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.     

Temperature and humidity effects on adhesion of polyimide film to a silicon substrate

A 90° peel tester with substrate heating capability was built to evaluate the adhesion strength of polyimide films to a silicon substrate. The effects of polyimide film thickness and peel rate on polyimide adhesion to a silicon substrate under high or low humidity, and at elevated temperatures, have been evaluated. In a high humidity environment, a low peel strength was measured. The influence of moisture on the peel strength increases with decreasing peel rate. Peeling at elevated temperature reduces the moisture effect even under high humidity conditions. Using a low peel rate in a high humidity environment, the measured peel strength showed a maximum as the polyimide film thickness increased. No striations in peeled polyimide films were observed for peeling in a high humidity environment.     

Indentation test for adhesion measurement of polyimide films

An indentation technique was used to determine the adhesion of polyimide films on a ceramic substrate. Experimental results were obtained by indenting 13 μm thick polyimide films with a conical indenter at different indentation loads. Among the process variables investigated were the amount of adhesion promoter added to the polyimide and the exposure to temperature and humidity. The technique provides a measure of the bond strength, based on the analysis of indentation debonding of thin films. For well adhered films, no debonding could be induced, indicating the usefulness of the test only for the poorly bonded films.     

常压辉光放电等离子体研究进展及聚合物表面改性

综述了常压辉光放电等离子体(APGDP)的产生机理及研究进展。介绍了难以产生稳定的APGDP 是由于辉光放电容易向细丝放电和弧光放电过渡,其解决措施是选择合适的介质板材料、电极间距、电源电压及频率、气体成分等。指出APGDP对化纤聚合物表面改性的效果与聚合物的分子结构、等离子体气体、介质板材料等因素有关,且改性效果具有时效性,要根据聚合物的分子结构选择合适的等离子体。     

辉光放电等离子体辅助碱浸铜冶炼烟灰中铜砷分离

采用辉光放电等离子体辅助Na₂S-NaOH浸取体系对铜冶炼烟灰（简称“烟灰”）进行研究,在放电时间10 min、放电功率500 W、放电压强150 Pa、极板间距0.9 cm的条件下,砷的浸出率为92.52%,铜的浸出率为7.76%,实现了砷和铜的有效分离。采用该方法处理后烟灰中的砷从7.11%降到0.45%,铜从2.62%变为2.42%,为烟灰的进一步利用创造了条件。XPS、XRD和重金属形态分析的综合分析结果表明,辉光能将As（Ⅲ）氧化为As（Ⅴ）、Cu（Ⅰ）氧化为Cu（Ⅱ）,且在碱性条件下As（Ⅴ）比As（Ⅲ）更易浸出。因此,辉光放电预氧化有利于砷和铜在碱浸体系中选择性分离。     

Adhesion enhancement of thin copper film on polyimide modified by oxygen reactive ion beam etching

Polyimide (PI) films were modified by O₂ reactive ion beam etching (RIBE) to enhance the adhesion of subsequently deposited copper films. The adhesion of evaporated copper on the O₂ RIBE-modified PI consisted of three different regimes. The first regime involved chemical reaction between PI and Cu atoms; the second regime involved the mechanical interlocking of the grass-like structure of the modified PI with Cu; and in the third regime, overetching was observed. The locus of failure was also analyzed to understand the adhesion mechanism of Cu on the PI. A 10% decrease in adhesion strength was observed after thermal cycling. Furthermore, humidity tests showed that the adhesion enhancement by mechanical interlocking of the grass-like structure is not affected by the presence of moisture.     

聚酰亚胺薄膜表面无钯活化化学镀铜

为了增加聚酰亚胺薄膜表面与化学镀铜层的结合力,采用NaOH溶液对其表面进行化学改性,然后在其表面制备出具有催化活性的银微粒,进而化学镀铜。使用傅里叶变换衰减全反射红外光谱仪(FTIR-ATR)和能谱分析仪(EDS)对聚酰亚胺的表面结构和组成进行了表征和分析,利用X射线衍射(XRD)及扫描电子显微镜(SEM)表征铜镀层的结构及表面微观形貌。结果表明,聚酰亚胺表面在NaOH溶液中发生水解,在AgNO3溶液中实现Ag+与Na+间的离子交换,Ag+通过化学吸附附着在聚酰亚胺表面。在镀铜液中,Ag+先被甲醛还原成银微粒,从而引发化学镀铜反应的发生,并可获得结合力良好的化学镀铜层。     

Effect of DC glow discharge treatment on the surface energy and surface resistivity of thin film of polypropylene

