CN109093251B - A laser packaging device and packaging method - Google Patents

Abstract

The present invention provides a laser packaging device and a packaging method. The laser packaging device irradiates a laser beam onto a packaging substrate to form a light spot, and the edge of the light spot reaches the edge of the light spot on a surface perpendicular to the direction of the laser beam's travel path. The light intensity at the center of the light spot gradually decreases, the light spot includes a first section near the edge of the light spot and a second section near the center of the light spot, and the light intensity drop ratio of the first section is smaller than that of the first section. The light intensity drop ratio of the two sections, and the boundary position between the first section and the second section is the first inflection point. Using the laser beam of the spot provided by the present invention to encapsulate the packaging substrate effectively improves the uniformity of the dose irradiated on the glass frit, and further improves the sealing performance of the glass frit.

Description

A laser packaging device and packaging method

technical field

The invention relates to the field of optoelectronic semiconductors, in particular to a laser packaging device and a packaging method.

Background technique

Optoelectronic semiconductor devices have been widely used in various fields of life. Among them, OLED (Organic Light-Emitting Diode) has become a research hotspot due to its good color ratio, wide viewing angle, and high response speed, and has good application prospects. However, the electrodes and organic layers in OLED devices are very sensitive to oxygen and moisture. Oxygen and moisture penetrating into the OLED device from the external environment can seriously shorten the lifetime of the OLED device. Therefore, it is very important to provide effective hermetic sealing for OLED devices. There are the following requirements for hermetic sealing of OLED devices:

An airtight seal should provide a barrier to oxygen ( ^{10-3 cm3} / ^m2 /day) and water ( ^10-6 g/ ^m2 /day).

The size of the hermetic seal should be as small as possible (eg, <2mm) so that it does not adversely affect the size of the OLED display.

The temperature generated during the sealing process should not damage the materials in the OLED display (eg electrodes and organic layers, etc.).

Gases released during the sealing process should not contaminate the substances in the OLED display.

Hermetic seals should allow point-connection components such as thin-film chrome electrodes to enter the OLED display

In recent years, a sealing method using frit-assisted laser heating has been applied to the sealing of OLED displays. Then in practical applications, due to the constraints of the shape of the laser spot focused on the frit layer (circular TOP-HAT), poor uniformity and other factors, as well as the size of the package pattern, the upper limit of the scanning speed and other factors, the traditional scanning The packaging technology has been difficult to meet the requirements for OLED display packaging, for example, the glass frit forms dense holes (bubbles) in its interior and near the edge, which affects the packaging quality.

SUMMARY OF THE INVENTION

In view of this, the purpose of the present invention is to provide a laser packaging device and packaging method to solve the problem of poor sealing performance of the glass packaging body.

In order to solve the above technical problems, the present invention provides a laser packaging device, the laser packaging device irradiates a laser beam onto a packaging substrate, and forms a light spot on a surface perpendicular to the direction of the laser beam traveling route. The light intensity from the edge of the light spot to the center of the light spot gradually decreases, the light spot includes a first section close to the edge of the light spot and a second section close to the center of the light spot, and the light intensity decrease ratio of the first section is The demarcation ratio of the light intensity of the second section is smaller than that of the second section, and the boundary position between the first section and the second section is the first inflection point.

Optionally, the energy distribution of the laser beam is symmetrically distributed with respect to the direction of the travel path of the laser beam.

Optionally, the light intensity at the center of the light spot is greater than or equal to 95% of the light intensity at the first inflection point.

Optionally, the first section includes a near-center section in which the light intensity near the center of the light spot gradually decreases, and a near-edge section near the edge portion whose descending speed is greater than that of the near-central section, The boundary position between the near-center section and the near-edge section is the second inflection point.

Optionally, the second inflection point is symmetrically distributed with respect to the center of the light spot.

Optionally, the first section is a curved section with a gradually decreasing drop ratio or a straight section with a fixed drop ratio.

Optionally, the first inflection point is symmetrically distributed with respect to the center of the light spot.

Optionally, the energy distribution of the light spot further includes a third section with uniform light intensity, and the third section is located outside the first section.

Optionally, the energy distribution of the light spot further includes a third section in which the light intensity decreases from the inside to the outside, the third section is located outside the first section, and the light intensity of the third section decreases The ratio is greater than the light intensity drop ratio of the first section.

