Electroless Plating Bath Research Articles

Adhesion between Flat Copper Surfaces and Epoxy Insulation Resin without Roughening.

Adhesion strength between flat copper and epoxy resin was studied by forming sulfur codeposited copper films or sulfide films on the flat copper surface, with the following results:1. Copper films from an electroless coper plating bath with sodium sulfide strongly adhered to epoxy resin. Adhesion strength was particularly improved by adding over 100ppm sodium sulfide tothe plating bath.2. The formation of sulfide films on the copper surface using sodium sulfide solution also effectively improved adhesion. Triazine dithiole treatment also showed a similar effect.

EQCM study of the effect of ligands on the rate of CuII reduction by formaldehyde

An increase in the stability of copper(II) complexes (ligands: HEDTA, EDTA, DTPA, CDTA, TTHA) has been found to decrease their cathodic reduction rate in most cases, with considerable specific effects with some ligands (DTPA, CDTA). Similar dependences of the Cu deposition kinetics on CuII complex stability were also found for the electroless Cu plating process at open-circuit potential. A potential dependence of the CuII reduction partial current on the electrode potential has been extracted from the EQCM data in the complete electroless plating bath. An increase in CuII reduction rate has been found to occur in electroless plating solution compared with that in formaldehyde-free solutions. Possible reasons for the acceleration of the partial CuII reduction reaction and the overall process kinetics are discussed using a reaction sequence involving intermediate copper oxy-species and active Cu* formation as well as development of the preferred Cu surface structure.

Method of monitoring constituents in electroless plating baths

Method of monitoring constituents in electroless plating baths

Electroless plating bath for forming black coatings

Electroless plating bath for forming black coatings

Study of the role of sodium hypophosphite in electroless nickel bath solution

Cyclic voltametric investigations have been made to understand the electrochemical behaviour of sodium hypophosphite in electroless plating bath solution. The possible reaction steps at the anode and cathode have been identified. An ECE type of mechanism appears to be operative in the overall reaction during electroless plating. Both organic and inorganic species in the bath solution influence the voltammetric pattern of the hypophosphite. Temperature enhances the peak currents and changes the reaction mechanism. The oxidation potentials of the reaction steps vary with temperature and also the presence of organic components in the both solution.

Electrochemical Study of the Gold Thiosulfate Reduction

The electrochemical reduction of gold thiosulfate has been studied and compared to the reduction of gold cyanide. Gold thiosulfate is a potential replacement for gold cyanide in electro and electroless plating baths. Gold thiosulfate has a more positive reduction potential than gold cyanide and eliminates the use of cyanide. The standard heterogeneous rate constant, transfer coefficient, and diffusion coefficient for gold thiosulfate reduction were found to be , 0.23 and , respectively. The effect of sulfite as an additive to gold thiosulfate solutions was examined.

表面処理とリサイクル 無電解めっき浴の長寿命化技術

表面処理とリサイクル 無電解めっき浴の長寿命化技術

Selective electroless copper metallization on a titanium nitride barrier layer

Electroless copper plating is demonstrated as a novel low temperature, selective technique for metallization of TiN. The properties of the as-deposited copper from two electroless plating baths of different composition were examined. It was found that the as-deposited Cu layer (0.50 μm) from a commercial bath, containing high amounts of Na and K, had a resistivity of ∼2.70 μΩ cm, and the as-deposited Cu layer (0.50 μm) from a research bath with low mobile ion levels had a lower resistivity of ∼2.20 μΩ cm. The topography of both deposits was examined using SEM (Scanning Electron Microscopy) and AFM (Atomic Force Microscopy). ICP (Inductively Coupled Plasma) and SIMS (Secondary Ion Mass Spectrometry) techniques were used to examine the contaminant levels in the plating solutions and in the Cu surface, respectively. The uniformity of the Cu layer on TiN was also examined for both the commercial and research systems and it was found that the uniformity of sheet resistance was better when the commercial plating bath was used to deposit Cu, at an average value of ∼4% as compared to the average value of ∼35% for the research bath. This improvement in deposit uniformity could be due to the greater amount of stabilisers and additives included in the composition of the commercial solution.

無電解ニッケルめっきによる異方性導電微粒子の作製

Demand for mechanical solderless chip connection methods using anisotropic conductive particles has increased in the field of electronic devises. In this study, the preparation of conductive resin particles (5 to 10μm in diameter) by electroless nickel plating and the surface morphology of nickel film were investigated. Since the surface area of particles are much larger than in a bulk substrate, a batch-type electroless plating bath is unstable. Therefore, we applied the continuous dropping method to improve the stability of the Electroless nickel plating. The surface morphology of the deposited nickel was greatly influenced by the complexing agent used, the bath temperatrue and solution pH. Uniform deposits on the particles were obtained at pH 5 by using ammonium acetate as the complexing agent. In contrast, extraneous deposits were recognized at pH 5 when using sodium tartrate as the complexing agent and in baths at pH6. This extraneous deposition could be decreased by lowering the bath temperature.

