MCM—C倒装焊工艺技术研究

简要介绍了主要倒装焊技术，重点研究了实用性强、可行性好的超声热压倒装焊、导电环氧粘接倒装、ACA粘接倒装以及MCM—C基板上的芯片倒装焊区制作、倒装后芯片的下填充等工艺技术，总结了芯片倒装互连质量的主要检验要求。     

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.     

MCM芯片安装互连及其相关技术

本文重点介绍了MCM芯片安装技术、三种基本的芯片互连技术(WB、TAB和FCB)、三种关键支撑技术(凸点制作、KGD、下填充)和微型凸点焊、ACA互连倒装、导电环氧互连倒装、无凸点微焊接等芯片装连新型技术途径。     

LCD驱动芯片CoF封装技术的现状及发展

挠性封装基板具有可弯折、重量轻、厚度薄等特点。基于挠性基板的CoF互连技术逐渐成为薄膜晶体管液晶显示屏(TFT-LCD)驱动芯片的主流封装技术。针对液晶显示系统中驱动芯片CoF封装技术的4种主要互连技术——ACA连接技术、NCA连接技术、焊料连接技术和金-金热压技术的原理、特点、研究现状和发展前景进行了总结,提出了未来CoF互连技术可能出现的新工艺和发展方向。     

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。     

倒装芯片的底部填充材料和涂布

倒装芯片是当今半导体封装领域的一大热点,它既是一种芯片互连技术,更是一种理想的芯片粘接技术。以往后级封装技术都是将芯片的有源区面朝上,背对基板粘贴后键合(如引线键合和载带自动键合TAB)。而倒装芯片则是将芯片有源区面对基板,通过芯片上呈阵列排列的焊料凸点来实现芯片与衬底的互连。显然,这种芯片互连的方式能够提供更高的I/O密度。     

基于各向异性导电胶的板间垂直互连研究

提出一种基于各向异性导电胶(ACA)的封装方法,即利用ACA实现介质基板之间垂直互连过渡。该方法与传统的锡铅焊料工艺相比,ACA板间互连工艺具有互连距离短、固化温度低、工艺流程简单、绿色环保等特点。测试结果表明,ACA在垂直互连过程中拥有良好的微波传输性能。在0.1~19.0GHz内,回波损耗小于-10dB,插入损耗小于1.5dB;在26~30GHz频段范围内,回波损耗小于-10dB,插入损耗小于3dB。测试结果与电磁仿真结果吻合。     

HgCdTe芯片粘接可靠性设计

根据ＨｇＣｄＴｅ材料的特性和７７Ｋ低温下工作的要求,结合目前研磨抛光的技术水平,从粘接机理和传热学等方面分析计算了粘接界面的最小接触高度、接触热阻和热应力,给出理想粘接界面的模型,介绍了胶层厚度对器件性能的影响,提出选择ＨｇＣｄＴｅ芯片粘接剂的主要依据和减小粘接界面接触热阻的技术途径。     

微电子组装用导电胶的最新发展

导电胶正广泛地应用于电子封装中,例如,裸芯片的粘贴与互连,元器件的固定,以及作热转换和电互连的目的,本文将介绍导电胶应用于电子元器件组装中的最新进展,着重描述各向 异性导电胶（以下称ACA）这种新兴的电子互连材料及其组装工艺,同时介绍导电胶在电子封装领域以及在不久将来的更多产品的应用中所起举足轻重的作用,最后,讨论了发展趋势和存在的问题。     

集成电路芯片上光互连研究的新进展

讨论了集成电路向高集成度、高工作频率和高传输速率继续发展时 ,常规金属互连出现的困难以及集成电路芯片上光互连具有的潜在优势 .介绍了组成芯片上光互连的光发射器件、光接收器件和光传输器件等三种基本器件及其与硅集成电路集成的研究新进展 .最后展望了集成电路芯片上光互连的应用前景 .     

Electrical Interconnection with a Smart ACA Composed of Fluxing Polymer and Solder Powder

The interconnection mechanisms of a smart anisotropic conductive adhesive (ACA) during processing have been characterized. For an understanding of chemorheological mechanisms between the fluxing polymer and solder powder, a thermal analysis as well as solder wetting and coalescence experiments were conducted. The compatibility between the viscosity of the fluxing polymer and melting temperature of solder was characterized to optimize the processing cycle. A fluxing agent was also used to remove the oxide layer performed on the surface of the solder. Based on these chemorheological phenomena of the fluxing polymer and solder, an optimum polymer system and its processing cycle were designed for high performance and reliability in an electrical interconnection system. In the present research, a bonding mechanism of the smart ACA with a polymer spacer ball to control the gap between both substrates is newly proposed and investigated. The solder powder was used as a conductive material instead of polymer‐based spherical conductive particles in a conventional anisotropic conductive film.     

Electrical and mechanical characterization of an anisotropic conductive adhesive with a low melting point solder

For the highly reliable interconnection in a micro-packaging technology requiring an excellent electrical and mechanical performance, the new anisotropic conductive adhesive (ACA) system with a low melting point solder was designed and characterized. An optimum flip-chip bonding cycle considering the chemo-rheological properties of a polymer matrix and solder was proposed. The bonding mechanism of the new ACA system was experimentally observed by the optical microscope. The electrical properties such as electrical resistance of about 5.6 mΩ and current density of 10,000 A/cm² were measured by the 4-point probe test. The measured shear strength was 304 MPa after bonding process.Electrical and mechanical performances were measured and compared before and after a pressure cooker test (PCT). In order to get a more stable ACA system during processing, the polymer matrix mixed with a reductant and a low melting point solder powder will be continuously developed in the near future.     

