Part IV - The Driving Forces Behind Die Extraction for Reassembly – Increased Temperature Reliabilit
Bare Die Regeneration/High Temperature Reliability
Die extraction, followed by gold ball removal and ENIPIG (Electroless Nickel, Immersion Palladium, Immersion Gold) plating of the aluminum pads has been presented as a bare die alternative for smaller die quantities, or when bare die are not available for purchase in wafer form. Initial results validating high temperature performance of this regenerated interface are presented below in Figure 2.
High temperature reliability validation was performed by accelerated aging of devices under static conditions at 250C, while monitoring for electrical resistance shifts and bond pull strength. After 1000 hours at 250C, I/O resistance shifts measured 1% or less and bond pull strength remained stable (roughly equivalent to 4000 hours at 200C using typically cited empirical activation energies for Horsting voiding). Following exposure to the ENIPIG process, these die are ready for package assembly or installation into multi chip modules where high temperature reliability is desired.
Figure 2: Bond Pull Force vs. Time @ 250C