-alignment section.

Next, the Z-direction stepping motor 65 is driven in forward rotation to raise the bonding stage 72, and the ICC
When the bump b of the tough m comes to a position spaced downward from the indoor surface 77a of the guide rail 77 by a minute distance l (for example, 0.5 m'm), the Z direction stepping motor 65 is stopped.

The reason why the ICC tough m stops being located below the guide surface 77a is because when the operator adjusts and moves the lead frame RF in the X direction and Y direction while looking at the monitor display in the next process, the lead frame RF This is to avoid sliding contact with the bump b of the ICC tough m. The minute interval l is a size that falls within the depth of focus of the microscope 41.

Next, the inner lead portion IR of the lead frame RF photographed by the microscope 41,! : The relative positional relationship of the TC chip m with the bump b is displayed on the monitor display, but the operator operates the X-Y joystick without looking at the monitor display screen and moves the X-direction stepping motor 52. By driving the Y-direction stepping motor 59, each inner lead portion IR and each bump b
Align them in both the X and Y directions.

After completing this positioning, when the start switch (not shown) is turned on, the Z of bonding stage unit A is
The direction stepping motor 65 is driven to rotate in the normal direction again, the bonding stage 72 rises again, and when the upper surface of the ICC tough m comes to the same height as the guide surface 77a of the guide rail 77, the Z direction stepping motor 65 is stopped. .

As a result, the inner lead portion IR to be bonded comes into contact with the bump b of the ICC tough m.

Next, as the air cylinder 3 of the bonding tool drive unit B is extended and its piston rod 3a is lowered, the bonding tool 10 is lowered together with the bonding tool holding block 5. In conjunction with this lowering, the link mechanism operates to retire the reflecting mirror unit 42 from the lowering path of the bonding tool holding block 5. The lowered bonding tool 11 joins the aligned inner lead portion IR and bump b.

In this case, when the bonding tool holding block 5 is displaced as the air cylinder 3 is expanded, the tension spring 32 is expanded by the amount of the displacement and provides a reaction force to the thrust of the air cylinder 3. The closer the bonding tool 10 is to the joint to the ICC tough m, the more the tension spring 32 stretches and the more the reaction force increases. Therefore, the speed of the stroke movement of the air cylinder 3 gradually decreases, and I
Alleviates the impact force applied to CC tough m.

The relationship between the downward movement speed V of the bonding tool 10 and the time t is shown in FIG. 6(B). vl represents the speed when a reaction force is applied by the tension spring 32, and ■2 represents the speed when the tension spring 32 is not provided. The 0 mark indicates the joining start point.

If there is no tension spring 32, the speed v2 is constant and a large speed is maintained even at the welding start point, so
The impact force applied to ICC tough m is large. In order to avoid this, if the speed is lowered to v3, it will take too much time to start joining, resulting in a decrease in productivity.

On the other hand, when the tension spring 32 is provided, the speed v
1 gradually decreases, the speed at the welding start point becomes considerably low, and the impact force on the ICC tough m is alleviated. However, since the initial speed is high, the time required to start bonding is shorter than in the case of speed V.

When a predetermined period of time has elapsed since the air cylinder 3 reached the end of its expansion stroke, the air cylinder 3 is contracted and the bonding tool 10 is raised. At the same time, the negative pressure applied to the vacuum suction lower 4 of the bonding stage 72 is released, and the adsorption and holding by the bonding stage 72 to the ICC tough m is released.

After this suction holding is released, the Z-direction stepping motor 65 is driven in reverse, and the bonding stage 72 is lowered. Note that in conjunction with the rise of the bonding tool 10, the link mechanism operates in the opposite direction, and the reflector unit 42 returns to its original position.

In the above embodiment, the bump b was formed on the IC chip m side, but the bump b may be formed on the inner lead part IR side.

<Effect of the invention> According to the present invention, the following effects are achieved.

As the bonding tool holding block is displaced by the operation of the air cylinder, the tension spring applies a reaction force to the thrust of the air cylinder, and the reaction force increases in proportion to the displacement, so the speed of the air cylinder stroke movement gradually increases. As a result, the impact force applied to the chip can be alleviated. Therefore, it is possible to reduce the incidence of chip breakage and improve yield.

Since the bonding pressure is adjusted by changing the initial length of the tension spring, the troublesome adjustment work with the regulator in the compressed air supply system can be eliminated, and the adjustment work can be done quickly and easily. Fine adjustment of bonding pressure can be performed accurately.

[Brief explanation of the drawing]

1 to 7 relate to one embodiment of the present invention, in which FIG. 1 is a partially cutaway front view showing the specific structure of the bonding tool drive unit, and FIG. 2 is a partially cutaway side view of the same structure. 3 is a partially broken plan view of the same structure, FIG. 4 is a partially broken front view showing the specific structure of the bonding stage unit, and FIG. 5 is a partially broken side view of the same structure. FIGS. 6 and 7 are explanatory diagrams of the operation. 3... Air cylinder 3a... Piston rod 5... Bonding tool holding block 10... Bonding tool 20... Initial length adjustment mechanism 32... Tension spring applicant Dainippon Screen Mfg. Co., Ltd. agent Person Patent Attorney Tsutomu Sugitani Figure 2. 1+x Figure 3

Claims (1)

[Claims] (1) An air cylinder whose thrust is fixed at a required constant value, a bonding tool holding block attached to the piston rod of this air cylinder, and one end of which is attached to the tool holding block, A semiconductor bonding pressure adjustment device comprising: a tension spring that applies a reaction force; and an initial length adjustment mechanism that attaches the other end of the tension spring to change the initial length of the tension spring.