Attachment 0002 Prohibited Parts Materials and Processes.pdf

PROHIBITED PARTS, MATERIALS AND PROCESSES

Revision Date: Jan 2012

Contents

1. SCOPE

2. APPLICABLE DOCUMENTS

3. REQUIREMENTS

3.1. Prohibited Part Specifications and Pedigree

3.2. Prohibited Active Electrical Components

3.3. Prohibited Passive Electrical Components

3.4. Prohibited Electromechanical and Mechanical Components

3.5. Prohibited Component Package Types

3.6. Prohibited Materials

3.7. Prohibited Processes

3.8. Prohibited Design Practices

4. LIST OF ABBREVIATIONS AND ACRONYMS

Preparing Activity:

US Army RDE Command (RDECOM), Aviation and Missile Research, Development and Engineering Center (AMRDEC), Engineering Directorate, Manufacturing Science and Technology Division

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UNCLASSIFIED

1. SCOPE

1.1 Purpose. The purpose of this document is to define the parts, materials, and processes (PMP) that are considered to be reliability suspect, have limited application, involve restricted or special controls, or are otherwise unacceptable for use in Army Missile System and Army Aviation System electronic hardware and associated mechanical hardware.

1.2 Intended Use. This document establishes a baseline for suspect selection, design, and application practices proposed for use within Army Missile and Aviation System electronic and associated mechanical hardware. All PMP shall meet the requirements herein unless otherwise approved by the Government project/program office or their designated representative prior to use in hardware manufacture/assembly. Deviations must be evaluated and approved in a manner as agreed to by the Government, and may be granted specifically for the intended application only. Proposed deviations will be evaluated in light of the current state of technology of the part, material or process and the intended application. Either the contractor or its subcontractors may accomplish the evaluation and implementation required, however, the prime contractor has the responsibility for ensuring all requirements are met.

1.3 General Notes.

1.3.1 The term part is used interchangeably with component.

1.3.2 Unless otherwise designated by contract, the term “customer” used herein refers to the Government procuring agency program or project office. The term customer is used interchangeably with Government.

2. APPLICABLE DOCUMENTS

The following documents form a part of this document to the extent specified herein.

2.1. U.S. Government Documents

AR 11-9 Army Regulation 11-9: Army Radiation Safety Program FAR 52.211-5 Federal Acquisition Regulation - Material Requirements FAR 27.201-2(b) Federal Acquisition Regulation – Contract Clauses FAR 32.1009 Federal Acquisition Regulation – Title FAR 33.209 Federal Acquisition Regulation – Suspected Fraudulent Claims MIL-DTL-5541 Military Specification, Chemical Conversion Coatings on Aluminum and

Aluminum Alloys MIL-HDBK-1250 Corrosion Prevention and Deterioration Control in Electronic Components and Assemblies MIL-DTL-13924 Coating, Oxide, Black, for Ferrous Metals MIL-HDBK-1568 Material and Processes for Corrosion Prevention and Control in Aerospace

Weapons Systems MIL-PRF-19500 General Specification for Semiconductor Devices MIL-PRF-38534 General Specification for Hybrid Microcircuits MIL-PRF-38535 General Specification for Integrated Circuits (Microcircuits) Manufacturing MIL-PRF-39006/22 Capacitors, Fixed, Electrolytic (Nonsolid Electrolyte), Tantalum, (Polarized, Sintered Slug), 85 Degrees C (Voltage Derated to 125 Degrees C), Established Reliability, Style CLR79

MIL-PRF-39006/25 Capacitors, Fixed, Electrolytic (Nonsolid Electrolyte), Tantalum, (Polarized, Sintered Slug), (Extended Range) 85 Degrees C (Voltage Derated to 125 Degrees C), Established Reliability, Style CLR81

MIL-STD-186 Manufacturing Process Protective Finishing for Army Missile Weapon Systems

MIL-STD-883 Test Method Standard Microcircuits

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2.2. Industry Standards

AEC-Q100 Automotive Electronics Council Stress Qualification For Integrated Circuits AEC-Q101 Automotive Electronics Council Stress Test Qualification For Discrete

Semiconductors ASTM B117 American Society of Testing and Materials (ASTM) Standard Practice for

Operating Salt Spray (Fog) Apparatus ASTM B298 American Society of Testing and Materials (ASTM) Standard Specification for Silver-Coated Soft or Annealed Copper Wire.

ASTM B488 American Society of Testing and Materials (ASTM) Standard Specification for Electrodeposited Coatings of Gold for Engineering Uses AWS D17.1 American Welding Society Specification for Fusion Welding for Aerospace

Applications EIA-STD-4899 Standard for Preparing an Electronic Components Management Plan GEIA-HB-0005-1 Program Manager's Handbook for Managing the Transition to Lead-free

Electronics in Aerospace and Military Systems GEIA-STD-0005-1 Performance Standard for Aerospace and High Performance Electronic

Systems Containing Lead-free Solder GEIA-STD-0005-2 Standard for Mitigating the Effects of Tin Whiskers in Aerospace and High

Performance Electronic Systems IDEA-STD-1010-A Acceptability of Electronic Components Distributed in the Open Market IPC/EIA J-STD-001 Requirements for Soldered Electrical and Electronic Assemblies J-STD-002 Solderability Tests for Component Leads, Terminations, Lugs, Terminals and

Wires J-STD-003 Solderability for Printed Boards J-STD-004 Requirements for Soldering Fluxes J-STD-005 Requirements for Soldering Paste J-STD-006 Requirements for Electronic Grade Solder Alloys and Fluxed and Non-Fluxed

