各向异性导电胶粘接可靠性研究进展

介绍各向异性导电胶导电机理和粘接工艺,以及影响它的粘接可靠性因素和最佳参数的研究,如粘接温度、固化时间、粘接压力、粒子含量等。对各向异性导电胶粘接可靠性中的开路、短路、接触电阻与粘接压力和温度循环的关系进行了讨论,并介绍了各向异性导电胶可靠性的理论计算模型。     

各向异性导电胶与FPC的引线连接技术

各向异性导电胶是一种同时具有粘接、绝缘和导电三种功能的高分子复合材料。它适用于多线数电极线端与软印刷线路板(FPC)之间的对接,具有效率高、成本低、操作方便、性能稳定可靠等特点。各向异性导电胶是在高分子材料中加入添加剂(防老剂、增塑剂等),并均匀分散细微导     

各向异性导电胶倒装封装电子标签的可靠性

各向异性导电胶(ACA)广泛用于RFID电子标签芯片封装,具有芯片对位方便、热压温度低和工艺时间短的优点.但ACA互连本质上是机械接触,其互连可靠性强烈依赖于粘接界面性质、胶水粘接力及环境稳定性.本文试验表明,168 h高温高湿和D20 mm心轴弯曲对芯片粘接点的电接触性能有所影响;铜模组良品率显著高于铝天线Inlay.     

微波芯片元件的导电胶粘接工艺与应用

导电胶常用于微波组件的组装过程,其粘接强度、导电、导热和韧性等性能指标严重影响其应用范围.分析了导电胶的国内外情况和主要性能参数,总结了混合微电路对导电胶应用的指标要求.通过微波芯片元件粘接工艺过程,分析了导电胶的固化工艺与粘接强度和玻璃化转变温度的关系、胶层厚度与热阻的关系、胶点位置和大小与粘片位置控制等方面的影响关系.测试结果显示,经导电胶粘接的芯片元件的电性能和粘接强度等指标均满足设计和使用要求,产品具有较好的可靠性和一致性.     

导电胶粘接元件接触电阻的稳定性研究

为解决导电胶粘接元件接触电阻不稳定的问题,研究了在温度及压力应力条件下,导电胶在不同界面的导电性和体电阻率的变化情况,分析了导电胶接触电阻不稳定的机理。试验结果表明,导电胶粘接片式元件的接触电阻的稳定性不仅与工艺加工过程有关,而且与元件端头金属基材表面金属化层的电极电动势密切相关;采用Ag基或Au基端头元件时,其导电胶粘接元件的接触电阻在粘接装配工艺过程中是最稳定的。     

粘接技术在微组装中的应用

本文讲述了微组装中粘接技术需采用性能良好的导电胶,从粘接理论入手,结合实施结果和实践经验,详细论述了如何选择适当的导电胶,并具体分析了粘接工艺中胶层厚度,固化温度、时间、压力及粘接表面对粘接强度,导电性、导热性和可靠性等的影响。     

环境对各向异性导电胶膜性能参数的影响

各向异性导电胶膜(ACF)的玻璃转化温度T_g是它的一个重要性能参数,用差示扫描热示计(DSC)分别测定商用各向异性导电胶膜固化前和固化后的玻璃转化温度,并确定不同的固化时间对它的玻璃转化温度的影响,以及高温高湿(85℃,85%RH)环境对它的玻璃转化温度影响,得到各向异性导电胶玻璃转化温度下降是其粘接强度下降的原因之一。     

环境对各向异性导电胶膜性能参数的影响

各向异性导电胶膜(ACF)的玻璃转化温度Tg是它的一个重要性能参数,用差示扫描热示计(DSC)分别测定商用各向异性导电胶膜固化前和固化后的玻璃转化温度,并确定改变固化时间对它的玻璃转化温度的影响,以及高温高湿(85℃,85%RH)环境对它的玻璃转化温度的影响,得到各向异性导电胶玻璃转化温度下降是其粘接强度下降的原因之一。     

再流焊高温对导电胶粘接工艺可靠性影响研究

该文描述了H20E导电胶粘接工艺优化为先粘接固化再回流焊接工艺流程后过程经过高温冲击,对该工艺流程下环氧胶粘接强度、电气连接可靠性进行验证.通过剪切强度评价、可靠性试验考核、接触电阻测试统计分析、电容粘接界面切面微观金相研究,表明工艺流程优化为先粘接再回流焊接,H20E导电胶粘接工艺满足可靠性需求.     

