BR102022014545A2 - METHOD OF METAL FILM DEPOSITION BY SPRAYING - Google Patents

Abstract

metal film deposition method by sputtering. The present invention patent discloses a method of deposition of a metallic film obtained from austenitic, martensitic or ferritic (fe-cr-ni-mn) stainless steel alloy targets through the cathodic spraying technique, with said film it is preferably used as an interlayer to promote adhesion between a substrate and another coating, such as a paint or a layer of chromium or nickel that can be obtained through electrodeposition, for example. Advantageously, the method of the present invention allows adjusting and improving process variables, such as power density, target sample distance and deposition time in order to promote better adhesion between the substrate and the fe-cr-ni-mn film.

Description

[0001] The present invention patent discloses a method of deposition of a metallic film obtained from targets of austenitic, martensitic or ferritic stainless steel alloys (Fe-Cr-Ni-Mn) through the cathodic spraying technique, whereby said film is preferably used as an interlayer to promote adhesion between a polymeric substrate and another coating, such as a paint or a layer of Chrome or Nickel that can be obtained through electrodeposition, for example.

[0002] Advantageously, the method of the present invention allows adjusting and improving process variables, such as power density, target sample distance and deposition time in order to promote better adhesion between the substrate and the Fe-Cr-Ni film -Mn.

State of the art

[0003] The wide use of polymeric materials in everyday life reflects the increased development of research and technologies in this area. Some factors justify the use of polymers instead of other materials such as metals and/or ceramics. For example, replacing metals with polymers such as ABS (acrylonitrile-butadiene-styrene terpolymer) has the benefit of reducing the mass and energy associated with production and transportation, being favorable from an economic point of view.

[0004] However, in many applications where polymeric materials are used, the range of colors available is limited according to the characteristics of the chosen plastic material. The polymer acrylonitrile butadiene styrene, known as ABS, for example, is normally injected white and in order to change its color, additives are needed in its composition during injection. However, there are limitations in the color spectrum, mainly in relation to metallic colors, given the low affinity of the physicochemical characteristics of polymer chains such as the composition used in paints.

[0005] In short, it is not possible to directly paint ABS and other polymers without previously treating their surface.

[0006] Thus, the search for surface treatments as an alternative to improving physical properties and aesthetic characteristics of polymers has become increasingly greater, since treatments give the polymer more applications aimed at decorative coatings, given that they provide a surface bright and pleasant, and functional coatings, providing good electrical conductivity.

[0007] In several industry sectors, the metallization of polymeric materials is widely used as a surface treatment, since this technique promotes the combination of the properties of both metallic and polymeric materials.

[0008] To meet this demand, some metallization techniques are used, highlighting the chemical processes CVD (chemical vapor deposition) and electroplating for the synthesis of inorganic thin films, which, disadvantageously, produce toxic residues harmful to human health. and the environment, such as hexavalent chromium.

[0009] This type of waste is quite common in chemical metallization industries and is in the process of being banned from use in many countries. In addition to chromium, other harmful elements such as cadmium, zinc, nickel, sulfates and cyanides are also present in metallization and, consequently, require special disposal and treatment of effluents after the electroplating process.

[0010] The electrodeposition or galvanization process is currently the most used in the sanitary materials and automobile sector. Although films obtained by chemical processes present high quality with precise structural controls at the atomic level, this is a technique considered outdated and which also generates too much waste, such as toxic, corrosive and flammable gases, which cause environmental damage and human health. Furthermore, CVD techniques should generally not be used on polymeric substrates with low resistance to thermal degradation, due to deposition occurring at high temperatures.

[0011] Another state-of-the-art surface treatment is PVD (physical vapor deposition), a technique widely used for the deposition of thin metallic films on different types of substrates that overcomes some of the inconveniences caused by chemical processes, since it has the lower processing temperatures are characteristic, this method being suitable for deposition of films on polymeric substrates with low thermal resistance.

[0012] The PVD process takes place inside a vacuum chamber, where the material to be deposited is initially vaporized and ionized forming a plasma. Due to the potential difference, the ions, in pure form or combined with nitrogen and/or carbon atoms, are attracted to the surface of the parts to be coated.

