WIXLIB

December 1999IPC-SM-782ATable of Contents1.0SCOPE . 11.11.21.31.41.51.6Purpose.Performance Classification .Assembly Types .Presentation .Profile Tolerances.Land Pattern Determination .1122222.0APPLICABLE DOCUMENTS . 42.12.22.32.4IPC .Electronic Industries Association .Joint Industry Standards (IPC) .American Society of Mechanical Engineers.44553.0DESIGN REQUIREMENTS . 53.13.23.33.43.53.63.7Terms and Definitions. 5Component Acronyms . 7Dimensioning Systems . 7Design for Producibility . 17Environmental Constraints . 18Design Rules . 20Outer Layer Finishes . 344.0QUALITY AND RELIABILITY VALIDATION . 374.14.24.3Validation Techniques . 37Test Patterns—In-Process Validator . 38Stress Testing . 385.0TESTABILITY . 455.15.25.35.45.55.65.7Testing Considerations .Nodal Access.Full Nodal Access.Limited Nodal Access.No Nodal Access .Clam Shell Fixtures Impact.Printed Board Test Characteristics .6.0PACKAGING AND INTERCONNECTINGSTRUCTURE TYPES . 486.16.26.36.46.5General Considerations.Organic-Base Material P&IS.Non-Organic Base Materials .Supporting-Plane P&I Structures .Constraining Core P&I Structures .7.0ASSEMBLY CONSIDERATIONS FORSURFACE MOUNT TECHNOLOGY (SMT) . 537.17.2SMT Assembly Process Sequence . 53Substrate Preparation Adhesive,Solder Paste . 8.48.58.68.78.88.98.108.11Component Placement .Soldering .Cleaning .Repair/Rework .DISCRETE COMPONENTSChip ResistorsChip CapacitorsInductorsTantalum CapacitorsMetal Electrode Face (MELF) ComponentsSmall Outline Transistor (SOT) 23Small Outline Transistor (SOT) 89Small Outline Diode (SOD) 123Small Outline Transistor (SOT) 143Small Outline Transistor (SOT) 223Modified Through-Hole Component (TO) 2529.0COMPONENTS WITH GULLWING LEADS ONTWO SIDES9.19.29.3Small Outline Integrated Circuits (SOIC)Small Outline Integrated Circuits (SSOIC)Small Outline Package Integrated Circuit(SOPIC)Thin Small Outline PackageCeramic Flat Pack (CFP)9.49.510.010.110.210.310.453565757COMPONENTS WITH J LEADS ON TWO SIDESSmall Outline Integrated Circuits with(SOJ)–7.63 mm [0.300] Body SizeSmall Outline Integrated Circuits with(SOJ)–8.88 mm [0.350] Body SizeSmall Outline Integrated Circuits with(SOJ)–10.12 mm [0.400] Body SizeSmall Outline Integrated Circuits with(SOJ)–11.38 mm [0.450] Body SizeJ LeadsJ LeadsJ LeadsJ Leads11.0COMPONENTS WITH GULLWING LEADS ONFOUR SIDES11.111.211.311.4Plastic Quad Flat Pack (PQFP)Shink Quad Flat Pack (SQFP), SquareShrink Quad Flat Pack (SQFP), RectangularCeramic Quad Flat Pack (CQFP)12.0COMPONENTS WITH J LEADS ON FOUR SIDES12.112.212.3Plastic Leaded Chip Carrier (PLCC), SquarePlastic Leaded Chip Carrier (PLCC), RectangularLeadless Ceramic Chip Carrier (LCC)13.0MODIFIED DUAL-IN-LINE PIN (DIP)COMPONENTSiv

