3.1.1 Purpose of Continuity Testing

Before a test program can evaluate the quality of a device under test (DUT), the DUT must be connected to the ATE tester using a test fixture such as a device interface board (DIB). A typical interconnection scheme is shown in Figure 3.1. When packaged devices are tested, a socket or handler contactor assembly provides the contact between the DUT and the DIB. When testing a bare die on a wafer, the contact is made through the probe needles of a probe card. The tester's instruments are connected to the DIB through one or more layers of connectors such as spring-loaded pogo pins or edge connectors. The exact connection scheme varies from tester to tester, depending on the mechanical/electrical performance tradeoffs made by the ATE vendor.

Figure 3.1: ATE test head to DUT interconnections.

In addition to pogo pins and other connectors, electromechanical relays are often used to route signals from the tester electronics to the DUT. A relay is an electrical switch whose position is controlled by an electromagnetic field. The field is created by a current forced through a coil of wire inside the relay (Figure 3.2). Relays are used extensively in mixed-signal testing to modify the electrical connections to and from the DUT as the test program progresses from test to test.

Figure 3.2: Electromechanical relays.

Any of the electrical connections between a DUT and the tester can be defective, resulting in open circuits or shorts between electrical signals. For...