KR20220083629A - Laser reflow method of laser reflow apparatus - Google Patents

Abstract

The present invention for achieving the above object is by irradiating a laser beam to the bonding object through the pressing member while pressing and pressing a bonding object on which a plurality of electronic components are arranged on a rectangular substrate with a light-transmitting pressing member. A laser reflow method of a laser reflow apparatus for bonding a component to a substrate, the laser reflow method comprising: a) disposing a plurality of solder bumps on a bottom surface of the electronic component; b) forming a plurality of electrode pads having a self-alignment groove (SAG) on the upper surface of the substrate; c) pre-aligning the solder bumps by seating each of the solder bumps in the self-alignment recessed grooves of the electrode pad; d) As the laser beam is irradiated to the temporarily seated solder bump, the spherical solder bump is melted and flowed, and after being completely positioned in the self-alignment recess, the laser beam is blocked and the solder bump is fixed in the self-alignment recess. a self-alignment step; e) when the step d is completed, the light-transmitting pressing member is moved downward to press the bonding object and irradiating a laser beam to the bonding object through the light-transmitting pressing member; f) when the irradiation of the laser beam is completed, moving the light-transmitting pressing member upward to release the pressing state; includes.

Description

Laser reflow method of laser reflow apparatus

The present invention relates to a laser reflow method, and more particularly, to a laser reflow method of a laser reflow apparatus for bonding electronic components by irradiating a laser while pressing a plurality of electronic components with a light-transmitting pressing member. .

In industrial laser processing, an application field with micron (㎛) precision is micro laser processing, which is widely used in the semiconductor industry, display industry, printed circuit board (PCB) industry, and smartphone industry. Memory chips used in all electronic devices have developed technologies to reduce the circuit spacing to a minimum to realize the degree of integration, performance, and ultra-high speed communication speed, but now, the required technology level has been achieved just by reducing the circuit line width and line width gap. It is difficult to do so, and it has reached the level of stacking memory chips in a vertical direction. The stacking technology up to 128 layers has already been developed by TSMC, and the stacking technology up to 72 layers is being applied to mass production by Samsung Electronics and SK Hynix.

In addition, technology development for mounting a memory chip, a microprocessor chip, a graphic processor chip, a wireless processor chip, a sensor processor chip, etc. in one package is intensely researched and developed, and a considerable level of technology has already been applied in practice.

However, in the process of developing the aforementioned technology, more and more electrons have to participate in the signal processing process inside the ultra-high-speed/ultra-high-capacity semiconductor chip, so the power consumption increases, and the issue of cooling treatment for heat has been raised. In addition, in order to achieve the requirements of ultra-high-speed signal processing and ultra-high-frequency signal processing for more signals, a technical issue that large amounts of electrical signals must be transmitted at high speed has been raised. In addition, since the number of signal lines has to be increased, it is no longer possible to process the signal interface lines to the outside of the semiconductor chip using a one-dimensional lead wire method, but a ball grid array (BGA) method (Fan-In BGA) that processes two-dimensionally at the bottom of the semiconductor chip. Or Fan-in Wafer-Level-Package (FIWLP)) and a signal layout redistribution layer under the ultra-fine BGA layer under the chip, and a second fine BGA layer is installed under it. The method (referred to as Fan-Out BGA or Fan-Out Wafer-Level-Package (FOWLP) or Fan-Out Panel-Level-Package) is being applied.

Recently, in the case of semiconductor chips, products with a thickness of 200 μm or less including an EMC (Epoxy-Mold Compound) layer have appeared. As such, in order to attach a micron-level ultra-thin semiconductor chip with a thickness of only several hundred microns to an ultra-thin PCB, the same mass reflow (SMT) standard process, Thermal Reflow Oven technology, is used. When the MR) process is applied, the semiconductor chip is exposed to an air temperature environment of 100 to 300 degrees (℃) for a period of several hundred seconds. - Various types of soldering bonding defects such as border warpage (PCB-Boundary Warpage) and Random-Bonding Failure by Thermal Shock may occur.

Accordingly, looking at the configuration of a laser reflow device that has recently been in the spotlight, a laser head module presses a bonding object (semiconductor chip or integrated circuit IC) for a few seconds while irradiating a laser to bond the semiconductor chip or integrated circuit. (IC) Bonding is performed by irradiating a laser in the form of a surface light source corresponding to the size.

For a laser reflow method of such a pressurization method, referring to Korea Patent Registration No. 0662820 (hereinafter referred to as 'Prior Document 1'), the flip chip is heated by irradiating a laser to the rear surface of the flip chip, while the flip chip is heated. A configuration of a flip-chip hot-pressing module for pressing a chip to the carrier substrate is disclosed.

However, the laser reflow method of the conventional pressurization method disclosed in Prior Document 1 includes a means for a pressurizing head module to adsorb a chip and move it to a bonding position, and heating the back surface of the chip through a laser while simultaneously carrying the chip as a carrier. Since it is separated by means for pressing on the substrate, when bonding a plurality of semiconductor chips such as a semiconductor strip, the operation time is increased because the operation of irradiating a laser while pressing one semiconductor chip must be repeatedly performed as many as the number of semiconductor chips. had no choice but to

Meanwhile, referring to Korean Patent Application Laid-Open No. 2017-0077721 (hereinafter referred to as 'Prior Document 2'), in the laser reflow method mentioned in the same patent, the laser head moves in a horizontal direction while the pressure head simultaneously presses several flip chips. In general, it is mentioned that bonding processing is possible by irradiating each flip chip with a laser one by one or by simultaneously irradiating lasers on several flip chips by a single laser head.

