Modeling with structure of resins in electonic compornents

In recent years, interfacial fracture becomes one of the most important problems in the assessment of reliability of electronics packaging. Especially, underfill resin is used with solder joints in flip chip packaging for preventing the thermal fatigue fracture in solder joints. In general, the interfacial strength has been evaluated on the basis of interfacial fracture mechanics concept. However, as the size of devices decrease, it is difficult to evaluate the interfacial strength quantitatively. Most of researches in the interfacial fracture were conducted on the basis of the assumption of the perfectly bonding condition though the interface has the micro-scale structure and the bonding is often imperfect. In this study, the mechanical model of the interfacial structure of resin in electronic components was proposed. Bimaterial model with the imperfect bonding condition was examined by using a finite element analysis (FEA). Stress field in the vicinity of interface depends on the interfacial structure with the imperfect bonding. In the front of interfacial crack tip, the behavior of process zone is affected by interfacial structure. However, the instability of fracture for macroscopic crack which means the fracture toughness is governed by the stress intensity factor based on the fracture mechanics concept.Comment: Submitted on behalf of TIMA Editions (http://irevues.inist.fr/tima-editions

New Reliability Assessment Method for Solder Joints in BGA Package by Considering the Interaction between Design Factors

As the integration and the miniaturization of electronics devices, design space become narrower and interactions between design factors affect their reliability. This paper presents a methodology of quantifying the interaction of each design factor in electronics devices. Thermal fatigue reliability of BGA assembly was assessed with the consideration of the interaction between design factors. Sensitivity analysis shows the influence of each design factor to inelastic strain range of a solder joint characterizing the thermal fatigue life if no interaction occurs. However, there is the interaction in BGA assembly since inelastic strain range depends on not only a mismatch in CTE but also a warpage of components. Clustering can help engineers to clarify the relation between design factors. The variation in the influence was taken to quantify the interaction of each design factor. Based on the interaction, simple evaluating approach of inelastic strain range for the BGA assembly was also developed. BGA package was simplified into a homogeneous component and equivalent CTE wascalculated from the warpage of BGA and PCB. The estimated equation was derived by using the response surface method as a function of design factors. Based upon these analytical results, design engineers can rate each factor's effect on reliability and assess the reliability of their basic design plan at the concept design stage.Comment: Submitted on behalf of TIMA Editions (http://irevues.inist.fr/tima-editions

Reliability Evaluation Method for Electronic Device BGA Package Considering the Interaction Between Design Factors

The recent development of electric and electronic devices has been remarkable. The miniaturization of electronic devices and high integration are progressing by advances in mounting technology. As a result, the reliability of fatigue life has been prioritized as an important concern, since the thermal expansion difference between a package and printed circuit board causes thermal fatigue. It is demanded a long-life product which has short development time. However, it is difficult because of interaction between each design factor. The authors have investigated the influence of various design factors on the reliability of soldered joints in BGA model by using response surface method and cluster analysis. By using these techniques, the interaction of all design factors was clarified. Based upon the analytical results, design engineers can rate each factor's effect on reliability and assess the reliability of their basic design plan at the concept design stage.Comment: Submitted on behalf of TIMA Editions (http://irevues.inist.fr/tima-editions

Spin current and magneto-electric effect in non-collinear magnets

A new microscopic mechanism of the magneto-electric (ME) effect based on the spin supercurrent is theoretically presented for non-collinear magnets. The close analogy between the superconductors (charge current) and magnets (spin current) is drawn to derive the distribution of the spin supercurrent and the resultant electric polarization. Application to the spiral spin structure is discussed.Comment: 5 pages, 2 figure

Evaluation Technique for The Failure Life Scatter of Lead-Free Solder Joints in Electronic Device

