SCOPE: Prescribes the minimum requirements for the control of cuprous / cupric oxide corrosion (a.k.a. Red Plague) of silver-coated copper wire, cable, and harness assemblies. PURPOSE: Targeted for applications where exposure to assembly processes, environmental conditions, and contamination may promote the development of cuprous / cupric oxide corrosion (a.k.a. Red Plague) in silver-coated copper wire, cable, and harness assemblies. Does not exclude any alternate or contractor-proprietary documents or processes that meet or exceed the baseline of requirements established by this document. Use of alternate or contractor-proprietary documents or processes shall require review and prior approval of the procuring NASA activity

Cooke, Robert W.

NASA Technical Reports Server

RED PLAGUE CONTROL PLAN (RPCP)
The Control of Cuprous / Cupric Oxide Corrosion (Red Plague) in
Silver-Coated Copper Wire, Cable, and Harness Assemblies	 4 Actr
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Robert Wm. Cooke	 ^^ a
NASA / Johnson Space Center
S&MA Quality and Flight Equipment Division, Special Processes Group	
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281.335.2413
robert.w. coo ke(a-nasa.gov
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https://ntrs.nasa.gov/search.jsp?R=20100009723 2019-08-30T09:06:26+00:00Z
What Is "Red Plague" / (Cu20)?
The sacrificial corrosion of copper in a galvanic cell of silver (cathode) and
copper (anode), resulting in the formation of red cuprous oxide (Cu 20) and
black cupric oxide (CuO).
• Promoted by the presence of moisture (H 20) and oxygen (02 ) at an exposed copper-
silver interface.
— Exposed conductor end (crimp terminations)
— Poor plating quality control (pin-hole, porosity, thin coating)
— Mechanical damage during stranding or handling (scratches, nicks, abrasion)
— Corrosion (chemical, atomic oxygen, silver migration)
— Wicking of moisture, oxygen, flux residue, solvents under the Teflon jacket
• Color may vary depending on the amount of oxygen available, commonly noted as a
red / reddish-brown surface discoloration — hence the term "Red Plague".
• Once initiated, the sacrificial corrosion of the copper base conductor can continue
indefinitely in the presence of oxygen (02).
• Severity
— Minor: Some loss of cross-sectional area
• Most commonly found in shield braiding, but can develop in main conductors
— Major: Consumption of cross-section, "Silver Straw"
WHAT MECHANISMS ARE REQUIRED TO INITIATE RED PLAGUE?
— MECHANICAL DAMAGE
Mechanical damage resulting in exposure of the
copper-silver interface.
• Wire manufacturing (i.e.- drawing, stranding, application of
insulation jackets, etc.)
• Improper assembly and installation practices (i.e.- tool damage,
excessive flexing. improper bend radius, etc.)
• Abrasion by packaging materials (cardboard).
— ENVIRONMENTAL CONDITIONS
A galvanic cell must form between the copper base metal and the silver coating in the presence of
water (H 20) and oxygen (02).
• Protection from high humidity and oxygen is considered the greatest significant mitigation against Red Plague.
• Water quench, wet dielectric testing, and aqueous cleaning processes must not be used.
— INADEQUATE COATING THICKNESS
Porous, discontinuous, and thin silver coatings are more likely to develop Red Plague since a
greater number of sites for galvanic cells to form are possible.
• 0.5 micron (-20 micro-inches): Easily damaged during manufacturing and handling
• 1 micron (— 40 micro-inches): Good flight history, provided procurement and environmental controls used.
• 2 micron (— 80 micro-inches): Improved resistance to handling / environmental damage and corrosion.
WHAT MECHANISMS ARE REQUIRED TO INITIATE RED PLAGUE? (cont.)
— HIGH TEMPERATURE
Migration of the copper base metal through the silver coating
Though the upper continuous operating temperature rating of most silver-coated wiring is +200 C (+392 F),
exposure to temperatures approaching +200 C (+392 F) or higher, induces migration of the copper base metal
through the silver coating.
• This may reduce the silver coating thickness and create porosity sites for cuprous/cupric oxide corrosion to
occur.
