Composite graphene conductive solution for PCB hole metallization applications

In comparison to the high-pollution and high-cost electroless copper plating method, the direct plating technique offers significant advantages, including environmental sustainability, cost reduction, and ease of processing. Herein, a graphene-based hole process is developed, achieved by impregnating the PCB board with the graphene composite solution followed by heat treatment. When the ratio of graphene to carbon nanotubes is 6:4, the particle size of the solution is D₅₀ = 0.14 μm, the viscosity is 3.8 mPa s, the conductivity of the film is 1500 S/m, and the solution's concentration decreases by only 1.2% after one month of static storage. The composite solution exhibits excellent dispersibility, fluidity, and electrical conductivity. In the graphene-based hole process, the negatively charged composite solution adheres to the modified hole wall through electrostatic interactions and van der Waals forces, forming a dense and conductive film. Backlight test results demonstrate that the resulting film exhibits completeness, density, and strong adhesion to the hole wall. Copper plating results further reveal a uniform and fully deposited copper layer on the hole walls, with a thickness of approximately 17 μm in THs (AR = 7.5). The throwing power (TP) value reach 113.8% at a composite solution solid content of 3 wt%. After undergoing three or five thermal shock tests at 288 °C and the cold-heat cycle test, the copper layer in the hole remained intact, without any cracking, meeting the stringent standards of the PCB industry. This work demonstrates that the graphene-based hole metallization process is a viable and promising alternative for PCB manufacturing.