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The Definitive Guide to an Electronic Assembly Design Review

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The Definitive Guide to an Electronic Assembly Design Review / 10 This table provides helpful information when you consider surface finish attributes and their performance based on the intended use. The table reveals positives and negatives associated with each finish. Additionally, the application environment and operating conditions must also be considered to ensure the best surface selection. 5 PCB Analysis (cont.) Surface Finish Cost Corrosion Resistance ICT Hole Fill Fine Pitch Cosmetics Comments Imm Silver Low Low Low Mod High Poor Mod Good Good Mod Good Poor Good Good Good Mod Poor Good Mod Good Good Good Mod Good Good Poor Mod Good Mod Good Good surface finish for soldering and testing, tarnish & creep corrosion are the weaknesses Required pasting of test pads/vias. Difficult to achieve LF hole fill, especially on >0.062 boards. Phenolic laminate recommended. New equipment required. Flatness is better than SnPb. Solderability/hole-fill may be a problem on double sided PCBs. Shelf life. Galvanic driven creep corrosion canoccur if Cu is exposed. Ni-Sn interface is brittle with LF. Black pad issues remain. HST OSP LF HASL Imm Tin ENIG

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