功率器件微互连非均质界面的热性能及宏-微观失效分析

Interconnect materials with inhomogeneous fillers show improved thermal conductivity in comparison with those with monomodal ones, and are more suitable for the interconnect and heat transfer in packaging with high-powered devices/components. The micro-structures in the joint matrix vary with different filler contents and distribution patterns, and become more complicated due to the types of particles involved and their anisotropy, showing obvious size effect in the interconnect. In this project, firstly experimental measurement and mechanism analysis will be carried out on the effective thermal conductivity of composite materials with inhomogeneous fillers. A complete data sheet will be obtained by systemic sample preparation and measurement. At the same time, a more comprehensive model will be developed to predict thermal conductivity of the composite material studied, and factors such as the matrix and filler materials, micro-structures and geometries as well as fillers' layout and conductivities will be included. Especially, the influences of heat transfer between bimodal filler particles, thermal resistance, and the shrinkage of epoxy resin during curing will be taken into consideration in the model establishment. Then a series of numerical simulations will be carried out on the characteristic parameters and thermal performance of the inhomogeneous interconnect materials for high-powered chip and other applications requiring effective thermal management. Furthermore, the development of a macro-microscale interface model is also part of the project work, in which a cohesive zone model will be introduced into high-order micropolar frame to describe the delamination initiation and propagation of the representative microstructure in the inhomogeneous interconnect. The microscopic behavior will be coupled with the macroscopic interface deformation, and a macro-microscale failure model of the interconnect interface will be established. Then the model will be implemented by FEM and applied to the reliability prediction of high-powered component/device packaging.

针对功率器件高密度封装的微互连和有效散热要求，包含非均质填料互连材料的热传导性能明显优于单一填料情形。不同体积分数和颗粒配比形成的填料分布和各向异性特征，导致其内部微结构复杂性大为增加，互连界面尺度效应突出。本项目首先对非均质填料复合材料有效导热率进行实验测量和机理分析，实验制备测量得到系列样品完整数据表；建立更完善的有效导热率理论模型，考虑环氧基体与非均质填料的材料、微结构和尺度特征，尤其是不同类型填料配比在基体内的排列、传导特性等。分析非均质组合型填料颗粒在基体内的传导、不同材料间热阻，以及固化过程中基材非弹性行为对此复合材料整体导热性能的影响，得到适应功率芯片高效散热而研发互连材料的特征参数和传热性能的精细预测。同时，在高阶微极界面理论框架内引入内聚力模型，以描述界面内裂纹的萌生和发展，并与界面宏观变形耦合，建立宏-微观界面失效分析模型，以有限元实现并应用于功率器件互连可靠性分析。

目前高密度、细间距电子器件集成技术发展对封装材料适应连接微细化、机械连接可靠性和传导性能、环境友好提出了更高要求，研发具有优良导电、散热性能及可靠性的新型微互连材料，是电子封装材料和集成技术发展的关键问题之一。本项目主要研究适用于功率器件高密度封装的非均质填料环氧胶，选用具有良好导电和导热性能的填料与聚合物基体混合，可以在保持良好机械连接和导电性能的同时，满足高功率器件互连散热要求。本项目按照项目计划任务书研究计划执行，通过系统实验测试、理论模型和数值模拟，制备具有较高传导性能的非均质混合填料环氧胶，完善相应的复合材料有效导热率理论模型，建立含复杂微结构互连界面的多尺度失效分析模型，按期圆满完成项目计划任务书既定的研究内容：（1）样品制备、参数表征及性能测试方面，采用不同材料、尺寸、形状的填料制备系列样品，通过传导性能、剪切强度和可靠性实验测试，得到样品特征数据表。通过优化样品配方及工艺，得到适用于刚性和柔性基板上不同器件表面贴装的非均质填料样品。（2）有效导热率模型及传导机理分析方面，基于热阻网络模型，并计及颗粒-基体之间相互作用等微观结构的作用，建立较为完备的非均质填料环氧胶有效导热率模型。通过模型基础上的数值模拟，分析得到总填充率、基体材料、非均质填料混合比例、颗粒之间接触情况等关键参数对复合材料有效导热率的影响，为实验样品配方优化提供参考依据。（3）非均质互连界面的多尺度失效分析模型方面，根据互连层内微结构选取代表性体积单元，采用高阶微极理论并结合内聚力模型，建立能够刻画微观分层萌生和扩展的多尺度界面模型。将理论模型以有限元方法实现，应用于含复杂微结构的互连界面可靠性分析。