PRINTED WIRING BOARD UNIT, HIERARCHICAL MOUNTING AUXILIARY SUBSTRATE AND ELECTRONIC APPARATUS

摘要

A rectangular frame-form hierarchical mounting auxiliary substrate (14) is mounted surrounding a semiconductor component (15) mounted on a printed wiring board (11), and another semiconductor component (16) is mounted at a position above the semiconductor component (15) while being supported on the substrate (14) and with its terminals connected with the substrate (14). The hierarchical mounting auxiliary substrate (14) has wiring patterns (35a) and through holes (34a) and has inside thereof a power supply layer (32) and a ground layer (33) with printed wiring pads on the lower surface dispersed in comparison with component board pads (23a) on the upper surface. Therefore, a gap space (41) between adjacent pads (40a), on the printed wiring board (11), corresponding to the semiconductor component (16) is widened so that a wiring pattern (43), on the printed wiring board, extending outwardly from a pad (21a) to be connected with the semiconductor component (15) can easily pass through the gap space (41).