Element evaluation is performed on a sample of randomly selected parts from a production lot, (if die, they are assembled into packages). These parts are then subjected to a series of tests selected to verify the reliability of the parts (Electrical, screening, environmental, endurance and mechanical tests) and the production lot from which they originated.
The Element Evaluation is performed to show that the parts performance, materials and manufacturing processes are able to meet their specified electrical, mechanical and physical performance characteristics for which they were designed-and as a result, their suitability for use in the application in which they are intended to be used.
It is essential to perform the element evaluation prior to use in production and to verify all materials prior to their use in production devices to minimise the risks of a lot failure (see table C-I).
The Element evaluation flow may vary or be modified by the manufacturer based on:
1. Element quality and reliability history.
2. Device quality and reliability history.
3. Best commercial practice/Supplier history.
4. Supplier/manufacturer relationship.
5. Possible impact of element evaluation failure after assembly.
The purpose of the Element Evaluation is to assess the performance, quality and reliability of each of the parts to be used in the assembly of a hybrid to minimise latent failure mechanisms, catastrophic failures and rework.
Test samples are usually assembled following industry standard processes that are similar to the assembly methods and conditions to be used in the Hybrid production assembly. This information originates from the users/customers/manufacturers making the hybrids.
Element Evaluation is performed following an approved set of standards and processes within a controlled and approved specification MIL-PRF-38534. There are five levels of test/reliability within this document, and the level selected depends on the Programme P.A. requirement, the level of assurance, schedule and cost for the intended application.