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倒装芯片下填充工艺的新进展(一) 总被引:1,自引:0,他引:1
为了增加在有机基板上倒装芯片安装的可靠性,在芯片安装后,通常都要进行下填充。下填充的目的是为了重新分配由于硅芯片和有机衬底间热膨胀系数失配产生的热应力。然而,仅仅依靠填充树脂毛细管流动的传统下填充工艺存在一些缺点。为了克服这些缺点,人们研究出了一些新的材料和开发出了一些新的工艺。 相似文献
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为了预测倒装芯片封装中的下填充过程,通常要首先通过繁复的方法来求解平均毛细压.为了避免此问题,从能量的角度分析了倒装芯片封装工艺中的下填充流动过程.认为下填充是较低表面能的界面代替较高表面能的界面的过程,所释放的表面能用于形成流体流动的动能和克服阻力的能量损耗,期间能量守恒.在此分析的基础上建立了下填充流动的新模型.建立了可视化的下填充流动实验装置,并用下填充实验验证了所建立新模型的准确性.该模型避免了计算平均毛细压的复杂过程,并可方便地扩展到焊球排布形式不同的倒装芯片. 相似文献
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《电子工艺技术》2000,21(3)
责任编辑吕淑珍 20000301 提高倒装片工艺的成品率和可靠性一 Brian J Lewis.SMT,1999,13(11):64~68(英文) 尽管有一些成熟的工艺适用于PCB上的裸芯 片贴装,但倒装片技术是最独特的,芯片被直接倒装 在基板上.倒装片工艺的最关键问题之一是由于热 膨胀系数不同而引起的芯片与基板之间的应力,为 了消除这一应力,下填充工艺被应用于基板与芯片 之间.为了提高倒装片组装的成品率和可靠性,本 文研究了一些相关参数,并介绍了在工艺中怎样检 验每一参数的作用以及必须进行的调整. 20000302 免洗焊膏的改进-Smith Brian.SMT, 相似文献
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对倒装芯片不流动底部填充胶进行压迫流动填充,底部填料会对倒装芯片产生流体静态压力,阻碍芯片向下放置。根据牛顿流体挤压流动的静态近似分析估算出底部填料对芯片的作用力,分别计算在两种不同工艺条件下放置压力达到最大时,两种不同规格芯片与基板的间隔距离,比较与芯片凸点高度,然后计算使芯片凸点与基板键合区实现接触所需放置压力的最小保持时间,从正反两个方面讨论关键参数等对倒装芯片工艺设计影响。 相似文献
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倒装芯片封装中的下填充流场可以假设为多孔介质流场,其渗透率的求解对研究下填充流动过程至关重要。根据下填充流场所具有的周期性结构,通过单胞数值模拟的方法得到了下填充流场的渗透率。通过对渗透率数据的分析,发现了渗透率和下填充流场参数之间的关系,并建立了计算渗透率的幂律模型。其中幂律模型的底是下填充流场的孔隙率,系数仅与芯片和基板的间隙有关,指数仅与芯片和基板的间隙相对于焊球直径的比值有关。通过实例分析表明,与其他模型相比,用基于幂律模型的渗透率所计算出的填充时间更符合实验结果。 相似文献
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底部填充包封材料起初应用于提高早期氧化铝(Al2O3)基材的倒装芯片的可靠性。在芯片最外围的焊点易疲劳而导致芯片功能失效.相对较小的硅片和基材间的热膨胀差异是芯片在经受热循环时产生这种问题的根源.这样,热循环的温度范围及循环的次数就决定了芯片的使用寿命.在芯片和基板间填充可固化的包封材料,可以很好地把热膨胀差异带来的集中于焊点周围的应力分散到整个芯片所覆盖的范围。
随着引入环氧材料作为倒装芯片的基材,底部填充材料的研发大大地加快了。为了延缓焊点的应力疲劳,较大的基材和芯片硅片材料间的热膨胀差异使得底部填充剂的应用成为必然.而在底部填充材料和芯片接合界面的分层及底部填充剂中的空洞是触发许多芯片产生问题的根本原因之一。本篇将要讨论的是减少底部填充剂中的空洞的一些方法.[编者按] 相似文献
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In order to enhance the reliability of a flip-chip on organic board package, underfill is usually used to redistribute the thermomechanical stress created by the coefficient of thermal expansion (CTE) mismatch between the silicon chip and organic substrate. However, the conventional underfill relies on the capillary flow of the underfill resin and has many disadvantages. In order to overcome these disadvantages, many variations have been invented to improve the flip-chip underfill process. This paper reviews the recent advances in the material design, process development, and reliability issues of flip-chip underfill, especially in no-flow underfill, molded underfill, and wafer-level underfill. The relationship between the materials, process, and reliability in these packages is discussed. 相似文献
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Kuo-Ning Chiang Zheng-Nan Liu Chih-Tang Peng 《Components and Packaging Technologies, IEEE Transactions on》2001,24(4):635-640
This research proposes a parametric analysis for a flip chip package with a constraint-layer structure. Previous research has shown that flip-chip type packages with organic substrates require underfill for achieving adequate reliability life. Although underfill encapsulant is needed to improve the reliability of flip chip solder joint interconnects, it will also increase the difficulty of reworkability, increase the packaging cost and decrease the manufacturing throughput. This research is based on the fact that if the thermal mismatch between the silicon die and the organic substrate could be minimized, then the reliability of the solder joint could be accordingly enhanced. This research proposes a structure using a ceramic-like material with CTE close to silicon, mounted on the backside of the substrate to constrain the thermal expansion of the organic substrate. The ceramic-like material could reduce the thermal mismatch between silicon die and substrate, thereby enhancing the reliability life of the solder joint. Furthermore, in order to achieve better reliability design of this flip chip package, a parametric analysis using finite element analysis is performed for package design. The design parameters of the flip chip package include die size, substrate size/material, and constraint-layer size/material, etc. The results show that this constraint-layer structure could make the solder joints of the package achieve the same range of reliability as the conventional underfill material. More importantly, the flip chip package without underfill material could easily solve the reworkability problem, enhance the thermal dissipation capability and also improve the manufacturing throughput 相似文献
