KR20200137628A - Laser reflow device - Google Patents

Abstract

The present invention relates to a laser reflow apparatus. The laser reflow apparatus includes: a laser light source radiating a laser beam; a flat top converter receiving the laser beam radiated from the laser light source, and homogenizing and outputting energy in accordance with the displacement of the received laser beam; and an optical part moving a radiation area of the laser beam by controlling an optical flow path by reflecting the laser beam output from the flat top converter. The optical part includes: a first optical flow path control part controlling a first axial flow path of the laser beam; and a second optical flow path control part controlling a second axial flow path of the laser beam. The optical part maintains the homogeneity of the energy in accordance with the displacement of the laser beam in regard to control on the flow paths of the laser beam.

Description

Laser reflow device {LASER REFLOW DEVICE}

The present invention relates to a laser reflow apparatus, and more particularly, to a scanning type laser reflow apparatus with improved soldering speed and quality.

In general, the manufacturing process of a semiconductor package includes a reflow process. In the mass reflow process, which is mainly used in the reflow process, an array of substrates attached with solder materials such as solder balls, solder pads, and solder pastes is placed on a conveyor belt, and the entire substrate array is continuously moved by the conveyor belt. In the meantime, the heating section provided with an infrared heater is passed for a predetermined time. In this case, infrared heaters are provided on the upper and lower sides of the conveyor belt, and the infrared heater applies heat to solder balls on the substrate to attach the semiconductor elements to the substrate.

However, the mass reflow process has a problem in that it takes about 10 to 30 minutes for the infrared heater to apply heat to the solder ball to bond the semiconductor device to the substrate, which is not economical.

In addition, recently, semiconductor devices such as passive devices and IC devices are attached to one substrate in order to reduce the thickness of the semiconductor package and reduce the cost. Since these semiconductor devices have different coefficients of thermal expansion, if they collectively undergo a mass reflow process, some IC devices may be damaged, or some devices may not be accurately bonded.

In order to solve the above problems, a laser selective reflow (LSR) method has been proposed in which a partial region on a substrate is heated and soldered in a short time.

1 is a view showing a laser reflow apparatus to which a conventional laser selective reflow method is applied, and FIG. 2 is a diagram illustrating an energy distribution according to displacement of a laser beam irradiated to a substrate array by a conventional reflow apparatus.

Looking at a conventional laser reflow apparatus with reference to FIG. 1, the laser beam irradiated from the laser light source 1 is a substrate by condensing the laser beam passing through the optical system 2 and the optical system 2 for adjusting the path of the laser beam. And a condensing lens 3 that irradiates a partial area on the array 10. This laser beam solders the entire soldering area by sequentially scanning the soldering area on the substrate array.

In this case, the condensed laser beam has an energy distribution in the form of a Gaussian function according to a position in the irradiation area as shown in FIG. 2. That is, the intensity of energy of the laser beam increases toward the center of the irradiation area, and the intensity of energy decreases toward the edge of the irradiation area.

In this case, when an IC device having poor heat resistance is located in the center of the irradiation area, the IC device may be damaged due to thermal shock. In addition, since sufficient energy is not supplied to the periphery of the irradiation area, there may be a problem in that the device and the substrate 10 are not properly bonded.

In addition, since the energy of the laser beam is concentrated in the center of the irradiation area, soldering is performed only in a narrow area that satisfies the energy condition required for soldering. That is, since the area that can be soldered with one laser irradiation is narrow, it takes a lot of time to solder the entire substrate array.

In addition, since the soldering area is narrow, a highly precise control technique is required to scan the soldering area on the substrate array. This caused an increase in the manufacturing cost of the laser reflow device.

In order to solve the above problems, a technical problem to be achieved by the present invention is to provide a scanning type laser reflow apparatus with improved soldering speed and quality.

