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 of vacuum-deposited thin cobalt metal film to poly(ethylene terephthalate) pretreated with RF plasma

Specific polar groups were introduced on a poly(ethylene terephthalate) (PET) film surface by radio-frequency (RF) plasma treatment. These polar groups were analyzed quantitatively by ESCA, and their effect on the adhesion strength of vacuum-deposited thin cobalt metal film on the plasma-treated PET film surface was investigated. Hydroperoxide and hydroxyl groups introduced onto the PET film surface by RF plasma under an argon or oxygen atmosphere greatly increased the adhesion strength. In particular, oxygen plasma treatment at high RF power was most effective. A large number of amino groups were introduced by the ammonia plasma treatment, but they did not increase the adhesion strength.     

Chemical modification of LDPE film

Low‐density polyethylene (LDPE) film was chemically modified by chromic acid treatment to generate polar groups on the surface. The film samples were etched by chromic acid with variation of temperature at a constant time (30 min) and variation of time at a constant temperature (room temperature = 26°C). The variation of weight and thickness of the film samples before and after etching was measured. The surface morphology of the etched films was studied by Scanning Electron Microscopy (SEM). IR and XPS analysis revealed the introduction of polar groups like  COOH, 〉CO,  SO₃H on the etched LDPE film surface, which exhibited improved printability. Etching also enhanced adhesion with epoxy resin. The mechanical properties of the laminates of the two specimens of the same film sample with epoxy resin were also measured. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 1041–1048, 1999     

The effect of TiO2 morphology on the surface modification of poly (ethylene terephthalate) for electroless plating

In this study, a surface modification of the poly (ethylene terephthalate) (PET) film using TiO₂ photocatalytic treatment was investigated. In order to enhance the adhesion strength between the PET film and the electroless copper film, the effects of TiO₂ crystal forms, TiO₂ particle sizes, and TiO₂ content, as well as treatment condition, upon the surface contact angle, surface characterization, and adhesion strength were investigated. Anatase TiO₂ with a particle size of 5 nm had a high catalytic activity and dispersibility in aqueous solution. After the optimal photocatalytic treatment, the surface contact angle of the PET film decreased from 84.4° to 19.8°, and the surface roughness of the PET film increased from 36 to 117 nm. The adhesion strength between the PET film and the electroless copper film reached 0.89?KN?m^?1. X-ray photoelectron spectroscopy analyses indicated the carbonyl group was formed on the PET surface after photocatalytic treatment, and the surface hydrophilicity was improved. Consequently, TiO₂ photocatalytic treatment is an environmentally friendly and effective method for the surface modification of the PET film.     

Plasma surface modification of polyimide for improving adhesion to electroless copper coatings

The influences of oxygen plasma treatment of polyimide (PI) films on the adhesion of electroless copper coatings as well as on the chemical composition of the film surface and the PI surface morphology were investigated. The plasma operating parameters were 1800 W forward power with O₂ flowing at a rate of 300 cm³/min at a pressure of 200 mTorr. The peel strength increased with decreasing plasma treatment temperature. However, extension of the treatment time at higher temperatures had a positive effect on adhesion. A correlation between the enhancement in peel strength and the content of oxygen-containing groups at the PI surface (investigated using XPS) was observed. A change in the morphology as a result of plasma etching was also observed, in the formation of pits in the film surface. The pits ranged from 3 to 6 μm in depth and the diameter varied from 10 to 200 μm. Comparison of the data obtained after plasma treatment with the results of chemical etching in alkaline solutions of permanganate showed approximately the same adhesion increase (to 0.6 kN/m) in both cases. However, chemical etching did not affect the surface morphology and increased the oxygen content at the PI surface less than the plasma treatment.     

Surface modification of plasma‐pretreated high density polyethylene films by graft copolymerization for adhesion improvement with evaporated copper

Surface modification of Ar plasma‐pretreated high density polyethylene (HDPE) film via UV‐induced graft copolymerization with glycidyl methacrylate (GMA) and 2‐hydroxyethylacrylate (HEA) was carried out to improve the adhesion with evaporated copper. The surface compositions of the modified HDPE surfaces were characterized by X‐ray photoelectron spectroscopy (XPS). The adhesion strengths of evaporated copper with the graft‐copolymerized HDPE films were affected by the Ar plasma pretreatment time, the monomer concentration used for graft copolymerization, and the graft concentration. Post‐treatments, such as plasma post‐treatments after graft copolymerization and thermal treatment (curing) after metalization, further enhanced the adhesion strength of the Cu/HDPE laminates. The T‐type peel strengths of the laminates involving the graft‐modified and plasma posttreated HDPE films were greater than 15 N/cm. The enhanced adhesion strength resulted from the strong affinity of the graft chains for Cu and the fact that the graft chains were covalently tethered on the HDPE surface. XPS characterization of the delaminated surfaces of the Cu/HDPE laminates revealed that the failure mode of the laminates with T‐peel adhesion strengths greater than 5 N/cm was cohesive in nature.     

