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Assembling technology in 48 hours

   
 
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SHORTEST involved scientific institutes and large and small high technology manufacturing companies in the development, evaluation, and promotion of new testing methods for electronic components.
The new tests were shown to be highly effective as a means of validating reliability in a wide range of sub-technologies and can be completed in just 48 hours. In addition to giving improved measurement resolution, they provide failure kinetics and physics failure information.
A number of the test benches have been industrialised or are already in use within partner businesses, and the consortium is actively promoting the adoption of the methodology as a new European standard.

Reliability testing is a critical element in the development of new electronic technologies. In particular, reliability tests are central to the evaluation of alternative sub-component technologies, and to the validation of production processes.
Current testing methodologies are based on the statistical analysis of failure rates among test samples subjected to 'accelerated ageing'. Typically, samples are tested following exposure to high temperatures for one thousand hours or more.
SHORTEST aimed to demonstrate the industrial applicability of faster and more accurate 'in situ' reliability testing methods.

The basis for built-in reliability

Conventional accelerated ageing tests are inherently slow, and involve exposing test samples to stresses far higher than those encountered in actual use. Repeated handling of the samples is also required, and this introduces reproducibility errors and measurement uncertainties which compromise the test results.
In theory at least the 'in situ' reliability testing concept, first developed by IMO-LUC at the University of Limburg, offers clear advantages to the electronics industry. It involves applying stress at levels which are much closer to those of normal use, and avoids the need to handle the samples. This is because resistance, current leakage, impedance and thermal resistance are measured while the unit is under stress rather than afterwards. Measuring accuracy is also greatly improved, and data is yielded for performance in all phases of the stress test. Higher resolution measurement allows for the effective evaluation of reliability in just 48 hours.
For the manufacturers of critical components for computing, avionics and telecommunications applications, these advantages combine to open up the possibility of improved designs with built-in reliability, and of a substantial reduction in the time taken to bring new products to market.

Testing techniques

Besides IMO-LUC itself, the SHORTEST partnership involves the leading manufacturers Alcatel Espace and IBM, as well as smaller specialist high technology companies. One of these, the Belgian company Destin, is a commercial arm of IMO-LUC, which manufactures and supplies the electrical test equipment and holds the background patent covering all the electrical tests.
In all, five different electrical and optical test techniques were developed and applied by the partners in the investigation of three basic failure mechanisms. 'In situ' resistance, leakage and impedance spectroscopy test benches were built, and were used to determine electrical performance. 'In situ' electrical and infra-red thermal resistance benches were used to measure the degradation of thermal resistance under continuous power cycling. IMO-LUC, IBM, Alcatel Espace, CEM and Destin each evaluated one bench.
Each technique was assessed in relation to ten sub-technologies representative of the wide range of components used in high reliability products. Samples of each component were tested using conventional procedures as well as by the new 'in situ' short test methods, and results were correlated to provide a comparison between the two approaches.

Towards a new European standard

The results, though not yet completed for the full range of tests, were so positive that the partners have already submitted a preliminary guidance document to the reliability working group of the CENELEC Electronic Components Committee (CECC). The document sets out the principles of the new technique, the test results, and the consortium's recommendations in relation to the design of suitable test samples.
Establishing new standards is always a slow process, but the partners expect the SHORTEST techniques to lead to new European reliability testing standards in the early years of the next century. They will then provide European industry with an extremely valuable alternative to existing test methods, improving the flexibility of technological development and allowing manufacturers to bring their products to market more quickly.

Immediate benefits

Until new standards are approved, widespread industrialisation of the advances achieved by the project will be constrained by what is referred to as the normative problem where most customers will continue to demand contracts which specify the validation of the product against existing standards.
However, for the project's partners themselves and for some of their customers, there will be immediate benefits. Alcatel Espace, for example, has almost completed the full industrialisation of one test technique, and is planning the introduction of a second for the evaluation of microwave active devices.
IBM has such confidence in the value of the SHORTEST technique that it is considering a validation programme applied to interconnections under humidity and/or during thermo-cycling tests on the plastic packaging of computer chips.
Both companies will use the techniques to improve their own test facilities and, by negotiation with specific customers, in the development of new products in advance of CECC approval.
Destin, meanwhile, will continue to build high performance benches for 'in situ' short testing for electromigration. Though it also has the capability to perform tests itself, the company plans to focus on the assessment of testing requirements and the specification of test methods for new technologies.

Studying the industry

An important final stage of this project involved a study designed to establish current demand for the new testing techniques among European electronic industries. Detailed research revealed a high level of dissatisfaction with current standard test methods, and particularly with their slowness.
In general, few of those surveyed felt ready to invest in the equipment themselves. However, as many as 50 of the 200 industrial and academic experts who responded to the questionnaire asked for an opportunity to evaluate the new techniques in relation to their own products. These requests were referred to laboratories already using the SHORTEST benches.
Progress is therefore unlikely to be spectacular until the 'in situ' short test methodology is adopted as a European standard. IMO-LUC represents the consortium on the CECC's reliability working group, and will continue to promote this goal.
If not spectacular, however, take-up of the new technique is certain to be steady, both in Europe and elsewhere. Guy Grégoris of Alcatel Espace, who acted as project coordinator, presented its results to an American industry workshop in late summer 1996, and expects to interest both US standards bodies and potential US customers.

 

 

Project Title:  
Short duration 'in situ' tests. A new approach to the reliability evaluation of electronic assemblies

Programmes:
Industrial and Materials Technologies (BRITE-EURAM/CRAFT/SMT)

Contract Reference: BE-5675

Cordis DatabaseFor more information on this project,
go to the CORDIS Database Record

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