NASA TECHNICAL STANDARD NASA-STD-8739.1B Change 2
Measurement System Identification:Metric (English)NASA TECHNICAL STANDARDNASA-STD-8739.1BChange 2National Aeronautics and Space AdministrationApproved: 2016-06-30Superseding NASA-STD-8739.1BChange 1WORKMANSHIP STANDARD FOR POLYMERICAPPLICATION ON ELECTRONIC ASSEMBLIES
NASA-STD-8739.1BDOCUMENT HISTORY pproval DateDescription1999-08-06Initial Release2008-03-04Technical corrections and addition of sectionscovering bonding and encapsulation.2009-07-23Editorial errata to paragraphs 2.1.2, 2.1.3, 4.1.4,4.5.2.a, 5.1.3, 5.2.1, 5.5.1, 6.2.2, 6.3.1.1, 6.5.1.a,6.6.1.b, 6.6.2.b, 6.8.1.2, Table 6-1, 8.1.3, 8.4.4,Table 8-1 Notes 2/4, 9.1.2.3, 9.1.2.4, 9.1.3.f,9.1.4.3.c/d/e/f/g, 9.2.1.2, Figures 91/2/3/4/5/6/7/10, 10.2.5, 10.2.7.f, Figure 10-3,Table 10-1, 12.3, 12.3.2/3/6/8, Figures 12-1/2,13.2.2.a, 13.3.g, 13.6.2.d/i thru p, 13.6.3.b/g,13.7.2.a. 13.7.3.d/e, 13.8.1, 13.9.2.j, l errata to Foreword paragraph 2, andparagraphs 1.0, 1.3, 1.4.1, 1.4.2, 4.2.2, and 12.1.Format Page numbers. Add reference to NASASTD 8709.22 in paragraphs 2.1.2 and 3.2.(JWL4)RevisionB2016-06-30 Throughout: changes to accommodate standardformat Throughout: general requirements moved toNASA-STD-8739.6 or updated to synchronizewith NASA-STD-8739.6. Refer to some industry standard definitions inIPC-T-50 and NASA standard definitions inNASA-STD-8709.22. Apply industry standard test method forevaluating sensitivity to ultrasonic cleaning. Update or improve definitions for: Accelerator,Bonding, Catalyst, Conformal Coating TestSpecimen, Encapsulation, EngineeringDocumentation, Glass Transition and GlassTransition Temperature High Voltage, KeepOut Areas, Non-common Conductors, Part2 of 53
NASA-STD-8739.1B Lead, Pot Life, Solvent, Specimen, MaterialsMix Test, Staking, Staking Material, StressRelief and Test Specimen.Consolidate duplicate requirements.Keep out areas must be documented for stakingand conformal coating.Layouts must provide enough room for staking.The supplier shall define bond line acceptancelimits.High voltage assemblies shall be identifiedwhen they will be encapsulated.Underfill of area array packages is considerednon-standard.Criteria that must be met added for usingmaterial with expired shelf life.Require process controls when baking outboards at 100 C or hotter.Accommodate pre-mixed and small-volumebatches of mixed polymer in mix test andtraceability requirements.Include conformal coating in mix testrequirement.Allow mix test in parallel with use of thematerial with prior approval.Use length side staking fillet for both sleevedand sleeveless axial leaded components.Remove requirement for end staking forsleeved axial leaded components.Clarify that fastener staking is not required.Fastener staking shall be residue-free andremovable.Correction to figure 9-10Coating or staking in keep out areas is a defect.Metric conversion correction in Fig 10-2Caption corrected for Fig 10-5.Limit scope of bonding requirements to PWAapplications.Ensure bonding material is under fastenerflanges to avoid damaging torques on thepackage body.Duplicate requirements removed from Chapter13.(JFP)3 of 53
NASA-STD-8739.1BChange12016-10-07Change22021-10-04 Corrected cross references of paragraphs andfigures: paragraphs 4.3.6, 8.5.2, 9.1.5.c.(7),9.2.2.c, 9.2.3.b, 9.3.1.a, and 10.2.3. Correctedformatting of superscript in paragraphs 7.4.1.aand 7.5.1.d. Deleted “(See Fig. 12-2)” inparagraph 12.3.3 and “CONFORMALCOATING” in the title for Figure 9-10.(JFP)Revalidated with changes to:a. Replace references to NPD 8730.5, whichhas been canceled, with NPR 8735.2.b. Add Section 2.3 Order of Precedence.c. Include other editorial edits to Chapter 1,Chapter 2, and Chapter 3 to align with theOSMA guidance for developing standards4 of 53
NASA-STD-8739.1BFOREWORD5 of 53