Optionally, the laser packaging device includes:

a light source assembly for providing a laser beam;

a shaping component for shaping the shape of the light spot of the laser beam;

a scanning galvanometer for scanning the laser beam onto the packaging substrate;

A light source assembly for providing the laser beam, a shaping assembly for shaping the spot shape of the laser beam, a scanning galvanometer for scanning the laser beam, and a Imaging mirror set for laser beam imaging.

Optionally, an imaging mirror group is provided on the scanning galvanometer, and the scanning galvanometer scans the laser beam onto the packaging substrate through the imaging mirror group.

Optionally, the imaging lens group is a telecentric field lens group.

Optionally, the focal length of the imaging lens group ranges from 290mm to 310mm.

Optionally, the laser packaging device further includes:

Beam expander group, used to zoom the laser beam;

The beam expander group is located between the light source assembly and the shaping assembly.

Optionally, the zoom range of the beam expander group is 1-2 times.

Optionally, the light source component is an infrared laser.

Optionally, the infrared laser includes a light source and a collimating lens group, the light source emits a laser beam, and is collimated by the collimating lens group to form a parallel laser beam.

Optionally, the shaping component is a diffractive optical element or a refractive optical element or a deformable mirror or a spatial light modulator.

Optionally, the scanning galvanometer is a two-dimensional scanning galvanometer, and the scanning angle range of the two-dimensional scanning galvanometer is ±20°.

Another aspect of the present invention provides a packaging method for a packaging substrate. The packaging method uses a laser beam to irradiate a to-be-packaged area of the packaging substrate to encapsulate the packaging substrate, including the following steps:

establishing a to-be-packaged area of the package substrate;

The laser beam is irradiated to the to-be-packaged area of the packaging substrate, wherein the laser beam forms a light spot, and the distance from the edge of the light spot to the center of the light spot is on the surface perpendicular to the direction of the laser beam traveling route. The light intensity gradually decreases, the light spot includes a first section near the edge of the light spot and a second section near the center of the light spot, and the light intensity drop ratio of the first section is lower than that of the second section The light intensity drop ratio of , the boundary position of the first section and the second section is the first inflection point;

The laser beam travels the package along the area to be packaged of the package substrate.

Optionally, the energy distribution of the laser beam is symmetrically distributed with respect to the direction of the travel path of the laser beam.

Optionally, the light intensity of the laser beam irradiated at the center of the substrate is greater than or equal to 95% of the light intensity at the first inflection point.

Optionally, the first section includes a near-center section in which the light intensity near the center of the light spot gradually decreases, and a near-edge section near the edge portion whose descending speed is greater than that of the near-central section, The boundary position between the near-center section and the near-edge section is the second inflection point.

Optionally, the second inflection point is symmetrically distributed with respect to the center of the light spot.

Optionally, the first section is a curved section with a gradually decreasing drop ratio or a straight section with a fixed drop ratio.

Optionally, the first inflection point is symmetrically distributed with respect to the center of the light spot.

Optionally, the energy distribution of the light spot further includes a third section with uniform light intensity, and the third section is located outside the first section.

Optionally, the energy distribution of the light spot further includes a third section in which the light intensity decreases from the inside to the outside, the third section is located outside the first section, and the light intensity of the third section decreases The ratio is greater than the light intensity drop ratio of the first section.

In the laser packaging device and packaging method provided by the present invention, a new type of light spot is designed, which includes a first section close to the edge of the light spot and a second section close to the center of the light spot. The light intensity drop ratio is lower than the light intensity drop ratio of the second section, and the encapsulation substrate is encapsulated by using the laser beam of this spot to effectively improve the uniformity of the dose irradiated on the glass frit, and further improve the sealing performance of the glass frit; In addition, the light source assembly, shaping element and scanning galvanometer are used to realize the shaping of the laser beam spot shape, forming the required spot shape, and solving the bubble problem caused by the uniformity of the dose of the glass package; and by replacing the shaping element Different shapes and sizes of light spots can be realized, and the diameter of the light spots can cover tens of um to tens of mm, which can effectively improve the process adaptability and save costs.

