Study On The Photocurable System Of Epoxy Acrylate Resin And The Photoimageable Ink For Build-up Multilayer Printed Circuit Board

The Ultraviolet (UV) radiation curing technology is one of the most rapidly developing fields in the entire coatings industry. The low toxicity, cheapness, speed, control and ease of formulation and operation are some of the main advantages of this growing technology. In this paper, research progresses of radiation curing materials were reviewed. It included photochemistry, photo radical polymerization, photo initiator, UV curing, photo sensitive resin and reactive monomers. UV curing is used to induce photochemical polymerization or crosslinking of a monomer, prepolymer formulation containing a certain type of unsaturation, such as an acrylic group, and an appropriate initiator. The latter is used to absorb the light energy and transform it into active species, such as radicals or ions, capable of inducing such reactions.Build-up multilayer ( BUM) printed circuit boards comprise a stack of individual printed circuit boards or innerlayers separated by dielectrical material. The circuitry of the several innerlayers is electrically connected by bored and plated-through holes. BUM boards provide circuitry in a three-dimensional array and are therefore advantageously space-saving, relative to conventional printed circuit boards, which provide at most two layers of circuitry on a two-sided board. Available technologies for BUM formation in the dielectric layers include, laser ablation, photovia techniques, plasma etching. The boards to be used as inner layers of a BUM board are formed using a UV ink that is not only photoimageable but is hardenable to form a permanent dielectric material.The UV ink may be applied by a variety of methods such as screen printing, electrostatic spray coating, curtain coating et al. The UV ink is then exposed to radiation and developed in an appropriate developer to remove either the exposed or non-exposed portions of the UV ink. Next, the processed board is subjected to an alkaline etch or an etch with an acidic solution of cupric/cuprous chloride that removes the metal layers from those regions where the UV ink has been removed. The UV ink, rather than being stripped after exposure, development and etching, is left on the inner layers as a supplement or replacement of the prepregs normally used to form dielectric layers between the inner layers.The photocuring process of epoxy acrylate was monitored by differential photocalorimetry(DPC). The curing kinetics were found to be affected by various factors, such as photoinitiator concentration and UV light intensity. The dependence...