NASA-STD-8739.1BTABLE OF CONTENTSDOCUMENT HISTORY LOG . 2FOREWORD. 5TABLE OF CONTENTS . 6LIST OF APPENDICES . 7LIST OF FIGURES . 8LIST OF TABLES . 81.1.11.2SCOPE . 9Purpose. 9Applicability . 92.2.12.22.3APPLICABLE AND REFERENCE DOCUMENTS . 9Applicable Documents . 9Reference Documents . 10Order of Precedence . 103.3.13.2ACRONYMS AND DEFINITIONS . 11Acronyms . 11Definitions. 124.4.14.24.3GENERAL REQUIREMENTS . 16General . 16Electrostatic Discharge Control Requirements . 16Selection and Approval Requirements for Polymeric Materials . 165.5.1TRAINING AND CERTIFICATION PROGRAM . 18General . 186.6.16.26.36.46.56.66.7FACILITIES, TOOLS, AND MATERIALS . 18Safety . 18Environmental Conditions . 18Silicone Operations . 19Tool and Equipment Control . 19Material Storage and Records Retention . 19Inspection and Inspection Optics . 20In-Process Storage and Handling . 207.7.17.27.37.47.57.6CLEANLINESS REQUIREMENTS . 20General . 20Cleanliness Testing . 21Test Limits . 22Resistivity of Solvent Extract Test (ROSE Test) . 22Sodium Chloride Salt Equivalent Ionic Contamination Test . 22Demoisturizing . 236 of 53
NASA-STD-8739.1B8.8.18.28.38.48.5PREPARATION FOR POLYMERIC APPLICATIONS . 24Masking. 24Priming. 25Material Preparation. 25Material Mix Test Specimen . 27Conformal Coating Test Specimens . 279.9.19.29.3STAKING . 28Requirements . 28Fastener Staking . 34Torque Striping . 3610.10.110.210.310.4CONFORMAL COATING . 36Purpose. 36Requirements . 36Cleanup . 40Touchup/Rework. 4011.11.1BONDING . 45Requirements. . 4512.12.112.212.312.412.5ENCAPSULATION . 47General . 47Pre-cure Examination. 47Post-cure Inspection . 47Uses of Encapsulation with Connectors used with Shielded Cable . 50Cleanup . 5113.13.1QUALITY ASSURANCE . 51General . 51LIST OF APPENDICESCONFORMAL COATING PROBLEMS . 527 of 53
NASA-STD-8739.1BLIST OF FIGURESFigure 9-1. Default Staking for Horizontally-Mounted Sleeved or Sleeveless Cylindrical Part . 31Figure 9-2. Single Wire Staking . 31Figure 9-3. Staking for Radial Lead Components . 31Figure 9-4. Staking for Radial Multi-lead Rectangular Components . 32Figure 9-5. Default Staking of a Single Vertically-Mounted Rectangular Part . 32Figure 9-6. Default Staking for an Array of Vertically-Mounted Rectangular Parts . 33Figure 9-7. Wire Bundle Staking . 33Figure 9-8. Locking of Screws and Bolts with Nuts. 35Figure 9-9. Thread Locking of Blind Screw . 35Figure 9-10. Torque Striping Methods . 36Figure 10-1. Spray Application. 38Figure 10-2. Conformal Coating – Bubbles. 41Figure 10-3. Conformal Coating – Scratches . 42Figure 10-4. Conformal Coating - Lifting and Peeling . 43Figure 10-5. Conformal Coating – Coverage Defects . 44Figure 11-1. Component Bonding - Excess Bonding Material. 46Figure 12-1. Encapsulating Wires at Connector . 49Figure 12-2. Module Encapsulation . 50LIST OF TABLESTable 7-1. Cleanliness Test Values . 23Table 7-2. Recommended Demoisturizing Schedules for Polymeric Applications . 24Table 10-1. Conformal Coating Thickness . 388 of 53
NASA-STD-8739.1BWORKMANSHIP STANDARD FOR POLYMERICAPPLICATION ON ELECTRONIC ASSEMBLIES1.SCOPEThis standard prescribes NASA’s technical and quality assurance requirements for polymericapplications for electrical and electronic assemblies.1.1PurposeThis publication sets forth requirements for staking, conformal coating, bonding, andencapsulation of components used in electronic hardware.1.2Applicability1.2.1This standard is applicable to NASA Headquarters and NASA Centers, includingComponent Facilities and Technical and Service Support Centers. This language applies to theJet Propulsion Laboratory (a Federally-Funded Research and Development Center), othercontractors, recipients of grants, cooperative agreements, or other agreements only to the extentspecified or referenced in the applicable contracts, grants, or agreements.1.2.2This standard applies to production and processing of mission hardware as defined byNPR 8735.2, Hardware Quality Assurance Program Requirements for Programs and Projects.Use of the