Laser control structure and laser bonding method using the same

Abstract

A laser control structure and a laser bonding method using the same are provided. The laser bonding method includes forming a bonding portion on a substrate; disposing a bonding object on the bonding portion; disposing a laser control structure on the bonding object or the substrate; irradiating the bonding object and the bonding portion with laser light; controlling an amount of the laser light absorbed by the laser control structure; heating the bonding portion and the bonding object to a bonding temperature using the controlled amount of the laser light; and bonding the bonding portion with the bonding object. The laser control structure includes a first substrate including a first region and a second region; a first thin film laminate on the first region; and a second thin film laminate on the second region. The first thin film laminate includes at least one first thin film layer and at least one second thin film layer; the second thin film laminate includes at least one third thin film layer and at least one fourth thin film layer; and the first thin film laminate and the second thin film laminate have different reflectivity or absorptivity.

Description

[0001] This patent application claims priority to Korean Patent Application No. 10-2021-0080104, filed on June 21, 2021, and Korean Patent Application No. 10-2022-0073094, filed on June 15, 2022, the entire contents of which are incorporated herein by reference. Technical Field

[0002] This disclosure relates to a laser source control structure and a laser bonding method using the laser source control structure, and more specifically, to a laser bonding method that can be used to bond semiconductor components, etc. Background Technology

[0003] Advances in the electronics industry have led to a growing demand for more powerful, faster, and smaller electronic components. Consistent with this trend, connectors that link chips to substrates are also becoming smaller.

[0004] Solder bumps and similar materials are used to connect chips to a substrate. Heat may be applied to ensure the chip is connected to the substrate via solder bumps. When heat is applied during the packaging process, components may lose their function (e.g., warping due to differences in the coefficients of thermal expansion between components, or damage to a portion of each component).

[0005] In traditional thermo-press laser bonding processes, the difference in thermal expansion coefficients between the substrate and the component causes warping, and the semiconductor component and substrate are heated and pressurized, resulting in almost no selective bonding process. Recently, the application of flexible substrates / components has rapidly increased, and in this process, heat-induced damage to the substrate / component during high-temperature welding only allows for low-temperature welding, leading to reduced reliability. The bonding process technology that overcomes these drawbacks is laser-assisted bonding (LAB).

[0006] Lasers are currently used in welding to replace traditional welding processes in the fabrication of highly integrated circuits and to prevent structural defects caused by thermal effects. Laser welding is used to join printed circuit boards (PCBs), central processing unit (CPU) connectors, RF / HP boards, and various sensors in the electrical / electronic, semiconductor, and automotive industries. The benefits of laser welding include minimizing the heat-affected portion and forming intricate microstructures through rapid heating and cooling of the solder. Furthermore, welding can be performed in confined spaces using a laser beam that can be precisely aimed at the target point, and due to non-contact bonding and low heat input, less intermetallic compound formation occurs at the joint interface, resulting in low thermal stress. On the other hand, because the absorptivity or reflectivity of the laser beam varies for each material, precise control of the laser beam is required.

[0007] Recently, environmentally friendly processes have gained attention due to environmental concerns, and there is a growing need to develop processes that can flexibly meet the demands of low-volume production and customized special parts in the electrical and electronics fields. To meet these practical needs, research is underway on precision laser processing technologies for application in the electrical / electronics, semiconductor, and automotive industries. Summary of the Invention

[0008] This disclosure provides a laser bonding method, because in the laser bonding process, the photothermal conversion efficiency of the laser source depends only on the substrate and the bonding object, so high-temperature welding can be performed even at low laser power.

[0009] This disclosure also provides a laser bonding method that relies on the beam size of a laser surface source in the laser bonding process to prevent thermal deformation or degradation when the same laser power is applied to components or portions that do not need to be bonded.

[0010] This disclosure also provides a laser bonding method that simplifies the process of bonding regions with different melting points by using a single laser irradiation.

[0011] This disclosure relates to a laser bonding method. Embodiments of the inventive concept provide a laser bonding method comprising: forming a bonding portion on a substrate; disposing a bonding object onto the bonding portion; disposing a laser control structure onto the bonding object or the substrate; irradiating the bonding object and the bonding portion with a laser; controlling the amount of laser absorbed through the laser control structure; heating the bonding portion and the bonding object to a bonding temperature using the controlled amount of laser; and bonding the bonding portion to the bonding object, wherein the laser control structure comprises: a first substrate including a first region and a second region; a first thin film laminate on the first region; and a second thin film laminate on the second region, wherein: the first thin film laminate includes at least one first thin film layer and at least one second thin film layer laminated on the first region; the second thin film laminate includes at least one third thin film layer and at least one fourth thin film layer laminated on the second region; the reflectivity or absorptivity of the first thin film laminate relative to the laser is different from the reflectivity or absorptivity of the second thin film laminate; and the bonding temperature varies according to the amount of laser. Attached Figure Description

[0012] The accompanying drawings are included to provide a further understanding of the inventive concept, and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments of the inventive concept and, together with the description, serve to explain the principles of the inventive concept. In the drawings:

[0013] Figure 1 This is a flowchart illustrating a laser bonding method according to an embodiment of the present invention;

[0014] Figures 2 to 4 This is a cross-sectional view illustrating a laser control structure according to an embodiment of the present invention;

[0015] Figure 5 This is a perspective view illustrating a patterned laser control structure according to an embodiment of the present invention, and Figures 6A to 6D This is a plan view illustrating a patterned laser control structure according to an embodiment of the concept of the present invention;

[0016] Figures 7A to 15 This is a cross-sectional view illustrating a laser bonding method according to an embodiment of the present invention; and

[0017] Figure 16 and Figure 17 This is a graph showing the photothermal conversion efficiency of an embodiment based on the concept of the present invention. Detailed Implementation

[0018] To fully understand the structure and effects of the present invention, preferred embodiments of the present invention will be described in more detail below with reference to the accompanying drawings.