Solid Solders for Electronic Soldering Applications IPC-A-610 Acceptability for Electronic Assemblies IPC-WHMA-A-620 Requirements and Acceptance For Cable and Wire Harness Assemblies IPC 2221 Generic Standard on PWB Design IPC 2222 Sectional Standard on Rigid PWB Design IPC 2223 Sectional Design Standard for Flexible Printed Boards IPC-6011 Generic Performance Specification of Printed Boards IPC-6012 Qualification and Performance Specification for Rigid Printed Boards IPC-6013 Qualification and Performance for Flexible Printed Boards IPC-6015 Qualification and Performance Specification for Organic Multichip Module

(MCM-L) Mounting and Interconnecting Structures IPC-6016 Qualification and Performance Specification for High Density Interconnect

(HDI) Layers or Boards IPC-6018 Microwave End Product Board Inspection and Test IPC 7711A/7721A Rework of Electronic Assemblies; Repair and Modification of Printed Boards and Electronic Assemblies JESD22-A121 Measuring Whisker Growth on Tin and Tin Alloy Surface Finishes JESD 201 Environmental Acceptance Requirements for Tin Whisker Susceptibility of

Tin and Tin Alloy Surface Finishes SAE AMS-QQ-P-416 Plating, Cadmium (Electrodeposited) SAE AMS-STD-1595 Qualification of Aircraft, Missile & Aerospace Fusion Welders SAE AS-5553 Counterfeit Electronic Parts; Avoidance, Detection, Mitigation, and

Disposition

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2.3. Other

Microelectronic Packaging Handbook, 1989, Tummala, Rao

3. REQUIREMENTS

3.1. Prohibited Part Specifications and Pedigree

3.1.1. For the purposes of this document the term "parts" means electrical, electronic, electro-mechanical (EEE) and associated mechanical components, parts or elements as listed here.

3.1.2. Parts and materials used outside of the vendor’s specifications for the specific part or material (e.g.

minimum temperature, maximum voltage, etc.).

Rationale: Can be a high liability risk. Can be a high reliability/performance risk if not characterized properly.

Use EIA-STD-4899 for guidance. Complex devices may be very difficult to characterize and manage due to manufacturer non-disclosures.

3.1.3. Parts not qualified for intended application life cycle environmental stress and duty cycle requirements.

Rationale: Parts without qualification data to support use in the application pose a significant risk of failing to meet the system requirements.

3.1.4. Parts or materials procured from a source other than the original manufacturer or the original manufacturer’s certified/franchised distributor without a Government approved process. The Government approved process shall include requirements for participating in the Government Industry Data Exchange Program (GIDEP) including submission of counterfeit information to the customer and/or the GIDEP agency. The Government approved process shall consider FAR clauses 27.201- 2(b), 32.1009, and 33.209, DFAR 252.246-7003, FAR 52.203-13, FAR 52.211-5 and the FY12 National Defense Authorization Act (NDAA). Any item/material whose identity or pedigree has been deliberately altered, misrepresented, or offered as an unauthorized product substitution is considered a counterfeit/non-conforming product.

Rationale: Counterfeit items are widespread and difficult to detect, procuring from franchise distributors minimizes counterfeit component and material procurement. Most counterfeit parts have performance, workmanship, or reliability issues. Additionally, the potential exists for receiving parts with unknown histories, storage or handling conditions (e.g., failed, rejected or scrapped parts, ESD damaged parts, or used parts). Reference SAE AS-5553,. IDEA-STD-1010-A, and .ANSI/ITAA Engineering Bulletin:

Counterfeit Parts & Materials Risk Mitigation for counterfeit avoidance process developments.

3.1.5. Reused, reinstalled, recycled, reattached, or salvaged parts and materials without a specific process approved by the Program Office and the Government Contracting Officer or Contracting Officer Technical Representative. Parts or materials previously installed or otherwise attached to another assembly are considered used and not new.

Rationale: New failure modes and/or latent failure conditions are introduced, part/assembly life can be shortened, overall reliability is unknown and can be difficult to determine. Mechanical fasteners pose a special risk due to the ease of removal and reinstallation. Reference FAR clause 52.211-5.

3.1.6. Parts with date codes more than 5 years old at the time of assembly without a Government approved process.

Rationale: Depending on construction, handling, and storage, parts can become unsolderable, contaminated, damaged, and otherwise degraded. Recertification can eliminate most concerns of damage issues associated with long term handling and storage and provides baseline properties for reliability forecasting.

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3.2. Prohibited Active Electrical Components

3.2.1. Discrete semiconductors not equivalent to or better than MIL-PRF-19500 JANTX, AEC-Q101.

Rationale: These components should utilize known standards as much as possible. Other industry standards, such as aerospace or telecommunications, may be considered equivalent depending on the application and subject to customer agreement.

3.2.2. Microcircuits not equivalent to or better than MIL-PRF-38535/38534 QML/SMD classes M, B, Q, or H, or AEC-Q100.

Rationale: These components should utilize known standards as much as possible. Other industry standards, such as aerospace or telecommunications, may be considered equivalent depending on the application and subject to customer agreement.

3.2.3. Selenium rectifiers.

Rationale: Degradation and reliability concerns

3.2.4. Discrete diodes that are not Category I (as defined by MIL-PRF-19500) or equivalent metallurgically bonded-thermally matched with double plug construction, diodes that contain point whisker/wire conductors, or diodes with plated silver button contacts.

Rationale: Metallurgical bonding is a more robust bonding method; coefficient of thermal expansion (CTE) issues may arise if not thermally matched.

3.2.5. Non-hermetic microcircuits and semiconductors without a Government approved selection, qualification and control process.