Treatment of chelated iron and copper wastes by chemical oxidation

Abstract Chelating agents are used commonly to remove deposits from surfaces of industrial equipment and to solubilize metals in electroless plating baths. The destruction of chelate (Ethylenediaminetetraacetic acid, EDTA) in chemical cleaning wastes using hydrogen peroxide and/or ozone as oxidants is described. The experiments were conducted in a batch reactor using simulated wastes containing elevated levels of iron, copper, and EDTA. With hydrogen peroxide as the oxidant, the pH, hydrogen peroxide dose, temperature, and initial composition of the solvent had the greatest effects on chelate destruction. A pH between 4 and 5, a 20:1 molar ratio of hydrogen peroxide to EDTA and a temperature of 40–60 °C consistently produced >95% destruction of the chelate. For ozone, EDTA removal was more dependent on the initial iron and EDTA concentrations than on the pH or ozone flowrate. Overall, hydrogen peroxide alone at above ambient temperatures was judged to be the most effective oxidant for destroying chelates ...

ChemInform Abstract: Pattern Formation of Cu Layer by Photocatalytic Reaction of ZnO Thin Film.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Pattern Formation of Cu Layer by Photocatalytic Reaction of ZnO Thin Film

A new, fully additive‐based, electroless plating process for the formation of fine Cu patterns without using a conventional photoresist has been developed which utilizes a photocatalytic reaction on thin films prepared on ceramic substrates for printed circuit boards. The layer serves both as an adhesive layer and as a photosensitive layer. The Cu patterns could be easily fabricated in an electroless Cu plating bath after Pd nuclei, which act as catalytic sites for the electroless plating, were patterned via an area‐selective photocatalytic reaction. This was achieved by adsorbing Pd(II) onto the surface and selectively exposing the surface with UV light through a photomask. The unexposed regions can be freed of Pd(II) using ethylenediamine, which can form a stable complex with Pd(II). Cu patterns 17 μm wide, with adhesion strengths suitable for practical use, have been achieved on alumina substrates with this electroless plating method.

Area selective deposition of gold on silicon surface patterned by tip-induced anodization in scanning probe microcopy

The difference in chemical reactivity between silicon (Si) and anodic oxide surfaces was used to fabricate gold (Au) nanostructures. By means of scanning tunneling microscope tip-induced anodization, a Si surface terminated with hydrogen (Si–H) was patterned with the anodic oxide. Subsequently, the patterned sample was treated in an electroless plating bath to deposit Au on it. Using a scanning electron microscope, an energy dispersion x-ray spectroscope, and an atomic force microscope, we confirmed that the Au deposition selectively occurred on the Si–H surface where it was not anodized. The anodic oxide surface served as a mask to prevent Au deposition. Au lines of less than 200 nm in width could be fabricated on the Si–H surface.

Reaction Mechanism of Electroless Metal Deposition Using ZnO Thin Film (I): Process of Catalyst Formation

The reaction mechanism of electroless metal deposition proceeding selectively on a thin film coated on a glass substrate was investigated by x‐ray diffraction, x‐ray photoelectron spectroscopy, and inductively coupled plasma measurements. The thin film was activated for electroless metal deposition just by immersion in solution adjusted to pH 2.5. In this process, Pd(II) was selectively adsorbed on the thin film while simultaneously the underwent dissolution. The dissolution of thin film easily occurred on the (002) face with polarity. The strongly adsorbed Pd(II) was reduced to Pd(0) by a reducing agent in the electroless plating bath and this served as a catalyst center. As a result, metal layers were obtained selectively on the thin film in the electroless plating bath.

‘One-pot’ electrochemical determination of copper and formaldehyde in electroless copper plating baths

A simple electrochemical method has been developed for the determination of copper and formaldehyde concentrations in electroless copper plating baths. This method uses dc amperometry and anodic stripping voltammetry for the determination of formaldehyde and copper concentrations, respectively. The analyses are done sequentially using a single gold electrode in the same sample solution. The advantages of this ‘one-pot’ technique are simplicity and speed of analysis, important advantages over alternative methods of analysis which are either more time consuming, involve multiple samples, or use more elaborate instrumentation. A commercial plating bath was analysed using the described technique, yielding results which had a precision of within 5% for formaldehyde and copper. While not rigorously precise, this method can be used in process control to indicate when bath replenishment or replacement is necessary. The method can easily be implemented in plating facilities by operators using portable equipment, and an automated, on-line procedure is also possible.

