Hello,

About the "Why protect an IC from UV?" asked by Dave and others, good information can be found in the AN0878 application note from Silicon Labs : https://www.silabs.com/documents/public/application-notes/AN0878.pdf

This might fit with the considered case as, like Joyce guessed first, I think the component of interest should use a WLP package, i.e. a non-molded unprotected die (referred to as CSP in the Silicon Labs application note).

The referenced AN can be summarized as follows : 
- Exposure to light can result in increased leakage currents for CMOS IC that are not fully encapsulated.
- These increased leakage currents typically do not affect digital IC, but can impact low-energy microcontrollers or precision analog IC.
- Recommended prevention techniques are the use of a light-blocking enclosure or Glob Top.
- The WLP backside coating or the use of a board-level underfill are not opaque enough and do not fully encapsulate the package, thus they are  not effective solutions.

Best regards,

AG