Issue link: https://iconnect007.uberflip.com/i/1379105
46 SMT007 MAGAZINE I JUNE 2021 Assessment of the cause of the damaged plating 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 was dam- age in the Sn plating which was likely due to an improper component storage condition. It is assumed that the damage to the component was made while the components were being handled. e example shows how a damaged plating can cause de-wetting of solder. e plating surface is damaged during handling or shipping which causes the inner layer to be exposed. As the inner layer is oxidized, solder does not wet, and partially wetted solder may be observed. Discussion on possible solutions to the dam- aged plating defect e main area to focus on would be to review component storage conditions to eliminate the damage on the Sn plating surface. Improper process condition setting (Case Study 5) Figure 21 shows the de-wetting issue on the pad substrate. e board surface treatment was Ni-P/Au (nickel-phosphorus/gold). Analysis of improper process condition setting results e de-wetted area indicated offset paste printing due to improper printing conditions. Since solder did not wet to the areas with- out paste deposits, the right-hand corners of each board pad showed de-wetting. When de-wetting is caused by offset paste printing, de-wetting is shown regularly as described in the following schematic image (Figure 22). is de-wetting was caused by misalignment during printing of the solder paste, not by contamination at the board pad. Assessment of the cause of the improper process condition setting 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 was off- set paste printing of solder paste. e example shows that an improper process printing con- dition setting can be a cause of solder de-wet- ting. In addition to improper paste printing, dewetting could also be caused by improper component mounting/placement, and/or reflow profile settings. Figure 21: De-wetting issue on the pad substrate. Figure 22: Microscopy images of good and de-wetted pads and schematic of offset paste printing causing de-wetting.