高功率激光钕玻璃椭圆片硬包边残余应力研究

硬包边是激光钕玻璃减少放大自发辐射和抑制寄生振荡的包边技术之一,残余应力是硬包边的一个重要参数。详细描述了激光钕玻璃硬包边过程中残余应力的来源,并利用有限元分析软件COMSOL Multiphysics,对硬包边浇注熔接过程中不同膨胀系数匹配条件和不同包边玻璃浇注温度下的残余应力分布进行了数值模拟。结果显示,激光钕玻璃和包边玻璃的膨胀系数差异愈小,产生的残余应力愈小;包边玻璃浇注温度愈高,则产生的残余应力愈大。硬包边实验结果表明:包边玻璃的膨胀系数和激光钕玻璃的膨胀系数愈相近,则残余应力就愈小,当包边温度在700～1200℃范围内时,残余应力随着包边温度的增加而增大。模拟结果与实验结果吻合,所以在硬包边的浇注熔接过程中,为了使残余应力最小,最佳策略是激光钕玻璃的膨胀系数和包边玻璃的膨胀系数尽量接近甚至相等,且包边温度尽量低。     

组分变化对无铅低熔玻璃使用特性的影响

采用阿基米德排水法、热机械分析、失重法和扫描电镜法研究了V2O5-P2O5-Sb2O3-Bi2O3体系玻璃的密度、热膨胀系数和化学稳定性。结果表明:随着Sb2O3取代部分V2O5,玻璃的密度显著升高,膨胀系数略有增长,化学稳定性显著增强;随着Sb2O3取代部分P2O5,玻璃的密度显著升高,膨胀系数下降,化学稳定性增强;随着P2O5取代部分V2O5,玻璃的密度略有下降,膨胀系数增长较大,化学稳定性增强。90%的样品的密度、膨胀系数和化学稳定性都能满足使用要求。这是由于Sb2O3和P2O5取代V2O5进入钒酸盐玻璃中,玻璃结构由层状转化为立体交联结构,玻璃结构得到增强的结果。     

玻璃金属多针封接件的过渡环封研究

"14针密排"玻璃-金属封接件在生产及应用过程中常会出现玻璃炸裂,继而引起元件封接强度、气密性、热稳定性及耐冲压性等综合性能降低甚至报废。结合其特殊的导电性能和气密性设计要求,分析认为玻璃产生微裂纹的原因是封接元件膨胀系数不相匹配。利用"环封"工艺逐级过渡玻璃和金属之间的膨胀系数差异,同时结合玻璃抗压不抗拉的特性,达到"匹配封接",彻底解决普遍存在于该类元器件中的致命问题。     

Bi2O3对Al2O3-ZnO-Bi2O3-B2O3低熔玻璃结构和性能的影响

采用传统的熔淬技术制得了低熔Al2O3-ZnO-Bi2O3-B2O3玻璃,研究了玻璃结构、玻璃特征温度、线膨胀系数(α1)以及密度随Bi2O3含量的变化关系.结果表明:随着Bi2O3含量的增加,玻璃网络中[BO4]取代了部分[BO3],玻璃网络中出现Bi-O结构,玻璃中非桥氧的数量也逐渐增多;软化温度(ts)、玻璃化温度(tg)都是先上升后下降,而线膨胀系数先减小后逐渐增大,玻璃密度先是线性增加,然后增加趋势变大.     

Bi2O3对Al2O3-ZnO-Bi2O3-B2O3低熔玻璃结构和性能的影响

采用传统的熔淬技术制得了低熔Al2O3-ZnO-Bi2O3-B2O3玻璃,研究了玻璃结构、玻璃特征温度、线膨胀系数(αl)以及密度随Bi2O3含量的变化关系。结果表明:随着Bi2O3含量的增加,玻璃网络中[BO4]取代了部分[BO3],玻璃网络中出现Bi—O结构,玻璃中非桥氧的数量也逐渐增多;软化温度(ts)、玻璃化温度(tg)都是先上升后下降,而线膨胀系数先减小后逐渐增大,玻璃密度先是线性增加,然后增加趋势变大。     