[0013] Among the PVD processes, there is the Sputtering technique, which has been studied since the 19th century, and its characteristic is the acceleration by the electric field of the ion present in the plasma towards the cathode, which is called target. Some phenomena may occur during the process, depending on the energy of the ion and the nature of the target, for example: - The ion is reflected and neutralized in the process; - The ejection of electrons from the target caused by the impact of the ion, called secondary electrons; - Ionic implantation, when the ion penetrates the target; - Rearrangement in the structure of the material caused by the impact of the ion, which may be the change in the position of the atoms, creation of gaps and network defects; - Or the phenomenon of sputtering effectively, with the chain collision of target atoms and ejection of some of them.

[0014] Thus, the formation of a film on the substrate is caused by the condensation of the atoms that were ejected by the target. The morphology of the film formed is influenced firstly by the temperature of the substrate, and secondly by the pressure of the deposition chamber. Deposition parameters, such as voltage, current, electrical power and pressure, directly influence the properties of the film formed.

[0015] The energy of the atoms ejected from the target and reaching the substrate is another important factor in determining the microstructure of the films, since crystalline defects can be created or eliminated, the density of the film can be modified, residual stress levels can be grow or shrink, and thus directly influence properties such as adhesion, reflectivity and conductivity of the film.

[0016] When working with the deposition of metallic films on a polymeric substrate, the energy of the atoms that are deposited must be controlled, being mainly observed by the temperature of the sample, due to the tendency of polymer degradation when this is high. The evaporation of low molar mass volatiles and chemical modification of the substrate, due to the increase in temperature, can directly influence the morphology of the film obtained.

[0017] Another point of attention is the difference between the thermal expansion coefficients between the materials used, which can influence the morphology of the film, considering that if there is heating and/or cooling of the materials during the process, surface tensions may arise when there is a very large difference between the coefficient of thermal expansion of the substrate and the film and can cause defects on its surface, such as cracks with thicknesses of the order of 100 nm, seen in figure 1.

[0018] In table 1 it is possible to observe the difference between the coefficient of thermal expansion of stainless steel, copper and ABS. Table 1 - Thermal expansion coefficient

[0019] The sputtering technique extends into several other processes, which are named according to the origin and orientation of the process. Various energy sources can be used in the process and, depending on the energy configuration, the working pressure of the process chamber varies. Some of these variants are DC sputtering, radiofrequency sputtering, reactive sputtering, magnetron sputtering, among others.

[0020] Magnetron sputtering consists of introducing a magnetic field into the discharge through a set of permanent magnets placed internally to the cathode in order to generate a magnetic field with a strong component parallel to the surface of the substrate. The trajectories of the electrons are defined by the electric field between the cathode and the anode, that is, the electrons are accelerated with high speed towards the anode.

[0021] Currently, treatments that use the magnetron sputtering technique to change surface properties and improve the bond strength between a polymeric substrate material and a metallic film are found in the state of the art, such as For example, patent document KR1020140038771, filed on 09/21/2012, entitled “Method for depositing metallic thin film on a substrate”.

[0022] The aforementioned Korean document KR1020140038771 reveals an improvement in adhesion between a copper film and a polymer due to the waveform characteristics of the electrical voltage signal, however, disadvantageously, the process uses a power density of 10W/cm2 at 10kW/cm2, which requires high energy consumption. Furthermore, the document reveals a coating thickness of 400 nm, which also increases energy consumption and, consequently, the deposition time, as well as the amount of material.

[0023] Another example is patent document CN104694878, filed on 03/04/2015, which discloses a vacuum decoration coating technique for a polymeric material. The film prepared by the technique mainly comprises a Cr base layer by a high-power magnetron spraying process to improve the film-substrate bonding strength, however, the coating comprises a thickness of the Cr primer layer is 0. 5-2 μm, which impairs the adhesion of a subsequent paint layer, as well as increasing production time and, consequently, costs.

[0024] Thus, with the aim of solving the problems existing in the prior art, the present invention reveals the use of a thin layer of Fe-Cr-Ni-Mn on the surface of a polymer that is adherent to the plastic substrate, in in order to expand the possibility of modifying the color spectrum of the polymer surface through applications of paints and/or coatings obtained by electrodeposition without compromising the loss of paint/polymer adhesion.

[0025] It is an objective of the invention to provide a method of deposition of a metallic film with suitable parameters capable of reducing the deposition time compared to the state of the art, at the same time that these parameters promote better adhesion of the film to the substrate.

