US Patent 11488843 Underfill between a first package and a second package

A method includes forming a release film over a carrier, attaching a device over the release film through a die-attach film, encapsulating the device in an encapsulating material, performing a planarization on the encapsulating material to expose the device, detaching the device and the encapsulating material from the carrier, etching the die-attach film to expose a back surface of the device, and applying a thermal conductive material on the back surface of the device.