On the modeling of shape evolution in through-mask electrochemical micromachining of complex patterned substrates

This study is about the optimization of the shape evolution of a printed circuit board (PCB) by means of an auxiliary electrode. Predicting the shape evolution of such complex workpieces calls for a significant reduction of the nodal points in discretization. The authors applied a hierarchic modeling strategy, which breaks the overall problem into three spatial scales: the macroscopic, the mesoscopic and the microscopic scale. Simulations on each scale are performed by considering influences from the other scales in a simplified way. The strategy yields the shape evolution of any chosen trench of the workpiece and allows for the consideration of an auxiliary electrode. The auxiliary electrode was optimized in terms of its geometry and potential. The uniformity of the etch rate was governed by an interplay of different extrema caused by the complex patterning of the workpiece. This interplay was cleared up by investigating the current density of each extremum as a function of the parameters.     

Local etching of copper films by the Scanning Electrochemical Microscope in the feedback mode: A theoretical and experimental investigation

A model of the Scanning Electrochemical Microscope (SECM) as a lithographic tool is presented and used to get quantitative kinetic information from lithographic experiments. It is illustrated in the specific case of the local etching by anodic dissolution of a copper substrate by the SECM in the feedback mode. A theoretical model presents the expected profile of the etched hole in the simple case of the positive feedback behaviour. A steady-state behaviour is expected for the dimensionless shape of the hole, which depends only on the tip-substrate separation distance. The hole depth is then expected to linearly depend on the etching time. The model is then confronted to different experimental conditions where a Cu substrate is locally oxidized by a tip-electrogenerated Fe(bpy)₃³⁺ oxidant. The experiments agree with the theoretical predictions (steady-state dimensionless profile and linear evolution of the depth with time). Even though the system behaves under positive feedback, the kinetics of the etching process can readily be extracted from the hole characterization and its conversion into Faradaic yield.     

Activation of Ag/Pd triangular nanoshells with different sizes on depositing electrolessly copper

Ag/Pd triangular nanoshells of different sizes are prepared for catalyzing electroless copper deposition. As supported by the analysis of quartz crystal microbalance and mixed potential theory, the alloy nanoshells can be successfully used as new activators and have the excellent activity for electroless copper bath. For a comparison of deposition rates with a system of triangular Ag/Pd nanoshells, the large Ag/Pd nanoshell is found to have the maximum activity toward electroless bath.     

Cementation-induced recovery of self-assembled ultrafine copper powders from spent etching solutions of printed circuit boards

Ultrafine copper powders have been recovered from spent etching solutions of printed circuit boards by cementation on helical-form iron scrap chips. The tested solution is an ammoniacal copper solution containing 135 g/l copper with minor impurities. The influences of contact time, temperature, pH, initial copper concentration and Fe stoichiometry on the yield, purity and grain size and shape of the precipitated copper powders were studied. Ultrafine self-assembled copper nanocubes with high purity of about > 99% was obtained at temperature 25 °C, time 20 min, pH 2, Fe stoichiometry 1X and initial copper concentration 20 g/l Cu. It was proposed that the precipitation of copper from the solution involved two main processes: (1) adsorption of copper ions on the surface of the iron chips due to the iron oxides present on it and (2) cementation of copper ions onto the metallic iron contained in the chips. Scrap iron chips is seen to be an effective material for copper powder recovery from spent etching solutions in a pure and fine form.     

Catalytic characterization of hollow silver/palladium nanoparticles synthesized by a displacement reaction

Hollow Ag/Pd nanoparticles have been successfully prepared by a galvanic displacement reaction, in which a small amount of Pd(NO₃)₂ is allowed to react with previously synthesized Ag nanoparticles that act as templates. The resulting hollow Ag/Pd (Ag/Pd_hollow) nanoparticles are found to be icosahedral and decahedral in structure. The kinetics of electroless copper deposition (ECD) catalyzed by these bimetallic (Ag/Pd_hollow) nanoparticles are analyzed using an electrochemical quartz crystal microbalance (EQCM). The results reveal that these Ag/Pd_hollow nanoparticles have better catalytic activities than monometallic Ag and Pd nanoparticles. Furthermore, the catalytic activities of these hollow nanoparticles in the ECD bath can be controlled by tuning their alloy ratios in a suitable manner.     