[0026] The reduction in deposition time reduces the energy expenditure of the process, as well as reducing the thickness of the film formed (approximately 50 nm), which, consequently, requires less raw material, while at the same time promoting an improvement in the adhesion of paints and/or other coatings that give color to the polymer.

[0027] Furthermore, the present invention significantly contributes to an improvement in the corrosion resistance and degradation by ultraviolet or infrared light of the polymer, as the Fe-Cr-Ni-Mn film protects the polymer from solar radiation and/ or artificial.

[0028] Another important aspect of the invention is that it uses an environmentally clean process, since, unlike electroplating, it does not use acids or solvents to obtain improved paint adhesion on the surface of a polymeric substrate.

[0029] Thus, the present invention makes it possible to modify the color of parts, products and/or utensils according to the application and desire of the industry using paints and/or coatings.

Brief description of the figures

[0030] Figure 1 of the prior art illustrates a crack caused due to the difference in the expansion coefficient between the materials.

[0031] Figure 2 of the prior art illustrates the equipment used for deposition of the metallic film using the magnetron sputtering technique.

[0032] Figure 3 illustrates the electron microscopy analysis to measure the thicknesses of the films deposited at five points of each sample A01 to A04.

[0033] Figure 4 illustrates the electron microscopy analysis to measure the thicknesses of the films deposited at five points of each sample A05 to A08.

[0034] Figure 5 illustrates the reflective property after deposition of the film, making it possible to observe the clear reflection of the camera in the photo.

[0035] Figure 6 illustrates the adhesion determination test with grid cutting, for sample A10. A) Test 1, b) Test 2, c) Test 3 and d) Magnification by optical microscopy showing the adhesion between the AISI 304 film and the polymer.

[0036] Figure 7 illustrates the adhesion determination test with grid cutting, for sample A11. A) Test 1, b) Test 2, c) Test 3 and d) Magnification by optical microscopy showing the adhesion between the AISI 304 film and the polymer.

[0037] Figure 8 illustrates the adhesion between the substrate and film/paint, using the X-cut adhesion determination test, with Figure 8a relating to the sample with AISI 304 film between the paint and ABS and Figure 8b without the AISI 304 film between the paint and the ABS.

[0038] Figure 9 illustrates the result achieved with the use of the metallic interlayer proposed by the present invention, with figure 9a referring to before corrosion and figure 9b after corrosion.

Detailed description of the invention

[0039] The present invention patent discloses a method of deposition of a metallic film through the cathodic spraying technique, with said metallic film being preferably used as an interlayer to promote adhesion between a polymeric substrate and another coating, such as such as paint or a layer of Chrome or Nickel.

[0040] The film deposition method uses equipment (E) configured by a cylindrical discharge chamber (1) made of stainless steel with at least two windows (2) for coupling devices and checking the processes. A vacuum system composed of a mechanical pump (3) and a turbomolecular pump (4), which, connected in series, allow a pressure of the order of 1.3 x 10-4 Pa (10-6Torr) to be achieved, in addition to an argon flow controlled by flow meters. The equipment is illustrated in Figure 2.

[0041] Inside the equipment (E), the target, made of stainless steel, with a diameter of 100 mm, is positioned in the upper part, fixed to the magnetron (6) and in the lower part of the chamber, the sample holder (7) is positioned. . The separation distance between the target surface and the samples can be adjusted between 5 and 30 cm.

[0042] Stainless steel is a material well known for having anti-corrosive properties and high heat resistance, and the film obtained from this material maintains these characteristics. Thus, using this material it is possible to obtain homogeneous stainless steel films with a chemical composition very similar to that of the target, but with a smaller grain size in the structure, which delays the formation and growth of corrosive processes, mainly pitting corrosion (the most common in AISI 304), changing the geometry and growth mechanism of the pits.

[0043] During the deposition process, parameters are used that configure different characteristics for the same metallic coating, such as: deposition time; power; voltage; electric current; pressure; gas flow and temperature.

