Electrical Degradation Can Exist Without Visible Die Damage

What the evidence preview establishes

Physical examination did not reveal the cause of the electrical degradation. Bond wires, pads, and die surfaces appeared normal, with no visible corrosion, EOS, or ESD site. Subtle junction contamination, an invisible parametric ESD defect, or lead damage remained possible.

Why this case matters

When electrical shifts are repeatable but the die looks normal, treat physical inspection as a narrowing step. Add temperature-dependent parametric testing, comparison-lot data, emission microscopy, deprocessing, and lead-resistance checks.