IPC-SM-782A13.114.014.114.2December 1999DIPCOMPONENTS WITH BALL GRID ARRAYCONTACTSPlastic Ball Grid Array1.27 mm Pitch Rectangular PBGA JEDECMS-028FiguresFigure 4–1Component temperature limits . 37Figure 4–2General description of process validationcontact pattern and interconnect. 39Figure 4–3Photo image of IPC-A-49 test board forprimary side. 39Figure 4–4Flat ribbon, ‘‘L,’’ and gullwing lead jointdescription . 40Figure 4–5Round or flattened (coined) lead jointdescription . 40Figure 1–1Electrical assembly types. 3Figure 4–6‘‘J’’ lead joint description . 41Figure 3–1Examples of typical package styles andpackage descriptive designators. 9Figure 4–7Rectangular or square end components. 41Figure 4–8Figure 3–2Lead-form (or terminal-shape) examples. 10Cylindrical end cap terminations—jointillustration . 42Figure 3–3Profile tolerancing examples . 11Figure 4–9Bottom only terminations. 42Figure 3–4Example of C1206 capacitor dimensioningfor optimum solder fillet conditions . 12Figure 4–10Leadless chip carriers with castellatedterminations—joint description . 43Figure 3–5Profile dimensioning of a gullwingleaded SOIC. 13Figure 4–11Butt joint description. 43Figure 4–12Thermal cycle excursion rate . 44Figure 3–6Pitch for multiple-leaded components. 15Figure 5–1Test via grid concepts . 47Figure 3–7Simplified electronic developmentorganization . 20Figure 5–2General relationship between test contactsize and test probe misses . 49Figure 3–8Recommended minimum land-to-landclearances . 21Figure 5–3Test probe feature distance fromcomponent. 50Figure 3–9Component orientation for wave solderapplications. 21Figure 7–1Typical process flow for undersideattachment type 2c (simple) surface mounttechnology . 54Figure 7–2Typical process flow for full surfacemount type 1b and 2b surface mounttechnology . 54Figure 7–3Typical process flow for mixed technologytype 2c (complex) surface mounttechnology . 55Figure 3–10Alignment of similar components . 22Figure 3–11Local/global fiducials . 23Figure 3–12Panel/global fiducials. 23Figure 3–13Fiducial types for vision systems . 24Figure 3–14Fiducial clearance requirements . 24Figure 3–15Fiducial locations on a printed circuit board . 25Figure 3–16Packaging and geometries. 25Figure 7–4In-line placement equipment . 55Figure 3–17Surface mount conductor widths/clearances vs. routing grids . 26Figure 7–5Simultaneous placement equipment . 55Figure 7–6Sequential placement equipment. 56Figure 3–18Section view of multilayer board withvias on 1.0 mm [0.040 in] centers . 26Figure 7–7Sequential/Simultaneous placementequipment. 56Figure 3–19Narrowed conductor . 27Figure 3–20Conductor routing. 27Figure 3–21Surface routing geometries . 28Table 3–1Terminal Position Prefixes. 8Figure 3–22Conductor routing capability test pattern . 28Table 3–2Package-Outline-Style Codes . 8Figure 3–23Routing channels under SOIC landpattern with 28 pins. 29Table 3–3Lead-Form (or Terminal-Shape) Suffixes . 11Table 3–4Tolerance Analysis Elements for Chip DevicesFigure 3–24Land pattern to via relationships. 29Table 3–5RLP Numbers. 17Figure 3–25Examples of via positioning concepts. 30Table 3–6Figure 3–26Vias under components . 30Worst-Case Environments and AppropriateEquivalent Accelerated Testing . 19Figure 3–27Conductor characteristics. 31Table 3–7Component Stand Off . 23Figure 3–28Examples of modified landscapes . 32Table 3–8Figure 3–29Typical copper glass laminate panel. 33Typical Values to Be Added or Subtracted toNominal Production to Achieve DesiredNominal Conductor Width . 31Figure 3–30Conductor clearance for V-groove scoring . 34Table 3–9Conductor Width Tolerances . 32Figure 3–31Breakaway (routed pattern). 35Table 6–1Figure 3–32Routed slots . 35Packaging and Interconnecting StructureComparison . 51Figure 3–33Gang solder mask window. 36Table 6–2P & I Structure Selection Considerations . 52Pocket solder mask windows. 36Table 6–3P & I Structure Material Properties . 52Figure 3–34vTables

