Magnetic bubble device testing

A computer-controlled system has been developed for testing magnetic bubble devices. One version tests bubble chips in wafer form, automatically stepping through the wafer; the other version tests finished packages which contain 4 bubble device chips. The system hardware and programming are described in general terms. Testing strategy and results are given for 68 kbit chips using 16 μm period propagation circuits. Approximately 3000 5 cm diameter wafers and 200 4-chip packages have been tested with these systems. On the basis of this experience, it is concluded that the system design is satisfactory from the viewpoints of flexibility, reliability and reproducibility.