Study on interfacial morphology of microelectronic solder joints with electroless Ni-Zn-P under bump metallization

• Main Authors: Chia-Ching Wen, 溫家慶
• Other Authors: Jen-Ming Song
• Format: Others
• Language: zh-TW
• Published: 2010
• Online Access: http://ndltd.ncl.edu.tw/handle/15156848023369648859

碩士 === 國立東華大學 === 材料科學與工程學系 === 98 === In order to improve the performance of electroless Ni-P as under bump metallizations (UBM), this study developed ternary Ni-Zn-P electroless deposited films and investigated the compositional effect on their crystallization behavior and interfacial reactions with SAC solders. With the combination of the XRD and DSC results, the dissolution of Zn into Ni-P was detrimental to the amorphousness of films. The eletroless deposits with the composition of Ni-5.5wt%P were amorphous, while those with Ni-7.5wt%-6.8wt%P and Ni-2.7wt%Zn-5.2wt%P were with the microcrystalline structure. Upon heating, the three endothermal peaks representing the crystallization of Ni, metastale Ni5P2 and Ni3P respectively could be detected for the former two films, but the latter exhibited only one peak for the formation of Ni3P. The low P films with the compositions of Ni-5.3wt%Zn-3.4wt%P and Ni-5.5wt%Zn-2.8 wt%P were well crystallined and showed two endothermal peaks for the precipitation of Ni5P2 and Ni3P upon heating, of which the peak temperatures were higher than those of the high P films. Nanoindentation data indicate that well crystalline low P films possessed greater hardness, Young’s modulus and ability for plasticity than high P films. Observation on the interfacial morphology depicts that Ni3P, Ni-Sn-P and (Ni,Cu)3Sn4 formed and located in sequence between Ni-Zn-P substrate and the solder of the Ni-5.5wt%P/SAC joints. Ni3P was absent for the low P samples regardless of the reflow times. Interestingly, Zn may give rise to the detachment and dissolution of Ni-Sn-P after 3-time reflows. In summary, low P Ni-Zn-P electroless films are able to retard the growth of brittle P-rich phases (Ni3P, Ni-Sn-P) at interface, and thus have the potential to be used as UBMs when reliability under drop or impact is a concern.