Rationale: Most non-hermetic parts are commercial/industrial grade and vary widely in construction, quality, and reliability and change without notice. Many non-hermetic devices are not intended for high reliability applications like aerospace, medical ,or military and can present a reliability risk.

3.3. Prohibited Passive Electrical Components

3.3.1. Silver case wet slug tantalum capacitors.

Rationale: Cannot tolerate reverse voltage very well. Silver electroplating from the case onto and beneath the oxide layer increases current leakage paths, resulting in increased dissipation and internal heat rise, liberation of gasses, and catastrophic failure. The formulation of hydrogen and oxygen gasses at the electrodes creates excessive internal pressure, and can result in electrolyte leakage or bursting of the case. Note: Tantalum cased capacitors may be used, but shall be per MIL-PRF-39006/22 and MIL-

PRF-39006/25.

3.3.2. Aluminum electrolytic capacitors.

Rationale: Elastomer seal allows evaporation of electrolyte under long term storage or use conditions resulting in degradation of part. Use at high altitude or in a vacuum accelerates electrolyte evaporation. Non-hermetic construction makes parts susceptible to corrosion from some circuit board cleaning agents.

Excessive ripple current causes heating, which accelerates evaporation of electrolyte.

3.3.3. Non-hermetically sealed plastic film capacitors.

Rationale: Susceptible to insulation resistance failure from moisture introduced in humid environments or by board cleaning processes.

3.3.4. Polyester capacitors.

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Rationale: In extended charge and elevated temperatures, polyester capacitors have been shown to be prone to material breakdown under steady state DC and at high temperatures (i.e. 80° C or higher).

3.3.5. Reed relays, relays that are not hermetically sealed or relays that are not solid state.

Rationale: Reed relays: differentials of CTE in materials may lead to fracturing of the switches under temperature cycling inherent in military applications. Prohibition of reed relays dates back to the early 1970’s due to the poor reliability reputation of these parts at that time. Non-hermetic relays are not preferred for military applications due to the introduction of contaminants and moisture. For non-solid state rationale, see mechanized switches.

3.3.6. Mechanically adjustable (variable) devices including capacitors, resistors, and magnetic devices where the value is intended to be fixed in the application.

Rationale: Mechanically adjustable parts are subject to contamination, oxidation, etc, resulting in catastrophic failure or parametric changes such as resistance drift. Designs requiring variations due to manufacturing or interface differences should use fixed-value (select on test) parts when the needed parameter is determined. Staking may reduce risk

3.3.7. Passive components with failure rate level greater than 0.1% per 1000 hours or not manufactured for high reliability applications.

Rationale: Supplier quality and device reliability are generally unacceptable. Passives intended for medical, military, aerospace, and automotive applications are candidates when failure rate data is not known, subject to Gov approval.

3.3.8. Carbon composition resistors

Rationale: They readily absorb moisture and the value increase significantly. If approved only use MIL-SPEC established failure level R or S and in very dry conditions.

3.3.9. Resistors using nichrome film elements.

Rationale: They are susceptible to corrosion/dissolution when operated under humid conditions causing large increases in resistance values or open circuit failures. If used (maybe in non tactical applications) care must be taken during handling, storage, and board assembly so as not to compromise the integrity of the outside coating.

3.3.10. Circuit protection fuses.

Rationale: Reliability and maintenance concerns. Trip free circuit breakers (with arc/noise protection for semiconductor devices) and semiconductor/passive protection schemes are preferred.

3.3.11. Vacuum tubes.

Rationale: Reliability and maintenance concern, in most applications semiconductors are more reliable. In some applications, exceptions can include cathode-ray tubes or application specific qualified traveling wave tubes with customer approval.

3.3.12. Crystals without adequate mounting support. Disc crystals (including those in oscillators) with fewer than 4 point mounts

Rationale: Two- and three-point mount disc crystals are inadequate for military vibration and shock requirements. Cantilevered (“diving board”) rectangular crystals are discouraged.

3.4. Prohibited Electromechanical and Mechanical Components

3.4.1. Slide-on or snap-on BNC connectors.

Rationale: Coupling integrity during severe environments; concerns for moisture and mechanical wear. Twist lock BNC connectors are acceptable.

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3.4.2. Fiber inserts, sheet spring nuts, and sheet spring washers as locking devices. Lock washers Rationale: Vibration risks and shape retention issues for long-term reliability.

3.4.3. Miniature switches or connectors not environmentally protected and/or encapsulated.

Rationale: Introduction of contaminants during board cleaning processes, coating procedures, storage, etc.

3.4.4. Mechanized switches.

Rationale: Generally a high failure rate item. Many switch internal mechanisms not proven for long-term reliable operation. Subject to moisture and contamination ingestion leading to failures (e.g. shorts, opens, high resistance, etc.). Contact oxidation can cause intermittent operation. Hot spot heating, arcing, and mechanical wear (fretting), all of which can lead to excessive oxidation, unreliable operation, and switch failure. Note: For some applications, special lubricants may provide an acceptable mitigation.

3.4.5. Lock washers

Rationale: Lock washers can generate metal shavings when secured. Reduce the possibility of metal shavings being generated or distributed in the system. Split type or star type should not be used as locking devices. By “biting” into the surface they often damage it and create debris. In addition, their overall effectiveness is poor.

3.4.6. Cinch, compression, or spring style connectors

Rationale: Contamination and foreign object issues. Concern with long term robustness of spring and/or compression style materials and contact function.

3.4.7. Un-keyed multipin connectors.

Rationale: Production issues, potential hardware damage in assembly. Maintenance issues for external ground connections.

