Fracture mechanism of microporous Ag-sintered joint in a GaN power device with Ti/Ag and Ni/Ti/Ag metallization layer at different thermo-mechanical stresses
Fracture mechanism of microporous Ag-sintered joint in a GaN power device with Ti/Ag and Ni/Ti/Ag metallization layer at different thermo-mechanical stresses
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DOI：
10.1007/s10853-021-05924-z
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发表时间：
2021-02-25
影响因子：
4.5
通讯作者：
Suganuma, Katsuaki
中科院分区：
文献类型：
--
作者：
Kim, Dongjin;Lee, Sangmin;Suganuma, Katsuaki
银烧结连接技术正在成为高温应用中下一代功率模块的一种芯片贴装材料。热冲击试验表明，烧结银接头的断裂特性和可靠性受热机械应力的影响。本研究旨在了解在热冲击试验过程中，在直接键合铝（DBA）基板上设计有不同金属化层的烧结银接头在不同热机械应力下的微观结构、垂直裂纹形成和断裂行为。设计了两种金属化层，即Ti/Ag和Ni/Ti/Ag层。有限元模型（FEM）模拟证实，在 -50℃至250℃的热冲击试验期间，Ni层抑制了Al丘状变形，并产生了不同的热机械应力。根据两种银烧结接头界面的退化情况，从电子背散射衍射（EBSD）分析结果来看，对长期可靠性方面的结合强度有主要影响的烧结银晶粒颈缩厚度和包括银晶粒结构在内的微观结构特征存在显著差异。本文提出了一种新型金属化技术，该技术可通过有效抑制界面退化，使烧结银接头完全再结晶从而导致接头断裂。通过实验和有限元模拟对该技术的机理进行了系统分析。
Ag sinter joining technology is emerging as a die attach material for next-generation power modules in high-temperature applications. Thermal shock test has revealed that the fracture characteristics and reliability of sintered Ag joint were influenced by thermo-mechanical stress. This was study conducted to understand the microstructure, vertical crack formation, and fracture behavior of sintered Ag joints which were designed with different metallization layers on a direct bonded aluminum (DBA) substrate, at different thermo-mechanical stresses during thermal shock tests. Two kinds of metallization layers were designed as Ti/Ag and Ni/Ti/Ag layers. A finite element model (FEM) simulation confirmed that the Ni layer prohibited Al hillock-like deformation and generates different thermo-mechanical stresses during the thermal shock test from - 50 degrees C to 250 degrees C. Depending on the degradation of the interfaces for both of the Ag-sintered joints, the sintered Ag grain necking thickness and microstructure characteristics including the Ag grain structures, which have a dominant influence on the bonding strength in terms of long-term reliability, are considerably different from the results by an electron back scatter diffraction (EBSD) analysis. This paper proposes a novel metallization technology that can induce joint fracture with complete recrystallization of sintered Ag joints by effectively suppressing interfacial degradation. The mechanism of this technology was systematically analyzed through experiments and FEM simulations.