Method for regulating and controlling interface between laser reduction deposition metal and transparent substrate

Abstract

The invention belongs to the technical field of laser manufacturing, and relates to a method for regulating and controlling an interface between laser reduction deposited metal and a transparent substrate, which comprises the following steps of: coating a precursor material on the surface of the transparent substrate, and irradiating the interface between the precursor material and the transparent substrate by adopting ultrashort pulse laser through the transparent substrate; and the ultra-short pulse laser scans the interface of the precursor material and the transparent substrate for multiple times according to a preset path for laser direct writing, and a patterned metal structure is obtained. The ultra-short pulse laser penetrates through the transparent substrate from the back to irradiate the precursor material / substrate interface, thickness limitation on the precursor material is avoided, and in the multiple laser scanning process, the temperature of the metal / substrate interface exceeds the chemical bond fracture and recombination temperature, so that more chemical bonds are formed on the two sides of the transition layer, and the performance of the transition layer is improved. The chemical bonding degree of a metal / substrate interface is improved, interface regulation and control of the metal and the transparent substrate are achieved, and a patterned metal structure is obtained.

Description

Technical Field

[0001] This invention belongs to the field of laser manufacturing technology and relates to a method for controlling the interface between laser reduction deposited metal and transparent substrate. Background Technology

[0002] Metal-patterned / transparent substrate functional devices are widely used in optics, microfluidics, and electronics. The interfacial bonding strength between the metal and substrate significantly affects the device's lifespan; metal pattern detachment can cause device failure. The interaction between the metal pattern and the substrate mainly consists of mechanical locking, physical adsorption, and chemical bonding. Physical adsorption is a weak interaction where atoms and molecules near the substrate surface are primarily adsorbed onto the substrate by van der Waals forces. When chemical bonds on the substrate surface break, the resulting unsaturated bonds react chemically with the metal, forming a chemical bond between the metal and the substrate. Compared to the strength of van der Waals forces and hydrogen bonds (less than 50 kJ / mol) corresponding to physical adsorption, the strength of chemical bonds (100-1000 kJ / mol) is much higher. Therefore, forming chemical bonds at the metal-substrate interface can greatly enhance the interfacial bonding strength of the metal / substrate bilayer structure.

[0003] Based on their material, transparent substrates can be divided into glass and flexible polymers, which differ significantly from metals, making strong bonding between the substrate and the metal somewhat difficult. Flexible polymer films are mostly made of high-molecular-weight polymer materials. Polymer materials have low surface energy and few active groups, which is not conducive to chemical reactions.

[0004] Processes for depositing patterned metal layers on transparent substrates include screen printing, selective electroless plating, and magnetron sputtering. Each of these three processes requires multiple manufacturing steps, resulting in relatively low manufacturing efficiency. Screen printing requires a screen printing plate of a specific shape to achieve patterned metal deposition, and the sample needs to be sintered after printing the ink. Furthermore, the limitations of screen printing make it difficult to achieve high-precision manufacturing of patterned metals. Selective electroless plating requires surface modification of the substrate before plating, followed by pre-placement of catalysts in the corresponding patterned modification areas. Magnetron sputtering, as a physical deposition process, relies on the accumulation and migration of atoms to form the metal layer. The bonding strength between the metal layer deposited by magnetron sputtering and the substrate is generally low. After magnetron sputtering, wet etching and laser etching are required to fabricate the patterned metal structure, making the process quite complex. Summary of the Invention

[0005] The main objective of this invention is to overcome the deficiencies in the prior art and to provide a method for controlling the interface between laser reduction deposited metal and transparent substrate in order to create a patterned metal layer on a transparent substrate that forms a transition layer and chemical bonds with the substrate.

[0006] To achieve the above objectives, the specific technical solution is as follows: This invention provides a method for controlling the interface between laser reduction deposited metal and transparent substrate. A precursor material is coated on the surface of a transparent substrate, and an ultrashort pulse laser is used to irradiate the interface between the precursor material and the transparent substrate through the transparent substrate. The ultrashort pulse laser scans the interface between the precursor material and the transparent substrate multiple times according to a preset path to perform laser direct writing and obtain a patterned metal structure. The transparent substrate is an amorphous material, and the thickness of the transparent substrate is 0.1-5 mm.

