电信产品和PCB设备一般需求

Generic Physical Design Requirements for Telecommunications Products and EquipmentTR-TSY-000078 Issue 2, December 19881.0 IntroductionThis specification covers the requirements for physical construction of products intended for a telecommunications environment. Some of the content is repeated several times, once for the designer, once for the manufacturer. I have abstracted only those items that are outside standard Astec practices or where Astec standards are known to be different. I have left out some areas, such as backplane requirements on the basis that we are unlikely to need them.I have left in headings under relevant areas so that the reader can tell that specific requirements exist, although they may already have been described elsewhere or be irrelevant to our type of product.2.0 Requirements for All Products2.1 GeneralThis section basically says that the product shall be designed according tospecification, meets general expectations in terms of construction and marking andshall be safe and undamaged. It also requires that, where practical, all parts shall be marked to allow traceability. Parts with special features such as moving parts should be implemented such that they are easy to use.2.2 Electrical and Mechanical IntegrityThis section requires that the electrical and mechanical functions of any parts andassemblies used shall survive normal manufacturing processes. It also requires thatthe reliability of any new technology shall be demonstrated, typically usingaccelerated life testing.2.3 Administration of RequirementsThis requires that the manufacturer makes sure that any part used meets therequirements of this spec. Items can be defined as critical or non-critical. All criticalitems have to meet the spec. A power supply would be a critical item.Inspection and auditing must be used to maintain this. Supplier quality data can beused provided regular audits are carried out to verify the supplier is following therequirements.3.0 Materials and Finishes Requirements3.1 GeneralThis section requires that materials used should meet industry standards and thatfragile material or materials subject to ageing shall not be used without carefulconsideration.3.2 Materials3.2.1 Fire Resistance RequirementsThis section states that all materials used shall meet the flammabilityrequirements referenced in Belcore TR-EOP-000063, section 4.3.3.2.2 Fire Risk AnalysisThis section repeats part of TR-EOP-000063. This requires that all polymermaterials used in any assembly shall be identified by reference code (e.g.circuit id) and its material and flammability characteristics are identified. Thisis a report that is not usual in Astec.3.2.3 FluxesThis simply references the requirement for fluxes in section 13.1 of thedocument.3.2.4 Conductor and Protective FinishesThis section requires that silver or silver-based materials must not be usedwhere silver migration could cause functional failure. It also requires than tin,zinc and cadmium must not be used where whisker growth could causefailure. It does allow for the use of tin-plating containing less than 2% leadprovided that it is reflowed or annealed.3.2.5 SiliconesSilicones are NOT permitted unless any contact surfaces that might suffer fromsilicone migration are protected. This includes silicones used in some mould releases used in the manufacture of plastic parts.3.3 Finishes – Organic, Inorganic and MachineThis section provides detail requirements for various finishes. Zinc alloys must beplated, all finishes must be undamaged, plating must not be applied over solder andany plating must not expose the base metal. Detail requirements for thickness andcomposition are elsewhere in the spec.4.0 Separable Connector Requirements4.1 GeneralThis section applies to all separable connectors. There are detail requirements fordifferent types of connector later in the spec. It also defines contact resistance as the resistance at the separable surface, specifically excluding the bulk resistance of theconnector.4.1.1 Design ConsiderationsThis section has detail requirements for connectors. Both surfaces of aconnector must be the same metal; connectors should use a combination ofbase metal and plating to secure springiness as well as good contactresistance.Contact resistance must be less than 20mΩ for noble metal connectors andless than 30mΩfor base metal connectors.Connectors must be designed so that mounting stresses are NOT transferred to solder joints as shear or tensile stress. They should preferably be designed with alternate mechanical fixings.Connectors must be designed to