As electronic devices are getting smaller and lighter, the density of copper lines on
flexible printed circuit board (FPCB) is getting higher. Conventionally, subtractive method was used
for copper line on a flexible films, however, as the line pitch is getting smaller, the lateral etching of
copper cause serious problem. To replace the subtractive method, semi-additive method was used
for fine pitch copper line fabrication. In semi additive process, sputtered layer for the
electroplating copper was required. The feasibility of electroless plating to replace high cost
sputtered copper seed layer was investigated. Electroless depositions of copper were conducted on
different substrate to find optimum conditions of electroless copper plating. To find optimum
conditions, the effects and selectivity of activation method on several substrates were also
investigated. The adhesion strength between polyimide and copper was improved by treating the
polyimide surface with butylamines. Pretreatment prior to electroless plating is very sensitive and
surface dependent. Surface morphologies were investigated with FESEM.
Effect of Ni Content in the Electroless Copper Plating Film on Recrystallization at the Bottom of via in Printed Circuit Board