Process Control by Means of Accelerated Testing

High temperature operating life test gives quick feedback on the processes used in fabrication of semiconductor wafers. The relatively high failure rate of the (so-called) freaks is quickly demonstrated in such a test and can indicate a marginal or out of control process. This method of process control concentrates on the initial fallout as a means of determining the reliability of final products. Greater than 150°C stress temperatures should not be applied to plastic encapsulated devices. Since most epoxies have glass transition temperatures in the range of 150°C to 180°C permanent damage to the package could result.