Concern:
      1. A batch of “dual analog switch” circuits were mounted on a PCB, and after conformal coating, a few samples showed deterioration in input characteristics.
      2. After removing the aluminum, very small breakdown holes were found in the oxide layer on the n+ ring.

prescription:
      1. After failure analysis, it was found that a short circuit and leakage occurred at the input (base) where the aluminum metallization spans the diffusion layer of the n+ protection ring.
      2. Photolithographic etching is faster and electrostatic discharge damage occurs.
      3. Photolithographic etching is faster and electrostatic discharge damage can occur.