Recently, the electronic device equipment using a semiconductor is widespread to all industrial fields. Solder is used to mount electronic parts, such as resistors and capacitors, on printed-circuit boards in almost all electronic devices. However, since in many cases the thermal expansion coefficients of electronic parts and PCBs are different, cyclic thermal stress and strain causes solder fatigue and device failure. Especially in the power electronic module and car electric module, the evaluation of thermal fatigue life is important. It is understood that the fatigue life of some electronic devices shows large scatter in the thermal cycle test, even if their design is the same. The dispersion of design factors such as shape, size and material properties of solder joints is thought as one of these reasons. Moreover, in the case of chip components, it is thought that the interacting effect by the structural asymmetry due to the unbalance solder joints would influence reliability. At the same time, the changeover from eutectic Sn-Pb solder to lead-free solder has been driven by environmental concerns. Therefore, it cannot be disregard as the main factor of the reliability evaluation in the solder joints. In this study, how the dispersion of design factors and the interacting effect between the design factors influences the fatigue life in lead-free solder joint was investigated by the analytical approach. It is understood that the thermal fatigue life of solder joints can be estimated by the inelastic strain range obtained from the FEM analysis. Recently, it is demanded to evaluate the final failure life of electronic components. So, it is necessary to evaluate not only crack initiation but also crack propagation. In this study, crack propagation analysis was carried out by using a new approach and the failure life was evaluated on the basis of Manson-Coffin's law and Miner's rule. Moreover, sensitivity analyses were carried out to study the main effect of the dispersion of each factor on solder joints. And then, the interacting effect between the factors on the reliability was studied by considering the structural asymmetry due to the unbalanced solder joints. As a result, a practical evaluating technique for the failure life scatter of solder joints was proposed

Segmenting Motion Capture Data Using a Qualitative Analysis

Many interactive 3D games utilize motion capture for both character animation and user input. These applications require short, meaningful sequences of data. Manually producing these segments of motion capture data is a laborious, time-consuming process that is impractical for real-time applications. We present a method to automatically produce semantic segmentations of general motion capture data by examining the qualitative properties that are intrinsic to all motions, using Laban Movement Analysis (LMA). LMA provides a good compromise between high-level semantic features, which are difficult to extract for general motions, and lowlevel kinematic features, which often yield unsophisticated segmentations. Our method finds motion sequences which exhibit high output similarity from a collection of neural networks trained with temporal variance. We show that segmentations produced using LMA features are more similar to manual segmentations, both at the frame and the segment level, than several other automatic segmentation methods

Fibrosis Evaluation by Transient Elastography in Patients With Long-Term Sustained HCV Clearance

BACKGROUND: Reversibility of advanced fibrosis after HCV-clearance is an important goal of therapy. OBJECTIVES: Measuring liver stiffness (LS) by transient elastography (TE) might be helpful in this setting. PATIENTS AND METHODS: We evaluated 104 patients with biopsy-proven chronic hepatitis C (CHC) and sustained virological response (SVR) after Peg-Interferon (IFN) plus ribavirin since at least 18 months. HCV-eradication was confirmed searching for serum HCV-RNA (TMA® sensitivity > 5-10 IU/ml). Data from literature reported the best LS cut-off values for different stages of liver fibrosis were 7.1 kPa for Metavir stage 2 (F2), 9.5 kPa for F3 and 12.5 for cirrhosis (F4). RESULTS: TE was not reliable in four SVR obese patients. Metavir-stage of biopsy was F0-1 in 28, F2 in 47, F3 in 17 and F4 in eight patients. The median interval elapsed since achieving SVR was 36 months (range: 18-77, SD¬¬:18). Stratifying patients according to the histological stage assessed before treatment, a clear-cut gradient of LS values was observed from F0-1: median: 3.8 kPa (range: 3.5-4.9) to F2: 4.6 kPa (3.8-6.0), F3: 6.2 kPa (4.8-8.6) and F4: 8.4 kPa (6.2-9.2) (P = 0.001). Overall, 86 patients had lower values of LS than the expected LS values according to Metavir-stage. At multivariate logistic analysis γ-GT and histological steatosis were independently associated with persistence of higher values of LS. CONCLUSION: Long term responders to IFN-based therapies have lower LS values than those who are untreated and still viraemic. High levels of γ-GT and liver steatosis, all markers of insulin resistance, may hamper reduction of liver stiffness after HCV-clearance