3.4.8 Electrical connectors with contacts/pins that are not gold plated Rationale: Other contact finishes are very susceptible to tarnish, oxidation, also see the requirements for gold plating herin.

3.5. Prohibited Component Package Types

3.5.1. Open type magnetic devices (i.e. exposed core/coils/wire/internal elements) not environmentally protected and/or encapsulated.

Rationale: Possible introduction of corrosive contamination during board cleaning operations, susceptible to mechanical stresses during board assembly, damage to windings and posts if not protected, and long-term moisture/contamination intrusion.

3.5.2. Sockets and socketed devices for any electronic device, such as relays, integrated circuits, discrete semiconductors, and CCA-level slide-on or press-fit terminations.

Rationale: Inadequate retention of parts. Possible intermittent contact in shock and vibration environments.

Sockets in general are subject to oxidation between the leads and socket contacts, aka “fretting”. For some ground applications, lubricants may provide an acceptable mitigation. Not intended to cover board connectors or cable connectors.

3.6. Prohibited Materials

3.6.1. Not compliant to MIL-STD-186, except as noted herein.

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Rationale: Contains general Military industry best practice for protecting components and for material selection for corrosion and deterioration control. Note some MIL-STD-186 items are listed herein for emphasis and additional clarification however MIL-STD-186 must be referred to for additional specific design considerations.

3.6.2. Not compliant to MIL-HDBK-1250 except as noted herein.

Rationale: Contains missile system best practice for protecting components and for material selection for corrosion and deterioration control. Note some MIL-STD-1250 items are listed herein for emphasis and additional clarification however MIL-STD-1250 must be referred to for additional specific design considerations.

3.6.3. Not utilizing applicable policy and guidance from the DoD Corrosion Prevention and Control Planning Guidebook, Spiral 3.

Rationale: This document implements public law 10 U.S.C. 2228 and contains specific DoD policy, guidance, and technical considerations for developing and implementing a corrosion prevention and control program for DoD weapon systems and infrastructure. Guidance is in accordance with the DoD Corrosion Prevention and Control policy letter, signed by the Acting Under Secretary of Defense for Acquisition, Technology, and Logistics (USD[AT&L]), 12 November 2003 (see Attachment 1), and the Facility Corrosion Prevention and Control memorandum, signed by the Deputy Under Secretary of Defense for Installations and Environment, 10 March 2005 (Appendix F to Volume III).Note some items are listed herein for emphasis and additional clarification however this document must be referred to for additional specific technical and design considerations.

3.6.4. Paints, finishes, coatings, and materials not adequate for corrosion/deterioration protection in the intended application, and not utilizing MIL-STD-186 and MIL-HDBK-1250 or approved equivalent.

Rationale: Contains industry best practices for protecting components and materials for corrosion and deterioration control, and shall be used.

3.6.5. Tin alloy solders, coatings, and finishes with less than 3% Pb by weight that are internal and/or external to electrical, electronic, and electro-mechanical (EEE) parts/components, related hardware, and mechanical surfaces. Plating over an existing pure tin or tin alloy coating or finish with less than 3% lead. Exceptions are tin-plated insulated electrical wire compliant to applicable military or ASTM standards. Other than parylene or urethane conformal coat for tin whisker risk mitigation. Risk mitigation plans for use of pure tin or tin alloys with less than 3% Pb shall require Government approval.

Rationale: Potential for tin whisker and tin pest. Must evaluate finish and application for risk mitigation for EEE applications especially terminals and leads. Surfaces with tin should be coated with a tin alloy containing not less than 3% Pb alloy. Applies to all piece parts - internal and external. The restriction also includes plating over an existing pure tin finish, see GIDEPs from 2003. Risk mitigation techniques must be evaluated on a case-by-case basis. Incoming lot inspection with XRF or EDS should be utilized. GEIA-STD-0005-1, GEIA-STD-0005-2, GEIA-HB-0005-1, JESD22-A121 and JESD 201 are available for guidance on tin whisker testing and risk mitigation. Level 2C shall be the minimum, however, these documents require tailoring with customer approval for detail requirements.

The required conformal coating for whisker mitigation is parylene or a verified minimum MIL-I- 46058, type UR urethane (eg Conathane) thickness of 3-4 mil on leads. Other coatings are subject to customer approval. A customer approved robotic process is required.

3.6.6. Solder fluxes with activity levels classified as high.

Rationale: Must have demonstrated appropriate verification methods to ensure the removal of residual contaminants. Ionic contamination is a concern.

3.6.7. Aluminum alloys 2024-T3 or T4 (use T6, T8, or 5000/6000 series).

Rationale: Subject to stress corrosion cracking. The 2024-T3 and -T4 heat treat conditions are susceptible to stress corrosion cracking (SCC) and exfoliation corrosion.

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3.6.8. Aluminum alloys 7001-T6, 7278-T6, 7050-T6, and 7075-T6 (use in the over-aged condition such as the T73 or T76 tempers).

Rationale: Subject to stress corrosion cracking. The 7xxx series alloys are susceptible to stress corrosion cracking (SCC) and exfoliation corrosion in the high strength T6 condition. Use these alloys in the over-aged conditions (T7x) which have slightly lower properties but improved corrosion resistance.

3.6.9. Magnesium and magnesium alloys.

Rationale: Corrodes easily and difficult to protect from corrosion. Flammability risk. Uncoated magnesium will readily corrode in many environments. Magnesium may also have severe galvanic corrosion issues because of its voltage potential (extremely anodic to most other metals).

3.6.10. Mercury and compounds containing mercury.

Rationale: Hazardous concerns .

