Chip Carriers Mounted on Large Thick Film Multilayer Boards

Two memory systems with 8 MHz clock frequency have been designed. One system contains 67 chip carriers mounted on an alumina substrate 9 x 12.5 cm and the other system contains 79 chip carriers mounted on an alumina substrate 9 x 14 cm. The experiences from the prototype manufacturing and testing are reported. Electrical measurements are made and the signals are compared with the same signals in a wire-wrapped prototype. Comparisons are also made with the capacitances usual in epoxy multilayer boards (MLB's). From an electrical point of view the ceramic multilayer boards made with thick film technique have both advantages and disadvantages compared with epoxy two-sided and multi!ayer boards. Thermal measurements are reported and a building technique is presented which allows a very powerful airborne computer consisting of 650 chip carriers to be built occupying a volume of 3 x 16 x 23 cm, i.e., 1.1 liters. It is shown that the combination of this building system with the chip carriers mounted on big alumina substrates give a system which is very reliable and occupies a very small volume compared with conventional technique (dual in-line packages (DIP's) and printed circuit boards (PCB's)). Yet the total hardware cost of the system is the same or lower for the chip carrier system as for the conventional system.