A flame-retardant copper-clad laminate composite made of (metallocenebased cyclic olefin copolymer/glass)/ cresol-novolak epoxy with low dielectricity

Abstract

A CNE (cresol-novolak epoxy) composite of CCL (copper-clad laminate), comprising glass fabrics and mCOC (metallocenebased cyclic olefin copolymer) fabrics with various laminated structures, was fabricated and its dielectricity at high frequency was examined. The dielectric constant, D _k , at 5 GHz of a conventional glass/CNE composite is 4.0, whereas that of a seven alternately layered mCOC/glass/CNE composite with an externally facing mCOC layer is 2.3. In the same manner, the former has a loss tangent, D _f , of 0.035, whereas the latter has a loss tangent, D _f , of 0.007. In addition, the decrease of D _f with increasing mCOC content is not linear but logarithmical. The T _g (glass transition temperature) and scanning electron microscope results reveal the good compatibility of the mCOC and CNE at the interface between them. An optimal compression process, which involved a pressure of 20 kg/cm² at 185℃ for 120 min, was followed by setting at 120℃ for 30 min, to relax the residual stress that built up inside the mCOC prepregs, with the purpose of fabricating a mCOC/glass/CNE CCL without any tilt angle. The worsening of the flame retardancy that is caused by replacing some of the nonflammable glass layers with organic mCOC layers can be overcome by blending more 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide dicyandiamide hardener into the CNE matrix. The highest flame-retardant standard, of grade UL 94 V0, can be achieved with a phosphorus content of the glass/CNE and glass/mCOC/CNE CCLs of 8000 and 12,500 ppm, respectively. Briefly, a flame-retardant mCOC/glass/CNE composite of CCL operated at high frequency is successfully produced.