3.6.11. Precipitation hardening stainless steels in the H900, H950, or H1000 tempers (use H1025 or higher temper). CRES 400 series stainless steels, without passivation and a top coating. Exceptions are fasteners in the CH950 condition, springs in the CH 900 condition, 17-4 PH castings aged at 1000 degrees F, and PH13-8Mo H1000.

Rationale: Stress corrosion concerns. See MIL-HDBK-1568 for 400 series requirements. These high strength tempers are prohibited due to resulting low elongation, susceptibility to stress corrosion cracking, and rapid crack growth properties, Use H1025 or higher in most cases. The use of PH13-8Mo H1000 is commonly accepted for high strength/corrosion resistant applications due to the elongation values.

Precipitation hardening steels should be aged at temperatures not less than 1025°F (i.e. H1025).

Exception is made for castings that may be aged at 1000°F ±15°F, for fasteners that may be used in the CH950 condition, and for springs, which have optimum properties in the CH 900 condition.

3.6.12. Lubricants and greases or other materials, which contain graphite.

Rationale: Graphite is a concern for corrosion (galvanic incompatibility with a variety of metals).

Graphite/carbon compounds when used as other than a lubricant may be acceptable in some applications .

3.6.13. PVC plastics and PVC electrical insulation.

Rationale: PVC is subject to degradation from out-gassing and depletion of plasticizers, subject to acceleration by vacuum and/or high ambient temperatures. Flammable and gives off toxic fumes when burning.

Plasticizer out-gassing may also introduce contamination source.

3.6.14. Corrosive type RTV adhesives/sealants (emit acetic acid during cure).

Rationale: Acetic acid is corrosive. Some RTVs revert under military use conditions. Suspect RTVs include, Dow Corning, DC 140, DC 731, DC 732, DC 734, DC 891, DC 1890, DC 20-078, DC 30-079, DC 30-121, DC 92-007, General Electric, RTV 102, RTV 103, RTV 106, RTV

108, RTV 109, RTV 112, RTV 116, RTV 118, RTV 192, RTV 198.

3.6.15. Adhesives, sealants, foam, and potting materials that are susceptible to reversion.

Rationale: Out-gassing, corrosion, poor adhesion, and ineffective protection can be a result. The tin-catalyzed family of silicones are susceptible to depolymerization (reversion) under high heat and/or oxygen-starved environments (such as nitrogen purged electronic housings). Oxygen is an inhibitor to silicone reversion. Use platinum or alcohol cured silicone systems in nitrogen purged environments. Also see 3.6.14.

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3.6.16. Rubber and plastics not protected from exposure that are susceptible to ozone damage or degrade with exposures to UV light.

Rationale: Susceptible to cracking, becomes an ineffective seal or insulator. Certain rubbers and plastics have very limited life expectancies in air with excessive ozone or with excessive UV exposure.

3.6.17. Silver-plated wire that has less than 40 micro inches of silver and without manufacturer certification for passing deterioration control tests per ASTM B298. Certification and shelf life of bulk material must be controlled. Immediately after wire samples are cut, open ends in the bulk material must be sealed against moisture intrusion. For long term storage (more than 1 year) wire must be stored in dry pack bags that are sulfur and chlorine free, PH neutral, at less than or equal to 30C and less than 50% moisture with indicators. Before using wire samples that have been in storage for more than one year, the user must verify the manufacturers ASTM B298 certificate, the storage conditions, and perform solderability per JSTD-003B or newer rev with specimens from each end of the sample wire taken from the bulk material. In addition, wire stored longer than 10 years must be approved by the Gov.

Rationale: Corrosion red plague. Mitigated if wire is compliant to ASTM B298 testing and certification by the manufacturer. Wire with 80 microinches or more silver is preferred. It is essential that platings be defect free and of uniform thickness. Imperfections ranging from porosity to deep scrapes penetrate the silver plating and reveal the copper core of a wire strand. Such damage may result from the use of defective wire-drawing dies, wear action between strands during stranding and braiding operations or when conductor strands are wound and re-wound from reels to bobbins. For confidence in wire to be used after 2 years of storage it must be recertified to ASTM B298 and data suggests it should have more than 80 microinches silver to pass more than 10 years of storage. Wire stock shall be handled with extreme care during storage and use to prevent mechanical damage to the plating and shall be stored in a controlled environment which minimizes exposure to humidity.

3.6.18. Wire with polytetrafluoroethene (PTFE) insulation in applications with a high probability of producing cold flow of the insultion.

Rationale: Can be a much lower wear resistance. Insulation cold flow concerns which can lead to shorting wherever the wire is routed over sharp corners or contrained. May be mitigated by wire routing and protection against sharp edges and pressure points on insulation. MIL-W-16878 does not have a QPL and is not a preferred choice.

3.6.19. Wire with fluoropolymer insulation, such as radiation cross-linked Ethylene-Tetrafluoroethylene (XL-

ETFE).

Rationale: If stored in sealed plastic/metal bags or other enclosures for several months or longer corrosion can occur on metal surfaces and optics. GIDEP and user 2003 data shows baking out is not enough to reduce risk. Hot-humid conditioning may be acceptable for some applications. Long-term field storage affects are not well characterized but may be minimized by allowing insulation to outgas in open air or dry gas environments prior to assembly. See NASA historical information.

3.6.20. Bare hook-up wire with the exception of grounding straps.

Rationale: More susceptible to arcing, and handling/environment degradation if not coated.

3.6.21. Aluminum without chromate conversion coating in accordance with MIL-DTL-5541 or equivalent.

Surfaces requiring low electrical resistance that are not Class 3 coated IAW MIL-DTL-5541.

