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{1316}
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ref: -0 tags: polyimide adhesion chromium copper tie layer upilex date: 06-24-2015 23:14 gmt revision:3 [2] [1] [0] [head]

Adhesion Evaluation of Adhesiveless Metal/Polyimide Substrate for MCM and high density packaging

  • Adhesion degradation after thermal and humidity stresses can occur for a number of reasons.
    • Copper diffusion can promote adhesion loss at elevated temperatures and can be inhibited by coating a barrier layer of metal – tie layer2.
    • Oxygen diffusion through polyimide film to the metal/polyimide interface plays a critical role in promoting degradation too3. Adhesion of Cr/polyimide interface is degraded significantly upon exposure to high temperature and humidity environment due to the hydrolysis of polyimide4,5 .
    • Catastrophic adhesion loss has been linked to moisture induced oxidation of chromium interfaces based on studies using radioactively tagged water4, 5.
  • That said, most of these vendors use Cr (20nm) as and adhesion layer, and Cu (200nm) as the conductor.
  • Upilex A faired very well after the pressure cooker test -- > 60% retention after 192 hours.
  • Seemingly Ta and Cr both adhere similarly to PI -- {1317}
    • Though Ta is much more ductile, and forms a stronger carbide, Cr is preferred... cheaper?