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.     

Surface modification of polyether ether ketone (peek) films for flexible printed circuit boards

The surface of polyether ether ketone (PEEK) films was modified using plasma treatment, corona, or surface etching to improve their adhesion with regard to glued copper foils and copper layers generated by physical vapor deposition. After the pretreatments, surface chemical analysis was performed by X-ray photoelectron spectroscopy (XPS). The wetting behavior was qualitatively investigated by contact angle measurements. Surface topography was monitored by laser scanning microscopy (LSM). After coating, the adhesion strength of the copper layer was measured by a peel force test. Plasma treatment, corona discharge, or etching lead to a significant increase in adhesion. This increase is caused by a change in surface topography as well as by the incorporation of polar groups into the surface.     

Surface modification of polyether ether ketone (peek) films for flexible printed circuit boards

The surface of polyether ether ketone (PEEK) films was modified using plasma treatment, corona, or surface etching to improve their adhesion with regard to glued copper foils and copper layers generated by physical vapor deposition. After the pretreatments, surface chemical analysis was performed by X-ray photoelectron spectroscopy (XPS). The wetting behavior was qualitatively investigated by contact angle measurements. Surface topography was monitored by laser scanning microscopy (LSM). After coating, the adhesion strength of the copper layer was measured by a peel force test. Plasma treatment, corona discharge, or etching lead to a significant increase in adhesion. This increase is caused by a change in surface topography as well as by the incorporation of polar groups into the surface.     

Superficial modification in recycled PET by plasma etching for food packaging

An oxygen plasma treatment has been used to improve the adhesion of amorphous hydrogenated carbon (a‐C:H) films onto surfaces of recycled poly(ethylene terephthalate) (PET). Modifications produced by the oxygen plasma on the PET surface in chemical bonds and morphology were investigated by X‐ray photoelectron spectroscopy and atomic force microscopy, respectively. Contact angle measurements were used to study the changes in the surface wettability. Adhesion of the a‐C:H film onto the PET surface was investigated by the tape test method. It was observed that the improvement in film adhesion is in good correlation with the increase in surface roughness, due to plasma etching, and with the appearance of oxygen‐related functional groups at the surface. The results of this study indicate that a‐C:H‐coated recycled PET can be used in food packaging. The a‐C:H film could be used as a functional barrier to reduce or prevent migration of contaminants from the polymer to the package content. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Adhesion improvement of electroless copper to a polyimide film substrate by combining surface microroughening and imide ring cleavage

In order to enhance the adhesion strength of copper metal film to a polyimide (PI) film substrate, a method combining surface microroughness formation and imide ring cleavage was investigated. The results showed that imide rings were cleaved with a KOH treatment while carboxyl and amide groups were formed on the surface of the PI film. The surface micro-roughness did not change with the KOH treatment, and the adhesion strength of the copper metal film to the PI film was slightly improved to 30 g/mm, which could be attributed to the interaction of both carboxyl and amide groups with the copper atoms. When the PI films were successively treated with an alkaline permanganate and a KOH solution, many recesses were formed on the surface in an alkaline permanganate solution, and the size and depth of the recesses increased with alkaline permanganate treatment time. The results of the AFM measurements showed that the average roughness (R) increased from 3.54 to 10.23 nm after combined treatment with alkaline permanganate and KOH solutions. The adhesion strength of the copper metal film to the PI film reached 150 g/mm, which was five times greater than that achieved with the KOH treatment only.     

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.     

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 thermotropic poly(oxybenzoate‐co‐oxynaphthoate) copolyester by remote oxygen plasma for copper metalization

Poly(oxybenzoate‐co‐oxynaphthoate) (POCO) film surfaces were modified with remote oxygen plasma, and the effects of the modification on the adhesion between the copper layer and POCO were investigated. The remote‐oxygen‐plasma treatment led to a noticeable decrease in the contact angle, which was mainly due to the C? O functional groups on the surface. The modification of the POCO surface by remote oxygen plasma was effective in improving the adhesion with copper metal. The peel strength for the copper metal/POCO system was enhanced from 10 to 127.5 mN/5 mm by the surface modification. The failure mode of the copper metal/POCO system was an interface layer between the oxidized micro‐POCO fibril surface and the copper metal layer. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 2400–2408, 2003     

Surface modification of polyester films by RF plasma

Plasma treatment of PET films was carried out under argon, followed by exposure to an oxygen atmosphere. The films underwent considerable changes in surface composition and morphology, as demonstrated by contact angle measurements, FTIR‐ATR, AFM, and XPS. It was found that the surface acquired oxygen containing polar functional groups such as —C=O, —OH, and —OOH, which increased in number as the plasma treatment time increased. During storage, the treated films underwent significant surface reorganization, and both the time and temperature contributed to the increase in the contact angle. As revealed by AFM measurements, these changes were accompanied by an increase in roughness in the form of ridges. The ridges were observed to grow in height with increasing treatment time, although their spacing showed little evolution. A correlation among the observations obtained from various techniques was established, giving a comprehensive picture of the structure and dynamics of plasma‐treated PET surfaces. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 1083–1091, 2000     

