Surface modification of polyimide by combining swelling and TiO2 photocatalytic treatments for adhesion improvement of electroless Cu

In order to enhance the adhesion strength between the PI film and the electroless copper film, a combination of swelling and TiO₂ photocatalytic treatments was used to modify polyimide (PI) film. The effects of the swelling solution composition and TiO₂ photocatalytic condition on the surface performance were investigated. After the optimal swelling and photocatalytic treatment, the surface contact angle of the PI film decreased from 85 to 28.7°, and the surface average roughness of the PI film only increased from 1.3 to 13.6?nm, indicating no obvious change for the surface topography of PI film after the photocatalytic treatment. However, the adhesion strength between electroless copper film and the PI film reached to 0.6?KN·m^?1. The FT-IR spectra and XPS analyses indicated that –COOH group was formed on the PI surface after the treatment, and the surface hydrophilicity was improved, which improved the adhesion strength between the PI film and the electroless copper film.     

Surface modification of ABS by photocatalytic treatment for electroless copper plating

Surface roughness of acrylonitrile–butadiene–styrene (ABS) resin prior to metallization is treated generally with sulphuric/chromic acid system. However, the presence of chrominum (VI) ion imposes serious environmental problems. In this work, TiO₂ photocatalytic treatment was used to enhance the adhesion strength between the ABS surface and the electroless copper film. Effects of the TiO₂ content, irradiation time and UV power upon the surface topography, surface characterization and the adhesion strength were investigated. The results indicated that the surface hydrophilicity of ABS resin and the adhesion strength between the electroless copper film and ABS surface increased with an increase in the UV power and a prolongation in irradiation time, and did not increase linearly with an increase of TiO₂ content. Though the surface topography of ABS changed little, the adhesion strength reached 1.25?kN/m, which was higher than that in the optimal H₂SO₄–MnO₂ colloid. The surface chemistry results indicated that –COOH and –OH groups formed with the photocatalytic treatment and the absorption strengths increased with the UV power. XPS analysis results further demonstrated that the contents of C=O and –COOH reached 6.4 and 4.9% with the photocatalytic treatment, which was much higher than that of the H₂SO₄–MnO₂ colloid (3.9 and 3.1%). The high contents of C=O and –COOH groups enhanced the surface hydrophilicity of the ABS resin and improved the adhesion strength between the electroless copper film and ABS resin. The results indicated that the photocatalytic treatment was an environment-friendly and effective method to replace the commercial wet chemical process for ABS surface modification.     

A study of the environmentally friendly polycarbonate surface etching system containing H2SO4–MnO2 colloid

In this paper, an environmentally friendly etching system containing H₂SO₄–MnO₂ colloid was used to investigate surface etching for polycarbonate (PC). The effects of swelling condition, H₂SO₄ concentrations and etching times on surface topography and surface roughness were studied. With the etching treatment, the surface average roughness (R _a) of PC substrates increased from 3 to 76?nm and the adhesion strength between the electroless copper and PC substrate reached 1.08 KN/m. Surface chemistry of PC substrates was investigated by the contact angle measurement and X-ray photoelectron spectroscopy spectra (XPS). After the etching treatment, PC surface became hydrophilic and the contact angle decreased from 95.2 to 39.6^o. XPS analyses indicate that hydroxyl and carboxyl groups are formed on the PC surface as a result of the etching treatment, which improve the adhesion strength between PC substrate and electroless copper film.     