term “supplier” applies to any entity who is manufacturing or processing missionhardware in accordance with the requirements herein including NASA Centers, NASA primecontractors, and subcontractors.1.2.3In this standard, all mandatory actions (i.e., requirements) are denoted by statementscontaining the term “shall.” The terms “may” denotes a discretionary privilege or permission,“can” denotes statements of possibility or capability, “should” denotes a good practice and isrecommended, but not required, “will” denotes expected outcome, and “are/is” denotesdescriptive material.2.APPLICABLE AND REFERENCE DOCUMENTS2.1Applicable DocumentsThe documents listed in this section contain provisions that constitute requirements of thisStandard as cited in the text. Use of more recent issues of cited documents may be authorized bythe responsible SMA Technical Authority. The applicable documents are accessible via theNASA Standards and Technical Assistance Resource Tool at http://standards.nasa.gov or may beobtained directly from the Standards Developing Organizations or other document distributors.2.1.1Government DocumentsNPR 7120.5NASA Spaceflight Program and Project Management Handbook.9 of 53
NASA-STD-8739.1BNPR 8705.4Risk Classification for NASA Payloads.NPR 8735.2Hardware Quality Assurance Program Requirements forPrograms and ProjectsNASA-STD-8739.6 Implementation Requirements for NASA WorkmanshipStandards.2.1.2Non-Government DocumentsASTM D22402.2Standard Test Method for Rubber Property – DurometerHardness.Reference DocumentsThe documents listed in this section do not constitute requirements of this standard, but are citedin the text to provide further clarification and guidance.2.2.1Government DocumentsNASA-HDBK-8709.22Safety and Mission Assurance Acronyms, Abbreviations,and Definitions.2.2.22.3Non-Government DocumentsIPC T-50Terms and Definitions for Interconnecting and PackagingElectronic Circuits.IPC-TM-650Test Method 2.6.9.1, Test to Determine Sensitivity of ElectronicAssemblies to Ultrasonic Energy.IPC-TM-650Test Method 2.6.9.2, Test to Determine Sensitivity of ElectronicComponents to Ultrasonic Energy.Order of Precedence2.3.1Where conflicts exist between this standard and applicable Federal and Stateregulations, the applicable regulations take precedence.2.3.2Where conflicts exist between this standard and applicable Agency directives, theapplicable Agency directives take precedence.2.3.3Where conflicts exist between this standard and standards that contain provisions thatconstitute requirements of this standard as cited in the text, this standard takes precedence,except in the case where those standards are to Federal or State regulations.10 of 53
NASA-STD-8739.1B2.3.4Where conflicts exist between a requirement that is meant to be applied generallyacross all technical disciplines and a requirement that is applicable to a specific technicaldiscipline, the requirement that is applicable to a specific technical discipline takes precedence.2.3.5Clarification and further resolution of conflicts is resolved by the responsible SMATechnical Authority.3.ACRONYMS AND DEFINITIONS3.1AcronymsASTMAmerican Society for Testing and MaterialsCOBChip on BoardCTECoefficient of Thermal ExpansionCVDChemical Vapor DepositionDIPDual-In-Line PackageEEEElectrical, Electronic, and ElectromechanicalESDElectrostatic DischargeFODForeign Object DebrisNASANational Aeronautics and Space AdministrationNASA-STDNASA StandardNPDNASA Policy DirectiveNPRNASA Procedural RequirementsOSMAOffice of Safety and Mission AssurancePCBPrinted Circuit BoardPRTPlatinum Resistance ThermometerPTHPlated Through HolePWAPrinted Wiring AssemblyQAQuality AssuranceROSEResistivity of Solvent Extract11 of 53
