Electrical test system with vision-guided alignment

An electrical testing system configured to test a series of devices fabricated on successive frames of a web of substrate, each frame including a plurality of fiducial marks and a device having a series of test pads, comprising:

• a web transport system for advancing the web of substrate along a web transport path;
• an electrical test fixture including a set of test probes adapted to make electrical contact with the test pads of a particular device on the web of substrate;
• a test instrument associated with the set of test probes;
• a digital imaging system configured to capture a digital image of at least a portion of a particular frame including the test pads of the particular device and the fiducial marks;
• a fiducial sensing system including a plurality of fiducial sensors, each adapted to sense a position of an associated fiducial mark;
• and
• a controller configured to:
• analyze a digital image captured by the digital imaging system to determine spatial relationships between positions of test pads and positions of the fiducial marks in the captured digital image;
• determine positions of the fiducial marks using the fiducial sensing system;
• adjust a position of the electrical test fixture responsive to the determined spatial relationships between positions of test pads and positions of the fiducial marks and the determined positions of the fiducial marks so that the test probes are aligned with corresponding test pads;
• move the test probes into electrical contact with the test pads;
• and
• perform an electrical test of the particular device using the test instrument.