封装树脂与PKG分层的关系

PKG内部分层是电子封装中很普遍的一种现象,也是必须要解决的一种主要缺陷,它会严重影响电子封装的可靠性。造成和影响PKG分层的原因很多,文章主要对封装树脂与PKG分层的关系进行了探讨。经研究表明,降低封装树脂的应力、改善封装树脂的吸湿性和提高封装树脂的粘接性是改善PKG内部分层现象的有效方法。     

集成电路分层的失效分析

在集成电路封装中,分层是一个很普遍的现象,同时又是导致集成电路失效的主要原因之一。所谓分层泛指集成电路封装中不同材料之间的界面分离,以及同种材料内部的空洞。针对不同的封装,总结了扫描声学显微镜及X-ray检测系统（包括2D、 3D）两种无损检测分层现象的方法。并在此基础上,结合失效分析案例,阐述了两种方法在失效分析过程中的应用,以及分层导致集成电路失效的机理。     

浅谈IC封装材料对产品分层的影响及改善

IC封装不仅要求封装材料具有优良的导电性能、导热性能以及机械性能,还要求具有高可靠性、低成本和环保性,这也是引线框架、环氧树脂成为现代电子封装主流材料的主要原因,其市场份额约占整个封装材料市场的95%以上。由于环氧树脂封装是非气密性封装,对外界环境的耐受能力较差,尤其是受到湿气侵入时,产品会出现一些可靠性问题,最容易发生的现象是分层。简要分析了框架和环氧树脂对产品可靠性的影响,在此基础上提出一些改善措施。     

QFN封装分层失效与湿-热仿真分析

采用湿度敏感度评价试验及湿-热仿真方法,分析了温湿度对于QFN封装分层失效的影响.通过C-SAM和SEM等观察发现,QFN存在多种分层形式,分层大多发生在封装内部材料的界面上,包括封装塑封材料和芯片之间的界面、塑封材料和框架之间的界面等.此外,在封装断面研磨的SEM图像上发现芯片粘结剂内部有空洞出现.利用有限元数值模拟的方法,对QFN封装的内部湿气扩散、回流过程中的热应力分布等进行了模拟,分析QFN分层失效的形成原因.结果表明,由于塑封器件材料、芯片、框架间CTE失配,器件在高温状态湿气扩散形成高气压条件下易产生分层.最后提出了改善QFN分层失效的措施.     

水汽对塑封集成电路、分立器件可靠性的影响

塑料封装是一种非气密性封装,所用封装材料主要是由改性环氧树脂和填充料配制而成,它具有一定的亲水性,因此具有容易在其表面吸附环境中的水汽的特点。当吸附了水汽的器件处在高温环境时,器件内部吸附的水汽被汽化,产生的蒸汽压力急剧升高,导致器件内部各界面间产生分层和焊线损伤,甚至发生"爆米花"现象等。本文例举一个典型案例,来说明水汽对塑封器件的影响,寻找降低水汽对器件影响的措施。     

塑料封装集成电路分层浅析及改善研究

当环境温度、湿度发生变化时,塑料封装集成电路内部的不同物质界面会产生分层,分层导致电路回路的开路或间歇性接触不良,极大地影响IC的功能和使用寿命。封装主要材料BOM(如芯片/框架/装片胶/塑封料环氧树脂)是确定IC MSL等级和分层水平的基础,封装制程的工艺设计、组装过程的控制方法、产品防范外力破坏及热电应力防护都是影响分层的因素,BOM组合需要考虑加强材料间的粘结强度及接近的热膨胀系数、设计芯片PO层减少电路表面凹凸落差、框架沟槽凸台设计、制造过程防污染/防氧化控制等,都是改善IC产品内部分层的有效思路。DOE对比试验有助于从复杂的产品制造过程中发现分层产生的根源。     

引线框架塑料封装集成电路分层及改善

分层是塑料集成电路封装过程和可靠性试验后常见的问题,如何解决分层问题是封装材料供应商、封装工程师、可靠性试验工程师共同研究与改善的课题。通过对封装产品结构、材料、工艺方法等方面进行深入的解析,详细阐述了引线框架塑料封装集成电路分层产生机理,描述了分层对集成电路的危害以及如何预防分层的发生,进而提出了有效的改善措施。结果表明,这些措施的应用能够有效预防分层问题的发生,提高塑料封装集成电路的可靠性。     