[0007] This invention utilizes ultrashort pulse lasers with short pulse duration, low average power, but high peak power density to perform laser reduction direct writing on a transparent substrate, causing the formation of a metal oxide transition layer at the interface and the formation of chemical bonds, resulting in a patterned metal structure. For example... Figure 1 As shown, during laser direct writing, the laser beam irradiates the precursor material / substrate interface. The heat generated by the laser irradiation causes the precursor material at the interface to be reduced to metal nanoparticles under photothermal action, thus forming a metal layer. At this point, the laser penetrates the substrate and irradiates the surface of the metal layer at the interface, generating localized high temperatures in the irradiated area. This causes the interface temperature to rapidly rise above the glass transition temperature (Tg), a crucial characteristic temperature for amorphous materials. When the substrate temperature exceeds Tg, the substrate transitions to a viscous state and begins to undergo plastic deformation. These changes lead to the creation of more voids in localized areas within the substrate, thereby promoting metal diffusion into the substrate. Furthermore, since amorphous materials are typically formed by rapid cooling from a molten state, they are in an energy-unstable state. When the temperature exceeds Tg, amorphous materials tend to undergo structural restructuring to a lower energy state through structural relaxation. This restructuring is accompanied by the breaking of chemical bonds, resulting in numerous active groups on the substrate surface. These active groups react with the diffused metal at the interface to form a metal oxide layer. This metal oxide layer acts as a transition layer, forming metallic and covalent bonds with both the metal and the substrate, achieving chemical bonding between the metal and the substrate.

[0008] In this invention, during direct writing, the laser passes through the transparent substrate from the back and irradiates the precursor material / substrate interface. There is no thickness limitation on the pre-placed precursor material. During multiple laser scans, the metal / substrate interface is always kept at a high temperature, which allows more chemical bonds to form on both sides of the transition layer, improving the degree of chemical bonding at the metal / substrate interface and realizing the interface control between the metal and the transparent substrate. The process is simple, requires no mask, and has a high degree of flexibility.

[0009] Furthermore, the transparent substrate is pretreated using one of the following methods: acetone cleaning, ultraviolet light irradiation, or oxygen plasma treatment.

[0010] This invention pretreatment of transparent substrates involves acetone cleaning to remove oil and other contaminants from the substrate surface, and ultraviolet light irradiation and oxygen plasma treatment to increase the number of active groups on the substrate surface, thereby increasing the sites for chemical reactions at the interface and increasing the oxygen content on the substrate surface. This promotes the formation of a metal oxide transition layer at the interface during direct writing and facilitates the formation of chemical bonds.

[0011] Furthermore, the precursor material also includes metal salts or metal oxides, reducing solvents, deionized water, and dispersants.

[0012] Furthermore, the metal salt contains an electrophilic metal ion, preferably one of copper nitrate, copper chloride, silver nitrate, silver acetate, and tetrachloroauric acid, and the metal oxide is selected from one of CuO, Cu2O, and ZnO.

[0013] Furthermore, the reducing solvent is selected from one of methanol, ethanol, ethylene glycol, isopropanol, and n-butanol.

[0014] Furthermore, the dispersant is selected from one or more of polyvinylpyrrolidone (PVP), polymethyl methacrylate, and citric acid.

[0015] Furthermore, the transparent substrate is selected from one of glass, polycarbonate (PC), polyimide (PI), polystyrene (PS), and polymethyl methacrylate (PMMA).

[0016] The aforementioned transparent organic polymer substrate can have more active groups introduced on its surface through ultraviolet light irradiation or oxygen plasma treatment, thereby increasing the surface energy of the substrate.

[0017] Further, the mass ratio of the metal salt to the dispersant is (8-12):1, preferably 10:1; the volume ratio of the reducing solvent to deionized water is (3-5):1, preferably 4:1.

