Stress resistant micro-via structure for flexible circuits

A method of forming a chip package comprising:

• providing a silicon wafer having an integrated circuit (IC) thereon and a plurality of die pads formed on a top surface thereof;
• applying an adhesive layer to the top surface of the silicon wafer;
• adhering the silicon wafer to a free-standing polyimide flex layer by way of the adhesive layer;
• forming a plurality of vias through the free-standing polyimide flex layer and the adhesive layer, each of the plurality of vias extending to a respective one of the plurality of die pads;
• and
• forming a plurality of metal interconnects on the free-standing polyimide flex layer such that each of the plurality of metal interconnects extends through a respective via to electrically connect to a respective die pad, wherein forming the plurality of metal interconnects comprises:
• determining a desired metal interconnect thickness based on a thickness of the adhesive layer;
• depositing a metal material on the free-standing polyimide flex layer and in the plurality of vias having the desired metal interconnect thickness;
• and
• patterning and etching the metal material to form the plurality of metal interconnects having the desired thickness.

A chip package comprising:

• a silicon wafer having a plurality of die pads formed on a top surface thereof;
• an adhesive layer deposited on the silicon wafer;
• a dielectric layer affixed to the adhesive layer and having a plurality of vias formed therethrough each extending through the adhesive layer to a respective one of the plurality of die pads;
• and
• a plurality of metal interconnects formed on the polyimide flex film such that each of the plurality of metal interconnects extends through a respective via to form an electrical connection with a respective die pad, each of the plurality of metal interconnects comprising:
• a cover pad covering a portion of a top surface of the polyimide flex film;
• a base forming an electrical connection with a respective die pad;
• and
• a sidewall extending between the cover pad and the base along a perimeter of the via;
• wherein each of the base and the sidewall is constructed to have a thickness equal to or greater than a thickness of the adhesive layer.