Due to the advantage of flip-chip design in power distribution but controversial peripheral IO placement in lower design cost, redistribution layer (RDL) is usually used for such interconnection. Sometimes RDL is so congested that the capacity for routing is insufficient. Routing therefore cannot be completed within a single layer even for manual routing. Although [2] proposed a routing algorithm that uses two layers of RDLs, but in practice the required routing area is a little more than one layer. We overcome this problem by adopting the concept of pseudo single-layer. With the heuristics for routing on mapped channels and observations on staggered pins to relieve vertical constraints, the area of 2-layer routing can be minimized and the routability is 100%. Comparisons of routing results between manual design, the commercial tool, and the proposed method are presented. We have shown the effectiveness on a real industrial case: it originally required fully manual design, the proposed method can finish RDL routing automatically and effectively.