Cathode drum of top skin tempered by equal electric field for thin film electrolytic deposition and manufacturing method thereof

Abstract

The present invention relates to a cathode drum of a top skin tempered by an equal electric field for thin film electrolytic deposition, which homogenizes the structure of a parent material and a weld part by means of a drum surface modification treatment and a final polishing-cleaning surface treatment, and to a manufacturing method thereof. The cathode drum is formed by inserting an inner cylinder into an outer cylinder, the outer cylinder comprising: a drum skin parent material having an annular structure having a V-shaped weld part so as to connect one side and the other side thereof; a welding bead formed to be lower than the surface of the drum skin parent material, inside the welding bead; a friction stir pressure-welding cladded layer formed at the surface height of the drum skin parent material on the welding bead of the weld part; a friction stir weld layer formed at the weld part between the friction stir pressure-welding cladded layer and the drum skin parent material; a friction stir growth layer formed on the friction stir weld layer and the drum skin parent material adjacent thereto; and a friction stir modified layer tempered by an equal electric field formed on the entire top skin surface in the same manner as the V-shaped weld part and a metal crystal structure of the drum skin parent material including the V-shaped weld part.

Description

Cathode drum with top skin quenched by equal electric field for thin film electrolytic deposition and manufacturing method thereof

[0001] The present invention relates to a thin film electrolytic deposition apparatus, and more particularly, to a cathode drum having a top skin that is quenched with an equal electric field for thin film electrolytic deposition so as to maintain a uniform current density on the surface of the cathode drum, and a method for manufacturing the same.

[0002] In general, thin plates of electrolytic copper, nickel, aluminum, etc. are widely used as positive and negative electrode conductive materials for secondary batteries used in the electrical and electronic industries and as substrate materials for printed circuit boards (PCBs). The demand for these materials is rapidly increasing, especially for small products such as slim notebook computers, personal digital assistants (PDAs), e-books, MP3 players, next-generation mobile phones, and ultra-thin flat panel displays.

[0003] In recent years, the trend toward lighter, thinner, and smaller electrical and electronic devices has accelerated, and the circuitry embedded in these devices is also becoming increasingly miniaturized. Consequently, circuits formed on printed circuit boards (PCBs) are also becoming increasingly thinner. Consequently, electrolytic copper foils are also becoming thinner, further increasing the importance of high-quality electrolytic copper foils.

[0004] These electrolytic copper plates are manufactured by a device including a cathode drum and an anode electrode housed in an electrolytic cell at a certain interval from the cathode drum.

[0005] However, depending on the quality and performance of the cathode drum of the copper foil maker, the thickness and surface grain size of the copper foil become uneven, resulting in a deviation in the width of the copper foil and the weight in the grinding direction.

[0006] And the weld bead mark in the longitudinal direction of the cathode drum joint is transferred in the width direction of the electrolytic copper foil.

[0007] As a result, discoloration such as spots occurs and hot spot defects occur in the high current density operating range, which significantly reduces the quality of the copper foil.

[0008] Figure 1 is a schematic diagram showing a typical thin film electrolytic deposition device.

[0009] A typical thin film electrolytic deposition device, as shown in Fig. 1, includes an electrolytic cell (1) in which an electrolyte (2) is stored, a cathode drum (3) that rotates while being partially immersed in the electrolyte (2) stored in the electrolytic cell (1), and an anode electrode (4) that is immersed in the electrolyte (2) and arranged at a constant distance from the cathode drum (3) along the shape of the cathode drum (3).

[0010] Typically, the electrolyte (2) is a copper sulfate solution containing sulfuric acid, copper ions, and chloride ions, and has strong acidic properties. The electrolyte (2) is supplied and circulated at a relatively high speed within the electrolytic cell (1) to prevent copper ion deficiency near the cathode drum (3).

[0011] In addition, the surface material of the cathode drum (3) is made of titanium, which maintains acid resistance against the electrolyte (2) and facilitates the peeling of the electrolytic copper plate (5). In this configuration, when a high-density current is applied between the cathode drum (3) charged with a negative potential and the anode electrode (4) charged with a positive potential using the electrolyte (2) as a medium, the copper in the positive ion state contained in the electrolyte (2) is deposited on the cathode drum (3), thereby solidifying and precipitating as a solid.

[0012] The above-deposited copper is formed into an electrolytic copper thin film (5) in the form of a metal film along the surface of a rotating cathode drum (3), and the formed electrolytic copper thin film (5) is wound on a bobbin (7) under the guidance of guide rolls (6).

[0013] Figure 2 is a perspective view schematically showing a cathode drum for thin film electrolytic deposition according to a conventional technology.

[0014] As shown in Fig. 2, the cathode drum (3) is composed of an inner cylinder (10) made of stainless steel and a copper alloy and an outer cylinder (20) having an outer shell made of titanium and surrounding the inner cylinder (10).

[0015] The inner cylinder (10) and outer cylinder (20) are each manufactured by forming a flat plate into a circular shape, bending it, welding both ends, connecting them with a welding bead (40), and then mechanically fitting the inner cylinder (10) into the outer cylinder (20) by heat pressing.

[0016] However, as described above, the current density becomes uneven on the entire surface of the cathode drum (3) manufactured by forcibly fitting the inner cylinder (10) and the outer cylinder (20) together by means of a welding bead (40) using physical and mechanical force.

[0017] The current density formed unevenly in this way has a very significant negative effect on the production of the electrolytic copper plate (5).

[0018] Therefore, it causes discoloration defects on the surface of the copper foil, weight deviation defects in the width and length directions of the copper foil, and serious defects due to thickness deviation.

[0019] Additionally, it causes hot spot defects in high current density range operation.

[0020] And the weld joint bead mark formed in the longitudinal direction of the drum cylinder joint is transferred in the width direction of the electrolytic copper sheet. Ultimately, it is known to be the main cause of the production of poor electrolytic copper sheet (5), which leads to a decline in quality.

[0021] A major defect of the existing cathode drum (3) is that the current is concentrated and biased in a specific area on the surface of the skin, resulting in a continuously uneven current density.

[0022] That is, if the distribution or current density of the electrolyte supplied between the cathode drum (3) and the anode electrode (4) is uneven, the copper foil electrolytically deposited on the surface of the titanium cathode inevitably has a thickness difference, which causes the quality of the copper foil to deteriorate and requires additional processing.

[0023] In addition, since the current density is uneven depending on the weld bead (40) of the longitudinal joint weld of the outer cylinder (20), the electrodeposition and precipitation of copper ions become uneven. This causes the film thickness and grain size to become uneven, resulting in discoloration defects on the film surface and weight deviation defects in the width and length directions of the film.

[0024] In addition, in the high current density operating range, a defect occurs in which a hot spot defect and a weld bead mark (trace) in the longitudinal direction of the drum cylindrical joint are transferred to the width direction of the thin film formed by electrolytic-electrodeposition-deposition-continuous plating.

[0025] Due to various problems like these, the quality of the product is deteriorating and thus it is a major cause of the increase in the cost of the product.

[0026] And when the cathode drum is operated for a long time, hydrogen adsorbed on the surface of the titanium drum skin layer due to reduction polarization damages the TiO₂ titanium oxide film layer on the surface of the titanium skin layer, and hydrogen penetrates to generate Ti hydrate.

[0027] As a result, the production of the thin film must be stopped because unevenness and foreign substances occur on the surface of the cathode drum skin.

[0028] Therefore, the cathode drum of the plating machine had to be dismantled at great expense and periodically polished to remove Ti hydrates, etc., from the surface of the Ti cathode drum skin layer.

[0029] The above outer cylinder (20) is manufactured by joining both sides by welding, and the welding area is divided into a base material area, a heat affected zone, and a welded area. At this time, the base material shows a uniform equiaxed structure, while the heat affected zone and the welded area show a coarse and irregular columnar structure that is different from the base material structure.

[0030] In this way, as the structures of the base material and the welded area are formed differently, there is a problem in which a belt-shaped defect of a different shape occurs on the surface of the final product (metal foil).

[0031] That is, since the weld undergoes a rapid thermal cycle of melting, solidification, and cooling in a short period of time, its structure is completely different from that of the base material, and the material behavior of the weld that occurs during welding includes recovery and recrystallization, grain coarsening, precipitation, and phase transformation, and the weld metal exhibits a structure that is significantly different from that of the base material as it is a structure that is rapidly solidified after the welding material reaches a molten state.