accommodate WORST-CASE tolerancestackup.Contact normal force must be greater than 100gm over all temperature andhumidity conditions.Worst case temperatures must be below the distortion temperature of anypolymeric materials used.4.1.2 Noble MetallisationsThis section specifies different standards for noble metal plating. Refer to thespecification for the requirements.It also requires that the noble metal thickness is recorded and the information kept for at least one year.4.1.3 Base MetallisationsBase metal connector systems must ensure GAS TIGHT HERMETICITY atthe contact surfaces. This has to be verified using a Mil. Std. Test or othersuitable industrial atmosphere test.4.1.4 LubricationALL separable connectors must be lubricated using a suitable lubricant. Thissection provides a table of recommended lubricants for various contact types.The only exceptions are “cutting type” connectors (e.g. screws with starwashers) or certain grades of gold plated connectors.4.1.5 PerformanceThis section defines acceptance tests for connectors. Refer to specificationfor details.4.2 Two-part and PWB Edge Card Connectors4.2.1 DesignThis provides requirements for connector design such as radiusing orchamfering, roughness specifications etc. Refer to spec.4.2.2 PolarisationThis requires that connectors be polarised and keyed to prevent wronginsertions OR that all connectors in a system use a common connectionscheme.4.2.3 DurabilityNoble metal connectors must have a life of at least 200 insertions. Basemetal connectors must be tested to establish life and used only in conditionswhere the connector life meets the specified life for the application.Acceptance criteria are defined.4.2.4 Insertion and Removal ForcesIn general, maximum insertion or removal force must be less than 32lb.There are detail requirements for latch type insertion methods and single pintype connectors.4.3 Component Sockets4.3.1 DurabilityAll sockets must have their useful life established by testing.4.3.2 UsageSockets must not be used when the life established by testing is shorter thanthe design life of the equipment.4.4 Zero Insertion Force ConnectorsZIF connectors must be designed for no contact engagement during insertion.4.5 Coaxial Connectors4.6 Crimped ConnectorsSee Section 5.1.44.7 Optical Connectors5.0 Wire and Cable Requirements5.1 Electrical Wire and Cable5.1.1 MaterialsWires and cables must be fire resistant, compatible with the applicationenvironmental stress and permanently marked.5.1.2 PerformanceThis section refers to another spec. for 20,22 and 24AWG annealed copperwire. This section covers all other wires. This covers elongation, breakingstrain, insulation (must exceed the performance of PVC), cut-throughresistance ratio and stripping force for insulation.Power and interface leads shall be separated. Insulation between power andother leads shall be capable of withstanding 600V AC for one minute.5.1.3 Wire and Cable PreparationThis section has recommendations on preparations such as machines shouldbe used as much as possible.No wires with nicked or damaged conductors or insulators can be used.Substitution of colours is only allowed if they cannot result in incorrectidentification of a coded cable.5.1.4 Cable and Wire TerminationThis section defines required crimp strength. Refer to spec. for breakingstrain and torque requirements.5.2 Optical Fiber and Optical Fiber Cables6.0 Printed Wiring Board Requirements6.1 GeneralAll PCB’s are covered not just glass reinforced types. Laminate refers to anysubstrate on which circuitry is mounted.6.1.16.1.26.1.3 Materials6.1.3.1 LaminatesAll laminates are required to meet the referenced flammabilityrequirements.6.1.3.2 Solder MasksThis states that the solder mask, in combination with the laminate,shall meet the flammability limits. The solder mask must be atmaximum thickness tolerance for this spec. The acceptance criteriaare in the later part of this spec.6.1.3.3 Legend InksRefers to acceptance criteria later in the spec.6.1.3.4 Repair PolymersRefers to acceptance criteria later in the spec.6.1.3.5 Conductor Materials and FinishesSilver shall not be used as a conductor or contact finish unlessacceptable reliability data can be supplied.Tin shall not be used as a conductor or contact finish unlessreflowed. Tin plating with minimum 2% lead is acceptable withoutreflow.6.1.4 Design6.1.4.1 DimensioningAny measurements that affect interfacing must be based on worstcase tolerances.6.1.4.2 Keying/PolarisingA PWB with noble metal contact fingers must be keyed and polarisedto prevent damage due to wrong insertion.6.1.4.3 Interlayer