Organic coatings and the challenge-no clean presents

Organic solderability preservatives (OSP´s) are rapidly being implemented within the PCB fabrication industry. OSP´s have shown to be excellent corrosion inhibitors and solderability preservatives. However, little has been reported on the “processability” during second level assembly. A small number of PCB assemblers, IBM included, have successfully used Benzotriazole (BTA) based OSP for a number of years. The BTA/OSP the Austin facility has been using will be compared to a new, next generation Benzimidazole (BIM) OSP on the market. Sequential Electrochemical Reduction Analysis (SERA) is an analytical method designed to correlate the type and amount of oxide species present on a PCB metal surface to its solderability, However, in this study we have attempted to characterize and correlate the PCB´s processability, i.e., reflow atmosphere and In-Circuit Test, to the SERA results. This paper will report on the process challenges OSP´s must meet for successful use in No-Clean solder assembly