[0032] To solve these problems, attempts are continuously being made to form the metal structure of the welded portion similar to the metal structure of the base material when manufacturing an electrodeposited cathode drum using titanium plates.

[0033] After forming the above outer cylinder into a circular shape, melt welding such as TIG welding or plasma welding is performed, and then additional overlay welding is performed on the welded portion, or forming work is performed before and after welding to manufacture the welded portion thicker than the base material thickness, and then post-processing work is performed.

[0034] Here, the post-processing process refers to a process of reducing the thickness of the weld by applying strain energy to the weld and then performing recrystallization heat treatment at an appropriate temperature, thereby obtaining a weld structure similar to the grain size of the base material.

[0035] However, because these post-processing processes involve applying strain energy to the material, they pose a problem: reduced final product yield and increased manufacturing costs. Furthermore, the irregular strain energy applied to the weld joint can lead to the formation of grains of uneven size depending on the location of the weld joint after post-processing.

[0036] The present invention has been devised to solve the above problems, and its purpose is to provide a cathode drum with a top skin that is tempered with an equal electric field for thin film electrolytic deposition so that the crystal structure of the base material and the weld can be uniformly formed through drum surface modification treatment and final polishing cleaning surface treatment, and a method for manufacturing the same.

[0037] In order to achieve the above object, the cathode drum of the top skin tempered with an equal electric field for thin film electrolytic deposition according to the present invention is characterized in that the cathode drum is formed by inserting an inner cylinder into an outer cylinder, wherein the outer cylinder comprises a drum skin base material having an annular structure having a "V"-shaped weld portion for connecting one side and the other side, a weld bead formed lower than the surface of the drum skin base material inside the weld portion, a friction stir welding clad layer formed at the surface height of the drum skin base material above the weld bead of the weld portion, a friction stir welding layer formed at the weld portion between the friction stir welding clad layer and the drum skin base material, a friction stir build-up layer formed on the friction stir welding layer and the drum skin base material adjacent thereto, and a friction stir modified layer tempered with an equal electric field formed on the entire top skin surface so as to be identical to the metal crystal structure of the drum skin base material including the "V"-shaped weld portion.

[0038] In addition, the method for manufacturing a cathode drum of a top skin that has been tempered with an equal electric field for thin film electrolytic deposition according to the present invention for achieving the above purpose comprises the steps of: preparing a plate-shaped drum skin base material; A step of forming the drum skin base material into a cylindrical shape so as to have a "V" shaped weld portion; A step of performing friction stir welding on the weld portion to form a weld bead connecting one side and the other side of the drum skin base material; A step of selectively removing the weld bead inside the weld portion from the surface to a predetermined depth; A step of performing friction stir welding on the surface of the weld bead to form a friction stir welding clad layer; A step of softening the weld portion on which the friction stir welding clad layer has been formed by friction welding and applying pressure to form a friction stir welding layer between the friction stir welding clad layer and both sides of the drum skin base material; A step of forming a friction stir building layer by building a softened material by the friction building principle on the weld portion on which the joined friction stir welding clad layer has been formed; A step of surface modifying the entire surface including the friction stir building layer by a friction stir process to form a friction stir modified layer; A step of performing ultrasonic nano-modification surface treatment and CO2 cleaning on the entire surface of the friction stir modified layer; A step of performing ultrasonic nano-modification surface treatment and CO2 cleaning on the cleaned friction stir modified layer It is characterized by including a step of surface treatment with a laser beam and plasma.

[0039] The cathode drum of the top skin, which is tempered with an equal electric field for thin film electrolytic deposition according to an embodiment of the present invention, and the manufacturing method thereof have the following effects.

[0040] First, the crystal structure of the top skin base material and weld can be formed uniformly through drum surface modification treatment and final polishing cleaning surface treatment.

[0041] Second, by applying friction technology, the bonding interface between the inner (lower) cylindrical plate of the cathode drum and the outer plate can be completely integrated without defects by removing weak intermetallic compounds, voids, lattice defects, cracks due to differences in thermal expansion coefficients, and thermal stress defects.

[0042] Therefore, by integrating the metallurgical properties and chemical composition at the bonding interface of the cathode drum with the base material, electrochemical, metallographic, and mechanical integration is achieved, and a high current-conducting efficiency can be maintained at the cathode drum surface while maintaining an equal electric field.

[0043] Third, by applying friction technology, the structure of the base material and the welded part is uniformly formed at the joint interface through surface treatment, modification, and joining. In addition, no fumes are generated during the work, the thermal efficiency is high, and no protective gas is required, allowing for environmentally friendly work.

[0044] Figure 1 is a schematic diagram showing a typical thin film electrolytic deposition device.

[0045] Figure 2 is a perspective view schematically showing a cathode drum for thin film electrolytic deposition according to a conventional technology.

[0046] Figure 3 is a perspective view showing a cathode drum of a top skin that has been tempered with an equal electric field for thin film electrolytic deposition according to the first embodiment of the present invention.

[0047] Figures 4 to 11 are cross-sectional views showing a process for manufacturing a cathode drum of a top skin that is tempered with an equal electric field for thin film electrolytic deposition according to the first embodiment of the present invention.

[0048] Fig. 12 is a perspective view showing a cathode drum of a top skin that has been tempered with an equal electric field for thin film electrolytic deposition according to a second embodiment of the present invention.

[0049] Figures 13 to 20 are cross-sectional views showing a process for manufacturing a cathode drum of a top skin that is tempered with an equal electric field for thin film electrolytic deposition according to a second embodiment of the present invention.

[0050] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, detailed descriptions of well-known functions or components that may obscure the gist of the present invention will be omitted in the following description and the accompanying drawings. It should also be noted that, where possible, identical components are indicated with the same reference numerals throughout the drawings.

[0051] The terms and words used in this specification and claims described below should not be interpreted as limited to their conventional or dictionary meanings, but should be interpreted with meanings and concepts that conform to the technical idea of ​​the present invention based on the principle that the inventor can appropriately define the concept of the term in order to explain his own invention in the best way. Therefore, it should be understood that the embodiments described in this specification and the configurations illustrated in the drawings are only the most preferred embodiments of the present invention and do not represent all of the technical idea of ​​the present invention, and that there may be various equivalents and modified examples that can replace them at the time of filing this application.

[0052] Fig. 3 is a perspective view showing a cathode drum of a top skin that has been tempered with an equal electric field for thin film electrolytic deposition according to the first embodiment of the present invention.

[0053] The cathode drum (100) of the top skin annealed with a uniform electric field for thin film electrolytic deposition according to the first embodiment of the present invention, as shown in FIG. 3, has a drum skin base material (110) having a ring-shaped structure having a "V"-shaped welded portion (A) for connecting one side and the other side, a weld bead (120) formed lower than the surface of the drum skin base material (110) inside the welded portion, a friction stir welding clad layer (130) formed at the surface height of the drum skin base material (110) on the weld bead (120) of the welded portion, a friction stir welding pressure layer (140) formed at the welded portion between the friction stir welding clad layer (130) and the drum skin base material (110), a friction stir build-up layer (150) formed on the friction stir welding pressure layer (140) and the drum skin base material (110) adjacent thereto, and a "V"-shaped It is composed of a friction stir modified layer (160) formed on the entire top skin surface with an equal field, identical to the metal crystal structure of the drum skin base material (110) including the welded portion (A).

[0054] Here, the drum skin base material (110) and the welding bead (120) are made of the same material.

[0055] In addition, although not clearly shown in the drawing, a CO₂ cleaning, laser beam and plasma surface treatment layer are formed on the surface of the friction stir modification layer (160) as well as an ultrasonic nano-modification surface treatment layer.

[0056] Figures 4 to 11 are cross-sectional views showing a process for manufacturing a cathode drum of a top skin that is tempered with an equal electric field for thin film electrolytic deposition according to the first embodiment of the present invention.

[0057] The method for manufacturing a cathode drum of a top skin tempered with an equal electric field for thin film electrolytic deposition according to the first embodiment of the present invention prepares a plate-shaped drum skin base material (110) as shown in FIG. 4.

