JPH01251729A - Inner-lead bonding apparatus - Google Patents

Abstract

PURPOSE:To bond a semiconductor element of different thicknesses without a need for a difficult adjustment operation and without a change in the pressurization time and a pressurization force by controlling that a prescribed pressurization process is completed in a definite time from a moment when it is detected that a bonding tool has been brought into contact with the semiconductor element. CONSTITUTION:A cam 7 is installed at an output axis of a servomotor 20 and drives a bonding tool 4. In addition, a gap sensor 23 used to detect a gap between a part of a rocking lever 11 and a part of a rocking lever 12 facing the lever directly above it is installed on the side of a point of action of the rocking lever 11. This gap sensor 23 is connected to a control circuit 22 at the outside and controls the servomotor 20. For example, when the bonding tool 4 is lowered and it is detected that its tip part has come into contact with the surface of a semiconductor element, a control operation to quicken a speed of revolution of the servomotor 20 is executed. A pressurization process by using the cam 7 is finished after a definite time. Accordingly, both the shift time of a cylinder (damper means) 14 for adjusting an operating amount of the bonding tool and a sinking amount of a rod become always constant.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to an inner lead bonding apparatus for bonding a semiconductor element to a lead.

(Prior art) For bonding, an inner lead bonding device is used to bond electrode bumps (electrodes) formed on a semiconductor element.
There is one that is bonded to the inner lead of the lead frame.

Some of these inner bonding devices use a motor to raise and lower a bonding tool, as shown in Japanese Patent Application No. 64307/1983 filed by the present applicant.

That is, as shown in FIG. 4, a bonding tool 4 supported by a tool holder 2 and a compression spring 3 so as to be movable up and down is provided above the workpiece holder 1. Further, an AC motor 8 having a disk-shaped cam 7 attached to its output shaft is installed on the base 6 above the X-Y drive unit 5 that supports the workpiece holding unit 2, and the cam 7 and the bonding The tool 4 is connected to the tool 4 via a motion conversion mechanism 9. Specifically, the motion conversion mechanism 9 includes a first swinging lever 11 adjacent to the output shaft side of the AC motor 8 to which a cam follower 10 that is combined with the cam 7 is attached; A crank-shaped second swing lever 12 is rotatably supported on the action point side of the swing lever 11. The action point side of the second swing lever 12 is rotatably supported on the upper end of a press rod 13 which is connected to the bonding tool 4 and is movable up and down in the vertical direction. An air cylinder 14 serving as a damper means for adjusting the tool movement amount is interposed between the force side of the second swing lever 12 and the force side of the first swing lever 11. , when the cam 7 rotates following the operation of the AC motor 8, the movement is converted into a linear movement along the vertical direction by the first and second swing levers 11, 12, and The bonding tool 4 is lowered and the semiconductor element is pressed against the lead frame 15 by the suppressing portion 4a at the tip. This suppression causes the electrode bumps of the semiconductor element to be crimped onto the inner leads of the lead frame 15. When the thickness of the semiconductor element changes, the rod of the air cylinder 14 sinks accordingly, changing the amount of swing of the second swing lever 12.

Note that 13a is a guide body that supports the press rod 13 so as to be able to move up and down, and 11a is a support that supports the first swing lever 11.

(Problem to be Solved by the Invention) By the way, since the bonding tool 4 of such an inner bonding apparatus has a constant cam height, the time (bonding time) T applied to the semiconductor element depends on the thickness (height) of the semiconductor element. There is a problem that the pressure changes due to the pressure applied by the bonding tool 4. Moreover, there is a problem in that the pressurizing force F also changes due to a change in the amount of depression of the air cylinder 14 that operates together with it.

Specifically, regarding the pressurizing time T, if rAJ is the time when there is no semiconductor element on the upper surface of the workpiece holding part 1 in the tool stroke H of the bonding tool 4 as shown in FIG. , Hl (H,<Hl
), the tool stroke H
changes to rBJ and rcJ accordingly. However,
Here, as the tool stroke H changes, due to the characteristics of the cam 7, the timing at which suppression begins and the timing at which suppression ends also changes, so as the thickness increases, the time T applied to the semiconductor element increases. As shown by rTtJ and rTzJ, it becomes longer than the initial set time To. Of course, this is the same even if the lowering speed of the bonding tool 4, which is represented by the inclination of the tool stroke, is changed.

