A method of forming a multilayer device includes providing a core substrate having opposing first and second core surfaces and forming top and bottom inner conductive patterns on each of the first and second core surfaces, respectively. A first dielectric layer is formed on the first core surface, and the top inner conductive pattern. A second dielectric layer is formed on the second core surface, and the bottom inner conductive pattern. The first and second dielectric layers are laminated with top and bottom outer conductive layers, respectively. A first via is provided through the core substrate extending from the top outer conductive layer to the bottom outer conductive layer. The first via is filled with solder. Magnetic particles are attracted by a magnetic force into the first via.