Effect of electroplated Au layer on bonding performance of Ag pastes
Effect of electroplated Au layer on bonding performance of Ag pastes
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DOI：
10.1016/j.jallcom.2017.09.279
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发表时间：
2018-01
影响因子：
6.2
通讯作者：
Taikun Fan;Hao Zhang;P. Shang;Cai-Fu Li;Chuantong Chen;Jianxin Wang;Zhi-Quan Liu;K. Suganuma
中科院分区：
文献类型：
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作者：
Taikun Fan;Hao Zhang;P. Shang;Cai-Fu Li;Chuantong Chen;Jianxin Wang;Zhi-Quan Liu;K. Suganuma
在银的烧结连接过程中，不仅粘结材料，而且金属化层对粘接的可靠性起着重要的作用。与银相比，由于成本较高，金的使用频率较低，但对于许多需要多次回流工艺的应用来说，镀金是必然的选择。研究了烧结工艺对银浆粘接强度的影响，以及电镀Au层对不同类型银浆粘接在印刷电路板基板上的碳化硅芯片连接性能的影响。制备了Ni/Pd/Au电镀层作为本研究的衬底金属化。剪切测试结果表明，与0.15μm和0.3μm厚的Au层相比，具有0.8μm厚的Au层的衬底具有更高的剪切强度。在本研究的所有接头中，靠近衬底一侧的多孔银内部的断裂是主要的断裂方式。截面形貌分析表明，在烧结过程中，由于Ag向镀金方向的迁移，在衬底一侧形成了一层弱结合层。迁移率与表面镀金的晶粒度成反比，会影响弱结合层，从而影响接头的结合强度。结果表明，颗粒尺寸较大的镀金层具有较高的结合强度。
In the silver sinter joining process, not only the bonding materials but also the metallization layer play important roles in bonding reliability. Compared with Ag, Au is utilized less often due to its higher cost, however Au plating is the inevitable choice for many applications which require a multiple reflow processes. In our research, the influence of the sintering process on the bonding strength of joints using Ag paste, as well as the influence of the electroplated Au layer on the joining property of SiC chips bonded on a printed circuit board (PCB) substrates with various types of Ag pastes was investigated. Electroplated layers of Ni/Pd/Au were prepared as a substrate metallization for this research. The shear test results revealed that higher shear strength was achieved on substrates with 0.8 μm-thick Au layer compared to those with 0.15 μm and 0.3 μm-thick Au layers. Fracturing inside the porous Ag near the substrate side was the main fracture mode for all joints in this research. The cross-section morphologies revealed that a weak bonding layer would form on the substrate side which was caused by the migration of Ag towards Au plating during the sintering process. The migration rate, which is in inverse proportion to the grain size of exterior Au plating, would impact the weak bonding layer, and thereby influence the bonding strength of joints. According to our results, higher bonding strength can be achieved on Au plating with larger grain size.