ConnectionsElectrical interconnections between surfaces on double-sided boardsmust be made with plated through holes. Clinched wires or rivets,soldered at assembly can be used to make a small number ofinterconnects on non-plated-through hole boards.Tooling and mechanical support holes must not be used as functionalplated through holes.PTH must be separated by a minimum of 0.050 inch of undisturbedlaminate.6.1.4.4 Contact Fingers6.1.4.5 Copper PlatingPTH holes must have a minimum wall thickness of 0.0008 inch ofcopper. For multilayer or thick PCB’s this is considered inadequateand plating should be thicker.6.1.4.6 Solder Finishes6.1.4.7 WarpageWarpage limits must be specified. The common industry standard of0.010 inch/inch is considered unsatisfactory for SMD. SMD PCB’sshould use a limit of 0.0075 inch/inch.6.1.4.8 Protective CoatingsEither a solder mask or conformal coating is required6.1.5 Manufacturing6.1.5.1 Conductor Widths and SpacingConductor widths have to be at least 70% of the specificationnominal dimension. There are also restrictions on the size ofscratches & pinholes etc.6.1.5.2 Conductor AdhesionPCBs must comply with the Bond Strength (Unsupported Holes)requirement of MIL-P-55110D.6.1.5.3 Plated-Through HolesThe requirements here are very similar to Astec standards.6.1.5.4 Noble Metal PWB Contact Fingers6.1.5.5 Solder Masks6.1.5.6 Insulation ResistancePCBs must have a minimum insulation resistance of 104 MΩ prior tomasking.6.1.5.7 Solvent Extract Conductivity (SEC)This section describes limits for surface contamination, before andafter solder masking.6.1.5.8 Solder Coating6.1.5.9 Mechanical Damage6.1.5.10 Laminate and Processing Defects6.1.5.11 Electrical6.1.5.12 RepairsThis section defines the type and number of repairs that areacceptable on a damaged PCB in production.6.1.5.13 ModificationsThis section defines the type and number of repairs that areacceptable on a production PCB, such as cut and strap.6.2 Multilayer PCBs – General RequirementsThis section is very similar to the section for double-sided PCB’s, with extensions for the additional layers.6.2.1 Design6.2.1.1 Dimensioning6.2.1.2 Interlayer Connections6.2.1.3 Construction6.2.2 Manufacturing6.2.2.1 Construction6.2.2.2 Conductor Widths and Spacings6.2.2.3 Interlayer Separation6.2.2.4 Plated Through Holes6.2.2.5 Plating6.2.2.6 Insulation Resistance6.2.2.7 Solvent Extract Conductivity6.2.2.8 Laminate and Processing Defects6.2.2.9 Electrical Requirements6.2.2.10 Repairs6.2.2.11 Modifications6.3 Printed Wiring Boards For Surface MountingThese are categorised into wavesolder and reflow type boards.6.3.1 General Requirements6.3.1.1 MaterialsThis section emphasises that FR4 is not dimensionally stable enoughfor large SMD parts. The rest of the section states that materialsused should be able to withstand the related manufacturing heatingstresses.6.3.1.2 DesignThis section identifies pad design limitations. These are in line withAstec design guidelines. The difference is that these arerequirements, not simply guidelines.6.3.1.3 PCB’s for Adhesive-and-Wavesolder SolderingProcesses6.3.1.4 PWBs for Reflow Surface Mount SolderingProcesses6.4 Printed Wiring Boards for Backpanels7.0 PWB Assembly Requirements7.1 GeneralThese requirements apply to ALL types of PCB.7.1.1 Materials7.1.1.1 Conformal Coatings7.1.1.2 Fluxes7.1.2 Assembly Design7.1.2.1 GeneralThis requires that there should be NO exposed copper on completedassemblies UNLESS there is evidence that corrosion does not causelong term reliability problems. It also points out that design shouldmake allowance for dust, vibration etc.7.1.2.2 ComponentsThis section says that only qualified components should be used.Where practical they should be preferred values only.All insulators shall have a minimum withstand of 500V AC.7.1.2.3 LayoutThis section describes good layout practice.7.1.2.4 Separable Connections7.1.2.5 Conformal CoatingsThis section requires that, if there is no solder mask, then conformalcoating must be used. I.e. – no bare PCB allowed.7.1.3 Manufacturing7.1.3.1 GeneralThis section describes good manufacturing practice.7.1.3.2 Lead FormsThis section requires that any lead forming NOT done by the vendorof the component shall have a minimum of 0.04” clearance betweenthe point of emergence from the component and the bend.7.1.3.3 ClearancesThis section basically says that designed clearances should bemaintained in the manufacturing process.7.1.3.4 Solderability7.1.3.5 SolderingThis section describes good soldering practice.7.1.3.6 Warpage7.1.3.7 Solder Masks7.1.3.8 Conformal Coatings7.1.3.9 Insulation Resistance7.1.3.10 