Rationale: Corrosion concern The low electrical resistance of MIL-DTL-5541 Class 3 chromate conversion coating does not provide adequate protection for many aluminum alloys in applications requiring handling or exposed climatic conditions. Use MIL-DTL-5541 Class 1A coating for most applications.

The brand name “chem film” or equivalent as a the primary single coating is not considered adequate for corrosion protection.

3.6.22. Cadmium plating not in accordance with SAE AMS-QQ-P-416 Type II (supplementary chromate treatment).

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Rationale: Contamination concern, not an adequate corrosion resistance finish for most applications without a treatment. Is considered an EPA toxic material. Cadmium will corrode, it acts as the sacrificial anode for the base metal. It requires a supplementary treatment and should also be overcoated with at least a primer for exterior applications. The use of Cadmium should state the type II that involves the supplementary treatment.

3.6.23. Zinc or zinc alloys with greater than 20% zinc, including plating. If approved by the Gov for specific applications zinc plating must have a Type II supplementary treatment.

Rationale: zinc plating without a Type II supplementary chromate treatment is a contamination concern and not an adequate corrosion resistance finish for most applications without a treatment. Zinc will corrode, it acts as the sacrificial anode for the base metal. It requires a supplementary treatment and should also be over coated with at least a primer for exterior applications. Also see AMS 2417, AMS 2402 for cautions on corrosion rate, volume of corrosion product, supplementary treatment and corrosion testing.

3.6.24. Gold plated electrical contacts/pins not equivalent to ASTM B488, Class 1.25 thickness outerplating (50 microinches or more). Gold plated contacts/pins without 50 microinch or more Ni undercoating in the contact area. Gold plated electrical contacts/pins with silver undercoating.

Rationale: Lack of underplating can allow copper and gold to diffuse into each other, increasing contact resistance and corrosion degradation. 50 microinches gold thickness and Ni underplate is considered a minimum to prevent diffusion and durability issues in most applications. Silver migrates easily and is not a very effective diffusion barrier.

3.6.25. Silver-or silver alloys used for electrical connections for example inside relays, pins on connectors, terminations on chip devices, leads on electronic devices, balls on area array packages, traces on printed wiring boards (for example Immersion silver), solder (including SAC), etc.

Rationale: Silver gets a contaminated (dirty) surface from reacting to gases/contamination in the air like sulfur.

In the presence of moisture and an electric field, silver migrates and can create short circuits very rapidly. Reference Microelectronic Packaging Handbook, 1989, Tummala, Rao: soldering of silver-plated lugs and contacts is frequently a delicate operation because of the solubility (leaching) of silver in tin due to silver scavenging. Silver can create a dissimilar metal reaction if in contact with exposed copper. SAC solder and solder balls can grow whiskers, SAC solder formulations may not be as durable in some applications and vendors will change formulations without notice. SAC solders/solder balls must be thoroughly tested for a given solder process and application and closely monitored for alloy content. High content silver is a reliability risk in tin-lead solder processes, see IPC-HDBK-001.

Chip devices with silver or silver and palladium have, in general, greatly reduced resistance to solder leaching/dissolution but must have leach resistance barriers such as nickel or copper between the termination and the solder. IPC 4553 does not recommend immersion silver for high reliability applications including military systems.

3.6.26. Tapes that are kapton with silicone adhesives, fabric electrical (adhesive or friction type), or textile electrical (adhesive or friction types), including temporary usage during assembly of electronic hardware .

Rationale: Susceptible to moisture absorption, sources of contamination due to outgassing and surface migration of adhesives.

3.6.27. Bare corrodible metal surfaces and/or galvanic metal couples with over 100mV potential difference.

Exceptions are allowed in accordance with MIL-STD-186.

Rationale: Galvanic corrosion concern. Mitigation techniques shall be approved by the Government. MIL- STD-186, MIL-STD-889, and MIL-HDBK-1250 may be used as guidance. Dissimilar metal couples up to 350mV may be acceptable in desiccated moisture controlled environment with visual indicators but must have written Government approval for each specific application.

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3.6.28. Materials not inherently moisture and fungus resistant.

Rationale: Materials are required to be non-nutritive to fungus. Contamination may be a concern. Materials that are environmentally sensitive to moisture and fungus attack may degrade and not perform as expected. Open-cell materials are a moisture concern. Organically filled phenolic materials are a fungus concern.

3.6.29. Nickel-plated aluminum construction.

Rationale: See MIL-STD-186. Nickel plated aluminum is a concern for use in corrosive environments due to galvanic corrosion concerns from use of dissimilar metals. Other surface treatments, including anodizing, chem film, and cadmium plating, are corrosion resistant and more damage tolerant than nickel plating.

3.6.30. Nickel-plated aluminum connectors.

Rationale : See MIL-STD-186. For connectors, rough handling of nickel-plated aluminum connectors may crack the hard nickel plating on the soft aluminum substrate in corrosive environments, this can lead to pitting corrosion of the aluminum. If nickel plating is used a double zincate coating shall proceed the nickel. Cadmium plating (or new approved cadmium substitutes) is preferred and shall always have a supplemental chromate surface treatment (see cadmium plating herein), SAE AMS-QQ-P-416 Cadmium Type II plating is the preferred plating on aluminum connectors in corrosive environments.

Mating of Nickel-plated aluminum connectors with Cadmium plated connectors is prohibited.

3.6.31. Polyimide (including Kapton, Upilex) as an electrical insulator.

Rationale: FN and HN grade Polyimide is susceptible to moisture degradation and subsequent arcing problems.

