Ex⁃situ Measurement of Internal Deformation in Ball Grid Array Package with Digital Volume Correlation

In spacecraft electronic devices,the deformation of solder balls within ball grid array(BGA)packages poses a significant risk of system failure.Therefore,accurately measuring the mechanical behavior of solder balls is crucial for ensuring the safety and reliability of spacecraft.Although finite element simulations have been extensively used to study solder ball deformation,there is a significant lack of experimental validation,particularly under thermal cycling conditions.This is due to the challenges in accurately measuring the internal deformations of solder balls and eliminating the rigid body displacement introduced during ex-situ thermal cycling tests.In this work,an ex-situ three-dimensional deformation measurement method using X-ray computed tomography(CT)and digital volume correlation(DVC)is proposed to overcome these obstacles.By incorporating the layer-wise reliability-guided displacement tracking(LW-RGDT)DVC with a singular value decomposition(SVD)method,this method enables accurate assessment of solder ball mechanical behavior in BGA packages without the influence of rigid body displacement.Experimental results reveal that BGA structures exhibit progressive convex deformation with increased thermal cycling,particularly in peripheral solder balls.This method provides a reliable and effective tool for assessing internal deformations in electronic packages under ex-situ conditions,which is crucial for their design optimization and lifespan predictions.

聚酮酸和聚醌的合成与表征

以均苯四甲酸酐、二苯醚为原料，以１，２－二氯乙烷为溶剂，无水三氯化铝为催化剂，在吡啶存在下，通过低温傅－克亲电反应合成了具有梯形结构的聚酮酸和聚醌，考察了溶剂体系对反应的影响 不同温度下聚酮酸的热关环，用ＩＲ、ＴＧ等方法对其进行了表征，研究表明它们具有优良和耐热性和耐溶剂性。

A Bibliometric Analysis of Chinese Ecological and Environmental Research on Urbanization

Based on an urbanization research database,a bibliometric analysis of Chinese ecological environmental research on urbanization was conducted that examined output,focused fields,topics,theories and methods.Results show that research output in this field has been increasing since 2005.Land and industry fields in resource research,economics in ecological research,and climate and urban environments in environmental research have been studied from 1992–2011.Keywords analysis discovered that ＂Land Use＂ and ＂Heat Island Effect＂ were major keywords,making up 0.15% and 0.09% of the total frequency,respectively.＂Heat Island Effect＂ and ＂Climate Change＂ were the most recent popular keywords.Main theories were derived from ecology,mathematics,resource environmental economics and environmental science.Ecological footprint has been a core theory since 2002.The stochastic impacts by regression on population,affluence and technology model（STIRPAT）,Environmental Kuznets Curve（EKC）,and slope,land use map,excluded area,urban area,transportation map and hillside area model（SLEUTH） are the latest popular theories.During 1992–2011,the main research methods can be divided into four groups： statistics（65.17%）,systems（13.11%）,mechanisms（11.79%） and evaluation（9.93%）.Grey System Analysis from system methods and rescaled range（R/S） analysis from evaluation are the latest popular methods.Topics from macro subfields,including land use,heat island effects,water resources and the agricultural ecological environment received more attention than micro subfields such as urban environmental health problems.As urbanization problems evolve,resource environmental economic comprehensive models will advance with modeling progress and some models,such as STIRPAT and land use change simulation models,will be developed for evaluation and simulation of the ecological environmental impacts of Chinese urbanization.