1、Lessons Learned Entry: 0362Lesson Info:a71 Lesson Number: 0362a71 Lesson Date: 1994-11-04a71 Submitting Organization: JPLa71 Submitted by: A.G. GussnerSubject: Magellan Radio Transmitter A Modulation Failure Abstract: Loss of Magellan telemetry data was traced to moisture contamination due to a subc
2、ontractors failure to use dry gas in the repackaging of an operational amplifier. Recommendations involve use of fault tree analysis, appropriate component screening and qualification, minimizing power cycling, and using dry gas.Description of Driving Event: After a star calibration during the Magel
3、lan third extended mission, the X Band telemetry and high rate data were missing from the down link (22 kHz and 960 kHz subcarriers were missing). A subsequent attempt to use the 360 kHz subcarrier also resulted in no significant subcarrier in the down link.The most likely failure is a HA 2520 opera
4、tional amplifier used as a summing amplifier in the telemetry signal conditioner (although a failure in the phase modulator circuitry is also a possible cause). It failed after 20,600 hours of flight operation and 2,600 power cycles (resulting in 10-15 degree thermal cycles). A prelaunch failure on
5、this component type indicated the possibility that during the repackaging process by the subcontractor of the HA 2520, moisture was trapped inside the electronic component. This moisture would combine with the phosphorus dopant in the glass passivation forming phosphoric acid that would enter throug
6、h pinholes in the passivation layer and attack the nickel-chromium resistors causing failure. The subsystem contractor did not use a dry gas during the repackaging process; instead air with a moisture content of greater than or equal to 5,000 PPM water was used. The prime contractor, with JPL concur
7、rence, felt that additional screening had been sufficient to identify any other faulty HA 2520 amplifiers.It was concluded that the in-flight failure may be related to stress induced by thermal cycles resulting Provided by IHSNot for ResaleNo reproduction or networking permitted without license from
8、 IHS-,-,-from on-off power cycling.As a result of this failure, the degraded transmitter B had to be used to return science data at a lower rate for the remainder of the mission.Additional Keyword(s): IC Manufacturing and PackagingReference(s): PFR #52621Lesson(s) Learned: 1. In-flight failures cann
9、ot always be conclusively analyzed using available telemetry data.2. Failure to qualify electronic components and assembly capabilities to mission environmental requirements (including numerous power/thermal cycles) increases risk.3. Power cycling can create thermal cycle effects on internal failure
10、 mechanisms for electronic components and assemblies.4. Not using dry gas in the repackaging process can allow moisture to be trapped inside electronic components (hermetically sealed packages with a cavity) and possibly create pinholes if they dont already exist. Water can also evolve from thermall
11、y induced decomposition of the epoxy die attach. Moisture could then combine with the phosphate glass to generate corrosive phosphoric acid that can make the electronic component inoperative.Recommendation(s): 1. Consider using a fault tree matrix during the design phase to identify critical telemet
12、ry parameters needed to analyze failures.2. Match component screening and qualification to the mission, including any expected significant thermal cyclic excursions.3. Minimize mission designed power cycling to reduce thermally induced stress.4. Use of dry gas with moisture content below 5000 PPM in
13、 repackaging electronic components is a must.Evidence of Recurrence Control Effectiveness: N/ADocuments Related to Lesson: N/AMission Directorate(s): Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-N/AAdditional Key Phrase(s): a71 Environmenta71 Part
14、s Materials & Processesa71 Test & VerificationAdditional Info: Approval Info: a71 Approval Date: 1995-01-23a71 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-,-,-