Copper alloy wire and flex circuits require a secondary protective layer or adhesive overcoat, such as multilayer TFE/Polyimide/TFE. Polyimide insulation maybe used in exoatmospheric applications with Government approval due to limited radiation resistant insulating material.

3.6.32. Desiccants, organic or polymeric materials (e.g. lacquers, varnishes, coatings, adhesives, or greases) inside cavities of packages/housings with bare microcircuit/semiconductor die, optics, or other elements. Materials compliant with MIL-STD-883 Method 5011- Evaluation and acceptance procedures for polymeric materials, or equivalent industry specification, are acceptable.

Rationale: Potential for out-gassing and corrosion. Not effective for long term harsh environments without adequate characterization. ASTM E595 maybe an acceptable test for vacuum environments.

3.6.33. Materials used in the end item configuration that may demonstrate unintended flammable properties in item-specified worst case environments.. Plastic/polymer materials exceeding UL 94, defined levels V-0, VTM-0, 5VA, or HBF as applicable, or UL 1694 SC-0 or SC-TC 0. Flammable or combustible liquids as defined in OSHA 1910.106.

Rationale: Fire hazard, "flammable" is subjective, refer to applicable UL (solids), and OSHA (liquids) definition levels. Test methods and degrees of flammability for polymers are defined in UL 94 and UL 1694. Flammable materials that may ignite in worst case environments are undesirable in military applications. Systems using ordnance items intended to become flammable generally require Government agency fuse and safety board type approvals.

3.6.34. Cotton and linen.

Rationale: Very flammable material. Degradation of insulating properties over time.

3.6.35. Radioisotopes/radioactive materials except as allowed by AR 11-9.

Rationale: Safety concerns and require extensive accountability. AR 11-9, The Army Radiation Safety

Program, allows some specific exceptions. OSHA and export regulated.

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3.6.36. Electroless Nickel Immersion Gold (ENIG) without a Gov approved process, and storage/handling controls.

Rationale: Boards are very sensitive to plating bath control, handling and storage. Solderability issues arise from “black pad,” gold porosity, contamination from environment storage and handling. See IPC 4552 for requirements and controls.

3.6.37. Pentachlorophenol, commonly referred to as "Penta" or "PCP" as a wood product preservative. Use 2 percent copper naphtheate, 3 percent zinc naphthenate, or 1.8 percent copper 8 quinolinolate.

Rationale: Highly reactive. Generally applies to shipping and storage containers.

3.6.38. Black metal oxide coating on metal parts as defined by MIL-DTL-13924.

Rationale: Black oxide coating is primarily for decorative purposes and is not for corrosion protection.

3.6.39. Platinum catalyzed silicone rubber in contact with high sulfur content materials.

Rationale: Platinum catalyzed silicone rubber, when used as coatings, thermal barriers, or potting compounds on Circuit Card Assemblies (CCAs), when in contact with materials with high sulfur content (such as black foam padding used for mechanical protection/damping, PSA tapes, etc.) will not cure. The sulfur reacts with the platinum catalyst and which precludes catalyzation of the silicone rubber, i.e. it will not cure.

3.6.40. Class 1 ozone depleting chemicals (ODCs) and highly toxic chemicals.

Rationale: Environmental laws, EPA regulated. Refer to your contractual hazardous materials requirements and all applicable federal and state guidelines.

3.7. Prohibited Processes

3.7.1. Solder iron mounting or rework of multilayer ceramic capacitors (MLCCs) or other ceramic parts without a customer approved and validated procedure.

Rationale: MLCCs are easily damaged (e.g., microcracks, dielectric damage, etc.) by touch-up and rework with soldering irons.

3.7.2. Welding operators not qualified in accordance with SAE AMS-STD-1595, and without certification level II or III NDE/NDI. Operators not provided the necessary training and qualifications requirements to certify each operator and the applicable welding equipment for specific welding tasks.

Rationale: This area is critical with small “mom & pop” shops that support larger subs. They need to have certified operators in the areas of welding and brazing according to the process spec. call out on the drawing. The preferred welding spec. would be AWS D17.1 and brazing spec. shall meet the requirements of the applicable AWS spec. replacement for MIL-B-7883.

3.7.3. Lead forming or changes to lead finishes without adequate inspections for component degradation Rationale: Need to follow military and industry specifications for inspections such as, seal testing, scanning acoustic microscopy, solderability, and high power visuals, and electrical testing to qualify and monitor processes. In appropriate fixture, handling, and processes will damage and degrade parts affecting long term reliability.

3.7.4. Except as noted in this document, soldering and assembly not in accordance with IPC/EIA J-STD-001, Class 3, acceptance requirements not in accordance with IPC-A-610, Class 3.

Rationale: Workmanship, quality and reliability are generally not acceptable. Also refer to the companion IPC document IPC-HDBK-001.

3.7.5. Except as otherwise noted in this document, printed wiring boards not in accordance with IPC 6011, 6012, 6013, 6015, or 6016 as applicable, except as noted herein.

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Rationale: Workmanship, quality and reliability are generally not acceptable

3.7.6. For CCA/PWA rework/repair, the use of IPC 7711A/7721A, Method 3.2, Method 3.5.2, Method 3.5.3, Method 4.5.2, Method 4.2.6, Method 4.2.7, Method 4.3.2, Method 4.3.3, Method 4.3.4, Method 5.2, Method 5.3, Method 6.2.1, Method 6.2.2, Method 6.3.

Rationale: These methods introduce unacceptable risk in the repair/rework processes.

3.7.7. Except as otherwise noted in this document, assembly materials not in accordance with J-STD-004, J- STD-005, or J-STD-006.

