Polytetrafluoroethylene (PTFE) films containing glass fillers have been shown to be promising materials in the development of high speed microelectronic packaging applications. Printed circuit board (PCB) manufacturing requires the use of copper foils that typically contain some surface modification for adhesion enhancement. The surface treatments of copper foils vary in composition and morphology. This study evaluates their chemical and physical characteristics before and after lamination to commercially available fluoropolymer dielectric films containing two different types of glass fillers. The peel strengths of the resulting interfaces are followed before and after PCB fabrication. The roles of surface composition, surface roughness, and fluoropolymer filler type are described in terms of the resulting adhesion of the metal/polymer interfaces.

Three commercial copper foils containing various degrees of surface roughness and a chemically similar surface treatment were laminated to a fluoropolymer composite and also subjected to water-based photolithographic and stripping processes. Surface analysis performed on the processed foils indicated that the highly basic pH of the stripping process was effective in removing zinc oxide, a component of the surface treatments on these foils. Morphologically, however, the surfaces did not seem to change. Ninety degree peel measurements of the resulting interfaces with aud without a photoresist processes showed that the resulting practical adhesion seemed to be mainly controlled by mechanical interlocking and to a lesser amount, by chemical factors. When 50 pm wide lines were subjected to the photolithographic process and a full fabrication sequence, adhesion variability seemed to be affected by interfacial attack of the fluoropolymer/metal foil interface by the alkaline medium of stripping and other process chemicals. Reliable interfacial adhesion of narrow lines is only possible when process parameters have been optimized.

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