[0019] The inventive concept can be implemented in different forms and can be modified and altered in various ways, and should not be construed as being limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the inventive concept to those skilled in the art. In the accompanying drawings, the dimensions of various elements are exaggerated for ease of description, and the proportions of various elements may be exaggerated or reduced.

[0020] The terminology used herein is not intended to define embodiments of the inventive concept, but rather to describe them. Unless otherwise defined, all terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0021] Unless otherwise stated, singular terms may include plural forms. It should also be understood that, when used in this specification, the term "comprising" specifies the presence of the said element, step, operation, and / or component, but does not exclude the presence or addition of one or more other elements, steps, operations, and / or components.

[0022] It should be understood that when a layer is referred to as being "on top of" another layer, it can be formed directly on the upper surface of the other layer, or a third layer can be inserted between them.

[0023] Although terms such as "first" and "second" are used in this specification to describe various regions and layers, regions and layers are not limited to these terms. These terms are used only to distinguish one region or layer from another. Thus, a portion referred to as a first part in one embodiment may be referred to as a second part in another embodiment. The embodiments described and illustrated herein include complementary embodiments thereof. The same reference numerals always denote the same elements.

[0024] In the following text, reference will be made to Figures 1 to 17 A detailed description is provided of embodiments of the laser control structure and the laser bonding method using the laser control structure according to the present invention.

[0025] Figure 1 This is a flowchart illustrating a laser bonding method according to an embodiment of the present invention. Figure 7A and Figure 7B This is a cross-sectional view illustrating a laser bonding method according to an embodiment of the present invention. Hereinafter, the direction perpendicular to the upper surface of the substrate 100 is referred to as the first direction D1, and the direction parallel to the upper surface of the substrate 100 is referred to as the second direction D2.

[0026] Reference Figure 1 According to an embodiment of the present invention, the laser bonding method may include: forming a bonding portion on a substrate (S1), placing a bonding object on the bonding portion (S2), placing a laser control structure on the bonding object (S3), controlling the amount of laser absorbed by the laser control structure, heating the bonding portion and the bonding object to a bonding temperature using the controlled amount of laser (S4), and bonding the bonding portion and the bonding object (S5).

[0027] Reference Figure 1 and Figure 7A Forming a bonding portion (S1) on the substrate is a process of forming bonding portions 310 and 320 on upper pads 200 disposed on the upper surface of the prepared substrate 100. The substrate 100 may include, for example, a printed circuit board (PCB). Upper pads 200 may be disposed on the upper surface of the substrate 100. Upper pads 200 may include a conductive material. Upper pads 200 may include a metallic material. For example, upper pads 200 may include copper (Cu) or aluminum (Al). External components of the substrate 100 and internal circuitry of the substrate 100 may be electrically connected to each other via the upper pads 200. As used herein, "connection" may include direct connections and indirect connections via other components. Multiple upper pads 200 may be provided. Upper pads 200 may be spaced apart from each other in a second direction D2.

[0028] Bonding portions 310 and 320 may also be disposed on the upper surface of the substrate 100. More specifically, bonding portions 310 and 320 may be formed on the upper surface of the upper pad 200. Bonding portions 310 and 320 may be disposed in the form of a paste or a film. Bonding portions 310 and 320 may include a base resin, a reducing agent, a curing agent, and a catalyst.

[0029] The base resin may include thermosetting resins. Base resins may include epoxy resins, phenoxy resins, bismaleimides, unsaturated polyesters, urethane, urea, phenol-formaldehyde, vulcanized rubber, melamine resins, polyimides, epoxy phenolic resins, cyanate esters, oxetane resins, acrylic resins, ethylene resins, or combinations thereof.

[0030] The reducing agent can remove the oxide film of solder powder included in the joints 310 and 320. The reducing agent may include carboxyl groups. The reducing agent may include formic acid, acetic acid, lactic acid, glutamic acid, oleic acid, rosehip acid, 2,2-bis(hydroxymethylene)propionic acid, butyric acid, propionic acid, tannic acid, gluconic acid, valeric acid, hexanoic acid, hydrobromic acid, hydrochloric acid, uric acid, hydrofluoric acid, sulfuric acid, benzylglutaric acid, glutaric acid, malic acid, phosphoric acid, oxalic acid, uranic acid, hydrochloric acid, perchloric acid, gallic acid, phosphorous acid, citric acid, malonic acid, tartaric acid, phthalic acid, cinnamic acid, hexanoic acid, propionic acid, stearic acid, ascorbic acid, acetylsalicylic acid, azelaic acid, diphenylethanolic acid, fumaric acid, glutamine, amino acids, or combinations thereof.

