Liquid crystal polymers (LCP) are used in electronics, automotive, medical, and communications applications, but their naturally smooth, low-energy surfaces make direct electroless copper plating difficult. The established industrial solution is potassium hydroxide (KOH) treatment, a strong alkaline chemical that requires special safety precautions and process infrastructure. This study, published via Semiconductor Engineering, evaluated whether plasma processing could provide a practical alternative.
Using the Nordson MARCH MaxVIA system, the team developed a three-step plasma process: material warm-up, hole wall roughening, and surface activation. Initial evaluation confirmed that etch rate and uniformity met specifications, with no detectable LCP residue on copper surfaces. Cross-sectional analysis and SEM inspection verified roughening throughout the treated structures. Comparative experiments showed that the activation step was necessary: samples processed without it did not achieve good plating coverage.
The team also optimized treatment duration, testing 20, 30, and 60 minutes. They found that 30 minutes maintained acceptable results while improving process efficiency. Activated samples demonstrated good copper coverage and adhesion, and solder float testing confirmed effectiveness on both four-core and eight-core structures. The authors conclude that plasma can serve as a viable alternative to KOH for LCP metallization, delivering the required surface characteristics without the chemical handling burden.