However, according to the conventional laser pressure head configuration of the above-mentioned Prior Document 2, since a single laser source is used, the homogenized laser beam is irradiated and defective as the laser beam is incident at various angles on a plurality of flip chips disposed on the substrate. Reflowing a plurality of flip chips without it is expected to be technically difficult.

Therefore, in the prior art, as a single flip chip is sequentially pressurized and reflowed one by one, the total working time has to be increased, and a single laser is applied to a plurality of flip chips horizontally arranged on various substrate sizes for a plurality of processes. Even if the beam is irradiated at the same time, it is virtually difficult to evenly transmit sufficient thermal energy to each flip chip, so there is still a problem in that it is difficult to improve the bonding defect rate.

In particular, in recent years, the application of a flexible PCB is expanding, and the thickness of the flexible substrate and electronic components is becoming thinner. problems are involved

For this reason, when pressurizing or irradiating electronic components with different height deviations on the flexible substrate as they are for bonding, the solder bumps of the electronic components leave the electrode pads, causing severe electrical open or short circuits. Since defects occur frequently, improvement is urgently needed.

Accordingly, the present invention was invented to solve the above problems, and the present invention self-positions so that the solder bumps of the electronic components located below are aligned with the precise fusion points of the electrode pads before the light-transmitting pressing member is pressed. By self-alignment, the pressure delivered to the electronic component when pressed by the light-transmitting pressure member is evenly pressed without being biased to one side, so that electrical open or short defects occurring between the solder bump and the electrode pad are eliminated. Accordingly, it is an object to provide a laser reflow method of a laser reflow device that enables mass processing while reflowing a plurality of electronic components at the same time by simultaneously pressurizing and irradiating a laser beam to improve the defect rate. .

The present invention for achieving the above object is by irradiating a laser beam to the bonding object through the pressing member while pressing and pressing a bonding object on which a plurality of electronic components are arranged on a rectangular substrate with a light-transmitting pressing member. A laser reflow method of a laser reflow apparatus for bonding a component to a substrate, the laser reflow method comprising: a) disposing a plurality of solder bumps on a bottom surface of the electronic component; b) forming a plurality of electrode pads having a self-alignment groove (SAG) on the upper surface of the substrate; c) pre-aligning the solder bumps by seating each of the solder bumps in the self-alignment recessed grooves of the electrode pad; d) As the laser beam is irradiated to the temporarily seated solder bump, the spherical solder bump is melted and flowed, and after being completely positioned in the self-alignment recess, the laser beam is blocked and the solder bump is fixed in the self-alignment recess. a self-alignment step; e) when the step d is completed, the light-transmitting pressing member is moved downward to press the bonding object and irradiating a laser beam to the bonding object through the light-transmitting pressing member; f) when the irradiation of the laser beam is completed, moving the light-transmitting pressing member upward to release the pressing state.

In addition, according to an embodiment, in the self-alignment of step d), in the process of melting and flowing solder bumps formed on electronic components in the self-alignment concave groove of the electrode pad, the self-alignment concave groove is formed by gravity. After being moved and positioned to the exact center, the vertical center axis of each solder bump and self-alignment concave groove coincides with each other while forming a spherical shape with surface tension.

Also, according to an embodiment, the temperature of the laser beam in step d) is higher than the melting point of the solder bump.

Also, according to an embodiment, any one of steps a) to d) further includes the step of performing vision imaging.

In addition, according to an embodiment, the laser beam is irradiated by overlapping the laser beam from two or more laser modules.

Also, according to an embodiment, each of the laser modules is arranged symmetrically to each other, and each of the laser beams has the same beam irradiation angle.

In addition, according to an embodiment, laser beams are simultaneously or sequentially irradiated from each of the laser modules.

In addition, according to an embodiment, at least one of the laser modules is continuously irradiated with a laser beam without interruption in the process from step d) to step e).

In addition, according to an embodiment, after step c), the board and electronic components are further moved using vibration or a jig so that the pre-aligned solder bump is located in the exact center of the self-alignment concave groove. sort

According to the present invention as described above, the pressure acting on the plurality of electronic components disposed on the substrate is biased by adjusting the position of the light transmitting pressure member so that the pressure is evenly distributed so that the light transmitting pressure member does not tilt the electronic component to one side and press it. Accordingly, there is an effect of preventing an electrical open or short fault occurring between the solder bump and the electrode pad.

In addition, there is an effect of preventing shift (Shift) when the pressing member is pressed by performing self-alignment through laser irradiation before the light-transmitting pressing member is pressed on the electronic component.

In addition, since a plurality of electronic components can be pressed and simultaneously irradiated with a homogenized laser beam, productivity is greatly improved by mass reflow processing.

1 is an exemplary view showing the overall configuration of a laser reflow apparatus used to practice the laser reflow method of the present invention
2 is a block diagram of FIG. 1
3 is a conceptual diagram of a single laser beam module according to an embodiment of the present invention laser reflow method
4 is a conceptual diagram of a multi-laser beam module according to another embodiment of a laser reflow method of the present invention;
5 is a configuration diagram of a multi-laser module according to another embodiment of the laser reflow method of the present invention;
6 to 9 are diagrams of a laser optical system applicable to a single or multi-laser module of the laser reflow method of the present invention.
10 is a state diagram showing the operation relationship of each process step of the laser reflow method of the present invention, a) is a state in which the light-transmitting pressing member is moved upwards of the center line Cn+1, b) is a state in which the light-transmitting pressing member is pressed at the center line Cn+1 and In the state of laser irradiation, c) is the state in which the light-transmitting pressing member is moved above the center line Cn+2, d) is the state in which the position of the light-transmitting pressing member is corrected to the center line Cn+2′, e) is the state in which the light-transmitting pressing member is moved to the center line Cn Pressurized and laser irradiated at +2′
11 is a flowchart of a laser reflow method according to an embodiment of the present invention;
12 is an exemplary view showing the self-alignment process according to the laser irradiation of the present invention

The terms used herein are used only to describe specific embodiments, and are not intended to limit the present invention. The singular expression includes the plural expression unless the context clearly dictates otherwise. In the present specification, terms such as "comprise" or "have" to "have" are intended to designate that the features, numbers, steps, operations, components, parts, or combinations thereof described in the present specification exist, but one It should be understood that it does not preclude the possibility of the presence or addition of or more other features or numbers, steps, operations, components, parts, or combinations thereof.

