Improvement in Etching Factor of Micro Patterns by Controlling Residual Stress of Copper Thin Foil
The effectiveness of residual stress on forming copper patterns of printed circuit board was investigated during applied thermal conditions. Generally, the electrolytic copper foil showed a compressive residual stress about -55~-60MPa as received, which easily caused to form copper patterns irregularly when the pattern was etched finely. The compressive residual stress was relaxed with applying heat-treatment for a few hours. However, we observed that the compressed residual stress of copper foil tended to be relaxed, constant, and compressed again during heat-treatment process, which is mainly considered as that the grain of copper is grown restrictively within a Cu thin foil layer. We suggested a quantitative method for controlling grain size, grain distribution and relaxing stress of copper foil, which was very helpful for increasing an etching factor to decrease pattern width.
Joong Hee Lee
H. S. Lee and H. J. Lee, "Improvement in Etching Factor of Micro Patterns by Controlling Residual Stress of Copper Thin Foil", Advanced Materials Research, Vols. 123-125, pp. 479-482, 2010