Electroless Copper Deposition Performance for Printed Circuit Board with Magnetic Field AITranslate

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Basic Information:

DOI：10.13373/j.cnki.cjrm.XY25040023

Chinese Library Classification Number:TQ153.14

Citation Information:

Printed circuit boards (PCBs), serving as critical carriers for electrical interconnections among numerous electronic components, are widely employed in computers, communications, aerospace, and medical applications. Electroless copper deposition is a key step in PCB manufacturing, involving the chemical deposition of a thin copper layer (2~3 μm) on the insulating via walls to establish conductive interconnections between different circuit layers or copper foils. The quality of this deposited copper layer directly determines the electrical connectivity performance of PCB. However, due to limitations in production equipment capabilities or outdated electroless copper plating technology, defects such as copper voids on via walls, rough copper surfaces, uneven copper thickness, microcracks, and poor copper adhesion may occur. During soldering or normal operational life cycles, PCBs are subjected to high-temperature reflow soldering or repeated thermal cycling, imposing stringent requirements on the uniformity, surface roughness, adhesion strength, and thermal shock resistance of the deposited copper layer. These challenges drive manufacturers to continuously explore methods for achieving stable and reliable electroless copper deposition. Extensive research has been conducted by scholars worldwide to investigate the influence of magnetic fields on the physicochemical properties of materials. It has been well-documented that external magnetic fields can exert directional control over the deposition rate, surface morphology, and crystal growth orientation in chemical deposition processes. In this study, electroless copper plating was conducted on Flame Retardant 4(FR-4) substrates under different magnetic fields with central intensities of 30 and 60 mT. The copper deposition rate was measured gravimetrically, while scanning electron microscopy (SEM) was employed to analyze the microstructure of deposited copper layers. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were utilized to investigate the effects of magnetic fields on deposition processes at different copper ion concentrations and the resulting corrosion resistance. The results indicated that the copper deposition rate peaked at approximately 2.5 min before stabilizing. During the stable phase, the applied magnetic field increased the deposition rate from 8 to 10 mg·dm⁻²·min⁻¹, representing a 25% enhancement. The plating tank size significantly influenced the deposition rate during the pre-peak phase, with smaller tanks yielding higher peak rates. Visual and SEM observation revealed that magnetic field-assisted deposition produced brighter, smoother, and more uniform copper layers with improved density. While negligible effects were observed at low copper ion concentrations (<1 g·L⁻¹), significant changes occurred at 2~5 g·L⁻¹ concentrations under magnetic fields：increased cathodic polarization accompanied by negative shifts in deposition potential peaks, with the shift magnitude being concentration-dependent. Specifically, at 60 mT, the reduction peak potential for 5 g·L⁻¹ copper solution shifted from –0.85 to –0.89 V, with current density increasing from 2.11 to 2.34 A·dm⁻². EIS analysis confirmed that magnetic field-deposited copper layers exhibited higher charge transfer resistance during electrochemical corrosion, indicating superior corrosion resistance.