Description of drawings

1 is a schematic structural diagram of a laser packaging device in an embodiment of the present invention;

2 is a top view of a glass package in an embodiment of the present invention;

3 is a top view of an OLED display in an embodiment of the present invention;

4 is a two-dimensional light spot morphology generated in an embodiment of the present invention;

FIG. 5 is the shape of the light spot after the light spot generated in an embodiment of the present invention is integrated along the scanning direction;

6 is a block diagram of a glass frit packaging system according to an embodiment of the present invention;

7 is a comparison diagram of an example of the present invention in a non-scanning temperature curve and a conventional M-type light spot;

8 is an observation image of a glass package packaged in an embodiment of the present invention under a microscope;

Fig. 9 is the observation image of the glass package body encapsulated in the prior art under a microscope;

10 is a cross-sectional view of a slice of glass frit encapsulated by a laser beam spot formed in an embodiment of the present invention.

In the figure: 110 - control system; 111, 112, 113, 114, 115 - laser packaging device; 1110 - light source; 1111 - collimating lens group; 1112 - beam expander group; 1113 - shaping component; ; 1115 - telecentric field lens; 120 - glass substrate; 121 - glass package; 1211 - cover glass; 1212 - frit; 1213 - substrate glass; 1214 - electrode; 1215 - OLED layer; A - second section ; B-first segment; C-third segment.

Detailed ways

The laser packaging device and packaging method proposed by the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. The advantages and features of the present invention will be apparent from the claims and the following description. It should be noted that, the accompanying drawings are all in a very simplified form and in inaccurate scales, and are only used to facilitate and clearly assist the purpose of explaining the embodiments of the present invention.

Referring to FIG. 1 , this embodiment provides a laser packaging device, which can form a light spot appearance as shown in FIGS. 4 and 5 on the packaging substrate, and the edge of the light spot on the surface perpendicular to the direction of the laser beam travels The light intensity at the center of the light spot gradually decreases. Please refer to Fig. 4. The light intensity distribution of the light spot can be divided into a first section B and a second section A. The first section B decreases from the strongest light intensity I2 to I1. , the second section A is suddenly decreased by 0-5% from I1 to I0, wherein the decline ratio of the second section A from I1 to I0 is greater than that of the first section B from the strongest light intensity I2 to ratio at I1 and the first inflection point is formed at I1. Figure 5 shows the topography of the scanning spot after integration along the scanning direction. It can be seen from Figure 5 that the intensity of the scanning spot at the center position is lower than the surrounding area in the actual application scenario. Since the area to be encapsulated is an approximately rectangular area, this In the example, the cumulative light intensity along the center of the scanning path is consistent with the cumulative light intensity on both sides of the scanning path, so as to ensure the uniformity of the package. The energy distribution of the light spot formed by the laser beam irradiating the substrate is symmetrical with respect to the plane parallel to the traveling path. The light intensity I0 at the center point is greater than or equal to 95% of the light intensity I1 at the first inflection point, that is, I0>=I1*95%. The first section that decreases from the strongest light intensity I2 to I1 can have various forms, which can be a straight line section with a fixed decreasing ratio, a curved section with a gradually decreasing decreasing ratio, or a decreasing ratio. A polyline segment with a reduced segment, wherein the polyline segment may have one or more inflection points, and the above-mentioned inflection points are symmetrically distributed with respect to the center line of the light spot.

The above-mentioned light spot can also include a third section C, which is located outside the first section B. It can be a section with uniform light intensity distribution, or a section with a rapid decrease in light intensity from inside to outside. The segment is located at the edge area of the light spot irradiated by the laser beam in the area to be encapsulated on the substrate. The third segment C may or may not participate in encapsulation, depending on the specific working conditions.

