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In current VLSI circuits, there can be hundreds of required I/O pins. BGA(Ball Grid Array) packaging is commonly used to realize the huge number of connections between VLSI and PCB. In this paper, we propose a global routing method for two-layer BGA packages. In our routing model, the global routing for each net is uniquely determined by a via assignment. Our global routing method begins with an initial feasible via assignment and incrementally improves the via assignment to minimize the total wire length and wire congestion. In each iteration, a via assignment is improved by exchanging adjacent two vias, rotating three vias, or by moving vias to their adjacent grids one by one. Our method is a greedy-based heuristic. The algorithm efficiently generates better global routes than initial routes with respect to wire congestion and total wire length.

In this paper, we propose a global routing method for 2layer BGA packages. In our routing model, the global routing for each net is uniquely determined by a via assignment of each net. Our global routing method starts from an initial monotonic via assignment and incrementally improves the via assignment to optimize the total wire length and the wire congestion. Experimental results show that our proposed method generates a better global routing efficiently. key words: ball grid array, monotonic routing, via assignment, wire congestion, total wire length, heuristic

In VLSI layout design, certain nets in a given net set are required to propagate their signals within a tolerable skew of delays. Though the delay of the signal on a wire is determined by a complex environment, it is hard to satisfy this requirement unless all the concerned nets are routed within a certain skew of length. In this paper, we propose L-equidistance routing, which routes the concerned nets with a prescribed length L. After a basic technique of L-equidistance routing of a single 1-sink net, an algorithm is presented for the channel routing of plural multi-sink nets. The key idea is in the symmetric-slant grid interconnect scheme by which the problem is reduced to a grid routing problem. In L-equidistance routing of a channel, the total length of a n-sink net is not unique for nX3: An algorithm based on dynamic programming to solve this minimization problem is presented. Then, L-equidistance switch-box routing is discussed based on the L-equidistance channel routing. Algorithms are explained on the Euclidean space. But it is shown that a straightforward transformation of the routes to those on the Manhattan grid is possible keeping the property of equidistance. The proposing channel routing algorithm was implemented and applied to random data to demonstrate their ability.