In order to achieve the above technical problem, an embodiment of the present invention is a laser light source for irradiating a laser beam; A flat top converter configured to receive the laser beam irradiated from the laser light source, homogenize and output energy according to the displacement of the received laser beam; And an optical unit for moving the irradiation area of the laser beam by reflecting the laser beam output from the flat top converter and adjusting an optical path, wherein the optical unit adjusts a path in the first axis direction of the laser beam. 1 light path control unit; And a second optical path control unit for adjusting a path in the second axis direction of the laser beam, wherein the optical unit maintains a homogeneity of energy according to the displacement of the laser beam in adjusting the path of the laser beam. It provides a laser reflow device.

In an embodiment of the present invention, the first optical path adjusting unit includes a first reflecting unit reflecting the laser beam; And a first optical path controller configured to control a movement of the first reflector to adjust a path in a first axis direction of the laser beam, wherein the second optical path controller includes a second reflector configured to reflect the laser beam; And a second optical path controller configured to control a movement of the second reflector to adjust a path in the second axis direction of the laser beam.

In an embodiment of the present invention, control operations of the first optical path controller and the second optical path controller may be performed independently.

In an embodiment of the present invention, the laser reflow apparatus may include a transfer unit having a transfer belt for moving the substrate while the substrate is seated on the upper side, and a transfer module providing power to the transfer belt.

In an embodiment of the present invention, the laser reflow device further includes an image relay unit for relaying the laser beam output from the flat top converter to guide the laser beam to the optical unit, and the image relay unit The shape of the laser beam can be enlarged or reduced.

In an embodiment of the present invention, the image relay unit may be configured to maintain a homogeneity of energy according to the displacement of the laser beam when relaying the laser beam.

In an embodiment of the present invention, the flat top converter includes an optical fiber having a core through which a laser beam passes, and the core may have a rectangular cross section.

In an embodiment of the present invention, the optical fiber further includes a cladding extending in a longitudinal direction to surround the core, and the cladding may be made of a material having a lower refractive index than the core.

In an embodiment of the present invention, the optical fiber is made of a flexible material, and the optical fiber may have a shape bent at least one or more times.

According to the embodiment of the present invention, since the laser beam is homogenized while passing through the flat top converter, the energy distribution in the region to which the laser beam is irradiated can be uniform. Accordingly, a problem in which some passive elements located in the irradiation area of the laser beam fail due to thermal shock or not attached to the substrate due to insufficient heat can be prevented.

Further, according to the embodiment of the present invention, since the laser beam is homogenized while passing through the flat top converter, the irradiation area satisfying the laser energy condition required for soldering can be expanded. That is, since the area that can be soldered with the same laser energy is expanded compared to the conventional technology, the speed of soldering can be improved.

Further, according to the embodiment of the present invention, unnecessary consumption of laser energy can be prevented.

In addition, according to the exemplary embodiment of the present invention, since laser energy is concentrated in the irradiation area, elements outside the irradiation area can be safe from thermal shock.

In addition, according to an embodiment of the present invention, since laser energy required for soldering a unit area is small, the cost required for a laser reflow process can be reduced.

In addition, according to an embodiment of the present invention, since the width of the general-purpose size substrate can be sufficiently covered by the area of the irradiated laser beam, the time required for the process can be reduced, and soldering can be performed more stably.

1 is a view showing a laser reflow apparatus to which a conventional laser selective reflow method is applied.
2 is an energy distribution diagram according to displacement of a laser beam irradiated onto a substrate by a conventional reflow apparatus.
3 is a view showing a laser reflow apparatus according to an embodiment of the present invention.
4 is an energy distribution diagram according to displacement of a laser beam irradiated to a substrate by a reflow apparatus according to an embodiment of the present invention.
5 is a view showing in detail a flat top converter according to an embodiment of the present invention.

Hereinafter, the present invention will be described with reference to the accompanying drawings. However, the present invention may be implemented in various different forms, and therefore is not limited to the embodiments described herein. In the drawings, parts irrelevant to the description are omitted in order to clearly describe the present invention, and similar reference numerals are assigned to similar parts throughout the specification.

