Good question, the WLCSP are an SnAgCu alloy
Might be different across the BGA's as they have often been out-sourced
@Imen DAHMEN Technical Notes seemed a bit lacking, and wider search didn't yield any ST BGA specific notes, or any material safety docs
https://www.st.com/content/st_com/en/products/microcontrollers-microprocessors/stm32-32-bit-arm-cortex-mcus/stm32-high-performance-mcus/stm32h7-series.html#documentation