Unless defined otherwise herein, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

Terms such as those defined in a commonly used dictionary should be interpreted as having a meaning consistent with the meaning in the context of the related art, and should not be interpreted in an ideal or excessively formal meaning unless explicitly defined in the present specification. shouldn't

Hereinafter, a reflow apparatus according to the present invention will be described in detail with reference to the accompanying FIGS. 1 and 2 .

FIG. 1 is an exemplary view showing the overall configuration of a laser reflow apparatus used to practice a laser reflow method of the present invention, and FIG. 2 is a block diagram of FIG. 1 .

The laser pressure head module 300 of the laser reflow apparatus according to the present invention, as shown in FIGS. 1 and 2, a stage 111 in which a porous material or vacuum hole having a structure capable of applying heat to the lower portion is formed. ) and at least one multi-laser module (310, 320) for irradiating a laser in the form of a surface light source to the bonding object 11, which is supported and transported, and the laser module (310, 320) and is installed independently from the surface light source It is configured to include a light-transmitting pressing member 100 that transmits the laser in the form of a protective film 200 for protecting the light-transmitting pressing member 100 from contamination.

First, the plurality of multi-laser modules 310 and 320 convert a laser generated from a laser oscillator and transmitted through an optical fiber into a surface light source and irradiated to the bonding object 11 . The laser modules 310 and 320 include a beam shaper (see FIG. 5) that converts a spot type laser into a surface light source type, and a surface light source disposed under the beam shaper and emitted from the beam shaper to the bonding object (see FIG. 5). 11), the plurality of lens modules may be embodied by including an optical unit (refer to FIGS. 5 to 9 ) in which the plurality of lens modules are spaced apart from each other at an appropriate distance inside the barrel to be irradiated to the irradiation area.

The laser modules 310 and 320 may rise or fall along the z-axis, move left or right along the x-axis, or move along the y-axis for alignment with the bonding object 11 .

The pressure head 300 of the laser reflow apparatus according to the present invention includes a light-transmitting pressure member 100 for pressing the bonding object 11 and laser modules 310 and 320 for irradiating a laser in the form of a surface light source to the bonding object 11 . ) by separating and forming each other independently, the laser modules 310 and 320 are moved to a plurality of irradiation positions of the bonding object 11 in a state where the bonding object 11 is pressed with the light-transmitting pressing member 100 and then driven By doing so, it is possible to realize shortening of the tact time for one bonding object 11 and speeding up the bonding operation for the plurality of bonding objects 11 as a whole.

At this time, the light-transmitting pressing member 100 is moved to a working position or a standby position by a light-transmitting pressing member transfer unit (not shown) of a predetermined shape. For example, the light-transmitting pressing member transfer unit lowers or It can be raised or moved to the left or right to descend or rise.

In addition, although not shown in the drawings, the laser pressure head module 300 of the laser reflow device according to the present invention uses data input from a pressure sensor (not shown) and a height sensor (not shown) to a light-transmitting pressure member It further includes a control unit (not shown) for controlling the operation of the transfer unit.

The pressure sensor and the height sensor may be installed on the stage 111 supporting the light-transmitting pressure member 100 and the light-transmitting pressure member transfer unit and the bonding object. For example, the control unit receives data from the pressure sensor to control the translucent pressing member transfer unit so that the pressure reaches a target value, and receives data from the height sensor to control the translucent pressing member transfer unit to reach the target value of the height.

In addition, the support part (not shown) supports the light-transmitting pressing member transfer part (not shown) to be movable. For example, the support part may be implemented as a pair of gantry extending in parallel with the stage 111, and includes a configuration for supporting the light-transmitting pressure member transfer part to be movable in the x-axis, y-axis, or z-axis. should be interpreted as

The pressure head 300 of the laser reflow device according to the present invention includes one or more actuators for applying pressure to the light-transmitting pressure member 100 and at least one pressure sensor for detecting the pressure applied to the light-transmitting pressure member 100 and light-transmitting It may be implemented including one or more height sensors for detecting the height of the pressing member. The pressure sensor may be implemented as, for example, at least one load cell, and the height sensor may be implemented as a linear encoder.

By adjusting the pressure applied to the bonding object through the pressure sensor, in the case of a large area, it is possible to control so that the same pressure is transmitted to the bonding object through a plurality of actuators and a plurality of pressure sensors, and also one or more or multiple It provides technical data to check the height position value at the moment the bonding object is bonded through the height sensor or to find a more accurate bonding height value. functions that can be controlled.

In addition, the light-transmitting pressing member 100 may be implemented as a base material that transmits the laser output from the laser modules 310 and 320 . The base material of the light-transmitting pressing member 100 can be implemented with any beam-transmitting material.

