| 摘要 |
<p>The invention provides an alkaline aqueous developable photoimageable composition, useful as a photoresist for forming a solder mask on a printed circuit board. The photoimageable composition comprises A) between 20 and 50 wt% of a binder polymer, the binder polymer (A) comprising a backbone formed of between 45 and 75 mole percent styrene and between 25 and 55 mole percent maleic anhydride, the binder polymer being esterified with an organic alcohol or mixture of organic alcohols each having a molecular weight between 32 and 200 so as to at least half-esterify the anhydride functionality provided by maleic anhydride. The polymer has an acid number between 110 and 270 and a weight average molecular weight between 10,000 and 150,000. Between 20 and 75 wt% of the photoimageable composition comprises B) photopolymerizeable compounds, including between 20 and 60 wt% of acrylate-functional oligomers selected from: B1) acrylate functional urethane oligomers having weight average molecular weights between 400 and 3000, and/or B2) epoxy acrylate oligomers having weight average molecular weights between 400 and 3000. To achieve a final hardening cure, the composition further contains C) between 1 and 5 wt% of an aminoplast which, at elevated temperatures reacts with any hydroxyl functional present and with the acid functionality of the binder polymer (A). The composition further contains D) between 1 and 15 wt% of a photoinitiator chemical system to promote polymerization of the photopolymerizeable compounds (B) when exposed to actinic radiation.</p> |