[0031] Curing agents can induce a curing reaction with the base resin. Curing agents may include amines, aromatic amines, alicyclic amines, phenylalkylamines, imidazoles, carboxylic acids, acid anhydrides, polyamide-based curing agents, phenolic curing agents, phenyl pyrithione (PMDA) dianhydrides, and water-based curing agents, or combinations thereof.

[0032] Catalysts can control the reaction rate. Catalysts may include 1-methylimidazole, 2-methylimidazole, dimethylbenzylimidazole, 1-decyl-2-methylimidazole, benzyldimethylamine, trimethylamine, triethylamine, diethylaminopropylamine, pyridine, 18-diazocyclo[5,4,0]undec-7-ene, 2-heptadecylimidazole, boron trifluoride, or combinations thereof.

[0033] The joints 310 and 320 may include a conductive material. For example, the joints 310 and 320 may include a conductive filler. The conductive filler may be a solder of tin, silver, copper, lead, indium, bismuth (Bi), cadmium, antimony, gallium, arsenic, germanium, zinc, aluminum, gold, silicon, nickel, phosphorus, or combinations thereof. The conductive filler may include alloys of tin, silver, copper, lead, indium, bismuth (Bi), cadmium, antimony, gallium, arsenic, germanium, zinc, aluminum, gold, silicon, nickel, phosphorus, or Bi / 33In, Sn / 52In, Sn50In, Sn / 58Bi, Sn / 20Bi / 10In, Sn / 8Zn / 3Bi, Sn / 9Zn, Sn / Ag3.0 / Cu0.5, Sn / 2Ag, Sn / 3.8 / 0.7Cu, and combinations thereof. In this case, the volume fill factor may be from about 0% to about 50%. The joints 310 and 320 may include a metallic material as a conductive material.

[0034] The bonding portions 310 and 320 may include non-conductive particles, thermal acid generators, photoacid generators, sensitizers, alumina, silicon dioxide, aluminum nitride, silicon carbide, dyes, carbon black, graphene, carbon nanotubes, or combinations thereof. In this case, the content may be from about 0% to about 30%. The non-conductive particles can control the distance between the substrate 100 and the bonding object 500. The non-conductive particles can prevent conductivity between adjacent bonding portions 310 and 320.

[0035] Reference Figure 1 and 7A Setting the bonding object onto the bonding portion (S2) is the process of setting the bonding object 500 on the upper surface of the bonding portions 310 and 320. For example, the bonding object 500 may include a semiconductor chip, a sensor element, a solar cell element, or an optical element. A lower pad may be set on the lower surface of the bonding object 500. That is, the bonding portions 310 and 320 may be inserted between the lower pad and the upper pad 200 of the substrate 100. The lower pad in the second direction D2 may have a smaller width than the bonding portions 310 and 320 in the second direction D2. Therefore, a portion of the upper surface of the bonding portions 310 and 320 may be exposed. The lower pad may include a conductive material. The lower pad may include a metallic material. For example, the lower pad may include any conductive material, such as copper (Cu) or aluminum (Al). The lower pad may be pressed down from the lower surface of the bonding object 500 in the first direction D1. Multiple lower pads may be set. The lower pads may be spaced apart from each other in the second direction D2.

[0036] Reference Figure 1 and Figure 7ASetting the laser control structure onto the bonding object (S3) is the process of setting the laser control structure 700 onto the bonding object 500 or the substrate 100. The laser control structure 700 can be configured to contact the upper surface of the bonding object 500. Alternatively, the laser control structure 700 can be configured to be spaced apart from the bonding object 500 in the first direction D1. That is, the laser control structure 700 can be inserted between the surface light source 900 of the laser bonding apparatus and the bonding object 500. The bonding object 500 is not directly exposed to the laser L by means of the laser control structure 700. Therefore, in the bonding process described later, the bonding object 500 can be protected from the heat source. The laser control structure 700 may include a first substrate 710, a first thin film laminate 720, and a second thin film laminate 730. The laser control structure 700 can convert the laser L absorbed by the surface light source 900 into heat energy to control the heat energy delivered to the bonding portions 310 and 320. Alternatively, the laser control structure 700 can be a photomask.

[0037] Reference Figure 1 and 7A The laser control structure 700 may include a first substrate 710 comprising a first region N1A and a second region JA, a first thin film laminate 720 on the first region N1A, and a second thin film laminate 730 on the second region JA. The first region N1A may correspond to a non-bonded region on the substrate 100. The second region JA may correspond to a bonded region on the substrate 100.

[0038] The first substrate 710, including the first region NJA and the second region JA, may include a material with high transmittance to laser L applied from the surface light source 900. For example, the first substrate 710 may include polydimethylsiloxane (PDMS), glass, quartz, or combinations thereof. The first substrate 710 may include a thermally conductive material. The first substrate 710 may have a thickness of about 1 μm to about 100 mm.

