Ultra low temperature PBO-polymer for wafer level packaging applications
Thin Film Polymers are key building block for all WLP and related technologies like WLP (Wafer Level Packaging), IPD (integrated passives) and 3D-SiP (system in Package). A couple of different classes of photo-sensitive polymeric materials are commercially available for these types of integration: Polyimide (PI), Polybenzoxazole (PBO), Benzocyclobuten (BCB) and Epoxy. Curing plays an imporntant role due to temperature sensitive devices ans the stress in the underlying films. A new PBO has been introduced which has a curing temperature below 250°C. The material properties have been compared to other high performance polymers and haveshown superior properties with respect to the low curing temperature. A test chip has been redistributed with this low temperature PBO. The board-level reliability of this new polymer has been evaluated. 1000 cycles have been passed on board level using underfiller without any electrical failures using a test chip of 9mmx9mm with 256 I/Os redistributed to a 400µm or a 500µm full area array pitch.