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.     

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.     

Adhesion Improvement of ABS Resin to Electroless Copper by H2SO4–MnO2 Colloid with Ultrasound-Assisted Treatment

The adhesion strength between electroless copper and acrylonitrile-butadiene-styrene (ABS) resin can be improved significantly by an environmentally friendly etching system containing H₂SO₄–MnO₂ colloid as a replacement for conventional chromic acid etching solutions. In this paper, the effects of the H₂SO₄ concentration and ultrasound-assisted treatment (UAT) on the surface roughness and adhesion strength were investigated. When the H₂SO₄ concentration was 11.8～12.7 M, good etching was obtained. With UAT, many uniform cavities formed on the ABS surface with the average surface roughness (R _a) and maximum roughness (R _max) of ABS substrates decreasing from 386 and 397 nm to 278 and 285 nm, respectively, which were much lower than that etched by CrO₃–H₂SO₄ colloid (420 and 510 nm, respectively). The average adhesion strength increased from 1.29 to 1.39 kN/m, which was close to that obtained with chromic acid etching treatment (1.42 kN/m). The surface contact angle measurement indicated that the density of the polar groups on the ABS surface increased with increasing time of UAT. The results indicated that surface etching with UAT not only improved the uniformity of cavities, but also enhanced the oxidation rate of ABS resin, which in turn resulted in greater adhesion strength and a lower surface roughness.     

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.     

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 rapid one-step process for fabrication of superhydrophobic surface by electrodeposition method

Superhydrophobic surfaces are commonly prepared by a combination of low surface energy materials and micro/nano structures. In this work, a rapid one-step electrodepositing process is developed to fabricate superhydrophobic cathodic surface by copper plate in an electrolytic solution containing nickel chloride(NiCl₂·6H₂O), myristic acid and ethanol. Scanning electron microscopy (SEM) images, Fourier-transform infrared (FTIR) spectrometer, X-ray diffraction (XRD) and contact angle measurement have been performed to characterize the morphological features, chemical composition and superhydrophobicity property. The results demonstrate that the micro/nano scales cauliflower-like structure are composed of Ni crystals and Ni[CH₃(CH₂)₁₂COO]₂ crystals. The maximum contact angle is about 164° and rolling angle is less than 2°. The needed electrolytic time is largely shortened to 1 min. This method is rapid, easy and effective, and it will have great prospects for industrial applications.     

Effects of different surface cleaning procedures on the superficial morphology and the adhesive strength of epoxy coating on aluminium alloy 1050

This study reports the effects of different cleaning procedures on the surface characteristics of the aluminium alloy 1050 substrates and on the adhesive strength of the epoxy coating to this alloy's surface. The cleaning procedures used in this study were (1) degreasing by acetone, (2) alkaline etching by 5 w/w% NaOH solution and (3) alkaline etching by 5 w/w% NaOH solution followed by acid cleaning by 50 v/v% HNO₃ solution. The surface morphology, chemical composition and topography of the cleaned substrates were investigated by field-emission scanning electron microscope (FE-SEM), energy dispersive spectroscopy (EDS) and atomic force microscope (AFM), respectively. The effectiveness of the cleaning procedures was also studied by polarization test and open circuit potential (OCP) measurements. The surface free energy and work of adhesion were obtained on the cleaned samples using contact angle measuring device. Pull-off test was conducted to evaluate the adhesion strength of the epoxy coating on the aluminium substrates. Results revealed that the surface cleaning of aluminium alloy by alkaline etching followed by acid cleaning method was the most efficient procedure for removing the oxide layer from the surface of aluminium compared to other cleaning procedures. The surface roughness, surface free energy, electrochemical activity and adhesion strength of the epoxy coating to the aluminium surface were significantly increased using this surface cleaning procedure.     

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     

Direct synthesis of carbon nanofibers on the surface of copper powder

A novel approach to synthesize carbon nanofibers (CNFs) directly on the surface of metal μm-sized particles to evenly disperse the carbon nanomaterials in a composite material was proposed. As a metal matrix, 5–10 μm copper particles were utilized. As a carbon source, C₂H₂, CH₄ and CO were examined. The best conditions were found to be in C₂H₂ (30 cm³/min) and H₂ (260 cm³/min) atmosphere at the temperature of 750 °C. The composites based on copper and CNFs prepared by vacuum hot pressing showed the increase in hardness from 35 to 60 kg/mm² almost retaining pure copper electrical properties.     

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.     

