Quality improvement of phase noise in signal anayzer product : a case study in electronic industry

Phase noise have been a known quality issue for the N9030A PXA Signal Analyzer encountered by the Keysight Technologies production team since November 2014 (i.e.Field Failure and Line Failures).The Field Failure is the failure return from the customer within the warranty period of 3 years and Line Failures are the failures occurs at Keysight Contract Manufacturer(CM)production line during the instrument testing for its functionality test especially for the phase noise before the instrument shipped to the Keysight Technologies.The instrument fails the phase noise test at 1 kHz at room temperature upon turned on for 24 hours.This failure caused return back ofUSD 3.47 Million impact and accumulated rework cost of USD 134,000 from November 2014 to September 2015.The objectives of this project is to investigate-the root causes of the phase noise failures.Secondly,is to provide the solution for the phase noise failure.Thirdly is to reduce the line failure at CM from average 19.98% of the line failure to less than 3% a month.Subsequently, a set of team from Keysight USA and Malaysia (Wafer Fabrication team,Component Failure Analysis team,Materials Engineering team and Instrument Engineering team) is formed to perform the failure analysis.Based for the Failure Analysis date,the solution for the phase noise by using the Lean Manufacturing tools and techniques such as WHY-WHY Analysis and Fish Bone Diagram used to narrow down the potential cause of the phase noise.In addition,the Failure Mode Effect Analysis (FMEA) was conducted involving team from Keysight Penang and Key sigh Santa Rosa to determine the improvement of the phase noise failure for the PXA instrument.Based from the highest Risk Priority Number (RPN) determined and the WHY-WHY Analysis was performed to drive the solutions.The first solution will be the four corner method rule replacing the existing three corner method rule for the proper epoxy coverage on the chip placement in the QFN package as even distribution of the epoxy will provide a proper heat distribution.The second improvement is to increase the backside via Au layer from 5 um to 25 um for the heat distribution.Eighteen samples with the both improvement evaluated before the cut in of the improved part 1GC1-4299 to the mass production and phase noise have improved significantly and meeting the specifications required 103.9 dBc/Hz.The phase noise failure were monitored for three months shows that the phase noise reduced from average 19.98% (November 2014-September 2015) to less than 3% for the Line Failures and zero return from Field Failures