导电胶在倒装芯片互连结构中的应用进展

介绍了导电胶的基本分类以及导电胶的渗透理论;讨论了各向异性导电胶(ACA)、各向同性导电胶(ICA)、绝缘粘合剂(NCA)在倒装芯片互连结构中的应用;分析了导电胶互连的可靠性。最后展望了导电胶的发展趋势。     

一种新的混合并行蚁群算法研究应用

提出了一种新的混合并行蚁群算法,在单机多核机及多核集群机下分别实现了MPI并行蚁群算法及MPI+TBB并行蚁群算法,应用于真实路网车辆路径问题(Vehicle Routing Problem,VRP),对两者进行了实验对比,实验结果表明MPI并行蚁群算法具有较高的加速比,和问题规模关系不大,刚开始呈现线性加速比。较MPI并行蚁群算法,MPI+TBB混合并行蚁群算法具有更好的可扩展性,在进程数较多时仍具有较高的加速比。     

Theoretical analysis of RF performance of anisotropic conductive adhesive flip- chip joints

The RF performance of a single flip-chip joint using anisotropic conductive adhesive (ACA) was modeled using three-dimensional finite difference in time domain (FDTD) methodology. The effects of the number, the distribution of ACA conductive particles, as well as the ACA resin, on RF transition of the joint were studied. The results show that the number and the distribution of conductive particles as well as the adhesive resin have limited influence on the RF performance of an ACA flip-chip joint. Based on the FDTD simulation results, an equivalent circuit model of a single ACA flip-chip joint was also proposed.     

基于SIS框架和蚁群算法的非线性多目标跟踪

该文提出一种新的非线性多目标跟踪方法用蚁群算法实现数据关联和SIS(Sequential Importance Sampling)实现对单目标的跟踪。首先根据数据关联问题对蚁群算法进行修改,考虑目标运动中的约束条件对关联概率的影响,重新定义蚁群算法中的路径和路径长度,从而利用蚁群算法寻找最短路径的能力实现对数据关联。由于SIS框架是针对非线性系统的一种较好的状态估计方法,该文将其作为对单目标进行跟踪的框架,和蚁群算法共同解决非线性情况下的多目标跟踪问题。实验对一维平面和二维平面中的多个目标进行了仿真,结果表明,将蚁群算法应用于解决数据关联问题是行之有效的。     

倒装芯片封装材料-各向异性导电胶的研究进展

介绍了两种新型各向异性导电胶ACA(Anisotropic Conductive Adhesive)结构,分析了邦定压力和导电颗粒特性对常用ACA互连接触电阻的影响,综合叙述了环境因素、邦定参数、误对准、凸点高度等对ACA互连可靠性影响的研究进展.     

多Agent系统中蚁群算法的设计与实现

介绍了蚁群算法的基本思想与原理，以及在多Agent系统中的设计、实现方法．给出了在多Agent系统环境中的仿真实验结果。仿真结果表明，将蚁群算法与Agent的行为规则有机结合，可以有效地改善Agent的群体行为。     

Anisotropic conductive adhesives with enhanced thermal conductivity for flip chip applications

This paper presents the development of new anisotropic conductive adhesives (ACAs) with enhanced thermal conductivity for improved reliability of adhesive flip chip assembly under high current density condition. As the bump size in the flip chip assembly is reduced, the current density through the bump also increases. This increased current density causes new failure mechanisms, such as interface degradation due to intermetallic compound formation and adhesive swelling resulting from high current stressing. This process is found especially in high current density interconnection in which the high junction temperature enhances such failure mechanisms. Therefore, it is necessary for the ACA to become a thermal transfer medium that allows the board to act as a new heat sink for the flip chip package and improve the lifetime of the ACA flip chip joint. We developed the thermally conductive ACA of 0.63 W/m·K thermal conductivity by using a formulation incorporating the 5-μm Ni-filled and 0.2-μm SiC-filled epoxy-based binder system. The current carrying capability and the electrical reliability under the current stressing condition for the thermally conductive ACA flip chip joints were improved in comparison to conventional ACA. This improvement was attributed to the effective heat dissipation from Au stud bumps/ACA/PCB pad structure by the thermally conductive ACA.     