Study of an environment-friendly surface pretreatment of ABS-polycarbonate surface for adhesion improvement

In this paper, an environmentally friendly etching system containing MnO₂–H₃PO₄–H₂SO₄ colloid was used to investigate surface etching for ABS- polycarbonate (PC/ABS) as a replacement for conventional chromic acid etching solutions. In order to obtain a good etching performance, a swelling system, containing tetramethylammonium hydroxide (TMAH), and 1-Methyl-2-pyrrolidinone (NMP), was used to investigate the surface swelling for PC/ABS resin. Then the effects of H₂SO₄ concentration, and etching time on the surface topographies and surface contact angle were investigated. After the optimal swelling and etching treatment, the surface contact angle of PC/ABS resin decreased from 95.7° to 28.3°, and the adhesion strength between electroless copper film and PC/ABS resin reached to 1.04 KN m⁻¹. The FT-IR spectra and XPS analyses indicated that hydroxyl and carboxyl groups formed on the PC/ABS surface as a result of the swelling and etching treatment, which improved the adhesion strength between PC/ABS substrate and elctroless copper film.     

Adhesion improvement of electroless copper to PC substrate by a low environmental pollution MnO2–H3PO4–H2SO4–H2O system

A low environmental pollution etching system, MnO₂–H₂SO₄–H₃PO₄–H₂O colloid, was used to investigate surface etching performance of polycarbonate (PC) as a replacement for the chromic acid etching solution. The effects of H₂SO₄ concentrations, H₃PO₄ concentrations and etching times upon the surface topography, surface chemistry and surface roughness were studied. With the appropriate etching treatment, the surface average roughness (R_a) of PC substrates increased from 3 to 177 nm, and the adhesion strength between the electroless copper and PC substrate also reached 1.10 KN m⁻¹. After the etching treatment, the PC surface became hydrophilic and the surface contact angle decreased from 95.2° to 24.8°. The intensity of C–O groups increased and the new functional groups (–COOH) formed on the PC surface with the etching treatment, which improved the adhesion strength between PC substrate and elctroless copper film.     

Effects of titania content and plasma treatment on the interfacial adhesion mechanism of nano titania-hybridized polyimide and copper system

Nano-titania (TiO₂) incorporated into polyimide (PI) matrix can significantly enhance the adhesion strength for PI/TiO₂ hybrid film and copper system. Surface modifications by various plasma treatments (Ar, Ar/N₂ and Ar/O₂) were also applied in this study to improve the adhesion strength. The Ar/N₂ plasma treatment is regarded as the more effective way in promoting the adhesion strength. The maximum adhesion value of 9.53 N/cm was obtained for the PI/TiO₂-1 wt% hybrid film with Ar/N₂ plasma treatment. It is enhanced about 10 times as large as pristine PI. Furthermore, by Ar/O₂ plasma treatment, a weak boundary of copper oxide was formed at the interlayer between PI/TiO₂ hybrid film and copper which decreases the adhesion strength. The effects of plasma treatment and content of nanosized TiO₂ on the adhesion strength between PI/TiO₂ hybrid film and copper system were studied. Atomic force microscope and contact angle analyses were used to measure the changes in surface morphology and surface energy as a result of plasma treatment. Besides, the interfacial states of peeled-off polymer side and copper side were investigated by X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). Based on the result of XPS spectra, the peeled-off failure mode between PI/TiO₂ hybrid film and copper was proposed in this study.     

Surface modification of low‐density polyethylene (LDPE) film and improvement of adhesion between evaporated copper metal film and LDPE

To improve the interfacial adhesion between evaporated copper film and low‐density polyethylene (LDPE) film, the surface of LDPE films was modified by treating with chromic acid [K₂Cr₂O₇/H₂O/H₂SO₄ (4.4/7.1/88.5)]/oxygen plasma. Chromic‐acid‐etched LDPE was exposed to oxygen plasma to achieve a higher content of polar groups on the LDPE surface. We investigated the effect of the treatment time of chromic acid in the range of 1–60 min at 70°C and oxygen plasma in the range of 30–90 sec on the extent of polar groups created on the LDPE. We also investigated the surface topography of and water contact angle on the LDPE film surface, mechanical properties of the LDPE film, and adhesion strength of the evaporated copper metal film to the LDPE film surface. IR and electron spectroscopy for chemical analysis revealed the introduction of polar groups on the modified LDPE film surface, which exhibited an improved contact angle and copper/LDPE adhesion. The number of polar groups and the surface roughness increased with increasing treatment time of chromic acid/plasma. Water contact angle significantly decreased with increasing treatment time of chromic acid/plasma. Combination treatment of oxygen plasma with chromic acid drastically decreased the contact angle. When the treatment times of chromic acid and oxygen plasma were greater than 10 min and 30 sec, respectively, the contact angle was below 20°. With an increasing treatment time of chromic acid, the tensile strength of the LDPE film decreased, and the film color changed after about 10 min and then became blackened after 30 min. With the scratch test, the adhesion between copper and LDPE was found to increase with an increasing treatment time of chromic acid/oxygen plasma. From these results, we found that the optimum treatment times with chromic acid and oxygen plasma were near 30 min and 30 sec, respectively. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 1677–1690, 2001     

