Method for making a multilayer flexible printed circuit board

A method for making a multilayer flexible printed circuit board comprising:

• providing an inner wiring substrate and at least one single-sided copper substrate, each single-sided copper substrate comprising an adhesive plate;
• defining at least one through hole in each single-sided copper substrate;
• forming an intermediate product by attaching the adhesive plate of each single-sided copper substrate onto one surface of the inner wiring substrate to expose the inner wiring substrate through the through hole, and heating and pressing the single-sided copper substrate together to cause the adhesive of the adhesive plate to extend towards a center of the through hole along a direction substantially perpendicular to a center axis of the electrically conductive hole to form a stepped portion;
• covering each single-sided copper substrate of the intermediate product with a dry film, wherein the dry film is further formed over exposed inner wiring substrate, and then pressing the dry film to cause the dry film to fill gaps formed by the exposed inner wiring substrate;
• and
• forming an outer wiring plate by etching each single-sided copper substrate of the intermediate product, and removing the dry film to form the multilayer flexible printed circuit board.