IPC Releases IPC-7351 Library Generation Tools for CAD Land Pattern Design

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Northbrook, Ill. — IPC — Association Connecting Electronics Industries, in conjunction with the International Electrotechnical Commission (IEC) and world electronics industry standard groups, have released library generation tools in support of the forthcoming IPC-7351, Generic Requirements for Surface Mount Design and Land Pattern Standard for CAD land pattern.

Consisting of an array of calculator and viewer tools developed between IPC and PCB Libraries, the IPC-7351 library generation tool set introduces the following for CAD libraries:

• An intelligent land pattern naming convention, which will aid in the standardization of electronic schematic symbols for engineering.
• Zero component rotations to allow CAD land patterns to be built with the same rotation for the purpose of assembly machine automation.
• Three new application-specific land pattern geometry variations that support various levels of product complexity. This three-tier CAD library system will support the following variations for each device family: 1) Least Environment Land Pattern for miniature devices where the land pattern has the least amount of solder pattern to achieve the highest component packing density; 2) Nominal Environment Land Pattern for products with a moderate level of component density and providing a more robust solder attachment; and 3) Most Environment Land Pattern for high component-density applications typical of portable/handheld products and products exposed to high shock or vibration. The solder pattern is the most robust and can be easily reworked if necessary.
• A placement courtyard excess that has been redefined to accommodate the three land pattern geometry variations.
• Clear definitions for silkscreen and polarity marking sizes, copper to ink clearances and locations.
• Land pattern origins to aid pick-and-place machine automation.
• Incorporation of enhanced mathematical algorithms for determining pad sizes and spacing within the three-tier environment. These algorithms account for fabrication, assembly and component tolerances to calculate a precise land pattern.
• New 3-D modeling for mechanical verification using maximum component outlines and maximum component height.

This array of CAD library generation tools complements the IPC-7351 concept of defining those properties crucial for global standardization and future acceptance of a "One World CAD Library," whose main objective is to achieve the highest level of "Electronic Product Development Automation." Developed in conjunction with PCB Libraries, these tools include browsers for quick location of land patterns, viewers for accessing component data for parts within a CAD library and calculators for defining exact land pattern dimensions from user supplied component and process data through the application of IPC mathematical algorithms.

The IPC-7351, like predecessor IPC-SM-782A, Surface Mount and Land Pattern Design, will provide the appropriate size, shape and tolerance of surface mount land patterns, while allowing for inspection, testing and rework of component solder joints. In addition, the new standard will provide updated surface mount design rules, addressing the complexity of land pattern design for increasingly higher density electronics. IPC-7351 is anticipated for release in May 2004.

PCB Libraries is a team of individuals within the printed circuit board (PCB) industry who seek to eliminate the waste of resources associated with the creation of CAD libraries. Land pattern calculators furnished by PCB Libraries in conjunction with IPC have been tested and are currently used by designers and engineers at companies such as Intel, Honeywell, AGFA, Panasonic, Sandia National Laboratories and Coretec. For more information, visit www.pcblibraries.com.

IPC is a trade association dedicated to the competitive excellence and financial success of its more than 2,200 member companies, which represent all facets of the electronic interconnection industry, including design, printed circuit board manufacturing and electronics assembly. For more information, visit www.ipc.org.