Effect of triethanolamine on deposition rate of electroless copper plating

Abstract

The addition of bis(3-sulphopropyl) disulphide in Cu electroless plating results in Cu superfilling. However, the deposition rate of superfilling copper plating is decreased, which hinders its application for filling Cu into via holes of ultralarge scale integrations. In the present study, the effect of triethanolamine (TEA) on the deposition rate of electroless copper plating was investigated. The deposition rates of electroless plated copper both in traditional and superfilling copper plating were accelerated with an addition of TEA, which was attributed to a decrease in reaction activation energy of a dominant reduction reaction. X-ray diffractometry and atomic force microscopy measurements indicated that with an addition of TEA, the peak intensity ratio /(111)//(200) of electroless plated Cu film was increased and the average surface roughness was decreased.     

Effect of direct current and pulse plating parameters on tin whisker growth from tin electrodeposits on copper and brass substrates

Abstract

Electroplated tin finishes are widely utilised in the electronics industry due to their advantageous properties such as excellent solderability, electrical conductivity and corrosion resistance. However, the spontaneous growth of tin whiskers during service can be highly deleterious, resulting in localised electrical shorting or other harmful effects. The formation of tin whiskers, widely accepted as resulting from the formation of compressive stresses within the electrodeposit, has been responsible for a wide range of equipment failures in consumer products, safety critical industrial and aerospace based applications. The numbers of failures associated with tin whiskers is likely to increase in the future following legislation banning the use of lead in electronics, the latter when alloyed with tin, being an acknowledged tin whisker mitigator. Using a bright tin electroplating bath, the effect of process parameters on the characteristic structure of the deposit has been evaluated for deposition onto both brass and copper substrates. The effect on whisker growth rate of process variables, such as current density and deposit thickness, has been evaluated. In addition, the effect of pulse plating on subsequent whisker growth rates has also been investigated, particularly by varying duty cycle and pulse frequency. Whisker growth has been investigated under both ambient conditions and also using elevated temperature and humidity to accelerate the growth of whiskers. Studies have shown that whisker formation is strongly influenced by pulse plating parameters. Furthermore, increasing both current density and thickness of the deposit reduce whisker growth rates. It is also observed that whisker formation is greatly accelerated on brass substrates compared with copper. The basis for this observation is explained.     

Electroless plating of palladium and copper on polypyrrole films

A novel process for the metallization of polypyrrole (PPY) film surface through consecutive electroless plating of palladium and copper in the complete absence of the SnCl₂ sensitization step was demonstrated. X-ray photoelectron spectroscopy (XPS) technique was used to characterize the polymer surface at each stage of the metallization process. It was found that only the fully reduced PPY film could reduce palladium ions to palladium metal (Pd(0)) in substantial amounts from either the Pd(NO₃)₂ or PdCl₂ acid solution. The palladium metal was necessary for catalyzing the subsequent electroless plating of copper. The reduction of Pd(II) ions in acid solution to Pd(0) on the film surface was accompanied by a simultaneous increase in intrinsic oxidation state and doping level of the film. The copper plating process after the palladium uptake step was highly dependent on the [Pd]/[N] ratio on the film. Through XPS and Auger photoeletron spectroscopy measurements, it was postulated that during the electroless copper plating process, the Cu(II) ions were first reduced to Cu(I) on the PPY film surface before complete reduction to copper metal.     

化学镀锡反应动力学特性研究

目的研究化学镀锡反应过程的动力学特性。方法在硫脲-柠檬酸-酒石酸三元络合体系中,以次磷酸钠为还原剂,以Sn Cl2为主盐,在铜片上化学沉积锡镀层,研究温度、主盐、还原剂、H+和络合剂的浓度对沉积速度的影响规律。结果镀锡过程中,Sn2+,H+和次磷酸钠的反应级数分别为0.302,0.21和0.192;硫脲、柠檬酸和酒石酸的反应级数分别为0.237,0.213和0.081;速度常数为0.013,总反应级数为1.235级,表观活化能为11.184 k J/mol。结论建立了化学镀锡反应的动力学方程,对化学镀锡沉积工艺的选择和产物的控制具有一定的参考作用。     

Electroplating High Aspect Ratio Through Holes in Thick Printed Circuit Boards

Plating small diameter through holes in thick PC boards that utilize SMT poses a difficult technical challenge. The research reported in this paper has optimized the acid copper bath inorganic and additive chemistry to enable these boards to be plated. Boards 5.8 mm thick with 18:1 aspect ratio holes were plated to give a hole:surface thickness ratio of 0.80:1 at a current density of 1.1 A/dm². Levelling and deposit mechanical properties are excellent. Recommendations for PTH electroless and electrolytic plating processes, equipment, and controls to enable successful plating of high aspect ratio through holes are given.     

