New High Yield, High Reliability Materials System for Silver Multilayer Construction Available to Purchase

Complex mixed metallurgy multilayers require a very robust dielectric to withstand shorting or blistering effects, together with high density for long‐term reliability in humid environments. The development and performance of a new multilayer dielectric which meets these needs is presented here. A dielectric frit chemistry has been developed with a view to eliminating short circuits and blistering induced by the proximity of dissimilar metallurgies on multiple refiring. Appropriate filler technology has also been developed to optimise dielectric density, toughness and laser‐trim properties. High density has yielded excellent HBT (High Bias Temperature) and HHBT (High Humidity Bias Test) performance. Data on multilayer circuit bowing are presented which take account of the interaction of conductor frit and the dielectric on firing. Silver conductor is employed in inner layers to optimise conductivity and cost. A new 1:3 PdAg conductor for termination of components and resistors also permits heavy Al wire bonding with good aged performance. 25 µm Au and 37 µm Al wire bonding is facilitated by gold conductor on dielectric. The laser trim characteristics of a new resistor series on dielectric are described. The materials system has been tested in a complex multilayer structure which, with the use of a new silver via fill conductor, resulted in defect‐free circuits with zero yield loss.