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|Title:||Effects of immersion zincation to the electroless nickel under-bump materials in microelectronics packaging|
|Citation:||Ng, Wei-Chin,Ko, Tze-Man,Chen, William,Qi, Guo-Jun (1998). Effects of immersion zincation to the electroless nickel under-bump materials in microelectronics packaging. Proceedings of the Electronic Packaging Technology Conference, EPTC : 89-94. ScholarBank@NUS Repository.|
|Abstract:||One of the methods to mount a flip chip is by solder bumping that utilizes Ni/Au metallurgy as the under-bump material. Electroless nickel plating has been preferred over conventional electroplating due to its simplicity, good control, and reproducibility. Experiments are carried out to determine the optimum conditions of the aluminum surface for nickel adhesion, through the studies of surface morphology and transformation during pretreatment. Zincation baths are used to condition the aluminum surfaces for nickel plating. The effects of the period and the number of times of the zincation process to the mechanical strength of the electroless nickel deposits are investigated. From the SEM and AFM characterization, transitions of zinc gram size and surface roughness are observed. Grains are large with distinct grain boundaries for immersion time of 5 s but decrease in size and lose their characteristic shapes as the zincation time increases. A double zincation produces a more compact deposit with smaller size grains compared to single zincation. Length of immersion time during the 2nd zincation also affects the physical properties such as shear strength after 1 h of electroless nickel plating on the 80 μm×80 μm Al bond-pads of a commercial bare microchip. By using SEM-EDX and XPS, the elemental composition transitions of the zinc deposits formed by different zincation time and bath compositions are also investigated.|
|Source Title:||Proceedings of the Electronic Packaging Technology Conference, EPTC|
|Appears in Collections:||Staff Publications|
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