Investigation of Conformal Coatings for Electronic Circuits

Dielectric coating of semiconductor device packages is important not only for insulation and humidity protection but also to protect the metal leads of a package from being exposed to nuclear weapon x-rays. If exposed, these leads emit electrons, creating unwanted currents which could disrupt electronic circuits or damage sensitive electronic devices. As electronic devices have become more complex, so have their packages. A consequence of this complexity is the difficulty of thoroughly coating all the leads (pins) of the device with at least 3 mils of dielectric and assuring that there are no voids around any of the pins. Seven products were evaluated for their ability to uniformly coat (void-free) the pins of a 244-pin grid array. Four products, Conap EN-11, Dow Corning 93-500, McGhan Nusil CU-2500, and Solithane 113, were found to be acceptable. Of the four, Solithane 113 and Conap EN-11 are the most cost effective. The report provides the experimental procedure, pricing information, and technical data sheets which list specific information on those products that were found to be acceptable. Original contains color plates: All DTIC and NTIS repdoductions will be in black and white.