SHORTEST involved scientific institutes
and large and small high technology manufacturing companies in the
development, evaluation, and promotion of new testing methods for
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
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
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.
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
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.