Package on package structures and manners of formation are described. In an embodiment, an array of trenches is formed partially through a fan-out substrate. In an embodiment, a plurality of laterally separate locations thermal interface material is dispensed onto an array of embedded bottom die. In an embodiment a thermal compression tool including an array of cavities corresponding to an array of top packages is brought into contact with the array of top packages and underlying fan-out substrate during PoP joint formation. The fan-out substrate may be secured to a vacuum chuck during several processing operations.