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International standards for pad requirements

Tid: 2012-05-18

The 6118 standard of the International Electrotechnical Commission IEC International Eletrotechnical Commission recognizes the need for different targets for solder fillet or pad bump conditions. This new international standard confirms two basic methods for providing information on the development of pad shapes:

1). Accurate information based on industrial component specifications, PCB copy board manufacturing and component placement accuracy capabilities. These pad shapes are limited to a specific component and have a number that identifies the shape of the pad.

2). Some equations can be used to change the given information to achieve a more robust solder joint, which is used in special cases where the accuracy is assumed for mounting or mounting the device than when determining the pad details. There are more or less differences.

This standard defines the maximum, medium, and minimum material conditions for pads used to mount various pin or component terminals. Unless otherwise indicated, this standard marks all three "desired targets" as Level 1, Level 2 or Level 3.

Level 1: Max - For low density product applications, the "maximum" pad conditions are used for crest or flow soldering leadless chip components and pinned fin components. The geometry configured for these components, as well as the inward "T" shaped lead components, provides a wider process window for hand soldering and reflow soldering.

Level 2: Medium - Products with medium to medium component densities can be considered for this "medium" pad geometry. Much like the IPC-SM-782 standard pad geometry, a medium pad configured for all component types will provide a robust soldering condition for the reflow soldering process and should be leadless and winged. Wave or flow soldering provides the proper conditions.

Level 3: Minimal - Products with high component densities are typically portable product applications that can take into account the "minimum" land geometry. The choice of the minimum pad geometry may not be suitable for all products. Before using the smallest pad shape, use this should consider the product's constraints and test based on the conditions shown in the table.

The pad geometries provided in IPC-SM-782 and configured in IEC 61188 should accommodate component tolerances and process variables. While pads in the IPC standard already provide a robust interface for most of the user's assembly applications, some companies have expressed the need for minimum pad geometries for portable electronics and other unique high densities. application.

The International Pad Standard (IEC61188) understands the requirements for higher part density applications and provides information on the pad geometry for a particular product type. The purpose of this information is to provide the appropriate size, shape and tolerances of the surface mount pads to ensure adequate areas of proper solder fillet and to allow inspection, testing and rework of these solder joints.

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