Regarding the pressing force F, the characteristics of the damper means,
That is, looking at the characteristics of the air cylinder 14, as shown in FIG.
There is a relationship in which a predetermined pressing force is obtained after the rod has stroked to "Sl". In other words, “S
If the air cylinder 14 is not stroked beyond "Sl", the predetermined pressing force will not be obtained.On the other hand, if the thickness of the semiconductor element is thin and the stroke is smaller than the rod stroke "Sl", the predetermined pressing force will not be reached. bring. Specifically, if a predetermined pressing force of rcJ is reached at "T2" in FIG. 5, then rToJ.

At "T1", the predetermined pressing force cannot be obtained as shown by rag and rbJ below.

For this reason, when semiconductor elements having different thicknesses are bonded, there is an inconvenience that the bonding state changes due to changes in pressurizing time (bonding time) and pressurizing force.

Therefore, if the thickness of the semiconductor element changes, it may be possible to adjust the tool stroke by changing the height of the workpiece holder 1 each time, but this adjustment is delicate and is quite difficult. , and also consumes a considerable amount of time, and improvements are desired.

This invention was made with attention to these circumstances,
It is an object of the present invention to provide an inner lead bonding device capable of bonding semiconductor elements of different thicknesses without requiring difficult adjustment work and without changing pressurizing time and pressurizing force.

[Structure of the Invention (Means for Solving the Problem) In order to achieve the above object, a sensor is provided to detect when the bonding tool comes into contact with a semiconductor element, and the bonding tool is activated in response to a detection signal from the sensor. A control means is provided for controlling the rotational speed of the driving motor and for terminating the suppression process by the bonding tool after a predetermined period of time has elapsed from the time when the bonding tool came into contact with the semiconductor element.

(Operation) When it is detected that the bonding tool has touched the semiconductor element, the bonding tool is moved at a certain time from that moment in order to complete the predetermined suppression process. As a result, the desired bonding is completed within a certain period of time regardless of the difference in the thickness of the semiconductor elements. At the same time, the desired bonding is always performed at a constant time, so that the damper means is brought to a level where a constant pressing force can be obtained.

(Example) The present invention will be described below based on an example shown in FIGS. 1 to 3. However, in the drawings, components that are the same as those described in the "Prior Art" section are given the same reference numerals and their explanations are omitted, and in this section, different parts that are the main parts of the invention will be explained. I'll decide.

That is, this embodiment differs in that the drive system of the bonding tool 4 is controlled. Specifically, a servo motor 20 having a position and speed control function is used in place of the AC motor, and a cam 7 is provided on the output shaft of this servo motor 20. Further, on the action point side of the first swing lever 11, there is a gap sensor 23 for detecting a gap between a portion of the first swing lever and a portion of the second swing lever directly above the first swing lever. (corresponding to the sensor of this invention) is provided. Then, this gap sensor 23
The servo motor 20 is connected to an external control circuit 22 (corresponding to control means) as shown in the figure to control the servo motor 20.

A window comparator 26 is connected via the hold 25. Further, the output section of the amplifier 24 is directly connected to the remaining human power section of the window comparator 26.

The structure is such that a control section 27 is connected to the window comparator 26. And sample hold 25
According to the sample hold signal from the control section 27,
The sensor output before the bonding tool 4 contacts the semiconductor element is sampled and held, and this sampled and held output is supplied to the window comparator 26 as a reference value. Also window comparator 2
6 has a configuration in which a non-detection level region of a predetermined width is set by arithmetic processing with the reference value as a center value,
Based on a level comparison between the non-detection level region and the output from the gap sensor 23, a detection signal can be generated when the detection output deviates from the non-detection level region. Then, as the gap between the first swing lever 11 and the second swing lever 12 becomes smaller, the detection output goes out of the non-detection level region. It is determined that the object has definitely come into contact with the top surface of the object. The control unit 27 is also set to change the rotational speed of the cam 7 so that when it recognizes that it has come into contact with a semiconductor element, the process necessary for suppression is completed within a certain period of time rToJ from that position, and based on this setting, the servo The structure is such that the rotational speed of the motor 20 is controlled. Further, the control unit 27 controls the servo motor 20 to control the bonding tool 4 in a combination of a high speed movement region It is also imposed on

Thus, in such an inner lead bonding device, when the servo motor 20 rotates, the cam 7 rotates following the rotation of the servo motor 20. As a result, the first swing lever 11
begins to swing downward via the cam follower 10, and the press rod 13 moves downward via the second swing lever 12. This movement at the beginning of the descent is carried out at a considerable speed, and then the speed slows down midway through. As the pressing rod 13 descends, the bonding tool 4 descends against the elastic force of the compression spring 3, and the tip of the bonding tool 4 comes into contact with the upper surface of the semiconductor element.

