Embedded transformer

An embedded transformer, comprising:

• a board, said board including at least one opening and a conductive pattern formed on an upper surface of said board, a part of said conductive pattern serving as a primary coil;
• a first insulating sheet, formed on said conductive pattern;
• a preformed coil, formed on said first insulating sheet, said preformed coil serving as a secondary coil;
• a second insulating sheet, formed on said preformed coil;
• a first core, formed on said second insulating sheet, said first core including a first central post and a plurality of first side posts, said first central post and said first side posts embedded in said board
• a second core, formed on a lower surface of said board, said second core including a second central post and a plurality of second side posts, said second central post and said second side posts embedded in said board;
• and
• wherein said second central post penetrates said second insulating sheet, said preformed coil, said first insulating sheet and said board so as to be coupled to said first central post, said first side posts being coupled to said second side posts through said opening.