1、Public Lessons Learned Entry: 4176Lesson Info:a71 Lesson Number: 4176 a71 Submitting Organization: JPL a71 Submitted by: David Oberhettinger Subject: Do Not Reuse Anti-Static Bags Abstract: A digital processing board suffered a short circuit during an initial functional test because the flight hardw
2、are had been placed in a used anti-static bag that is believed to have contained conductive debris. Only a new, unused, anti-static bag should be used to store flight hardware. Description of Driving Event: Anti-static bags- plastic envelopes coated with a metallic film- are used to ship electronic
3、parts and assemblies that are prone to damage from electrostatic discharge (ESD). After the shipped items are received, they are often stored in the bags for protection against ESD damage incidental to handling. A digital processing circuit board, destined for use as flight equipment for the Gravity
4、 Recovery and Interior Laboratory (GRAIL) project, failed the initial power-on test procedure during assembly functional testing at the NASA/Caltech Jet Propulsion Laboratory (JPL). A visual inspection (Reference (1) revealed that a fine piece of copper wire debris, similar to No. 2 solder braid, ha
5、d created a short circuit (Figure 1) from a memory pin to an adjacent data pin (Reference (2). Since the test was conducted in a clean room, the contamination is believed to have resulted from placing the board into a “used“ anti-static bag for storage. It has been documented (Reference (3) that ant
6、i-static bags are frequently reused in JPL shops and labs and may accumulate rosin and other contaminants.Figure 1. Arrow indicates location and approximate size of copper debrisAnalysis determined that the stress to the components resulting from the short was minimal. However, because Provided by I
7、HSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-the data pin connects to a field-programmable gate array (FPGA) and a microprocessor, the short could instead have caused mission-critical latent damage to these components. Following this incident, the GRAIL projec
8、t banned the reuse of anti-static bags and purchased a supply of new anti-static bags. References: 1. “Conductive debris on FM103,“ JPL Problem/Failure Report No. 15446, September 21, 2009. 2. “PFR 15446 - MMFL16016604S-C-MS Stress and Risk Mitigation,“ JPL IOM 335-JAD-20091015-016, October 15, 2009
9、. 3. “Manufacturing Processes and Procedures for Assembly and Wiring of Electronic Equipment and Assemblies,“ Revision I, JPL Document No. DocID 35514, July 20, 2004, p. 435.Lesson(s) Learned: The reuse of anti-static bags previously used to ship or store electronic parts and assemblies can introduc
10、e debris and contamination that can damage flight equipment. Recommendation(s): Do not return an electronic part or assembly to the anti-static bag or envelope from which the item, or another item, was withdrawn. Dispose of the original bag, and use a new anti-static bag. Evidence of Recurrence Cont
11、rol Effectiveness: JPL has referenced this lesson learned as additional rationale and guidance supporting Paragraph 6.12.5.4 (“Engineering Practices: Protection and Security of Flight Hardware“) in the Jet Propulsion Laboratory standard “Flight Project Practices, Rev. 7,“ JPL DocID 58032, September
12、30, 2008. Documents Related to Lesson: N/A Mission Directorate(s): a71 Exploration Systems a71 Aeronautics Research a71 Science Additional Key Phrase(s): N/A Additional Info: a71 Project: Gravity Recovery and Interior Laboratory (GRAIL) Approval Info: a71 Approval Date: 2010-11-17 a71 Approval Name: mbell a71 Approval Organization: HQ Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-
