Authors: Karl Wengenroth, Eric Stafstrom, and John Fudala Company: Enthone-OMI Date Published: 5/4/2000
Surface Finishes Forum
Abstract: Organic Solderability Preservatives (OSPs) have been utilized as a final surface finish for over 20 years. Over the last six years, organic coatings utilizing substituted benzimidazole chemistry have provided a wide assembly window and have become true Hot Air Solder Leveling (HASL) alternatives. The flat co-planer pads and optimum bond strengths provided by OSPs are now requirements for electronic assemblies using BGA, chip scale and flip chip packages. However, as the assembly and packaging market has changed so have the requirements for the final surface finish. New OSPs have been developed to address these changes. By optimizing the preclean process and the chemical balance of the coating chemistry, thinner more robust coatings have been developed to address in-circuit testing, compatibility with compliant pins, and provide a pristine gold surface for contacts or bonding applications. The new OSP processes continue to meet the electronics industry’s needs by providing a cost-effective solution to metallic surface finishes.