This FPGA is used in module with proper grounded metal casing and controlled environment w.r.t atmosphere (there almost four layers metallic enclosures from sun expose). Really doubt can cosmic rays travel all through and effect the same and also there are other modules sitting next to impacted on with same FPGA chip and configuration). Need to make sure the increased trend in CRC failures are not because of some other controllable causes if they can be any.
This is happening on device, which is in service for years. Almost 50 failures are observed in a span of two years, which are in service for last 10 years to 2 months old installations. Interested to know what are all possible reasons for SEU (FPGA CRAM CRC error), is there any trend shows increase of such failures in recent years (from other Altera Cyclone II chips users).