Throughout the specification, when a part is said to be "connected (connected, contacted, bonded)" with another part, it is not only "directly connected", but also "indirectly connected" with another member in the middle. "Including the case. In addition, when a part "includes" a certain component, it means that other components may be further provided, rather than excluding other components unless specifically stated to the contrary.

The terms used in the present specification are only used to describe specific embodiments, and are not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In this specification, terms such as "comprise" or "have" are intended to designate the presence of features, numbers, steps, actions, components, parts, or a combination thereof described in the specification, but one or more other features. It is to be understood that the presence or addition of elements or numbers, steps, actions, components, parts, or combinations thereof, does not preclude in advance.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

3 is a view showing a laser reflow apparatus according to an embodiment of the present invention, FIG. 4 is an energy distribution diagram according to the displacement of a laser beam irradiated to a substrate by the reflow apparatus according to an embodiment of the present invention, and FIG. 5 Is a diagram showing in detail a flat top converter according to an embodiment of the present invention.

As illustrated in FIG. 3, the laser reflow apparatus may include a laser light source 100, a flat top converter 200, and an optical unit 300.

The laser light source 100 may irradiate a laser beam toward the flat top converter 200. As an example, the laser beam may be a laser beam having an energy distribution in the form of a Gaussian distribution.

In addition, the laser beam may be irradiated to the soldering area on the substrate 10 by sequentially passing through the flat top converter 200 and the optical unit 300. In this case, the substrate 10 may be a single substrate 10 or a substrate array in which a plurality of substrates 10 are arranged in an array.

The area to which the laser beam is irradiated may be smaller or larger than the soldering area of the substrate 10. In addition, the optical unit 300 may control the laser beam to sequentially or selectively scan the soldering area by adjusting the path of the laser beam.

Here, the laser beam may have an area of 80mm*80mm irradiated to the substrate, and an error range of +-8mm. Of course, it can be changed according to design requirements.

For example, when the width of the substrates arranged in an array is 75mm, irradiation with an area of 80mm*80mm is more stable, and there is an advantage of being able to perform fast scanning within an error range. In addition, it can be said that the area of 80mm*80mm is the most preferable since the size of the generalized substrate is 70mm~80mm most often.

Of course, when the size of the width of the substrate is greater than 75 mm, the area size of the irradiated area may be changed.

In addition, as the area to which the laser beam is soldered increases, the power increases, and it may have an output within 1KW to 10KW. In this case, the output may increase according to the area to be soldered of the laser beam, but the output may vary depending on a material such as a substrate or a die (chip) mounted on the substrate.

On the other hand, the irradiation time on the object may also have a time of at least 1 second to a maximum of 10 seconds per cycle, depending on the above-described substrate and materials such as a mounted die (chip).

The flat top converter 200 may receive and homogenize the laser beam irradiated from the laser light source 100, and may output the homogenized laser beam toward the optical unit 300.

The energy distribution according to the displacement of the laser beam homogenized through the flat top converter 200 will be described in detail with reference to FIG. 4.

4A is a curve showing the energy distribution according to the displacement of the laser beam that has not passed through the flat top converter 200. In addition, FIG. 4B is a curve showing the energy distribution according to the displacement of the homogenized laser beam passing through the flat top converter 200. In addition, E of FIG. 4 shows the intensity of laser energy required for melting the solder member.

Referring to FIG. 4A, the laser beam before passing through the flat top converter 200 may concentrate energy in the center of the irradiation area. For this reason, the irradiation area satisfying the energy required for melting of the solder member in the irradiation area of the laser beam can be formed narrow.

At this time, since the energy in the center of the irradiation area exceeds the energy required for melting the solder member, unnecessary energy consumption occurs. In addition, the energy in the center of the irradiation area may exceed the allowable energy of a device mounted in the center of the irradiation area. This may cause damage or failure of the device.

On the other hand, referring to B of FIG. 4, the laser beam homogenized by passing through the flat top converter 200 has uniform energy according to the displacement within the irradiation area. That is, the energy of the laser beam is uniform from the center of the irradiation area to the edge of the irradiation area, and when it leaves the irradiation area, the energy of the laser beam rapidly decreases.

