Surface property of passivation layer on integrated circuit chip and solder mask layer on printed circuit board

Abstract

Adhesion of underfill to passivation layer on integrated circuit chip and solder mask layer on printed circuit board is critical to the reliability of an underfilled flip chip package. In this study, the surface properties of solder mask and four passivation materials: benzocyclobutene (BCB), polyimide (PI), silicon dioxide ( 2 ), and silicon nitride (SiN) were investigated. A combination of both wet and dry cleaning processes was very effective to remove contaminants from the surface. The element oxygen, introduced during 2 plasma treatment or 3 treatment, led to the increase of the base component of surface tension. X-ray photoelectron spectroscopy (XPS) experiments confirmed the increase of oxygen concentration at the surface after 3 treatment. Wetting of underfill on passivation and solder mask was slightly improved at higher temperatures. Although 3 cleaning and 2 plasma treatment significantly improved the wetting of underfill on passivation materials, they did not improve adhesion strength of epoxy underfill to passivation. Therefore, the wetting was not the controlling factor in adhesion of the system studied.

Surface Energy Characterization of Partially Cured Benzocyclobutene for 3D Interconnect Applications

“…Significant oxidation has been shown to increase the surface energy of BCB by increasing its capability to interact with materials in a polar fashion [30]. In this work, samples oxidized to ~56 a/a% using UV/ozone treatment exhibited an increase in surface energy of about 30% due to an increase in polar interactions.…”

“…In the van Oss analysis method, the polar component can be split into two components so three probe liquids are required to separate all components of the surface energy [26]. Previous work by Luo and Wong has shown that untreated BCB is essentially apolar, while cleaned and UV ozone treated BCB has only Lewis base polarity [30]. In this respect a single probe test should provide a reasonable approximation of surface energy for unoxidized BCB, while a two probe liquid approach should provide a reasonable approximation if the surface is oxidized.…”

Superior Surface-Insulated Polymers with Low Leakage Current Enabled by Tailored Coatings Deposited with Colliding Plasma Jets

“…This module uses a PTFE ultrathin substrate as the high-frequency and high-speed substrate . The potting material is epoxy resin, and PI is the passivation layer of dies . The multiterminal lead-out and the magnetic field cancelation circuit design can make the parasitic inductance of the module extremely low (several nH) .…”

“…35 The potting material is epoxy resin, 26 and PI is the passivation layer of dies. 36 The multiterminal lead-out and the magnetic field cancelation circuit design can make the parasitic inductance of the module extremely low (several nH). 37 The performance advantages have made this type of design the most popular choice today.…”