[0058] Here, the drum skin base material (110) is a part that becomes the outer skin of the cathode drum of the present invention, and is made of one of titanium, zirconium, Hastelloy, Inconel, duplex, Monel, and sanitary materials or an alloy thereof as a corrosion-resistant material in an electrolytic deposition solution.

[0059] Meanwhile, in the embodiment of the present invention, in consideration of corrosion resistance and hydrogen embrittlement characteristics, etc., as the drum skin base material (110), titanium Grade 1 corresponding to pure titanium or Grade 1 modified by adding additives such as ruthenium (Ru) and copper (Cu) to Grade 1 to improve corrosion resistance may be used, but the present invention is not limited thereto.

[0060] As an example, the drum skin base material (110) may include, in weight %, iron (Fe): 0.06% or less, oxygen (O): 0.1% or less, hydrogen (H): 150 ppm or less, the remainder titanium (Ti), and other unavoidable impurities. More advantageously, it may include iron (Fe): 0.04% or less, oxygen (O): 0.08% or less, hydrogen (H): 60 ppm or less, the remainder titanium (Ti), and other unavoidable impurities.

[0061] In addition, the drum skin base material (110) has a grain size of 4 to 10, and more advantageously, it can have a grain size of 5 to 9. Since the size of the currently commercialized cathode drum is approximately 2 to 4 m in diameter, 1 to 2 m in width, and 7 to 12 mm in thickness, the drum skin base material (110) is prepared similarly. Specifically, a titanium plate having a thickness of 7 to 15 mm, a width of 1 to 2 m, and a length of 6 to 12 m can be used.

[0062] The above drum skin base material (110) is maintained in a smooth surface state by removing oxides and foreign substances formed on the surface through mechanical processing and polishing.

[0063] The titanium plate used as the above drum skin base material (110) is used to maintain corrosion resistance against the electrolyte and to facilitate peeling of the electrolytic copper plate, and has a thickness of 4 to 10 mm.

[0064] Meanwhile, the thickness of the drum skin base material (110) is limited to 4 to 10 mm, but the thickness can be arbitrarily selected and used depending on the size of the cathode drum.

[0065] As shown in Fig. 5, the drum skin base material (110) is formed into a cylindrical shape to have a circular structure.

[0066] Here, the shape of the above molding process may ideally be manufactured in the shape of a sine curve to generate a uniform current density, but may be manufactured in the shape of a semicircle or a quarter circle for convenience of processing.

[0067] Meanwhile, when the drum skin base material (110) is formed into a cylindrical shape, a welding part (A) is created to connect one side and the other side.

[0068] As shown in Fig. 6, a welding part (A) for connecting one side and the other side of the drum skin base material (110) is welded with a welding bead (120) to form a cylindrical drum.

[0069] Here, the welding bead (120) for connecting the above welding part (A) is performed using a composite process of GTAW and LBW using titanium as a material.

[0070] In addition, unlike conventional TIG welding or melting welding such as plasma, in the embodiment of the present invention, the welding can be performed by performing friction stir welding (FSW). The friction stir welding (FSW) is a method of performing welding by inserting a probe of a rotating tool into the joint of the materials to be welded, and then rotating the tool along the butt surface of the joint, i.e., the welding line, thereby generating frictional heat by friction between the materials to be welded and the tool, and heating the joint to a temperature sufficient to soften and lower the deformation resistance of the materials to be welded from the frictional heat.

[0071] When the tool is rotated to heat the joint, the material softens around the pin of the tool, creating a plastic zone. When mechanical force is applied to move the tool along the welding line, the heated area is extruded from the front to the back of the tool, forming a solid joint through a combination of frictional heat and mechanical processing.

[0072] When the rotation speed of the above tool is the same, the moving speed is changed so that the recrystallized crystal grains do not become coarser due to excessive increase in process temperature, thereby allowing the crystal grains to become finer due to plastic processing of FSW.

[0073] In the FSW of the above titanium and titanium alloys, the tool rotation speed (rpm) and moving speed (mm / min) are key process conditions. This is because the tool rotation speed and moving speed have a significant impact on the process temperature. The results of investigating the change in the maximum process temperature according to the tool moving speed in the FSW of CP Ti showed that the maximum process temperature decreased as the tool moving speed increased, showing a temperature change of 498℃ from a maximum of 843℃.

[0074] As a result, CP Ti does not exhibit any phase transformation and therefore does not exhibit any strengthening other than grain refinement.

[0075] The hardness of the above FSW weld is higher than that of the GTAW weld. This is because the welding temperature of GTAW, which is one of the fusion welding methods, is high, causing grain coarsening, and the cooling speed of FSW is significantly faster than that of GTAW, forming hard needle-shaped a'martensite. In addition, due to the influence of the melting temperature, the HAZ area of ​​GTAW is wider than that of FSW.

[0076] The weld formed through friction stir welding can have a fine, spheroidized crystal structure due to static recrystallization without melting.

[0077] Depending on the thickness of the material to be welded, i.e., the titanium plate, the specifications of the tool used in the friction stir welding can be appropriately selected.

[0078] As an example, a tool having a shoulder diameter of 18 to 30 mm and a pin diameter of 5 to 15 mm can be used for the friction stir welding, and at this time, the rotation speed of the tool can be set to 130 to 300 rpm and the welding speed can be set to 0.5 to 4 mm / sec.

[0079] In this way, the present invention is significant in manufacturing a titanium ring for an electrodeposition drum through solid-state welding rather than conventional melt welding, thereby manufacturing a cylindrical cathode drum having a welded portion having a structure similar to that of the base material.

[0080] Meanwhile, the titanium and titanium alloys mentioned above, like steel, are among the materials that undergo isotropic transformation depending on temperature and alloying element addition. When performing FSW, if the heat input is not controlled, it is difficult to obtain a sound weld due to isotropic transformation during the process, so it is performed within a range where phase transformation does not occur. The grain structure of the weld is composed of very fine equiaxed grains with a size of about 10㎛ in the center.

[0081] Here, the welding bead (120) is formed in a shape that protrudes more than the upper surface of the drum skin base material (110) adjacent to the welding portion (A) while embedding the welding portion.

[0082] Meanwhile, when welding the above-mentioned welded portion (A), the typical welding method results in a rapid thermal cycle of melting, solidification, and cooling in a short period of time, resulting in defects such as maximization of the structure, organization, and porosity, which result in inferior wear and heat resistance compared to the base material. However, friction stir welding, a solid-state welding technology, can overcome the problems of fusion welding because melting does not occur in the material during the welding process.

[0083] The above friction stir welding process performs welding by utilizing the frictional energy of the shoulder and the plastic flow of the pin by moving the inserted welding tool along the welding line.

[0084] Therefore, in friction stir welding, tool selection is crucial, as it determines the frictional energy, heat input, and plastic flow of the shoulder. Furthermore, adjusting the rotational speed of the welding tool changes the grain size of the weld, so selecting the appropriate tool type can produce finer grains. Differentiating the diameters and rotational speeds of the welding tool and pin can reduce the defect rate in friction stir welding.

[0085] In this way, friction stir welding joins dissimilar metals in contact with each other by friction of the tool, so the joining progresses due to plastic flow within the material caused by frictional heat, and thus the joining is performed below the isotopic transformation point, which can suppress high-temperature oxidation and intrusion of active gases, and dynamic recrystallization occurs within the weld, which can improve mechanical properties due to fine grain size.

[0086] As shown in Fig. 7, the welding bead (120) formed in the welding portion (A) is selectively removed from the surface of the drum skin base material (110) by a predetermined thickness.

[0087] At this time, as the above welding bead (120) is selectively removed, a portion of both sides of the drum skin base material (110) among the above welding portion (A) is exposed.

[0088] As shown in Fig. 8, a friction stir bonding clad layer (130) made of the same material as the drum skin base material (110) is formed in the area where the welding bead (120) has been removed using a friction stir bonding method.

[0089] Here, the formation of the friction stir bonding clad layer (130) by the friction stir bonding method has the advantage of refining crystal grains, and this characteristic is applied to surface modification.

[0090] In other words, the friction stir welding method applies pressure to the base material by rotating a rod-shaped tool, and causes a stirring action by moving the base material. At this time, the rotation of the tool and the relative movement with the base material generate frictional heat and plastic flow in the base material, thereby eliminating the bonding of the surface layer and simultaneously refining the structure, and improving hardness by uniformly dispersing the second phase particles in the microstructure.