[0018] Furthermore, the mass ratio of the metal oxide to the dispersant is (2.5-3.5):1, preferably 3:1.

[0019] Furthermore, the pulse width of the ultrashort pulse laser is 10. -15 -10 -12 The pulse repetition frequency is 50 kHz-10 MHz.

[0020] Furthermore, the scanning parameters of the ultrashort pulse laser are a laser energy density of 10. -3 J / cm 2 -10 -1 J / cm 2The scanning speed is 1-5000 mm / s; for line scanning, the number of scans is 5-1000; for area scanning, the number of scans is 1-50, and the inter-line overlap rate of the scan lines is 70%-98%.

[0021] This invention precisely controls the temperature at the precursor / substrate interface above the temperature required for chemical bond breaking and reforming by adjusting the irradiation time of an ultrashort pulse laser per unit area. This promotes metal diffusion into the substrate and the generation of active groups on the substrate surface while simultaneously achieving reduction sintering to form a metal layer. The diffused metal reacts with the active groups on the substrate surface to form a metal oxide transition layer at the interface, thereby achieving chemical bonding between the metal and the transparent substrate. The metal atoms in the transition layer form covalent bonds with atoms within the substrate, while simultaneously maintaining metallic bonds with the metal atoms within the metal layer. By increasing the irradiation time of the ultrashort pulse laser per unit area, the substrate remains at a high temperature for an extended period, promoting the formation of more metal oxide transition layers. By controlling the formation of the metal oxide transition layer, the degree of chemical bonding between the metal and the substrate is controlled, achieving interface regulation between the metal and the transparent substrate.

[0022] In one specific embodiment of the present invention, the transparent substrate is glass, the wavelength of the ultrashort pulse laser is 515 nm, the laser pulse width is 800 fs, and the pulse repetition frequency is 600 kHz (green light); the scanning parameters of the ultrashort pulse laser are a laser energy density of 5.1 × 10⁻⁶. -3 J / cm 2 The scanning speed was 200 mm / s; the area was scanned 4 times, and the inter-line overlap rate of the scan lines was 92%.

[0023] In one specific embodiment of the present invention, the wavelength of the ultrashort pulse laser is 515 nm, the pulse width is 800 fs, and the pulse repetition frequency is 600 kHz; the scanning parameters of the ultrashort pulse laser are a laser energy density of 5.3 × 10⁻⁶. -3 J / cm 2 The scanning speed is 5 mm / s; the number of surface scans is 2, and the inter-line overlap rate of the scan lines is 75%.

[0024] In one specific embodiment of the present invention, the wavelength of the ultrashort pulse laser is 515 nm, the laser pulse width is 800 fs, and the pulse repetition frequency is 600 kHz; the scanning parameters of the ultrashort pulse laser are a laser energy density of 6.1 × 10⁻⁶. -3 J / cm 2 The scanning speed is 200 mm / s; the number of line scans is 200.

[0025] The above combination of ultrashort pulse laser and scanning parameters can more effectively promote the formation of a metal oxide transition layer at the metal / substrate interface, thereby promoting the chemical bonding between the metal and the substrate.

[0026] Compared with the prior art, the present invention has the following significant advantages: This invention promotes chemical bonding between the metal and the substrate by pretreating the substrate or controlling the irradiation time of an ultrashort pulse laser per unit area, thereby forming a metal oxide transition layer at the metal / substrate interface.

[0027] This invention uses ultrashort pulse lasers to output energy in pulse form. Due to the extremely low pulse duty cycle, the time the substrate is in the heating phase is much shorter than the cooling phase during laser irradiation, thereby effectively reducing thermal damage to the substrate.

[0028] In this invention, during direct writing, the laser passes through the transparent substrate from the back and irradiates the precursor material / substrate interface. There is no thickness limitation on the precursor material, and patterned metal layers of different thicknesses can be obtained by changing the number of scans.