December 1999IPC-SM-782AThis Page Intentionally Left Blankvi

December 1999IPC-SM-782ASurface Mount Design and Land Pattern Standard1.0 SCOPECLASS 1This document provides information on land pattern geometries used for the surface attachment of electronic components. The intent of the information presented herein is toprovide the appropriate size, shape and tolerance of surfacemount land patterns to insure sufficient area for the appropriate solder fillet, and also to allow for inspection andtesting of those solder joints.Includes consumer products, some computer and computerperipherals, as well as general military hardware suitablefor applications where cosmetic imperfections are notimportant and the major requirement is function of thecompleted printed board or printed board assembly.1.1 Purpose Although, in many instances, the land pattern geometries can be slightly different based on the typeof soldering used to attach the electronic part, whereverpossible, land patterns are defined in such a manner thatthey are transparent to the attachment process being used.Designers should be able to use the information containedherein to establish standard configurations not only formanual designs but also for computer aided design systems. Whether parts are mounted on one or both sides ofthe board, subjected to wave, reflow, or other type of soldering, the land pattern and part dimensions should be optimized to insure proper solder joint and inspection criteria.Although patterns are standardized, since they are a part ofthe printed board circuitry geometry, they are subject to theproducibility levels and tolerances associated with plating,etching, or other conditions. The producibility aspects alsopertain to the use of solder mask and the registrationrequired between the solder mask and the conductor patterns. (See paragraph 1.2.2).1.2 Performance Classification Three general endproduct classes have been established in associated IPCstandards and specifications to reflect progressive increasesin sophistication, functional performance requirements andtesting/inspection frequency. It should be recognized thatthere may be an overlap of equipment between classes.Design requirements determine class. Class definitions areuseful for identifying degrees of precision needed to meetdesign/performance requirements of packaging and interconnecting structures, and establish communication mediabetween design and manufacture and disciplines.The printed board user has the responsibility to determinethe class to which his product belongs. The contract shallspecify the performance class required and indicate anyexceptions to specific parameters, where appropriate. In theevent of conflict between the design requirements and theclasses defined herein, the former shall take precedenceand be reflected in the master drawing.These classes are:CLASS 2General Electronic ProductsDedicated Service Electronic ProductsIncludes communications equipment, sophisticated business machines, instruments and military equipment wherehigh performance and extended life is required, and forwhich uninterrupted service is desired but is not critical.Certain cosmetic imperfections are allowed.CLASS 3High Reliability Electronic ProductsIncludes the equipment for commercial and military products where continued performance or performance ondemand is critical. Equipment downtime cannot be tolerated, and functionality is required for such applications aslife support items, or missile systems. Printed boards andprinted board assemblies in this class are suitable for applications where high levels of assurance are required andservice is essential.The land patterns in this standard have the capability ofaccommodating all three performance classifications.1.2.1 End-Use Applications In addition to the three performance classifications, the Surface Mount Council hasestablished end use applications for electronic products.These are:1.Consumer products including games, toys, audio andvideo electronics. In general, convenient size andmaximum functionality are important but product costis extremely important.2.General purpose computers, as used in businesses andpersonal applications. Compared to consumer products, customers expect longer life and more consistentservice.3.Telecom products including telephone, switching systems, PBXs, and exchanges. These products are usedin applications expecting long service life and enduring relatively harsh environments.4.Commercial aircraft requiring small size, light weightand high reliability.5.Industrial products and passenger compartment automotive applications. Size and function is a byword ofthese products. Cost is very important, provided thatreducing product cost doesn’t forfeit the highestachievable product quality, performance, and function.1