On the other hand, while the bonding tool 4 is being lowered, the sample hold 25 samples and holds the output from the gap sensor 23, and outputs the sample hold output to the window comparator 26 as a reference value. Then, when the gap between the first swing lever 11 and the second swing lever 12 becomes smaller and the output from the gap sensor 23 exceeds the non-detection level region calculated by the window comparator 26, the control unit 27 Then, it is recognized that the tip of the bonding tool 4 has securely contacted the upper surface of the semiconductor element, and from that moment on, it moves by a certain amount of stroke required for suppression in a certain period of time.

That is, as shown in FIG. 3, for example, when rAJ is a state in which there is no semiconductor element on the upper surface of the workpiece holder 1,
Assuming that the pressurizing time rTo J is set as in the case of the "prior art", when a semiconductor element with a different thickness "Hl" is placed on the workpiece holder 1, the upper surface of the semiconductor element When it is detected that the bonding tool 4 has come into contact with
Control is performed to increase the rotational speed of the servo motor 20 by -ToJ, and the suppression process by the cam 7 is ended at "To".

In addition, semiconductor elements with different thicknesses "H2" are held in the workpiece holding part 1.
When it is placed in
Control is performed to increase the rotational speed of the cam 7, and the pressing process by the cam 7 is completed at rToJ.

Of course, regardless of the thickness of the semiconductor element, the pressurization time is always set to "To", as is clear from the diagrams of rag, rbJ, and rcJ in FIG. Both the time and the amount of depression of the rod of the cylinder 14 are always constant.

Through this suppression process, the electrode bumps of the semiconductor element are crimped to the inner leads of the lead frame.
They are bonded.

In this way, even if the thickness of the semiconductor element changes, bonding can be performed without changing either the pressurizing time or the pressurizing force. Of course, after the bonding tool 4 contacts the semiconductor element, the stroke is simply moved by a certain amount in a certain period of time, so even if the descending speed of the bonding tool 4 changes, the pressurizing time and force will not change. .

Therefore, even if the thickness changes, the bonding state will not change. In addition, by adopting a structure in which the bonding tool 4 is lowered at high speed at the beginning and lowered at low speed from the middle, damage when the bonding tool 4 collides with the semiconductor element is minimized, and until the bonding tool 4 contacts the semiconductor element. time (takt time) can be shortened. Particularly, this is because the descending speed of the bonding tool 4 can be slowed down just before the bonding tool 4 makes contact.

Moreover, the difficult adjustment work described in the section of ``Prior Art'' is almost eliminated.

In one embodiment, the present invention was applied to an inner lead bonding device having a motion conversion mechanism configured using two swing levers, but the present invention is also applicable to inner lead bonding devices having other motion conversion mechanisms. You can.

[Effects of the Invention] As explained above, according to the present invention, semiconductor elements of different thickness can be bonded without changing the pressurizing time and the pressurizing force, preventing changes in the bonding state, Bonding defects can be eliminated. Moreover, hardly any difficult adjustment work is required.

[Brief explanation of the drawing]

Figures 1 to 3 show one embodiment of the present invention.
The figure is a side view showing the inner lead bonding device, Figure 2 is a block diagram showing its control circuit, Figure 3 is a diagram showing the movement of the bonding tool during bonding together with the movement of the air cylinder, and Figure 4 is a diagram showing the movement of the bonding tool during bonding. A side view showing a conventional inner lead bonding device, Fig. 5 is a diagram showing the movement of the bonding tool during bonding together with the movement of the air cylinder, and Fig. 6 shows the characteristics of the damper means composed of the air cylinder. FIG. 4... Bonding tool, 9... Movement conversion mechanism,
14...Air cylinder (damper means), 20...
- Servo motor, 22... control circuit (171) control means), 23... gap sensor. Applicant's agent Patent attorney Takehiko Suzue Figure 2 Figure 3

Claims (1)

[Claims] The cam of a motor provided with a cam on its output shaft and a bonding tool that can be raised and lowered are connected via a motion conversion mechanism configured with a cam follower that is combined with the cam, and the driving force of the motion conversion mechanism is In an inner lead bonding apparatus, a damper means for adjusting the amount of tool movement is interposed in the middle of a transmission path, and the semiconductor element is pressed and bonded to the inner lead by vertical movement of the bonding tool by the cam, wherein the bonding tool is attached to the semiconductor element. A sensor is provided to detect when the bonding tool contacts the semiconductor element, and the rotational speed of the motor is controlled in response to a detection signal from the sensor, and the bonding tool An inner lead bonding apparatus characterized in that it is provided with a control means for terminating a pressing process.