The base material of the light-transmitting pressing member 100 may be implemented with, for example, any one of quartz, sapphire, fused silica glass, or diamond. However, the physical properties of the light-transmitting pressing member made of quartz are different from the physical properties of the light-transmitting pressing member made of sapphire. For example, when irradiating a 980 nm laser, the transmittance of the light-transmitting pressing member made of quartz material is 85% to 99%, and the temperature measured at the bonding object is 100°C. On the other hand, the transmittance of the light-transmitting pressing member made of sapphire is 80% to 90%, and the temperature measured at the bonding object is 60°C.

That is, in terms of light transmittance and heat loss required for bonding, quartz exhibits superior performance than sapphire. However, the inventor of the present application repeatedly tested the light-transmitting pressure member 100 while developing the laser reflow device. As a result, the light-transmitting pressure member 100 made of a quartz material is cracked during laser bonding. It was found that there was a problem in that the bonding quality was poor due to burning or the occurrence of burning on the bottom surface. It was analyzed that the gas (fumes) generated during laser bonding adheres to the bottom surface of the light-transmitting pressing member 100, and the heat source of the laser is concentrated on the part to which the gas (fumes) is adhered, thereby increasing thermal stress.

In order to prevent damage to the light-transmitting pressure member 100 made of a quartz material and to improve durability, a thin film coating layer may be formed on the bottom surface of the light-transmitting pressure member made of a quartz material. The thin film coating layer formed on the bottom surface of the light-transmitting pressing member 100 may be implemented as a dielectric coating or SiC coating or metallic material coating, which is a conventional optical coating.

The laser pressurizing head module 300 of the laser reflow device according to the present invention, as shown in FIG. 1, is a light-transmitting pressurizing member 100, a lower portion of the light-transmitting pressurizing member 100, a gas (fumes) generated during laser bonding is a light-transmitting pressurizing member 100 ) is implemented to further include a protective film 200 to prevent sticking to the bottom surface and a protective film transfer unit 210 for transferring the protective film 200 .

The protective film transfer unit 210 may be implemented in a reel-to-reel manner in which the protective film 200 wound in a roll shape is unwound and transferred to one side. The protective film 200 is preferably implemented with a material having excellent heat resistance, for example, the maximum use temperature is 300 degrees Celsius or more, and the continuous maximum use temperature is 260 degrees or more. For example, the protective film 200 may be implemented with a polytetrafluoroethylene resin (commonly referred to as a Teflon resin; Polytetrafluoroethylene, PTFE) or a purple alkoxy resin. Perfluoroalkoxy resin (Per Fluoro Alkylvinyether copolymer; PFA) is a product that improves the heat resistance of fluorinated ethylene propylene resin.

3 is a conceptual diagram of a single laser beam module according to an embodiment of the laser reflow method of the present invention, and FIG. 4 is a conceptual diagram of a dual laser module according to another embodiment of the laser reflow method of the present invention.

Referring to FIG. 3 , the present invention includes a single laser module 310 according to an embodiment, and thus irradiates a single laser beam onto the FPCB substrate. At this time, referring to FIG. 3 , the laser beam irradiated by the first laser module 310 is irradiated on the substrate in a state in which the laser beam intensity is transformed into a homogenized square beam shape.

Meanwhile, referring to FIG. 4 , the multi-laser module according to another embodiment of the present invention includes, for example, a first laser module 310 and a second laser module 320 , and an electronic component of the bonding object 11 . At this attachment position, the homogenized overlapping laser beam is irradiated by irradiating the first and second laser modules in an overlapping state.

4 shows that the first laser beam has a square shape and the second laser beam has a circular shape, but both laser beams may have a square shape. In addition, the first laser beam and the second laser beam may be simultaneously irradiated, or the second laser beam may be sequentially irradiated after preheating the bonding object 11 by the first laser beam.

5 is a configuration diagram of a dual laser module according to another embodiment of the laser reflow method of the present invention.

In FIG. 5 , each laser module 310 , 320 , ... 330 includes a laser oscillator 311 , 321 , 331 having a cooling device 316 , 326 , 336 , and a beam shaper 312 , 322 , 332 , respectively. , optical lens modules 313 , 323 , 333 , driving devices 314 , 324 , 334 , control devices 315 , 325 , 335 , and power supply units 317 , 327 , 337 .

Hereinafter, except where necessary, the first laser module 310 among laser modules having the same configuration will be mainly described in order to avoid overlapping description.

The laser oscillator 311 generates a laser beam having a wavelength and output power in a predetermined range. The laser oscillator is, for example, a diode laser (Laser Diode, LD) having a wavelength of '750 nm to 1200 nm' or '1400 nm to 1600 nm' or '1800 nm to 2200 nm' or '2500 nm to 3200 nm' or a rare-earth medium fiber laser (Rare-Earth- It may be a Doped Fiber Laser) or a Rare-Earth-Doped Crystal Laser, and alternatively, a medium for emitting alexandrite laser light having a wavelength of 755 nm, or Nd Yag (Nd) having a wavelength of 1064 nm or 1320 nm :YAG) may be implemented including a medium for emitting laser light.

The beam shaper 312 converts a spot type laser generated from a laser oscillator and transmitted through an optical fiber into an area beam type having a flat top. The beam shaper 312 may be implemented by including a square light pipe, a diffractive optical element (DOE), or a micro-lens array (MLA).

The optical lens module 313 adjusts the shape and size of the laser beam converted from the beam shaper to the surface light source shape to irradiate the electronic component mounted on the PCB board or the irradiation area. The optical lens module constitutes an optical system by combining a plurality of lenses, and the detailed configuration of the optical system will be described later in detail with reference to FIGS. 6 to 9 .

