As electronic products evolve toward higher performance and greater reliability, the failure issues encountered during PCB (Printed Circuit Board) manufacturing have also become increasingly complex. Traditional inspection methods often struggle to reveal the root cause of problems, whereas Scanning Electron Microscopy (SEM) combined with Energy Dispersive Spectroscopy (EDS) has gradually become a powerful tool in the industry for resolving challenging issues.


The following classic PCB failure cases based on SEM & EDS analysis demonstrate the powerful capabilities of this technology in microscopic failure localization and elemental composition identification.


Case 1: Exposed Copper in Electroless Nickel/Gold Plated Holes
A customer discovered that in a few instances during the electroless nickel/gold (ENIG) process, nickel and gold were not deposited inside certain holes. SEM & EDS analysis revealed the presence of residual tin on the copper surface inside the holes. It was ultimately confirmed that incomplete tin stripping during the etching process led to tin residues, which obstructed the subsequent plating. This issue highlights the importance of thorough tin stripping, especially in the production of ENIG boards.


Case 2: Bulk Returns Due to Hole Wall Separation After SMT
After surface-mount technology (SMT) processing, a customer reported instances of hole wall separation in some PCBs. EDS analysis detected a high concentration of aluminum in the separation areas, confirming that the contamination originated from residual aluminum cover plates used during drilling. Further investigation found that inadequate vacuum suction allowed aluminum chips to remain in the holes. This case underscores the importance of maintaining dust extraction equipment during production.


Case 3: Poor Solderability of ENIG Boards
In a rush order, the customer reported poor solderability. SEM & EDS analysis revealed the presence of sodium carbonate crystals on the board surface. Tracing the issue back, it was discovered that the developer was forced to continue operating during a water outage, resulting in developer residue. This case once again emphasizes that forced production under abnormal conditions can easily lead to widespread failures.