JP2507640B2 - Bonding apparatus and bonding method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a bonding apparatus and a bonding method in which a plurality of bumps on an IC chip and inner leads are superposed and pressed by a tool for connection. is there.

[Conventional technology]

Regarding this type of bonding, JP-A-57-37842
The technique described in Japanese Patent Publication is known. In this known technique, in order to ensure the parallelism between the IC chip surface on which bumps are formed and the tool lower surface, a copying mechanism including a spherical sliding portion is provided on the bonding stage on which the IC chip is mounted.

FIG. 8 (a) shows the structure of the known device.
A spherical seat 22 installed on the base 21 holds the spherical sliding member 23 in a rotatable and slidable state. Above spherical sliding member
The IC chip 25 is mounted on the 23, and when the tool 14 is unbalanced due to uneven heights of the bumps 26a and 26b formed on the IC chip 25 or the initial inclination of the tool 14, spherical sliding occurs. The member 23 rotates and slides to the state shown in FIG. In this conventional example, since the bump 26a is taller than the bump 26b,
(B) As shown in the figure, the spherical sliding member 23 rotates clockwise in the figure to eliminate the one-sided contact.

[Problems to be Solved by the Invention]

In the copying operation in the conventional bonding apparatus shown in FIG. 8, consideration is given to the fact that the frictional force of the sliding portion differs depending on various causes (for example, the contact state of the sliding portion such as a change in sliding area due to rotation). However, there is a problem that the characteristics of the copying operation change according to the amount of posture correction for each bonding. For example, there is a problem that one-sided contact cannot be avoided if the applied pressure is smaller than the frictional force.

Further, in the above-mentioned conventional technique, since the copying is passively performed according to the unbalanced load received from the tool, the temporal behavior of the copying operation is influenced by the pressing force of the tool, the speed of the tool at the time of contact start, and the magnitude of the unbalanced load. Therefore, there is a problem that the reproducibility is easily damaged.

A first object of the apparatus and method according to the present invention is to achieve a copying operation having the same characteristics regardless of the amount of posture correction between the IC chip surface and the tool surface.

A second object of the apparatus according to the present invention is to achieve a copying operation with improved reproducibility in the behavior during the period from when the tool starts to contact the leads and bumps to when the tool is uniformly pressed. .

[Means for solving the problem]

The basic principle of the present invention created in order to achieve the above object will be outlined below in comparison with the conventional example (FIG. 8).

In the conventional example, when a biased force is applied, the posture is corrected by the biased force (FIG. 8 (b)) to actuate followingly. On the other hand, in the present invention, the above-mentioned biased force is detected, and the bias is actively taken to eliminate the bias.
Controls the attitude of the IC (specifically, the member on which the IC chip is mounted).

As a specific configuration based on the above-described principle, the bonding apparatus of the present invention has an IC chip mounted in a bonding apparatus in which a plurality of bumps on an IC chip and inner leads are superposed and pressed by a tool for connection. Supports the member against the base,
An actuator that can be expanded and contracted in the vertical direction, a means for detecting the distribution of stress received by a member mounted with the IC chip when the IC chip is pressed by the tool, and an output signal of the stress distribution detection means are input. And an automatic control device for expanding and contracting the actuator so as to make the stress distribution uniform.

Further, the bonding method of the present invention, in a bonding device in which a plurality of bumps and inner leads on an IC chip are overlapped and connected by pressing with a tool, a member on which an IC chip is mounted is supported with respect to a base.
Provided with an actuator capable of expanding and contracting in the vertical direction, provided with means for detecting the distribution of stress received by the member mounted with the IC chip when the IC chip is pressed by the tool, and the stress distribution detection means When an output signal is input, the actuator is expanded and contracted so as to make the stress distribution uniform.

[Action]

According to the above-described device and method, the scanning operation is not performed by the pressing force, but the uneven stress distribution is detected and the actuator is actively expanded / contracted to make the stress uniform. The copying operation with the same characteristics is performed regardless of the amount of posture correction), and the second purpose (improvement of reproducibility) is achieved.