Solvent Extract Conductivity7.1.3.11 LubricationThis section states that ALL separable connections shall belubricated, according to requirements stated elsewhere in the spec.Note that Astec does NOT do this…..7.1.3.12 Mechanical Damage and Defects7.1.3.13 Repair of PWB AssembliesThis section describes good repair practice.7.1.4 Modifications to PWB Assemblies7.1.4.1 GeneralThis section describes, in detail, acceptable rework methods. Theseare more demanding than Astec workmanship requirements.7.1.4.2 Modification Wiring7.1.4.3 PWB Modifications7.1.4.4 Component Modifications7.2 PWB Assemblies – Through-Hole Mounted ComponentsThis section describes basic good practices.7.2.1 Assembly Design7.2.1.1 Components7.2.2 Manufacturing7.2.2.1 Soldering7.3 PWB Assemblies – Surface Mounted ComponentsThis section describes basic good practices7.3.1 Materials7.3.1.1 Solder Joint Metallurgy7.3.1.2 Solder Creams and Fluxes7.3.1.3 Solder Masks7.3.1.4 Adhesives7.3.2 Assembly Design7.3.2.1.1 General7.3.2.1.2 Components7.3.2.1.3 Thermal Considerations7.3.2.1.4 Lead Forms7.3.2.1.5 Termination Metallisations7.3.3 Reliability7.3.4 Manufacturing7.3.4.1 Lead Forms7.3.4.2 Soldering7.3.4.3 Warpage7.3.4.4 Repairs7.3.4.5 Electrical Requirements7.3.4.6 Modifications7.4 Backpanel PWB Assemblies8.0 Equipment Sub-Assembly & Assembly Requirements8.1 General8.1.1 Materials, Pieceparts and Sub-Assemblies8.1.2 Sub-Assemblies and Assemblies8.1.3 DesignThis section requires that design rules consider dust collection on equipment.It also requires that any fan-cooled equipment be fitted with a filter that canbe replaced.All screw down power connections MUST be fitted with a lock washer.8.2 Manufacturing8.2.1 Connections8.2.1.1 GeneralThis section describes good connection practices.8.2.1.2 Soldered Connections8.2.1.3 Solderless Wrapped Connections8.2.2 Wiring and CablingThis section describes good wiring practices.8.3 Equipment Frame ModificationsThis section describes how equipment should be modified or re-worked, describinggood practices. Key requirement is that any modified product be clearly identified byraising revision or issue level to avoid confusion with any unmodified product.8.4 Performance8.4.1 GeneralThis requires that equipment be capable of reliable operation for the designlife, in the specified environmental conditions, including airbornecontaminants.8.4.2 Operation Under Environmental ExtremesThis emphasises that equipment must be able to operate reliably at extremecorners of the environmental specification without exceeding the temperaturederating limits.9.0 Electrostatic Discharge9.1 GeneralThis section describes the problems of ESD damage and specifies requirements fordesign and test for ESD9.2 Susceptibility9.3 ESD Resistance9.3.1 Equipment Assemblies9.3.2 Non-Installed Circuit PacksThis requires that uninstalled subassemblies be able to survive up to 15kVdischarges. The discharge model is 100pF and 1500Ω.9.4 Circuit Pack ESD Test Methods and Requirements9.5 Electrostatic Discharge Warning Label RequirementsThis section recommends that any sub-assemblies containing static sensitive parts be labelled and provides wording for the labels.10.0 Product Identification & Markings RequirementsThis section describes good marking practices. It specifically requires that all markings shall be visible at end of life for the equipment. For Telco equipment this may be as long as 10 years. It also strongly recommends bar coding.11.0 Package RequirementsThis section requires proper packaging and references TR-TSY-000081.12.0 Repair of Customer Plug-In Units12.1 GeneralThis section describes requirements for repair of returned units. There are specificrequirements for how repaired units should be marked. There is also a requirement that any unit returned twice with no fault found has to be retained for failure analysis and the customer informed. A replacement unit should be provided.12.2 MarkingThis section describes the required format for marking repaired or up-dated units.12.3 RepairsThis section describes what may be repaired and how the repairs should be carried out. Certain faults may NOT be repaired.13.0 Qualification Test ProceduresThis section covers test and qualification procedures for many of the requirements above. Subjects covered include solder and fluxes, conformal coatings, solder resists and legend inks.14.0 Tests and MethodsThis section covers test and qualification procedures for many of the requirements above. Subjects covered include noble metal contact finishes, plated through holes on PCB’s, and PCB’s that use conformal coating.。