Insulation reliability of fine-pitch through-vias in glass fiber reinforced halogen-free epoxy substrates Article

Ramachandran, K, Ready, WJ, Raj, PM et al. (2014). Insulation reliability of fine-pitch through-vias in glass fiber reinforced halogen-free epoxy substrates . JOURNAL OF MATERIALS SCIENCE-MATERIALS IN ELECTRONICS, 25(4), 1687-1695. 10.1007/s10854-014-1784-7

cited authors

  • Ramachandran, K; Ready, WJ; Raj, PM; Sundaram, V; Tummala, R

authors

abstract

  • Insulation failures from electrochemical migration is a major reliability concern for achieving reliable small conductor spacings in glass fiber reinforced substrates in the presence of humidity and DC bias voltage. In this study, insulation reliability of fine-pitch copper plated-through-vias in two different halogen-free epoxy substrates was investigated using accelerated testing condition (85 °C, 85 % RH and 100 V DC). The test vehicles included two different conductor geometry: (1) through-via to through-via (spacing: 100 and 150 μm) and (2) through-via to surface-trace (spacing: 75 μm). In accelerated testing, the through-via to through-via test vehicles exhibited insulation failures (failure criterion: 1 M) with a strong dependence on via spacing with through-via spacing of 100 μm showing significantly shorter time to failures compared to test vehicles with spacing of 150 μm. Failure analysis revealed cracking in resin-glass fiber interfaces and within the resin matrix between the failed through-vias. The through-via to surface-trace test vehicles, on the other hand, did not exhibit failures based on the 1 M criterion. However, occurrence of electrochemical migration was visible after optical inspection of the test vehicles. Elemental characterization revealed the presence of copper and chlorine in the resin-glass fiber interface, similar to the previously reported chloride-containing conductive anodic filament compound in printed wiring boards. Accelerating testing and failure analysis in this study indicates a strong dependence of insulation reliability on conductor spacing, geometry and substrate material properties. © 2014 Springer Science+Business Media New York.

publication date

  • January 1, 2014

published in

Digital Object Identifier (DOI)

start page

  • 1687

end page

  • 1695

volume

  • 25

issue

  • 4