Pressurized Underfill Encapsulation of Flip Chip on Board

板上倒装芯片的加压底部填充封装

• 批准号: 9522929
• 负责人: Kuo Wang
• 金额: --
• 依托单位: Cornell University
• 依托单位国家: 美国
• 项目类别: Continuing grant
• 财政年份: 1996
• 资助国家: 美国
• 起止时间: 1996-01-01 至 1997-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9522929&HistoricalAwards=false
• 关键词: Pressurized; Underfill; Encapsulation; Flip; Chip

9522929 Wang Flip Chip of Board (FCOB) technology generally requires encapsulation of the solder joints to reduce the loads on such joints during thermal excursions. At present the encapsulation process constitutes the primary obstacle to widespeard acceptance and implementation of FCOB technology because of the long process times involved, and because of the subsequent lack of repairability. Underfill process times are long because current practice involves dispensing a filled epoxy resin along the edges of the chip and relying on capillary flow (i.e. a surface-tension-driven effect) to fill the space between chip and substrate. Because of the small driving force, this is unavoidably slow, requiring anywhere from one to ten minutes to underfill a typical chip. This is clearly unacceptable as an in-line process in mass-production. In this project an alternative encapsulation process with a significantly shorter duration on the order of seconds, rather than minutes will be explored. This will involve using positive pressure as a driving force in some kind of miniaturized transfer-molding process. The project will also include characterization of encapsulant properties (such as rheology and curing kinetics) as well as process modeling. Such property characterization and modeling can be used to optimize the process. Current underfill materials require cure times on the order of hours (this long cure time is due to the long filling time), thus requiring that the process be done in a batch mode, and do not allow for subsequent removal for repair if chip or board proves to be defective. However, the new process to be developed will allow for considerably more flexibility in materials selection. With the possibility of replacing current epoxy-based thermoset encapsulants with faster-curing thermosets or even with a thermoplastic polymer. The latter would allow repairability of the board, when required. Close collaboration with industry ensures that this research is not only relevant to the electronics manufacturing sector but also that if successful, it will have the necessary market pull for bringing the technology into commercialization. The flip-chip market is estimated at only 5% of the total semi conductor chip sector with the most applications in the automotive industry (for example sensors for air bags and sensors for electronic fuel injectors). Successful completion of this research has the potential to drive down the manufacturing cost and enable repairability option in the flip chip allowing for far wider applications into the computer and telecommunications industries.

小行星9522929 板倒装芯片（FCOB）技术通常需要封装焊接接头以减少热偏移期间这种接头上的负载。 目前，封装过程构成了FCOB技术被接受和实施的主要障碍，因为所涉及的处理时间长，并且因为随后缺乏可修复性。 底部填充工艺时间较长，因为目前的实践涉及沿芯片的边缘沿着分配填充的环氧树脂并依赖于毛细流动（即表面张力驱动效应）来填充芯片和衬底之间的空间。 由于驱动力很小，这是非常慢的，需要一到十分钟来修复一个典型的芯片。 作为大规模生产中的在线工艺，这显然是不可接受的。 在本项目中，将探索一种持续时间明显较短的替代封装过程，持续时间为秒，而不是分钟。 这将涉及使用正压作为某种小型化传递模塑工艺的驱动力。 该项目还将包括封装特性（如流变学和固化动力学）的表征以及工艺建模。 这种性质表征和建模可用于优化工艺。 当前的底部填充材料需要数小时量级的固化时间（这种长固化时间是由于填充时间长），因此需要以批量模式完成该过程，并且如果芯片或电路板被证明有缺陷，则不允许随后取出进行修复。 然而，即将开发的新工艺将允许在材料选择方面有更大的灵活性。 有可能用更快固化的热固性材料甚至热塑性聚合物取代目前的环氧基热固性材料。 后者将允许在需要时对董事会进行维修。 与工业界的密切合作确保了这项研究不仅与电子制造业有关，而且如果成功，它将具有必要的市场拉动力，使这项技术实现商业化。 据估计，倒装芯片市场仅占半导体芯片行业的5%，在汽车工业中的应用最多（例如安全气囊传感器和电子燃油喷射器传感器）。 这项研究的成功完成有可能降低制造成本，并使倒装芯片的可修复性选项，允许更广泛的应用到计算机和电信行业。