[0039] A first thin-film laminate 720 may be disposed on a first region NJA, and a second thin-film laminate 730 may be disposed on a second region JA. Regions in the second region JA where the second thin-film laminate 730 is not disposed may exist. The first thin-film laminate 720 may include at least one first thin-film layer 721 and at least one second thin-film layer 722 laminated on the first region NJA. The first thin-film layer 721 and the second thin-film layer 722 may be laminated alternately. The structure of alternating lamination of the first thin-film layer 721 and the second thin-film layer 722 may be repeated. The first thin-film layer 721 and the second thin-film layer 722 may include SiO2 and SiN. xThe first thin film layer 721 and the second thin film layer 722 may comprise cesium tungsten oxide (CWO), lanthanum hexaboride, indium tin oxide (ITO), antimony-doped tin oxide (ATO), or combinations thereof. The first thin film layer 721 and the second thin film layer 722 may be formed by ALD, PVD, CVD deposition processes, solution coating processes, or photolithography processes. The first thin film layer 721 and the second thin film layer 722 may have a thickness of approximately 100 μm to approximately 0 μm.

[0040] The second thin-film laminate 730 may include at least one third thin-film layer 731 and at least one fourth thin-film layer 732 laminated on the second region JA. The third thin-film layer 731 and the fourth thin-film layer 732 may be laminated alternately. The third thin-film layer 731 and the fourth thin-film layer 732 may include SiO2 and SiN. x The material can be metal, ceramic, or a combination thereof. The third thin film layer 731 and the fourth thin film layer 732 may include cesium tungsten oxide (CWO), lanthanum hexaboride, indium tin oxide (ITO), antimony-doped tin oxide (ATO), or a combination thereof. The third thin film layer 731 may include the same material as the first thin film layer 721, and the fourth thin film layer 732 may include the same material as the second thin film layer 722. The third thin film layer 731 and the fourth thin film layer 732 may be formed by ALD, PVD, CVD deposition processes, solution coating processes, or photolithography processes. The third thin film layer 731 and the fourth thin film layer 732 may have a thickness of about 100 μm to about 0 μm. The third thin film layer 731 may have a thickness different from that of the first thin film layer 721, and the fourth thin film layer 732 may have a thickness different from that of the second thin film layer 722.

[0041] The first thin-film laminate 720 and the second thin-film laminate 730 can reflect or absorb the wavelength band of laser L applied from the surface light source 900. Specifically, the first thin-film layer 721 and the second thin-film layer 722 of the first thin-film laminate 720 can be formed of different materials. Therefore, the refractive indices of the first thin-film layer 721 and the second thin-film layer 722 relative to the laser L can be different. Due to the difference in refractive index at the interface between adjacent first thin-film layers 721 and 722, the laser L can be reflected. The more the first thin-film layer 721 and the second thin-film layer 722 are laminated, the greater the reflection of the laser L can be. In addition, the first thin-film layer 721 and the second thin-film layer 722 are formed of different materials, and their absorption rates to the laser L can be different. The more the first thin-film layer 721 and the second thin-film layer 722 are laminated, the lower the absorption efficiency of the laser L at the interface between the thin-film layers 721 and 722 can be. The third thin-film layer 731 and the fourth thin-film layer 732 of the second thin-film laminate 730 can be formed of different materials. Therefore, the same principle applies to how the first thin film laminate 720 works.

[0042] Each of the first thin-film laminate 720 and the second thin-film laminate 730 can change the number of laminated thin-film layers 721, 722, 731, and 732, and thus control the reflectivity or absorptivity of laser L in each region of the first substrate 710. The first thin-film laminate 720 and the second thin-film laminate 730 can be positioned adjacent to each other on the first substrate 710. Alternatively, the first thin-film laminate 720 and the second thin-film laminate 730 can be positioned spaced apart from each other on the first substrate 710 in a second direction D2. In this case, the reflectivity or absorptivity of laser L in each region of the first substrate 710 can be controlled by changing the position of the respective first thin-film laminate 720 and the second thin-film laminate 730. The reflectivity or absorptivity of laser L in each region of the first substrate 710 can be controlled by changing the thickness of the respective first thin-film laminate 720 and the second thin-film laminate 730. Specifically, as the thickness of each of the thin film layers 721, 722, 731, and 732 constituting the thin film laminates 720 and 730 increases, the reflection and absorption rates of the laser L can decrease. This is because the material inside the thin film layers 721, 722, 731, and 732 can be obstacles that impede the performance of the laser L.

[0043] The laser control structure 700 may also include an interposer. The interposer can be inserted between the first substrate 710 and the first thin film laminate 720 and the second thin film laminate 730. The interposer may be a microcircuit board and can physically connect the first substrate 710 to the first thin film laminate 720 and the second thin film laminate 730.

[0044] Reference Figure 1 and Figure 7A Controlling the amount of laser absorbed by the laser control structure and heating the joint and the joint object to the joint temperature using the controlled amount of laser (S4) may include controlling the amount of laser L absorbed by the laser control structure and heating the joint 310 and 320 and the joint object 500 to the joint temperature using the adjusted amount of laser L.

[0045] The amount of laser L is controlled via a process that controls the first thin-film laminate 720 on the first region NJA and the second thin-film laminate 730 on the second region JA. The amount of laser light can be defined as the quantity of light energy of the laser L applied from the surface light source 900. That is, the amount of laser light energy is proportional to the amount of laser light applied and absorbed from the surface light source. The first thin-film laminate 720 can be a high-reflectivity (HR) thin-film laminate. The first thin-film laminate 720 can reflect the applied laser L with high reflectivity. Therefore, laser L may not be applied to the first region NJA. That is, laser L may not be applied to the bonding object 500 in the first region NJA. The second thin-film laminate 730 can be an anti-reflectivity (AR) thin-film laminate. The second thin-film laminate 730 can reflect the applied laser L with a lower reflectivity than the first thin-film laminate 720. That is, the amount of reflected laser L can be reduced, and the amount of non-reflective laser L can be absorbed by the bonding object 500. Therefore, laser L can be applied to the second region JA.