The driving device 314 moves the distance and position of the laser module with respect to the irradiated surface, and the controller 315 controls the driving device 314 to form a beam when the laser beam reaches the irradiated surface and the size of the beam area. , adjust the beam sharpness and beam irradiation angle. The control device 315 may also integrally control the operation of each part of the laser module 310 in addition to the driving device 314 .

On the other hand, the laser power adjustment unit 370 is supplied to each laser module from the power supply unit 317, 327, 337 corresponding to each laser module (310, 320, 330) according to a program received through the user interface or a preset program. control the amount of power The laser output adjustment unit 370 receives the reflow state information for each part, each area, or the entire reflow state on the irradiation surface from one or more camera modules 350 and controls each power supply unit 317 , 327 , 337 based on the received information. Contrary to this, the control information from the laser power adjusting unit 370 is transmitted to the control devices 315, 325, 335 of each laser module 310, 320, 330, and in each of the control devices 315, 325, 335, respectively. It is also possible to provide a feedback signal for controlling the corresponding power supply 317 . In addition, unlike FIG. 6 , it is also possible to distribute power to each laser module through one power supply unit. In this case, the laser output adjusting unit 370 needs to control the power supply unit.

When implementing the laser overlap mode, the laser output adjustment unit 370 is configured so that the laser beam from each laser module (310, 320, 330) has a required beam shape, beam area size, beam sharpness and beam irradiation angle to each laser module and Controls the power supply (317, 327, 337). The laser overlap mode uses the first laser module 310 to preheat the area around the debonding target position and uses the second laser module 320 to further heat the narrower reflow target area, as well as the preheating function to It also applies when controlling each laser module to have a required temperature profile by properly distributing the additional heating function between the first, second, and third laser modules (310, 320, ... 330).

Meanwhile, when one laser light source is distributed and input to each laser module, a function for simultaneously adjusting the output and the phase of each distributed laser beam may be provided in the laser power adjusting unit 370 . In this case, the beam flatness can be significantly improved by controlling the phase to induce destructive interference between the respective laser beams, which further increases the energy efficiency.

On the other hand, when implementing the multi-position simultaneous processing mode, the laser power adjusting unit 370 makes a part or all of the laser beams from each laser module different so that the beam shape, beam area size, beam clarity, and beam irradiation of each laser beam are different. Controls one or more of angle and beam wavelength. Even at this time, when one laser light source is distributed and input to each laser module, a function for simultaneously adjusting the output and phase of each distributed laser beam may be provided in the laser power adjusting unit 370 .

Through this function, bonding between the electronic components and the substrate in the irradiation surface can be performed or bonding can be removed by adjusting the laser beam size and output. In particular, when a damaged electronic component is removed from the substrate, the application of heat by the laser beam to other adjacent or normal electronic components existing on the substrate can be minimized by minimizing the area of the laser beam to the corresponding electronic component area. Accordingly, it is possible to remove only the damaged electronic component to be removed.

On the other hand, when a plurality of laser modules emit laser beams having different wavelengths, the laser module is a laser module in which a plurality of material layers (eg, EMC layer, silicon layer, solder layer) included in electronic components absorb well. It can consist of individual laser modules with wavelengths. Accordingly, the laser debonding apparatus according to the present invention selectively raises the temperature of the electronic component and the temperature of the intermediate bonding material such as solder, which is a connection material between the printed circuit board or the electrode of the electronic component, to optimize bonding (attaching or bonding). Bonding) or separation (Detaching or Debonding) process may be performed. Specifically, it penetrates both the EMC mold layer and the silicon layer of the electronic component so that all energy of each laser beam is absorbed by the solder layer, or the laser beam does not penetrate the EMC mold layer and heats the surface of the electronic component to lower the electronic component It is also possible to conduct heat to the bonding part of the

On the other hand, by utilizing the above function, a predetermined area of the substrate including the electronic component area to be reflowed and its surroundings is preheated to a predetermined preheating temperature by at least one first laser beam, and then at least one second laser beam is applied. By this, the temperature of the electronic component area to be reflowed is selectively heated up to the reflow temperature at which solder melting occurs.

6 to 9 are diagrams of a laser optical system applicable to a single laser beam or a multi-laser module of the laser reflow method of the present invention.

6 is an optical system of the simplest structure applicable to the present invention. When the laser beam emitted from the beam transmission optical fiber 410 is focused through the convex lens 420 and is incident on the beam shaper 430, the beam shaper 430 ), converts the spot-shaped laser beam into a flat-top-shaped surface light source A1, and the square laser beam A1 output from the beam shaper 430 is the desired size through the concave lens 440. It is irradiated to the image-forming surface (S) with the expanded surface light source (A2).

7 is a block diagram of a laser optical system according to another embodiment of the present invention.

The surface light source B1 from the beam shaper 430 is enlarged to a predetermined size through the concave lens 440 to become the surface light source B2 irradiated to the first imaging surface S1. If the surface light source B2 is to be further enlarged and used, the boundary of the edge portion of the surface light source B2 may become more unclear according to the additional enlargement, so that the final irradiation surface is the second imaging surface S2 ), the edge is trimmed by installing the mask 450 on the first imaging surface S1 in order to obtain the irradiated light with a clear edge.

The surface light source passing through the mask 450 is reduced (or enlarged) to a desired size while passing through the zoom lens module 460 composed of a combination of one or more convex and concave lenses, and the second imaging surface on which electronic components are disposed. A rectangular irradiation light B3 is formed in (S2).

8 is a block diagram of a laser optical system according to another embodiment of the present invention.