[0091] The surface layer of the friction stir bonding clad layer (130) has refined crystal grains and uniformly distributed eutectic elements, and the surface layer has the same hardness as the base material by suppressing softening due to the refinement of the structure and uniform distribution of eutectic elements, which are hard particles.

[0092] Meanwhile, the tool may be used to form a friction stir bonding clad layer (130) having a depth of about 2 to 4 mm by using a tool having a flat shape.

[0093] As shown in Fig. 9, surface treatment and surface modification are performed on the portion where the friction stir bonding clad layer (130) is formed using the friction welding method.

[0094] Here, the friction welding method is a method of joining by softening the material through frictional heat generated between the joining members and applying pressure, and during this process, a plastic change occurs in the material. At this time, the friction welding method is characterized by rapid joining in a solid state.

[0095] In this way, through the friction welding method, the friction stir welding clad layer (130) is softened by frictional heat and pressure is applied between the friction stir welding clad layer (130) and the drum skin base material (110) on both sides to form the friction stir welding layer (140).

[0096] As shown in Fig. 10, a material softened by the friction-stir welding principle is grown on the surface of the bonded friction-stir welding clad layer (130) to form a friction-stir welding layer (150).

[0097] Here, the friction-stirring principle is a method of directly growing a material softened by frictional heat on the surface of a plate, and forms a stable friction-stirring growing layer (150) by plastically compressing the base material with the frictional heat generated at the interface between the growing material of a rotating circular bar and the base material.

[0098] As shown in Fig. 11, the entire surface including the friction stir layer (150) is surface modified using a friction stir process to form a friction stir modified layer (160).

[0099] Here, since the friction stir process is a technology that applies the friction stir welding method, its principle is similar to the friction stir welding method. That is, taking the surface modification of a plate material using the friction stir process as an example, first, the workpiece is fixed, and then the pin part of the friction stir tool that is rotating at high speed is inserted into the part of the workpiece to be modified, and then the tool is moved in an arbitrary direction along the surface of the workpiece.

[0100] At this time, the temperature of the workpiece increases due to the frictional heat generated by the friction between the pin portion and the shoulder portion of the tool and the workpiece, thereby softening the machined portion, and at the same time, the softened workpiece is mechanically stirred by the pin inserted into the workpiece and rotating at high speed, thereby causing rigid plastic deformation. As a result, dynamic recrystallization occurs inside the workpiece, thereby refining the crystal grains and forming a friction stir modified layer (160), and the thickness of the friction stir modified layer (160) can be controlled by adjusting the length of the pin, etc.

[0101] Next, ultrasonic nano-modification surface treatment is performed on the entire surface including the friction stir modification layer (160) to remove frictional residual stress generated during the friction stir process.

[0102] Here, the CO2 cleaning principle is utilized together with the ultrasonic nano-modification surface treatment. The CO2 cleaning is a cleaning technology that removes only unwanted substances without damaging the surface of the product by spraying dry ice particles together with a carrier gas. This substance contracts instantly due to the cold nature of dry ice (-78.5℃), making it easy to peel or fall off the product, and removes foreign substances through physical impact.

[0103] In addition, since the dry ice sublimates into the air after being sprayed, no additional contaminants are generated, and the CO2 scrubber removes foreign substances by controlling the spraying speed of the carrier gas, the amount of CO2, and the distance.

[0104] Meanwhile, the above cleaning method is divided into a method of directly spraying dry ice pellets and a method of converting liquid carbon dioxide into a solid and spraying it.

[0105] And, surface treatment (surface modification) is performed on the entire surface including the friction stir modification layer (160) through a laser beam and plasma process.

[0106] Here, the surface treatment using the laser beam and plasma is performed by injecting gases such as Ar, H2, O2, etc., singly or in combination, depending on the surface material, into a low vacuum chamber, and applying electric energy of an electric field between two electrodes, so that electrons are emitted from the cathode to the anode, and these electrons are accelerated by the electric field, and by the collision of the accelerated electrons, the injected gas is activated into a plasma state in which ions or highly reactive radicals are generated as the outermost electrons of molecules and atoms leave their orbits.

[0107] That is, when electrons with sufficient energy (tens to hundreds of eV) collide with air molecules, the air molecules are ionized and plasma is formed.

[0108] These electrons ultimately collide with the dielectric (product) between the two discharge electrodes, charging the dielectric surface. If the energy of the colliding electrons is sufficiently high (tens of eV or more), they break the bonds of surface molecules and activate them.

[0109] Because these activated surface molecules have unstable molecular structures, they exhibit a strong tendency to bond with other substances (chemical activity). Radicals within the plasma are highly reactive, reacting rapidly with each other and with the activated molecular surfaces.

[0110] The combination of the above air radicals (plasma) and the active molecules on the product surface changes the molecular structure of the surface, and the changed surface molecular structure is more unstable than the molecular structure before the change, and thus has a stronger tendency to combine with other substances.

[0111] In addition, this process activates the product surface, changes the surface molecular structure, and lowers the surface tension of the object. This surface tension can be controlled by adjusting the discharge voltage and discharge amount (discharge cycle, discharge time).

[0112] In addition, by discharging using a special gas other than air in the discharge space, a large amount of special types of radicals are formed and activated, and this surface modification method is also called plasma surface modification to distinguish it from surface modification under simple air radicals.

[0113] The above plasma cleaning process is performed through chemical reactions with radical oxygen, hydrogen, fluorine, or chlorine species, or through energetic ion sputtering by heavy ions such as argon ions. The plasma cleaner equipment is a device that chemically generates reactive radicals and energetic ions through a plasma discharge process. The plasma is generated by RF, microwave, DC glow discharge, etc.

[0114] The ions or radicals of the gas generated in this plasma state collide with the surface of the material to be treated, thereby inducing physical and chemical changes on the surface, such as removal of a fine oil film and formation of fine roughness, thereby improving various types of adhesive adhesion, preventing defects in plastic injection painting, and increasing the adhesion of various types of electrodeposition plating.

[0115] In general, when discharging plasma, it is easier to generate it at a pressure lower than atmospheric pressure, about 1 mTorr to 100 Torr, than at atmospheric pressure, about 760 Torr. For this reason, most plasmas are discharged at pressures lower than atmospheric pressure.

[0116] However, generating plasma at such low pressures requires several constraints, such as the need to manufacture a vacuum vessel and install a vacuum pump to maintain the vacuum. For this reason, much research is being conducted on methods to generate plasma at atmospheric pressure rather than in a vacuum.

[0117] In addition, atmospheric pressure plasma discharge has recently been developed significantly and is increasingly being applied to the surface treatment of fabrics and metal materials.

[0118] The above plasma is classified into atmospheric pressure plasma and low pressure plasma according to the pressure at which it is generated, and on the other hand, it can be divided into thermal plasma discharge and non-thermal plasma discharge according to the method of generating the plasma.

[0119] The above thermal plasma discharge is a method of ionizing a gas by heating it using Joule heating, etc., and the non-thermal plasma discharge is a method of ionizing a gas by heating electrons primarily while minimizing heating of the gas.

[0120] Meanwhile, atmospheric pressure plasma technology has made plasma processing, which was commercialized in a vacuum, possible even under atmospheric pressure. As a result, the field of application is organic matter cleaning using atmospheric pressure plasma, and expansion of the oxide film etching process is in progress.

[0121] These plasmas are generated by applying electrical energy in a vacuum, and are widely applied to ultra-fine processes such as CVD (chemical vapor deposition) and dry etcher in the semiconductor and FPD (flat panel display) industries.

[0122] In contrast, atmospheric pressure plasma is a technology that generates plasma at atmospheric pressure.

[0123] Examples of the above atmospheric pressure plasma types include corona discharge and DBD (dielectric barrier discharge).

[0124] The above corona discharge is a phenomenon in which partial discharge occurs stably due to an unequal electric field when voltage is applied to the edge of a needle electrode, thin wire conductor, or sharp protruding part.

[0125] In the case of the above dielectric barrier discharge, when the surfaces of one or both electrodes are covered with an insulator (dielectric) such as ceramic and an AC voltage is applied, charges are accumulated in the dielectric, and a uniform discharge can be obtained by using this.