D890树脂处理线路板厂低浓度硝基氮废水

针对印制线路板(PCB)厂蚀刻、板面电镀、表面处理3工段产生的低浓度硝基氮废水,采用离子交换新技术,用D890树脂处理,可完全去除废水中NO3-。探究了D890树脂对NO3-吸附的穿透曲线、交换容量、SO24-和pH值对交换容量的影响、再生液洗脱效果并分析了本研究的工业应用和展望,为PCB线路板厂废水总氮达标提供新思路。     

Recovery of nickel powder from copper bleed electrolyte of an Indian copper smelter by electrolysis

When nickel concentration increases in the copper sulphate electrolyte during electrolysis, it starts electrodepositing on the copper cathode thereby affecting the purity of the copper. In order to produce high quality copper cathodes with less than 1 ppm Ni, it became necessary to bleed-off large volumes of foul electrolyte contaminated with nickel and other impurities. The study reported in this paper was part of the effort aimed at devising a cost effective and an ecofriendly method for the production of value added powders from a waste stream, for P/M application. A part of copper salts and regenerated acid was used back into the system. As discussed in our paper on copper recovery from copper bleed stream (CBS), a process involving decopperisation and crystallisation-solvent extraction (SX) separation-electrowinning (EW) has been attempted as an alternative to the conventional process. Optimum conditions for nickel recovery from this type of solution have been investigated through a series of experiments carried out in a rectangular electrolytic bath with SS as cathode and Pb-Sb as anode. A quantitative and selective recovery was found for nickel deposition under suitable conditions. The purity of the electrolytic nickel powders so produced was found to be 99.89%. The compact density of the annealed nickel powder was 7.72 g/cc. Other properties of the nickel powders such as flow-ability, particle size, etc. were also evaluated to assess its suitability for its use in P/M applications.     

Protection of copper corrosion by modification of dodecanethiol self-assembled monolayers prepared in aqueous micellar solution

A novel method of preparing 1-dodecanethiol (DT) self-assembled monolayers (SAMs) on copper in aqueous micellar solution is explored. The resulting SAMs are characterized by XPS, contact angle tests and electrochemical measurements. It is found that DT dissolved in aqueous micellar solution can adsorb rapidly to the copper surface through strong thiolate bonds to form well-organized SAMs, which have properties comparable to those formed in ethanol solution. The electrochemical measurements show that the inhibition efficiency (IE) increases with an increase in the immersion time of copper in the aqueous micellar solution. After self-assembly for 1 h, the SAMs are able to effectively protect the underlying copper against corrosion in chloride-containing solution by hindering the cathodic process. Overall, the inhibition efficiency can reach 98.94%.     

不同还原体系银油墨打印对聚酰亚胺基板化学镀铜制备印制电路板的影响

先在普通打印机上用活化导电银油墨将线路图打印在聚酰亚胺(PI)基板上,固化后再化学镀铜制得印制电路板(PCB)。研究了导电银油墨的还原剂对不同体系镀液化学镀铜层厚度、导电性、结合力和抗氧化性的影响。结果表明,油墨的还原剂相同时,甲醛体系化学镀铜层的综合性能优于乙醛酸镀液。导电银油墨的最佳还原剂为丙酸,即油墨的最佳配方为:丙酸0.5 mol/L,Ag NO3 0.5 mol/L,10%(质量分数)OP乳化剂适量。采用0.5 mol/L丙酸油墨–甲醛镀液体系制得厚度为3.10μm的铜镀层,其抗氧化时间为44 s,电阻率为1.00×10-7?·m,与PI基板间的结合力良好,综合性能最佳。     

The shape evolution of TiCx prepared by mechanical alloying of Ti-Al-C system after HF treatment

