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.