〔Example〕

FIG. 1 shows an embodiment of a bonding apparatus according to the present invention, (a) is a perspective view and (b) is an exploded perspective view.

1a, 1b and 1c shown are piezoelectric actuators, 2 is a steel ball support, 3 is a steel ball, 4 is a support, 5 is a conical recess,
6 is a tension spring, 7 and 8 are hooks, 9 is a base fixed on the alignment stage, and 10 is a detection stage.

The three piezoelectric actuators 1a, 1b, 1c are fixed to the base 9 in an upright posture as shown in the figure. A steel ball 3 is held in a recess formed on the upper surface of a steel ball support 2 fixed to the upper surface of each piezoelectric actuator. The report 4 is attached so as to hold the steel balls from above in the recesses 5 provided on the lower surface corresponding to the positions of the steel balls.
The tension spring 6 applies a preload to each contact portion so that the base 9, the piezoelectric actuator 1, the steel ball support 2, the steel ball 3, and the support 4 are not separated from each other. Support 4
On the top surface of the
10 is installed. In this embodiment, the detection stage 10
It also serves as a bonding stage for mounting the IC chip 25.

Next, the details of the detection stage 10 will be described with reference to FIG. 6A is a sectional view of the mechanism attached to the support 4, FIG. 8B is a view of the detection stage 10 seen from below, and FIG. 7C is a view showing a configuration of a detection circuit.

The periphery of the detection stage 10 is fixed to the support 4, and the central portion of the detection stage 10 is in contact with the spherical sliding member 15. The spherical sliding support 16 is fixed to the support 4.

As shown in FIGS. (A) and (b), the detection stage 10 is provided with a concentric groove-shaped notch portion 17 so as to be easily bent and deformed, and strain gauges 11a to 11h are circled on the upper surface thereof. 90 around
Four sets are attached at intervals of °. 2 each 1
The set of strain gauges is composed of active gauges 11a to 11d that detect the amount of strain due to elastic deformation, and dummy gauges 11e to 11h arranged for temperature compensation. The output signal line of the strain gauge 11 is connected so as to be assembled in a bridge circuit at the positions of point symmetry with each other on the circumference, as shown in FIG.

Next, the operation of the present bonding stage posture correction mechanism will be described with reference to FIG.

For convenience of explanation, as shown in FIG.
Assuming an x-axis and a y-group on a diagonal line passing through, rotation pitching around the x-axis and rotation around the y-axis are called rolling.

FIGS. 3 (a) and 3 (b) show states before and after correction of the pitching posture, and FIG. 3 (c) and FIG.
(D) shows the rolling posture before and after correction.

The notch 17 has a thin member and is made easily to be elastically deformed. Therefore, when the tool 14 comes into partial contact with the IC chip and the detection stage receives an eccentric load, the notch 17 is cut as shown in FIG. The notch portion 17 elastically deforms, and the strain gauge 11c on the right side of the pair of left and right strain gauges extends and the strain gauge 11a on the left side contracts. For this reason, a signal roughly equal to the magnitude of the unbalanced load is generated in the circuit in which these strain gauges are assembled in the bridge circuit. By detecting and processing this signal, the magnitude of the unbalanced load can be obtained in real time at any time.

When it is detected that an eccentric load is applied, the control device controls the amount of expansion and contraction of each piezoelectric actuator 1a, 1b, 1c so that the piezoelectric actuator on the side where the tool is one-sided is relatively short. This is done by changing the voltage applied to each piezoelectric actuator 1a, 1b, 1c. In the case of FIG. 3 (a), as shown in FIG. 3 (b), the actuator 1a is expanded by pressure so that the piezoelectric actuators 1b, 1c are contracted by more than the reference length. As a result, the support 4 changes its posture, and the contact state between the tool and the detection stage returns to the one-sided contact state. That is, the spherical sliding member 15 that supports the detection stage can perform bonding while maintaining its reference position.

