US Patent No. 10,015,889


Patent No. 10,015,889
Issue Date July 03, 2018
Title Method For Constructing An External Circuit Structure
Inventorship Zhongyao Yu, Beijing (CN)
Yu Sun, Beijing (CN)
Zhidan Fang, Beijing (CN)
Assignee National Center for Advanced Packaging Co., Ltd., Wuxi, Jiangsu (CN)

Claim of US Patent No. 10,015,889

1. A method for constructing an external circuit structure, applied to an inner circuit substrate, which comprises: a core board, both surfaces of which are coated with copper circuits; at least one via-hole, drilled through the core board and filled with conductive medium, wherein, the method comprises:laminating a copper foil and a prepreg on the inner circuit substrate; wherein, the prepreg is laminated between the copper foil and the inner circuit substrate;
drilling at least one blind via from the copper foil through the prepreg to reach one of the copper circuits coated on the core board;
desmearing the at least one blind via;
after the desmearing step, corroding off the copper foil;
after the corroding step, electroless copper plating on the prepreg to form an electroless plating copper layer on the prepreg; wherein, during the electroless copper plating process, swelling a surface of the prepreg with alkaline swelling liquid, thereby increasing a distance between molecules of the surface of the prepreg and superficial area of a micro structure of the prepreg; and neutralizing the alkaline swelling liquid left on the surface of the prepreg.