The most representative test conditions for electronics components are simply extended periods of time in the conditions at which they are required to operate. However, this is often not a viable option since most components are designed to last many years. Limited accelerated testing is available for high temperature electronics but care must be taken to ensure the tests are stressing the components in a representative manner and not inducing alternative failure modes.
For standard electronic components, many years of data acquisition have allowed a number of models to be formulated that can predict failure in components. These models are used to carry out accelerated ageing of conventional electronics components. The methods usually involve testing at increased temperatures, in humid environments, (e.g. 85°C/85% relative humidity), or the use of accelerated stress testing such as HAST, HALT HARASS. These tests often rely on a temperature difference between the upper operating temperature of the device and the temperature of the test.
For high temperature electronics (>200°C), accelerated testing can be an issue since the upper temperature limit of most tests is below the operating temperature of the device. Increasing the temperature of the test is not always feasible since either the high temperatures required to accelerate ageing could induce different failure modes in the device than those experienced in life, or the models for accelerated ageing at these temperatures have not been developed. Work on new and improved models and tests is underway in various laboratories world-wide.
TWI is currently investigating methods of testing and life prediction in a Joint Industry Project on High Temperature Materials and Packaging for Electronics and Sensors.