Failure Analysis Case Studies on Solder De-Wetting for Electronics Products

An IPC APEX EXPO Technical Conference Session

Failure analysis case studies on solder de-wetting for electronics products will be covered during IPC APEX EXPO technical conference session 03 on Wednesday, March 10. Koki Solder America has used defect analysis to determine the root cause of various defects experienced in the field. Over the many years of defect analysis, it has been determined that approximately 25 percent of all case studies have been due to de-wetting issues.

De-wetting is an issue with the solder joint where the molten solder and the substrate/component repel each other during the soldering process. Due to this, a very weak intermetallic bond (or no bond at all) is formed at the interface after reflow leading to defective and unreliable solder joints.

Case studies will be reviewed based on root cause analysis and countermeasures to prevent these defects. These case studies are related to inferior component/board plating quality, contaminated plating on both the PCB as well as the component, Foreign Object Debris (FOD) as a cause of the de-wetting of solder, damaged component plating and improper off-set solder paste printing.

For the Inferior board plating/ surface finish quality case study, solder de-wetting occurred on the pad substrate. The surface and cross-sectional observation of the HAL (Hot air solder level) board surface finish treatment was performed using an optical microscope and a SEM (Scanning Electron Microscope).

For the Contaminated plating case study, solder de-wetting occurred on the pad substrate which had an OSP (Organic Solderability Preservative) board surface finish. SEM (Scanning Electron Microscope) with EDX (Energy Dispersive X-ray) analysis and X-ray observation was performed on the pad substrate for both good and poor solder wetting.

For the Foreign Object Debris (FOD) case study, de-wetting occurred at the SOT (Small Outline Transistor) component lead. By observing the SOT solder joint having de-wetting issues by optical microscope the foreign object debris was found. FT-IR (Fourier Transform Infra-Red) analysis was performed on the foreign object debris to identify it.

For the Damaged plating case study, solder de-wetting occurred on the tin (Sn)-plated component. The plated surface of the good and inferior solder wetted components was observed by SEM (Scanning Electron Microscope) with EDX (Energy Dispersive X-ray) analysis.

For the improper process condition setting case study, solder de-wetting occurred on the nickel-gold (NiAu) board pad substrate. Pad substrates with good and poor solder wetting were observed by optical microscope.

Assessment of the cause of the defects was based on company experience and knowledge with soldering defects, soldering materials and background/ experience with failure analysis work with discussion on possible solutions to defects observed. 

For more information on this technical conference session, visit the IPC APEX EXPO agenda planner.