A new electroless copper plating process, namely, an alternating one-side air stirring method, was studied to improve the throwing power of high-aspect-ratio through-holes in multilayer printed wiring boards. The throwing power can even be improved for through-holes of a 40-aspect ratio under an appropriate flow velocity of the solution because the generation of differential-pressure between the front and the back of the board enhances supplying the solution into the through-holes. The necessary flow velocity can be estimated by considering the consumption rate of copper ions in a through-hole and calculating it on the basis of Bernoulli's and Hagen-Poiseuille's equation. (C) 2017 The Electrochemical Society. All rights reserved.