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The purpose of this paper is to illustrate the new technical demands and reliability challenges to printed circuit board (PCB) designs, materials and processes when the transmission frequency increases from Sub-6 GHz in previous generations to millimeter (mm) wave in fifth-generation (5G) communication technology.

The approach involves theoretical analysis and actual case study by various characterization techniques, such as a stereo microscope, metallographic microscope, scanning electron microscope, energy dispersive spectroscopy, focused ion beam, high-frequency structure simulator, stripline resonator and mechanical test.

To meet PCB signal integrity demands in mm-wave frequency bands, the improving proposals on copper profile, resin system, reinforcement fabric, filler, electromagnetic interference-reducing design, transmission line as well as via layout, surface treatment, drilling, desmear, laminating and electroplating were discussed. And the failure causes and effects of typical reliability issues, including complex permittivity fluctuation at different frequencies or environments, weakening of peel strength, conductive anodic filament, crack on microvias, the effect of solder joint void on signal transmission performance and soldering anomalies at ball grid array location on high-speed PCBs, were demonstrated.

The PCB reliability problem is the leading factor to cause failures of PCB assemblies concluded from statistical results on the failure cases sent to our laboratory. The PCB reliability level is very essential to guarantee the reliability of the entire equipment. In this paper, the summarized technical demands and reliability issues that are rarely reported in existing articles were discussed systematically with new perspectives, which will be very critical to identify potential reliability risks for PCB in 5G mm-wave applications and implement targeted improvements.

The purpose of this paper is to solve the issue of via filling and pattern plating simultaneously by concentration optimization of accelerator and leveler in the electroplating bath.

This paper designs a series of experiments to verify the performance of pattern plating with the via filling plating formula. Then the compositions of electroplating solution are optimized to achieve via filling and pattern plating simultaneously. Finally, the mechanism of co-plating for via and line is discussed in brief.

To achieve excellent performance for via filling and pattern plating simultaneously, proportion of additives are comprehensively considered in optimization of electroplating process. Effects of additives on the via filling and pattern plating should be taken into consideration, especially in achieving flat lines.

This paper discusses the different effects of accelerator and leveler on the via filling and the pattern plating, respectively. The process of co-plating for the via and the line is presented. The superfilling of via and the flat line are simultaneously obtained with the optimized via filling formula.

This paper aims to investigate the corrosion inhibition ability of 4–(4-nitrophenyl) thiazol-2-amine (NPT) on the copper in 1 M HCl.

The corrosion inhibitory ability of NPT on the copper in 1 M HCl was studied by electrochemical impedance spectroscopy, scanning electron microscopy and atomic force microscopy. Theoretical calculations (molecular dynamics simulation, density functional theory and the nucleus independent chemical shift [NICS] as aromaticity indicator of the molecule) were also performed.

The corrosion inhibition efficacy of this compound was about 80%. Nyquist plots display a small arc contributed to the film or oxide layer resistance and a large loop associated with charge transfer resistance. The inhibitor adsorption was under Langmuir’s adsorption model. ΔG⁰_ads values point to the presence of physical and chemical adsorption. Results of quantum chemical calculations showed that NPT has better interaction with copper than NPTH⁺. NICS of NPT in benzene or thiazole rings was less negative compared to NICS of NPTH⁺. Thus NPT shows less aromaticity compared with NPTH⁺, showing NPT can have better interaction with copper than NPTH⁺. NPT had more negative E_int value and more interactions with the Cu relative to NPTH⁺, this result was in agreement with the results of quantum chemical calculations.

NPT is an efficient corrosion inhibitor for copper in HCl. Theoretical calculations showed that NPT can have better interaction with copper than NPTH⁺. The results of the theoretical studies were in good agreement with the experimental studies.