氧化锌及氟化钙对钡钙玻璃性能的影响

研究了ZnO和CaF2的加入对钡钙玻璃烧结和性能的影响。用单因素法探讨了ZnO和CaF2的加入量对玻璃性能的影响,得到了线膨胀系数范围在(60~70)×10-7/℃和焊接温度小于1100℃的钡钙玻璃,结果表明,ZnO和CaF2对改善玻璃性能有显著的作用。     

CeO2掺杂对SiO2-Al2O3-CaO-MgO玻璃的改性研究

采用高温熔融的方法制备了掺杂不同质量分数的CeO2的SiO2-Al2O3-CaO-MgO玻璃,研究了所制玻璃的物理化学性能。结果表明:掺杂少量CeO2可以使SiO2-Al2O3-CaO-MgO玻璃的网络结构更加完整,降低玻璃的转变温度;随着CeO2含量的增加,玻璃的线膨胀系数呈现先降低后增加的变化趋势;掺杂CeO2的玻璃相对介电常数高于未掺杂的玻璃,随着CeO2含量增加,玻璃的相对介电常数呈现下降的趋势。     

SiO_2对碲铅铋硅系玻璃粉结构和热学性能的影响

采用熔融法制备出不同SiO2含量的TeO2-PbO-Bi2O3-SiO2系玻璃粉,研究了SiO2的加入量对该系玻璃结构、线膨胀系数αl、膨胀软化温度ts和热稳定性的影响。结果表明:SiO2以[SiO4]四面体的形式参与玻璃网络形成,随SiO2含量的增加,玻璃粉的膨胀软化温度升高,线膨胀系数先减小后增大,热稳定性则表现出相反的规律。当SiO2的加入质量分数为5%时,玻璃粉的线膨胀系数最小,为90.12×10–7/℃,玻璃粉热稳定性最好。     

建筑用玻璃/不锈钢、玻璃/钛合金激光焊接机理研究

开展了玻璃/不锈钢和玻璃/钛合金的激光焊接试验研究,重点分析了焊缝的断口形貌、截面形貌及焊缝处物相的差异。结果表明,玻璃/不锈钢、玻璃/钛合金焊接的机理类似,焊缝中玻璃与金属形成的镶嵌结构及分布在界面处的粘附物是两者能连接的主要原因;玻璃与钛合金的线膨胀系数差异较小是玻璃/钛合金焊接件拉断力高的主要原因;激光作用下玻璃与钛合金形成化学结合,生成化合物Ti5Si3,而玻璃与不锈钢主要为机械混合。     

GKZ-A型石英与钨的高温扩散封接

石英玻璃广泛地应用于高功率的放电器件和电光源中.由于石英的膨胀系数比钨小很多,不能直接封接.过去主要采用多道过渡玻璃封接或钼箔封     

影响环氧塑封料应力、黏度因素分析及解决

环氧塑封料是微电子工业和技术发展的基础材料, 作为IC后道封装三大主材料之一, 随着IC封装技术的发展, 对其特性的要求愈来愈严格, 尤其对应力、黏度等性能的要求更高。文章简要分析了影响环氧塑封料应力和黏度的因素, 并提出了多个解决方案。通过实验的方式得出数据并加以分析, 通过膨胀系数的数据来反映应力大小, 膨胀系数越小, 在封装过程中产生的应力越小, 不易产生翘曲、分层现象。通过黏度数据大小来反映环氧塑封料流动性能的变化。同时文章还介绍了环氧塑封料膨胀系数和黏度的测试方法。     

厚铜箔印制板尺寸稳定性研究

伴随着电源模块等大功率元器件的市场需求量不断加大,厚铜箔印制电路板的产量也不断增加,其对品质的要求也越来越严格。众所周知,厚铜箔印制电路板在其生产制作中产生的热膨胀系数量一直是影响其品质的重要因素,本文正是着眼于信息产业高科技、高精度的要求,通过对厚铜箔板的工艺流程、材料本身特点、设计三个因素来试验找出厚铜箔印制板系数补偿的重点考虑因素,同时对热膨胀系数量进行统计分析,从而保证厚铜板涨缩控制在范围之内,达到客户的要求。     

电路板设计中的膨胀系数匹配问题

电子产品设计是一个系统性的问题,设计人员的注意力只集中到了原理的设计,注重产品的电性能指标.对于元器件、原材料的膨胀系数匹配问题容易忽视.本文从元器件、基板、焊料等材料膨胀系数的匹配问题入手,对此问题进行了分析.解决了在产品使用中由于膨胀系敷不匹配可能会造成的质量问题.     

