Photoimageable Liquid Solder Masks with High Resolution Properties

By H. Ahne, W. Plundrich, 1. Zapf, Siemens AG - RadTech Europe Conference 1989

Details of newly developed photo-patternable solder masks based on polyether resins with photo-crosslinkable side groups are reported.

The synthesis of the basic photopolymers follows a chlorine-free route by addition of olefinically unsaturated isocyanates to the secondary hydroxy groups of a polyether with bisphenol-A partial structures. The photopatterned and crosslinked passivating and insulating layers show high edge acuity and resolution. The resins are provided with excellent electric values and soldering bath resistance. addition they stand out for reliable edge protection of the conductors and good adhesion to the substrate.