Thermally enhanced face-to-face semiconductor assembly with built-in heat spreader and method of making the same

A face-to-face semiconductor assembly with a built-in heat spreader, comprising:

• a subassembly that includes a first semiconductor device, a balance layer and a first routing circuitry having a first surface and an opposite second surface, wherein the first semiconductor device is electrically coupled to the first routing circuitry from the first surface of the first routing circuitry and the balance layer laterally surrounds the first semiconductor device and covers the first surface of the first routing circuitry;
• a second semiconductor device;
• and
• an interconnect board that includes a heat spreader and a second routing circuitry disposed over the heat spreader, wherein the heat spreader is made entirely of a metal or an alloy and laterally extends to peripheral edges of the second routing circuitry to support the entire second routing circuitry,
• wherein
• (i) the second semiconductor device is attached to the heat spreader and laterally surrounded by the second routing circuitry and electrically coupled to the first routing circuitry by an array of first bumps,
• (ii) the second routing circuitry is electrically coupled to the first routing circuitry by an array of second bumps, and
• (iii) both the first bumps and the second bumps are disposed at the second surface of the first routing circuitry, and
• wherein the second routing circuitry of the interconnect board includes first terminal pads and second terminal pads at its exterior surface facing the first routing circuitry, wherein the first terminal pads are in contact with the second bumps to be electrically coupled to the first routing circuitry, and the second terminal pads have larger pad size and pad pitch than those of the first terminal pads.