A decoupling package stack including a circuit board, a substrate mounted on and electrically coupled to the circuit board, a semiconductor die mounted on and electrically coupled to the substrate a deformable elastomeric support mounted on the substrate, one or more mounts coupled to the circuit board and a heatsink. The heatsink includes a contoured heatsink base having a spacer attached thereto, the spacer operable to determine and maintain a desired bondline of a first thermal interface material (TIM) between the semiconductor die and the contoured heatsink base. The heatsink also includes one or more contact portions for contacting the deformable elastomeric support and one or more compressing surfaces coupled to the one or more mounts. A method for assembling a decoupling package stack.