Layer minimization in escape routing for staggered-pin-array PCBs

As the technology advances, the pin number of a high-end PCB design keeps increasing. The staggered pin array is used to accommodate a larger pin number than the grid pin array of the same area. Nevertheless, escaping a large pin number to the boundary of a dense staggered pin array, namely multilayer escape routing for staggered pin arrays, is significantly harder than that for grid pin arrays. This paper addresses this multilayer escape routing problem to minimize the number of used layers in a staggered pin array for manufacturing cost reduction. We first present an escaped pin selection method to assign a maximal number of escaped pins in the current layer and also to increase useful routing regions for subsequent layers. Missing pins are also modeled in our routing network to utilize the routing resource effectively. Experimental results show that our approach can significantly reduce the required layer number for escape routing.