The posture correction operation is similarly performed for the rolling postures shown in FIGS. 3C and 3D, and the one-side contact state can be avoided. In this case, the piezoelectric actuator 1c is made longer than the reference length, and the piezoelectric actuator 1b is made shorter than the reference length.

In accordance with the principle described above, the piezoelectric load is applied to the detection stage 10 so that it becomes zero (that is, the stress distribution of the detection stage 10 becomes uniform and the amount of expansion and contraction of each strain gauge becomes zero). By applying electrical operation to the actuator, the posture correction operation can be performed for each bonding.

Due to the above-described action, the posture relationship between the detection stage 10 and the spherical sliding portion 15 that are the portions that detect the eccentric load is always constant, and the reproducibility of the detection characteristics and the scanning characteristics can be kept high.

4A and 4B show an example of a bonding tool drive mechanism used together with the above-described bonding stage posture correction mechanism, wherein FIG. 4A is a front view and FIG. 4B is a side view.

Although the bonding stage posture correction mechanism described with reference to FIGS. 1 to 3 is provided between the base 29 and the IC chip 25, the illustration is omitted to simplify the drawing.

For convenience of explanation, three orthogonal axes X, Y, Z are entered, but these coordinate axes are different from the x-axis and y-axis in FIG. 1 (a) described above.

The tool stage 30 is guided so as to be movable in parallel to the Y direction with respect to the base 29, and the Y axis is moved by the servo motor 31.
It is reciprocally driven in the direction.

A servo motor 32 is fixed on the tool stage 30 described above, and an input link 34a of a link mechanism 34 is connected via a speed reducer 33.
It has a structure that can change the angle of. The output link 34c of the above link mechanism is held so as to be vertically movable along the slide guide mechanism 35, and the head base 36 connected to this is held.
Also, the tool 14 is configured to be driven up and down.

The head base 36 has a notch 37 formed therein, and the tool 14 pressurizes the IC chip 25 so that the notch 37 is formed.
The load cell 38 held on the upper surface of the head base is pressed against the set screw 39 by the elastic deformation of 37, and the strain signal generated at that time is detected from the load cell. It can be detected at some point.
With this detection mechanism, it is possible to detect the pressing force without including an error caused by friction existing in the sliding portion. However, since the elastic force of the notch part is a structure that balances with a part of the pressing force of the tool, the pressing operation is performed with a known pressing force in advance, and the strain signal of the load cell at that time is measured,
It is necessary to calibrate.

The tool 14 is driven by inputting output pulse signals of pulse encoders 40 and 41 arranged coaxially with the servomotors 31 and 32 to a pressurizing mechanism controller (not shown) to obtain the rotation angle of the servomotors. Then, the position of the tool 14 in the front-rear direction (Y direction) and the vertical direction (Z direction) is obtained, and the target current value to be output to the servo motor is calculated based on this position. Further, from the position where the tool 14 can come into contact with the IC chip, the above-mentioned pressing force detection is simultaneously performed in parallel, and the above calculation is performed based on both the position detection value of the tool 14 and the pressing force detection value.

FIG. 5 is an example of a control block diagram of a bonding apparatus using the above-described bonding stage attitude correction mechanism. In the figure, the pressurizing mechanism control device 42 has a tool driving algorithm 43 and a copying motion control algorithm 44 simultaneously processed therein in parallel.

The tool driving algorithm 43 described above detects the reaction force received by the tool 14 coming into contact with the IC chip 25 by the load cell 38 described above, and detects this by the amplifier 45 and the A / D converter 4
The servo motor 32 that drives the tool is controlled based on the detection value taken in through 6. A pulse encoder 41 is attached to the servo motor 32, and a counter 47 processes this pulse to obtain information on the position and deceleration of the tool. The tool is driven by the power amplifier 48 keeping the value of the motor current 49 based on the detected value of the reaction force and the detected value of the position and speed of the tool.