[0046] The amount of laser L applied from the surface light source 900 can be controlled by the first thin film laminate 720 and the second thin film laminate 730. Therefore, the amount of laser L delivered to the bonding object 500 and the bonding portions 310 and 320 can be controlled. Abnormally high temperatures that could occur in the bonding object 500 due to the applied laser L can be prevented. Furthermore, defects or damage to the bonding object (e.g., a semiconductor device) during the laser bonding process can be prevented.

[0047] Heating the joints 310 and 320 and the joint object 500 to a joining temperature using a controlled amount of laser L is a process of heating to a joining temperature that will not damage the joint object 500. The joint object 500 and the joints 310 and 320 can absorb the laser L applied through the laser control structure 700. The joint object 500 and the joints 310 and 320 can convert the absorbed laser L into heat. Therefore, the temperature of the joint object 500 and the joints 310 and 320 can be increased. The joining temperature can also be the temperature at which the joints 310 and 320 are joined with the joint object 500 without causing damage or defects. In other words, the joint object 500 can be heated to a target joining temperature using the laser control structure 700.

[0048] Reference Figure 1 and 7A The joining of the joint and the joining object (S5) is a process of joining the joint 310, 320 with the joining object 500 at a heated joining temperature. At the target joining temperature, the joining object 500 can be joined with the joint 310 and 320. Therefore, laser joining is allowed without damaging the joining object 500.

[0049] In this embodiment, references to the above will be omitted. Figure 1 and Figure 7A The technical features described are repeated, and the differences will be described in detail. (Refer to...) Figure 7A and Figure 8A The thin film laminates 720 and 730 of the laser control structure 700 may be disposed below the first substrate 710. The thin film laminates 720 and 730 may be disposed at any position where the laser L applied from the surface light source 900 can be controlled.

[0050] Reference Figure 7B The laser control structure 700 can change the laser L through Figure 2 The reflectivity or absorptivity of the first thin film laminate 720 and the second thin film laminate 730. That is, the reflectivity or absorptivity of each of the first and second thin film layers may be different. Therefore, the heat energy delivered to each of the joints 310 and 320 may be different. In other words, according to the reflectivity or absorptivity of the first thin film laminate 720 (… Figure 2 The first joint 310 can be heated to a first temperature by the heat energy delivered by the second film laminate 730, and according to the heat energy delivered by the second film laminate 730. Figure 2 The heat energy delivered can heat the second joint 320 to a second temperature. The first temperature and the second temperature may be different.

[0051] Return to reference Figure 7B Multiple joining objects 500 can be provided. These multiple joining objects 500 can correspond to a first sub-joining object and a second sub-joining object. That is, the first sub-joining object and the second sub-joining object can correspond to a first joining portion 310 and a second joining portion 320, respectively. The joining temperature for heating each sub-joining object can be different. The temperature at which the first joining portion 310 and the first sub-joining object are heated can be a first joining temperature, and the temperature at which the second joining portion 320 and the second sub-joining object are heated can be a second joining temperature.

[0052] The first bonding portion 310 can fix the first sub-bonded object to the substrate 100 at a first temperature heated by the delivered heat energy. The second bonding portion 320 can fix the second sub-bonded object to the substrate 100 at a second temperature heated by the delivered heat energy. Therefore, bonding objects 500 with different melting points can be bonded by a single bonding process. That is, the processing time can be shortened to improve the efficiency of the bonding method. In addition, controlling the reflectivity or absorptivity of each area to which the laser L is applied through the laser control structure 700 can prevent thermal damage and warping of surrounding components. For each area to which the laser is applied, the thin film laminates 720 and 730 ( Figure 4 The thickness of ) or the arrangement of thin film laminates 720 and 730 ( Figure 3 The position of the laser can improve photothermal conversion efficiency to allow selective laser bonding.

[0053] Figures 8B to 15 This is a cross-sectional view showing a laser bonding method according to another embodiment. Figure 1 , Figure 2 , Figure 7A and Figure 7B The descriptions in this document are substantially the same as those for the substrate 100, the upper pad 200, the bonding portions 310 and 320, the bonding object 500, the surface light source 900, and the laser L, and the descriptions in the overlapping areas will be omitted below.

[0054] Reference Figure 8B The laser control structure 700 may include a first substrate 710 and a first thin film laminate and a second thin film laminate disposed on the lower surface of the first substrate 710. The first thin film laminate and the second thin film laminate may be configured to be spaced apart from the upper surface of the bonding object 500 in a first direction D1. The first substrate 710 may include a material having high laser L transmittance. Therefore, a laser control structure as shown in this embodiment can be provided.