[0029] This invention can also obtain patterned metal layers with various shapes that form a strong bond with a transparent substrate by controlling the laser scanning path through a computer. It has a high degree of flexibility and a wide range of applications. Attached Figure Description

[0030] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0031] Figure 1 This is a schematic diagram of the laser reduction direct writing process of the present invention; Figure 2 This is an EDS line scan image of Cu, O, and Si at the copper-glass interface in Embodiment 1 of the present invention; Figure 3 This is an HR-TEM image of the cross-section at the copper-glass interface in Embodiment 1 of the present invention; Figure 4 This is an HR-TEM image of the cross-section at the copper-glass interface in Embodiment 2 of the present invention; Figure 5 Here is an HR-TEM image of the cross-section at the copper-glass interface in Comparative Example 1; Figure 6 The image shows a cross-sectional HR-TEM image of the copper-glass interface in Comparative Example 2. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0033] Example 1 This embodiment provides a method for controlling the interface between ultrashort pulse laser reduction deposition of metallic copper and a glass substrate, the steps of which are as follows: (1) Weigh 4 g of copper nitrate and 0.4 g of polyvinylpyrrolidone (PVP) and add them to a solvent of 6 ml of ethylene glycol and 1.5 ml of deionized water to obtain a copper ion solution.

[0034] (2) 50 mg of silicon nanoparticles were placed in a copper ion solution to increase the absorption of laser energy by the precursor. After thorough ultrasonic dispersion, the precursor material was obtained.

[0035] (3) Clean the glass surface with acetone and then rinse it with deionized water.

[0036] (4) Apply the precursor material to a flat surface to form a 100 μm thick pre-layer, and then cover the surface of the pre-layer with a glass substrate.

[0037] (5) The glass covering the surface of the pre-formed layer is placed on a laser processing platform with a wavelength of 515 nm, a pulse width of 800 fs, and a repetition frequency of 600 kHz green light, so that the emitted beam passes through the glass and irradiates the precursor material / glass interface; the laser energy density during direct writing is 5.1 × 10⁻⁶. -3 J / cm 2 The scanning speed was 200 mm / s, and the scanning method was four area scans with a line overlap rate of 92%. During the laser direct writing process, copper ions were reduced to copper nanoparticles under photothermal action, and then a metallic copper layer was gradually formed during laser sintering. The laser reduction direct writing process is as follows: Figure 1 As shown.

[0038] (6) The precursor material in the unscanned area of ​​the laser is washed away with deionized water to obtain a metal layer that forms a transition layer with the glass substrate and is chemically bonded.

[0039] Figure 2The image shows EDS line scans of Cu, O, and Si at the copper / glass interface obtained in Example 1. The intensities of Si and O elements rise rapidly from the copper layer into the glass interior, and then gradually stabilize. The intensity of Cu element, on the other hand, decreases rapidly before approaching the glass, and then slowly decreases until it disappears after entering the glass interior. The regions where the intensities of Si and O elements rise rapidly and the intensity of Cu element decreases rapidly correspond to the metal oxide transition layer.

[0040] Figure 3 The image shows a cross-sectional HR-TEM image of the copper / glass material obtained in Example 1 at the interface. The crystalline region near the copper side of the interface is Cu2O(200), which corresponds to the metal oxide transition layer. Between the metal oxide transition layer and the amorphous glass, there is an amorphous region that differs from the amorphous state of the glass. This region corresponds to a chemically bonded region, and it is speculated that this region is a Cu-O-Si system formed by the chemical reaction between Cu2O and the glass.

[0041] Example 2 The preparation method in this embodiment is basically the same as that in Example 1, except that the scanning parameters of the ultrashort pulse laser are a laser energy density of 5.3 × 10⁻⁶. -3 J / cm 2 The scanning speed was 5 mm / s; the number of surface scans was 2, and the inter-line overlap rate of the scan lines was 75%. Figure 4 The image shows a cross-sectional HR-TEM image of the copper / glass material obtained in Example 2 at the interface. The crystalline region near the copper side of the interface is Cu2O(200), which corresponds to the metal oxide transition layer. Between the metal oxide transition layer and the amorphous glass, there is an amorphous region that differs from the amorphous state of the glass. This region corresponds to a chemically bonded region, and it is speculated that this region is a Cu-O-Si system formed by the chemical reaction between Cu2O and the glass.