A change in the surface energy and surface resistivity of a thin film of polypropylene (PP) of thickness 100 μm was investigated, using direct current (DC) glow discharge. The thin film of the PP was treated for various discharge powers and treatment time and the modification in the surface energy and the surface resistivity was observed. To investigate the modification in the surface energy after DC glow discharge treatment, contact angle of two test liquids formamide and de‐ionized water over the surface of PP film was measured. By measuring the contact angle the change in surface energy and its two polar and dispersive components have been measured. It was observed that at a given power level of DC glow discharge surface energy and its polar component increases with increase of the treatment time, attains a maximum value, and then becomes almost constant. Correspondingly, with increase in surface energy, a decrease in surface resistivity was observed. Also, a change in surface morphology was observed by atomic force microscopy and by FT‐IR spectra generation of polar groups at the surface of PP film. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 767–772, 2007     

Effects of environment and heat treatment on an oxygen plasma-treated polyimide surface and its adhesion to a chromium overcoat

—The effects of oxygen plasma treatment time, duration of storage, and heat treatment on the surface chemistry of and Cr adhesion to Dupont RC5878 and Kapton polyimides were investigated using X-ray photoelectron spectroscopy (XPS), and contact angle and peel strength measurements. The XPS results indicate that the initial stage of plasma treatment involves oxygen adsorption with insignificant modification of the surface chemistry. After 5 s of plasma treatment the surface chemistry is modified, as suggested by the changes in the carbonyl and partially oxidized carbon functional groups' contributions to the C(1s) line shape. These modifications resulted in an increase in the peel strength and a decrease in the contact angle of water. Over the first month of storage, the intensity of the carbonyl functional group peak decreased, while the contact angle increased and reached a steady-state value of 30° after 20 days of storage. These changes are mainly attributed to moisture absorption. Importantly, the metal adhesion to polyimide remained fairly constant over the storage period. The aged plasma-treated surface experienced loss of moisture when baked at 150°C for less than 5 min. This was followed by an increase of the partially oxidized carbon at the expense of the plasma-induced carbon-oxygen bonds at higher baking temperatures or longer times.     

Investigation of the locus and mechanism of adhesion failure during peel tests on copper-chromium coated polyimide systems

Auger depth profiling and X-ray photoelectron spectroscopy (XPS) techniques were used to elucidate the adhesion process in copper-chromium coated polyimide. Metal layers were sputter-deposited on polyimide, which was modified by glow discharge under various conditions. The results showed that glow discharge could increase the chromium coverage on polyimide, improve or deteriorate adhesion at various interfaces, and change the locus of adhesion failure. Auger depth profiles could explain the various failure modes by revealing the chemistry at each interface. Additional information was provided by XPS results obtained from surfaces generated by failure. The effects of accelerated aging on this metal-polymer system were also studied.     

Improvement in the adhesion between copper metal and polyimide substrate by plasma polymer deposition of cyano compounds onto polyimide

The surface modification of Kapton film by means of plasma polymer deposition is discussed from the viewpoint of improving the adhesion between copper metal and Kapton film substrate. Plasma polymers of AN (acrylonitrile) and FN (fumaronitrile) were used for the surface modification, and the adhesion between the copper metal and the plasma polymer-coated Kapton film was evaluated by the T-peel strength measurement. The surfaces of peeled layers were analyzed by X-ray photoelectron spectroscopy (XPS) and the failure mode is discussed. The plasma polymer deposition of AN and FN shows an effective improvement in the adhesion between the copper metal and Kapton film; in particular, the AN plasma polymer deposition increased the peel strength 4.3 times. Failure occurred mainly in the Kapton film, and the adhesion between the AN plasma polymer and the Kapton film and that between the copper metal and the AN plasma polymer were found to be quite strong.     

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 characterization and antibacterial activity of chitosan‐grafted poly(ethylene terephthalate) prepared by plasma glow discharge

Poly(ethylene terephthalate) (PET) texture was exposed to oxygen plasma glow discharge to produce peroxides on its surfaces. These peroxides were then used as catalysts for the polymerization of acrylic acid (AA) in order to prepare a PET introduced by a carboxylic acid group (PET‐A). Chitosan and quaternized chitosan (QC) were then coupled with the carboxyl groups on the PET‐A to obtain chitosan‐grafted PET (PET‐A‐C) and QC‐grafted PET (PET‐A‐QC), respectively. These surface‐modified PETs were characterized by attenuated total reflection Fourier transform IR spectroscopy, electron spectroscopy for chemical analysis, and a contact angle goniometer. The amounts of AA, chitosan, and QC grafted on the PET surfaces as determined by the gravimetric method were about 6, 8, and 9 μg/cm², respectively. The antibacterial activity of the surface‐modified PET textures was investigated using a shake flask method. After 6 h of shaking, the growth of bacteria was markedly inhibited by PET with ionically (86% in PET‐A^?‐C⁺) and covalently (75% in PET‐A‐C) grafted chitosan and with covalently grafted QC (83% in PET‐A‐QC). After the laundering the inhibition of the growth of the bacteria was maintained in the range of 48–58%, showing the fastness of the chitosan‐grafted PET textures against laundering. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 2769–2778, 2001     

