Low-Loss Flat Cable Signal Lines With Arch Cross-Sections for UHF FPCB

The patent replaces the traditional mechanical etching process with an electroforming process. Instead of using chemical etchants to remove material and create signal lines, the invention uses electrochemical deposition to build up conductive patterns on a cylindrical mold. This substitution eliminates the rough, irregular surfaces caused by etching and produces smooth-walled signal lines with precise cross-sectional shapes (circular, elliptical, or arch-type), directly reducing transmission loss while maintaining manufacturing feasibility

The patent changes the fundamental parameter of signal line formation from material removal (etching) to material deposition (electroforming). By controlling electroforming parameters such as current density, plating time, and mold rotation speed, the process produces signal lines with optimized cross-sectional geometries. The cylindrical mold rotation combined with electroforming creates uniform thickness distribution and smooth surfaces, transforming the signal line geometry parameters to minimize skin effect and transmission loss at high frequencies

The patent substitutes the chemical etching system with an electroforming system. Instead of using toxic etchants like ferric chloride or ammonium persulfate that require special handling and disposal, the invention employs an electrochemical cell with benign electrolyte solutions. The conductive patterns are formed through controlled metal deposition from the electrolyte, eliminating the need for hazardous chemicals while maintaining the ability to create precise signal line patterns on the flexible substrate

The patent converts the potential harm of chemical processing into benefit by using electroforming, which transforms electrical energy into controlled material deposition. The process turns what would be waste electrical energy into useful conductive material buildup, creating signal lines without generating toxic waste streams. The cylindrical mold serves as a reusable template that can be repeatedly coated and stripped without degradation, reducing overall material consumption and environmental burden

The patent merges multiple separate process steps into a single integrated electroforming operation. The cylindrical mold fabrication, signal line pattern formation, and surface smoothing are all achieved in one continuous electroforming process rather than through sequential etching, rinsing, drying, and coating steps. This consolidation reduces process complexity and equipment requirements while maintaining production capability, directly addressing the cost-precision tradeoff by simplifying the manufacturing system

The cylindrical mold serves multiple functions simultaneously: it acts as the substrate for signal line formation, the template for pattern definition, the rotating component for uniform deposition, and the surface for final product transfer. This multi-functionality eliminates the need for separate components for each function, reducing device complexity and manufacturing cost while enabling continuous production of high-precision signal lines with optimized geometries for low transmission loss