环氧模塑料（EMC）对翘曲的影响与解决方案

翘曲是树脂封装过程中常见的现象，产生封装体翘曲的原因很多，本文主要研究封装树脂环氧模塑料对翘曲产生的影响，并提出有效的解决方案。     

半导体封装中的可视化技术

树脂传递模封装是广泛使用的可靠性量产性均好的半导体封装方法。但随着封装体（PACKAGE）尺寸的日益薄型化和多腿化,不可避免地会发生与树脂在模腔中流动状态有关的空隙等使制品失效的不良模式。这样,通过观察树脂流动状态及对空隙的分布进行研究,对于研究空隙发生机理从而抑制空隙发生具有重要意义。本文将着重介绍两种新的研究实验方法：（1）应用玻璃嵌入式新型可视化模具观察树脂在模腔中的流动状态;（2）采用超声波探查图像装置（简称SAT）进行树脂封装体内部的观察。     

银基离子聚合物金属复合材料的封装工艺及其致动性能

离子聚合物金属复合材料(IPMC)是一种典型的电活性聚合物,具有响应速度快、驱动电压低的突出优势,但全氟磺酸树脂在空气中易失水的缺陷,导致基于全氟磺酸树脂的IPMC会产生非常严重的松弛现象,限制了其作为柔性驱动材料的各项性能。因此,在此基础上提出了一种从物理封装角度抑制IPMC易于松弛的方法。通过聚二甲基硅氧烷(PDMS)和聚氯乙烯(PVC)的组合方式对IPMC进行封装,测量封装后的IPMC的含水率、偏移角度、输出力以及稳定性。结果表明,这种在表面增加膜结构的方法不仅减少了内部水分的流失,使IPMC在空气中的含水率提高了约35%,而且为其致动提供了更高的机械强度,产生了更大的输出力,改善了其在空气中工作的稳定性。这种方法弥补了该材料制备驱动器时的主要不足,为其更广泛的应用奠定了基础。     

HDI多层印制电路板无铅再流焊爆板问题研究

HDI多层印制电路板在无铅再流焊接中的爆板现象是严重威胁产品质量、导致生产线不能正常运转甚至停线的较严重的质量事件.重点分析了无铅再流焊接过程中最常见的爆板现象,讨论了爆板发生的机理,并在此基础上探讨了抑制爆板的技术措施.     

Investigation of delamination control in plastic package

Interfacial delamination control is important for the mechanical reliability of plastic package, especially facing the challenge of lead-free requirement. Efforts of delamination performance improvement including structure, material and process for plastic package were made. It was demonstrated that the improvement of packaging material mechanical properties should depend on the package and purpose and should be the comprehensive consideration of advantage and disadvantage. The fracture mechanics was introduced to explain the mechanism of bumpy interface as the delamination retardant. The moisture absorption experiments of three kinds of molding compound were carried out to confirm that large difference of delamination performance among different molding compounds for the same device in our project was induced by moisture absorption difference, and the relation between the moisture weight absorbed and weight ratio of resin was obtained, given compounds of the same resin. It was substantiated that the moisture absorption of molding compound observes the Fick’s law at (Moisture Sensitivity Level 3) MSL3. Quantitative analyses of the moisture influence at the risk location were conducted to evaluate the risk of delamination with the consideration of vapor pressure during solder reflow, moisture and thermal expansion.     

Multichip package delamination and die fracture analysis

Multichip mechatronic power packages have been developed in Motorola for automotive applications. Copper heat sink based metal substrates were used to improve thermal and electrical performance. In the early stage of development, mold delamination and die cracking have been observed after assembly. With some mold compound materials, die backside have large delaminated areas, while with other mold compound, delamination stops early but die cracks. Finite element analysis, incorporated with interface fracture mechanics method, has been conducted to understand these phenomena. Impact of mold material properties and package geometry on post-assembly delamination has been evaluated. Good agreements have been obtained between experimental data and the simulation results. The phenomenon of crack branching into the die was also studied. Finite element simulation can be used to predict whether and when the crack at the interface will turn and crack the die. With a thorough understanding of the failure mechanism, both mold delamination and die cracks have been eliminated in the final package development.     

