叠层芯片应用的封装挑战与解决方法

叠层管芯封装的不断发展导致该技术能有效地在同一基底内增大电子器件的功能和容量,作为单个芯片。蜂窝电话及其它消费类产品中叠层芯片封装的应用增长促使能够在给定封装尺寸中封装多层芯片。介绍了叠层芯片封装技术中最主要是满足总封装高度的要求。用于叠层芯片封装的技术实现方法包括基片减薄、薄裸芯片贴装、小形貌引线键合、与无支撑的边缘键合以及小偏倒成形等。集中介绍了叠层管芯互连要求。介绍了倒装芯片应用中的正向球形键合、反向球形键合和焊凸凸焊技术,讨论了优点和不足。说明球形键合机的发展能够满足叠层芯片封装的挑战,即超低环形状、长引线跨距和悬空键合等。     

超薄芯片叠层封装器件热可靠性分析

采用通用有限元软件MSC.Marc,模拟分析了一种典型的多层超薄芯片叠层封装器件在经历回流焊载荷后的热应力及翘曲分布情况,研究了部分零件厚度变化对器件中叠层超薄芯片翘曲、热应力的影响。结果表明:在整个封装体中,热应力最大值(116.2 MPa)出现在最底层无源超薄芯片上,结构翘曲最大值(0.028 26 mm)发生于模塑封上部边角处。适当增大模塑封或底层无源芯片的厚度或减小底充胶的厚度可以减小叠层超薄芯片组的翘曲值;适当增大底层无源超薄芯片的厚度(例如0.01 mm),可以明显减小其本身的应力值10 MPa以上。     

TSOP叠层芯片封装的介绍

叠层芯片封装技术,简称3D,是指在不改变封装体外型尺寸的前提下,在同一个封装体内于垂直方向叠放两个以上的芯片的封装技术,它起源于快闪存储器(NOR/NAND)及SDRAM的叠层封装。叠层芯片封装技术具有大容量、多功能、小尺寸、低成本的特点,2006年以来3D技术逐渐成为主流。随着NAND快闪存储器市场的高速增长及3D技术的兴起,加之TSOP封装成本低、柔韧性强,所以TSOP封装得以重新焕发生机。     

多芯片叠层封装中的芯片应力分析及结构优化

针对典型的四层芯片叠层封装产品,采用正交试验设计与有限元分析相结合的方法研究了芯片、粘合剂、顶层芯片钝化层和密封剂等十个封装组件的厚度变化对芯片上最大热应力的影响,并利用找到的主要影响因子对封装结构进行优化.结果表明,该封装产品可以在更低的封装高度下实现,并具有更低的芯片热应力水平及更小的封装体翘曲,这有助于提高多芯片叠层封装产品的可靠性.     

夹层式叠层芯片引线键合技术及其可靠性

随着电子封装技术的快速发展,叠层封装成为一种广泛应用的三维封装技术,该技术能够满足电子产品高性能、轻重量、低功耗、小尺寸等日益增长的需求。针对陶瓷封装腔体中的夹层式叠层芯片结构,键合点与键合引线处于陶瓷外壳空腔中,未有塑封料填充固定,区别于塑封叠层芯片封装器件,优化其引线键合技术,并做了相应可靠性评估试验。键合引线偏移长度最大为0.119 mm,未出现键合引线间隙小于设计值、碰丝短路等情况,为高可靠叠层芯片封装研究提供了参考。     

芯片叠层封装的失效分析和热应力模拟

通过高温高湿加速实验对双芯片叠层封装器件的失效进行了研究,观察到存在塑封料与上层芯片、BT基板与塑封料或贴片胶的界面分层和下层芯片裂纹等失效模式．结合有限元分析对器件内热应力分布进行了计算模拟,分析了芯片裂纹的失效机理,并从材料性能和器件结构角度讨论了改善叠层封装器件可靠性的方法．     

芯片叠层封装的失效分析和热应力模拟

通过高温高湿加速实验对双芯片叠层封装器件的失效进行了研究,观察到存在塑封料与上层芯片、BT基板与塑封料或贴片胶的界面分层和下层芯片裂纹等失效模式.结合有限元分析对器件内热应力分布进行了计算模拟,分析了芯片裂纹的失效机理,并从材料性能和器件结构角度讨论了改善叠层封装器件可靠性的方法.     

