Title:
Chemical and Mechanical Adhesion Mechanisms of Sputter-Deposited Metal on Epoxy Dielectric for High Density Interconnect Printed Circuit Boards
Chemical and Mechanical Adhesion Mechanisms of Sputter-Deposited Metal on Epoxy Dielectric for High Density Interconnect Printed Circuit Boards
Author(s)
Wong, C. P.
Martin, Lara J.
Martin, Lara J.
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Abstract
Strong chemical reactions between metal and
polymer substrates significantly enhance adhesion of the metal
to the polymer. This study investigated the adhesion of three
types of thin film metals, including Cu, NiCr, and Cr, to a fully
epoxy-based polymer. Before depositing these thin film metals, the
epoxy surface was treated with either an Ar or O [subscript 2] plasma etch.
It was found that NiCr and Cr produced higher peel strengths
than Cu, but NiCr and Cr did not produce different peel strengths
than each other. It was also found that O[subscript 2 ] plasma etch produced
significantly higher peel strengths than Ar plasma etch for Cu and
Cr, but not for NiCr. An XPS (X-ray photoelectron spectroscopy)
study was performed to investigate the reactivities and possible
chemical adhesion mechanisms of the metal thin films with the
epoxy. It was determined that Cr reacted more strongly than Ni in
forming metal oxide at the metal-epoxy interface. Cu was not seen
to react strongly in forming oxide with the epoxy. Thermodynamic
information supported the relative amounts of oxides found by
XPS. Thermodynamic information also suggested that O [subscript 2] plasma
etch did not produce significantly higher adhesion than Ar plasma
etch on the NiCr samples due to the large Ni component of the
NiCr thin film. An AFM (atomic force microscopy) study was performed
to investigate possible mechanical adhesion mechanisms.
Implications of the AFM results were that the main adhesion
mechanism for all samples was chemical and that the Cu oxide
that was available on the Cu samples was beyond the detection
limits of the XPS equipment.
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Date Issued
2001-09
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