scholarly journals Virtual qualification of aircraft parts: test simulation or acceptable evidence?

2019 ◽  
Vol 24 ◽  
pp. 526-540
Author(s):  
Filippo Cianetti ◽  
Giulia Morettini ◽  
Massimiliano Palmieri ◽  
Guido Zucca
Author(s):  
Zhengfang Qian

This paper presents a damage mechanics-based methodology for the progressive damage and virtual qualification of advanced electronic packages such as BGAs, DCAs, CSPs, and Flip-chips. The key technique is to implement the material nonlinearity into commercially available software tools. A unified viscoplastic constitutive framework with the damage evolution and failure criteria has been successfully implemented into the ABAQUS® code to model time-rate-temperature dependent material properties. The framework has been successfully applied to solder alloys, polymer films, and underfill encapsulants. The mathematical structure and numerical algorithm development of the unified constitutive framework as well as the key implementation techniques for commercial FEA codes have been summarized in this paper. Both crack initiation and propagation of a solder joint with damage evolution under mechanical cyclic loading have been demonstrated. Virtual simulations of TSOP component failure under mechanical cyclic loading and BGA package under thermal cyclic loading have also been presented.


Land ◽  
2020 ◽  
Vol 9 (1) ◽  
pp. 8 ◽  
Author(s):  
Fabrizio Battisti ◽  
Orazio Campo ◽  
Fabiana Forte

According to Italian legislation for a particular type of real property—lands/areas subject to buildability, but not yet currently buildable—there is a problem related to their “qualification”, or whether or not they must be considered buildable for the purposes of their recurrent taxation. These potentially buildable (POBU) areas, that were previously zoned as “agricultural”, have been rezoned as “general urban planning instruments/regulations” (the General Urban Development Plans or variances, which regulate land governance), whose approval path has yet to be concluded. Their value—the taxable base underpinning their taxation—clearly depends on their qualification (whether or not they are considered buildable). This has produced, in recent years, several disputes between owners and local governments; the law did not give univocal solutions: Today (2019), there is a conflict of case law in relation to considering these areas as being building areas, as it is not clear what estimating procedures should be used. This article is thus based on the assumption that responding to the problems connected with taxing POBU areas must be considered separately from (overcoming, in this way, conflicting case law) the “virtual” qualification of agricultural or buildable area, but must instead, and more simply, be considered as the actual condition it is found in (likelihood of having building potential in the future), and therefore its limitations (present at the time of taxation) and the time necessary for the building to actually be built and not just “potential”. The approach proposed in this article thus offers a solution to the problem that has been raised, by modifying the current de jure approach (defining the moment when the building right is manifested) towards an assessment/appraisal approach (defining the value of the potentially buildable (POBU) area, in relation to its actual conditions). To implement this approach, a methodology—proposing an upgrade of the traditional analytic procedure for the assessment of transformation value has been structured in a way such that consideration may be made of the components characterizing the potentially buildable areas by means of appropriate assessment parameters that go towards forming these areas’ value: These are the market value discount rate of the POBU area in relation to the uncertainty and risk of reaching effective and concrete buildability, and the estimated time needed to complete the procedural path for making the area actually buildable.


Author(s):  
Zhengfang Qian ◽  
Joe Tomase

This paper presents a critical overview of the current state-of-the-art of Accelerated Reliability Tests (ALTs) and field reliability. Investigations have been focused on a few critical issues, including test philosophy, test physics, test procedure, and test statistics. It has been identified that there is a huge gap between ALT and field reliability. Challenges and solutions include bridging gap between deterministic and statistical approaches, identifying failure modes/mechanisms and their interaction, making scientific judgement of complicated ALT procedures, determining sample size and targeted failure rate for test plans, building databases of ALT and field reliability for knowledge discovery, and developing powerful and integrated tools for virtual qualification and reliability prediction.


2005 ◽  
Vol 127 (4) ◽  
pp. 512-522 ◽  
Author(s):  
Qian Zhang ◽  
Abhijit Dasgupta ◽  
Peter Haswell

This study is motivated by the urgent need in the electronics industry for mechanical properties and durability of Pb-free solders because the use of Pb will be banned in the EU by July 1, 2006. The isothermal mechanical durability of three NEMI recommended Pb-free solders, 95.5Sn-3.9Ag-0.6Cu, 96.5Sn-3.5Ag, and 99.3Sn-0.7Cu, is tested on the thermo-mechanical-microscale (TMM) setup under two test conditions: room temperature and relatively high strain rate, and high temperature and low strain rate. The test data are presented in a power law relationship between three selected damage metrics (total strain range, inelastic strain range, and cyclic work density) to 50% load drop. The obtained mechanical durability models of three Pb-free solders are compared with those of the eutectic 63Sn-37Pb solder at the two selected test conditions and at the same homologous temperature of 0.75. The results of this study can be used for virtual qualification of Pb-free electronics during design and development of electronics under mechanical loading.


2000 ◽  
Author(s):  
Rajiv Raghunathan ◽  
Raghuram V. Pucha ◽  
Suresh K. Sitaraman

Abstract The objective of this work is to develop qualification guidelines for Flip-Chip on Board (FCOB) and Flip Chip Chip-Scale Packages (FCCSP) used in implantable medical devices, automotive applications, computer applications and portables, taking into consideration the thermal history associated with the field conditions. The accumulated equivalent inelastic strain per cycle and the maximum strain energy density have been used as damage parameters to correlate solder fatigue damage during field use and thermal cycling. The component assembly process mechanics, the time and temperature-dependent material behavior, and the critical geometric features of the assembly have been taken into consideration for developing the comprehensive virtual qualification methodology.


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