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Thermal fatigue damage of flip chip solder joints is a serious reliability concern, although it usually remains tolerable
with the flip chip connections (of smaller chips) to ceramic boards as practiced by IBM for over a quarter century. However,
the recent trend in microelectronics packaging towards bonding large chips or ceramic modules to organic boards means a larger
differential thermal expansion mismatch between the board and the chip or ceramic module. To reduce the thermal stresses and
strains at solder joints, a polymer underfill is customarily added to fill the cavity between the chip or module and the organic
board. This procedure has typically at least resulted in an increase of the thermal fatigue life by a factor of 10, as compared
to the non-underfilled case. In this contribution, we first discuss the effects of the underfill to reduce solder joint stresses
and strains, as well as underfill effects on fatigue crack propagation based on a finite element analysis. Secondly, we probe
the question of the importance of the effects of underfill defects, particularly that of its delamination from the chip side,
on the effectiveness of the underfill to increase thermal fatigue life. Finally, we review recent experimental evidence from
thermal cycling of actual flip chip modules which appears to support the predictions of our model. 相似文献
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Tran S.K. Questad D.L. Sammakia B.G. 《Components and Packaging Technologies, IEEE Transactions on》1999,22(4):519-524
Flip chip attach on organic carriers is a novel electronic packaging assembly method which provides advantages of high input/output (I/O) counts, electrical performance and thermal dissipation. In this structure, the flip chip device is attached to organic laminate with predeposited eutectic solder. Mechanical coupling of the chip and the laminate is done via underfill encapsulant materials. As the chip size increases, the thermal mismatch between silicon and its organic carrier becomes greater. Adhesion becomes an important factor since the C4 joints fail quickly if delamination of the underfill from either chip or the solder mask interface occurs. Newly developed underfills have been studied to examine their properties, including interfacial adhesion strength, flow characteristics, void formation and cure kinetics. This paper will describe basic investigations into the properties of these underfills and also how these properties related to the overall development process. In addition, experiments were performed to determine the effects on adhesion degradation of flip chip assembly processes and materials such as IR reflow profile, flux quantity and residues. Surface treatment of both the chip and the laminate prior to encapsulation were studied to enhance underfill adhesion. Accelerated thermal cycling and highly accelerated stress testing (HAST) were conducted to compare various underfill properties and reliability responses 相似文献
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Thorpe R. Baldwin D.F. Smith B. McGovern L. 《Electronics Packaging Manufacturing, IEEE Transactions on》2001,24(2):123-135