Al2O3陶瓷表面化学镀铜工艺及其低温连接

进行了Al2O3陶瓷表面的化学镀铜处理,制定了前处理流程.研究了硫酸铜浓度、甲醛浓度、施镀温度、施镀时间等对镀层沉积速率的影响,对镀层进行了金相分析,在此基础上得到化学镀铜的优化工艺.进行了镀铜后Al2O3陶瓷低温钎焊工艺试验,研究了不同化学镀工艺条件对接头组织及力学的影响.结果表明,在试验条件下,随着焊接温度升高,接头致密度变差;焊接时间增加,焊缝宽度也增加;硫酸铜,甲醛浓度增加,镀层厚度增加,相对影响了钎焊焊缝宽度和质量.     

Preparation of Fe–Zn alloy deposits by electroless plating

Abstract

Fe–Zn binary alloys have been deposited by electroless plating. The films were prepared on a copper substrate in contact with an aluminium strip. The effects of the concentration of ligand, reducing agent, pH value, temperature of plating bath and plating time on the deposition rate, and structure and morphology of the films have been studied. A practical electroless plating solution has been developed.     

锡青铜化学镀 Ni-P 合金工艺及镀层性能

目的在锡青铜基体上化学镀Ni-P合金镀层,提高锡青铜的耐磨性和耐腐蚀性。方法以酸性含锌活化液活化锡青铜试样,在相同的条件下实施化学镀,并对镀态试样进行不同温度(250,400,500℃)下的热处理。对比基体、镀态试样和热处理试样的性能,研究热处理温度对锡青铜化学镀Ni-P合金层微观结构、显微硬度、耐磨性和耐腐蚀性的影响。结果锡青铜表面形成了Ni-P合金镀层,并且镀层无孔隙缺陷,与基体结合良好,沉积速率较快,为10.00μm/h。经热处理后,镀层的微观结构由非晶态向晶态转变,在500℃热处理的镀层显微硬度最大,耐磨性最好。镀态镀层和经250℃热处理的镀层在10%HNO3溶液和10%H2SO4溶液(10%均为体积分数)中的耐腐蚀性明显好于锡青铜基体,镀态镀层在两种介质溶液中的腐蚀速率分别为0.225,0.146 mg/(cm2·d)。结论采用酸性含锌活化液活化锡青铜基体,可以在锡青铜表面制备出化学镀Ni-P合金镀层,且镀覆效果较好。这表明紫铜化学镀Ni-P合金工艺同样适用于锡青铜。     

镀铜石墨粉的制备研究

表面镀铜的非金属材料是当前功能材料开发的一个热点.利用化学镀的方法在石墨粉的表面进行化学镀铜,通过对化学镀铜沉积速度和镀层表面形貌进行分析,探讨了如何获得表面包覆良好的镀层.石墨粉表面化学镀铜工艺可以分为表面预处理、化学镀和性能测试三大步骤.研究重点放在化学镀施镀步骤上,对化学镀铜的影响因素进行了研究,得出最佳的镀铜工艺配方,并将此配方应用于实际,得到了色泽光亮、分散性好的石墨镀铜粉.     

Catalytic Activity and Stability of Mixed PdCl2/SnCl2 Catalysts

The catalytic activity and stability of the PdCl₂/SnCl₂ mixed catalyst for electroless copper plating were investigated. Such performances of the mixed catalyst were dependent on the preparation conditions of the stock solution. The mixed catalyst adsorbed on the substrate initially seems to be a water soluble complex or colloidal state. Subsequently, palladium and tin palladium alloy are gradually formed by the oxidation of Sn(II).     

Morphological and Chemical Comparisons of Electroless Nickel and Electroless Copper Film Growth

A detailed study was undertaken on one practical system used in electroless plating of ABS plastics. The macroscopic appearances were examined after short and standard etch times, after catalytic and accelerating steps as well as after electroless copper and nickel plating steps. X-ray Photoelectron Spectroscopy was used to examine the chemical status of the surface during different plating steps and Transmission Electron Microscopy was used to analyze polymer-metal interface dependence on etching conditions. Heterogeneous multilayer structure is a characteristic of these systems. The structural region of interest extends from the bulk polymer to the oxidized polymer interphase, the sorbed tin and palladium, the initial surface reaction product, structures of microscopic islands of electroless metal, to finally the continuous film. Contrasts are shown between electroless nickel and electroless copper deposits.     

