Alpha particles are emitted from certain element isotopes, and can potentially change the binary output of a semiconductor from a 0 to a 1 or from a 1 to a 0. This is a cause for concern in high reliability devices.
Alpha emission is measured in counts/(square centimeter x hour). This measurement refers to the amount of particles that are collected by a sensor over a given amount of time. This measurement falls into various categories such as low count class 1 (LC1) 0.2-0.5 count/centimeter x centimeter/hour.
Tomorrow I will describe how solder suppliers like Indium Corporation can help lower alpha particle emission within an electronic component.