添加錫至銅基材對於銅基材與無鉛焊料之介面反應的影響

Abstract

扇出型晶圓級構裝可容納高I/O數，為具優勢之封裝結構，但其線路重佈層中之銅線路可能在熱應力作用下斷裂。取代銅線路的材料必須兼顧好的機械性質及介面反應性質，銅錫合金錫含量10wt%以內具有良好強化效果，但銅錫合金與焊料之介面反應少有文獻探討。本研究中觀察Cu/solder、Cu-3Sn/solder、Cu-6Sn/solder、Cu-10Sn/solder等介面在迴焊後以及在150℃、180℃、200℃下持溫後之介金屬形貌及厚度，進而得出介金屬成長速率及活化能。實驗結果顯示基材中的錫含量越高，Cu3Sn的成長速率僅微幅增加。此外Cu-3Sn/solder、Cu-6Sn/solder、Cu-10Sn/solder等介面之介金屬形貌皆與Cu/solder相似。

Fan-out wafer-level packaging (FOWLP) technology is gaining popularity for its performance and for its ability to meet high I/O counts. However, cracks were detected on Cu RDL under thermal stress. The material that can replace Cu must have better mechanical properties and good solder joint reliability after soldering and thermal aging. The fact that Cu-Sn alloys have good strengthening effect when tin is below 10wt% has been studied. Few studies have investigated the interfacial reaction between solder and Cu-Sn alloys. In this study, the interfacial reaction between Cu-xSn(x=0, 3, 6 and 10wt%) substrates and SAC305 solder after reflow, and aging at 150℃, 180℃, 200℃, respectively, are investigated. The morphology and the thickness of intermetallic compound (IMC) can be observed. Moreover, the activation energy and the growth rate of IMC corresponding to the diffusion can be obtained. The experimental result shows that the growth rate of Cu3Sn is slightly accelerated if there is higher concentration of Sn in Cu-xSn substrates. In addition, all the morphology of IMC in Cu-3Sn/solder、Cu-6Sn/solder、Cu-10Sn/solder are similar to that of Cu/solder.