PRETREATMENT FOR ELECTROLESS PLATING

摘要

PURPOSE:To obtain a uniformly etched surface and to form a uniform and dense underlying film for electroless plating by subjecting an aluminum alloy substrate for a magnetic disk for 1-5min with a bath contg. a specific amt. each of nitric acid and ammonium hydrogenfluoride in a pickling stage. CONSTITUTION:The aluminum alloy substrate is immersed for 1-5min at an ordinary temp. into a soln. contg. 5-10wt% nitric acid and 25-40wt% ammonium hydrogenfluoride in the pickling stage. The nitric acid of the components of the pickling soln. has an effect of adequately etching the aluminum alloy substrate in a concn. range of 5-10wt%. The power to remove the oxide of the aluminum surface is low if the acid concn. is below 5wt%. The etching effect is too large and the uniformly etched surface is not obtainable if the acid cocn. exceeds 10wt%. The treatment temp. in the pickling stage is an ordinary temp. and is more particularly preferably 0-30 deg.C. The reaction is slow if the treatment temp. is too low. The etching effect of the nitric acid is too strong and large pits are formed on the surface of the aluminum alloy substrate and such is inconvenient if the temp. is too high.