芯片叠层封装工艺技术研究

随着大量电子产品朝着小型化、高密度化、高可靠性、低功耗方向发展,将多种芯片封装于同一腔体内的芯片叠层封装工艺技术将得到更为广泛的应用,其封装产品的特点就是更小、更轻盈、更可靠、低功耗。芯片叠层封装是把多个芯片在垂直方向上堆叠起来,利用传统的引线封装结构,然后再进行封装。芯片叠层封装是一种三维封装技术,叠层封装不但提高了封装密度,降低了封装成本,同时也提高了器件的运行速度,且可以实现器件的多功能化。随着叠层封装工艺技术的进步及成本的降低,多芯片封装的产品将更为广泛地应用于各个领域,覆盖尖端科技产品和应用广大的消费类产品。     

叠层封装变得更薄

许多种将芯片堆叠起来的方法已经在小型化的旗号下得到广泛的运用．尤其是在移动应用中。叠层封装排布方式有利于将多个经过测试和高温筛选后的已封装芯片装配起来。日前．Tessera公司为其可堆叠的封装开发出一种全新的接触结构．能够使叠层封装的总厚度显著降低。在2006年的SMTA国际会议上．一篇论文披露了这种微接触阵列技术的部分细节。     

叠层CSP芯片封装热应力分析与优化

对四层叠层CSP（SCSP）芯片封装器件,采用正交试验设计与有限元分析相结合的方法研究了芯片和粘结剂——8个封装组件的厚度变化在热循环测试中对芯片上最大热应力的影响．利用极差分析找出主要影响因子并对封装结构进行优化。根据有限元模拟所得结果．确定了一组优选封装结构,其Von Mises应力值明显比其它组低,提高封装器件的可靠性。     

多层芯片应用中的封装挑战和解决方案

The continuous growth of stacked die packages is resulting from the technology‘s ability to effectively increase the functionality and capacity of electronic devices within the same footprint as a single chip.The increased utilization of stacked die packages in cell phone and other consumer products drives technologies that enable multiple die stacks within a given package dimension.This paper reviews t6he technology requirements and challenges for stacked die packages.Foremost among these is meeting package height is 1.2mm for a single die package.For stacked die packages,two or more die need to fit in the same area.That means every dimension in the package has to decrease,including the die thickness.the mold cap thickness,the bond line thickness and the wire bond loop profile.The technology enablers for stacked die packages include wafer thinning,thin die attachment,low profile wire bonding,bonding to unsupported edges and low sweep molding.     

A Neural Network-Based Prediction Model in Embedded Processes of Gold Wire Bonding Structure for Stacked Die Package

The trend in the consumer electronics market is to offer lighter, smaller outline, and more functional products, especially for portable products. This trend has pushed electronic packages to be thinner, with a lower profile and with multiple chips in one package. When the package becomes thinner, the space of the package correspondingly becomes an important issue. In order to obtain higher density and thinner package, we have to develop an embedded gold wire bonding assembly technology. It provides a simple structure with a thick adhesive layer to fix the upper layer die and bottom layer die gold wire. The developed technology can use exactly the same die size as for wire bonding interconnections without any additional processing. All electrical connections of the upper and the lower die are achieved by wire bonding to the substrate, independently. We have performed this stacking assembly by precise control of the die attach film layer thickness and low wire loop shape.      

Wire bond loop profile development for fine pitch-long wireassembly

Die size reductions can be achieved through “optical shrinks,” compaction of existing layouts, or redesigns to finer fab geometries. For some die the limiting factors for die size reduction are bond pad pitch and bond pad size. In these “pad limited” designs, the circuitry is concentrated in the center of the die. Precious empty space exists between the bond pads in the periphery of the die and the circuitry in the die core. The only hope for die size reductions in these designs lies in advances in assembly technology that allow for reductions in bond pad pitches and bond pad size. Fine pitch assembly poses a number of challenges for conventional wire bond technology. Reducing bond pad pitch increases the probability of ball shorting, bond wire shorting, and bond wire damage. On the other hand, decreasing the die size by reducing the bond pad pitch results in longer wire lengths thus limiting some assembly options such as moving to smaller diameter bonding wires. Wire loop profile becomes a critical factor for control in fine pitch assembly. In this paper a statistical design of experiment is used in developing a wire bond loop profile control. The effect of major bonding parameters, such as kink-height, reverse loop, loop factor, wire tension, and their impact on loop profile are analyzed. The results obtained define the bond parameter requirements that must be met in order to control the wire loop profile to optimize fine pitch wire bond assembly yields     

