GROUP PROBING STRATEGY FOR TESTING LARGE NUMBER OF CHIPS.

An approach to optimal testing of a large number of identical chips, called group probing, is presented. Initially, all chips are divided into several groups, and the same test vector is applied in parallel to all chips in a group. For a given test input vector, the group test outcome determines whether all or some chips responded incorrectly. If the group test outcome is fault-free, the whole group is fault-free (with respect to the test vector applied). Otherwise, the group in question is divided into two subgroups and group probing continues in the same manner until all faulty chips are identified (binary tree search technique). A mathematical formulation of the approach is presented, and the optimal (initial) group size which minimizes the expected number of tests is derived. Group testing is shown to be effective in various testing stages, e. g. , early testing for design faults and testing for (random) production faults.