On the other hand, the scanning operation algorithm 44 takes in the biased load component detected by the strain gauge 11 via the amplifier 50 and the A / D converter 51, and the reaction force and the tool applied to the tool obtained by this and the tool driving algorithm 43. Calculate the command value to the piezoelectric actuators 1a to 1c based on the speed, and use the D / A converter 52a.
-C and amplifiers 53a-c through piezoelectric actuator 1a
Outputs the voltage applied to ~ 1c.

FIG. 6 is a block diagram of posture correction control calculation for each unbalanced load of pitching and rolling. here,
54p is a target value of the pitching moment, 58p is a detected value of the pitching moment, 55 is an integral calculator, 56 is a proportional constant coefficient unit, 57p is a pitching attitude correction signal, and 59 is an addition calculator. 54r is the target value of rolling moment, 58r
Is a detected value of the rolling moment, and 57r is a rolling posture correction signal. Here, a feedback loop is formed for each component of pitching and rolling, and then each component is distributed to each piezoelectric actuator.

All of the above-described detection of the eccentric load component, calculation of the output voltage to the piezoelectric actuator, detection of the reaction force of the tool pressure force, detection of the tool position and speed, and calculation of the output to the tool drive motor Pressurization mechanism controller 42 shown in the figure
It is activated at a fixed time interval by the timer inside,
Appropriate actions are taken to make the dynamic copying behavior desirable.

By the above-described operation, the posture correcting operation can be performed accurately and with good reproducibility, and the pressing operation that is uniform for each bump can be achieved. Therefore, there is a practical effect that the reliability of bonding is improved.

FIG. 7 shows an apparatus of an embodiment different from the above, FIG. 7A is a sectional view of the stress distribution detecting mechanism portion, and FIG. 7B is a plan view.

The difference from the above-described embodiment is that a steel ball 60 is mainly used instead of the spherical sliding member 15 shown in FIG. 2 (a). By accurately arranging the contact point between the steel ball 60 and the detection stage 10 at the center of pressurization, an unbalanced load can be detected by the same principle as the detection mechanism using the spherical sliding member 15 in FIG.

In the present embodiment (FIG. 7), the bonding stage 61 is fitted in a hole 62 provided in the central portion of the detection stage 10 and attached so as to come into contact with the steel ball 60 held by the support 4. 63 is a set screw.

In this embodiment, since there is no sliding portion, the posture correcting operation can be realized with higher accuracy.
Further, there is a feature that the characteristic of the posture correcting operation can be made constant even if the tool is kept in an arbitrary one-side contact state.

For example, when the bump arrangement on the IC chip is not uniform and the tool has to be placed on one side at a certain ratio in order to make the load on each bump uniform, the device of the embodiment of FIG. If is applied, it can be handled only by changing the reference value of the motion control.

In the embodiment of the method of the present invention described above, the posture is corrected every bonding operation. Next, an embodiment of a method different from the above will be described.

It is widely known that a large number of IC chips in the same lot have a similar tendency when industrially mass-producing IC chips.

Depending on the lot of IC chips, the bump heights may be relatively uniform, and the initial parallelism deviation between the tool and the bonding stage may be larger. In such a case, the method of the embodiment described below is suitable.

According to the method of the present embodiment, the posture correction operation is performed only once when the apparatus is started up, and the resulting scanning angle is kept as the uniform pressure posture in the subsequent bonding. Then, when the unbalanced load detection value exceeds a predetermined threshold value, the posture correction operation is performed again.

According to this embodiment, the initial parallel alignment at the time of exchanging the tool is possible with only one bonding, and the parallelism deterioration can be promptly corrected. Therefore, there is a peculiar effect that the disconnection time at the time of switching the IC chip type can be shortened.

In each of the embodiments described above, the contact of the tool,
The in-plane uniform pressing operation, that is, the uniform pressing force distribution, can be achieved with good reproducibility over the entire period of pressing by the tool and rising of the tool. A remarkable effect can be obtained in reducing the defect rate and extending the life of a certain IC chip.

