Lead-Free Solder Flip Chips on FR-4 Substrates with Different Assembly Processes and Materials

摘要

This study is focused on using different assembly options such as dip fluxing, flux jetting and reflow encapsulate for 200-250um pitch lead-free (SnAgCu) flip chips on FR4 substrates. The impact of different PCB surface finishes (OSP and ENIG), was investigated from an assembly perspective. Different underfill materials including an acid anhydrate based material and two non-acid anhydrate based materials were evaluated for compatibility with the flux and lead-free solder bumps and process. A reflow encapsulate designed for lead-free soldering is also studied from an assembly point of view.