1 , the laser packaging device provided in this embodiment includes: a light source assembly (including a light source 1110 and a collimating lens group 1111 ), a beam expander lens group 1112 , a shaping assembly 1113 , a scanning galvanometer 1114 and an imaging lens group. The light source assembly 1110 is an infrared laser, including a light source 1110 and a collimating lens group 1111. The light source 1110 emits a divergent laser beam, which is collimated by the collimating lens group 1111 to form a parallel laser beam, wherein the collimating lens group 1111 Used for collimating the laser beam output by the light source 1110 . The beam expander group 1112 is used to change the magnification of the spot of the laser beam, the shaping assembly 1113 is used to shape the shape of the spot of the laser beam, and the scanning galvanometer 1114 scans the laser beam to form a scanning laser. The telecentric field mirror 1115 and the telecentric field mirror 1115 image the formed scanning laser on the glass package. During operation, the divergent laser beam from the light source 1110 reaches the collimating lens group 1111, and is collimated by the collimating lens group 1111 to form a parallel laser beam, which reaches the beam expander group 1112, and the beam expander group 1112 changes the magnification of the laser beam spot. After adjustment, it reaches the shaping component 1113. The shaping component 1113 shapes the spot shape and then reaches the scanning galvanometer 1114. The scanning galvanometer 1114 scans the laser beam, and forms a scanning laser to reach the telecentric field mirror 1115. The telecentric field mirror 1115 will The laser beam is imaged onto the glass package 121 to perform laser encapsulation on the glass package 121 .

Among them, the beam expander group 1112 plays the role of changing the magnification of the laser beam, and can control the size of the laser beam spot to control the laser power. The beam expander group 1112 is located between the light source assembly and the scanning galvanometer 1114, and the beam expander group 1112 can achieve 1 to 2 times of variable magnification. By adjusting the beam expander group 1112 and switching the shaping component 1113, the spot size can be converted.

The shaping component 1113 can be selected from DOE (Diffractive Optical Elements, Diffractive Optical Elements), ROE (Refractive Optical Elements, Refractive Optical Elements), deformable mirror or spatial light modulator, and the achievable shaping spot diameter is 650um. The laser beam generated by the light source 1110 is an infrared Gaussian beam with a wavelength of 1064 nm. The scanning galvanometer 1114 is a two-dimensional scanning galvanometer, and the scanning angle range of the two-dimensional scanning galvanometer is ±20°. The focal length of the telecentric field lens 1115 ranges from 290 to 310 mm, preferably 300 mm. According to the diffraction limit, the spot diameter of the laser beam incident on the shaping component 1113 can be calculated as follows:

D _spot =4×λ×M ² ×f/(π×D)

where λ is the wavelength, M ² is the Gaussian beam quality factor, f is the focal length of the field lens, π is the circumference, and D _spot is the spot diameter of the laser beam incident on the shaping component 1113 . After calculation, the minimum diameter of the light spot that can be realized by the present invention can reach several tens of um.

The two-dimensional profile of the spot formed in this embodiment is shown in Figure 4. The profile is symmetrically distributed. After the highest spot intensity I2 continuously decreases to I1, the spot intensity suddenly drops by 5% to the lowest point I0. In this embodiment, the shape of the light spot after integration along the scanning direction is shown in FIG. 5 , and the intensity of the light spot I3 is lower than the intensity of the strongest light spot I4 by about 5%.

Referring to FIGS. 2 to 3 , the common form of the glass package processed by the technical solution of the present invention is shown in FIG. 2 , a typical example of the glass substrate 120 is an OLED display, and the glass substrate 120 is covered with the same glass package 121 , The structure of the single glass package 121 includes a cover glass 1211 , a glass frit 1212 , a substrate glass 1213 , an OLED layer 1215 and an electrode 1214 . The laser packaging device can configure the number of glass packaging bodies 121 according to the requirement of productivity.

This embodiment provides a glass frit packaging system, referring to FIG. 6 , the glass frit packaging system includes: a control system 110 and the laser packaging device provided in the first embodiment, the control system 110 is connected to each of the laser packaging devices, It is used for controlling the laser encapsulation device to carry out the glass frit encapsulation operation. In this embodiment, there are five laser packaging devices, including laser packaging devices 111 , 112 , 113 , 114 , and 115 .

Specifically, the control system 110 is connected to the light source 1110 in the light source assembly, and the control system 110 can control the turning on and off of the light source 1110 and adjust the laser power of the laser beam emitted by the light source assembly. The control system 110 is also connected with the scanning galvanometer 1114 , the control system 110 controls the scanning galvanometer 1114 to form a scanning laser, and makes the laser power of the light source assembly match the scanning speed of the scanning galvanometer 1114 .

In order to facilitate the grasp of the spot temperature on the glass package during laser scanning, the glass frit packaging system provided in this embodiment further includes a temperature measurement device, which is connected to the control system 110, and the temperature measurement device is used to measure the image on the glass package. The real-time temperature of the light spot on 121 is fed back to the control system 110 .