[0055] Reference Figure 3 and Figure 9 The laser control structure 700 may include a first substrate 710 and a first thin-film laminate 720 and a second thin-film laminate 730 disposed on the upper surface of the first substrate 710. The first substrate 710 may include a first region AR1, a second region AR2, and a third region AR3. The first thin-film laminate 720 and the second thin-film laminate 730 may be spaced apart in a second direction D2. In this case, the region where the thin-film laminates 720 and 730 are not disposed is referred to as the third region AR3. Since the heat energy delivered to each of the joints 310, 320, and 330 disposed below the first region AR1, the second region AR2, and the third region AR3 is different, joints 310, 320, and 330 with different melting points can be joined by a single process. More specifically, in the case of crowded joints, the reflectivity can be reduced by the thin-film laminate to increase the heat energy delivered to the joint. That is, the joint objects 500 can be joined at low temperatures. In the case of no joints, the reflectivity can be increased by the thin-film laminate to reduce the heat energy absorbed by the joint. In other words, the temperature rise caused by laser L irradiation can be minimized.

[0056] Reference Figure 4 and Figure 10The laser control structure 700 may include a first substrate 710 and a first thin film laminate 720 and a second thin film laminate 730 disposed on the upper surface of the first substrate 710. The first substrate 710 may include a first region AR1, a second region AR2, and a third region AR3. The first thin film laminate 720 and the second thin film laminate 730 may be spaced apart in a second direction D2. In this case, the region where the thin film laminates 720 and 730 are not disposed is referred to as the third region AR3. The height LV1 of the upper surface of the first thin film laminate 720 may be greater than the height LV2 of the upper surface of the second thin film laminate 730. Since the heat energy delivered to each of the joints 310 and 320 disposed below the first region AR1 and the second region AR2 is different, the joints 310 and 320 with different melting points can be joined by a single process. According to this embodiment, as Figure 9 As shown, since the heat delivered to each of the joints 310, 320 and 330 located below the first region AR1, the second region AR2 and the third region AR3 is different, the joints 310, 320 and 330 with different melting points can be joined by a single process.

[0057] Figure 5 This is a perspective view illustrating a patterned laser control structure according to an embodiment of the present invention, and Figures 6A to 6D This is a plan view illustrating a patterned laser control structure according to an embodiment of the concept of the present invention. Figure 10 This is a cross-sectional view showing a laser bonding method according to another embodiment.

[0058] Reference Figure 5 , Figures 6A to 6D and Figure 10 The laser control structure 700 may include a first substrate 710 and a patterned thin-film laminate 750. The patterned thin-film laminate 750 may be formed by CMP or photolithography. This process allows control over the thickness of the thin-film laminate in each region of the first substrate 710. (Return to reference) Figures 6A to 6D The laser control structure 700 may include a thin film laminate 750 patterned in various forms. The region where the thin film laminate 750 patterned on the first substrate 710 is disposed may be connected to... Figure 4 The first region AR1 or the second region AR2 corresponds to it. The region of the thin film laminate 750 not patterned on the first substrate 710 can be associated with... Figure 4 The third region AR3 corresponds.

[0059] Reference Figure 11 and 12 The laser control structure 700 may include Figure 3The first thin film laminate 720 and the second thin film laminate 730. In this case, the first substrate 710 of FIG7 can be provided without the first substrate 710. Figure 3 The first thin film laminate 720 and the second thin film laminate 730. (Return to reference) Figure 12 A pre-bonded bonding object 510 can be provided on the substrate 100. In this case, the laser control structure 700 can be provided on the unbonded bonding object 500. That is, the bonding portions 310 and 320 with different melting points can be bonded by a single bonding process.

[0060] Reference Figure 13 The laser control structure 700 can be disposed on the substrate 100. That is, the laser control structure 700 can be inserted between the substrate 100 and the lower portions of the first joint 310 and the second joint 320. (Refer to...) Figure 14 The laser control structure 700 can be disposed on the substrate 100. That is, the laser control structure 700 can be inserted between the substrate 100 and the lower portions of the first bonding portion 310 and the second bonding portion 320. In this case, the surface light source 900 of the laser bonding device can be disposed below the substrate 100. (Return to reference) Figure 14 According to an embodiment of the present invention, and Figure 13 Compared to the previous embodiment, the bonding object 500 is not directly exposed to the laser L. Therefore, the bonding object 500 can be protected from the heat source.

[0061] Reference Figure 15 A joining object 500 can be provided on adjacent first joining portions 310 and second joining portions 320. Adjacent first joining portions 310 and second joining portions 320 can be spaced apart in the second direction D2. The close arrangement of the first joining portions 310 and second joining portions 320 can improve the efficiency of the joining process.

[0062] [Example 1]

[0063] SiO2 was deposited using PECVD. A total of four 10×10 mm samples (samples 1-4) with varying film thicknesses were prepared using a semiconductor wet etching process with a SiO2 etching solution. The reflectance of these samples corresponding to the laser-controlled structure film layers was measured using a UV-Vis spectrometer. The differences in reflectance based on SiO2 thickness are confirmed by Table 1 below.

[0064] [Table 1]

[0065] Sample number 1 2 3 4 Reflectance (%) 46.44 22.85 18.87 15.78

[0066] Pressure is applied to a silicon chip on which a laser-controlled structure film is deposited, causing the thermocouple to contact the lower surface of the chip. A 980nm laser is then applied directly to the upper surface, where a light-reflecting / absorbing film is deposited, converting the absorbed laser light into heat and delivering it to the thermocouple. The photothermal conversion temperature is measured.