Experimental Analysis of Mechanical and Electrical Characteristics of Metal-Coated Conductive Spheres for Anisotropic Conductive Adhesives (ACAs) Interconnection

An accurate characterization for the deformation behavior of conductive particles is important: 1) to understand the anisotropic conductive adhesive (ACA) interconnection and 2) to optimize the ACA bonding parameter. This paper introduces an experimental technique, which has been developed to allow continuous monitoring of deformation characteristics of a single conductive particle. The load-deformation curve of a single conductive particle is measured, which provides the quantitative estimation of the mechanical and electrical characteristics of metal-coated polymer spheres used in ACAs. Based on the load-deformation result of a single conductive particle and the number of trapped particles on a bump, equivalent spring models are used to predict the deformation degree of conductive particles after flip chip assembly. For two kinds of conductive particles with different polymer cores, the mechanical and electrical characteristics of ACA interconnection were studied. Such results are used to further achieve a more sophisticated approach of the ACA bonding process and contact reliability.     

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.     

Effects of different bonding parameters on the electrical performance and peeling strengths of ACF interconnection

The effects of different bonding parameters, such as temperature, pressure, curing time, bonding temperature ramp and post-processing, on the electrical performance and the adhesive strengths of anisotropic conductive film (ACF) interconnection are investigated. The test results show that the contact resistances change slightly, but the adhesive strengths increase with the bonding temperature increased. The curing time has great influence on the adhesive strength of ACF joints. The contact resistance and adhesive strength both are improved with the bonding pressure increased, but the adhesive strengths decrease if the bonding pressure is over 0.25 MPa. The optimum temperature, pressure, and curing time ranges for ACF bonding are concluded to be at 180–200 °C, 0.15–0.2 MPa, and 18–25 s, respectively. The effects of different Teflon thickness and post-processing on the contact resistance and adhesive strength of anisotropic conductive film (ACF) joints are studied. It is shown that the contact resistance and the adhesive strength both become deteriorated with the Teflon thickness increased. The tests of different post-processing conditions show that the specimens kept in 120 °C chamber for 30 min present the best performance of the ACF joints. The thermal cycling (−40 to 125 °C) and the high temperature/humidity (85 °C, 85% RH) aging test are conducted to evaluate the reliability of the specimens with different bonding parameters. It is shown that the high temperature/humidity is the worst condition to the ACF interconnection.     

各向异性导电胶互连技术的研究进展

随着微电子封装技术的发展,各向异性导电胶作为一种绿色的连接材料,广泛应用于电子产品中。文中主要介绍各向异性导电胶互连器件的粘接原理和影响其可靠性的各种因素,如粘接工艺参数、外界环境的干扰、各向异性导电胶的物理特性等。     

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.     

Role of bonding time and temperature on the physical properties of coupled anisotropic conductive-nonconductive adhesive film for flip chip on glass technology

Using thermosetting epoxy based conductive adhesive films for the flip chip interconnect possess a great deal of attractions to the electronics manufacturing industries due to the ever increasing demands for miniaturized electronic products. Adhesive manufacturers have taken many attempts over the last decade to produce a number of types of adhesives and the coupled anisotropic conductive-nonconductive adhesive film is one of them. The successful formation of the flip chip interconnection using this particular type of adhesive depends on, among factors, how the physical properties of the adhesive changes during the bonding process. Experimental measurements of the temperature in the adhesive have revealed that the temperature becomes very close to the required maximum bonding temperature within the first 1 s of the bonding time. The higher the bonding temperature the faster the ramp up of temperature is. A dynamic mechanical analysis (DMA) has been carried out to investigate the nature of the changes of the physical properties of the coupled anisotropic conductive-nonconductive adhesive film for a range of bonding parameters. Adhesive samples that are pre-cured at 170, 190 and 210 °C for 3, 5 and 10 s have been analyzed using a DMA instrument. The results have revealed that the glass transition temperature of this type of adhesive increases with the increase in the bonding time for the bonding temperatures that have been used in this work. For the curing time of 3 and 5 s, the maximum glass transition temperature increases with the increase in the bonding temperature, but for the curing time of 10 s the maximum glass transition temperature has been observed in the sample which is cured at 190 °C. Based on these results it has been concluded that the optimal bonding temperature and time for this kind of adhesive are 190 °C and 10 s, respectively.     

导电胶粘接可伐载板工艺的仿真与优化

导电胶是一种很有潜力的互连材料,其粘接可靠性是制约其应用的主要因素。基于对某混频模块粘接失效的分析,探索温度试验条件及载板尺寸对可伐载板粘接可靠性的影响。通过仿真和试验设计,研究不同温度试验条件下不同尺寸载板在粘接界面处的应力分布情况,并优化了可伐载板粘接工艺。结果表明,温度试验条件越严苛,载板尺寸越大,可伐载板粘接可靠性越差,可采取环氧绝缘胶加固或柔性导电胶粘接的方式对其粘接工艺进行优化。