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Original Authors: Gerd Van den Branden, ON Semiconductor Belgium
Edited by Cyth Systems
Developing a high-end, scalable, and cost-effective mixed-signal automated test equipment (ATE) production tester that enables wafer sort and final test for ON Semiconductor’s new generation image sensors.
Customizing the STS T4 system test head concept to meet our requirements for image sensor test of our full product portfolio. This solution is internally called the Pretty Image Sensor Tester from ON Semiconductor (PISTON tester).
ON Semiconductor is a worldwide supplier of silicon solutions for energy-efficient electronics. At the Mechelen site, we develop high-end image sensors for a wide range of industries including cinematics, space, industrial and medical. We develop our CMOS image sensors to provide high frame rates (in the kilohertz range) at megapixel resolutions. These sensors also feature large resolution and high-speed parallel and serial digital outputs. To meet our quality standards, we needed a high-performance platform capable of providing stimuli to the sensors and handling the intense data rates in combination with static and dynamic parametric test functionality and massive image processing computing power. Furthermore, we needed a test system that could grow with future product requirements.
We concluded that existing testers on the market could not meet these requirements without significant modification. We wanted to get away from doing everything ourselves, so we looked at the test and measurement market and asked NI for a proposal. We were doing characterization test with a custom test setup that used multiple custom-designed FPGA boards. This solution had major drawbacks in terms of data streaming and full frame rate capturing increasing our test times significantly. The PXI Express platform seemed like a promising fit to solve some of these problems, but the system could not handle the intense data throughput that our chips could produce. On the other hand, the PXI Express platform was open and modular, so other vendors could tie into it or develop custom modules for it. This meant we could combine the best of multiple worlds and build a hybrid solution.
NI engineers told us they were developing the Semiconductor Test System (STS) and showed us some of the designs for this production tester. We looked into the specific technical requirements and found out that even though the STS T4 system was not designed with our application in mind, NI worked with Sisu Devices to help us customize the system. The idea was to create a scalable tester that could test all our new products. This was a very exciting time where each partner stepped up to meet our criteria.
We worked with NI system engineers and Sisu Devices to build a hybrid test solution using off-the-shelf components when possible and custom design when needed.
For example, Sisu Devices assisted in the mechanical design and thermal housekeeping design for our PISTON tester. Multiple customizations were implemented to the STS T4 core to optimize the machine for image sensor test. NI system engineers assisted us with all our questions regarding custom PXI Express modules, system timing synchronization and more.
Based on a combination of NI PXI and PXI Express modular instrumentation, an in-house developed PXI Express timing engine, frame grabber and synchronization modules, we succeeded in outperforming other commercially available test systems in terms of cost, bandwidth, throughput, and configurability. The PISTON tester offers per pin test capability at speeds up to 1.2 Gbps on all 680 device under test (DUT) I/O pins, configurable I/O standards over a -2 V to 6.5 V range, multiple 24-bit accurate analog data channels, controlled over test temperature ranges from -40 to 125 degrees C, 100 percent correlation to characterization results, and more.
We released our PISTON tester in production, and so far we have seen great results. Not only can we test all of our product portfolio again without having to make compromises, but we have also seen test time reductions and enhanced performance benefits with our I/O count and image transfer bandwidth. See Figure 1 for details.
The PISTON tester has been on the production floor for over a year, and we have had excellent results with the system. Within approximately one year of the PISTON tester being deployed it fully paid back our hardware and development costs. Based on the open NI PXI and PXI Express platforms with NI modular instrumentation, in combination with the in-house developed PISTON timing engine, PXI Express frame grabber, and synchronization modules, we were able to develop a production tester that outperforms commercially available test equipment currently available in terms of cost, bandwidth, throughput, and product flexibility. Based on these positive results, we are confident we will have success with any future PISTON tester deployments.
Gerd Van den Branden, ON Semiconductor Belgium
Edited by Cyth Systems