Mechanical fatigue test method for chip/underfill delamination in flip-chip packages

Underfill resin between Si chips and printed circuit boards is useful for improving the reliability of flip-chip packages. Generally, thermal cycle tests (TCTs) are applied to electronic packages under development in order to prove their reliability. At the early stage of development, however, a more effective test method is desirable, because TCTs are time-consuming. A new mechanical fatigue test for the underfill resin in flip-chip packages, namely the four points support test method, is proposed in this paper. The validity of the mechanical test method could be verified from the results of stress analyses and experiments. Considering the chip/underfill delamination statistically based on the assumption of Markov process, it was shown that the delamination probability during cyclic loads could be estimated with equations of the displacement range and number of cycles.     

热–机械应力和湿气引起QFN器件层间开裂分析

采用通用有限元软件分析和计算器件在潮湿环境下的潮湿扩散,并计算由于吸潮使器件在无铅回流的高温下产生蒸汽压力,并对层间开裂现象进行分析。结果表明,气压是层间开裂的主要原因,在气压和热机械应力的作用下,层合面上的微孔洞扩张并结合起来,导致器件最后失效。     

Thermo-mechanical analysis and interfacial energy release rate estimation for metal-insulator-metal capacitor device

The metal-insulator-metal (MIM) capacitor device is the most popular structure that has been massively used in system circuit designs in IC and PCB processes. The characteristics of system will be changed and electrical performances will be impaired if large deformations are resulted in MIM capacitor device. Therefore, the concerns of reliability for MIM capacitor devices are very important issues. For the purpose of realizing the probability of delamination of GaAs/Si₃N₄ interface in MIM capacitor device, the four-point bend experiment is employed to evaluate the critical energy release rate, which is an important index to determine the possibility of inducing interfacial delamination. Moreover, to validate the phenomenon of delamination in MIM capacitor device, the finite element analysis (FEA) and modified virtual crack closure technique (MVCCT) are adopted. Thermo-mechanical stress distributions in MIM capacitor device that under reliability test conditions can be illustrated. The results show that the maximum stress occurs at the layer of Si₃N₄ or its corresponding interfaces. These stress concentration areas are critical places to be fractured. Furthermore, the designs of experiments (DOE) analysis is also employed to have better geometric parameters in MIM capacitor device to reduce stresses. It is believed that this study will be useful design guideline to prevent the phenomenon of interfacial delamination and enhance the reliability.     

埋铜块层压板耐热可靠性研究

埋铜块层压板铜块与树脂结合力差,大批量生产板在焊接时存在一定比例分层,因此通过机理分析和实验验证,确定其可靠性影响因素,通过工艺和参数优化以提高其耐热可靠性.     

Thermal transient characteristics of die attach in high power LED PKG

The reliability of packaged electronics strongly depends on the die attach quality because any void or a small delamination may cause instant temperature increase in the die, leading sooner or later to failure in the operation. Die attach materials have a key role in the thermal management of high power LED packages by providing the low thermal resistance between the heat generating LED chips and the heat dissipating heat slug. In this paper, thermal transient characteristics of die attach in high power LED PKG have been studied based on the thermal transient analysis using the evaluation of the structure function of the heat flow path. With high power LED packages fabricated by die attach materials such as Ag paste, solder paste and Au/Sn eutectic bonding, we have demonstrated for characteristics such as cross-section analysis, shear test and visual inspection after shear test of die attach and how to detect die attach failures and to measure thermal resistance values of die attach in high power LED PKG. From the differential structure function of the thermal transient characteristics, we could know the result that die attach quality of Au/Sn eutectic bonding with the thermal resistance of about 3.5 K/W was much better than this of Ag paste and solder paste with the thermal resistance of about 11.5–14.2 K/W and 4.4–4.6 K/W, respectively. From this results, it is possible to fabricate high power LED with a small thermal resistance and a good die attach quality by applying Au/Sn eutectic bonding die attach with a high reliability and a good repeatability.