NASA-STD-8739.1B3.2SMTSurface Mount TechnologyTMTest MethodTOTransistor OutlineUVUltravioletDefinitionsNote: Definitions for SMA terms are found in NASA-HDBK-8709.22, Safety and MissionAssurance Acronyms, Abbreviations, and Definitions. Terms unique to this NASA-STDare listed below.Accelerator. A compounding material used in small amounts to increase the cure rateor to change the conditions of the reaction (e.g. cause it to occur at a lowertemperature). Accelerators get consumed by the process.Area array package. A package with an X-Y grid interconnect pattern on the undersurface (i.e., ball grid array, column grid array, land grid array, pin grid array).Batch. That quantity of material that was subjected to unit chemical processing orphysical mixing, or both, designed to produce a product of substantially uniformcharacteristics.Blister. Undesirable rounded elevation of the surface of a polymer, whose boundariesmay be more or less sharply defined.Bonding. Method for joining surfaces of parts or materials using a polymer.Catalyst. A substance that changes the rate of a chemical reaction without undergoingpermanent change in its composition or getting consumed by the process.Coefficient of thermal expansion (CTE). The measure of the fractional change indimension per unit change in temperature.Conductor. A lead or wire, solid, stranded, or printed wiring path serving as anelectrical connection.Conformal coating. A thin electrically nonconductive protective coating thatconforms to the contours of the printed wiring assembly (PWA) or electronicassemblies.Conformal coating test specimen. See Specimen, Conformal Coating Test.Contaminant. An impurity or foreign substance present in a material that affects oneor more properties of the material. A contaminant may be either ionic or nonionic. Anionic, or polar, compound forms free ions when dissolved in water, making the water a12 of 53
NASA-STD-8739.1Bmore conductive path. A nonionic substance does not form free ions, nor increase thewater’s conductivity. Ionic contaminants are usually processing residue such as fluxactivators, fingerprints, and etching or plating salts.Cure. A chemical reaction that hardens and changes the physical properties of amaterial(s).Deterioration. (as in the context of the condition of stored polymer materials) Achange in the material that can be observed prior to its use, or during use, that indicatesit no longer meets its performance requirements. Deteriorated in this context includesdegraded or separated.Dielectric. A material with a high resistance to the flow of electrical current, andwhich is capable of being polarized by an electrical field.Diluent. Any material that reduces the concentration of the fundamental resin; usuallya liquid added to the resin to afford lower viscosity.Encapsulation. The complete encasement of a component or module in a resin. Otherterms used in the electronics industry to indicate encapsulation are “potting,”“embedment,” and “molding.”Filler. A material added to polymers in order to reduce cost or modify physicalproperties.Fillet. A smooth, generally concave, buildup of material between two surfaces (e.g., abuildup of conformal coating material between a part and the printed circuit board(PCB)).Flatpack. A part with two straight rows of leads (normally on 1.27mm (0.050 inch)centers) that are parallel to the part body.Flux. A chemically-active compound that, when heated, removes minor surfaceoxidation, minimizes oxidation of the basis metal, and promotes the formation of anintermetallic layer between solder and basis metal.Gelling. Formation of a semi-solid system consisting of a network of solid aggregatesin which liquid is held; the initial gel-like solid phase that develops during theformation of a resin from a liquid.Glass transition. A reversible change in an amorphous polymer or in amorphousregions of a partially crystalline polymer from (or to) a viscous or rubbery condition to(or from) a hard and relatively brittle one. Not only do hardness and brittlenessundergo rapid changes in this temperature region, but other properties, such asdissipation factor, thermal expansibility, and specific heat, also change rapidly.Glass transition temperature (Tg). The approximate midpoint of the temperaturerange over which glass transition takes place. The observed transition temperature can13 of 53
