A Via Assignment and Global Routing Method for 2-Layer Ball Grid Array Packages

Abstract

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

A global routing method for 2-layer ball grid array packages

“…We introduce the concept of monotone in global routing and in via assignment [6,7]. If a monotonic via assignment is given, the monotonic global routing on layer 1 is uniquely determined.…”

“…Our method begins with an initial monotonic via assignment and incrementally improves the via assignment. The heuristic method in [6,7] modifies a via assignment by moving a via to the adjacent grid node one by one. In this paper, two more modifications, which exchange two adjacent vias or rotate three adjacent vias, are added to the method in [6,7].…”

Routability driven modification method of monotonic via assignment for 2-layer Ball Grid Array packages

“…In our proposed method, an initial monotonic via assignment is generated by the method proposed in [5]. Then the initial via assignment is iteratively improved.…”

“…EXC, ROT, and MSEQ have been proposed in [5] to improve the wire congestion of layer 1 while keeping the wire length of layer 2 as small as possible. Examples of them are shown in Fig.…”

“…A via assignment and global routing method for singlechip two-layer BGA packages that considers total wire length and wire congestion have been proposed as the first stage of package substrate routing in [5], and this method has been improved in [6]. In these papers, the concepts of monotonic global routing and monotonic via assignment focusing mainly on layer 1 are introduced.…”