Adhesion Properties and Structure of Ion-Beam Modified Polyimide Films

Polyimide (PI) surface modification was carried out by an ion beam treatment to improve the adhesion between the polyimide film and copper. The PI film surface was treated with an ion-beam source at ion doses ranging from 1.96 × 10¹³ to 2.38 × 10¹³ ions/cm² using a mixture of nitrogen (N₂) and hydrogen (H₂). Contact angle measurement, atomic force microscopy and X-ray photoelectron spectroscopy, respectively revealed an increase in the surface roughness, a decrease in contact angle, and the formation of oxygen complexes and functional groups on the treated PI surfaces. Adhesion between the copper and PI film treated with the beam was superior to that of the untreated PI film. The 90° peel test revealed the highest peel strength of 7.8 N/cm.     

Surface modification of polymers and improvement of the adhesion between evaporated copper metal film and a polymer. I. Chemical modification of PET

To improve the interfacial adhesion between evaporated copper film and poly(ethylene terephthalate) (PET), the surface of PET films was modified by treating with hydrazine monohydrate. The effect of the treatment time in the range of 5-20 min with 80 wt% hydrazine monohydrate at 60 °C on the number of polar groups created on PET was investigated. The surface topography of and water contact angle on the PET film surface, the mechanical properties of the PET film, and the adhesion strength of evaporated copper metal film to the PET film surface were also investigated. The introduction of polar groups on the modified PET film surface was examined by FT-IR and ESCA analyses. The amount of polar groups increased to the maximum value with increasing treatment time to 10 min, and thereafter it decreased markedly. The surface roughness increased with increasing treatment time up to 10 min and cracks occurred after 20 min. The water contact angle and tensile properties decreased with increasing treatment time. Using the scratch test, the adhesion between Cu film and PET was found to increase with increasing treatment time up to 10 min and thereafter there was a remarkable decrease in adhesion. From these results, it was concluded that the optimum treatment time with hydrazine monohydrate (80 wt%) at 60°C was about 10 min to improve copper-PET adhesion.     

Fabrication of superhydrophobic titanium surfaces by anodization and surface mechanical attrition treatment

A superhydrophobic surface of titanium was fabricated by anodization in sodium chloride solution followed by immersion in perfluorodecyltriethoxysilane. The surface characteristics of the anodic film (morphology, composition, microstructure, and adhesion) were investigated by scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, and scratch testing. The anodic film was comprised of TiO₂ and TiCl₃ with a thickness of 50 nm. The anodized titanium surface exhibited a hierarchical structure, which consisted of a microscale horn structure with a nanoscale strip-overlay. This structure provided superhydrophobicity (water contact angle: 151.9° and sliding angle: 3°) following the immersion process. Furthermore, coverage of the hierarchical structure on the anodized titanium surface was improved by performing surface mechanical attrition treatment (SMAT) to grain-refine titanium surface which was then anodized and it enhanced a slightly increased water contact angle. The thickness (200 nm) of the anodic film on the SMAT-pretreated titanium surface was much higher than that on the titanium surface (50 nm). This resulted from a large number of grain boundaries on the surface serving as a fast diffusion path during anodization. However, the adhesion of the SMAT-and-anodized film was worse than that formed by anodization only. This is due to a large number of pores within the SMAT-and-anodized film.     

