31 January 2012
Analog Devices Inc (ADI) provides analogue, mixed-signal, and digital signal processing (DSP) integrated circuits (ICs) that convert, condition, or otherwise process light, sound, temperature, motion, or pressure into electrical signals for use in electronic equipment. Over the past two decades, the company has invested in microelectromechanical systems (MEMS) inertial sensing technology and has produced the fully integrated integrated Micro Electrical Mechanical System (iMEMS) accelerometers and gyroscopes, helping electronic designers incorporate acceleration, tilt, shock, vibration, rotation, and multiple degrees-of-freedom (DoF) motion into their designs. MEMS testing poses a number of challenges for the production test process. An ATE system was needed that met the demands of the product test plan with the lowest possible cost, while ensuring product quality. The company’s traditional ‘big iron’ ATE solution was far too costly, too highly featured, and was physically too large to meet the requirements of a dedicated MEMS tester. An application-specific test system for the company MEMS products with a subset of the measurement capability of a big-iron ATE system was required.A COTS alternativeA number of options were evaluated as an alternative to the traditional production ATE platform. The company wanted to leverage as much commercial off-the-shelf (COTS) technology as possible to reduce the overhead required for a custom test solution. We also needed a test platform that was flexible enough to accommodate custom MEMS test requirements while not sacrificing instrumentation speed or performance.The PXI platform from National Instruments offered the test instrumentation capability we needed to meet our challenge. PXI is a widely adopted, open standard that has existed for more than 10 years and been implemented across a variety of industries. PXI gives us a high level of flexibility and modularity to develop a targeted MEMS test system, which is reconfigurable for various test needs. For multisite testing, we can duplicate test resources by plugging in additional modules without changing any of our software, allowing us to scale our test equipment as needed based on our throughput demands. The software environment also needed to be inherently easy to use with the ability to create operator, program, and data interfaces to existing tools to ease the process of integrating a new ATE system into our production floor. We chose LabVIEW software to meet these challenges as it was already widely used in the characterisation and design labs. We had considered using ANSI C or C++ for our test software, but after performing a number of benchmarks with LabVIEW, we were impressed with its performance and ability to take advantage of multicore technology.The flexibility of the PXI system, combined with the ease of use of LabVIEW made it possible for our engineers to quickly design and prototype the solution. Test times were comparable or better with the new test system based on PXI and LabVIEW versus our previous production ATE test system. We felt confident in deploying a PXI-based production test solution based on NI technology for our MEMS devices.Using PXI and LabVIEW, the company has developed an application-specific MEMS test platform that it is able to scale from production to lab characterisation, enabling a big cost reduction in the total cost of MEMS testing.Benefits of COTS technologyThe new system offers a dramatic reduction in capital equipment expenditures, footprint, weight, and power requirements for MEMS production test using PXI and LabVIEW.Cost savings: The previous ATE system cost more for its basic configuration than the new PXI system’s total all-inclusive cost. The PXI system also takes up very little space. In fact, the entire system is now physically small enough to wheel around on a cart.Reduced footprint on production floor: The new PXI-based ATE system truly offers a zero-footprint tester. The system is small enough that can be physically moved around on a cart, saving space on the production floor.Smaller, easier-to-use system: The weight comparison between the two systems offers a reduction in shipping costs. Now, if any problems arise, it is possible to simply switch out PXI instruments on-site using local spares, or even ship the entire test system back to the development labs from the production line with very little overhead. Decreased power usage: Previously it was necessary to involve the facilities department months in advance to modify power grids and cooling systems to accommodate additional testers. The new PXI system is now capable of running off of a standard power plug with absolutely no modifications required. Increased test quality: The new system improved the overall quality of testing. Because the team designed the tester, they can ensure that every tester shipped to its branch facilities features the exact same hardware and runs the exact same programming and code sequences. Furthermore, with LabVIEW controlling the system, the programmed test code is modular and reusable for future test programs or in development labs.Same test system for characterisation and production: The added flexibility and ease of use for test development led to teams using the same system in other phases outside of production, including design, characterisation, and metrology. The same ATE equipment is now being used in all environments without incurring an impact on cost.
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