Leaky insulating paint for preventing discharge anomalies on circuit boards

A semi-insulting paint has been formulated and tested for preventing pulse discharges from causing damage to circuits on heavily irradiated circuit boards. The paint is tin-oxide-filled phenoxy resin with a bulk resistivity of 10/sup 8/ ohm-cm. A typical coating is then 10/sup 10/ ohms per square. It is applied over the finished, conformally coated circuit board and connected to ground where possible on the board. It works by minimizing the stored electric field energy prior to the discharge. With such high resistivity it cannot load down most circuits. Tests were performed on circuit boards with and without the paint using energetic electron beams to simulate very high space exposure levels. Many potential damaging pulses were seen without the paint; application of the paint removed all large pulses, and only a few small pulses were seen. >