Growth behavior of titanium dioxide thin films at different precursor temperatures

The hydrophilic TiO₂ films were successfully deposited on slide glass substrates using titanium tetraisopropoxide as a single precursor without carriers or bubbling gases by a metal-organic chemical vapor deposition method. The TiO₂ films were employed by scanning electron microscopy, Fourier transform infrared spectrometry, UV-Visible [UV-Vis] spectroscopy, X-ray diffraction, contact angle measurement, and atomic force microscopy. The temperature of the substrate was 500°C, and the temperatures of the precursor were kept at 75°C (sample A) and 60°C (sample B) during the TiO₂ film growth. The TiO₂ films were characterized by contact angle measurement and UV-Vis spectroscopy. Sample B has a very low contact angle of almost zero due to a superhydrophilic TiO₂ surface, and transmittance is 76.85% at the range of 400 to 700 nm, so this condition is very optimal for hydrophilic TiO₂ film deposition. However, when the temperature of the precursor is lower than 50°C or higher than 75°C, TiO₂ could not be deposited on the substrate and a cloudy TiO₂ film was formed due to the increase of surface roughness, respectively.     

Surface modification of polyimide film by coupling reaction for copper metallization

In this study, Upilex-S [poly(biphenyl dianhydride-p-phenylene diamine)], one of polyimide films, was modified by coupling reactions with N,N-carbonyldiimidazole (CDI) to increase adhesion to copper for flexible copper clad laminate (FCCL). Imidazole groups show strong interaction with copper metal to make charge transfer complexes. Because polyimide film did not have active site with coupling agent, the film surfaces were modified by aqueous KOH solutions and reacted with dilute HCl solutions.Surface modified Upilex-S was analyzed by X-ray photoelectron spectroscopy (XPS) to examine the surface chemical composition and film morphology and investigated by scanning electron microscopy (SEM) and atomic force microscopy (AFM). Changes in the wettability were evaluated by measuring contact angle with the sessile drop method. After deposition of copper on surface modified Upilx-S, the adhesion strength of the copper/polyimide system was measured by a 90° peel test using the Instron tensile strength tester. The peel strength of the copper/polyimide system increased from 0.25 to 0.86 kg_f/cm by surface modification. This result confirmed that the CDI coupling reaction is an effective treatment method for the improvement of the adhesion property between copper metal and polyimide film.     

Study on the pretreatment method of glass-epoxy resin in the presence of TiO2 sol prepared by hydrothermal method

In the present study, the pretreatment of glass-epoxy resin using photoreaction of TiO₂ sol prepared by hydrothermal method was investigated. The surface properties for the pretreated substrate were examined, and the change of contact angle was measured to confirm the hydrophile property caused by the photocatalytic reaction. After the pretreatment, the surface was oxidized with showing no changes in its morphology. However, the surface roughness at nano-scale order increased with the photocatalytic reaction time. When UV light was irradiated for 60 min in TiO₂ sol, the adhesion strength of electroless-plated Cu film was most excellent in other test conditions.     

Improving the hydrophobic,water barrier and crystallization properties of poly(ethylene terephthalate) by incorporating monodisperse SiO2 particles

This paper details an improvement in the properties of poly(ethylene terephthalate) (PET) with respect to its use in petroleum engineering by incorporating uniform (monodisperse; 35 to 380 nm) silica (SiO₂) particles and polystyrene? SiO₂ core–shell particles by melt mixing. The resulting high‐performance nanocomposite (SNPET) films are presented. The results of contact angle and water absorption tests showed that the contact angle of the amorphous SNPET films increased from 72° to 118.5° as the core–shell particle load increased from 0 to 6.0 wt%. The contact angle reached 128.0° when the films were annealed. Decreasing the SiO₂ particle size demonstrably improved the SNPET film hydrophobicity and lowered the water diffusion coefficient, i.e. SiO₂ particles of 35 nm in size gave the greatest enhancement of water barrier properties. Results of transmission electron microscopy, scanning electron microscopy, atomic force microscopy and optical measurements showed the homogeneous particle dispersion and nanostructure in the SNPET films. Their transparency and haziness increased as the particle size decreased. Use of such core–shell structures meant that the uniform (monodisperse) SiO₂ particles could be dispersed homogeneously in PET, and effectively improved the surface, thermal and crystallization behavior of SNPET films to produce materials with high barrier stability against water. Copyright © 2010 Society of Chemical Industry     

