Issue link: https://iconnect007.uberflip.com/i/1379105
44 SMT007 MAGAZINE I JUNE 2021 Assessment of the cause of the foreign object debris (FOD) defect Based on company experience and knowl- edge with soldering defects, soldering mate- rials and background/experience with failure analysis work, the cause of the defect could be cellulose which is used in paper towels; thus, a piece of the paper towel may have been le dur- ing stencil cleaning which settled on the printed solder paste. Another source of the cellulose could be from the under-stencil wipe material. In this case, foreign object debris, seem- ingly irrelevant to soldering, caused de-wet- ting of solder. is can be derived from mate- rials of the PCB and/or components, as well as foreign object debris (FOD) from the process. Some foreign objects are related to non-sol- dering material, such as fiber, hair, etc. Discussion on possible solutions to the foreign object debris (FOD) defect e main area to focus on would be to review the stencil cleaning process. Damaged plating (Case Study 4) Analysis of damaged plating results Observations revealed damaged Sn plat- ing on the component lead with a copper sub- strate. e damaged area's copper substrate was oxidized which resulted in solder de-wet- ting. An organic substance was observed at the damaged area which was determined by EDX observation. SEM images of the compo- nent plating surface with EDX analysis for the good and poor solder wetting areas are shown in Figures 19 and 20. Figure 20 shows damage on the tin plating surface with the copper sub- strate exposed. Figure 18: FT-IR analysis result for foreign object debris. Figure 20: SEM image on component plating surface with EDX analysis (poor solder wetting). Figure 19: SEM image on component plating surface with EDX analysis (good solder wetting).