What is reliability? There are many definitions that all discuss maintaining performance over time or some other boring set of words. But let’s talk about some real measures of reliability. The DLP® Chip, also known as the Digital Micromirror Device or DMD, was invented in 1987, started development in 1992, and was introduced commercially in 1996. Throughout that time, Texas Instruments tested thousands of devices through a variety of stress tests to identify design weaknesses. In each case, the design was enhanced to make the device progressively more robust. Once the DLP Chip was proven robust, Texas Instruments started shipping devices to our customers. There have been millions of devices shipped since 1996 with excellent field reliability and exceptionally long life measured in tens of thousands of hours.
Our strategy was, and continues to be, to create tests that truly challenge the device. We do not want to simply test to specification limits or customer requirements. We want to stress to failure to find weaknesses. Why? Because if you know the limits of a design you have a better understanding of the capability of the design. Also, as limits are identified, designers have the option of making the device even more robust. In the example of the DLP chip, there were many opportunities to enhance the device to assure reliability.
One of my favorite examples is a test we started in December 1995. We placed some DLP Chips on an accelerated test where we cycled the mirrors back and forth as quickly as possible at high temperature and high stress conditions. We tested these devices most recently in December 2007 on their 12th birthday. As of that point, the devices had completed over 100,000 actual operating hours and each mirror had cycled over 5.3 trillion times (5.3 x 10^12) without a failure. Under normal operating conditions, this is equivalent to over 368,000 operating hours. In a typical projector application that is operated for 1000 hours per year, this is equivalent to over 368 years of operation without a failure. Not too wimpy! Another interesting piece of information from this test is: there are 9 devices on test, each device has 500,000 mirrors, and each mirror has cycled over 5.3 trillion times. When you add that up, there have been over 24 quintillion (24 x 10^18) mechanical cycles with no broken mirrors. No wimps there!
These devices are still on test with no signs of fatigue. They are due to be tested again in December 2008 for their 13th birthday. Our babies are almost teenagers. I will update you in a subsequent blog on how they behaved at their birthday party. Start lighting the candles.
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