Patent ID: 8898895

Claim:
A method for producing a multilayer substrate, comprising: a base pretreatment step in which two steps are performed in random order, the two steps including a boring step for boring a core base having at least an insulating layer disposed as an uppermost layer and a first metal layer provided on one surface of the insulating layer to form in the insulating layer holes each extending from the other surface of the insulating layer to the first metal layer, and a metal deposition step for depositing a metal selected from the group consisting of metals having an atomic number of 13 to 14, 21 to 33 and 39 to 50 or an ion thereof on the other surface of the insulating layer; a desmearing step for performing desmear treatment by plasma etching after the base pretreatment step; a cleaning step for cleaning the core base with an acidic solution after the desmearing step; and a plating step for applying a plating catalyst or its precursor to the insulating layer to perform plating treatment to thereby form on the insulating layer a second metal layer electrically connecting with the first metal layer through the holes.