1.2 Documentation Hierarchy This st

1.2 Documentation Hierarchy This standard identifies the generic physical design principles involved in thecreation of land patterns for surface mount components, and is supplemented by a shareware IPC-7351 Land Pattern viewer that provides, through the use of a graphical user interface, the individual component dimensions and corresponding land pattern recommendations based upon families of components. The IPC-7351 Land Pattern Viewer is provided on CD-ROM as part of the IPC-7351.Updates to land pattern dimensions, including patterns for new component families, can be found on the IPC website(www.ipc.org) under ‘‘PCB Tools and Calculators.’’ See Appendix C for more information on the IPC-7351 Land1.2.1 Component and Land Pattern Family StructureThe IPC-7351 provides the following number designationwithin the IPC-7350 series for each major family of surfacemount components to indicate similarities in solder jointengineering goals:IPC-7352 – Discrete ComponentsIPC-7353 – Gullwing Leaded Components, Two SidesIPC-7354 – J-Leaded Components, Two SidesIPC-7355 – Gullwing Leaded Components, Four SidesIPC-7356 – J-Leaded Components, Four SidesIPC-7357 – Post (DIP) Leads, Two SidesIPC-7358 – Area Array Components (BGA, FBGA, CGA)IPC-7359 – No Lead Components (QFN, SON, LCC)1.3 Performance Classification Three general endproductclasses have been established to reflect progressiveincreases in sophistication, functional performance requirementsand testing/inspection frequency. It should be recognizedthat there may be an overlap of equipment betweenclasses.The end product user has the responsibility for determiningthe ‘‘Use Category’’ or ‘‘Class’’ to which the productbelongs. The contract between user and supplier shallspecify the ‘‘Class’’ required and indicate any exceptions oradditional requirements to the parameters, where appropriate.Class 1 General Electronic Products – Includes consumerproducts, some computer and computer peripherals, andhardware suitable for applications where the major requirementis function of the completed assembly.Class 2 Dedicated Service Electronic – Products Includescommunications equipment, sophisticated businessmachines, and instruments where high performance andextended life is required, and for which uninterrupted serviceis desired but not mandatory. Typically the end-useenvironment would not cause failures.Class 3 High Reliability Electronic Products – Includesall equipment where continued performance orperformance-on-demand is mandatory. Equipment downtimecannot be tolerated, end-use environment may beuncommonly harsh, and the equipment must function whenrequired, such as life support systems and other criticalsystems.The IPC-7351 land patterns have the capability of accommodatingall three performance classifications.