KR20230024511A - A flip chip laser assisted bonder with precise pressing device - Google Patents

Abstract

In the present invention, disclosed is a flip chip laser bonding machine equipped with a precision pressurizing device (400) to mechanically bond, without error, the bending and misalignment of a chip and a substrate that occur during laser bonding. The precision pressurizing device (400) consists of: a fixing unit (410) for fixing a pressurizing tool (H) for pressurizing the semiconductor chip and the substrate; a vertical guide (420) for guiding the fixing unit (410) in the Z-axis direction; and an actuator (430) that vertically elevates the fixing unit (410). The fixing unit (410) is provided with a pressure roller (412) at the upper outer center of the pressurizing tool (H). The actuator (430) comprises: a servomotor (432) fixed to the upper part of a vertical support plate (V); a ball screw (434) axially coupled to the servomotor (432); a lifting block (436) that is vertically lifted by the ball screw (434); and a pressure beam (438) that is horizontally attached to the lifting block (436) and raises and lowers the fixing unit (410) by contacting the pressure roller (412).

Description

Flip chip laser bonding machine with precision pressing device {A FLIP CHIP LASER ASSISTED BONDER WITH PRECISE PRESSING DEVICE}

The present invention relates to a flip chip laser bonding machine for bonding a semiconductor chip to a substrate, and more particularly, to a flip chip equipped with a precision pressurizing device for mechanically bonding the chip and substrate warp and positional distortion without errors occurring during laser bonding. It relates to a chip laser bonding machine.

In general, the flip chip bonding process is performed by passing a bump structure called a lead-free lead or Cu pillar through convection reflow. Due to the structure of the reflow method, the substrate and the semiconductor chip receive heat at the same time, causing unwanted problems. . When the substrate is heated, it expands, and due to a difference in thermal expansion coefficient between the semiconductor chip and the substrate, bonding is not properly performed, and a bump or a microcircuit layer of the semiconductor chip is damaged.

A breakage of even one of the thousands of bumps can compromise package functionality, so great efforts have been made to ensure that the bumps do not get damaged during reflow.

In order to solve this problem, a laser assisted bonding technique has been studied. In general, the time to pass through reflow is about 5 to 7 minutes, but laser assist bonding using laser technology applies heat to only the chip part for a very short time of 1 to 2 seconds per area for bonding. Therefore, a high temperature is maintained only in the semiconductor chip and its surroundings, and the temperature in other regions is relatively low. Since the time exposed to heat is short and the area is localized, the thermal stress generated in the semiconductor chip and bump is relatively low. In addition, laser bonding is about 1/7 smaller than conventional convection reflow equipment, and it is very excellent in terms of space utilization because it does not require N ₂ gas.

In addition, for integration of the latest semiconductor IC and diversification of functions, it is necessary to form as many bump pads as possible within a single semiconductor chip, so the pitch between terminals is narrowed, and the board to meet the trend of light weight and multifunctionality. and semiconductor chips are also undergoing change. Film-type substrates are being used, and chip thicknesses are getting thinner to be suitable for high-density mounting, and bonding areas are widening, and the application rate of 2.5D/3D packages is increasing.

For this reason, in the bonding process of semiconductor chips, a method of bonding by heating local heat in a short time has recently been introduced. However, even if heat is applied directly to the chip, if something does not precisely press the chip, distortion or bumps and bumps will cause quality degradation due to curvature of the chip due to its influence. Existing laser bonding / soldering methods including Patent Document 1 1 and 2, the pressure device 10 includes a cantilever 12 to which a pressure tool H including a bonding head is fixed, and an actuator 14 for lifting the cantilever 12 And since it takes a structurally simple cantilever form comprising an LM guide 16 that supports one side of the cantilever 12 so as to be able to move up and down, when pressurized using a pressurizing device made of such a cantilever form, shown in FIG. As shown schematically, the deformation that inevitably occurs in the structure of the cantilever, that is, the minute deformation of the cantilever 12 by the reaction when the force pressing the cantilever 12 is applied to the pressing tool H, that is, the bending moment ) occurs, so the force is distributed less towards the free end (left side in the drawing) than the fixed end (right side in the drawing) of the cantilever 12, and the table T and the semiconductor chip C where the substrate S is placed ) is broken in the parallelism and perpendicularity between the fixed pressing tool H, which causes an angular error and a positional error between the semiconductor chip C and the substrate S during pressing, which in a partially enlarged view of FIG. As can be seen, the bump B1 of the semiconductor chip C and the bump B2 of the substrate S do not match each other, causing a state in which conduction is not conducted, resulting in bonding failure.

