Soft errors are random and transient errors in a memory device that are caused by the device's exposure to radioactive particles such as alpha particles.

  

This video provides a nice tutorial on the potential hazards of the occurrence of soft errors in electronic products.  It also discusses how the environment, chip design, and device packaging can affect soft error rates.  It then explains what engineers should take into consideration in the risk assessment and reliability engineering of devices as far as soft errors are concerned.