• Typically experienced only in long duration operation at temperatures beyond the wire's continuous rating, or
where the wiring is exposed to excessive heat during test or highly accelerated burn-in.
— CHEMICAL ATTACK
Attack and degradation of the mechanical integrity of the silver coating.
Exposure to chemicals present in the environment (oxygen, sulfur compounds, salt, etc.) may result in corrosion
and corrosion by-products that attack and compromise the mechanical integrity of the silver coating.
• Common "green" packaging materials often contain and outgas small amounts of sulfur
paper wrapping materials
rubber bands
cardboard boxes
• Exposure to contaminants during transport (diesel fumes)
• Exposure to condensing and corrosive atmosphere (coastal launch facilities)
• Exposure to atomic oxygen (AO) in spaceflight applications has been shown to tarnish and pit silver coatings.
Why Is Silver-Coated Copper Wire Used?
Advantages
• Good electrical conductivity
• Excellent:
— Solderability. Silver improves wettability of SnPb solder
— Crimpability
» Negligible difference in tensile test values for 20, 40, and 80 micro-inch
» Isn't hard and slippery like nickel-coated copper
— Flexibility
• Non-magnetic
— No signature (useful if you don't want to be seen / detected)
• Low skin effect losses in high speed data and RF transmission applications
• No tin whiskers!!
• Extensive flight experience in US and Europe
Why Is Silver-Coated Copper Wire Used?
Disadvantages
• Galvanic Couple: Silver (cathode), Copper (anode) _ - 0.46 volt potential
• Environmentally Sensitive
— Shipping, Storage, Assembly Restrictions
» Moisture
» Oxygen
» Organic compounds (Background gasses — biologic activity; sulfur-bearing materials — cardboard)
— Application Restrictions
» Temperature Limits (+200 C (+392 F) )
• Inter-strand bonding, silver migration, and oxidation of the copper strands if operated at upper limits for
extended periods of time.
» Atomic Oxygen
— Limited Life Article
)) 10 years from date of manufacture
• Cost
— Silver tied to commodities market
» 40 micro-inch silver is commonly used in spaceflight applications, AS22759
» 80 micro-inch is presently considered "special" , MIL-DTL-29606A (Proposed)
Red Plague Isn't A New / Previously Unknown Concern
Concerns about galvanic corrosion of silver-coated copper wire are in many documents
used by NASA, ESA, military, and aerospace.
• ASTM B 961 — 08	 Standard Specification for Silver Coated Copper and CopperAlloy Stranded Conductors
for Electronic Space Application
• ECSS-Q-ST-70-20C	 Determination of the Susceptibility of Silver-Plated Copper Wire and Cable to "Red-
Plague" Corrosion
• JPR 8080.5A	 JSC Design and Procedural Standards, E-24
• JSC49879	 JSC Wire & Cable Integrity Compliance Program
• JSC49894	 Electronic Part Selection and Design Guidelines for Low Criticality Space Flight Payloads
• MIL -HDBK-338B	 Electronic Reliability Design Handbook
• MIL -HDBK-978B (NASA) NASA Parts Application Handbook, Vol. 5
• MIL -STD-1547B (USAF)	 Electronic Parts, Materials, and Processes for Space and Launch Vehicles
• MSFC-STD-3012	 EEE Parts Management And Control For MSFC Space Flight Hardware
• NASA TM X-53522	 Evaluation of High Temperature Stranded Hook-up Wire (1966)
• NASAITP-2003 -212242	 EEE-INST-002: Instructions for EEE Parts Selection, Screening, Qualification, and
Derating
• SAE AIR4487	 Investigation of Silver Plated Conductor Corrosion (Red Plague)
• SAE AS50881 C	 Wiring Aerospace Vehicle
• TOR-2006(8583)-5236	 Technical Requirements for Electronic Parts, Materials, and Processes Used in Space
and Launch Vehicles
WHY DID JSC DEVELOP A RED PLAGUE CONTROL DOCUMENT?
Push-back from the projects and programs, with the view:
• VAGUE TECHNICAL GUIDANCE
— "All the documents say is that there is a concern. So What?"
— "No formal requirements / procedures document. No QA criteria. How do I implement?