Reference numeral L in the drawing is a laser generator for irradiating laser light to the semiconductor chip and the substrate through the pressure tool H.

Therefore, there is a need to provide a precise means for applying heat using a laser and pressurizing to prevent quality deterioration due to bending of the chip, and to prevent bending with respect to the pressing surface, and the position when pressing by the pressing tool A flip chip laser bonding machine equipped with a very precise pressing device capable of making the distortion error within the current highest accuracy of 2 μm is required.

Korean Registered Patent No. 10-2248159 (registered on April 28, 2021) Korean Patent Publication No. 10-2020-0142953 (published on December 23, 2020) Korean Patent Publication No. 10-2021-0052274 (published on May 11, 2021) Korean Registered Patent No. 10-0709614 (registered on April 13, 2007)

The present invention has been made to solve the above problems, and an object of the present invention is to solve non-wet bonding due to displacement of a semiconductor chip and a substrate in a pressurizing device made of a cantilever method in the existing laser bonding method. It is an object of the present invention to provide a flip chip laser bonding machine having a precision pressing device with an improved structure that can be used.

In addition, the basic structure of the pressing device is made in the form of a cantilever, so that the structure and size of the pressing device are simplified and minimized, while improving the precision of the structure that can solve the bonding defect due to the positional change and distortion that may occur during pressing It is an object of the present invention to provide a flip chip laser bonding device having a pressing device.

On the stage, a laser oscillation and precision pressing device is installed to be movable in the X-Y direction by a gantry, and laser bonding is performed by pressing the chip and substrate moved from the chip and substrate loading zone of the stage to the bonding zone. Flip chip bonding in terms of

The precision pressing device includes a fixing unit for fixing a pressing tool for pressing a semiconductor chip and a substrate, a vertical guide for guiding the lifting of the fixing unit in the Z-axis direction, and an actuator for vertically lifting the fixing unit. done by;

The fixing unit is provided with a pressure roller at the upper outer center of the pressure tool,

The vertical guide consists of a horizontal support plate fixed horizontally to a vertical support plate in a cantilever manner and a guide bar vertically installed below the horizontal support plate to guide the fixing unit to be vertically raised and lowered,

The actuator includes a servomotor fixed to an upper portion of a vertical support plate, a ball screw shaft-coupled to the servomotor, an elevating block vertically elevated by the ball screw, and a horizontally attached to the elevating block to contact the pressure roller. Provided is a flip chip laser bonding machine having a precision pressing device composed of a pressing beam for elevating a fixing unit.

In a preferred embodiment, a load cell is installed between the lift block and the press beam, and the servomotor has a flip chip with a precision press device that is controlled with two target values of the pressure sensed by the load cell and the position of the press tool. A laser bonding machine is provided.

According to the embodiment of the present invention, although the precision pressing device is made in the form of a cantilever, when pressing the semiconductor chip toward the substrate, since it is made in such a way that the center of the fixing unit to which the pressing tool is fixed is pressed, the vertical guide is horizontal during pressing. There is no deformation in the support plate and no deformation in the pressing beam, so there is no positional error or angle error. That is, since the pressing beam has the structure of a cantilever beam, structurally one-sided deformation inevitably occurs. However, in the present embodiment, the horizontal support plate of the vertical guide where no deformation occurs directly allows the fixing unit to precisely pressurize without error due to one-sided deformation. Since the semiconductor chip and the substrate are prevented from being displaced, the bonding position accuracy between the semiconductor chip and the substrate is improved, thereby improving bonding quality and minimizing a defect rate.

1 is a front view showing a pressing state of a conventional flip-chip bonding pressing device having a cantilever structure;
Figure 2 is a view for explaining the cause of deformation in the pressurizing device of the cantilever structure shown in Figure 1;
3 is a perspective view of a flip chip laser bonding machine equipped with a precision pressing device according to an embodiment of the present invention;
4 is a front view of the flip chip laser bonding machine shown in FIG. 3;
5 is a side view of the flip chip laser bonding machine shown in FIG. 3;
Figure 6 is a bottom perspective view of the precision pressing device shown in Figure 5;
Figure 7 is a perspective view of the precision pressing device shown in Figure 5;
8 is a side view of the precision pressing device shown in FIG. 5;
9 shows a bonding state between a chip and a substrate in the bonding machine of the present invention.