[0126] This technology improves the adhesion of the next process, electrodeposition plating, by inducing physical and chemical changes such as the ions and radicals generated in this way being accelerated by continuous collisions and electrical attraction, colliding with the surface of the material, destroying molecular bonds within a few ㎛, shaving off a certain thickness inside the hole, creating fine surface irregularities, and forming functional groups of gas components.

[0127] The above atmospheric pressure plasma surface treatment device is not suitable for mass chemical engineering industrial production because the volume of plasma generated around the electrode in the case of corona discharge is not large. However, it is easy to generate ion wind in the air through corona discharge, so it can be used as a dust collector for factory chimneys by charging particles such as dust.

[0128] In the case of dielectric barrier discharge, it is currently the basic electrode form of most atmospheric pressure plasma developers, and it is also basically applied to devices such as ozone generators, air purifiers, PDP (plasma display panels), and UV lamps.

[0129] The surface cleaning principle of the above atmospheric pressure plasma is that when an alternating electric field is applied between opposing electrodes, electrons in the reaction gas are accelerated to high energy by the electric field, and electrons accelerated to a certain level or higher of energy collide with oxygen molecules to create oxygen ions (O2+) or are separated into oxygen atomic ions (2O+).

[0130] Because the ionic state is highly unstable, it combines with surrounding electrons to form oxygen radicals (O*) or combines with other oxygen ions to create ozone (O3). Ozone then collides with electrons to decompose into oxygen molecules and oxygen radicals. The oxygen radicals thus generated are emitted onto the subject to be treated to remove organic matter.

[0131] The biggest feature of the above atmospheric pressure plasma surface treatment is that the energy of the surface of the cleaning object can be controlled as desired at atmospheric pressure rather than in a vacuum.

[0132] After the above atmospheric pressure plasma treatment, it can be seen that the glass surface becomes hydrophilic and wettability increases, and the same effect can be seen in the organic film.

[0133] As above, by using atmospheric pressure plasma, the surface energy can be adjusted to suit the desired process conditions and provided in a state suitable for subsequent processes.

[0134] The principle of plasma cleaning and polishing of the cathode drum top skin manufactured as described above is to inject gases such as Ar, H₂, and O₂, singly or in mixtures depending on the surface material, into a low vacuum chamber, while applying high voltage to both electrodes at a certain interval.

[0135] Then, a discharge is formed in the space between the electrodes, and the injected gas is ionized by collisions of accelerated electrons, causing the outermost electrons of molecules and atoms to leave their orbits, and is activated into a plasma state in which ions or highly reactive radicals are generated.

[0136] Radicals that reach the drum skin surface react directly with skin atoms and become volatile gases that gradually escape from the surface, causing the drum skin surface to gradually wear away, resulting in etching.

[0137] At the same time, by accelerating ions in the plasma and irradiating them onto the skin surface, the etching reaction of the surface where the ions hit is promoted, enabling directional etching.

[0138] This method is called reactive ion etching (RIE). When ions are accelerated to high energies of several hundred eV or more and collide with a solid material, sputtering occurs, causing the atoms that make up the material to be ejected.

[0139] In this plasma state, gas ions or radicals are accelerated by continuous collisions and electrical attraction, collide with the surface of the material, and destroy molecular bonds within a few micrometers.

[0140] And by cutting off a certain thickness of the drum TOP SKIN surface or colliding with the surface of the material to be treated, the surface of the material is cleaned, and the micro-macro size is controlled by removing micro-oil films, micro-foreign substances, removing nano-scale surface impurities, changing the surface roughness, forming micro-roughness, and forming polar functional groups.

[0141] And, by inducing physical and chemical changes in the porous bulk surface properties, the surface is modified, which has a remarkable effect in improving the uniform electrodeposition of various thin film ions.

[0142] Generally, the bulk properties of the cathode drum skin surface, and particularly mechanical properties that are suitable for electrodeposition suitability, are required. For this reason, surface treatment technologies that can modify the surface properties while maintaining the bulk material properties of the cathode drum skin are being applied.

[0143] The application of plasma-based surface treatment technology to electrodeposited cathode skin materials has the advantages of being reliable, reproducible, economical, and capable of simultaneously performing surface patterning.

[0144] In addition, in the cleaning principle using a laser beam, the laser has the advantages of low damage to the matrix material, high cleaning accuracy, zero emission, and no pollution.

[0145] In the 1960s, renowned physicist Schawlow first proposed laser cleaning. The scope of laser cleaning for removing contamination is extremely broad, ranging from thick rust layers to fine particles on the surface of objects.

[0146] Among these, shortwave ultraviolet output lasers have made great strides in energy output, wavelength range, laser quality and energy conversion efficiency with the development of advanced lasers ranging from lightweight and compact fiber lasers, continuous output lasers to nanosecond, even picosecond and femtosecond short pulse lasers, and visible light output to long-wave infrared.

[0147] Pulsed laser cleaning processes depend on the properties of the light pulses generated by the laser and are based on photophysical reactions resulting from the interaction between the high-intensity beam, the short-pulse laser, and the contaminated layer.

[0148] Meanwhile, the physical principles of a laser beam are as follows.

[0149] a) The laser beam is absorbed by the contaminated layer of the surface to be treated.

[0150] b) Absorption of high energy creates a shock wave by forming a rapidly expanding plasma (highly ionized unstable gas).

[0151] c) Shock waves fragment and remove contaminants.

[0152] d) Absorbs the energy of the laser beam to instantly heat the target material and evaporate or burn it to remove it.

[0153] e) The optical pulse width must be sufficiently short to avoid heat build-up that could damage the treated surface.

[0154] f) When there is an oxide on the metal surface, plasma is generated on the metal surface.

[0155] Compared with conventional cleaning methods such as general mechanical friction cleaning, chemical corrosion cleaning, liquid-solid strong impact cleaning and high-frequency ultrasonic cleaning, laser cleaning has six distinct advantages.

[0156] The above laser cleaning is a kind of "green" cleaning method that does not require chemicals or cleaning solutions. Traditional abrasive cleaning methods often involve contact cleaning, which applies mechanical force to the surface of the object to be cleaned, damaging the surface of the drum skin or causing the cleaning medium to adhere to the surface of the skin, making it impossible to remove and causing secondary contamination.

[0157] However, lasers are non-contact devices that remove contaminants, oxide layers, and functional layers in just seconds. With high pulse peak power, the laser vaporizes a very thin layer of drum top skin without affecting the surface.

[0158] Because it removes the target instantaneously, it does not affect the surface of the parent material, and the amount removed can be controlled very precisely by manipulating the wavelength, pulse length, and scan speed of the laser.

[0159] The non-abrasive, non-contact and non-thermal effects of the above laser cleaning can easily solve these problems as it does not damage the drum skin surface.

[0160] Simultaneously with laser radiation, an inert gas is used to spray the workpiece surface. As contaminants are removed from the surface, they are blown away by the gas, preventing contamination and oxidation of the clean surface.

[0161] By effectively applying surface treatment to titanium using ultra-fine femtosecond laser technology, drum TOP SKIN has a hydrophilic surface. This allows for a high degree of electrolytic deposition and stable, uniform thickness electroplating, resulting in improved film quality.

[0162] The pulsed Nd:YAG laser cleaning process relies on the properties of the light pulses generated by the laser, based on the photophysical reactions resulting from the interaction between the high intensity beam, the short pulse laser, and the contaminant layer.

[0163] The cleaning principle of the above laser beam can be summarized as follows.

[0164] That is, plasma occurs only when the energy density exceeds a threshold that depends on the contaminant or oxide layer being removed. This threshold effect is crucial for the effective cleaning of the base material.

[0165] Each laser pulse removes a contaminant layer of a defined thickness.

[0166] If the above contamination layer is thick, multiple pulses are required for cleaning. The number of pulses required to clean a surface depends on the degree of surface contamination.

[0167] The structure and three reactions of the above laser cleaner are as follows.

[0168] These include sublimation, thermal expansion, and laser pulse vibration. The sublimation process differs between the base material and the contaminant due to differences in chemical composition, resulting in different laser absorption rates. The base substrate reflects more than 95% of the laser light without damage, while the contaminant absorbs most of the laser energy and reaches its sublimation temperature.