— "No failures attributed to Red Plague reported in PRACA or NASA Lessons Learned database."
— "We have extensive flight experience with silver-coated copper wire. No failures attributed to Red Plague ."
— "All problems were in the past and caused by poor wire manufacturing process controls. Processes are better
and we're smarter!"
Conclusion: 4 Red Plague is an Urban Myth!
• LATENT FAILURE MECHANISM
— "Red Plague takes +10 years to develop."
— "My project will ONLY fly for 1 flight, and it's located in the habitable section of the vehicle."
— "My project is CRIT 3, and it doesn't matter if it works or not!"
Conclusion: 4 Risk of failure is low!
• CONTRACT CHANGE RESULTED IN A JSC WAREHOUSE FULL OF WIRE
— Some wire believed to be more than 15 years old — no QA paperwork
— Wire reportedly all Flight (Class A), but not identified as such — no QA paperwork
— Retesting / recertifying all of the wire through JSC RITF would have swamped the lab
• NOT ON CONTRACT
$$$ Schedule impact if implemented / $$$ Cost savings if not implemented
BUT  ---
RED PLAGUE CONFIRMED IN FLIGHT HARDWARE (JANUARY 2010)
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JSC 64647 - RED PLAGUE CONTROL PLAN (RPCP)
THE CONTROL OF CUPROUS / CUPRIC OXIDE CORROSION (RED PLAGUE) IN SILVER -
COATED COPPER WIRE, CABLE, AND HARNESS ASSEMBLIES
• SCOPE
— Prescribes the minimum requirements for the control of cuprous / cupric oxide corrosion (a.k.a.
Red Plague) of silver-coated copper wire, cable, and harness assemblies.
• PURPOSE
— Targeted for applications where exposure to assembly processes, environmental conditions, and
contamination may promote the development of cuprous / cupric oxide corrosion (a.k.a. Red
Plague) in silver-coated copper wire, cable, and harness assemblies.
— Does not exclude any alternate or contractor-proprietary documents or processes that meet or
exceed the baseline of requirements established by this document. Use of alternate or
contractor-proprietary documents or processes shall require review and prior approval of the
procuring NASA activity.
• APPLICABILITY
— All JSC projects and programs involved in the design, manufacture and inspection of electronic,
electrical and electro-mechanical hardware, and printed wiring assemblies (PWA) for Aerospace
And High Performance (AHP), spaceflight and mission essential support equipment applications.
JSC 64647 - RED PLAGUE CONTROL PLAN (RPCP)
• CONDUCTOR STRAND MATERIAL AND COATING
— All strands shall conform to the applicable ASTM or ANSI standards for the proper material listed
in Table 1.
— After stranding, strands shall be free from lumps, kinks, splits, scraped or corroded surfaces, and
skin impurities.
TABLE 1 CONDUCTOR STRAND MATERIAL AND COATING
Designator Strand material Thickness Application ASTM orANSI standard
SCC Annealed copper 1 MICRON (-40 MICRO-INCH) ASTM-13298
SCC1 Annealed copper 2 MICRON (-80 MICRO-INCH) ASTM-13298ASTM-13961
SCA High strength copper alloy 1 MICRON (-40 MICRO-INCH) ASTM B298ASTM-13624
ASTM B298
SCA1 High strength copper alloy 2 MICRON (-80 MICRO-INCH) ASTM-13624
ASTM-13961
SCU Ultra-high strength copper alloy 1 MICRON (-40 MICRO-INCH) None
JSC 64647 - RED PLAGUE CONTROL PLAN (RPCP)
• SILVER COATING REQUIREMENTS
— 1 MICRON (-40 MICRO-INCHES)
Primary and shield conductors: Not less than 1 micron (-40 micro-inches) average, when
measured in accordance with ASTM B 298-07.
— 2 MICRON (-80 MICRO-INCHES)
Primary and shield conductors: Not less than 2 micron (-80 micro-inches) average, when
measured in accordance with ASTM B 298-07. After stranding, the coating thickness on each of
the individual conductor strands shall not be less than 1 micron (-40 micro-inches) when
inspected using micro-section analysis in accordance with ASTM B 961-08.