Surface modification of ABS with Cr6+ free etching process in the electroless plating

ABS resin is widely used after the plating process. The traditional ABS resin surface etching process uses a chromic acid system, which is a great threat to environmental protection. This paper examines a new environment-friendly measure in the etching system, which is composed of HNO₃, H₂SO₄, and NiSO₄. With this system, the solution will be etching at 60?°C for 20?minutes on an ABS resin surface and causing the surface roughness of the ABS resin to become larger, and an increase of hydrophilicity. It is observed that the root mean square (RMS) of the surface roughness of the ABS resin increased from 3.21?nm to 27.5?nm after etching, and the surface contact angle of ABS resin decreased from 88.04° to 65.29°. After the etching process, the surface of ABS can be electroless plated successfully and the bonding force of coating and resin can reach 2.09 MPa. The FT-IR spectra and XPS analyses showed that hydroxyl and nitro groups on the ABS surface are as a result of etching treatment, which improves the bonding strength between ABS substrate and electroless copper plating. This new etching system can be a substitute for the traditional chromic acid system in the industry, which will greatly reduce the pollution caused by the traditional process.     

Photocatalytic decomposition of gaseous HCHO over a titanium dioxide film formed on a hydrophobic PET sheet

BACKGROUND: The authors (Chem Eng J 148, 234 (2009)) previously demonstrated the excellent performance of a photocatalytic reactor with a parallel array of nine light sources. To enhance the possibility of practical application of this reactor, the present work explores the use of a PET (polyethylene terephthalate) sheet as a new cheap material to support TiO₂, as an alternative to glass tubes. A method of coating the hydrophobic PET sheet with a TiO₂ film using an aqueous coating solution is investigated and the performance of the TiO₂‐PET sheet prepared evaluated. RESULTS: The affinity of the coating solution for the PET sheet is greatly enhanced by addition of 0.01% (w/w) nonionic surfactant (polyoxyethylene lauryl ether). A relatively uniform thin TiO₂ film is formed on the entire surface of the PET sheet by applying the coating solution to the PET sheet and drying it at 100 °C. Decomposition experiments of gaseous HCHO indicate that the photocatalytic activity, although initially low, is increased with repeated use. This is because surfactant molecules added interfere initially with the decomposition of HCHO. After their decomposition, the TiO₂–PET sheet decomposes HCHO at almost the same rate as does the TiO₂–glass tube. CONCLUSION: The photocatalytic reactor with a parallel array of nine light sources can utilize a PET sheet as TiO₂ support with a reduction in material cost. Copyright © 2011 Society of Chemical Industry     

Low-temperature fabrication of TiO<Subscript>2</Subscript> film on flexible substrate by atmospheric roll-to-roll CVD

Titanium dioxide (TiO₂) thin film was fabricated using titanium isopropoxide as a precursor through an atmospheric low-temperature roll-to-roll chemical vapor deposition method. TiO₂ was deposited on the PET substrate in the temperature range of room temperature to 100°C, and the working pressure was 740 Torr. The surface morphology of TiO₂ thin film was analyzed by field emission scanning electron microscopy and a 2D surface profiler. The results revealed that the growth rate of TiO₂ film was 31 nm/min at 100°C, and it also showed that the surface is uniform and smooth. Moreover, the lowest root mean square roughness (R _q) value of 1.87 nm was obtained for TiO₂ film prepared at 100°C. The composition of TiO₂ film was confirmed by X-ray photoelectron spectroscopy (XPS) analysis. The film showed very good chemical and optical properties while increasing the substrate deposition temperature. The UV–Vis spectroscopy analysis revealed that TiO₂ films exhibited excellent optical transmittance, more than 91% observed in the visible region.     