This work has investigated the shape evolution of the TiC particles after immersion in the hydrofluoric acid (HF) solutions at different times. The TiC particles were prepared by mechanical alloying of the Ti-Al-C system. The field-emission scanning electron microscopy (FESEM) and X-ray diffraction (XRD) patterns were used to study the phase and morphological evolution of the powders. In addition, the changes in the chemical composition of the solutions were investigated by atomic absorption spectroscopy (AAS). However, the relative intensity, X-ray diffraction full width at half maximum (FWHM) value and the position of the peaks were significantly changed after HF treatment. Results showed that the only detected phase in the XRD patterns of HF-treated samples was TiC. However, there were significant differences between the peaks of the XRD patterns. The results showed that the relative intensity of the (111) planes increased as a function of the immersion time up to 48?h. Moreover, the FWHM values of the peaks revealed that a recrystallization phenomenon occurred for TiC particles after immersion into the HF solutions. The FESEM observations demonstrated that with increasing the time of HF treatment the shape of TiC particles changed from near-spherical to the octahedron and finally cubic morphology.     

Selective steam reforming of methanol over silica-supported copper catalyst prepared by sol–gel method

Silica-supported copper prepared by a sol–gel method can selectively catalyze methanol steam reforming to hydrogen and carbon dioxide at 250 °C. The catalytic activity increases with the copper content up to 40 wt.%. The selectivity to carbon monoxide with the catalysts containing 20–40 wt.% of copper is significantly lower than that with a commercial Cu/ZnO/Al₂O₃ catalyst. Copper particles are highly dispersed in the catalyst whose Cu content is 20 wt.% or less. After the reaction at 250 °C the particles are present as Cu₂O with the mean crystallite size less than 4 nm. In the catalyst with the Cu content of 30–50 wt.%, the fine Cu₂O particles coexist with large metallic Cu particles whose mean crystallite size is 30–40 nm after the reaction. The large metallic particles are supposed to contribute to the reaction as well as the fine Cu₂O particles although the surface area is estimated to be significantly smaller than that of the latter.     

Effects of (NH4)2SO4 and BTA on the nanostructure of copper foam prepared by electrodeposition

Copper foam with dendritic copper nanostructure was synthesized by an electrodeposition process using hydrogen bubbles as dynamic templates. To modify the morphology of the copper nanostructure in the foam walls, (NH₄)₂SO₄ and BTA (benzotriazole) were introduced into the electrolytic bath as chemical additives, and their influences on the morphologies and the structural characteristics of copper deposits were examined by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The mechanical strength and stiffness of the copper foam were evaluated by the compression test. The corncob-like deposits of the copper foam were changed to needle-like nanodendrites by the addition of (NH₄)₂SO₄, which significantly improved the mechanical strength and stiffness due to the self-supporting effects of the tightly interlocked needle-like nanodendrites. In contrast, the copper foam prepared from the solution with (NH₄)₂SO₄ and BTA shows high ductility but low mechanical strength due to the formation to grape-like copper deposits. Both the copper foams exhibited higher mechanical properties than the one with corncob-like deposits formed in the additive-free solution. The reaction mechanism of (NH₄)₂SO₄ and BTA on the nanostructure of the copper foam at high cathodic current density was clarified by analyzing the effects of the additives on the copper deposition reaction and hydrogen gas evolution reaction, respectively.     

Synthesis, characterization and electrochemical properties of copper phosphide (Cu3P) thick films prepared by solid-state reaction at low temperature: a probable anode for lithium ion batteries

Copper phosphide (Cu₃P) was produced as thick films over copper foils. The synthesis was performed by solid-state reaction at low temperature (400 °C). Similar attempts were carried out for other transition metals of the first series without success. Scanning electron microscopy (SEM) revealed the formation mechanism of the Cu₃P thick films. First, phosphorus diffuses into the copper foil followed by the subsequent formation of the binary compound. During this process, the Cu₃P particles seem to dig the copper foil, producing holes, where the Cu₃P crystallites nucleate and growth. Then, the thick films are formed by the conjugation of several agglomerates and their morphology is not homogeneous. Oxidation of Cu₃P occurs to a small extend on the top surface of the films. The electrochemical behaviour of the thick film was compared with a standard Cu₃P composite electrode, in which the active material is mixed with carbon and a binder. Although the two different electrodes presented some differences in their electrochemical behaviour, both electrodes showed promising qualities to be used as anode materials in lithium ion batteries or hybrid devices.