A New Surface Etching Method Using MnO2/H2SO4 Colloid for Adhesion Improvement of Epoxy Polymer

Abstract

A new surface etching method using MnO₂/H₂SO₄ as the etchant to improve the adhesion between an epoxy polymer surface and a metallic layer, was studied. The effects of bath temperature, etching time and H₂SO₄ concentration on the surface topography and chemical properties were investigated. After the etching treatment of the MnO₂–H₂SO₄ colloid, not only did the surface roughness increase remarkably, but also the surface of epoxy became hydrophilic and the contact angle of the epoxy surface was also decreased from 93.5° to about 8.0°. The X-ray photoelectron spectroscopy analysis indicated that as a result of the etching treatment, hydroxyl, carbonyl and carboxylic acid groups formed on the epoxy surface. The adhesion strength was markedly enhanced with the appropriate etching treatment, which was attributed to the improvement of the surface roughness and the increased hydrophilicity.     

Thin-film nanocomposites of diamond-like carbon and titanium oxide; Osteoblast adhesion and surface properties

Thin films of a novel, nanocomposite material consisting of diamond-like carbon and polycrystalline/amorphous TiO_x (DLC-TiO_x, x ≤ 2) were prepared using pulsed direct-current plasma enhanced chemical vapour deposition (PECVD). Results from Raman spectroscopy indicate that the DLC and TiO_x deposit primarily as segregated phases. Amorphous TiO₂ is found to be present on the surface region of the film and there is evidence for the presence of crystalline TiO in the bulk of the film. The hydrophilicity of the DLC-TiO_x films increased with increasing titanium content. Culture studies with human osteoblasts revealed that the differences in three-day cell adhesion properties (count, morphology and area) between DLC and DLC-TiO_x films containing up to 13 at.% Ti were not statistically significant. However, the cell count was significantly greater for the films containing 3 at.% of Ti in comparison to those containing 13 at.% of Ti. A post-plasma treatment with Ar/O₂ was used to reduce the water contact angle, θ, by nearly 40° on the DLC-TiO_x films containing 3 at.% of Ti. A cell culture study found that the osteoblast count and morphology after three days on these more hydrophilic films did not differ significantly from those of the original DLC-TiO_x films. We compare these results with those for SiO_x-incorporated DLC films and evaluate the long-term osteoblast-like cell viability and proliferation on modified DLC surfaces with water contact angles ranging from 22° to 95°.     

Synthesis,surface characteristics,and electrochemical capacitance of Cu-doped carbon xerogel microspheres

Small-amplitude oscillatory shear tests were used to determine the rheological properties of a copper acetate-doped resorcinol–formaldehyde mixture at between 30 and 40 °C. The apparent activation energy of the sol–gel transition was 76.6 ± 0.6 kJ/mol. Organic gel microspheres were only obtained when the sol was emulsified immediately before the gelation point and not at the gelation point itself, due to the fast gelation kinetics of the copper acetate-doped resorcinol–formaldehyde mixture. The microspherical shape was preserved after carbonization. Cu-doped carbon xerogel microspheres were steam-activated at 840 °C. All samples comprised isolated well-formed microspheres, whose size increased with higher degree of activation. The surface area and porosity varied with the activation degree. Copper was detected as CuO, which acted as gasification catalyst during activation, and its size increased with higher activation degree. Electrochemical measurements were conducted with a three-electrode cell in 1 M H₂SO₄. A very large volumetric capacitance, 146 F/cm³, was found for the 30%-activated Cu-doped activated carbon xerogel, attributable to the high particle density resulting from the very compact packing of the microspheres. This sample also showed the lowest equivalent series resistance, due to its pore texture and high surface Cu content.     

Patterning ZrO2 films surface: Superhydrophilic and superhydrophobic properties

A photosensitive sol-gel method was used to pattern the surface of ZrO₂ film with a groove or a processus mastoideus structure. The surface roughness enhanced by the pattern structure had a strong effect on the ZrO₂ film wettability. Compared to an un-patterned ZrO₂ film, the patterned film showed a smaller static water contact angle (CA) and exhibited superhydrophilicity. Interestingly, the patterned ZrO₂ film did not require the use of UV irradiation to induce the superhydrophilicity and exhibited an excellent anti-fogging behavior. The surface modification with a 1H,1H,2H,2H-perfluorooctyltrichlorosilane (PFOTCS) layer was found to induce the change in the wettability of the patterned ZrO₂ films from superhydrophilicity to hydrophobicity/superhydrophobicity. The PFOTCS-modified ZrO₂ film patterned with the processus mastoideus surface resulted in the highest CA value of 155° and the sliding angle (SA) value of about 7°, and almost did not change under UV irradiation or after being annealed below 350 °C. The surface patterning by using a photosensitive sol-gel method was proved to be a practical approach to fabricate the ZrO₂ film with superhydrophilic/superhydrophobic properties.     

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.     

Fabrication of fluorine-terminated diamond-like carbon thin film using a hyperthermal atomic fluorine beam

Surface modification of diamond-like carbon (DLC) film was performed using a hyperthermal atomic fluorine beam on the purpose of production of hydrophobic surface by maintaining the high hardness of DLC film. By the irradiation of atomic fluorine beam of a 1.0 × 10²⁰ atoms/cm², the contact angle of a water drop against the DLC surface increased from 73° to 111°. The formation of CF₃, CF₂ and CF bonding on the modified DLC surface was confirmed from the measurements of X-ray photoelectron spectra and near-edge X-ray absorption fine structure spectra. Irradiation of hyperthermal atomic fluorine beam was concluded to produce insulator fluorine-terminated DLC film, which has high F content on the surface, by the taking of the use of neutral atomic beam as a fluorine source.     