[0067] Figure 16 and Figure 17 This is a graph illustrating the photothermal conversion efficiency according to an embodiment of the present invention. (Refer to...) Figure 16 and Figure 17 The temperature was measured at 252°C at the thickness of the film with the highest reflectivity, and at 305°C at the thickness of the film with the lowest reflectivity. This means that higher reflectivity results in less heat delivered by the laser, and therefore a lower temperature at the junction. Conversely, lower reflectivity results in more heat delivered by the laser, and therefore a higher temperature at the junction.

[0068] [Example 2]

[0069] An infrared absorption coating solution for implementing an embodiment of the laser control structure thin film layer according to an embodiment of the present invention was prepared by mixing epoxy silicone resin (Hybrid Plastics, EP0408.04.30) (24.1 wt%), photoinitiator (UVI-6976) (1.2 wt%), cesium tungsten oxide particles (Alfa Aesar) (2.4 wt%), and propylene glycol methyl ether acetate (Sigma Aldrich) (72.3 wt%). The prepared infrared absorption coating solution was spin-coated onto a quartz substrate and then dried at approximately 100°C for approximately 10 minutes to form a coating film with a thickness of approximately 10 μm. Subsequently, a laser control structure thin film layer using the infrared absorption coating was formed only on specific portions of the quartz substrate using a photolithography process. In the prepared laser control structure, transmittance was measured in the 1000 nm wavelength band of the portions where the laser control structure thin film layer was formed and the portions where the laser control structure thin film layer was not formed using a UV-Vis spectrometer. The transmittance was confirmed using Table 2 below.

[0070] [Table 2]

[0071] Thin film thickness (μm) 0 10 Transmittance (%) 92 34

[0072] When the laser control structure prepared according to embodiments of the present invention is used in the bonding process, the photothermal conversion efficiency can be selectively controlled for a uniformly applied laser surface light source. Therefore, bonding processes with different bonding conditions can be performed with a single laser irradiation.

[0073] According to embodiments of the laser bonding method conceived in this invention, the photothermal conversion efficiency can be controlled by adjusting the reflectivity or absorptivity of the region where laser light is applied via a laser control structure. Controlling the thickness of the laser application region or arranging a thin film layer of the laser control structure can improve the photothermal conversion efficiency, thereby allowing for selective laser bonding.

[0074] In another embodiment of the laser bonding method conceived according to the present invention, thermal damage and warping of surrounding components can be prevented by controlling the reflectivity or absorptivity of the area where laser light is applied via a laser control structure. Furthermore, joints with different melting points can be bonded using a single laser bonding process to reduce process time and thus improve efficiency.

[0075] The effects of this invention are not limited to those described above, but those skilled in the art will clearly understand from the following description other effects not described herein.

[0076] Although embodiments of the inventive concept have been described above with reference to the accompanying drawings, those skilled in the art can implement the inventive concept in other specific forms without altering its technical concept or essential characteristics. Therefore, it should be understood that the above embodiments are exemplary in all respects and not restrictive.

Claims

1. A laser bonding method, comprising: A bonding portion is formed on the substrate; The mating object is set onto the mating portion; The laser control structure is disposed on the bonding object or the substrate; Irradiate the joining object and the joining portion with a laser; The amount of laser light absorbed through the laser control structure is controlled. The joint and the joined object are heated to the joining temperature using a controlled amount of laser light; as well as The joining portion is joined to the joining object. The laser control structure includes: The first substrate includes a first region and a second region; A first thin film laminate, on a first region; and The second thin film laminate, on the second region The first thin film laminate includes a plurality of first thin film layers and a plurality of second thin film layers that are alternately and repeatedly laminated on a first region. The second thin-film laminate includes at least one third thin-film layer and at least one fourth thin-film layer laminated on the second region, wherein the third thin-film layer has a thickness different from that of the first thin-film layer, and the fourth thin-film layer has a thickness different from that of the second thin-film layer. The reflectivity or absorptivity of the first thin-film laminate relative to the laser is different from that of the second thin-film laminate, and The bonding temperature varies depending on the amount of laser light absorbed. The thickness of the first thin film layer is less than the thickness of the third thin film layer. The thickness of the second thin film layer is less than the thickness of the fourth thin film layer. The thickness of the first thin film laminate is greater than the thickness of the second thin film laminate. Each of the first and third thin film layers includes a first material. Each of the second and fourth thin film layers includes a second material that is different from the first material. The number of the first thin film layer is greater than the number of the third thin film layer. The number of the second thin film layer is greater than the number of the fourth thin film layer, and The laser control structure is in direct contact with the bonding object.

2. The laser bonding method as described in claim 1, wherein: The joint includes a first joint and a second joint; The joining object includes a first sub-joining object and a second sub-joining object; The step of heating to the bonding temperature includes heating the first bonding portion and the first sub-bonding object to the first bonding temperature using a controlled amount of laser light, and heating the second bonding portion and the second sub-bonding object to the second bonding temperature. The joining step includes joining a first joining portion to a first sub-joining object, and joining a second joining portion to a second sub-joining object; as well as The first bonding temperature generated by heating with the amount of laser light is different from the second bonding temperature generated by heating with the amount of laser light.

3. The laser bonding method as described in claim 1, wherein, The first thin film laminate and the second thin film laminate have different thicknesses.

4. The laser bonding method as described in claim 1, wherein, The first and second thin film laminates are patterned and arranged.

5. The laser bonding method as described in claim 1, wherein, The first substrate includes polydimethylsiloxane (PDMS), glass, quartz, or a combination thereof.

