Rheological Studies of Reworkable Photocuring Resins

Abstract

Rheological studies of reworkable photocuring resins were 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 thermally-cleavable tertiary ester moiety in a molecule, were employed as the reworkable monomers. When the cured reworkable monomers were irradiated and baked in the presence of a photoacid generator, the storage moduli of the cured resin decreased at elevated temperatures. The decreased storage moduli revealed by the rheological studies were due to the acid-catalyzed decomposition of the tertiary ester linkages in the cured reworkable monomers.

Secondary Patternable UV-Imprinted Reworkable Resin by Additional Photoirradiation

“…4 (b) shows the area with high storage moduli. The values of the storage moduli were about 1.7 MPa, which agree with the value observed by the photorheometer (1.4 MPa) [20]. A deviation in the two images was observed at the border of the irradiated and unirradiated areas.…”

“…After degradation, the value decreased to 55 kPa at 150 o C [20]. These results strongly suggest that the hardness of the surface of the photocured reworkable resins is patternable upon irradiation.…”

“…We recently reported the rheological studies of the photocured MOBH using a photorheometer [20]. The storage modulus of the photocured MOBH was 1.4 MPa [20].…”

“…Since, in particular, UV-NIL uses UV curable resins, it is almost impossible to remove the cured resins that adhere to the surface of the master mold. We reported a series of "reworkable" resins [13][14][15][16][17][18][19][20], which are thermosets thermally or chemically degradable under a given condition, and applied them to UV-NIL [15][16][17].…”

“…The reworkable monomer, 1-methyl-1-(6methyl-7-oxabicyclo[4.1.0]-hept-3-yl)ethyl methacrylate (MOBH) [18][19][20], was selected in this study. MOBH is a methacrylate monomer which has both an epoxy moiety and a thermally-cleavable tertiary ester moiety in a molecule.…”