NASA-STD-8739.1Bvary significantly depending on the specific property chosen for observation and ondetails of the experimental technique (for example, rate of heating, frequency).Therefore, the observed Tg should be considered only an estimate.High voltage. An application voltage that will support coronal discharge or thedevelopment of charged plasma due to the environment’s atmospheric conditions (i.e.elemental gasses or vacuum, and pressure) unless mitigations such as rounded surfacesat interconnections and insulative layers of staking or conformal coating are applied.Keep out areas. Surfaces on PWAs that must remain free of polymeric materialfollowing bonding, staking, conformal coating or encapsulating processes to enablesubsequent system assembly processes and system performance requirements (e.g.fastener or electrical ground interfaces). Masking is used to prevent polymeric materialfrom coming into contact or covering keep out areas during polymeric applications.Lifting. Any separation of conformal coating from the PWA.Manufacturing documentation. Instructions, drawings, specifications, work orders,travelers and all other documents provided to manufacturing operators and inspectorsdefining the intended design, manufacturing methods, and quality controls.Mission hardware. Items made of a material substance that make up, or are integratedinto, spacecraft, launch vehicles, or aircraft used to execute a NASA mission. SourceNPR 8735.2.Mix record. A record of the procedure followed for mixing the polymeric compounds.Module. A separable unit in a packaging scheme.Non-common conductors. Conductive surfaces that are not attached to the sameelectric node.Part lead. The conductor attached to an electrical, electronic or electromechanical(EEE) part.Peeling. The separation of conformal coating from the PWA, usually due to improperpreparation or abrasion. Peeling is distinguished from lifting in that the layer ofconformal coating is not continuous.Polymer. A compound of high molecular weight that is derived from either the joiningtogether of many small similar or dissimilar organic molecules or by the condensationof many small molecules by the elimination of water, alcohol, or a solvent.Pot life (aka. Working life). The length of time a material, substance, or product is inuse while it meets all applicable requirements and remains suitable for its intended use(IPC T-50).14 of 53
NASA-STD-8739.1BPrinted circuit board (PCB). A composite structure incorporating point-to-pointinterconnections for electronic circuits. It may include embedded components. (Thisincludes single-sided, double-sided, multi-layer, rigid, rigid-flex, and flex constructions(IPC T-50)).Printed wiring assembly (PWA). The PWA consists of the PCB, components, andassociated hardware and materials.Resin. Generally, any synthetic organic material produced by polymerization.Solvent. A non-reactive liquid substance that is capable of dissolving anothersubstance (IPC T-50). Other terms used are: chemistry, cleaner (of any type), cleaningsolution, cleaning solvent, detergent, saponifier, etc.Specimen, conformal coating test. A spare PCB or similar substrate that is coatedwith the same material and process as used for the mission hardware that is used forevaluation of the quality of the conformal coating thickness.Specimen, materials mix test. A test sample that meets the requirements in ASTMD2240, that is used to evaluate polymer mix quality using a hardness test. The sampleof cured material is at least 6mm (0.24 in) thick by 24 mm (0.96 in) in diameter.Squeeze-out. The resin and/or reinforcement that is visible at the