6. The laser bonding method as described in claim 1, wherein, The first to fourth thin film layers include SiO2 and SiN. x Metals, ceramics, or combinations thereof.

7. The laser bonding method as described in claim 1, wherein, The first to fourth thin film layers include cesium tungsten oxide (CWO), lanthanum hexaboride, indium tin oxide (ITO), antimony tin oxide (ATO), or combinations thereof.

8. The laser bonding method as described in claim 1, wherein, The joint is in the form of a paste or film and includes a base resin, a reducing agent, a curing agent, and a catalyst.

9. The laser bonding method as described in claim 8, wherein, The joint also includes a conductive filler. The conductive filler includes tin, silver, copper, lead, indium, bismuth (Bi), cadmium, antimony, gallium, arsenic, germanium, zinc, aluminum, gold, silicon, nickel, phosphorus, or combinations thereof.

10. The laser bonding method as described in claim 8, wherein, The junction also includes non-conductive particles, thermal acid-generating agents, photo-acid-generating agents, sensitizers, alumina, silicon dioxide, aluminum nitride, silicon carbide, dyes, carbon black, graphene, carbon nanotubes, or combinations thereof.

11. The laser bonding method as described in claim 8, wherein, The base resin includes epoxy resin, phenoxy resin, bismaleimide, unsaturated polyester, urethane, urea, phenol-formaldehyde, vulcanized rubber, melamine resin, polyimide, epoxy phenolic resin, cyanate ester, oxetane resin, acrylic resin, ethylene resin, or combinations thereof.

12. The laser bonding method as described in claim 8, wherein, The reducing agent includes formic acid, acetic acid, lactic acid, glutamic acid, oleic acid, rosehip acid, 2,2-bis(hydroxymethylene)propionic acid, butyric acid, propionic acid, tannic acid, gluconic acid, valeric acid, hexanoic acid, hydrobromic acid, hydrochloric acid, uric acid, hydrofluoric acid, sulfuric acid, benzylglutaric acid, glutaric acid, malic acid, phosphoric acid, oxalic acid, uranic acid, hydrochloric acid, perchloric acid, gallic acid, phosphorous acid, citric acid, malonic acid, tartaric acid, phthalic acid, cinnamic acid, hexanoic acid, propionic acid, stearic acid, ascorbic acid, acetylsalicylic acid, azelaic acid, diphenylethanolic acid, trans-butenedioic acid, glutamine, amino acids, or combinations thereof.

13. The laser bonding method as described in claim 8, wherein, The curing agent includes amines, aromatic amines, alicyclic amines, benzylamines, imidazoles, carboxylic acids, acid anhydrides, polyamide-based curing agents, phenolic curing agents, PMDA, and water-based curing agents or combinations thereof.

14. The laser bonding method as described in claim 8, wherein, The catalyst includes 1-methylimidazole, 2-methylimidazole, dimethylbenzylimidazole, 1-decyl-2-methylimidazole, benzyldimethylamine, trimethylamine, triethylamine, diethylaminopropylamine, pyridine, 18-diazocyclo[5,4,0]undec-7-ene, 2-heptadecylimidazole, boron trifluoride, or combinations thereof.

15. The laser bonding method as described in claim 1, wherein, The control structure further includes an interpolator disposed between the first substrate and the first thin film laminate and the second thin film laminate.

16. A laser control structure, comprising: The first substrate includes a first region and a second region; A first thin film laminate, on a first region; as well as The second thin film laminate, on the second region The first thin film laminate includes a plurality of first thin film layers and a plurality of second thin film layers that are alternately and repeatedly laminated on a first region. The second thin-film laminate includes at least one third thin-film layer and at least one fourth thin-film layer laminated on the second region, wherein the third thin-film layer has a thickness different from that of the first thin-film layer, and the fourth thin-film layer has a thickness different from that of the second thin-film layer. The reflectivity or absorptivity of the first thin-film laminate relative to the laser is different from that of the second thin-film laminate. A first thin-film laminate is disposed on the bonding object and the first bonding portion, such that the first bonding portion is heated to a first temperature by the laser. A second thin film laminate is disposed on the bonding object and the second bonding portion, such that the second bonding portion is heated to a second temperature by the laser, and The first temperature is different from the second temperature. The thickness of the first thin film layer is less than the thickness of the third thin film layer. The thickness of the second thin film layer is less than the thickness of the fourth thin film layer. The thickness of the first thin film laminate is greater than the thickness of the second thin film laminate. Each of the first and third thin film layers includes a first material. Each of the second and fourth thin film layers includes a second material that is different from the first material. The number of the first thin film layer is greater than the number of the third thin film layer. The number of the second thin film layer is greater than the number of the fourth thin film layer. The bonding object is between the first film laminate and the first bonding portion. The bonding object is between the second film laminate and the second bonding portion, and The laser control structure is in direct contact with the bonding object.

17. The laser control structure as described in claim 16, wherein, The first thin film laminate and the second thin film laminate are disposed on the first substrate at a distance from each other.

18. The laser control structure as described in claim 16, wherein, The first thin film laminate and the second thin film laminate have different thicknesses.

19. The laser control structure as described in claim 16, wherein, The first and second thin film laminates are patterned and arranged.

20. The laser control structure as described in claim 16, further comprising: An interposer is disposed between the first substrate and the first thin film laminate and the second thin film laminate.

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