REG NASA-LLIS-0607-1998 Lessons Learned Handling and Storage of Flight Spares.pdf

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1、Lessons Learned Entry: 0607Lesson Info:a71 Lesson Number: 0607a71 Lesson Date: 1998-12-10a71 Submitting Organization: JPLa71 Submitted by: K.Clark/D.OberhettingerSubject: Handling and Storage of Flight Spares Abstract: White spots, identified as “mealing,” were observed on 10 spare Mars Observer cir

2、cuit boards, withdrawn from long term storage for use on Mars Global Surveyor. Although the cause of the defects was not established, the handling and warehousing of these flight spares may not have been consistent with their status as potential flight hardware for future projects. Treat flight spar

3、es as though they are going to be flown.Description of Driving Event: White spots were observed on ten, conformally coated, electrical power subsystem (EPS) printed wiring assemblies. The anomaly was noted when the boards, built as Mars Observer (MO) spares, were withdrawn from long term storage for

4、 use as Mars Global Surveyor (MGS) flight hardware. refer to D descriptionD Mealing of MO Spares Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-The spots were identified as “mealing,“ which involves significant levels of ionic contaminants concentra

5、ted primarily at the interface between the conformal coating and the substrate material. Exposure to warm, damp conditions is known to promote the growth of mealing. This growth can cause electrically conductive paths along interfacial surfaces, or between components and traces.Speculated contributo

6、rs to the problem are:1. The ionic contaminants may have been imbedded during board manufacture, or at some later time such as during cleaning prior to conformal coating.2. Moisture normally present within the fiberglass board substrate might also migrate to the interface.3. Exposure to excess humid

7、ity during the 3 years the coated boards were warehoused may have caused atmospheric water vapor to permeate the conformal coating and reach the interface, or prevent dissipation of the moisture from within the board.The ten boards were reworked to remove mealing and eliminate potential electrical a

8、nomalies. Narrow strips of conformal coating were removed from critical areas followed by cleaning of the exposed board laminate and touch-up of the conformal coating.Additional Keyword(s): Contamination, Corrosion, Inherited HardwareReference(s): MGS Problem/Failure Report (PFR) No. Z20617Lesson(s)

9、 Learned: The care given to the handling and warehousing of flight spares is not always consistent with their status as potential flight hardware for future projects.Recommendation(s): Treat flight spares as though they are going to be flown. Storage of any duration should be maintained under a cont

10、rolled environment; especially low humidity (typically 30 to 50 percent) and room temperature or less.Evidence of Recurrence Control Effectiveness: N/ADocuments Related to Lesson: N/AProvided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-Mission Directorate

11、(s): N/AAdditional Key Phrase(s): a71 Hardwarea71 Logisticsa71 Packaging Handling Storagea71 Parts Materials & ProcessesAdditional Info: Approval Info: a71 Approval Date: 1998-12-14a71 Approval Name: Carol Dumaina71 Approval Organization: 125-204a71 Approval Phone Number: 818-354-8242Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-