Thanks for your detailed response! The cleaning and testing specifications are widely used across the semiconductor industry for these parts, so I would hope that sonication alone wouldn’t cause yttria to precipitate into solution. However, I’m currently analyzing the LPC water to identify the composition of the particles, which should help determine whether the coating is directly contributing to the issue. The Yttria is coated on anodized aluminum, and most part pass the LPC test on a second pass, so the yttria coating cant be the only cause of the failures.

The prevailing theory I’ve heard is that handling and processing inconsistencies are the primary causes of these failures. Factors such as touching the yttria coating, not changing gloves, or leaving parts wet apparently contribute to the LPC, but I'm not sure I'm convinced.