Evaluation of Lead-free Solders, Halogen-free Laminates, and Nanomaterial Surface Finishes for Assembly of Printed Circuit Boards for High Reliability Applications
There has been a global effort in the electronics industry recently to adopt green materials for the production of printed circuit boards (PCB's). However, there are technical and economic challenges that remain to hinder the universal implementation of green materials, especially for high reliability electronics applications.
The research presented in this paper was conducted by the members of the New England Lead-free Electronics Consortium. The objective was to evaluate the solder joints of electronics assemblies produced with various lead-free, halogen-free, and nano materials for use in high reliability applications. The test vehicle was 0.110” thick and densely populated with various components, which greatly increases the assembly challenge and differentiates this research from industry work with thinner, less populated test vehicles. Visual inspection procedures for this research meet IPC Class 3 standards for High Performance Electronics Products. This Class 3 standard is utilized for inspecting electronics assemblies used for high reliability applications. The lead-free materials that were evaluated during the assembly included four PCB surface finishes, two through hole technology (THT) solders, and three different surface mount technology (SMT) solder pastes. The results of the lead-free assemblies were compared against baseline data obtained by assembling similar test vehicles using tin/lead materials.
The assembly of lead-free electronics for high reliability applications is achievable with equal or less solder joint defects than tin/lead assemblies. This is viable with the careful selection of both lead-free solder and surface finish materials.