Patent ID: 7781681

Claim:
A multilayer printed wiring board comprising: a core substrate; a built-up wiring layer comprising a plurality of conductor circuits and a plurality of insulating resin layers, the built-up wiring layer having a first surface provided in contact with the core substrate and a second surface opposing the first surface, the second surface of the built-up wiring layer including a mounting area on which at least one semiconductor device is to be mounted; a plurality of first through-hole conductors formed in a first portion of the core substrate which corresponds to the mounting area of the second surface; a plurality of second through-hole conductors formed in a second portion of the core substrate which corresponds to an area of the second surface other than the mounting area; a plurality of third through-hole conductors formed in a processor core area of the first portion of the core substrate which corresponds to a processor core section of the at least one semiconductor device; and a plurality of pads provided on the second surface, wherein the first through-hole conductors have a pitch which is smaller than a pitch between the second through-hole conductors, the third through-hole conductors have a pitch which is smaller than the pitch of the first through-hole conductors, the pads and the first, second and third through-hole conductors satisfy an equation, Bc/Tc<Bp−Bc/Tp−Tc, where Bc represents the number of pads arranged in an area directly below the processor core section of the semiconductor device, Tc represents the number of through-hole conductors arranged in an area directly below the processor core section of the semiconductor device, Bp represents the total number of pads of the printed wiring board, Tp represents the total number of through-hole conductors of the printed wiring board, the first, second and third through-hole conductors satisfy an equation, Pc<Pm<Ps, where Pc represents the pitch of the third through-hole conductors, Pm represents the pitch of the first through-hole conductors, and Ps represents the pitch of the second through-hole conductors.