After the square surface light source C1 from the beam shaper 430 is enlarged to a predetermined size through the concave lens 440, it passes through at least a pair of cylindrical lenses 470 and is enlarged (or reduced) in the x-axis direction, for example. (C2) and again passing through at least a pair of cylindrical lenses 480, for example, is reduced (or enlarged) in the y-axis direction and converted into a rectangular-shaped surface light source C3.

Here, the cylindrical lens is a shape in which a cylindrical shape is cut in the longitudinal direction, and functions to expand or reduce the laser beam according to the shape in which each lens is disposed in the vertical direction, and the lens on the surface on which the cylindrical lens is disposed is x, y The laser beam is adjusted in the x-axis or y-axis direction according to the shape arranged in the axial direction.

Then, the surface light source C3 is enlarged (or reduced) to a desired size while passing through the zoom lens module 460 composed of a combination of one or more convex and concave lenses, and the second imaging surface S2 on which electronic components are disposed. ) to form a rectangular irradiation light C4.

9 is a configuration diagram of a laser optical system according to another embodiment of the present invention.

The optical system of FIG. 9 has a configuration for trimming the edge of the laser beam by applying a mask to the optical system of FIG. 8, and it is understood that the final surface light source D5 having a sharper edge can be obtained compared to the case of FIG. will be able

10 is a state diagram showing the operation relationship of each process step of the laser reflow method of the present invention. Hereinafter, the laser reflow method for each process step will be described according to an embodiment.

First, FIG. 10A is a diagram illustrating a state in which the light-transmitting pressing member 100 is moved above the center line (Cn+1). When the pressing surface 102 of the light-transmitting pressing member 100 is positioned at the center line (Cn+1), the vision unit A reference numeral 934 captures the electronic components 11b positioned below the pressing surface 102 of the light-transmitting pressing member 100 . In this case, when viewed from the side as shown in FIG. 10A , in the vision unit 934 , the electronic components 11b are left and right symmetrical with respect to the center line Cn+1 of the pressing surface 102 of the light-transmitting pressing member 100 . It is determined whether or not the

That is, whether the shape in which the electronic components 11b positioned directly below the pressing surface 102 of the light-transmitting pressing member 100 are positioned to correspond to the area of the pressing surface 102, for example, as in FIG. 10A In a state in which the electronic components 11b are arranged in three rows, it is determined whether the electronic components 11b are symmetrically arranged in 1.5 rows with respect to the center line Cn+1 of the pressing surface 102 . Accordingly, when the pressing surface 102 of the light-transmitting pressing member 100 presses the range (area) in which the electronic components 11b are arranged in three rows, the pressure is balanced by pressing without biasing the pressure to either side. be able to

In addition, referring to the drawings, the electronic components 11b of the bonding object 11 are arranged in a position to be bonded together with the solder 11c for bonding on the upper surface of the substrate 11a, at this time the substrate 11a. is vacuum-adsorbed by the lower vacuum chuck 940 and is in a fixed state. At this time, as the heating block 942 is provided inside the vacuum chuck 940, the substrate 11a, the electronic component 11b, and the solder 11c, which are the bonding objects 11, are continuously heated to a predetermined temperature. warm up For example, the preheating temperature is preferably set below the melting temperature of the solder. can

If the bonding object 11 is not preheated as described above, the bonding object 11 must be rapidly heated from room temperature to the melting temperature of the solder 11c only with the thermal energy of the laser beam during the laser reflow process, which is this process. The rapid heating may cause bonding defects such as overflow in the solder 11c. Therefore, as the temperature is gradually increased from the preheating temperature to the melting temperature of the solder 11c, the solder 11c is stably melted and the bonding defect can be minimized. For example, here, the melting temperature of the solder 11c may be different depending on the material of the solder, but may be 200° C. or higher, which is the melting temperature of a general solder paste.

10B is a state diagram in which the light-transmitting pressing member 100 is pressed and irradiated with a laser at the center line Cn+1. As shown in FIG. 10A, the pressing surface 102 of the light-transmitting pressing member 100 by the vision unit 934 When it is determined that the center line Cn+1 coincides with the center line of the electronic components 11b to be bonded, the light-transmitting pressing member 100 moves downward to press the electronic component 11b.

At this time, the laser beam may be irradiated simultaneously or sequentially with the pressing of the light-transmitting pressing member 100 , for example, the multi-laser module and the first laser module positioned above the light-transmitting pressing member 100 at the same time as pressing. A laser beam from the 310 and the second laser module 320 may be superimposed on the electronic components 11b.

Accordingly, the bonding object 11 is heated step by step from the preheating temperature to the melting temperature of the solder 11c by the overlapping irradiated laser beam, and eventually the solder 11c positioned under the electronic components 11b is As it melts, bonding of the electronic component 11b to the substrate 11a is completed. (The difference in height before bonding and after bonding is denoted by h _c in FIG. 10A)

Figure 10c is a state diagram in which the light-transmitting pressing member is moved upwards the center line (Cn+2), Fig. 10d is a state in which the position of the light-transmitting pressing member is corrected to a new center line (Cn+2'), and Fig. 10e is the light-transmitting pressing member It is a state diagram of pressurization and laser irradiation at the center line (Cn+2′).

Referring to FIG. 10C , after the laser reflow process is completed, the light-transmitting pressing member 100 presses and laser reflows the electronic components 11b in three rows in the next predetermined range, that is, three rows of electrons. It moves horizontally to the center line (Cn+2) of the parts 11b. At this time, the vision unit 934 photographs the arrangement shape of the electronic components 11b disposed below the pressing surface 102 of the light-transmitting pressing member 100 again.