A novel electrolyte for the high speed electrodeposition of bright pure tin at elevated temperatures

A new tin electroplating process capable of producing fully bright, pure tin deposits from an electrolyte operated at temperatures of up to 50°C has been developed. Unlike conventional bright tin deposits, the tin deposit from the new process has an increased grain size and low carbon content. In addition, the deposit demonstrates excellent ductility, solderability, and low tendency for whisker growth. Production trials conducted by various industries have proven that the new pure tin deposit is suitable for connector applications, as well as for corrosion protection and decorative uses. In this article, the characteristics of the tin electrolyte and the bright tin deposit are described.Electrodeposition of bright tin, characterized by its silvery-white decorative appearance, excellent solderabilty, conductivity, good corrosion and tarnish resistance, and non-toxic nature, has been widely used in the electronic industry and protective-decorative applications. The industrial importance of tin electrodeposition has been markedly extended with the introduction of lead-free solder in the electronic marketplace. However, certain drawbacks of commonly used bright tin plating processes have limited the acceptance of electrodeposited bright tin. The operation and control of bright tin plating solutions is more difficult compared to that of matte tin processes, since the additive system of conventional bright tin electrolytes usually contains many volatile organic components that act as brightening agents. Because of the volatile nature of the organic brightening agents, a cooling system is usually required in conventional bright tin plating baths, in order to maintain the bath temperature between 20 to 25°C where most brightening agents are effective. For high-speed plating, the use of a cooling system becomes essential since the bath temperature naturally rises rapidly during plating. A key concern with the use of bright tin in certain applications is the relatively low ductility often associated with bright deposits and the reportedly higher tendency towards tin whisker growth compared to matte deposits. For demanding automotive applications, where the use of bright tin-lead has been permitted for a limited period of time, continuing efforts are being made by both the electronics industry and suppliers of plating chemistry to replace bright tin-lead with bright pure tin. Tin whisker performance has become one of the most critical characteristics in qualification of any bright pure tin plating process for use in the electronics industry.The newly developed plating bath, SOLDERON? BHT-350 bright tin, has been designed to be operated at temperatures between room temperature and 50°C, while producing ductile, bright deposits with low whisker growth tendency. Production trials conducted by different industries have demonstrated that the new process is able to produce bright tin deposits under high speed reel-to-reel plating conditions, and the simple additive system facilitates automatic or manual dosing during operation. The resulting bright tin deposits are suitable for connectors, contacts, wire and other items requiring a bright tin finish. In this article, the characteristics of the electrolyte and the properties of the bright tin deposit, including microstructure, carbon content, ductility, texture, solderability and whisker performance are described in detail.     

MN型亮铜故障的两种大处理方法

在镀液里积累了 2 -巯基苯并咪唑 (简称 M)会造成亮铜镀层表面麻砂现象。为排除此故障 ,比较了双氧水 -活性碳处理方法和高锰酸钾处理方法 ,后一种方法大大简化了处理过程 ,缩短了处理周期。     

Electrodeposition of Tin Alloys from Alkaline Stannate Baths

The paper reports on a small development programme designed to concentrate on devising a relatively simple technique for the deposition of copper only in drilled holes of a conventionally produced printed wiring board. It is essential to start with a laminate containing catalysed resin base, producing the printed wiring pattern in the normal manner and plating up holes using autocatalytic electroless copper. Thickness measurements and microsections of electroless copper deposits have been obtained and appear to be encouraging.     

Optimisation of the Quality of Plated Through-holes in Printed Circuit Boards

The quality of electroless copper deposition is of fundamental importance to the final quality of through-hole plated printed circuit boards. Two of the major factors which determine electroless copper quality are through-hole coverage and adhesion.

Two-level fractional factorial experimentation has been used to determine the effects of process variables on electroless copper deposition onto the drilled surfaces of PCB's. The experimental design has been augmented to study quadratic relationships. Regression analysis has been used to estimate the precise relationship between the variables and their effect on through-hole coverage and adhesion. Using these relationships working ranges are established which will maximise through-hole quality.

A colloidal copper activation system has been used throughout and pre-cleaning in alkaline potassium permanganate was an integral part of the process.     

A method for polyaniline coatings on solid polystyrene surfaces and electroless copper deposition

A new efficient method is presented for electroless copper deposition on solid polystyrene surfaces via polyaniline (PANI) coatings. It was demonstrated that, partial polymerization of aniline by catalytic air oxidation in the presence of dissolved polystyrene (PS) (M_n: 87.000 K) gives viscous solution of PANI-PS mixture in aniline. Direct application of the polymerization mixture with copper catalyst onto polystyrene sheets (5 × 15 cm) resulted in extension of the polymerization by air oxygen to give a smooth PANI-PS composite layer on the host surface. Treatment of the surface with a similar PANI solution without PS gave Emeraldine base film with homogenously dispersed copper. Reduction of the surface copper by diluted hydrazine (5%) yielded zero-valent copper serving as seed points for accumulation of more copper from an electroless plating solution in the following process. Experiments showed that, the method presented offers a simple pathway to produce excellent copper deposits on PS substrate. This method is superior to traditional electroless plating process, since tedious surface etching and expensive palladium activation steps are being avoided. The surface characteristics were examined by X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), adhesion tests and contact angle measurements. The results showed that, the electroless plating process gives a homogeneous and highly robust copper layer with 34.2 μm of thickness within 48 h. Adhesion of the copper layer to the underlining surface was satisfactory as inferred from pull-off measurements (1.6 N/mm²).     