The control system 110 includes a computer and a controller connected to the computer. The controller controls the laser encapsulation device to perform glass frit encapsulation and exchanges data with the computer.

The present embodiment also provides a packaging method for a packaging substrate. The packaging method uses a laser beam to irradiate a to-be-packaged area of the packaging substrate to encapsulate the packaging substrate, including the following steps:

Step 1: establishing the to-be-packaged area of the package substrate;

Step 2: irradiating the laser beam to the to-be-packaged area of the package substrate;

The laser beam forms a light spot, and the light intensity from the edge of the light spot to the center of the light spot gradually decreases on a surface perpendicular to the direction of the travel path of the laser beam. A section and a second section close to the center of the light spot, the light intensity drop ratio of the first section is lower than the light intensity drop ratio of the second section, and the first section is different from the first section. The boundary position of the two sections is the first inflection point;

Step 3: The laser beam travels along the to-be-packaged area of the package substrate for packaging.

7 is a comparison diagram of the temperature curve in the non-scanning direction and the conventional M-type light spot in this embodiment, wherein the solid line is the shape of the conventional M-type light spot, and the dotted line is the shape of the light spot in this embodiment.

FIG. 8 is the observation result of the glass package packaged in the embodiment of the present invention under the microscope, and FIG. 9 is the observation result of the glass package packaged in the prior art under the microscope. It can be seen that there are many holes generated in FIG. 9 , the temperature uniformity of the laser beam spot produced by the embodiment of the present invention is obviously better than the temperature uniformity of the laser beam spot in the prior art. 10 is a sectional view of the glass frit encapsulated by the laser beam spot formed in the embodiment of the present invention. It can be seen that the glass package encapsulated by the laser beam spot produced by the embodiment of the present invention has no obvious holes, and the encapsulation effect is good.

To sum up, in the laser packaging device and packaging method provided by the present invention, a new type of light spot is designed, which includes a first section close to the edge of the light spot and a second section close to the center of the light spot. The light intensity drop ratio of the first section is lower than the light intensity drop ratio of the second section. Using the laser beam with this spot to encapsulate the packaging substrate can effectively improve the uniformity of the dose irradiated on the glass frit and further improve the glass frit. In addition, the light source components, shaping elements and scanning galvanometers are used to realize the shaping of the laser beam spot shape, forming the required spot shape, and solving the bubble problem caused by the uniformity of the dose of the glass package; And by replacing the shaping element, the shape and size of the light spot of different shapes can be realized, and the diameter of the light spot can cover tens of um to tens of mm, which effectively improves the process adaptability and saves costs.

The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments, and the same and similar parts between the various embodiments can be referred to each other. For the system disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant part can be referred to the description of the method.

The above description is only a description of the preferred embodiments of the present invention, and is not intended to limit the scope of the present invention. Any changes and modifications made by those of ordinary skill in the field of the present invention based on the above disclosure all belong to the protection scope of the claims.

Claims (26)

1. A laser packaging device is characterized in that a laser beam is irradiated onto a packaging substrate by the laser packaging device to form a light spot, the light intensity from the edge of the light spot to the center of the light spot is gradually reduced on a surface perpendicular to the direction of the traveling route of the laser beam, the light spot comprises a first section close to the edge of the light spot and a second section close to the center of the light spot, the light intensity reduction ratio of the first section is smaller than that of the second section, and the boundary position of the first section and the second section is a first inflection point;

wherein the first section comprises a near-center section with gradually reduced light intensity near the center of the light spot and a near-edge section with a reduced speed near the edge part larger than that of the near-center section, and the boundary position of the near-center section and the near-edge section is a second inflection point.

2. The laser packaging apparatus of claim 1, wherein the energy distribution of the laser beam is symmetrically distributed with respect to the direction of the path of travel of the laser beam.

3. The laser package of claim 1, wherein the intensity of light at the center of the spot is greater than or equal to 95% of the intensity of light at the first inflection point.

4. The laser packaging apparatus of claim 1, wherein the second inflection points are symmetrically distributed with respect to a center of the spot.

