… first responders in Cupertino learn directly of a defective iPhone in New York, Paris, or Tokyo as soon as a Genius Bar staffer reports it. The phone goes on the nextFedEx (FDX) plane to California. Using the serial numbers in each device, Apple can trace a problem down to individual workers on an assembly line.
That paid off with the original iPhone in 2007, when many were quickly returned with faulty touchscreens, according to an engineer involved in fixing them. Some suppliers manufactured iPhones with a flaw near the earpiece that let sweat from a person’s face seep in, shorting the screen. The EFFA team added a new coating to shield the leaky area and told their suppliers to do the same on their assembly lines. Other EFFA workers, investigating the failure of early iPhone speakers, concluded that the problem was a lack of airflow that caused the speakers to build up pressure and implode during flights from Chinese factories to the U.S. The team relieved the pressure by poking holes in the speakers. Apple declined to comment.
http://www.businessweek.com/articles/2014-09-04/for-iphone-6-defects-apple-has-failure-analysis-team-ready
http://en.wikipedia.org/wiki/Failure_analysis
