HYBRID TIMs FOR ELECTRONIC PACKAGE COOLING

Structural combinations of TIMs and methods of combining these TIMs in semiconductor packages are disclosed. An embodiment forms the structures by selectively metallizing a backside of a semiconductor chip (chip) on chip hot spots, placing a higher performance thermal interface material (TIM) on the metallized hot spots, selectively metalizing an underside of a lid in one or more metalized lid locations, and assembling a lid over the backside of the chip to create an assembly so that metalized lid locations are in contact with the higher performance TIMs. A lower performance TIM fills the region surrounding the higher performance TIM on the underside of the lid enclosing the chips. Disclosed are methods of disposing both solid and dispensable TIMs, curing and not curing the thermal interface, and structures to keep the TIMs in place while assembly the package and compressing dispensable TIMs. Alternative method steps are disclosed, such as: injecting the lower performance TIM through injection holes in a pre-assembled assembly, using solid preform TIMs with cutouts, and using high performance TIM structures that have collapsible rails to prevent lower performance TIM from spilling onto the surface of the higher performance TIM to permit good/bonding.