That is, since excessive energy supply to the device located in the center of the irradiation area is prevented, damage or failure of the device can be prevented. In addition, since the same level of energy is supplied to the device located at the edge of the irradiation area as in the center, a bonding failure between the device located at the edge of the irradiation area and the substrate 10 can be prevented.

Further, since the supply of energy to the outside of the irradiation area rapidly decreases, unnecessary energy supply to the outside of the irradiation area can be prevented. According to this, a thermal shock applied to an element located outside the irradiation area can be prevented.

On the other hand, the laser beam homogenized through the flat top converter 200 may expand the irradiation area that satisfies the laser energy condition required for melting the solder member compared to the laser beam before passing through the flat top converter 200. .

Specifically, the total energy of the laser beam homogenized by passing through the flat top converter 200 may be maintained at the same level as the total energy of the laser beam before passing through the flat top converter 200. At this time, the homogenized laser beam is formed wider than the laser beam before the homogenization of the irradiation area satisfying the laser energy condition required for melting the solder member.

That is, the region in which the homogenized laser beam can be soldered may be expanded compared to the laser beam before homogenization. Therefore, the soldering speed and energy efficiency of the laser reflow device can be improved.

In addition, since the area where soldering is performed is expanded, the precision of the control technique required to scan the soldering area on the substrate 10 may be reduced. Accordingly, the manufacturing cost of the laser reflow device can be reduced.

The flat top converter 200 according to an embodiment of the present invention will be described in detail with reference to FIG. 5.

Prior to the description, it may be a flat top converter configuration in which two or more sets of plate-shaped cylindrical lenses are arranged in a combination in the X and Y axis directions.

As shown in FIG. 5, the flat top converter 200 may include an optical fiber 210.

The optical fiber 210 includes a core 211 and a cladding 212. Specifically, the core 211 may have a rectangular cross section and may be provided to extend in a column shape, and a hollow portion through which a laser beam may be transmitted may be provided inside the core 211. In this case, the core 211 may have a square or rectangular cross section, and the ratio of the length of the cross section to the length in the first axis direction and the length in the second axis direction may be easily changed. In addition, the cladding 212 may be provided to extend in the longitudinal direction of the core 211 so as to surround the outer peripheral surface of the core 211.

In addition, the core 211 and the cladding 212 may be made of a material having a predetermined refractive index. Specifically, the material of the core 211 and the cladding 212 may be made of any one of quartz, glass, and plastic, or an alloy thereof. However, the material of the core 211 and the cladding 212 is not limited thereto, and may include all insulator materials capable of minimizing laser beam loss with a predetermined refractive index. In addition, the cladding 212 may be made of a material having a lower refractive index than the core 211 so that the laser beam incident on the core 211 may be totally reflected at the interface between the core 211 and the cladding 212. In this case, the laser light source 100 capable of irradiating the laser beam to the inner hollow portion of the core 211 is located at the entrance side of the optical fiber 210 and may be provided to surface irradiate the laser beam.

The core 211 and the cladding 212 provided as described above are integrated to form one optical fiber 210, and the laser beam incident to the inside of the core 211 is at the interface between the core 211 and the cladding 212 Total reflection and move to the exit side. Specifically, light has a property of going straight because its wavelength is short, and has a property of being reflected or refracted. Accordingly, the laser beam incident to the inner side of the core 211 is totally reflected as the refractive index of the interface between the core 211 and the cladding 212 changes and moves toward the exit side. At this time, the laser beam that is totally reflected at the interface between the core 211 and the cladding 212 and moves may be homogenized while passing through the core 211.

In addition, a coating layer (not shown) may be further provided on the outer circumferential surface of the cladding 212 to prevent loss of the laser beam.

In addition, as the length of the optical fiber 210 increases, the homogenizing effect of the laser beam may increase, and since the optical fiber 210 is made of a flexible material, it can be used in a state in which bending occurs as shown in FIG. It is also possible to use it by bending it twice.

7 illustrates a flat top converter 200 according to another embodiment of the present invention may include a light pipe.

