A flexible film interposer for stacking a flip chip semiconductor die onto a second semiconductor die, semiconductor devices and stacked die assemblies that incorporate the flexible film interposer, and methods of fabricating the devices and assemblies are provided. A method of the invention includes positioning the lead frame facing downward and bringing the lead fingers into contact with a pool of adhesive material. The clamp engages a flow-through heater and biases it against the bottom of a warmer plate that is retained by the support ring. The systems and methods present the estimated effect to an operator for viewing, reading, or offloading.