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Sherlock reveals how to achieve a 25 year lifetime, saving Silicon Hills thousands in repair and warranty costs.

The Challenge

Silicon Hills Design Inc., a leading PCB design, assembly, and box-build company, needed to determine why Thrust Reverser Control Units (TRCU) were continually returning for repair during a 6 month warranty period. The TRCUs had been flying in business jets for 22 years.

The Background

The TRCU was originally designed in 1990 using conventional FR-4 material for the circuit board and Sn/Pb solder for assembly. At that time, the customer of the design did not impose a 25 year life requirement on the product, but was more focused on creating a conformally coated assembly that could survive a rain test. Since 1990, several thousand units have been assembled and put into use on business jet aircraft.

The DfR Solution

The new customer driven reliability requirement for the TRCU was that it perform for 25 years with a 30% probability of failure. DfR’s Sherlock analysis demonstrated that the TRCU would have a 98.2% failure rate over that timeframe due to the stresses from random vibration during flight and solder joint fatigue. Essentially, the analysis indicated that multiple components needed to be changed out as each TRCU came in for repair, not just the part causing the actual test failure.

Component replacements were performed on all devices identified by Sherlock. Since doing so, no units repaired have come back within the 6 month additional warranty period offered. This saved the company countless thousands of dollars performing repairs on units that were definitely in the end of life stage that would then come back for additional repairs within the warranty period.

In Their Own Words

Theo Painter – VP Operations-Silicon Hills Design, “The information you provided in this report is very comprehensive and provides me with a tool to inform customers that if they are concerned with the life expectancy of their product, a study of this magnitude is necessary. Furthermore, I am able to make more informed decisions about the warranty of the services we provide.”