Synthesis and performance of imidazole epoxy-octane copolymer as a leveler for the through-hole electroplating copper of printed circuit board

Abstract

A functional agent, imidazole epoxy-octane (IDEO) copolymer, is synthesized as a leveling additive for the through-hole (TH) electroplating of copper on printed circuit boards (PCBs). The efficacy of this agent in enhancing the TH reliability is then tested and verified. The polymerization process utilizes imidazole and 1,2,7,8-diepoxyoctane as the raw materials. A series of electrochemical tests demonstrate that when used in conjunction with other additives, IDEO significantly inhibits copper deposition and subsequently facilitates the thickness and leveling regulation of electroplating copper in the inner layer of the THs of PCBs. At the optimal concentration, the TH throwing power value reaches 85 %. In addition, the surface morphology of copper plates plated under different leveler solutions is compared. The comparison, conducted using scanning electron microscopy and atomic force microscopy tests, reveals that the addition of IDEO can effectively reduce the roughness of the copper surface. And computational chemistry and molecular dynamics simulations also indicate that IDEO has a high binding energy, forming an effective adsorption with the copper surface. Furthermore, the leveling mechanism of IDEO additive is surmised by X-ray photoelectron spectroscopy and chrono potential tests on copper plates, which validates the effectiveness and potential application of IDEO leveler in PCBs.