edges of a bond.Staking. The process of bonding and securing components or parts to PCBs andelectronic assemblies by means of an adhesive material, with the intention to provideadditional mechanical support.Staking material. An electrically nonconductive adhesive material used for additionalsupport.Stress relief. The formed portion of a conductor whose geometry minimizes stress onthe mechanically clamped terminations.Substrate. That surface upon which an adhesive is spread for any purpose, such ascoating; a broader term than “adherent.”Test specimen. See Specimen.Traceability code. The code uniquely identifying the production lot by themanufacturer, equivalent to batch code, lot code, or date code.Transmissivity. The fractional quantity of incident radiation transmitted by matter.Viscosity. A measure of the resistance of a material to flow under stress.15 of 53
NASA-STD-8739.1B4.GENERAL REQUIREMENTS4.1General4.1.1When there is a conflict between the requirements of NASA-STD-8739.6 and thoseherein, the requirements in NASA-STD-8739.6 shall take precedence.4.1.2A program shall be established to assure continuing process capability.4.1.3Controls shall be developed for process parameters and equipment settings thatinfluence product compliance with critical performance and quality requirements.Electrostatic Discharge Control Requirements4.24.2.1When Electrostatic Discharge (ESD) control is required during workmanshipoperations defined herein, the ESD control requirements in NASA-STD-8739.6 shall apply.4.3Selection and Approval Requirements for Polymeric Materials4.3.1The polymeric material(s) shall be:a. Workable using the processes described herein such that the intended performance of thepolymer is realized in the application. This includes continuous and consistent coverage forconformal coating, material volume control for staking material, and bond line control forbonding materials.b. Suitable to the complexity of the assembly and the mission lifetime defined by theproject.c. Compatible with, and adheres to, the intended substrates (e.g. the PCB, electrical,electronic, and electromechanical (EEE) parts, jumper wires, cable ties, metal brackets,enclosure surfaces).d. Stable with respect to moisture exposure, the project’s test, operating, storagetemperature range, and vacuum conditions (including thermal-vacuum). Otherenvironmental conditions may be applicable such as ionizing radiation and UV radiation.e. Noncorrosive to the electronic assembly for which it is selected.f. Curable under processing conditions compatible with the assembly on which it is located.g. Selected to enable the finished assembly to meet all mechanical, thermal, electrical, andoptical requirements associated with test and mission use, with consideration given to thefollowing characteristic
NASA-STD-8739.1B 10 of 53 NPR 8705.4 Risk Classification for NASA Payloads. NPR 8735.2 Hardware Quality Assurance Program Requirements for Programs and Projects NASA-STD-8739.6 Implementation Requirements for NASA Workmanship Standards. 2.1.2 Non-Government Documents ASTM D2240 Standard Test Method for Rubber Property - Durometer Hardness.
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NASA-STD-8739.1 NASA-STD-8739.2 NASA-STD-8739.3 NASA-STD-8739.4 NASA-STD-8739.5 IPC J-STD-001xS ESD Rules for Registering for Training An initial class is required. Typically lasts one week. If the prior training was completed within 27 months, then a shortened retraining
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MTL-STD-1629A 3. DEFINITIONS 3.1 Terms. The definitions of terms used herein are in accordance with the definitions in MIL-STD-280, MIL-STD-470, MIL-STD-721, MIL-sTD-780, MIL-STD-785, MIL-STD-882, and MIL-sTD-1388, with the exception and addition of the following: 3.1.1 Contractor. A private sector enterprise engaged to
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