FIG. 6 shows a cross sectional side by side comparison of a prior art electronic component assembly 601 and an electronic component assembly 621 according to the one embodiment of the present invention. Prior art assembly 601 includes a substrate 605, a substrate 607, and an interposer 609 located in between. Interposer 609 includes filled vias (613). Each filled via (613) includes a plate (618) located on major surface 604 of interposer 609 and a plate (619) located on major surface 606 of interposer 609. Each pad (610) of a substrate is electrically attached to a plate (618) of a filled via (613) with a solder ball (611). The filled vias can be filled with conductive material or nonconductive material (e.g. polymer).

Assembly 621 (shown) as a cross sectional view in FIG. 6 includes substrates 623 and 625 and interposer 627, which are the same size as substrates 605 and 607 and interposer 609 of assembly 601 respectively. Interposer 627 includes plated openings (629) with a sidewall plating (631). Each plated opening (629) of interposer 627 includes a vent opening (not shown in the cross sectional view of FIG. 6 that allows gasses to escape during a reflow process in the formation of the solder joints (633) for electrically coupling the sidewall plating (631) to a conductive structure (634) of the substrates (623). In the view of FIG. 6, the vent opening can be in front of, behind, or at a diagonal to the cross section shown in FIG. 6.