PEMs_Summary

  • PEMs are Plastic Encapsulated Microcircuits.
  • A PEM uses organic packaging material, either transfer molded or coated, for environmental protection. PEMs are not a hermetically sealed cavity.
  • Cost and obsolescence issues are forcing the military/space hardware designers to move from military/space specific applications products to the use of commercial grade PEMs.
  • There are certain precautions and considerations that must be adhered to in order to select, screen, and test PEMs to acceptable levels of project risk.
  • PEMs have been primarily (and initially) designed for use in benign environments where equipment is easily accessible for repair or replacement.
  • PEMs shall be selected for their functional advantage and availability.
  • A PEM shall not be substituted for a form, fit, and functional equivalent, high-reliability, hermetic device in space flight applications.
  • No PEMs are considered acceptable in high-reliability applications “as is” without additional testing and analysis to assure adequate reliability and radiation tolerance.
  • Major improvements in Materials, Material attributes, Lead frame design, Die coatings, Die design, Material characteristics, Fabrication equipment, and Testing procedures3 have led to acceptance in the use of PEMs in the Aerospace and Defense industry.
  • Concerns associated with their increased usage, especially military, include:
    • Uncertainty regarding their long term reliability in harsh environments
    • Lack of reliability/quality assurance procedures
    • Insufficient military environment reliability data (operating and storage)3
    • Existing OEM procurement expertise
  • Specific concerns include: storage, handling, screening, derating, and qualification
  • Primary Elements of the Product Assurance System: Screening, Qualification (including Radiation Hardness and DPA)
  • APL uses a four-step approach to part selection:
    1. concurrent engineering
    2. evaluation of each part for its intended application
    3. partnership with world-class suppliers
    4. review of the manufacturer’s reliability data
  • APL utilizes a five-step testing regime for qualification:
    1. Radiation hardness assurance
    2. Temperature cycling
    3. Steady-state temperature-humidity bias life test
    4. Destructive physical analysis (DPA)
    5. High-temperature operating life