Effects of silica filler and diluent on material properties and reliability of nonconductive pastes (NCPs) for flip-chip applications

In this paper, thermomechanical and rheological properties of nonconductive pastes (NCPs) depending on silica filler contents and diluent contents were investigated. And then, thermal cycling (T/C) reliability of flip chip assembly using selected NCPs was verified. As the silica filler content increased, thermomechanical properties of NCPs were changed. The higher the silica filler content was added, glass transition temperature (T/sub g/) and storage modulus at room temperature became higher while coefficient of thermal expansion (CTE) decreased. On the other hand, rheological properties of NCPs were significantly affected by diluent content. As the diluent content increased, viscosity of NCP decreased and thixotropic index increased. However, the addition of diluent deteriorated thermomechanical properties such as modulus, CTE, and T/sub g/. Based on these results, three candidates of NCPs with various silica filler and diluent contents were selected and used as adhesives for reliability test of flip chip assemblies. T/C reliability test was performed by measuring changes of NCP bump connection resistance. Results showed that flip chip assembly using NCP with lower CTE and higher modulus exhibited better T/C reliability behavior because of reduced shear strain in NCP adhesive layer.     

Guidelines to select underfills for flip chip on board assemblies and compliant interposers for chip scale package assemblies

The effect of thermomechanical properties of underfill and compliant interposer materials, such as coefficient of thermal expansion (CTE) and stiffness (Young's modulus) on reliability of flip chip on board (FCOB) and chip scale packages (CSPs) under thermal cycling stresses is investigated in this study. Quasi-three-dimensional viscoplastic stress analysis using finite element modeling (FEM) is combined with an energy partitioning (EP) model for creep-fatigue damage accumulation to predict the fatigue durability for a given thermal cycle. Parametric FEM simulations are performed for five different CTEs and five different stiffnesses of the underfill and compliant interposer materials. The creep work dissipation due to thermal cycling is estimated with quasi 3-D model, while 3-D model is used to estimate the hydrostatic stresses. To minimize the computational effort, the 3-D analysis is conducted only for the extreme values of the two parameters (CTE and stiffness) and the results are interpolated for intermediate values. The results show that the stiffness of the underfill material as well as the CTE play important role in influencing the fatigue life of FCOB assemblies. The fatigue durability increases as underfill stiffness and CTE increase. In the case of compliant interposers, the reverse is true and durability increases as interposer stiffness decreases. Furthermore, the interposer CTE affects the fatigue durability more significantly than underfill CTE, with durability increasing as CTE decreases. The eventual goal is to define the optimum design parameters of the FCOB underfill and CSP interposer, in order to maximize the fatigue endurance of the solder joints under cyclic thermal loading environments.     

金属陶瓷封装器件安装中典型失效及注意事项

文章对金属陶瓷封装器件安装使用中与封装有关的三种典型失效模式进行了分析。安装使用中过多的热积累导致壳体引脚脱落;安装区域线胀系数差异过大造成的额外应力,导致壳体引脚拉断;安装位置不平整或受挤压,致使壳体内部芯片、陶瓷电路片开裂。并且根据这三种失效机理提出了金属陶瓷封装器件安装使用中的相关注意事项,对提高金属陶瓷封装器件的使用可靠性具有一定的参考价值。     

Very High-Temperature Joints Between Si and Ag–Copper Substrate Made at Low Temperature Using InAg System