However, at this time, as shown in FIG. 10c , the electronic components 11b disposed below the pressing surface 102 of the light-transmitting pressing member 100 are not arranged symmetrically with respect to the center line (Cn+2). If judged, do not proceed with pressurization or laser irradiation immediately. The reason is that when the light-transmitting pressing member 100 is pressed and pressed in this state, the electronic components 11b are asymmetrically arranged based on the center line (Cn+2) of the pressing surface 102 of the light-transmitting pressing member 100 . Therefore, the pressing force is biased to either side during pressurization, which causes bonding defects.

Therefore, in the present invention, in order to prevent this, the control unit (not shown) moves the horizontal position of the light-transmitting pressing member 100 to a new center line (Cn+2′) as shown in FIG. 10D, and accordingly the corrected center line ( Cn+2'), the horizontal position of the light-transmitting pressing member 100 is corrected. Accordingly, the horizontal position is corrected so that the electronic components 11b disposed below the light-transmitting pressing member 100 are symmetrically disposed on the basis of the corrected center line (Cn+2′), and in this state, as shown in FIG. 10E , The light-transmitting pressing member 100 moves downward to press the electronic components 11b and irradiate the laser beam.

Meanwhile, referring to FIG. 10E , the light-transmitting pressing member 100 moves to the corrected center line (Cn+2′) and pressurizes, but at this time, the first and second laser modules 310 and 320 are aligned with the corrected center line. The laser beam is irradiated based on the center line (Cn+2) before the correction without correcting the horizontal position as (Cn+2′).

As described above, the reason why the laser modules 310 and 320 do not correct the horizontal position along the light-transmitting pressing member 100 is that when the laser beam is irradiated based on the corrected center line (Cn+2′), bonding has already been completed. There is a risk that the laser beam is re-irradiated to the electronic components 11b, and when the laser beam is re-irradiated to the solder 11c that has been reflowed, the solder 11c may be melted again, thereby causing bonding defects. because it can Therefore, in the present invention, when pressing and irradiating the asymmetrically arranged electronic component 11b with a laser, only the transmissive pressing member 100 is corrected without the position correction of the first or second laser modules 310 and 320 , Cn+ 2'), and after correcting the position, the occurrence of various bonding defect factors can be minimized as described above by irradiating pressure and laser.

11 is a flowchart of a laser reflow method according to an embodiment of the present invention.

The present invention, as described above in FIGS. 1 to 10b , a bonding object 11 in which a plurality of electronic components 11b are disposed on a rectangular flexible PCB 11a is a light-transmitting pressing member 100 . The flexible substrate 11a generated in the laser reflow device for bonding the electronic component 11b to the substrate 11a by irradiating a laser beam to the bonding object 11 through the pressing member 100 while pressing, and The present invention relates to an improved laser reflow method for resolving a shift phenomenon caused by distortion of an electronic component 11b and electrical open or short defects between a solder bump SB and an electrode pad EP. .

11 , the present invention may be more specifically subdivided into the following steps.

Step a (S100) : A plurality of solder bumps SB are disposed on the bottom surface of the electronic component 11b.

For example, the solder bumps SB may be lead-free solder including tin (Sn), and may be spherical solder bumps for a flip chip process.

Step b(S200) : A plurality of electrode pads EP having a self-alignment groove (SAG) are formed on the upper surface of the substrate 11a.

The self-alignment concave groove (SAG) may be a concave concave groove such as a sphere or a triangle, and in FIG. 11 , it is illustrated as a triangular concave groove in which the central portion forms the lowest point according to an embodiment.

Step c(S300) : The solder bumps SB are respectively seated in the self-alignment concave grooves SAG of the electrode pads EP to pre-align them.

According to an embodiment, the pre-alignment refers to a process in which the solder bumps SB are seated and contacted in the self-alignment concave groove SAG of the electrode pad EP.

In addition, in the present invention, after step c), the flexible substrate 11a and the electronic component 11b so that the pre-aligned solder bump SB is positioned at the exact center of the self-alignment concave groove SAG. They can be further aligned using vibration or a jig.

Step d(S400) : As the laser beam is irradiated to the temporarily seated solder bumps SB, the solder bumps SB are melted and flowed, and after being completely positioned in the self-alignment concave groove SAG, the laser beam is irradiated By blocking the solder bumps SB are fixed in the self-alignment concave groove SAG.

That is, the aforementioned step is defined as a self-alignment step.

Here, in the self-alignment of step d), the solder bumps SB formed on the electronic components 11b are melted and flowed in the self-alignment concave groove SAG of the electrode pad EP by gravity. After being moved and positioned to the exact center of the self-alignment concave groove (SAG) by do.

In addition, the temperature of the laser beam in step d) is higher than the melting point of the solder bump SB.

For example, a melting point of the solder bumps SB may be 216°C, and a temperature range of a laser beam irradiated for self-alignment of the solder bumps SB may be within a range of 230°C to 280°C.

In addition, the irradiation time of the laser beam may be within 5 seconds, the irradiation time of the laser beam may be shortened in inverse proportion to the set temperature of the laser beam, and also to add fluidity for self-alignment to the solder bumps (SB) For this reason, the solder bump may be completely melted or only the surface may be melted instantaneously.

Step e (S500) : When step d is completed, the light-transmitting pressing member is moved downward to press the bonding object, and a laser beam is irradiated to the bonding object through the light-transmitting pressing member.

As described above, according to an embodiment of the present invention, the laser beam may be irradiated by overlapping laser beams from two or more laser modules.

