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2008
Conference Paper
Titel
Immersion Ag as an alternative in 'Green' COB technology
Abstract
Immersion (electroless) Ag, which is only 200 ? 400 nm thin, is a viable alternative to Ni/Au or Ni/Pd/Au for Au wire bonding on PCB. Most promising advantages of this metallization as a lead-free solderable finish that can be glued or wire bonded are its smoothness and comparatively uniform and extremely small thickness, and therefore lower material and energy consumption. Soldering on immersion Ag is particularly well-established and this type of finish has been increasing throughout the world in recent years. However, the first generations of immersion Ag had the great disadvantage of not being particularly suitable for wire bonding over a longer period once it had been taken out of inert gas. The Ag finish was detrimentally affected by oxygen and sulfur and this reduced the bondability very quickly. In contrast, the latest generation of immersion Ag promises longterm surface stability and, therefore, bondability thanks to a more robust and consistent plating process (chemistry).