European test service for CMOS image sensors up to 12in in diameter

Creating uniform illumination over a large area makes testing wafer-scale CMOS image sensors tricky, according to San Jose-based Presto Engineering, which has just revealed its computer-controlled solution that illuminates sections of the wafer in turn – working for arrays of large sensors, or even single sensors filling a 12in wafer.


“An entire wafer can be tested in a laboratory using a similar method,” said Presto Engineering v-p sales Martin Kingdon. “However laboratories are not geared up for fast commercial testing so we designed our own solution to test any size wafer. We can do this in small to medium sized test runs in Europe at our Class 10K cleanroom facility in France, near Aix-en-Provence. We believe that we are probably the only such commercial test service to be available in Europe.”

The need for larger image sensors is being driven, according to Presto, by medical and aerospace imaging, that are switching from CCD to CMOS, and can require whole wafer sensors.

“Similarly, security and military applications are wanting larger, better sensors to provide clear sharp images,” said the firm. “The tester is located in Presto’s EAL 5/6+ facilities, so that it meets the security needs of sensitive applications.”

Based on a Teradyne IP750Ex, the system provides 80x100mm illumination uniform to +/-2% at up to 10,000 lux at a range of colour temperatures. Built-in infra-red filtering prevents sensor damage.

Devices up to 32Mpixel at speeds up to 200MHz can be handled.

Presto will be at Image Sensors Europe (14 and 15 March).

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