Hereinafter, preferred embodiments that do not limit the present invention will be described in detail with reference to the accompanying drawings.

3 to 9 show detailed structures of a flip chip laser bonding machine and a precision pressing device equipped with a precision pressing device according to an embodiment of the present invention.

First, in this embodiment, the laser oscillation device 300 and the precision pressing device 400 are installed to be movable in the X-Y direction by the gantry 200 on the stage 100, and the chip and substrate of the stage 100 In the flip chip bonding machine 1 configured to perform laser bonding by pressing a chip and a substrate moved from a loading zone to a bonding zone,

The precision pressing device 400 includes a fixing unit 410 for fixing a pressing tool H for pressing a semiconductor chip and a substrate, and a vertical guide for guiding the lifting of the fixing unit 410 in the Z-axis direction. 420 and an actuator 430 for vertically lifting the fixing unit 410;

The fixing unit 410 is provided with a pressure roller 412 at the upper outer center of the pressure tool T,

The vertical guide 420 is composed of a horizontal support plate 422 horizontally fixed to the vertical support plate V in a cantilever manner and a guide bar 424 vertically installed below the horizontal support plate 422. The fixing unit 410 ) is guided so that it is vertically lifted,

The actuator 430 is vertically operated by a servomotor 432 fixed to the top of the vertical support plate V, a ball screw 434 shaft-coupled to the servomotor 432, and the ball screw 434. It consists of a lifting block 436 that moves up and down, and a pressure beam 438 attached horizontally to the lifting block 436 and lifting the fixing unit 410 in contact with the pressure roller 412.

On the other hand, the lifting block 436 is fixed to the vertical support plate (V) by the LM guide 439 so as to be able to move up and down vertically.

In the figure, reference numeral 210 denotes an X-axis moving part of the gantry 200 for transferring the laser transmission device and the bonding head, and reference numeral 220 denotes a Y-axis moving part.

Further, reference numeral 426 is a through hole through which the laser irradiated from the laser oscillator 300 penetrates the housing of the pressure tool H under the fixing unit 410 and is irradiated to the semiconductor chip and the substrate. is a substrate transfer device for transferring a substrate on which a semiconductor chip is placed from a loading zone to a bonding zone.

In addition, in this embodiment, between the lifting block 436 and the pressing beam 438 shown in FIG. As shown, the load cell 440 is installed, and the servomotor 432 is controlled with two target values of the pressure sensed by the load cell 440 and the position of the pressure tool H.

To explain this, although not specifically shown in the drawing, the precision pressing device 400 according to the present embodiment has the pressing tool H from the initial position to the set low-speed conversion height by the Z-axis up-down motor, which is not shown. and descends to the contact height of the semiconductor chip (C) by driving the servo motor 432 of the precision pressing device 400, and in the low-speed descending step, the pressing tool (H) contacts the semiconductor chip (C) When the minimum pressure detectable by the load cell 440 is reached, it is determined that the pressure tool (H) and the semiconductor chip (C) are in contact. The device 300 oscillates and irradiates laser to perform bonding, and when bonding is completed, the pressure tool H rises to the final height to complete the bonding operation. In the section where the thermal expansion of the chip C and the substrate S occurs, the precision press device 400 switches from pressure control to instantaneous position control to prevent the non-wet phenomenon.

In the present embodiment, as shown in FIG. 9 , the fixing unit 410 to which the pressing tool H for pressurizing the semiconductor chip C is fixed can move up and down vertically by the vertical guide 420 . It is installed, and since the pressure roller 412 provided in the center of the upper outer side of the pressure tool H of the fixing unit 410 is pressed by the pressure beam 438 of the actuator 430, the actual fixing unit ( The pressure applied to the pressing tool H provided at the bottom of 410) is a difference in pressing force between the left and right (inside and outside) that inevitably occurs in the existing simple cantilever type fixing unit, that is, the structure that presses the pressing tool H And since the positional change between the semiconductor chip and the substrate due to deformation of the cantilever does not occur, bonding between the semiconductor chip C and the substrate S, that is, the bump B1 formed on the semiconductor chip C and the substrate S ,B2) has the advantage of maximizing the bonding quality and significantly reducing the defect rate by improving the positional accuracy between B2).