化工库的温度湿度自动测试

本文介绍一种检测化工库温度、湿度的自动检测系统原理,并给出硬件结构框图和软件流程图。     

An XPS study of argon ion beam and oxygen RIE modified BPDA-PDA polyimide as related to adhesion

Modification of polymer surfaces by changing the chemical structure, surface energy, and bonding characteristics has considerable technological importance in the area of adhesion. Reactive ion etching (RIE) and ion beam (IB) bombardment were employed to modify the surfaces of fully imidized 3,3',4,4'-biphenyl tetracarboxylic acid dianhydride-p-diaminophenyl (BPDA-PDA)-based polyimide (PI) films. These modification techniques affect only a shallow surface region, approximately 10-20 nm, and the bulk properties of the polymer are unaffected. The angle-resolved X-ray photoelectron spectroscopy (XPS) technique was used to characterize the PI surfaces modified by argon IB bombardment or oxygen RIE treatment. On the argon ion-bombarded surfaces, the XPS spectra indicate that the carbonyl and imide groups are decreased. Oxygen RIE treatment resulted in an increase in the atomic concentration of oxygen. To understand the surface aging effect, the freshly modified PI surfaces were exposed to laboratory air for 1 and 2 days. The changes in composition as a function of the depth of the modified surface region right after treatment and after aging were determined by the angle-resolved XPS technique (ARXPS). Contact angle measurements were used to determine the polar and dispersion components, the sum of which is the surface free energy. The polar component of the surface free energy shows the greatest change, with an increase of 8.0-9.4 times for both the oxygen RIE and ion beam treatments as compared with the as-cured PI surface. Aging of these modified surfaces resulted in a decrease of surface free energy as compared with the just-modified surfaces. In the case of oxygen RIE treatment, the dispersion component of the surface free energy showed little or no change from the as-cured sample. Adhesion of chromium/copper/chromium (Cr/Cu/Cr) films on PI was determined by peel strength measurements. Significant increases in peel strength, by a factor of 10-80, were shown for the modified surfaces. A good correlation between the peel strength and the experimentally determined polar component of surface energy was shown.     

Influence of "glow discharge plasma" as an external stimulus on the self-assembly, morphology and binding affinity of gold nanoparticle-streptavidin conjugates

In this study, we investigate the influence of glow discharge plasma (GDP) on the self-assembly, morphology and binding affinity of streptavidin coated gold nanoparticles (Au-NP-SV) and biotinylated antibody (bAb) adsorbed on a highly oriented pyrolytic graphite (HOPG) substrate. Atomic force microscope (AFM) was used to image the pre- and post-GDP treated samples. The analysis of the AFM images showed a considerable change in the aggregation and morphology of Au-NP-conjugates after treatment with GDP. To our knowledge, this is the first report on using GDP to enhance and speed-up the aggregation (sintering) of adsorbed NP biomolecular conjugates. These results show a promising route that could be generalized for other NPs and their conjugates. It can also be considered as an alternative and cheap aggregation method for controlling the binding affinity of biomolecular species on different surfaces with interesting applications.     

Surface characterization of 8‐quinolinyl acrylate‐grafted poly(ethylene terephthalate) prepared by plasma glow discharge and it's antibacterial activity

Poly(ethylene terephthalate) (PET) film was exposed to oxygen plasma glow discharge to produce peroxides on its surface. These peroxides were then used as catalysts for the polymerization of 8‐quinolinyl acrylate (QA) to prepare the PET grafted with QA (PET‐Q). The surface‐modified PET was characterized by attenuated total reflection Fourier transform infrared spectroscopy (ATR‐FTIR) and X‐ray photoelectron spectroscopy (XPS). The introduction of QA to the PET surface was confirmed by observing the presence of nitrogen in the XPS survey scan and high‐resolution spectra. The amount of QA grafted on to the PET surface as measured by the gravimetric method was about 5.2 μg cm^?2. The antibacterial activity of the surface‐modified PET texture was investigated by using a shake‐flask and an inhibition zone test method. After 6 h of shaking, the PET grafted with QA showed the inhibition (91%) of the growth of the gram‐positive microorganism, S. aureus. Even after laundering ten times, an effectiveness of the inhibition was found. However, little inhibition was shown with the gram‐negative microorganism, K. pneumoniae. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 863–868, 2006     

