Design for Cost Effective Scan Testing by Reconfiguring Scan Flip-Flops

A new scan architecture called reconfigured scan forest is proposed for cost-effective scan testing. Multiple scan flip-flops can be grouped based on structural analysis that avoids new unstable faults due to new reconvergent fanouts. The proposed new scan architecture makes all scan flip-flop groups have similar size because of flexibility of the scan flip-flop grouping scheme, where many scan flip-flops become internal scan flip-flops. The size of the exclusive-or trees can be reduced greatly compared with the original scan forest. Therefore, area overhead and routing complexity are reduced greatly. It is shown that test application cost and test power with the proposed scan forest architecture can be reduced to even less than 1% of the conventional full scan design with a single scan chain