MOUNTING BOARD

PURPOSE:To enhance reliability and a production yield by a method wherein a thin-film wiring layer laminated by many layers is divided into several layers of unit wiring parts and the parts are connected via connecting pads formed at through hole parts between the units. CONSTITUTION:A high-integration-density LSI 13 is connected, by using solder balls 14, to a thin-film wiring layer 12 which has been formed on a ceramic substrate 11. The layer 12 is divided into four units UN 121 to UN 124. The individual UN's excluding the UN 124 are constituted of signal line layers 28, 29 crossing at right angles to each other and of power-supply layers and ground layers 27, 30 on both sides of them. The UN 124 is constituted of pads 15 for connection use to the LSI 13 and of expansion layers 16 used to adjust the pitch of through holes. The individual UN's are connected by using opposite connecting pads 31 formed inside the layers 27, 30 on the surface of the UN's. The size of the pads 31 is made larger than that of through holes 32. Thereby, a connecting operation can be executed easily, and reliability and a yield can be enhanced.