US Patent 9484327 Package-on-package structure with reduced height

To achieve a package-on-package having an advantageously reduced height, a first package substrate has a window sized to receive a second package die. The first package substrate interconnects to the second package substrate through a plurality of package-to-package interconnects such that the first and second substrates are separated by a gap. The second package die has a thickness greater than the gap such that the second package die is at least partially disposed within the first package substrate's window.