Plasma surface modification of poly(phenylene sulfide) films for copper metallization

Poly(phenylene sulfide) (PPS) films were modified by Ar, O₂, N₂ and NH₃ plasmas in order to improve their adhesion to copper metal. All four plasmas modified the PPS film surfaces, but the NH₃ plasma modification was the most effective in improving adhesion. The NH₃ plasma modification brought about large changes in the surface topography and chemical composition of the PPS film surfaces. The peel strength for the Cu/plasma-modified PPS film systems increased linearly with increasing surface roughness, R _a or R _rms, of the PPS film. The plasma modification also led to considerable changes in the chemical composition of the PPS film surfaces. A large fraction of phenylene units and a small fraction of sulfide groups in the PPS film surfaces were oxidized during the plasma modification process. Nitrogen functional groups also were formed on the PPS film surfaces. The NH₃ plasma modification formed S—H groups on the PPS film surfaces by reduction of S—C groups in the PPS film. Not only the mechanical interlocking effect but also the interaction of the S—H groups with the copper metal may contribute to the adhesion of the Cu/PPS film systems.     

低温等离子体处理及丙烯酸接枝改性膨化聚四氟乙烯薄膜

采用He等离子体对膨化聚四氟乙烯(ePTFE)薄膜进行表面亲水处理,并引发接枝丙烯酸单体实现持久亲水改性.实验探究了不同等离子处理工艺和接枝工艺对ePTFE薄膜亲水性能的影响,并利用接触角、X光电子能谱(XPS)进行表征.研究结果表明,等离子体预处理后,ePTFE薄膜表面的接触角由145°降至102°;再接枝丙烯酸单体...     

Improvement of adhesion between poly(ethylene terephthalate) and polyethylene

Three-layer films were prepared with polyethylene (PE) and poly(ethylene terephthalate) (PET) films as the outer layers and a film of high-density polyethylene (HDPE)/ethylene-methyl acrylate-glycidyl methacrylate (E-MA-GMA) terpolymer blend as the inner layer using compression molding. E-MA-GMA, an elastomer containing an epoxy functional group, was used as the adhesion promoting agent in the multilayer films. The effects of processing temperature, pressure application time and elastomer concentration on adhesion were investigated. The adhesion strength between PE and PET films increased with increasing bonding temperature, bonding time and elastomer concentration. From contact angle measurements, it was observed that the work of adhesion between the polymers increased with increasing amount of elastomer. Improved adhesion between PET and HDPE with 30% elastomer films was confirmed by SEM analyses of the film layers. Using FT-IR analysis of PE/HDPE-30% elastomer/PET delaminated film, the decrease in peak intensity of the epoxy groups tends to indicate reaction of epoxy functionality with functional groups in PET.     

Adhesion Improvement of Poly(Phenylene-Vinylene) Substrates Induced by Argon-Oxygen Plasma Treatment

Copper films evaporated on argon-oxygen plasma-treated poly(phenylene-vinylene) films have been studied by scratch test, X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). The adhesion of the metallic film to the polymer substrate was greatly enhanced after treatment and found to increase with the treatment time. SEM observation of the treated samples revealed that the morphology of the polymer surface was gradually changed with the treatment time as compared with that of the bare polymer film. On the other hand, XPS analysis of the polymer-metal interface showed that the bonding between carbon, oxygen and copper were subsequently modified as compared with those obtained in untreated samples. The high adhesion strength observed on these substrates was related to the modification in the surface morphology on the one hand and to the formation of new compounds at the polymer-metal interface on the other. The nature of the interfacial layer and its influence on the adhesion of the copper layer was discussed by comparing the results with those obtained in poly(phenylene-vinylene) (PPV)-Al systems.     

Adhesion Improvement of Poly(Phenylene-Vinylene) Substrates Induced by Argon-Oxygen Plasma Treatment

Copper films evaporated on argon-oxygen plasma-treated poly(phenylene-vinylene) films have been studied by scratch test, X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). The adhesion of the metallic film to the polymer substrate was greatly enhanced after treatment and found to increase with the treatment time. SEM observation of the treated samples revealed that the morphology of the polymer surface was gradually changed with the treatment time as compared with that of the bare polymer film. On the other hand, XPS analysis of the polymer-metal interface showed that the bonding between carbon, oxygen and copper were subsequently modified as compared with those obtained in untreated samples. The high adhesion strength observed on these substrates was related to the modification in the surface morphology on the one hand and to the formation of new compounds at the polymer-metal interface on the other. The nature of the interfacial layer and its influence on the adhesion of the copper layer was discussed by comparing the results with those obtained in poly(phenylene-vinylene) (PPV)-Al systems.