[0169] The above thermal expansion causes the contaminant particles to absorb thermal energy and rapidly expand to the point of explosion. The impact of the explosion overcomes the adhesive forces (attraction between different materials), detaching the contaminant particles from the metal surface. Because the laser irradiation time is extremely short, it can generate a large acceleration of explosive impact force instantaneously, providing sufficient acceleration of the fine particles in the bonding of the base material.

[0170] And because the pulse width of the laser beam is relatively narrow, the repetitive motion of the pulses creates ultrasonic vibrations to clean the workpiece, and the shock waves shatter contaminant particles.

[0171] The above laser cleaning is a process of removing contaminants such as rust, oil, and oxides from a surface using laser technology. This is done through laser cutting, which can selectively remove contaminants with little effect on the surface of the target.

[0172] Powerful, very short, and fast-moving laser pulses generate micro-plasma disruptions, shock waves, and thermal pressures that sublimate and expel contaminants.

[0173] Metal surfaces are ideal for laser cleaning applications, as the optimized beam settings are precisely adjusted to avoid reacting with the metal surface, so only the coatings, residues or oxides being removed are affected.

[0174] The purpose of the above laser beam surface modification is to create a drum top skin structure with a hydrophilic surface by forming fine crystal grains through a rapid cooling effect, generating unstable or amorphous phases, and forming a homogeneous microstructure without segregation.

[0175] The above laser cleaning is a so-called laser cleaning technology that uses a high-energy laser beam to irradiate the surface of a workpiece to immediately vaporize or peel off dust, rust spots or coatings on the surface, and effectively remove surface attachments or surface coatings.

[0176] The laser has high directivity, monochromaticity, high coherence and high brightness, and the energy can be concentrated into a small spatial and temporal range through focusing and Q-switching of the lens.

[0177] Meanwhile, the following laser characteristics are mainly used in the laser cleaning process.

[0178] First, lasers can achieve high energy concentration in time and space, and the focused laser beam can generate high temperatures of thousands or tens of thousands of degrees near the focus, which can instantly vaporize, vaporize, or decompose dust.

[0179] Furthermore, because the laser beam has a small divergence angle and good directionality, it can be collected into light spots of various diameters through a light collection system. By controlling laser beam spots of different diameters under the same laser energy conditions, the laser energy density can be adjusted, and contaminants can expand due to heat. If the contaminant's expansion force is greater than the dust's adhesion to the skin surface, the contaminant is separated from the skin surface.

[0180] Additionally, the laser beam generates ultrasound waves on solid surfaces, which can cause mechanical resonance, causing foreign matter to break and fall off.

[0181] The above laser cleaning technology utilizes the aforementioned laser characteristics to achieve its cleaning objectives. Depending on the skin surface to be cleaned and the optical properties of the dust to be removed, laser cleaning mechanisms can be divided into two categories.

[0182] One approach is to significantly increase the difference in absorption coefficients between the cleaning drum skin (also known as the substrate) and surface adhering matter (dust) for laser energy of a specific wavelength. Most of the laser energy irradiated onto the surface is absorbed by the surface adhering matter, causing it to heat, vaporize, or expand instantaneously. This, in turn, is driven by the resulting airflow to separate it from the target surface, achieving the cleaning purpose.

[0183] However, due to the extremely low absorption energy of the laser at this wavelength, the substrate is not damaged, and other types of cleaning methods are suitable for cleaning substrates and surface attachments with minimal differences in laser energy absorption coefficient. These methods typically use a high-power, high-repetition-rate pulsed laser to impact the surface to be cleaned, converting a portion of the beam into sound waves.

[0184] After the sound wave hits the lower hard surface, the return section interferes with the incident sound wave generated by the laser to generate high energy waves that detonate the foreign matter in a small area, compressing the foreign matter oxide film into powder and then removing it.

[0185] These laser cleaning features include grinding, non-contact, heatless and cleaning capabilities suitable for a wide range of materials.

[0186] This type of laser scale remover works by instantly evaporating rust when exposed to high temperatures. After plasma separation, the underlying metal's high reflectivity to light leaves the rust-removed area undamaged even when exposed to the laser.

[0187] The heat treatment of the drum top skin surface using the above laser beam is a process of heating the surface and changing the microstructure of the surface area with heat generated by the reaction between the LASER BEAM and the drum top skin surface without melting the surface.

[0188] Not only does it create an ultra-fine structure and increase the solubility of solute atoms through the rapid cooling effect of the self-conducting heat conduction on the cathode drum surface, but it also creates a metastable phase and phase transformation through rapid heating and cooling, and there is no deformation due to local heating.

[0189] Therefore, the above laser cleaning technology involves using a high-energy laser beam to irradiate the surface of a workpiece, causing surface dust, rust spots, or coatings to instantly evaporate or peel off, effectively removing surface adhesion or surface coatings from the clean object at high speed, and thus achieving a cleaning process. It is a novel technology based on the interaction effect between the laser and the material.

[0190] The laser is characterized by high directivity, monochromaticity, high coherence, and high brightness. Through lens focusing and Q-switching, the energy can be concentrated within a small spatial and temporal range. The following characteristics of the laser are primarily utilized in laser cleaning processes.

[0191] The laser can achieve high concentrations of energy in time and space, and the focused laser beam can generate high temperatures of thousands or tens of thousands of degrees near the focus, which can cause dust to evaporate, vaporize, or instantly disintegrate.

[0192] In addition, since the laser beam has a small divergence angle and good directivity, it can be focused into spots of different diameters through a focusing system, and laser spots of different diameters can be controlled under the condition of the same laser energy.

[0193] The energy density of the above laser can be adjusted so that the dust expands when heated, and if the expansion force of the dust is greater than the adhesion force of the dust to the substrate, the dust is separated from the surface of the object.

[0194] The operating principles of the above laser cleaning can include both physical and chemical processes. In most cases, physical processes dominate.

[0195] When a high-energy laser beam is irradiated onto a material surface, the surface absorbs the laser energy from the surface to the underlying substrate. Simultaneously, the surface temperature rapidly increases, reaching its vaporization point, causing contaminants to vaporize from the material surface. This selective vaporization typically occurs when the laser beam absorption rate of contaminants on the surface is significantly higher than that of contaminants on the substrate.

[0196] Based on this principle, contaminants on the drum skin surface are rapidly vaporized due to their high laser absorption rate. When cleaning contaminants, the skin surface has very low absorption rate, most of the laser energy is scattered by contaminants on the skin surface, and the temperature change on the skin surface is very small. Therefore, the skin surface is protected from damage while contaminants are removed.

[0197] Fig. 12 is a perspective view showing a cathode drum of a top skin that has been tempered with an equal electric field for thin film electrolytic deposition according to a second embodiment of the present invention.

[0198] The cathode drum (200) of the top skin annealed with a uniform electric field for thin film electrolytic deposition according to the second embodiment of the present invention has a ring-shaped structure having a "V"-shaped welded portion for connecting one side and the other side, as shown in FIG. 12, and comprises a plate-shaped inner cylindrical metal plate (210) and an outer cylindrical drum skin base material (220) that are sequentially laminated, and a low-melting insert (230) interposed between the metal plate (210) and the drum skin base material (220), a weld bead (240) formed lower than the surface of the drum skin base material (220) inside the welded portion, a friction stir bonding clad layer (250) formed at the surface height of the drum skin base material (220) on the weld bead (240) of the welded portion, and a friction stir bonding layer (250) formed at the welded portion between the friction stir bonding clad layer (250) and the drum skin base material (220). It comprises a pressure-welding layer (260), a friction-stir-welding layer (270) formed on the drum skin base material adjacent to the friction-stir-welding layer (260), and a friction-stir-modified layer (280) formed on the entire top skin surface with the same metal crystal structure as the "V"-shaped welded portion (A) and the drum skin base material (210) including the same, and an equal-field-tempered layer.

[0199] Here, the drum skin base material (220) and the welding bead (240) are made of the same material.

[0200] In addition, although not clearly shown in the drawing, a CO₂ cleaning, laser beam and plasma surface treatment layer are formed along with an ultrasonic nano-modification surface treatment layer on the surface of the friction stir modification layer (280).

[0201] Figures 13 to 20 are cross-sectional views schematically showing a method for manufacturing a cathode drum of a top skin that is tempered with an equal electric field for thin film electrolytic deposition according to a second embodiment of the present invention.

