Uniformity of an electroless plated Ni on a pad connected to different size pads or a Pn junction for under bump metallurgy in a flip-chip assembly

Akihiro Ikeda, Tsubasa Saeki, Atsushi Sakamoto, Yosuke Sugimoto, Yasuhiro Kimiya, Fukunaga Fukunaga, Reiji Hattori, Hisao Kuriyaki, Yukinori Kuroki

研究成果: Contribution to journalArticle査読

6 被引用数 (Scopus)

抄録

We investigated electroless Ni uniformity on Al metal pads connected to different size pads or a pn junction for under bump metallurgy in flip-chip assemblies. In an electrically isolated pad, Ni thickness decreased as the pad size decreased. Because of nonlinear diffusion of Pb2+ stabilizer in the plating solution, fewer electrons were supplied to the smaller pad than to the larger pad by an anodic oxidation reaction on the pad surface. In pads smaller than 50 mum square, the Ni thickness increased when connected to a 100 μm square pad. This increase might be caused by electrons flowing from the 100 μm square pad to the smaller pad to produce an equipotential for the connected pads. In addition, the Ni thickness was increased by electrical connection to an n-type Si in the presence of fluorescent light illumination for a pn junction area larger than 100 μm2. For a pad connected to a p-type Si, however, Ni thickness decreased in comparison to that of an electrically-isolated pad, regardless of the light illumination or pn junction area. The change of Ni height on pads connected to the pn junction is attributable to photoelectrons injected into the n-type Si, or to electron-hole recombination in the p-type Si. These results indicate that the pads should be of the same size within a chip for better Ni uniformity. Moreover, blocking light during Ni electroless plating can eliminate Ni thickness differences due to an n-type Si connection.

本文言語英語
ページ(範囲)494-499
ページ数6
ジャーナルIEEE Transactions on Components and Packaging Technologies
30
3
DOI
出版ステータス出版済み - 2007

All Science Journal Classification (ASJC) codes

  • 電子材料、光学材料、および磁性材料
  • 電子工学および電気工学

フィンガープリント

「Uniformity of an electroless plated Ni on a pad connected to different size pads or a Pn junction for under bump metallurgy in a flip-chip assembly」の研究トピックを掘り下げます。これらがまとまってユニークなフィンガープリントを構成します。

引用スタイル