We present a fluxless bonding process between silicon and Ag–copper dual-layer substrate using electroplated indium/silver solder. The nucleation mechanism of In plated over Ag layer is first investigated. It is interesting to discover that In atoms react with underlying Ag to from ${hbox {AgIn}}_{2}$ compound layer during electroplating. A novel Ag laminating technique on Cu substrates is developed. The Ag cladding functions as a strain buffer to manage the large mismatch in coefficient of thermal expansion (CTE) between semiconductors such as Si (3 ${hbox {ppm}}/^{circ}{hbox {C}}$) and Cu (17 ${hbox {ppm}}/^{circ}{hbox {C}}$) substrates. To bond Si chips to the Ag layer on copper substrates, In-based alloy (InAg) is used. A fluxless bonding process is developed between Si/Cr/Au/Ag and Cu/Ag/In/Ag. The process is performed in 50-militorr vacuum to suppress solder oxidation. No flux is used. The resulting joints consist of three distinct layers of Ag, ${hbox {Ag}}_{2}{hbox {In}}$ and Ag. Microstructure and composition of the joints are examined using scanning electron microscope (SEM) with energy dispersive X-ray spectroscopy (EDX). Bonded samples are further annealed to convert the ${hbox {Ag}}_{2}{hbox {In}}$ phase into solid solution phase (Ag). The joint has a melting temperature above 850 $^{circ}{hbox {C}}$. This technique presents our success in overcoming the very large CTE mismatch between silicon and copper. It can be applied to mounting numerous high-power silicon devices to Cu substrates for various industrial applications.      

基于稳健设计的PBGA器件焊点热机械疲劳可靠性的优化设计

基于稳健设计与有限元法,研究了加速热循环测试条件下塑封球栅阵列(PBGA)焊点的热机械疲劳可靠性.考虑PCB大小(A)、基板厚度(D)、硅片热膨胀系数(G)、焊点热膨胀系数(H)等八个控制因素,使用L₁₈(2¹×3⁷)混合正交表,以对焊点热机械疲劳寿命的考核为目标,对PBGA焊点进行了优化设计.结果表明,影响焊点可靠性的显著性因素依次是基板热膨胀系数、焊点的热膨胀系数、基板厚度、芯片的热膨胀系数;最优方案组合为A1B2C3D1E2F1G3H1.进一步的验证试验结果表明,与原始方案相比,该优化方案的最大等效应变降低了66%,信噪比提高了22.4％.     

Effects of radiofrequency energy on human chondromalacic cartilage: an assessment of insulation material properties

The objective of this study was to establish guidelines for the selection of an insulation material used to surround the electrode of radiofrequency energy (RFE) probes used for thermal chondroplasty. These guidelines were established by identifying which insulation materials resulted in the least amount of chondrocyte death while smoothing the surface of chondromalacic cartilage. RFE causes electrolyte oscillation and molecular friction in the tissue to heat it and subsequently smooth the surface. Material properties investigated included the coefficient of thermal expansion (CTE), thermal conductivity (TC), and volume resistivity (VR). Fresh human chondromalacic cartilage samples of Outerbridge grades II and III were obtained from patients undergoing total knee arthroplasty. Stiffness measurements were taken pretreatment and posttreatment. RFE was applied to a 1-cm2 area for 15 s in a paintbrush treatment pattern. The insulation materials evaluated included Macor (decrease CTE, decrease TC, increase VR; in relation to CTE = 10 x 10(-6)/degrees C at 20 degrees C, TC = 3 W/mK, VR=1 x 10(14) ohm x cm), zirconia toughened alumina (ZTA) and 99.5% alumina (decrease CTE, increase TC, increase VR), aluminum nitride (decrease CTE, increase TC, decrease VR), Teflon (PTFE) (increase CTE, decrease TC, increase VR), partially stabilized zirconia (YTZP) (decrease CTE, decrease TC, decrease VR), and Ultem (increase CTE, decrease TC, decrease VR). There were no significant differences between pretreatment and posttreatment stiffness of the cartilage for any material investigated. Subjectively scored scanning electron microscopy (SEM) images revealed that the surfaces of all samples treated with RFE were relatively smooth with melted fronds. Prototype probes made with Macor, 99.5% alumina, and ZTA had TC < or = 30 W/mol x K and resulted in a mean of 35% less cell death (176+/-56 microm, 130+/-48 microm, and 114+/-33 microm, respectively) than aluminum nitride, PTFE, and YTZP (246+/-68 microm, 231+/-108 microm, and 195+/-89 microm, respectively). Macor, 99.5% alumina, and ZTA prototype probes all had VR > or = 1 x 10(14) ohm x cm and resulted in a mean 37% less cell death than aluminum nitride or YTZP. There was no apparent relationship between CTE and the depth of chondrocyte death.