— SODIUM POLYSULFIDE TEST
The continuity (non-porosity) of the coating shall be determined on representative samples by
the sodium polysulfide test, in accordance with ASTM B 298-07.
— RED PLAGUE CORROSION TEST
Representative samples shall conform to codes 0 — 3 of the accelerated corrosion test for un-
insulated silver-plated conductors as outlined in ASTM B 961-08 [9.2].
— MICRO-SECTION ANALYSIS
Micro-section inspections shall be in accordance with ASTM B 961-08 except that the coating
thicknesses specified herein shall be in effect.
JSC 64647 - RED PLAGUE CONTROL PLAN (RPCP)
• PROCUREMENT REQUIREMENTS
— QUALIFIED /APPROVED SUPPLIERS
Procured in accordance with the wire procurement specification, from suppliers listed on the
Qualified Manufacturers List (QML) or suppliers approved by the procuring NASA activity.
— LOT TRACEABILITY AND CERTIFIED TEST REPORTS
Full lot traceability and certified test reports.
Test reports, and all tested and untested micro-section analysis coupons, shall be preserved
and available for review by the procuring NASA activity on request.
— LIMITED LIFE ARTICLE
Stock wire and cable with a shelf life exceeding 10 years from manufacturing date shall be
segregated and shall not be used on in harness assemblies and hardware.
Completed cable, harness assemblies, and hardware incorporating silver-coated copper wire
and cable, with a combined storage and use life exceeding 10 years from date of assembly
shall be identified, periodically inspected and tested, and tracked as a "Limited-Life Article".
JSC 64647 - RED PLAGUE CONTROL PLAN (RPCP)
• ENVIRONMENTAL REQUIREMENTS
— Silver-coated copper wire and cable shall be protected to reduce and control exposure to
environmental conditions and contamination that promote the development of cuprous / cupric
oxide corrosion (Red Plague).
— SHIPPING AND STORAGE
Shipped and stored in sealed water-vapor-proof packaging (i.e.- Moisture Barrier Bag, dry pack,
etc.), with capped ends, activated desiccant, and an irreversible humidity indicator card (1-HIC).
Wire and cable shall not be stored in paper wrapping materials or cardboard boxes.
Packaging. MIL-STD-2073-1 E Method 51. Moisture Barrier Bags (MBB) shall meet MIL-PRF-
81705, TYPE 1.
Capping. Wire and cable ends shall be capped with heat shrinkable end-caps conforming to
SAE-AMS-DTL-23053/4, or dipped in insulating electrical varnish for a length of approximately
2.5 cm (1 in).
Desiccant (Activated). MIL-D-3464 Type 2. The minimum quantity of desiccant to be based on
the protective package's interior exposed surface area, in accordance with MIL-STD-2073-1E,
Method 50, Formula 1.
Irreversible Humidity Indicator Card (1-HIC). Irreversible Indication (50-60-70-80-90% RH), or a
combination Irreversible / Reversible Humidity Indicator (50-60-70-80-90% RH) conforming to
MIL-1-8835.
JSC 64647 - RED PLAGUE CONTROL PLAN (RPCP)
• ENVIRONMENTAL REQUIREMENTS (cont.)
— ASSEMBLY
All assembly processes, including Receiving Inspection and Kitting, shall be conducted in an
environmentally-controlled and monitored area where dew point is not attained and the relative
humidity is less than 70%RH.
Wire and cable shall not be removed from its protective packaging until it has reached thermal
equilibrium with the assembly environment to reduce the risk of condensation formation.
Unused Wire
Prior to returning wire back to storage, wire ends shall be capped and stored in water-vapor-
proof packaging OR an environmentally-controlled and monitored area where dew point is not
attained and the relative humidity is less than 70%RH.
Work In Progress
Stored in water-vapor-proof packaging OR an environmentally-controlled and monitored area
where dew point is not attained and the relative humidity is less than 70%RH.
Completed Hardware
Stored in water-vapor-proof packaging OR in an environmentally-controlled and monitored area
where dew point is not attained and the relative humidity is less than 70%RH.
Cleaning
Aqueous solvents and cleaning systems shall not be used.



Red Plague Control Plan (RPCP)

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