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1.
Bae-Kyun Kim Seong-Jae Lee Jong-Yun Kim Kum-Young Ji Yeo-Joo Yoon Mi-Yang Kim Song-Hae Park Jong-Soo Yoo 《Journal of Electronic Materials》2008,37(4):527-534
We suggest a unique mechanism for surface defect generation causing solder joint or bonding failures in printed circuit boards
(PCBs). Surface defects can be defined as corroded holes or spikes of the Ni-P layers on the soldering or wire bonding pads
of PCBs. The typical defects are the black pad or pinhole pad defects generated after final finishing by the electroless nickel
immersion gold (ENIG) process. Once corroded voids or spikes are plentifully created in nickel/gold interfaces, the bonding
strength of solder or wire bonding joints is reduced. Therefore, it is important to characterize the details of these surface
defects. In this paper, the defect microstructures and the P content variation with the ENIG processes are investigated. The
surface defect selectivity with pad size and pad connectivity is suggested based on the key findings of P content variation.
An overall mechanism is proposed based on a mixed mode of concentration cell corrosion and galvanic cell corrosion. Based
on these results, more reasonable root causes are suggested. 相似文献
2.
Electroless Ni/Immersion Au interconnects: Investigation of black pad in wire bonds and solder joints 总被引:1,自引:0,他引:1
Black Pad was observed on Electroless Ni/Immersion Au (ENIG) wire bond pads. Thick immersion Au on highly corroded electroless
Ni was detected. It was determined that the pads were electrically connected to the Cu ground plane due to a Ni bridge formed
inside normally open photovias. The mechanism of the bridge formation was verified and preventative actions were taken; it
was demonstrated that formation of Black Pad could be switched on and off. The mechanism of Black Pad formation is proposed
to be defective ENIG plating involving variation of both the electroless Ni and immersion Au plating processes. The intermetallic
structures of solder joints on the above pads were studied. The study was conducted on both defective and non-defective pads
to show differences in intermetallic structure and composition. Me2Sn4 and Me2Sn2 (Me=Cu, Ni, and Au) intermetallics were formed on non-defective pads, which nucleated on the Ni layer and grew inside the
molten solder. However, only the Me3Sn intermetallic was formed on defective pads inside the corroded Ni Layer. Both mechanisms of intermetallic formation were
found on pads with mildly corroded Ni and intermediate Au thickness (4.5–7 in). 相似文献