[0044] Thus, the method of deposition of a metal film by sputtering of the present invention comprises the following steps: a) Mounting a polymeric substrate on a substrate support located within a vacuum chamber equipped with a stainless steel target; b) Adjust the separation distance between the surface of the polymeric substrate and the surface of the target from 5 to 30 cm; c) Remove residual gases from the inside of the chamber using a vacuum pump until a pressure of 1.0 to 3.0 x 10-4 Pa is reached d) Introduce an inert gas into the vacuum chamber to maintain constant internal pressure from 0.5 to 10 mTorr; e) Adjust a power supply to a power of 50 to 300 W, in order to obtain a power density of 0.6 W/cm2 to 2.5 W/cm2 on the magnetron sputtering cathode; f) Apply the power determined in step e) for a period between 5 and 35 minutes at room temperature.

[0045] In a preferred embodiment of the invention, the vacuum pump is of the mechanical, turbo molecular or diffuser type and the internal pressure in the vacuum chamber must be constant from 1 to 10 mTorr.

[0046] In a preferred embodiment of the invention, the power density applied to the deposition source via magnetron sputtering is 0.6 W/cm2, since with lower power density energy consumption is reduced, reducing the amount of ions and the energy of the atomic species incident on the cathode surface, as a consequence, there is a decrease in the deposition rate due to the smaller number of atoms ejected from the target.

[0047] In this way, the thickness of the deposited metallic film is 50 to 400 nm, preferably 100 nm, considering that this reduced thickness value results in adequate adhesion between another coating, such as paint, metallic film and substrate. Furthermore, smaller thicknesses result in shorter deposition times, which, consequently, contributes to a reduction in energy consumption in the process.

[0048] In a preferred embodiment of the invention, the separation distance between the surface of the polymeric substrate and the surface of the target is 11 cm, this distance advantageously providing improved adhesion between the metallic film and the substrate polymeric, since the attenuation of the energy of the atoms being deposited is smaller for shorter distances.

[0049] Furthermore, in the deposition method of the present invention, a power of 50 to 400 W is used, preferably 50, 100, 200 W or 300 W, and a deposition time of 5 to 35 minutes.

[0050] The process temperature is 20 to 25°C, that is, the film is deposited at room temperature, without auxiliary heating on the substrate.

[0051] In table 2 it is possible to observe the chemical composition of the stainless steel target, in percentage by atomic weight: Table 2 - Chemical composition of the target in percentage by weight.

[0052] In another embodiment of the invention, a target with an atomic weight percentage of 100% Copper can be used, since this presents a similar result to the stainless steel target, which becomes advantageous when compared to processes of the state of the art that use copper through chemical routes, such as, for example, electroplating. Therefore, in the present invention, Copper is used via PVD magnetron sputtering, becoming a cleaner process environmentally speaking.

[0053] In one embodiment of the invention, the substrate is a polymeric material, such as poly(styrene-co-acrylonitrile) - AES, Polyethylene terephthalate - PET, Polybutylene Terephthalate - PBT, Polyamides - PA6 and PA6.6, Polyvinyl chloride - PVC, High impact polystyrene - PSAI, Acrylic resins, polyethylene - (HDPE and LDPE), Polypropylene-PP, polyester resin and epoxy resin, preferably acrylonitrile-butadiene-styrene - ABS.

[0054] The description that has been made so far of the object of the present invention should be considered only as a possible embodiment or embodiments, and any particular characteristics introduced therein should be understood only as something that was written to facilitate understanding. Therefore, they should not be considered as limiting the invention, which is limited to the scope of the claims.

