Valeria L. Scarano

Software automated testing: A solution to maximize the test plan coverage and to increase software reliability and quality in use

Software plays an increasingly important role in complex systems, especially for high-tech applications involved in important fields, such as transportation, financial management, communication, biomedical applications and so on. For these systems, performances such as efficient operation, fault tolerance, safety and security have to be guaranteed by the software structure, whose quality in use is assuming a growing importance from the industrial point of view. The basic problem is that the complexity of the task which software has to perform has often grown more quickly than hardware. In addition, unlike hardware, software cannot break or wear out, but can fail during its life cycle (dynamic defects) [1]. Software problems, essentially, have to be solved with quality assurance tools such as configuration management, testing procedures, quality data reporting systems and so on [2]. In this context, the paper proposes a new approach concerning the automated software testing as an aid to maximize the test plan coverage within the time available and also to increase software reliability and quality in use [3]. In this paper a method which combines accelerated automated tests for the study of software regression and memory overflow will be shown, in order to guarantee software with both a high quality level and a decrease of the testing time. The software will be tested by using test sequences reproducing the actual operating conditions and accelerated stress level. Moreover the research wishes to define some parameters of the software life and to show the generality of the proposed technique.

A Novel Approach To Automated Testing To Increase Software Reliability

Software plays an increasingly important role in equipment and systems, both in terms of technical relevance and of development cost (often higher than 50% even for small systems). Unlike HW, SW does not go through a production phase. Also, SW cannot break or wear out. However, it can fail to satisfy its required function because of defects which manifest themselves while the system is operating (dynamic defects). A fault in the SW is thus caused by a defect, even if appears randomly in time, and SW problems are basically quality problems which have to be solved with quality assurance tools (configuration management, testing, and quality data reporting systems). In order to grant a software high quality level against a reasonable cost, the testing planning phase has to be study in detail. In order to do so, an adequate coverage of the product functionality has to be supplied to reduce the test time. The aim of the paper is suggesting an automated software testing as a solution to the problem of having to maximize the test plan coverage within the available time and to increase software reliability and quality in use.

Definition of Safety Levels and Performances of Safety: Applications for an Electronic Equipment Used on Rolling Stock

This work presents a safety analysis on an electronic equipment used on rolling stock in according to the international safety standard, IEC 61508. Alternative methods, the fault tree analysis (FTA) and the Markov-Chain analysis, are shown and discussed in this paper. Such methods allow to cover wider reliability configuration classes with respect to the formulas suggested in the standard.

Optimization of the Soldering Process With ECAs in Electronic Equipment: Characterization Measurement and Experimental Design

With the introduction of the European Directives restrictions of hazardous substances, electrically conductive adhesives (ECAs) have received great attention in the field of electronics as a possible replacement of the traditional tin-lead soldering technology. So, in this new context, the analysis and the characterization of these alternative materials represent a fundamental topic, above all, from the industrial point of view. Nevertheless, studies on ECAs have rarely been reported in the literature, but more recently research has started to focus on this specific topic. After a comparative assessment concerning soldering materials, this paper focuses attention on their characterization through measurement in order to verify the electrical behavior of the isotropic silver conductive adhesive. In addition, since the soldering process is affected by a large number of variables such as the thickness of the conductive adhesive film, radial velocity, and curing temperature, the optimal selection of the factors is carried out through experimental design theory and the dual-response approach by means of generalized linear models. In this paper, the experimental and comparative studies on soldering made up of epoxy adhesives are carried out, in particular, the adhesives constituted by metallic particles (silver), normally in the form of flakes, in a polymer matrix are considered. The novelty of the kind of adhesive considered is the Ag filler loadings of 50-65% by volume. At these loadings, the materials achieve the percolation threshold and are electrically conductive in all directions after the materials are cured. Two different types of conductive adhesives, characterized by different chemical structures and compositions, are experimented and tested. Then, since the lead-free soldering process is characterized by several critical factors, a statistical approach is used to optimize this process. Experimental results obtained by testing samples with ECA materials prove the validity of this paper. The value of this paper is in the application of a statistical approach to these adhesive materials in order to achieve the optimization of the soldering process with a small number of treatment combinations, satisfying at the same time the stringent requirements and achieving robust electrical interconnections.

