With the electronics industry rapidly moving to lead-free soldering and requirements for long term reliability of the assembly becoming more critical, fabricators and OEMs must determine the most cost effective and reliable means of achieving bare board solderability and component attachment. OSPs have long provided a reliable and inexpensive means of satisfying these requirements. However, greater solderability requirements, (measured as joint strength, paste spreadability and hole fill), and higher temperatures of lead-free soldering, have greatly diminished the use of conventional (standard substituted benzimidazole based) OSPs. However, with the development of third and fourth generation organic solderability preservatives based on a novel aryl-phenyl imidazole compound, OSP has regained its leadership role as a final finish, particularly in Asia and Europe. In addition, the technology shift to bare copper PWBs with selectively plated gold features is requiring OSPs that do not tarnish or deposit on the gold. This paper will explore the development and implementation of the next generation OSP for lead-free soldering. The OSP performance will be compared to other surface finishes (ENIG, ImTin, Immersion Silver, conventional OSP) in terms of solder paste spreadability, solder hole fill and solder joint strength. Reliability studies will be performed with both standard lead based solders and lead-free solders and include solderability performance with multiple reflows and artificial aging conditions.