| Summary: | 碩士 === 國立成功大學 === 材料科學及工程學系 === 88 === The objective of this research was to determine the impact of different deposition conditions on the electroless Ni plating and its diffusion barrier properties as the UBM for solder bump. Experimentally the concentration of stabilizers, Thiourea or Lead Acetate, and the pH of plating solution were investigated to analyze the properties of electroless Ni. It was also investigated the barrier behavior of the Cu/Ni-P/63Sn-37Pb during multi-reflow and 150℃ heat aging for 1000 hours to find out the suitable deposition condition. The properties of Ni bumps were also analyzed respect to with different stiring method.
The experimental results revealed that the addition of Thiourea increases the deposition rate of Ni plating, but the addition of Lead Acetate does not show such behavior. The deposition rate increased with pH of plating solution regardless of Thiourea or Lead Acetate. However, the deposition rate may decrease when the concentration of stabilizer is over 2ppm.
The structure of Ni-P deposit plated in the presence of Thiourea was crystalline with less than 7 wt% P. When the pH of plating solution is below 4.6, the structure of Ni-P deposit plated in the presence of Lead Acetate was amorphous with over 7 wt% P, while a crystalline structure was obtained when P content is less than 7 wt%. The addition of Thiourea enlarge the grain size of electroless Ni-P, but not the Lead Acetate .
The Ni Bump with flat surface could be deposited by interval pumping; the adhesion strength between Ni/Cu is strong.
The intermatallic compounds formed during reflow or aging between the Ni/63Sn-37Pb are Ni3Sn4 and Ni3Sn2. Besides the IMC, the electroless Ni formed a continuous layer of Ni3P. Cu did not penetrate Ni-P layer with Cu/Ni-P(3μm)/ 63Sn-37Pb and Cu/Ni-P(5μm)/ 63Sn-37Pb after 10 reflows and aging for 1000 hrs regardless of stabilizer.
|
|---|
