Structural, Electrical, and Adhesion Properties of Electroless Ni-P Coating on Thin Polyethylene Terephthalate Foil for Flexible Circuit Application
摘要
The work involved a comprehensive analysis of the morphological, chemical, structural, electrical, and adhesion properties of electroless Ni-P coating on thin, flexible polyethene terephthalate (PET) foils. The deposition duration was varied from 1 to 5 min to assess its impact on coating growth behavior and properties. Rapid growth in coating thickness, up to 1 μm, was observed during the first 2 min of deposition. However, localized outgrowths increasingly appeared as deposition extended. The drop in electrical resistivity from 2.57 × 10−4 to 1.13 × 10−4 Ω·cm could be correlated with an improvement in microstructural continuity, an increase in grain size, and a drop in P content. Thicker coatings, beyond 1 μm, however, exhibited poor adhesion performance in the scotch tape and scratch adhesion tests. While the qualitative adhesion dropped from 5B to 0B, the average critical load of adhesion reduced from 16 N to 3.5 N. However, the 1-μm-thick coating did not exhibit any delamination even under 180° bending and effectively conducted electric current to illuminate a light-emitting diode. In the cyclic bending test, the same exhibited a good mechanical stability and a gradual rise in sheet resistance, suggesting its potential for flexible circuit applications.