The light pipe 700 has a shape of a hexahedron and has an inclined angle from the incident surface 710 to the exit surface 720. At this time, the inclined angle may form 2° to 4°.

Such an inclined angle has an effect of condensing the laser beam more, thereby increasing light efficiency.

In addition, when a laser beam is incident on the light pipe, various beam shapes may be formed on the exit surface through total internal reflection according to the shape thereof. In the present embodiment, a square-shaped exit surface is employed, and the shape of the final output beam is a square-shaped beam.

In addition, the light pipe must have a transmittance of 90% or more of the laser beam, and the internal reflectivity may be adjusted by coating all or some according to design requirements.

Meanwhile, the light pipe is a kind of flat top converter, but in some cases, it may be configured as a combination of lenticular lenses, and furthermore, the lenticular lenses may be configured as a plurality of sets.

Meanwhile, the laser reflow apparatus according to an embodiment of the present invention may further include an image relay unit (not shown).

The image relay unit may relay the homogenized laser beam through the flat top converter 200 to guide the laser beam to the optical unit 300, and may be provided adjacent to the outlet side of the flat top converter 200.

Specifically, the image relay unit may adjust the laser beam output through the flat top converter 200 into a preset shape. For example, the image relay unit may expand or reduce the area to which the laser beam is irradiated. In addition, when the image relay unit optically relays the laser beam, it is possible to maintain homogeneity of energy according to the displacement of the laser beam.

Accordingly, the homogeneity of energy according to the displacement of the laser beam can be maintained at the same level even after the shape of the laser beam is changed through the image relay unit.

Next, the optical unit 300 may guide the homogenized laser beam to the soldering region on the substrate 10 by adjusting the path of the homogenized laser beam through the flat top converter 200.

In this case, the area to which the laser beam is irradiated may be a smaller area than the soldering area on the substrate 10. In addition, the optical unit 300 may control the area to which the laser beam is irradiated to scan the entire soldering area on the substrate 10 by adjusting the path of the laser beam. Such scanning may be performed sequentially or may be selectively performed only at preset scanning points.

For example, the optical unit 300 controls the laser reflow device to operate in a laser selective reflow (LSR) method by moving the irradiation area of the laser beam selectively irradiated to a partial area of the substrate 10 can do.

The optical unit 300 may include a first optical path adjustment unit 310 and a second optical path adjustment unit 320.

The first optical path adjusting unit 310 may reflect the laser beam output from the flat top converter 200 and guide it to the second optical path adjusting unit 320. In this case, the first optical path adjusting unit 310 may adjust a path in the first axis direction of the laser beam output from the flat top converter 200.

Specifically, the first optical path adjusting unit 310 may include a first reflecting unit 311 and a first optical path controlling unit 312.

The first reflector 311 may totally reflect the laser beam output from the flat top converter 200 and guide the laser beam to the second optical path adjusting unit 320.

In addition, the first reflector 311 may have a flat shape. According to this, the homogeneity of the laser beam can be maintained at the same level even after being reflected from the first reflector 311.

In this case, the first optical path controller 312 may control the movement of the first reflector 311. For example, the first optical path controller 312 may control a path in the first axis direction of the laser beam reflected by the first reflector 311 by rotating the first reflector 311 at a predetermined angle. .

Meanwhile, the second optical path adjustment unit 320 may reflect the laser beam reflected from the first optical path adjustment unit 310 again to guide the laser beam to the substrate 10. Also, the second optical path adjusting unit 320 may adjust a path in the second axis direction of the laser beam. In this case, the second axis may be an axis orthogonal to the first axis.

Specifically, the second optical path controller 322 may include a second reflector 321 and a second optical path controller 322.

The second reflecting unit 321 may totally reflect the laser beam reflected from the first optical path adjusting unit 310, and may guide the reflected laser beam to the soldering area on the substrate 10.

In addition, the second reflector 321 may have a flat shape. According to this, the homogeneity of the laser beam may be maintained at the same level even after being reflected from the second reflector 321.