[0202] The method for manufacturing a cathode drum of a top skin tempered with an equal electric field for thin film electrolytic deposition according to the second embodiment of the present invention is as shown in Fig. 13, in which a plate-shaped inner cylindrical metal plate (210) and an outer cylindrical drum skin base material (230) are prepared, respectively.

[0203] Here, the metal plate (210) is a copper or stainless steel plate, and the drum skin base material (230) is made of any one of titanium, zirconium, Hastelloy, Inconel, duplex, Monel, and sanitary materials as a corrosion-resistant material in an electrolytic deposition solution.

[0204] Next, a low-melting-point insert of a process alloy component is inserted between the metal plate (210) and the drum skin base material (230), and the metal plate (210) and the drum skin base material (230) are joined by applying a transition liquid phase diffusion bonding technique.

[0205] Meanwhile, in the embodiment of the present invention, in consideration of corrosion resistance and hydrogen embrittlement characteristics, etc., as the drum skin base material (230), titanium Grade 1 corresponding to pure titanium or Grade 1 modified by adding additives such as ruthenium (Ru) and copper (Cu) to Grade 1 to improve corrosion resistance may be used, but the present invention is not limited thereto.

[0206] As an example, the drum skin base material (230) may include, in weight %, iron (Fe): 0.06% or less, oxygen (O): 0.1% or less, hydrogen (H): 150 ppm or less, the remainder titanium (Ti), and other unavoidable impurities. More advantageously, it may include iron (Fe): 0.04% or less, oxygen (O): 0.08% or less, hydrogen (H): 60 ppm or less, the remainder titanium (Ti), and other unavoidable impurities.

[0207] In addition, the drum skin base material (230) has a grain size of 4 to 10, and more advantageously, it can have a grain size of 5 to 9. Since the size of the currently commercialized cathode drum is approximately 2 to 4 m in diameter, 1 to 2 m in width, and 7 to 12 mm in thickness, the drum skin base material (230) is prepared similarly. Specifically, a titanium plate having a thickness of 7 to 15 mm, a width of 1 to 2 m, and a length of 6 to 12 m can be used.

[0208] The above drum skin base material (230) is maintained in a smooth surface state by removing oxides and foreign substances formed on the surface through mechanical processing and polishing.

[0209] The titanium plate used as the above drum skin base material (230) is used to maintain corrosion resistance against the electrolyte and to facilitate peeling of the electrolytic copper plate, and has a thickness of 4 to 10 mm.

[0210] Meanwhile, the thickness of the drum skin base material (230) is limited to 4 to 10 mm, but the thickness can be arbitrarily selected and used depending on the size of the cathode drum.

[0211] The above insert (230) forms a process alloy at the bonding interface between the metal plate (210) and the drum skin base material (220), thereby actively diffusing between the component atoms. Accordingly, it is isothermally solidified without defects, and the metallurgical chemical components are homogeneously integrated, thereby preventing the formation of weak intermetallic compounds, voids, lattice defects, cracks due to differences in thermal expansion coefficients, and thermal stress bonds.

[0212] In addition, the occurrence of bonding defects in the dissimilar metal laminated cladding due to changes in physical properties and metal chemical composition at the contact interface and reduction in current conduction efficiency is prevented.

[0213] In addition, the low melting point insert (230) of the above-mentioned process alloy component prevents the occurrence of an unequal electric field due to an unequal change in electrochemical properties, so that the bonding interface between the metal plate (210) and the drum skin base material (220) becomes integrated with the base metal in terms of metallurgical chemical composition and electrochemical and physical properties.

[0214] In addition, the low-melting point insert (230) of the above-mentioned process alloy component functions as a filler metal that forms a transition diffusion liquid-phase bond. This function and effect increases the current conduction efficiency flowing from the metal plate (210) to the drum skin base material (220) and ensures that the current density is evenly distributed.

[0215] Here, the insert (230) forms a process alloy between a low-conductivity titanium material and a high-conductivity copper or stainless steel material. This results in mutual diffusion and homogenization and equalization of the constituent elements, thereby lowering the interfacial contact resistance and enhancing adhesion at the bonding interface. Ultimately, the bonding interface unifies the metallurgical and chemical composition.

[0216] Therefore, the insert (230) of the process alloy component is inserted between the metal plate (210) and the drum skin base material (220) to form a process alloy and enable transition diffusion bonding.

[0217] As shown in Fig. 14, the metal plate (210) and the drum skin base material (220) joined through the insert (230) are formed into a cylindrical shape to have a ring-shaped structure.

[0218] Here, the shape of the above molding process may ideally be manufactured in the shape of a sine curve to generate a uniform current density, but may be manufactured in the shape of a semicircle or a quarter circle for convenience of processing.

[0219] Meanwhile, when the metal plate (210) and the drum skin base material (220) are formed into a cylindrical shape, a welding part (A) is created to connect one side and the other side.

[0220] As shown in Fig. 15, friction stir welding is performed on the welding portion (A) to form a welding bead (240) connecting one side and the other side of the metal plate (210) and the drum skin base material (220).

[0221] Meanwhile, since the friction stir welding is performed in the same manner as the first embodiment of the present invention, a detailed description thereof will be omitted.

[0222] Here, the welding bead (240) is formed in a shape that protrudes more than the upper surface of the drum skin base material (220) adjacent to the welding portion (A) while embedding the welding portion.

[0223] As shown in Fig. 16, the welding bead (240) formed in the welding portion (A) is selectively removed from the surface of the drum skin base material (220) by a predetermined thickness.

[0224] At this time, as the above welding bead (240) is selectively removed, a portion of both sides of the drum skin base material (220) of the above welding portion (A) is exposed.

[0225] As shown in Fig. 17, a friction stir bonding clad layer (250) made of the same material as the drum skin base material (220) is formed in the portion where the welding bead (240) is selectively removed using a friction stir bonding method.

[0226] Here, the formation of the friction stir bonding clad layer (250) by the friction stir bonding method has the advantage of refining crystal grains, and this characteristic is applied to surface modification.

[0227] The surface layer of the friction stir bonding clad layer (250) has refined crystal grains and uniformly distributed eutectic elements, and the surface layer has the same hardness as the base material by suppressing softening due to the refinement of the structure and uniform distribution of eutectic elements, which are hard particles.

[0228] Meanwhile, the tool may be used to form a friction stir bonding clad layer (250) having a depth of about 2 to 4 mm by using a tool having a flat shape.

[0229] As shown in Fig. 18, the friction stir welding clad layer (250) is formed on the welded portion (A) by the friction welding method, and the friction stir welding layer (260) is formed between the friction stir welding clad layer (250) and both sides of the drum skin base material (220) by softening the welded portion (A) with friction heat and applying pressure.

[0230] As shown in Fig. 19, a friction stir bonding layer (270) is formed by forming a softened material using the friction stir bonding principle on the welded portion (A) where the friction stir bonding clad layer (250) is formed.

[0231] As shown in Fig. 20, the entire surface including the friction stir layer (270) is surface modified using a friction stir process to form a friction stir modified layer (280).

[0232] Next, ultrasonic nano surface modification treatment and cleaning are performed on the entire surface of the friction stir modified layer.

[0233] Here, the effect of the above ultrasonic nano-modification surface treatment is to make the crystal grains of the surface nano-level and to achieve a uniform nano-level roughness with high wear resistance. In addition, the presence of twins within the crystals is reduced to 25% or less, thereby stabilizing the structure.

[0234] Here, the ultrasonic nano-modification surface treatment utilizes the CO2 cleaning principle. The CO2 cleaning is a cleaning technology that removes only unwanted substances without damaging the surface of the product by spraying dry ice particles together with a carrier gas. This substance contracts instantly due to the cold nature of dry ice (-78.5℃), making it easy to peel or fall off the product, thereby removing foreign substances through physical impact.

[0235] In addition, since the dry ice sublimates into the air after being sprayed, no additional contaminants are generated, and the CO2 scrubber removes foreign substances by controlling the spraying speed of the carrier gas, the amount of CO2, and the distance.

[0236] And the friction stir modified layer (280) that has undergone the above cleaning is surface treated with a laser beam and plasma.

