Electroless application of copper@ base coat to reinforced teflon substrate - by removing copper@ lining on substrates with caustic ammonia etching bath, purifying substrate, catalysing substrate, chemical copper@ plating, drying and annealing

摘要

Currentless coating of Cu-lined Teflon substrates (glass fibre reinforced or filled with ceramic powder) with a thin layer of Cu is effected by: (i) removal of the Cu-lining in a caustic ammonia etching bath, (ii) substrate purificn. using an alkaline purifying agent at 60-80 deg.C., (iii) catalysis of the substrate at 30-32 deg.C. for 12-14 min. using a Cu colloid-based catalyst, concn. 320-350 ml/l and pH 3.5 +/- 0.2, (iv) chemical Cu of the substrate at 220 +/- 1 deg.C. for 18-20 mins. using a Cu bath contg. 3 +/- 0.3 g/l Cu, 16-19 g/l Na0H and 16-18 ml/l 37% formaldehyde soln., and (v) drying and annealing the substrate at 140-180 deg.C. for at least 30 min. in an atmos. of N2. The substrate is rinsed between steps. Substrate purificn. is pref. at 60-62 deg.C. and drying and annealing pref. at 150 +/- 5 deg.C.. Rinsing of the substrate between steps by plunging into an overflow rinse both is at room temp. for 4-5 min.. USE - Used for mfg. of circuit line constructions having selected surge impendan