REG NASA-LLIS-0301--1993 Lessons Learned Electrostatic Discharge (ESD) Wrist Strap Contamination of Magellan Flight Hardware.pdf

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1、Lessons Learned Entry: 0301Lesson Info:a71 Lesson Number: 0301a71 Lesson Date: 1993-09-15a71 Submitting Organization: JPLa71 Submitted by: J. E. KochSubject: Electrostatic Discharge (ESD) Wrist Strap Contamination of Magellan Flight Hardware Abstract: A short circuit during subsystem level testing o

2、f the Magellan Command and Data Subsystem (CDS) was traced to a conductive fiber likely shed by an ESD wrist strap.Use non-shedding ESD wrist straps. All personnel who work near critical hardware must take special care to avoid contamination. Description of Driving Event: During subsystem level test

3、ing of the Magellan Command and Data Subsystem (CDS), the test support equipment indicated an extra event for the relay controlling Critical Enable (CE) Event B03. It was theorized that a short between two specific pins of the CE relay could have caused the observed failure. When the relay was probe

4、d to verify the cause, the failure characteristic disappeared. Close visual inspection revealed a fine hairlike structure lying on one relay pin and possibly making contact with others. The object was removed and analyzed using a Scanning Electron Microscope (SEM) and an Energy Dispersive Spectromet

5、er (EDS). The analysis revealed that the object was a conductive metal fiber, identical in diameter (.0003“), surface characteristics and composition to metal fibers woven into the fabric of elastic Electrostatic Discharge (ESD) wrist straps.Reference(s): PFR #44931Lesson(s) Learned: Electrostatic D

6、ischarge (ESD) wrist straps can shed conductive metallic fibers into electronic hardware.Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-Recommendation(s): 1. Fabric type Electrostatic Discharge (ESD) wrist straps containing conductive metallic fiber

7、s should not be used in the assembly, fabrication, or handling of electronic hardware. Nonshedding ESD wrist straps are available.2. Special care is required from all personnel who work in close proximity to critical hardware to avoid contamination of any type.3. All aspects of fabrication and test

8、of critical hardware should be carefully reviewed before initiation of an activity.Evidence of Recurrence Control Effectiveness: N/ADocuments Related to Lesson: N/AMission Directorate(s): N/AAdditional Key Phrase(s): a71 Energya71 Hardwarea71 Parts Materials & ProcessesAdditional Info: Approval Info: a71 Approval Date: 1988-12-05a71 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-,-,-