Akira Chinda

Advanced trench filling process by selective copper electrodeposition for ultra fine printed wiring board fabrication

A trench filling type process to fabricate ultra-fine pitch printed wiring boards was developed by combining nano-imprint lithography (NIL) and selective copper deposition. Copper was electorodeposited selectively inside the trenches fabricated in the dielectric layer by NIL process, without causing excess deposition on the surface. The selective deposition was realized by a novel electrodeposition bath employing Cyanine dye as an inhibiting additive. The recessed interconnections with 10 µm line and space dimension were successfully fabricated. The developed process shows significant advantages to the processes employing non- or less- selective deposition, which require planarization to remove excess copper deposited on the surface, and may potentially replace the state of the art semiadditive process.

Investigation of high reliability micro bump plating technique on tape carrier

This paper describes the continuous copper bump plating technique for TAB tape carriers. We investigated the copper plating bath, pre-treatment agents and the bath agitation method. For high speed and uniform plating, the selection of an appropriate copper plating bath is most important. Through our investigations, we found the most suitable bath for copper plating bumps, which obtained good appearance and high reliability bumps at 20 A/dm/sup 2/ or more. The tape carriers with copper plating bumps were applied to the new stacking board and the burn-in socket substrate for a 0.5 mm pitch BGA package. In both cases, it was confirmed that the tape with bumps had high reliability. Then, a continuous reel to reel plating machine for TAB tape carrier was designed and manufactured.