| 摘要 |
PURPOSE:To decrease the number of wirings for signal pins to one from two, and to lessen the total number of wirings for the whole substrate by connecting memory elements having the pin arrangement of specular symmetry and the same function near a connecting land for the signal pins each faced to both surfaces of the substrate through through-holes. CONSTITUTION:A normal DRAM element 1 is mounted onto the upper surface of a printed substrate 2, and a DRAM 3 having the pin arrangement of specular symmetry to the DRAM element 1 and the same function is mounted onto the lower surface. When the DRAM elements 1 and 3 are faced oppositely at that time, control signals CAS, WE and address signal terminals A0-A8 are connected through a through-hole 4 because signal pins having each function can be aligned at corresponding positions, and respective signal terminal is connected to another DRAM element by each one wiring. NC represents 'an empty pin' as a popular name in which circuit connection is not conducted. In a wiring pattern (a) on a first layer (the surface), on which the DRAM element 1 is mounted, and a wiring pattern (b) on a second layer (the rear), on which the specular symmetry element 3 to the wiring pattern (a) is mounted, rectangular hatching sections represent soldered-joint terminals for the printed substrate corresponding to pin arrangement and the through-hole connecting sections 4 balloons. |
