The use of Plastic Encapsulated Microcircuits (PEMs) is permitted on NASA Goddard Space Flight Center (GSFC) spaceflight applications, provided each use is thoroughly evaluated for thermal, mechanical, and radiation implications of the specific application and found to meet mission requirements.  PEMs shall be selected for their functional advantage and availability, not for cost saving; the steps necessary to ensure reliability usually negate any initial apparent cost advantage.  A PEM shall not be substituted for a form, fit and functional equivalent, high reliability, hermetic device in spaceflight applications. 

Due to the rapid change in wafer-level designs typical of commercial parts and the unknown traceability between packaging lots and wafer lots, lot specific testing is required for PEMs, unless specifically excepted by the Mission Assurance Requirements (MAR) for the project.  Lot specific qualification, screening, radiation hardness assurance analysis and/or testing, shall be consistent with the required reliability level as defined in the MAR. 

Developers proposing to use PEMs shall address the following items in their Performance Assurance Implementation Plan: source selection (manufacturers and distributors), storage conditions for all stages of use, packing, shipping and handling, electrostatic discharge (ESD), screening and qualification testing, derating, radiation hardness assurance, test house selection and control, data collection and retention.  Use of PEMs outside the manufacturer’s rated temperature range requires written approval from GSFC.

Specifically, PEMs must be:

• Stored under temperature controlled, clean conditions, protected from ESD and humidity,
• Traceable to the branded manufacturer,
• Procured from the manufacturer or their approved distributor,
• Tested to verify compliance with the performance requirements of the application environment over the intended mission lifetime,
• Tested using practices and facilities with demonstrated capabilities sufficient to handle and test the technologies involved. 
  

Testing in accordance with 311-INST-001 shall be performed as necessary to qualify and screen the devices, in order to verify compliance with the application requirements and project risk level, defined in the program Mission Assurance Requirements (MAR).  Radiation evaluation shall address all threats appropriate for the technology, application and environment, including Total Ionizing Dose (TID), Single Event Effects (SEE) and displacement damage.  Existing radiation data can be used only with the review and approval of the project radiation specialist.

PEMs with manufacture dates older than 3 years before the time of installation shall not be used without GSFC approval.  Derating of PEMs must be addressed with consideration of specific material, device construction, device characteristics and application requirements. 

Use of PEMs with pure tin plated terminations requires special precautions to preclude failures caused by tin whiskers.  GSFC approval of mitigation strategies is required. 

Exceptions to testing required by 311-INST-001 may be permitted by GSFC on a case-by-case basis, where it can be demonstrated that either existing lot specific test data show acceptable results, or the use of high risk PEMs represents low risk of functional loss should the part fail.  All rationale for such exceptions shall be documented.

NASA will use part performance data collected in accordance with this policy to evaluate the policy’s effectiveness and to develop recommendations for future improvements and streamlining.