Formulation and characterization of anisotropic conductive adhesive paste for microelectronics packaging applications

There has been a steadily increasing interest in using electrically conductive adhesives as interconnecting materials in electronics manufacturing. In this paper, several anisotropic conductive adhesive (ACA) pastes were formulated, which consist of diglycidyl ether of bisphenol F or diglycidyl ether of bisphenol A as polymer matrix, imidazoles as curing agents, and different sizes of silver (Ag) powders or gold (Au)-coated polymer spheres as conductive particles. The effects of ACA resin and different curing agents, as well as different conductive particles, on flexible substrate of the flip-chip joint were studied. The results show that the size and type of different conductive particles have very limited influence on an ACA flip-chip joint. The ACA resin as well as the curing agent can affect the reliability of the joint. The same results can be applied for the failure analysis of ACA flip-chip technology.     

Investigation of Mechanical and Electrical Characteristics for Cracked Conductive Particle in Anisotropic Conductive Adhesive (ACA) Assembly

In an anisotropic conductive adhesive (ACA) assembly, the electrical conduction is usually achieved with the conductive particles between the bumps of integrated circuit (IC) and corresponding conductive tracks on the glass substrate. Fully understanding of the mechanical and electrical characteristics of ACA particles can help to optimize the assembly process and improve the reliability of ACA interconnection. Most conductive particles used in the ACA assembly are with cracks in the metal coating of the particles after the ACA bonding. This paper introduced the fracture analysis by applying the cohesive elements in the numerical model of the nickel-coated polymer particle and further simulating the cracks initiation and propagation in the nickel coating during the ACA bonding. The simulation results showed that the stress distribution on the nickel-coated particle with cracks was significantly different from that on the nickel-coated particle without crack, indicating that the stress analysis by taking the crack into consideration is very important for the reliability assessment of the ACA interconnection. The stress analysis of cohesive elements indicated that the cracks initiated at the central area of the nickel coating and propagated to the polar area. Furthermore, by the introduction of a new parameter of the virtual resistance, a mathematical model was established to describe the electrical characteristics of the nickel-coated particle with cracks. The particle resistance of the nickel-coated particle with cracks was found to be much higher than that of the particle without crack in the optimized bonding pressure range, indicating that it is necessary to take the crack into consideration for the particle conduction analysis as well. Therefore, the fracture analysis on the conductive particle by taking the crack into consideration could accurately evaluate the reliability of ACA interconnection and avoid serious reliability issues.     

The adaptive cross approximation algorithm for accelerated method of moments computations of EMC problems

This paper presents the adaptive cross approximation (ACA) algorithm to reduce memory and CPU time overhead in the method of moments (MoM) solution of surface integral equations. The present algorithm is purely algebraic; hence, its formulation and implementation are integral equation kernel (Green's function) independent. The algorithm starts with a multilevel partitioning of the computational domain. The interactions of well-separated partitioning clusters are accounted through a rank-revealing LU decomposition. The acceleration and memory savings of ACA come from the partial assembly of the rank-deficient interaction submatrices. It has been demonstrated that the ACA algorithm results in O(NlogN) complexity (where N is the number of unknowns) when applied to static and electrically small electromagnetic problems. In this paper the ACA algorithm is extended to electromagnetic compatibility-related problems of moderate electrical size. Specifically, the ACA algorithm is used to study compact-range ground planes and electromagnetic interference and shielding in vehicles. Through numerical experiments, it is concluded that for moderate electrical size problems the memory and CPU time requirements for the ACA algorithm scale as N/sup 4/3/logN.     

Study on the shear strength degradation of ACA joints induced by different hygrothermal aging conditions

The effect of the different hygrothermal conditions on the shear strength degradation of ACA joints and the difference among them are studied in this paper using experiments and numerical simulations. First of all, several hygrothermal aging tests with different accelerating levels are carried out to explore the hygrothermal environment induced degradation paths of interfacial strength of ACA joints. It is found that the shear strength degradation paths differ from each other when the ACA joints are tested under different hygrothermal conditions, while they are similar to each other. For each case, the shear strength firstly decreases rapidly and then slowly approximates to a fixed value, and the shear strength difference between each other goes to an approximate constant after certain early test hours. After that, to understand the degradation mechanism better, finite element modeling is achieved to study the relationship of moisture concentration in ACA layer and shear strength of the ACA joints, and it is found that moisture saturation and diffusion rate are considered to be the main causes of the shear strength degradation.