In the above embodiments, the description has been limited to the TAB inner lead bonding apparatus, but the present invention can be applied to a technique of pressing or adhering with a tool, such as a die bonder, a pellet bonder, or an inner transfer bump using transfer bump. It can also be applied to bump transfer technology in lead bonding, inner lead bonding to IC chips, tool pressure operation in tool heating solder reflow technology, and generally pressure bonding, bonding, and adhesion technology by surface pressure. High quality bonding can be achieved.

〔The invention's effect〕

As described above, when the bonding operation is performed using the apparatus and method of the present invention, the stress distribution of the member that receives the pressing force is made uniform, and the physical state of the portion that receives the unbalanced load is always constant. Since it is possible to operate the copying mechanism, there is an effect that a tracing operation with the same characteristics can be achieved regardless of the amount of posture correction between the IC chip surface and the tool surface. Furthermore, since the control of the tool speed and the copying operation can be set separately, it is possible to achieve reproducible inner lead bonding with regard to the behavior during the period from when the tool starts contacting the leads and bumps to when the tool is uniformly pressed. effective.

[Brief description of drawings]

FIG. 1 shows an embodiment of the bonding apparatus of the present invention,
FIG. 3A is a perspective view of the bonding stage, and FIG. 3B is an exploded perspective view of the same. 2A is a sectional view of the copying mechanism portion in the above embodiment, FIG. 2B is a bottom view of the same, and FIG. 2C is an explanatory view of a connected state of a strain gauge. 3 (a), (b), (c), and (d) are explanatory views of the posture correcting operation in the above embodiment. FIG. 4 shows a tool driving mechanism used in combination with the above-mentioned embodiment, (a) is a side view and (b) is a front view. 5 and 6 are block diagrams of the control mechanism in the above embodiment. FIG. 7 shows a stress distribution detecting mechanism in an embodiment different from the above, (a) is a sectional view and (b) is a plan view. 8A and 8B are schematic cross-sectional views showing a conventional bonding apparatus. 1a, 1b, 1c …… Piezoelectric actuator, 2 …… Steel ball support, 3 …… Steel ball, 4 …… Support, 6 …… Tension spring,
9 ... Base, 10 ... Detection stage, 11a-11h ... Strain gauge.

Claims (7)

(57) [Claims] 1. A bonding apparatus for stacking a plurality of bumps on an IC chip and inner leads and pressing and connecting them with a tool to support a member on which the IC chip is mounted with respect to a base, and expand and contract in the vertical direction. A possible actuator, a means for detecting the distribution of stress received by a member mounted with the IC chip when the IC chip is pressed by the tool, and the output signal of the stress distribution detecting means is input, An automatic control device for expanding and contracting the actuator so as to make the distribution uniform, a bonding device. 2. The bonding apparatus according to claim 1, wherein the actuator is a piezoelectric actuator. 3. A spherical member having rigidity is interposed between the actuator and a member on which the IC chip is mounted, and an upper surface of the actuator and a lower surface of the member on which the IC chip is mounted. Each of the above is provided with a concave portion that engages with the spherical member.
The bonding apparatus according to. 4. A tension spring is interposed and engaged between the base and a member on which the IC chip is mounted to preload the actuator and the spherical member. The bonding apparatus according to claim 3. 5. A bonding apparatus for stacking a plurality of bumps on an IC chip and an inner lead and pressing and connecting them with a tool to support a member on which the IC chip is mounted with respect to a base, and expand and contract in the vertical direction. In addition to providing a possible actuator, a means for detecting the distribution of the stress received by the member mounted with the IC chip when the IC chip is pressed by the tool is provided, and the output signal of the stress distribution detecting means is input. Then, the bonding method is characterized in that the actuator is expanded and contracted so as to make the stress distribution uniform. 6. The actuator is expanded and contracted by using an automatic control device which receives the output signal of the stress distribution detection means and expands and contracts the actuator so as to make the stress distribution uniform. Claim 5
Bonding method described in. 7. A spherical member having rigidity is interposed between the actuator and the member on which the IC chip is mounted, and the upper surface of the actuator and the lower surface of the member on which the IC chip is mounted. The bonding method according to claim 5 or 6, wherein a concave portion that engages with the spherical member is provided in each of the.