Novel reworkable fluxing underfill for board level assembly
Novel reworkable fluxing underfill for board level assembly
复制标题
用于板级组装的新型可返修助焊剂底部填充剂
DOI：
10.1109/ectc.2003.1216403
复制
发表时间：
2003
期刊：
影响因子：
--
通讯作者：
C. Wong
中科院分区：
文献类型：
--
作者：
Zhuqing Zhang;Haiying Li;C. Wong
下填料传统上用于倒装芯片应用。最近，越来越多的电路板级组件（包括球栅阵列（BGAs）和芯片级封装（csp））使用下填料，以提高恶劣环境下的可靠性和抗机械冲击的能力。无流底充工艺消除了毛细管流动，将充注和底充合二来，使底充BGAs和csp的组装兼容SMT。然而，缺乏可返工性阻碍了在板级组装中使用下填料。在本文中，开发了无流底填配方，以提供助熔剂能力，可返工性，高抗冲击性和良好的可靠性，为板级组件。采用差示扫描量热仪（DSC）、热机械分析仪（TMA）和动态机械分析仪（DMA）对所设计的下填料进行了表征。利用高温模剪试验对下填土的可再加工性进行了评价。%点弯曲试验和DMA频率扫描表明，该材料具有较高的断裂韧性和良好的阻尼性能。CSP组件使用我们开发的底料组装在板上。实现了高互连成品率。论证了下填土的可返工性。在空对空热冲击（AATS）中，对部件的可靠性进行了评估。所开发的配方对于板级元件具有潜在的高可靠性。
Underfills are traditionally applied for flip-chip applications. Recently, there is an increasing use of underfill for board-level assembly including Ball Grid Arrays (BGAs) and Chip Scale Packages (CSPs) for enhancing reliability in harsh environment and impact resistance to mechanical shocks. No-flow underfill process eliiates the capillaq flow and combmes fluxing and underfilling into one process step, which makes the assembly of underfilled BGAs and CSPs SMT compatible. However, the lack of reworkability prevents the usage of underfill in board level assembly. In this paper, no-flow underfill formulations are developed to provide fluxing capability, reworkability, high impact resistance, and good reliability for the board level components. The designed underfill materials are characterized with Differential Scanning Calorimeter (DSC), Thermal Mechanical Analyzer (TMA), and Dynamic Mechanical Analyzer (DMA). The potential reworkability of the underfills is evaluated using die shear test at elevated temperature. The %point bending test and the DMA frequency sweep indicate that the developed materials have high fracture toughness and good damping properties. CSP components are assembled on the board using our developed underfill. High interconnect yield is achieved. Reworkability of the underfills is demonstrated. Reliability of the components is evaluated in air-to-air thermal shock (AATS). The developed formulations have potential high reliability for board level components.