[0042] Comparative Example 1 The steps of this comparative example are the same as those of the direct writing method in Example 1, except that: when scanning the laser surface, the number of scans is 2, and the inter-line overlap rate of the scan lines is 67%.

[0043] like Figure 5 As shown, no obvious chemical bonding layer was formed between copper and glass in this comparative example. The crystalline region near the metal side at the interface is Cu(111), indicating that no metal oxide transition layer was formed between the copper and glass, making it difficult to achieve chemical bonding between the metal and glass.

[0044] Comparative Example 2 The steps of this comparative example are the same as those of the direct writing method in Example 1, except that: the laser used is a continuous laser; the laser scanning parameters are: laser power of 1 W, spot diameter of 200 μm, scanning speed of 5 mm / s; the number of surface scans is 2, and the inter-row overlap rate of the scan lines is 75%.

[0045] like Figure 6 As shown, in this comparative example, the copper layer is mainly composed of nanoparticles, without forming a continuous metal layer, and no obvious chemical bonding layer is formed between the copper and the glass. The crystalline region near the metal side at the interface is Cu(200), indicating that no metal oxide transition layer is formed between the metallic copper and the glass, thus making it difficult to achieve chemical bonding between the metal and the glass.

[0046] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for interface control of laser reduction deposition of metal on a transparent substrate, comprising: Coating a precursor material on a surface of a transparent substrate, irradiating the precursor material and the transparent substrate interface with an ultrashort pulse laser through the transparent substrate, and performing laser direct writing on the precursor material and the transparent substrate interface by scanning the ultrashort pulse laser according to a preset path for multiple times to obtain a patterned metal structure. The precursor material comprises a metal salt or a metal oxide, a reducing solvent, deionized water and a dispersing agent; the transparent substrate is an amorphous material, and the thickness of the transparent substrate is 0.1-5 mm.

2. The method for controlling the interface between laser-reduced deposited metal and a transparent substrate according to claim 1, characterized in that, The transparent substrate is pretreated by one of acetone cleaning, ultraviolet irradiation and oxygen plasma treatment.

3. The method of claim 2, wherein the transparent substrate is a glass substrate. The metal salt contains a metal ion with electrophilicity.

4. The method of claim 3, wherein the transparent substrate is a glass substrate. The metal salt is selected from one of copper nitrate, copper chloride, silver nitrate, silver acetate and tetrachloroauric acid; and / or, the metal oxide is selected from one of CuO, Cu2O and ZnO.

5. The method of claim 3, wherein the transparent substrate is a glass substrate. The transparent substrate is selected from one of glass, polycarbonate, polyimide, polystyrene and polymethyl methacrylate.

6. The method of claim 4, wherein the transparent substrate is a glass substrate. The reducing solvent is selected from one of methanol, ethanol, ethylene glycol, isopropanol and n-butanol; and / or, the dispersing agent is selected from one or more of polyvinylpyrrolidone, polymethacrylate and citric acid.

7. The method of claim 3 or 6, wherein the transparent substrate is a glass substrate. The mass ratio of the metal salt and the dispersing agent is (8-12):1, preferably 10:1; and the volume ratio of the reducing solvent and the deionized water is (3-5):1, preferably 4:

1.

8. The method of claim 7, wherein the transparent substrate is a glass substrate. The mass ratio of the metal oxide and the dispersing agent is (2.5-3.5):1, preferably 3:

1.

9. The method of claim 1 or 2 or 3 or 6 or 8, wherein, The pulse width of the ultra-short pulse laser is 10 -15 -10 -12 s, and the pulse repetition frequency is 50 kHz-10 MHz.

10. The method of claim 9, wherein the transparent substrate is a glass substrate. The scanning parameters of the ultra-short pulse laser are that the laser energy density is 10 -3 J / cm 2 -10 -1 J / cm 2 , the scanning speed is 1-5000 mm / s; when line scanning, the scanning times are 5-1000 times; when surface scanning, the scanning times are 1-50 times, and the interline overlap rate of the scanning lines is 70%-98%.

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