In addition, each of the laser modules 310 and 320 may be disposed symmetrically to each other, and each of the laser beams may have the same beam irradiation angle.

In addition, laser beams may be simultaneously or sequentially irradiated from each of the laser modules 310 and 320 .

In addition, at least one of the laser modules 310 and 320 may be continuously irradiated without interruption of the laser beam in the process from step d) to step e).

Step f (S600) : When the irradiation of the laser beam is completed, the light-transmitting pressing member 100 is moved upward to release the pressing state.

Accordingly, the laser reflow method of the laser reflow apparatus of the present invention may be sequentially performed according to the above-described steps a) to f).

Meanwhile, according to an embodiment, any one of steps a) to d) may further include the step of performing vision imaging.

Accordingly, the self-alignment process can be automatically monitored through the vision shooting, and it is determined whether the shape in which the self-aligned electronic components 11b are disposed corresponds to the pressing surface, or when a defect occurs, the process is immediately stopped and errors Normalization measures such as correction can be performed.

12 is an exemplary view showing the self-alignment process according to the laser irradiation of the present invention.

The self-alignment process related to steps a) to d) of the present invention described above with reference to FIG. 12 will be described in more detail as follows.

First, when a laser beam is irradiated during the process of mounting the electronic component (Die) on the board (PCB), the electrode pad (EP) and the solder bump (SB) of the electronic component (Die, 11b) move up and down through the surface tension. The central axis of the solder bump SB coincides with the central axis of the electrode pad EP of the substrate 11a. In this case, the electronic components 11b may be a micro-sized LED die or a molding package.

The method may further include determining whether the shape in which the self-aligned electronic components 11b are disposed corresponds to the pressing surface.

When it is determined that these electronic components 11b are positioned to correspond to the pressing surface, the light-transmitting pressing member 100 is moved downward to press the bonding object 11 and, together with the light-transmitting pressing member 100, the bonding object 11 Including the step of irradiating a laser beam to (S500).

In this process, by performing the above-described self-alignment in advance before pressing, the bonding object 11 is prevented from being shifted when pressed, thereby preventing an electrical open or short.

This effect can reduce the processing time of mass production and significantly improve the yield when a plurality of electronic components 11b are pressed and laser bonded on the flexible substrate 11a.

Finally, stopping the irradiation of the laser beam and moving the light-transmitting pressing member 100 upward to release the pressing state (S600).

In addition, the present invention is not limited only by the above-described embodiment, and since it is possible to create the same effect even when changing the detailed configuration, number, and arrangement of the device, those of ordinary skill in the art will present the present invention It is specified that various additions, deletions, and modifications are possible within the scope of the technical idea of

11: bonding object 11a: substrate (PCB)
11b: Electronic component (Die) 11c: Solder
100: permeable pressing member 102: pressing surface
200: protective film 210: protective film transfer unit
310: first laser module 320: second laser module
500: holder unit 934: vision unit
940: vacuum chuck 942: heating block
SB: Solder Bump EP: Electrode Pad
SAG : Self Alignment Groove

Claims (9)

A laser of a laser reflow device for bonding electronic components to a substrate by pressing and pressing a bonding object on which a plurality of electronic components are disposed on a rectangular substrate with a translucent pressing member and irradiating a laser beam to the bonding object through the pressing member. In the reflow method,
a) disposing a plurality of solder bumps on a bottom surface of the electronic component;
b) forming a plurality of electrode pads having a self-alignment groove (SAG) on the upper surface of the substrate;
c) pre-aligning the solder bumps by seating each of the solder bumps in the self-alignment recessed grooves of the electrode pad;
d) As the laser beam is irradiated to the temporarily seated solder bump, the spherical solder bump is melted and flowed, and after being completely positioned in the self-alignment recess, the laser beam is blocked and the solder bump is fixed in the self-alignment recess. a self-alignment step;
e) when the step d is completed, the light-transmitting pressing member is moved downward to press the bonding object, and irradiating a laser beam to the bonding object through the light-transmitting pressing member;
f) when the irradiation of the laser beam is completed, moving the light-transmitting pressing member upward to release the pressing state; including,
A laser reflow method in a laser reflow device. The method of claim 1,
In the self-alignment of step d), the solder bumps formed on the electronic components are melted and flowed in the self-alignment concave groove of the electrode pad. After forming a spherical shape with surface tension, the vertical central axis of each solder bump and the self-alignment concave groove coincides with each other.
A laser reflow method in a laser reflow device. The method of claim 1,
characterized in that the temperature of the laser beam in step d) is higher than the melting point of the solder bump,
A laser reflow method in a laser reflow device. The method of claim 1,
Any one of steps a) to d) further comprises the step of performing vision imaging,
A laser reflow method in a laser reflow device. The method of claim 1,
The laser beam is characterized in that the laser beam is overlapped and irradiated from two or more laser modules,
A laser reflow method in a laser reflow device. 6. The method of claim 5,
Each of the laser modules is arranged symmetrically to each other, characterized in that each laser beam has the same beam irradiation angle,
A laser reflow method in a laser reflow device. 6. The method of claim 5,
Characterized in that the laser beam is irradiated simultaneously or sequentially from each laser module,
A laser reflow method in a laser reflow device. 6. The method of claim 5,
At least one of the laser modules is characterized in that the laser beam is continuously irradiated without interruption in the process proceeding from step d) to step e),
A laser reflow method in a laser reflow device. The method of claim 1,
After the step c), the board and electronic components are further aligned using vibration or a jig (JIG) so that the pre-aligned solder bump is located at the exact center of the self-alignment concave groove, characterized in that,
A laser reflow method in a laser reflow device.

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