Analytical investigation on thermal-induced warpage behavior of ultrathin chip-on-flex (UTCOF) assembly

The serious warpage issues of ultrathin chip-on-flex (UTCOF) assembly induced by mismatched thermal stresses have greatly affected the mechanical stability and reliability of emerging ultrathin chip packaging technology. Currently, a theoretical prediction as a convenient and straightforward approach is still lacked for describing effectively the thermal-mechanical behavior of UTCOF during the adhesive curing and cooling process. In consideration of the adhesive thickness approximating to ultrathin chip and flexible substrate thickness, we develop a layerwise-model of ultrathin chip-adhesive-flex structure under plain strain condition, where the behavior of thick adhesive bonding can be described precisely through increasing the subdivided mathematical plies. Further, the analytical results show that the concave and convex forms of ultrathin chip warpage yield at the end of the curing and cooling process respectively. Meanwhile, the effects of its structure dimensions and material properties are also revealed for discussing a way to relieve the extent of ultrathin chip warpage. Additionally, in order to verify the validity of the theoretical prediction, we also introduce the corresponding numerical technique and experimental method. These results suggest that a kind of rigid and ultrathin flexible substrate such as metal foil should be adopted for small warpage of ultrathin assembly.     

氨基磺酸系高效减水剂合成工艺探讨

通过对氨基苯磺酸、苯酚、甲醛三元单体在低浓和高浓条件下共缩聚反应,合成了氨基磺酸系高效减水剂。并对两种产品进行水泥净浆流动度及其经时损失值测试。在相同共聚单体配比情况下,采用相同合成工艺,比较和分析反应浓度对产品分散性能的影响。采用变浓工艺,合成了性能得到较大改善的低浓氨基磺酸系高效减水剂。在不降低性能的前提下,使其成本大大降低。     

Relationship between FAC at plasma sheet boundary layers and AE index during storms from August to October, 2001

Unlike the previous single (dual) satellite observation, the four Clusterll satellites make it possible to directly compute the continuous field-aligned current (FAC) density according to the magnetic data from them and to enable the investigation of the relationship between the FAC and geomagnetic activity. This paper analyzes the observation data when the Cluster satellites crossed the plasma sheet boundary layer (PSBL) in the magnetotail during the two magnetic storms in August to October 2001. According to the data, during the magnetic storms the relationship between the variations of FAC and AE index turned out to be: 1) FAC was obviously increasing during the storms; 2) FAC density was approximately negatively correlated with AE index from the sudden commencement to the early main phase of the storm; 3) they were approximately positively correlated during the late main phase and early recovery phase; 4) they were no apparent correlation during the late recovery phase. Supported by the CAS International Partnership Program for Creative Research Teams and the National Natural Science Foundation of China (Grant Nos. 40621003, 40674091 and 40390150     

Near-Earth bursty bulk flows and AE index

With the 4-s resolution data of the magnetometer and the ion plasma analyzer on TC-1 from June to November of each year during the period of 2004-2006, we statistically analyzed the occurrence rate of both convective and field-aligned bursty flows (FABFs). A near-Earth bursty bulk flow (NEBBF) occurred during both the quiet time and substorm process. In general, the magnetic field and the plasma density began oscillating with the appearance of the NEBBF associated with a distinct increase of the AE index. The increase of AE index during the NEBBF was more than 100 nT in both quiet time and substorm process. The statistical analysis indicated that the occurrence rates of the FABFs were nearly the same in the different stages of the AE index, but the occurrence rate of the NEBBFs was much higher in the growth stage of the AE index, indicating that the NEBBFs were directly related to the growth and expansion phases of the substorm. The observations suggested that the quite large number of BBFs from the mid magnetotail could enter into the near-Earth tail and play important role in triggering the substorm onset. Supported by the National Natural Science Foundation of China (Grant Nos. 40704031, 40674091 and 40536030)     

A new processing method for the <Emphasis Type="Italic">AE</Emphasis> index

In this paper, we introduce an effective processing method to acquire the time derivative of the AE index as a coefficient. Using this coefficient, the AE index can be divided into the four stages: quiet, ascending, descending and active stages. The statistical results show that the ascending and descending stages of the AE index are dominant and occupy two thirds of the whole period. An analysis of the relationship between the occurrence frequencies of the Dst index and AE index in solar cycle 23 shows that the monthly variation of the occurrence frequencies of the ascending stage of AE is closely related to the decrease of the Dst index. Supported by the National Natural Science Foundation of China (Grant Nos. 40704031, 40536030)     

一类非自治机械系统的混沌同步控制研究

根据拉格朗日运动方程和牛顿力学定律, 建立机械式离心调速器的动力学方程, 运用数值仿真, 研究受外部扰动的离心调速器系统动力学行为, 该系统具有较复杂的动力学特性.利用系统的全局分岔图和李雅普诺夫指数谱,准确刻画出系统的局部动力学行为, 并讨论离心调速器系统参数变化对机械系统运动状态的影响,由此得知该系统在适当参数下处于混沌运动.运用Poincaré映射图揭示该系统的Hopf分岔与混沌形成过程.基于Lyapunov稳定性理论, 采用耦合反馈同步控制方法与自适应同步控制方法实现混沌同步, 并给出实现自同步的条件及控制律参数的选取范围.最后运用数值仿真证实同步控制方法的有效性.     

Flexible electronics manufacturing technology and equipment

Flexible electronics such as mechanically compliant displays, sensors and solar cells, have important applications in the fields of energy, national defence and biomedicine, etc. Various types of flexible electronics have been proposed or developed by the improvements in structural designs, material properties and device integrations. However, the manufacturing of flexible electronics receives little attention, which limits its mass production and industrialization. The increasing demands on the size, functionality, resolution ratio and reliability of flexible electronics bring several significant challenges in their manufacturing processes. This work aims to report the state-of-art technologies and applications of flexible electronics manufacturing. Three key technologies including electrohydrodynamic direct-writing, flip chip and automatic optical inspection are highlighted. The mechanism and developments of these technologies are discussed in detail. Based on these technologies, the present work develops three kinds of manufacturing equipment, i.e., inkjet printing manufacturing equipment, robotized additive manufacturing equipment, and roll-to-roll manufacturing equipment. The advanced manufacturing processes, equipment and systems for flexible electronics pave the way for applications of new displays, smart sensing skins and epidermal electronics, etc. By reviewing the developments of flexible electronics manufacturing technology and equipment, it can be found that the existing advances greatly promote the applications and commercialization of flexible electronics. Since flexible electronics manufacturing contains many multi-disciplinary problems, the current investigations are confronted with great challenges. Therefore, further developments of the reviewed manufacturing technology and equipment are necessary to break the current limitations of manufacturing resolution, efficiency and reliability.