Durable superhydrophobic Zn/ZnO/TiO2 surfaces on Ti6Al4V substrate with self-cleaning property and switchable wettability

Durable superhydrophobic (SHP) Zn/ZnO/TiO₂ surfaces with dendritic structures on Ti₆Al₄V substrate were obtained by chemical etching, electrodeposition and following annealing process. The resultant coatings electrodeposited at ?1.5 V for 10 min and annealed at 190 °C for 60 min showed fine superhydrophobicity with a water contact angle of 160° and a rolling angle less than 1°, showing excellent rolling-off and self-cleaning properties. The morphology, chemical components and growth mechanism of samples were investigated by scanning electron microscopy (SEM), X-ray diffraction pattern (XRD), Energy-dispersive spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS). Surface tribological properties were characterized by a universal mechanical tester (UMT). The as-prepared Zn/ZnO/TiO₂ surface still kept excellent SHP stability after exposure to the air, buried in soil and cold storage at 5 °C in the fridge for one year, as well as excellent repellence to some daily-used liquids such as coke, coffee, red wine, milk and tea. The surface can be reversibly switched between superhydrophobicity and superhydrophilicity by alternating UV illumination and dark storage or heating, which offer possibilities to widen future applications.     

Effect of PI film surface on printing of Pd(II) catalytic ink for electroless copper plating in the printed electronics

Pd(II) catalytic ink was synthesized by the hydrolysis of PdCl₂, followed by treatment with a small amount of stabilizing agent. The Pd(II) ink has excellent storage stability and the same low viscosity and surface tension as water. Polyimide film was used as a substrate for inkjet printing of the Pd(II) ink, while various characteristic changes of the printing were observed according to the contact angle on the substrate surface. The contact angle was affected by the concentration of KOH solution, and a surface condition suitable for composing Copper circuit was obtained by printing Pd(II) catalyst ink and electroless plating when it was treated in 1 M KOH solution for 10 min. The physical properties of Pd(II) ink were analyzed using a surface tension meter, viscometer, pH meter and UV–visible spectrophotometer, whereas the surface properties of polyimide film were analyzed using a contact angle instrument, FTIR-ATR, video microscope, XPS, FESEM and AFM. The physical properties of Pd(0) particles were analyzed by XPS and AFM, while the characteristics of electroless copper plating were analyzed by video microscope and XPS.     

Micro-structure of ITO ceramics sintered at different temperatures and its effect on the properties of deposited ITO films

Structural characterizations of two ITO ceramics that were respectively sintered at 1560 °C and 1600 °C were focused on and the results indicate that the lower sintering temperature is good for ITO ceramics to have the triangle fine grains, larger elemental concentration gradients of indium and tin and more content of In₄Sn₃O₁₂ phase which displays the stronger grain orientation growth along the crystallographic direction of [0-11]. ITO films with 100 nm thickness deposited at 25 °C–230 °C were used to investigate the effect of micro-structure on the film properties. Grain orientation growth of In₄Sn₃O₁₂ phase is conductive to form ITO films of columnar structure. Otherwise, uniform micro-structure and higher solubility of SnO₂ in In₂O₃ main phase contribute to deposit ITO films of higher sheet resistance, less thickness uniformity and higher transmittance at 25 °C, smaller etching angle and lower etching rate at 230 °C.     

Enhanced adhesion of epoxy-bonded steel surfaces using O2/Ar microwave plasma treatment

Steel surfaces have been modified using low pressure microwave plasma to enhance its adhesion with an epoxy adhesive. Optimization of the wettability of the surface was done using contact angle measurements for varying plasma parameters. Maximum wettability (19.9°) was obtained at 1000 W microwave power with 20 min of treatment time, −50 V sample bias and 1.67% O₂/Ar gas flow rate ratio. Enhanced wettability of the steel surface was attributed to increased surface roughness and oxide deposition. Using atomic force microscopy, surface roughness was observed to increase from 64.4 nm for the untreated surface to 76.7 nm for the O₂/Ar plasma treated surface. Deposition of oxides on the steel surface was also confirmed by the energy dispersive x-ray spectroscopy. Moreover, the increase in the total surface energy to 53.2 mN/m for the O₂ plasma treated steel surface supported the enhancement of its wettability, and hence, the adhesion with epoxy. Based on tensile test results, the adhesion strength of epoxy-bonded O₂/Ar plasma treated surfaces at optimum settings was increased to 3816.0 N, which is significantly higher compared to 3038.3 N for the epoxy-bonded untreated surfaces.