Copper patterned polystyrene panels by reducing of surface bound Cu (II)-sulfonyl hydrazide complex

A modified electroless metal deposition method has been developed for copper plating of polystyrene (PS) surfaces. The modified procedure avoids the plasma conditioning and surface activation steps in the classical electroless metal plating process.First step of the present procedure is chlorosulfonation of PS surface by soaking into chlorosulfonic acid, yielding chlorosulfonated surface with density of 0.046-0.110 mmolcm^− 2 depending on contact time (10-60 min).In the second step chlorosulfone groups on the surface are converted to sulfonyl hydrazides almost quantitatively by reaction with hydrazine solution (80%). Green Cu (II)-sulfonylhydrazide complex is formed at the surface, in the third step, by interaction with ammoniacle Cu (II) solution at room temperature. The copper in the complex is reduced rapidly in the fourth step, by immersing the specimen into 5% of hydrazine solution. The elemental copper deposited onto the surface serves activating sites to accumulate more (5-7 mg per cm²) elemental copper from electroless copper solutions in the final step. The present method avoids the surface activation with palladium and allows preparing copper patterns with reasonably high pull-off strengths (3.77 Nmm^− 2) on PS panels.In the study the copper deposition has been investigated using standard analytical procedures, X-ray photoelectron spectrometry (XPS) and Scanning Electron Microscopy.     

氧化铝陶瓷基板化学镀铜工艺优化

目的化学镀铜是氧化铝陶瓷基板金属化的一种重要手段,为了进一步优化氧化铝陶瓷基板化学镀铜工艺,研究了化学镀铜液配比(尤其是镀液中铜离子和甲醛含量)对氧化铝陶瓷覆铜板微结构和导电性的影响。方法在对氧化铝陶瓷基板经过前期处理后,采用化学镀铜法在基板上镀铜。采用X射线衍射仪、光学显微镜对氧化铝基板上的化学镀铜层物相和形貌进行观察。采用覆层测厚仪、四探针测试仪对化学铜镀层的膜厚和方阻进行测量。结果 XRD结果表明,不同配比镀液得到的化学镀铜层均具有较好的晶化程度,镀液中甲醛和铜含量较低的镀液可制备出晶粒更为细小的化学镀铜层。甲醛和铜离子含量均较高时,沉积速度过快,使镀铜层的均匀性和致密性不佳。但当甲醛含量较高、铜离子含量较低时,沉积速度适中,从而获得了均匀性和致密性较好的镀铜层,同时这种镀层具有良好的导电性。结论采用表面活性化学镀铜工艺,当镀液中甲醛浓度为0.25 mol/L和硫酸铜质量浓度为1.2 g/L时,无需高温热处理,即获得了均匀性和致密性俱佳的铜镀层,可满足覆铜板的使用要求。     

化学镀镍作为钢酸性镀铜前处理工艺的应用研究

为了防止钢表面酸性电镀铜出现置换铜,采取在电镀铜前增加化学镀镍工序,研究了化学镀镍工艺对酸性电镀铜的影响。结果表明,化学镀镍时间超过6 min时(镍层厚度>2.5～3μm),工件在酸性镀铜液中浸泡10 min,无置换铜出现。化学镀镍层对后续的酸性镀铜层的表面形貌和附着力均无明显影响,表明化学镀镍可作为钢酸性镀铜的底层。     

Investigation of electroless copper plating on polyurethane foam,as an initial step of open cell foam production process

Abstract

Coating of polymeric foams is known as a method for production of metallic foams, which produces foams with high volume of porosity and controllable pore size. In this research, this method was employed to produce open cell copper foam by use of polyurethane foam with an average pore size of 0.4?mm as the substrate. Since polyurethane foam as a non-conductive material is not able to be coated directly by electrolytic deposition, the substrate was initially metallised by electroless copper plating. In the electroless plating process, the effects of the main parameters such as bath chemical composition, solution pH and temperature on deposition rate and thickness of the coatings obtained were investigated. The results showed that the optimum condition of the process is obtained when CuSO₄ concentration in the deposition bath is 12?g?L^??1, pH is 13 and plating temperature range is 55–60°C.