As a concept to achieve low-cost, high-throughput flip chip on board (FCOB) assembly, a new process has been developed implementing next generation flip chip processing based no-flow fluxing underfill materials. The low-cost, high throughput flip chip process implements large area underfill printing, integrated chip placement and underfill flow and simultaneous solder interconnect reflow and underfill cure. The goals of this study are to demonstrate feasibility of no flow underfill materials and the high throughput flip chip process over a range of flip chip configurations, identify the critical process variables affecting yield, analyze the yield of the high throughput flip chip process, and determine the impact of no-flow underfill materials on key process elements. Reported in this work is the assembly of a series of test vehicles to assess process yield and process defects. The test vehicles are assembled by depositing a controlled mass of underfill material on the chip site, aligning chip to the substrate pads, and placing the chip inducing a compression type underfill flow. The assemblies are reflowed in a commercial reflow furnace in an air atmosphere to simultaneously form the solder interconnects and cure the underfill. A series of designed experiments identify the critical process variables including underfill mass, reflow profile, placement velocity, placement force, and underfill material system. Of particular interest is the fact that the no-flow underfill materials studied exhibit an affinity for unique reflow profiles to minimize process defects 相似文献
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Schubert A. Dudek R. Leutenbauer R. Doring R. Kloeser J. Oppermann H. Michel B. Reichl H. Baldwin D.F. Jianmin Qu Sitaraman S.K. Swaminathan M. Wong C.P. Tummala R. 《Electronics Packaging Manufacturing, IEEE Transactions on》1999,22(4):255-263
Solder joints, the most widely used flip chip on board (FCOB) interconnects, have a relatively low structural compliance due to the large thermal expansion mismatch between silicon die and the organic substrate. The coefficient of thermal expansion (CTE) of the printed wiring board (PWB) is almost an order of magnitude greater than that of the integrated circuit (IC). Under operating and testing conditions, this mismatch subjects the solder joints to large creep strains and leads to early failure of the solder connections. The reliability of such flip chip structures can be enhanced by applying an epoxy-based underfill between the chip and the substrate, encapsulating the solder joints. This material, once cured, mechanically couples the IC and substrate together to locally constrain the CTE mismatch. However, the effects of CTE mismatch are assumed to become more severe with increasing chip size. Even with the addition of an underfill material, it has been supposed that there are limits on the chip size used in flip chip applications 相似文献
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Jicun Lu Busch S.C. Baldwin D.F. 《Electronics Packaging Manufacturing, IEEE Transactions on》2001,24(3):154-159
Wafer-level flip chips provide an innovative solution in establishing flip chip as a standard surface mount process. In this paper, the wetting of solder bumps within confining underfill during the reflow of a wafer-level flip chip assembly is addressed. For real time monitoring of an assembly during the reflow process, a system using a high-speed camera is utilized. The collapse of solder bumps on the chip in the vertical direction is found to be a prerequisite of solder wetting. Underfill voids and outgassing are found to cause chip drift and tilt during the reflow process. In addition, symmetry of the underfill flow and fillet formation is identified as a critical factor in maintaining chip to substrate alignment. During solder wetting of the metallization pads on the substrate, the underfill needs to maintain a low viscosity. With the selection of a thermally stable underfill and corresponding process development, wafer-level flip chip assemblies with good solder interconnects are demonstrated 相似文献
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从热疲劳故障的角度论述了倒装芯片底部填充的必要性,介绍了倒装芯片底部填充的参数控制。通过正确的底部填充,可提高倒装芯片组装的成品率和可靠性。 相似文献