Structurally explaining this reason, the guide bar 424 is arranged on the left and right sides around the pressing tool H installed at the bottom of the fixing unit 410, so that the vertical lifting movement of the fixing unit 410 is stable. Despite the descent of the pressing beam 428, the horizontal support plate 422 supporting the guide bar 424 is not directly connected, so no deformation force is applied, and the fixing unit The pressure roller 412 provided on the outside of the pressure tool 410 is disposed on the upper outer center of the pressure tool H, that is, on the same center line as the pressure tool H, so that the pressure beam 438 of the actuator 430 When it is pressed while descending, mechanical deformation is applied to the press beam 438, and the deformed value slides horizontally by the roller 412 to offset the positional error that occurs when pressing, so that the press tool ( By ensuring that the pressure applied to H) is uniformly distributed throughout, pressure deviation does not occur, and even if a bending moment occurs in the pressure beam when the pressure beam 438 descends, this bending moment passes through the pressure roller 412 to the pressure tool Since it does not affect the maintenance of parallelism between the substrate and the semiconductor chip pressed by (H), angle errors between the semiconductor chip (C) and the substrate (S) are prevented from occurring during pressurization, thereby preventing the semiconductor chip (C) from occurring. Normal bonding can be performed in a state in which the positions of the bump B1 and the bump B2 of the substrate S are precisely aligned with each other.

As described above, in the flip chip laser bonding machine having the precision pressing device according to the present embodiment, the fixing unit 410 in which the pressing tool H is installed is supported by the vertical guide 420 so that the lifting operation can be performed vertically. In the state in which the pressure beam 438 of the actuator 430 is configured to press the pressure roller 412 provided at the central position of the fixing unit 410, the pressing force of the pressure beam 438 is applied to the lower portion of the fixing unit 410. Since the pressure tool (H) of the pressure tool (H) is uniformly dispersed and applied, a phenomenon in which the semiconductor chip (C) pressed by the pressure tool (H) and the substrate (S) fixed to the table (T) is displaced or parallelism is broken. Since bonding between bumps can be performed in a pressurized state without any pressure, it is possible to solve the problem of poor bonding in the existing cantilever-type pressurizing device. There are advantages such as being able to solve the defect problem.

1 : Flip chip laser bonding machine
100: stage
200: gantry
300: laser oscillation device
400: precision pressurization device
410: fixed unit
412: pressure roller
420: vertical guide
422: horizontal support plate
424: guide bar
426: through hole
430: actuator
432: servo motor
434: ball screw
436: lifting block
438: pressurized beam
440: load cell
500: substrate transfer device
B1,B2: bump
C: semiconductor chip
H: bonding tool
S: Substrate
T: table
V: vertical support plate

Claims (3)

On the stage 100, the laser oscillation device 300 and the precision pressing device 400 are installed to be movable in the XY direction by the gantry 200, and from the chip and substrate loading zone of the stage 100 to the bonding zone In the flip chip bonding machine 1 configured to perform laser bonding by pressing the moved chip and the substrate,
The precision pressing device 400 includes a fixing unit 410 for fixing a pressing tool H for pressing a semiconductor chip and a substrate, and a vertical guide for guiding the lifting of the fixing unit 410 in the Z-axis direction. (420) and an actuator (430) for vertically lifting the fixing unit (410);
The fixing unit 410 is provided with a pressure roller 412 at the upper outer center of the pressure tool T,
The vertical guide 420 is composed of a horizontal support plate 422 horizontally fixed to the vertical support plate V in a cantilever manner and a guide bar 424 vertically installed below the horizontal support plate 422. The fixing unit 410 ) is guided so that it is vertically raised,
The actuator 430 is vertically operated by a servomotor 432 fixed to the top of the vertical support plate V, a ball screw 434 shaft-coupled to the servomotor 432, and the ball screw 434. A precision pressing device characterized in that composed of a lifting block 436 that is elevated and a pressure beam 438 attached horizontally to the lifting block 436 to lift the fixing unit 410 in contact with the pressure roller 412 Flip chip laser bonding machine having a.
The method of claim 1,
The guide bar 424 is disposed on the left and right sides of the pressure tool H installed at the bottom of the fixing unit 410, and the pressure roller 412 provided on the outside of the fixing unit 410 is the pressure tool ( H) flip chip laser bonding machine with a precision pressing device, characterized in that arranged on the same center line.
The method of claim 1,
A load cell 440 is installed between the lift block 436 and the pressure beam 438, and the servomotor 432 has two targets, the pressure sensed by the load cell 440 and the position of the pressure tool H. A flip chip laser bonding machine having a precision pressing device characterized in that it is controlled with a value.

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