Method for preparing ball grid array board

A method for preparing the BGA board containing a plurality of printed circuit boards, in which a conductor circuit, an inner hole for mounting a semiconductor chip and a bonding pad to be electrically connected with the semiconductor chip are formed, comprising the steps of:

• a) providing top and bottom boards having neither inner hole nor conductor circuit, a board to contact with a bottom side of said top board in which an inner hole is established without a conductor circuit, and at least one of boards in which a conductor circuit and an inner hole are established;
• b) forming a primary-laminated structure with an opening part in an upper part thereof, by arraying the lower boards except said top board, and laminating the lower boards together by use of an adhesive to form a step-typed combination of the inner holes;
• c) forming a secondary-laminated structure by overlaying said top board onto the primary-laminated structure by use of the adhesive;
• d) forming through-holes in the secondary-laminated structure, followed by establishing a conductor circuit on the secondary-laminated structure including the through-holes by copper plating, dry film lamination, exposure, developing and etching;
• e) removing parts of the top and bottom boards which covers the step-typed combination of the inner holes to form a cavity with both vertical ends opened, followed by providing a bonding pad in the cavity to give an individual BGA board;
• and
• f) bonding a heat sink to a lower part of said individual BGA board by use of the adhesive.