5. The laser packaging apparatus of claim 1, wherein the first section is a curved section in which a drop rate is gradually decreased or a straight section in which a drop rate is fixed.

6. The laser packaging apparatus of claim 1, wherein the first inflection points are symmetrically distributed with respect to a center of the spot.

7. The laser package of claim 1, wherein the energy profile of the spot further comprises a third segment of uniform intensity, the third segment being outside the first segment.

8. The laser packaging apparatus of claim 1, wherein the energy distribution of the light spot further comprises a third section with a light intensity decreasing from inside to outside, the third section is located outside the first section, and a light intensity decreasing rate of the third section is greater than a light intensity decreasing rate of the first section.

9. The laser packaging apparatus of any of claims 1-8, wherein the laser packaging apparatus comprises:

a light source assembly for providing a laser beam;

the shaping component is used for shaping the appearance of the light spot of the laser beam;

and the scanning galvanometer is used for scanning the laser beam to the packaging substrate.

10. The laser packaging apparatus of claim 9, wherein the scanning galvanometer is configured with a set of imaging mirrors, and the scanning galvanometer scans the laser beam onto the package substrate through the set of imaging mirrors.

11. The laser packaging apparatus of claim 10, wherein the imaging mirror is a telecentric field mirror.

12. The laser packaging apparatus of claim 10, wherein the focal length of the imaging lens group is in a range of 290mm to 310 mm.

13. The laser packaging apparatus of claim 9, further comprising:

the beam expanding lens group is used for zooming the laser beam;

the beam expander set is positioned between the light source assembly and the shaping assembly.

14. The laser packaging apparatus of claim 13, wherein the variable magnification range of the beam expander set is 1-2 times.

15. The laser package of claim 9, wherein the light source assembly is an infrared laser.

16. The laser packaging apparatus of claim 15, wherein the infrared laser comprises a light source and a set of collimating mirrors, the light source emitting a laser beam that is collimated by the set of collimating mirrors to form a parallel laser beam.

17. The laser packaging apparatus of claim 9, wherein the shaping component is a diffractive optical element or a refractive optical element or a deformable mirror or a spatial light modulator.

18. The laser packaging apparatus of claim 9, wherein the scanning galvanometer is a two-dimensional scanning galvanometer having a scanning angle range of ± 20 °.

19. A packaging method of a packaging substrate, which adopts laser beam irradiation to a region to be packaged of the packaging substrate to package the packaging substrate, comprises the following steps:

establishing an area to be encapsulated of the encapsulation substrate;

irradiating the laser beam to a region to be packaged of the packaging substrate, wherein the laser beam forms a light spot, the light intensity from the edge of the light spot to the center of the light spot is gradually reduced on a surface vertical to the direction of the traveling route of the laser beam, the light spot comprises a first section close to the edge of the light spot and a second section close to the center of the light spot, the light intensity reduction ratio of the first section is lower than that of the second section, and the boundary position of the first section and the second section is a first inflection point;

the laser beam is packaged along a region to be packaged of the packaging substrate;

wherein the first section comprises a near-center section in which the light intensity gradually decreases near the center of the light spot, and a near-edge section in which the light intensity gradually decreases near the edge portion at a rate greater than that of the near-center section, and the boundary position between the near-center section and the near-edge section is a second inflection point.

20. The packaging method of claim 19, wherein the energy distribution of the laser beam is symmetrically distributed with respect to the direction of the laser beam travel path.

21. The encapsulation method according to claim 19, wherein an intensity of light with which the laser beam is irradiated at the center of the substrate is 95% or more of an intensity of light at the first inflection point.

22. The packaging method of claim 19, wherein the second inflection points are symmetrically distributed with respect to a center of the light spot.

23. The method of claim 19, wherein the first section is a curved section in which a drop rate is gradually decreased or a straight section in which a drop rate is fixed.

24. The packaging method of claim 19, wherein the first inflection points are symmetrically distributed with respect to a center of the light spot.

25. The method of claim 19, wherein the energy distribution of the light spot further comprises a third segment of uniform intensity, the third segment being outside the first segment.

26. The packaging method according to claim 19, wherein the energy distribution of the light spot further includes a third section in which the intensity decreases from inside to outside, the third section is located outside the first section, and the rate of decrease in the intensity of the third section is greater than the rate of decrease in the intensity of the first section.

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