The achievements so far are the development and validation of seven in-situ test techniques. Five of the test techniques demonstrate capability of detecting failure mechanisms at 48 hours with moderate tress conditions and 50% of the in-situ test results obtained at 48 hors on 10 subtechnologies correlate with conventional tests. The application of the method for Quality Assurance and Building-in reliability is foreseen.
The SHORTEST principles are under validation within the consortium for the evaluation of active devices. An industrial version of the in-situ resistance test bench is now available and further industrial test bench developments are in progress. In parallel, a guidance based on the SHORTEST principles has been submitted to the CECC.
Today industry, most reliability and life duration tests for the qualification of electronic subassemblies are based on accelerated ageing under some kind of stress (isothermal or cycling temperature stress, corrosive of oxiditing stress, or combination of those). The major disadvantage of those tests is that they are in general very time consuming if the applied stress is kept at reasonable levels (i.e. levels at which the acutal ageing of the component under real life conditions is merely accelerated, without introducing ageing processes associated with the high stress level that will never occur under real life conditions). A typical test time for a conventional test is in the order of 1000 hours or even more.
This will no more be acceptable owing to the encreasing complexity of the products. The trend is to qualify elementary processes rather than final product and to build reliability at design, what is referred to as "the new wave" in reliability evaluation.
The proposed project will aim at demonstrating that there exist an alternative approach - increasing the measuring resolution during accelerated ageing - which is more appropriate. The basic idea of this approach is to measure the physical quantity characterizing the ageing of the tests structure with a higher resolution, so that one can detect ageing phenomena on a "48 hours" time scale. A higher measuring resolution should also allow to analyse the ageing kinetics in more detail, so that the calculaztion ofthe acceleration factor - and hence the lifetime prediction - should be more accurate. The best available solution consists of in-situ measurements. In-situ means under the stresses applied during the classical (accelerated or not) duration tests.
The three failure mechanisms encountered in electronic subassemblies: solid state migration, electromechanical migration, thermo-mechanical stress will be regarded in this project. The potentially applicable test technics include D.C. resistance, leak current, A.C. impedance spectroscopy, acoustic microscopy and interferometry. The project will perform relevant short duration and long term tests on critical elementary processes like oldering, wire bonding metal-ceramic interfaces and on functional assemblies. The results will be compared, providing the required correlation study for pertinent transfer to design, manufacturing and qualification in industrial environment and for recommandation to CEEC standards. The consortium covers computer, automotives, avionics and space telecommunication sectors and qualifies for large dissemination of the results in Europe through the test house SMES envolved in the project. The expected industrial benefits are better designs "(built-in-reliability), shorter qualificaion flows (X10) and reduced time to market (3 monts on a 18 month window).
Funding SchemeCSC - Cost-sharing contracts
20059 Vimercate Milano