Proximal probe study of self-assembled monolayer resist materials

A scanning tunneling microscope (STM) has been used to investigate organosilane self-assembled monolayer films (SAMs) as imaging layers for low voltage e-beam lithography. We have studied three different SAMs [(aminoethylaminomethyl)phenethyltrimethoxysilane (PEDA), 4-chloromethylphenyltrichlorosilane (CMPTS), and n-octadecyltrichlorosilane (OTS)] deposited on the native oxide of Si. We have found OTS to act as a positive resist in wet etch processing upon exposure to 50 keV electrons, in agreement with Lercel [J. Vac. Sci. Technol. B 11, 2823 (1993)]. Identically processed samples patterned with low voltage (−10 to −25 V tip–sample bias) electrons in the STM exhibit a negative tone. STM biases below −10 V were insufficient to expose the film. An improved etch for STM-generated patterns, leading to smoother surfaces, was developed. STM exposure of PEDA and CMPTS SAMs leads to a destruction of ligand functionality. An exposure threshold of −4 V bias for CMPTS and −8 V for PEDA has been established. As an example of post-exposure processing, these latent images were metallized with an aqueous Pd(II) catalyst solution followed by an electroless Ni plating bath. The patterned, thin (25 nm) Ni layers grown in this way are shown to be excellent masks for reactive ion etching (RIE) with SF6, exhibiting at least a 1:200 etch selectivity on Si. Linewidths after metallization of 20 nm and etched (CBrF3/O2 RIE) trench widths of 25 nm are shown.

Characterisation of a PdCl 2/SnCl 2 electroless plating catalyst system adsorbed on barium titanate-based electroactive ceramics

A PdCl 2/SnCl 2 metallisation catalyst system, of the type used to activate non-conducting surfaces for electroless metal deposition, has been characterised by X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). The substrate is a barium titanate (BaTiO 3)-based electroactive ceramic of the type used in the fabrication of multilayer ceramic capacitors (MLCC). The treatment of the substrate surface with the PdCl 2/SnCl 2 “sensitiser” solution leads to the adsorption of catalytically inactive compounds of palladium and tin. Subsequent treatment of this surface with an “accelerator” solution removes excess oxides, hydroxides and salts of tin thereby leaving the active catalyst species, Pd x Sn y , on the surface. Such sites, on exposure to the appropriete electroless plating bath, are then responsible for the metal deposition. In this study, the chemical state and relative quantities of the various surface species present after each of the processing stages have been determined by XPS. The surface roughness of the substrate results in less of the tin compounds present thereon being removed on washing the catalysed surface in the accelerator solution than normally reported for such systems, thereby affecting the measured Pd: Sn ratio. SEM studies show that the accelerator solution treatment generates crystalline areas, which may be a result of coagulation of the Pd x Sn y particles present, in the otherwise amorphous catalyst coating.

無電解めっき浴中におけるステンレス鋼不働態皮膜の安定性

The stability of passivation films on SUS304 and SUS316 stainless steels used for the bath container of an electroless nickel plating bath was studied by immersion test and electrochemical polarization method.The stainless steel specimens which had been passivated in 32.5% HNO3 for 3h at 313K were simultaneously immersed in the plating bath with a SS41 steel specimen. The concentration of phosphonic acid that was formed by oxidation of phosphinic acid in the bath increased during the immersion with the metal turnover. When the concentration exceeded 2mol·dm-3 in the bath, steady nickel deposition did not occur on SS41 steel.The anodic polarization curves of the stainless steels in 1N H2SO4 solution were measured by immersing them in the plating bath after passivation in 32.5% HNO3. The passive current on the polarization curve increased with immersion time and the corrosion potential moved to the positive direction. After the immersion for 60h the SUS304 specimen did not reveal any passivation on the polarization curve, but the SUS316 specimen did it even after the immersion for 144h. This indicates that the passivation film formed on SUS316 in 32.5% HNO3 is more stable than that on SUS304. The concentrations of phosphonic and phosphinic acids seem to be most influencial on the stability and breakdown of passivation films on the stainless steels.

Electrochemical characterization of surface-modified negative electrodes consisting of hydrogen storage alloys

Negative electrodes consisting of MmNi 3.6Mn 0.4Al 0.3Co 0.7 alloy powder filled in a porous nickel substrate were modified by using different electroless plating baths or alkaline solutions containing hypophosphite as a reducing agent. The deposited metals function as a microcurrent collector and then increase the discharge capacity of the negative electrodes. In contrast, modification with a reducing agent gives rise to high electrocatalytic activity of the negative electrodes which leads to a remarkable reduction in overvoltage in charging and discharging even at the first cycle. It was found that such simple surface modifications improved the performance of negative electrodes under appropriate conditions with respect to the amount of electroless deposit or the concentration of reducing agent.

Surface modification of metal hydride negative electrodes and their charge/discharge performance

Negative electrodes consisting of a multicomponent alloy (MmNi 3.6Mn 0.4Al 0.3Co 0.7) in a porous nickel substrate were modified by using different kinds of electroless plating baths or alkaline solutions containing hypophosphite as a reducing agent. Electrochemical properties of the negative electrodes such as discharge capacity, electrocatalytic activity for the hydrogen electrode reaction (HER), and high-rate dischargeability were examined in a 6 M KOH solution. It was found that such simple surface modifications as described above improved the performance of negative electrodes.