Implementation and Characterization of a Medical Ultrasound Phased Array Probe With New Pb-Free Soldering Materials

The application of the European Directive on the Restriction of Hazardous Substances, named RoHS, and correlated documents concerning the restriction of the use of hazardous substances in electrical and electronic equipment is critical and expensive, above all when the use of new substances needs to review consolidated production processes. The use of innovative materials (Sn-Ag-Cu alloys or electrically conductive adhesives (ECAs), for instance) instead of the traditional Sn-Pb solder joints and the design review of the electronic equipment when “not-RoHS-compliant” components must not on sale in the market are typical examples. In this context, this paper takes into account a new soldering production process with a conductive adhesive. In particular, we focus on the soldering phase with the adhesive for the design and implementation of ultrasound transducers for an industrial biomedical application. The use of new Pb-free soldering materials, such as a silver conductive adhesive, is considered in this paper in order to implement an ultrasound array transducer. With this component being fundamental for the functionality of the equipment (echocardiography system), a measurement system for the electroacoustic probe characterization is proposed, and some results, in terms of both joint performance and electrical properties of the new electronic device with Pb-free solder joints, are presented. This paper shows the use of conductive adhesives for the implementation of a medical phased array probe, where the soldering material is located among a platelet of the piezoelectric and fingers. A comparison between electroacoustic measures on the elements soldered with an ECA and with the traditional technology Sn-Pb will be also shown. Moreover, in the field of biomedical application, it is also fundamental to assure that the performances of the transducer are maintained in the time. To this aim, some laboratory tests for the evaluation of the reliability performances of the new Pb-free soldering material are proposed, and the preliminary results are presented in this paper.

Thermal stress on silver conductive adhesive solder joints: Performance evaluation of medical ultrasound array transducer

RoHS European Directive, recently introduced, makes a restriction of hazardous substances, e.g. Lead (Pb) and so on, traditionally used in soldering process of electric components and equipments. The paper presents preliminary results concerning new electronic Pb-free solder joints, in terms of both joint performances and electronic properties. A particular application of silver conductive adhesive solder joints between a plate of piezoelectric material and fingers, brass micro-connections between the substrate of piezoelectric material and the printed circuit, is considered. Factors that influence the soldering process like “thickness of the conductive glue” and “temperature of polymerization” are analysed by means of the Design of Experiments technique. The aim is to realise samples for the experimental tests. Measurements of electrical resistance, parameter chosen like failure pointer, and morphologic and micro-chemical analyses were carried out in order to verify the samples behaviour to the thermal stresses.

Experimental Stress Characterization of a Biomedical Ultrasound Probe Soldered With Innovative Silver Isotropically Conductive Adhesive

In the coming years, biomedical instrument manufacturers will have to inform the Notified Body of RoHS conformity assessment of the new medical instruments. In particular, in the case of lead-free solders, the Notified Body will require evidence that such solders are equally reliable as tin-lead, for the proposed use and lifetime of the product. So, biomedical instrument manufacturers are strongly interested in evaluating the performance of new soldering lead-free material used for the implementation of electronic parts. In order to support them and fill the technology knowledge gap, this paper presents a novel 128-channel phased-array probe for echocardiograph applications realized by new soldering technique where isotropic silver electrically conductive adhesive is used. In particular, the new soldering material is taken into consideration in the design phase of ultrasound array transducer, which is the core of a linear phased-array probe that is able to monitor the cardiac muscle. Being such material innovative in the application, a detailed study of the failure condition regarding the phased-array probe by means of accelerated qualification testing is proposed in order to assure its performances under stress and over time. A comparison of the electroacoustic measurement results with respect to the conventional probe, soldered with Sn-Pb, is also presented in this paper.

Environmental Stress Screening for electronic equipment by random vibration: a critical approach to reliability estimation and planning

Individuated a deficiency of manufacturing practice and standards in environmental stress screening, ESS, we proposed a process of screening with random vibrations in which the time of test is optimized according to the components and the layout board, trying also to minimize the cost of the same test. The screening test is implemented and the results are discussed in this paper.

Reliability Tests and Experimental Analysis on Radioreceiver Chains

In this work two solutions (coaxial cable and optical fiber) of receiver chains for the new SKA radiotelescope are evaluated by their reliability performance in their operating environment. In the case of the most reliable solution (optical fiber), other reliability test have been performed and their results are here reported

Optimization of ADC Channels of A Smart Energy Meter Including Random Noise Effects

This paper proposes a multiresponse process optimization through mixed response surface models. The robust design approach is used by involving noise effects in the optimization step. In order to illustrate our proposal, a prototype of an energy meter, based on an open source concept, is studied. The proposed device architecture assures easy development of new applications for the imminent migration to smart grid infrastructures and simple adjustments to comply with possible changes in the international power quality standards. The measurement data of the acquisition channels are collected from signals generated using a high-accuracy waveform generation module. Satisfactory results are obtained, and the multiresponse process optimization provides useful information about the smart energy meter firmware in relation to the suitable acquisition strategy in the signal frequency range of interest. Copyright