Wednesday, February 25, 2009

The Impact of Alpha Particles in packaging materials

Alpha particles are charged particles emitted by radioactive
elements that can be found within the integrated circuit (wafer or package).
Alpha particles can generate errors and malfunctions of the electronic component, throughout the life of the device. These malfunctions are called Soft Errors.

Examples of radioactive elements found in wafer and packaged materials are Uranium, Thorium, Radon, Lead and all their decay chain. It takes a very small amount of these radioactive materials (almost impossible to detect) to generate enough alpha particles for dramatic errors to occur.
Alpha Counting is required by package houses or Integrated Circuit designer to be performed
by their supply chain. Supply chain Vendors sell both Low Alpha (LA) materials and packages or Ultra Low Alpha (ULA) ones. Low Alpha means that the emission rate is below 0.1 alpha/cm2/hr Ultra Low Alpha materials produce emission rates below 0.01 alpha/cm2/hr.
Emissions as low as .0001 alpha/cm2/hr can be detected.
Obviously the pricing and conditions of application of LA and ULA materials are different, making alpha measurement result an important input to both technical and economical decision.
The measurement is either part of the regular quality control procedure at the assembly house, or it can be used to verify the performance of the finished good with respect to the client specification.
Alpha Counting is performed on many forms of samples: raw material, wafers, pellets, solder balls, powder, paste and glue,liquid. It can even be performed on finished goods like integrated
circuits, trays, finished good package.

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