Surface modification of HDPE and PP by mechanical polishing and DC glow discharge and their adhesive joining to steel

To improve the strengths of the adhesive joints of high density polyethylene (HDPE) and polypropylene (PP) to steel, the surfaces of HDPE and PP sheets have been treated by DC glow discharge to increase the polar component of surface energy significantly. Present study investigates the effect of mechanical polishing prior to surface modification of substrates of HDPE and PP sheets by exposure to DC glow discharge, on the surface energy and their adhesive joint strength to steel. The mechanical polishing has been carried out by abrading with 120, 220, 400, 600, 800, and 1000 grade emery paper of grit sizes 8.33, 4.54, 2.5, 1.67, 1.2, and 1 micron, respectively. The surface energy of a given surface has been evaluated by measuring contact angles of sessile drops of two test liquids of known surface tension components, such as deionized water and formamide. It is observed that 800‐grade emery paper of grit size 1.2 micron has been found most effective in terms of their reduction in contact angles and enhancement of their surface energies. The change in surface energy due to surface modification has also been evaluated by measuring the surface energies of unpolished sheets exposed to DC glow discharge. The surface modification of the polymers by glow discharge for 120 s at a power level of 13 W decreases the contact angle more on mechanically polished specimens than that observed on unpolished sheets. Due to glow discharge treatment, the polar component of surface energy increases significantly in HDPE and PP, especially when they are mechanically polished (800 grade) prior to glow discharge. However, in case of the HDPE sheets, the effect of glow discharge on the polar component of surface energy is significantly higher compared to that for dispersion component of surface energy, whereas the polar component of surface energy of the PP sheet is lower than the dispersion component of surface energy. But in both the cases, mechanical polishing prior to glow discharge appears to affect the polar component of surface energy. Mechanical polishing of the HDPE and PP sheets by abrading with 800‐grade emery paper prior to glow discharge treatment, increases the adhesive joint strengths over those observed in case of unpolished polymers exposed to glow discharge. However, the use of prior mechanical polishing increases the joint strength only by a little more than 10% compared to a five to seven times increase in strength observed as a consequence of exposure to glow discharge of as received samples. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 1140–1149, 2001     

Correlating the adhesion of an acrylic coating to the physico-mechanical behavior of a polypropylene substrate

In this study, the adhesion strength of an acrylic coating onto a polypropylene (PP) based substrate was studied. The adhesion strength of the PP containing various wt% of oxidized wax was found to be dependent on the surface free energy of the substrate. To this end, the geometric mean and the acid-base approaches were used to estimate the surface free energy, both of which shown to exist a direct relation between surface hydrophilicity and the content of the oxidized wax. The viscoelastic behavior of the adherend also contributed to the coating adhesion. The viscoelastic response of the blends was investigated using dynamic mechanical thermal analysis (DMTA) and universal testing machine (UTM) for the bulk properties of the substrate and a depth sensing indentation technique for its near-surface, respectively. Bulk and near-surface moduli were decreased as a result of incorporation of wax additive into PP matrix. These were attributed to the homogeneous distribution of low molecular weight wax chains in the polymeric matrix and hence their impact on substrate integrity. The DMTA analysis showed a single phase matrix for all blends. Using a linear trend line, the adhesion test results revealed a good correlation to surface free energy calculations compared with the substrate modulus. The weaker effect of substrate modulus on surface adhesion was ascribed to the substrate plasticity and/or development of internal stresses in the coating layer. However, the glass transition temperature of the coating suggested that the internal stresses in coating layer were responsible to relax prior to conducting adhesion measurement.     

XPS/AFM study of the PET surface modified by oxygen and carbon dioxide plasmas: Al/PET adhesion

The formation of the interface between aluminium and O₂ or CO₂ plasma-modified poly(ethylene terephthalate) (PET) has been investigated by X-ray photoelectron spectroscopy (XPS). As demonstrated by the changes in the C 1s, O 1s, and A1 2p core level spectra upon A1 deposition, the metal was found to react preferentially with the original ester, with the plasma-induced carboxyl and carbonyl groups to form interfacial complexes. The phenyl ring at the modified PET surface was seen to be involved in the formation of the interface, but to a lesser extent. This confirms the high reactivity of the oxygen-containing groups towards the deposited A1 atoms. The adhesion between A1 and the plasma-modified PET films was evaluated by means of a 180° peel test. A considerable (up to ten times) improvement in adhesion was achieved by plasma treatment of the PET substrate, but for either plasma gas the adhesion strength was found to depend strongly on the plasma power and treatment time. The results are discussed in terms of the concentration of oxygen-containing groups at the polymer surface, the surface topography, and the possible presence of low-molecular-weight materials at the metal-polymer interface.