IPC-SM-782A6.December 1999High performance products consisting of ground-basedand shipbound military products, high speed and highcapacity computers, critical process controllers, andlife supporting medical systems. Quality, reliabilityand performance are paramount, closely followed bysize and function. Cost is optimized based on theserequirements but is less important.7.Space products include all of the products above whichare built to meet harsh outer space conditions. Thisimplies high quality and performance over a widerange of environmental and physical extremes.8.Military avionics products built to meet demandingmechanical and thermal changes. Size, weight, performance and reliability are paramount.9.Under the hood automotive electronics productsendure the harshest of all use environments. Theseproducts face extreme temperatures and mechanicalvariations. Adding to this is the pressure of achievingthe lowest cost and optimum manufacturability in highvolumes.1.2.2 Producibility Levels When appropriate this standard will provide three design complexity levels of features, tolerances, measurements, assembly, testing ofcompletion or verification of the manufacturing processthat reflect progressive increases in sophistication of tooling, materials or processing and, therefore progressiveincreases in fabrication cost. These levels are:Level AGeneral Design Complexity—PreferredLevel BModerate Design Complexity—StandardLevel CHigh Design Complexity—Reduced ProducibilityProducibility levels also pertain to the assembly. The threecomponent mounting complexity levels which reflect progressive increases in sophistication of tooling, assemblyand joining techniques and therefore progressive increasesin cost are:Level Asimple assembly techniques used to describethrough the board component mounting;Level Bmoderate assembly techniques used todescribe surface component mounting andLevel Ccomplex assembly techniques used todescribe intermixing of through-the-boardand surface mounting on the same assembly.Classification of complexity should not be confused withthe performance classification of end-item use described inparagraph 1.2.1.3 Assembly Types A type designation signifies furthersophistication describing whether components are mounted2on one or both sides of the packaging and interconnectingstructure. Type 1 defines an assembly that has componentsmounted on only one side; type 2 is an assembly withcomponents on both sides. Type 2 is limited to only classB or C assemblies.Figure 1–1 shows the relationship of two types of assemblies.The need to apply certain design concepts should dependon the complexity and precision required to produce a particular land pattern or P&I structure. Any design class maybe applied to any of the end-product equipment categories;therefore, a moderate complexity (Type 1B) would definecomponents mounted on one side (all surface mounted) andwhen used in a Class 2 product (dedicated service electronics) is referred to as Type 1B, Class 2. The productdescribed as a Type 1B, Class 2 might be used in any of theend-use applications; the selection of class being dependenton the requirements of the customers using the application.1.4 Presentation Dimensions and tolerances areexpressed in millimeters (mm) or microns (mn) as appropriate. When no unit of measurement is shown, the unitshall be assumed to be ‘‘mm.’’ Reference information forinch conversion is shown in the appendix.Profile tolerances are used in thedimensioning system for determining the relationshipbetween component outlines and land pattern geometries.The details are described in Section 3.3, and follow theprinciples set forth in ANSI Y14.5. All dimensions are considered maximum or minimum material condition (depending on the features being analyzed), thus the profile tolerances are unilateral (one-direction—maximum tominimum, or minimum to maximum) as opposed to bilateral (plus or minus) from a nominal characteristic.1.5 Profile Tolerances1.6 Land Pattern DeterminationThis document discusses two methods of providing information on land patterns:(1) exact details based on industry component specifications, board manufacturing and component placementaccuracy capabilities. These land patterns are registered to a specific component, and have a registeredland pattern number, see Table 3.5 and paragraph3.3.3.4.(2) equations that can be used to alter the given information to achieve a more robust solder connection, whenused in particular situations where the equipment forplacement or attachment are more or less precise thanthe assumptions made when determining the exact landpattern details.In general, a product is agood candidate for SMT if it needs to be:1.6.1 General Usage of SMT

December 19

IPC-SM-782A Includes: Amendment 1 and 2 Surface Mount Design and Land Pattern Standard ASSOCIATION CONNECTING ELECTRONICS INDUSTRIES 2215 Sanders Road, Northbrook, IL 60062-6135 Tel. 847.509.9700 Fax 847.509.9798 www.ipc.org IPC-SM-782A August 1993 A standard developed by IPC Amendment 1 October 1996 Amendment 2 April 1999