Control of Pinhole Defects Formation in Semi-flexible Coaxial Cable by Vertical Tin-Plating Process

Holistic tin-plating on the outer conductor is one of the key processes in the manufacture of semi-flexible coaxial cable, which is widely applied to the third generation (3G) mobile communication system. However, in the traditional horizontal tin-plating process, disadvantages such as the pinhole defects and low productivity effect cannot be avoided. In this paper, a vertical tin-plating process was proposed to reduce the pinhole defects and improve the tincoating quality. Compared with the traditional horizontal tin-plating process, the immersion length was reduced from 300-400 mm to 10-100 mm and the tin-plating time was reduced from 7 s to 3 s in the proposed method. The experimental results indicate that immersion length and time are key parameters for the tin-plating quality. With this new tin-plating process, the experimental results show that the pinhole defects can be eliminated effectively by controlling the immersion depth below 100 mm and tin-plating time at 3 s. The thickness of tin-coating increased from not more than 5 μm to 12.3 μm with the proposed vertical tin-plating process. Meanwhile, the thickness of the intermetallic compounds (IMCs) layer between the tin-coating and copper wires was reduced from 3.26 μm to 0.62 μm if the immersion time decreased from 30 s to 1 s. Besides, a self-developed flux, which possesses a boiling point or decomposed temperature of active components over 300℃, exhibits a better efficiency in reducing the pinhole formation.

Corrosion Behavior of Epoxy-Coated Rebar with Pinhole Defect in Seawater Concrete

Experiments were carried out to investigate the corrosion behavior of epoxy-coated rebar （ECR） with pinhole defect（diameter in hundreds of microns） immersed in the uncarbonated/carbonated simulated pore solution （SPS） of seawaterconcrete. Corrosion behavior was analyzed by electrochemical impedance spectroscopy. The composition and morphologyof corrosion products were characterized by X-ray diffraction, energy-dispersive spectrometry and scanning electronmicroscopy. Meanwhile, oxide film produced by preheating before spray coating was investigated by X-ray photoelectronspectroscopy and Mott-Schottky technology. Results indicated that corrosion behavior of ECR with pinhole defectexhibited three stages when immersed in the uncarbonated/carbonated SPS. In the initial stage, steel in defect waspassivated when exposed in the uncarbonated SPS and corroded when exposed in the carbonated SPS, due to competitiveadsorption between chloride and hydroxyl ions. In the second stage, the oxide film under coating reconstituted （thethickness and defects density decreasing） in the uncarbonated SPS, which was caused by the synergy between highhydroxide and chloride activity, while in the carbonated SPS, crevice corrosion happened under the coating around pinhole,because of the different oxygen concentrations cell at the coating/steel interface. In the third stage, localized corrosionoccurred under the coating around the pinhole in the uncarbonated SPS, which was probably induced by ion diffusion at thenano-scale coating/steel interface. The corrosion products adjacent to the defects were re-oxidized from FeCIa.4HaO andFe2（OH）3Cl to Fe2O3.H2O, and the corrosion area was expanded outward in the carbonated SPS.

Suppressing Leakage Currents and Improving Performance of Indoor Organic Photovoltaic Devices

Organic photovoltaic(OPV) devices hold great promise for indoor light harvesting,offering a theoretical upper limit of power conversion efficiency that surpasses that of other photovoltaic technologies.However,the presence of high leakage currents in OPV devices commonly constrains their effective performance under indoor conditions.In this study,we identified that the origin of the high leakage currents in OPV devices lay in pinhole defects present within the active layer(AL).By integrating an automated spin-coating strategy with sequential deposition processes,we achieved the compactness of the AL and minimized the occurrence of pinhole defects therein.Experimental findings demonstrated that with an increase in the number of deposition cycles,the density of pinhole defects in the AL underwent a marked reduction.Consequently,the leakage current experienced a substantial decrease by several orders of magnitude which achieved through well-calibrated AL deposition procedures.This enabled a twofold enhancement in the power conversion efficiency(PCE) of the OPV devices under conditions of indoor illumination.