Method of forming an assembly board with insulator filled through holes

A method of forming a board base comprising the steps of:

• forming a through-hole through a board base having a first surface and a second surface;
• forming a single continuous conductive layer inside said through-hole and on part of the first surface and part of the second surface around the through-hole;
• filling said through-hole with insulating material;
• and
• forming a wiring pattern on the first surface of the board base, the wiring pattern traversing the through-hole filled with the insulating material.

A method of making a semiconductor device, comprising the steps of:

• forming through-holes through a board base;
• forming a metal layer inside each of said through-holes;
• filling the through-holes with synthetic resin;
• forming an insulator layer on the board base and on the synthetic resin filling said through-holes;
• forming via-holes at predetermined positions through the insulator layer;
• forming a wiring pattern on the insulator layer to traverse a position where one of the through-holes is located, the wiring pattern being electrically connected to the metal layer via one of the via-holes;
• and
• connecting a semiconductor chip to the wiring pattern electrically.