Background of Research
Accelerating performance requirements are driving the demand for high-speed, multilayer PCBs. Traditional manufacturing methods for laminating these layered boards and removing residue from the vias are no longer effective. The use of radio frequency driven, low-pressure plasma provides an efficient, cost-effective and environmentally friendly method for surface treatment and cleaning of the boards.
Chemical processing with permanganate chemistry is limited due to the inability of the fluid to penetrate the small vias found in multilayer PCBs. In addition, permanganate does not effectively clean the very small via holes that are usually located at the inner layer level of laser-drilled via holes. Other wet chemistries, such as acid etching fluids, have difficulties etching polyimide dielectric materials.
Plasma processing overcomes these limitations due to the inherent penetrating nature of plasma and the ability to precisely control the process. Plasma can etch high aspect ratio vias, and is environmentally benign with a relatively low operation cost. Complex and sophisticated boards with ever increasing layer counts and circuit densities need the benefits of plasma for descum, desmear/carbon removal, etchback, TeflonR activation, and surface preparation. Examples include: multilayer boards with 6 to 64 or more inner layers; boards with high-aspect ratio holes; PCBs with microvias, buried vias, blind vias, and laser formed vias; and those PCBs manufactured from new types of resin, TeflonR-based materials, and chemically inert materials.
Objective
To compare the performance of two desmear processes, wet chemical process and low pressure plasma process on PCB material and its plated through hole surfaces,
To determine the optimum parameter settings for low pressure plasma process,
To evaluate the effect of low pressure plasma and atmospheric plasma on copper and polymer surfaces with various experimental conditions
