Shape Evolution of Electrodeposited Bumps into Deep Cavities | Zendy

K. Hayashi | Zendy; Kunihiro Fukui | Zendy; Zennosuke Tanaka | Zendy; Kazuo Kondo | Zendy

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Shape Evolution of Electrodeposited Bumps into Deep Cavities

Author(s) -

K. Hayashi,

Kunihiro Fukui,

Zennosuke Tanaka,

Kazuo Kondo

Publication year - 2001

Publication title -

journal of the electrochemical society

Language(s) - English

Resource type - Journals

SCImago Journal Rank - 1.258

H-Index - 271

eISSN - 1945-7111

pISSN - 0013-4651

DOI - 10.1149/1.1346602

Subject(s) - cathode , materials science , enhanced data rates for gsm evolution , natural convection , composite material , aspect ratio (aeronautics) , diffusion , convection , current (fluid) , mechanics , chemistry , electrical engineering , thermodynamics , telecommunications , physics , computer science , engineering

Metal posts and finer pitch solder bumps are the indispensable microconnectors for chip size packaging and are formed by electrodeposition into deep cavities. It is difficult to stir inside these deep cavities. Natural convection due to density difference is effective in stirring inside cavity with 200 mum cathode width of aspect ratio of one. The bump shape increases toward lower side in a vertical cathode arrangement with placement angle of Theta = 90 degrees. This increase in bump height results from a collision of flow along the lower side of the resist sidewall which enlarges local current and thickens the lower edge of bumps. The effect of natural convection is also evident in the neighboring two cavities of 200 mum cathode width. The natural convection is not effective for cavities with less than 100 mum cathode width. The bump shapes become flat. Only diffusion occurs within these smaller than 100 mum cavities. (C) 2001 The Electrochemical Society. All rights reserved.

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