In this case, the second optical path controller 322 may control the movement of the second reflector 321. As an example, the second optical path controller 322 may control a path in the second axis direction of the laser beam reflected by the second reflector 321 by rotating the second reflector 321 at a predetermined angle.

In addition, movements of the first optical path adjustment unit 310 and the second optical path adjustment unit 320 may be independently controlled. According to this, the irradiation area of the laser beam irradiated on the substrate 10 can be freely moved.

As described above, the homogenization of the laser beam is performed before passing through the optical unit 300. In addition, the optical unit 300 is configured such that the laser beam is not condensed or spectralized in the process of guiding the received laser beam to the substrate 10.

That is, since the homogeneity of the laser beam is maintained at the same level even after passing through the optical unit 300, the laser beam irradiated to the substrate 10 may have uniform energy according to the displacement.

Meanwhile, the laser reflow apparatus may further include a transfer unit 500. The transfer unit 500 includes a transfer belt 510 and a transfer module 520. Specifically, the transfer belt 510 may be provided to move the substrate 10 while the substrate 10 is mounted on the upper side. The transfer belt 510 may be a conveyor belt, but is not limited thereto, and all are included in one embodiment as long as the substrate 10 can be stably moved. The transfer module 520 may provide power to the transfer belt 510 so that the transfer belt 510 transfers the substrate 10. At this time, the transfer module 520 may allow the transfer belt 510 to transfer the substrate 10 in stages. In more detail, the device may be attached to the substrate 10 when the laser beam is irradiated for a period of 1 second to 2 seconds. Accordingly, the transfer module 520 may move the transfer belt 510 step by step so that the substrate 10 can be sequentially moved to a preset position and irradiated by the laser beam in a stopped state.

The above description of the present invention is for illustrative purposes only, and those of ordinary skill in the art to which the present invention pertains will be able to understand that it can be easily modified into other specific forms without changing the technical spirit or essential features of the present invention. will be. Therefore, it should be understood that the embodiments described above are illustrative in all respects and not limiting. For example, each component described as a single type may be implemented in a distributed manner, and similarly, components described as being distributed may also be implemented in a combined form.

The scope of the present invention is indicated by the claims to be described later, and all changes or modified forms derived from the meaning and scope of the claims and their equivalent concepts should be interpreted as being included in the scope of the present invention.

Substrate: 10
Laser light source: 100
Flat Top Converter: 200
Optical part: 300
1st optical path control unit: 310
1st reflector: 311
1st optical path controller: 312
Second optical path control unit: 320
Second reflector: 321
2nd optical path control unit: 322
Transfer part: 400
Transfer belt: 410
Transfer module: 420

Claims (10)

A laser light source that irradiates a laser beam;
A first flat top converter configured to receive the laser beam irradiated from the laser light source, homogenize and output energy according to the displacement of the received laser beam;
Including; an optical unit for moving the irradiation area of the laser beam by reflecting the laser beam output from the first flat top converter to adjust the optical path,
The first flat top converter is a laser reflow device that is a light pipe. The method of claim 1,
The laser reflow apparatus further comprises a second flat top converter disposed at the front end of the first flat top converter and homogenizing energy according to the displacement of the laser beam. The method of claim 1,
The light pipe is made of a hexahedron and has an inclined angle from the incident surface to the exit surface. The method of claim 3,
The inclined angle is between 2° and 4° laser reflow device. The method of claim 1,
The material of the optical unit is a laser reflow device including any one of fused silica or fused quartz. The method of claim 1,
The laser reflow apparatus wherein the refractive index of the optical unit is 1.33 or more and 2.00 or less. The method of claim 1,
The laser reflow device is that the object is an array-type substrate. The method of claim 1,
The laser reflow device to irradiate the object sequentially without overlapping the laser beam irradiating the object. The method of claim 1,
The laser reflow device that the output of the laser beam is within a minimum of 1KW ~ maximum 10KW. The method of claim 1,
The laser reflow device that the irradiation time of the laser beam is within a minimum of 1 second to a maximum of 10 seconds.

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