DC Field | Value | Language |
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dc.contributor.author | Jeon, Young Doo | - |
dc.contributor.author | Paik, Kyung Wook | - |
dc.contributor.author | Bok, Kyoung Soon | - |
dc.contributor.author | Choi, Woo Suk | - |
dc.contributor.author | Cho, Chul Lae | - |
dc.date.accessioned | 2008-01-11T09:19:07Z | - |
dc.date.available | 2008-01-11T09:19:07Z | - |
dc.date.issued | 2000-01 | - |
dc.identifier.citation | Journal of Electronic Materials v.31 n.5, 520-528 | en |
dc.identifier.issn | 0361-5235 | - |
dc.identifier.uri | http://hdl.handle.net/10203/2731 | - |
dc.description.abstract | The electroless-deposited Ni-P under bump metallurgy (UBM) layer was fabricated on Al pads for Sn containing solder bumps. The amount of P in the electroless Ni film was optimized by controlling complexing agents and the pH of plating solution. The interfacial reaction at the electroless Ni UBM/solder interface was investigated in this study. The intermetallic compound (IMC) formed at the interface during solder reflowing was mainly Ni3Sn4, and a P-rich Ni layer was also formed as a by-product of Ni-Sn reaction between the Ni-Sn IMC and the electroless Ni layer. One to four microns of Ni3Sn4 IMC and a 1800–5000 Å of P-rich Ni layer were formed in less than 10 min of solder reflowing depending on solder materials and reflow temperatures. It was found that the P-rich Ni layer contains Ni, P, and a small amount of Sn (∼7 at.%). Further cross-sectional transmission electron microscopy (TEM) analysis confirmed that the composition of the P-rich Ni layer was 75 at.% Ni, 20at.%P, and 5at.%Sn by energy-dispersive x-ray spectroscopy (EDS) and the phase transformation occurred in the P-rich Ni layer by observing grain size. Kirkendall voids were also found in the Ni3Sn4 IMC, just above the P-rich Ni layer after extensive solder reflow. The Kirkendall voids are considered a primary cause of the brittle fracture; restriction of the growth of of the P-rich Ni layer by optimizing proper processing conditions is recommended. The growth kinetics of Ni-Sn IMC and P-rich Ni layer follows three steps: a rapid initial growth during the first 1 min of solder reflow, followed by a reduced growth step, and finally a diffusion-controlled growth. During the diffusion-controlled growth, there was a linear dependence between the layer thickness and time1/2. Flip chip bump shear testing was performed to measure the effects of the IMC and the P-rich Ni layers on bump adhesion property. Most failures occurred in the solder and at the Ni3Sn4 IMC. The brittle characteristics of the Ni-Sn IMC and the Kirkendall voids at the electroless Ni UBM-Sn containing solder system cause brittle bump failure, which results in a decreased bump adhesion strength. | en |
dc.description.sponsorship | This work was supported by the Center for Electronic Packaging Materials of Korea Science and Engineering Foundation, Taejon (Korea). | en |
dc.language.iso | en_US | en |
dc.publisher | Springer Verlag (Germany) | en |
dc.subject | UBM | en |
dc.subject | electroless Ni | en |
dc.subject | solder interfacial reaction, | en |
dc.subject | flip chip | en |
dc.title | Studies of electroless nickel under bump metallurgy—Solder interfacial reactions and their effects on flip chip solder joint reliability | en |
dc.type | Article | en |
dc.identifier.doi | 10.1007/s11664-002-0109-4 | - |
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