多个叠层芯片封装技术

叠层芯片封装在与单芯片具有的相同的轨迹范围之内,有效地增大了电子器件的功能性, 提高了电子器件的性能。这一技术已成为很多半导体公司所采用的最流行的封装技术。文章简要叙述了叠层芯片封装技术的趋势、圆片减薄技术、丝焊技术及模塑技术。     

Integrated transient thermal and mechanical analysis of molded PBGApackages during thermal shock

During thermal shock, large thermal gradients exist within a molded plastic ball grid array (PBGA) package. The conventional assumption of uniform temperature distribution becomes invalid. In this paper, an integrated thermal-mechanical analysis was performed to evaluate the transient effect of thermal shock. For comparison, an isothermal analysis was also conducted. The computational fluid dynamics (CFD) method was used to obtain the thermal boundary conditions surrounding the package. The heat transfer coefficient obtained through CFD was compared to two analytical solutions. It was found that the analytical values were not acceptable in the time period of interest. Therefore, to obtain the actual maximum die stress, CFD solution has to be used instead of analytical solutions to derive the thermal boundary condition. This boundary condition was then applied to the package and a sequentially coupled heat transfer and thermal stress analysis was performed. The transient analysis has shown that high stresses occur in the die due to thermal shock, which can not be seen under the traditional isothermal assumption. The impact of plastic ball grid array (PBGA) package parameters on transient die stress was also studied, including mold thickness and substrate thickness. The results in this paper could be applied to either wire bond or flip-chip PBGA packages     

基于MCM-D工艺的3D-MCM工艺技术研究

基于MCM-D薄膜工艺,开展了3D-MCM相关的无源元件内埋置、芯片减薄、芯片叠层组装、低弧度金丝键合、芯片凸点,以及板级叠层互连装配等工艺技术研究。通过埋置型基板、叠层芯片组装、板级叠层互连,实现了3D-MCM结构,制作出薄膜3D-MCM样品;探索出主要的工艺流程及关键工序控制方法,实现了薄膜3D-MCM封装。     

金凸点键合工艺在国产陶瓷外壳中的应用

国产陶瓷外壳已经逐渐应用于高可靠要求的各类电子元器件的封装上。在IC封装过程中, 随着封装密度的提高,因其键合指状引线的质量难以满足键合工艺要求,为使其能达到工艺控制要求, 我们开发出一些相应的封装技术,提高了产品的可靠性。金凸点键合工艺用于提高国产陶瓷外壳键合指 上的键合引线强度有非常明显的效果,是一项较新的技术。     

An investigation into warpages,stresses and keep-out zone in 3D through-silicon-via DRAM packages

This paper aims to measure and simulate the warpages of 3D through-silicon via (TSV) die-stacked dynamic-random-access-memory (DRAM) packages during the manufacturing process. The related die stresses and keep-out zone (KOZ) for the stacked dies in the packages at room temperature are further calculated with the validated simulation model. The out-of-plane deformations (or warpages) of the packages from the full-field shadow moiré are documented under temperature loading and found consistent with those from finite-element method (FEM). The results of the stresses and KOZs at the proximity of a single TSV for each die in the package at room temperature are presented. It is found that the sizes of KOZs in four-die stacked DRAM packages with and without epoxy molding compound (EMC) at room temperature are dominated by the horizontal pMOS transistors and more than double the size in wafer-level die. The sizes of KOZs at each die are similar in this four-die stacked DRAM package, even though the stresses at each die are apparently different.     

Fine grain thermal modeling and experimental validation of 3D-ICs

3D die stacking is a promising technique to allow miniaturization and performance enhancement of electronic systems. Key technologies for realizing 3D interconnect schemes are the realization of vertical connections, either through the Si die or through the multilayer interconnections. The complexity of these structures combined with reduced thermal spreading in the thinned dies complicate the thermal analysis of a stacked die structure. In this paper a methodology is presented to perform a detailed thermal analysis of stacked die packages including the complete back end of line structure (BEOL), interconnection between the dies and the complete electrical design layout of all the stacked dies. The calculations are performed by 3D numerical techniques and the approach allows importing the full electrical design of all the dies in the stack. The methodology is demonstrated on a 2 stacked die structure in a BGA package. For this case the influence of through-Si vias (TSVs) on the temperature distribution is studied. The modeling results are experimentally validated with a dedicated test vehicle. A thermal test chip with integrated heaters and diodes as thermals sensors is used to successfully validate the detailed temperature profile of the hot spots in the top die of the die stack.