[0055] The examples that will be presented illustrate the scope of the invention proposed here. Example 1 - Morphological characterizations of the film Using the scanning electron microscopy technique, the thickness of the films deposited at five points of each sample was measured, which can be seen in figure 2. The first group of samples was worked with a fixed time and different powers , as shown in Table 3. Table 3- Deposition conditions for the first group of samples Thus, based on the values presented in Table 4, it is possible to observe that the film thickness increases as the power density is also increased in the depositions, in addition to following a linear growth trend for samples 01 to 04. Table 4- Thickness average of the films for samples 01 to 04. For the second group of samples, shown in Table 5, thicker films were obtained, with approximately 300 nm (figure 4), maintaining the same powers used previously. Table 5- Deposition conditions for the second group of samples Through table 6, it can be seen that for the second group of samples, greater thicknesses were obtained with the same power densities in samples 05 to 07, as desired. Sample 08 had a smaller film thickness, but very close to sample 04, both deposited with the highest power density used, that is, 300W. Table 6- Average film thickness for samples 05 to 08. Example 2 - Qualitative analysis of the films The films produced did not present visible macroscopic defects, they are mirror-like (reflective property), their color is similar to that of polished stainless steels, which are important aesthetic characteristics for application in various products, depending on the requirements of each industry. The reflective property can be seen in Figure 5, where it is possible to observe the clear reflection of the camera in the photo. The adhesion aspects of the films to the substrate were analyzed using the grid-cut adhesion determination test. The test provides a qualitative result of the adhesion of the coating to the polymer, and is widely used because it is simple to do and provides immediate results. Samples A10 and A11 were used, deposition conditions in table 7, and the test was carried out in triplicate for each sample, with the result observed in figures 6 and 7. Table 7- Deposition conditions for the third group of samples According to the reference for the degree of adhesion classification, shown in Table 8 below, the samples are generally classified as Gr1, that is, they showed coating peeling of more than 5% and less than 15% (NBR 11003:2009). Table 8 - Classification of the degree of adhesion according to NBR 11003:2009 Example 3 - Analysis of adhesion between the substrate and film/paint The analysis of adhesion between the substrate and the film/paint was carried out following NBR 11003:2009 which prescribes the methods for determining adhesion in paints, using method A, cut in X, and by method B, cut grid. adhesion tests were carried out between an ABS polymeric substrate and the metallic film/paint. The result can be seen in figure 8, with figure 8a relating to the sample with AISI 304 film between the paint and ABS and figure 8b without the AISI 304 film between the paint and ABS. It is noted that in figure 8b there was a detachment, since the metallic interlayer proposed by the present invention was not deposited using the cathodic spraying technique. Example 4 - Salt spray test for corrosion analysis For the corrosion test, the NBR 8094 standard was used, which prescribes the method for carrying out tests on exposure to salt spray on coated metallic materials. In figure 9 it is possible to observe the result achieved with the use of the metallic interlayer proposed by the present invention. In figure 9a it is shown before corrosion and in figure 9b after corrosion, it is possible to notice that there was no degradation of the surface of the deposited metallic film. after 240 hours of exposure to salt spray.

Claims (8)

1- “Method of deposition of a metallic film by sputtering” characterized by comprising the following steps: a) Mounting a polymeric substrate on a substrate support located inside a vacuum chamber equipped with a stainless steel target; b) Adjust the separation distance between the surface of the polymeric substrate and the surface of the target from 5 to 30 cm; c) Remove residual gases from the inside of the chamber using a vacuum pump until a pressure of 1.0 to 3.0 x 10-4 Pa is reached d) Introduce an inert gas into the vacuum chamber to maintain constant internal pressure from 0.5 to 10 mTorr; e) Adjust a power supply to a power of 50 to 300 W, in order to obtain a power density of 0.6 W/cm2 to 2.5 W/cm2 on the magnetron sputtering cathode; f) Apply the power determined in step e) for a period between 5 and 35 minutes at room temperature. 2- “Method of metal film deposition by sputtering”, according to claim 1, characterized in that the vacuum pump is mechanical, turbo molecular or diffuser. 3- “Method of metal film deposition by sputtering”, according to claim 1, characterized in that the gas is argon. 4- “Method of metal film deposition by sputtering”, according to claim 1, characterized in that the polymeric substrate is poly(styrene-co-acrylonitrile) - AES, Polyethylene terephthalate - PET, Polybutylene Terephthalate - PBT, Polyamides - PA6 and PA6.6, Polyvinyl Chloride - PVC, High impact polystyrene - PSAI, Acrylic resins, polyethylene - (HDPE and LDPE), Polypropylene-PP, polyester resin, epoxy resin or acrylonitrile-butadiene-styrene - ABS. 5- “Method of metal film deposition by sputtering”, according to claim 1, characterized by obtaining a metal film with a thickness of 50 to 400 nm. 6- “Method of metal film deposition by sputtering” according to claims 1 and 5, characterized by obtaining a metal film with a thickness of 100 nm. 7- “Method of metal film deposition by sputtering”, according to claim 1, characterized in that the pressure is from 1 to 10 mTorr. 8- “Method of metal film deposition by sputtering”, according to claim 1, characterized in that the power is 50 W, 100W, 200 W or 300W.