A rheological study of visible-light sensitive reworkable photocuring resins was carried out using reworkable monomers. A dimethacrylate monomer containing tertiary ester units in a molecule and a methacrylate monomer, which has both an epoxy moiety and a thermallycleavable tertiary ester moiety in a molecule, were employed as the reworkable monomers. The reworkable monomers were successfully cured by green light irradiation (530-nm light) using a visible-light sensitive photoradical initiator.

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... When the cured reworkable resins were baked after UV light irradiation (365-nm light) in the presence of a photoacid generator, the storage moduli of the cured resin decreased at elevated temperatures. The decreased storage moduli revealed by rheological studies were due to the acid-catalyzed decomposition of the tertiary ester linkages in the cured reworkable monomers. The effect of the chemical structure on the rheological properties was discussed.