Preparation of super-hydrophilic amorphous titanium dioxide thin film via PECVD process and its application to dehumidifying heat exchangers

The super-hydrophilic amorphous titanium dioxide (TiO₂) thin film was prepared by plasma-enhanced chemical vapor deposition (PECVD) process for an application to dehumidifying finned-tube heat exchangers. The chemical components and surface structure were characterized by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and scanning electron microscope (SEM). The wettability and long-term durability were investigated by measuring the water contact angle and by performing wet/dry cycles. The samples were subjected to 1000 times of wet/dry cycles to establish long-term durability. The water contact angle of the amorphous TiO₂ thin film was about 8° at as-deposited film with O₂ plasma treatment and was about 15° after 1000 wet/dry cycles. The amorphous TiO₂ thin film had excellent wettability and long-term durability under full wetting conditions.     

Preparation of hydrophobic SiO<Subscript>2</Subscript>@(TiO<Subscript>2</Subscript>/MoS<Subscript>2</Subscript>) composite film and its self-cleaning properties

TiO₂/MoS₂ composite was encapsulated by hydrophobic SiO₂ nanoparticles using a sol–gel hydrothermal method with methyltriethoxysilane (MTES), titanium tetrachloride (TiCl₄), and molybdenum disulfide (MoS₂) as raw materials. Then, a novel dual functional composite film with hydrophobicity and photocatalytic activity was fabricated on a glass substrates via the combination of polydimethylsiloxane adhesives and hydrophobic SiO₂@(TiO₂/MoS₂) composite particles. The influence of the mole ratios of MTES to TiO₂/MoS₂ (M:T) on the wettability and photocatalytic activity of the composite film was discussed. The surface morphology, chemical compositions, and hydrophobicity of the composite film on the glass substrate were investigated by scanning electron microscopy, transmission electron microscopy, X-ray powder diffraction, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and water contact angle (water CA) measurements. The results indicated that the composite film exhibited stable superhydrophobicity and excellent photocatalytic activity for degradation of methyl orange (MO) even after five continuous cycles of photocatalytic reaction when M/T was 7:1. The water CA and degradation efficiency for MO remained at 154° and 94%, respectively. Further, the composite film showed a good non-sticking characteristic with the water sliding angle (SA) at about 4°. The SiO₂@(TiO₂/MoS₂) composite consisting of hydrophobic SiO₂ nanoparticles and TiO₂/MoS₂ heterostructure could provide synergistic effects for maintaining long-term self-cleaning performance.     

Fabrication of superhydrophobic TiO2 quadrangular nanorod film with self-cleaning,anti-icing properties

Superhydrophobic TiO₂ quadrangular nanorod film was fabricated by hydrothermal reaction and stearic acid modification. X-ray diffractometer and Fourier transform infrared spectrometer were employed to characterize the surface crystal structures and chemical compositions of the superhydrophobic TiO₂ film, respectively. The effects of the titanium source (titanium tetraisopropoxide (TTIP)) amount and reaction time on the morphology and wettability of the TiO₂ film were studied by scanning electron microscope and contact angle meter. The results show that the diameter of the TiO₂ quadrangular nanorods increases and then the water contact angle on modified TiO₂ film decreases with the increase of the reaction time and TTIP amount. Moreover, when the TTIP amount is 0.3?mL and solvent is 30?mL, the wetted state of the superhydrophobic TiO₂ film surface conforms to an improved Cassie model. Besides, the superhydrophobic TiO₂ film shows good low adhesion, self-cleaning and anti-icing properties. Particularly, the anti-icing property decreases with the increase of the reaction time and TTIP amount.