Rationale: Use standard materials if not otherwise noted as an issue in this document or determined to be a reliability risk in high reliability applications.

3.7.8. Solderability not in accordance with MIL-STD-883, J-STD-002, or J-STD-003 as applicable.

Rationale: Use industry accepted methods.

3.7.9. Cable and wire harness not in accordance with IPC-WHMA-A-620.

Rationale: Workmanship, quality and reliability are generally not acceptable

3.7.10 Soldering and assembly not compliant to J-STD-001, Class 3, and the visual acceptability requirements of IPC-A-610, Class 3.

Rationale: Use industry accepted methods for high reliability assemblies.

3.8. Prohibited Design Practices

3.8.1. Not using Gov approved electronic derating criteria.

3.8.2. Not using IPC design standards 2221, 2222, 2223, or additional design considerations in IPC documents listed herein.

3.8.3. Printed wiring assemblies (PWAs) without 3-4 mil urethane coat (see tin alloy restriction for type) or parylene-c conformal coatings.

Rationale: Protection of circuit card assemblies from exterior contaminants and handling. Shown to reduce component mounting fatigue during vibration and shock, must be compatible with rigid components like glass body diodes. Parylene is preferred and shows superior performance in the areas of protection for tin whisker, handling protection, prevention of moisture contamination, prevention of arcing, low out gassing, and ease of rework.

3.8.4. PWAs with stacked or piggybacked mounted components, or components/leads using other components/leads for support or attachment, including butt joint connections.

Rationale: Difficulty with consistently mounting parts in "nonstandard" configurations leads to collateral damage. Serviceability issue, all components should be accessible for replacement without disturbing other components. Reliability concerns with degrading parts and attachment areas. When stacked capacitors are approved, use stacked capacitors in accordance with MIL-PRF-49470 "T" level.

3.8.5. Jumper wires not detailed on the engineering drawing and approved by the customer.

Rationale: If too dense, then reliability is an issue, can introduce EMI and noise into circuit, can cause performance problems if operators do not follow exact routing. Mounting process can easily degrade part and attach reliability.

3.8.6. Glass bodied components and magnetic elements not evaluated for coefficient of thermal expansion (CTE) matching to mounting substrate and to coating/staking materials, and not protected by buffer material when epoxy coatings are used.

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Rationale: Breakage of components at low temperature, and temperature cycling in general. See 2003 GIDEPs for 4148 diodes. High modulus (greater than 0.5 X 106 psi) encapsulants or coatings have been known to crack devices.

3.8.7. Parts or components overhanging the edge of a PWA.

Rationale: Damage to parts. Possible installation interference.

3.8.8. Through-hole components mounted on both sides of a PWA.

Rationale: Susceptible to wave solder damage. Must be mounted by hand which is labor intensive and operator sensitive.

3.8.9. Large-bodied components mounted without adequate support and staking.

Rationale: Leads subject to damage or breakage under vibration environment.

3.8.10. High heat-dissipation components mounted without adequate heat sinks.

Rationale: Heat degrades surrounding components, creates hot spots and degrades reliability of most EEE components. Need to pay attention to surrounding materials and temperature sensitive parts and may require exotic cooling techniques. May be difficult to meet component derating guidelines. Refer to manufacturers application notes for best heat sinking.

3.8.11. Multiple leads or wires mounted in a single plated through hole.

Rationale: All components should be accessible for replacement without disturbing other components. Can be difficult to get a good solder joint and can easily degrade the integrity of the joint and the hole.

3.8.12. Crimped Aluminum electrical aircraft wire.

Rationale: Due to high CTE of aluminum, thermal cycling causes loosing of crimps resulting in increased electrical resistance. Possible fire hazard from overheating at wire junctions due to corrosion of aluminum wire and increased junction resistance.

3.8.13. Traps or crevices susceptible to moisture collection.

Rationale: These areas are overly prone to corrosion conditions.

3.8.14. Unsealed permanent fasteners (recommend installing with wet primer of polysulfide sealant).

Rationale: Extends life by helping to prevent accelerated corrosion.

3.8.15. Unprotected bearings.

Rationale: Helps prevent shortened life.

3.8.16. Untested adhesively bonded designs, long term/accelerated environment testing such as temperature cycling, humidity and vibration must be considered.

Rationale: These connections/interfaces are difficult to model and characterization is not adequately performed by the manufacturer for many applications.

3.8.17. Lead forming or changes to lead finishes without adequate inspections for component degradation.

Rationale: Devices are susceptible to breakage and degradation from fixtures, handling, and heat Need to follow military and industry specifications for inspections such as, seal testing, scanning acoustic microscopy, solderability, and high power visuals, and electrical testing to qualify and monitor processes. Inappropriate fixture, handling, and processes will damage and degrade parts affecting long term reliability.

3.8.18. Maintenance procedures for corrosion protection without customer logistics and product assurance program approval.

Rationale: These procedures can become unacceptable cost and personnel burdens to the Government and must be coordinated with the responsible agencies.

3.8.19. Use of tantalum capacitors without surge testing and adequate series impedance

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Rationale: Tantalum capacitors are increasingly being used in low impedance circuits, and In Circuit Test machinery (ICTs) and fast rise time functional testers for board test purposes As a result they are more likely to see a surge condition. Surge testing should not be done in parallel charge circuits. Surge testing on 100% of capacitors at the manufacture simulates worst case conditions normally seen by the user. Extra derating in the application and series impedance can reduce the concern The reason for including a separate resistance into the circuit is to act as protection against voltage spikes and limit current surges to the capacitor. Additionally, in high ripple applications, it acts as an external heat sink and limits thermal stress to the dielectric by sharing the load.