[0237] While the technical concepts of the present invention have been described above with reference to the accompanying drawings, they are merely illustrative of preferred embodiments of the invention and are not intended to limit the scope of the invention. Furthermore, it is readily apparent that anyone skilled in the art will be able to make various modifications and imitations without departing from the scope of the technical concepts of the present invention.

[0238] The present invention can uniformly form the crystal structure of the base material and weld joint through drum surface modification treatment and final polishing cleaning surface treatment. Therefore, the thin plates of electrolytic copper, nickel, aluminum, etc. have industrial applications, such as as positive and negative electrode conductive materials for secondary batteries used in the electrical and electronic industries.

Claims

1. In a cathode drum formed by inserting an inner cylinder into an outer cylinder, the outer cylinder A drum skin base material having a circular structure with a "V" shaped weld to connect one side and the other side, A welding bead formed lower than the surface of the drum skin base material inside the above welding part, A friction stir welding clad layer formed at the surface height of the drum skin base material on the upper part of the weld bead of the above welded portion, A friction stir welding layer formed at the weld between the friction stir welding clad layer and the drum skin base material, The friction stir welding layer and the friction stir welding layer formed on the drum skin base material adjacent thereto, A cathode drum of a top skin annealed with an equal field for thin film electrolytic deposition, characterized in that it comprises a friction stir modified layer annealed with an equal field formed on the entire top skin surface identical to the metal crystal structure of the drum skin base material including the above-mentioned "V" shaped weld portion.

2. A cathode drum of a top skin tempered with an equal electric field for thin film electrolytic deposition, characterized in that in the first paragraph, the drum skin base material and the welding bead are made of the same material.

3. In the first paragraph, the drum skin base material is a part that becomes the outer skin of the cathode drum, and is characterized in that it is made of one of titanium, zirconium, Hastelloy, Inconel, duplex, Monel, sanitary materials or an alloy thereof as a corrosion-resistant material in the electrolytic deposition solution, and is a cathode drum having a top skin that is annealed with an equal electric field for thin film electrolytic deposition.

4. A cathode drum of a top skin that is tempered with an equal electric field for thin film electrolytic deposition, characterized in that, in the first paragraph, a CO₂ cleaning, laser beam and plasma surface treatment layer is formed together with an ultrasonic nano-modification surface treatment layer on the surface of the friction stir modification layer.

5. A cathode drum having a ring-shaped structure with a "V"-shaped welded portion for connecting one side and the other side, in which a low-melting-point insert material of a process alloy component for transition liquid phase diffusion bonding and a drum skin base material for an outer cylinder are sequentially laminated, and a metal plate for an inner cylinder is provided. A welding bead formed lower than the surface of the drum skin base material inside the above welding part, A friction stir welding clad layer formed at the surface height of the drum skin base material on the upper part of the weld bead of the above welded portion, A friction stir welding layer formed at the weld between the friction stir welding clad layer and the drum skin base material, The friction stir welding layer and the friction stir welding layer formed on the drum skin base material adjacent thereto, A cathode drum of a top skin annealed with an equal field for thin film electrolytic deposition, characterized in that it comprises a friction stir modified layer annealed with an equal field formed on the entire top skin surface identical to the metal crystal structure of the drum skin base material including the above-mentioned "V" shaped weld portion.

6. A cathode drum of a top skin tempered with an equal electric field for thin film electrolytic deposition, characterized in that the welding bead fills the inside of the "V" shaped weld joint in the fifth paragraph.

7. A cathode drum of a top skin that is tempered with an equal electric field for thin film electrolytic deposition, characterized in that, in the fifth paragraph, a CO₂ cleaning, laser beam and plasma surface treatment layer is formed together with an ultrasonic nano-modification surface treatment layer on the surface of the friction stir modification layer.

8. Step for preparing a plate-shaped drum skin base material; A step of forming the above drum skin base material into a cylindrical shape to have a “V” shaped weld; A step of forming a welding bead connecting one side and the other side of the drum skin base material by performing friction stir welding on the above welding part; A step of selectively removing the welding bead inside the above-mentioned welded portion from the surface to a predetermined depth; A step of forming a friction stir welding clad layer by performing friction stir welding on the surface of the above welding bead; A step of softening the welded portion on which the friction stir welding cladding layer is formed by friction welding and applying pressure to form a friction stir welding layer between the friction stir welding cladding layer and both sides of the drum skin base material; A step of forming a friction stir bonding layer by bonding a softened material using the friction stir bonding principle on the welded part where the above-mentioned friction stir bonding cladding layer is formed; A step of forming a friction stir modified layer by surface modification treatment on the entire surface including the above friction stir breeding layer using a friction stir process; A step of performing ultrasonic nano-modification surface treatment and CO2 cleaning on the entire surface of the above friction stir modification layer; A method for manufacturing a cathode drum of a top skin for thin film electrolytic deposition, characterized in that it comprises a step of surface-treating the friction stir modified layer, which has undergone the above cleaning, with a laser beam and plasma.

9. In the 8th paragraph, the drum skin base material is a part that becomes the outer skin of the cathode drum, and is characterized in that it is formed of one of titanium, zirconium, Hastelloy, Inconel, duplex, Monel, sanitary materials or an alloy thereof as a corrosion-resistant material in an electrolytic deposition solution, and a method for manufacturing a cathode drum with a top skin annealed with an equal electric field for thin film electrolytic deposition.

10. A method for manufacturing a cathode drum with a top skin annealed with an equal electric field for thin film electrolytic deposition, characterized in that in paragraph 8, the metal plate is formed of a copper or stainless steel plate, and the drum skin base material is formed of one of titanium, zirconium, Hastelloy, Inconel, duplex, Monel, and sanitary materials or an alloy thereof as a corrosion-resistant material in an electrolytic deposition solution.

11. A method for manufacturing a cathode drum of a top skin with a uniform electric field for thin film electrolytic deposition, characterized in that in the 8th paragraph, the cleaning treatment removes foreign substances by controlling the injection speed of the carrier gas, the amount of CO2, and the distance.

12. A method for manufacturing a rotating cathode drum for manufacturing an ultra-thin film, characterized in that in the 8th paragraph, the ultrasonic nano-modification surface treatment applies compression energy of 20,000 times or more per second to the surface to cause strong plastic deformation and elastic deformation on the surface.

13. A method for manufacturing a cathode drum of a top skin tempered with an equal electric field for thin film electrolytic deposition, characterized in that in paragraph 8, the drum skin base material and the welding bead are made of the same material.

14. Step of preparing a metal plate for the inner cylinder and a drum skin base material for the outer cylinder, respectively; A step of inserting a low-melting-point insert of a process alloy component between the metal plate and the drum skin base material and applying a transition liquid phase diffusion bonding technique to bond the metal plate and the drum skin base material; A step of forming the above-mentioned joined metal plate and drum skin base material into a cylindrical shape to have a “V” shaped weld joint; A step of forming a welding bead connecting one side and the other side of the metal plate and the drum skin base material by performing friction stir welding on the above welding part; A step of selectively removing the welding bead inside the above-mentioned welded portion from the surface to a predetermined depth; A step of forming a friction stir welding clad layer by performing friction stir welding on the surface of the above welding bead; A step of softening the welded portion on which the friction stir welding cladding layer is formed by friction welding and applying pressure to form a friction stir welding layer between the friction stir welding cladding layer and both sides of the drum skin base material; A step of forming a friction stir bonding layer by bonding a softened material using the friction bonding principle on the welded portion where the friction stir bonding cladding layer is formed; A step of forming a friction stir modified layer by surface modification treatment on the entire surface including the above friction stir breeding layer using a friction stir process; A step of performing nano surface modification treatment and CO2 cleaning on the entire surface of the above friction stir modification layer; A method for manufacturing a cathode drum of a top skin for thin film electrolytic deposition, characterized in that it comprises a step of surface-treating the friction stir modified layer, which has undergone the above cleaning, with a laser beam and plasma.

15. A method for manufacturing a cathode drum with a top skin annealed with an equal electric field for thin film electrolytic deposition, characterized in that in the 14th paragraph, the friction stir bonding layer is formed on the upper part of the friction stir bonding cladding layer and on the drum skin base material adjacent thereto, the "V" shaped weld portion and the metal crystal structure of the drum skin base material including the same are identical.

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